REMOVAL OF STRONTIUM AND BARIUM FROM AQUEOUS SOLUTIONS BY ADSORPTION ONTO EXPANDED PERLITE

The adsorption of strontium and barium from aqueous solution onto expanded perlite (EP) has been investigated as a function of pH, contact time, adsorbent dosage, and temperature. Sorption experiments indicated that the sorption capacity was dependent on operating variables and the process was strongly pH-dependent. Equilibrium isotherm data were analysed using Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The adsorption was well described by Langmuir isotherm model. The maximum adsorption capacity was found to be 1.14 and 2.486 mg/g for Sr (II) and Ba (II) from the Langmuir isotherm model at 20 degrees C, respectively. Two simplified kinetic models viz. pseudo-first-order and pseudo-second-order models were tested to describe the adsorption process. The kinetic data indicated that adsorption fitted well with the pseudo-second-order kinetic model. Using the equilibrium constant value obtained at four (20, 30, 40, and 50 degrees C) different temperatures, the thermodynamic parameters of the adsorption (Delta G degrees, Delta H degrees, and Delta S degrees) were also determined. The results showed that the adsorption of Sr (II) and Ba (II) ions on EP was exothermic and spontaneous.