Materials, methods and techniques for generating rare earth carbonates

#The present disclosure relates to rare earth carbonates. More specifically, materials and methods disclosed and contemplated herein relate to production of rare earth carbonates with low sulfate from rare earth sulfate solutions.

#Rare earths may be obtained through the processing of mined rare earth minerals. These mined rare earth minerals are processed in a sequential manner until they are of a form that may be used as an input to rare earth separation processes. Monazite, a rare earth mineral, is processed by mining and acid cracking using concentrated sulfuric acid, followed by leaching in water. The output of this sequential process is a rare earth sulfate solution. Before the rare earth sulfate solution may be introduced into a solvent extraction process to separate the rare earth elements, the rare earth sulfate solution must be converted to a rare earth chloride solution, which can be further processed to isolate various rare earths of interest.

#Generally, three methods are currently used for producing mixed rare earth chloride solutions from mixed rare earth sulfate solutions. A first method involves precipitating a mixed rare earth double salt with sodium chloride (NaCl), converting the mixed rare earth double salt to mixed rare earth hydroxide with caustic soda and, downstream, dissolving with hydrochloric acid. A second method is to precipitate a mixed rare earth carbonate using ammonium bicarbonate and, downstream, dissolving rare earth carbonate with hydrochloric acid (HCl). A third method is to extract the rare earths from the sulfate solution with a solvent extraction process, such as using di-(2-ethylhexyl)phosphoric acid (DEPHA), and then strip the solvent using hydrochloric acid. All of these processes will produce a mixed rare earth chloride solution with low sulfate content.

#The FIGURE is a schematic depiction of an exemplary system for generating mixed rare earth carbonate.

#Materials, methods and techniques disclosed and contemplated herein relate to generating mixed rare earth carbonates. Generally, exemplary mixed rare earth carbonates may be generated with precipitation and sulfate removal operations. These operations may be performed as continuous processes. Exemplary mixed rare earth carbonates may comprise less than about 2 wt. % sulfate.

#Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Example methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing of the present disclosure. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

#The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures. The singular forms “a,” “an” and “the” include plural references unless the context clearly dictates otherwise. The present disclosure also contemplates other embodiments “comprising,” “consisting of” and “consisting essentially of,” the embodiments or elements presented herein, whether explicitly set forth or not.