Kinetics of Cr(VI) adsorption on used black tea leaves

Kinetic investigations were carried out to evaluate the applicability of used black tea leaves (UBTLs) as a low-cost adsorbent to the removal of chromium(VI) from aqueous solutions. The effects of various kinetic parameters were investigated using a batch process. The adsorption of Cr(VI) on UBTLs occurs rapidly in the first day, followed by a slow process that requires more than 10 days to reach its equilibrium. The initial adsorption rate increases with increasing initial concentration of Cr(VI) in the solution and processing temperature. The adsorption kinetics follows Richie's pseudo-second order rate equation better than the Lagergren's pseudo-first order one. The rate constant of the pseudo-second order adsorption is affected by the processing conditions such as the initial Cr(VI) concentration, solution pH, temperature and foreign ions. The results of the kinetic experiments showed that the adsorption of Cr(VI) on UBTLs is an endothermic process and the activation energy of adsorption is 16.3 kJ mol(-1).