Hydrothermal Synthesis of Multifunctional Biochar-supported SALEN Nanocomposite for Adsorption of Cd(II) Ions: Function, Mechanism, Equilibrium and Kinetic Studies

Facile hydrothermal synthetic technique was employed for the fabrication of bis(salicylidene)ethylenediamine (SALEN) grafted multifunctional nanocomposite biochar, aiming at the efficient removal of cadmium (Cd). The elemental composition and structure of the composite and the cadmium loaded sorbent were characterized using EDX, FTIR and SEM. Variables affecting cadmium removal such as initial metal ion concentration, contact time and pH were investigated by batch experiment. Maximum adsorption capacity of 8220 mg kg-1 was obtained at optimal pH 5 with percentage removal efficiency of 99.30% for 4480 ppm initial metal ion dosage. The data simulated using the adsorption and kinetic models were fitted well in the Freundlich isotherm implicating multilayer adsorption-chemisorption process and pseudo-second-order kinetic as the rate limiting steps. Critical examination of the adsorption mechanism showed that inner-sphere complexation, ion exchange, co-precipitation and electrostatic attraction are the main driving force in the mechanistic interaction of the Schiff base N2O2 surface functionalized nanocomposite biochar with cadmium. The new nanocomposite is of low cost, benign, effective and efficient for the removal of cadmium in comparison with industrial sorbents and other functionalized biomaterials, and highly recommended for decontamination of cadmium polluted sites.