The effect of electrolyte anion on Cu adsorption–desorption by clinoptilolite

Abstract

Copper adsorption by and desorption from clinoptilolite (natural zeolite) are reflected in this document. The Ca, Mg, and Na release from the substrate, Si, Al dissolution, and Cl −, NO 3 −, SO 4 2− movement were examined. Experimental variables were Cu concentration and electrolyte anion. Three different electrolytes of 0.01 N were used (KCl, KNO 3, K 2SO 4). Tested solutions had different pH values due to different Cu concentrations used. Thus, solution pH was also taken as a variable, and the effects of [H +] differentiation on Cu adsorption and on Si/Al dissolution were also examined. Copper adsorption was found to be higher when KNO 3 was used as electrolyte, compare to KCl and K 2SO 4, which gave almost equal Cu adsorption. Copper desorption follows the order: K 2SO 4>KNO 3>KCl. Large amounts of K + from bulk solution were also adsorbed by the substrate. The dissolution of Al from the zeolitic framework during Cu adsorption was enhanced in the presence of SO 4 2− ions, whereas the presence of Cl − limited the dissolution. The dissolution of Si from the zeolite framework was not found to be affected by the three anions. Cl − and NO 3 − ions were adsorbed by the substrate whereas, SO 4 2− ions were not. From the study of FTIR spectra significant changes for the bands assigned to Si–OH–Al bridges and to hydrogen bonds at the region between 3650 and 3400 cm −1 were observed. After Cu adsorption the monomeric H-bonds for samples in K 2SO 4, are not as extensively destroyed as those for samples in KCl and KNO 3. Such a destruction is a reflection of the extent of Cu 2+ adsorption and on the impact of Cl − and NO 3 −.