Silica Gel Functionalized with Cu, Ag and ZnO as an Absorbent System in Active Packaging

Silica gel was synthesized from rice husk silicate, a sustainable feedstock, and functionalized with Ag, Cu, and ZnO nanoparticles to evaluate the liquid absorption capacity of these nanocomposites and their potential use in active packaging. From a two-level full factorial experiment, where pH, silicate modulus and SiO2 concentration were tested, silicas with varied surface areas (250-750 m2/g) and pore volume (0.4-1.0 cm3/g) were obtained. The silica with the highest porosity (1.0 cm3/g) was synthesized from a solution containing silicate with a modulus of 2.0 and a SiO2 concentration of 20 g/L, by acidification to pH 6. The product obtained showed the highest absorption of water and simulated body fluid (190%) and was chosen as the matrix for functionalization with nanoparticles produced from chemical reduction (Cu, Ag) and precipitation (ZnO) methods. The incorporation of ZnO nanoparticles into the silica matrix had an additional contribution to liquid absorption, at a rate of 0.04%/ppm.