铁锌双金属机械化学球磨法高效降解污染土壤中滴滴涕的机理研究

As a non-incineration POPs treatment technology, mechanochemical dehalogenation (MD) has great potential for commercialization. It's featured by mild reaction conditions, simple process, low energy consumption, high efficiency, applicability for a wide range of pollutants and low risk of secondary contamination. Therefore, it has advantages over other physical and chemical treatment technologies. Although MD technology is being commercialized in developed countries, it remains in the bench scale or pilot scale studies in China. Most studies focus on treatment of pure chemicals or solid waste such as fly ash with little work done on POPs contaminated soil. And the research on the MD processes and mechanism is still in its infancy in China. The promotion and application of MD technology is hindered by the lacking of deep understanding of the reaction processes and mechanisms. In the preliminary studies, the project team has successfully developed bimetallic iron and zinc powder as a cost-effective mechanochemical ball milling agent. Based on that, the proposed project is aimed to further improve the Fe-Zn mechanochemical ball milling system by screening high efficient additives and optimizing the process parameters. The reaction kinetics will be studied by experiments and model simulation. Then advanced chemical analysis and material characterization techniques will be used to detect degradation products, probe into the DDTs dehalogenation processes, and elucidate possible degradation pathways. The project will enrich the theoretical basis for the development of mechanochemical treatment technology for sites heavily contaminated by multiple organochlorinated pesticides.

机械化学脱卤技术是一种极具应用潜力的非焚烧POPs处理技术。与其他物化技术相比，它具有反应条件温和、工艺流程简单、能耗小、效率高、广谱性、二次污染风险小等优点。虽然机械化学修复技术已在少数发达国家进入商业化应用，但我国相关研发仍处于小试和中试阶段，且多针对纯化学品或飞灰等固废的处理，对POPs污染土壤的研究较少。我国对机械化学反应过程和机理的研究刚刚起步，相关研究的不足已成为阻碍该技术推广应用的瓶颈。项目申请人团队在前期预研究中成功研发了经济高效的Fe-Zn双金属机械化学球磨药剂，本项目拟在此基础上通过筛选高效球磨助剂，优化工艺参数，进一步完善Fe-Zn双金属机械化学球磨体系；通过试验及计算机模拟研究其反应动力学，并综合运用化学分析和材料表征等手段，开展DDTs降解产物、反应过程及机理研究，为我国有机氯POPs农药场地高浓度复合污染土壤的机械化学处理技术研发充实理论基础。

因反应条件温和、工艺流程简单、效率高、应用范围广、无二次污染等优点，机械化学球磨技术在POPs化学品及重污染土壤无害化处置方面具有广阔应用前景。然而，国内目前相关研究主要集中于POPs化学品和飞灰的处置，利用机械化学球磨技术处理高浓度POPs污染土壤的研究甚少。本项目以实际场地高浓度DDT污染土壤为研究对象，从药剂筛选、工艺参数优化、土壤性质的影响、反应动力学、反应途径与机理、产物资源化利用、安全处置与生态风险评估等角度展开系统研究。.研究发现，（1）与CaO、零价铁等常见药剂相比，Fe-Zn双金属去除土壤DDTs的效率最高、DDE残留最少，反应最彻底；（2）Fe-Zn双金属球磨处理高浓度DDT污染土壤的最佳工艺参数为：球料比28:1、转速500rpm、Fe/Zn比例7:3、物料比10:5；（3）向土壤中添加有机质（生物炭）会显著降低机械化学球磨的效率，且球磨产物中残留DDTs的化学有效性显著下降；（4）通过正交试验与离散元模拟（DEM）建立了反应速率常数、体系碰撞能量同转速和球料比的函数关系。Fe-Zn双金属球磨DDT化学品和土壤的反应动力学都符合Delogu模型而CaO等金属氧化物处理则都符合拟二级动力学模型；（5）通过GC-MS、红外光谱、拉曼光谱、扫描电镜能谱、X射线光电子能谱等化学分析和材料表征，本研究认为Fe-Zn双金属在球磨过程中对DDT的降解主要是在脱氯的同时进行苯环裂解，在此期间虽有少量苯环发生聚合但最终都碳化成了石墨和无定形碳；（6）球磨产物可作为球磨药剂多次使用或作为氯代烃污染水体的还原脱氯药剂，基于水泥的固化-稳定化技术可实现球磨产物的安全处置；（7）向土壤中添加球磨产物，未对赤子爱胜蚓产生显著的慢性毒性。.本项目研究成果为Fe-Zn双金属机械化学球磨技术体系的建立，装备研发以及该技术在包括DDT在内的POPs高污染土壤处置中的实际应用提供了理论基础，积累了系统的试验数据。