Optimization and identification of key process parameters for in-situ leaching of uranium in the Barun uranium deposit, China

Abstract

Ascertaining the optimal process parameters for in-situ leaching (ISL) of uranium is crucial for maximizing both uranium leaching rates and enhancing the production efficiency of uranium mining endeavors. Nevertheless, limited research has been conducted on the chemical composition of uranium ore within the Barun uranium deposit, with a notable absence of indoor leaching experiments and in-depth discussions pertaining to the ISL technology for uranium and the identification of optimal leaching parameters tailored to this specific deposit. Therefore, the present study focuses on the analysis of uranium ore from the Barun uranium deposit, utilizing X-ray fluorescence spectrometry (XRF) and elemental chemical analysis. Furthermore, a series of experiments were conducted, encompassing acid consumption tests, acid concentration determination, and various oxidant leaching tests. The findings reveal that: (1) The uranium ore within the deposit is abundant in minerals that exhibit resistance to acid dissolution, notably quartz and silicates (with SiO₂ and Al₂O₃ contents reaching as high as 77.62 % and 15.65 %), whereas the content of minerals readily soluble under acidic conditions, such as carbonates, iron minerals, and sulfides, is relatively low (with the proportions of total carbon, total iron, and sulfur content being as low as 0.128 %, 0.881 %, and 0.26 %, respectively). The mineralogical attributes of this deposit suggest its suitability for the application of acid ISL. (2) During the acid leaching process of uranium ore, an optimal H₂SO₄ concentration of 5 g/L was observed to yield a superior uranium leaching rate of 78.76 %, accompanied by a reduced sulfuric acid consumption of 115.8 tons per ton of uranium extracted. Notably, the pH of the leaching solution remained largely unaffected by the oxidant utilized. Under the influence of 1.5 g/L of 30 % H₂O₂, the uranium leaching rate achieved its maximum value of 90.27 %, significantly outperforming other oxidant conditions. (3) The acid leaching methodology is a viable option for the ISL of uranium from the Barun deposit. It is advisable to employ a concentration of 5 g/L H₂SO₄ while maintaining the pH of the leaching solution below 2 for optimal performance. In response to the anticipated decrease in uranium concentration during the intermediate and later stages of the leaching process, the strategic addition of 1.5 g/L of 30 % H₂O₂ is recommended to facilitate the oxidative dissolution of tetravalent uranium minerals, thereby enhancing the overall leaching efficiency. This study offers significant insights and valuable references for future research on ISL of uranium in the Barun uranium deposit, as well as in other sandstone-hosted uranium deposits that possess comparable mineralogical characteristics.