Method for recovering valuable metals

Abstract

A method for recovering valuable metals, such as lead, silver and gold from the residue of an electrolytic zinc process, wherein the residue from the zinc process is suspended and sulfidized for converting the lead and silver compounds into sulfidic form, and further flotated for forming a flotation concentrate that contains valuable metals, wherein the sulfidizing and flotation processes are controlled electrochemically, so that the content of the sulfide ions fed in the sulfidizing stage is adjusted by means of the redox potential to a level where the grain size of the created valuable metal sulfides is sufficient for flotating them, and that the redox potential of the flotation stage is adjusted to be within a range where the collector chemical is adhered to the mineral to be flotated, but the sulfides are not oxidized.

Description

field of invention

[0001] The present invention relates to a process for the recovery of valuable metals such as lead, silver and gold from the residues of the electrolytic zinc process. Background of the invention

[0002] In addition to zinc, zinc concentrates also contain other valuable metals such as lead, silver and gold, and recovery of these metals is of significant importance when looking at the zinc process in general. The behavior of these elements must be considered when making process changes. When electrolytically producing zinc metal from zinc sulfide concentrates, the concentrate is first fully or partially roasted, wherein the zinc sulfide of the concentrate is oxidized to oxides, since zinc oxide is more easily leached than sulfides. Most of the zinc oxide is leached into the zinc sulfide in the neutral leaching stage. During roasting, part of the concentrate forms zinc-containing ferrites, leaching of ferrites requires a higher acid content than leaching ...

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