Abstract
Porous glass was prepared by the hydrothermal reaction of sodium borosilicate glass, and oxygen-ion characterization was used to identify the hydroxyl groups in its surface area. A substantial amount of “water” was introduced into the ionic structure as either OH− groups or H2O molecules through the hydrothermal reaction. When the hydrothermally treated glass was reheated at normal pressures, a porous structure was formed due to the low-temperature foaming resulting from the evaporation of H2O molecules and softening of the glass. Although it was expected that the OH− groups would remain in the porous glass, their distribution required clarification. Oxygen K-edge X-ray absorption fine structure (XAFS) spectroscopy enables the bonding states of oxygen ions in the surface area and interior to be characterized using the electron yield (EY) and fluorescence yield (FY) mode, respectively. The presence of OH− groups was detected in the O K-edge XAFS spectrum of the porous glass prepared by hydrothermal reaction with a corresponding pre-edge peak energy of 533.1 eV. In addition, comparison of the XAFS spectra obtained in the EY and FY modes revealed that the OH− groups were mainly distributed in the surface area (depths of several tens of nanometers).
Highlights
Metallurgical processes produce a large amount of slag and waste glass as by-products, which consist of various oxide components such as SiO2, CaO, Al2 O3, and Na2 O
(please see Figure 3), we focused on the relationship between the peak energy and the bond strength between a cation (Mn+ ) and oxygen anion, where we assumed that each oxygen makes the other bond with a silicon cation
Bond dissociation, the peak energy E2 corresponds to the hydroxyl group associated with the silicon cation (Si–OH) because the bond dissociation energies (D) of the M–O diatomic molecule defined by Luo [35] satisfy the following relationship: D(Na–O) < D(H–O) < D(Si–O), corresponding to the peak energy relationship E1 < E2 < E3
Summary
Metallurgical processes produce a large amount of slag and waste glass as by-products, which consist of various oxide components such as SiO2 , CaO, Al2 O3 , and Na2 O. These materials are currently recycled in road or concrete materials, additional value should be added to them for further beneficial use. The authors have proposed that the introduction of “interfaces” enhances the exergy of even waste slag and glass [1,2], which means that these reagents with low exergies could be transformed into value-added porous ceramic materials such as heat insulators, water-retentive materials, or filters for liquid or gas purification. Matamoros-Veloza et al [3,4] previously proposed
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