Comment on “Preliminary assessment of modified borosilicate glasses for chromium and ruthenium immobilization”, by Farid and Rahman

Publication date: 1 May 2017
Source:Materials Chemistry and Physics, Volume 192
Author(s): Neil C. Hyatt, Claire L. Corkhill, Daniel J. Bailey, Adam J. Fisher, Russell J. Hand
Farid and Rahman recently reported an investigation of the microstructure and alteration of borosilicate glasses designed for the immobilisation of UK radioactive wastes [Preliminary assessment of modified borosilicate glasses for chromium and ruthenium immobilization, Materials Chemistry and Physics, 186 (2017) 462–469]. The authors draw conclusions concerning the partitioning of elements within two devitrified spinel phases, at variance with previous studies of these materials. The authors also present solution chemistry and surface analysis data for alteration of these glasses, and postulate micro-cracks apparent in the gel layer of the altered glass to govern the extent of alteration. From analysis of data presented by Farid and Rahman, and comparison with previous studies, we show that their data are consistent with the presence of a single spinel phase of complex chemical composition, (Mg,Zn,Ni)(Cr,Fe,Al)2O4. We show the chemistry and surface analysis data presented by Farid and Rahman to be contradictory, in terms of the relative alteration behaviour of these glasses, as verified by previous studies, and deduce that an alternative explanation is required to rationalise their observations. We also comment on other aspects of the report which require clarification.

Graphical abstract

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