Borosilicate glass is widely used to immobilize hazardous elements such as radionuclides and heavy metals by encasing them in a chemically stable matrix. However, groundwater infiltration can slowly dissolve this glass, raising safety concerns for storage facilities that must remain secure for millennia.
A research team from Peking University, the University of Cambridge, and Shenyang Agricultural University analyzed how boron isotopes move within dissolving glass to trace the mechanisms behind the corrosion process. Their findings, published in Environmental and Biogeochemical Processes, show that boron diffusion is highly sensitive to glass composition and exposure time.
In experiments, samples of two borosilicate glasses - one containing magnesium and one without - were immersed in pure water at 90oC for up to 112 days. At first, boron was released evenly from the surface, but as the glass aged, diffusion through an altered layer became the main pathway for release. In the magnesium-rich glass, secondary mineral formation created a dense, protective barrier that slowed dissolution. The magnesium-free glass, by contrast, developed a porous surface layer that allowed boron to continue escaping.
"Boron isotopes provide a sensitive and direct tracer of how waste glasses interact with water," explained lead author Thomas L. Gout. "They help reveal when the glass dissolves uniformly and when the process becomes controlled by diffusion through a transformed surface layer."
By using isotope "fingerprints," scientists can better model how glass corrosion evolves and how contaminants migrate into groundwater. The approach offers a valuable framework for assessing the long-term safety of nuclear and industrial waste storage.
Research Report:Boron isotope tracers of diffusion during glass dissolution
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