Valuable metals in smelting sludge from smelting industry have a recovery value. In this work, for realizing waste recycling effectively, selective and multi-step leaching of valuable metals was investigated with scrap copper-smelting sludge as research object. The effect of the concentration of sulphuric acid on leaching rates of valuable metals was investigated first. The results showed that the leaching rates of Cu, Zn and Ni were 6.1%, 59.4% and 63.3% at the acid concentration of 65g/L. Then, the results of the selective and multi-step leaching indicated that the leaching rates of Cu, Zn and Ni were over 90% after two-step leaching. In third step, the content of Cu in leached residue was 6.68%, which was higher than origin sludge. Repeat three-step leaching process above, Zn and Ni were leached selectively and Cu was accumulated in leached residue continually.
The anode slime comes from the process of scrap copper electrolysis which contains high content of copper, stannum and some other metals, such as lead, antimony and precious metals. The result of particle size distribution showed that copper exist in large particle-size parts more than in small ones, while most of stannum concentrate in small particle ones. XRD and MLA were employed to characterize the anode slime. Copper is occurrence in copper sulfide, while stannum is in stannic oxide. Selective leaching by using hydrochloric acid has been conducted based on initial analysis. 97.86% of antimony, 96.24% of stannum and 93.68% of lead were leached. 82.5% of copper remained in the residue. Copper can be separated with antimony, Stannum and lead effectively.
In this work, the traditional two-stage hydrometallurgy leaching process and the neutralization-flocculation leaching process were used for treating the dust, produced in steelmaking process. The results of the comparison of two processes show that traditional techniques could produce the accumulation of silicone gel generated by cycles which hampers the followed filtration process seriously. These situations make it unable to meet the production requirements. By contrast, the filtration process was fast after the acidic leaching when considering the neutralization-flocculation process. Furthermore, leaching solution processing performed better while adding iron and charcoal for improving the effect of the treatment processes. The results showed that zinc leaching rate was above 93%, and desilication rate was above 99%. Meanwhile, filtration rate of the iron-silicon residue was as fast as 4.7 m3.m-2.h-1.
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