Argilas pilarizadas e modificadas de Fe, Ni e Mn para o processo de degradação e adsorção de poluentes orgânicos

Abstract

Innovation and continuous development of new materials are essential to leveraging scientific and technological progress, enabling more efficient and sustainable solutions. In general, clays are abundant, cheap, and accessible. They are constituted by silicon tetrahedrons and aluminum octahedra (2:1) coordinated to oxygen atoms; in their genesis they can present isomorphic substitutions that configure a negative charge in their lamellae, consequently, there are cations which are interlamellar charge compensators, and in aqueous solution they can be exchanged by other cations. Pillarization is a well-known modification where intercalating polyoxocation agents are exchanged (inserted) to increase the distance between the lamellae, generating oxide pillars after calcination. The Keggin ion is the pioneering intercalating agent, presenting a complex structure, containing aluminum and oxygen. However, studies propose the insertion of new metals in its structure (Keggin íon) , by replacing partially or completely the aluminum atoms by other metals, like Fe, Ni and Mn. In this work, chemometrics and multivariable optimization have been used to predict combinations of mole replacement percentages of Fe salts, to insert Ni and Mn; furthermore, sought to understand the amount in mmol of total ions per grams of clay would be the ideal intercalating. A literature review defined the working range, setting the maximum and minimum levels, as the starting point. From the originating data the experimental design, the intercalating agents were prepared for the pillarization process, however, although the cation exchange seems simple, many steps are necessary until calcination, where metal oxides are generated, and then become pillars and/or aggregates on the clay surface. The ordered structure of the natural clay after modification can infer in a structural disorder, with an intensity decreasing and widening of the d(001) peak, which often indicates an exfoliated or a delaminated clay. These new clayey materials were used to remove organic contaminants in aqueous solution, whereas, even that disorder occurs, new possibilities of interaction with the adsorbate may arise. In this perspective, the second part of this work comprises an article containing the synthesis, characterization, and adsorptive/degradation tests of the modified clay with Fe, Ni and Mn, aiming to remove the methylene blue dye, covering the isothermal, thermodynamic, kinetic and cytotoxicity models. These studies could be used as a starting point for new heavy metal adsorption tests, as well as degradation tests in different systems.