SORPTION OF CADMIUM AND ZINC ON MAGNETICALLY MODIFIED PEANUT HUSKS Lucia ROZUMOVÁ 1, Jana SEIDLEROVÁ 1, Ivo ŠAFAŘÍK 2, Mirka ŠAFAŘÍKOVÁ 2

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1 SORPTION OF CADMIUM AND ZINC ON MAGNETICALLY MODIFIED PEANUT HUSKS Lucia ROZUMOVÁ 1, Jana SEIDLEROVÁ 1, Ivo ŠAFAŘÍK 2, Mirka ŠAFAŘÍKOVÁ 2 1 VŠB TU Ostrava, Nanotechnology Centre, 17. listopadu 15/2172, Ostrava Poruba, Czech Republic 2 Department of Nanobiotechnology, Institute of Nanobiology and Structural Biology of GCRC, Na Sádkach 7, České Budějovice, Czech Republic Abstract The increase of industrial activities has intensified environmental pollution problems and the deterioration of several ecosystems with the accumulation of many pollutants, especially heavy metals. Effluents containing heavy metals are discharged from various industrial processes. These pollutants concentration must be reduced to meet ever increasing legislative standards, and recovered where feasible. Cadmium and zinc are dangerous for the soil and water environment. The treatments of polluted water contaminated with heavy metals include chemical precipitation, coagulation, ionic exchange, performance liquid extraction, membrane processes and reverse osmosis. The disadvantages of many of these methods are: high cost, the need for continuous feed of chemicals and production of toxic sludge. Another method how to eliminate lead from wastewater is sorption. The use of low-cost biological material peanut husks, a waste material, has been investigated as a replacement for the current expensive methods of removing heavy metals from wastewater. With a view to find a suitable application of the material, peanut husk have been magnetically modified, characterized and utilized for the removal of cadmium (II) and zinc (II) ions. Material was studied at different values of concentration and was assessed in batch experiments. The experimental data were assessed by using Langmuir and Freundlich sorption isotherm. Study were focused also on desorption properties of the material. A flame atomic absorption spectrometer was used for determination the Cd(II) and Zn(II) concentration before and after both experimental surveys. Keywords: Magnetically modified peanut husks, cadmium, zinc, sorption 1. INTRODUCTION The contamination of the environment by heavy metals is of growing concern because of the numerous health risks to animals and humans following exposure. Common sources of metal polluted wastes include electroplating plants, metal finishing operations, as well as many mining, nuclear and electronics industries. All of these contribute to anomalously high concentrations of metals in the environment relative to the normal background levels [1]. Their presence in the environment has become a major threat to plant, animal and human life due to their bioaccumulating tendency and toxicity; therefore they must be removed from municipal and industrial effluents before discharge [2]. The conventional methods for heavy metal removal from water and wastewater include oxidation, reduction, precipitation and ion exchange/sorption [3]. The effectiveness of commonly employed methods of treating heavy metal-polluted wastes, including, amongst others, precipitation and ion exchange, remains limited [4]. In the last decade an alternative treatment method, biosorption, has been developed [5]. Biosorption involves the accumulation of heavy metals by biological material. Unlike physical and chemical treatments, biosorption generally does not entail high operational costs and many potential sources of suitable biological material are cheaply and readily available [6]. The use of various sorbents such as nut shells [7] wool, olive cake, pine needles, almond shells, cactus leaves and papaya wood [8], maize leaf [9], leaf powder [10], peanut hull pellets [11], tree fern [12], rice husk ash and neem bark [13], grape stalk wastes [14], sago waste

