Highly Efficient Removal of Sr2+ by a Layered Potassium Phosphatoantimonate under Neutral and Acidic Conditions
Radiostrontium remediation is crucial for ecological protection and sustainable development of nuclear energy. However, efficient removal of 90Sr from complex radioactive liquid waste, especially under acidic conditions, remains challenging due to material instability and intense proton competition. Herein, the rapid and highly selective capture of Sr2+ in neutral and even acidic solutions has been achieved by a layered potassium phosphatoantimonate KSbP2O8 with excellent radiation and thermal stability. Under neutral conditions, it possesses high maximum adsorption capacity (qmSr = 110.25 mg g−1), rapid adsorption kinetics (the removal rate (RSr) of 91.54% within 30 min), and excellent selectivity for Sr2+, and facile regeneration. Particularly, even under acidic conditions (pH 2.0), KSbP2O8 still maintains excellent Sr2+ removal capacity (qmSr = 79.38 mg g−1), fast kinetics, and high selectivity. A mechanism study by multiple characterizations reveals that the efficient Sr2+ removal of KSbP2O8 mainly stems from ion exchange between Sr2+ and interlayer K+ in KSbP2O8, which is attributed to the synergy between the Sb5+-induced Brønsted acidity and the high charge density of the anionic framework. This study demonstrates the exceptional capability of phosphatoantimonates to selectively capture Sr2+ under acidic conditions, highlighting the potential of phosphatoantimonates as effective scavengers for radiostrontium remediation.