Changes in Physico-Chemical Properties of some Clay Minerals by Reducing Extraction Reagents

Helios Rybicka, E. and Calmano, W., 1988. Changes in physico-chemical properties of some clay minerals by reducing extraction reagents. Appl. Clay Sci., 3: 75-84. An extraction sequence in three steps with buffered hydroxylamine hydrochloride, oxalate and dithionite solutions was used for removal of Fe-oxide coatings from standard clay minerals: ka-olinite, illite and mixed layer smectite/illite. After each extraction step the cation exchange ca-pacity, specific surface area and the concentrations of A1, Si, Fe, Mg, K and Ca in solution were measured. For all minerals the specific surface area increases after treatment with hydroxylamine hydro-chloride and oxalate, but it decreases after treatment with dithionite solution. The cation ex-change capacity shows no significant change for smectite/illite, a small decrease for illite and a continuous increase for kaolinite after treatment with the extractants. K, Ca, and Mg are mainly extractable by hydroxylamine hydrochloride. After each extraction step an additional exchange of these cations could be observed by treatment with ammonium acetate