Synthesis of Ni,N co-doped TiO<Subscript>2</Subscript> using microwave-assisted method for sodium lauryl sulfate degradation by photocatalyst

A titanium dioxide (TiO₂) photocatalyst was modified with nickel (Ni) and nitrogen (N) in titanium tetra-isopropoxide (TTIP) as a precursor through a microwave-assisted method. The Ni and N dopants led to a decrease in the TiO₂ band gap and made it able to function with visible light irradiation. The results of X-ray diffraction analysis demonstrated that the crystalline size of Ni–N–TiO₂ was 13.275 nm in anatase form with a specific peak in 2θ = 25.32°. Ni–N–TiO₂ was analyzed by scanning electron microscopy, which showed the smaller morphology and thin particles, and this was further supported by energy-dispersive X-ray data regarding the elemental composition of Ni and N being 4.50 and 2.39%, respectively. Fourier transform infrared spectroscopy results demonstrated the absorption spectrum in wavenumbers of 1197 and 1149 cm^?1, indicating an N–TiO₂ bond, a Ti–O bond at 648 cm^?1, and an Ni–O bond at 469 cm^?1. TiO₂ modified by Ni and N exhibited a decrease in the band gap at 1.95 eV, suggesting the Ni and N dopants successfully inserted onto the TiO₂ crystalline surface to be visualized with visible light. Photoactivity testing was carried out to degrade sodium lauryl sulfate surfactants under visible irradiation, where the degradation efficiency was 93.75%.     

Room Temperature Photocatalytic Oxidation of Carbon Monoxide Over Pd/TiO2–SiO2 Catalysts

The photocatalytic oxidation of carbon monoxide over TiO₂–SiO₂ and Pd/TiO₂–SiO₂ catalysts was studied. The catalyst samples were synthesized by using sol–gel technique coupled with hydrothermal treatment and all samples were hydrothermally treated before calcination in air. The catalyst samples were characterized by XRD, BET and DRIFTS techniques. The photocatalytic activity of the samples was determined by using circulated batch photoreactor coupled with in line gas transmission FTIR cell charged with 2,000 ppm carbon monoxide in air initially over 0.5 g of catalyst sample under 33 W (254 nm) irradiation power. XRD and BET results confirmed the presence of anatase phase and the decrease on the crystallite size of TiO₂ with SiO₂ addition which yield higher surface area and better dispersion of TiO₂ over mesoporous SiO₂. DRIFTS results indicated the presence of surface hydroxyls coordinated to Ti⁴⁺ and Si–O–Ti sites. All samples containing 10–90 % TiO₂ over SiO₂ exhibited significant photo oxidation activity at room temperature. The photocatalytic oxidation rate of carbon monoxide is favored by SiO₂ addition due to high surface area, better dispersion of TiO₂ particles and higher surface defects. The addition of PdO improves the photocatalytic activity significantly and the synergy between the TiO₂ and PdO phases.     

Large-scale preparation of nanoporous TiO2 film on titanium substrate with improved photoelectrochemical performance

Fabrication of three-dimensional TiO₂ films on Ti substrates is one important strategy to obtain efficient electrodes for energy conversion and environmental applications. In this work, we found that hierarchical porous TiO₂ film can be prepared by treating H₂O₂ pre-oxidized Ti substrate in TiCl₃ solution followed by calcinations. The formation process is a combination of the corrosion of Ti substrate and the oxidation hydrolysis of TiCl₃. According to the characterizations by scanning electron microscopy (SEM), X-ray diffraction (XRD), and diffuse reflectance spectroscopy (DRS), the anatase phase TiO₂ films show porous morphology with the smallest diameter of 20 nm and possess enhanced optical absorption properties. Using the porous film as a working electrode, we found that it displays efficient activity for photoelectrocatalytic decolorization of rhodamine B (RhB) and photocurrent generation, with a photocurrent density as high as 1.2 mA/cm². It represents a potential method to fabricate large-area nanoporous TiO₂ film on Ti substrate due to the scalability of such chemical oxidation process.     

