Badinsk Zeolite Application for Ground Water Treatment

Olga B. Naz renko, Rayisa F. Zarubina, Anastasya S. Veisgeim Tomsk Polytechnic University

Tomsk, Russia obnaz@mail.ru

Abstract — In this paper the natural zeolite from the Badinsk deposit (Byryat Republic) was tested as adsorbent for Fe2+, Fe3+

removal from aqueous solutions and Kozhevnikovsky ground water (Tomsk Region) under dynamic conditions. The physicochemical and adsorption properties of the zeolite were studied by XRD, TGA, DTA, FTIR spectroscopy and chemical analyses. It is found that Fetotal removal efficiency achieved from 69 wt% to 100 wt% depending on the initial concentration.

Keywords - natural zeolite; water treatment; ion exchange

I. INTRODUCTION

Surface waters of West Siberia and the Tomsk region are heavily polluted due to wastewater discharges of industrial and agricultural enterprises, oil and gas complex. Therefore, the source of drinking water supply in the Tomsk region is mainlyunderground water. Ground water of artesian well exploited in the Tomsk region of West Siberia is characterized by high content of iron up to 20 mg/L, manganese up to 13 mg/L, ammonium up to 5 mg/L. Iron in ground water is contained as a divalent ion Fe2+. After lifting the water to the surface and oxidation by atmospheric oxygen, iron Fe2+ transforms to the trivalent form Fe3+. Such water usage requires special water treatment which includes aeration to convert Fe2+ in ferric Fe3+, settling and filtration.

Several treatment technologies, such as ozonization, electric discharge treatment, have been developed for ground water purification. However, high power consumption and expenses are required for operation and maintenance of the equipment. Wide spread, cheapness and high sorption properties of natural minerals, including zeolites, allow to consider them as perspective sorbents for different impurities removal.

Natural zeolites are crystalline hydrated alumosilicates with a framework structure containing pores. The general formula of a zeolite is follows:

m/n [(AlO2)x · (SiO2)y] · zH2O, where M is monovalent (Na+, K+, Li+) or divalent (Ca2+, Mg2+, Ba2+, Sr2+) exchangeable cations, m is number of cations M, nis cation charge, ratio y/x =1–6 depending on the structure, z is number of water molecules [1, 2]. Natural zeolites are characterized with high cation-exchange ability and molecular sieve properties; they are low-cost materials, easily available in large quantities. That is why zeolites are widely used for drinking water and wastewater treatment [3–6].

Despite the large number of different experimental and theoretical studies of wastewater and water treatment based on natural zeolites, each type of zeolite raw material possesses unique properties; therefore each zeolite rock requires a separate study. Our past research has been devoted to studying the properties of the sakhaptinsk zeolite and the possibility of its use for purification of groundwater from the iron, calcium and ammonium ions [7].

The present work aim is study the possibility of using the Badinsk zeolite for Fe2+, Fe3+ ion removal from synthetic aqueous solutions and Tomsk Region well water under dynamic conditions.

II. MATERIALS AND METHODS

A. Samples Zeolite rock from the Badinsk deposit (Buryat Republic)

was used in this study. The Badinsk deposit of zeolite rock is placed in Buryat Republic. Content of zeolite-rich minerals varies from 50 to 75 %. The chemical composition of the Badinsk rock sample was determined by classical chemical analysis (Tables 1).

TABLE I. CHEMICAL COMPOSITION OF THE BADINSK ZEOLITE

Component Value (%)

SiO2 68,0…72,0 Fe2O3 0,6…0,8 Al2O3 11,4…12,0 TiO2 0,16 MnO 0,16 Cao 2,1…3,7

MgO 0,6…1,7 K2 0,6…1,7 Na2O 0,4…1,5 H2O till10,0

The zeolite samples were ground in a metal mortar and divided into fractions by mechanical sieves. The fraction 1.0–2.0 mm was washed with distilled water to remove turbidity and dried at room temperature.

Badinsk zeolite was characterized by using X-ray diffraction (XRD), thermal (TGA), Fourier transform infrared (FTIR) and chemical analyses techniques.

978-1-4673-1773-3/12/$31.00 ©2013 IEEE

XRD analysis of the sample was performed using diffractometer DRON-3.0 with CuK -radiation. TG curve was measured from 20 °C to 1000 °C at a rate of 10 °C min–1 with SDT Q600 apparatus. The water concentration in the sample was determined from the TG curve mass loss. The infrared spectra of the zeolite rock were obtained using a Fourier transform infrared spectrometer Nicolet 5700. The FTIR spectra in the wave number range from 400 to 4000 cm−1 were obtained by using KBr pellet technique.

