ADSORPTION KINETIC OF COPPER FROM AQUEOUS SOLUTION ON PALYGORSKITE CLAY

The adsorption kinetics characteristics of Cu~(2+) in water on palygorskite based on the purification of palygorskite clay were studied through static adsorption experiments,with a discussion on the adsorption kinetics models,the apparent activation energy, activation thermodynamic parameters of adsorption and the rate-limiting step of adsorption.The results show that the adsorption proceeds rapidly and the equilibrium is reached after about 60min under the experimental conditions.The adsorption processes are found to follow Lagergren pseudo-second-order equation most effectively and the rate constant of pseudo-second-order equation increases with decreasing initial concentration and the rise of temperature.The apparent adsorption activation energy is 18.82kJ/mol and the adsorption belongs to active chemical adsorption.The adsorption activation enthalpy is 16.26 kJ/mol,activation Gibbs free energy varies in the range of 75.40-79.38 kJ/mol and the activation entropy of adsorption is-198.50 J/(mol·K).The activation process is endothermic and it belongs to the association reaction mechanism.The adsorption rate is controlled by film diffusion and intra -particle diffusion simultaneously through the entire adsorption period.The film diffusion plays an important role at low initial concentration and the effect of intra-particle diffusion is more obvious at high initial concentration.