application of perfluorooctylalumina in the ozonated decomposition of humic acids

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Application of Perfluorooctylalumina in the OzonatedDecomposition of Humic AcidsYing-Shih Ma a & Cheng-Nan Chang ba Department of Environmental Engineering and Health , Yuanpei University , Hsinchu,Taiwanb Department of Environmental Science and Engineering , Tunghai University , Taichung,TaiwanPublished online: 30 Jul 2010.

To cite this article: Ying-Shih Ma & Cheng-Nan Chang (2010) Application of Perfluorooctylalumina in the OzonatedDecomposition of Humic Acids, Ozone: Science & Engineering: The Journal of the International Ozone Association, 32:4,265-273, DOI: 10.1080/01919512.2010.493501

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Ozone: Science & Engineering, 32: 265–273

Copyright # 2010 International Ozone Association

ISSN: 0191-9512 print / 1547-6545 online

DOI: 10.1080/01919512.2010.493501

Application of Perfluorooctylalumina in the OzonatedDecomposition of Humic Acids

Ying-Shih Ma1 and Cheng-Nan Chang2

1Department of Environmental Engineering and Health, Yuanpei University, Hsinchu, Taiwan2Department of Environmental Science and Engineering, Tunghai University, Taichung, Taiwan

The present study deals with the application of ozonewith perfluorooctylalumina in humic acids decomposition.Ozonation with perfluorooctylalumina addition destroys thecomplex structures in humic acids into relatively simpleones and color removal based on ADMI (American DyeManufacture Index) measurement was greater than 95% inall tests. The rate of humic acids decomposition wasdescribed by using a first-order rate expression with respectto the decrease of A254. A central pH level (pH 7) andperfluorooctylalumina addition is helpful in humic acidsdecomposition. The modified-Nernst equation could beused to predict humic acids decomposition at varying reac-tion conditions.

Keywords Ozone, Humic Acids, Perfluorooctylalumina,Oxidation Reduction Potential, Nernst equation

INTRODUCTION

Heterogeneous catalysis is a novel method in advancedoxidation processes (AOPs) and catalytic ozonation maybecome a new tool for water treatment (Kasprzyk-Hordern and Nawrocki, 2003; Ma et al., 2005). Severalresearchers pointed out that the application of various cat-alysts coupled with ozone can significantly degrade differentorganic compounds present in wastewater/contaminated-water. Moreover, the treatment efficiency can be enhancedby the addition of catalyst during ozonation.

Catalysts such as manganese dioxide (Andreozzi et al.,1996; Andreozzi et al., 1998; Ma and Graham, 1997; Maand Graham, 1999; Andreozzi et al., 2000), titaniumdioxides or alumina-supported catalysts such as Me/

TiO2, Me/Al2O3 (Leitner et al., 1999; Lin et al., 2000),TiO2/Al2O3, Fe2O3/Al2O3 (Copper and Burch, 1999;Gracia et al., 2000a, 2000b, 2000c) were proposed toenhance the efficiency of ozonation in organic matterdecomposition.

Alumina possesses a great adsorption capacity towardsthe perfluorinated surfactant (Lai et al., 1995). Therefore,the use of bare alumina during water treatment processesor two related procedures such as adsorption of perfluori-nated surfactant from water and subsequent usage ofperfluorinated alumina as a catalyst of ozonation canenhance the performance of wastewater treatment.Kasprzyk-Hordern and Nawrocki (2003) reported thatthe dissolution of perfluorinated moleculesinto the aqu-eous phase can be prevented by immobilization of theperfluoroalkyl phase through the chemical bond on thesurface of alumina.

This particular system is based on the liquid-liquidextraction of organic substances from aqueous phaseinto organic phase (non-polar fluorinated hydrocarbonsolvent saturated with ozone) and subsequent oxidationby molecular ozone dissolved in the organic phase.Kasprzyk-Hordern et al. (2004) investigated the efficiencyof natural organic matter ozonation in the presence ofalumina modified with perfluorooctanoic acid.

UV254-absorbance analysis indicated that the O3/perfluorooctanoic acid system increases the efficiency ofcolor removal from treated water when compared withozonation alone and ozonation in the presence of alu-mina. Moreover, the total organic carbon (TOC) analysisproved that the O3/perfluorooctanoic acid system is alsoresponsible for natural organic matter (NOM) degrada-tion in water. Bhattacharyya et al. (1995) cited that two-phase systems consisting of an organic phase (an inertsolvent saturated with ozone) and an aqueous phase con-taining organic substances, improved the efficiency ofozonation.

