Perpustakaan Digital ITB

Rare earth elements (REE) are widely applied in various technologies. A significant amount of REE can be found in Indonesia associated with monazite minerals, especially those from Bangka Island. Monazite in Bangka Island can be found as a by-product of cassiterite mineral processing. Despite significant efforts to recover REE from monazite, commercial extraction of REE from monazite has not been realized in Indonesia. This may be due to difficulties in extracting the REE economically and separating the REE from radioactive elements such as thorium (Th) and uranium (U), which are present in Bangka’s monazite. Hence, this study aims to extract and separate REE from Th and U from Bangka monazite. A series of experiments was carried out to investigate the process of separating REE from Th and U. In this study, caustic fusion was chosen to remove phosphorus (P) from the ore making the REE amenable for leaching using hydrochloric acid (HCl). The conditions for the caustic fusion and acid leaching followed the optimal ones found by the previous investigator, who used the same monazite sample. The precipitation process was carried out after leaching using ammonium hydroxide as the precipitating agent. Subsequently, the Th- and U-rich precipitates were leached in mildly acidic conditions to re-leach any co-precipitated REE. The experimental results showed that about 92.37% of P could be removed from the monazite concentrate after water leaches the caustic fusion product. The leaching process of the washed residue using 6 M HCl at a temperature of 70 °C, solid-to-liquid ratio of 100 g/L monazite, and leaching duration of 4 h can dissolve up to 90.98% of REE. In the precipitation process, Th and U were precipitated at pH below REE precipitation conditions allowing for selective precipitation of REE. At the optimum condition, i.e., at a pH of 5.0 under ambient conditions, the precipitation of REE, Th, and U were 19.3%, 99.5%, and 99.9%, respectively. The results of selective leaching of the precipitate with mildly acidic solutions at pHs ranging from 1.5–3.0 showed that the dissolution of elements decreased as the pH value increased. REE in the precipitate at pH 5 can be separated from Th and U with selective leaching at pH 3 with percent leaching of REE, Th, and U respectively were 90%, 0.55%, and 54%.