UDK: 54+66+502/504 ISSN 2232-755X

G L A S N I KHEMIČARA, TEHNOLOGA I EKOLOGA

REPUBLIKE SRPSKE

15

BANJA LUKABOSNA I HERCEGOVINA

DECEMBAR, 2019.

Glasnik hem. teh. i ek. RS GHTERS 15 1-38

Glasnik hemičara, tehnologa i ekologa Republike SrpskeGazette of Chemists, Technologists and Environmentalists of

Republic of Srpska

Izdavač - PublisherTehnološki fakultet, Univerzitet u Banjoj Luci

Faculty of Technology, University of Banja Luka

Za izdavača – For PublisherProf. dr Borislav Malinović – Dekan (Dean)

Glavni i odgovorni urednik - Editor-in-ChiefProf. dr Ljiljana Vukić

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Sekretar – SecretaryJovanka Todić

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Međunarodni uređivački odbor – International Editorial BoardDr Slavko Mentus, akademik, University of Belgrade, Faculty of Physical Chemistry, Serbia;

Dr Vlada Veljković, University of Niš, Faculty of Technology, Serbia;Dr Dragoljub Novaković, University of Novi Sad, Faculty of Technical Sciences, Serbia;

Dr Branko Bugarski, University of Belgrade, Faculty of Technology and Metallurgy, Serbia;Dr Tatjana Rijavec, University of Ljubljana, Faculty of Natural Sciences and Engineering, Slovenia;

Dr Aleksandar Jovović, University of Belgrade, Faculty of Mechanical Engineering, Serbia;Dr Todor Vasiljević, Victoria University, School of Biomedical and Health Sciences, Australia;

Dr Savvas G. Vassiliadis, Piraeus University of Applied Sciences, Department of Electronics Engineering, Greece;Dr Cotolan Nicoleta, Babes-Bolyai University, Faculty of Chemistry and Chemical Engineering, Romania.

Uređivački odbor iz BiH - Editorial Board from B&HDr Branko Škundrić, akademik, Akademija nauka i umjetnosti Republike Srpske;

Dr Miomir Pavlović, Univerzitet u Istočnom Sarajevu, Tehnološki fakultet Zvornik;Dr Midhat Jašić, Univerzitet u Tuzli, Tehnološki fakultet;

Dr Zoran Kukrić, Univerzitet u Banjoj Luci, Tehnološki fakultet;Dr Slavica Grujić, Univerzitet u Banjoj Luci, Tehnološki fakultet;

Dr Slavica Sladojević, Univerzitet u Banjoj Luci, Tehnološki fakultet;Dr Biljana Kukavica, Univerzitet u Banjoj Luci, Prirodno-matematički fakultet;

Dr Petar Gvero, Univerzitet u Banjoj Luci, Mašinski fakultet.

Kompjuterska priprema – Computer prepressBranka Ružičić

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Časopis je indeksiran u bazama: EBSCO, Citefactor, J-Gate, Cosmos, Google Scholar, DOI Srpska i Cobiss.

SADRŽAJTABLE OF CONTENTS

R. Petrović, Z. Levi, J. Penavin-Škundrić, B. Škundrić, D. Bodroža, Lj. Bera

ADSORPCIJA AMONIJUM JONA I AMONIJAKA IZ VODENE SREDINENA BENTONITU I MORDENITU 1

ADSORPTION OF AMMONIA IONS AND AMMONIUM FROM AQUEOUS SOLUTIONS ON BENTONITE AND MORDENITEE

R. Petrović, D. Gajić, Z. Obrenović, D. Bodroža, N. Popadić, D. Davidović, M. Ćulumović

KINETICS OF CR(VI) ADSORPTION FROM AQUEOUS MEDIUM ONTO BENTONITE 9

KINETIKA ADSORPCIJE CR(VI) JONA IZ VODENE SREDINE NA BENTONITU

M. Ćorović, A. Milivojević, M. Carević, K. Banjanac, D. Bezbradica

HyDROLySIS OF SUNFLOwER SEED MEAL LIGNOCELLULOSICFRACTION By FREE AND IMMOBILIZED CELLULASES 17

HIDROLIZA LIGNOCELULOZNE FRAKCIJE SUNCOKRETOVE SAčME PRIMENOM SLOBODNIH I IMOBILISANIH CELULAZA

S. Škaljac, M. Jokanović, V. Tomović, T. Peulić, P. Ikonić, B. Šojić, M. Ivić, Lj. Petrović, J. Babić, N. Hromiš

UTICAJ DIMLJENJA NA FORMIRANJE BOJE I SADRžAJ POLICIKLIčNIH AROMATIčNIH JEDINJENJA U TRADICIONALNOJ FERMENTISANOJ KOBASICI 25

IMPACT OF SMOKING ON FORMATION OF COLOUR AND POLyCyCLICAROMATIC HyDROCARBONS IN TRADITIONAL FERMENTED SAUSAGE

S. Janjić, V. Ivanović, B. Lazić

ADSORPCIJA JONA BAKRA IZ VODENIH RASTVORA VLAKNIMA DOMAĆE VUNE 33

ADSORPTION OF COPPER CATIONS FROM AQUEOUS SOLUTIONS By DOMESTIC wOOL FIBERS

Glasnik hemičara, tehnologa i ekologa Republike Srpske, 15 (2019) 1-8

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Adsorpcija amonijum jona i amonijaka iz vodene sredine na bentonitu i mordenituRada Petrović1*, Zora Levi1, Jelena Penavin-Škundrić1, Branko Škundrić2, Darko Bodroža1, Ljubiša Bera1

1Univerzitet u Banjoj Luci, Tehnološki fakultet, RS, B&H2Akademija nauka i umjetnosti Republike Srpske, RS, B&H

ISSN 2232-755XUDK: 541.128:66.097]:548.48DOI: 10.7251/GHTE1915001POriginalni naučni rad

U radu su prikazani rezultati adsorpcije amonijaka iz vodene sredine na dva različita adsorbensa: bentonitu i sintetskom zeolitu mordenitu.

Dobijeni eksperimentalni rezultati su testirani primjenom Freundlich-ovog i Langmuir-ovog modela izotermi. Na osnovu vrijednosti koeficijenta korelacije (R2) utvrđeno je da se adsorpcija amonijaka iz vode na bentonitu i mordenitu pokorava Freundlich-ovom adsorpcionom modelu. Rezultati pokazuju da bentonit ima veći adsorpcioni kapacitet nego mordenit.

Rad primljen: 13.05.2019.Rad prihvaćen: 19.11.2019.Rad dostupan od 31.12.2019. na https://glasnik.tf.unibl.org/

Ključne riječi: bentonit, mordenit, Freundlich-ova izoterma,Langmuir-ova izoterma.

UVOD

U zemljištu i otpadnim vodama, kao i vodi za piće, azot se može naći u obliku azotovih oksida, nitrita, nitrata, amonijaka i dr., (Rožić et al., 2000). Najveći izvori zagađenja azotovim jedinjenjima su otpadne vode iz domaćinstava, prehrambene industrije, naftnih rafinerija, poljoprivredne industrije, i drugih izvora, (Camargo & Alonso, 2006; Miladinovic & Weatherley, 2008; Penn et al., 2010; Shin et al., 2015). Prisustvo jedinjenja azota u životnoj sredini, je štetno za zdravlje ljudi i životinja i može izazvati ozbiljne ekološke probleme.

Amonijak je najvažnije jedinjenje azota, i najčešće jedinjenje azota prisutno kao polutant u otpadnim vodama. U vodenom rastvoru amonijak se može javiti u dva oblika, koja su u ravnoteži, nejonizovanom obliku (NH3·nH2O) i/ili jonizovanom obliku (NH4

+) u zavisnosti od pH rastvora, jonske jačine i temperature (Burgess et al., 2003; Nollet & De Gelder, 2014). Jednačina koja izražava ovu ravnotežu može se zapisati kao:

NH3(g) + nH2O(l)↔NH3·nH2O(aq)↔NH4+ + OH- + (n-1)H2O(l) (1)

Za vodene organizme nejonizovani amonijak je toksičan čak i u malim koncentracijama. Nejonizovani amonijak je mnogo više toksičan od jonizovanog oblika zbog toga što neutralne molekule slobodno difunduju kroz epitel membrana vodenih organizama, dok NH4

+ difunduje u znatno manjoj mjeri (USEPA, 2013). To dovodi do oštećenja epitela škrga i gušenja, stimuliše glikolizu, smanjuje kapacitet krvi za prenošenje kiseonika zbog progresivne acidoze, oštećuje krvne sudove i utiče na funkciju jetre i bubrega (Augspurger et al., 2003). Takođe, prisustvo amonijaka u vodi izaziva neželjene mirise i neke bolesti, a višak azotovih jedinjenja dovodi do smanjenja rastvorljivosti kiseonika, eutrofikacije vodenih bazena, remeti ekološku ravnotežu, pretvara aerobni medij u anaerobni, i dr., (Kardag et al., 2006; Yusof et al., 2010; Kučić et al., 2012; Godini et al., 2017). Osim toga, povećana koncentracija amonijaka u vodi za piće je indikator fekalnog zagađenja (Mažeikien et al., 2010). Po preporuci Svjetske zdravstvene organizacije (WHO, 2003) maksimalna dozvoljena koncentracija amonijaka u vodi za piće je 1,5 mg/L.Tradicionalne metode za uklanjanje amonijaka iz vode uključuju: biološke procese (Du et al., 2016), hemijsku precipitaciju (Huang et al., 2014), jonsku izmjenu (Lin & Wu, 1996; Ding & Sartay, 2016) adsorpciju i dr. (Eturki et al., 2012). Zbog svojih osobina poput efikasnosti, cijene, ekološke prihvatljivosti, jednostavnosti postupka i opreme, adsorpcija se smatra superiornom u poređenju sa drugim dostupnim metodama za uklanjanje amonijaka (Liang et al., 2016; Sen et al., 2011).

* Korespondentni autor: Rada Petrović, Univerzitet u Banjoj Luci, Tehnološki fakultet, Vojvode Stepe Stepanovića 73, Banja Luka, RS, B&H; email: rada.petrovic@tf.unibl.orgRad je izložen na naučnom skupu XII Savjetovanje hemičara, tehnologa i ekologa Republike Srpske, novembar 2018.

R. Petrović i sar.: ADSORPCIJA AMONIJUM JONA I AMONIJAKA IZ VODENE SREDINE...

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Poslednjih godina fokus istraživanja usmjeren je na pronalaženju prirodnih, jeftinih, netoksičnih, efikasnih i lako dostupnih adsorbenasa, za uklanjanje amonijaka iz vode, posebno iz otpadnih voda. Većina istraživača za adsorbense koristi prirodne materijale, najčešće prirodne zeolite (Wang et al., 2007; Tosun, 2012; Lin et al., 2013; Mažeikien & Valentukevičienė, 2016; Chen et al., 2018; Jmayai et al., 2018). Međutim, nema mnogo radova koji se bave adsorpcijom amonijaka na prirodnim glinama (Eturki et al., 2012; Buragohain, 2013; El-Shafey, 2014). I zeoliti i gline su hidratisani aluminosilikati, ali imaju različitu kristalnu strukturu. Takođe, oni imaju relativno visoke vrijednosti specifične površine i pokazuju visok afinitet prema amonijaku.

U ovom radu ispitivana je efikasnost uklanjanja amonijaka iz vodenog rastvora adsorpcijom na prirodnoj glini-bentonitu i sintetskom zeolitu-mordenitu. Adsorpcija amonijaka na ovim adsorbensima izvedena je na tri različite temperature a ispitan je i uticaj mase adsorbensa i vremena kontakta na efikasnost uklanjanja amonijaka. Eksperimentalno dobijeni podaci analizirani su primjenom Freundlich-ovog i Langmuir-ovog modela izotermi.

MATERIJALI I METODE RADA

U ispitivanjima su kao adsorbensi korišteni uzorci prirodne bentonitne gline (Šipovo, RS) i sintetskog zeolita mordenita (sintetizovan na PMF-u u Beogradu).

Fizičkohemijska karakterizacija adsorbenasa je obuhvatala određivanje hemijskog sastava, rendgensko difrakcionu analizu i određivanje specifične površine.

Hemijski sastav bentonita i mordenita određen je primjenom različitih metoda ispitivanja: gravimetrijskih (sadržaj SiO2), volumetrijskih (sadržaj Fe2O3 i Na2O), spektrofotometrijskih (sadržaj TiO2 i CaO) i potenciometrijskih titracija (sadržaj Al2O3) a dobijeni rezultati prikazani su u Tabeli 1. Rezultati prikazani u Tabeli 1 pokazuju da mordenit pored strukturnih katjona (silicijum i aluminijum) sadrži još samo natrijum. Natrijum je kompenzacioni katjon, a ovakav hemijski sastav mordenita je očekivan s obzirom da se radi o sintetskom zeolitu. Iz analize hemijskog

sastava bentonita uočava se visok sadržaj silicijuma i aluminijuma, što i ne iznenađuje, jer je hemijski sastav prirodne gline u najvećoj mjeri određen njenim faznim sastavom, tj. prisustvom glinenih i neglinenih minerala. Prisustvo željeza u uzorku gline rezultat je izomorfne supstitucije aluminijumovih jona u oktaedarskom sloju jonima željeza, dok prisustvo oksida kalcijuma (i oksida natrijuma i titana u tragovima) ukazuje da su međuslojni izmjenjljivi katjoni, u najvećoj mjeri katjoni Ca2+.

Fazni sastav adsorbenasa je određen primjenom metode rendgenske difrakcije praha (XRD) na difraktometru PHILIPS PW-1710, korištenjem CuKα zračenja (napon 40 kV, jačina struje 50 mA, ugaoni raspon 5-60º). Identifikacija prisutnih faza u uzorcima je izvršena korištenjem računarskog softvera koji sadrži bazu podataka sa ASTM karticama koje sadrže karakteristične d-vrijednosti i vrijednosti relativnih inteziteta za svaku kristalnu supstancu. Na Slici 1, prikazan je rendgenski difraktogram praha bentonita i mordenita. XDR analiza je pokazala da se bentonit sastoji od minerala montmorilonita i smjese ilit-montmorilonit, a od pratećih minerala ima najviše kvarca i kalcijum silikata. Na rendgenskom difraktogramu mordenita prisutni su samo pikovi karakteristični za zeolit mordenit, što i ne iznenađuje jer se radi o sintetskom uzorku zeolita.

Specifične površine bentonita i mordenita određene su BET-metodom, adsorpcijom azota na 77 K. Dobijena vrijednosti specifične površine za bentonit je 88,80 m2/g a za mordenit 402,54 m2/g.

Sorbent/ SorbentHemijski sastav/Chemical composition, (%)

SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O TiO2 GŽ H2O

Bentonit/ Bentonite 52,88 23,72 6,80 1,80 - 0,02 - 0,83 12,62 -

Mordenit/ Mordenite 90,25 3,64 - - - 6,11 - - - 13,32

*GŽ – gubitak žarenjem/loss through ignition; **procenti oksida kod mordenita računati su na 100 g suvog materijala/ percentages of oxides in the mordenite were calculated for 100 g of dry material

Tabela 1. Hemijski sastav adsorbenasaTable 1. The chemical composition of adsorbents

Slika 1. Rendgenski difraktogram praha bentonita i mordenita

Figure 1. X-ray powder diffraction pattern of bentonite and mordenite

Glasnik hemičara, tehnologa i ekologa Republike Srpske, 15 (2019) 1-8

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Za sve eksperimente korištene su hemikalije analitičke čistoće a za pripremu rastvora korištena je destilovana voda. Vodeni rastvori amonijaka koncentracija: 0,02; 0,03; 0,04; 0,05; 0,06; 0,07 i 0,08 mol/L pripremljeni su razblaživanjem osnovnog rastvora amonijaka koncentracije 2,0 mol/L. Tačne koncentracije amonijaka prije i nakon adsorpcije određene su titracijom sa 0,1 mol/L standardnim rastvorom HCl uz metiloranž kao indikator. Količina adsorbovanog amonijaka po gramu adsorbensa qe (mol/g), i procenat uklonjenog amonijaka E (%), iz rastvora je računata na osnovu jednačina:

( )m

Vccq e

e⋅−

= 0 (2)

( )0

0 100(%)

ccc

E e ⋅−= (3)

gdje su c0 i ce početna i ravnotežna koncentracija (u mol/L) amonijaka u rastvoru, m je masa adsorbensa (kg), a V je zapremina vodenog rastvora amonijaka (u L) iz kog je vršena adsorpcija.

Adsorpcija amonijaka iz vodenog rastvora na bentonitu i mordenitu praćena je na tri temperature: 293, 303 i 313 K. Eksperimenti adsorpcije izvedeni su u termostatu (WiseCircu WCR, model WCR-P22, Witeg, Wertheim, Germany) a nakon završenog eksperimenta uzorci su profiltrirani kroz 0,45 μm mikroporozni membranski filter. Za sve eksperimente su korišteni uzorci oba sorbenta prethodno sušena 2 časa na 383 K i svi eksperimenti su duplirani pod identičnim uslovima. Vrijeme kontakta i masa adsorbensa su jedni od najvažnijih parametara koji utiču na efikasnost adsorpcije. Uticaj mase adsorbensa za izabrane adsorbense je ispitan pri masi bentonita od 0,1 do 1,0 g i mordenita od 0,5 do 3,0 g za zapreminu rastvora od 50 mL i za početnu koncentraciju amonijaka od 0,08 mol/L tokom 4 časa na 293 K. Uticaj vremena kontakta na kapacitet adsorpcije pri početnoj koncentraciji amonijaka od 0,08 mol/L i za zapreminu rastvora od 50 mL ispitan je u periodu od 4 časa za bentonit i 24 časa za mordenit. Dobijeni eksperimentalni rezultati su analizirani korištenjem Freundlich-ove i Langmuir-ove adsorpcione izoterme.

Adsorpcione izoterme pokazuju kako se molekule adsorbata distribuiraju između tečne faze i čvrste faze kada proces adsorpcije dostigne ravnotežno stanje. Freundlich-ova adsorpciona izoterma je empirijski izraz koji se koristi za opis višeslojne adsorpcije sa interakcijom između adsorbovanih molekula. Ovaj model izoterme pretpostavlja da je površina adsorbensa heterogena sa neujednačenom distribucijom toplote adsorpcije na površini adsorbensa. Freundlich-ova adsorpciona izoterma data je jednačinom:

neFe cKq1

⋅= (4)

gdje je: ce ravnotežna koncentracija adsorbata u rastvoru (mol/L); qe je količina adsorbovane supstance u ravnoteži (mol/kg); KF i 1/n su parametri Freundlich-ove adsorpcione izoterme. Vrijednost parametra KF ((mol/L)(mol/kg)1/n) ukazuje na adsorpcioni kapacitetet adsorbensa, 1/n je faktor heterogenosti i povezan je sa intezitetom adsorpcije. Linearni oblik Freundlich-ove adsorpcione izoterme je:

(5)

Jednačina (5) predstavlja jednačinu prave u koordinatnom sistemu lnqe naspram lnce. Nagib ove prave daje vrijednost 1/n, dok presjek sa ordinatom daje vrijednost za lnKF.

