Estudo do comportamento térmico, propriedade antibacteriana e adsorventes do óxido de nióbio e filossilicatos modificados com moléculas orgânicas contendo grupos nitrogenados

Abstract

Clays are composed of clay minerals that have a structure and chemical properties that can be modified through ion exchange, silanization or addition of oxides, resulting in multifunctional materials. In this study, three sets of materials were produced: i. Bentonite organofunctionalized with the surfactant hexadecyltrimethylammonium bromide (CTAB) and the organosilane 3-aminopropyltrimethoxysilane (APTMS), both subsequently modified with niobium oxide; ii. Vermiculite modified with CTAB and niobium oxide; iii. niobium oxide modified with APTMS and CTAB. The solids were characterized by X-ray diffraction, infrared spectroscopy, zeta potential measurements, CHN elemental analysis, scanning electron microscopy, thermogravimetric analysis, RAMAN spectroscopy, diffuse reflectance UV-Vis spectroscopy and N2 adsorption/desorption. The characterization results indicate that organic molecule interacts with the clay in a way that influences its interaction with niobium oxide particles (Nb2O5 nH2O). In solids modified by silanization with APTMS, there was intercalation of niobium species, forming stable pillars after calcination, resulting in an increase in surface area. In bentonite modified with CTAB and niobium oxide, the surfactant is intercalated in the interlayer region, which apparently directs the niobium species to the external surface of the clay. In the thermal study of these materials, an adaptation to the Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sonuse (KAS) kinetic models was observed. Niobium oxide modified with surfactant and organosilane were evaluated in the adsorption of the red dye remazol RB in which pH, adsorbent mass, reaction time and dye concentration were varied. The organosilane-modified niobium oxide showed significantly faster kinetics than the surfactant-modified material, removing 96% of the dye in 5 min of reaction. Antibacterial tests were carried out with vermiculite modified with CTAB and niobium oxide after tetracycline adsorption, revealing bactericidal activity from a concentration of 125 μg mL-1 for S aureus and 1000 μg mL-1 for E coli.