Kinetic and thermodynamic studies of the adsorption of nickel (ii) ions from aqueous solutions by smectite clay from Sabga-cameroon

The adsorption of Ni (II) ions from aqueous solution on smectite from Sabga (Sa0) has been investigated. The influences of the initial concentration, Co, temperature, T °C, and contact time, t, on the adsorption performances have been experimentally verified by a batch method. These results have showed that the amount of Ni (II) ions adsorbed increases with increased contact time, t, and that equilibrium adsorption is reached in 15 minutes. The experimental results obtained are described by Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich (D-K-R) isotherm models. The Langmuir adsorption isotherm described the adsorption data very well at all studied temperatures. The maximum adsorption capacity; Qo, determined from the Langmuir adsorption isotherm studies was found to be 6.68 mg/g at 328 °K. Pseudo-first order, pseudo-second order, the mass transfer, Elovich and the intraparticular diffusion kinetic models were used to describe the kinetic data obtained. The experimental data fitted well to the pseudo-second order kinetic model, which indicates that chemical adsorption is the rate-limiting step. Thermodynamic parameters, such as ∆G°, ∆H°, and ∆S° were also calculated using adsorption equilibrium constant obtained from the Langmuir isotherm studies. These results suggest that the adsorption of nickel (II) ions on smectite is a spontaneous and endothermic process.