Adsorption of Copper Ions by Microwave Treated Bentonite

Changes of bentonite surface structure under the influence of direct microwave irradiation during adsorpion of Cu2+ from concentrated solutions were investigated by X-ray and EDS analysis. The microwave treated bentonite (MTB) has been proved to have enhanced adsorption capacity for copper due to improved pore structure and some peculiarities of adsorption mechanism. The non-linear fitting of experimental data to the theoretical isotherms have demonstrated that the adsorption on natural bentonite fitted the Toth model, whilst microwave-treated bentonite fitted the Langmur-Freundlich model. The isotherm modeling allowed predicting the maximal adsorption capacities 44.8 mg/g. XRD and SEM analysis of MTB sample after adsorption indicated formation of microcrystals of individual copper compound. The adsorption on MTB sample takes place not only in pores or in monomolecular layer on the bentonite surface, but the prevalent mechanism is surface-induced co-precipitation of copper as microcrystals of individual copper compound.