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.