Purification of Copper Electrolyte by Solvent Extraction and Ion-Exchange Techniques

Abstract

A couple of refineries have adopted the solvent extraction (SX) process in place of the electrolytic route which is commonly employed for the purification of copper electrolyte with respect to various impurities. The SX process based on TBP (Tri n-Butyl Phosphate) solvent is particularly effective in the separation of arsenic from the electrolyte. Also, an ion-exchange (IX) process using a chelating resin, has been developed and employed in three other refineries for the removal of antimony and bismuth impurities from the electrolyte through preferential adsorption.

The paper presents the results of the experimental studies as well as of the operation trials conducted in these refineries on the purification of the copper electrolyte by the removal of Va group elements employing the SX and IX processes. The paper also discusses the details of the investigations carried out on a} the revovery of TBP from the extraction raffinate by scrubbing with carbon tetra chloride, b) preferential sulfidation of copper in arsenate solution, c) the recovery of arsenic tri-oxide powder by freeze-melt technique, d) development of a closed circuit stripping system involving regeneration of ammonia by addition of lime to NH₃-(NH₄) ₂, S0₄ stripping solution and e) the cyclic use of HCl-NaCl eluant in a chelating resin process of regeneration of HCl.

Keywords:

• Copper electrolyte
• purification
• solvent extraction
• ion exchange
• arsenic
• antimony
• bismuth
• Tri m-butyl phosphate