阴极去极化驱动的海绵铁/脱硫弧菌耦合体系对铀矿冶废水的协同修复机理研究

The uranium-bearing radioactive wastewater generated by the uranium mining and milling industry has posed a serious challenge for the nuclear energy development in China. This prickly problem should be attached great importance. In recent years, much attention has been paid to the application of microbial mineralization based on sulfate-reducing bacteria (SRB) to remove radionuclide contamination from surface or ground water bodies. However, some environmental factors, such as acidity, nitrate and dissolved oxygen, limit its application potential. In this project, we intend to build a series of iron-bacteria coupled system on the basis of cathodic polarization theory (SRB-induced corrosion of steel and iron). In these coupled systems, sponge iron with large surface area and high porosity will be used as a carrier to load Desulfovibrio desulfurican, a most common strain of SRB in nature which can bioreduce U(VI) as well as drive corrosion of steel and iron. Then the relationship among the iron scale, morphological structure, microbial loading stability and desulfurization performance of those coupled systems will be clarified based on which the coupled system with stable iron-bacteria combination and efficient desulfurization performance will be screened out for the following kinetic and mechanism research. Batch and column reactor experiments will be conducted to study the removal kinetics of U(VI) and sulfate as target pollutants and identify key factors affecting the conversion of pollutants. The interactions among sponge iron, Desulfovibrio desulfurican, target pollutants and their transformation products and interface effects will be revealed. The mechanism on the integrated elimination of radionuclide contamination by the coupled system will also be elucidated. The goal of this study is to explore an integrated chemical and biological remediation theory and technology on the treatment of uranium-bearing wastewater and to open up a new way to decrease the release of radioactive effluent effectively in China.

铀矿冶行业所产生的含铀放射性废水已成为中国核电发展面临的严峻问题，亟待高度重视。近年来，应用硫酸盐还原菌(SRB)生物矿化法消除地表/下水体中的核素污染受到关注，但环境中的酸度、硝酸根和溶解氧等因素限制了其应用潜力。本课题拟以比表面积大且孔隙率高的海绵铁为载体，负载具有生物还原U(VI)能力和促进钢铁腐蚀的最常见的一种SRB-脱硫弧菌，基于SRB驱动钢铁腐蚀的阴极去极化作用构建铁?-菌耦合体系，确定铁粉尺度、耦合体系结构形态、菌体负载稳定性和脱硫性能之间的关系，筛选铁-菌组合稳定和高效脱硫的体系，进而通过血清瓶和柱反应器模拟修复实验，研究其对目标污染物U(VI)和硫酸根的去除动力学，查明关键影响因子，揭示海绵铁、脱硫弧菌以及污染物及其转化产物之间的交互作用规律及界面效应，阐明核素污染的联合消除机理。本研究旨在探索含铀废水的化学生物联合修复理论和技术，为有效减少我国放射性废水排放开辟新途经。

铀矿冶行业所产生的含铀废水已成为中国核电发展面临的严峻问题，亟待高度重视。本项目利用脱硫弧菌(Desulfovibrio desulfurican)和海绵铁(direct reduced iron, DRI)相结合，根据钢铁电化学腐蚀的基本原理，构建D. Desulfurican+DRI耦合体系对模拟含铀废水进行了室内修复，揭示了D. desulfurican、DRI和复合核素污染物(铀酰、含氧酸根和重金属离子)之间的相互作用规律，阐释了污染物的化学生物联合修复机理。首先，通过批次实验考察了温度、pH值和底物浓度等因素对D. desulfurican生长代谢的影响，探索了DRI对D. Desulfurican脱硫性能的强化作用及强化机理，建立了D. desulfurican和D. Desulfurican +DRI两个体系的硫酸盐还原反应动力学模型和反应速度的经验公式。其次，研究了DRI去除铀酰的反应动力学和反应机理。XRD和XPS分析表明，铀酰溶液与DRI接触后，铀酰以非晶相六价UO3沉积在海绵铁表面。再次，考察了pH、共存含氧酸根阴离子、重金属和DRI电化学腐蚀产物赤铁矿(Fe2O3)和针铁矿(FeOOH)等环境因子对铀生物沉淀过程的影响。结果表明，pH值对D. desulfurican生物沉淀U(VI)的过程存在显著影响，随pH值的升高其沉淀率也不断升高，当pH=6.0时U(VI)沉淀效率达到最大。含硝酸根的氧化性环境不利于铀的生物沉淀过程，通过反硝化作用去除环境中的硝酸根成为消除环境中铀污染的前提。U(VI)的生物还原速度受赤铁矿抑制作用较大，受针铁矿抑制作用较小。最后，利用柱式反应器研究了D. desulfurican和DRI联合处理模拟含铀废水的效果。结果说明，D. desulfurican +DRI反应器在碱化废水pH值、脱硫和固定U(VI)的效率方面均优于D. desulfurican反应器，因此DRI对于利用D. Desulfurican处理含铀废水具有显著强化作用。本研究建立了科学的化学生物耦合修复理论，优化了反应墙设计模式，为利用我国丰富的地微生物和铁资源来治理核素污染奠定了基础。项目相关研究工作获地厅级成果奖1项；发表论文15篇，其中SCI收录13篇，EI收录1篇，ISTP收录1篇；培养博士后1名和博士生2名。该项目较好的完成了研究任务。