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Structural drivers controlling sulfur solubility in alkali aluminoborosilicate glasses
Author(s) -
Xu Xinyi,
Youngman Randall E.,
Kapoor Saurabh,
Goel Ashutosh
Publication year - 2021
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.17778
Subject(s) - solubility , borosilicate glass , vitrification , sulfate , alkali metal , sulfur , silicate , chemical engineering , materials science , polymerization , mineralogy , inorganic chemistry , chemistry , polymer , composite material , organic chemistry , metallurgy , medicine , engineering , andrology
If the direct feed approach to vitrify the Hanford's tank waste is implemented, the low activity waste (LAW) will comprise higher concentrations of alkali/alkaline‐earth sulfates than expected under the previously proposed vitrification scheme. To ensure a minimal impact of higher sulfate concentrations on the downstream operations and overall cost of vitrification, advanced glass formulations with enhanced sulfate loadings (solubility) are needed. While, the current sulfate solubility predictive models have been successful in designing LAW glasses with sulfate loadings <2 wt.%, it will be difficult for them to design glass compositions with enhanced loadings due to our limited understanding of the fundamental science governing these processes. In this pursuit, this article unearths the underlying compositional and structural drivers controlling the sulfate solubility in model LAW glasses. It has been shown that the SO 4 2 ‐preferentially removes non‐framework cations from the modifier sites in the silicate network, thus, leading to the polymerization in the glass network via the formation of ring‐structured borosilicate units. Furthermore, though the sulfate solubility slightly decreases with increasing Li + /Na + in the glasses, the SO 4 2 ‐prefers to be charge compensated by Na + , as it is easier for SO 4 2 ‐to break Na–O bonds instead of Li–O bonds.