Synthesis and sorption properties of some clay-like minerals

A trial has been made to prepare montmorillonite-like minerals by refluxing silica and alumina gels, with SiO2/Al2O3 molar ratios of 1.5 and 5, in presence of 0.1 and 1M Zn, Ni or Co acetate for different periods. Investigation of the products obtained by X-ray and DTA has shown that montmorillonite-like structures begin to appear after 45 days and that the most developed structures together with the lowest percent of unreacted gels (about 10%) are obtained with the lower SiO2/Al2O3 ratio, higher transition metal concentration, and a refluxing time of 90 days. Bivalent ion exchange on the synthesized minerals obeys the simple mass action law and a selectivity for Co2+ over Mg2+ and Sr2+, and specially over Sr2+, is displayed by all the synthetic materials. The product prepared in the presence of Co has the highest selectivity to it and a tentative explanation for this fact is given