Sustainable ambient pressure-dried silica aerogel from waste glass

Abstract

Silica aerogels are outstanding insulation materials, and applying them as building insulation could significantly enhance the energy efficiency of dwellings. However, the current high price of aerogels hinders their use on large scales, in part due to the embedded costs of production such as raw materials and their energy-intensive drying process. This study proposes a method relying on the upcycling of waste mixed fine soda lime glass as a silica source for subsequent aerogel synthesis via ambient pressure drying (APD). The optimal conditions for the dissolution of silica from waste glass were found to be a 24-h reaction with a 4 M NaOH solution under 80 °C and a liquid-to-solid ratio of 10. The investigation of silica dissolution considers the balance between the yield of silica and the practical scalability. The resulting aerogel is hydrophobic, has a thermal conductivity of 26 mW m⁻¹ K⁻¹, a specific surface area of 608 m² g⁻¹, and a density of 121 kg/m³. These properties are comparable to commercial aerogel, and to a reference aerogel made from commercial sodium silicate. Additionally, the heat treatment of aerogel at 500 °C for 4 h further improved its properties, suggesting a potential for targeted property enhancements.