Solar is one of the cleanest energy sources around, according to Our World in Data, but manufacturing the panels is one part of the energy-making system that can account for some pollution and exert an environmental toll.
However, as detailed by Interesting Engineering, part of that process may get a planet-friendly upgrade after scientists at Italy's University of Camerino discovered how to recover silver from old solar cells with a 98.7% success rate.
As the team highlighted in its study, the market for photovoltaics (which convert sunlight into energy) is on the upswing, experiencing a 35% increase in annual capacity from 2021 to 2022.
This makes finding end-of-life recycling solutions all the more crucial to ensure the market for low-cost, non-polluting energy continues to be sustainable, as reusing the metals protects the supply of rare materials and takes much less energy than mining for new ones.
"Disposing of end-of-life solar panels in landfills would be a hazardous approach, displaying a direct threat to the environment," the researchers explained in their analysis, which was published in Environmental Technology & Innovation.
One of the end-of-life challenges, as Interesting Engineering noted, is recovering precious metals used in the panels, with silver among the hardest to extract, along with copper, because both metals are part of the solar cells' electrical circuits.
To address this problem, researchers generated a chemical reaction using a persulfate and ammonia system, and they activated the persulfate with the "strong base" of sodium hydroxide, according to the study.
The result of the reaction is copper oxide, which creates a layer to prevent the copper from contaminating the silver — leading to a highly successful recovery.
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To further refine this method to reach the 98.7% mark, the team implemented an existing system known as EDRR, or electrodeposition-redox replacement. According to Interesting Engineering, one benefit is that EDRR meant researchers didn't need additional chemicals for their silver leaching method.
"The EDRR technique is highly selective of silver … making it highly favorable over conventional processes," Interesting Engineering explained.
The researchers wrote in their study that their work is "an exceptionally competitive approach for silver recovery from side streams of hydrometallurgical processes, with the potential to have a significant influence on the circular economy."
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