Physicochemical properties of new cellulose-TiO2 composites for the removal of water pollutants: Developing specific interactions and performances by cellulose functionalization

Cellulose-TiO2 composites are developed using microcrystalline cellulose (MCC). The closed MCC structure was solubilized by liquid-phase treatments with nitric (HNO3) or phosphoric acids (H3PO4) to improve the TiO2-dispersion. These pretreatments simultaneously generate different types of oxygen and phosphorus functionalities on the cellulose chains that determine the interactions with Ti-alkoxide precursor during impregnation, leading to composite materials with different Ti-loadings and physicochemical characteristics. The morphological, textural, chemical and crystalline properties of both cellulose derivatives and cellulose-TiO2 composites were studied by complementary techniques. Microporous composites with round-shaped anatase-TiO2 microcrystals were obtained by using HNO3 treatments, while H3PO4 favours the formation of mesoporous composites with flat and non-crystalline-TiO2 particles. The photocatalytic efficiency of the obtained cellulose-TiO2 composites always improve the results obtained with the commercial TiO2-photocatalysts used as reference materials; this behaviour was analysed taking into account the physicochemical characteristics of the samples.