Photoelectrocatalytic Reduction of CO<Subscript>2</Subscript> to Chemicals via ZnO@Nickel Foam: Controlling C–C Coupling by Ligand or Morphology

The CO₂ reduction is a very attracting research field in the environmental, material and chemical sciences in light of the energy crisis and greenhouse effect. A new photoelectrocatalytic system composed of a photoanode BiVO₄ and a photocathode of nickel foam supported ZnO semiconductor was designed, assembled and applied to CO₂ reduction in water. The photocathodes with different morphology could be made from electrochemical deposition method and well characterized by SEM, UV–Vis, XRD, and XPS. The photoelectrocatalytic cell of ZnO/Ni-30|KHCO₃|BiVO₄ can produce ethanol and acetic acid in a rate of 12.5 µM h^?1 cm^?2 with 100% selectivity for C₂ product, attributing to the controlling of 3D-spaces of nanorod. The cell of A-ZnO/Ni-15|KHCO₃|BiVO₄ produces ethanol and acetic acid with 75% selectivity for C₂ product under 100 mW cm^?2 simulated sunlight irradiation, attributing to controlling of both amine ligand and morphology of ZnO, which reveal a new way to increase the selectivity of products.     

Mesoporous TiO<Subscript>2</Subscript> microspheres synthesized via a facile hydrothermal method for dye sensitized solar cell applications

Mesoporous TiO₂ microspheres were successfully synthesized by a facile hydrothermal process and the obtained product was sintered at 450 °C. The sintered TiO₂ powder was characterised by powder X-ray diffraction pattern and the result shows pure anatase phase with good crystalline nature. The morphological image of field emission scanning electron microscopy and high resolution transmission electron microscopy shows spherical shape and size of the particles is around 100 to 300 nm. The Brunauer–Emmett–Teller surface area of synthesized TiO₂ material was 56.32 m² g^?1 and average pore width of synthesized materials was 7.1 and 9.3 nm. Bimodal pore structure of TiO₂ microspheres has been very effective for electrolyte diffusion into photoanode in dye sensitized solar cells. The synthesized anatase TiO₂ microsphere based dye sensitized solar cells have high surface area with light scattering effect to enhance the photocurrent and conversion efficiency than the commercial P25 photoanode material. The power conversion efficiency of synthesized mesoporous TiO₂ microspheres and commercial P25 material is 4.2 and 2.7 % respectively. Therefore bimodal mesoporous anatase TiO₂ microsphere appears to be a promising and potential candidate for dye sensitized solar cells (DSSC) application.     

Synthesis and electrochemical properties of TiO2/nanodiamond nanocomposite

Undoped nanodiamond (ND) powders were coated with TiO₂ through two steps: firstly Ti lay was deposited by cycled vacuum-feeding chemical vapour deposition from gaseous TiCl₄/H₂, and secondly an oxidation treatment was carried out in air. The structure and the morphology of the TiO₂/ND composite were characterized by Raman spectrum and transmission electron microscopy. The electrochemical properties of the TiO₂/ND powder electrode in a solution containing [Fe(CN)₆]^3?/4? or NO₂^? were investigated. The results showed that a continuous coating consisting of Ti nanoparticles covered on ND particle after the deposition. The following oxidation at 500 °C resulted in the formation of anatase phase TiO₂ nanoparticles of about 10 nm. The electrochemical results confirmed that the TiO₂/ND powder electrode exhibited higher electrochemical activity than the pristine ND electrode, especially higher catalytic ability toward the oxidation of nitrite anions. Moreover, the TiO₂/ND powder electrode presented fast response towards nitrite oxidation with a detection limit of 0.55 µM and a linear range of 0.05 to 1.0 mM.     

Lifetime of Carbon-Modified TiO2 Photocatalysts Under UV Light Irradiation

Carbon-modified photocatalyst was obtained by modification of the commercial anatase TiO₂ (Police, Poland) in a pressure reactor in an ethanol atmosphere at 120 °C for 4 h. The activity was tested during monoazo dye decomposition under UV light irradiation (Reactive Red 198 with λ_max = 516 nm). The reusability aspect of carbon-modified TiO₂ photocatalysts was predominantly studied. Using the additional aeration process caused to stabilization the “decolourisation time” of aqueous solution of Reactive Red 198. To compare the activity of obtained material the commercial TiO₂ P25 was used and only on its surface the presence of carbon deposits were observed.     

