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Photodegradation of 4-chlorophenol using ZnO/SnO2/carbon xerogel composite as catalyst

Grant number: 19/03641-3
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): May 01, 2019
Status:Discontinued
Field of knowledge:Engineering - Materials and Metallurgical Engineering
Principal Investigator:Liana Alvares Rodrigues
Grantee:Clarice Moreira Goes
Home Institution: Escola de Engenharia de Lorena (EEL). Universidade de São Paulo (USP). Lorena , SP, Brazil
Associated scholarship(s):19/25257-0 - Polysaccharide beads as catalyst support material, BE.EP.IC

Abstract

The main objective of this project is to explore the development of new hybrid photocatalysts by utilizing a ternary material (which is formed by two semiconductors and a carbonaceous matrix made of carbon xerogel), with the aim to increase the quantum efficiency of the photodegradation process. The study will be focused at the degradation of persistent organic pollutants (POPs), with the utilization of 4-chlorophenol as reference for the degradation tests. The photocatalysis applied to the degradation of POPs has been oftenly studied due to its capacity of degradation from toxic to nontoxic compounds. ZnO and SnO2 were the chosen semiconductors, what configurates an important technological innovation, due to the fact that this combination and the catalytic effect provided by it has never been studied on the literature. The ZnO was chosen due to properties such as the ability of absorption at a large range of the solar spectrum, the efficient generation of H2O2 and because it has a more reactive surface, with a large number of reaction sites. However, this compound presents some disadvantages, being its photocorrosion and low absorption under visible light, what results in a faster recombination and, consequently, a decrease in the efficiency of the photocatalysis. Thereby, a good way to deal with this problem is to use the coupling between two conductors by means of type II heterojunctions or the Z-scheme, which are able to promote the transference of photogenerated charges from a semiconductor to another and, consequently, are responsible for the improvement of the efficiency in their separation, what results in the increase of photocatalytic efficiency. The SnO2 was chosen because, in this form of heterojunction, it is necessary for the conduction and the valence bands to be different. On the other hand, the heterojunction alone cannot achieve the desired degradation rate on the visible region, so, carbon xerogel (that came from tanino) will be added to the semiconductors, due to the fact that this is the most environmental friendly option and the cheaper choice. The carbon xerogel has great electrical conductivity, large surface area and porosity, which can be easily manipulated. Diffuse reflectance spectroscopy will be used for the purpose of determining the gap energy and the quantity of pollutant adsorbed by the samples. The morphology, the elemental analysis and the crystalline structure of the materials will be obtained by using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD), respectively. In conclusion, the photocatalytic action of the material will be evaluated by the 4-chlorophenol decomposition in a batch reactor.