Optimization of Acid Leaching of Rare-Earth Elements from Mongolian Apatite-Based Ore

Abstract

Abstract:Optimization of the acid leaching process for Mongolian apatite-based ore containing rare-earth elements (REEs) was studied. The ore contained approximately 10% of REEs as total rare earth oxides, and the major impurities were Ca (33% as CaO) and Fe (23% as Fe 2 O 3 ). Fe bearing minerals could be removed by passing the sample through a wet high-intensity magnetic separator before leaching. After magnetic separation, basic leaching tests were conducted to investigate the influence of the acid type and concentration, temperature, and the pH on the REE leaching level and kinetics. Hydrochloric acid was found to be the most effective leaching agent, leaching more than 90% of REEs in an hour. However, the concentrations of Ca ions in the leachate were also high, which would complicate recovery of the REEs. Therefore, to reduce the amount of Ca ions in the leachate, a two-stage leaching procedure was attempted. In stage 1, the sample was preleached using 1.0 M hydrochloric acid to dissolve Ca. In stage 2, the solid residue of stage 1 was leached using 2.0 M hydrochloric acid to dissolve REEs. Consequently, this two-stage leaching significantly reduced the Ca concentration in the final leachate without affecting the leaching levels of REEs.

Sulfonic-functionalized algal/PEI beads for scandium, cerium and holmium sorption from aqueous solutions (synthetic and industrial samples)

“…The recovery of REEs from secondary sources may involve pyrometallurgical steps (oxidation/roasting) [13][14][15]; however, acidic leaching remains the technique the most frequently used for processing wastes and secondary resources [14,[16][17][18][19]. This first step in the process transfers target metals (and other base metals) from solid to leachates that require complementary steps for enriching, separating and recovering the metals.…”

A study of cerium extraction from Bangka tin slag using hydrochloric acid

“…Thus, the reaction between slag and HCl can occur more effectively. HCl concentration is the first parameter observed, and the results obtained indicate that increasing HCl concentration causes higher Ce extraction [25]. Unfortunately, an increasing HCl concentration of more than 2.5 M indicates a decrease in Ce extraction.…”

Hydrochloric Acid Leaching Study of Rare Earth Elements from Moroccan Phosphate

“…In addition to temperature, acid concentration, and time, our study also tested the influence of stirring and S/L ratio that were neglected in other leaching optimization work of rare earths from phosphate as the case of the study conducted by Kim et al [18].…”