城市污泥热解过程中重金属的形态转化模拟研究

Simulation on speciation transformation of heavy metals in the sewage sludge during pyrolysis

利用重金属Cd,Cu,Zn和Pb的碳酸盐、可溶性盐(如硫酸盐、硝酸盐、氯化盐)或硫化物作为污泥中重金属的模拟化合物,在不同条件下对模拟化合物进行热解.通过对热解产物进行X-射线衍射分析,确定产物的组成,从而推断污泥热解时重金属的形态变化过程.结果表明:Cd的碳酸盐热解过程中向更加稳定的CdS发生转变;Cu的碳酸盐和硫化物生成Cu2S;Zn的离子交换态和Pb的碳酸盐与离子交换态热解之后均生成相应的氧化物和硫化物.

Carbonates, soluble salts and sulfides of Cd, Cu,Zn and Pb were used as model com- pounds in sewage sludge, which were pyrolyzed together with sewage sludge under different conditions. The pyrolysis products of the model compounds were analysed by a X-ray diffrac- tion（XRD） to investigate the speciation transformation mechanism of the heavy metals. The results show that the cadmium carbonate transforms into CdS which is more stable. The car- bonate and sulfide of copper form Cu2S. The exchangeable state of Zn, carbonates and ex- changeable state of Pb produce corresponding oxides and sulfides during pyrolysis.