Received 7/23/2009; Accepted 3/26/2010Address correspondence to Ying-Shih Ma, Department of

Environmental Engineering and Health, Yuanpei University, 306Yuanpei Street, Hsinchu, Taiwan. E-mail: [email protected]

Ozonated Decomposition of Humic Acids July–August 2010 265

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In addition, Kasprzyk-Hordern et al. (2003) pro-posed that efficient two-phase ozonation has beenprovided by the immobilization of perfluorinatedhydrocarbons on the surface of alumina so as to avoidthe dissolution of perfluorinated molecules into theaqueous phase and it was found that ozone solubilityin fluorinated hydrocarbon solvents was 10 timeshigher than that in water. Several hazardous organicsincluding chlorinated organics and aromatic hydrocar-bons present in the aqueous systems were removed to agreater extent by two-phase ozonation system com-pared with ozonation alone (Stich and Bhattacharyya,1987; Bhattacharyya et al., 1995; Freshour et al., 1996;Kasprzyk and Nawrocki, 2002).

From this discussion, it is clear that perfluorooctylalu-mina has the capability to adsorb ozone and to enhanceits stability and solubility in water. Therefore, perfluor-ooctylalumina is adapted in this investigation to enhancethe decomposition efficiency of refractory compounds inozonation.

NOM in dissolved, colloidal and particulate forms isubiquitous in surface and ground waters. It is composedof a heterogeneous mixture of humic substances, hydro-philic acids, proteins, lipids, carbohydrates, carboxylicacids, amino acids, and hydrocarbons (Ma, 2004). Inaddition, humic substances can be broadly divided intofulvic acids and humic acids. Humic acids are known toform trihalomethanes during chlorination (Galapateet al., 1999; Korshin et al., 1999). Thus, humic acidsshould be removed from the drinking water to greaterextent to decrease the formation of trihalomethanes andother disinfection by-products. Moreover, it is essential toknow the intermediates produced and the reactionmechanisms during ozonation of humic acids.

Poznyak and Araiza (2002) found the formation ofmuconic acid during ozonation of phenol by high perfor-mance liquid chromatography. Subsequent oxidationmetabolites of muconic acid such as fumaric acid, oxalicacid and catechol were also reported. Chang et al. (2002)proposed that profiles of functional groups during theoxidation of organic compounds contained in real watersample were helpful to understand the reason of disinfec-tion by-products reduction by ozonation. It is found thatthree types of functional groups such as O-H, C-O, andC-H were decreased by ozonation, which lead to thedecrease in the formation of disinfection by-products.

Ma (2004) indicated that several functional groupsincluding aromatic rings (C¼C bond), aromatic (C-Hbond), alkenes (C¼C bond), amines and amides (N-Hbond) were observed in the humic acids solution. Afterozonation, C¼C and C-H bonds were diminished signifi-cantly. Additionally, the C-O bond, alcohol O-H bond,alkenes C-H bond and alkyl halide C-Cl bond structureswere generated after ozonation and the presence of car-boxylic acid, ester and ether fractions were observed inthe system. Therefore, understanding the profiles of

functional groups during the oxidation process is valuableto estimate the efficient condition for ozonation.

However, the reaction kinetics and mechanism of O3/perfluorooctylalumina for humic acids decomposition inwater are not well understood. There is a need to betterunderstand an appropriate selection of the reaction con-ditions to upgrade the ozonation efficiency. Therefore,the humic acid is subjected to ozonation for studyingprofiles of absorption at a wavelength of 254 nm (A254)and color removal (based on American Dye ManufactureIndex (ADMI) measurement), reductions of total organiccarbon (TOC), modification of functional groups andvariation of oxidation reduction potential (ORP), and tostudy the interactions among these parameters leading tothe reaction mechanism. The objectives of this study are:(1) application of successfully prepared perfluorooctyla-lumina as the catalyst in ozonation, (2) simulation of theoverall system by Nernst equation and (3) investigation ofthe change in humic acid structure during ozonation byFourier Transform Infrared Spectrometry (FTIR).

