PHOTOCATALYTIC EFFICIENCY OF TiO2 IN BIOTEMPLATES FORM IN THE DECOLORATION OF ORGANIC DYE AND INHIBITION OF E. COLI GROWTH

Anatase TiO2 is widely used for pollutant degradation due to its photocatalytic property. Exposure of the surface to UV radiation (sunlight or artificial) generates an electron-hole pair that is responsible for the formation of free radicals such as O2•−in the presence of atmospheric oxygen and HO• in the presence of water. Biomorphic TiO2 plates were produced by infiltration of paper with titanium isopropoxide (TTiP) solution followed by hydrolysis in NH4OH and calcination at temperatures up to 600-1000 ºC, as a new way of fixing TiO2 with the aim of delaying the phase transition from anatase (photoactive) to rutile (inactive). In order to study the effect of addition of zirconia as a dopant on the microstructure and the phase transition from anatase to rutile, the same procedure was used, but with the addition of 5% (m/m) of ZrO(NO3)2 to TTiP. The biomorphic materials were characterized by XRD, specific surface area measurement (using the BET method), EPR, and SEM. Their photocatalytic efficiencies were evaluated in the decoloration of Orange II dye and the inhibition of growth of E. coli bioluminescent bacteria. Using 5% Zr-doped TTiP, with calcination at 800 ºC, bacterial growth was reduced by 23% after 180 minutes, and 70% dye decoloration was achieved in30 hours

Obtenção de placas fotocatalíticas de TiO2 a partir de estruturas biomórficas

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, Florianópolis, 2015.Nesta tese de doutorado foram desenvolvidas e caracterizadas placas finas e planas de dióxido de titânio (TiO2) a partir da infiltração de soluções precursoras de titânio em matriz orgânica (papel), seguido de hidrólise em hidróxido de amônio, como uma alternativa tridimensional para a fixação do TiO2. O grande interesse de obter placas finas deve-se à maior relação superfície/volume, com grande área superficial ativa. A ação fotocatalítica é especialmente favorecida por TiO2 na faixa nanométrica e pela fase anatase majoritária, que é a fase ativada sob radiação ultravioleta (UV-A). Além disso, as placas foram produzidas por infiltração direta, evitando a geração de subprodutos de síntese. A adição de cargas através da incorporação de íons dopantes (Ba2+ e La3+) nas soluções precursoras introduz cargas na rede cristalina, e a incorporação de íons Zr4+ pode causar tração na rede por agir como um íon substitucional de raio atômico levemente maior que o do Ti4+. Foram também avaliados os efeitos das adições dos íons Ba2+, La3+ e Zr4+ na transição de fase anatase para rutilo. Foi avaliado o efeito da matriz orgânica e das diferentes temperaturas de infiltração e calcinação no processo de transição de fase, conteúdo de fase e da incorporação de dopantes através de caracterizações por microscopia eletrônica de varredura, difratometria de raios-X e por área superficial específica. Foram ainda determinados o tamanho dos cristalitos pela equação de Scherrer e as energias do bandgap pela análise dos espectros na região do UV-Vis. Os parâmetros de rede das amostras refinadas pelo Método de Rietveld, foram determinados pelo programa JANA2000. Os radicais gerados nos ensaios de fotoatividade foram caracterizados por espectroscopia de ressonância paramagnética eletrônica. Já os subprodutos da descoloração do corante laranja II foram avaliados por cromatografia líquida. A matriz orgânica fornece a microestrutura para a geração de placas de TiO2, e essa microestrutura aumenta a temperatura de transição de fase anatase para rutilo. A fase anatase esteve majoritária até 800 ºC e presente acima de 1000 ºC. A eficiência fotocatalítica foi eficaz para todos os testes realizados (meio aquoso, gasoso e biológico), e melhor quando comparada ao pó comercial P25 usado como padrão.Abstract : In this PhD thesis, were developed and characterized flat thin-plates of titanium dioxide (TiO2) infiltration from the titanium precursor solution in the organic matrix (paper), followed by hydrolysis in ammonium hydroxide as a tridimensional alternative to the fixing of TiO2. The great interest to obtain thin plates is due to the higher surface/volume ratio, with large active surface area. The photocatalytic action is especially favored by TiO2 in the nanometer range and the majority anatase phase which is the active layer under ultraviolet radiation (UV-A). Furthermore, the TiO2 plates were produced by direct infiltration, avoiding the generation of synthesis products. Charge addition by the addition of dopants ions (Ba2+ and La3+) in the precursor solutions introduces loads in the crystal lattice, and addition of Zr4+ ions can cause strain on the lattice to act as an atomic radius of substitutional ion slightly larger than Ti4+ ion. Were also evaluated the addition effects of Ba2+, La3+ and Zr4+ ions on TiO2-anatase-rutile phase transition. The effect of the organic matrix and the different temperatures of infiltration and calcination on the phase transition, phase content and the addition of dopants were investigated, by Scanning Electron Microscopy characterization, X-ray diffraction and Specific Surface Area. We also determined the size of the crystallites by Scherrer equation and the bandgap energy by UV-Vis analysis. The lattice parameters of samples refined by the Rietveld method were determined by JANA2000 program. The radicals generated in photoactivity tests were characterized by Electron Paramagnetic Resonance Spectroscopy. Since the Orange II dye discoloration by-products were evaluated by Liquid Chromatography. The organic matrix microstructure provides for the generation of TiO2 plates, and this increases the microstructure phase transition temperature of anatase to rutile. The anatase phase was majority up to 800 ºC and this above 1000 ºC. The photocatalytic efficiency was effective in all tests (aqueous, gaseous and biological), and much better when compared to commercial powder P25 used as standard

