Zhang Yuyao, Xie Xianjun, Sun Shutang, Wang Yanxin
State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, Wuhan, China.
State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, Wuhan, China; State Environmental Protection Key Laboratory of Source Apportionment and Control of Aquatic Pollution, Ministry of Ecology and Environment, 430074 Wuhan, China.
Sci Total Environ. 2023 Oct 10;894:164941. doi: 10.1016/j.scitotenv.2023.164941. Epub 2023 Jun 19.
Iron (hydr)oxides are effective sorbents of arsenic that undergo reductive dissolution when exposed to dissolved sulfide, which significantly impacts the movement and repartition of arsenic in groundwater. This study investigated the sulfidation of As-bearing ferrihydrite and its consequences on arsenic repartitioning as well as formation and transformation of secondary minerals induced by sulfide in batch experiments. The sulfidation of As(III) and As(V) adsorbed on ferrihydrite shows very different results. In the As(V) system, sulfidation resulted in the production of significant amounts of elemental sulfur (S) and Fe, and Fe and sulfide combine to form mackinawite. Subsequently, Fe adsorbed and catalyzed the conversion of residual ferrihydrite to lepidocrocite. However, in the As(III) system, As(III) was protonated in the presence of sulfide to produce thioarsenate, which accounted for 87.9 % of the total aqueous arsenic concentration. The formation of thioarsenate also consumed the S produced by the sulfidation, resulting in no detectable S during solid phase characterization. The adsorption of thioarsenate on iron minerals notably affected the surface charge density of ferrihydrite, hindering the further formation of secondary minerals. Studies on the influence of thiolation on As-Fe-S system are of great significance for understanding the migration and redistribution of arsenic in groundwater systems under sulfur-rich conditions.
铁的（氢）氧化物是有效的砷吸附剂，当暴露于溶解的硫化物时会发生还原溶解，这对地下水中砷的迁移和重新分配有重大影响。本研究通过批量实验研究了含砷水铁矿的硫化作用及其对砷重新分配的影响，以及硫化物诱导的次生矿物的形成和转化。吸附在水铁矿上的As(III)和As(V)的硫化作用表现出非常不同的结果。在As(V)体系中，硫化作用导致产生大量元素硫（S）和铁，铁与硫化物结合形成马基诺矿。随后，铁吸附并催化残余水铁矿向纤铁矿的转化。然而，在As(III)体系中，As(III)在硫化物存在下质子化生成硫代砷酸盐，其占总溶解态砷浓度的87.9%。硫代砷酸盐的形成也消耗了硫化作用产生的S，导致在固相表征过程中未检测到S。硫代砷酸盐在铁矿物上的吸附显著影响了水铁矿的表面电荷密度，阻碍了次生矿物的进一步形成。研究硫醇化对As-Fe-S体系的影响对于理解富硫条件下地下水中砷的迁移和再分配具有重要意义。
