AIST Recovers Rare Element from Discarded Solar Panel Glass
October 2, 2025
On September 29, the National Institute of Advanced Industrial Science and Technology (AIST) announced that, in collaboration with Chubu Electric Power, it has developed a mild process to extract antimony (Sb), a rare element contained in the coated glass of solar panels.
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Antimony oxide (Sb₂O₃) is added to solar panel glass coatings to prevent bubble formation during production and to enhance transparency. Since antimony is a heavy metal and Japan depends heavily on imports, the supply risk is very high, making recycling technology essential.
The purpose of this study is to establish a foundational technology for recycling coated glass used in solar panels. With an average lifespan of 20–30 years, a significant amount of coated glass is expected to be discarded by the late 2030s as panels reach end-of-life.
X-ray diffraction (XRD) graph. Here’s the English translation of the Japanese text labels:
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Y-axis: Diffraction Intensity (arbitrary units)
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X-axis: Diffraction Angle (degrees)
Legend (right side, for the three curves):
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6時間処理 → 6 hours treatment (blue curve)
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1時間処理 → 1 hour treatment (red curve)
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未処理ガラス粉末 → Untreated glass powder (green curve)
This XRD chart shows how the crystal structure (phase formation and crystallinity) of glass powder evolves depending on the treatment duration (untreated, 1 hour, and 6 hours).
The team focused on hydrothermal treatment technology as an energy-saving and efficient method to extract, separate, and recover antimony. They tested multiple waste glass samples under different hydrothermal conditions to identify more effective extraction parameters.
In the experiments, crushed coated glass from used solar panels was mixed with water in a sealed container, stirred, and subjected to hydrothermal treatment for 1–6 hours at temperatures below those of conventional pressure vessels. The resulting slurry was separated into liquid and precipitate (powder) by centrifugation. Antimony extraction ratios were calculated using X-ray fluorescence (XRF), and products were identified via X-ray diffraction (XRD).
The results showed that the antimony extraction ratio increased with treatment time, reaching about 80% after 6 hours. XRD analysis further confirmed that silicon, the main component of glass, crystallized after hydrothermal treatment, while dissolved antimony remained in the liquid phase instead of being incorporated into the crystals.
These findings suggest that hydrothermal treatment can effectively dissolve and extract antimony from waste glass under mild, industrially feasible conditions.
Looking ahead, AIST aims to improve the efficiency of antimony extraction, scale up the process, and move toward practical applications. The institute also plans to develop technologies for separating, recovering, and recycling antimony from extracted components, as well as reusing the glass powder obtained during processing.
