Study on biosorption of Cr(VI) by Mucor hiemalis

Many investigations have been carried on metal binding capacity of different groups of microorganisms. However, the reports on the kinetic, thermodynamic and desorption study of biosorption process are quite limited. The present study was carried out in a batch system using Mucor hiemalis for its sorption and desorption study of Cr(VI). M. hiemalis exhibited the highest Cr(VI) uptake of 53.5 mg/g at an initial pH of 2.0. Equilibrium data fitted well to Langmuir isotherm model. Biosorption showed pseudo-second order rate kinetics at different initial concentration of Cr(VI) and different dose of M. hiemalis. The activation energy of the biosorption (Ea) was estimated as 4.0 kJ/mol using Arrhenius equation. Using the equilibrium constant value obtained at different temperature, the thermodynamics properties of the biosorption (ΔG°, ΔH° and ΔS°) were also determined. The biosorption of Cr(VI) onto M. hiemalis was found to be endothermic. Desorption data showed that nearly 99% of the Cr(VI) adsorbed on M. hiemalis could be desorbed using 0.1N NaOH. Study with the cyclic use of a batch of M. hiemalis repeatedly after desorption, showed that it retain its activity up to five sorption and desorption cycles.