Langmuir-ov model izoterme pretpostavlja monoslojnu adsorpciju adsorbata na homogenoj površini adsorbensa koja sadrži ograničen broj identičnih adsorpcionih mjesta i odsustvo interakcije između adsorbovanih molekula. Langmuir-ov model izoterme dat je jednačinom:

(6)

gdje je: ce ravnotežna koncentracija adsorbata u rastvoru (mol/L); qm (mol/kg) teorijski monoslojni adsorpcioni kapacitet (maksimalni adsorpcioni kapacitet); KL (L/kg) Langmuir-ova konstanta povezana sa energijom adsorpcije. Linearni oblik Langmuir-ove adsorpcione izoterme je:

(7)

Konstante Langmuir-ov izoterme qm (mol/kg) i KL (L/kg) se određuju grafički iz dijagrama ce/qe naspram ce, nagib dobijene prave je jednak 1/qm a presjek sa ordinatnom osom daje vrijednost 1/KLqm.

REZULTATI I DISKUSIJA

Masa adsorbensa je važan parametar jer određuje kapacitet adsorbensa za datu početnu koncentraciju adsorbata. Slika 2, prikazuje procenat uklonjenog amonijaka za različite mase bentonita (od 0,1 g do 1,0 g) i mordenita (od 0,5 g do 3,0 g) za zapreminu rastvora od 50 mL i za koncentraciju amonijaka od 0,08 mol/L u toku 4 časa na 293 K. Sa Slike 2, se vidi da sa povećanjem mase oba adsorbensa raste i procenat uklonjenog amonijaka i dostiže ravnotežne vrijednosti od 19,44 % za 0,5 g mordenita i 43,96 % za 0,2 g bentonita. Ovakvo ponašanje može se pripisati povećanju aktivne površine adsorbensa i povećanju broja slobodnih adsorpcionih mjesta. Dalje povećanje mase bentonita do 1,0 g ne dovodi do povećanja procenta uklonjenog amonijaka, dok povećanje mase mordenita do 3,0 g neznatno povećava procenat uklonjenog amonijaka. Masa od 0,5 g mordenita i masa od 0,2 g bentonita je izabrana za dalje proučavanje adsorpcionog procesa.

R. Petrović i sar.: ADSORPCIJA AMONIJUM JONA I AMONIJAKA IZ VODENE SREDINE...

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Uticaj vremena kontakta na promjenu procenta uklonjenog amonijaka sa fiksnom masom bentonita (0,2 g) i mordenita (0,5 g) je ispitan u periodu od 4 časa za bentonit i 24 časa za mordenit. Vrijednost ostalih parametara je: zapremina rastvora 50 mL, koncentracija rastvora amonijaka 0,08 mol/L i temperatura 293 K. Sa Slike 3, se vidi, da se ravnoteža postiže nakon 3 časa na bentonitu kada je maksimalan procenat uklonjenog amonijaka 23,28 % i nakon 24 časa na mordenitu kada je maksimalan procenat uklonjenog amonijaka 33,98 %. Brzo uklanjanje amonijaka u početnoj fazi na oba adsorbensa se pripisuje velikom broju slobodnih aktivnih mjesta na površini adsorbenasa. Postepenim zauzimanjem ovih mjesta dolazi do zasićenja aktivnih centara a procenat uklonjenog amonijaka vrlo malo se povećava i nakon određenog vremena uspostavlja se ravnoteža. Vrijeme kontakta od 3 časa za bentonit i 24 časa za mordenit je izabrano kao optimalno vrijeme u svim ostalim eksperimentima.

Adsorpcione izoterme daju ključne podatke o adsorbat/adsorbens interakcijama tokom procesa adsorpcije i omogućavaju izračunavanje količine uklonjenog adsorbata iz rastvora. Slika 4, prikazuje adsorpcione izoterme za adsorpciju amonijaka iz vodene sredine na bentonitu i na mordenitu na temperaturama: 293, 303 i 313 K.

Kao što se vidi na Slici 4, adsorpcione krive za amonijak na oba adsorbensa i na svim posmatranim temperaturama prolaze kroz više „platoa“ i prema Giles-ovoj klasifikaciji (Giles et al., 1960) spadaju u izoterme S4-tipa koje opisuju višeslojnu adsorpciju. Izoterme S4-tipa su rezultat kooperativne adsorpcije i jake kompeticije za adsorpciona mjesta između molekula rastvarača i molekula rastvorene supstance. Kooperativna adsorpcija se javlja kada molekule adsorbata imaju mali afinitet prema adsorbensu, tj. kada se ima slaba adsorbat/adsorbens interakcija. Slaba adsorbat/adsorbens interakcija uzrokuje mali iznos adsorpcije pri nižim koncentracijama, ali kada se molekule adsorbata adsorbuju, adsorbat/adsorbens interakcije potpomažu adsorpciju narednih molekula iz rastvora-„koopeartivnim procesom“ i adsorpcija se odvija lakše (Hinz, 2001). Ranija istraživanja adsorpcije amonijaka na alumosilikatnim adsorbensima dali su izoterme istog tipa (Levi i sar., 2006; Levi i sar.., 2016; Penavin-Škundrić i sar., 2017; Penavin-Škundrić i sar., 2010).

U uvodu je već pomenuto da u vodenom rastvoru amonijaka egzistiraju dva oblika: nejonizovani oblik koji se konvencionalno predstavlja kao NH3 i jonizovani oblik koji se predstavlja kao NH4

+. Izraz „ukupni

Slika 2. Uticaj mase adsorbensa na procenatuklonjenog amonijaka

Figure 2. The effect of the mass of adsorbent on the percentage of the removed ammonia

Slika 3. Uticaj vremena kontakta na procenat uklonjenog amonijaka

Figure 3. The effect of contact time on the percentage of the removed ammonia

Slika 4. Adsorpcione izoterme amonijaka na a) mordenitu i b) bentonituFigure 4. The adsorption isotherms of ammonia on a) mordenite and b) bentonite

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amonijak“ se odnosi na zbir ova dva oblika (NH3+NH4+).

Studije su pokazale da je pH rastvora kritičan faktor u procesu sorpcije, posebno kod adsorpcije amonijaka jer utiče na odnos ova dva oblika i na efikasnost uklanjanja amonijaka (Ji et al., 2007). Poznato je da se odnos ova dva oblika amonijaka mijenja sa promjenom pH rastvora i temperature, sa porastom pH i temperature raste koncentracija NH3, i u rastvorima sa pH>9,5 dominantan oblik je NH3 (Emerson et al., 1975; Chen et al., 2017). Kako su za eksperimentalni rad korišteni vodeni rastvori amonijaka čije su koncentracije u rasponu od 0,02-0,08 mol/L, jasno je da je pH ovih rastvora iznad 9,5, i da je u ovim rastvorima NH3 dominantan oblik. Zbog toga se, pretpostavlja da je proces adsorpcije glavni mehanizam uklanjanja amonijaka, dok je proces jonske izmjene zanemarljivo prisutan.

Prema podacima iz literature (Rožić et al., 2000; Lin et al., 2013) jonska izmjena je glavni mehanizam uklanjanja amonijum jona na zeolitu a na glini (bentonitu) je rezultat i jonske izmjene i adsorpcije; proces adsorpcije se javlja na površini a jonska izmjena unutar aluminosilikatne mreže.

Eksperimentalno dobijeni rezultati su fitovani prema Freundlich-ovom i Langmuir-ovom linearizovanom teorijskom modelu. “Podudaranje“ sa odgovarajućim modelom adsorpcije određuje se na osnovu vrijednosti koeficijenata korelacije (R2) dobijenih nakon linearnog fitovanja. Vrijednosti koeficijenata korelacije za Langmuir-ov adsorpcioni model su za oba adsorbensa niske (R2≤0,0500) i sugerišu da eksperimentalni podaci pokazuju veoma nizak stepen korelacije sa Langmuir-ovim adsorpcionim modelom, zbog čega se neće dalje komentarisati. Za razliku od Langmuir-ovog modela, adsorpcione izoterme po Freundlich- ovom modelu pokazuju visok stepen korelacije sa eksperimentalnim rezultatima za oba adsorbensa na posmatranim temperaturama (R2>0,9000, Tabela 2). Visoka vrijednost koeficijenta korelacije ukazuje da fizička sorpcija preovladava u ukupnoj sorpciji amonijaka, u prilog ovoj pretpostavci ide i tip dobijenih adsorpcionih izotermi.

Konstante Freundlich-ovog modela izoterme, KF i n, za adsorpciju amonijaka iz vodene sredine na bentonitu i mordenitu na temperaturama: 293, 303 i 313 K dati su u Tabeli 2. Kao što se može vidjeti u Tabeli 2, vrijednost konstante KF za oba adsorbensa raste sa porastom temperature, što ukazuje na endotermnu prirodu adsorpcionog procesa a upućuje i na zaključak da se pored fizičke adsorpcije dešava i hemisorpcija. Dobijeni rezultati pokazuju da je adsorpcioni kapacitet bentonita veći nego mordenita (veća vrijednost konstante KF), što se moglo i pretpostaviti jer je, s obzirom na uslove eksperimenta, proces adsorpcije dominantan mehanizam uklanjanja amonijaka, što je u saglasnosti sa literaturnim podacima (Şahin et al., 2018).

Vrijednost parametra 1/n je mjera za sorpcioni intezitet. Za n=1 raspodjela između dvije faze je nezavisna od koncentracije i adsorpcija je linearna, vrijednost 1/n<1 odnosno n>1 ukazuje na favorizovanu adsorpciju a vrijednost 1/n>1 ukazuje na kooperativnu adsorpciju (Güzel et al., 2012). Vrijednost parametra 1/n za oba adsorbensa (osim za bentonit na 293 K) leži između 1,0906 i 1,3373 i sugeriše da je adsorpcija amonijaka na oba adsorbensa rezultat kooperativne adsorpcije a što je u saglasnosti i sa tipom dobijenih adsorpcionih izotermi. Za adsorpciju amonijaka na bentonitu na 293 K vrijednost parametra 1/n je manja od jedan, i ukazuje na favorizovanu adsorpciju.

ZAKLJUČCI

Ispitana je adsorpcija amonijaka iz vodene sredine na bentonitu i mordenitu na tri različite temperature: 293, 303 i 313 K. Adsorpcione krive za amonijak na oba adsorbensa i na svim posmatranim temperaturama prolaze kroz više „platoa“ i prema Giles-ovoj klasifikaciji spadaju u izoterme S4-tipa. Ove izoterme opisuju višeslojnu adsorpciju i rezultat su „kooperativne adsorpcije“. Eksperimentalni rezultati su u saglasnosti sa Freundlich-ovim modelom adsorpcije. Glavni mehanizam uklanjanja amonijaka je proces adsorpcije. Adsorpcija amonijaka na bentonitu je veća nego na mordenitu.

LITERATURA

Augspurger, T., Keller, A. E., Black, M. C., Cope, W. G., & Dwyer, F. J. (2003). Water quality guidance for protection of freshwater mussels (Unionidae) from ammonia exposure. Environmental Toxicology and Chemistry, 22(11), 2569–2575. https://doi.org/10.1897/02-339

Adsorbens/ Adsorbent T (K) KF

((mol/L)(mol/kg)1/n) 1/n R2

Bentonit/Bentonite

293 0,0397 0,9303 0,9829

303 0,4450 1,0906 0,9742

313 1,2317 1,1948 0,9427

Mordenit/ Mordenite

293 0,0247 1,1851 0,9447

303 0,0692 1,2788 0,9430

313 0,2806 1,3373 0,9456

Tabela 2. Konstante Freundlich-ove adsorpcione izoterme za adsorpciju amonijaka i amonijum jona iz vodene sredine na bentonitu i mordenituTable 2. The constants of Freundlich adsorption isotherms for the adsorption of ammonia and ammonium ion from the aqueous medium on mordenite and bentonite

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Adsorption of ammonia ions and ammonium from aqueous solutionson bentonite and mordenite

Rada Petrović1*, Zora Levi1, Jelena Penavin-Škundrić1, Branko Škundrić2, Darko Bodroža1, Ljubiša Bera1 1University of Banja Luka, Faculty of Technology, RS, B&H2Academy of Sciences and Arts of the Republic of Srpska, RS, B&H

exponential model and conventional kinetic models. International Journal of Environmental Research and Public Health, 9(3), 970-984. https://doi.org/10.3390/ijerph9030970

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Wang, Y. F., Lin, F., & Pang, W. Q. (2007). Ammonium exchange in aqueous solution using Chinese natural clinoptilolite and modified zeolite. Journal of Hazardous Materials, 142(1-2), 160-164. h t t p s : //d o i . o r g / 1 0 . 1 0 1 6 / j .j h a z m a t . 2 0 0 6 . 0 7 . 0 7 4

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This paper studies adsorption of ammonium ions and ammonia from aqueous solution onto bentonite and on a synthetic zeolite mordenite. Bentonite and mordenite are characterized by chemical composition and specific surface determination, and X-ray diffraction analysis. The removal of ammonium ions and ammonia was performed in a batch system. The influence of various parameters, such as adsorbent weight, contact time and temperature, on adsorption process was examined. Optimal contact time for reaching adsorption equilibrium is 3 hours for bentonite and 24 hours for mordenite, while the optimal weights are 0,2 g and 0,5 g respectively. The pH values of the solution and temperature are the parameters which affect the equilibrium of the non-ionized form of ammonia (NH3 · nH2O) and/or the ionized form (NH4

+). In the acidic medium, the predominant form of ammonia is NH4

+, while in the alkali medium (pH over 9,5) the dominant form is NH3. As aqueous solutions of ammonia in the concentration range 0,02-0,08 mol/L are used in this study, pH of these solutions is over 9,5 and dominant form in this case is NH3. Due to this, it can be assumed that adsorption process is the primary mechanism of ammonia removal, while the ion exchange process is negligible.

Temperatures effect on adsorption process was studied at three temperatures: 293, 303 and 313 K. The adsorption capacity of both adsorbents increases with increasing temperature, which indicates that adsorption process is endothermic and chemisorption occurs in addition to physical adsorption.

Experiments show that adsorption curves of both adsorbents, at all observed temperatures, pass through multiple “plateaus” and, according to Giles classification, these isotherms are S4-type. This type of isotherms described multilayered and cooperative adsorption. The obtained results were fitted to Freundlich’s and Langmuir’s linear theoretical model. Based on the values of the correlation coefficient (R2), the results showed that the adsorption of ammonium ions and ammonia from aqueous solution obeys the Freundlich adsorption model. Bentonite proved to be a better adsorbent than mordenite.

Keywords: ammonium ion, ammonia, bentonite, mordenite, Freundlich’s isotherm, Langmuir’s isotherm.

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Kinetics of Cr(VI) adsorption from aqueous medium onto bentonite

Rada Petrović1*, Dragana Gajić2, Zoran Obrenović3, Darko Bodroža1, Nevena Popadić1, Danka Davidović2, Mirjana Ćulumović2 1University of Banja Luka, Faculty of Technology, RS, B&H2University of Banja Luka, Faculty of Natural Sciences and Mathematics, RS, B&H3University of East Sarajevo, Faculty of Technology, Zvornik , RS, B&H

ISSN 2232-755XUDC: 548.48:[66.097:541.128DOI: 10.7251/GHTE1915009POriginal scientific paper

Because of its abundance and toxicity, heavy metals have become a serious environmental problem. The presence of heavy metals, such as Cr(VI), in the watercourses leads to numerous health problems in humans and animals. Cr(VI) is highly toxic, even in low concentrations. Because of its carcinogenic, mutagenic and teratogenic effects on human beings, Cr(VI) is considered one of the most critical pollutants. Due to this, it is necessary to remove Cr(VI) from wastewater prior to its discharge into the recipient.

This paper studied the possibility for application of bentonite as an adsorbent for Cr(VI) from aqueous medium. The characterization of bentonite was determined with chemical composition, specific surface, XRD method and FTIR. Optimal parameters such as pH of solution, adsorbent weight, time of adsorption and temperature were examined. Values of those parameters were: initial pH value of solution pH=2, adsorbent weight 2 g, time of adsorption 60 min, temperature 308 K. Experimental data were obtained by Freundlich and Langmuir isotherm adsorption models as well as pseudo-first and pseudo-second order kinetics. Results were best described with Freundlich isotherm adsorption model and pseudo-second order kinetics.

Paper received: 18 Nov 2019Paper accepted: 27 Nov 2019Paper available from 31 Dec 2019at https://glasnik.tf.unibl.org/

Keywords: bentonite, adsorption, Cr(VI), kinetics, isotherms.

INTRODUCTION

Chromium is not naturally found in watercourses. However, its presence was found in wastewaters of various industries, such as leather processing, textile, photographic and glass industries, ceramics, metal and wood processing industries, pigment production, inorganic chemicals, electrical and electronic equipment, etc. (Hu et al., 2009; Gupta et al., 2010). Although there are few different oxidation states of chromium, contaminated soil and water contain trivalent (Cr(III)) and hexavalent (Cr(VI)) chromium. While trivalent chromium is important for glucose, lipids and proteins metabolism, hexavalent chromium is highly toxic, and has carcinogenic and mutagenic effect on people and environment (Haney et al., 2014; Dupont & Guillon, 2003). Acute exposure to hexavalent chromium compounds causes nausea, diarrhea, lung cancer, leads to liver, kidney and stomach damage, respiratory problems and internal bleeding (Bhattacharyya & Gupta, 2006; Costa & Klein, 2006;

Shouman et al., 2013; Shekhawat et al., 2015). Due to the toxic, mutagenic and cancerogenic effect of Cr(VI), American Environment Protection Agency (U.S. EPA., 2010) announced this oxidation form of chromium as a high risk pollutant.

According to the recommendation of the World Health Agency (WHO, 2019), the maximum permissible concentration of chromium in drinking water is 0.05 mg/L. According to the order of hygienic safety of drinking water of the Republic of Srpska, the maximum concentration of total chromium is 0.05 mg/L (Official Gazette of the Republic of Srpska, Nos. 16/02 and 10/98).

Among the numerous physical, chemical and biological methods for the removal of Cr(VI) compounds from aqueous solutions, the adsorption method is the applicable method based on its simplicity and cost-effectiveness. Various numbers of different materials such as natural clays (Zachara et al., 1988; Ajouyed et al., 2011; Li et al., 2016; Algamal et al., 2018), natural zeolites (Faghihian & Bowman, 2005; Jorfi et al., 2017), agricultural and industrial waste material (Šćiban & Klašnja, 2002), different carbon materials, activated carbon (Mohan & Pittman, 2006) etc. were tested as an adsorbent for Cr(VI) compounds from aqueous medium.

