柠檬酸强化电动去除和回收污泥中的重金属

探讨了柠檬酸对污泥中重金属形态的影响，并以柠檬酸为络合剂、以杭州七格污水处理厂城市污泥为研究对象，在0.8 mA·cm-2恒定电流密度条件下运行120 h，在5组柠檬酸浓度分别为 0.00、0.05、0.10、0.20和0.30 mol·L-1的条件下，采用自行设计的双层双阳极反应器对污泥中重金属进行电动去除和回收实验。结果显示，柠檬酸能促使污泥中大量的Zn由可还原态转化为酸可提取态，但对Cu的形态影响不大。电动处理实验中，添加柠檬酸后Zn和Cu的去除率都有明显提高，当柠檬酸浓度为0.20 mol·L-1时，Zn的去除率最大达58.3%，Cu的去除率为42.4%；当柠檬酸浓度为0.10 mol·L-1时，Cu的去除率最大为51.7%，Zn的去除率为46.4%。柠檬酸的最佳添加浓度为0.10~0.20 mol·L-1，当柠檬酸添加量超过0.20 mol·L-1，Zn和Cu的去除率反而会因为络合物在阳极区的沉淀而降低。

Electrokinetic removal and recycling of heavy metals from sewage sludge with citric acid complexation

In this paper, municipal sewage sludge from Hang-Zhou Qige Waste Water Treatment Plant were studied to investigate the effect of citric acid complexant on the distribution of heavy metals species. Five groups of experiments were electrified with 120 hours at a constant electric current density of 0.8 mA·cm-2 under the addition of citric acid at 0.00,0.05,0.10,0.20 and 0.30 mol·L-1 respectively. And a self developed double-deck and double-anode electrokinetic reactor was used to remove and recycle heavy metals in sewage sludge using citric acid as complexing agent. The results of parallel tests showed that citric acid can make a lot of reducible zinc turn to weak acid soluble zinc, but it had little influence on the species distribution of Cu. After electrokinetic remediation experiment, the removal rate of Zn and Cu increased with the addition of citric acid. When the concentration of added citric acid was 0.20 mol·L-1,the biggest removal rate of zinc was achieved at 58.3% while the Cu removal rate was 42.4%;The biggest Cu removal rate was observed at 0.10 mol·L-1 reached to 51.7%, and the removal rate of Zn was 46.4%;The optimal concentration of citric acid in this research is 0.10 to 0.20 mol·L-1;But after the citric acid was over-added more than 0.20 mol·L-1, the removal rate of Zn and Cu both dropped since most of heavy metals has turned to complex precipitation in anode region.