EXPERIMENTAL METHODS

Materials

A synthetic humic acid solution was prepared inlaboratory by dissolving a commercial humic acid powder(Fluka, 56380, Switzerland) in aqueous solution with thepH adjusted to 11 using 0.1 N sodium hydroxide (R.D.H.,30620, Germany) and filtered through a 0.45 mm glass fiberfilter. To prevent the effect of photolysis on the change ofhumic acid structure, the solution was reserved in brownglass bottle at 4 �C. The initial humic acid concentrationwas 40 mg/L where the TOC concentration was 19.4 mg/L.The aluminum hydroxide (Al(OH)3, Merck, Germany) wasused in this study to prepare the perfluorooctylalumina. Theparticle size of more than 95% of aluminum hydroxide wasless than 45 mm.

Catalyst Preparation

The protocol reported by Wieserman et al. (1991) wasadopted for catalyst preparation. In the sol-gel method,40 g aluminum hydroxide and 800 mL isopropanol weremixed in the reactor under ultrasonic shaking for 20 minthen the isopropanol-water mixture of 213 mL was dosedinto the reactor at the rate of 3 mL min-1 to get thealuminum particles. The prepared aluminum particles of10 g with 100 mL of 0.15 M perfluorooctanoic acid (PFA)aqueous solution were mixed at 60 �C for 4 h. Theobtained aluminum/PFA particles were defined as per-fluorooctylalumina particles. The organic structure ofsynthetic catalyst was identified by FTIR (FT/IR-460plus, Jasco Co., Japan). After each ozonation test, theperfluorooctylalumina was recycled by filtration througha 0.45 mm glass fiber filter and reused after drying at 60�C for 4 h.

266 Y.-S. Ma and C.-N. Chang July–August 2010

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Experimental Design

The experimental setup for batch ozonation experiments isshown in Figure 1. The working volume of reactor was 1 Land during the reaction, contents of the reactor were mixedby a mechanical stirrer at 275 rpm. The temperature wasmaintained at 25 � 2 �C by submerging in water bath out-fitted with a temperature controller. Ozone was produced byan ozone generator (KA-1600, AirSep Corp., USA) and wascontinuously introduced into the reactor at a flow rate of10.53 g/h. The maximum practical ozone concentration indeionizer distilled water was found to be 2.5 mg/L by on-line ozone analyzer (Suntex, Ozone transmitter, OT-710). Inaddition, two sensors (ORP, Mettler, 3261965, Switzerlandand pH, Mettler, 3288376, Switzerland), oscilloscope(Yokogawa, OR100E, Japan), absorbance sensor, and spec-trophotometer (Cary-50, EL04083211, Australia) wereequipped within the reactor to obtain the instantaneousexperimental data during ozonation.

A two-channel digital oscilloscope recorder (Yokogawa,OR100E, Japan) connected with pH and ORP sensors wasused to collect the instantaneous ORP and pH profiles to apersonal computer by the WaveStarTM Software. Thecomprehensive data collection system can store 16,000data per second, which is useful to understand the directand indirect ozonation reactions. The on-line spectrophot-ometer equipped with a UV detector and probe of opticalfiber was used to collect A254 data during ozonation. Theprobe of optical fiber connected with UV detector, andequipped into the reactor was used to monitor the changeof data. The Cary Win UV software was used to set themonitoring condition.

ANALYTICAL METHODS

The gaseous ozone concentration in- and off-gas fromthe reactor is measured with iodometric method. TOC

concentration of sample was determined using a TOCanalyzer (Model TOC-5000, Shimadzu Co., Kyoto,Japan). The changes in functional groups of humic acidsbefore and after ozonation were analyzed by FT-IR 460plus analyzer. After grinding the freeze-dried sample andmixing with potassium bromide (KBr) at weight ratios of1:100–200, the sample was pressurized to generate atransparent thin slice.

The transmittance spectra were scanned over the wavenumber from 400 to 4,000 cm-1 and then processed byKnowItAIR Information System 3.0 software (Bio-RadLaboratories, Inc. USA) transformation to display as aspectrum form. Besides the analysis of organic structures,the change in ADMI during the ozonation was used toinvestigate the efficiency of humic acids decomposition.To obtain the ADMI for the sample, the transmittance atthe wavelength of 590, 540 and 438 nm in a spectrophot-ometer (U-2000, Hitachi Co) was measured to obtain thetristimulus value, which was used to determine theMunsell values and intermediate value (DE).

