TERNARY CATION-EXCHANGE EQUILIBRIA (K, CA , MG) ON SYNTHETIC ALUMINOSILICATES

The K-Ca-Mg exchange selectivity on a synthetic aluminosilicate (Al-Si ) was studied through ternary cation exchange equilibria. The effects of equilibrium temperature (4 degrees C and 25 degrees C), the equival ent fraction of K in solution (0-0.6), and sequential coatings of iron oxide and organic matter were considered. In general, the selectivity sequence K > Ca > Mg was observed. There is no temperature effect on exchange selectivity but the Cation Exchange Capacity (CEC) slightly i ncreases when temperature changes from 4 degrees C to 25 degrees C.The iron oxide and organic matter coatings result in a 20 to 30% reductio n of CEC and decreases the selectivity of Ca over Mg in relation to th at of Al-Si. When the equivalent fraction of K in solution increases, the selectivity of Ca over Mg decreases in both samples (with and with out coatings), and the CEC associated with Ca + Mg decreases. With the se results, it is concluded that there are K selective exchange sites.