Extraction of Au(III) using aromatic ethers via ion solvation from acidic chloride media: Structural factors that influence extraction

Abstract

Ethereal compounds, such as the commercially available extractant dibutyl carbitol (DBC), can extract Au(III) from acidic chloride media by ion solvation. Herein, various aromatic ether compounds comprising an aromatic ring and aliphatic chains were prepared to compare the extraction affinity toward Au(III) without dilution. Aromatic monoethers are not useful for the extraction of Au(III). Conversely, the extraction of Au(III) using aromatic 1,2-diethers increases as a function of hydrochloric acid concentration. For aromatic 1,2-diethers, the shorter the aliphatic chain, the higher the extraction affinity toward Au(III). 1,2-Dimethoxybenzene (o-DMB), which has the shortest side chains, exhibits the highest extraction affinity. 1,3-Dimethoxybenzene (m-DMB), which is a regioisomer for o-DMB, was not suitable for the extraction of Au(III). The extraction selectivity toward Au(III) over that of Fe(III) and Ga(III) using o-DMB, under high concentrations of hydrochloric acid, is higher than that using DBC. Selected aromatic 1,2-diethers, including o-DMB, show a significantly higher extraction capacity toward Au(III) than the industrial requirement of 30 g/dm3. Au(III) extracted using o-DMB was quantitatively recovered by reduction with oxalic acid. In a separation test from a mixed system comprising seven metals, Au(III) was selectively extracted and with a recovery percentage, after reduction, reaching 95.7%.