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°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°C) different temperatures, the thermodynamic parameters of the adsorption (Δ G °, Δ H °, and Δ S °) were also determined. The results showed that the adsorption of Sr (II) and Ba (II) ions on EP was exothermic and spontaneous.