Coupling effects in borosilicate glass leaching: A study on La/V doping

Borosilicate glass could solidify high-level radioactive waste (HLW), and the research on the leaching behavior can optimize the composition, thereby improving its stability and durability. In this work, the leaching behaviors of borosilicate glass in the presence of La/V and their coupling effects were investigated. The results revealed significant coupling effects among La3+, VO43−, and CO2 in an aqueous environment. The existence of LaCO3OH and zircon-type LaVO4 was confirmed by grazing incident X-ray diffraction spectra, and their structures were characterized by infrared and Raman spectra in which the vibration models of CO32−, La-O bond, and VO43− were identified. At the initial leaching stage, orthorhombic LaCO3OH and zircon-type LaVO4 crystals emerged on the glass surface. While the formation of lanthanum-containing layers slowed down the initial leaching rate, it also enriched lanthanum on the glass surface. This enrichment posed a potential risk of leakage since lanthanum was previously uniformly dispersed in the glass network. Therefore, the doping and coupling effects in the design of glass compositions should be considered. The crystallization process, induced by coupling effects between the compositions of borosilicate glass and the solidified waste, plays an important role in understanding the leaching behaviors of nuclear glass.