EFFECT OF DIFFERENT CONDITIONS ON Cu(II) AND Cr(VI) BIOSORPTION BY DRIED WASTE TEA FUNGAL BIOMASS. Radojka N. Razmovski and Marina B.

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1 APTEFF, 38, (2007) UDC: : DOI: /APT R BIBLID: (2007) 38, Original scientific paper EFFECT OF DIFFERENT CONDITIONS ON Cu(II) AND Cr(VI) BIOSORPTION BY DRIED WASTE TEA FUNGAL BIOMASS Radojka N. Razmovski and Marina B. Š iban Some industrial wastewaters contain high quantities of non-toxic salts besides heavy metal ions. The presence of salt ions leads to a high ionic strength of water, which may significantly affect the performance of the biosorption process, so that the effect of salts on the biosorption of heavy metal ions should be investigated. In this study the effect of different salts concentrations (0.1; 0.5 and 1 mol L -1 ) and dosage of tea fungal biomass (0.15; 0.25 and 0.5 g L -1 ) dried at different temperatures: 20 C, 70 C, 80 C, 105 C and 125 C on Cu(II) and Cr(VI) biosorption was studied in a batch system. Biosorption at an ionic strength of 0.1 mol L -1 of all salts investigated had a decreasing effect on Cu(II) and Cr(VI) removal. It was observed that (NH 4 ) 2 SO 4 at the concentrations of 0.5 mol L -1 and 1 mol L -1 was more efficient than other salts for metal ions removal. In case of Cr(VI) the most efficient removal was obtained for the water with K 2 SO 4 at a concentration of 0.5 mol L -1. The lowest biosorbent dosage (0.15 g L -1 tea fungal biomass dried at 20 C in the case of Cu(II) biosorption and at 80 C in the case of Cr(VI) biosorption) resulted in the highest metal uptake of 38 mg g -1 in case of Cu(II) and 33 mg g -1 in case of Cr(VI). KEYWORDS: Biosorption, waste tea fungal biomass, copper(ii), chromium(vi) INTRODUCTION Environmental pollution caused by the increased industrial activities is one of the most significant problems. Copper ions at excessive concentration are toxic to humans and other creatures, especially fish (1). Chromium ions, with its great economic importance in the industrial use, is a major metal pollutant of the environment. The effluents discharged by a variety of industries such as textile, dyes and pigments production, leather tanning, electroplating and metal finishing, may contain undesirable amounts of chromium(iii) and toxic chromium(vi) compounds, according to EPA (US Environmental Protection Agency), at concentrations ranging from tens to hundreds of mg L -1. Dr. Radojka N. Razmovski, Prof., Dr. Marina B. Š iban, Assist. Prof., University of Novi Sad, Faculty of Technology, Novi Sad, Bul. Cara Lazara 1, Serbia 149

2 Wastewaters generated by these industries usually contain significant quantities of salts such as sodium chloride, so the effects of these salts on the removal of chromium(vi) should be investigated (2,3). Biosorption is used to indicate a number of metabolism-independent processes (physical and chemical adsorption, electrostatic interaction, ion exchange, complexation, reduction, chelating and microprecipitation) taking place essentially on the cell surface. However, these methods are either inefficient or expensive when heavy metals exist in low concentrations. Additionaly, these methods may also risk the generation of secondary wastes, which are difficult to treat (4,5). Consequently, it is urgent to find new technologies or materials for removing heavy metal ions from wastewater. Various types of biomass, including bacteria (6), yeast (7), fungi (8) and algae (9), have been investigated with the aim of finding more efficient and costeffective metal-removal biosorbent. These investigations include the determination of biosorption capacity of different biomass (type, species, age, pretreatment), influence of competing ions, along with several physicochemical factors (temperature, ph, and ionic concentration). To our best knowledge, there is a relative lack information about sorption ability of waste tea fungal biomass (10). Therefore, tea fungus, as new material, was chosen as biosorbent in this study. Fungal biomass is available as a by-product or waste material from various fermentation processes. Furthermore, since dead fungal biomass is of little use and is abundant, it may be a good source of biomaterial for the removal of heavy metals from industrial wastewaters. The role of salts in metal biosorption by biomass has not been investigated extensively (11). Hence, it was necessary to investigate the effect of salts on copper(ii) and chromium(vi) biosorption by tea fungal biomass. In this work, biosorption features of waste tea fungal biomass were investigated as a function of different salts concentrations and dosage of waste tea fungal biomass dried at different temperatures. EXPERIMENTAL Tea fungus as biosorbent The tea fungus (a symbiont of yeasts Saccharomycodes ludwigii, Saccharomyces cerevisiae, Saccharomyces bisporus, Torulopsis sp., Zygosaccharomyces sp. and a bacterium of the genera Acetobacter) was obtained from the Faculty of Technology in Novi Sad (Serbia). The tea fungal biomass was washed with an adequate amount of distilled water to obtain it free from the metabolites, and then dried at different temperature: 20 C, 70 C, 80 C, 105 C and 125 C until constant weight. The dry tea fungal biomass was ground using a laboratory mill. Preparation of metal and salt solutions The stock solutions of Cu(II) and Cr(VI) (0.25 mol L -1 ) were prepared by dissolving CuSO 4 x 5H 2 O or K 2 Cr 2 O 7 in distilled water. Other concentrations were obtained by dilution and the ph value in the adsorbate solutions was adjusted to desired values with 0.1 mol L -1 HCl. 150

