THE EXTRACTION OF SILVER FROM CYANIDE SOLUTIONS WITH ION EXCHANGE RESINS

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Abstract
The ability of various ion exchange resins to extract silver from synthetic cyanide solutions was evaluated. It was found that weak base resins such as DUOLITE A-7, DOWEX WGR-2, DOWEX MWA-1, DOWEX XFS-4195, and AMBERLITE IRA-35 extract silver significantly only when the pH is lower than 8. At higher pH, the same resins exhibited little or no silver extraction. A comparison among weak base resins showed that DUOLITE A-7 and DOWEX MWA-1 have the best characteristics in terms of capacity and elution efficiency. Strong base resins such as DOWEX MSA-1 and AMBERLITE IRA-910 extract silver in the entire pH range from 4 to 12. When the aqueous feed solution contains only one metal, these resins have a significantly larger capacity for silver than for copper, iron or zinc. But, if one or more base petals are added to the cyanide feed solution, the silver extraction is depressed to an extent which depends on the contact time. The silver extraction can be maximized by decreasing the concentration of free cyanide in the aqueous solution and by stopping the extraction before the resin attains the saturation point

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