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Recycling solar panels made easy

Simply soaking silicon wafers in an alkaline hot water bath converts them to useful silica nanoparticles

by Lakshmi Supriya, special to C&EN
September 26, 2020 | A version of this story appeared in Volume 98, Issue 37


Old, dusty solar panels mounted on a metal frame.
Credit: Shutterstock
Experts estimate that 60 million metric tons of used silicon solar panels will be ready for recycling by 2050.

Solar panels past their useful lives could get a bright new start. Researchers report a simple and environmentally friendly method for completely converting bulk silicon wafers, like those used to make silicon solar panels, to silica nanoparticles (ACS Sustainable Chem. Eng. 2020, DOI: 10.1021/acssuschemeng.0c03783). Silica nanoparticles are used as additives in rubber and construction materials, as substrates to assist drug delivery, and in a growing number of other applications. The market for silica nanoparticles will reach $5.1 billion by 2025, according to market research company Grand View Research. At the same time, few options exist for economically recycling the roughly 60 million metric tons of old silicon solar panels that could be piling up for disposal by 2050. In the new study, Stanislav A. Evlashin of the Skolkovo Institute of Science and Technology and colleagues soaked silicon wafers, including commercial solar cells, in an ammonium hydroxide solution and heated the mixture in an autoclave to various temperatures, up to about 180 °C. They found that in as little as 2 h, the wafers decomposed into white powders of silica nanoparticles 8–50 nm in diameter. Although the method is simple and does not require expensive equipment, the large-scale practicality of the approach is still undetermined.


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