污泥与不同添加剂共热解对重金属的影响

Effects of Co-pyrolysis of Sludge and Different Additives on Heavy Metals in Biochar

该文以聚乙烯塑料(PE)、茶渣(TL)和高岭土(KL)为典型代表,开展高分子材料、生物质材料以及无机材料与污泥(SS)共热解实验,采用BCR连续提取法探究不同添加剂对SS热解生物炭中重金属形态及安全性影响。结果表明:SS中重金属含量高低为Cr>Mn>Zn>Pb>Ni>Cd,100%SS热解生物炭中Cr、Mn、Ni、Zn含量明显富集,Cd和Pb则由于高温热解挥发而下降,且各重金属的残渣态比例均增大;添加PE与SS共热解生物炭中Cr、Mn、Ni、Zn、Cd中残渣态比例进一步增大;添加TL或KL与SS共热解生物炭中重金属固化效果整体略低于PE,故此添加高分子材料更有利于促进污泥生物炭中重金属的固化稳定。潜在生态风险评估表明3种添加剂与SS共热解生物炭均属于重金属轻微风险。

Polyethylene plastic(PE), tea leaves(TL) and kaolin(KL), as three typical representatives of polymer materials,biomass materials and inorganic materials, were carried out for co-pyrolysis experiments with sludge(SS). BCR continuous extraction method was used to explore the effects of different additives on the immobilization of heavy metals of pyrolysis biochar, and potential ecological risk index was conducted for safety evaluation. The results showed that the content of heavy metals in SS was in the order of Cr>Mn>Zn>Pb>Ni>Cd. The contents of Cr, Mn, Ni, and Zn in the biochar prepared by 100%SS pyrolysis were significantly enriched, while Cd and Pb were reduced due to volatilization under high temperature pyrolysis conditions. The proportion of the residual fraction(F4 fraction) of Cr, Mn, Ni, Zn, Cd, and Pb in sludge biochar increased.Further research found that in the biochar obtained by PE and SS co-pyrolysis, the F4 fraction of Cr, Mn, Ni, Zn, and Cd can be further increased. The F4 fraction of each heavy metal in the biochar prepared by TL or KL and SS co-pyrolysis was reduced slightly than that of PE. Therefore, the addition of polymer materials was more conducive to promoting the immobilization of heavy metals in the sludge biochar. The potential ecological risk assessment of heavy metals indicated that the potential risk coefficients of the biochar obtained by the co-pyrolysis of the three additives with sludge were all at a slight level.