Surface chemistry of novel collectors and their application to froth flotation of rare earth minerals

Abstract

Rare earth elements have been receiving a considerable amount of attention over the last few decades because of their increasing demand and limited supply in today’s industry. Gaining independence from China’s monopoly of rare earths is an incentive to produce a viable method for rare earth production. Bastnaesite, a rare earth fluorocarbonate, is one of the most abundant minerals that contain rare earth elements comprised of cerium, lanthanum, praseodymium, and other light rare earth elements. The focus of this research was to find a novel collector that increases desired concentrate grade and recovery while rejecting gangue minerals such as calcite and barite. Fundamental surface chemistry experiments including zeta potential, adsorption density, and microflotation were done to find the top three performing collectors out of the 19 collectors tested. N,2-dihydroxybenzamide, N-hydroxycyclohexanecarboxamide, and N,3-dihydroxy-2-naphthamide were chosen for a bench scale flotation screening analysis. A design of experiment matrix was conducted to determine the following effects and interactions: collector type, collector concentration, pH, pH modifier, continuation of pH through the experiment, temperature, and depressant concentration. N,2-dihydroxybenzamide was determined to be the optimal collector. A rougher flotation experiment produced a rare earth oxide grade and recovery of 41% and 78%, respectively with a 91.5% rejection of calcite. This is a significant improvement from the fatty acid rougher flotation, which produced approximately 30% REO grade, 60% REO recovery, and 70-80% rejection of calcite. An optimization study may be able to improve these values. A preliminary economic analysis provided a profitable outcome and a sensitivity analysis.