* Corresponding author: Rada Petrović, University of Banja Luka, Faculty of Technology, Vojvode Stepe Stepanovića 73, Banja Luka, RS, B&H; email: rada.petrovic@tf.unibl.org

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Great specific surface, layered structure, high ion exchange capacity, as well as chemical and mechanical stability are the properties of clays, which are specified as good adsorbents for cationic, anionic and neutral metal forms. Bentonite is natural clay. Main component of bentonite is mineral montmorillonite (over 60 %). Montmorillonite is the type of smectite clay minerals, layered silicate structure type 2:1, where one octahedral layer (AlO4 octahedral) is positioned between two tetrahedral layers (SiO4 tetrahedral).

This paper studied the possibility of natural clay bentonite application as an adsorbent for Cr(VI) from aqueous medium. Experimental data were obtained by Freundlich and Langmuir adsorption isotherms and pseudo-first and pseudo-second kinetic models.

MATERIALS AND METODS

Natural clay bentonite, product of “Bentoprodukt” d.o.o., Šipovo, Republic of Srpska, was used in this study. Physicochemical properties of bentonite were determined with chemical composition method, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and specific surface method.

Chemical composition of bentonite was specified with different experimental methods: gravimetric (content of SiO2), volumetric (content of Fe2O3 and Na2O), spectrophotometric (content of TiO2 and CaO) and potentiometric titration (content of Al2O3).

Mineralogical analysis of bentonite was performed by X-ray diffraction analysis on a powder sample at instrument PHILIPS PW-1710 with CuKα radiation (voltage 40 kV, current strength 50 mA, 2θ range 5-60°). XRD spectrum was indentified in ASTM standard base.

Specific surface of bentonite was determined with BET method, by adsorption of nitrogen at 77 K at instrument Flowsorb II 2300. FTIR analysis was performed on FTIR-spectrophotometer Bruker “Tensor 27” in range from 4000 to 400 cm-1.

Batch adsorption experiments were processed in Erlenmayer flasks in thermostat (WiseCircu WCR, model WCR-P22, Witeg, Wertheim, Germany). The effect of the initial pH of the solution, the weight of the adorbent, the contact time and temperature of the adsorption process were examined. For adsorption experiments, volume of 50 mL of Cr(VI) solution (concentration 10 mg/L) was always taken, while the other parameters varied from experiment to experiment. When the adsorption equilibrium was established, the suspensions were centrifuged for 20 minutes at 13 000 rpm (Alresa Mod, Digicen) and the content of Cr(VI) in supernatant was determined by spectrophotometric method. All the experiments were performed twice.

Stock solution of K2Cr2O7, concentration 100 mg/L, was prepared by dissolving 0.2828 g of K2Cr2O7, p.a. in 1000 mL of distilled water. Solutions for adsorption study (2; 4; 6; 8 and 10 mg/L) were prepared by diluting the stock solution. Concentration of chromium, which is at the pH=2 in the form of hydrogen chromate ion (HCrO4

-) was determined by spectrophotometer (Perkin Elmer Lambda 25) with 1,5 diphenylcarbazide method (DPC). DPC forms with Cr(VI) red-violet complex in acid sulfate media (pH=2). Intensity of color is proportional to the concentration of Cr(VI) in the aqueous solution and was measured at λmax.=541.17 nm. 2.5 mL of the solutions was taken and diluted for spectrophotometric measurements, pH of the solution was adjusted to 2 and 2 mL od DPC was added. 0.25 % DPC solution was prepared by dissolving 0.2590 g DPC, a.p. in 100 mL acetone. For pH adjusting sulfuric acid was used (H2SO4:H2O=1:1). pH of the solution was adjusted wih Jenway 3520 pH meter with accuracy ±0.1. The amount of adsorbed Cr(VI) per gram of bentonite, qe (mg/g) and efficiency of adsorption, E (%), was calculated by using the following equations:

( )m

Vccq e

e⋅−

= 0 (1)

(2)

c0 and ce are initial and equilibrium concentration of Cr(VI) (mg/L) in solution, respectively, V is the volume of solution for adsorption (L) and m is weight of adsorbent (g).

The adsorption kinetics and batch adsorption study of Cr(VI) from aqueous medium onto bentonite was performed at initial Cr(VI) concentration 10.0 mg/L, volume 50 mL and optimal parameters (pH=2.0; m=2.0 g; t=60 min. and T= 308 K). Kinetics of adsorption was studied during 180 min. Reaction times were 10, 20, 30, 40, 50, 60, 90, 120, 150 and 180 min. After that, suspensions were centrifuged and content of Cr(VI) in supernatant was measured spectrophotometrically.

RESULTS AND DISCUSSION

Characterization of adsorbent

The chemical composition of bentonite in mass % is presented in Table 1. The results showed that the main components of bentonite are SiO2 and Al2O3. Of the other constituents, Fe2O3 and trace of CaO, Na2O and TiO2 are detected.

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The bentonite diffractogram (Figure 1. left) showed that this clay is the mixture of different mineral phases, the most represented mineral is montmorillonite and mixture illite-montmorillonite, as well as quartz and calcium silicates.

FTIR spectrum provides the information about the structure and type of functional groups at the surface of the material. Figure 1. (right) shows FTIR spectrum of bentonite. According to the literature data (Madejova, 2003; Ikhtiyarova et al., 2012), a group of peaks with wave number 3750-3500 cm-1 correspond to vibrational bands of –OH groups from adsorbed water onto bentonite. A peak with wave number 3624 cm-1 is typical for smectite with large amount of Al in octahedral layer, while peak with wave number of 1634.33 cm-1 corresponds to –OH deformations in water. Minerals from carbonate group showed peak at 1431 cm-1 and quartz at 796 and 690 cm-1. The characteristic peaks in the range of wave numbers 1200-900 cm-1 (995 and 912 cm-1) are the result of the stretching vibrations of the various Si-O groups and

bending vibrations of the Al-O-Al groups, while the peaks with the wave numbers 600-400 cm-1 (519 and 459 cm-1), attributed to the bending vibration bands of Si-Al-O and Si-O groups, respectively.

Adsorption potential of adsorbent depends on specific surface, and those parameters are proportional. Specific surface of bentonite was determined by BET method and the value is 88.80 m2/g.

Influence of the initial pH of the solution on the adsorption of Cr(VI)

One of the most important parameters of adsorption process is the pH value of aqueous media in which adsorption is carried out, because this parameter affects the ionization state of functional groups on the surface of the adsorbent and the state of ionic groups of metal in solution (Özcan et al., 2004). The effect of the initial pH of the solution was examined in these conditions: 1.0000 g/ 50 mL of solution, concentration of Cr(VI) 10 mg/L, contact time of 2 hours and at the temperature of 293 K. Depending on the pH value in the medium and concentration, chromium exists in different species, such as oxianion dichromate Cr2O7

2-

, hydrogen chromates HCrO4-, chromates CrO4

2-. In the solution concentrations bellow 1 g/L hydrogen chromate HCrO4

- is dominant species, while in the range above 1 g/L dichromate Cr2O7

2- species exists. Based on this literature data, pH values for these experiments were 2, 3, 4 and 5 and the obtained results are shown in Figure 2a.

AdsorbentChemical composition (mass %)

SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O TiO2 GŽ H2O

Bentonite 52.88 23.72 6.80 1.80 - 0.02 - 0.83 12.62 -

Table 1. The chemical composition of adsorbent (bentonite)

Figure 1. XRD pattern of bentonite (left) and FTIR spectrum of bentonite (right)

Figure 2. a) The efficiency of chromium Cr (VI) adsorption in function of initial pH (conditions: m = 1.0000 g; V = 50 mL; c0 = 10 mg / L; T = 293 K; t = 2 h); b) The effect of the adsorbent weight on the adsorption of Cr(VI) (conditions:

V = 50 mL; T = 293 K; c0 = 10 mg /L; t = 2 h; pH=2.0)

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Figure 2a. shows that adsorption efficiency onto bentonite increases when pH value of the solution decreases. The highest adsorption efficiency was obtained for the lowest initial pH= 2 (E=45.85 %), which is in good correlation with literature data (Ajouyed et al., 2011; Tichapondwa & Van Biljon, 2019). At this pH value of the solution, the surface of bentonite is protonated (due to excess of H+ ions) and positively charged. In these conditions, hydrogen chromate HCrO4

- dominates, and the process of the adsorption is the consequence of electrostatic attraction between the positively charged bentonite surface and negatively charged HCrO4

- ions (Akar et al., 2009; Brum et al., 2010). pH=2 value was chosen as an optimal parameter for further studies.

Effect of the adsorbent weight on adsorption of Cr(VI)

Adsorbent weight is an important parameter in the adsorption process, because it determines the capacity of the adsorbent for a different initial concentration of adsorbate. The efficiency of Cr(VI) adsorption onto bentonite was studied on different weights of adsorbent (0.5; 1.0; 1.5 and 2.0), while the other parameters were constant: initial Cr(VI) concentration 10.0 mg/L, pH of the solution was 2, volume 50 mL, contact time 2 hours and temperature was 293 K. The obtained results are shown in Figure 2b. The results showed that adsorption efficiency increases with bentonite weight and reaches maximum (53.60 %) at weight of 2.0 g. This is explained by the fact that when the weight of adsorbent increases, total surface for the binding metal ions increases as well as the number of the adsorption sites (Wanees et al., 2013). Optimal weight of bentonite for further studies was 2.0 g. Suspensions with higher weights than 2 g were dense and contact between adsorbate and adsorbent was aggravated and they were not studied.

Effect of contact time on adsorption of Cr(VI)

The effect of contact time on the adsorption of Cr(VI) onto bentonite was studied at an initial concentration 10 mg/L, volume 50 mL, pH=2 and temperature 293 K. Adsorption was examined through a period of 120 min. The effect of contact time on adsorption process is presented in figure 3a. Based on the obtained results, it can be concluded that adsorption of Cr(VI) onto bentonite takes place in two phases. The first phase is very fast and occurs in the first 60 min of the interaction of the bentonite with Cr(VI) solution, when the maximum adsorption efficiency is reached (56.32 %). This phase took place fast, due to high concentration of active sites onto bentonite surface and high concentration of metal ions. The second phase is slower and during this phase the adsorption efficiency decreases slightly, as the number of free active sites as well as the initial Cr(VI) concentration decreases. Electrostatic repulsion can take place between bonded HCrO4

- ions and HCrO4- species, which are remaining

in the solution (Algamal et al., 2018). Contact time t=60 min was chosen as an optimal parameter for further experiments.

Effect of temperature on adsorption of Cr(VI)

Figure 3b. shows the effect of temperature on the adsorption efficiency of Cr(VI) from aqueous solution onto bentonite. Three different temperatures (293; 298 and 308 K) were considered, while the other parameters were constant: V=50 mL; c0=10 mg/L; t=60 min; m=2.0000 g and pH=2.0). Increasing the temperature in this adsorption study positively affected the efficiency of this process and the maximum was reached at the temperature 308 K (41.60 %). These results showed that adsorption of Cr(VI) onto bentonite is of chemical nature and has endothermic character. For further studies, temperature of 308 K was selected as optimal.

Figure 3. a) The efficiency of chromium Cr (VI) adsorption in function of time (conditions: m = 2.0000 g; V = 50 mL; pH=2.0; c0 = 10 mg / L; T = 293 K); b) The effect of temperature on adsorption of Cr(VI) (conditions: m=2.0000 g;

V = 50 mL; c0 = 10 mg /L; t = 60 min; pH=2.0)

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Kinetic study

Kinetic adsorption models provide insights into the rate of adsorption process and its mechanism, involving mass transfer, diffusion (external and internal) and the interaction of adsorbates particles with active sites onto adsorbent surface. The most commonly used kinetic adsorption models are pseudo-first and pseudo-second order kinetic models.

The pseudo-first order kinetic model, as well known as Lagergren’s kinetic model, is one of the most commonly used models. In this model, adsorbate reacts with active center and forms an adsorption complex. The pseudo-first order model is represented by the equation:

(3)

qe is the amount of adsorbed particles at the equilibrium (mg/g), qt is the amount of adsorbed particles at the time t (mg/g), k1 is the pseudo-first order adsorption rate constant (min-1). After integration from t=0 to t=t and qt=0 to q=qt, equation (3) takes the following form:

(4)

For practical reasons, equation (4) goes to linear form:

(5)

The constant k1 is obtained from the graph of the dependence ln(qe-qt)=f(t).

The pseudo-second order kinetic can be represented by the equation:

(6)

Integration equation (6) from t=0 to t=t and qt=0 to qt=qt, equation gets the following form:

(7)

where k2 is the pseudo-second order adsorption rate constant (g mg-1 min-1), while the other quantities have the same content as in the previous model. The linear form of equation (7) is:

(8)

qe and k2 can be obtained from the graph of dependence t/qt=f(t). The pseudo-second order model describes the chemisorptions on solid adsorbents.

The kinetic of Cr(VI) adsorption from aqueous solution onto bentonite was studied at optimal parameters:

V=50 mL; c0=10 mg/L; pH=2.0; m=2.0000 g and T=308 K and different adsorption times. The values of the kinetic parameters for applied kinetic models are presented in Table 2. The consistency between the experimental data and proposed kinetic models was determinated by the value of correlation coefficient R2. The greater value of this coefficient, gives more information about the proposed theoretical model. Results showed (Table 2) that adsorption of Cr(VI) onto bentonite follows pseudo-second order kinetic (R2=0.9917). Pseudo-second order kinetics indicates that the adsorption and ion exchange occurs on the adsorbent surface and that the limiting factor of adsorption rate is chemical binding to active sites (Wanees et al., 2013).

Adsorption istoherms

Adsorption isotherms are important for determination of maximum adsorption capacity of adsorbents as well as for describing the interactions between adsorbates and adsorbents. Freundlich and Langmuir adsorption isotherms are the most commonly used isotherms for the characterization of adsorption process.

Freundlich adsorption model describes adsorption on energetically heterogeneous surface with interactions between adsorbents and adsorbed molecules. This model confirms multilayered adsorption. This isotherm is presented by the equation:

(9)

where qe is the equilibrium adsorption capacity (mg/g), ce is the equilibrium concentration of adsorbate in solution (mg/L) and KF and n are constants of the Freundlich adsorption isotherm. The Freundlich constant KF (mg g-1)(L mg-1)1/n indicates the adsorption capacity of the adsorbent while the constant n describes the affinity of the adsorbent to the adsorbate and to the heterogeneity of the surface. The logarithmic form of the equation (9) is:

(10)

Pseudo-first order kinetic model

Pseudo-second order kinetic model

k1 ( min-1)

qe (mg g-1) R2 k2

(g mg-1 min-1)qe

(mg g-1) R2

0.0021 1.4827 0.4681 0.9807 0.1748 0.9917

Table 2. Kinetic parameters for adsorption of Cr(VI) onto bentonite

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The constant KF and n are obtained from dependence of lnqe on lnce, as the intercept and slope on the graph, respectively.

Langmuir’s model of adsorption isotherm refers to the adsorption on an energy uniform surface without any interactions between adsorbed molecules. Only one molecule can bind to one adsorption site and the maximum amount of adsorption is the formation of a monomolecular layer on the surface of the adsorbent. The Langmuir adsorption isotherm is described in the equation:

(11)

where qe is the equilibrium adsorption capacity (mg/g), ce is the equilibrium concentration of adsorbate in solution (mg/L), KL is the Langmuir adsorption energy constant (L/mg), related to the adsorption energy and qm is the maximum adsorption capacity (mg/g). The linear form of this isotherm is:

= ce + (12)

Graph dependence ce/qe vs. ce determines constant values 1/(KLqm) from intercept and 1/qm from slope.

The adsorption of Cr(VI) from aqueous solution onto bentonite was studied at the optimal parameters: V=50 mL; pH=2.0; m=2.0000 g; t=60 min, T=308 K and different initial concentrations of Cr(VI) (2; 4; 6; 8 and 10 mg/L). The values of Freundlich and Langmuir isotherm parameters are presented in Table 3. Based on the value of the correlation coefficients, the Freundlich isotherm model (R2=0.913) is more suitable for describing adsorption of Cr(VI) onto bentonite than Langmuir’s (R2=0.795). The obtained results were in accordance with the previously presented data (Bentchikou et al., 2017; Tsafam et al., 2019). The Freundlich model assumes an energetically heterogeneous surface of adsorbents and Cr(VI) can bind to multiple types of active sites (Šćiban et al., 2014).

The Freundlich constant n is related to the intensity of adsorption and the heterogeneity of the surface. When the parameter value is n=1, adsorption follows a

linear function, for n<1 adsorption is unfavorable and when n>1 adsorption is favored (Güzel et al., 2012). The value of parameter n in this adsorption process is 1.4206 and suggests that adsorption of Cr(VI) onto benotnite is favored.

CONCLUSIONS

The results of this study showed that bentonite has a potential to remove Cr(VI) from aqueous solution. Although, the maximum adsorption efficiency was obtained at pH=2.0 (E=45.85 %), the experimental data showed that even at pH=5.0 bentonite binds a certain amount of Cr(VI). The pseudo-second order kinetic model best describes adsorption process in this study. Analysis of adsorption data indicates that the adsorption of Cr(VI) onto bentonite obeys the Freundlich isotherm model.

Acknowledgment: Research study was funded by Ministry’s for Scientific-Technological Development, Higher Education and Information Society project: “Possibility of application of natural and modified bentonite and zeolites from the territories of The Republic of Srpska for the formation of antimicrobal films for prolonging the shelf life of food products“ (19/6-020/961-63/18).

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Langmuir adsorption isotherm

Freundlich adsorption isotherm

KL (L mg-1)

qm (mg g-1) R2 KF

(mg g-1)(mg L-1)1/n n R2

0.2994 0.2982 0.7950 0.0665 1.4206 0.9130

Table 3. Parameters of the adsorption isotherms

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Kinetika adsorpcije Cr(VI) jona iz vodene sredine na bentonitu

Zbog svoje brojnosti i toksičnosti teški metali su postali ozbiljan ekološki problem. Prisutnost teških metala, kao što je Cr(VI) u vodenim tokovima dovodi do brojnih zdravstvenih problema kod ljudi i životinja. Cr(VI) je veoma toksičan, čak i u malim koncentracijama. Zbog svojih kancerogenih, teratogenih i mutagenih dejstava na ljude Cr(VI) se smatra jednim od najkritičnijih zagađivača. Stoga je potrebno ukloniti Cr(VI) iz otpadnih voda prije njihovog ispuštanja u recipijent.

