Kinetics and Thermodynamics of Cadmium Adsorption and Desorption on Montmorillonite

An experimental study of adsorption kinetics and thermodynamics for Cd2+ on the montmorillonite and desorption kinetics and thermodynamics for Cd2+ with simulated acid rain were conducted by simulating the natural environment. The results indicated that the adsorption kinetics and desorption kinetics were fitted to the Lagergren quasi-second equation，the correlation coefficients (R) were larger than 0.98 when the temperatures were 30℃,40℃,and 50℃, respectively. The adsorption capacity of cadmium on montmorillonite exhibited a process of rise- fall-rise-balance with the time delay at different temperature, and desorption capacity were increased at first and then equilibrium with increase of time. Adsorption process of cadmium on montmorillonite was a spontaneous endothermic process, and it was affected little by temperature. Desorption process was a non-spontaneous exothermic process, and temperature had a big influence on it.