Physicochemical aspects of smithsonite flotation

The wide use of zinc and the exhaustion of traditional sulfide zinc resources provide the motivation to consider oxide zinc mineral resources. Smithsonite is the most abundant nosulfide zinc mineral but it is hard to be separated from other carbonate minerals by flotation techniques. Therefore, potassium lauryl phosphate was evaluated as a new flotation collector with respect to physicochemical aspects. For comparison, dodecylamine was also considered as a common collector reported in the literature for smithsonite flotation. Crystal structure analysis results indicate that the distances between zinc atoms on the smithsonite cleavage plane are smaller than the distances between calcium atoms on the calcite cleavage plane. The carbonate phase was the only predominant solid phase over all pH values in an open system, both for smithsonite and calcite. Zeta potential measurements suggest that potassium lauryl phosphate adsorbs on both smithsonite and calcite. An obvious difference between contact angles for smithsonite and calcite was observed with potassium lauryl phosphate as the collector from pH 6 to 9. On the other hand, there is no great difference between smithsonite and calcite contact angles with dodecylamine as the collector for all pH values studied. The flotation response shows an obvious difference between the flotation recovery of smithsonite and that of calcite using potassium lauryl phosphate as a collector for the pH 5 to pH 10 region. However, when dodecylamine was used as a collector, no significant difference in smithsonite and calcite flotation recovery was observed at any pH value. The adsorption states of collectors were described from sum frequency generation experiments. It is suggested that with potassium lauryl phosphate as the collector a closely packed layer was formed on the smithsonite surface from pH 3 until pH 9. On the other hand, the adsorption density on the calcite surface decreases and disorder of the interface increases from pH 4. The SFG spectra also suggested that the adsorption of dodecylamine started from pH 10 for both smithsonite and calcite. These findings suggest that potassium lauryl phosphate will be an effective collector for the flotation recovery of smithsonite from oxide zinc ores.