Jin Yanchao, Qiu Yuchen, Kumar Rohit, Chan Tingshan, Yan Li
College of Environmental and Resource Sciences, Fujian Normal University, Fuzhou 350117, Fujian, China; Fujian Key Laboratory of Pollution Control & Resource Reuse, Fuzhou 350117, China.
College of Environmental and Resource Sciences, Fujian Normal University, Fuzhou 350117, Fujian, China.
Sci Total Environ. 2024 Jan 1;906:167823. doi: 10.1016/j.scitotenv.2023.167823. Epub 2023 Oct 14.
The geochemical cycling of antimony (Sb) in aquatic system is primarily influenced by the dissolution and transformation of stibnite (SbS) in the presence of iron minerals. Here, SbS oxidative dissolution and sequestration on goethite were investigated to mimic the environmental fate of SbS. The results demonstrated that goethite accelerated the rate of SbS oxidative dissolution by a factor of 9.4 times under sunlight. The significant SbS oxidation on goethite was attributed to a heterogeneous electron transfer from SbS to goethite, as proved by XANES analysis. This electron transfer facilitated the generation of hydroxyl radicals (OH) on SbS, and superoxide radicals (O) on goethite. Radical trapping experiments confirmed that O was the dominant oxidant for Sb(III) oxidation with 91 % contribution. Thus, goethite plays a dominant role in O generation and SbS oxidative dissolution. Meanwhile, the total dissolved Sb was decreased by 69 % in SbS and goethite coexisting system compared to a single SbS system, indicating the retention of dissolved Sb on goethite. Density functional theory (DFT) calculations deciphered that Sb(III) oxidation on mineral-water interfaces with O radicals was thermodynamically preferential to OH radicals. Additionally, the Sb was anchored on goethite as a bidentate binuclear structure with a favorable adsorption energy. Our findings shed the light to understand the geochemical cycles of SbS in natural environment.
水生系统中锑（Sb）的地球化学循环主要受辉锑矿（SbS）在铁矿物存在下的溶解和转化影响。在此，研究了辉锑矿在针铁矿上的氧化溶解和固存，以模拟辉锑矿在环境中的归宿。结果表明，在阳光下，针铁矿将辉锑矿的氧化溶解速率提高了9.4倍。针铁矿上显著的辉锑矿氧化归因于从辉锑矿到针铁矿的异质电子转移，X射线吸收近边结构（XANES）分析证明了这一点。这种电子转移促进了辉锑矿上羟基自由基（OH）的产生以及针铁矿上超氧自由基（O）的产生。自由基捕获实验证实，O是氧化Sb（III）的主要氧化剂，贡献率为91%。因此，针铁矿在O的产生和辉锑矿的氧化溶解中起主导作用。同时，与单一辉锑矿体系相比，辉锑矿和针铁矿共存体系中的总溶解锑减少了69%，表明溶解态锑在针铁矿上的保留。密度泛函理论（DFT）计算表明，在矿物-水界面上用O自由基氧化Sb（III）在热力学上比用OH自由基更有利。此外，Sb以双齿双核结构锚定在针铁矿上，具有良好的吸附能。我们的研究结果有助于理解自然环境中辉锑矿的地球化学循环。
