生活垃圾焚烧飞灰重金属在浸出柱中的浸出规律

通过浸出柱实验,研究生活垃圾焚烧飞灰中重金属的动态浸出规律.结果表明,浸出液中各种重金属的质量浓度均随浸取剂与飞灰比值(L/S)增大而减小,并在L/S＞2后趋于稳定.除Pb外,浸出质量浓度均低于污水综合排放标准(GB 8978-1996)限值.对比原灰与浸出残留物重金属多级提取结果表明,飞灰的重金属在浸出柱实验中释放能力由强到弱依次为:Cd、Ni、Cu、Pb、Zn和Cr.受浸取剂pH值和固液接触方式影响,浸出柱重金属累计浸出量都小于国家标准(GB 5086.2-1997)浸出量(Cd除外),尤其Cr、Hg和Pb的浸出柱累计浸出量分别是国标浸出量的23.25%、1.29%和14.29%

Leaching behavior of heavy metals from MSWI APC residues by column leaching test

This paper aims to present the results of the authors' study of the leaching behavior of heavy metals in air pollution control (APC) residues from the urban solid waste (MSW) incinerator through the so-called flow-through column test. It was concluded that the concentrations of heavy metals in the leachate decreased sharply with the increase of cumulative liquid to solid (L/S) ratio at first, and then became relatively stable when the L/S ratio reached 2. Most heavy metals, except Pb, when combined with the integrated wastewater, would reveal a discharge standard lower when the L/S ratio was over 2. Then the paper analyzed the chemical characteristics of the heavy metals in the ash and the remaining ash after leaching by using the sequential extraction procedures. Our results have shown that, Cd and Ni leached from the column was mainly exchangeable and acid soluble; leachable Cu was mainly acid soluble; Cr was almost insoluble, thus less Cr was released from the column test. At the same time, leachable Pb was mainly acid soluble and organically bound. On the other hand, leached Zn was mainly iron oxide occluded. From the sequential extraction procedure for the APC residues, the leach ability order of the heavy metals was Cd > Ni > Cu > Pb > Zn > Cr. Influenced by pH value of the leachate and the mode of liquid and then solid contact, the accumulative quantities of the heavy metals leached from the APC residues proves to be smaller than the values obtained from the international column leaching test. Thus, by the Testing Method Standard for Leaching Toxicity of Solid Wastes, especially for Cr, Hg and Pb, the values obtained from the international column leaching test proves 4.3, 77.5 and 7.0 times than ours.