Extraction Properties Of Palladium(Ⅱ) With Synthetic Sulfide-Containing Extractants

A group of new asymmetric alkyl sulfoxides was synthesized and applied in Pd(Ⅱ) extraction for the first time. According to the experimental data, the HCl concentration in aqueous phase greatly influenced Pd(Ⅱ) extraction. The extraction decreased firstly and increased subsequently as HCl concentration increased, which could be interpreted by different mechanisms. Pd(Ⅱ) was extracted by these sulfoxides via ligand substitution mechanism at low HCl concentration and ion association mechanism at high HCl concentration, both S and O atom participated in the coordination in ligand substitution mechanism, In regard to structure effect, the extraction capacities of sulfoxides enhanced with the increasing alkyl chain length, while the steric hindrance of branched alkyl showed negative influence on the extraction performance of sulfoxides. On the basis of thermodynamic analysis, it demonstrated that higher temperature exerted positive influence on the Pd(Ⅱ) extraction reaction. Furthermore, ammonia solution was proven to be an efficient stripping agent for palladium recovery from organic phase.Isooctyl n-amyl sulfoxide (OASO) was applied to from hydrochloric acid medium for the first time. We discussed the separation parameters which can influence the separation of Pd(Ⅱ) and Pt(Ⅳ) under room temperature. According to the experimental data, the obtained optimal separation parameters were summarized as the following:OASO concentration 0.2 mol L-1 OASO, phase ratio (Ro:a)= 1, HCl concentration 0.1 mol L-1 and 5 min for contacting. The separation coefficient reached 279.3 under these optimal parameters, In regard to the separation mechanism, Pd(Ⅱ) was extracted by OASO via ligand substitution mechanism while no coordination between Pt(Ⅳ) and OASO at low HCl concentration, which could come to the good separation performance. High HCl concentration showed negative influence on separation which can be attributed to that both Pd(Ⅱ) and Pt(Ⅳ) could be extracted into the organic phase via ion association mechanism. In addition, Pd(Ⅱ) and Pt(Ⅳ) loaded in the organic phase could be stripped efficiently using 3.0 mol L-1 ammonia solution and distilled water respectively.A group of novel thioamide derivatives were synthesized and firstly applied in Pd(Ⅱ) extraction from hydrochloric acid medium. The HCl concentration in aqueous phase exerted remarkable influence on Pd(Ⅱ) extraction, the extraction decreased rapidly at first and then increased slowly as HCl concentration increased. As to the extraction mechanism, according to Job’s method, Pd(Ⅱ) was extracted by these sulfoxides via ligand substitution mechanism with the extracted complex which contained 2 thioamide derivative molecules and 1 Pd(Ⅱ) ion formed at low HCl concentration. The trend observed at high HCl concentration could be attributed to the fact that ionic strength in the aqueous phase increased constantly under this condition which contributed to the transfer of organometallic compounds into organic phase. In the study of extraction structure effect, increasing alkyl chain length benefited the extraction capacities of thioamide derivatives, while the introduce of benzene ring could weaken their capacities. Moreover, the 0.1 mol L-1 thiourea in 1.0 mol L-1 HCl solution was highly effective in stripping Pd(Ⅱ) from the loaded thioamide derivatives.