Analytical Methods in Photoelectrochemical Treatment of Phenol

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Photocatalytic and photoelectrochemical treatment effects on the killing of escherichia coli cells

In this study, we report the efficiency of photocatalytic and photoelectrochemical treatment using titanium dioxide as semiconductor and its applications in water disinfection. It was compared the efficiency of the two methods on the killing of E.coli cells. The photoelectrochemical treatment with electric field enhancement showed a good result and could be a new technology to water treatment.

Photocatalytic and photoelectrochemical inactivation of Escherichia coli and Staphylococcus aureus

Water disinfection usually requires expensive chemicals or equipment. Chlorination is a common disinfection method, although it is not able to inactivate all pathogens. High concentrations of residual chlorine also cause an unpleasant taste and smell in drinking water. As an alternative, photocatalysis and photoelectrochemical treatment has a high disinfection potential in drinking water by using solid catalysts, such as titanium dioxide. Highly reactive hydroxyl radical generated during the process serves as the main oxidant, capable of inactivating a wide range of microorganisms. In this study, we proposed a novel comparison between Gram-positive and gram-negative microorganisms. An immobilized TiO2 film promoted higher efficiency in water disinfection processes. The treatment effectively inactivated Escherichia coli and Staphylococcus aureus bacterial microorganisms in a shorter period than other alternative methods.

Avaliação de processos de degradação de corantes dispersos por técnicas eletroquímica e fotoeletroquímica usando eletrodos de Pt, filmes finos e nanotubos de 'TI'/'TIO IND. 2' e bicomponentes 'W'/'WO IND. 3'/'TIO IND. 2'

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Photoelectrochemical oxidation of p-nitrophenol on an expanded graphite-TiO2 electrode

In the quest for more efficient photoanodes in the photoelectrochemical oxidation processes for organic pollutant degradation and mineralisation in water treatment, we present the synthesis, characterisation and photoelectrochemical application of expanded graphite-TiO2 composite (EG-TiO2) prepared using the sol-gel method with organically modified silicate. The Brunauer-Emmett-Teller surface area analyser, ultraviolet-visible diffuse reflectance, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, Raman spectrometry and X-ray photoelectron spectroscopy were employed for the characterisation of the composites. The applicability of the EG-TiO2 as photoanode material was investigated by the photoelectrochemical degradation of p-nitrophenol as a target pollutant in a 0.1 M Na2SO4 (pH 7) solution at a current density of 5 mA cm(-2). After optimising the TiO2 loading, initial p-nitrophenol concentration, pH and current density, a removal efficiency of 62% with an apparent kinetic rate constant of 10.4 x 10(-3) min(-1) was obtained for the photoelectrochemical process as compared to electrochemical oxidation and photolysis, where removal efficiencies of 6% and 24% were obtained respectively after 90 min. Furthermore, the EG-TiO2 electrode was able to withstand high current density due to its high stability. The EG-TiO2 electrode was also used to degrade 0.3 x 10(-4) M methylene blue and 0.1 x 10(-4) M Eosin Yellowish, leading to 94% and 47% removal efficiency within 120 reaction time. This confirms the suitability of the EG-TiO2 electrode to degrade other organic pollutants.

Photoelectrochemical degradation of eosin yellowish dye on exfoliated graphite-ZnO nanocomposite electrode

In the quest for harnessing more power from the sun for water treatment by photoelectrochemical degradation, we prepared a novel photoanode of exfoliated graphite (EG)-ZnO nanocomposite. The nanocomposite was characterised by X-ray diffractometry, energy dispersive spectroscopy, Brunauer-Emmett-Teller surface area analyser, thermal gravimetric analyser, and X-ray photoelectron spectroscopy. The EG-ZnO nanocomposite was fabricated into a photoanode and applied for the photoelectrochemical degradation of 0.1 x 10(-4) M eosin yellowish dye in 0.1 M Na2SO4 under visible light irradiation. The degradation was monitored with a visible spectrophotometer. The photoelectrochemical degradation process resulted in enhanced degradation efficiency of ca. 93 % with kinetic rate of 11.0 x 10(-3) min(-1) over photolysis and electrochemical oxidation processes which exhibited lower degradation efficiencies of 35 and 40 % respectively.