U radu je ispitana mogućnost upotrebe prirodnog bentonita kao adsorbensa Cr(VI) iz vodenog rastvora. Karakterizacija bentonita obuhvatala je određivanje hemijskog sastava, specifične površine, XDR-analizu i FTIR analizu. Ispitani su osnovni parametri koji utiču na proces adsorpcije kao što su: inicijalna pH vrijednost rastvora, masa adsorbensa, vrijeme kontakta i temperatura. Nađeni optimalni parametri adsorpcije su: inicijalna pH vrijednost rastvora pH=2,0; masa adsorbensa 2 g; vrijeme kontakta 60 min.; temperatura 308 K. Eksperimentalno dobijeni rezultati analizirani su upotrebom Frojndlihovog i Lengmirovog modela adsorpcionih izotermi i kinetičkih modela pseudo-prvog i pseudo-drugog reda. Utvrđeno je da se eksperimentalni podaci pokoravaju Frojndlihovom modelu adsorpcione izoterme i kinetičkom modelu pseudo-drugog reda.

Ključne riječi: bentonit, adsorpcija, Cr(VI), kinetika, izoterme.

Rada Petrović1, Dragana Gajić2, Zoran Obrenović3, Darko Bodroža1, Nevena Popadić1, Danka Davidović2, Mirjana Ćulumović2

1Univerzitet u Banjoj Luci, Tehnološki fakultet, RS, BiH2Univerzitet u Banjoj Luci, Prirodno-matematički fakultet, RS, BiH3Univerzitet u Istočnom Sarajevu, Tehnološki fakultet Zvornik, RS, BiH

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Tichapondwa, S., & Van Biljon, J. (2019). Adsorption of Cr(VI) pollutants in water using natural and modified attapulgite clay. Chemical Engineering Transactions, 74, 355-360. https://doi.org/10.3303/CET1974060

Tsafam, A., Domga, R., Dangwang Dikdim, J. M., Nyounaï, F., Gnowe, D. W., Kagongbe, D., Nko’o, G. E., & Noumi, G. B. (2019). Adsorption of Cr (VI) onto clay modified by sodium chloride and clay modified by aluminum hydroxide of Karewa (North Cameroon). International Research Journal of Advanced Engineering and Science, 4(1), 247-255. Retrieved October 30, 2019 from https://zenodo.org/record/2602724#.Xd0jCNQwjs0

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Zachara, J. M., Cowan, C. E., Schmidt, R. L., & Ainsworth, C. C. (1988). Chromate adsorption by kaolinite. Clays and Clay Minerals, 36(4), 317-326. https://doi.org/10.1346/CCMN.1988.0360405

Wanees, S. A., Ahmed, A. M. M., Adam, M. S., & Mohamed, M. A. (2013). Adsorption studies on the removal of hexavalent chromium-contaminated wastewater using activated carbon and bentonite. Asian Journal of Chemistry, 25(15), 8245-8252. https://doi.org/10.14233/ajchem.13559

WHO. (2019). Chromium in drinking-water. (Draft Background document for development of WHO Guidelines for Drinking-water Quality). Geneva: World Health Organisation. Retrieved October 30, 2019 from https://www.who.int/water_sanitation_health/water-quality/guidelines/chemicals/draft-chromium-190924.pdf

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Hydrolysis of sunflower seed meal lignocellulosic fraction by free and immobilized cellulases

Marija Ćorović1*, Ana Milivojević2, Milica Carević1, Katarina Banjanac2, Dejan Bezbradica1

1 Department of Biochemical Engineering and Biotechnology, Faculty of Technology and Metallurgy, University of Belgrade, Serbia2 Innovation Center, Faculty of Technology and Metallurgy, University of Belgrade, Serbia

ISSN 2232-755XUDC: 582.28:[543.632.254:62-665.9DOI: 10.7251/GHTE1915017ĆOriginal scientific paper

Lignocellulosic biomass is widely abundant in nature and recognized as potential renewable energy source. Its efficient transformation into bio-based fuels is enabled only after adequate pretreatment, followed by enzymatic sacharification and microbial fermentation. Hereby we present application of two cellulase preparations – from Aspergillus niger and Trichoderma reesei (Celluclast®) in treating sunflower seed meal lignocellulosic fraction (SSMLF). Temperature and pH optimums of two enzymes were determined – 52 °C and pH4.8 for A. niger cellulase and 55 °C and pH4.5 for Celluclast®. At optimized conditions, milled SSMLF was hydrolyzed by both biocatalysts. With A. niger cellulase higher initial reaction rates were accomplished and yield of 70 mM glucose equivalent was obtained with 6 % (w/v) of enzyme after 6 hours. On the other hand, application of Celluclast® led to lower initial reaction rates and yielded 25 mM of glucose equivalent with 10 % (v/v) of enzyme. To ensure cost-effective application of A. niger cellulase, the possibility of its immobilization on different supports was investigated. By using porous methacrylate-based carrier with C6 spacer arm and primary amino groups – LifetechTM ECR8409, preparation with highest activity was produced. This preparation was successfully applied in saccharification of SSMLF and showed unchanged catalytic efficiency comparing to free enzyme.

Paper received: 27 Nov 2018Paper accepted: 28 Nov 2019Paper available from 31 Dec 2019at https://glasnik.tf.unibl.org/

Keywords: sunflower seed meal, lignocellulose, cellulase, immobilization

INTRODUCTION

Sunflower seed meal is produced in large quantities as a byproduct of oil extraction industry and is currently used as a livestock feed for ruminants and as a fertilizer (Bautista et al., 1990). Within fractionation process, high quality protein concentrate and isolate could be produced from this material. Different approaches could be applied for that purpose, including wet and dry procedures (Kumar & Sharma, 2017). As a waste-product, lignocellulose rich hulls are being obtained, hence ideally suited for further processing. Lignocellulose represents complex matrix composed of three basic biopolymers – cellulose, hemicellulose and lignin – organized into the ununiformed tridimensional structures of various morphologies and structures. Conversion of lignocellulosic substrates, including

sunflower seed meal lignocellulosic fraction (SSMLF), into products with high added value such as biofuels and fine chemicals requires multi-step processing comprised of thermo-mechanical, chemical or biological pretreatment, subsequent enzymatic hydrolysis (most commonly by microbial cellulases) and final microbial fermentation.

Cellulases (EC 3.2.1.) are enzymes which catalyze hydrolysis of cellulose and could demonstrate endoglucanase, exoglucanase and β-glucosidase activity. Currently, cellulases are widely applied in numerous industry branches such as food, pharmaceutic, textile, paper and pulp industry, as well as agriculture (Bhat & Bhat, 1997; Kuhad et al., 2011). Potential for their cost-effective application in the treatment of lignocellulosic biomass for the production of second generation biofuels is nowadays attracting increasing attention of scientific community (Tran et al., 2019; Sukumaran et al., 2005). Different microbial cellulases were so far used for that purpose. However, relatively high price of available enzyme preparations combined with high dosages required for efficient cellulose hydrolysis represents one of the main challenges for process commercialization.

*Corresponding author: Marija Ćorović, Department of Biochemical Engineering and Biotechnology, Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade, Serbia, email: mstojanovic@tmf.bg.ac.rs*The paper was exposed on XII Conference of Chemists, Technologists and Environmentalists of Republic of Srpska

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A convenient method for overcoming these issues is immobilization on adequate solid supports, providing increased operational and storage stability and reusability (Vaz et al., 2016). During the last decades, various microbial cellulases were immobilized onto different nanoparticles (Xu et al., 2011; Gokhale et al., 2013; Lima et al., 2017; Han et al., 2018; Simon et al., 2018), magnetic chitosan microspheres (Miao et al., 2016), kaolin (Lima et al., 2019), etc. However, most of these immobilized preparations are not applicable for the saccharification of natural lignocellulosic substrates due to their high prices.

Main goal of this research was to examine the possibility of application of free and immobilized cellulases for the hydrolysis of SSMLF. Within current study, two commercial cellulase preparations - from Aspergillus niger and Trichoderma reesei (Celluclast®), were examined as a catalysts for (SSMLF) saccharification. Two biocatalysts were first characterized in terms of pH and temperature optimums and subsequently, at optimized conditions, applied in the SSMLF hydrolysis. Their performances were assessed by analyzing initial reaction rates and final concentration of reducing sugars produced from carboxymethyl cellulose (CMC) as a substrate. Furthermore, eight carriers with different polarity, porosity and functionality (Table 1) were screened as supports for immobilization of A. niger cellulase. LifetechTM series carriers were chosen due to their good mechanical properties, high chemical resistance and facile separation and regeneration after application. Moreover, immobilized biocatalyst with highest cellulolytic activity was tested in a reaction of SSMLF saccharification in order to evaluate its perspective for application in enzymatic pretreatment during bio-fuels production.

MATERIALS AND METHODS

Materials

Two cellulase preparations were used - Aspergillus niger cellulase (powder, ≥0.3 units/mg solid, Sigma-Aldrich Chemie GmbH, Steinheim, Germany) and Trichoderma reesei (Celluclast®, Novozymes, Bagsvaerd, Denmark) as biocatalysts. Substrates were low viscosity carboxymethyl cellulose sodium salt (Sigma-Aldrich Chemie GmbH, Steinheim, Germany) and lignocellulosic fraction obtained after fractionation of local sunflower seed meal. LifetechTM immobilization supports were provided by Purolite Corporation (Bala Cynwyd, PA, USA). For DNS reagent preparation following chemicals were used: 3,5-dinitrosalicylic acid (98 %, Acros Organic, New Jersey, USA), NaOH (p.a., Sigma-Aldrich Chemie GmbH, Steinheim, Germany) and potassium sodium tartarate (p.a., Sigma-Aldrich Chemie GmbH, Steinheim, Germany). Salts used for buffer solutions preparation were: Na2CO3 (Zorka Pharma, Šabac, Serbia), sodium citrate (Alkaloid, Skopje, Macedonia) NaH2PO4 (Centrohem, Stara Pazova, Serbia), Na2HPO4 (Superlab, Belgrade, Serbia), all analytical grade.

Determination of enzyme activity

Activity of free and immobilized cellulases was determined spectrophotometrically by DNS method with 2 % CMC in a buffer (50 mM) as a substrate. When temperature and pH optimums for two preparations were examined, temperature was varied between 35 and 70 °C and pH was in range 3.5-8. Predefined amount of free (1 mg/ml of A. niger cellulase and 1 μl/

Carrier Functional group Polarity and porosity

LifetechTM ECR8305F amino C2 methacrylatesmaller pores

moderately hydrophilicporous

LifetechTM ECR8309F amino C2 methacrylatelarger pores

moderately hydrophilicporous

LifetechTM ECR8404F amino C6 methacrylatesmaller pores

moderately hydrophilicporous

LifetechTM ECR8409F amino C6 methacrylatelarger pores

moderately hydrophilicporous

LifetechTM ECR1508 stirene/DVB withtertiary amino groups moderately hydrophobic

LifetechTM ECR1604 stirene/DVB withquaternary amino groups moderately hydrophobic

LifetechTM ECR8806M octadecyl acrylate moderately hydrophobicporous

LifetechTM ECR8285 epoxy/butyl methacrylate moderately hydrophobic

Table 1. Characteristics of applied immobilization carriers

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ml of Celluclast®) or immobilized (25 or 50 mg in 2 ml) cellulase was incubated with substrate at defined conditions (pH, temperature) and samples were taken during time (up to 5 minutes). 50-125 µl of sample were added to 250 µl of DNS reagent to achieve final volume of 0.5 ml and immersed into boiling water bath for 5 minutes. Reaction was stopped by adding 2 ml of distilled water and absorbance was measured at 540 nm. Enzyme activity was determined according to previously described calculations (Ćorović et al., 2017).

Fractionation of sunflower seed meal and hydrolysis of its lignocellulosic fraction

Fractionation of SSM was performed according to standard procedure. By mixing 100 g of minced SSM and 1 l of distilled water, three fractions were obtained – lignocellulosic fraction (LF, upper layer) was separated by perforated spoon from middle layer (liquid fraction) and precipitate (solid fraction). LF was dried at 180 W of microwave power within 10 cycles lasting 5 minutes, until dry matter content was above 98 %.

Hydrolysis reactions were performed at pH 4.8 and 52 °C in a 100 ml Erlenmyer flasks orbitally shaken at 150 rpm in a thermostat. 1 g of substrate was mixed with 10 ml of buffer solution and reaction was initiated by adding predefined amount of free or immobilized enzyme. Samples were taken during reaction and subjected to DNS analysis, according to previously described procedure.

Immobilization procedure

Enzyme immobilization was conducted at room temperature, in 2 ml volume Eppendorf® tubes under stirring on a roller mixer (Stuart, Paris, France). 25 or 50 mg of immobilization support particles were measured and 0.5 or 1 ml of enzyme solution (predefined

concentration of enzyme in immobilization buffer) was added. For amino-functionalized immobilization supports, 50 mM phosphate buffer pH 6 was applied in order to enable undisturbed establishment of ionic interactions with enzyme molecules, while for hydrophobic carrier and epoxy-functionalized resin, pH 7 and higher buffer molarity, 1 M, was applied. After 24 h, supernatant was separated, while particles with immobilized enzyme were washed three times with 0.5 or 1 ml of distilled water and used for activity determination. For application in SSMLF hydrolysis the same procedure was applied but with 0.5 g of immobilization support.

RESULTS AND DISCUSSION

Temperature and pH optimum determination

In order to achieve the highest possible performances in terms of catalytic activity, each enzyme should be examined at various reaction temperatures and pH values. For that purpose two cellulases were at first used at temperatures ranging from 35 to 70 °C, while other reaction parameters were kept at constant values and the obtained results are presented in Fig. 1.

As it can be seen, highest hydrolytic activity of both examined biocatalysts was in the mid part of examined range – at 52 °C for A. niger cellulase and at 55 °C for Celluclast®. It could be noted that both preparations demonstrated broad temperature optimums. Namely, A. niger callulase maintained approximately 50 % of its initial activity at 35 and 70 °C, while Celluclast® showed slightly lower activity at low temperatures (approximately 35 % of initial activity at 35 °C), but significantly higher activity at increased temperatures – over 90 % at 60 °C and over 60 % at 70 °C. When

Figure 1. Determination of temperature optimums for cellulases:(A) from A. niger and (B) from T. reesei.

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it comes to pH optimums (Fig. 2), two preparations demonstrated highest activities at slightly acidic conditions - pH 4.8 for A. niger cellulase and pH 4.5 for Celluclast®. A. niger cellulase kept over 50 % of its initial activity in a pH range 3.5-6.5, while Celluclast® demonstrated slightly higher activity at different pH values which resulted in over 70 % preserved activity within the same pH range. Determined optimums were applied within the consequent part of the study.

Hydrolysis of sunflower seed meal lignocellulosic fraction

Cellulolitic enzymes are nowadays widely examined in the valorization of agro-industrial waste based on their ability to catalyze saccharification of lignocellulosic substrates and enable their application for second generation bio-fuels production.

Potential of two chosen cellulases for hydrolysis of SSMLF was therefore assessed under previously optimized conditions. The obtained reaction courses are presented in Fig. 3. As it can be seen, higher enzyme loadings led to higher release rates of reducing sugars in both cases and within 6 hours maximum of 70 mM reducing sugars was liberated with A. niger cellulase, while with Celluclast only 25 mM of reducing sugars was detected. Also, significantly higher initial reaction rates were accomplished with A. niger cellulase. Based on these results, it could be concluded that A. niger cellulase possess a much higher potential for SSMLF hydrolysis. Economic feasibility of such application could be notably improved by enzyme immobilization onto suitable solid support since multiple use of the same biocatalyst batch significantly lowers overall process costs. Further steps were, therefore, directed towards examination of different immobilization methods.

Figure 2. Determination of pH optimums for cellulases:(A) from A. niger and (B) from T. reesei.

Figure 3. Hydrolysis of SSMLF by different concentrations of free: (A) A. niger and (B) T. reesei cellulase. Reactions were performed at 52 °C, pH 4.8 and 150 rpm, with 1 g of substrate in 10 ml of reaction mixture.

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Immobilization of Aspergillus niger cellulase

A. niger cellulase was immobilized onto eight different LifetechTM carriers with main characteristics shown in Table 2. Displayed performances of the obtained preparations (after 24 h of immobilization) are implying that there is a significant impact of immobilization support functionality, porosity and polarity on their catalytic activity. Regarding carrier hydrophobicity, it is evident that the more hydrophilic support surface was the higher activity of immobilized cellulase was achieved. Namely, highly hydrophobic LifetechTM ECR8285 octadecyl acrylate based carrier was the least suitable, followed by two moderately hydrophobic supports comprised of styrene/divinyl benzene with tertiary (LifetechTM ECR1508) and quaternary (LifetechTM ECR1604) amino groups, and the highest activities were obtained by using four hydrophilic methacrylate carriers with primary amino group. Among them, pronounced influence of pore size (smaller pores 30-60 nm and larger pores 60-120 nm) and functional group spacer arm length (C2 and C6) was observed. It seems that longer spacer arm (C6) provided optimum distance between carrier surface and enzyme molecule, ensuring its unhindered catalytic acting and leading to 37 % higher hydrolytic activity. Furthermore, diffusion of substrate molecules was apparently more efficient through the larger pores, and facilitated approach to the active sites of cellulase molecules immobilized inside the pores enabled approximately 30 % higher activities comparing to preparations obtained by using carriers with smaller pores. Therefore, the most promising support for further examinations is LifetechTM ECR8409F. Hence, it was applied within the subsequent hydrolysis of SSMLF.

Application of immobilized callulase for the hydrolysis of SSMLF

Final goal of current study was to investigate the possibility of the application of the obtained immobilized biocatalyst in the treatment of SSMLF. For that matter, immobilized enzyme was incubated with SSMLF and reaction course was monitored and compared with free enzyme (same amount of CMC units). Initial reaction rates were very similar for two preparations – 30 mM/h, indicating that there were not significant diffusion limitations for substrate to access active sites of immobilized enzyme, probably due to large pore diameter of used carrier. Also, enzyme molecules located inside the pores are protected from the negative influence of shear stress which can cause their deactivation and/or desorption (Sowana et al., 2001). Regarding obtained yields, after 6 h of reaction 68 mM of glucose equivalents were liberated from SSMLF, which is in range with the results obtained using free enzyme. It could be observed that reducing sugar concentration could be even higher if longer reaction times were analyzed. Therefore, immobilized A. niger cellulase could be efficiently utilized for the pre-fermentation treatment of SSMLF during bio-ethanol production and all relevant reaction parameters including enzyme and substrate concentration and reaction time should be analyzed in details before potential process scale-up.

Carrier Activity, IU/g

LifetechTM ECR8305F 13.47

LifetechTM ECR8309F 19.17

LifetechTM ECR8404F 21.30

LifetechTM ECR8409F 30.24

LifetechTM ECR1508 17.30

LifetechTM ECR1604 10.03

LifetechTM ECR8806M 0

LifetechTM ECR8285 3.53

Table 2. Activities of A. niger cellulase immobilized onto diffrent LifetechTM carriers

Figure 4. Hydrolysis of SSMLF by immobilized A. niger cellulase. Reactions were performed at 52 °C, pH 4.8

and 150 rpm, with 1 g of substrate in 10 ml of reaction mixture, with 90 IU/g of substrate.

