Kinetics, equilibrium and thermodynamics studies on Cd(II) removal from aqueous solution by magnesite tailing

Abstract

Magnesite tailing for the removal of Cd(II) from aqueous solutions has been investigated using batch process. The effects of various parameters such as initial pH, adsorbent dosage, contact time and temperature on the removal of Cd(II) have been investigated. Kinetic models are applied to describe the adsorption kinetics of Cd(II) onto magnesite tailing. The adsorption kinetics follows well the pseudo second order kinetic model. The Langmuir, Freundlich and D-R isotherm models have been used for the analysis of adsorption equilibrium. The Langmuir isotherm model fits the equilibrium data. The monolayer adsorption capacity of magnesite tailing is found to be 38.46 mg/g at 45°C. The thermodynamic parameters show that the adsorption process is feasible, spontaneous and endothermic. The Cd(II) - magnesite tailing interactions are confirmed by the Scanning electron microscope (SEM) and the Fourier transform infrared spectroscopy (FTIR). A single stage batch adsorber was designed for different adsorbent dosage using Langmuir isotherm. It is determined that approximately 99% of Cd(II) from aqueous solution could be removed at a pH value of 6, an adsorbent dosage of 0.3 g / 50 mL solution, a contact time of 24 h, an initial solution concentration of 10 mg/L and a temperature of 25°C. The results indicate that magnesite tailing could effectively be used for the removal of Cd (II) from aqueous solutions.