Strontium and calcium ion adsorption by molecularly imprinted hybrid gel

The adsorption of strontium and calcium ions by strontium ion-imprinted hybrid gel derived from bis(trimethoxysilylpropyl)amine (TSPA) was comparatively studied. The effects of initial solution pH, ionic strength, initial metal ion concentration, and temperature on the equilibrium adsorption amount and the separation factor between strontium and calcium ions were comprehensively investigated. In description of the adsorption kinetics, the pseudo second-order model was found to be more suitable than the pseudo first-order model. In general, the equilibrium adsorption amount of both Sr2+ and Ca2+ ions was found to increase with the increase in both the initial metal ion concentration and pH, but not to be so sensitive to ionic strength and temperature. The separation of Sr2+ and Ca2+ ions could rely on the difference in adsorption kinetics, because Sr2+ ions were found to adsorb more rapidly than Ca2+ ions at the early adsorption stage.