Extraction and purification of thorium and rare earth elements from bastnaesite mineral: a comprehensive leaching and precipitation study

The present study focuses on investigating the conditions for acid leaching of Th and REEs and sequential oxalate precipitation to remove impurities from leach liquor. The effects of preheat treatment, leaching time, liquid/solid ratio, and acid concentration on Th, Sm, Pr, Nd, Ce, La, and U leaching yields were investigated. The best results were obtained at 400 °C preheated sample using 1 mol/L H₂SO₄, liquid/solid ratio of 1 mL/g, 60 min leaching time, and 30 °C leaching temperature. The leaching yields of Th, Sm, Pr, Nd, Ce, La, and U were found to be 41.7, 65.0, 68.2, 66.9, 84.3, 82.6, and 55.0% respectively. Th and REE liquors were treated with 0.5–1.5 mol/L H₂C₂O₄ solutions in the precipitation step. Purity was enhanced through three sequential precipitation cycles, resulting in a purity grade of 98.59%.