Preferential Precipitation and Selective Separation of Rh(III) from Pd(II) and Pt(IV) Using 4-Alkylanilines as Precipitants

Kazuya Matsumoto; Sumito Yamakawa; Yuto Sezaki; Hiroshi Katagiri; Mitsutoshi Jikei

doi:10.1021/acsomega.8b03435

Preferential Precipitation and Selective Separation of Rh(III) from Pd(II) and Pt(IV) Using 4-Alkylanilines as Precipitants

ACS Omega. 2019 Jan 23;4(1):1868-1873. doi: 10.1021/acsomega.8b03435. eCollection 2019 Jan 31.

Authors

Kazuya Matsumoto¹, Sumito Yamakawa¹, Yuto Sezaki¹, Hiroshi Katagiri², Mitsutoshi Jikei¹

Affiliations

¹ Department of Materials Science, Graduate School of Engineering Science, Akita University, 1-1 Tegatagakuen-machi, Akita-shi, Akita 010-8502, Japan.
² Department of Chemistry and Chemical Engineering, Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan.

Abstract

Rhodium (Rh) is the most expensive platinum group metal (PGM) and is of great industrial importance. Although the recycling of PGMs from secondary sources is in high demand, the preferential and selective separation of Rh from PGM mixtures remains a great challenge. Here, a selective Rh separation method involving the precipitation of Rh from an HCl solution containing palladium (Pd), platinum (Pt), and Rh is reported. 4-Butylaniline and 4-hexylaniline were used as precipitants for Rh, and selective Rh precipitation was achieved at high HCl concentrations. We revealed that Rh in HCl selectively forms a unique and highly stable ion-pair complex comprising [RhCl₆]^3-/anilinium/chloride ions in a 1:6:3 ratio. The formation and high stability of the Rh complex were found to play important roles in the selective recovery of Rh from PGM mixtures.