Kinetic and Thermodynamic Studies of Ni(II) Adsorption onto Activated Carbon of Abelmoschus manihot from Aqueous Solutions

Adsorption behavior of Ni(II) onto activated carbon of Abelmoschus manihot (AC-AM) is studied as a function of temperature and time under optimized adsorbent dosage, pH, and concentration of adsorbate. In order to investigate the kinetic mechanism of adsorption and potential rate controlling steps; Lagergren pseudo-first-order, Elovich, Ritchie, Blanchard, second-order, intraparticle diffusion, and pseudo-second-order kinetic models have been used to fit the experimental data. Out of all the models tested, the pseudo-second-order kinetic model provided the best fit in the present case. Thermodynamic study revealed that nickel adsorption onto AC-AM is exothermic in nature and adsorption is spontaneous. The estimated thermodynamic parameters indicate that the adsorption follows physisorption, with nickel removal as high as 94%.