Investigation of the reaction pathway for degradation of emerging contaminant in water by photo-Fenton oxidation using fly ash as low-cost raw catalyst

In this work, fly ash from a Brazilian thermal power plant was employed as a low-cost raw catalyst for Procion red degradation by photo-Fenton process. The ash was characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms (BET), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDX). The material had an iron content of 4.10 wt%, distributed homogeneously on the solid surface. The ash particles showed mainly spherical morphology between 0.5 and 20 µm. The catalyst presented promising activity, reaching 93% of dye decolorization at 60 min of reaction, and 85% of organic load removal at 240 min. The predominant oxidizing species involved on the degradation of dye molecules during the photo-Fenton reaction were the hydroxyl radicals (HO·). The material showed remarkable stability and reusability after five successive cycles of reuse. The reaction intermediates were identified by LC/MS analysis and a reaction pathway was proposed

Improved catalytic activity of EDTA–modified BiFeO3 powders for remarkable degradation of procion red by heterogeneous photo–Fenton process

For the first time, heterogeneous photo–Fenton degradation of Procion Red dye under visible irradiation was investigated using ferrite bismuth (BiFeO3) catalysts synthesized by hydrothermal method with and without EDTA. The results and analysis revealed that the presence of EDTA affected the crystallinity degree and morphology of BiFeO3 particles, but almost not changed their specific surface area and band–gap energy values. The BiFeO3 catalyst prepared with EDTA exhibited superior catalytic activity, reaching 99% of degradation in 120 min, when compared to the BiFeO3 prepared without EDTA, which obtained 70% degradation under the same conditions. This result may be associated with the synergistic enhancement effects between the morphology and the degree of crystallinity of the particles. In addition, the EDTA–modified catalyst showed high reusability and stability even after five cycles. Radical scavenger experiments were developed to determine that •OH and •O2− were the main active species involved on the dye degradation. A possible simplified mechanism for the photo–Fenton reaction was also proposed coupled with the identification of reaction intermediates

Influência da adição de cério em pigmento nanométrico à base de TiO2 - MoO3

Pigmentos são pós ou partículas, de origem inorgânica ou orgânica, que devido às propriedades óticas são empregadas, principalmente, para dar cor. É comum as propriedades químicas conferirem aos pigmentos eficiência protetora à corrosão. Este trabalho consiste em estudar um sistema óxido composto de TiO2 e MoO3, na forma de pigmento nanoestruturado e o efeito da adição de Ce2O3. A caracterização colorimétrica dos pós foi feita através da técnica de espectroscopia UV-visível para análise de absorção da luz dentro de uma faixa espectral definida e a determinação das coordenadas colorimétricas do método CIELab. O material foi caracterizado através da técnica de microscopia eletrônica de varredura, difração a laser e difração de raios X. O resultado do sistema estudado foi um pigmento inorgânico com coloração amarela intensa que apresenta propriedades favoráveis para a aplicação em peças cerâmicas e na indústria em geral, até uma temperatura de 1200C.Pigments are powders or particles of organic or inorganic origin, and due to their optical properties are mainly used to color. The chemical properties of the pigments often confer efficient protection against corrosion. The aim of this work is to study a system composed of MoO3 and TiO2 oxides in the form of a nanostructured pigment and the effect of Ce2O3 additions. The colorimetric characterization of the powders was done using UV-visible spectroscopy technique for the analysis of light absorption within a defined spectral range and the determination of colorimetric coordinates of the CIELAB method. The material was characterized using scanning electron microscopy, laser diffraction, and X-ray diffraction. The result of the system studied was an inorganic pigment with an intense yellow color with favorable properties for application in ceramic industry in general, and to a temperature of 1200C

Synthesis of biomorphic paper-derived anatase

Biomorphic anatase-based plates were obtained using paper as template for fixing TiO2. Ceramics with a microstructure similar to paper were produced by infiltration in TiCl4 and hydrolysis in NH4OH at temperatures between -25 and 25 degrees C, followed by air drying and calcination up to 1000 degrees C. After thermal treatment, the samples were characterized by XRD, TG/DTA, BET, SEM and EDX. Plates manufactured by infiltration in TiCl4 and hydrolysis in NH4OH at 0 degrees C presented anatase as major phase, whose amount decreases with increasing calcination temperature. The results showed that by decreasing the infiltration and hydrolysis temperature, the surface area decreased, crystallite size increased and the anatase-to-rutile transformation was inhibited. (C) 2014 Elsevier B.V. All rights reserved

