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Researchers at Cornell have produced a “twofer” of sorts, a method that reduces environmental pollution is two ways. First, it recovers the gold content from electronic waste without using harsh or poisonous substances, and second, the recovered gold can then be used as a catalyst in a reaction that removes carbon dioxide from the atmosphere, converting the CO2 to substances that can be used in chemical synthesis.
(Source: See here and here.)
Humans throw away their electronic devices at a rate of about 50 million tons a years, of which only about 20 % is currently recycled. A small but valuable component in that waste is a certain amount of gold. It is estimated that there is at least 10 times more gold in e-wast than in gold ore, and given the cost, difficulty, and health and safety hazards of processing gold ore, or other methods devised to process e-waste, there is significant incentive for finding an alternate way to recover this gold.
Synthesis of TTF-COF and TPE-COF. Credit: Nature Communications (2024).
The researchers in this study synthesized organic scaffold of molecules to which gold atoms would adhere. The scaffolds are called vinyl-linked organic covalent frameworks (VOCFs). At their nexuses of these frameworks, is the molecule tetrathiafulvalene (TTF), each of which contains four sulfur atoms. (In the figure on the right, the sulfur atoms are highlighted in yellow.) Gold atoms strongly adhere to sulfur atoms, and this is what happens when treated e-waste was brought into contact with the synthesized frameworks. Gold recovery was determined to be 99.9 % complete, with only small amounts of other metals present (such as nickel and copper).
The researchers further showed that the resulting gold-loaded framework could be used as a catalyst to remove carbon dioxide from the atmosphere by reacting the CO2 with a class of organic compounds called alkynes (which contain a triple bond between two carbons). The process coverts a CO2 molecule and an alkyne molecule into an organic acid, which can be converted through additional reactions into other useful substances. This gold-catalyzed reaction was observed to take place at ambient pressures at a temperature of 50o Celsius (122o F). Further, the framework was taken through 6 cycles of this process with no loss of catalytic activity.
The hope is that it will be possible to find similar methods that will allow the recovery of other critical metals from e-waste (such as the rare earths) with the specificity of the process reported in this research. However, the catalytic properties of the framework were an added bonus.
Comments are below the fold.
P. S. This diary will publish while I’m at a meeting, so I won’t be able to respond to any comments for more than an hour.
Top Comments (January 2, 2025):
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From inkstainedwretch:
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