The Sorption of Ni(II) by Grape Shell Ash from Aqueous Solution: Kinetic and Thermodynamic Studies

The sorption of Ni(II) onto grape shell ash (GSA) was studied by performing batch kinetic sorption experiments. The influences of major parameters in Nickel(II) ions sorption on GS such as initial of pH, initial concentration of Ni(II) ions, the initial temperatures of solution, and contact time were investigated. The maximum increase in the rate of sorption of Ni(II) ions on GS was observed at an initial pH = 5, initial concentration of nickel 50 mgL−1, temperature of solution (328 K), and t=90 min. The rate constants and the equilibrium sorption capacities were calculated. The results indicate that the sorption process follows the second-order kinetics and the values of rate constants were found to be 0.224, 0.402, 0.193 and 0.123 min−1 at 298, 308, 318, and 328 K, respectively. The values of correlation coefficients for the adsorption of Ni(II) on GSA from all the systems were found to be 0.999, and the values of predicted equilibrium sorption capacities showed good agreement with the experimental equilibrium uptake values. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) of the adsorption process were calculated, and these parameters showed that the adsorption process is spontaneous