Hydrogen peroxide (H2O2) is encapsulated in silica hydrogels using sol‐gel method and the effects of the K+ : Na+ ion ratio on gelation time, hydrogel structure, stability, and release rate of H2O2 were investigated. As the amount of K+ ions increased relative to the amount of Na+ ions at the same pH, the gel structure became less compact and the pore diameter increased. Hydrogen peroxide retention values up to 90 and 80% were observed at the end of 7 and 20 days, respectively, in the presence of K+ ions at low pH values when the initial H2O2 concentration was 19.9 wt %. Release rate of hydrogen peroxide decreased with decreasing pH for the two K+ : Na+ ion ratios studied. This work presents an environmentally friendly, low cost, and easy to scale up method to increase the stability of high initial concentrations of H2O2 at room temperature and customize the release rate. © 2016 American Institute of Chemical Engineers AIChE J, 63: 409–417, 2017

Encapsulating hydrogen peroxide (H2O2) in silica hydrogels is a simple, environmentally friendly, and cost-effective method that is easy to scale up. Sodium silicate is the most commonly used aqueous silicate in sol–gel chemistry. Previously, we studied the effects of Na+ and K+ ions in the starting silicate precursor on the structure of hydrogels and the stability of entrapped H2O2. In the present study, we present the results obtained when divalent ions, Mg2+ and Ca2+, were introduced in the sol. The use of divalent metal ions resulted in hydrogel structures that are different from those previously obtained. H2O2 stability increased with the addition of Mg2+ and Ca2+ ions and with decreasing pH. At low pH values, 93% of the peroxide was retained at the end of 10 days with Mg2+-containing hydrogels, compared to 91% retention with Ca2+-containing hydrogels, 87% retention with K+-containing hydrogels, and 68% retention with a unmodified sodium silicate precursor. The results show that the structure of the hydrogels can be changed using different types and amounts of metal ions to tailor the release of H2O2 for an intended application.