Advanced methods for bastnaesite concentrate leaching

Abstract

With the world’s rapid advancement of technology, the demand and need for the materials that make up that technology has exploded. An important group of materials needed in this rapid advancement are the rare earth elements (REE) used in countless necessary applications. One source of rare earths found in the United States is bastnaesite, a rare earth bearing fluorocarbonate, mined at the Mountain Pass Mine in California. To increase production, it has been essential to optimize existing processes and create new ones to exploit current reserves. This research program was run to expand the understanding of the bastnaesite leaching system. A novel single stage hydrochloric leach system was created to optimize the rare earth extraction from bastnaesite. Typically, this process has utilized a two-stage leach system involving a high temperature hydrochloric acid leach followed by a caustic crack.A series of single stage leach experiments were run by reacting locked cycle REE flotation concentrate with hydrochloric acid. The results of these single stage tests showed rare earth recoveries significantly higher than reported recoveries of the leach used in the historic two stage caustic crack process. These results also indicated a decrease in the amount of reagents needed to extract rare earths. This novel single stage leach was than assessed for economic performance compared to the historic two stage caustic crack process using a cashflow value added model. This economic analysis showed that the single stage leach had better economic performance showing higher created economic value and lower total costs over the lifetime of the process. This economic analysis also identified that the driving force on profitability is the rare earth leaching recovery. In summary, the results of this research a novel single stage hydrochloric leach was developed and shown to recover rare earth elements from concentrated bastnaesite ore significantly higher than the leach of the historic two stage caustic crack process, while using less reagents, and creating more economic value.