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CONCLUSIONS

In the current study, it has been shown that microbial cellulases could be successfully applied for the saccharification of SSMLF as an attractive stock material for bio-ethanol production. The obtained results revealed that A. niger cellulase is very promising catalyst for the hydrolysis process, particularly in its immobilized form. By examining a wide range of LifetechTM immobilization supports with various characteristics (porosity, functionality and polarity), it was proven that hydrophilic, moderately porous carrier with primary amino groups and C6 space arm – LifetechTM ECR8409F is most suitable for obtaining highly active preparation. Further studies should, therefore, be directed towards more detailed optimization of immobilization conditions and examination of immobilized biocatalyst performances under different operating terms.

Acknowledgements: This work was supported by the Serbian Ministry of Education, Science and Technological Development (project numbers III46010 and TR31035).

LITERATURE

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Bhat, M. K., & Bhat, S. (1997). Cellulose degrading enzymes and their potential industrial applications. Biotechnology Advances, 15(3-4), 583-620. https://doi.org/10.1016/S0734-9750(97)00006-2

Gokhale, A. A., Lu, J., & Lee, I. (2013). Immobilization of cellulase on magnetoresponsive graphene nano-supports. Journal of Molecular Catalysis B: Enzymatic, 90, 76-86. https://doi.org/10.1016/j.molcatb.2013.01.025

Han, J., Wang, L., Wang, Y., Dong, J., Tang, X., & Ni, L. (2018). Preparation and characterization of Fe3O4-NH2@4-arm-PEG-NH2, a novel magnetic four-arm polymer-nanoparticle composite for cellulase immobilization. Biochemical Engineering Journal, 130, 90-98. https://doi.org/10.1016/j.bej.2017.11.008

Juturu, V., & Wu, J. C. (2014). Microbial cellulases: Engineering production and applications. Renewable and Sustainable Energy Reviews, 33, 188-203. https://doi.org/10.1016/j.rser.2014.01.077

Kuhad, R. C., Gupta, R., & Singh, A. (2011). Microbial cellulases and their industrial application. Enzyme Research, 2011(280696), 1-10. https://doi.org/10.4061/2011/280696

Kumar, A., & Sharma, S. (2017). Recent updates on different methods of pretreatment of lignocellulosic feedstocks: A review. Bioresources and Bioprocessing, 4(7), 1-19. https://doi.org/10.1186/s40643-017-0137-9

Lima, J. S., Araújo, P. H. H., Sayer, C., Souza, A. A. U., Viegas, A. C., & de Oliveira, D. (2017). Cellulase immobilization on magnetic nanoparticles encapsulated in polymer nanospheres. Bioprocess and Biosystems Engineering, 40(4), 511-518. https://doi.org/10.1007/s00449-016-1716-4

Lima, J. S., Costa, F. N., Bastistella, M. A., de Araújo, P. H. H., & de Oliveira, D. (2019). Functionalized kaolin as support for endoglucanase immobilization. Bioprocess and Biosystems Engineering, 42(7), 1165-1173. https://doi.org/10.1007/s00449-019-02113-w.

Miao, X., Pi, L., Fang, L., Wu, R., & Xiong, C. (2016). Application and characterization of magnetic chitosan microspheres for enhanced immobilization of cellulase. Biocatalysis and Biotransformation, 34(6), 272-282. https://doi.org/10.1080/10242422.2016.1247830

Simon, P., Lima, J. S., Valério, A., de Oliveira, D., Araújo, P. H. H., Sayer, C., De Souza, A. A. U., & Guelli U De Souza, S. M. A. (2018). Cellulase immobilization on poly(methyl methacrylate) nanoparticles by miniemulsion polymerization. Brazilian Journal of Chemical Engineering, 35(2), 649-657. https://doi.org/10.1590/0104-6632.20180352s20160094

Sowana, D. D., Williams, D. R. G., Dunlop, E. H., Dally, B. B., O’Neill, B. K., & Fletcher, D. F. (2001). Turbulent shear stress effects on plant cell suspension cultures. Chemical Engineering Research and Design, 79(8), 867-875. https://doi.org/10.1205/02638760152721370

Sukumaran, R. K., Singhania, R. R., & Pandey A. (2005). Microbial cellulases - production, applications and challenges. Journal of Scientific and Industrial Research, 64, 832-844. Retrieved October 22, 2019 from https://pdfs.semanticscholar.org/67c0/ce7deacdf66a6f133ee2f4f3d0a0f8097fe3.pdf

Tran, T. T. A., Le, T. K. P., Mai, T. P., & Nguyen, D. Q. (2019). Bioethanol production from lignocellulosic biomass. IntechOpen, https://doi.org/10.5772/intechopen.86437

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Hidroliza lignocelulozne frakcije suncokretove sačme primenom slobodnih i imobilisanih celulazaMarija Ćorović1*, Ana Milivojević2, Milica Carević1, Katarina Banjanac2, Dejan Bezbradica1

1Katedra za biohemijsko inženjerstvo i biotehnologiju, Tehnološko-metalurški fakultet, Univerzitet u Beogradu, Srbija2Inovacioni centar Tehnološko-metalurškog fakulteta u Beogradu, Univerzitet u Beogradu, Srbija

Lignocelulozna biomasa je široko rasprostranjena u prirodi i prepoznata je kao potencijalni obnovljivi izvor energije. Njena efikasna tranfromacija u bio-goriva moguća je samo nakon adekvatnih predtretmana, nakon kojih slede enzimska saharifikacija i mikrobna fermentacija. U okviru ovog rada, prikazana je primena dve različite celulaze producenata Aspergillus niger i Trichoderma reesei (Celluclast®) u tretiranju lignocelulozne frakcije suncokretove sačme (LFSS). Utvrđeno je da temperaturni i pH optimum iznose 52 °C i pH 4.8 za A. niger celulazu i 55 °C and pH 4.5 za Celluclast®. Pod optimizovanim uslovima, mlevena LFSS hidrolizovana je korišćenjem oba biokatalizatora. Primenom A. niger celulaze ostvarene su veće početne brzine i nakon 6 sati postignut prinos od 70 mM ekvivalenata glukoze korišćenjem 6 % (w/v) enzima. Sa druge strane, primenom Celluclast®-a postignute su niže početne brzine i dobijeno 25 mM ekvivalenata glukoze sa 10 % (v/v) enzima. U cilju ekonomične primene celulaze producenta A. niger, ispitana je mogućnost njene imobilizacije na različite nosače. Korišćenjem poroznog metakrilatnog nosača sa C6 “dugom nožicom” i primarnim amino-grupama - LifetechTM ECR8409, dobijen je imobilisani enzim najveće aktivnosti. Ovaj preparat uspešno je primenjen u saharifikaciji LFSS, pri čemu je pokazao nepromenjenu katalitičku aktivnot u odnosu na slobodan enzim.

Ključne reči: suncokretova sačma,lignoceluloza,celulaza, imobilizacija.

Vaz, R. P., Moreira, L. R. S., & Ferreira Filho, E. X. (2016). An overview of holocellulose degrading enzyme immobilization for use in bioethanol production. Journal of Molecular Catalysis B: Enzymatic, 133, 127-135. https://doi.org/10.1016/j.molcatb.2016.08.006

Xu, J., Huo, S., Yuan, Z., Zhang, Y., Xu, H., Guo, Y., Liang, C., & Zhuang, X. (2011). Characterization of direct cellulase immobilization with superparamagnetic nanoparticles. Biocatalysis and Biotransformation, 29(2-3), 71-76. https://doi.org/10.3109/10242422.2011.566326

Ćorović, M., Mihailović, M., Banjanac, K., Carević, M., Milivojević, A., Milosavić, N., & Bezbradica, D. (2017). Immobilization of Candida antarctica lipase B onto Purolite® MN102 and its application in solvent-free and organic media esterification. Bioprocess and Biosystems Engineering, 40(1), 23-34. https://doi.org/10.1007/s00449-016-1671-0

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Uticaj dimljenja na formiranje boje i sadržaj policikličnih aromatičnih jedinjenja u tradicionalnoj fermentisanoj kobasiciSnežana B. Škaljac1*, Marija R. Jokanović1, Vladimir M. Tomović1, Tatjana A. Peulić2, Predrag M. Ikonić2, Branislav V. Šojić1, Maja Đ. Ivić1, Ljiljana S. Petrović1, Jelena M. Babić3 i Nevena M. Hromiš1

1Univerzitet u Novom Sadu, Tehnološki fakultet, Novi Sad, Srbija2Univerzitet u Novom Sadu, Naučni institut za prehrambene tehnologije, Novi Sad, Srbija3Naučni institut za veterinarstvo “Novi Sad”, Novi Sad, Srbija

ISSN 2232-755XUDК: 637.523.7:664.85.037.5DOI: 10.7251/GHTE1915025ŠOriginalni naučni rad

U ovom radu ispitan je uticaj tradicionalnog dimljenja i sušenja na instrumentalne parametre boje (CIE L*a*b* sistem: svetloća boje-L*; udeo crvene boje-a*; udeo žute boje-b*; nijansa boje-h; zasićenost boje-C*) Petrovačke kobasice, fermentisane suve kobasice zaštićene geografskom oznakom porekla.

Na kraju procesa sušenja (60 dana) utvrđeno je na površini Petrovačkih kobasica statistički značajno manje (P<0.05) vrednosti L*-25.59, a*-10.31, b*-8.20 i C*-13.18, dok vrednosti nijanse boje (h-38.76) nisu se statistički značajno razlikovale (P>0.05) u odnosu na vrednosti utvrđene nulti dan proizvodnje (L*-43.63; a*-23.07; b*-21.42; C*-31.48 i h-42.85), formirana je crvena boja koja je tamnija, manje čistoće i sa znatno većim udelom sivih tonova.

Takođe u uzorcima Petrovačkih kobasica ispitan je i sadržaj policikličnih aromatičnih ugljovodonika sa prioritetne liste Američke agencije za zaštitu životne sredine (US-EPA PAH). Svi ispitani uzorci Petrovačkih kobasica ispunjavali su uslove (BaP ≤ 2 µg/kg; PAH4 ≤ 12 µg/kg) propisane domaćim Pravilnikom (Sl. glasnik RS broj 29/2014) i Regulativom Komisije Evropske unije (EC 835/2011).

Dobijeni rezultati ispitivanja potvrđuju da tradicionalan način dimljenja definisan i ispitan u ovom radu (8 dana; 6 sati dnevno; prosečne vrednosti t~9 °C i RV~79 %) daje za rezultat Petrovačku kobasicu karakteristične površinske boje i sa veoma niskim sadržajem policikličnih aromatičnih ugljovodonika.

Rad primljen: 03.07.2019.Rad prihvaćen: 19.11.2019.Rad dostupan od 31.12.2019. na https://glasnik.tf.unibl.org/

Ključne riječi: tradicionalni proizvod od mesa,dimljenje,PAH,benzo[a]piren.

UVOD

Kvalitetne tradicionalne fermentisane kobasice u novije vreme zauzimaju veoma važno mesto na svetskom tržištu, što je sigurno povezano sa povećanim interesovanjem savremenih potrošača za proizvodima specifičnog i prepoznatljivog kvaliteta (European Commission [EC], 2007; Lorenzo et al., 2011; Ikonić et al., 2012; EC, 2019).

Jedan takav proizvod koji je veoma cenjen u Srbiji je i Petrovačka kobasica. Petrovačka kobasica je suva fermentisana kobasica koja se proizvodi bez dodatka aditiva i starter kultura na tradicionalan način u Bačkom Petrovcu (Srbija) i predstavlja kulturno nasleđe vojvođanskih Slovaka. Zahvaljujući naglašenim, specifičnim i prepoznatljivim senzorskim svojstvima, ovaj proizvod je u Srbiji zaštićen oznakom geografskog porekla. Među prepoznatljivim senzorskim svojstvima dominira pikantno ljut ukus i aroma zrelog svinjskog mesa, sa blagom notom dima, belog luka i kima, kao i prepoznatljiva tamnocrvena boja površine kobasica

(Petrović et al., 2007; Ikonić et al., 2013; Škaljac et al., 2014; Škrbić et al., 2014; Šojić et al., 2014).

Tamnocrvena boja površine Petrovačke kobasice, formira se zahvaljujući i specifičnom načinu tradicionalnog dimljenja. Naime, upotrebom nekarakterističnih vrsta drveta u praksi dimljenja, kao što su višnja i trešnja postiže se specifična boja i aroma ove suve fermentisane kobasice (Škaljac et al., 2018a). Pored toga što dimljenje povoljno utiče na više procesa u samim proizvodima, u dimu se formiraju i nepoželjna jedinjenja iz grupe policikličnih aromatičnih ugljovodonika koja imaju štetno dejstvo na zdravlje ljudi (Malarut & Vangnai, 2018).

Policiklična aromatična jedinjenja (polycyclic aromatic hydrocarbons-PAH) predstavljaju veliku grupu organskih jedinjenja sa dva ili više kondenzovana benzenova prstena. Smatra se da PAH jedinjenja u krvotoku čoveka daljim metaboličkim aktivnostima mogu preći u oblike koji dovode do mutacije DNK, kao i da uzrokuju pojavu kancerogenih procesa u organizmu čoveka (Ledesma et al., 2016). S obzirom na navedenu činjenicu određivanje policikličnih aromatičnih

*Korespondentni autor: Snežana B. Škriljac, Univerzitet u Novom Sadu, Tehnološki fakultet, Novi Sad, Srbija, email: snezanasavatic@gmail.com

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ugljovodonika u dimljenim proizvodima od mesa je veoma važno, posebno kod tradicionalnih proizvoda, gde je proces dimljenja intenzivan, uslovi pri kojima se dim proizvodi se mogu minimalno kontrolisati, a proizveden dim ne podleže procesu prečišćavanja. Poslednjih godina naučne institucije zainteresovane su za proučavanje sadržaja PAH-ova, sa ciljem da ispitaju i dokažu bezbednost tradicionalnih dimljenih proizvoda od mesa, kao i da se definišu uslovi tradicionalnog dimljenja koji osiguravaju najmanji sadržaj policikličnih aromatičnih ugljovodonika u dimljenim proizvodima a da pri tome prepoznatljiva senzorska svojstva ostaju očuvana (Đinović et al., 2008; Lorenzo et al., 2010; Lorenzo et al., 2011; Gomes et al., 2013; Alves et al., 2017; EC, 2019).

Uzimajući u obzir napred navedene činjenice, odlučeno je da se u ovom radu ispita uticaj tradicionalnog dimljenja na sadržaj policikličnih aromatičnih ugljovodonika i boju površine Petrovačke kobasice, suve fermentisane kobasice zaštićene geografskom oznakom porekla.

MATERIJAL I METODE RADA

Materijal

Nadev za Petrovačku kobasicu izrađen je od svinjskog mesa prve i druge kategorije (oko 85 %) i čvrstog masnog tkiva (oko 15 %). Na masu usitnjenog mišićnog i masnog tkiva (ø ≈ 10 mm) dodati su sledeći sastojci: crvena ljuta mlevena začinska paprika (2.50 %), kuhinjska so (1.80 %), beli luk (0.20 %), kim (0.20 %) i šećer (0.15 %). Nakon dodavanja navedenih sastojaka usledilo je mešanje nadeva i odmah nakon mešanja, nadev kobasica je punjen u veštačke (kolagena) omotače. Kobasice su zatim ostavljene na ceđenju (oko 24 h; na temperaturi od 9 °C), posle čega je usledio proces dimljenja. Proces dimljenja obavljen je u tradicionalnim uslovima u pušnicama sa otvorenim ložištem. Kobasice poređane na štapove visile su u pušnici iznad ložišta na visini maksimalno do 3 metra i tokom celokupnog procesa dimljenja bile su izložene direktno uticaju dima. Dimljenje je trajalo 10 dana (6 sati dnevno, sa pauzama 4. i 8. dana), a za proces dimljenja korišćena je mešavina komada drveta (trešnja : višnja : bukva = 1:1:1). Tokom procesa dimljenja kontinuirano su registrovani pomoću Mini Data Logger parametri vazduha (prosečna vrednost temperature: t~9 °C i prosečna vrednost relativne vlažnosti: RV~79 %).

Potom su kobasice prenete u klimatizovanu prostoriju za sušenje u registrovan objekat, gde je implementiran takav model sušenja koji za 60 dana obezbedi lagano i ujednačeno izdvajanje vlage iz kobasica odnosno sadržaj vode u kobasicama manji od 35 %.

Tokom procesa sušenja zadata je temperatura od 8 °C (maksimalna vrednost temperature od 9.20 °C izmerena je 12. dana; dok minimalna vrednost od 7.40 °C utvrđena je 26. dana) i minimalna cirkulacija vazduha od 0.5 m/s. Relativna vlažnost vazduha postepeno je opadala od vrednosti 90 % do 75 % prema sledećem modelu: od 10. dana do 20. dana opadala od vrednosti 90 % do 85 %; od 10. dana do 20. dana opadala od vrednosti 85 % do 80 %; od 30. dana do 50. dana održavana je vrednost RV~80 %; od 50. dana do 60. dana opadala od vrednosti 80 % do 75 %. Kobasice su nakon završetka procesa sušenja (60. dana), ostavljene na skladištenje neupakovane (poređane na štapove) i čuvane u kontrolisanim uslovima za skladištenje (10 °C; RV 75 %; prirodna cirkulacija vazduha; bez prisustva svetlosti) do 270. dana.

Uzorci Petrovačkih kobasica za utvrđivanje instrumentalnih parametara boje, sadržaja vlage, sadržaja ukupne masti i sadržaja policikličnih aromatičnih ugljovodonika uzeti su 0. dana proizvodnje, 60. dana (kraj sušenja) i 270. dana (kraj skladištenja).

Metode rada

Određivanje instrumentalnih parametara boje

Instrumentalni parametri boje izmereni su na površini svakog uzorka Petrovačke kobasice (preko omotača). Za određivanje parametara boje korišćen je kolorimetar Minolta Chroma Meter CR-400 sa otvorom 8 mm na mernoj glavi i standardnim nastavkom za merenje CR-A33b (Konica Minolta Inc., Osaka, Japan). Merenja su izvršena u D-65 osvetljenju sa standardnim uglom zaklona od 2 °. Instrument je pre svake serije merenja kalibrisan korišćenjem bele kalibracione ploče CR-A43, standardnom procedurom prema proizvođačkim instrukcijama. Karakteristike boje su iskazane u CIE L*a*b* (International Commission on Illumination, 1976; Škaljac et al., 2018a), koji je zasnovan na tri koordinate preko kojih se definiše boja uzoraka: L* (svetloća boje), a* (+a*-udeo crvene boje; -a*-udeo zelene boje) i b* (+b*-udeo žute boje; -b*-udeo plave boje). Izmerene vrednosti CIE L*a*b* su neposredno očitane sa uređaja, a na osnovu tih vrednosti pomoću adekvatnih matematičkih relacija određene su vrednosti i sledećih parametara boje: h (hue angle – nijansa boje) i C* (zasićenost boje) (Bozkurt & Bayram, 2006). Rezultati parametara boje su prikazani kao aritmetička sredina šest merenja dobijenih na tri slučajno izabrana uzorka Petrovačkih kobasica.

