Adsorption isotherms and thermal behavior of hybrids based on quercetin and inorganic fillers

We investigated the adsorption process of quercetin onto several inorganic fillers, such as kaolinite, calcium carbonate and alumina. Firstly, we performed equilibrium adsorption studies in order to determine the quercetin/filler adsorption isotherms, which were successfully fitted through the Langmuir model. Based on the adsorption data analysis, we estimated the maximum adsorption capacity of each filler as well as the Langmuir constant, which is related to the affinity between quercetin and the surfaces of the inorganic particles. Then, we prepared hybrids formed by fillers saturated with quercetin. The obtained composites were characterized by thermogravimetric analysis with the aim of determining the loading efficiency as well as the effect of the adsorption process on the quercetin thermal stability. According to the Langmuir isotherms, alumina revealed the most efficient support for quercetin adsorption. Finally, we observed that the interactions with the fillers' surfaces induce a reduction in the quercetin degradation temperature.