Concentration of K-feldspar from a pegmatitic feldspar ore by flotation

摘要

Abundant reserves of Na-feldspar (albite) and K-feldspar (orthoclase or microcline) are found in granites, syenite, tracite and pegmatites. As both feldspar minerals have similar chemical structure and physicochemical properties, their separation is challenging. Flotation is known to be the only technique to enable their separation. The fundamentals on the separation of these minerals were well documented in our earlier studies. In this study, a pegmatite ore with a K_2O/Na_2O (3.78:3.37) ratio of 1.12 was studied in a Denver flotation cell both at natural and acidic pH using HF and H_2SO_4. Because of the perthitic structure of the ore no significant separation is observed at natural pH. Interestingly, a selective separation was achieved at low pH using HF and H_2SO_4 (pH 2.5-2.8). The selectivity is induced by the addition of Na~+ ions through depression of albite. Selective separation has been carried out by stagewise flotation using the tree technique. Accordingly, a pegmatite ore composed of 3.37 percent Na_2O and 3.78 percent K_2O is upgraded to 10.51 percent K_2O and 3.02 percent Na_2O with a K_20/Na_2O=3.48 in HF medium and to 2.55 in H_2SO_4 medium. It is shown that products recovered in other stages are also considered as commercially significant. Especially, quartz, which is recovered in the tailings in HF medium, is suitable for glass industry. The overall results show that commercial utilization of these results is possible.