Behaviour and fate of vanadium during the aerobic neutralisation of hyperalkaline slag leachate

Hobson, Andrew J.; Stewart, Douglas I.; Bray, Andrew W.; Mortimer, Robert J.G.; Mayes, William M.; Riley, Alex L.; Rogerson, Michael; Burke, Ian T.

Abstract

© 2018 Vanadium is a toxic metal present in alkaline leachates produced during the weathering of steel slags. Slag leaching can therefore have deleterious effects on local watercourses due to metal toxicity, the effects of the high pH (9–12.5) and rapid carbonation (leading to smothering of benthic communities). We studied the fate and behaviour of V in slag leachate both through field observations of a heavily affected stream (Howden Burn, Consett UK) and in controlled laboratory experiments where slag leachates were neutralised by CO2ingassing from air. V was found to be removed from leachates downstream from the Howden Burn source contemporaneously with a fall in pH, Ca, Al and Fe concentrations. In the neutralisation experiments pH reduced from 12 → 8, and limited quantities of V were incorporated into precipitated CaCO3. The presence of kaolinite clay (i.e. SiOH and AlOH surfaces) during neutralisation experiments had no measureable effect on V uptake in the alkaline to circumneutral pH range. XANES analysis showed that V was present in precipitates recovered from experiments as adsorbed or incorporated V(V)indicating its likely presence in leachates as the vanadate oxyanion (HVO42−). Nano-scale particles of 2-line ferrihydrite also formed in the neutralised leachates potentially providing an additional sorption surface for V uptake. Indeed, removal of V from leachates was significantly enhanced by the addition of goethite (i.e. FeOOH surfaces) to experiments. EXAFS analysis of recovered goethite samples showed HVO42−was adsorbed by the formation of strong inner-sphere complexes, facilitating V removal from solution at pH < 10. Results show that carbonate formation leads to V removal from leachates during leachate neutralisation, and the presence of both naturally occurring and neoformed Fe (oxy)hydroxides provide a potent sink for V in slag leachates, preventing the spread of V in the environment.

Citation

Hobson, A. J., Stewart, D. I., Bray, A. W., Mortimer, R. J., Mayes, W. M., Riley, A. L., …Burke, I. T. (2018). Behaviour and fate of vanadium during the aerobic neutralisation of hyperalkaline slag leachate. The Science of the total environment, 643, 1191-1199. https://doi.org/10.1016/j.scitotenv.2018.06.272

• Journal Article Type: Article
• Acceptance Date: Jun 22, 2018
• Online Publication Date: Jul 4, 2018
• Publication Date: Dec 1, 2018
• Deposit Date: Jul 5, 2018
• Publicly Available Date: Jul 5, 2018
• Journal: Science of The Total Environment
• Print ISSN: 0048-9697
• Electronic ISSN: 1879-1026
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 643
• Pages: 1191-1199
• DOI: https://doi.org/10.1016/j.scitotenv.2018.06.272
• Keywords: Environmental Engineering; Waste Management and Disposal; Pollution; Environmental Chemistry
• Public URL: https://hull-repository.worktribe.com/output/911654
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S0048969718323489
• Additional Information: This article is maintained by: Elsevier; Article Title: Behaviour and fate of vanadium during the aerobic neutralisation of hyperalkaline slag leachate; Journal Title: Science of The Total Environment; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.scitotenv.2018.06.272; Content Type: article; Copyright: © 2018 The Authors. Published by Elsevier B.V.