TY - JOUR
T1 - Mechanism of Vanadium Leaching during Surface Weathering of Basic Oxygen Furnace Steel Slag Blocks
T2 - A Microfocus X-ray Absorption Spectroscopy and Electron Microscopy Study
AU - Hobson, Andrew J.
AU - Stewart, Douglas I.
AU - Bray, Andrew W.
AU - Mortimer, Robert J.G.
AU - Mayes, William M.
AU - Rogerson, Michael
AU - Burke, Ian T.
PY - 2017/7/18
Y1 - 2017/7/18
N2 - 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 (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.
AB - 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 (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.
UR - http://www.scopus.com/inward/record.url?scp=85025648489&partnerID=8YFLogxK
U2 - 10.1021/acs.est.7b00874
DO - 10.1021/acs.est.7b00874
M3 - Article
C2 - 28627883
AN - SCOPUS:85025648489
VL - 51
SP - 7823
EP - 7830
JO - Environmental Science & Technology
JF - Environmental Science & Technology
SN - 0013-936X
IS - 14
ER -