Biological degradation coupled to photocatalysis by ZnO/polypyrrole composite for the treatment of real textile wastewater

The novelty of this work lies in the use of a real textile wastewater (RTW), without a pretreatment, without additional carbon sources and undiluted, with coupling a photocatalysis by using an unprecedented composite for this application. The collected RTW containing the azo dye Direct Black 22 (205.15 mg L−1 TOC: 672.7 mg L−1), was treated with a bacterial consortium and after 96 h the sequential photocatalysis process was employed using ZnO/Polypyrrole during 60 min. The coupling of both treatment processes resulted in a total decolorization efficiency of 95.7 % and 99.8 % of TOC degradation (8.76 mg L−1 TOC: 1.33 mg L−1). Degradation product analysis was carried out by LC–MS/MS and a degradation pathway is proposed. The textile wastewater treatment proposed in this work is an attractive alternative and it is highly recommended to apply this system before the disposal of textile effluents in water bodies.Fil: Ceretta, Maria Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Ingeniería Química. Grupo de Ingeniería Bioquímica; ArgentinaFil: Vieira, Yasmin. Universidade Federal de Santa Maria; BrasilFil: Wolski, Erika Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Ingeniería Química. Grupo de Ingeniería Bioquímica; ArgentinaFil: Foletto, Edson L.. Universidade Federal de Santa Maria; BrasilFil: Silvestri, Siara. Universidade Federal de Santa Maria; Brasi

Polypyrrole-TiO2 composite for removal of 4-chlorophenol and diclofenac

In this work, we successfully synthesized TiO2-polypyrrole (PPy) composite material via polymerization method using the sulfuric acid (H2SO4) as an oxidizing agent. Different characterization techniques, including electrostatic force microscopy, confirmed that TiO2 was intimately attached on PPy. The photocatalytic activity of PPyTiO2 composite was studied experimentally for the conversion of diclofenac (DCF)– one of the most frequently detected pharmaceutical compounds in the aquatic environment – and 4-chlorophenol (4-CP) - largely used in the bleaching of cellulose pulp in the paper industry, as herbicide and pesticide - under simulated solar light irradiation at environmental conditions. This is the first time that a composite PPy-TiO2 was used as photocatalyst for the conversion of 4-CP. Results showed that the PPy-TiO2 was able to convert more than 90% of DCF and 40% of 4-CP in just 60 min, showing stability and efficiency over five consecutive cycles of reuse for both pollutants. The produced PPy-TiO2 showed higher photocatalytic efficiency compared to that of TiO2, thus proving itself to be a promising photocatalyst.info:eu-repo/semantics/publishedVersio

Application of a novel rGO-CuFeS2 composite catalyst conjugated to microwave irradiation for ultra-fast real textile wastewater treatment

The disposal of wastewater containing large amounts of dyes is a public health and environmental problem, due to its toxicity into the aquatic biota, the reduction in sunlight penetration, which consequently interference in photosynthetic activity. In the present study a new composite, based on the heterojunction of reduced graphene oxide (rGO) and chalcopyrite (CuFeS2), was developed to treat a real textile wastewater (RW). The efficiency of the composite assisted by microwave irradiation was evaluated to catalyze the decolorization and degradation of RW containing a high concentration of the azo Direct Black 22 (DB22). A small amount (0.5 w/w%) of rGO on CuFeS2 was enough to uplift the efficiency of decolorization to 74 % of DB22 and 97 % TOC in the RW, only in the first min of treatment, and 97 % and 99 %, respectively, at 6 min. The improvement in catalytic activity can be attributed to the dipolar polarization effect, hot spots and the generation of hydroxyl radicals. Additionally, a synergistic effect between the composite and microwave irradiation, assisted by hydrogen peroxide, reduced the RW phytotoxicity, improving the radicle length of Lactuca sativa three times (from 0.87 cm to 2.65 cm with the application of a single minute of treatment). The reduction in phytotoxicity led to an increase in the germination percentage from 36 % to 53 %. Finally, the use of MW irradiation coupled to a novel rGO-CuFeS2 composite, in presence of H2O2 under acid medium, provides a feasible and highly rapid method to treat RW, reducing its phytotoxicity. Capsule: A novel rGO-CuFeS2 catalyst was developed and applied together with microwave irradiation for an ultra-fast degradation treatment (6 min) in real textile wastewater.Fil: Vieira, Yasmin. Universidade Federal de Santa Maria; BrasilFil: Ceretta, Maria Belen. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Ingeniería Química. Grupo de Ingeniería Bioquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Foletto, Edson Luiz. Universidade Federal de Santa Maria; BrasilFil: Wolski, Erika Alejandra. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Ingeniería Química. Grupo de Ingeniería Bioquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Silvestri, Siara. Universidade Federal de Santa Maria; Brasi

Synthesis of PPy-ZnO composite used as photocatalyst for the degradation of diclofenac under simulated solar irradiation

info:eu-repo/semantics/publishedVersio