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In this study, we propose the development of a rapid and reliable method to control and to monitor microbial water quality. The methylene blue (MB) decolorization assay was based on the analysis of spectral profiles of dye in interaction with a different bacterial concentration. The determination of dye decolorization rate (DDR) shows a correlation between the MB reduction rate and the bacterial density. Moreover, the kinetic of the monomer and dimer equilibrium of MB in water mainly, the monitoring of bounded MB species in relationship with a knowed concentration of target bacteria, was allowed to establish a relationship between MB decolorization rate and bacterial density. Furthermore, this method was applied to evaluate the water quality after photocatalysis. Based on this method, the photocatalytic effects on bacterial density was highlighted by the decrease in DDR after photocatalytic treatment with fractioned times (0 to 5 h); this increase was followed by a decrease of bounded MB species and, an increase in free MB forms miming the reduction of bacterial density due to the biocide effects of photocatalysis process. However, the analysis of spectra profiles shows a weak but a continuous decrease in bounded MB dimer and monomer forms in the treated water samples exempt of culturable bacteria. Moreover, the MB spectra profiles were tended toward a negative control spectrum without superposition. Thus, the possibility of the presence of viable but non-culturable bacteria was expected; therefore, to optimize this tertiary water treatment process, an extending on proceeding time was recommended to avoid the bacterial resuscitation after photocatalysis.

The bacterial cells dwelling within the biofilm usually develop resistance against common disinfectants. In this current study, to improve the effectiveness of photocatalytic treatment, a natural sensitizer in combination with unsupported titanium dioxide nanoparticles (TiO2-NPs) was used to optimize the absorbance of NPs in the visible region and, to enhance the catalytic activity of the semiconductor. Different kinetic parameters were determined according to the first-order and the biphasic models to evaluate the ability of tested bacteria to form biofilm under different photocatalytic treatment conditions. As a result, the addition of red cabbage anthocyanins (RCA) as photosensitizer allows the enhancement of biocide activity of TiO2-NPs and the reduction of biofilm formation by tested bacteria.

We purpose in this study to develop a reliable and low-cost method for the detection of Viable but nonculturable (VBNC) bacteria. Indeed, after water disinfection, injured-VBNC bacteria can be underestimated using conventional assessment methods, causing false-negative results and, posing a significant and potential health risk. The VBNC bacterial survival strategy can hide the real microbial quality of treated water. To overcome this bacterial assessment limitation, we were used a specific and lytic phage to monitor the presence of active bacteria

International audience; Nowadays water scarcity represents a threat for human and living beings. Therefore, to satisfy the demands of people for clean and safe water, new technologies for wastewater treatment have been developed. Thus, photocatalysis has emerged as a green chemical approach for such treatment. In this context, new polyoxometalate (POM)/polymer composites with relevant photocatalytic properties have been developed via an easy and cheap photopolymerization process upon mild visible light irradiation at 405 nm. This fruitful association between POM and polymer allowed the obtention of shaped materials facile to collect and reuse at the end of the photocatalytic treatment avoiding then the usual time-consuming regeneration methods. The prepared photocomposites displayed excellent photocatalytic performance for the removal of bisphenol-A from water under different sources of irradiation. Hence, 100%, 88%, and 50% of this model compound were decomposed by the phosphomolybdic composite under just 90 min of UV lamp, solar and LED@375 nm irradiations, respectively. The effectiveness of these developed photocatalysts towards the degradation of other organic compounds, as well as the degradation mechanism based on the generation of highly reactive chemicals such as •OH radicals promoting the degradation were already reported. Bisphenol-A degradation pathway and the identification of the photoproducts were discussed using mass spectroscopy technique. Therefore, this paper highlighted the photocatalytic efficiency of the new manufactured materials for the photodegradation of the bisphenol-A, thus expanding their application fields, under different sources of irradiation and under pure solar irradiation which make their applications more interesting and less energy consuming.

