Preliminary Study of the Effect of pH on Ce, Nd, La, Pr Recovery from REOH Concentrate

Abstract

The separation of uranium, thorium, and rare earth elements (REE) from monazite sand was carried out using the PLUTHO pilot plant facility. The REEs were produced in the form of hydroxide concentrates (REOH). Further separation process must be carried out to obtain high-purity elements for application in advanced industries such as polisher material for hard materials, infrared protective glass, and Ni-metal hydride batteries. The Major Element of REEs are Cerium (Ce), Lanthanum (La), Neodynium (Nd), and Praseodymium (Pr). Those elements can be separated by various methods such as fractional precipitation, extraction, ion exchange, and others. This research was carried out using the Fractional Precipitation method. Rare earth elements have chemical properties that permit ready dissolution and easy precipitation. The fractional precipitating reagent commonly used is NH4OH because it will not contaminate the precipitate due to the volatility of NH3. The parameter used in this preliminary study was pH from 4 to 9. The separation process was started with the dissolution of the REOH concentrate in a solution of HNO3 to obtain RE nitrate. After the dissolution process, oxidation and precipitation were carried out by the addition of KMnO4 as an oxidizing agent and Na2CO3 as a precipitating agent at pH 4 to obtain high recovery efficiency of cerium. The precipitation was pH varies continued by pH adjustment using NH4OH starting from pH 4 to pH 9 to separate La, Nd, and Pr. The analysis of Ce, La, Nd, and Pr concentration was carried out using ICP-OES. The optimum pH recovery for Ce, Nd, and Pr was found at pH 4 with a concentration of 19986.4 ppm, 3532.34 ppm, and 3796.81 ppm, respectively, while at pH 8.5 for La with a concentration of 5846.59 ppm.