Removal of Antimony and Bismuth from a Copper Electrolyte Solution with Puromet™ MTS9510PF
The industrial production of copper consists of two steps: (1) production of blister copper via smelting of concentrate, followed by (2) electrolysis to produce high purity copper (>99.99%). Some impurity metals report to the electrolysis process, most notably antimony and bismuth. Their removal is required to ensure the production of a high purity final copper product. Ion exchange resins with aminomethyl phosphonic acid (AMP) functionality have very good selectivity for antimony and bismuth and have been used for several years in copper electrolysis operations to remove these impurities. A drawback of the process is the introduction of chlorides into the system. The presence of chlorides has a negative effect on the quality of the copper deposit.
What Was Done
Bismuth and antimony are eluted from the loaded resin using 6 N HCl. This is followed by a displacement rinse and conditioning of the resin with 18% H2SO4, and then the resin can be returned to the adsorption circuit. Since HCl is the most efficient eluant for this application, it was decided to stick to the current elution/conditioning regime and investigate the possibility of changing the resin. The goal was to produce a resin that outperforms conventional AMP resins in terms of chloride leakage while retaining its good capacity to remove the copper electrolyte's target impurities. The result was the Puromet MTS9510PF.
Extensive testing was done to ensure that the resin abides by these specifications and has sufficient osmotic shock stability to be economically viable. To be able to test the osmotic shock stability, the resin was repeatedly contacted (100 cycles) with 15% w/v NaOH followed by 15% w/v H2SO4, to simulate the effect of osmotic shock (the successive swelling and shrinking of a resin bead when contacted with alkaline and acidic liquors). Such swelling and shrinking weakens the resin over time and ultimately results in resin breakage and loss.
The Puromet MTS9510PF (fresh and cycled) was compared to conventional AMP resin. Regular samples of the barren liquor were taken during the different treatment steps, i.e., HCl treatment, water wash, H2SO4 displacement and analyzed for chlorides.
The Puromet MTS9510PF outperformed the conventional AMP resin, and efficient displacement of HCl was achieved within three-bed volumes of the water rinse (a bed volume equals the volume of resin). Very low chloride leakage (<20 ppm) was detected in the barren during the subsequent sulphuric acid treatment step.
Similar results were achieved for the cycled and fresh resin, confirming the stability of the resin over an extended service lifetime.
Laboratory loading tests indicated a 10-20% increase in antimony and bismuth capacity when compared with a competitor’s conventional AMP resin. This was confirmed by the customer in their operation.
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If you have any questions or would like more information about this application, please contact your local Purolite technical sales representative.