2 [15], peanut hulls [16], hazelnut shell [17], saw dust [18], chitin beads [19], thermally treated rice husk ash [20], waste banana [21], orange peels [21], cocoa shells [22], coffee residue [23], palm kernel fibre [24], olive stone waste [25], orange peel [26], grape stalk [27], coir [28] and bagasse fly ash [29] have been reported for the removal of heavy metal from aqueous solutions. In view of the environmental significance, we have studied the sorption of Cd and Zn on low-cost magnetically modified biological waste materials peanut husks under exactly defined experimental conditions in order to ascertain their use as sorbents to remove Cd and Zn from wastewater. 2. EXPERIMENTAL WORK Peanut husks samples used in this study were collected from locally available roasted peanuts. Peanut husks were milled in a coffee mill and fraction smaller than 0.5 mm was collected and used for magnetic modification. Magnetic iron oxide nanoparticles (ferrofluid) ranged from 10 to 20 nm in size. The relative magnetic fluid concentration (25.2 mg/ml) is given as the iron (II, III) oxide content determined by a colorimetric method [30]. Three grams of powdered peanut husk in a 50 ml polypropylene centrifuge tube were suspended in 40 ml of methanol and then 6 ml of ferrofluid was added. The suspension was mixed for 1 h and samples were then twice washed with methanol and air dried [30]. Magnetically modified material (0.2 g) was suspended in 50 ml of solution with defined concentration of Cd 2+ and Zn 2+. The suspension was mixed for 1 hour at the laboratory temperature and then samples were separated by filtration. For the characterization of samples, scanning electron microscopy SEM (QUANTA 450 FEG) combined with energy dispersive X-ray spectrometer was used. Specific surface area was measured with the Sorptomatic 1990 using nitrogen and calculated by the Advanced Data Processing software according to the BET isotherm. Particle size was measured by using Laser Scattering Particle Size Distribution Analyzer Horiba LA-950. In order to determine the metal concentration, atomic absorption spectroscopy with flame atomization (UNICAM 969) was applied. The experimental data were processed by using Langmuir and Freundlich sorption isotherm. 3. RESULTS AND DISCUSSION 3.1 Material characterizations Chemical analysis of magnetically modified peanut husks composition showed high concentration of Fe2O3 (6.22 wt. %), which was added to the peanut husks during the magnetization procedure. Surface area was determined at 9.45 m 2 /g and median particle size was 136 µm. A scanning electron microscopy picture of the original peanut husks is presented in Fig. 1; peanut husks sample after adsorption of metal is shown in Fig. 2. In comparison with the images in Fig. 1, SEM images after adsorption of Cd show larger area of clusters than on the sample before adsorption. In SEM image of Zn (Fig. 2 right), cluster is also visible, though not as large.

3 Fig. 1 SEM images of magnetically modified peanut husks before adsorption (left SEM images, right - mapping content of C, O, Fe) Fig. 2 SEM images of magnetically modified peanut husks after adsorption of Cd (left) and Zn (right) Adsorption isotherms are essential for the description of how Cd and Zn ion concentration will interact with magnetically modified peanut husks and are useful for optimization of their use as an adsorbent. Therefore, empirical equations (Langmuir and Freundlich isotherm model) are important for adsorption data interpretation and predictions. The adsorption data were fitted to the Langmuir equation in linearized form (1) is written as: c a 1 b.a c m a m (1) where a (expressed in mg/g or mg/ml) is the amount of the adsorbed ion of metal per unit mass or sedimented volume of magnetically modified biomass and c (expressed in mg/l) is the unadsorbed ion of metal concentration in solution at equilibrium. a m is the maximum amount of the ion of metal per unit mass or sedimented volume of biomass to form a complete monolayer on the surface bound at lead concentration and b is a constant related to the affinity of the binding sites (expressed in dm 3 /mg) [30]. The Freundlich equation (2) is normally written as: 1/n a k.c (2) where a is the amount of metal ion adsorbed per unit weight of adsorbent, k and n are the Freundlich constants and c is the equilibrium concentration of metal ion.

