Alkali metal and alkaline earth metal ion exchange with Na-4-mica prepared by a new synthetic route from kaolinite

Abstract

The ion exchange selectivities of a high-charge-density fluorophlogopite mica, Na-4-mica (ideal chemical composition Na ₄ Mg ₆ Al ₄ Si ₄ O ₂₀ F ₄ ·xH ₂ O) were investigated for alkali metal ions (Li ⁺ , K ⁺ and Cs ⁺ ) and alkaline earth metal ions (Sr ²⁺ and Ba ²⁺ ). The ion exchange isotherms were obtained at room temperature using Na-4-mica with a hydrated 12.11 Å lattice, which was easily and economically prepared from a mixture of NaF, MgO and calcined kaolinite. The selectivity depended considerably on the degree of loading of metal ions in the mica for the alkaline earth metals, but not for the alkali metal ions. The selectivity increased in the order: Li ⁺ < Cs ⁺ < K ⁺ < Na ⁺ for alkali metal and Sr ²⁺ < Ba ²⁺ for alkaline earth metal ions. Mg ²⁺ -exchanged Na-4-mica with an expanded 13.33 Å lattice was also prepared and its strontium and barium ion exchange were studied.