Organic Aqua Regia: Discovery, Fundamentals, and Potential Applications

Abstract

Noble Metals 336 possible mechanism for the Au dissolution in the SOCl 2-py mixture. A surface reaction mechanism is proposed. Section 4 discusses some potential applications of OAR such as etching of metals in microelectronics industry, and recovery of noble metals from catalysis industry and consumer products, etc. Our recent progress is presented.

Oxidative Dissolution of Metals in Organic Solvents

“…Organic aqua regia can be formed not only with pyridine but also with other polar organic solvents. 85 The following solvents or organic compounds have been found to be able to effectively dissolve gold in the presence of SOCl 2 : pyrrole, pyrrolidine, pyrrolidone, isoxazole, isothiazole, pyrazole, imidazole, thiazole, oxazole, pyrazolone, bipyrazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, indole, quinoline, purine, pteridine, phthalocyanine, N,N’ -dicyclohexylcarbodiimide, DMF, N,N’ -dimethylbenzylamine, dodecyltrimethylammonium bromide, tri p -tolyl-phosphine, etc. However, effective dissolution of gold in a mixture of SOCl 2 with any of the following chemicals has not been observed: maleimide, azobis(isobutyronitrile), aniline, polyaniline, phenanthroline, methylbenzyl cyanide, 2-acetyl-1-methylpyrrole, and benzyltriethylammonium tetrafluoroborate.…”

“…A qualitative study has shown that copper, iron, nickel, tin, indium, silver, and palladium dissolve in the SOCl 2 –Py mixture, whereas platinum, titanium, tungsten, tantalum, and chromium do not. 85 The fact that some metals cannot be dissolved in SOCl 2 –Py is probably due to surface passivation.…”

“…The etching rate was found to be much faster than any currently used etchant for copper. 85 Subsequently, this solvent was successfully applied for the separation of platinum from a mixture of gold and platinum nanoparticles and from a Au/Pt core–shell nanoparticle catalyst, with the purity of the recovered platinum above 95%. 86 This organic aqua regia was also applied in organic synthesis, for activation of gold/activated-carbon catalysts for hydrochlorination of acetylene.…”

Recovery of Gallium, Indium, and Arsenic from Semiconductors Using Tribromide Ionic Liquids

“…21,22 These trihalide ILs can thus be regarded as halogen carriers with negligible vapor pressure, in contrast to other halogen carries, such as bromine−methanol, that are aggressive and volatile solutions. [23][24][25][26][27] This makes trihalide ILs useful as oxidizing agents for organic and metallic compounds, while enhancing process safety. [28][29][30][31][32] They are capable of dissolving both metals and alloys without the formation of any gases, as shown in previous research.…”

“…In this article, trihalide ionic liquids will be used for the leaching and recycling of semiconductors. This special group of ionic liquids contains an anion that is composed of a bound cluster of halogen atoms bearing a negative charge smaller than the total number of halogen atoms present in the anion. − Therefore, they show a strong tendency to take up electrons, but have negligible vapor pressure since they are ILs. , These trihalide ILs can thus be regarded as halogen carriers with negligible vapor pressure, in contrast to other halogen carriers, such as bromine–methanol, that are aggressive and volatile solutions. − This makes trihalide ILs useful as oxidizing agents for organic and metallic compounds, while enhancing process safety. − They are capable of dissolving both metals and alloys without the formation of any gases, as shown in previous research. ,− In this article, the dissolution of GaN, GaAs, and InAs in tribromide ILs and the selective recovery of gallium, indium, and arsenic from this IL are investigated. Most experiments are carried out with the ionic liquid tributyldecylphosphonium bromide, [P 44410 ]­[Br 3 ].…”