Peneiras moleculares do tipo MCM-41 incorporadas com nióbio e tântalo obtidos a partir do beneficiamento de mineral columbita para remoção de corante azul de metileno

Abstract

The intense human activity, the population growth and the adverse effects of climate changes have impacted the planet's water supply, especially in the poorest countries. This is mainly due to the lack of rainfall and the contamination of water bodies by organic and inorganic pollutants, such as dye effluents from various industrial activities. Adsorption processes have been shown to be an economically advantageous alternative in the treatment of these wastewater. This work aimed to study the synthesis of MCM-41 type mesoporous molecular sieves modified with the inclusion of niobium and tantalum atoms from the hydrometallurgical processing of columbite ore, varying the molar ratio Si/M = 15, 30 and 60 (M = Nb and Ta). The materials obtained were characterized by XRD, SEM, TEM, FTIR, N2 adsorption and diffuse UV/vis reflectance, and the replacement of silicon atoms in the MCM41 structure by Nb and Ta atoms was demonstrated, with no prejudice to the characteristic hexagonal ordering of these materials. The molecular sieves were used as adsorbents to remove Methylene Blue dye. The effect of pH, adsorbent dosage and initial dye concentration on removal were evaluated. The adsorption kinetics and the equilibrium isotherm models showed a good fit of the experimental data to the pseudo-second order and Freundlich models, respectively, indicating the heterogeneity in the surface of these adsorbents. Furthermore, thermodynamic parameters indicated a spontaneous endothermic process. The materials obtained proved to be promising adsorbents for MB removal at pH=10, reaching high removal percentages (>99%) even in short contact times.