Adsorption of Nickel, Ni(II), in Aqueous Solution by Modified Zeolite as a Cation-Exchange Adsorbent

In this study, the modified zeolite (MZ) and zeolite 3A (RZ) were used as adsorbents for removal of Ni(II) from aqueous solution. Both adsorbents were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The process parameters were the ratio of modifier to adsorbent, adsorbent dosage, pH, time, initial metal concentration, and temperature. At 298 K and 200 ppm Ni(II), the optimal conditions for the modifier to zeolite 3A ratio, adsorbent dosage, pH, and time were 1.7, 12 kg/m(3), 7, and 240 min, respectively. MZ adsorbed 95% of Ni(II) in optimal conditions which is 20% higher than RZ in the same experimental conditions. Kinetic data for adsorption of Ni(II) on both adsorbents indicated pseudo-second order, Elovich and intra particle diffusion models fitted well with experimental data. Among the isotherms, Langmuir and Freundlich fitted well for adsorption of Ni(II) on MZ, with q(m) = 0.433 mol/kg (298 K) while for RZ, the best fit was obtained by Langmuir, with q(m) = 0.28 mol/kg (298 K). At different temperatures, the thermodynamic parameters (Delta S-0, Delta G(0) and Delta H-0) illustrated spontaneous and endothermic nature for adsorption of Ni(II) on MZ, and their values were 0.182 kJ/mol K, -5.89, 48.47 kJ/mol, respectively, at 298 K.