Photocatalytic H2 Production from Ethanol–Water Mixtures Over Pt/TiO2 and Au/TiO2 Photocatalysts: A Comparative Study

Pt/TiO₂ (Pt loadings 0–4 wt%) and Au/TiO₂ (Au loadings 0–4 wt%) photocatalysts were synthesized, characterized and tested for H₂ production from ethanol–water mixtures (80 vol% ethanol, 20 vol% H₂O) under UV excitation. Average metal nanoparticle sizes determined by TEM were 1–3 nm for Pt in the Pt/TiO₂ photocatalysts and 5–7 nm for Au in the Au/TiO₂ photocatalysts. Au/TiO₂ showed an intense localized surface plasmon resonance feature at ~570 nm, typical for metallic Au nanoparticles of diameter ~5 nm supported on TiO₂. X-ray photoelectron spectroscopy and X-ray diffraction analyses established that Pt and Au were present in metallic form on the TiO₂ support. X-ray fluorescence revealed close accord between nominal and actual Pt and Au loadings. The Au/TiO₂ and Pt/TiO₂ photocatalysts both displayed very high activities for H₂ production under UV irradiation, with the Au/TiO₂ samples affording slightly superior rates of H₂ production at most metal loadings. The 2 wt% Au/TiO₂ and 1 wt% Pt/TiO₂ photocatalysts showed the highest H₂ production rates (32–34 mmol g^?1 h^?1). Photoluminescence studies confirmed that Pt and Au nanoparticles positively enhance the photocatalytic properties of P25 TiO₂ for H₂ production by acting as electron acceptors and thereby suppressing electron–hole pair recombination in TiO₂.     

CO Oxidation over Anatase TiO2 Supported Au: Effect of Nitrogen Doping

Nitrogen doped yellowish anatase phase of titania support (TiO_2?x N _x ) was prepared by hydrolysis of titanium (IV) butoxide with 15% NH₄OH followed by filtration, drying and calcination at 450 °C for 3 h. For comparison, TiO₂ was prepared by hydrolysing titanium (IV) butylate with distilled water. Deposition precipitation method was used for Au loading on TiO_2?x N _x and TiO₂. These were characterised by XRD, Laser Raman spectroscopy, transmission electron microscopy, BET surface area analyser, and UV–visible spectrophotometry. UV–visible (diffused reflectance) spectrum of TiO_2?x N _x support shows a distinct absorption band around 450 nm wavelength indicating for N doping. Whereas, TiO₂ does not show any absorption band in the visible region. The activity of gold loaded on these supports was tested for CO oxidation reaction. Effect of different pre-treatment conditions and effect of moisture on these catalysts were studied, and the results obtained were interpreted on the basis of nitrogen doping, optoelectronic properties, ability of oxygen uptake of the support and particle size of gold.     

Photocatalytic enamel/TiO2 coatings developed by electrophoretic deposition for methyl orange decomposition

The aim of this study was to obtain photocatalytic coatings, capable to decompose organic pollutants, through Electrophoretic Deposition (EPD) of enamels containing respectively 0%, 5%, 10%, 15% (in wt%) of TiO₂ onto carbon steel substrates. High quality and homogeneous coatings were obtained by applying 12.5?V during 10?s, as the best EPD conditions. The layers were subsequently heat treated at 740?°C for 10?min, in order to obtain dense glazes.Rietveld refinement of XRD patterns and Raman results show that, after the heat treatment at 740?°C, TiO₂ mostly exists as anatase, responsible of the photocatalytic effect. Semi-quantitative chemical analysis indicate segregation of TiO₂ on the coatings surface, reaching saturation in the sample with 10?wt% TiO₂. FEG-SEM observations reveal rod-like and spherical Ti-rich phases along the cross section of the coatings; some Ti was also dissolved into the enamel. 3D topographical mapping shows that, by adding TiO₂, surface roughness increases significantly.Photocatalytic tests were carried out using a 2?×?10^?5 M aqueous solution of Methyl Orange (MO) as an organic pollutant. By comparing the decomposition rate of MO achieved with the pure enamel (0% of TiO₂) and with the sample with 10% of TiO₂, it was shown that the addition of 10% of TiO₂ results in 90% photocatalytic efficiency.Moreover, the permeation of organic compounds and their UV degradation were studied by measuring the water contact angle onto the enamel surface directly after dipping into oleic acid and after various UV irradiation times. The longer the UV irradiation time, the lower the contact angle, down to a minimum of 14.54° after 8?h of UV irradiation. This means, the compound was initially adsorbed on the enamel/TiO₂ coating surface (10?wt% TiO₂) but was efficiently decomposed upon UV irradiation.     

