Removal of cesium and strontium from liquid nuclear waste by using melamine and styrene based network

Removal of strontium and cesium have a vital importance for radioactive waste management because of their long half-life about 30 years. In this work melamine and styrene based polymeric sorbent was synthesized and characterized by FTIR, XRD, SEM, BET and TGA. Melamine styrene based polymer (MSBP) utilized as an adsorbent for removing Cs+ and Sr2+ ions from solution. In this respect, adsorption behaviors of Cs+ and Sr2+ onto melamine styrene based polymer was studied as a function of pH, amount of adsorbent, initial Sr2+ and Cs+ concentration, contact time, temperature and particle size. Also, adsorption rate of radioactive strontium and cesium were investigated by using LSC (liquid scintillation counter) and gamma spectroscopy. The adsorption data were fitted to Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Melamine based polymer reached maximum adsorption capacity for Cs+ as 333 mg.g-1, for Sr2+ as 142,9 mg.g-1. At five different temperatures of 293 K, 303 K, 313 K, 323 K and 333 K the thermodynamic parameters such as free energy ΔG, entropy ΔS and enthalpy ΔH of Cs+ and Sr2+ adsorption on MSBP were examined. Adsorption mechanism presented endothermic feature for strontium with positive ΔH values and exothermic feature for cesium with negative ΔH values. The negative values of Gibbs free energy ΔG and the positive entropy ΔS revealed that both Cs+ and Sr2+ adsorption on MSBP occurred spontaneously and irreversible, respectively. Pseudo first order and second order rate equation were investigated as a function of kinetic parameters. And it was seen that pseudo second order rate equation was more convenient for adsorption of both Cs+ and Sr2+ onto MSBP.