Abstract: This study compared the extraction efficiencies of Cu, Zn and Pb from the fly ash of municipal solid waste incineration (MSWI) by three different processes: water washing, acid washing and wash+acid washing. XRD and SEM/EDS analysis were exploited to illustrate the variation of morphology, mineralogical and chemical composition for treated fly ash during different processes. Results show that the treatment of fly ash by water washing or acid washing can not separate Cu, Zn and Pb from fly ash. Meanwhile, the water washing process followed by the acid washing process can effectively extract Cu and Zn, and Pb will be kept in the residue. In this combining process, the acid-residue ratio is the key parameter for the metal extraction. The optimum process parameters for the metal extraction are water-washing (water/ash=3∶1) combining acid-washing (acid/ash=6∶1). Results of XRD analysis demonstrate that the water washing or acid washing process remove several kinds of soluble compounds and mineralogy phases are newly formed. Results of SEM/EDS analysis show that contents of Si and O in the residues will increase due to the solubility of salts and hydration of some oxide compounds.

Key words: municipal solid waste incineration, fly ash, water washing, acid washing, extraction ratio, XRD, SEM/EDS

摘要： 以垃圾焚烧的一次飞灰为研究对象，比较了水洗，酸洗以及水洗结合酸洗工艺对飞灰中重金属元素Cu，Zn和Pb的洗脱率的影响，并应用XRD，SEM/EDS等研究了飞灰在水洗和酸洗过程中颗粒形态和矿物相组成的变化。结果表明：单独水洗和单独酸洗均不能实现Cu，Zn和Pb的分离；酸洗结合水洗时，Cu和Zn洗脱率均较单独水洗和单独酸洗大幅提高，Pb基本沉淀在酸洗后的残渣中。经水洗后酸洗阶段的酸灰比是影响金属洗脱效果的主要因素。分离Cu和Zn和Pb的最佳工艺参数为：水洗（水灰比为3∶1）+10%H₂SO₄酸洗（酸灰比为6∶1）。XRD结果表明，水洗过程易溶于水的物质其峰形基本消失；酸洗过程中，生成了含Pb的矿物质和Zn的结晶化合物。SEM/EDS分析结果表征了飞灰在水洗、酸洗过程中主要晶相的生成以及主要元素Ca，Si，O和Al的变化规律。

关键词: 垃圾焚烧, 飞灰, 水洗, 酸洗, 金属洗脱率, XRD, SEM/EDS