Synthesis and Characterization of Hierarchical Biomorphic Mesoporous TiO2 Nanosheets Using Caltrop-Stem as Biotemplate

Biomorphic TiO₂ nanosheets with hierarchical mesoporous structures were synthesized through facile infiltration and thermal decomposition using caltrop stems as biotemplates. Thermo-gravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscope, atomic force microscopy, N₂ adsorption–desorption equipment and UV–visible diffuse reflectance spectra were applied to characterize the microstructures of the samples. Results indicate that the as-synthesized TiO₂ nanosheets with thickness of about 5 nm are composed of anatase phase. The surfaces of TiO₂ nanosheets were constructed by a large number of mesopores, which pore diameter is in the range of 3.5–9 nm. Compared to TiO₂ powders (P25), the as-synthesized TiO₂ nanosheets exhibit a clear red shift (20 nm) showing an enhanced visible photocatalytic activity. The photocatalytic activity of the TiO₂ nanosheets for the decolorization of methylene blue under sunlight irradiation is superior to P25 powders.     

Preparation of TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> composite oxide and its photocatalytic degradation of rhodamine B

The composite semiconductor photocatalyst TiO₂/SiO₂ was prepared by template-hydrothermal method using carbon spheres as the template. The structural and optical properties of TiO₂/SiO₂ were characterized by XRD, SEM, BET, UV–Vis DRS, TG-DTA, PL techniques. The formation of hydroxyl radical on the surface of TiO₂/SiO₂ was studied with terephthalic acid as the probe molecule, combined with fluorescence technique. The results showed that the specific surface area of TiO₂/SiO₂ composite was 327.9 m²/g, and the specific surface area of TiO₂/SiO₂ was larger than that of pure TiO₂. Photocatalytic degradation of rhodamine B showed that TiO₂/SiO₂ composite oxide under visible light illumination 40 min, the degradation rate was 98.6 % and the degradation rate of pure TiO₂ was only 11.9 %. The apparent first-order rate constant of TiO₂/SiO₂ was 33 times that of pure TiO₂ and more than 6 times that of P25 when the molar ratio of Ti to Si was 1:1 under visible light irradiation. Moreover, it’s also as much as 5 times that of pure TiO₂ and is more than 1 times that of P25 under UV light irradiation 25 min. Based on the experimental results, ^·O₂ ^? and h⁺ were suggested to be the major active species which was responsible for the degradation reaction. The increased photocatalytic activity of TiO₂/SiO₂ may be mainly attributed to effectively suppressing the recombination of hole/electron pairs. After the photocatalyst TiO₂/SiO₂ was reused 5 times, the degradation rate of rhodamine B could reach 89.2 % under visible light irradiation. Moreover, The composite semiconductor photocatalyst TiO₂/SiO₂ was selective towards the degradation of rhodamine B.     

Photocatalytic functional coatings of TiO2 thin films on polymer substrate by plasma enhanced atomic layer deposition

We prepared photocatalytic TiO₂ thin films which exhibited relatively high growth rate and low impurity on polymer substrate by plasma enhanced atomic layer deposition (PE-ALD) from Ti(NMe₂)₄ [tetrakis (dimethylamido) Ti, TDMAT] and O₂ plasma to show the self-cleaning effect. The TiO₂ thin films with anatase phase and bandgap energy about 3.3 eV were deposited at growth temperature of 250 °C and the photocatalytic effects were compared with commercial Activ glass. From contact angles measurement of water droplet and photo-induced degradation test of organic liquid, TiO₂ thin films with anatase phases showed superhydrophilic phenomena and decomposed organic liquid after UV irradiation. The anatase TiO₂ thin film on polymer substrate showed highest photocatalytic efficiency after 5 h UV irradiation. We attribute the highest photocatalytic efficiency of TiO₂ thin film with anatase structure to the formation of suitable crystalline phase and large surface area.     