3 The salt solutions were prepared at different ionic strength by dissolving of NaCl, K 2 SO 4, (NH 4 ) 2 SO 4 and Na-acetate in distilled water, respectively. The solutions of K 2 SO 4 and Na-acetate with concentrations higher than 0.5 mol L -1 and 0.1 mol L -1 respectively, could not be prepared because of their low solubility. Fresh dilutions were used for each experiment. All chemicals used were of A.R. grade. Biosorption experiments The biosorption experiment was performed by mixing 0.15; 0.25 or 0.5 g L -1, tea fungal biomass dried at different temperature in 200 ml of the metal ion solutions or metal-salt mixture with metal concentration of 0.4 mmol L -1 at ph 4 for Cu(II) and ph 2 for Cr(VI), respectively. Batch experiments were carried out at 25 C in Erlenmeyer flasks on rotary shaker at 200 rpm. Samples were taken after two hours (10), filtered by using filter paper Watman N 1 to remove the suspended biomass and analyzed for residual Cu(II) and Cr(VI) concentrations. The concentrations of heavy metal ions before and after biosorption were determined by complexometric method (12). The biosorbed quantity of metal ions per g of tea fungal biomass can be calculated based on the mass balance: q (mmol g -1 ) = V (C o C) / m where q is the amount of metal uptake per unit mass of the biosorbent (mmol g -1 ); C o and C (mol L -1 ) are the initial and residual concentrations of metal ion, respectively; V is the volume of the solution (L); m is the dry mass of the biosorbent (g). The removal percentage was calculated as: Removal (%) = ( (C o -C)/C o ) x 100 Each batch experiment was carried out in duplicate and average results are presented. RESULTS AND DISCUSSION Copper(II) and chromium(vi) biosorption properties on dried tea fungal biomass were investigated as a function of initial concentration of different salts (NaCl, K 2 SO 4, (NH 4 ) 2 SO 4 and Na acetate) and dosage of tea fungal biomass dried at different temperatures (20, 70 C, 80 C, 105 C and 125 C). Ionic strength, beside ph is also one of the important factors that influence the heavy metal ions removal. The effect of ionic strength on the biosorption of copper(ii) and chromium(vi) is very interesting. Industrial wastewater often contains other ions such as Mg +, Ca +, Na + and K + which may interfere with the uptake of heavy metal ions by biomass. These metal ions are known to interact with fungal cell through weak electrostatic bonding and play an important role in many biological functions, such as in metal transport channels or pores in the membrane of fungal cells. They may also be used in cationic exchange with metal ions such as Co 2+, Cd 2+, Cu 2+, Zn 2+, Cr 3+, resulting in their uptake. This cationic exchange can occur either in the cell wall, cell membrane or cytoplasm. Thus, the knowledge of the effect of these metal ions is important for efficient 151

4 application of the biomass as biosorbent. The effect of ionic strength was tested by the addition of different concentrations of salts to the heavy metal solutions. Three different values of ionic strength, 0.1, 0.5 and 1 mol L -1 of salts were used and the results were compared with those obtained for metal solutions without salts. Copper(II) and chromium(vi) removal by dried tea fungal biomass in the absence and presence of different salts was studied and the results shown in Fig. 1 and Fig. 2, respectively Copper(II) removal (%) M 0.5 M 1 M Salt Concentration without salt with Na-chloride with K-sulphate with ammoniumsulphate with Na-acetate Fig. 1. Copper(II) removal by dried tea fungal biomass from water in the absence and the presence of different salts (C o =0.4 mmol L -1 ; ph 4; adsorbent dose 0.25 g L -1 ) 25 Chromium(VI) removal (%) M 0.5 M 1 M Salt concentration without salt with Na-chloride with K-sulphate with ammoniumsulphate with Na-acetate Fig. 2. Chromium(VI) removal by dried tea fungal biomass from water in the absence and the presence of different salts (C o =0.4 mmol L -1 ; ph 2; adsorbent dose 0.25 g L -1 ) 152

