Recovery of Rhodium by Solvent Extraction using N, N, N′, N′, N″, N″-Hexahexyl-nitrilotriacetamide and Electrodeposition

Abstract

The development of solvent extraction and direct electrodeposition processes is crucial for reducing the volume of secondary waste. In this study, the extraction behavior of Rh(III) using N, N, N, N’, N’’, N’’-hexahexyl nitrilotriacetamide (NTAamide(C6)) was investigated with three different diluents that have relatively high dielectric constants. Slope analysis revealed that the extraction mechanism of Rh(III) is based on ion-pair extraction.
The electrochemical behavior of the extracted Rh(III) complexes in each diluent was investigated using cyclic voltammetry. Rh(III) was reduced to Rh(0) through a three-electron transfer in the NTAamide(C6)/ acetophenone, 1,2-dichloroethan, and 1-octanol systems. Moreover, the diffusion coefficient of the extracted Rh(III) complex was evaluated using semi-differential analysis. The electrodeposits were recovered through continuous solvent extraction and direct electrodeposition. The electrodeposits were identified as Rh metals by X-ray photoelectron spectroscopy and X-ray diffraction analyses.