Bulk synthesis and selective exchange of strontium ions in Na ₄Mg₆Al₄Si₄O₂₀F ₄ mica

ONE of the principal long-term problems associated with nuclear fission reactions is the generation of large amounts of radioactive strontium isotopes, particularly 90Sr. An effective method for the removal and entrapment of strontium from contaminated environments is therefore desirable to prevent potential health problems associated with radionuclide ingestion1-5. In this context, inorganic cation exchangers have been useful by virtue of their capacity for structure-specific ion exchange6-12. We report here that 'Na-4-mica'13-15, a highly charged sodium fluorophlogopite mica (Na ₄Mg₆Al₄Si₄O₂₀F ₄), can be used for the selective removal of strontium ions from solution and for strontium immobilization at room temperature. We also report a novel method for bulk synthesis of 'Na-4-mica' as a pure phase. This material is unique among highly charged or brittle micas because of its ability to undergo a hydration reaction, which allows the material to be used as a highly selective strontium-ion sieve. This or similar compounds could find potential application in the decontamination and disposal of nuclear waste.