Biosorption of cr (vi) by resting cells of aspergillus sp.
Hexavalent chromium (Cr (VI)) is one of the major pollutants in the environment and is frequently present in wastewaters from industries such as dyes, electroplating, metal cleaning, leather industries, plating, photography, tanneries etc. The conventional treatment techniques used for removal of Cr (VI) ions from wastewaters are expensive and result in the production of harmful by-products and are not efficient when initial Cr (VI) concentration is in the range of 10-100 mg/L (Aksu et at., 2001). The potential application of microorganisms as biosorbent for the removal of heavy metals has been recognized as an alternative to the existing conventional methods for detoxification of industrial wastewaters. Removal of Cr (VI) from aqueous solution is reported by using the growing, resting and non-living cells of microorganisms (Muter et at., 2001, Srinath et at., 2002). However, most of the work to remove Cr (VI) have been carried out using non-living fungal cells (Nourbaksh et at., 1994, Gupta et at., 2001, Srinath et at., 2002) having advantages over growing and resting cells due to the absence of toxicity limitations, requirements of growth media and nutrients. The metal uptake by the growing as well as the resting cells, though is a function of cell age, composition of growth media and pH of the solution, the cells can be maintained biologically active to remove Cr (VI) from aqueous solution by maintaining the suitable cell energetic biological reaction conditions, whereas biological reactions are no longer continued in case of non-living biomass as the cells are dried. Resting cells have the advantage that they require very low maintenance energy to remain biologically active. The present study has been conducted to evaluate the potential of the resting cells of the Aspergittus sp. as a sorbent for Cr (VI) removal from aqueous solution. Effects of pH, initial Cr (VI) concentration, biomass concentration and age of the culture on Cr (VI) removal from aqueous solutions were studied using synthetic Cr (VI) solution in batch bioreactors. The adsorption constants were determined from the equilibrium Langmuir adsorption isotherm.