Pure gold dissolution with hydrogen peroxide as the oxidizer in HBr or HI solution

Hojo, Masashi; Iwasaki, Shunsuke; Okamura, Kei

doi:10.1016/j.molliq.2017.09.080

“…Main established Au recovery processes include environmentally challenging and toxic methods, such as cyanidation[ 4 , 6 , 16 , 17 , 18 , 19 ] (Figure 1 , a), and in less developed regions, even the amalgam process. [20] Other dissolution procedures,[ 4 , 5 , 6 , 16 , 17 , 18 , 19 ] including aqueous iodine‐iodide leaching[ 5 , 6 , 7 , 8 , 16 , 17 , 18 , 19 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ] (Figure 1 , b), come with marked improvements in safety and environment issues. As previously reported, elemental halogens can oxidize Au 0 to Au I or Au III cations and stabilize the formed Au cations in the solution as Lewis bases.…”

Section: Introductionmentioning

confidence: 99%

“…[ 32 , 33 ] Nevertheless, in addition to the moderate toxicity and costly production, over stoichiometric amounts of iodine are usually needed to afford a quantitative dissolution of Au, hence making this procedure less sustainable and less financially feasible. [ 5 , 16 , 18 , 21 , 34 ] Even with the assist of more environmentally benign oxidants, especially aqueous H 2 O 2 ,[ 5 , 6 , 19 , 21 , 23 , 24 , 25 , 26 , 27 ] large amounts of iodine are consumed in the processes.…”

Section: Introductionmentioning

confidence: 99%

Iodine‐Catalysed Dissolution of Elemental Gold in Ethanol

Zupanc

¹

,

Heliövaara

²

,

Moslova

³

et al. 2022

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Gold is a scarce element in the Earth's crust but indispensable in modern electronic devices. New, sustainable methods of gold recycling are essential to meet the growing eco-social demand of gold. Here, we describe a simple, inexpensive, and environmentally benign dissolution of gold under mild conditions. Gold dissolves quantitatively in ethanol using 2-mercaptobenzimidazole as a ligand in the presence of a catalytic amount of iodine. Mechanistically, the dissolution of gold begins when I 2 oxidizes Au 0 and forms a [Au I I 2 ] À species, which undergoes subsequent ligand-exchange reactions and forms a stable bis-ligand Au I complex. H 2 O 2 oxidizes free iodide and regenerated I 2 returns back to the catalytic cycle. Addition of a reductant to the reaction mixture precipitates gold quantitatively and partially regenerates the ligand. We anticipate our work will open a new pathway to more sustainable metal recycling with the utilization of just catalytic amounts of reagents and green solvents.

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“…cially aqueous H 2 O 2 , [5,6,19,21,[23][24][25][26][27] large amounts of iodine are consumed in the processes.…”

Section: Introductionmentioning

confidence: 99%

Iodine‐Catalysed Dissolution of Elemental Gold in Ethanol

Zupanc

¹

,

Heliövaara

²

,

Moslova

³

et al. 2022

View full text Add to dashboard Cite

Gold is a scarce element in the Earth's crust but indispensable in modern electronic devices. New, sustainable methods of gold recycling are essential to meet the growing eco-social demand of gold. Here, we describe a simple, inexpensive, and environmentally benign dissolution of gold under mild conditions. Gold dissolves quantitatively in ethanol using 2-mercaptobenzimidazole as a ligand in the presence of a catalytic amount of iodine. Mechanistically, the dissolution of gold begins when I 2 oxidizes Au 0 and forms a [Au I I 2 ] À species, which undergoes subsequent ligand-exchange reactions and forms a stable bis-ligand Au I complex. H 2 O 2 oxidizes free iodide and regenerated I 2 returns back to the catalytic cycle. Addition of a reductant to the reaction mixture precipitates gold quantitatively and partially regenerates the ligand. We anticipate our work will open a new pathway to more sustainable metal recycling with the utilization of just catalytic amounts of reagents and green solvents.

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“…Bromide is a possible substitute for cyanide for leaching gold and other precious metals [50][51][52][53][54][55][56][57], which can be complexed by the bromide ion (Br − ) and oxidized by bromine (Br 2 ). The mechanism proceeds according to the following equations [44,50]:…”

Section: Introductionmentioning

confidence: 99%

Leaching Chalcopyrite with an Imidazolium-Based Ionic Liquid and Bromide

Rodríguez

¹

,

Ayala

²

,

Robles

³

et al. 2020

Metals

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The unique properties of ionic liquids (ILs) drive the growing number of novel applications in different industries. The main features of ILs are high thermal stability, recyclability, low flash point, and low vapor pressure. This study investigated pure chalcopyrite dissolution in the presence of the ionic liquid 1-butyl-3-methylimidazolium hydrogen sulfate, [BMIm]HSO4, and a bromide-like complexing agent. The proposed system was compared with acid leaching in sulfate media with the addition of chloride and bromide ions. The results demonstrated that the use of ionic liquid and bromide ions improved the chalcopyrite leaching performance. The best operational conditions were at a temperature of 90 °C, with an ionic liquid concentration of 20% and 100 g/L of bromide.

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Pure gold dissolution with hydrogen peroxide as the oxidizer in HBr or HI solution

Cited by 12 publications

References 28 publications

Iodine‐Catalysed Dissolution of Elemental Gold in Ethanol

Iodine‐Catalysed Dissolution of Elemental Gold in Ethanol

Iodine‐Catalysed Dissolution of Elemental Gold in Ethanol

Leaching Chalcopyrite with an Imidazolium-Based Ionic Liquid and Bromide

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