氨络合法电化学捕集去除城市污泥中重金属的研究

采用自行设计的电动污泥处理装置,以城市污水厂污泥作为试验对象,设置氨水添加比分别为0、0.08、0.10、0.12 (V:V,氨水/试样污泥),在恒定直流电压下运行120h,研究氨络合效应与直接利用阳极产酸对污泥中重金属捕集去除效果的影响.结果表明,阳极酸化对污泥中重金属有一定的溶出去除作用;氨水的添加对电动处理过程中污泥pH值的降低与电流密度的提高没有阻碍,但能够有效提高污泥中重金属的捕集去除率;当氨水添加比为0.12时,污泥中Zn和Cu的捕集去除效果最佳,分别达91.62%和71.49%.氨水添加比为0.08时,Pb的捕集去除率最佳,达47.85%.氨水的添加对污泥中重金属的形态和迁移性有明显影响,主要表现为稳定形态如残渣态、有机结合态的减少及可交换形态的增加.

Electrokinetic deposition and removal of heavy metals from sewage sludge enhanced with ammonia complexation

The experiment used an in-house designed electrokinetic equipment in order to remove heavy metals from municipal wastewater sludge. Ammonia was added and mixed with four groups of sludge samples at ratios of 0, 0.08, 0.10, 0.12 (V:V, NH3·H2O/sludge sample). The samples were electrolyzed for 120 hours at a constant DC voltage. The effects of anodic acid generation coupled with ammonia complexation on the enhanced removal of heavy metals from sewage sludge was measured. The results indicated that anodic acidification had a moderate removal rate on heavy metals. Although adding ammonia had no impact on pH and electric current density in the electrokinetic process, it enhanced the trapping and removal rate of heavy metals in the sludge. Results further indicated that different amount of ammonia exerted different levels of removal rates under electrokinetic treatment. When ammonia water was added at a ratio of 0.12, removal rates of Zn and Cu were 91.62% and 71.49%, respectively. Optimal remediation was achieved ata ratio of 0.08 for Pb with a removal rate of 47.85%. The enhanced removal effect by adding ammonia was presumably the result of decreased residual fractions and organic bound fractions, as well as the increased exchangeable fractions of these metals.