Assessment of the impact of grinding conditions and water quality on the flotation of rare earth elements bearing minerals using hydroxamic acid

Abstract

ABSTRACT Froth flotation is commonly used for the separation of rare earth minerals (REMs). A better understanding of flotation is of interest for REMs and non-sulfide minerals that carry other elements such as niobium and lithium. This study explores the effect of grinding conditions and water quality on the flotation performance of REMs at laboratory scale using material from the Ashram carbonatite deposit (Canada). Denver cell testing was used to evaluate how different particle sizes (P80 between 20 and 34 µm) and rod size distributions in conventional grinding impacted the performance of REM flotation using a hydroxamic acid collector (1120 g/t). The effect of water quality (i.e. presence of rust or other species) was also evaluated. REMs, mostly monazite, represented 3% of the feed material mass with dolomite as the main gangue mineral. A P80 of 24 µm strikes a compromise between sufficient liberation and limited entrainment. Grinding media corrosion negatively affected separation efficiency, causing recovery of quartz, which was possibly activated. While entrainment is responsible for over 50% of dolomite recovery, aggregation and/or slow gangue flotation account for another 40% and play an important role in achieving selectivity, highlighting the role of pulp chemistry in selective flotation of REMs.