市政污泥生物质炭重金属含量及其形态特征

Characteristics of the form and concentration of heavy mentals in the biochar made from municipal sewage sludge

为了探索污泥资源化利用的新途径,在200、300、500和700℃下裂解温度下,将干燥的市政污泥制备成生物质炭,分析其主要重金属形态及其含量,了解裂解温度对污泥生物质炭重金属形态及其含量的影响。结果表明:高温裂解处理不仅影响污泥生物质炭重金属总量,而且还影响其形态。随着裂解温度提高,污泥生物质炭中重金属含量增加;低温(200℃)裂解处理导致汞损失殆尽,但提高了酸溶态As、Cd、Mn和Zn的含量;裂解温度超过300℃,重金属残渣态含量大幅度增加,比例占50%以上,可氧化态、酸溶态和可还原态重金属含量均随裂解温度的提高而降低。结果显示,尽管污泥生物质炭重金属含量比干燥污泥高一些,但大部分转化为生物有效性极低的残渣态。

This study is concerned on the development of a new approach for resource utilization of municipal sewage sludge, The oven-dried municipal sewage sludge was pyrolized under 200,300,500 and 700 ℃. The product of biochar was analyzed for the form and concentration of heavy metals. The objective was to investigate the influence of pyrolysis temperature on the form and concentration of heavy metals in the biochar. The results showed that the pyrolysis treatment influenced not only the concentration, but the form of heavy metals in the biochar as well. The total heavy metals in the biochar increased with increasing pyrolysis temperature. Low temperature of 200 ℃ could result in complete ventilation of Hg,enhancing acid-extractable As, Cd, Mn and Zn. However, when the temperature was higher than 300℃, the proportion of residual heavy metals increased largely, usually up to 50% of the total. The proportions of oxidable, reducible and acid-extractable heavy metals increased with increasing pyrolysis temperature. It is evident that pyrolysis treatment of municipal sewage sludge reduces the bioavailability of heavy metals though enhances the concentration.