Highly efficient and selective removal of Sr2+ from aqueous solutions using ammoniated zirconium phosphate

Abstract

Radioactive wastewater contains high concentrations of 90Sr (strontium-90), which poses a serious threat to human health and ecosystems. Layered ammoniated zirconium phosphate (A-ZrP) was synthesized herein using a one-pot hydrothermal method for the adsorptive removal of Sr2+. ZrP was ammoniated between its structured layers to increase interlayer spacing and facilitate the access of Sr2+ ions to adsorption sites and realize adequate ion exchange. A-ZrP achieved a faster equilibration time (120–240 min) compared with that of other ZrPs (250–500 min). A-ZrP exhibited excellent Sr2+ uptake selectivity (Kd = 5.3 × 105 mL g−1) and maximum adsorption capacity (qm = 341 mg g−1) at a pH of 7. Moreover, A-ZrP displayed high selectivity in various contaminated solutions, with a high Kd value of 681 mL g−1, even in artificial seawater. The adsorption mechanism was found to involve ion exchange between NH4+ and Sr2+, primarily because of electrostatic interactions and chemical hardness. These results highlight the potential of A-ZrP as an efficient adsorbent for the selective removal of Sr2+ ions from wastewater.