Optimization of Parameters for Separation of the Medium Rare Earth Element Group from Other Rare Earth Elements by Precipitation Method Using Box- Behken Design

Rare earth elements (REEs) are important materials in various technologies and have high economic value. Indonesia has the opportunity to become a country that has the potential to produce rare earth metal because it has tin mining areas where the by-product is monazite sand that contains 50% REEs. Based on this, a precise and efficient method is needed for separating REEs from the mixture. This study is a continuation of previous studies that selected parameters that affect the separation of REEs in the medium group from other groups by the precipitation method. This research optimizes the parameters of the selected precipitation method using the response surface method (Box-Behnken Design). The method used in this study was the optimization of the selective deposition method of REE hydroxide samples based on the different REEs pH for heavy, medium, and light groups using Box-Behnken Design. The parameters used were the reactant concentration, temperature, stirring speed, and pH. The result of parameter optimization that gave relevance to the maximum response rate of the REEs medium group was the oxalic acid concentration (1.0 N), precipitation temperature with oxalic acid (25 °C), pH of heavy REEs precipitation (3.10), pH of the REEs medium group precipitation (7.30), and precipitation temperature (90 °C). The separation efficiency of the REEs from monazite-origin samples treated to obtain the REEs hydroxide was 72.55%.