• Chaurand, Perrine

Abstract

The pig iron conversion into steel generates a large quantity of residue, the Basic Oxygen Furnace steel slag (BOF slag), partially reused as aggregates in civil engineering. The objective of this study is to quantify and to explain the BOF slag leaching behavior (alteration and trace metals (Cr, V) release) by the identification of the molecular mechanisms which control the elements mobility within the solid phase. The experimental study is based on leaching tests (at a laboratory scale with CTG-Leachcrete and at a field-scale with lysimeter) and on X-ray absorption and fluorescence spectroscopies. This approach permits to identify elements speciation at an atomic scale : i.e. their oxidation state, symmetry and bearing phase(s).<br />Trivalent Cr, very stable in a dicalcium ferrite, is very few released during leaching tests in laboratory and in lysimeter. And a spinel-type phase, obtained from (Fe, Mn, Mg)O alteration, also controls the Cr(III) mobility. On the other hand, V(III) is oxidized to V(V) within its bearing-phase. It explains V release during laboratory tests.<br />These experimental data allowed to establish the thermodynamic equations describing BOF slag alteration (mineralogical evolution and release curves obtained from static and dynamic leaching tests), which are the basis of geochemical modeling (CHESS). Such model aims at predicting BOF slag long-term behavior.

Topics

• impedance spectroscopy
• chromium
• phase
• mobility
• Oxygen
• steel
• leaching
• iron
• vanadium