Process for leaching rare earth elements

Abstract

Described herein is a process for stepwise leaching of all rare earth elements capable of forming peroxide and superoxide compounds, in particular cerium, lanthanum, neodymium, europium, from minerals containing these elements, namely from bastnaesites, orthites, chevkinites, and britholites.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This U.S. nonprovisional application claims priority to German Application No. 102019003556.9 filed May 19, 2019, the entire contents of which are incorporated herein by reference.TECHNICAL DESCRIPTION OF THE INVENTION[0002]The present invention relates to the field of mining industry and specifically to the leaching of rare earth elements (REE).[0003]The direct leaching of rare earth elements takes place by means of hydrochloric acid, sulphuric acid, nitric acid or mixtures thereof.[0004]In patent RU 2547369 C2 dated 18 Feb. 2013 “Process for the complex treatment of residues from Domanik formations”, leaching is carried out by a multi-stage treatment with sulphuric acid of varying concentration, inter alia with the maximum aggressive concentration of 15 to 25%, at temperatures from 65° C. to 160° C. and at pressures from atmospheric pressure to 13 bar.[0005]The disadvantage of this process is that the use of aggressive sulphuric acid con...

AI Technical Summary

Benefits of technology

The present invention relates to a process for leaching rare earth elements using a combination of hydrochloric acid, sulphuric acid, nitric acid or mixtures thereof. The process involves a multi-stage treatment with the acidic solution, including a pre-treatment with synthetic surfactants. The use of aggressive concentrations of acid, temperatures above 95° C. and elevated pressures is required for the leaching process. The disadvantage of this process is the need for expensive equipment made of highly alloyed steel. The invention also proposes a process for leaching rare earth elements using crushed raw materials pre-treated with synthetic surfactants. The process includes a heap leaching or agitation leaching process and can be carried out at a ratio of solid to liquid of 1:1. The use of synthetic surfactants can lead to swamp formation and the formation of stable compounds with heavy metals, which further suppresses aerobic microflora. The process duration is long, with agitation leaching from 6 to 12 days and heap leaching up to several years.

Problems solved by technology

The disadvantage of this process is that the use of aggressive sulphuric acid concentrations requires the use of equipment made of highly alloyed molybdenum steel.

Moreover, when sulphuric acid is used, the fluorides decompose at temperatures above 95° C. to form gaseous and water-soluble compounds, which impair the environmental situation.