Hydrogen Peroxide Stability in Silica Hydrogels

Hydrogen peroxide (H₂O₂) is an environmentally friendly oxidant whose current applications are limited due to its instability. Silica hydrogels obtained by sol-gel process has the potential of increasing its stability due to strong hydrogen bonding between the H₂O₂ molecules and the silanol groups (Si-OH) at the silica surface.  The pH of the sol determines the structure of the hydrogel and in the previous studies to date; it is controlled by adding an acidic or alkaline solution. In the present study, the pH of the sol is adjusted by varying the sodium content of sodium silicate. The effect of sodium on the kinetics of sol-gel formation and the structure of the resulting hydrogel and xerogels are studied.  The surface area of the hydrogel/xerogel determines the availability of sites for H₂O₂ bonding in the presence of sodium ions. Therefore, the decomposition rate of H₂O₂ is studied at different sodium concentrations to understand the controlled release mechanism at room temperature. Samples are characterized by measuring the surface area, pore volume and average pore size using Brauner-Emmet-Teller (BET) analysis and scanning electron microscopy (SEM). Experiments are carried out with up to 50% initial concentration of H₂O₂.