No abstract

The treatment and hydrometallurgical recovery of Pb from zinc leaching residue (ZLR), a waste stream generated by the zinc refining process, is proposed in this work. Leaching achieved complete extraction of Pb (140 mg g −1 ) within 24 h contact time using a 0.8 M sodium citrate solution. The batch leaching process that operates at ambient temperature results in a pregnant leachate solution of dissolved lead citrate. Pb is recovered from the dissolved organometal complex as a precipitate of PbSO 4 after chemical reaction in acidic conditions that are maintained through continuous membrane electrolysis. In addition, an alkaline buffer is generated at the cell cathode to regenerate the leachate, so that the recycled lixiviant can be used in consequent leaching steps. Characterization of the final product by XRD, ICP-AES, and Raman spectroscopy identified an amorphous PbSO 4 phase with traces of lead citrate. The overall purity of Pb is 46 ± 4%, representing a 3.3 fold concentration of ZLR. The integrated process is capable to treat ZLR sustainably. It can resolve the need for landfilling the mineral tailing and treat historic dump sites, respecting the zero-waste rationale, while also recovering raw material from a secondary source.

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Copper producers face increased demand associated with increasing complexity in feedstock composition, including high amounts of impurity metals. In this work, linear sweep voltammetry was used to study the electrodeposition behavior of copper and arsenic, define strategies for the production of grade A copper, and the removal of arsenic from complex electrolytes. Our results show that the copper concentration is a key parameter to control in the electrodeposition process. The continuous deposition of arsenic from the electrolyte requires copper in solution (≤10 g L − 1 Cu(II) for 2 g L − 1 As(III)) to form copper arsenides. The deposition of metallic arsenic does not occur readily. Conversely, the use of a concentrated Cu(II) solution (e.g. 40 g L − 1 ) resulted in grade A copper from an electrolyte with a maximum of 2 g L − 1 As(III) under galvanostatic control at a current density of -42 mA cm − 2 . Time-of-Flight Secondary Ion Mass Spectrometry depth profile measurements on copper deposits revealed that arsenic contamination was entirely concentrated near the substrate side of the deposit and progressively decreased further into the deposit. The codeposition of arsenic occurred along with the initial copper nucleation, when the electrochemical potential for electrodepostion under galvanostatic control is temporarily lower. These findings provide important insights for future sustainable copper electrodeposition technologies from complex feedstocks.