4 Linearized form can be used for the calculation of the constats: log a log k 1 n log c (3) The adsorption data of Cd and Zn were fitted to the Langmuir or Freundlich isotherm in the linearized form which is shown in Fig. 3 and 4. Calculated correlation coefficient of these dependences is different (Cd: for Langmuir isotherm, for Freundlich isotherm; Zn: for Langmuir isotherm, for Freundlich isotherm). The results show that the Freudlich isotherms fitted better the adsorption of Cd and Zn on magnetically modified peanut husks than Langmuir isotherm. Fig. 3 Langmuir isotherm (left) and Freundlich isotherm (right) of Cd adsorption by magnetically modified peanut husks Fig. 4 Langmuir isotherm (left) and Freundlich isotherm (right) of Zn adsorption by magnetically modified peanut husks Dependence of the leaching proportion of Cd and Zn on the adsorbed amount shows that metal ions are relatively tightly bound as well. At higher adsorbed amount of metal ions, a higher desorption occurs though it does not exceed 7 % of the total adsorbed amount of metal ions (In Fig. 5). Leaching of iron was also observed. Leaching of iron during desorption of Cd is 0.18 %, leaching of iron during desorption of Zn is 0.11 %. The newly prepared material is stable even at high adsorbed amounts of cadmium and zinc ions.

5 Fig. 5 Leaching proportion of Cd at desorption (left) and leaching proportion of Zn at desorption (right) 4. CONCLUSION Peanut husks were modified with magnetic iron oxide nanoparticles ferrofluid. The study was carried out on the sorption and desorption of cadmium and zinc ions on magnetically modified peanut husks by dynamical method. The results obtained were assessed by Langmuir and Freundlich isotherm. The experimental data of cadmium and zinc revealed that the Freundlich isotherm was better in fitting the experiment results than the Langmuir isotherm. The results indicate multilayer adsorption. Desorption amount did not exceed 7 % of the adsorbed amount of Cd and Zn ions. Leaching of iron during desorption of Cd is 0.18 %, during desorption of Zn it is 0.11 %. This newly prepared material was found to be stable. ACKNOWLEDGEMENT Authors thank to the financial support of Projects: GAČR No S/P503. and collegs participating in the analysis (Ing. Soňa Študentová a Ing. Karla Čech Barabaszová, Ph.D.) LITERATURA [1] COSTLEY, S.C., WALLIS, F.M. Bioremediation of heavy metals in a synthetic wastewater using a rotating biological contactor. Water Research. 2001, vol. 35, pp [2] HORSFALL, M., ABIA, A. Sorption of cadmium(ii) and zinc(ii) ions from aqueous solutions by cassava waste biomass (Manihot sculenta Cranz). Water Research. 2003, vol. 37, pp [3] PURNA CHARNA RAO, G., SATYAVENI, S., RAMESH, A., SESHAIAH, K., MURTHY, K.S.N., CHOUDARY, N.V. Sorption of cadmium and zinc from aqueous solutions by zeolite 4A, zeolite 13X and bentonite. Journal of Environmental Management. 2006, vol. 81, pp [4] KRATOCHRIL, D., VOLESKY, B., DEMOPOULOS, G. Optimizing Cu removal/recovery in a biosorption column. Water Research. 1997, vol. 31, pp [5] MATHEIKAL, J.T., IYENGAR, L., VENKOBACHAR, C. Sorption and desorption of Cu(II) by Ganodeerma lucidium. Water Pollution Research. 1991, vol. 26, pp [6] WOOD, A. Trace metal removal from effluents. Water Waste treatment. 1992, vol. 32, p. 36. [7] ORHAN, Y., BUYUKGUNGOR, H. The removal of heavy metals by using agricultural wastes. Water Sci. Technology, 1993, vol. 28, p [8] SAEED, A., WAHEED, A.M., IQBAL, M. Removal and recovery of heavy metals from aqueous solution using papaya wood as a new biosorbents. Sep. Purif. Technology, 2005, vol. 45, p [9] BABARINDE, N.A.A., BABALOLA, J.O., SANNI, R.A. Biosorption of lead ions from aqueous solution by maize leaf. Int. J. Phys. Science, 2006, vol. 1, p [10] HANAFIAH, M.A.K., NGAH, W.S.W., ZAKARIA, H., IBRAHIM, S.C. Batch study of liquid phase adsorption of lead ions using Lalang (Imperata cylindrica) leaf powder. J. Biol. Science, 2007, vol. 7, p

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