Efficient Capture of Sr2+ Ions by a Layered Potassium Neodymium Phosphate

90Sr has a long half-life, strong radioactivity, and high mobility. The removal of radioactive strontium from the water environment is of great significance to human safety and the sustainable development of nuclear energy. In this study, a two-dimensional rare earth phosphate K3Nd(PO4)2 efficiently captured Sr2+ ions in aqueous solutions. At room temperature, the adsorption isotherm, kinetics, and pH dependence experiments of K3Nd(PO4)2 for Sr2+ ions were examined (V/m = 1000 mL/g, 12 h contact time). The experimental results show that the maximum adsorption capacity of K3Nd(PO4)2 for Sr2+ (qmSr) was 42.35 mg/g. The removal efficiency for Sr2+ (RSr) was 87.47% within 24 h. It had a good affinity with Sr2+ ions in neutral or even high alkaline environments (distribution coefficient KdSr = 1.46 × 106 mL/g, RSr = 99.93%). The adsorption mechanism was attributed to the ion exchange between Sr2+ and K+ ions by batch adsorption experiments combined with multiple characterizations, including XPS, EDS, and PXRD. This is the first report of Sr2+ removal by ion exchange via rare earth phosphate materials with a two-dimensional structure. This work provides insight into the future development of rare earth phosphates as ion exchange materials for radionuclide remediation.