Desenvolvimento de monolitos compósitos hierarquicamente porosos de acetato de celulose funcionalizados com TiO₂ para remoção de corantes em soluções aquosas por adsorção e fotocatálise

Abstract

The contamination of aquatic systems by organic dyes constitutes an important environmental problem due to the high chemical stability and low biodegradability of these compounds. In this work, hierarchically porous cellulose acetate monoliths (CAM), both pure and functionalized with TiO₂, were developed aiming at the removal of methylene blue and Rhodamine B dyes through combined adsorption and photocatalysis processes. The materials were obtained by non-solvent-induced phase separation, using DMF and 1-octanol, with the incorporation of different TiO₂ contents. The characterizations confirmed the formation of porous monolithic structures and the incorporation of the inorganic phase into the polymeric matrix. The presence of TiO₂ promoted morphological changes and a significant increase in the specific surface area, with the composites containing 2% and 11% TiO₂ standing out, presenting areas of 54.61 and 57.82 m² g⁻¹, respectively, compared to 23.17 m² g⁻¹ for the pure monolith. In the methylene blue adsorption assays, the materials showed a removal capacity influenced by the composition and porous structure of the monoliths. The kinetic data showed the best fit to the pseudo-second-order model, indicating that the adsorption process is mainly associated with interactions between the dye and the active sites present in the matrix, with contributions from surface area, porosity, and TiO₂ incorporation. In the cyclic adsorption/photocatalysis assays with methylene blue and Rhodamine B, the TiO₂-containing composites showed greater stability in removal capacity over four cycles, evidencing the contribution of photocatalysis to the partial regeneration of the adsorbent sites. Despite the observed diffusional limitations and structural heterogeneity, the results demonstrate that TiO₂-functionalized monoliths have potential for application in wastewater treatment processes, combining a renewable polymeric support, a hierarchically porous structure, and integrated photocatalytic activity.