International audience

International audience; In the last few years, pharmaceutical compounds classified as emerging pollutants have attracted the attention of many researchers, due to their massive presence in soil, surface, sewage, groundwater and drinking water, as well as to their harmful effects on human health and the environment. In this context, the degradation of four drugs with different chemical structures, Ciprofloxacin, Oxytetracycline, Ibuprofen and Erythromycin was investigated. Indeed, in this paper, we studied the impact of the presence in the aqueous solution of a newly developed POM/polymer composite on the removal of these different drugs from water. Synthesis details and characterizations of these materials have already been reported within our group. The various experiments carried out during this study revealed that the presence of the phosphomolybdic acid-based composite was not essential for the total degradation of Ciprofloxacin and Oxytetracycline which could be totally removed from water by simple photolysis under UV-Visible lamp irradiation. However, under the same experimental conditions, the use of this photocatalyst was indispensable for the total mineralization of Ibuprofen, more recalcitrant than the other selected drugs. In fact, only 20% of this pharmaceutical was degraded by simple photolysis vs. 100% and 94% upon respectively, 90 min of UV-Visible lamp and solar irradiation, in the presence of the phosphomolybdic acid-based composite which was more pertinent than the usually used photocatalyst, namely titanium dioxide. The Ibuprofen degradation pathway was identified thanks to mass spectrometry analysis, conducted at different time intervals. The obtained results demonstrated also that POM/polymer composite inhibits the degradation of Erythromycin through the formation of more toxic intermediates than the original drug

Recently, many researchers have focused their attentions on associating perovskites with polymers in order to enhance their processability and rigidity while protecting their interesting environmental properties. Therefore, this work reports the successful development of two different Perovskites/polymer composites via a simple, rapid, low-cost and eco-friendly photopolymerization process under mild visible Light Emitting Diode LED@405 nm irradiation. The as-synthesized composites exhibit excellent photocatalytic activity towards the removal of the Acid Black dye from water, reaching approximately 95% under just 30 min of UV light irradiation. The fruitful hybridization between the perovskites and the acrylate monomer allowed the collect and reuse of this photocatalyst for several successive cycles without external usual time-consuming methods. Furthermore, the new as-fabricated shaped materials were fully characterized by numerous characterization techniques including, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Analysis (EDX), X-Ray Diffraction Analysis (XRD), Atomic Force Microscopy (AFM), Dynamic Mechanical Analysis (DMA) and Thermogravimetric Analysis (TGA), which have verified on one side the successful immobilization of the perovskites into the polymer and the structural stability of the photocatalysts after hybridization and in the other side the high rigidity and thermal stability of the obtained molded composites.

Titanium dioxide thin films immobilized over treated stainless steel were prepared using the pulsed electrophoretic deposition technique. The effects of process parameters (deposition time, applied voltage, initial concentration, and duty cycle) on photocatalytic efficiency and adhesion properties were investigated. To optimize the multiple properties of the thin film, a response surface methodology was combined with a desirability optimization methodology. Additionally, a quadratic model was established based on response surface analysis. The precision of the models was defined based on the analysis of variance (ANOVA), R2, and the normal plot of residuals. Then, a desirability function was used to optimize the multiple responses of the TiO2 thin film. The optimum values of applied voltage, catalyst concentration, duty cycle, and deposition time were 4 V, 16.34 g/L, 90% DC, and 150 s, respectively. Under these conditions, the decolorization efficiency of tested dye solution reached 82.75%. The values of critical charges LC1, LC2, and LC3 were 5.9 N, 12.5 N, and 16.7 N, respectively.

Titanium dioxide thin films immobilized over treated stainless steel were prepared using the pulsed electrophoretic deposition technique. The effects of process parameters (deposition time, applied voltage, initial concentration, and duty cycle) on photocatalytic efficiency and adhesion properties were investigated. To optimize the multiple properties of the thin film, a response surface methodology was combined with a desirability optimization methodology. Additionally, a quadratic model was established based on response surface analysis. The precision of the models was defined based on the analysis of variance (ANOVA), R2, and the normal plot of residuals. Then, a desirability function was used to optimize the multiple responses of the TiO2 thin film. The optimum values of applied voltage, catalyst concentration, duty cycle, and deposition time were 4 V, 16.34 g/L, 90% DC, and 150 s, respectively. Under these conditions, the decolorization efficiency of tested dye solution reached 82.75%. The values of critical charges LC1, LC2, and LC3 were 5.9 N, 12.5 N, and 16.7 N, respectively.

Water disinfection using visible light-active photocatalyst has recently attracted more attention due to its potential to inactivate microbes. In this study, we have investigated the efficiency of ...

