Characterization of activated Acacia nilotica    seed pods for adsorption of Nickel from aqueous solution

The use of low-cost adsorbent has been investigated in the removal of nickel ions from aqueous solution. The adsorption of nickel is strongly dependent on various parameters such as pH, dosage, contact time and initial concentration of metal. The optimum pH for nickel removal is found to be 7.0. The removal of nickel ions increases with time and attains saturation in about 60–120 min. The experimental data were analyzed with various isotherms such as Freundlich, Langmuir Temkin and Dubinin–Radushkevich adsorption isotherm. The experimental data were fitted into the following kinetic models: Lagergren pseudo-first order, the chemisorption pseudo-second order, Elovich kinetic model, and the intraparticle diffusion model. It was observed that chemisorption pseudo-second-order kinetic model described the sorption process with high coefficients of determination better than any other kinetic models. The results indicate that the second-order model best describes adsorption kinetic data. The adsorbent was characterized; functional group was analyzed by Fourier transform infrared spectroscopy and surface morphology by scanning electron microscope, and energy dispersive X-ray diffraction were analysed.