Structural Investigation of Phosphorus in CaO-SiO 2 -P 2 O 5 Ternary Glass
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RODUCTION
CHINA’S annual crude steel production accounts for nearly half of world output and it surpassed 800 million tons in 2015.[1] It is estimated that the generated steelmaking slags were about 80 million tons.[2] With the low utilization at about 30 pct of the steelmaking slags and the concept of green circular economy, recycling the steelmaking slags into the iron- and steelmaking process was considered as the most efficient way to use the large amounts of steelmaking slags.[3] However, it will inevitably result in the enrichment of phosphorus and further increase the burden in the following dephosphorization process.[4] During the phosphorus recycling and comprehensive utilization of steelmaking slags, selective crystallization and phase separation (SCPS) method has been considered as the most effective approach to solve the problem,[5,6] i.e., the steelmaking slags were modified by different additives to enrich the phosphorus into a certain phase. Afterwards, the enriched phase can be separated and the residues can be recycled into iron- and steelmaking process. During the early 1960 and 1980s, a number of investigations have been conducted to detect the
ZHANJUN WANG, MEI ZHANG, and MIN GUO are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 100083 Beijing, P.R. China. SHENGJIA CAI is with the State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing. ZUOTAI ZHANG is with the School of Environmental Science and Engineering, South University of Science and Technology of China, 518055 Shenzhen, P.R. China. Contact e-mail: [email protected] Manuscript submitted September 4, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
dephosphorization process and n(2CaOÆSiO2-3CaOÆ P2O5) solid solution has been considered as the efficient P-enriched phase.[7–10] Based on the above theoretical research, many researchers have conducted a serious of studies of thermophysical properties of the complex CaO-SiO2-MgO-Al2O3-FetO-P2O5 multiphase, including viscous flow and crystallization behaviors.[2,11–18] Additionally, the effect of P2O5 on the structure has been investigated by Raman spectra,[2,19,20] FTIR[21] and MAS-NMR.[21,22] According to Li[19] and Mysen,[20] both P5+ and Si4+ are coordinated with four oxygen atoms to form [PO4]-tetrahedra and [SiO4]-tetrahedra, which can also copolymerize to form chain, layer, and network structures. It should be noted that there is one double P=O bond in [PO4]-tetrahedra, i.e., [PO4]-tetrahedra can form no more than three bridging oxygen. According to Tilocca,[23] almost all P5+ ions displayed as Q0P (PO3 4 ) 1 4 n and QP (P2 O7 ) (QP , n is the number of bridging oxygen in one [PO4]-tetrahedra) and very small amount of P5+ ions 3 appeared in the form of Q2P (PO2 3 ) and QP (P2 O5 ). However, the knowledge of the local structure and solution mechanism of P2O5 connected with the explanation of bridging and non-bridging oxygen is incomplete. Therefore, it is significant to study the phosphorus behavior
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