In this study, both TiO2 and WO3 were synthetized using controlled hydrolysis followed by dialysis. The produced transparent emulsions were dried into powders. Then, TiO2–WO3 photocatalyst films were deposited by pulsed electrophoretic deposition. The substrates were made of stainless steel pre-functionalized in a conversion bath. The conversion layer played an important role in the adhesion of the composite film into the substrate. Film surface morphology, crystallinity, roughness, thickness, and elemental composition were determined from XRD, optical profilometry and SEM–EDX measurements. The mechanical properties were resolute by nano-indentation test and adhesion was investigated using a scratch test. The photocatalytic decolorization of the Amido Black-10B dye was studied over TiO2–WO3 coatings under UV irradiation. TiO2 film doped 5% WO3 film exhibited the best photocatalytic activity due to its crystalline size and three-phase structure as well as a synergetic effect of TiO2–Fe2O3 and TiO2–WO3. This film showed also good adhesion properties.

International audience; Hybrid H3PMo12O40/polymer composites were proposed here for the simple photocatalytic decomposition of erythrosine B and rose Bengal because of their unwanted effect on the environmental microorganism. Interestingly, the composite exhibited efficient photocatalytic activity for the decomposition of dyes under both mild near UV irradiation and solar irradiation. High final conversions were obtained for both of dyes reaching 81% and 86% for the erythrosine B and rose Bengal respectively after 120 min of LED@375 nm illumination and 90% for both dyes after only 30 min of solar exposure. The photocatalytic stability was also demonstrated. The photoluminescence technique was used to prove hydroxyl radicals implication into the photo-decomposition reaction using H3PMo12O40/polymer. The efficiency of the proposed treatment was confirmed by the evaluation of the ecotoxicity effect of by-products of each dye on two bacterial strains.

In this study, TiO2 was synthesized using controlled hydrolysis of TiCl4, followed by dialysis. We produced a transparent emulsion that was later dried into TiO2 powder. TiO2 photocatalyst films were deposited applying the technique of pulsed electrophoretic deposition, which decreased bubble formation caused by direct current. The substrates were bare stainless steel (SS) and stainless steel pre-functionalized in a conversion bath. Film surface morphology, crystallinity, elemental composition, and wettability were determined using XRD, SEM–EDAX, and contact angle measurements. The mechanical properties were determined by nano-indentation test. The adhesion was investigated using scratch test. The obtained results showed that the TiO2 film over a conversion layer had better adhesion and mechanical properties than TiO2 over bare SS. The optical characteristics of TiO2 films were tested using PL measurement. The photocatalytic decolourization of the amido black-10B dye was studied over TiO2 coating under UV and visible light irradiation. TiO2 film over a conversion layer without heat treatment exhibited the best photocatalytic activity as a result of its crystalline size and three-phase structure as well as the synergetic effect of TiO2 and Fe2O3.

Titanium dioxide (TiO2) nanostructed films were obtained on stainless steel by electrophoretic deposition in aqueous media. After the sintering stage, crystalline phases were investigated by X-ray ...

Solar photocatalytic inactivation of Gram-negative bacteria with immobilized TiO2-P25 in a fixed-bed reactor was modeled with simplified kinetic equations. The kinetic parameters are the following: the photocatalytic inactivation coefficient (kd,QUV), the initial bacterial reduction rate (A) in the contact with the disinfecting agent, and the threshold level of damage (n) were determined to report the effect of QUV/TiO2-P25 on bacterial cultivability and viability and to compare the response of bacterial strains to photocatalytic treatment. In addition, the integration of the reactivation coefficient (Cr) in the photocatalytic inactivation equation allowed evaluating the ability of bacterial reactivation after photocatalytic stress. Results showed different responses of the bacteria strains to photocatalytic stress and the ability of certain bacterial strains such as Escherichia coli ATCC25922 and Pseudomonas aeruginosa ATCC4114 to resuscitate after photocatalytic treatment.

