A team led by Cornell researchers has devised an innovative method to recover gold from electronic waste and repurpose it as a catalyst for converting carbon dioxide (CO2) into organic compounds. This approach addresses two critical environmental challenges: the sustainable management of e-waste and the reduction of greenhouse gases.
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This technique could provide a productive use for some of the estimated 50 million tons of e-waste generated annually, of which only 20 % is recycled, according to Amin Zadehnazari, a postdoctoral researcher working in the lab of Alireza Abbaspourrad. Abbaspourrad is the Yongkeun Joh Associate Professor of Food Chemistry and Ingredient Technology at Cornell’s College of Agriculture and Life Sciences.
Zadehnazari developed two vinyl-linked covalent organic frameworks (VCOFs) capable of isolating gold ions and nanoparticles from electronic circuit boards. One of these frameworks demonstrated exceptional selectivity, capturing 99.9 % of the gold with minimal interference from other metals such as nickel and copper.
We can then use the gold-loaded COFs to convert CO2 into useful chemicals. By transforming CO2 into value-added materials, we not only reduce waste disposal demands, we also provide both environmental and practical benefits. It is kind of a win-win for the environment.
Amin Zadehnazari, Study Lead Author and Postdoctoral Researcher, Cornell University
The findings are detailed in the study, "Recycling E-waste Into Gold-loaded Covalent Organic Framework Catalysts for Terminal Alkyne Carboxylation," published on Dec. 30 in Nature Communications. Abbaspourrad served as the corresponding author, with Zadehnazari as the lead author.
Electronic waste is an abundant source of gold, with a ton of e-waste containing at least 10 times more gold than a ton of gold ore. With projections estimating e-waste to reach 80 million metric tons by 2030, developing efficient recovery methods is increasingly critical.
Conventional gold recovery methods rely on hazardous chemicals like cyanide, which present significant environmental concerns. Zadehnazari’s approach avoids such risks, employing chemical adsorption to capture gold particles onto a surface without using toxic substances.
Covalent organic frameworks (COFs), porous crystalline materials with a range of applications, were central to the method. Zadehnazari synthesized two VCOFs using tetrathiafulvalene (TTF) and tetraphenylethylene (TPE). The TTF-COF, rich in sulfur, exhibited superior gold adsorption due to gold’s natural affinity for sulfur. This material also demonstrated durability, retaining high adsorption efficiency even after 16 cycles of washing and reuse.
Under standard CO2 pressure at 50 degrees Celsius (122 degrees Fahrenheit), the gold-loaded COFs successfully converted CO2 into organic matter through carboxylation. Abbaspourrad noted that this method outperforms traditional e-waste recycling processes, which often yield impure recoveries of precious metals.
Knowing how much gold and other precious metals go into these types of electronic devices, being able to recover them in a way where you can selectively capture the metal you want in this case, gold is very important.
Alireza Abbaspourrad, Yongkeun Joh Associate Professor and Study Corresponding Author, Cornell University
The study’s co-authors include Amin Zarei and Ahmadreza Khosropour from the Abbaspourrad lab, former lab researcher Ataf Ali Altaf, Saeed Amirjalayer from the University of Münster, and Florian Auras from the Dresden University of Technology.
The research utilized facilities at the Cornell Center for Materials Research and the Cornell NMR facilities, both supported by the National Science Foundation.
Journal Reference:
Zadehnazari, A., et al. (2024) Recycling e-waste into gold-loaded covalent organic framework catalysts for terminal alkyne carboxylation. Nature Communications. doi.org/10.1038/s41467-024-55156-3.