Surface characterization and photocatalytic reactivity of innovative Ti/TiO2 and Ti/Pt−TiO2 mesh photoelectrodes

Novel Ti/TiO₂ and Ti/Pt–TiO₂ mesh photoelectrodes were produced by anodizing titanium mesh in H₂SO₄ solution. Their structural and surface morphology were examined by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The analytical results indicated that the crystal structure, morphology and pore size were affected significantly by the voltage and current density applied in anodization and the percentage platinum content. The results of XPS measurement showed that the binding energy of O 1s and Ti 2p increased slightly owing to platinum deposition (Pt⁰, Pt²⁺ and Pt⁴⁺) onto the TiO₂ surface. The photoelectrocatalytic (PEC) oxidation of methyl orange in aqueous solution using the Ti/TiO₂ and Ti/Pt–TiO₂ meshes was investigated. The experimental results demonstrated that Ti/TiO₂ mesh prepared at 160 V and 110 mA cm^–2 achieved the best PEC oxidation. The efficiency of PEC oxidation could be further enhanced by applying an electrical bias between the working electrode and counter electrode. An optimal electrical bias voltage was found to be 0.6 V, while an optimal platinum content was 3.37%.     

One-pot synthesis of bifunctionalized TiO<Subscript>2</Subscript> mesoporous photocatalyst with visible light response

A series of Fe-doped SH/TiO₂ mesoporous photocatalysts have been firstly prepared by one-pot method using P123 as structure-directing agent. This bifunctionalized mesoporous TiO₂ possesses perfect anatase crystal structure and high surface area. The surface area of Fe-doped SH/TiO₂ mesoporous material is 4 times higher than that of P25. Based on the EPR results, it was found that trivalent Fe ions exist at low spin state and substitutes a part of Ti⁴⁺ ions into TiO₂ lattice. Fe-dropping in TiO₂ extends the adsorption band side of the resulting material to about 600 nm. Much high photocatalytic activity in the degradation of phenanthrene was obtained on the bifunctionalized mesoporous TiO₂ under visible light irradiation (λ > 420 nm), which is 6 times higher than that of pristine mesoporous TiO₂. The enhancement in the photocatalytic activity of bifunctionalized TiO₂ is ascribed to the extended absorption to visible light and strong interaction between SH-groups and PHE molecules.     

Chemical Synthesis and Characterization of ZnO–TiO<Subscript>2</Subscript> Semiconductor Nanocomposites: Tentative Mechanism of Particle Formation

The compounds of ZnO–TiO₂ can combine the characteristics of the individual oxides which has allowed them to be used as photocatalysts in general, photodegradants in the degradation of dyes, photocatalytic oxidation of NO_x, antimicrobial, among other applications. In this study, ZnO–TiO₂ semiconductor nanocomposites were synthesized in a controlled way at low temperature. These samples of ZnO–TiO₂ were characterized using thermal analysis (TDA/TGA), IR and UV–Vis absorption spectroscopies, X-ray diffraction, and scanning electron microscopy. The primary particles showed a nanometric size (<?100 nm) and spheroidal morphology. All samples presented zincite as the main crystalline phase. When Ti⁴⁺ was added, the peaks of the diffractograms shifted slightly with respect to pure ZnO. This indicates the formation of a solid solution. Zn₂TiO₄ was observed in doped ZnO samples treated at 700 °C. The UV–Vis absorption spectra showed a band in the range between 350 and 425 nm, with a maximum around 375 nm (3.31 eV). With the addition of Ti⁴⁺, the nanocomposites showed a better absorbance in the visible range. Considering the nature of the synthesis process used, a mechanism was proposed to explanation of the formation of Nanocomposites.     

Improved Photocatalytic Degradation of Phenolic Compounds With ZnAl Mixed Oxides Obtained from LDH Materials

ZnAl layered double hydroxides (LDHs) with different M_II/M_III molar ratio (0.89–3.81) were synthesized by the co-precipitation method and calcinated at 723 K. High specific surface areas (228–155 m²/g) and semiconductor properties (band gap values from 3.32 to 3.07 eV) were obtained. The mixed oxides were reconstructed to the crystalline LDHs (memory effect) after being put in contact with aqueous solutions containing phenol and p-cresol. Using UV light, a maximum in photoactivity as a function of the Zn²⁺/Al³⁺ molar ratio was observed. The sample with a Zn²⁺/Al³⁺molar ratio of 1.48 photodegrades up to 95% of phenol and p-cresol after 4 and 6 h of irradiation, respectively. These values are lower than that obtained with ZnO and commercial P-25 TiO₂ photocatalysts. The results show the applicability of alternative photocatalysts for the degradation of organic pollutant compounds rather than others such as TiO₂.     

