Effect of magnetite on spodumene flotation performance: An experiment- and simulation-based study

Magnetite significantly deteriorates spodumene flotation by preferentially consuming sodium oleate. • Fe 3+ activates spodumene flotation by promoting oleate adsorption through hydrolyzed Fe species. • Molecular dynamics simulations reveal stronger oleate adsorption on magnetite than on spodumene. Low-grade lithium ores are abundant and have gradually emerged as key lithium sources for the energy storage industry; however, effective ore enrichment remains a challenge. Moreover, a key consideration factor is that common iron minerals severely interfere in the lithium flotation process. In this context, this study investigates the mechanism governing the adverse effect of magnetite on spodumene flotation. Specifically, flotation tests in a magnetite–spodumene–oleate flotation system showed that sodium oleate preferentially collects magnetite (recovery >65%), and spodumene recovery significantly decreases with an increase in magnetite content. Additionally, zeta potential measurements and adsorption tests indicated that the Fe ions dissolved from magnetite do not contribute to decreases in spodumene flotation, owing to Fe 3+ addition observably activating spodumene flotation. Such activation was achieved via the formation of hydroxyl–iron complexes as bridges for enhancing oleate collector adsorption on spodumene surface. Molecular dynamics simulations confirmed that the hydration film thickness at the mineral–water interface decreased with the addition of oleic acid, and the degree of thinning of the hydration film at the magnetite–water interface far exceeds that at the lithium–spodumene–water interface. This resulted from magnetite inherently possessing abundant surface Fe sites binding directly and strongly with oleate, although some Fe 3+ also adsorbed on the spodumene. An interfacial adsorption energy between magnetite and sodium oleate (–4.01 kcal · mol −1  · Å -2 ) significantly exceeding that of spodumene (–1.03 kcal·mol −1 ·Å -2 ) was obtained from calculations, further proving that the structural-preferential adsorption of oleate on magnetite surface is a key factor influencing spodumene flotation. Ultimately, these findings may provide a theoretical foundation for developing strategies to mitigate the interference of iron minerals in low-grade lithium ore flotation. Download: Download high-res image (121KB) Download: Download full-size image