RESULTS AND DISCUSSION

Characteristics of Perfluorooctanoic Acid,Perfluorooctylalumina and ReusedPerfluorooctylalumina

Before the use of perfluorooctylalumina in ozonationof humic acids, the analysis of perfluorooctanoic acid,perfluorooctylalumina and reused perfluorooctylaluminaby the FTIR were carried out and the spectra are shownin Figure 2. Typical peaks were observed in the IR wavenumber range of 1,100 to 1,250 cm-1 for perfluoroocta-noic acid, perfluorooctylalumina and reused perfluorooc-tylalumina. This could imply that the typicalcharacteristics of perfluorooctylalumina is acceptable,which is comparable to the results shown in Kasprzyk

KI

275

Flow meter

KI

Hood

pH meterORP meter

DO3meter

Temperaturecontroller

A254

Oscilloscape

O3

UV detector(Cary 50)

Mixer

FIGURE 1. Schematic diagram of ozonation reactor. Ozone was produced by an ozone generator (KA-1600, AirSep Corp., USA). The ORP

and pH meters, absorbance sensor are connected with an on-line oscilloscope and spectrophotometer to a personal computer.


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and Nawrocki (2002). Figure 2 also shows two majorpeaks representing the C¼O bond (1,650-1,750 cm-1)and O-H bond (3,500-3,600 cm-1).

These two functional groups are presented in the perfluor-ooctanoic acid. Based on the consideration of environmentalpollution problems with waste perfluorooctylalumina andsaving the cost of treatment, all perfluorooctylaluminaafter each tests were recycled by glass fiber filtration. Inaddition, the FTIR spectrum shown in Figure 2 indicatesthat the characteristics of 5th reused perfluorooctylaluminaare comparable with perfluorooctylalumina. Therefore, thereused perfluorooctylalumina is adapted to all the follow-ing tests in this study.

Decomposition of Humic Acids by the Process ofO3/Perfluorooctylalumina

Four parameters such as pH, A254, TOC and ADMIwere used to understand the decomposition of humicacids by ozonation at different reaction conditions. Thevariation of pH in humic acids decomposition by ozona-tion with and without perfluorooctylalumina at pH 2, 7and 10 in each runs are insignificant during 30 min ofreaction, which indicates that the effect of pH variationon the decomposition of humic acids or the formation ofintermediates could be ignored. Figure 3 shows the resultsof change in A254, TOC and ADMI during humic acidsdecomposition at pH 2, 7 and 10 by ozonation with andwithout perfluorooctylalumina.

To carry out the background test, the author intro-duced the humic acid sample into the reactor with andwithout oxidants addition for 30 min stirring only. Thereis no change in A254, TOC and ADMI during 30 minstirring (data not shown). Figure 3a shows the profiles ofA254,t/A254,0 in humic acids decomposition by ozonationwith and without perfluorooctylalumina at pH 2, 7 and

10. A better reduction in A254,t/A254,0 was observed at pH7 and pH 10. More than 90% reduction in A254,t/A254,0

was observed when the humic acids were decomposed byozonation with perfluorooctylalumina at pH 7 and pH10, which indicates that ozone can destroy the complexstructure of humic acids into relatively simple one.Among the pH values investigated, i.e., pH 2, 7 and 10without perfluorooctylalumina, the reduction of A254,t/A254,0, at pH 7 was slightly higher than pH 10.

Erol and Ozbelge (2008) applied the ozonation in theremoval of dye solution including AR-151 and RBBR atpH 2.5, 7 and 13. It was found that the removal rates ofdyes were almost the same at pH values of 2.5 and 7 forthe dye RBBR. At pH 13, an increase in the initial reac-tion rate was observed which was greater in the ozonationof AR-151 than in that of RBBR. In addition, the directoxidation of AR-151 by ozone molecules was probablyaccompanied with the indirect oxidation by reactivehydroxyl radicals formed due to the higher decomposi-tion rate of ozone at an alkaline pH of 13.

