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

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/dm(3). 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%.

Automated summary

This study investigated the extraction of Au(III) using various aromatic ether compounds, and found that compounds with 1,2-diether structures, especially o-DMB, showed higher extraction affinity towards Au(III) in high hydrochloric acid concentrations. The selectivity of o-DMB for Au(III) over Fe(III) and Ga(III) was also higher than that of commercial extractant DBC, with a recovery percentage of 95.7% after reduction with oxalic acid in a mixed metal system.