Valorization of Waste Soda Lime Silica Glass for the Fabrication of ZnO/SLS Glass System: Thermal and Compositional Analysis for Advanced Material Applications

Abstract

In the 21st century, the demand for sustainable solutions in advanced technologies has intensified, prompting significant interest in the valorization of industrial and post-consumer waste streams. Among these, waste glass particularly soda lime silica (SLS) glass has emerged as a promising precursor material for the development of low-energy optoelectronic components. This study investigates the thermal, compositional, physical, structural, and optical properties of a novel ZnO/SLS glass system. The precursor glasses were successfully synthesized via the conventional melt-quenching technique. Energy Dispersive X-ray Fluorescence (EDXRF) analysis revealed that all elemental constituents were measured in their oxide forms. The major oxide components identified were ZnO, SiO₂, CaO, and Na₂O, collectively accounting for approximately 95 wt.% of the total glass composition. Minor constituents included K₂O and MgO, while trace oxides such as BaO, Cr₂O₃, Fe₂O₃, and B₂O₃ were present in amounts typically below 1 wt.%. An increase in ZnO content within the SLS glass matrix led to a corresponding decrease in the concentration of other major oxides such as SiO₂, CaO, and Na₂O. This compositional adjustment was optimized to enhance the physical and elastic properties of the glass system, with improved durability attributed to the reduced CaO content. Differential Thermal Analysis (DTA) conducted at a heating rate of 10 °C/min indicated a decrease in both the glass transition temperature (Tg) and crystallization temperature (Tc) with increasing ZnO content. This thermal behavior is ascribed to the reduction in melt viscosity caused by the higher ZnO concentration, resulting in a Tg and Tc decrease of approximately 50–60 °C. Density measurements, performed to assess molecular packing efficiency, showed that the glass density increased from 2.520 to 2.842 g/cm³ with increasing ZnO content. This trend is primarily attributed to the higher atomic mass of Zn (65.390 amu) compared to Si (28.086 amu), Ca (40.078 amu), and Na (22.989 amu). Additionally, the increase in density corresponds to variations in the cross-link density within the glass network. The resulting ZnO/SLS glass system demonstrates promising characteristics for potential use in advanced material applications.