Batch kinetic study of sorption of methylene blue by perlite

Batch sorption kinetics of methylene blue by perlite have been studied in terms of pseudo-first-order, pseudo-second-order and intra-particle diffusion models. The results showed that sorption process was best described by the pseudo-second-order model. The correlation coefficients, r2, obtained from pseudo-second-order model were higher than 0.98 under all the experiment conditions. The effects of agitation speed, initial dye concentration and solution temperature on kinetic parameters (sorption rate constant, initial sorption rate, equilibrium sorption capacity, etc.) are discussed. While the values of sorption rate constants (k2) and initial sorption rates (h) increased with increasing agitation speeds and solution temperatures, it was seen that the values of k2 decreased and the values of h increased with increased initial dye concentration. The values of equilibrium sorption capacity from pseudo-second order (q2) were in the best agreement with experimental data (qe) in each experimental condition. Moreover, the activation energy (Ea) of sorption calculated using the pseudo-second-order rate constants was found to be 10.31 kJ/mol from an Arrhenius plot. The value of Ea indicated that sorption was controlled by an intra-particle diffusion mechanism as well as by pseudo-second-order kinetics.