In RBBR ozonation, the occurrence of the highestinitial dye removal rate at pH 13 suggests that radicalreactions played relatively a more significant role in theoxidation mechanism. In this study, a better result ofdecrease in A254, ADMI and TOC was observed at pH7 and 10. This indicates that the OH radical reaction isthe major oxidation mechanism. On the other hand,improvements in the A254 decay at 3 pH levels wereobserved when humic acids were ozonated with perfluor-ooctylalumina addition (Figure 3a). This could beexplained by the production mechanisms of hydroxylradicals.

It is well known that the hydroxyl radicals have stron-ger oxidation capability and less selective than ozonemolecule in simple ozonation (Chu and Wong, 2003;Gunten, 2003a, 2003b). Moreover, ozonation in the

FIGURE 2. The FTIR spectra of (a) Perfluorooctanoic acid, (b) perfluorooctylalumina, (c) reused perfluorooctylalumina and (d) 5th reused

perfluorooctylalumina.


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presence of perfluorooctylalumina results in a muchhigher level of ozonation efficiency in comparison toozonation alone (Kasprzyk and Nawrocki, 2003).

Removal of color by ADMI measurement is also dis-cussed in this study. Kasprzyk and Nawrocki (2002) pro-posed that the adsorption capacity of PFOA for toluene,chlorobenzene and cumene were 0.04, 0.037 and 0.06 mgper 1 g of PFOA. Therefore, in this study, the adsorptionof humic acids by perfluorooctylalumina could beneglected. In Figure 3b, a rapid decrease in color wasobserved in the first 5 min (56% to 95%). After 30 minof reaction, the color removal was reached around 95%.This shows that ozonation is useful in destroying the dye

functional groups in humic acids. However, the effect ofpH levels in ADMI reduction was not significant.

To investigate the effect of perfluorooctylaluminaaddition, it is found in Figure 3b that the addition ofperfluorooctylalumina will enhance the decrease rate ofADMI during ozonation. In the reaction of 3 min, morethan 90% of ADMI decrease is observed with perfluor-ooctylalumina addition at three different pH levels but50% without perfluorooctylalumina addition. After 30min reaction, the effect of perfluorooctylalumina additionon ADMI decrease is insignificant. In TOC reduction, theeffect of pH level and perfluorooctylalumina addition isalso investigated.

0

0.1

0.2

0.3

0.4

0.5

0.6

A25

4 ,t/A

254 ,

0A

DM

I t/A

DM

I 0

0.7

0.8

0.9

1

Time (min)

pH = 2 Ozone

pH = 7 Ozone

pH = 10 Ozone

pH = 2 Ozone/perfluorooctylalumina



00.10.20.30.40.50.60.70.80.9

1pH = 2 Ozone

pH = 7 Ozone

pH = 10 Ozone




(b)

(a)

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 5 10 15 20 25 30

TO

Ct/T

OC

0

pH = 2 OzonepH = 7 OzonepH = 10 Ozone

pH = 2 Ozone/perfluorooctylalumina pH = 7 Ozone/perfluorooctylalumina pH = 10 Ozone/perfluorooctylalumina

Time (min)0 5 10 15 20 25 30

(c) Time (min)0 5 10 15 20 25 30

FIGURE 3. The profiles of (a) A254 (b) ADMI (c) TOC in humic acids decomposition by ozonation (&) Ozone only at pH 2 (�) Ozone only at pH

7 (*) Ozone only at pH 2 (&) Ozone/perfluorooctylalumina at pH 2 (~)Ozone/perfluorooctylalumina at pH 7 (�)Ozone/perfluorooctylalumina atpH 10.


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After 30 min ozonation without perfluorooctylaluminaaddition, it is found that 19%, 18% and 35% of TOCreduction were observed at pH 2, 7 and 10, respectively;with perfluorooctylalumina addition, the results are 24%,46% and 38%. This fact indicates that addition of per-fluorooctylalumina is useful in enhancing the TOC reduc-tion at pH 7. In addition, the reduction efficiency of TOCis less than A254 and ADMI reduction for all tests. Thisshows that ozone can easily destroy the composition andfunctional groups of humic acids but difficult to miner-alize the humic acids.

Ozonation of humic acid was found to follow the first-order kinetics and the rate constants of humic acids decom-position presented as A254 decrease by ozonation with andwithout perfluorooctylalumina were 5.3�10-3/s and2.8�10-3/s at pH 2, and 5.2�10-3/s and 4.0�10-3/s at pH7, respectively. This shows that the addition of perfluorooc-tylalumina provides 1.9 and 1.3 times improvement in theremoval rate constants at pH 2 and pH 7, respectively.

