Efficient Gold Recovery from E-Waste via a Chelate-Containing Porous Aromatic Framework

Abstract

Extracting gold from wastes of electronic equipment (e-waste) is a sustainable strategy for the recovery of the precious metal, reducing environmental pollution, and addressing the growing demands for gold resources. In this work, we synthesized a thiourea-modified porous aromatic framework (PAF-1-thiourea) with exceptional gold-extraction ability. The optimum adsorption capacity for PAF-1-thiourea to gold reaches up to 2629.87 mg g–1. The adsorption process can be well fitted according to the pseudo-second-order kinetic model and Langmuir model, featuring strong affinity caused by strong soft–soft interactions between Au­(III) and the S and N donor atoms of the modified PAF and the electrostatic interactions between protonated amino groups and AuCl4 –. PAF-1-thiourea was especially capable of extracting gold rapidly and efficiently (capturing 98.73% of gold within 5 min) from a central processing unit (CPU) in extremely acidic conditions. It is found that PAF-1-thiourea captures gold ions and simultaneously converts it to a Au(0) solid, obtaining gold with purity up to 23.5 karat. PAF-1-thiourea with its high acid resistance and anti-interference against cheap metals in the recovery process presents a practical means to extract gold from e-waste.

A Facile Approach to Sulfur‐Rich Covalent Organic Frameworks for Selective Recovery of Trace Gold

“…Compared with Freundlich adsorption isotherm model, the larger value of R 2 for Langmuir was found and thus the experimental adsorption data fit the Langmuir adsorption isotherm model, indicating a kind of monolayer Au (III) adsorption behavior on the surface of SCOFs via coordination binding. [5,49] SCOFs displayed a fast adsorption rate and a relatively high adsorption capacity for Au (III) ions at extremely low ions concentration, which may possess great potential for gold recovery and water treatment. To further confirm the adsorption of Au (III) ions on SCOFs, the presence and distribution of Au in Au (III)-adsorbed SCOFs (Au-SCOFs) were identified by EDS and elemental mapping, as shown in Figure 3E,F.…”

“…Apparently, the scrapped electric and electronic devices are the main solid secondary sources for gold recovery, due to their relatively high content of gold (over 200 g ton -1 ). [5,6] To extract gold from electronic scraps, hydrometallurgy is primarily utilized to convert solid gold from the electronic waste into soluble Au (III) ions in acidic leachates, which are then subjected to the treatment of extraction and purification. [5,7] In addition, the secondary liquid sources of gold can be found in the spent process solutions produced in semiconductor industry and pregnant leach solutions, which are aqueous solutions containing a plenty of gold ions, mainly Au (III).…”

“…[5,6] To extract gold from electronic scraps, hydrometallurgy is primarily utilized to convert solid gold from the electronic waste into soluble Au (III) ions in acidic leachates, which are then subjected to the treatment of extraction and purification. [5,7] In addition, the secondary liquid sources of gold can be found in the spent process solutions produced in semiconductor industry and pregnant leach solutions, which are aqueous solutions containing a plenty of gold ions, mainly Au (III). Various technologies have been developed to concentrate and purify Au (III) ions from aqueous solutions, such as chemical precipitation, solvent extraction, membrane filtration, ion exchange and adsorption.…”

Supramolecular Gold Stripping from Activated Carbon Using α-Cyclodextrin

“…To achieve room-temperature stripping of gold, we hypothesized that a molecular receptor for Au­(CN) 2 – in aqueous solution might facilitate (Scheme ) gold transfer from the surface of activated carbon into solution. There are several reports of molecular receptors for gold halide anions relying on the use of cyclodextrins, , crown ethers, cucurbiturils, − amides, − cationic cyclophanes, and metal–organic frameworks, − which either form precipitates selectively with gold ions or function as gold extraction agents. Anion recognition − has witnessed a blossoming during the past two decades, where strong binding affinities and high selectivities have been achieved for a wide range of anions.…”

Precious metals recovery from aqueous solutions using a new adsorbent material

“…In the current stage of development are selected the materials with good adsorbent properties which represent a good technique for removal of PGM's from solutions with low concentrations due to low cost and higher efficiency. In this context where used adsorbent materials such as: chitosan 20 , iron oxide 21 , activated graphite 22 , zeolites 23 , and adsorbent materials obtained by synthesis or functionalization with pendant groups containing N, S or P atoms, having selective properties for these groups of metals 3,[24][25][26][27] .…”