Biosorption of Ni(II) from aqueous solutions by Litchi chinensis seeds

The potential of Litchi chinensis seeds (LCS) for biosorption of Ni(II) ions from aqueous solutions was investigated in batch systems in terms of kinetics, equilibrium and thermodynamics. Experimental data showed that the biosorption capacity of LCS was dependent on operating variables such as solution pH, initial Ni(II) concentration, contact time, and temperature. The optimum pH value for Ni(II) biosorption was 7.5. Significant enhancement of Ni(II) biosorption was observed by increasing initial metal concentration and temperature. Modeling of sorption kinetics showed good agreement of experimental data with the pseudo-second-order kinetic model. Langmuir model exhibited the best fit to experimental data. According to this isotherm model, the maximum Ni(II) biosorption capacity of LCS is 66.62 mg g−1. The calculated thermodynamic parameters showed that the biosorption of Ni(II) ions is an endothermic and non-spontaneous process. Results indicate that LCS can be used as an effective and environmentally friendly biosorbent to detoxify Ni(II)-polluted wastewaters.