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Kinetics and thermodynamics study of copper ions removal by natura clinoptilolite

The process of removal of copper ions by means of clinoptilolite type natural zeolite has been studied as a function of the particle size and temperature. Results shown that increase temperature and decrease of particle size improves removal of copper from aqueous solutions. The parabolic diffusion model well described process in all examined range of time and shows that calculated diffusion coefficients increases with temperature. This increase is more visible at higher particle sizes what assume diffusion through zeolite particle as main mass transfer mechanism. The film diffusion model provides calculation of initial sorption rate (k´) and dimensionless parameter proportional to the diffusion film thickness (xi), in relation of particle size and temperature. Diffusion from the surface of zeolite particles through the micro and macro pores is well described with homogenous diffusion model, where changes of the calculated overall rate constants is observed at 60 minute of the process. This indicates the change of mass transfer rate trough porous zeolite particle. The activation energy (Ea), activation enthalpy (delta_H), activation entropy (delta_S) and free energy of activation (delta_G) have been calculated based on kinetic data. These thermodynamic parameters characterize process as diffusion dependent, weakly endothermic and nonspontaneous, where structural changes in structure of natural zeolite particle are not observed.

clinoptilolite ; copper ; diffusion ; kinetic models ; thermodynamic parameters

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