SYNTHESIS OF NA-4-MICA FROM METAKAOLINITE AND MGO - CHARACTERIZATION AND SR2+ UPTAKE KINETICS

Na-Li-mica. a high-charge-density sodium fluorophlogopite mica of idea l chemical composition Na4Mg6Al4Si4O20F4 . xH(2)O has been prepared fr om a mixture of NaF, MgO and metakaolinite (the latter serving as an i nexpensive aluminosilicate source). Highly crystalline Na-4-mica can b e easily and economically synthesized from the above precursors in the temperature range 850-890 degrees C. Al-27 and Si-29 MAS NMR spectros copy revealed that the Na-4-mica synthesized from metakaolinite is mor e close to the ideal nearest neighbor distribution of Al and Si compar ed to that prepared from magnesium aluminosilicate gel. Selective Sr e xchange kinetic studies showed that the uptake was slow because of the somewhat large particle size as determined by scanning electron micro scopy as well as restricted interlayer spacing.