New Heterocyclic Dithioether Ligands for Highly Selective Separation and Recovery of Pd(II) from Acidic Leach Liquors of Spent Automobile Catalyst
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- 作者：Kannan Senthil ; Uichi Akiba ; Kenshu Fujiwara ; Fumio Hamada ; Yoshihiko Kondo
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2017
- 出版时间：February 1, 2017
- 年：2017
- 卷：56
- 期：4
- 页码：1036-1047
- 全文大小：660K
- ISSN：1520-5045
文摘
The solvent extraction behavior of Pd(II) from a hydrochloric acid solution with heterocyclic dithioether ligands, namely, 1,2-bis((5-methyl-1,3,4-thiadiazol-2-yl)thio)ethane (BMDTE) and 1,2-bis((5-(methylthio)-1,3,4-thiadiazol-2-yl)thio)ethane (BMTDTE) were investigated, for the first time, as potential extractants by using chloroform as diluent. Various experimental parameters such as effects of the concentration of hydrochloric acid, extractant concentration, hydrogen ion, chloride ion, and diluents on the extraction of Pd(II) was also investigated in detail. By comparing the extraction time, BMDTE exhibits a more rapid and quantitative extraction of Pd(II) even within 5 min than BMTDTE (30 min). The loading experiments indicated that the maximum loading capacity of BMDTE and BMTDTE for Pd(II) was determined to be 124 and 118 ppm, respectively. The stoichiometry of the extracted species during extraction was confirmed by 1H NMR and Job’s method analysis. Both of the two extractants exhibit high extraction percentage (>99%) and selectivity toward Pd(II) from an automotive catalyst residue (ACR) solution comprising platinum group (PGMs) metal ions (i.e., Pd(II), Pt(IV), Rh(II), La(III), Al(III) and Ce(III)). After Pd(II) is stripped from the loaded organic phase, the water-washed stripped organic phase can be reused for further extracting Pd(II). The numbers of theoretical stages needed for the effective recovery and stripping of Pd(II) has been determined by McCabe Thiele’s plot. Studies of the reusability of both extractants have shown no significant loss in activity even after five cycles of successive extraction and stripping experiments. On the basis of the extraction protocol, these two extractants may be promising candidates for high selectivity extraction of Pd(II) from an ACR solution.