粉煤灰协同水热法稳定飞灰中重金属及其机理探究

Stabilization and Mechanism of Heavy Metals in Municipal Solid Waste Incineration Fly Ash by Co-Hydrothermal Processing with Coal Fly Ash

生活垃圾焚烧产生的飞灰富含重金属,对环境构成威胁,被归类为危险废物.研究采用水热法协同处置飞灰和粉煤灰生成水热产物,并分析了产物的重金属浸出毒性、重金属含量及形态分布、微观形貌等,研究不同水热条件对重金属稳定化效果的影响,并初步探讨了水热反应稳定飞灰中重金属的机理.结果表明,研究所使用的飞灰与粉煤灰水热反应最佳条件为:飞灰与粉煤灰掺混比为7∶3、液固比10 mL/g、水热反应温度160℃、反应时间48 h、以0.5 mol/L NaOH作为碱性激发剂,在此条件下,产物中重金属Zn的固化率达到92.25%,重金属Pb、Cu、Cd、Cr、Ni的固化率均在99%以上.X-射线衍射结果表明,飞灰中的钙和粉煤灰中的硅铝在水热作用下生成了雪硅钙石,对重金属的稳定起到了重要作用.

Fly ash from municipal solid waste incineration(MSWI)is rich in heavy metals,which poses a threat to the environment and is classified as hazardous waste.In this paper,hydrothermal process was performed to treat MSWI fly ash and coal fly ash to produce hydrothermal products,and the leaching toxicity,content,morphology and distribution of heavy metals in the products were analyzed.The effects of different hydrothermal conditions on the stabilization of heavy metals were studied,and the mechanism of hydrothermal reaction for stabilizing the heavy metals in MSWI fly ash was preliminarily discussed.The results showed that the optimum conditions of hydrothermal reaction of MSWI fly ash and coal fly ash were as follows:the ratio of MSWI fly ash to coal fly ash was 7∶3,the liquid-solid ratio was 10 mL/g,the hydrothermal reaction temperature was 160℃,the reaction time was 48 h,and 0.5 mol/L NaOH was used as alkaline activator.Under these conditions,the solidification rate of heavy metal Zn reached 92.25%,and the solidification rates of heavy metal Pb,Cu,CD,Cr and Ni were all above 99%.The X-ray diffraction results indicated that the calcium in MSWI fly ash and the silicon aluminum in coal fly ash react and generate tobermorite under hydrothermal action,which plays an important role in the stabilization of heavy metals.