Clean hydrometallurgy processes, formed by “oxidant-ligand” systems, present promising strategies for gold leaching to mitigate the environmental impact of cyanidation. In this work, a Fenton oxidation-assisted thiourea system was proposed, employing reactive oxygen species (ROS, generated from Fenton reaction) as oxidant and thiourea as the ligand, respectively. By precise parameters control, 100% leaching of gold was rapidly achieved within 30 min from a roasted gold concentrate, highlighting extremely fast kinetics. Furthermore, this system was optimized by incorporating nitrilotriacetic acid (NTA) as an additive, which significantly reduced the thiourea consumption and produced the same gold leaching (100%, 60 min). Experimental results demonstrate that NTA lowers the solution potential (ORP) and eliminates the side reactions between iron ions and thiourea, thereby reducing thiourea decomposition. Surprisingly, the combination of Fenton oxidation and thiourea showed a high selectivity of the generation of ROS, with superoxide radical anion (•O) dominating, singlet oxygen (O) co-existing, but hydroxyl radical (•OH) absenting. Importantly, the moderate •O primarily contributes to gold leaching, which is generated through a chain reaction pathway between iron complex and HO (Fe-Ligand+HO → Ligand-Fe-OOH → Fe-Ligand+•O). Besides, the generation process of •O can be regulated by adding NTA. This work presented a prospective way in establishing the clean hydrometallurgy processes for efficient gold leaching.

中文翻译：

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芬顿氧化辅助硫脲系统中高效清洁湿法浸金工艺

由“氧化剂-配体”系统形成的清洁湿法冶金工艺为金浸出提供了有前景的策略，以减轻氰化对环境的影响。在这项工作中，提出了一种芬顿氧化辅助硫脲系统，分别采用活性氧（ROS，由芬顿反应产生）作为氧化剂，硫脲作为配体。通过精确的参数控制，在 30 分钟内从焙烧金精矿中快速实现金的 100% 浸出，凸显了极快的动力学。此外，通过加入次氮基三乙酸（NTA）作为添加剂对该系统进行了优化，显着降低了硫脲消耗量并产生了相同的金浸出率（100％，60分钟）。实验结果表明，NTA降低了溶液电位（ORP），消除了铁离子与硫脲之间的副反应，从而减少了硫脲的分解。令人惊讶的是，芬顿氧化和硫脲的组合显示出高选择性的ROS生成，其中超氧自由基阴离子（·O）占主导地位，单线态氧（O）共存，但不存在羟基自由基（·OH）。重要的是，适度的·O主要有助于金的浸出，这是通过铁络合物和H2O之间的链式反应途径产生的（Fe-配体+H2O→配体-Fe-OOH→Fe-配体+·O）。此外，通过添加NTA可以调控•O的生成过程。这项工作为建立高效金浸出的清洁湿法冶金工艺提供了一种前瞻性的方法。