Electrophoretic deposition was used to produce titanium dioxide (TiO2) nanostructured films on copper substrate in aqueous media for photocatalytic application. Polyvinyl pyrrolidone (PVP) with a weight rate from 0 to 15% was added to TiO2 P25 suspension in order to enhance film adhesion. The films were characterized by X-ray diffraction, optical microscopy, contact angle measurement, nanoindentation, scratch test and photoluminescence. The photocatalytic activity of the films was tested with amido black 10B under UV irradiation. The results indicated that the morphology and the mechanical properties of films depended on the added PVP amount. Scratch test showed that adhesion strength rose with increased PVP amount. The photocatalytic activity indicated that TiO2 film synthesized with 13% PVP had the highest efficiency.

Several Advanced Oxidation Processes (AOPs) including O3/H2O2, O3/TiO2, O3/activated carbon (AC), O3/Al2O3, O3/Fe2+/H2O2 and UV/TiO2 have been investigated and compared for the removal of diethyl phthalate (DEP), an endocrine disrupting compound, in aqueous solutions. Hydroxyl radicals were the main species responsible for DEP degradation and this was supported by computational chemistry calculation, scavenger experiments, and LC/MS/MS analysis. The change of the abundance of reaction products over time was determined. Organic acids as well as anhydride and hydroxylated products were found to accumulate in solution even after long reaction time (2 h). Careful choice of the operating parameters (pH, ozone concentration and catalyst dosage) was crucial to achieve enhanced performance of the combined processes above what each oxidant and catalyst can achieve alone. O3/AC process was found to reduce the oxidation efficiency of O3 at high ozone concentrations. Heterogeneous catalytic ozonation with Al2O3 was the most effective process for DEP removal (∼100% removal in about 15 min) and based on pseudo-first-order kinetics at pH7, the studied oxidation processes followed the order: O3/Al2O3(0.093 min−1)>O3/H2O2/Fe2+(0.076 min−1)>O3/AC(0.069 min−1)>O3/H2O2(0.053 min−1)>O3/TiO2(0.050 min−1)> O3 alone (0.039 min−1)>UV/TiO2(0.009 min−1).

International audience; In the present research, the optimization of the photocatalytic degradation of simulated textile effluent containing two pollutants (Methylene blue (MB) and Zinc) consisted of studying the variation of four parameters, namely initial MB concentration ([MB]I, mg/L), zinc concentration ([Zn2+]I, mg/L), sodium chloride concentration ([NaCl]I, M) and flow rate (Q, mL/min) through a design of experiment using the response surface methodology approach. Results showed that MB degradation depends by order of importance on NaCl concentration andgt; MB concentration andgt; ionic zinc concentration andgt; flowrate. Modeling results presented a good concordance between predicted and experimental values with acceptable correlation coefficients (R2 = 0.9879 and R2 (adjusted) = 0.9773). Desirability function was applied on the second-order polynomial equation to determine the optimal experimental condition for fastest total photocatalytic degradation and it was identified as follows For a maximal target of 85.91% and a desirability of d = 1.0, [MB] = 75 mg/L, [Zn2+] = 45 mg/L, [NaCl] = 0.125 M and Q = 500 mL/min. Moreover, results showed that zinc had a good affinity to cellulose material and contributed on enhancing the photocatalytic activity in terms of degradation. Mineralization of the dye was assessed for the optimal conditions using the TOC method. Moreover, special attention was also paid to better understand the effect of inorganic pollutant, scavenging effects of different molecules such as EDTA, isopropyl alcohol and CCl4 were examined and discussed.

This paper deals with the effect of Cr content on photocatalytic activity of TiO2 thin films deposited on quartz and intrinsic silicon substrates by using the RF magnetron co-sputtering process. Some physical investigations on such sputtered films were made by means of X-ray Diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy as well as UV-Vis-IR absorption techniques. The heat treatment under oxygen atmosphere at 550°C reveals that the crystalline structure of TiO2: Cr depends on Cr content. Anatase-to-rutile phase transformation occurs at a Cr content of about 7%. On the other hand, the band gap energy value of annealed TiO2: Cr films varies in terms of Cr doping and a transition around 7% of Cr is accrued. The photocatalytic activity of undoped and doped TiO2 films was evaluated by photo-degrading of the amido black under UV light irradiation. Modification of the chemical structure of titanium dioxide by Cr doping allows moving the photocatalytic activity of titanium dioxide towards visible light. The results indicate that films doped with 2% Cr exhibit the highest UV and visible light photocatalytic activity.

