Kinetics, equilibrium and thermodynamic studies on biosorption of hexavalent chromium by dead fungal biomass of marine Aspergillus niger

Quite a number of reports are available on metal binding capacity of different groups of microorganisms. However, reports on the equilibrium studies on biosorption by marine fungi are quite inadequate. The present study was carried out in a batch system using dead biomass of marine Aspergillus niger for the sorption of Cr(VI). The removal rate of Cr(VI) was increased with a decrease in pH and an increase in Cr(VI) and biomass concentration. A. niger exhibited the highest Cr(VI) uptake of 117.33 mg g−1 of biomass at pH 1.0 in the presence of 400 mg l−1 Cr at 50 °C. Kinetics studies based on fractional power, zero order, first order, pseudo-first order, Elovich, second order and pseudo-second order rate expressions have also been carried out. The experimental data were analyzed using five, two-parameter isotherms (Langmuir, Freundlich, Dubinin–Radushkevich, Temkin and Halsey). It was observed that Langmuir model exhibited the best fit to experimental data. Thermodynamic parameters of the biosorption (ΔG°, ΔH° and ΔS°) were also determined.