B. Sorption studies For analysis of the adsorption properties the glass column

was used in the experiments. The column was filled with the zeolite fraction of 1.0–2.0 mm and the volume of 25 mL. The preliminary activation of the zeolite sample with NaCl solution was carried out. Then, the treated sample of zeolite was washed with distilled water. The water was run through the column at filtration velocity of 7–8 mL/min. We selected sequentially every 100 mL of filtered water for analysis. After filtration the ion concentrations in the aqueous phase were measured using spectrophotometer KFK-2. The efficiency of impurities removal was estimated as the difference of pollutant concentrations in aqueous phase between the initial sample and the filtrate divided by the initial concentration of pollutant.

The water purification experiments were performed using the Kozhevnikovsky district well water (Tomsk region, West Siberia). The chemical composition of the well water is shown in Table II.

TABLE II. CHEMICAL COMPOSITION OF THE UNDERGROUND WATER

Component C (mg/L)

CO2 105,6 HCO3

– 439,2 SO4

2– < 2 Cl– 1,35

Ca2+ 108 Mg2+ 13,2 Na+ 23,5K+ 1,9

Fe total 1,48

The total dissolved solids is 588.6 mg/L, pH value is 6.7. Natural water is characterized by a high iron content.The results showed that the content of iron in natural water is 1.48 mg/L, significantly higher than normative and sanitary requirements.

III. RESULTS AND DISCUSSION

Powder X-ray diffractogram of the badinsk zeolite sample is presented in Fig. 1. As a result of X-ray data processing it was revealed that Badinsk zeolite consists of the following minerals: clinoptilolite, heulandite, quarz, montmorillonite, feldspar. The main phase (65–80 %) is clinoptilolite.

Clinoptilolite is one of the most common natural zeolite minerals belonging to the heulandite group [4, 5]. It is a thermally stable zeolite, characterized by high Si/Al ratio, more than 4.0.

Figure 1. Powder X-ray diffractogram of badinsk zeolite

Thermal behavior of the zeolite was investigated by means of TG analysis. TG curve of the badinsk zeolite sample is shown in Fig. 2.

The DTA curve of the sample displays a single endothermic effect with a maximum temperature of 87.5 °C as a result of a single-step dehydration process. The total weight loss for the sample determined by TG analysis is 10.0 %. Water loss continued smoothly from 20 °C to 700 °C. Such form of the curve is typical for the cliniptilolite. Most of the physically adsorbed water is lost between 80 °C and 300 °C and in the broad interval between 300 °C and 600 °C more strongly associated water is lost.

Figure 2. DTA-DTG curves of the zeolite: TG – temperature dependence of weight loss; DTA – temperature dependence of heat release at the heating

The results on the FTIR study are shown in Fig. 3. FTIR spectra were recorded for the raw zeolite rock and for the zeolite sample after the ground water treatment experiment.

Our results on the FTIR spectrum of the raw Badinsk zeolite rock (Fig. 3, a) show the most intensive vibrations in the band of 1100–1000 cm−1 corresponding to vibrations of the internal tetrahedron ties Si–O–Si and Si–O–Al [1]. The strongest vibrations of this band are observed at 1040 cm−1. The vibration band with peaks of 1625 cm−1 is assigned to the usual bending vibration of zeolite water in the channels of the sample. The strong wide band in 3253–3734 cm−1 can be

696,7°C

2,599 mg

140,0°C

-0,5

0,0

0,5

1,0

1,5

Q, V/g

25,5

26,0

26,5

27,0

27,5

28,0

28,5

m, %

0 200 400 600 800 1000Temperature (°C)

0,257 mg

Residue25,83 mg (90,0 %)

m0 = 28,71 mg

TG

DTA

characteristic of hydrogen bond of OH-groups of the water molecule.

Figure 3. FTIR spectra of the raw zeolite (a ) and the sample after filtration of the well water (b )

Fig. 3, b presents FTIR spectrum of the zeolite sample after purification of ground water. The sample after filtration shows an additional bands at 1446, 1822, 2535 cm–1, which are assigned to calcium and sodium carbonate.

The results of the ground water purification experiment are shown in Fig. 4.

00,20,40,60,8

11,21,41,6

0 100 200 300 400 500

Iron

conc

entra

tion,

mg/

l

Filtrate volume, ml

Figure 4. Correlation of iron total ions concentration and filtrate volume

Fig. 4 shows the effective absorption of iron by the zeolite sample. In accordance with the obtained results the efficiency of Fetotal removal in the experiments was 100 % after passing through column 200–400 mL of water.

