Synthesis of mesoporous-macroporous silica from rice husk and application in pickering emulsion stabilization

With the rising demand for porous materials for drug delivery and food applications at a sustainable cost, there is an urgent need for potential materials to achieve these goals. Therefore, this study aimed to synthesize and characterize mesoporous-macroporous silica (MMS) from rice husk and evaluate its emulsifying performance as a sole stabilizer. XRD analysis revealed that MMS is 92–98% amorphous, with an average crystallite size of 22.10 nm. BET characterization showed that MMS has an average pore size of 40 nm, a surface area of 118.599 m²/g, and a pore volume of 1.059 cm³ /g. The Type IV isotherm further indicates that MMS consists of meso/macro-pore particles. The MMS-stabilized Pickering emulsion formed oil-in-water (o/w) systems, requiring an average of 0.1 g of MMS particles as a sole stabilizer. Emulsion stabilization occur through a surface tension lowering and interconnected network formation mechanism. MMS particles formed adsorbed film at the interface while droplets are enclosed by the particle interconnected structural network. The high porosity and large pore size give rise to interconnected network formation and even particle distribution system. The application of MMS as a sole stabilizer at a neutral pH in food, cosmetics, pharmaceuticals and drug delivery applications without addition of other emulsifiers or surface modification will reduce cost of production, aligning with circular economy, sustainability and waste valorization goals.