Turning Tech Trash Into Precious Metals
By RIITTA-LEENA INKI, UNIVERSITY
OF HELSINKI
EDITOR'S NOTE: The first step to recovering otherwise wasted precious metals is to collect electronic waste for recycling. Fortunately, Charlestown is home to Indie Cycle LLC. Phyllis Hutnak and her crew have been collecting e-waste all over RI since 2010. In Charlestown, they often do drop-off/pick-ups at the Mini-Super on Old Post Road and have an up-coming collection day this Saturday, June 1 from 9 AM to noon. Check out their website to see the types of material they can handle. - Will Collette .JPG)
Photo by Will Collette
Waste computers and cell phones, solar panels, and other
electronic waste are becoming an important source of noble metals alongside
mining. Researchers at the University of Helsinki have developed sustainable
dissolution methods for noble metals.
The extraction methods currently in use consume a lot of
energy and are detrimental to the environment. The method of roasting is
particularly dangerous for its practitioners and the environment, into which it
releases hazardous chemicals, alike. In developing countries, noble metals are
to this day extracted under crude conditions in landfills.
Even though advanced hydrometallurgical processes are
safer and able to dissolve noble metals, the result is metal mixtures that
require further processing.
Innovative Research in Metal Extraction
Recent research led by Professor Timo Repo of the
Catalysis and Green Chemistry research group has been published in the
journal Angewandte Chemie. The article introduces a three-stage
process where copper is first dissolved from electronic waste, followed by
silver and, finally, gold. This way, metals can be selectively separated from
plastic, ceramics, and other materials, yielding pure noble metals. In
addition, the solvents used can be easily recycled.
Practical Applications and Environmental Benefits
Researchers at the University of Helsinki tested
organic solvents on crushed circuit boards, successfully extracting the gold
and copper contained in them. Silver was separated from crushed old solar
panels. This result is particularly interesting because solar panels are a
high-volume product whose recycling has thus far been extremely challenging.
“In this study, we used what are known as deep eutectic
solvents, liquids, that are made from substances that are solid in room
temperature and under normal pressure, such as choline chloride – also used in
poultry feed – and urea, as well as other safe organic compounds,” says
Postdoctoral Researcher Anže Zupanc from the Department of Chemistry,
University of Helsinki.
Deep eutectic solvents are a special type of solvent
composed of two or more simple compounds, which together form a mixture with a
low melting point. These solvents are known as deep eutectic, as their melting
point is considerably lower than the melting point of each component on its
own.
Deep eutectic solvents are environmentally friendly,
renewable, and in many cases biodegradable. They have many applications as
solvents, including in chemical reactions, catalysis and extraction techniques.
Solvent Reusability and Green Chemistry
In this study, lactic acid has also been
used as a solvent and hydrogen peroxide as an oxidant.
“An important result was that the solvents could be
reused, putting the principles of green chemistry into practice,” Professor
Repo notes.
According to Repo, the results obtained in laboratory
conditions constitute a significant step towards sustainable chemical
processes.
Reference: “Sequential Selective Dissolution of Coinage
Metals in Recyclable Ionic Media” by Anže Zupanc, Joseph Install, Timo Weckman,
Marko M. Melander, Mikko J. Heikkilä, Marianna Kemell, Karoliina Honkala and
Timo Juhani Repo, 14 May 2024, Angewandte Chemie International
Edition.
DOI: 10.1002/anie.202407147