Biosorptive removal of arsenite and arsenate from aqueous medium using low-cost adsorbent derived from 'Pods of green peas': Exploration of kinetics, thermodynamics and adsorption isotherms

The present work explores the biosorption characteristics of pods of green peas (PGP) for arsenite [As(III)] and arsenate [As(V)] removal from aqueous medium. Optimization of adsorption parameters like contact time, arsenic concentration, temperature, biosorbent dose and pH through batch mode of experiments was studied. Among the different isotherm models, Langmuir for As(III) and Temkin for As(V) provided the best fit for the obtained data of arsenic sorption onto PGP. D-R mean free energy (E) indicates the process is physisorption. Thermodynamics studies were found to be endothermic, feasible and spontaneous. Kinetically, adsorption follows the pseudo-second-order kinetics in sorption of As(III) and As(V) both. The desorption studies of exhausted PGP show 81% of As(III) and 72% of As(V) could be leached out. Reusability of biosorbent up to 7th cycles of incessant operation supports their commercial importance with very little effects of common ions on sorption capacity.