5 The results clearly demonstrate that in the absence of salts the fungus showed good ability for the Cu(II) and Cr(VI) biosorption. Moreover, the uptake of Cu(II) and Cr(VI) ions was significantly affected by the low concentrations of salts. However, increasing the salinity of (NH 4 ) 2 SO 4 led to a significant increase of the amount of Cu(II) and Cr(VI) removed from the aqueous solution and removal efficiency. Copper(II) removal by tea fungal biomass was 25% and 37% from 0.5 mol L -1 and 1 mol L -1 (NH 4 ) 2 SO 4 containing media, respectively. Chromium(VI) removal by tea fungal biomass was 8% and 12.5% from water with 0.5 mol L -1 and 1 mol L -1 (NH 4 ) 2 SO 4 containing media, respectively. Until even at 0.5 mol L -1 of K 2 SO 4, the biosorbent had a high uptake capacity and the dried tea fungal biomass has been used for efficient removal of chromium(vi) from aqueous solution. Chromium(VI) removal was 21% from 0.5 mol L -1 K 2 SO 4 containing media. The biosorption ability of microorganism with increasing salt concentrations may be a result of the biosorption mechanism. Deng et al. (13) showed that the presence of chloride, nitrate, sulphate and acetate did not greatly affect adsorption. Some inorganic anions existing in the solution such as chloride may also form complexes with metal ions, and therefore, affect adversely the adsorption process (14). On the basis of this results it can be concluded that the effect of ionic strength of different salts on the biosorption of Cu(II) and Cr(VI) depends of experimental conditions for the metal-biomass system. The influence of dried tea fungal biomass dosage on the Cu(II) and Cr(VI) biosorption was examined by varying dosage: 0.15; 0.25 and 0.5 g L -1. The tea fungal biomass was dried at different temperatures: 20 C, 70 C, 80 C, 105 C and 125 C. Figures 3 and 4 show typical sets of data obtained by varying biosorbent dosages during Cu(II) and Cr(VI) biosorption. 40 Chromium(VI) uptake q (mg/g) ,15 0,25 0,5 Adsorbent dose (g/l) o C Fig. 3. The influence of dosage of tea fungal biomass dried at different temperature on copper(ii) uptake (C o =0.4 mmol L -1 ; ph 4) Based on Figs. 3 and 4, the uptake of Cu(II) and Cr(VI) decreased with increase of the dosage of tea fungal biomass. The best results for Cu(II) biosorption of 138 mg g -1 was obtained with 0.15 g L -1 tea fungal biomass dried at 20 C. 153

6 35 Chromium(VI) uptake q (mg/g) ,15 0,25 0,5 Adsorbent dose (g/l) o C Fig. 4. The influence of dosage of tea fungal biomass dried at different temperature on chromium(vi) uptake (C o =0.4 mmol L -1 ; ph 2) In the case of Cr(VI) uptake, the best results of 33 mg g -1 was obtained with 0.15 g L -1 tea fungal biomass dried at 80 C. On the other hand, the metal uptake decreased with increasing the biosorbent dosage, which may be due to the complex interaction of several factors. Tangaromsuk et al. (15) observed this trend in their biosorption experiments. CONCLUSION Biosorption characteristics of dried tea fungal biomass for the removal of Cu(II) and Cr(VI) ions from saline water were examined as a function of salt concentrations and adsorbent dosage of tea fungal biomass dried at different temperatures (20 C, 70 C, 80 C, 105 C, 125 C). Biosorption at an ionic strength of 0.1 mol L -1 had decreasing effect on Cu(II) and Cr(VI) removal. It was observed that (NH 4 ) 2 SO 4 at the concentrations of 0.5 mol L -1 and 1 mol L -1 was more efficient than other salts for metal ions removal. In the case of Cr(VI) removal the best results were obtained with K 2 SO 4 at a concentration of 0.5 mol L -1. However, the salt addition (increasing ionic strength) affected the Cu(II) and Cr(VI) from saline waters due to salt effect. This work can provide useful data for removal of Cu(II) and Cr(VI) ions from salt-bearing waters by dried tea fungal biomass. In the present study, the lowest biosorbent dosage (0.15 g L -1 tea fungal biomass dried at 20 C in case of Cu(II) and at 80 C in case of Cr(VI), respectively) resulted in highest metal uptake of 38 mg g -1 in case of Cu(II) and 33 mg g -1 in case of Cr(VI) uptake. In the case of Cr(VI), better biosorption results were obtained with tea fungal biomass dried at a higher temperature. The tea fungal biomass dried at low temperature is better for Cu(II) biosorption. 154 REFERENCES 1. Terry, P.A. and W. Stone: Biosorption of Cadmium and Copper Contaminated Water by Scenedesmus abundans. Chemosphere 47 (2002)

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8 (0,1; 0,5 1 mol L -1 ) (0,15; 0,25 0,5 g L -1 ) (20 ; 70 ; 80 o ; 105 o 125 C) Cu(II) Cr(VI). - 0,1 mol L -1 - Cu(II) Cr(VI). (NH 4 ) 2 SO 4 0,5 mol L -1 1 mol L -1, Cu(II). - Cr(VI) K 2 SO 4 0,5 mol L -1. K 2 SO 4 Cr(VI) Cr(VI). - 0,15 g L C Cu(II) 80 C Cr(VI) -, 38 mg g -1 Cu(II) 33 mg g -1 Cr(VI). Received 29 May 2007 Accepted 13 July