Bentonitas modificadas com cátions orgânicos para aplicação na adsorção do corante aniônico vermelho de remazol

Abstract

One of the problems that has generated much discussion in recent years is the incorrect disposal of azo dye residues in water bodies, either because of its polluting potential or the large amount discarded annually, resulting in the need for efficient and economically viable technologies to alleviate this problem. This work aims to synthesize adsorbent hybrids based on bentonites abundant in the state of Paraíba modified with organic molecules and cations and apply in the adsorption of azo dye. The hexadecyltrimethylammonium cation was used as bentonite modifying agents. Hybrids modified by the hexadecyltrimethylammonium cation were synthesized using the ionic exchange method, varying the time (1 and 3h) and temperature (25 ºC and 60 ºC) of synthesis, as a way of evaluating the influence of these parameters on the formation of the hybrids. After the synthesis, the hybrids were characterized by XRD, FTIR and elemental analysis of CHN, applied in the process of adsorption of the red remazol RB azo dye, in which the influence of variables such as contact time, medium pH, mass was evaluated. of adsorbent and dye concentration to optimize the process. The characterization results of the synthesized hybrids demonstrate their efficient formation, since the XRD patterns presented displacement of the main peak of the montmorillonite to values lower than 2θ when compared to the crude bentonite, indicating an increase in the basal spacing of the clay (from 1.26 nm in the crude bentonite to up to 1.89 nm in the synthesized hybrids) and, consequently, the incorporation of the organic cation in this region. The FTIR spectra corroborated the XRD results and showed, for all hybrids, very evident bands at approximately 2922, 2850 and 1480 cm-1, these bands attributed to asymmetric and symmetric stretching of C-H bonds and CH3 stretching, respectively. These bands are characteristic of organic compounds and are not observed in the spectrum of crude bentonite, the results of the elemental analysis of CHN, confirmed the presence of nitrogen in the hybrids. All hybrids synthesized showed potential for adsorption of the red remazol RB dye, reaching 99.3% for the hybrid synthesized with 1 hour of stirring at a temperature of 60°C and 99.5% for the hybrid synthesized with 3 hours of stirring also temperature of 60°C.