Silvery nanoparticles

Scientists design a novel way to extract silver from solar panels

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University of Leicester researchers have found an alternative way to extract high-purity silver from used solar panels.

The process discovered is able to recover metals from end-of-life solar panels using cheap, environmentally friendly solvents (substances used to dissolve, extract, or suspend other substances).

Silver is an essential metal for the functioning of solar panels. However, the amount of naturally occurring silver found in ores is decreasing, making supply a concern for the future. This not only affects the production of photovoltaic (PV) cells – aka solar cells – but other essentials such as LED chips, nuclear reactors and equipment for the medical industry.

For this reason, the University of Leicester team set out to find a way to recover the silver used in discarded panels. 

“These new ‘unusual’ brines offer new possibilities for the processing of metals," said Dr Guillaume Zante, from the Centre for Materials Research at the University of Leicester. “Unlike ‘regular’ salted water made of sodium chloride, we used choline chloride and calcium chloride, but there are many different salts that can be investigated in further studies.

“Brines are a credible alternative to the toxic mineral acids used for metal processing because of their low price. We are now trying to apply the same approach for different metals from different sources of waste, such as smartphones, thermoelectric materials and magnets.”

As the world moves towards achieving net zero, the demand for renewable technologies is rapidly accelerating. Experts suggest the uptake of solar energy is set to increase 30-fold in the next 10 years.

Where the lifespan of a PV cell is 25-30 years, it is estimated there will be 80 megatonnes of waste from solar panels by 2050, if there is enough silver to power them all. 

Currently, the most common process to recover silver from solar panels involves mineral acids. In contrast, Zante's team used iron chloride and aluminium chloride dissolved in brines to extract the silver and aluminium from solar cells.

While brines are cheap and more environmentally friendly, mineral acids are hazardous chemicals like nitric acid, which contribute to acid rain, eutrophication and climate change by releasing nitrous oxide (a greenhouse gas) into the environment, the team said. 

The new method is said to be able to retrieve over 90 per cent of the silver and aluminium of a solar panel in 10 minutes. Moreover, the recovered silver is high purity, which means it can be reused in industrial settings.

According to the researchers, this is one of the first instances of using unusual brines instead of mineral acids to extract metals.

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