Highly Efficient Removal of Sr2+ by a Layered Potassium Phosphatoantimonate under Neutral and Acidic Conditions

• • KSbP2O8 achieves a maximum Sr2+ adsorption capacity of 110.25 mg g−1 under neutral conditions, outperforming many existing inorganic exchangers and enabling efficient remediation of neutral radioactive wastewater. • • At pH 2.0, KSbP2O8 retains a high capacity of 79.38 mg g−1, demonstrating exceptional acid resistance and addressing the bottleneck of material instability in acidic HLLW treatment. • • Rapid kinetics: 91.54% Sr2+ removal within 30 minutes under neutral conditions, facilitating fast, continuous-flow processing in industrial settings. • • The material exhibits excellent selectivity for Sr2+ over competing ions (e.g., Na+, Cs+) and facile regeneration, reducing secondary waste and operational costs.