Tungsten trioxide (WO3) influence as a doping agent was studied in order to improve Titanium dioxide (TiO2) photocatalytic efficiency under sunlight. Hydrolysis at low temperature, followed by dialysis and chemical reactive sputtering, has been applied to synthesise thin films. Morphological investigations were performed by X-ray diffraction (DRX) and atomic force microscopy (AFM). Gap energies were determined from transmission spectra (TS), a solar photocatalytic reactor was used to study photodegradation efficiency. The adhesion strength was performed by scratch test. Doping TiO2 by WO3 decreases the energy gap of the film; consequently an increase of photocatalytic activity under solar radiation is achieved. The degradation test under sunlight showed an efficiency of 10.37 mg m‒2h‒1 in the case of the non-doped film. However, the 5 wt% WO3 doped film had a degradation efficiency of 17.87 mg m‒2h‒1. The scratch test performed to the 5 wt% WO3 doped film has determined a critical load value of 2.6 N.

TiO2 electrodes are made by anodization of Ti at various applied voltages. The increase of voltage facilitates the generation of anatase and rutile at high potential (superior to 140 V). Photoelectrochemical properties of prepared electrodes are investigated with and without methanol. TiO2/Ti electrode obtained at 140 V presents high photoelectrochemical properties. The electrode presents better separation of photogenerated electron-hole pairs, high photocurrent and easy charge transfer. The reaction of adsorbed methanol with generated holes increases the photocurrent. When the electrode is anodically biased (application of 1 to 2 V), the photocurrent increases with increased methanol concentration and at alkaline pH.

In this work, we report on the photo-catalytic properties of TiO2–ITO nanocomposite deposited on low cost conventional clay ceramic substrates. The nanocomposite was formed by spraying a solution prepared from the P25 TiO2 powder (Degussa) mixed with an organometallic paste of a dissolved combination of indium and tin. A TiO2–ITO powder-like nanocomposite was prepared for X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterization. The mean particle size of the TiO2–ITO nanocomposite was found to be larger than that of pure TiO2. The optical features of TiO2–ITO-based layers (deposited on glass substrates) were investigated using UV–vis spectroscopy. The TiO2–ITO nanocomposite deposited layers were found to have higher light absorption than the P25 TiO2 powder. The photo-catalytic properties of the TiO2–ITO nanocomposite (deposited on low cost clay ceramic substrates) were tested under solar irradiation using a well-known polluting dye. It was shown that the TiO2–ITO nanocomposite exhibits higher degradation rates towards the pollutant dye than the P25 TiO2 powder. The optical band gap of the TiO2–ITO nanocomposite (2.79 eV) was found to be lower than that of pure TiO2 (3.1 eV), while ITO (indium tin oxide) has a band gap of about 4.2 eV. ITO was found to be entirely transparent to sun light, while it exhibits a slight photo-catalytic activity, signifying the possible existence of an indirect photo-catalysis phenomenon (sensitized semiconductor photocalysis) and potential degradation (oxidation) of the pollutant through electron transfer from the dye to conduction band of the semiconductor. All photo-catalytic activity results were discussed in light of the optical band gap of the various compounds.

Performances of solar photocatalytic pilot plant using TiO2-P25 (Degussa) were investigated for removal of commercial azo dye chosen as model compound. Experiments were carried out to optimize various parameters, influencing the performance of the operated thin-film fixed-bed reactor (TFFBR) with an area of 25 m2. The results showed kinetic dependency on flow rate, catalyst loading, and initial dye concentration. The best discoloration rate was obtained at the optimum flow rate of 3 m3/h. Increasing catalyst loading density up to 10 g/m2, does not lead to high improvement of the discoloration rate. The photocatalytic degradation kinetic of TOC is discussed in terms of Langmuir–Hinshelwood model. Initial mineralization rate expressed by mg kJ−1 reach a maximum value at initial TOC closed to 30 mg/L.