This implies that dosing the catalyst into the solutionwould enhance the reaction rate in the reduction oforganic compounds, especially for the organic compoundcontaining aromatic ring. However, at pH 10, the rateconstants of humic acids reduction were 2.8�10-3/s and3.9�10-3/s with and without perfluorooctylalumina addi-tion, which implies a 28% decrease in the rate constant bythe addition of perfluorooctylalumina.

Simulation of Ozonation Kinetics by the NernstEquation

Chang et al. (2004) tried to apply the Nernst equation(Equation [1]) in decolorizing of lignin wastewater usingthe photochemical UV/TiO2 process and proposed a mod-ified Nernst equation (Equation [2]) where the items ofproduct and reactants are replace by A254.

E ¼ E0 þRT

nFln

PRO½ �RET½ �

� �½1�

E ¼ E0 þRT

nFln

A254;t

� �A254;0

� �� Hþ½ � !

½2�

where E ¼ the electrode potential of chemical reactions(mV)

E0¼ the standard electron potential (mV)R ¼ gas constant (8.314 V-coulombs/K-mol)T ¼ the absolute temperature (k)n ¼ the number of electrochemical gram equivalent per

gram mole exchanged during the redox reaction(equivalent/mol)

F¼ Faraday’s constant (96,500 coulombs/mol)[RET] ¼ Concentration of the species to involve in the

chemical oxidation[PRO] ¼ Concentration of the species produced in the

chemical reaction

A254, 0, A254, t are the A254 at initial and time t.

The decomposition of humic acids by ozonation is atypical oxidation/reduction reaction, where the decrease inhumic acids is very difficult to measure directly. Therefore,Equation [2] was followed to investigate the reactionkinetics. The effect of pH change and profiles of A254

could be divided into two parts hence Equation [2] canbe rewritten as Equation. [3]. In addition, the change in pHvalues during 30 min of reaction was insignificant; theeffect of pH change could be neglected. In Equation [3],profiles of ORP could be represented as E and E0, and theequation can be re-written as Equation [4]. The relation-ship between ORP and A254,t/A254,0 is shown in Figure 4.

E ¼ E0 þRT

NFln Hþð Þ þRT

nFln

A254;t

� �A254;0

� � !

½3�

ORP ¼ a lnA254;t

� �A254;0

� � !

þ b ½4�

where a and b are constants.Table 1 summarizes the results of Nernst type ORP

model coefficients and linear correlation coefficient inhumic acids ozonation at different reaction conditions.The linear correlation coefficients for all simulationswere in the range of 0.71 to 0.90. The constant a inhumic acids ozonation at pH 2 and pH 7 with perfluor-ooctylalumina addition is greater than those withoutperfluorooctylalumina (Table 1). This also implies thataddition of perfluorooctylalumina is effective to catalyzethe ozone reaction and build high ORP values in thereaction. Moreover, In fact, as the model is developed, itcan practically be used to predict the ending ORP con-trol point based on calculated A254,t/A254,0 removalratios.

Table 2 shows the time in half A254,t/A254,0 reductionsas the humic acids are ozonated at different reactionconditions. The change in half reduction time for differ-ent reaction conditions gives us the important informa-tion. In Table 2, the half time of humic acidsdecomposition at pH 7 with perfluorooctylaluminaaddition is much faster than without perfluorooctylalu-mina addition (from 103.4 to 16.1 sec). This also indi-cates that the addition of perfluorooctylalumina cansignificantly save the time for humic acids ozonation atpH 7. At pH 2 and 10, the half-time of humic acidsdecomposition is decreased with the addition of per-fluorooctylalumina. However, the decreased of half-time in insignificant.

Change in Humic Acids Structure by Ozonation

The FTIR spectrum shown in Figure 5 is used toinvestigate the profiles of functional groups in humicacids before and after ozonation at different reaction


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conditions. A wide peak around the wave number 3,350cm-1 in the FTIR spectrum was defined as the O-Hgroup in alcohols type (Figure 5). In Figures 5a to 5c,it is found that the change of O-H group in this spectrumbefore and after ozonation at different pH values isinsignificant; that is, during ozonation, the O-H groupwould not be easily attached by OH radicals or ozonemolecules.

