Au(III)への抽出能力と工業的な物性要件を両立する抽出溶媒の網羅的探索

Ion solvation extraction has been used as a separation techniques for gold (Au(III)) from various metal ions in a hydrochloric acid media. Dibutyl carbitol (DBC) has been used as the most popular solvent to extract Au(III), while no better solvent has been found for many years. In the present review, the results of recent investigations by the authors to find valid solvents for ion solvation extraction are summarized. Ethers and ketones are suitable in view of the high extractability for Au(III) as well as the good properties including chemical stability. Ethers and ketones which have a smaller side chains and relatively higher polarity showed higher extractability, however, polar solvents would leak into the aqueous phase. Therefore suitable solvents with moderate polarity are narrowed down based on the balance between high extractability and low aqueous solubility. As the polarity affects the extractability, the logP value (octanol/water partition coefficient) and the Hansen solubility parameter would be one of the indexes for the Au(III) extractability. Solvents used in industrial processes are required to have not only high extractability but also good properties such as a low aqueous solubility and a high flash point. The comprehensive research revealed the requirements for solvents to extract Au(III) based on ion solvation. Additionally, several potential solvents which might replace DBC were suggested.