Selective and Preferential Separation of Rhodium (III) from Palladium (II) and Platinum (IV) Using a m-Phenylene Diamine-Containing Precipitant

Kazuya Matsumoto; Sumito Yamakawa; Kazutoshi Haga; Katsuyuki Ishibashi; Mitsutoshi Jikei; Atsushi Shibayama

doi:10.1038/s41598-019-48920-9

Selective and Preferential Separation of Rhodium (III) from Palladium (II) and Platinum (IV) Using a m-Phenylene Diamine-Containing Precipitant

Sci Rep. 2019 Aug 27;9(1):12414. doi: 10.1038/s41598-019-48920-9.

Authors

Kazuya Matsumoto¹, Sumito Yamakawa², Kazutoshi Haga³, Katsuyuki Ishibashi², Mitsutoshi Jikei², Atsushi Shibayama³

Affiliations

¹ Department of Materials Science, Graduate School of Engineering Science, Akita University, 1-1 Tegatagakuen-machi, Akita-shi, Akita, 010-8502, Japan. kmatsu@gipc.akita-u.ac.jp.
² Department of Materials Science, Graduate School of Engineering Science, Akita University, 1-1 Tegatagakuen-machi, Akita-shi, Akita, 010-8502, Japan.
³ Department of Earth Resource Engineering and Environmental Science, Graduate School of International Resource Science, Akita University, 1-1 Tegatagakuen-machi, Akita-shi, Akita, 010-8502, Japan.

Abstract

Although Rh is an industrially important and the most expensive platinum group metal (PGM), the selective and preferential separation of Rh from PGM mixtures still remains as a big challenge. In this work, the separation of Rh (III) from Pd (II) and Pt (IV) in a hydrochloric acid (HCl) solution was studied using a m-phenylene diamine-containing precipitant (m-PDA). At high HCl concentrations (6.0-8.0 M), most of the Rh (III) (>90%) was precipitated, and Pd (II) and Pt (IV) were hardly precipitated (<5%). On the other hand, over 85% of Pd (II) and Pt (IV) precipitated along with small amount of Rh (III) (<25%) at low HCl concentrations (1.0-2.0 M). As a consequence, m-PDA enabled selective and preferential precipitation of Rh (III) at high HCl concentrations. XPS and TG analyses revealed that the Rh-containing precipitate is an ion-pair complex composed of one [RhCl₆]^3- anion and three m-PDA cations. The Rh desorption from the precipitate as well as the recovery of m-PDA was successfully achieved using an NH₄OH solution. This method is a promising practical approach to Rh recovery.

Publication types

Research Support, Non-U.S. Gov't