城市污泥中Cu回收研究：生物沥浸-溶剂萃取-电积沉Cu技术

城市污泥通常含有大量有机质但也存在数量不等有害金属,在不影响污泥有益成分的基础上,去除和回收污泥中金属,既使污泥无害化又产生经济效益,意义重大.针对苏州某工业园区污泥重金属含量较高,研究利用生物沥浸-溶剂萃取-电积技术回收城市污泥中重金属Cu的工艺,并探讨了采用5-壬基水杨醛肟萃取剂M5640从城市污泥生物沥浸液中萃取分离Cu和Fe的最佳工艺参数.结果表明,经过生物沥浸处理72 h后,城市污泥中重金属Cu溶出率高达90%.当最佳工艺条件为:萃取剂体积分数为2%,相比(有机相与水相体积比,以O/A表示)为1/3,沥浸液pH为2.0时,沥浸液中Cu的一级萃取率达到95%以上,而Fe的共萃率低于10%;反萃取试验结果表明,在反萃取相比为2/1的条件下用1.5 mol/L硫酸溶液进行反萃取,Cu的一级反萃取率达到80.07%;反萃取后的富集Cu溶液作为电解液,在槽电压为2.1 V、电解温度为55℃条件下电积6 h,Cu回收率达到90%以上.在整个工艺中萃余液和反萃液均可循环利用无废液排放,对含Cu高的污泥,利用生物沥浸-溶剂萃取-电积技术回收有良好的应用前景.

Recovery of Copper from Sewage Sludge by Bioleaching-Solvent Extraction- Electrodeposition Process

Sewage sludge contains not only a lot of organic matter and plant nutrients, but also some harmful metals. Recovery of sludge-born metals for sewage sludge of high metal content is very important for safe reutilization of sewage sludge and for economic consideration. Here, we reported a recovery technique for sludge-born copper using bioleaching-solvent extraction-electrodeposition(L-SX-EW) process through batch experiments. The tested sludge containing 7 432 mg/kg Cu was collected from Suzhou Wastewater Treatment Plant located in industrial zone of Suzhou City, Jiangsu, China. The results showed that more than 90% of sludge-born Cu could be solubilized into aqueous phase within 72 h through bioleaching process. Furthermore, soluble Cu in the form of Cu~(2+) in bioleached sludge filtrate could be concentrated into organic phase through the extracting operation using 2% solvent extractant M5640 under the optimized condition of 1/3 phase ratio (O/A) and pH 2.0, in which Cu~(2+) extraction efficiency reached more than 95%, whereas the co-existing soluble iron extraction efficiency was less than 10%. Stripping results showed that the Stripping rate of Cu was 80.07% when the phase ratio (O/A) was 2/1 using 1.5 mol/L H_2SO_4 as stripping solvent. After the concentrated Cu~(2+) in acidic aqueous phase was electrolyzed for 6 h at 2.1 V bath voltage and 55 ℃ , more than 90 % of the Cu~(2+) recovery efficiency was achieved in the form of elemental Cu powder. There wasn' t any wastewater generation in this process. Therefore, this L-SX-EW technique exhibited a potential application for the recovery of metal for heavy metal-loaded sludge.