Određivanje sadržaja vlage i ukupne masti

Sadržaj vlage i sadržaj ukupnih masti određen je referentnim metodama SRPS ISO 1442 (1997) i SRPS ISO 1443 (1973) u homogenizovanom delu uzorka (n=3).

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Određivanje PAH jedinjenja

Kvalitativan i kvantitativan sadržaj 13 policikličnih aromatičnih ugljovodonika (acenaftilen, fluoren, fenantren, antracen, piren, benz[a]antracen, krizen, benzo[b]fluoranten, benzo[k]flouranten, benzo[a]piren, indeno[1,2,3-cd]piren, dibenz[a,h]antracen i benzo[ghi]perilen) sa prioritetne liste Američke agencije za zaštitu životne sredine (13 US-EPA PAH) određen je prema metodi opisanoj u radu Škaljac et al. (2014). Priprema uzoraka je rađena po QUECHERS (quick easy cheap effective rugged and safe) metodi koja predstavlja brzu, laku, jeftinu, efikasnu i sigurnu metodu. PAH jedinjenja su analizirana na gasnom hromatografu GC 6890N sa masenim spektrometrom MS 5975 (Agilent, Palo Alto, CA, USA). Razdvajanje PAH-ova je izvršeno upotrebom kapilarne kolone HP-5 MS i korišćenjem sledećeg temperaturnog programa: početna temperatura 70 °C, 2 min, gradijent 25 °C/min do 150 °C zatim gradijent 3 °C/min do 200 °C, i gradijent 8 °C/min do 280 °C.

Kvalitet i pouzdanost primenjene metode za PAH jedinjenja određene su utvrđivanjem granica detekcije (LOD) i efikasnosti, odnosno rikaveri („recovery“) za svaki pojedinačni PAH i prikazane u radu Škaljac et al. (2014). Na osnovu dobijenih rikaverija i LOD vrednosti utvrđeno je da izabrana metoda ispunjava kriterijume definisane Regulativom Evropske unije br. 836/2011 (EC, 2011b).

Statistička analiza

Rezultati u ovom radu su prikazani kao srednje vrednosti pojedinačnih rezultata tri slučajno uzorkovane kobasice ± standardna devijacija (SD). Podaci su obrađeni primenom softverskog paketa Statistica 12.0 (StatSoft, Inc., Tulsa, OK, USA). Značajnost razlika između aritmetičkih sredina određena je analizom varijanse sa jednom nezavisno promenljivom (One way ANOVA) i višestrukog testa intervala (Dankanov Post-hoc test) i izražena sa 95 % verovatnoće (P<0.05).

REZULTATI I DISKUSIJA

Uzimajući u obzir da proces dimljenjia, sušenja i skladištenja može da utiče na površinsku boju sušenih fermentisanih kobasica, prvi zadatak u ovom radu bio je određivanje instrumentalnih parametara površinske boje (L*, a*, b*, h i C*) Petrovačke kobasice dimljene na tradicionalan način.

Na osnovu rezultata prikazanih u Tabeli 1 vidi se da je proces dimljenja i sušenja uticao na promenu površinske boje kobasica. 60. dana proizvodnje utvrđena je na površini Petrovačkih kobasica statistički značajno manja vrednost (P<0.05) svetloće boje (L*), kao i manji udeo crvene (a*) i žute boje (b*) u odnosu na 0. dan proizvodnje. Formiranje tamnije boje je posledica taloženja čestica dima na površinu kobasica,

Parametri kvaliteta Petrovačke kobasiceQuality parameters of Petrovská klobása

0. dan proizvodnje0 day

of production

Kraj sušenja (60. dan)End of drying period

(60th day)

Kraj skladištenja (270. dan)End of storage period

(270th day)

Instrumentalni parametri boje (CIE L*a*b* sistem)Instrumental characteristics of colour (CIE L*a*b* system)

L* (svetloća/lightness) 43.63a ± 1.84 25.59b ± 2.58 23.88b ± 1.59

a* (udeo crvene boje/redness) 23.07a ± 1.95 10.31b ± 3.78 7.08b ± 3.05

b* (udeo žute boje/yellowness) 21.42a ± 2.08 8.20b ± 2.59 6.53b ± 2.01

h (nijansa boje/hue angle) 42.85ns ± 1.36 38.76ns ± 2.23 43.93ns ± 5.38

C* (zasićenost boje/chroma) 31.48a ± 2.84 13.18b ± 4.55 9.66b ± 3.56

Pokazatelji nutritivnog kvaliteta (%)Characteristics of nutritional quality (%)

Sadržaj vlageContent of moisture 55.63a ± 0.01 32.25b ± 0.10 16.19c ± 0.04

Sadržaj ukupnih mastiContent of total fat 22.35c ± 0.05 35.03b ± 0.67 42.41a ± 0,03

a–c - prosečne vrednosti u istoj koloni označene različitim slovima su statistički značajno različite (P < 0.05);a–c - different letters in the same row mean that values are significantly different (P < 0.05);

Tabela 1. Prosečne vrednosti instrumentalnih parametara boje (CIE L*a*b*) na površini Petrovačkih kobasica, sadržaja vlage i ukupnih masti u kobasicama (%) dimljenim na tradicionalan način Table 1. Characteristics of colour on the surface of Petrovská klobása, content of moisture and total fat in sausages smoked in traditional conditions

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Nadalje, iz rezultata instrumentalnih parametara boje vidi se da tokom procesa skladištenja nije došlo do promene površinske boje kobasica, jer nije utvrđena statistički značajna razlika (P>0.05) vrednosti parametara površinske boje (L*, a*, b*, h i C*) na kraju procesa skladištenja (270. dana) u odnosu na kraj sušenja (60. dana).

S obzirom da proces dimljenja, osim što utiče na formiranje površinske boje i arome Petrovačke kobasice, takođe utiče i na formiranje policikličnih aromatičnih ugljovodonika, drugi zadatak u okviru ovih istraživanja bio je da se ispita uticaj tradicionalnog dimljenja na sadržaj policikličnih aromatičnih ugljovodonika u Petrovačkoj kobasici. Rezultati određivanja sadržaja 13 US-EPA PAH jedinjenja kao značajnih pokazatelja zdravstvene bezbednosti dimljenih fermentisanih kobasica prikazani su u Tabeli 2.

kao i smanjenja sadržaja vlage kobasica (0. dan – 55.63 % i 60. dan – 32.25 %) tokom procesa sušenja (Sikorski & Kołakow, 2010; Ledesma et al., 2011; Gomes et al., 2013; Škaljac et al., 2018a). Kao što možemo videti iz rezultata za h vrednosti, nijansa boje površine kobasica se nije promenila na kraju sušenja u odnosu na 0. dan proizvodnje (P>0.05). Nijansa boje pripada crvenom delu spektra i na nju utiče sama formulacija nadeva, a proces dimljenja i sušenja nije uticao na promenu nijanse boje. Međutim vrednosti zasićenosti boje (C*) su statistički značajno manje na kraju procesa sušenja (60. dan - 13.18) u odnosu na 0. dan proizvodnje (0. dan - 31.45), što pokazuje da proces dimljenja i sušenja utiče na formiranje crvene boje koja je manje čistoće i sa znatno većim udelom svih tonova u odnosu na boju površine kobasica 0. dana proizvodnje.

Policiklični aromatični ugljovodonici (µg/kg)Polycyclic aromatic hydrocarbons (μg/kg)

0. dan proizvodnje0 day of production

Kraj sušenja(60. dan)

End of drying period (60th day)

Kraj skladištenja (270. dan)

End of storage period (270th day)

Acenaftilen/Acenaphthylen Acy 1.66a ± 0.08 9.80b ± 0.10 21.8c ± 1.85

Antracen/Anthracene Ant 1.67a ± 0.15 5.35a ± 0.55 12.5b ± 0.40

Fluoren/Fluorene Fln 4.45a ± 0.93 11.1b ± 0.10 13.0c ± 0.65

Fenantren/Phenanthrene Phe < 0.3 18.0b ± 1.40 26.3c ± 2.60

Piren/Pyrene Pyr < 0.4 2.27 ± 0.06 < 0.4

Krizen/Chrysene CHR < 0.3 < 0.3 < 0.3

Benz[a]antracen/Benz[a]anthracene BaA < 0.3 < 0.3 < 0.3

Benzo[b]fluoranten/Benzo[b]fluoranten BbF < 0.3 < 0.3 < 0.3

Benzo[k]fluoranhen/Benzo[k]fluoranthene BkF < 0.3 < 0.3 < 0.3

Benzo[a]piren/Benzo[a]pyrene BaP < 0.3 < 0.3 < 0.3

Indeno[1,2,3-cd]piren/Indeno[1,2,3-cd]pyrene IcP < 0.4 < 0.4 < 0.4

Dibenz[a,h]antracen/ Dibenz[a,h]anthracene DhA < 0.5 < 0.5 < 0.5

Benzo[ghi]perilen/ Benzo[ghi]perylene BgP < 0.6 < 0.6 < 0.6

Σ EU PAH41 nd nd nd

Σ 13 US-EPA PAH 7.78a ±1.16 46.52b ± 0.80 73.50c ± 4.20Σ 13 US-EPA PAH (µg/kg suve materije)

Σ 13 US-EPA PAH (μg/kg dry matter) 17.53 68.66 87.70

a – c - vrednosti sadržaja policikličnih aromatičnih ugljovodonika u istoj koloni označene različitim slovima su statistički značajno različite (P<0.05);a – c - different letters in the same row mean that values are significantly different (P < 0.05);1BaA; CHR; BbF; BaP

Tabela 2. Sadržaj policikličnih aromatičnih ugljovodonika (µg/kg) u Petrovačkoj kobasici dimljenoj u tradicionalnim uslovima Table 2. Content of polycyclic aromatic hydrocarbons (μg/kg) in Petrovská klobása smoked in traditional conditions

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Na osnovu prikazanih rezultata utvrđeno je da je tokom procesa dimljenja i sušenja došlo do povećanja sadržaja ∑13 US-EPA PAH jedinjenja (P<0.05) u poređenju sa nadevom kobasica (0. dan – 9.57 µg/kg; 60. dan – 46.52 µg/kg). Rezultati dobijeni u ovim istraživanjima su u saglasnosti sa podacima iz literature gde je takođe utvrđeno da proces dimljenja dovodi do porasta sadržaja policikličnih aromatičnih ugljovodonika u suvim fermentisanim kobasicama (Đinović et al., 2008; Lorenzo et al., 2010; Lorenzo et al., 2011; Gomes et al., 2013; Alves et al., 2017).

Iz rezultata prikazanih u Tabeli 2 vidi se da su na kraju procesa sušenja (60. dana) detektovana sledeća PAH jedinjenja: Acy, Fln, Phe, Ant i Pyr. Ostala ispitana PAH jedinjenja nisu bila detektovana, odnosno njihov sadržaj je bio ispod granice detekcije izabrane metode. Phe je bio najzastupljeniji od svih PAH jedinjenja u Petrovačkoj kobasici i njegov sadržaj je iznosio 18.0 µg/kg , dok je od PAH jedinjenja sa manjom molekulskom masom (sa dva ili tri benzenova prstena), jedino detektovan Pyr i njegova sadržaj je iznosio 2.27 µg/kg .Regulativom Komisije Evropske Unije u mesu i proizvodima od mesa je propisan maksimalni sadržaj BaP, kao i ukupan sadržaj grupe jedinjenja PAH4 (BaA, CHR, BbF i BaP) i od septembra 2014. godine maksimalno dozvoljen sadržaj BaP iznosi 2 µg/kg, a PAH4 iznosi 12 µg/kg (EC, 2011a). Propisi u Srbiji (Sl. glasnik RS, 2014) su u potpunosti u saglasnosti sa Regulativom EU. Značajno je napomenuti da na kraju procesa sušenja BaP, kao i PAH4 jedinjenja nisu detektovana u uzorcima Petrovačke kobasice. Dimljenje na tradicionalan način (8x6 sati) koje je definisano i opisano u ovom radu (prosečne vrednosti t~9 °C i RV~79 %) daje za rezultat Petrovačku kobasicu bezbednu za potrošača sa aspekta sadržaja policikličnih aromatičnih ugljovodonika.S obzirom da količina PAH jedinjenja u dimljenim proizvodima od mesa nije konstantna tokom skladištenja, odlučeno je da se ispita sadržaj PAH jedinjenja u Petrovačkoj kobasici i na kraju procesa skladištenja (270. dana), kako bi se proverila bezbednost proizvoda tokom celokupnog perioda upotrebe. Statistički značajno veći sadržaj PAH jedinjenja u Petrovačkim kobasicama utvrđen je na kraju procesa skladištenja (P<0.05), u odnosu na kraj procesa sušenja ovo je sigurno posledica daljeg smanjenja sadržaja vlage (60. dan - 32.25 %, 270. dan - 16.19 %), jer su skladišteni neupakovani uzorci Petrovačkih kobasica. Takođe, tokom skladištenja sadržaj PAH-ova može se povećati usled prodiranja čestica dima sa površine omotača kobasica u unutrašnjost proizvoda, ali može doći i do smanjenja sadržaja PAH jedinjenja jer dolazi do njihove interakcije sa proizvodima oksidacije masti (Ledesma et al., 2016; Škaljac et al., 2018b).

Na kraju procesa sušenja, kao i na kraju procesa skladištenja u uzorcima Petrovačke kobasice dimljenim u tradicionalnim uslovima utvrđeni sadržaj PAH jedinjenja sa tri i četiri benzenova prstena bio je manji u poređenju sa sadržajem tih jedinjenja utvrđenim u portugalskim kobasicama (Roseiro et al., 2011; Santos et al., 2011; Alves et al., 2017), dok su ove vrednosti bile veće u poređenju sa vrednostima utvrđenim u španskim dimljenim kobasicama (Lorenzo et al., 2010).Rezultati sadržaja PAH jedinjenja u Petrovačkoj kobasici dimljenoj na tradicionalan način su od izuzetne važnosti jer je prema Regulativi Evropske Komisije (EC, 2019) dozvoljeno je u nekim zemalja članicama EU da tradicionalni proizvodi od mesa mogu imati veći sadržaj PAH jedinjenja (BaP ≤ 5 µg/kg; PAH4 ≤ 30 µg/kg) kako ne bih došlo do gubitka karakterističnih organoleptičkih svojstava. Svi ispitani uzorci Petrovačkih kobasica ispunjavali su uslove (BaP ≤ 2 µg/kg; PAH4 ≤ 12 µg/kg) propisane domaćim Pravilnikom (2014) i Regulativom Komisije Evropske unije (2011a). Dobijeni rezultati ispitivanja u okviru ovih istraživanja potvrđuju da se može proizvesti tradicionalna Petrovačka kobasica karakteristične površinske boje sa niskim sadržajem policikličnih aromatičnih ugljovodonika.

ZAKLJUČAK

Proces dimljenja i sušenja u tradicionalnim uslovima uticao je na formiranje tamno crvene boje površine kobasica. Tokom procesa skladištenja nije došlo do promene površinske boje, jer na kraju procesa skladištenja vrednosti instrumentalnih parametara boje (L*-23.88; a*-7.08 i b*-6.53; h-43.93 i C*-9.66) se nisu statistički značajno razlikovali (P>0.05) u poređenju sa vrednostima parametara utvrđenim na kraju procesa sušenja (L*-25.59; a*-10.31; b*-8.20 h-38.76 i C*-13.18).Tradicionalan način dimljenja definisan i ispitan u ovom radu (8 dana; 6 sati dnevno; prosečne vrednosti t~9 °C i RV~79 %) daje za rezultat Petrovačku kobasicu karakteristične površinske boje sa niskim sadržajem policikličnih aromatičnih ugljovodonika (∑13 US-EPA PAH: 60. dan - 46.52 µg/kg; 270. dan – 73.50 µg/kg). Značajno je napomenuti da na kraju procesa sušenja, kao i na kraju procesa skladištenja BaP, kao i PAH4 jedinjenja nisu detektovana u uzorcima Petrovačke kobasice.

Zahvalnica: Prikazana istraživanja su deo doktorske disertacije prvog autora. Ovaj rad je rezultat na projektu broj TR-31032 i ON172050, koji je finansiran sredstvima Ministarstva za obrazovanje, nauku i tehnološki razvoj Republike Srbije.

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Impact of smoking on formation of colour and polycyclic aromatic hydrocarbons in traditional fermented sausage

Snežana B. Škaljac*1, Marija R. Jokanović1, Vladimir M. Tomović1, Tatjana A. Peulić2, Predrag M. Ikonić2, Branislav V. Šojić1, Maja Đ. Ivić1, Ljiljana S. Petrović1, Jelena M. Babić3 and Nevena M. Hromiš1

1University of Novi Sad, Faculty of Technology, Novi Sad, Serbia2University of Novi Sad, Institute of Food Technology in Novi Sad, Serbia3Scientific Veterinary Institute “Novi Sad”, Novi Sad, Serbia

The aim of this study was to determine the effects of traditional drying and smoking process on colour characteristics and content of polycyclic aromatic hydrocarbons in Petrovská klobasá. This sausage is dry fermented sausage with protected designation of origin according to Serbian legislation.

Instrumental colour characteristics (CIE L*a*b* system: lightness-L*; redness-a*; yellowness-b*; hue angle-h and chroma-C*) are determined on the surface of Petrovská klobasá at 0 day of production, at the end of the drying period (60th day of production) and at the end of storage period (270th day of production). Colour measurements were performed using the Minolta Chroma Meter CR-400. Petrovská klobasá had significantly lower (P<0.05) values of colour characteristics L*-25.59, a*-10.31, b*-8.20 and C*-13.18, but differences were not significant (P>0.05) for hue angles value (h-38.76) at the end of the drying period compared to those at zero day of production (L*-43.63; a*-23.07; b*-21.42; C*-31.48 and h-42.85). During the storage period there was no change in the surface colour, because instrumental colour parameters were not significantly different (P>0.05) at the end of the storage period (L*-23.88; a*-7.08 and b*-6.53; h-43.93 and C*-9.66) compared to the values of the colour characteristics determined at the end of the drying period.

Also, in the samples of Petrovská klobasá the contents of polycyclic aromatic hydrocarbons (acenaphthylene, fluorene, phenanthrene, anthracene, pyrene, benz[a]anthracene chrysene, benzo[b]fluoranthene, benzo[k]flouranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenz [a,h]anthracene and benzo[ghi] perylene) from Environmental Protection Agency list (13 US-EPA) were determined. PAH analyses were performed on gas chromatograph coupled with mass spectrometer. All examined samples of sausages met the criteria (BaP ≤ 2 μg/kg; PAH4 ≤ 12 μg/kg) prescribed by Serbian legislation (Official Gazette of the SCG, No 29/2014) and Regulations Commission of the European Union (EC 835/2011).

