No abstract

No abstract

Miniaturization has been a trend in the instrumentation of chemical analyzes. The interest in miniaturization stems from the perceived benefits of faster, easier, less expensive and less wasteful analyzes than the tradition analyses. Thus, this work proposes a miniaturization of photocatalytic tests using a microplate reader for the analysis of several results, using only microliters of solution. The present work investigates the heterogeneous photocatalysis of the eosin yellow, acid yellow 73 and basic yellow 2 dyes, in the presence of zinc oxide (ZnO) and titanium dioxide (TiO2) catalysts, under irradiation in the visible light and ultraviolet light. Dye degradation was evaluated using a microplate reader (Elisa Polaris®), a photometric device that performs colorimetric readings in the 0-3 absorbance (ABS) range at wavelengths of 405, 450, 492 and 630 nm. The kinetic study was performed using the Langmuir-Hinshelwood law. It was verified that the degradation rates were higher than 90% over a period of 120 minutes for all the studied systems, especially the system composed of acid yellow dye 73 and the ZnO catalyst, which reached a degradation of 96.23% in 120 minutes.

ResumoA versatilidade de materiais naturais como as argilas tem chamado a atenção para a sua aplicação em estudos científicos. Neste trabalho foi avaliado o enriquecimento dessas propriedades com a impregnação de SnO2 na superfície desse material, e seu comportamento como catalisador para a reação de transesterificação de óleo de soja. Para isso, uma bentonita foi selecionada, considerando os valores de capacidade de troca catiônica e teor de quartzo. A bentonita foi utilizada na forma pura e impregnada com SnO2 por dois métodos: solvotermal assistido por micro-ondas e Pechini modificado. Para avaliar a eficiência da impregnação, foram realizadas algumas caracterizações, como difração de raios X, adsorção de N2 e microscopia eletrônica de varredura, que mostraram uma melhor dispersão do SnO2no suporte utilizando o método Pechini modificado, o qual também apresentou melhor eficiência no teste catalítico para obtenção de biodiesel, reduzindo em 41,3% a viscosidade do óleo utilizado.

TiO 2 is a highly active photocatalyst, sometimes obtained with nanometric particle size, which improves its behavior but makes its removal from aqueous media more difficult. To avoid this drawback, this work aims to obtain a photocatalyst easily removable from aqueous media using magnetism. The core@shell system (Co,Mn) Fe 2 O 4 @TiO 2 was prepared by adding commercial (Co,Mn)Fe 2 O 4 nanoparticles to the titanium polymeric resin synthesized by the modified Pechini method. Optimization of photocatalyst properties was achieved by variation of the TiO 2 :ferrite ratio, synthesis temperature and time, followed by their evaluation in photodegradation of an azo dye. The highest efficiency was attained when anatase was the major crystalline phase, whereas TiO 2 :ferrite ratio was limited to 90% to retain the magnetic properties, which enabled its removal from aqueous media using simple magnets. The system (Co,Mn)Fe 2 O 4 @TiO 2 , synthesized with 90% TiO 2 and calcined at 500°C for 8 h, presented a discoloration of 76.3% after 16 h of exposure to UV light.

No abstract