Rodrigo Pereira Cavalcante

Application of Different Advanced Oxidation Processes for the Degradation of Organic Pollutants

Water is not only an economic, but also an increasingly important social commodity. Potable water is an essential resource for sustaining economic and social development in all sectors. A safe water supply and appropriate sanitation are the most essential components for a healthy and prosperous life. However, increases in human activities have led to exposure of the aqueous environment to chemical, microbial and biological pollutants as well as to micropollutants. Thus, liquid effluents containing toxic substances are generated by a variety of chemistry-related industrial processes, as well as by a number of common household or agricultural applications.

Synthesis and Characterization of Mesoporous Nb2O5 and Its Application for Photocatalytic Degradation of the Herbicide Methylviologen

This article reports the characterization of mesoporous Nb2O5 synthesized by the sol-gel method for application in photocatalysis. The emerging contaminant methylviologen was employed for photocatalytic tests. Parameters inherent to the synthesis process, such as stirring rate, aging temperature, and calcination temperature, were employed for a range of values to improve the synthetic route. The powders obtained were characterized by thermogravimetric analysis, X-ray diffraction, scanning and transmission electron microscopy, specific surface area, infrared spectroscopy, energy-dispersive spectroscopy, and diffuse reflectance spectroscopy. In samples calcined at 450 °C, a mixture of amorphous and hexagonal phases was observed, with a predominance of the former, while in samples calcined at 650 °C the orthorhombic phase predominated. Samples calcined at 450 °C exhibited larger specific surface areas. Mesoporous structures were confirmed for samples T8035M450 and T8045mi450, which displayed higher photoactivity, with roughly 90% removal of methylviologen.

H2O2-assisted photoelectrocatalytic degradation of Mitoxantrone using CuO nanostructured films: Identification of by-products and toxicity

CuO nanostructured thin films supported on silicon with 6.5 cm2 area (geometric area greater than the studies reported in the literature) were synthesized by a chemical bath deposition technique. The electrodes were characterized by MEV, XRD, XPS, contact angle, cyclic voltammetry and electrochemical impedance spectroscopy analyses. To evaluate the photoelectrochemical properties of the CuO films, photocurrent-voltage measurements were performed using linear voltammetry. The catalytic activities of CuO nanostructures were evaluated by monitoring photodegradation of Mitoxantrone (MTX) under UV-A light irradiation. The method of photoelectrocatalysis (PEC), applying a voltage of 1.5 V and assisted by adding H2O2, was undertaken. To the best of our knowledge, no studies on the degradation of anticancer agents using PEC process have been found in the literature. For comparison purposes, experiments were performed under the same conditions by assisted photocatalysis (PC) with H2O2 and direct photolysis. CuO deposits consist of a needle-like morphology. The presence of CuO in the tenorite phase was evidenced by XRD and the XPS spectra showed the presence of copper(II) oxide. The increase in current under illumination shows that CuO exhibits photoactivity. The PEC system showed a 75% level of MTX degradation, while the level achieved using PC was 50%. Under UV-A light alone only 3% removal was obtained after 180 min. Up to 10 by-products were identified by chromatography-mass spectrometry (LC-MS) with m/z values ranging between 521 and 285 and a plausible degradation route has been proposed. It is worth mentioning that 9 by-products identified in this work, were not found in the literature in other studies of degradation or products generated as metabolites. The toxicity tests of MTX before and after PEC treatment with Artemia Salina and Allium cepa showed a decrease in the acute toxicity of the medium as the antineoplastic was degraded.