Around 1,650 cm-1, a transmittance of C¼O bond inaldehydes or ketones is observed and the signal strength isdecreased after ozonation, especially at pH 2. This factindicates that the ozone molecules could significantlyattack the C¼O group at pH 2. In the other hands, anunsaturated C¼C group in alkenes type might be foundin the spectra around 1,610 – 1,680 cm-1. The C¼C groupcould be attached by the OH radicals or ozone molecules.However, it is found in Figure 3 that the decrease in A254

at pH 7 and 10 is better than pH 2. Therefore, summariz-ing the results shown in Figures 3 and 5, it is concludedthat the reaction mechanisms of C¼O group attached byozone molecules is the major one at pH 2. Additionally,after ozonation with perfluorooctylalumina addition atpH 2, the transmittance is flatter than that withoutperfluorooctylalumina.

CONCLUSIONS

The addition of perfluorooctylalumina and low pHvalues are useful for decomposing the humic acids based

TABLE 1. The Nernst Type ORP Model Coefficients and Linear Correlation Coefficient (R square value) of A254 Removed

During Ozonation with and without Perfluorooctylalumina

pH System a b R2

pH 2 Ozone -4347 341.5 0.88Ozone/perfluorooctylalumina -1559 457.1 0.89

pH 7 Ozone -2505.4 213.4 0.71Ozone/perfluorooctylalumina -430.7 242.2 0.90

pH 10 Ozone -1590.9 143.7 0.77Ozone/perfluorooctylalumina -4350.3 118.5 0.86

TABLE 2. Half-life in A254 Reduction as the Humic Acids Are

Ozonated at Different Reaction Conditions

Reaction conditions Time (sec)

pH 2 O3 99.0O3/perfluorooctylalumina 63.0



FIGURE 4. Relationships between ORP and A254,t/A254,0 as the humic acids were ozonated at (�with solid line) Ozone only at pH 2 (�with

dot line) Ozone/perfluorooctylalumina at pH 2 (. with solid line) Ozone only at pH 7 (. with dot line) Ozone/perfluorooctylalumina at pH 7 (&with solid line) Ozone only at pH 10 (& with dot line) Ozone/perfluorooctylalumina at pH 10.


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on the measurement of A254, TOC and ADMI decay.The addition of perfluorooctylalumina provides 1.9 and1.3 times improvement based on the removal rate con-stant enhancement at pH 2 and pH 7. It is well knownthat oxidation can decompose the complex functionalstructures in organic substances into the simple types.Experimental results reveal that the C¼C bond inalkenes containing in the poly-aromatic hydrocarbonstructure is decreased after ozonation. And, ozonationwith perfluorooctylalumina addition at pH 2 and pH7, the transmittance is flatter than those without

perfluorooctylalumina. At pH 10, ozone can’t effec-tively decompose the complex structures, i.e., thefunctional structures still remain the same fromobserved FT-IR spectrum.

ACKNOWLEDGMENT

The authors would like to express thanks for financialsupport by the National Science Council, ROC with pro-ject NSC 94-2211-E-029-001.

(a)

pH = 2 HA

pH =2 HA + Ozone

pH = 2 HA + Ozonation/perfluorooctylalumina

4000 3600 3200 2800 2400Wave number (1/cm)

Tra

nsm

itta

nce

(%)

2000 1600 1200 800 400

pH = 2 HA

pH =2 HA + Ozone

pH = 2 HA + Ozonation/perfluoff rooctylalumina

pH = 7 HA + Ozonation/perfluorooctylalumina Tra

nsm

ittan

ce (

%)

pH = 7 HA + Ozonation

pH = 7 HA

(b)4000 3600 3200 2800 2400

Wave number (1/cm)2000 1600 1200 800 400

pH = 7 HA + Ozonation/perflff uorooctylalumina


pH = 7 HA

Tra

nsm

ittan

ce (

%)

pH = 10 HA + Ozonation/perfluorooctylalumina

pH = 10 HA


(c)4000 3600 3200 2800 2400

Wave number (1/cm)2000 1600 1200 800 400

FIGURE 5. The FTIR spectra of humic acids before ozonation, after ozonation and ozonation with perfluorooctylalumina at (a) pH 2 (b) pH 7

(c) pH 10.


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application of perfluorooctylalumina in the ozonated decomposition of humic acids

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