Adsorption of Nickel Ions from Petroleum Wastewater onto Calcined Kaolin Clay: Isotherm, Kinetic and Thermodynamic Studies

Abstract

The removal of nickel ions onto calcined kaolin clay using a batch adsorption technique was conducted. The effect of the adsorbent mass, contact time and temperature on the removal process was investigated. The calcined kaolin clay was characterized using X-ray fluorescence (XRF) and Fourier-Transform InfraRed spectroscopy (FTIR). The adsorption data was analyzed by isotherm, kinetic and thermodynamic studies. The major chemical components in the clay are alumina (41.14 wt%) and silica (53.16 wt%). FTIR showed that the functional groups of aluminium monoxide (Al-O) and silicon monoxide (Si-O) are present in the clay. The study yielded a removal efficiency of 89.89% for nickel ions at 25°C. The adsorption process appeared to follow a Freundlich isotherm and pseudo-second order kinetics were found to be in good agreement with the experimental data. The thermodynamics of the rate processes showed the adsorption of nickel ions to be endothermic and negative values of Gibbs free energy indicated the spontaneity of these processes. This proves that calcined kaolin clay is a good material for the removal of nickel ions from the wastewater produced by petroleum refineries.