The apparent first-order rate constant, k(app), of the Acid Blue 113 textile azo dye photocatalytic disappearance in aqueous suspensions of 4 commercialized TiO(2) samples (50 m(2) g(-1)-Degussa P25; 54 m(2) g(-1)-Millennium Chemicals PC50; 250-270 m(2) g(-1)-Sachtleben Chemie Hombikat UV100; 320 m(2) g(-1)-Ishihara ST01) was determined from the decrease in the calibrated 566 nm-absorbance of the supernatant. Under the conditions used (1 liter-batch reactor; water-filtered irradiation from a Philips HPK 125-W high-pressure mercury lamp; [TiO(2)] = 1 g/L; [dye] = 70 mg/L), the k(app) ranking was: UV100 > PC50 > P25 > ST01. The corresponding maximal difference in k(app) was roughly equivalent to that caused by adding an optimal dose of H(2)O(2) to the P25 suspension. Taking into account the dye adsorbed amount, q(ads), in the dark, it is deduced that the recombination rate k(r) of photogenerated charges was higher for poorly crystallized TiO(2) samples, as expected; additionally, a low content of impurities is suggested to be at the origin of the low k(r) of UV100 relative to ST01. It is also argued that differences in the values of q(ads) divided by the surface area, S, was less due to pores inaccessible to the dye than to thicker layers of surface tightly bound water for the samples with high S. A FTIR study showed that the dye weakly interacted with TiO(2) and, however, remained the dominant adsorbed species during the degradation. This latter conclusion was in accord with the fact that the dye initial disappearance rates -- directly measured or calculated from k(app) -- were almost equal, indicating that the intermediate products of degradation did not significantly compete with the remaining dye for active species.

SSCI-VIDE+CARE:ECI2D+MME:ATR:HKO:CGU:GBE; International audience; The influence of lanthanum on the thermal stability and photocatalytic activity of calcined hydrogenotitanate nanotubes (HNT) was hereinevaluated. HNT samples were prepared through the hydrothermal treatmentof TiO2 P25 in a concentrated NaOH solution (11.25 M) at 130 degrees Cduring 20 h followed by acid washing. La-doped titanates nanotubes(La-HNT) photocatalysts with optimum 1 wt% of La were then elaborated byincipient wetness impregnation method using lanthanum nitrate asprecursor. La HNT and HNT samples were then calcined at temperaturesvarying between 400 degrees C and 700 degrees C. Samples werecharacterized by means of nitrogen adsorption-desorption isotherms at77K, X-ray diffraction (XRD), Raman spectroscopy, diffuse reflectancespectroscopy (DRS), photoluminescence spectroscopy (PL), transmissionelectron microscopy (TEM), ICP analysis and photocurrent experiments.The photocatalytic activities of La-HNT and HNT derived nanomaterialswere then evaluated through the photocatalytic degradation of formicacid (FA).Main results reveal that lanthanum inhibits TiO2 crystallite growthand retards anatase transformation into the less active rutile phase.The addition of La ions to TiO2 results in a charge imbalance creating ahigh proportion of oxygen vacancies as evidenced by photocurrent,photoluminescence and Raman experiments.The photocatalytic experiments reveal that La-doped TiO2 helps tomaintain a high photocatalytic activity level even after calcination athigh temperatures contrary to La-free photocatalysts. The determinationof kinetic parameters reveals that the maintaining of a highphotocatalytic activity results from the synergetic effect betweenrestriction of TiO2 crystallite size growth and formation of a highproportion of oxygen vacancies.

Photocatalysis is a promising technology for the purification of pretreated wastewaters in sun-rich countries if an economically applicable reactor system is available. Within this project the catalyst separation as an essential process step of suspended reactor systems was investigated. For the separation of suspended catalyst a sedimentation basin with and without lamella and a membrane filtration were investigated. The sedimentation was found to be very sensitive to the kind of the ion background of wastewater, the pH, the TiO2 influent concentration as well as the hydrodynamics in the clarifier. Under optimized conditions effluent concentrations of less than 5 mg SS/L and a clear water without turbidity could be reached with a specific flow rate of up to 0.7 m3/m2/h. The best performance for P25 was achieved with a TiO2 influent concentration of 5 g/L. Membrane filtration was the only method to guarantee a complete retention of the TiO2 as well as a rejection of microorganisms and high molecular compounds. With cross-flow velocities of 3 m/s and a transmembrane pressure of 100 kPa flux rates up to 1200 L/m2/h were achieved. A flow-film-reactor (FFR) was operated with the model compound DCA under identical conditions with fixed and suspended TiO2. Whereas the fixed system has the advantage that no separation step is necessary and a simple construction can be used, suspended systems offer a three times higher reaction velocity for a catalyst concentration of 10 g/L, but are also characterized by higher investment costs.

