Cen Ling, Cheng Hongguang, Liu Qingyou, Wang Shuai, Wang Xi
Key Laboratory of High-temperature and High-pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100039, China.
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
Environ Int. 2022 Dec;170:107558. doi: 10.1016/j.envint.2022.107558. Epub 2022 Oct 3.
Arsenopyrite (FeAsS) oxidative dissolution provides an important source for the occurrence of high arsenic in acid mine drainage (AMD). Biochar is a potent material that can dramatically sequestrate an array of heavy metals in water. However, little is known about the role of biochar on the fate of As from arsenopyrite in AMD. This study investigates the effects of biochar concentrations, AMD acidities, and temperatures on the release of As from arsenopyrite in a simulated AMD over a range of environmentally relevant conditions. Results show that biochar inhibits As release and further acidification without changing the arsenopyrite weathering mechanism. Arsenopyrite is first oxidized to Fe(II), As(III) and S and ultimately oxidized to Fe(III), As(V) and SO, respectively. Higher concentration, temperature or higher acidity promotes the arsenic release rate. Electrochemical studies showed that biochar inhibited As release and acidification for reduced the charge transfer resistance at the double layer and film resistance at the passivation layer, which was mainly attributed to Fe(III) ions in AMD being adsorbed, oxidized, and As complexed to biochar-Fe-As(V). This study reveals the release mechanism of As from arsenopyrite weathering in AMD and suggests the applicability of biochar in mitigating arsenic pollution and further acidification in sulfide mineral mine drainage.
毒砂（FeAsS）的氧化溶解是酸性矿山排水（AMD）中高砷含量产生的重要来源。生物炭是一种有效的材料，能够显著螯合水中的一系列重金属。然而，关于生物炭在AMD中毒砂砷归宿方面的作用，人们了解甚少。本研究在一系列与环境相关的条件下，考察了生物炭浓度、AMD酸度和温度对模拟AMD中毒砂砷释放的影响。结果表明，生物炭在不改变毒砂风化机制的情况下抑制了砷的释放和进一步酸化。毒砂首先被氧化为Fe(II)、As(III)和S，最终分别被氧化为Fe(III)、As(V)和SO。较高的浓度、温度或较高的酸度会促进砷的释放速率。电化学研究表明，生物炭抑制了砷的释放和酸化，这是因为它降低了双层电荷转移电阻和钝化层的膜电阻，这主要归因于AMD中的Fe(III)离子被吸附、氧化，以及砷与生物炭 - Fe - As(V)络合。本研究揭示了AMD中毒砂风化过程中砷的释放机制，并表明生物炭在减轻硫化物矿山排水中砷污染和进一步酸化方面的适用性。
