Kinetics and Thermodynamics of Methylene Blue Adsorption by Cereal Chaff

The effect of solution temperature and the determination of the kinetic parameters of methylene blue (MB) adsorption onto cereal chaff were performed to understand the adsorption mechanism. The pseudo-second order kinetic model was fitted to the experimental data and found it was good to predict the adsorption behavior using nonlinear regressive method, suggesting that the mechanism may be a chemisorption process. The activation energy of adsorption (E_a) was 22.4 kJ mol^-1. The thermodynamic parameters (ΔG⁰, ΔH⁰, and ΔS⁰) were also determined from the temperature dependence. The results showed that the process of adsorption MB was spontaneous and endothermic process and an increase in temperature favored the adsorption. The diffusion coefficient was also estimated.