Produção de fotocatalisadores de Nb2O5 imobilizado em suporte cerâmico para fotodegradação de corante sintético em efluentes líquidos

Abstract

Water pollution is a serious problem that affects the environment and human beings. Synthetic dyes make up an important class of contaminants that affect water quality, among which is methylene blue (MB). The objective of this work was to produce ceramic materials with photocatalytic property of Nb2O5 immobilized on a red ceramic support capable of removing micropollutants from synthetic effluents. For this purpose, two different types of ceramic materials were produced: in the first type, Nb2O5, in different proportions ranging from 10.8% to 19.2%, was incorporated into treated common clay and the mixture was homogenized with water to form a plastic mass that was moulded, dried and, finally, the materials were thermally treated at temperatures between 850°C and 1050°C; in the second type, the photocatalytic material was produced by applying a coating with 60% Nb2O5 on a red ceramic support, which was prepared similarly to the first type, but was only fired at 850° C. The materials were characterized by granulometric analysis, hygroscopic humidity, XRF, XRD, SEM, DRS, TGA, PCZ, technological properties. An experimental design of the CCD type with 22 factorial runs, 2.2 axial runs and 2 runs at the central point was used to choose the material with incorporated Nb2O5, using the removal of MB as a response variable, thus, the material produced with 15% of Nb2O5 and a firing temperature of 850°C was chosen because it removes 80.26% of the MB concentration. In the case of the material coated with 60% Nb2O5, as it was the only one, it was evaluated for MB removal as a function of the pH (5, 7 and 9) and [H2O2] (0, 50 and 100 mg/L) variables, in this case, a planning of the CCD-FC type was used with 22 factorial runs, 2.2 axial runs and 2 runs at the central point, the evaluation of the obtained model showed that the variable [H2O2] was not significant, in the range studied, and the Optimal pH for MB removal was 8.0. The material with incorporated Nb2O5 presented Eg = 1.95 eV and the one with 60% Nb2O5 coating presented Eg = 2.94 eV. In addition, both types of materials showed excellent regeneration capabilities after 5 cycles, maintaining removals close to 90%. The photocatalytic materials produced with Nb2O5 immobilized on red ceramic supports showed the ability to remove MB in synthetic effluent, with the material coated with Nb2O5 promising because it presents Eg close to that of the pure oxide, simplicity of obtaining, high removal and recovery capacities.