Highly Selective Precipitation of Platinum(IV) from HCl Solutions Using <i>m</i>-Phenylenediamine Utilizing Difference in Stability of Ionic Crystals
The development of a selective separation and recovery method for platinum-group metals (PGMs) is in high demand to establish efficient and practical recycling technologies for different secondary materials such as industrial automobile catalysts. In this study, the highly selective precipitation of...
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2025-02-01
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| author | Kazuya Matsumoto Yuki Hata Hiroshi Katagiri Mitsutoshi Jikei |
| author_facet | Kazuya Matsumoto Yuki Hata Hiroshi Katagiri Mitsutoshi Jikei |
| author_sort | Kazuya Matsumoto |
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| description | The development of a selective separation and recovery method for platinum-group metals (PGMs) is in high demand to establish efficient and practical recycling technologies for different secondary materials such as industrial automobile catalysts. In this study, the highly selective precipitation of Pt(IV) from hydrochloric acid (HCl) solutions containing Pd(II), Pt(IV), and Rh(III) was successfully achieved using <i>m</i>-phenylenediamine dihydrochloride (MPDA) as a precipitant. Pt(IV) selectivity was observed at HCl concentrations higher than 7 M, whereas the co-precipitation of Rh(III) could not be suppressed using 3–7 M HCl solutions. Successful recovery of Pt(IV)-containing precipitates with high Pt yield (94.6%) and Pt purity (98.5%) was also achieved using an actual catalyst leaching solution with a complex composition containing PGMs, base metals, and rare metals. Structural analyses revealed that the Pt(IV)-containing precipitate forms ionic crystals composed of [PtCl<sub>6</sub>]<sup>2−</sup>/protonated <i>m</i>-phenylenediamine (MPDA-2H<sup>+</sup>) in a 1:1 ratio. The high stability and insolubility of the Pt(IV)-containing ionic crystals, owing to their highly packed structure, resulted in the highly selective precipitation of Pt(IV) at high HCl concentrations. |
| format | Article |
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| issn | 2075-4701 |
| language | English |
| publishDate | 2025-02-01 |
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| spelling | doaj-art-ac3eb64e235f4742954667a0861bce8a2025-08-20T03:11:21ZengMDPI AGMetals2075-47012025-02-0115216510.3390/met15020165Highly Selective Precipitation of Platinum(IV) from HCl Solutions Using <i>m</i>-Phenylenediamine Utilizing Difference in Stability of Ionic CrystalsKazuya Matsumoto0Yuki Hata1Hiroshi Katagiri2Mitsutoshi Jikei3Department of Materials Science, Graduate School of Engineering Science, Akita University, 1-1 Tegatagakuen-machi, Akita-shi 010-8502, Akita, JapanDepartment of Materials Science, Graduate School of Engineering Science, Akita University, 1-1 Tegatagakuen-machi, Akita-shi 010-8502, Akita, JapanGraduate School of Organic Materials Science, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510, Yamagata, JapanDepartment of Materials Science, Graduate School of Engineering Science, Akita University, 1-1 Tegatagakuen-machi, Akita-shi 010-8502, Akita, JapanThe development of a selective separation and recovery method for platinum-group metals (PGMs) is in high demand to establish efficient and practical recycling technologies for different secondary materials such as industrial automobile catalysts. In this study, the highly selective precipitation of Pt(IV) from hydrochloric acid (HCl) solutions containing Pd(II), Pt(IV), and Rh(III) was successfully achieved using <i>m</i>-phenylenediamine dihydrochloride (MPDA) as a precipitant. Pt(IV) selectivity was observed at HCl concentrations higher than 7 M, whereas the co-precipitation of Rh(III) could not be suppressed using 3–7 M HCl solutions. Successful recovery of Pt(IV)-containing precipitates with high Pt yield (94.6%) and Pt purity (98.5%) was also achieved using an actual catalyst leaching solution with a complex composition containing PGMs, base metals, and rare metals. Structural analyses revealed that the Pt(IV)-containing precipitate forms ionic crystals composed of [PtCl<sub>6</sub>]<sup>2−</sup>/protonated <i>m</i>-phenylenediamine (MPDA-2H<sup>+</sup>) in a 1:1 ratio. The high stability and insolubility of the Pt(IV)-containing ionic crystals, owing to their highly packed structure, resulted in the highly selective precipitation of Pt(IV) at high HCl concentrations.https://www.mdpi.com/2075-4701/15/2/165platinum group metalmetal precipitationaromatic primary diamineionic crystalhydrochloric acid |
| spellingShingle | Kazuya Matsumoto Yuki Hata Hiroshi Katagiri Mitsutoshi Jikei Highly Selective Precipitation of Platinum(IV) from HCl Solutions Using <i>m</i>-Phenylenediamine Utilizing Difference in Stability of Ionic Crystals Metals platinum group metal metal precipitation aromatic primary diamine ionic crystal hydrochloric acid |
| title | Highly Selective Precipitation of Platinum(IV) from HCl Solutions Using <i>m</i>-Phenylenediamine Utilizing Difference in Stability of Ionic Crystals |
| title_full | Highly Selective Precipitation of Platinum(IV) from HCl Solutions Using <i>m</i>-Phenylenediamine Utilizing Difference in Stability of Ionic Crystals |
| title_fullStr | Highly Selective Precipitation of Platinum(IV) from HCl Solutions Using <i>m</i>-Phenylenediamine Utilizing Difference in Stability of Ionic Crystals |
| title_full_unstemmed | Highly Selective Precipitation of Platinum(IV) from HCl Solutions Using <i>m</i>-Phenylenediamine Utilizing Difference in Stability of Ionic Crystals |
| title_short | Highly Selective Precipitation of Platinum(IV) from HCl Solutions Using <i>m</i>-Phenylenediamine Utilizing Difference in Stability of Ionic Crystals |
| title_sort | highly selective precipitation of platinum iv from hcl solutions using i m i phenylenediamine utilizing difference in stability of ionic crystals |
| topic | platinum group metal metal precipitation aromatic primary diamine ionic crystal hydrochloric acid |
| url | https://www.mdpi.com/2075-4701/15/2/165 |
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