垃圾焚烧飞灰中重金属的分布规律及化学形态分析

Distribution features and chemical states of heavy metals in municipal solid waste incineration fly ash

研究了重庆市垃圾焚烧发电厂焚烧飞灰的粒径分布,分析了焚烧飞灰中重金属的含量、浸出特性和形态分布特征,讨论了不同粒径飞灰中重金属的分布特性。结果表明,大部分飞灰粒径集中在38-250μm,其中粒径为38-100 μm飞灰占总量的49,49%。飞灰浸出液中Pb和Zn的浓度均超出了《危险废物浸出毒性鉴别标准》(GB5085.3-2007),因此该焚烧飞灰被认定为危险废物。在<250μm粒径范围内,Cd、Cr、Cu、Mn和Pb普遍表现出向小颗粒富集的趋势;Zn的粒径分布则与上述5种元素表现出相反的趋势;Ni的分布与粒径的相关性不大,在各粒径上的分布较均匀。除Ni元素外,用BCR法分析所得的其他6种重金属形态分析结果和总量测定的结果基本吻合。飞灰中Cr、Ni、Zn和Mn主要以稳定态存在,而Cd、Pb和Cu则主要以不稳定态存在。

The given paper is concerned about our case study results on the distribution features and chemical states of heavy metals in the urban solid waste incineration fly ash. The samples we have selected come from the municipal solid waste incineration （MSWI） power plant in Chongqing city. In this paper, we have analyzed and determined the distribution amount and size of the ash particles, their constituent contents, leaching characteristics, chemical states of the heavy metals in the ash, along with the distribution characteristics of heavy metals in the size classified fractions. The results of our case study show that most of the fly ash （about 49.09 % ） have been accumulated in fractions of 38 - 250 μm and fractions of 38 - 100 μm. The MSWI fly ash has been considered as hazardous waste since the contents of Pb and Zn in the leaching solution exceeded the national fly-ash release standard for extraction procedure toxicity for hazardous wastes （GB 5085.3--2007）. Cd, Cr, Cu, Mn and Pb were mainly accumulated in fine fractions while Zn had opposite distribution trend when the particle size was 〈 250 μm, Ni was found existing homogeneously in each particle＇s size. The metal toxicity of MSWI fly ash does not only depend on their total content, but also is related to the floating and transforming behavior of different forms of metals in the environment. The results of the sequential chemical extraction and different forms of the concurrent metals in MSWI fly ash we have gained can probably be taken as starting point or scientific basis for treating and utihzing MSWI fly ash. Besides Ni, the results of speciation analysis by BCR method of the six other elements prove to be in conformity with the conclusions derived from the total quantity determination. Cr, Ni, Zn and Mn can be found to be existing in the air in somewhat stable state while Cd, Pb and Cu in somewhat unstable state.