The initial concentration of calcium in water was 108 mg/L. Decrease in the concentration was observed up to 26 mg/L, the removal efficiency was 76 %.

The main exchangeable ion during the process of water treatment on the zeolite is sodium ion. Pre-treatment of the zeolite by the NaCl solution before the experiments in water purification contributed to the saturation of the zeolite with exchangeable sodium ions, thus the zeolite was transferred to the Na-form. It is a cheap and inexpensive method of zeolite

preparation and regeneration, in the process of which the exchange effectiveness is increased significantly. Fig. 5 presents that an increase in the concentration of sodium ions from 23.5 mg/L takes place at the beginning of the cleaning process, and then decrease in concentration of sodium ion is observed.

Figure 5. Changes in Na+ concentration in the effluent during the filtration process

Decrease in the concentration of Fe2+ was 100 % for the initial concentration 15 mg/L in aqueous solution. For this sample it is observed an increase in Fe2+ concentration after passing through the filter 800 ml of water, that is connected with the work exchange capacity of the zeolite sample. In Fig. 6 the filtration curves of synthetic aqueous solutions polluted with iron Fe2+ at different concentrations are presented. Decrease in the concentration of Fe2+ was 80 and 69 % for the initial concentration 140 and 280 mg/L, respectively. The work ion-exchange capacity of the badinsk zeolite calculated on the basis of the data obtained was in average 8787 mg-equal/dm3, at the same time the total exchange capacity was 53871 mg-equal/ dm3.

0

50

100

150

200

250

300

0 200 400 600 800 1000

Iron

conc

entra

tion,

mg/

l

Filtrate volume, ml

1 2

Figure 6. Changes in Fe2+ concentration in the effluent during the filtration process: initial Fe2+ concentration is 140 mg/L (1); 280 mg/L (2)

The results indicate a high cleaning efficiency of natural water by passing it through a filter with zeolite loading.

0

20

40

60

80

100

400 800 1200 1600 2000 2400 2800 3200 3600 4000

Wavenumber, -1

I, %

12

Comparison of results of water purification by badinsk zeolite with the results obtained at water purification by sakhaptinsk zeolite showed that the efficiency is about the same. However, it was noted a significant mechanical destruction of the material while working with sakhaptinsk zeolite and a problem of fine dispersed phase separation from the effluent occurs, which is difficult to perform with conventional methods. So we decided to use badinsk zeolite in our further studies.

IV. CONCLUSION

In this study characterization of the Badinsk zeolite sample and its efficiency in the removal of Fe2+, Fe3+, Fetotal, Ca2+ ions from water have been investigated.

The results obtained indicate a high efficiency of natural ground water purification by passing it through the filter with zeolite loading.

The removal efficiency of water purification in the experiments was: 100 % of Fetotal for ground water and 69–100 % of Fe2+ for aqueous solution depending on the initial concentration. The concentration of these substances in the effluent after filtration through the column filled with zeolite did not exceed maximum permissible concentration. The total exchange capacity was 53871 mg-equal/dm3. In comparison with others national zeolite capacities it is high enough. Therefore, this studies performed suggest the efficiency of the

Badinsk zeolite for the treatment of ground water for drinking and technical goals.

REFERENCES

[1] D. Breck, Zeolite Molecular Sieves. Wiley, New York, 1974. [2] C. Murphy, O. Hrycyk, W. Gleason, Natural Zeolites: Occurence,

Properties, Use. Pergamon, Oxford, 1978. [3] E. Erdem, N. Karapinar, R. Donat, “The removal of heavy metal cations

by natural zeolites”, Journal Colloid and Interface Science 280 (2004) pp. 300–314.

[4] K. Saltali, A. Sari, M. Aydin, “Removal of ammonium ion from aqueous solution by natural Turkish (Yildizeli) zeolite for environmental quality”, J. of Hazardous Materials 141 (2007) pp. 258–263.

[5] S. Wang, Y. Peng, “Natural zeolites as effective adsorbents in water and wastewater treatment”, Chemical Engineering J. 156 (2010) pp. 11–24.

[6] M.K. Doula, “Simultaneous removal of Cu, Mn and Zn from drinking water with the use of clinoptilolite and its Fe-modified form”, Water Research, 43 (2009) pp. 3659-3672.

[7] O.B. Nazarenko, R.F. Zarubina, N.S. Volochova, “Application of Sakhaptinsk Zeolite for Ground Water Treatment”, Proceedings of 5th

International Forum on Strategic Technology IFOST-2010, Ulsan: University of Ulsan, 2010, pp. 281–284.