Remediation of Hg(II) ions from aqueous environments using plant gum and clay based nanobiocomposite beads: Equilibrium, kinetics, thermodynamics and Ex-situ studies

The current investigation presents a novel approach for the remediation of Hg (II) ions from aqueous environments using plant gum (PG) and clay based (CL) nanobiocomposite beads (NBC) composed of ZnO nanoparticles and chitosan. Experiments on optimization of parameters were conducted in a batch scale. Under optimized condition maximum removal of Hg (II) was noted as 95.47% and 83.03% in case of PG-NBC and CL-NBC respectively. Equilibrium studies suggested a homogenous mode of adsorption. A good linearity was observed for the pseudo-first-order kinetic model suggesting a physical mode of adsorption. Thermodynamic studies suggested an endothermic and spontaneous nature of the adsorption process. The mechanism was further elucidated using SEM, AFM, EDX and FTIR analyses. Ex-situ studies showed a maximum Hg (II) removal of 75.64% from mining wastewater using PG-NBC in column mode. Regeneration studies suggested that the plant gum based nanobiocomposite (PG-NBC) could be consistently reused up to 6 cycles.