Abstract
Spodumene is the most abundant lithium-bearing mineral found in pegmatite deposits across the Canadian Shield and can be concentrated through Dense Media Separation (DMS) and froth flotation. DMS typically produces coarse spodumene concentrates but lithium recovery can be limited if spodumene is not well liberated at coarse grain sizes, in which case recovery can be improved by including flotation in the process flowsheet. While high lithium recoveries are possible with flotation, producing high-grade spodumene flotation concentrates is notoriously challenging and poses a risk for future operations. Poor selectivity in spodumene flotation is largely driven by the sensitivity of fatty acid ionic collector species to pulp conditions like pH and concentration; but the understanding of this behaviour during conditioning is limited. Industrial literature indicates pulp density (>60% solids), conditioning time, and mixing intensity during conditioning are vital for proper collector adsorption and selective spodumene recovery. This study evaluated the relationship between spodumene rougher flotation performance and the pH behaviour during high-density conditioning using a 4-factor central composite experimental design investigating the effects of pulp pH, collector dosage, conditioning time, and power density. During high-density conditioning, the pulp pH dropped rapidly following the addition of the fatty-acid collector, while the resulting pH profile through the conditioning period differed depending on the test conditions. A strong relationship between the dynamic pH behaviour and rougher flotation performance was observed. It was determined that spodumene recovery was maximized when the pulp pH throughout conditioning was between 6.5 - 7.0, while rougher concentrate grade was maximized when the pulp pH at the end of the conditioning period exceeded 7.0. This work, which defined a relationship between the pH behaviour during high-density conditioning and flotation performance, has the potential to improve the operation and control of industrial spodumene flotation circuits.