重庆市垃圾焚烧飞灰特性及重金属浸出行为的研究

Study on characteristics and leaching behavior of heavy metals from municipal solid wastes incineration fly ash in Chongqing

通过激光粒度仪分析了重庆市垃圾焚烧飞灰颗粒粒径的分布特征,并研究了在GB5085.3-2007和USEPA-TCLP浸出条件下及不同pH、浸出液固比和浸出时间等因素下重庆市垃圾焚烧飞灰中重金属的浸出行为。结果表明,重庆市垃圾焚烧飞灰颗粒平均粒径为36.4μm,飞灰中主要重金属总量约1.04%,Zn、Pb含量较高,具有较大的环境风险,必须进行安全管理。GB5085.3-2007体系下飞灰的浸出毒性鉴别显示重庆市垃圾焚烧飞灰中重金属未超出浸出毒性限值,TCLP浸出体系下浸出毒性鉴别结果表明Pb和Cr浸出浓度分别为5.750 mg/L和1.890 mg/L,二者均超出标准限值。在较强酸度条件下飞灰中重金属浸出量大大增加,pH>2后浸出量则显著减少;浸出液固比<40时主要表现为重金属的溶出,>40后则主要表现为溶液稀释作用;飞灰重金属的浸出浓度与浸出时间呈显著对数正相关关系,浸出时间>240 h后浸出液浓度增加趋势不明显,在GB5085.3-2007体系下经函数拟合预测浸出时间为35 d时Pb浸出浓度超过标准限值。

In order to investigate characteristics and leaching behavior of heavy metals from municipal solid wastes incineration（MSWI） fly ash in Chongqing,China,grain size analysis and pH/liquid solid ratio/leaching time dependent experiments were conducted based on GB5085.3-2007 and USEPA-TCLP.Results indicated that the average particle size of the fly ash was 36.4 μm,the total fraction of the main heavy metals was about 1.04% in the fly ash,with Pb and Zn accounting for the highest fractions and environmental risks.Leaching toxicity of heavy metals in fly ash was investigated using the sulphuric acid and nitric acid method（GB5085.3-2007）,the results indicate that the heavy metals leaching toxicity of the fly ash was safe.However,the leaching toxicity exceeded the limited standard by USEPA-TCLP method with Pb and Cr leaching concentration of 5.750 mg/L and 1.890 mg/L,respectively.The leaching concentration increased when the leaching acid was stronger,but decreased markedly when pH2.While the liquid solid ratio was less than 40,the leaching of the heavy metals was ascribed to the surface dissolved into the aquatic,and when the liquid solid ratio exceeded 40,it was ascribed to the dilution by the solution.The relationship between the leaching heavy metals concentration and leaching time were the remarkably positive logarithmic correlativity,and the leaching heavy metals concentration increased gradually even when the leaching time was more than 240 h.After the forecasting under the GB5085.3-2007 procedure,the result showed that the leaching concentration of Pb will reach the limit standard concentration when the leaching time was up to 35 days.