Effect of P2O5 addition on enrichment behaviour of phosphorus in CaO–SiO2–FeO–P2O5 slag

Abstract

ABSTRACT The CaO–SiO2–FeO–P2O5 slag was measured by Raman spectra, and the changes in the structure and behaviour of phosphorus were analysed under different slag components. The results proved that phosphorus exists in two enrichment behaviours in the slag, which can be judged according to the mole fractions of Q1(Si), Q2(Si), and Q3(Si). When the content of P2O5 increases from 4.5% to 8.5%, the Q0(P) intensity changes most significantly. Since the Fe–O bond energy (390.4 kJ mol−1) is weaker than the P–O (410 kJ mol−1) bond energy, the silicon-oxygen network structure will show a behaviour change of depolymerization first and then polymerization. XRD analysis shows that with the increase of P2O5 content, different calcium silicate phases are added and decreased in the slag, and the content of a small amount of calcium ferrite phase changes, bonds or separates from each other, which is consistent with the change law of Raman analysis.