Synthesis and characterization of a novel layered tin(IV) phosphate with ion exchange properties

A novel layered tin(IV) phosphate, Sn(NH4PO4)(HPO4)·2H2O (δ-SnP–NH4), was synthesized under mild hydrothermal conditions (190°C) in the presence of urea. The treatment of this compound with mineral acids gave a new phase of tin(IV) bis(monohydrogenphosphate), Sn(HPO4)2·3H2O (δ-SnP–H). The layered nature of the solid was confirmed from amine intercalation, exfoliation in alkaline media, and the ion exchange behavior towards alkali and alkaline earth ions. High affinity (KdCs ∼ 5 × 104 to 2 × 105 mL g−1) and capacity (160–200 mg Cs+ per g of exchanger) for Cs+ makes these materials promising for selective radioactive cesium removal from contaminated groundwater and nuclear waste.