Modificação de argila bentonita com pentóxido de nióbio para remediação de efluentes têxteis

Abstract

In recent decades, large amounts of effluents have been discarded by the textile sector, representing a severe environmental threat by water pollution. Conventional methods have limited effectiveness in the treatment of these effluents and, consequently, new alternatives have been pursued. In this context, the Advanced Oxidation Process (AOP) stands out due to its high efficiency in industrial effluent remediation. However, AOP with the powder catalyst has not been successfully employed at an industrial scale. A new host of matrix alternatives have attracted the interest of scientists, specifically clay minerals due to their low cost, vast world reserves, and environment-friendly credentials. Clay minerals present unique features related to their composition, such as high adsorption capacity and a crystalline structure. These properties highlight such materials as potential new host matrixes for semiconductors that favor heterogeneous catalysis. In this study, Niobium pentoxide (Nb2O5) on a bentonite clay-host matrix was employed as a catalyst for QR-19 blue dye photo degradation by a heterogeneous catalysis process. The modified bentonite clay was supported on microscopic blades and in a pastille form, both forms were tested on the degradation process of QR-19 blue dye solution for a maximum period of five hours. The structures of the resulting bentonite/Niobium systems were examined under a number of methods: X-ray diffraction, Fourier-transform infrared spectroscopy, 27Al and 29Si Solid-State Nuclear Magnetic Resonance, Field Emission Scanning Electron Microscopy, Zeta Potential, and Diffuse Reflectance UV-Vis spectroscopy. The results indicate that the Nb2O5 was successfully supported on the surface of the bentonite clay matrix. The photo degradation tests suggest the reduction of maximum adsorption bands (594 nm) after 60 minutes. The bands referring to aromatic groups (300 nm) disappear almost entirely after 80 minutes, even for tests in the absence of hydrogen peroxide. Bentonite clay is also responsible for the reduction of electron-hole pair recombination, therefore increasing the photocatalytic efficiency. Consequently, the use of H2O2 is expendable. Based on these results, it is possible to state that the innovative bentonite/Niobium material performs as a photocatalyst with high efficiency. The exciting results of these proposed materials offer a cost effective alternative for the remediation process of textile dyes.