Determination of chromium valence state in the CaO–SiO ₂ –FeO–MgO–CrO _<i>x</i> system by X-ray photoelectron spectroscopy

Abstract

Abstract The chromium valence states in the CaO–SiO 2 –FeO–MgO–CrO x system were investigated by X-ray photoelectron spectroscopy (XPS). The results indicated that the XPS peaks of Cr 2p 3/2 and Cr 2p 1/2 locate at the binding energy of ∼577 and ∼586 eV, respectively. There are three kinds of chromium ions such as bivalent Cr( ii ), trivalent Cr( iii ), and hexavalent Cr( vi ) in the CaO–SiO 2 –FeO–MgO–CrO x slag. Cr( iii ) is the dominant valence state, and more than 77.99% Cr is trivalent Cr( iii ). The fraction of Cr( ii )/Cr is in the range of 11.24–17.22%. The fraction of Cr( vi )/Cr is below 4.80%. The fraction of Cr( ii )/Cr decreases with increasing slag basicity, Cr 2 O 3 content, temperature, or oxygen pressure log(PO 2 ), while the fraction of Cr( iii )/Cr increases with increasing basicity, Cr 2 O 3 content, temperature, or oxygen pressure. The trend of change is opposite. Low log(PO 2 ), high Cr 2 O 3 content, and high temperature are beneficial to reduce the toxic hexavalent Cr( vi ). The slag basicity has little influence on the fraction of Cr( vi )/Cr.