Chemie Ingenieur Technik, Vol.93, No.3, 473-481, 2021
Hydrothermal Dissolution of Technical Grade Vitreous Silica in NaOH Solutions to Liquid Water Glasses with Higher SiO2:Na2O Ratios
Technical grade vitreous silica was dissolved hydrothermally in NaOH lyes. Liquid sodium water glasses with silica concentrations of up to 26.4 wt % and molar SiO2:Na2O ratios of up to 3.5 were obtained. The dissolution behavior showed two temperature regimes: up to 130 degrees C the SiO2 content approached a final solubility limit controlled by cristobalite crystallization. Above 130 degrees C, crystallization of low quartz restricted solubility. The dissolution kinetics were governed by surface area reduction and saturation control according to the Noyce-Whitney law.