Mechanism of Vanadium Leaching during Surface Weathering of Basic Oxygen Furnace Steel Slag Blocks: A Microfocus X-ray Absorption Spectroscopy and Electron Microscopy Study

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

Abstract

© 2017 American Chemical Society. Basic oxygen furnace (BOF) steelmaking slag is enriched in potentially toxic V which may become mobilized in high pH leachate during weathering. BOF slag was weathered under aerated and air-excluded conditions for 6 months prior to SEM/EDS and μXANES analysis to determine V host phases and speciation in both primary and secondary phases. Leached blocks show development of an altered region in which free lime and dicalcium silicate phases were absent and Ca-Si-H was precipitated (CaCO 3 was also present under aerated conditions). μXANES analyses show that V was released to solution as V(V) during dicalcium silicate dissolution and some V was incorporated into neo-formed Ca-Si-H. Higher V concentrations were observed in leachate under aerated conditions than in the air-excluded leaching experiment. Aqueous V concentrations were controlled by Ca 3 (VO 4 ) 2 solubility, which demonstrate an inverse relationship between Ca and V concentrations. Under air-excluded conditions Ca concentrations were controlled by dicalcium silicate dissolution and Ca-Si-H precipitation, leading to relatively high Ca and correspondingly low V concentrations. Formation of CaCO 3 under aerated conditions provided a sink for aqueous Ca, allowing higher V concentrations limited by kinetic dissolution rates of dicalcium silicate. Thus, V release may be slowed by the precipitation of secondary phases in the altered region, improving the prospects for slag reuse.

Citation

Hobson, A. J., Stewart, D. I., Bray, A. W., Mortimer, R. J. G., Mayes, W. M., Rogerson, M., & Burke, I. T. (2017). Mechanism of Vanadium Leaching during Surface Weathering of Basic Oxygen Furnace Steel Slag Blocks: A Microfocus X-ray Absorption Spectroscopy and Electron Microscopy Study. Environmental Science and Technology, 51(14), 7823-7830. https://doi.org/10.1021/acs.est.7b00874

• Journal Article Type: Article
• Acceptance Date: Jun 19, 2017
• Online Publication Date: Jul 6, 2017
• Publication Date: Jul 18, 2017
• Deposit Date: Jul 14, 2017
• Publicly Available Date: Jul 14, 2017
• Journal: Environmental science & technology
• Print ISSN: 0013-936X
• Electronic ISSN: 1520-5851
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 51
• Issue: 14
• Pages: 7823-7830
• DOI: https://doi.org/10.1021/acs.est.7b00874
• Keywords: Vanadium, X-ray absorption spectroscopy
• Public URL: https://hull-repository.worktribe.com/output/453144
• Publisher URL: http://pubs.acs.org/doi/abs/10.1021/acs.est.7b00874
• Additional Information: Copy of article: Mechanism of Vanadium Leaching during Surface Weathering of Basic Oxygen Furnace Steel Slag Blocks: A Microfocus X-ray Absorption Spectroscopy and Electron Microscopy Study. Andrew J. Hobson, Douglas I. Stewart, Andrew W. Bray, Robert J. G. Mortimer, William M. Mayes, Michael Rogerson, and Ian T. Burke. Environmental Science & Technology 2017 51 (14), 7823-7830 DOI: 10.1021/acs.est.7b00874
• Contract Date: Jul 14, 2017