Efficient removal of gold complexes from water by precipitation or liquid–liquid extraction using ionic liquids

Abstract

Extraction of tetrachloroaurate or tetrabromoaurate anions has been carried out at acidic pHs (1 and 4) with several ionic liquids bearing halide or bis(trifluoromethanesulfonyl)imide NTf 2 − anions and cations 1-octyl-3-methylimidazolium, 1-octylpyridinium or 1-methyl-1-octylpyrrolidinium. The removal of gold anionic moieties from water was first studied by mixing aqueous solutions containing gold complexes and water soluble halide (chloride or bromide) ionic liquids. This lead to the formation of either a solid precipitate or a liquid phase corresponding to a hydrophobic ionic liquid based on a tetrahalogenoaurate anion. Values below 10 −6 for the solubility products of gold-bearing ionic liquids were obtained. Liquidliquid extraction of anionic gold complexes with hydrophobic ionic liquids was also carried out. Gold was successfully extracted from water whatever the pH and the ionic liquid used. Distribution coefficients ranged from 3 × 10 2 to 3 × 10 4 . Investigation on the extraction mechanism revealed an anion exchange between one anionic gold complex and one NTf 2 − anion.− , X representing a chloride or a bromide anion accordingly, is studied using IL. In order to study the influence of the cation ring (size and aromaticity of the ring, charge delocalization) on the removal of

Separation of Precious Metals by Using Undiluted Ionic Liquids

“…A long chain alkyl imidazolium ionic liquid with a bromide anion has been used in the microemulsion extraction of Au(III) [5]. Recently, ionic liquids with hydrophobic anions have also been studied as extractants for precious metal extraction, and it was shown that the extraction mechanism was one of anion exchange between the anionic metal chloro-complex and the anion contained in the ILs [6,7]. However, only a few studies on the separation of precious metals have been reported.…”

Extraction and Separation of Pt and Pd by an Imidazolium-Based Ionic Liquid Combined with Phosphonium Chloride

“…Phosphonium based ILs such as trihexyltetradecylphosphonium chloride, bromide and phosphinate have been applied to the separation of PGMs [21,22]. Recently, undiluted imidazolium based ILs have been reported to have a high extraction ability for Au(III) and Pt(IV), as well as the ability to separate these metals from Pd(II) [16,19,20]. Two different ILs [C 8 mim][Tf 2 N] and a phosphonium-based IL, [P 6,6,6,14 ][Br], have been applied to a two-step extraction and separation of Pt(IV) and Pd(II) [21].…”

“…Commercial extractants such as crown ethers and octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) and newly synthesized extractants have been used to extract cationic metal ions [10,12]. Furthermore, ILs have been used for extraction both dissolved in organic solvents [13][14][15] and as an undiluted extraction phase [16][17][18][19][20][21][22]. Phosphonium based ILs such as trihexyltetradecylphosphonium chloride, bromide and phosphinate have been applied to the separation of PGMs [21,22].…”

Determination of three physical properties of quinoline ionic liquids with hexafluorophosphate

“…Despite the great possibilities in application of the IL-PEG system, there are limited reports about their properties or fundamental data [4,5]. Recently, ILs shows great prospect as extraction solvents in liquidliquid extraction, solid-liquid extraction and liquid-phase extraction because of their good solubility property [6,7], and they play an important role in extracting compounds such as protein [8], heavy-metal ions [9], traditional Chinese medicine from complicated samples [10], and they can improve selectivity remarkably as well as efficiency. Furthermore, it was reported that waterimmiscible BF 4 -based ILs can be used in the extraction of metal ions from wasted water [11].…”