Estratégias para o desenvolvimento de materiais porosos hierárquicos voltados para aplicações em sistemas em fluxo

Abstract

The term "hierarchy" in relation to porous materials is often used, in a broad sense, for systems that contain only a certain number of different pore types in the form of independent bi- or multimodal pore size distributions, independent if and how the two or more different pore systems are interconnected. Many strategies for ranking porous structures have been and are being developed to improve the performance of final materials in different technical applications, such as adsorptive and catalytic processes. NaA-type zeolite was successfully synthesized on the surface of glass fiber previously activated by alkaline treatment. By varying the treatment time and the amount of silica and alumina precursors applied in the reaction mixture, a sample with higher zeolitic concentration was obtained. This material was evaluated for the water softening process, as an alternative substitute for the use of zeolite in powder form, in which several obstacles related to recovery and reuse limit its application. Water softening experiments, carried out in a continuous flow system, with a column containing the hierarchical material glass-zeolite NaA, showed high performance in reducing Ca2+ concentration, with complete removal achieved for 20 mL of simulated hard water (Ca2+ 100.0 mg L-1) using 500 mg of the sample in column form (10 mm diameter × 300 mm height). The sample maintained this performance over a wide pH range (3.0 - 9.0), and also showed viable regenerability, without decreasing its performance during the first four cycles of use, reaching 87.3% efficiency, when throughout the tenth cycle. In the second part of the work, hierarchical supports of aminofunctionalized mesoporous materials, incorporated in bacterial cellulose cartridges, showed good performance in the immobilization of enzymes from sweet potato peel extract. These materials were evaluated for their potential as support for enzymatic immobilization, through the enzymatic catalysis of the catechol substrate, in a flow injection system, previously designed for this purpose. The two mesoporous materials used as enzymatic immobilizers (CBMPC-APTES and CBMPF-APTES) showed efficiency in catalytic flow tests, with percentage enzyme retention values of 42.8% for the support CBMPC-APTES and 21.8%, for CBMPF-APTES support.