Sorption behaviour of copper on chemically modified chitosan beads from aqueous solution

In order to increase the copper sorption capacity (SC) of raw chitosan beads (CB), they were chemically modified into protonated chitosan beads (PCB), carboxylated chitosan beads (CCB) and grafted chitosan beads (GCB) which showed a significant SC of 52, 86 and 126 mg/g respectively while raw chitosan beads (CB) displayed only 40 mg/g. Among the sorbents studied, GCB experienced a higher SC than CB, PCB and CCB. Sorption experiments were performed by varying contact time, pH, presence of co-anions, different initial copper concentrations and temperature for optimization. The nature and morphology of the sorbents were discussed using FTIR and SEM analysis. The copper uptake onto PCB, CCB and GCB obeys the Freundlich isotherm. Thermodynamic studies revealed that the nature of copper sorption is spontaneous and endothermic.