有机螯合剂与磷酸盐联合稳定垃圾焚烧飞灰中重金属的作用机理

为探讨二硫代氨基甲酸型有机螯合剂(FACAR)和重过磷酸钙(TSP)对垃圾焚烧飞灰中重金属Pb、Cd、Ni的稳定作用机制，对稳定前后的飞灰采用BCR连续提取法、X射线衍射(XRD)分析以及扫描电镜-能谱(SEM-EDS)联用等分析方法进行了表征。结果表明：投加质量分数5%的FACAR能有效稳定飞灰中Pb、Cd和Ni，其浸出浓度低于《生活垃圾填埋场污染控制标准》(GB 16889-2008)规定的浸出浓度限值；采用3% FACAR和3% TSP复配药剂处理，可使飞灰达到GB 16889-2008进场要求；经复合药剂稳定处理后的飞灰颗粒表面孔隙度明显降低，飞灰中Pb、Cd和Ni的形态均由不稳定态向稳定态转化。该复合稳定剂的稳定机制主要为螯合、共沉淀和吸附联合作用机制，其中，有机螯合剂中含硫官能团是影响重金属稳定的主要因素，且重金属具有优先与含硫官能团结合的特性。

Stabilization mechanism of heavy metals in MSW incineration fly ash using organic chelating-phosphate complex agent

Municipal solid waste (MSW) incineration fly ash were stabilized by combining dithiocarbamate chelating resin agent (FACAR) with triple superphosphate (TSP). For the pristine and stabilized fly ash, BCR sequential extraction procedure, X-ray diffraction (XRD) analysis and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) measurement were performed to explore the mechanism of heavy metals stabilization. The results indicated that 5% FACAR addition could effectively stabilize heavy metal Pb, Cd and Ni in fly ash, and the leaching concentrations of Pb, Cd and Ni were lower than the limits stipulated in Standard for Pollution Control on the Landfill Site of Municipal Solid Waste (GB 16889-2008). Moreover, the fly ash treated by the combination of 3% FACAR and 3% TSP could meet the requirements of GB 16889-2008 and the cost obviously decreased, its surface porosity was reduced significantly, and the unstable forms of Pb, Cd and Ni changed to stable ones. The stabilization of Pb, Cd and Ni was mainly ascribed to the joint mechanisms of chelation, co-precipitation and adsorption. Furthermore, the sulfur functional groups contained in the FACAR were the main factors affecting the heavy metals stabilization, which could be preferentially bonded with the sulfur functional groups.