Kaolinte Based Microbial Composite in Cr(III) sorption from waste waters

This work emphasizes the use of a composite designed from A. niger biomass and kaolinite for the removal of trivalent chromium. Aspergillus niger (obtained from MTCC, Chandigarh) and kaolinite (from INDAL) were taken to develop the composite to treat the solution with 50 ppm Cr(III). Parameters such as ratio of biomass to clay in composite, pH, initial concentration of metal ion, temperature and amount of microbial composite were optimized for biosorption. Maximum biosorption of 61.6% chromium occurred with 2% (w/v) of composite having 1:6 ratio of Aspergillus niger- kaolinite at 5.0 pH and 35oC temperature for 50 ppm Cr(III) solution. The adsorption followed both Langmuir and Freundlich isotherm model with maximum Cr(III) sorption capacity of 4.33 mg g-1. The process was found to be endothermic with ^H = 35.4 kJmol-1 and entropy (^S) of 153.5 JK-1mol. The free energy (^Go) value in the range 10.1-15.6 kJ/mol suggested spontaneous reaction of Cr(III) on the composite. The kinetics of chromium (III) removal by the composite followed second order kinetics with the rate constant value of 3.2x10-2 g mg-1 min-1.