垃圾焚烧飞灰中重金属的稳定化研究

Stabilization of heavy metals in the fly ash from solid waste incineration

以华中某垃圾焚烧发电厂产生的飞灰为研究对象,分别考察了乙基黄原酸钾(乙基黄药)、硫化钠、高分子重金属离子捕集沉淀剂DTCR、磷酸钠、二乙基二硫代氨基甲酸锌(二乙氨基荒酸锌)以及磷酸钠与二乙氨基荒酸锌的混合药剂对飞灰进行稳定化处理的效果,运用X射线衍射分析(XRD)、扫描电子显微镜(SEM)和BCR三步提取法对飞灰中重金属的稳定化机理进行研究。研究结果表明:磷酸钠能有效稳定飞灰中重金属元素Pb、Cr,二乙氨基荒酸锌则对Cd、Ni等元素稳定化效果较好,采用8%磷酸钠和1%二乙氨基荒酸锌的混合药剂配伍方案添加处理飞灰,能满足国家的填埋标准。研究发现重金属与混合药剂反应没有生成晶体,而是在过程中与稳定化药剂反应生成絮状沉淀均匀地附着在飞灰颗粒表面及缝隙中,使其棱角变得模糊、表面变得致密,处理后的飞灰中重金属形态由不稳定态转化为稳定态,有效降低了飞灰中重金属的浸出浓度。

Stabilization of heavy metals in the fly ash from a municipal solid waste incineration power plant in central China has been investigated using six different chemical reagents： potassium ethylxanthate,Na2 S,DTCR,Na3PO4,zinc diethyldithiocarbamate,and a mixture of Na3PO4 and zinc diethyldithiocarbamate. X-ray powder diffraction（ XRD）,scanning electron microscopy（ SEM） and sequential chemical extraction were employed to analyze the mechanism of stabilization of heavy metals in the raw fly ash and the treated fly ash. The results showed that Na3PO4 afforded good stabilization of Pb and Cr,whilst zinc diethyldithiocarbamate gave excellent stabilization of Cd and Ni. By adding a mixture of 8% Na3PO4 and 1% zinc diethyl dithiocarbamate to treat fly ash,the leaching concentration of heavy metals in treated fly ash could satisfy the national landfill standard GB 16889—2008.The reaction between the heavy metal ions and the added reagents produced no crystalline phases,but the reaction generated a flocculent precipitate evenly attached on the surface of the fly ash particles,making its edges blurred and its surface compact. The proportion of heavy metals from treated fly ash in the reducible-extractable form decreased and whilst that in residual form increased,so that an unstable state became more stable. Therefore the leaching toxicity of fly ash could be effectively reduced.