Influences of salt concentration, loading and pH on strontium adsorption

Abstract

The adsorption of Sr on clay which contains zeolites and montmorillonite mixtures was investigated in solutions of NaCl by means of a batch technique. Sr retention was reduced with increasing NaCl concentration from 5.10(-4) to 5.10(-1) M. Distribution coefficients (K-d) linearly increased with pH in the acidic region but they were almost independent of pH in neutral and alkaline solutions. By fitting the data of the Dubinin-Radushkevich (D-R) isotherm, the mean energies of adsorption and adsorption capacities of Sr at different pH values were calculated. The results showed that the mode of adsorption below pH 4.5 is ion exchange, while above that value a multilayer adsorption occurs. Adsorption data were fitted to the Freundlich isotherm and from empirical Freundlich parameters a site distribution function was calculated.