Original Article

The effect of CaO/SiO₂ ratio and FeO content on the viscosity and structure of CaO-SiO₂-11.3 wt% V₂O₅-13.45 wt% MnO-FeO slag

School of Metallurgical Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, PR China

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Received: 25 November 2025
Accepted: 11 December 2025

Abstract

Converter vanadium slag serves as a critical medium in the efficient extraction of vanadium resources, with its viscosity and structural evolution governing the flowability and vanadium enrichment efficiency during the extraction process. This study investigated the CaO-SiO₂-11.3wt.% V₂O₅-13.45wt.% MnO-FeO slag system. The effects of basicity (CaO/SiO₂) and FeO content on the viscosity and structure of the slag were examined using the rotating cylinder method, Fourier Transform Infrared Spectroscopy (FTIR), and Raman spectroscopy. The results indicated that as basicity and FeO content increased, both the viscosity and apparent activation energy of the slag decreased substantially, thereby improving fluidity. Notably, the most significant variations in viscosity occurred when the basicity ranged from 0.5 to 1.0 and the FeO content was approximately 31wt.%. FTIR analysis revealed a decrease in the absorption intensity of [SiO₄] tetrahedra and a shift toward lower wavenumbers, with the trough depth of the Si-O-Si bond becoming shallower. The central wavenumber shifted from 484.09 cm⁻¹ to 498.64 cm⁻¹. Raman spectroscopy demonstrated that increases in FeO and CaO promoted the generation of free oxygen ions (O²⁻) and inhibited the transformation of Q⁰ and Q¹ species into Q² and Q³ species, consequently reducing the degree of polymerization and complexity of the slag. The most significant modification to the silicate network occurred when the basicity ranged from 0.2 to 0.5 and the FeO content ranged from 23.3% to 31.3%.