An introduction to a joint research project is given which deals with the technical application of solar photocatalysis for wastewater detoxification. A non-concentrating thin-film fixed-bed reactor (TFFBR) is used to study applications and areas where a solar-catalytic treatment or recycling of wastewater is possible. This reactor excels by its low cost and an easy-to-build construction using molecular oxygen in air as the oxidising agent. The design parameters of the reactor as well as the process itself have been determined from the reaction kinetics of a model substance, the hydrodynamics and the mass transfer. The treatment of different real wastewaters was successfully carried out, and biologically pre-treated textile wastewater maximum solar degradation rate was about 3 g COD h−1 m−2. A comparison of reaction rates with artifical and solar illumination shows the necessity of outdoor experiments. Due to the reaction rates observed, photocatalysis is suitable as the final stage of purification of biologically or physically pretreated wastewater and will offer a great opportunity for sunrich areas.

International audience; This work compares the behaviors of TiO 2 nanotube (TNTs) array obtained by anodization of Ti foils in an ethylene glycol/NH 4 F/ water electrolyte with different applied voltages during a constant anodization time, and for the same electrolyte composition. The crystal structure and surface morphology of the annealed anodic fi lms are investigated by X-Ray diffraction system, Raman spectroscopy and scanning electron microscopy, respectively. The TiO 2 nanotubes obtained at potentials of 20 - 40 - 60V show different inner diameters (42 - 89 - 124nm), tube length (1.2 - 3.3 - 12.7 μ m) and wall thicknesses (12 - 15 - 18nm). The in fl uence of these geometric parameterson the photoelectrochemical properties and the photocatalytic activity were investigated in detail. The results showed that the photocatalytic performances of TNT fi lms are improved when the speci fi c surface, the tube length and the solid fraction are increased, but the increase is slowed down when a limiting thickness of the layer is reached. The surface states which usually show high density in nanostructured layers do not seem to in fl uence signi fi cantly the photocatalytic activity of the layers.

One of the most promising ideas to enhance the photocatalytic efficiency of the TiO2 is to couple this photocatalyst with other semiconductors. In this work, we report on the development of photo-catalytic properties of two types of composites based on TiO2 – ITO (Indium Tin Oxide) and TiO2 – ZnO deposited on conventional ceramic substrates. The samples were characterized by X-ray diffraction (XRD) and transmission Electron Microscopy (TEM). The photo-catalytic test was carried out under UV light in order to reduce/oxidize a typical textile dye (Cibacron Yellow). The experiment was carried out in a bench scale reactor using a solution having a known initial dye concentration. After optimization, we found that both nanocomposites exhibit better photocatalytic activity compared to the standard photocatalyst P25 TiO2 .

The role of WO 3 in enhancing the photocatalytic activity of TiO 2 deposits has been investigated through the oxidation of salicylic acid using UV and vis-light irradiation. Different procedures of semiconductor loading and deposition were undertaken: firstly, TiO 2 -Degussa P25 was impregnated with tungstic acid solution and spread on the glass substrate. Secondly, precursor of WO 3 was ammonium paratungstate, mixed with a monomer and spincoated on the glass. Finally, a gel of WO 3 –TiO 2 was synthesized by sol–gel method and spincoated on the glass, TiCl 4 was used as the titanium dioxide precursor and ammonium paratungstate was introduced in the sol before precipitation of TiO 2 . The films obtained were characterized by UV–vis spectrophotometry, X-ray powder diffraction and scanning electron microscopy in order to better understanding the behavior and the effective role of WO 3 . A red-shift in the absorption edge wavelength was observed for coupled catalysts prepared by the first procedure, the bang gap energy decreased to respectively 2.7 and 2.6 eV for 0.5% and 2.5 wt.% of WO 3 . A tendency to agglomeration and a higher percentage of rutile in the catalysts were observed after WO 3 loading. The photocatalytic activity under visible light increased consequently for catalysts with 2.5 wt.% of WO 3 and variable inhibition was observed for lower loadings, but only a positive effect of WO 3 was observed under UV light. The inhibition of photocatalysis was also observed under visible light for some WO 3 loadings for coupled catalysts prepared by the procedure 2 and a great enhancement was observed at the 0.5 wt % of WO 3 under UV light. Concerning the catalysts prepared by the sol–gel method, a positive effect of the WO 3 introduction was noted: the coverage on the glass was improved, the band gap energy decreased to 2.3 eV with 4 wt.% of WO 3 and the corresponding photocatalytic activity was remarkably enhanced under visible light. A higher photocatalytic activity and a better response to WO 3 introduction was also observed under UV irradiation. The introduction of tungsten precursor before the crystallization of TiO 2 seems to be an appropriate method to ensure good contact and better charge transfer between the two semiconductors. As expected, the photocatalytic performances were generally higher under UV light than under visible light for all the catalysts and 0.5 wt.% WO 3 –TiO 2 was the common optimal loading for the 3 procedures exhibiting the best activity under UV light.

