Design of Refining Slag Based on Raman and NMR Spectroscopy Study for Removing Phosphorus for SoG-Si

Abstract

In present study, Nuclear magnetic resonance (NMR), Raman vibrational spectroscopy were used to investigate in detail the behavior and state of phosphorus (P) in a system SiO2–CaO–Na2O–P2O5 slag. The role of the degree of P–Silicon (Si) cross linking on the P removal from silicon using slag treatment was highlighted by comparing the dephosphorization data. The results show that adding Na2O into acidity slag (CaO/SiO2 = 0.5) from 0 to 30 wt% results in the first increase and then decrease of the removal ratio of P from silicon. When Na2O content is near 15 wt%, the removal ratio of P is above 60%. P2O5 oxidized of P from silicon can be incorporated into the silicate network through P–BO–Si bonds and be stabilized in slag in the form of Q3 (Si and P) species. The removal ratio of P presents a same trend as the relative amount of P–BO–Si bonds and Q3 (Si and P) species, demonstrating fixing P in slag could promote the P removal. Q2 (Si) species of the silicate network as primary intermediate structure could capture P to form Q3 (Si and P) species. When Na2O is less than 15 wt%, Q3 (Si and P) species is promoted to be formed by increasing Na2O, Conversely, it will be depolymerized as Na2O is added to more than 15 wt% to release P by the preferred break of P–BO–Si bonds.