Silver is becoming harder to mine, but researchers in Finland have found a creative and eco-friendly way to recover it from waste using common fatty acids and hydrogen peroxide.
These mild, green solvents not only dissolve silver efficiently but also allow for easy recycling of the acids themselves.
The Urgent Need for Silver Recycling
Recycling silver from electronic and industrial waste is becoming more crucial than ever. As demand for this precious metal grows and natural sources become harder to mine, scientists are racing to develop cleaner, smarter ways to recover it.
“Recycling silver from waste materials is becoming increasingly important for securing the supply of this precious metal. It is highly desirable to design new sustainable separation and recycling strategies to replace current processes that strain the environment,” says Postdoctoral Researcher Anže Zupanc from the University of Helsinki and the University of Birmingham.
Right now, less than 20% of silver produced each year gets recycled, even though the global push for renewable energy is generating more silver-containing waste. Silver plays a key role in technologies like solar panels, but silver ore is becoming scarcer. Over the last 25 years, the price of silver has increased sixfold, making effective recycling not just necessary, but economically attractive.
Now, researchers from the University of Helsinki and the University of Jyväskylä have introduced a breakthrough recycling technique, recently published in the Chemical Engineering Journal.
Why Does Metal Dissolve in Fats?
To extract silver safely, the team turned to common fatty acids, such as oleic, linoleic, and linolenic acids. When combined with a 30% solution of hydrogen peroxide, a powerful yet eco-friendly oxidant, these natural oils were able to dissolve silver under mild conditions. In this system, the fatty acids didn’t just act as a liquid medium—they also helped stabilize the dissolved silver ions.
“Computational chemistry enabled us to understand the solubility of metals by investigating the effect of solvents on the thermodynamics of dissolution,” says Professor Karoliina Honkala from the University of Jyväskylä.
Recovering Pure Silver from the Solution
The results made it possible to explain whether the insolubility of metals is caused by surface passivation or a thermodynamic barrier. Adding ethyl acetate to the silver–fatty acid solution enabled the separation of silver as silver carboxylates from the unreacted fatty acids, which can be recycled. The silver carboxylates were in turn reduced to metallic silver in a light-assisted reduction reactor, an efficient and safe method for separating silver.
“The goal of our research is to develop metal recycling techniques from multi-metal substrates using strategies that are inexpensive, sustainable, and selective by design,” says Professor Timo Repo from the University of Helsinki.
Fatty Acids: The Green Advantage
Using fatty acids as solvents has many benefits over using traditional mineral acids and aqueous solutions. In addition to originating in waste material, they are biocompatible, biodegradable, low in acid, and non-volatile. This makes them safe and non-corrosive compared with other acids and organic solvents, enabling recycling and reuse.
Since fatty acids are not water-based, metal compounds can be separated from unreacted reaction mixtures by using ethyl acetate and other antisolvents. This allows for both straightforward metal recovery and the recycling of fatty acids. In addition, the possibility of using 30% aqueous hydrogen peroxide as a green oxidant under mild conditions enables urban mining, that is, separating, for example, silver from keyboards with waste silver plating.
Reference: “Sustainable urban mining of silver with fatty acids” by Anže Zupanc, Joseph Install, Timo Weckman, Marko M. Melander, Marianna Kemell, Karoliina Honkala and Timo Repo, 31 March 2025, Chemical Engineering Journal.
DOI: 10.1016/j.cej.2025.162129
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2 Comments
Reading this article had a powerful effect on me. This fits my hopes for ambitious, industrious people in urban environments as another possible economic enabler in pursuing happiness. It enhances efficiencies, thereby reducing our load on the planet.
Had my circumstances allowed me to follow that path, I would have loved to be involved in this kind of project when I was that age, when I was a dead-on doppelganger of Anze Zupanc. In 1978, the Oil embargo hit. Our President was from a culture cut from the same cloth as mine, loves science and knowledge, and has a deep sense of ethical and moral conscience. These factors set my mind on fire with alternative energy and the circular economy ideas. I aimed to gain advanced engineering degrees and explore solutions to those challenges.
The corporate world, I thought, would enable those ambitions, but it redirected me into a blind alley. I watched almost every concept I sought to explore being explored and either eliminated or adopted and developed, only so tortuously slowly, resisted with demonic power-hoarding determination.
I now accept that the timeline progresses at its own pace, and going all Don Quixote on it would have destroyed me as I tend to drive all accelerator and no brakes. I was so impatient and so full of myself that I thought if I didn’t do it myself, I wouldn’t live long enough to witness even the turning point that would result in those visions to be manifested.
Then I saw this article about a young guy who looks just like I did when I had fantasies of doing tedious experimentation with discipline and patience (which I sometimes lack) and achieving because he was placed in the timeline at the correct time with the cosmic circumstances that cleared the path for him.
It’s like when one overindulges on Friday night and sleeps in on Saturday, only to discover that your son and his buddies have done your Saturday chores for you when you stumble out the door with a liter of coffee and a hangover. And they did an excellent job.
Reading this article had a powerful effect on me. This fits my hopes for ambitious, industrious people in urban environments as another possible economic enabler in pursuing happiness. It enhances efficiencies, thereby reducing our load on the planet.
Had my circumstances allowed me to follow that path, I would have loved to be involved in this kind of project when I was that age, when I was a dead-on doppelganger of Anze Zupanc. In 1978, the Oil embargo hit. Our President was from a culture cut from the same cloth as mine, loves science and knowledge, and has a deep sense of ethical and moral conscience. These factors set my mind on fire with alternative energy and the circular economy ideas. I aimed to gain advanced engineering degrees and explore solutions to those challenges.
The corporate world, I thought, would enable those ambitions, but it redirected me into a blind alley. I watched almost every concept I sought to explore being explored and either eliminated or adopted and developed, only so tortuously slowly, resisted with demonic power-hoarding determination.
I now accept that the timeline progresses at its own pace, and going all Don Quixote on it would have destroyed me as I tend to drive all accelerator and no brakes. I was so impatient and so full of myself that I thought if I didn’t do it myself, I wouldn’t live long enough to witness even the turning point that would result in those visions to be manifested.
Then I saw this article about a young guy who looks just like I did when I had fantasies of doing tedious experimentation with discipline and patience (which I sometimes lack) and achieving because he was placed in the timeline at the correct time with the cosmic circumstances that cleared the path for him.
It’s like when one overindulges on Friday night and sleeps in on Saturday, only to discover that your son and his buddies have done your Saturday chores for you when you stumble out the door with a liter of coffee and a hangover. And they did an excellent job. Thank you!