Salt aqua regia as a green solvent for recovering precious metals

Ding, Anting; Li, Ming; Liu, Chuanying; Zhang, Qizhou; Lei, Lecheng; Xiao, Chengliang

doi:10.1016/j.xcrp.2022.101159

Cited by 7 publications

(5 citation statements)

References 55 publications

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“…4b). 51 The photovoltaic effect in the solution generated • OH and • O 2 − , serving as effective oxidizing agents for noble metals. The oxidized metals with positive valence coordinated with Cl − in salt aqua regia.…”

Section: Advanced Noble Metal Leaching Strategiesmentioning

confidence: 99%

“…Additionally, the separation of noble metals from the leaching solution and the recycling of the solution necessitate significant energy input. 51 Consequently, numerous technological challenges and issues persist in actual production, requiring further improvement and resolution. Adsorption holds significant development potential due to its simplicity of operation, affordability, rapid adsorption speed, high capacity, excellent selectivity, negligible energy consumption, and minimal pollution.…”

Section: Techno-feasibility Analysismentioning

confidence: 99%

See 1 more Smart Citation

Trash or treasure? Sustainable noble metal recovery

Wei,

Zhang,

Gao

2024

Green Chem.

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Section: Advanced Noble Metal Leaching Strategiesmentioning

confidence: 99%

Section: Techno-feasibility Analysismentioning

confidence: 99%

Trash or treasure? Sustainable noble metal recovery

Wei,

Zhang,

Gao

2024

Green Chem.

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“…Recent examples of single noble metal selective dissolution include the use of specific ligands [39][40][41] or conditions. [42][43][44][45][46] Selectivity can also be controlled by the type of oxidant [47] or its concentration [48] or is relying on dissolution kinetics. [49] Deep eutectic solvents (DES), [50,51] a type of green ionic media, compared to ionic liquids (IL), present an affordable, safe, and potentially recyclable alternative with favorable features like low volatility and possible biodegradability.…”

Section: Introductionmentioning

confidence: 99%

“…Utilization of (biomass‐based) organic media for noble metal recycling [28–38] seems to offer a paradigm shift towards selective metal dissolution with enhanced sustainability (Figure 1). Recent examples of single noble metal selective dissolution include the use of specific ligands [39–41] or conditions [42–46] . Selectivity can also be controlled by the type of oxidant [47] or its concentration [48] or is relying on dissolution kinetics [49] .…”

Section: Introductionmentioning

confidence: 99%

Sequential Selective Dissolution of Coinage Metals in Recyclable Ionic Media

Zupanc,

Install,

Weckman

et al. 2024

Angewandte Chemie

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Coinage metals Cu, Ag and Au are essential for modern electronics and their recycling from waste materials is becoming increasingly important to guarantee the security of their supply. Designing new sustainable and selective procedures that would substitute currently used processes is crucial. Here, we describe an unprecedented approach for the sequential dissolution of single metals from Cu, Ag and Au mixtures using biomass‐derived ionic solvents and green oxidants. First, Cu can be selectively dissolved in the presence of Ag and Au with choline chloride/urea/H2O2 mixture, followed by the dissolution of Ag in lactic acid/H2O2. Finally, the metallic Au, which is not soluble in either solution above, is dissolved in choline chloride/urea/Oxone. Subsequently, the metals were simply and quantitatively recovered from dissolutions, and the solvents recycled and reused. The applicability of developed approach was demonstrated by recovering metals from electronic waste substrates such as printed circuit boards, gold fingers and solar panels. The dissolution reactions and selectivity were explored with different analytical techniques and DFT calculations. We anticipate our approach will pave a new way for contemporary and sustainable recycling of multi‐metal waste substrates.

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“…Most of the gold supply depends on gold mining 4 . Thus, recovering gold from secondary resources to decrease the supply risk is essential [5][6][7] . Additionally, platinum group metals (PGMs), such as platinum (Pt), palladium (Pd), and rhodium (Rh) which are rare PMs with high economic values, are often applied in automobile three-way catalysts 8,9 .…”

Section: Introductionmentioning

confidence: 99%

Recovering precious metals from spent catalysts by peroxydisulfate-based advanced oxidation process

Xiao

Ding

et al. 2023

Preprint

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The recovery of precious metals from discarded wastes is an attractive potential remedy for their supply disruption risk. Nevertheless, the use of conventional solvents in metallurgical processes has significant negative environmental effects. Here, we report peroxydisulfate (PDS)-based advanced oxidation process (AOPs) to develop a novel and efficient leaching process for recovering precious metals from spent catalysts. The PDS/NaCl photochemical system could fully dissolve palladium (Pd) and gold (Au) in 300 min. By introducing Fe(II), the PDS/FeCl2·4H2O solution functioned as Fenton-like system, which enhanced the leaching efficiency and required no xenon (Xe) lamp light irradiation. Electron paramagnetic resonance (EPR) and 18O isotope tracing experiments revealed the reactive oxidation species of SO4·-, ·OH and Fe(IV)=O were responsible for the oxidative dissolution of precious metals. Density functional theory calculations showed that the total energy barrier for the three species were 7.62, 18.46 and 17.52 kcal mol-1, respectively. Solvent leaching and one-step electrodeposition recovered high-purity precious metals and maintained solvent dissolution and electrochemical stability after 5 cycles. Strong acids, poisonous cyanide, volatile organic solvents, light irradiation, and photocatalysts were not used during recovery. This work will enable a green and sustainable precious metal recovery approach and encourage AOPs technology for secondary resource recycling.

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Salt aqua regia as a green solvent for recovering precious metals

Cited by 7 publications

References 55 publications

Trash or treasure? Sustainable noble metal recovery

Trash or treasure? Sustainable noble metal recovery

Sequential Selective Dissolution of Coinage Metals in Recyclable Ionic Media

Recovering precious metals from spent catalysts by peroxydisulfate-based advanced oxidation process

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