Analysis of breakthrough curves of Pb and Zn sorption from binary solutions on natural clinoptilolite

Abstract

The removal of Pb and Zn ions from binary aqueous solutions on fixed bed of natural clinoptilolite has been examined. Experiments were performed with different bed depths by using Pb+Zn solutions of the same total molar concentration but with different molar ratios of Pb/Zn. The breakthrough capacity of zeolite increases with bed depth due to longer contact times and higher numbers of mass transfer units. The capacity does not depend on the Pb/Zn ratio at H=4cm, while at H=12cm it slightly increases at higher Pb/Zn ratios. The results from service cycles have shown displacement of Zn ions bound on zeolite with Pb ions from the feeding solution due to the difference in selectivity of zeolite toward examined ions, which has been confirmed by results from regeneration cycles. This effect is more evident at higher bed depths. Column method examinations allow many service and regeneration cycles without a decrease in capacity or exhaustion of ion exchange ability of clinoptilolite. The Thomas model has provided satisfied agreement with experimental points and enables calculation of exhaustion capacity which is in agreement with experimentally obtained capacities for all examined experiments.