Acid leaching study of rare earth elements

The great evolution of the technology development given in the last decade is undoubtedly due to the use of Rare Earth Elements (REE). They directly modify both physical and chemical properties in materials. An example of this is the progress in smart and high-resolution technologies, such as cell phones, computer hard drives, hybrid and electric vehicles, and LED monitors and lighting, as well as the attractive economic value that rare earth oxides possess in the world market. The Chilean Nuclear Energy Commission (CCHEN), together with the National Mining Company (ENAMI), began geological and metallurgical research. These studies allowed them to identify a prospect in the Atacama Region for studies that justify the technical and economic feasibility in the exploitation of a rare earth deposit as a new mining alternative. These previously conducted studies allowed to understand the fundamental parameters in the REE concentration for a Davidite ore. These studies reached a 60% recovery of REE at sulfuric concentration of 5M for temperatures between 90 to 100^oC and a particle size less than 44 microns, with agitation being the only non-predominant parameter for this study. The purpose of this work is to increase the recovery of those elements that belong to the davidite ore, to obtain a leaching product with REE recoveries values greater than the previous studies, and reducing the concentration of the ions that affect negatively from post leaching processes. To validate this theory, the tests increased the leaching recovery of the impurity elements in the ore, especially iron, using two different methodologies. The first method incorporated NaCl into an H₂SO₄ leaching solution to increase the acid generation in the reaction, in order to enhance the dissolution of REE in leaching. This procedure showed that the increase in acid in the system over 2M and for NaCl concentration ranges between 0.5 to 1M, obtained recoveries over 60% REE. The second method included a reductive leaching in a H₂SO₄ leaching solution and the constant injection of sulphurous anhydride. This process dissolved the iron contained in the ore, and reduced it to its lower ionic state (ferrous ion). This addition allowed obtaining a recovery of 30% iron and fulfilling the purpose of the methodology, since the reaction potential in the system was over 600 mV, a range in which the ferrous ion is stable