First Potassium Fluoroaluminate Ionic Exchanger for Rapid and Selective Removal of Sr2+ with High Capacity

Abstract

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, K₂ [(AlF₅ )H₂ O], which was synthesized by a simple low-temperature one-step method. It adopts a 1D AlF₆ -chain structure, which consists of exchangeable potassium ions in between the infinite chains of octahedral Al centers. As a remarkable inorganic ionic exchanger, K₂ [(AlF₅ )H₂ O] has a high chemical stability (resistance of pH=~3-12) and thermal stability (≥~300 °C). It possesses an excellent adsorption selectivity (K_d =~6.1×10⁴ mL ⋅ g^-1 ) and a maximum adsorption capacity of q_m =~120.32 mg ⋅ g^-1 for Sr²⁺ . Importantly, it still keep a very good selectivity for Sr²⁺ ions even in the presence of competing Na⁺ , Mg²⁺ and Ca²⁺ aqueous solutions. K₂ [(AlF₅ )H₂ O] is the first example of fluoroaluminate ionic exchange materials that can capture Sr²⁺ . This result opens up a new way to design and synthesize inorganic ionic exchangers for the selective removal of Sr²⁺ ions from radioactive waste water.