The results obtained in this work confirmed that the traditional smoking process, which was defined in this study (8 days; 6 hours per day; average values of t~9 °C and RV~79 %), provided Petrovská klobasá with characteristic colour properties and very low content of polycyclic aromatic hydrocarbons.

Keywords: traditional meat product, smoking process, PAH, benzo[a]piren.

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Adsorpcija jona bakra iz vodenih rastvora vlaknima domaće vune

Svjetlana Janjić1*, Vesna Ivanović1, Biljana Lazić2

1Univerzitet u Banjoj Luci, Tehnološki fakultet, Banja Luka, Republika Srpska, BiH2Institut za javno zdravstvo Republike Srpske, Banja Luka, Republika Srpska, BiH

ISSN 2232-755XUDK: 677.31.022:546.562DOI: 10.7251/GHTE1915033JOriginalni naučni rad

Vunena vlakna dobijena od domaćih ovaca rase pramenka su veoma gruba, najvećim dijelom ostaju neiskorištena i tretiraju se kao “otpad”. S druge strane, zagađenje vode teškim metalima predstavlja jedan od najvećih problema u oblasti zagađenja vode. U okviru ovog rada ispitivana je sposobnost sorpcije jona bakra iz vodenih rastvora pomoću uzorka domaće vune koja je samo oprana i uzorka vune koja je nakon pranja dodatno odmašćena. Za ispitivanje su korišteni vodeni rastvori jona bakra koncentracije 20 mg/L i 40 mg/L pri pH vrijednosti 5,1. Metodom atomske apsorpcione spektrometrije (AAS) je mjerena koncentracija jona bakra u rastvoru nakon 3, 5, 10, 15 i 30 minuta, kao i nakon 24 časa od potapanja uzorka vune u rastvor. Rezultati su pokazali da vlakna domaće vune imaju dobra adsorpciona svojstva prema jonima bakra što ukazuje da je vuna potencijalni adsorbens za uklanjanje jona bakra iz kontaminirane vode.

Rad primljen: 19.11.2018.Rad prihvaćen: 19.11.2019.Rad dostupan od 31.12.2019. na https://glasnik.tf.unibl.org/

Ključne riječi: vuna, bakar, adsorpcija.

UVOD

Ubrzan industrijski razvoj ali i drugi oblici ljudskih aktivnosti istovremeno su povezani sa velikom upotrebom hemikalija i nekontrolisanim ispuštanjem toksičnih supstanci koje sadrže metale u neposredno okruženje, posebno vodene izvore (Florea & Büsselberg, 2006). Teški metali imaju tendenciju bioakumulacije u organizmima, teško se metabolišu, lako ulaze u lanac ishrane i direktno utiču na zdravlje ljudi i opstanak drugih živih vrsta. Izloženost teškim metalima predstavlja potencijalnu opasnost za žive organizme, posebno kada su u pitanju metalne komponente koje nemaju fiziološku ulogu u metabolizmu ćelije. Oni mogu izazvati poremećaje u krvi i kostima, oštećenje bubrega i nervnog sistema i smanjenje mentalnih sposobnosti (Järup, 2003; Khan et al., 2006).

Uklanjanje toksičnih supstanci iz vode je predmet interesovanja brojnih istraživača u svijetu. Za uklanjanje teških metala iz otpadnih voda koriste se različite metode, kao što su hemijska precipitacija,

hemijska oksidacija ili redukcija, elektrohemijski tretman, filtracija, reverzna osmoza, izmjena jona i membranske tehnologije. Međutim, ove metode imaju izvjesne nedostatke, prvenstveno zbog visokih troškova i problema sa odlaganjem otpada nakon završetka sorpcije. Biosorpcija se procjenjuje kao bezbjedna, efikasnija i ekonomičnija metoda za uklanjanje teških metala iz kontaminiranih voda od komercijalno dostupnih hemijskih ili fizičko-hemijskih tehnologija (Igwe & Abia, 2006). U posljednjih nekoliko godina su istraživani različiti jeftini biosorbenti, poput gljiva, algi, bakterija, lignoceluloznih poljoprivrednih nusproizvoda i različitih vrsta vlakana u pogledu njihovog biosorpcionog kapaciteta prema teškim metalima (Zhang et al., 1998; Wan Ngah & Hanafiah, 2008; Gundogdua et al., 2009). Prednost korišćenja biosorbenata kao što su prirodna vlakna je dobar apsorpcioni kapacitet vode i biorazgradljivost vlakana.

Ovčija vuna sa područja Republike Srpske i Bosne i Hercegovine je relativno slabog kvaliteta i samo njen mali dio se iskoristi u kućnoj radinosti dok najveći dio ostaje neiskorišten i predstavlja „otpad“. Međutim, vuna je veoma prihvatljiva sa ekološkog aspekta i mogla bi se koristiti za dobijanje nekonvencionalnih proizvoda kao što su filteri na bazi vunenih vlakana. Pretpostavka je da će domaća vunena vlakna, s obzirom na karakterističnu

*Korespondentni autor: Svjetlana Janjić, Univerzitet u Banjoj Luci, Tehnološki fakultet, Vojvode Stepe Stepanovića 73, Banja Luka, RS, B&H; email: svjetlana.janjic@tf.unibl.org*Rad je izložen na naučnom skupu XII Savjetovanje hemičara, tehnologa i ekologa Republike Srpske, novembar 2018.

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strukturu površine, hemijski sastav i veliki broj različitih funkcionalnih grupa u svojoj strukturi, uspješno sorbovati jone teških metala iz vodenih rastvora i da će se moći uspješno koristiti za prečišćavanje vode.

U skladu sa prethodno rečenim, u okviru ovog rada je ispitivana mogućnost upotrebe domaće vune kao biosorbenta za uklanjanje jona bakra (Cu2+) iz vodenih rastvora s ciljem što većeg iskorištenja domaće vune u industrijskim procesima.

MATERIJALI I METODE RADA

U radu su korištena vunena vlakna dobijena od domaćih ovaca rase pramenka, prosječne finoće 6 dtex i dužine 90 mm. U prvoj fazi je obavljen proces pretpranja vlakana destilovanom vodom temperature 22 °C u toku 10 min, a zatim su vlakna oprana na temperaturi 30 °C u toku 20 min, nakon čega su vlakna dva puta ispirana na temperaturi 22 °C u toku 5 min i osušena. Za sorpciju su korištena dva uzorka vlakana. Jedan uzorak su predstavljala vlakna koja su oprana prema prethodno opisanom načinu, a drugi uzorak su predstavljala vlakna koja su nakon pranja dodatno odmašćena (SRPS F.S1.021,1989).

Vodeni rastvori jona bakra (Cu2+) koncentracije 20 mg/L i 40 mg/L pripremljeni su rastvaranjem CuCl2. Uzorci vlakana mase 1 g su potapani u 200 mL rastvora uz konstantno miješanje na sobnoj temperaturi pri pH=5,1. Nakon 3, 5, 10, 15 i 30 min i nakon 24 časa od potapanja uzoraka u rastvor, određivana je koncentracija jona bakra u rastvoru pomoću atomskog apsorpcionog spektrometra (Agilent AA Duo), kako bi se odredila kinetika adsorpcije i adsorpcioni kapacitet vlakana. Sorpcioni kapacitet vlakana u odnosu na jone bakra određen je kao razlika između polazne i krajnje koncentracije jona u rastvoru. FTIR analiza je rađena u apsorpcionom modu tehnikom prigušene totalne refleksije (ATR-Attenuated total reflectance) na spektrometru marke Bruker Tenson 27 u spektralnom opsegu od 400 cm-1 do 4000 cm-1, pri rezoluciji 4 cm-1.

REZULTATI I DISKUSIJA

Vunena vlakna imaju karakterističnu strukturu površine, a kao keratinska vlakna posjeduju veliki broj funkcionalnih grupa, kao što su karboksilatne, amino, amido, disulfidne i tiolne, koje predstavljaju potencijalna mjesta za vezivanje metalnih jona. Zbog toga se vuna i njeni derivati pored ostalog mogu koristiti za uklanjanje toksičnih ali i vezivanje drugih metalnih jona iz industrijskih otpadnih voda ili prirodnih voda. U ovom radu je ispitivana sposobnost sorpcije jona bakra iz vodenih rastvora pomoću uzorka domaće vune koja je samo oprana i uzorka vune koja je nakon pranja dodatno odmašćena. Za ispitivanje su korišteni vodeni rastvori jona bakra koncentracije 20 mg/L i 40 mg/L pri pH vrijednosti 5,1 jer je utvrđeno da pH 4,5-6 najbolje pogoduje procesu sorpcije jona metala iz vodenih rastvora (Mitić, 2014).Rezultati mjerenja koncentracije jona bakra u rastvoru i adsorpcioni kapacitet vlakana u zavisnosti od vremena adsorpcije za početnu koncentraciju jona bakra u rastvoru 20 mg/L, prikazani su u Tabeli 1 i na Slikama 1 i 2. Na Slici 1 se može vidjeti da se povećanjem vremena sorpcije koncentracija jona bakra u rastvoru smanjuje za oba uzorka vune koja su korišteni kao adsorbensi. Pad koncentacije je najizraženiji u prvih 15 minuta, a naročito prve 3 minute od potapanja vune u rastvor što je posljedica istovremenog brzog procesa adsorpcije jona bakra na vlaknima koja služe kao adsorbens (Slika 2). Nakon toga su smanjenje koncetracije jona bakra u rastvoru i njihova adsorpcija na vlaknima manje izraženi. Proces se na sličan način i uz vrlo male razlike u izmjerenoj koncentraciji i adsorpcionom kapacitetu vlakana odvija i na opranoj i na odmašćenoj vuni. Nešto izraženije smanjenje koncentracije jona bakra u rastvoru (Slika 1) i posljedično povećanje adsorpcionog kapaciteta (Slika 2), za uzorak odmašćene vune u odnosu na uzorak oprane vune se uočava u periodu 3-15 minuta, a nakon toga su koncentracija rastvora i adsorpcioni kapacitet vlakana približno isti za oba uzorka.

Tabela 1. Zavisnost koncentracije rastvora i kapaciteta adsorpcije od vremena, početna koncentracija 20 mg/LTable 1. Dependence of solution concentration and adsorption capacity on sorption time, the initial solution concentration being 20 mg/L

Vrijeme adsorpcije (min)

Sorption time (min)

Koncentracija rastvora (mg/L)Solution concentration (mg/L)

Adorpcioni kapacitet vlakana (mg/g)Adsorption capacity of fibers (mg/g)

Oprana vuna Washed wool

Odmašćena vunaDegreased wool

Oprana vuna Washed wool

Odmašćena vunaDegreased wool

0 20 20 0 0

3 9,50 8,75 2,19 2,34

5 9,37 8,44 2,31 2,48

10 8,72 8,04 2,52 2,63

15 7,99 7,90 2,72 2,73

30 7,27 7,47 2,91 2,88

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Koncentracija jona bakra u rastvoru i adsorpcioni kapacitet vlakana izmjereni su i nakon 24 časa od potapanja uzorka vune u rastvor koncentracije 20 mg/L. Utvrđeno je da koncentracija jona bakra u rastvoru iznosi 3,36 mg/L za opranu vunu i 3,95 mg/L za odmašćenu vunu što znači da je koncentracija jona u rastvoru smanjena za 83,20 % kod upotrebe oprane vune kao adsorbenta i za 80,25 % kod upotrebe odmašćene vune kao adsorbenta, u odnosu na početnu koncentraciju. Istovremeno je adsorpcioni kapacitet vlakana iznosio 3,53 mg/g za opranu vunu i 3,45 mg/g za odmašćenu vunu. Koncentracija jona bakra u rastvoru i adsorpcioni kapacitet vlakana u zavisnosti od vremena adsorpcije mjereni su i za početnu koncentraciju jona bakra u rastvoru 40 mg/L, a dobijeni rezultati su prikazani u Tabeli 2. i na Slikama 3. i 4.Koncentracija jona bakra u rastvoru se smanjuje sa povećanjem vremena adsorpcije za oba uzorka vune koji su korišteni kao adsorbensi (Slika 3), a kao posljedica toga se istovremeno povećava količina jona na

vlaknima (Slika 4). Pad koncentacije je naročito izražen u prve 3 minute od potapanja vune u rastvor, a nakon toga su smanjenje koncentracije jona bakra u rastvoru i njihova adsorpcija na vlaknima manje izraženi. U toku kompletnog vremena adsorpcije, veći pad koncentracije jona u rastvoru i veći adsorpcioni kapacitet vlakana uočen je u slučaju kada je kao adsorbens korištena oprana vuna u odnosu na odmašćenu vunu.Velika brzina adsorpcije metalnih jona u prvih nekoliko minuta pokazuje mogućnost primjene ovog procesa u tretmanu otpadnih voda, što su utvrdili i drugi autori (Balköse & Baltacioğlu, 1992).Koncentracija jona bakra u rastvoru i adsorpcioni kapacitet vlakana izmjereni su i nakon 24 časa od potapanja uzorka vune za početnu koncentraciju jona u rastvoru 40 mg/L. Utvrđeno je da koncentracija jona bakra u rastvoru nakon 24 časa iznosi 10,87 mg/L za opranu vunu i 13,12 mg/L za odmašćenu vunu što znači da je koncentracija jona u rastvoru smanjena za 72,83 % kod upotrebe oprane vune kao adsorbensa i za 67,20 % kod upotrebe odmašćene vune kao adsorbensa

Tabela 2. Zavisnost koncentracije rastvora i kapaciteta adsorpcije od vremena, početna koncentracija 40 mg/LTable 2. Dependence of solution concentration and adsorption capacity on sorption time, the initial solution concentration being 40 mg/L

Vrijeme adsorpcije (min)

Sorption time (min)

Koncentracija rastvora (mg/L)Solution concentration (mg/L)

Adsorpcioni kapacitet vlakana (mg/g)Adsorption capacity of fibers (mg/g)

Oprana vuna Washed wool

Odmašćena vunaDegreased wool

Oprana vuna Washed wool

Odmašćena vunaDegreased wool

0 40 40 0 0

3 21,34 27,70 3,95 2,74

5 20,64 26,60 4,29 3,21

10 20,66 25,58 4,49 3,65

15 20,08 25,66 4,79 3,89

30 19,34 24,76 5,09 4,29

Slika 1. Zavisnost koncentracije rastvora od vremena adsorpcije za početnu koncentraciju rastvora 20 mg/L

Figure 1. Dependence of solution concentration on sorption time, the initial solution concentration being 20 mg/L

Slika 2. Zavisnost kapaciteta adsorpcije od vremena adsorpcije za početnu koncentraciju rastvora 20 mg/L

Figure 2. Dependence of adsorption capacity on sorption time, the initial solution concentration being 20 mg/L

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u odnosu na početnu koncentraciju. Istovremeno je adsorpcioni kapacitet iznosio 6,40 mg/g za opranu vunu i 6,16 mg/g za odmašćenu vunu.Za uzorke vune koja je korištena kao adsorbens, urađeni su ATR-FTIR spektri koji su prikazani na Slici 5 za opranu i Slici 6 za odmašćenu vunu.Na Slici 5 su prikazani uporedni ATR-FTIR spektri za oprana vunena vlakna: 1 – polazna vlakna, 2 – vlakna poslije adsorpcije u rastvoru koncentracije 20 mg/L i 3 – vlakna poslije adsorpcije u rastvoru koncentracije 40 mg/L.Na Slici 6 su prikazani uporedni ATR-FTIR spektri za odmašćena vunena vlakna: 1 – polazna vlakna, 2 – vlakna poslije adsorpcije u rastvoru koncentracije 20 mg/L i 3 – vlakna poslije adsorpcije u rastvoru koncentracije 40 mg/L.

Na spektrima svih ispitivanih uzoraka vlakana u području od 3600 cm-1 do 2800 cm-1 se javlja široka traka, karakteristična za apsorpciju hidroksilnih grupa. Pored toga, na dobijenim spektrima se može uočiti da su najvažnije apsorpcione trake i karakteristični pikovi u području ispod 2000 cm-1 što odgovara amidnim vezama (-CONH-) koje su karakteristične za keratinska vlakna. Posmatrajući karakterističan pik na 1724 cm-1 koji potiče od istezanja C=O veza karboksilnih grupa, uočeno je da se njegov intenzitet smanjuje kod uzoraka sa vezanim bakrom, a naročito kod uzorka oprane vune koja je korištena kao adsorbens u rastvoru početne koncentracije 40 mg/L i za koju je utvrđen najveći sorpcioni kapacitet 6,40 mg/g. Ova promjena nam daje informaciju o uticaju jona bakra, odnosno uključivanju slobodnih karboksilnih grupa u formiranju metalnih

Slika 3. Zavisnost koncentracije rastvora od vremena adsorpcije za početnu koncentraciju rastvora 40 mg/L

Figure 3. Dependence of solution concentration on sorption time, the initial solution concentration being 40 mg/L

Slika 4. Zavisnost kapaciteta adsorpcije od vremena adsorpcije za početnu koncentraciju rastvora 40 mg/L

Figure 4. Dependence of adsorption capacity on sorption time, the initial solution concentration being 40 mg/L

Slika 5. ATR-FTIR spektri za opranu vunu (1 - polazna vlakna, 2 - vlakna poslije adsorpcije u rastvoru

koncentracije 20 mg/L, 3 - vlakna poslije adsorpcije u rastvoru koncentracije 40 mg/L)

Figure 5. ATR-FTIR spectra of washed wool (1 - untreated fibers, 2 - fibers after adsorption in solution

concentration of 20 mg/L, 3 - fibers after adsorption in solution concentration of 40 mg/L)

Slika 6. ATR-FTIR spektri za odmašćenu vunu (1 - polazna vlakna, 2 - vlakna poslije adsorpcije u rastvoru

koncentracije 20 mg/L, 3 - vlakna poslije adsorpcije u rastvoru koncentracije 40 mg/L)

Figure 6. ATR-FTIR spectra of degreased wool (1 - untreated fibers, 2 - fibers after adsorption in solution

concentration of 20 mg/L, 3 - fibers after adsorption in solution concentration of 40 mg/L)

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kompleksa. Isto tako, uočene su promjene na spektrima uzoraka sa adsorbovanim jonima bakra u odnosu na polazni, netretirani uzorak vlakana oko 1380 cm-1 i 1402 cm-1 čiji intenzitet se povećava do 1445 cm-1. Ovu pojavu su uočili i drugi istraživači (Aluigi et al., 2011), a može se povezati sa konformacionim promjenama indukovanim Cu2+ kompleksacijom.

