| Abstract |
| Spent electroplating solutions contain a small amount of Pd(II). This Pd(II) can be concentrated by cementation with zinc metal powder. In order to recover pure palladium, a hydrometallurgical process consisting of leaching followed by solvent extraction was developed in this work. First, suitable extractants for the selective extraction of Pd(II) over Zn(II) were selected from synthetic sulfuric acid solutions. Among cationic, solvating and basic extractants employed in this work, Cyanex 301, LIX 63 and Aliquat 336 showed selectivity for Pd(II) over Zn(II) from 5 M sulfuric acid solutions. Stripping results for the loaded phases of these three extractants showed that HCl was effective at stripping Pd(II) from the loaded LIX 63 and Aliquat 336, while a mixture of inorganic acid and NaClO as an oxidizing agent was necessary to strip Pd(II) from the loaded Cyanex 301. The cemented Pd was completely dissolved using 5 M sulfuric acid solution at 25℃, and the concentration of Pd(II) and Zn(II) in the real leaching solution was 1.926 and 0.074 g/L, respectively. Application of the optimum conditions for the selective extraction of Pd(II) over Zn(II) to the real sulfuric acid leaching solution of cemented Pd indicated that only LIX 63 and Cyanex 301 could separate Pd(II) from Zn(II). The stripping efficiency of Pd(II) by a mixture of 5 M HCl and 3% NaClO was much higher from the loaded LIX 63 than from the loaded Cyanex 301. Considering the extraction and stripping characteristics of Pd(II), LIX 63 was selected as an optimum extractant for the separation of Pd(II) from the real sulfuric acid leaching solution of cemented Pd.
(Received October 6, 2021; Accepted November 2, 2021) |
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| Key Words |
| palladium, spent electroplating solution, sulfuric acid leaching, solvent extraction, commercial extractant |
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