The present work compares the efficiencies of titania nanotubes (NT) formed by anodizing of titanium at 20 V for 45 min in three kinds of electrolytes: ethylene glycol–ammonium fluoride–water (NT 1 ), tetrabutylammonium fluoride–formamide–water (NT 2 ) and sodium sulfate–ammonium fluoride–water (NT 3 ). The geometric characteristics were investigated by scanning electron microscopy (SEM). The photoactivities of the three layers were compared through photo-potential, photo-current measurements in an alkaline medium and in the presence of methanol as a hole scavenger. Impedance spectrometry was used for investigation of conduction and charge storage properties of the titania layer. Finally the photocatalytic properties were compared through the degradation rate of an azo dye, such as Amido Black (AB). In comparison to NT 2 and NT 3 , the NT 1 layer showed not only the highest photopotential, but also the highest photocurrent response. Photocatalytic results showed that the degradation of dye proceeds much faster in the presence of NT 1 as compared with other TiO 2 nanotube samples. Nevertheless photoinduced surface states were found to be more important in NT 2 , in comparison with the two other layers. All these results are discussed taking into account the geometric characteristics of the nanotubular layers, not only the specific surface on one hand, but also the solid fraction of the external surface, which determines the level of light absorption able to generate photo-charges.

International audience; The adsorption and photocatalytic efficiency of several TiO2 suspended catalysts were compared to see how well they could degrade the organic pollutant anthraquinone dye Reactive Blue 2 (RB2). The adsorption of RB2 on catalysts follows the Langmuir model and adsorption capacity's influence on degradation performance has been established. Correlations between degradation kinetics and the amount of dye adsorbed (qads) were then determined. The expected correlation between specific surface and qmax was verified. The addition of sulphate ions in the case of catalysts Degussa P25 and TiO2-Ishihara ST01 was found to inhibit adsorption of RB2 on the TiO2 surfaces. The hindrance of adsorption in acidic conditions improved the efficiency of the photocatalytic degradation of ST01. No adsorption was observed in alkaline pH and the photodegradation kinetic was generally higher in this condition except for that seen in photocatalysts with a low recombination rate.

Biological pre-treated landfill leachates of Djebel Chakir contains some macromolecular organic substances that are resistant to biological degradation. The aim of the present work is to assess the feasibility of removing refractory organic pollutants in biological pre-treated landfill leachate by solar photocatalyse process. Leachate pollutant contents are studied to assess their contribution to leachate pollution and their treatability by solar photocatalyse process. Phenol is chosen as model of pollutants, to evaluate its removal and the efficiency of the photocatalytic system. The experiments were carried out in suspended photocatalytic reactor, using TiO2 Degussa P25, under sunlight illumination (UV-A: 15–31 W/cm2). Under optimum operational conditions, applied to single reactant (phenol), the system presents a TOC removal of 90% (the degradation follows a first-order kinetic). Based on the TOC removal, the results shows that the degradation of biological pre-treated leachate follows a zero-order kinetic. After 5 h of sunlight exposure, 74% of COT is removed. The TOC removal is the best without any correction of the pH and at the TiO2 concentration of 2.5 g/L. The photocatalytic degradation of organic contaminants as well as the formation and disappearance of the by-products were followed by GC/MS. The solar photocatalysis processes induce several modifications of the matrix leading to more biodegradable forms: all the remaining and new compounds generated after the biological pre-treatment of leachate are degraded and other types of organics appear, mainly carboxylic acid, aliphatic hydrocarbons and phtalic acids.