First Potassium Fluoroaluminate Ionic Exchanger for Rapid and Selective Removal of Sr 2+ with High Capacity.

90 Sr, as a typical artificial radionuclide, poses a serious threat to human health and the ecological environment. The selective removal of this radionuclide from industrial nuclear waste is crucial for our environment. Here we report a novel potassium fluoroaluminate, K 2 [(AlF 5 )H 2 O], which was synthesized by a simple low-temperature one-step method. It adopts a 1D AlF 6 -chain structure, which consists of exchangeable potassium ions in between the infinite chains of octahedral Al centers. As a remarkable inorganic ionic exchanger, K 2 [(AlF 5 )H 2 O] has a high chemical stability (resistance of pH=~3-12) and thermal stability (≥~300 °C). It possesses an excellent adsorption selectivity (K d =~6.1×10 4  mL ⋅ g -1 ) and a maximum adsorption capacity of q m =~120.32 mg ⋅ g -1 for Sr 2+ . Importantly, it still keep a very good selectivity for Sr 2+ ions even in the presence of competing Na + , Mg 2+ and Ca 2+ aqueous solutions. K 2 [(AlF 5 )H 2 O] is the first example of fluoroaluminate ionic exchange materials that can capture Sr 2+ . This result opens up a new way to design and synthesize inorganic ionic exchangers for the selective removal of Sr 2+ ions from radioactive waste water.