Towards the efficient flotation of monazite from silicate-rich tailings with fatty acids collectors using a lanthanum salt as a selective phosphate activator

Abstract

The exploitation of massive rare-earth element (REE) deposits is frequently contested because of the pollution generated by the heavy mining operations and REE extractive metallurgy operations. In an effort to minimise the environmental footprint of the REE production and meet the increasing demand for these elements, mine wastes and extractive metallurgy tailings are attracting attention as alternative primary sources. However, these residues frequently contain small amounts of monazite [(Ce,La,Nd)PO4] in silicate-rich gangues, rendering the efficient and selective recovery via current flotation routes difficult. Herein, we investigated the use of LaCl3 as an activator to promote the selective adsorption of fatty acid collectors on the surface of phosphate minerals, thus improving the monazite flotation performance. Bench-scale flotation tests were performed on a low monazite-grade, silicate-rich residue and revealed that a low LaCl3 dosage (about 1 g t−1) selectively enhanced the floatability of monazite and gangue phosphate minerals. We found that the influence of LaCl3 on the monazite flotation performance depends on the LaCl3 dosage, collector dosage, and method of addition of these reagents to the pulp. The mineral composition of the flotation products was determined by mineral liberation analysis (MLA), which indicated that higher concentrations of lanthanum ions promote the adsorption of the collector on rutile and aluminium-rich minerals, thus reducing the selectivity of the monazite flotation separation. This study is a stepping stone towards the development of a new practice of monazite flotation with environmentally friendly collectors and may render low REE-grade residues a commodity.