Kinetic study of Malachite Green adsorption on used black tea leaves from aqueous solution

This study presents a kinetic evaluation on the adsorptive removal of Malachite Green (MG), a common pollutant in the textile waste water, by Used Black Tea Leaves (UBTL) as a low cost adsorbent. The adsorption kinetic experiments were carried out in batch process. The effects of contact time, concentration, solution pH and temperature on this removal process were investigated. UV-visible spectrophotometer was used for analysis of MG at pH 4.0. Kinetic studies have shown that the adsorption data partially follow simple first order, second order, pseudo first order and Elovich equation for different initial concentrations at pH 2.0 but well expressed by pseudo second order rate equation. Pseudo second order rate equation was used to determine the equilibrium amount adsorbed and equilibrium concentration for different initial concentrations, temperatures and pH. The equilibrium amount adsorbed and pseudo second order rate constant were found to increase with increasing temperature indicating chemical nature of adsorption. The numerical values of apparent activation energy, Ea and thermodynamic parameters ?Go, ?Ho, and ?So of the process also supported the chemisorption of MG on UBTL at pH 2.0. The effect of solution pH on the adsorption kinetics showed that the amount adsorbed linearly increase with increasing solution pH suggesting deprotonaton dominants the adsorption of MG on UBTL. The adsorption capacity of UBTL to MG was obtained 227.3 mg/g at pH 6.0 and 30o C.