Produção de membranas de nanofibrilas de celulose/MoO₃ para adsorção de azul de metileno de efluentes aquosos

Abstract

This study investigates the development and characterization of composite membranes based on cellulose nanofibrils (CNF) and molybdenum trioxide (MoO3) for the removal of the cationic dye methylene blue (MB) from aqueous effluents. The experimental approach systematically varied the concentrations of CNF (0.5–2.0%) and MoO3 (1–10%) to elucidate the relationship between the support matrix microstructure and the adsorptive performance of the active phase. Characterization was performed through structural analyses (SEM, XRD, FTIR, and porosity), kinetic studies, and adsorption isotherms. The results indicate that the incorporation of MoO3 promotes modifications in surface interactions, as reflected by the better fit to the pseudo-second-order kinetic model. The adsorptive process is predominantly governed by electrostatic interactions between the negatively charged membrane surface pHPZC (3,5) and the methylene blue in aqueous solution for both membranes with and without the oxide. The main finding of the study was the identification of an inverse relationship between CNF concentration and adsorption capacity. This behavior was attributed to a reduction in membrane porosity resulting from structural compaction (hornification), which limits mass transport and reduces accessibility to the active MoO3 sites. The N0.5Mo5 formulation (0.5% CNF and 5% MoO3) exhibited the best performance, with a maximum adsorption capacity of approximately 453,4 mg/g, resulting from a balance between high porosity and adequate dispersion of the active phase. The results demonstrate that the microstructural porosity of the support matrix is the dominant factor in the composite's performance, outweighing the influence of the amount of active material and establishing an important design principle for the development of high-performance adsorbent materials.