EXTRACTION OF RARE EARTH HYDROXIDE FROM BANGKA’S MONAZITE THROUGH LEACHING AND MULTILEVEL PRECIPITATION AFTER CAUSTIC FUSION

• Main Author: Purba Pramudya, Lisdhiyanto
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69388
• Institution: Institut Teknologi Bandung

Monazite is a by-product of tin processing containing elements of uranium (U), thorium (Th), and rare earth elements in the form of phosphate (REPO4). Indonesia has monazite reserves in the Bangka archipelago, That have not been processed commercially. The need and demand for rare earth metals for advanced industries increase every year. Therefore, it is necessary to research the extraction of rare earth metals from monazite. The purpose of this study was to determine the optimal variables for the leaching process after caustic fusion and the optimum pH for precipitation of the leached solution to produce a mixture of rare earth metals in the form of hydroxide compounds. This study used samples of monazite originating from the island of Bangka which has been processed by PT Timah. A series of agitated leaching experiments at atmospheric pressure was carried out to investigate the effect of hydrochloric acid concentration, temperature, solidliquid ratio, and leaching time on the percent extraction of rare earth metals. The experiment was started by making samples using the caustic fusion method. Leaching experiments were carried out with constant variables at 6 M acid concentration, the temperature at 70oC, leaching time in 2 hours, and a solid-liquid ratio of 100 grams per liter. An ICP MS analysis was used to determine the percent extraction of rare earth metals in the leached solution. Afterward, an experiment to determine the precipitation behaviour of hydroxide compounds on the leached solution was carried out by adding NH4OH solution to raise the pH and hold it in the range of 3-8. The residue from the process was weighed and ground for further testing using XRF and XRD The experiment on the effects of the leaching variables has resulted that the percent extraction of rare earth metals and thorium increasing with increasing temperature, leaching time, and concentration of hydrochloric acid. In addition, the increase in the solid-liquid ratio contributed to the reduction in the percent extraction of rare earth metals and thorium. The optimum leaching parameters were obtained at a concentration of 6 M acid, a temperature of 70oC, a leaching time of 4 hours, and a solid-liquid ratio of 100 gpl. As result, 94.9% rare earth metals and 94.89% thorium were extracted in that leaching condition. The results of the precipitation experiment showed that iron and thorium can be separated at a lower precipitation pH than rare earth metals. The pH for the precipitation process of iron and thorium 5 where the percentage of thorium precipitation was 97.82% and the percentage of iron precipitation was 97.36%.