城市污泥中重金属的去除与回收试验研究

Research on Removal and Recovery of Heavy Metals from Municipal Sludge

以天津东郊污水处理厂的剩余污泥为例,研究了城市污泥中重金属的含量和形态,分析了污泥中重金属的去除及回收方法。结果表明:天津东郊污水厂的剩余污泥中铜和锌的含量很高,分别为4 386.2 mg/kg和2 170.6 mg/kg,具有很高的回收利用价值;污泥中的铜和锌都以稳定性较好的硫化物及有机结合物、残渣态形式存在,生物毒性较小,通过对其去除及回收处理后可安全地进行土地利用。利用易获得、易降解的乙酸溶液(H2O2含量为2%),在室温、pH值为4的条件下反应4 h,可以达到去除污泥中铜和锌的目的(去除率>95%)。采用改进的铁氧体共沉淀法,用石灰乳溶液作中和剂,从污泥的乙酸—H2O2浸出液中回收铜、锌的结果表明,在pH值为9、反应温度为室温、FeCl3和FeSO4初始浓度分别为0.10 mol/L和0.05 mol/L及Fe3+/Mn+(Cu、Zn离子总和)=10(物质的量之比)的最佳工艺条件下,对铜、锌的回收率分别为94.5%、98%。

The content and speciation of heavy metals in excess municipal sludge from Tianjin Dongjiao WWTP were studied, and the removal and recovery of heavy metals from the sludge were analyzed. The results show that the contents of copper and zinc in this sludge are 4 386.2 mg/kg dry sludge and 2 170.6 mg/kg dry sludge, indicating a high recovery value. The copper and zinc in the municipal sludge exist in forms of sulfide, organic complex and residue. Due to low toxicity, the municipal sludge can be used as land resource after proper treatments. Under the conditions of pH 4, room temperature and 4 h reaction time, the copper and zinc of more than 95% can be removed using acetic acid solution with 2% H2O2. Using improved ferrite coprecipitation and lime milk for neutralization, the copper and zinc are recovered from the acetic acid/H2O2 extract of municipal sludge. The recovery rates of copper and zinc are 94.5% and 98% respectively when the initial concentrations of FeCl3 and FeSO4 are 0.10 mol/L and 0.05 mol/L, Fe^3＋/M^n＋ （total of Cu^2＋ and Zn^2＋ ） is 10, the pH value is 9, and the temperature is room temperature.