Sintered glass-ceramic foams from fluorite tailings and waste glass with calcium phosphate addition

Abstract

Lightweight glass-ceramic foams as novel building and decoration materials exhibit great advantages. Herein, fluorite tailings and waste glass were recycled to sinter glass-ceramic foams by introducing calcined kaolin and calcium phosphate. The effects of calcium phosphate addition and sintering temperature on the crystalline phase, microstructure evolution, fluoride leaching performance and physical properties of the glass-ceramic foams were systematically investigated using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectra, computed tomography, and differential scanning calorimetry. The obtained glass-ceramic foams sintered at 1110 °C exhibited relatively homogeneous pore sizes and distributions, low densities and thermal conductivities, and high compressive strengths. Moreover, the addition of calcium phosphate promoted the formation of fluorapatite, which benefited the toxic fluorine stabilization in the glass-ceramic foams. Thermodynamic data were calculated using Factsage 8.1 and verified through experiments to establish the physical structure transition during sintering. This study provides an efficient utilization route to convert fluorite tailings and waste glass into stable and valuable lightweight glass-ceramic foams.