Vanadium is a potential aquatic pollutant that can be released when steel slags are weathered, either during disposal or in conditioning of the material so it can be re-used as aggregate. Our study aimed to improve our understanding of how vanadium is released from slags into the surrounding environment using a range of geochemical techniques.
We found that vanadium is more readily released under aerobic conditions and that its release to water is controlled by calcium vanadate mineral phases. We also observed significant accumulation of newly-formed calcium silicate hydrate (C-S-H) phases in a rind around the surface of slag that is weathered. These surface minerals are also important in taking up some vanadium from solution.
An understanding of these weathering processes helps give us greater insight into the potential environmental risks of slag processing and re-use. The observed leaching and precipitation processes on the surface of the slag have positive implications for slag after-uses (e.g. as an aggregate). The presence of a surface rind may limit (or significantly slow) further dissolution, preventing significant alkalinity generation or the release of metals to the environment.
Written by Dr William Mayes (R3AW) University of Hull