Kinetic, mechanistic and thermodynamic studies of removal of arsenic using Bacillus arsenicus MTCC 4380 immobilized on surface of granular activated carbon/MnFe2O4 composite

The ability of biofilm of Bacillus arsenicus MTCC 4380 supported on Granular activated carbon/MnFe2O4 composite for removing As(III) and As(V) ions from wastewater were investigated, in terms of kinetics, mechanistic and thermodynamics. Optimum biosorption/bioaccumulation conditions were estimated as a function of contact time and temperature. The equilibrium was achieved after about 180 min at 30 °C temperature. Non-linear regression analysis was performed for determining the best-fit kinetic model based on three correlation coefficients and three error functions and for forecasting the parameters involved in kinetic models. The results exhibited that Brouser-Weron-Sototlongo for both As(III) and As(V) was able to provide realistic explanation of biosorption/bioaccumulation kinetic. Applicability of mechanistic models in the current study exhibited that the rate controlling step in the biosorption/bioaccumulation of both As(III) and As(V) was film diffusion rather than intraparticle diffusion. The estimated thermodynamic parameters ΔG0, ΔH0 and ΔS0 revealed that the biosorption/bioaccumulation of both As(III) and As(V) on the adsorbent attached with biofilm was feasible, spontaneous and exothermic in nature. The activation energy (Ea) assessed from Arrhenius equation indicated the nature of biosorption/bioaccumulation being ion exchange type. Increasing concentration of As(III) and As(V) furthermore improved the initial sorption rate, h. Acquired results indicated that the biofilm supported on adsorbent tried are very encouraging for removal of arsenic.