The Beneficiation and Hydrometallurgical Process Development for the Lofdal HREE Project

Abstract.

The Lofdal REE project is one of the few rare earth deposits in the world that contains mostly heavy rare earth elements (~75% HREO distribution). The mineralogy of the Lofdal project is complex, with xenotime as the primary rare earth mineral, and silicate, calcite, and iron oxide as the main gangue minerals. The beneficiation and hydrometallurgical flowsheets developed for the Lofdal project in previous studies were complicated and sub-economic. The recent development of the beneficiation testwork largely simplified the flowsheet with improved concentrate grade and recovery. The beneficiation process included ore sorting, magnetic separation, and flotation. The enhanced selectivity of xenotime against high reagent (acid, neutralizing reagent) consuming gangue minerals (calcite and hematite) was beneficial for the CAPEX and OPEX cost saving of the downstream hydrometallurgical process. The original caustic crack-based flowsheet was converted into an acid bake-based flowsheet treating the flotation concentrate capable of recoveries exceeding 95% of key HREE. Following several conventional liquor purification steps, a high-purity rare earth oxide concentrate at >98% total rare earth oxide with low impurity levels was produced. This paper highlights the findings from laboratory testing programmes conducted to develop the process.