| Industrial activities involving electroplating process would lead to the accumulation of a large number of waste liquid. Conventionally, chemical precipitation has been the method most often used to deal with those waste. However, this method has the largest disadvantage, that is, could produce lots of electroplating sludge. Different from the urban sewage sludge producing from treatment of municipal sewage, the electroplating sludge is mainly the precipitated hydroxides, which contain varies of high concentrations of heavy metals, such as Cu, Ni, Zn, Cr etc., is a typical toxic waste and should be treated safely. In this thesis, the situation of electroplating sludge treatment and resourceful utilization at home and broad are summarized. Meanwhile, according to the method of heavy metal waste water treatment and recovery, after analyzing the physical and chemical properties of electroplating sludge and the effect of acid leaching, the mix liquid containing heavy metal sulfates (simulating the electroplating sludge acid extract) as the main study object, a simple and reasonable process is also explored, which reduces not only damage to the environment of heavy metals, but also the resources waste through recovering the copper and nickel in the mix liquid.Based on analyzing the properties of electroplating sludge sampled from an electroplating plant in Qingdao, choosing the sulfuric acid as leaching reagent, this paper studies the optimum condition when the copper and nickel reach the maxing leaching rate, then simulats the sludge acid extract by mix liquid containing heavy metal sulfates (CuSO4,NiSO4,ZnSO4,FeSO4,Cr2(SO4)3) and explores a copper electrolytic recovery-Fe/Cr impurity-electrolytic nickel recovery process. In copper electrolytic test, the effect of electrode material, voltage, pH value on the copper recovery are the main considerations; in impurity investigation, comparative studies of hydroxide precipitation and yellow iron ammonium alum on the removal of Fe/Cr are conducted to select an appropriate method; the recovery of nickel is still carried out by electrolytic method, focusing on the effect of cell voltage, the initial pH value and the dose of boric acid on the nickel recovery.The results indicate the optimum conditions for copper electrolysis recovery: 2.7 V of cell voltage, 0.3 of original pH value, Ti coated with Ru and Ir as anode and stainless steel as cathode, 3.5 cm of electrode spacing and 8h of the electrolytic time.Under these conditions, the copper removal rate in the simulated solution could be close to 95%, but also to ensure that the solution is not contaminated by other metals; comparing the two impurity methods, yellow iron ammonium alum method is chosen to remove the Fe and Cr in the left solution, and after the treatment, the concentration of the Fe and Cr in solution are only 0.19mg/L and 6.25mg/l respectively, which could be negligible. At this point, the removal efficiency of zinc and nickel are 20% and 7%, and the concentrations are 2632mg/L and 16950mg/L respectively. For the nickel electrolysis experiment, higher original pH value leads higher nickel removal rate, and higher voltage is more conducive to the reduction of heavy metals in the cathode deposition, but the effect is not obvious; with the adding of boric acid, the removal rate of nickel is also increased, but overall, the nickel removal efficiency is not high, only 57% of the maximum.Integrated on the study, the composition of the electroplating sludge is complex, most of the copper and nickel could be leached by sulfuric acid leaching. The copper electrolytic recovery-Fe/Cr impurity-electrolytic nickel recovery process could recover most of the copper and certain of nickel, and the yellow iron ammonium alum residue could be reused, and the amount of sludge is reduced significantly, which have great significance for sludge liminization. So this process is simple and effective and this study provides a theoretical basis and technical support for the development of a new electroplating sludge treatment.
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