新型固化剂修复铅镉和石油烃复合污染黏土的机理及抗侵蚀性能研究

No studies regarding immobilization mechanisms and corrosion resistance of organic-metal co-contaminated soils, which are a serious problem in China, have been conducted to date. A new type of binder composed of oxidizing agent and industrial waste residues is used to solidify and stabilize the co-contaminated soils in this project. A clay soil is artificial polluted with lead (Pb), cadmium (Cd) and total petroleum hydrocarbons (TPH), and a series of laboratory tests and theoretical analyses are conducted to: ① investigate the leaching and strength properties of untreated and stabilized soils, obtain the binder composition design with best performance, and determine the main factors affect contaminated soil characters; ② measure the changes in leachability and strength of stabilized soil soaked in artificial corrosive solutions, and analyze the effects of both the new binder and corrosion environment on TPH removal, heavy metal immobilization, and the soil corrosion resistance; ③ clarify the main-minor reaction products and microscopic structures of stabilized clay, and address the interaction mechanisms between binder, contaminated soil and corrosive ions; ④ determine the diffusion parameters of contaminants and corrosive ions in stabilized soil under artificial corrosion environments, and quantitatively predict the contaminant transport in stabilized soil and its underlying aquifer using numerical simulation method. The results obtained from this project can remarkably improve the remediation technology of co-contaminated soils, and provide scientific basis and case support for the application of the solidification/stabilization in contaminated sites in China.

我国广布的重金属和有机物复合污染土的固化修复机理和化学侵蚀特征亟待深入研究。项目提出基于氧化剂去除有机物、工业废渣固定重金属的新型固化剂研发思路，采用试验和理论分析相结合的技术路线，以铅镉和总石油烃复合污染黏土为对象，重点研究以下关键问题：①系统研究固化污染土浸出和强度特性，提出新型固化剂最佳配比方案，阐明影响固化土性能的主控因素；②模拟多种离子溶液，查明化学侵蚀下固化土浸出毒性和强度演化规律，揭示新型固化剂和侵蚀环境对石油烃去除和重金属固定及固化土抗侵蚀性能影响机制；③明晰固化土中典型产物物相、微观形态特征，查明新型固化剂-污染土-侵蚀离子间相互作用机理；④模拟典型侵蚀环境，刻画侵蚀条件下固化土中污染物和侵蚀离子扩散特征，并结合数值模拟，定量预测分析固化土中污染物在周边水土介质的迁移规律。研究成果可提升复合污染土修复技术水平，为我国污染场地固化稳定化技术推广应用提供重要理论和科学技术支撑

我国沿海地区工业场地土体重金属和有机物复合污染严重，固化稳定化技术修复后的土体常面临含盐地下水侵蚀威胁，开发新型固化剂以解决化学侵蚀下固化效果稳定性问题迫在眉睫，然而现阶段尚缺乏对固化剂同步处置土中重金属和有机物，并有效抵抗外部侵蚀离子的相关宏观性能和微观机理系统研究。本项目通过室内试验、理论分析和数值模拟相结合的研究方法，以Pb、Cd 和石油烃(TPH)复合污染黏土为修复对象，开展了以下研究：1)考察了固化复合污染黏土浸出毒性、TPH全量、强度等关键性能规律，优化确定了新型固化剂最优配比，明确了修复效果主控因素及其最佳参数；同时针对固化剂净浆以及固化复合污染土，开展了热重、傅里叶红外光谱、X射线衍射和扫描电镜等分析，研究了TPH、氧化剂组分对相关物相及微观特征影响，揭示固化土浸出/强度控制主要控制机理。2)开展了单一和复合化学溶液浸泡下对固化土体侵蚀影响试验，通过考察固化土外观质量、浸出毒性、强度、pH值等变化，分析侵蚀离子、固化剂掺量、TPH对固化土关键性能影响规律，同时针对侵蚀条件下固化剂净浆和固化土，开展了侵蚀离子-固化剂-污染物-土间相互作用微观机理研究。3)基于半动态浸出试验获取了固化土在侵蚀条件下的重金属扩散系数，考察了侵蚀离子浓度、固化剂掺量、TPH污染对重金属和侵蚀离子扩散系数影响，查明化学侵蚀环境下的重金属浸出机制；基于土柱模型实验求解了重金属在固化土中的有效扩散系数和分配系数，利用POLLUTE软件模拟预测了复合盐溶液侵蚀下固化土向地下水和地表水中长期污染物释放影响。本项目在新型固化剂、固化污染土性能、抗化学侵蚀规律以及固化-侵蚀微观机理研究方面产出的一系列研究成果，具有良好的应用前景，可为固化稳定化技术在我国沿海地区应用推广提供可靠技术和理论支撑。