含砷硫化铁矿物光化学氧化过程与砷释放机制

The oxidation and dissolution of arsenic-containing iron sulfide minerals lead to the release of arsenic and subsequently cause environmental pollution, which poses serious threats to the ecological environments and human health. On the upper surface of soils exposed to air, abiotic chemical reactions contribute much to the oxidation and dissolution of arsenic-containing iron sulfide minerals with the release of arsenic in neutral aquatic systems. Reactive oxygen species including ·OH and H2O2 would act as intermediates and participate in these oxidation reactions. Solar irradiation on iron sulfide minerals and their oxidation products can also induce the production of reactive oxygen species such as ·OH, O2·- and H2O2. However, there is a lack of systematic research on the formation processes of these reactive oxygen species and the mechanism underlying the oxidation of iron sulfide minerals by reactive oxygen species. In addition, little is known about the influence of crystal impurities, associated ores, and environmental conditions on the photochemical reactions of arsenic-containing iron sulfide minerals. In this project, a photochemical reaction system will be constructed to study the oxidation of typical arsenic-containing iron sulfide minerals, such as arsenian pyrite and arsenopyrite. Photochemical oxidation reactions of arsenic-containing iron sulfide minerals will be conducted under UV/Vis light and solar irradiation. The effects of mineral types, crystal impurities, associated ores, common photoactive components, oxygen partial pressure, temperature, pH and light intensity will be investigated in the photochemical reaction processes. The formation routes of reactive oxygen species and corresponding oxidation mechanism of arsenic-containing iron sulfide minerals will be studied in detail. The key factors affecting the oxidation and arsenic release of arsenic-containing iron sulfide minerals will be also identified. The proposed work is expected to facilitate a better understanding of the migration and transformation of arsenic in the soils of different mining-impacted areas, and provide basic information on the potential environmental risks regarding the oxidation of arsenic-containing iron sulfide minerals. Besides, it may offer some theoretic guidance for retarding the oxidation rate of arsenic-containing iron sulfide minerals and reducing arsenic pollution.

含砷硫化铁矿物氧化溶解释放砷而污染环境，严重威胁矿区生态环境与人类健康。浅表层土壤偏中性有氧水体系，化学氧化是导致硫化铁矿物溶解释放砷重要原因，·OH和H2O2等活性氧多为中间体参与氧化反应。太阳光辐射硫化铁矿物及其氧化产物都会诱导产生·OH、O2·−和H2O2等活性氧，这些活性氧生成途径及其在氧化过程中作用机制尚缺乏系统研究，硫化铁矿物晶格杂质、伴生矿和环境条件对光化学反应影响尚不明确。本项目拟构建以含砷黄铁矿和毒砂矿为代表的含砷硫化铁矿物光化学氧化反应体系，系统考察不同矿区单矿物晶格杂质与伴生矿组成及含量、光活性组分、氧分压、温度、pH和光强等环境因素影响，阐明各活性氧产生途径及其在含砷硫化铁矿物氧化释放砷过程中作用机制，揭示硫化铁矿物光化学氧化机理及影响砷释放关键因素。以期为认识砷在不同硫化铁矿区土壤中迁移转化规律及潜在环境风险提供基础数据，为缓解硫化铁矿物氧化与砷污染提供理论指导。

含砷硫化铁矿物氧化是导致矿区土壤砷污染重要来源，太阳光辐射硫化铁矿物及其氧化产物都会诱导产生OH•、O2•−和H2O2等活性氧，这些活性氧生成途径及其在硫化矿物氧化过程中作用机制尚缺乏系统研究，硫化铁矿物组成和环境条件对光化学反应过程影响尚不明确。本项目在湖南、广西和贵州等矿区采集了黄铁矿、毒砂矿和斜方砷铁矿等，开展了矿物光化学氧化实验，考察了组成、典型环境组分对硫化铁矿物光化学氧化释放砷过程的影响。结果表明：太阳光辐射和溶解氧诱导含砷黄铁矿产生OH•、O2•−和H2O2等活性氧促进其氧化溶解。黄铁矿氧化释放的Fe2+可通过芬顿反应形成H2O2促进As(III)氧化。毒砂矿表面Fe(II)与氧气作用产生的H2O2和OH•有利于As(III)快速氧化生成As(V)，氧化速率随体系pH从3.0上升到7.0逐渐降低；紫外光照环境，柠檬酸盐和溶解氧促进Fe(III)-citrate和活性氧物种形成，进而加速氧化反应；SO42−存在时，毒砂矿溶解释放的Fe(II)能被氧化生成施氏矿物，通过施氏矿物-As(III)配合物电荷转移作用促进毒砂矿光化学氧化。雄黄表面硫缺陷位点诱导H2O分解及表面As(II)被溶解氧氧化产生OH•和H2O2等，进而加速其氧化并释放As(III)。太阳光激发雄黄产生电子与氧反应生成O2•−，催化加速氧化作用。光诱导雌黄表面产生活性氧物种OH•、H2O2和O2∙−加速了其自身氧化溶解及As释放。采用光辐射有效提高了铁锰复合氧化物对水溶液中As(III)的去除，而Fe(II)和As(III)的协同氧化显著促进了As的去除。紫外光辐射Fe(II)促进了O2•−和OH•等生成，进而加速As(III)氧化。这些结果揭示了典型硫化铁矿物光化学氧化机理及影响砷释放关键因素，为认识砷在不同硫化铁矿区土壤中迁移转化规律及潜在环境风险提供基础数据，可为缓解硫化铁矿物氧化及砷污染提供理论指导。以第一标注发表SCI论文8篇，第二标准和正在整理的论文多篇；培养研究生10余名；主持人入选国家“万人计划”领军人才，指导的博士生毕业后继续在本组开展博士后研究，获批教育部“博新计划”和国家自然科学基金青年项目。