Biosorption of bivalent metal ions from aqueous solution by an agricultural waste: Kinetics, thermodynamics and environmental effects

The ability of Neem oil cake (NOC), a bio-waste material to remove Cu(II) and Cd(II) ions from aqueous solution was investigated. The influence of pH, sorbent dose, concentration, temperature, and contact time on the sorption of Cu(II) and Cd(II) on NOC has been studied by batch process. The sorption was found to be maximum in acidic medium and increases with increase in initial concentration. Percent deviation (P) and regression coefficient (r2) for Langmuir and Freundlich sorption isotherms shows better fitting of the models. Thermodynamics parameters indicate that the process is endothermic and spontaneous. Activation energies for Cu(II) and Cd(II) were calculated from Dubinin–Redushkevich (D–R) isotherms are high 8.3–8.7 and 7.17–11.4 kJ mol−1 showing that chemisorption is involved. The sorption kinetics was found to follow pseudo-second-order model.