Ammonium–Potassium–Calcium Exchange on Vermiculite and Hydroxy-aluminum Vermiculite

Abstract

Binary and ternary cation-exchange reactions involving NH+4, K+, and Ca2+ on vermiculite and hydroxy-Al interlayered vermiculite (HIV) were investigated. In the case of vermiculite, NH4-Ca exchange was nearly indistinguishable from the nonpreference isotherm while HIV exhibited preference for NH+4 The presence of K+ had significant suppressing impact on the apparent NH+4 selectivity in NH4-Ca exchange in HIV most likely because of retardation of Ca2+ diffusion in the interlayer. For vermiculite, the presence of K+ in the NH4-Ca system induced apparent high affinity sites for NH+4 most likely because of interlayer collapse. The overall study demonstrated that cation-exchange selectivity coefficients in vermiculite and HIV are dependent on number and type of cations present.