Copper electrowinning processes produce slags Cd Cd metal as shown in FIG.
Fig.1 Process flow of metal cadmium electrowinning method from copper cadmium slag
The composition of copper cadmium slag generally ranges from 2.5% to 12% Cd, 35% to 60% Zn, 4% to 17% Cu, and 0.05% to 2.0% Fe. Copper cadmium slag also contains a small amount of As, Sb, SiO 2 , Co, Ni, T1, In and other impurities.
In order to accelerate the leaching process, some factories oxidize copper cadmium slag in the air before leaching. This also increases the loss of copper dissolution, which is only applicable when dealing with copper-cadmium slag with lower copper content. The copper slag composition obtained by the leaching process is: 30% to 50% Cu, 10% to 15% Zn, and 0.3% to 1.0% Cd.
In the leaching, in addition to the dissolution of zinc and copper, some Ni, Co, In, T1 enter the solution, and the obtained leaching liquid composition is: 120-130 g/L Zn, 8-16 g/LCd, 0.3-0.8 g/LCu, 3 to 9 g/LFe, 0.05 to 0.1 g/LCo, 0.05 to 0.1 g/L Ni. After the leachate is purified by adding zinc powder to remove copper, the zinc powder is sent to replace the precipitated cadmium. Displacement of precipitated cadmium is generally carried out in two stages. In the first stage, the temperature was maintained at 333 K to reduce the cadmium in the solution to 1 g/L. The second step of the solution after separating the copper cadmium slag by filtration can further reduce the cadmium content to 10-15 mg/L. The sponge cadmium (II) obtained in the second stage contains low cadmium and reverses the leaching process of copper cadmium slag. The solution after the second stage replacement contains Co, T1, In, etc., and the cobalt is removed by the xanthate to further recover T1 and In.
The sponge (I) obtained by replacing the precipitated cadmium in the first stage is leached with a cadmium electrolyte. The concentration of sulfuric acid in the solution is 200-250 g/L, the leaching temperature is 353-363 K, and MnO 2 or KMnO 4 is added to accelerate the dissolution of the cadmium sponge. The pH value of the leaching is 4.8-5.2, and the copper is hydrolyzed into the slag.
The cadmium cotton leaching solution after separating the copper slag, adding SrCO 3 to remove lead , adding zinc powder to replace copper, adding KMnO 4 to oxidize T1 and Fe, and then hydrolyzing and precipitating.
The electrowinning of cadmium solution generally adopts the system of non-circulating operation of electrolyte, and its operating conditions and technical indicators:
Add electrolyte component / (g · L -1 ) 160 ~ 220Cd, 20 ~ 30Zn, 12 ~ 15H 2 SO 4
Waste liquid component after electrowinning / (g·L -1 ) 15～20Cd, 150～180H 2 SO 4
Electrolyte temperature / K 303 ~ 308
Current efficiency /% 70 ~ 92
Cell voltage / V 2.5 ~ 2.6
Dielectric cycle / h 24
Power consumption / (kW·h·t -1 ) 1400～1700
Higher current efficiency can be obtained by using the electrolyte circulation production method.
Overview
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