Study On Recovery Technology Of Copper And Nickel In Electroplating Sludge By Ammonia Process

Electroplating-sludge is paid more and more attention as an important an important secondary resource of heavy metals, along with the shortage of resources and environmental pollution worsening in recent years. Complex of electroplating-sludge with low valuable metals grade and complex impurities is researched to extract copper and nickel for the resource utilization of sludge. Extracting nickel and copper from electroplating-sludge in ammonia leaching-system is put forward, based on the analysis of shortcomings and deficiencies in traditional acid leaching-system, the specific technological process is ammonia leaching-extraction separation of nickel and copper-ammonia recycle. The main research results from experiments are as follows:Leaching in ammonia system----The orthogonal experiment and process optimization experiment in selected ammonia-ammonium hydrogen carbonate system showed that:the first, chromium and iron in electroplating sludge are harmful to extraction ratio to copper and nickel, it has low leaching rates with high contents of chromium and iron in electroplating-sludge; the second, total ammonia concentration is the major parameter which influences the extracting rates. The results showed that leaching rates of nickel and copper are88%and95%respectively under the optimal conditions that total ammonia concentration is9mol-L-1, NH3/NH4+is1:2, the ratio of liquid to solid is4:1, leaching temperature is70％in4h even with low contents of copper and nickel(nickel0.81%, copper0.94%). The leaching rates of copper and nickel are97%and93%respectively under the two-stage countercurrent leaching.Extraction and separation of copper and nickel----It is showed that copper and nickel can be extracted and separated by Lix984in ammonia-ammonium system, and it has large saturated capacity than acid system. The extraction capacity of copper and nickel are respectively12.98g’L-1and9.24g.L-1when pH value is9in pure copper or nickel ammonia-ammonium system. Copper is extracted preferentially under the condition that nickel and copper are coexisting in solution. The separation coefficient of copper and nickel is856.7when the amount of copper excesses the capacity of0.3times. The saturation capacity of the copper in the organic phase reduced and saturation capacity of nickel unchanged when enhancing the concentration of total ammonia and enlarging the pH value (9-10.5). The process of extracting----washing pickling----tripping is chose to extract and separate copper and nickel in leaching solution. The concentration of copper and nickel in the raffinate are0.0034g-L"1and0.023g-L-1and extraction rate are99.7%and99.6%after two-stage extracting. The concentration of copper in stripping solution which generate from the loaded organic phase of the first extracting stage after washing-pickling----stripping is14.1g-L-1, and the ratio to copper to nickel is3525; the concentration of nickel and copper in stripping solution which generate from the loaded organic phase of the second extracting stage are32.35g-L-1and0.02g-L"1under the condition O/A is2:1, stripping concentration is1mol-L-1, oscillation time is5minutes and pH value of separation of nickel and copper is3-3.5, the ratio to nickel to copper is1618.The leaching rates of nickel and copper are86.8%and94.3%with recycle ammonia under adjustment which demonstrated the feasibility of ammonia recycling. The phosphate precipitation method can eliminate Ca, Mg and part of Fe, Cr impurity ions in solution effectively, the actual added is1.3times than theory added is favorable and improve the pH value facilitates the precipitation of impurity ions.The research provides a new option for resource utilization of sludge, and it is significant for the implementation of the whole process extracting nickel and copper from electroplating-sludge.