巯基化氧化石墨烯/铁锰氧化物复合纳米材料原位固定土壤/地下水中汞的机理研究

Mercury is one of the most pervasive, persistent, and extremely toxic metals in the environment, posing direct harm to human health and ecological safety. Hg(II) is the most predominant inorganic form of mercury, whereas methylmercury (MeHg) is the primary mercury species that accumulates in the food chain. However, only a few researchers reported thorough removal of inorganic and organic mercury from groundwater/soil. In situ remediation technology using nanoparticles have been consistently sought due to its unique advantages, such as low cost, reduced remediation time, less environmental disruption, and enhanced particle reactivity with contaminants. This research aims to develop a new class of thoil-functionalized graphene oxide/Fe-Mn oxide nanocomposites (SGO/Fe-Mn) and investigate effects of SGO/Fe-Mn on mobility, fate, and transport of inorganic and organic mercury (Hg(II) and MeHg) in soil and groundawter. The specific objectives are as follows: 1) prepare and characterize SGO/Fe-Mn; 2) investigate the effectiveness of SGO/Fe-Mn for in situ immobilization of Hg(II) and MeHg in soil and groundwater under typical subsurface hydrodynamic and environmental conditions; 3) examine the evolution of SGO/Fe-Mn, the interaction with soil, and the effects on soil physical and chemical properties; and 4) determine the transport behavior of SGO/Fe-Mn in the soil and the resulting effects on the physical, chemical, and biological availabilities of mercury in soil and groundwater. The outcome of the proposed research will establish the mechanism on the effects of SGO/Fe-Mn on the mobility of mercury, and provide important theoretical foundation and practical experience for in situ remediation of highly toxic heavy metals in soil and groundwater of China.

土壤/地下水汞污染是工业发展与城市化进程中的突出问题，危害人类健康和生态安全。目前可同时固定低浓度（ppb）无机汞和有机汞的方法报道很少。近年来低成本、无毒无害、周期短、固定化效果强的纳米材料的原位修复技术得到了广泛关注。本项目拟制备一种新型的巯基化氧化石墨烯/铁锰氧化物复合纳米材料（SGO/Fe-Mn），研究其对污染场地无机汞和甲基汞的迁移和宿命的影响。探讨我国代表性土壤和地下水条件下，SGO/Fe-Mn对土壤和地下水中无机汞和有机汞的固定速率、固定效果和固定机制；考察SGO/Fe-Mn的物理化学演变，与土壤的相互作用，对土壤理化性质等的影响；研究SGO/Fe-Mn在土壤中的迁移过程及运移诱发的污染物的迁移及固定。通过控制SGO/Fe-Mn的颗粒粒径和浓度加强汞的原位固定，降低其物理化学和生物可用性，为我国重金属污染的原位固定提供重要的理论支持和实践经验。

土壤/地下水汞污染是工业发展与城市化进程的突出问题，危害生态安全和人体健康，其治理修复具有挑战性。本项目制备了一种新型巯基化氧化石墨烯/铁锰氧化物复合材料，确定了材料的形成机制；系统研究了其对水体和土壤中无机汞和有机汞的固定化效果；借助现代谱学分析技术深入探讨固定化机制，并阐明了修复材料的环境效应。取得的研究成果包括：（1）材料的制备过程中，铁锰氧化物通过含氧基团和π-π作用结合在氧化石墨烯（GO）表面，形成GO/Fe-Mn。巯基化过程中，3-巯基丙基三甲氧基硅烷（3-MPTS）通过与GO/Fe-Mn表面的含氧官能团（如−OH、C=O、C−O−C和O=C−O等）和π-π作用负载在材料表面，形成SGO/Fe-Mn复合材料；（2）在典型环境条件下，SGO/Fe-Mn对水体中Hg2+和CH3Hg+的吸附能力强、吸附速度快、吸附容量高。去除机理包括静电吸引、表面配合和化学沉淀作用；（3）负载汞的SGO/Fe-Mn可再生利用，再生3次后其对Hg2+和CH3Hg+的去除率分别为98.1%和67.0%；（4）SGO/Fe-Mn可有效固定化土壤和地下水中的汞，将土壤中的汞从不稳定存在的形态（可交换态、碳酸盐结合态）转化为稳定存在的形态（铁锰氧化物结合态、有机物结合态和残余态），降低汞的浸出毒性，减小污染土壤的环境风险，且固定化的汞具有很好的长期稳定性；（5）复合材料的加入可有效提升土壤性能。研究结果将为新型修复材料在重金属原位修复领域中的应用提供理论支撑和技术支持，为重金属的治理修复提供新思路、新技术和新方法，具有很好的工业化应用前景。