Glass-ceramics prepared from desulfurized electrolytic manganese residue and the nucleation promotion effect of calcium fluoride in glass phase transition

Abstract

Electrolytic manganese residue (EMR) is toxic industrial solid waste. Electrolytic manganese enterprises have established a desulfurization and sulfuric acid production process to address its storage risks leaving desulfurized EMR (DEMR). In this study, DEMR was used as a raw material to prepare glass-ceramics. A method of melting and one-stage heat treatment was used to realize controlled crystallization of diopside, with calcium fluoride sludge (FS) as a nucleating agent. The impact of CaF2 on the glass network structure, as well as on the microstructure and performance of the glass-ceramics, are discussed. CaF2 can greatly improve the nucleation ability of glass precursors. When the addition of FS is small, the phase transition of glass is dominated by the diffusion of atoms and growth of diopside, forming dendritic crystals. When introducing more FS, the glass-ceramics form smaller island-shaped crystals due to many nucleation sites. The prepared glass-ceramics show excellent mechanical properties and chemical stability. Its hardness exceeds 6.5 GPa, with bending strength over 110 MPa. The acid resistance of glass-ceramics is higher than 99.5%, and the toxic metals in the raw materials are stable solidified. This study perfects the technology of EMR desulfurization pretreatment, which provides an effective graded recycling approach for EMR.