Photoelectrocatalytic treatment of p-nitrophenol using Ti/TiO2 thin-film electrode

The photoelectrochemical degradation of p-nitrophenol (PNP) was investigated using titanium dioxide thin-film photoelectrode. The effects of different supporting electrolytes, pH, applied potential and PNP concentration were examined and discussed. Complete photodegradation was obtained in perchlorate medium at pH 2 when the photoanode was biased at +1.0 V (versus SCE) during a 3-h experiment. Under these conditions, carbon removal of approximately 60% was achieved. (C) 2005 Elsevier B.V. All rights reserved.

Efficient Photoelectrochemical Reduction of Nitrite to Ammonium and Nitrogen Containing Gaseous Species Using Ti/TiO2 Nanotube Electrodes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Photoelectrochemical Hydrogen Generation and Concomitant Organic Dye Oxidation under TiO2 Nanotube

The present work describes the photoelectrochemical hydrogen generation during a photodegradation of an organic compound. For this, it was chosen the reactive black 5 dye as a model of organic pollutant and its oxidation under TiO2 nanotube in a two compartment cell. The photoelectrocatalysis is conducted in 0.1 mol L-1 Na2SO4 pH 6 medium under photoanode biased at +1.0 V (SCE) and activated by UV and visible light using 150W Xe-Arc lamp (Oriel) and 125 W Hg lamp (Osram). The concomitant hydrogen production was monitored at cathodic compartment using a Pt cathode. Using optimized condition of Na2SO4 0.1 mol L-1 pH 6 as supporting electrolyte, applied potential of +1.0V it was verified 100% of discoloration and 72% of TOC removal of 1.0 x 10(-5) mol L-1 Reactive Black 5 dye after 120 min of treatment (rate constant of 10.6 x10(-2) min(-1)). The concomitant hydrogen generation was 44% in this condition.

Unexpected toxicity decrease during photoelectrochemical degradation of atrazine with NaCl

This report shows an unexpected toxicity decrease during atrazine photoelectrodegradation in the presence of NaCl. Atrazine is a pesticide classified as endocrine disruptor occurring in industrial effluents and agricultural wastewaters. We therefore studied the effects of the degradation method, electrochemical and electrochemical photo-assisted, and of the supporting electrolyte, NaCl and Na2SO4, on the residual toxicity of treated atrazine solutions. We also studied the toxicity of treated atrazine solutions using Results show that at initial concentration of 20 mg L-1, atrazine was completely removed in up to 30 min using 10 mA cm(-2) electrolysis in NaCl medium, regardless of the electrochemical method used. The total organic carbon removal by the photo-assisted method was 82% with NaCl and 95% with Na2SO4. The solution toxicity increased during sole electrochemical treatment in NaCl, as expected. However, the toxicity unexpectedly decreased using the photo-assisted method. This finding is a major discovery because electrochemical treatment with NaCl usually leads to the formation of toxic chlorine-containing organic degradation by-products.

Structural and photoelectrochemical properties of porous TiO2 nanofibers decorated with Fe2O3 by sol-flame

The hybrid structure of Fe2O3 nanoparticles/TiO2 nanofibers (NFs), combines the merits of large surface areas of TiO2 NFs and absorption in ultraviolet light–visible light range. This structure can be used for many applications such as photoelectrochemical water splitting and photo-catalysis. Here, a sol-flame method is used for depositing Fe2O3 on TiO2 NFs that were prepared by hydrothermal on Ti sheets. The obtained materials were characterized by XRD, SEM, UV/Vis diffuse reflectance, Raman, and XPS. The results revealed the formation of rutile and anatase crystalline phases together with Fe2O3. This process moves the absorption threshold of TiO2 NFs support into visible spectrum range and enhances the photocurrent in comparison to bare TiO2 NFs, although no hole scavenger was used. The impedance measurement at low and high frequencies revealed an increase in series resistance and a decrease in resistance of charge transfer with sol-flame treatment time. A mechanism for explaining the charge transfer in these TiO2 NFs decorated with Fe2O3 nanoparticles was proposed.