生物电化学-电渗析耦合系统驱动垃圾焚烧飞灰中重金属的迁移与转化机理

The two major handling ways of highly leaching toxic heavy metals in municipal solid waste fly ash are recovery of heavy metals from fly ash and reducing heavy metals leachability by stabilization of heavy metals in fly ash. This work focus on studying the fly ash using theoretical analysis, model simulation, experimental research and comprehensive analysis.The integrative system of bioeletrochemical system and electrodialysis, driven by bioeletrochemical system as power supply, is constructed for treatment of fly ash. The mechanism on migration and transformation of heavy metals in fly ash at the coupling system was revealed. The feedback principle between the BES potential of anode and cathode, concentration and chemical speciation of heavy metals and the mineralogy/morphology of cathodic sediment under different conditions were established. The chemical speciation and concentration characteristics of heavy metals in leaching solution at anode of electrodialytic reactor, cation exchange membrane and solution at cathode of electrodialytic reactor were analyzed. Those were used to understand the migration and transformation of heavy metals in leaching solution at the coupling system. Both chemical speciation and concentration of heavy metals in fly ash or leaching solution and the leaching or surfacial features of fly ash were compared to identify the characteristics and mechanism of adsorption/desorption between fly ash and heavy metals in leaching solution along with the treatment by the coupling system. The results will be used to establish the theoretical foundation for disposal of municipal solid waste fly ash by BES-eletrodialytic coupling system, provide theoretical guidance and technical support to dispose and resource utilization of municipal solid waste fly ash.

垃圾焚烧飞灰含有高浸出浓度的有毒重金属，其主要处理方法有回收飞灰中重金属和重金属稳定化处置两种方式。该项目拟以垃圾焚烧飞灰为研究对象，采用理论分析、模型模拟、实验研究和综合分析相结合的研究方法。研究以生物电化学系统(BES)为电源的BES-电渗析耦合系统处理垃圾焚烧飞灰，揭示飞灰中重金属在耦合系统中的迁移与转化机理。建立BES阳极/阴极电位-电渗析阴极室中浸出液中重金属浓度及化学形态-电渗析阴极沉积物赋存状态之间的响应机制，考察不同条件下电渗析阳极室飞灰浸出液、阳离子交换膜和阴极室溶液中重金属浓度及化学形态的分布特征，探索飞灰浸出液中重金属在耦合系统中的迁移与转化机理；比较处理前后飞灰和浸出液中重金属浓度及化学形态以及飞灰的表面特性和浸出毒性，明确飞灰与浸出液中重金属的吸附/解析特性与机制。为BES-电渗析耦合系统处置飞灰奠定理论基础，也为飞灰的资源化处置提供可借鉴的理论指导和技术支撑。

经过三年的持续研究，本项目几乎实现了预期的科研目标，并在此基础上，针对垃圾焚烧发电厂的垃圾渗滤液进行了有效扩展。本项目执行中重点解决的问题包括：飞灰浸出液中重金属在 BES-电渗析耦合系统电渗析阴极室的转化机理，飞灰浸出液中重金属在 BES-电渗析耦合系统中的迁移与转化机理。飞灰与浸出液中重金属在 BES-电渗析耦合系统中的吸附/解析特性与机制。在本项目的支持下，发表学术论文6篇，其中SCI收录论文2篇，CSCD收录论文2篇。本研究的主要结果为：1.浸取剂种类对飞灰浸出效果有显著影响，无机酸可提升浸出液中重金属浓度，生物电化学系统可以将浸出液中Cu转化单质，对其余重金属的以化学沉淀为主附着在电极上，重金属浓度是影响转化效果的最显著因素。2.飞灰浸出液在电渗析迁移过程，表明重金属浓度也是重要的影响因素，在迁移过程中，提高系统输出电压导致离子交换膜上重金属沉积量增大，不利于重金属的迁移和转化,比较处理前后系统中重金属浓度变化，发现Cu转化效果明显。3.采用耦合系统处理飞灰混合液，液固比对体系中重金属迁移的影响最强，处理后飞灰中重金属残渣态比例显著提高，可交换态含量显著降低。本研究结果有助于正确认识重金属的电迁移和转化过程，也对飞灰稳定化处置提供一种思路，也对重金属污染治理提供科学依据。