ZAKLJUČCI

Rezultati su pokazali da vlakna domaće vune imaju dobra adsorpciona svojstva prema jonima bakra što ukazuje da je vuna potencijalni adsorbens za uklanjanje jona bakra iz kontaminirane vode. Najveća brzina adsorpcije metalnih jona je u prva 3 minuta, a nakon toga se proces odvija sporije.Utvrđeno je da su za rastvor početne koncentracije 20 mg/L, oprana i odmašćena vuna imale približno jednak uticaj na smanjenje koncentracije jona bakra u rastvoru i približno jednak adsorpcioni kapacitet koji je iznosio 3,53 mg/g za opranu i 3,45 mg/g za odmašćenu vunu. U rastvoru početne koncentracije 40 mg/L, oprana vuna je imala nešto veći uticaj na smanjenje koncentracije jona bakra u rastvoru i veći adsorpcioni kapacitet (6,40 mg/g) u odnosu na odmašćenu vunu (6,16 mg/g).ATR-FTIR spekti vunenih vlakana ukazuju da su jonske interakcije dominantan mehanizam vezivanja jona bakra na vunena vlakana.Navedena istraživanja imaju i veliki ekološki značaj jer se, pored uklanjanja toksičnih supstanci, kao adsorbens koristi prirodni, biodegradabilni materijal koji trenutno nema značajnu praktičnu primjenu i tretira se kao „otpad“.

LITERATURA

Aluigi, A., Tonetti, C., Vineis, C., Tonin, C., & Mazzuchetti, G. (2011). Adsorption of copper(II) ions by keratin/PA6 blend nanofibres. European Polymer Journal, 47(9), 1756-1764. https://doi.org/10.1016/j.eurpolymj.2011.06.009

Balköse, D., & Baltacioğlu, H. (1992). Adsorption of heavy metal cations from aqueous solutions by wool fibers. Journal of Chemical Technology and Biotechnology, 54(4), 393-397. https://doi.org/10.1002/jctb.280540414

Florea, A. M., & Büsselberg, D. (2006). Occurrence, use and potential toxic effects of metals and metal compounds. Biometals, 19(4), 419–427. https://doi.org/10.1007/s10534-005-4451-x

Gundogdua, A., Ozdes, D., Durana, C., Bulut, V. N., Soylak, M., & Senturka, H. B. (2009). Biosorption of Pb(II) ions from aqueous solution by pine bark (Pinus brutia Ten.). Chemical Engineering Journal, 153(1-3), 62–69. https://doi.org/10.1016/j.cej.2009.06.017

Igwe, J. C., & Abia, A. A. (2006). Bioseparation process for removing heavy metals from wastewater using biosorbents. African Journal of Biotechnology, 5(12), 1167-1179. https://doi.org/10.5897/AJB2006.000-5056

Järup L. (2003). Hazards of heavy metal contamination. British Medical Bulletin, 68(1), 167–182. https://doi.org/10.1093/bmb/ldg032

Khan, S., Cao, Q., Zheng, Y. M., Huang, Y. Z., & Zhu, Y. G. (2006). Health risks of heavy metals in contaminated soils and food crops irrigated with wastewater in Beijing, China. Environmental Pollution, 152(3), 686-692. https://doi.org/10.1016/j.envpol.2007.06.056

Mitić, D. (2012). Uklanjanje teških metala iz vode biosorbentom na bazi Lagenaria vulgaris (Doktorska disertacija). Preuzeto januara 20, 2019 sa https://www.pmf.ni.ac.r s /d o w n l o a d /d o k t o r a t i /d o k u m e n t a /disertacije/2012/2012-10-02-dlm.pdf

SRPS F.S1.021 (1989). Ispitivanje tekstila - Određivanje sadržaja stranih primesa na vlaknastim materijalima, rastvorljivih u organskim rastvaračima.

Wan Ngah, W. S., & Hanafiah, M. A. K. M. (2008). Biosorption of copper ions from dilute aqueous solutions on base treated rubber (Hevea brasiliensis) leaves powder: Kinetics, isotherm, and biosorption mechanisms. Journal of Environmental Sciences, 20(10), 1168-1176. https://doi.org/10.1016/S1001-0742(08)62205-6

Zhang, L., Zhao, L., Yu, Y., & Chen, C. (1998). Removal of lead from aqueous solution by non-living Rhizopus nigricans. Water Research, 32(5), 1437–1444. https://doi.org/10.1016/S0043-1354(97)00348-5

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Adsorption of copper cations from aqueous solutions by domestic wool fibers

Svjetlana Janjić1*, Vesna Ivanović1, Biljana Lazić2

1University of Banja Luka, Faculty of Technology, Banja Luka, Republic of Srpska, B&H2Public Health Institute Republic of Srpska, Banja Luka, Republic of Srpska, B&H

Wool fibers obtained from domestic sheep breed pramenka are very coarse, largely unused and treated as “waste”. Therefore, today wool fibers, as a biodegradable material, are the subject of testing for many different applications. On the other hand, pollution of water by heavy metals is one of the biggest problems in the field of water pollution. Heavy metals are prone to bioaccumulation in organism, they are difficult to metabolize, easily enter the food chain and directly affect human health.

The aim of this investigation was examination of the ability of sorption of copper ions from aqueous solutions by wool fibers as well as the extention of the field of use of domestic wool in industrial processes. Wool samples that are just washed and wool samples that are further degreased after washing were used in this investigation.

Adsorption of copper ions (Cu2+) was performed from aqueous solution of CuCl2 (20 mg/L and 40 mg/L of copper ions). Wool fiber samples (1 g) were added in 200 mL of copper ions aqueous solution pH value of 5.1 and treated at room temperature with constant shaking. The copper ion uptake was determined as the difference between the initial concentration copper ions in solution and the final concentration of copper ions in solution after 3, 5, 10, 15 and 30 minutes, as well as after 24 hours after immersion of the wool sample into the solution. For the determination of copper ions concentration in solution atomic absorption spectrometer (Agilent AA Duo) was used. The wool fibers, before and after adsorption in aqueous solution of copper ions, were characterized using Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). ATR-FTIR spectra of the samples were recorded in absorbance mode using FTIR Spectrometer Bruker Tenson 27 with a range of 400-4000 cm-1, at a resolution of 4 cm-1.

The results showed that the wool fibers have good adsorption properties against copper ions, indicating that wool is a potential adsorbent for removing copper ions from contaminated water. The maximum rate of adsorption of copper ions was reached in the beginning of the process. The process was slower after first 3 minutes. The experiments indicates that the efficiency of adsorption of copper ions depends on the type of fiber treating, but also on the initial concentration of copper ions in aqueous solution. Wool fiber samples adsorbed higher amount of copper ions at higher initial concentration of copper ions. Wool samples that are just washed and wool samples that are further degreased after washing adsorbed approximately equal amount of copper ions at initial concentration copper ions in solution 20 mg/L, 3,53 mg/g and 3,45 mg/g, respectively. At initial concentration copper ions in solution 40 mg/L, wool samples that are just washed adsorbed higher amount of copper ions than wool samples that are further degreased after washing, 6,40 mg/g and 6,16 mg/g, respectively. ATR-FTIR spectra of the wool samples indicates that ionic interaction is dominant mechanism of copper ions bonding to wool fibers.

This investigation is of great ecological importance not only because of the removal of toxic substances, but also because natural waste biodegradable material was used as adsorbent.

Keywords: wool, copper, adsorption.

UPUTSTVO AUTORIMA

Glasnik hemičara, tehnologa i ekologa RS objavljuje radove koji podliježu recenziji i svrstavaju se u sljedeće kategorije:• originalni naučni rad,• pregledni rad,• kratko ili prethodno saopštenje,• informativni prilog.

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Autor, A. A., Autor, B. B. & Autor, C. C. (godina). Naslov rada. Naslov Časopisa, volumen(broj), stranice. https://doi.org/xx.xxx/yyyy

Ukoliko časopis ima samo volumen, obrazac je sljedeći:

Autor, A. A., Autor, B. B. & Autor, C. C. (godina). Naslov rada. Naslov Časopisa, volumen, stranice. https://doi.org/xx.xxx/yyyy

(Primjeri su dati u daljem tekstu)

• U slučaju knjiga, članaka, poglavlja ili internet stranica velikim početnim slovom se piše: prva riječ u naslovu i podnaslovu, prva riječ nakon dvotačke ili crtice i odgovarajuće imenice (Italic).

• Kod knjiga je potrebno navesti samo izdavača, ali ne i mjesto izdavanja.

• U slučaju da je autor ujedno i izdavač, obično kod publikacija institucija, umjesto navođenja izdavača napiše se „Autor“ odnosno „Author“ ako je rad na engleskom.

• Ako datum publikacije nije dostupan koristiti skraćenicu „n.d.“.

Primjeri citiranja

Primjer citiranja naučnog časopisa koji nije dostupan u elektronskom obliku:

u tekstu: (Jovanović, 1999), citiranje rada jednog autora.u popisu literature: Jovanović, S. M. (1999). Ponovna upotreba polimernih materijala - recikliranje. Hemijska Industrija, 53(11), 319-335.

Primjer citiranja naučnog časopisa dostupnog u elektronskom obliku:

u tekstu: (Drljača i sar., 2016), citiranje rada više autora.(Olaoye & Kolawole, 2013), citiranje rada dva autora.u popisu literature: Drljača, D., Dalmacija, B., Vukić, Lj., i Zorić, S. (2016). Biološko uklanjanje amonijum jona iz vode za piće. Glasnik

Hemičara, Tehnologa i Ekologa Republike Srpske, 12, 9-16. https://doi.org/7251/GHTE1612009DOlaoye, O. S., & Kolawole O. S. (2013). Modeling of the kinetics of ethanol formation from glucose biomass in

batch culture with a non structured model. International Journal of Engineering Research and Applications (IJERA), 3(4), 562-565. Retrieved November 29, 2018 from http://pdfs.semanticscholar.org/d0a6/ f28ef1cc9028c97c585616aabe545a87abd6.pdf

Primjer citiranja knjige:

u tekstu:(Banks & Greenwood, 1975), citiranje rada dva autora.u popisu literature: Banks, W., & Greenwood, C. T. (1975). Starch and its components. University Press.

Primjer citiranja poglavlja u knjizi:

u tekstu: (Fogarty & Kelly, 1983).u popisu literature: Fogarty, W., & Kelly, C. (1983). Pectic enzymes. In W. Fogarty (Ed.), Microbial enzyme and biotechnology (pp. 131-

182). Applied Science Publishers.

Primjer citiranja rada objavljenog u zborniku sa naučne konferencije:

u tekstu: (Vojinović i sar., 2013), citiranje rada više od dva autoraili ... pri čemu su Vojinović i sar. (2013) objasnili da... .u popisu literature: Vojinović, Đ., Maksimović, M., i Gvero, P. (2013). Matematičko modelovanje procesa sagorijevanja prirodnog

gasa za potrebe CFD modelovanja. U M. Sorak (Ed.), Zbornik radova sa međunarodnog naučnog skupa: X Savjetovanje hemičara, tehnologa i ekologa Republike Srpske (str 176-186). Banjaluka: Univerzitet u Banjoj Luci, Tehnološki fakultet.

Primjer citiranja magistarskih radova i doktorskih disertacija:

u tekstu: Publikovane doktorske disertacije i magistarski radovi se nalaze u elektronskim bazama podataka, odnosno dostupni su na internetu, kao što je npr. disertacija Abeggelen-a (2008), te je u popisu literature obavezno navođenje baze podataka ili URL stranice sa koje je rad preuzet. Doktorske disertacije i magistarski radovi koje se ne nalaze u elektronskim bazama podataka navode se kao nepublikovane reference, npr. doktorska disertacija autora Papuga (2014) i magistarski rad autora Petrović (2001).u popisu literature: Abeggelen, C. K. (2008). Membrane bioreactor technology for decentralized wastewater treatment and reuse (Doctoral disseration). Retrieved February 23, 2017 from http://library.eawag.ch/EAWAG-Publications/openaccess/Eawag_05667.pdfPetrović, R. (2001). Dehidratacija etera na mordenitnim katalizatorima (Nepublikovan magistarski rad). Univerzitet u

Banjoj Luci, Tehnološki fakultet, Banja Luka. Papuga, S. (2014). Kopiroliza otpadne plastike i biomase (Nepublikovana doktorska disertacija). Univerzitet u Banjoj

Luci, Tehnološki fakultet, Banja Luka.

Primjer sekundarnog citiranja

u tekstu:

... Istraživanja Lewellen-a su pokazula izuzetnu važnost vremena boravka volatilnih produkata unutar pirolizirajuće strukture celuluze (citirano u Sinha, 2000).u popisu literature:

Sinha, S., Jhalani, A., Ravi, M. R., & Ray, A. (2000). Modelling of pyrolysis in wood: A review. SESI Journal, 10(1), 41-62.

Radovi, koji nisu napisani striktno po ovom uputstvu, neće biti prihvaćeni.

Народна и универзитетска библиотека Републике СрпскеNational and University Library of the Republic of Srpska

Јеврејска 30, 78000 Бања Лука Веб локација: www.nubrs.rs.ba, Е пошта: direkcija@nubrs.rs.ba

• централа: 051/215 859, 215 866 • е-пошта: direkcija@nubrs.rs.ba • директор/секретарица: (тел) 051/215 894, (факс) 051/217 040 • секретар: 051/215 822

• помоћник директора/матична служба: 051/215 750• JИБ: 4401722970003 • жиро рачун: 562-099-00001695-65

COBISS Kooperativni online bibliografski sistem i servisi COBISS

Glasnik hemičara, tehnologa i ekologa Republike Srpske

God. 10, br. 14 (2018)

- bibliografija članaka –

1BALABAN, Milica

Sinteza i karakterizacija poli(urea-siloksana) i poli(uretan-urea-siloksana) na bazi izoforon diizocijanata / Milica Balaban, Silvester Bolka, Vesna Antić. - Dostupno i na: http://dx.doi.org/10.7251/GHTE1814009B.

U: Glasnik hemičara, tehnologa i ekologa Republike Srpske. - ISSN 1840-054X. - God. 10, br. 14 (2018), str. 9-14.

678.073.026.2

COBISS.RS-ID 7980824

2

NUTRITIVNI kvalitet komercijalnih mješavina Arabika i Robusta kafe / Božana Odžaković, Natalija Džinić, Snežana Kravić, Marija Jokanović, Slavica Grujić. - Dostupno i na: http://dx.doi.org/10.7251/GHTE1814031O.

U: Glasnik hemičara, tehnologa i ekologa Republike Srpske. - ISSN 1840-054X. - God. 10, br. 14 (2018), str. 31-37.

547.857.4:577.112

COBISS.RS-ID 7981592

3PAPUGA, Saša

Matematičko modelovanje proizvodnje etanola u toku fermentacije medovine / Saša Papuga, Aleksandar Savić, Zvjezdana Kisin. - Dostupno i na: http://dx.doi.org/10.7251/GHTE1814015P.

U: Glasnik hemičara, tehnologa i ekologa Republike Srpske. - ISSN 1840-054X. - God. 10, br. 14 (2018), str. 15-22.

661.722:519.87

COBISS.RS-ID 7981080

4SAVANOVIĆ, Danica

Analiza proteina pšenice kapilarnom gel elektroforezom (CGE) / Danica Savanović, Radoslav Grujić, Aleksandra Torbica, Jovo Savanović. - Dostupno i na: http://dx.doi.org/10.7251/GHTE1814023S.

U: Glasnik hemičara, tehnologa i ekologa Republike Srpske. - ISSN 1840-054X. - God. 10, br. 14 (2018), str. 23-29.

633.11:547.96

COBISS.RS-ID 7981336

Народна и универзитетска библиотека Републике СрпскеNational and University Library of the Republic of Srpska

Јеврејска 30, 78000 Бања Лука Веб локација: www.nubrs.rs.ba, Е пошта: direkcija@nubrs.rs.ba

• централа: 051/215 859, 215 866 • е-пошта: direkcija@nubrs.rs.ba • директор/секретарица: (тел) 051/215 894, (факс) 051/217 040 • секретар: 051/215 822

• помоћник директора/матична служба: 051/215 750• JИБ: 4401722970003 • жиро рачун: 562-099-00001695-65

5

STUDY of adsorption of selected organic species from aqueous solution on nh4beta zeolite / Slavica Sladojević, Jelena Penavin-Škundrić, Zora Levi, Marina Rakanović, Dijana Peulić, Darko Bodroža. - Dostupno i na: http://dx.doi.org/10.7251/GHTE1814001S.

U: Glasnik hemičara, tehnologa i ekologa Republike Srpske. - ISSN 1840-054X. - God. 10, br. 14 (2018), str. 1-7.

549.67:633.81-114.7

COBISS.RS-ID 7980568

6TOROMANOVIĆ, Merima

Removal of organic pollutants from municipal wastewater by a horizontal pilot - scale constructed wetland utilizing Phragmites australis and Typha latifolia - Effectiveness monitoring per season / Toromanović Merima, Ibrahimpašić Jasmina, Topalić-Trivunović Ljiljana, Šišić Ifet. - Dostupno i na: http://dx.doi.org/10.7251/GHTE1814039T.

U: Glasnik hemičara, tehnologa i ekologa Republike Srpske. - ISSN 1840-054X. - God. 10, br. 14 (2018), str. 39-44.

581.55:628.3.034.2

COBISS.RS-ID 7981848

REGISTAR NASLOVA

• Analiza proteina pšenice kapilarnom gel elektroforezom (CGE) 4

• Matematičko modelovanje proizvodnje etanola u toku fermentacije medovine 3

• Nutritivni kvalitet komercijalnih mješavina Arabika i Robusta kafe 2

• Removal of organic pollutants from municipal wastewater by a horizontal pilot - scale constructed wetland utilizing Phragmites australis and Typha latifolia - Effectiveness monitoring per season 6

• Sinteza i karakterizacija poli(urea-siloksana) i poli(uretan-urea-siloksana) na bazi izoforon diizocijanata 1

• Study of adsorption of selected organic species from aqueous solution on NH4beta zeolite 5

Народна и универзитетска библиотека Републике СрпскеNational and University Library of the Republic of Srpska

Јеврејска 30, 78000 Бања Лука Веб локација: www.nubrs.rs.ba, Е пошта: direkcija@nubrs.rs.ba

• централа: 051/215 859, 215 866 • е-пошта: direkcija@nubrs.rs.ba • директор/секретарица: (тел) 051/215 894, (факс) 051/217 040 • секретар: 051/215 822

• помоћник директора/матична служба: 051/215 750• JИБ: 4401722970003 • жиро рачун: 562-099-00001695-65

IMENSKI REGISTAR

• Antić, Vesna (autor) 1

• Balaban, Milica 1

• Bolka, Silvester (autor) 1

• Grujić, Radoslav (autor) 4

• Ibrahimpašić, Jasmina (autor) 6

• Kisin, Zvjezdana (autor) 3

• Odžaković, Božana (autor) 2

• Papuga, Saša 3

• Savanović, Danica 4

• Savić, Aleksandar (autor) 3

• Sladojević, Slavica (autor) 5

• Toromanović, Merima 6