Equilibrium, Kinetic and Thermodynamic Studies for the Retention of Cesium-137 from Wastewater Using Low-Cost Sorbent

Herein, sorption of 137Cs onto modified activated carbon (MAC) was carried out implying kinetics and equilibrium studies. The sorption results obeyed to a pseudo-1st-order kinetic and were applied to different isotherm models. According to the correlation coefficients,R2, the Langmuir, Freundlich, and Frumkin isotherm models successfully described the obtained data rather than Temkin isotherm. Based on the R2, the equilibrium data followed the sequence Langmuir>Freundlich>Frumkin>Temkin isotherm. The negative values of Gibbs free energy revealed that the removal process was feasible and spontaneous. The negative values of enthalpy clarified that the process is an exothermic one, suggesting that retention of 137Cs decreased with raising reaction temperatures. The values of ΔH << 25 kJ/mol indicating that the adsorption process of cesium 137Cs ions onto MAC is a physical adsorption process while the positive entropy values demonstrated an increase in randomness among the solid-liquid phase during adsorption. Finally, the sorption results revealed that the MAC is a suitable material for the capture of 137Cs from low-level radioactive waste.