Application of recycled iron oxide for adsorptive removal of strontium

To remove strontium (Sr) efficiently from aqueous solutions is important as Sr-90 is a radionuclide and could be a serious threat to the environment. This study examines the feasibility of Sr-90 removal using BT9, generated from a FBR-Fenton facility that was utilized in treating tannery wastewater. A rapid increased of Sr adsorption was detected when the solution pH increased from 7.11 to 11.22. A maxima adsorption capacity was estimated to be 29.85 mg Sr/g BT9 at 323 K and pH 11.22. Additionally, Sr adsorption decreases with the increase of the M/Sr from 0 to 100, indicating that the outer-sphere mechanism was importantly involved in the Sr adsorption. This Sr adsorption is spontaneous and endothermic, supported by the negative changed standard free energy with temperatures (ΔG° = −5.75, −6.26, −6.72 kJ/mol at 288, 303, and 323 K, respectively) and the positive ΔH° values (2.14 kJ/mol). The positive ΔS° (27.49 J/mol K) further indicates that the randomness increased at solid-solution interface during Sr adsorption.