gold – Sustainable Electronics Initiative

June 29, 2020

Porphyrin May Provide Efficient, Cost-Effective Way to Reclaim Gold from E-Waste

An international team of researchers, lead by Yeongran Hong of the Korea Advanced Institute of Science and Technology, have demonstrated that a type of organic compound called a porphyrin could be used to retrieve precious metals, such as gold, from electronic waste in an effective, simple, and relatively inexpensive manner. The researchers used porphyrins to create a sorbent–a type of material that can collect molecules of another substance through adsorption, absorption or ion exhance–called COP-180. This compound remains stable in the acidic solutions which are used to remove metals from circuit boards and video screens.

From an article by Bob Yirka on Phys.org: “Testing the polymer showed it to be efficient at sorbing platinum and unexpectedly highly efficient at sorbing gold. A closer look at both showed that platinum dispersed evenly in an acid solution but gold clumped, allowing the sorbent to gather more of it than expected. Testing on real-world e-waste showed it was possible to collect 64 dollars’ worth of gold using only a gram of the sorbent, which costs five dollars to make. The researchers note that the sorbent can also be reused, making it even more economical.”

See Yeongran Hong et al. Precious metal recovery from electronic waste by a porous porphyrin polymer, Proceedings of the National Academy of Sciences (2020). DOI: 10.1073/pnas.2000606117

Diagram showing the process of using COP-180 to remove gold from an acid solution used to remove metals from circuit boards.

February 6, 2019

Scottish Researchers Work to Extract Gold from E-Scrap

According to an Oct. 3, 2018 article by Kirstin Linnenkoper in Recycling International, a research team at the University of Edinburgh, lead by Professor Jason Love, are developing a new chemical reagent to more effectively extract gold from electronic scrap.

“Around 7% of the world’s gold is inside e-scrap, of which less than one-third is currently salvaged, according to project leader Professor Jason Love. One tonne of gold ore contains around up to 5 grams of pure gold. However, a tonne of discarded mobile phones easily holds 300 grams of the valuable metal, Love says. The chemical reagent pioneered by in Edinburgh effectively recovers ‘a very high purity of gold’ from various types of discarded electronics. First, the researchers place the printed circuit boards in a mild acid to dissolve metallic parts. An oily liquid containing the new reagent is then added, which allows gold to be extracted selectively from the complex mixture of metals found inside electronics. Professor Love explains that, normally, one molecule of reagent binds directly to a metal molecule. The innovative compound uses a different type of chemistry and can bind to clusters of gold molecules instead of just one. ‘This means you can use a lot less of it to recover the same amount of gold,’ he says.”

The researchers hope to find ways to recover other metals, including valuable (e.g. palladium, platinum, and neodymium), common (e.g. copper and tin), and toxic (e.g. lead and cadmium) metals. Similarly, they are interested in exploring chemical means to more effectively recover plastics from electronic scrap.

Read the full article at https://recyclinginternational.com/e-scrap/scottish-researchers-find-way-to-target-metals-in-e-scrap/.

Learn more about the research of Professor Love’s group, and find links to their publications at https://jasonlovegroup.wordpress.com/.

The United Nations Environment Programme (UNEP) 2011 publication, “Recycling Rates of Metals: A Status Report” can provide further background context: https://wedocs.unep.org/bitstream/handle/20.500.11822/8702/-Recycling%20rates%20of%20metals%3a%20A%20status%20report-2011Recycling_Rates.pdf?sequence=3&isAllowed=y.

Finally, visit https://ifixit.org/recycling for more information on why electronics recycling is not as effective a practice as one might think.

close up of circuit board, showing gold

April 20, 2018

Researchers Use Ultrasound to Recover Gold from Electronic Scrap

The last few months have been ripe with reports on new research related to material recovery from electronic scrap (commonly referred to as “e-scrap” or “e-waste”), as highlighted in a previous post. I’ve learned of yet another exciting innovation in this field, thanks to a feature written by Jared Paben in the latest edition (4/19/18) of E-Scrap News.

As Paben reports, researchers from Sandia National Laboratories have developed a method to use ultrasonic waves, coupled with surfactants, to cheaply and efficiently recover gold from scrap electronics. Their experiments involved application of two different surfactants to the surface of a cell phone SIM card, which was then submerged in water. Ultrasonic waves were applied, which imploded micro-bubbles on the SIM card’s surface. Upon collapse of these micro-bubbles, micro-jets ejected gold nanoparticles from the card’s surface, and the nanoparticles were captured and stabilized by the surfactants.

According to the research group’s paper, published in the journal Small on 3/24/18), this mechanical method may not only present an effective way of reclaiming gold and other metals from electronic scrap, but could potentially be used to manufacture gold nanoparticles from native gold metal directly upon recovery from mining, which they say “may represent the greenest possible approach to nanoparticle synthesis.” (Citation: J. Watt, M. J. Austin, C. K. Simocko, D. V. Pete, J. Chavez, L. M. Ammerman, D. L. Huber, Small 2018, 1703615. https://doi.org/10.1002/smll.201703615)

You can read more about this research in a 4/3/18 article from New Scientist.

To learn about cavitation and cavitation bubbles, the phenomena which allow this mechanical process to work, see https://www.nsf.gov/news/special_reports/science_nation/cavitationbubbles.jsp and https://en.wikipedia.org/wiki/Cavitation.

For more information on gold in electronics, see How Much Gold is in Smartphones and Computers? and Uses of Gold in Industry, Medicine, Computers, Electronics, Jewelry.

To learn about the properties and applications of gold nanoparticles, see https://www.sigmaaldrich.com/technical-documents/articles/materials-science/nanomaterials/gold-nanoparticles.html.