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Mechanism of Vanadium Leaching During Surface Weathering of Basic Oxygen Furnace Steel Slag Blocks: A µXANES and SEM Study

DOI: 10.1021/acs.est.7b00874 DOI Help

Authors: Andrew James Hobson (University of Leeds) , Douglas I. Stewart (University of Leeds) , Andrew W. Bray (University of Leeds) , Robert J. G. Mortimer (Nottingham Trent University) , Will Mayes (University of Hull) , Michael Rogerson (University of Hull) , Ian T. Burke (University of Leeds)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Environmental Science & Technology

State: Published (Approved)
Published: June 2017
Diamond Proposal Number(s): 12696

Abstract: Basic oxygen furnace (BOF) steelmaking slag is enriched in potentially toxic V which may become mobilised 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 (CaCO3 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 Ca3(VO4)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 CaCO3 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.

Journal Keywords: vanadium surface weathering steel slag

Subject Areas: Environment, Materials

Instruments: I18-Microfocus Spectroscopy

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