Hydrogen Production from Aqueous Solutions of Glycerol on TiO<Subscript>2</Subscript>/Ru-MCM-41 Photocatalysts Using Solar Light

Ru-MCM-41 molecular sieves were prepared (Si/Ru atomic ratio?=?50 or 100) by a hydrothermal method and impregnated with TiO₂. The materials were characterized by XRD, N₂ physisorption, DRS, SEM and TEM. Their potential application to hydrogen production by photolysis of water using solar light was tested in a batch reactor using mixtures of water and glycerol (0–6.85 mol L^?1) at pH varying from 1 to 11. The photocatalytic efficiency under simultaneous UV (0.05 μW cm^?2) and visible light (90.07 W m^?2) irradiation was compared to the activity of TiO₂/MCM-41 (i.e., no Ru incorporated) and commercial Degussa TiO₂ P25. The most active material was 20%TiO₂/Ru-MCM-41(100) whose performance (220.6 µmol g_Ti ^?1 H₂) was approximately 47 times higher than TiO₂ P25. Characterization results showed the deposition of TiO₂ and revealed the formation of RuO₂ on the surface. Hydrogen generation was improved due to higher charge separation at the TiO₂/RuO₂ heterojunction and to the enhancement of visible light absorption caused by surface plasmon resonance (SPR). Hydrogen production increased with glycerol concentration, tending to stabilize around 40.3 µmol h^?1 g_Ti ^?1 above 4 mol L^?1 of glycerol. Hydrogen generation reached its maximum at extreme values of pH (1 and 11).     

Photoelectrocatalytic inactivation of E. coli XL‐1 blue colonies in water

BACKGROUND: The aim of the present work was the preparation of TiO₂ P‐25 working electrodes on Ti substrates (TiO₂/Ti), their characterization and the study of their photoelectrocatalytic activity towards the inactivation of E. coli XL‐1blue (E. Coli) colonies, used as model pathogenic bacteria, in a novel batch photoelectrochemical reactor. RESULTS: After annealing of the TiO₂/Ti specimens at 500 °C, the surface morphology and crystal structure of the TiO₂ film electrodes were examined by scanning electronic microscopy (SEM) and X‐ray diffraction (XRD), while from differential capacitance measurements the flat band potential was calculated (V_fb = ? 0.54 V versus Ag/AgCl). The results of photoelectrocatalytic (PEC) experiments concerning the disinfection of E. coli colonies were compared with those of electrochemical (EC) and photocatalytic (PC) inactivation of the pathogen and showed a significant synergy effect in the case of PEC disinfection, leading, at + 1.0 V vs Ag/AgCl cell voltage, to a 100% increase of the apparent rate constant, k_o, in comparison with the simple photocatalytic process. Reuse experiments showed that the working electrode retains its effectiveness after, at least, 15 times of reuse. CONCLUSIONS: The photoelectrocatalytic inactivation of E. coli colonies has been studied under artificial illumination in a novel photoelectrocatalytic reactor. The inactivation of 10³ CFU mL^?1 E. coli colonies followed first‐order kinetics, while parameters such as type of semiconductor and concentration of the microorganisms play an important role affecting the reaction rate constant. Copyright © 2010 Society of Chemical Industry     

Comparison of oxidation efficiency of disperse dyes by chemical and photoelectrocatalytic chlorination and removal of mutagenic activity

Degradation of Disperse Orange 1, Disperse Red 1 and Disperse Red 13 dyes has been performed using electrochemical oxidation on Pt electrode, chemical chlorination and photoelectrochemical oxidation on Ti/TiO₂ thin film electrodes in NaCl or Na₂SO₄ medium. 100% discoloration was obtained for all tested methods after 1 h of treatment. Faster color removal was obtained by photoelectrocatalytic oxidation in 0.1 mol L⁻¹ NaCl pH 4.0 under UV light and an applied potential of +1.0 V (vs SCE reference electrode), which indicates also values around 60% of TOC removal. The conventional chlorination method and electrochemical oxidation on Pt electrode resulted in negligible reduction of TOC removal. All dyes showed positive mutagenic activity in the Salmonella/microsome assay with the strain TA98 in the absence and presence of S9 (exogenous metabolic activation). Nevertheless, there is complete reduction of the mutagenic activity after 1 h of photoelectrocatalytic oxidation, suggesting that this process would be good option to remove disperse azo dyes from aqueous media.