仿生修饰载铁生物炭材料强化生物修复氯代烃污染地下水的性能及脱氯耦合机理

Preparing efficient remediation materials is an important technical link of the in-situ enhanced bioremediation of chlorinated hydrocarbon-contaminated groundwater. Biochar is commonly used as the carrier and adsorbent to improve the treatment performance of remediation materials. It was recently found that biochar, as an electron shuttle, can also stimulate iron redox cycling to enhance the dechlorination of chlorinated hydrocarbons induced by microbial dissimilatory iron reduction. However, the coupling effect and mechanism of biochar and zero-valent iron (ZVI) on dechlorination in this process is not yet clear. In this proposal, polydopamine with the capability of biomimetic modification will be used to prepare a composite remediation material containing organic carbon source- and iron-loaded biochars. We intend to ascertain the treatment performance, coupling effect on dechlorination and feasible practical application parameters of this composite for enhancing bioremediation of chlorinated hydrocarbon-contaminated groundwater. On that basis, associated technologies like spectrometry, electrochemistry, high-throughput sequencing and stable isotope probing will be adopted to deeply explore the multiple electron transfer pathways with biochar participation during the composite-enhanced dechlorination process, and to further identify responses of electron transfer activity, abundance and community structure of functional microbes to those pathways. Finally, we will uncover the coupling mechanism of biochar (as the solid-phase electron shuttle) and ZVI at the composite micro-interface on the dechlorination of chlorinated hydrocarbons enhanced by chemical and microbial dissimilatory iron reductions. The expected achievement of this study will not only provide an innovative technical support for the in-situ enhanced bioremediation of chlorinated hydrocarbon-contaminated groundwater, but also potentially improve the mechanism on the biogeochemical degradation of organic pollutants driven by iron cycling.

制备高效修复材料是原位强化生物修复氯代烃污染地下水的重要技术环节。生物炭常作为载体和吸附剂以提高修复材料的处理性能。最近发现其还可作为电子穿梭体加速铁氧化还原循环，进而促进氯代烃生物异化铁还原脱氯，但其中有关生物炭和零价铁的耦合作用效果和机理尚不清楚。本项目拟利用聚多巴胺的仿生修饰功能，构建负载有机碳源和零价铁的生物炭复合修复材料，探明其强化修复氯代烃污染地下水的性能、脱氯耦合效应和可行的现场应用技术参数。进一步采用谱学、电化学、高通量测序和稳定同位素探针等技术，深入解析复合材料强化脱氯过程中生物炭参与的多重电子传递途径，明确功能微生物电子传递活性、丰度和群落结构对其响应规律，最终揭示材料微界面上生物炭作为固态电子穿梭体和零价铁强化化学和生物异化铁还原脱氯的耦合机理。预期成果将为氯代烃污染地下水原位强化生物修复提供创新技术支持，并有望完善铁循环驱动的有机污染物生物地球化学降解机制。

地下水氯代烃污染是全球普遍关注的环境问题，亟需开发高效的修复技术对其进行治理。生物炭常作为零价铁载体用于地下水中氯代烃的物理吸附和化学降解去除，但其作为电子穿梭体激活零价铁介导的生物异化铁还原脱氯效果与机制尚不明确。本项目以聚多巴胺为表面仿生修饰层，制备了负载纳米零价铁和缓释碳源的生物炭基复合材料，评估了其协同微生物强化去除地下水中1,1,1-三氯乙烷的效果，确定了关键作用组分、最佳使用条件和可行技术运行参数，并从电子传递途径、铁物种变化和功能微生物活性与群落响应等角度，揭示了复合材料强化化学和生物异化铁还原脱氯的耦合作用机理。主要研究结果如下：1）纳米零价铁和聚乳酸颗粒均匀负载于生物炭表面，且经聚多巴胺修饰的复合材料具有较高释碳性、亲水性和电化学活性。2）复合材料能有效协同微生物去除地下水中1,1,1-三氯乙烷（最大去除率94.61%），关键组分生物炭、聚乳酸和纳米零价铁的最佳质量比为7:1:2，材料最佳投加量为1.0%（w/v），体系适宜pH为6~10且对不同浓度污染物均有明显去除效果。3）可行的现场工程参数：材料注射量为含水层介质干重的1.0%，注射压力800psi，注射深度6m，注射间隔0.5m，最佳作用时间0~60d，最佳作用半径2m。4）复合材料对污染物的去除方式主要为纳米零价铁快速化学还原脱氯和胞外呼吸菌异化铁还原脱氯的耦合作用，其中生物炭通过加快协同体系电子传递速率，增加吸附态Fe(II)含量，以提高材料的异化铁还原脱氯效率。研究结果可为氯代烃污染地下水原位修复提供新技术，也可为氯代有机污染物生物地球化学降解机制提供新思路，具有积极的理论意义和应用价值。