Didier Robert

Ethylene removal and fresh product storage: a challenge at the frontiers of chemistry. Toward an approach by photocatalytic oxidation.

Frontiers of Chemistry. Toward an Approach by Photocatalytic Oxidation Nicolas Keller,*,† Marie-Noel̈le Ducamp,‡ Didier Robert, and Valeŕie Keller† †Institut de Chimie et Proced́eś pour l’Energie, l’Environnement et la Sante ́ (ICPEES), CNRS, Strasbourg University, 25 rue Becquerel 67087, Strasbourg, France ‡UMR 95 QUALISUD, CIRAD, TA B 95/16, 73 Bd Jean-Franco̧is Breton, 34398 Montpellier Cedex 5, France Saint-Avold Antenna, Institut de Chimie et Proced́eś pour l’Energie, l’Environnement et la Sante ́ (ICPEES), CNRS, Strasbourg University, Universite ́ de Lorraine, rue Victor Demange 57500 Saint-Avold, France

Cerium doped red mud catalytic ozonation for bezafibrate degradation in wastewater: Efficiency, intermediates, and toxicity.

In this study, the performance of bezafibrate (BZF) degradation and detoxification in the aqueous phase using cerium-modified red mud (RM) catalysts prepared using different cerium sources and synthesis methods were evaluated. Experimental results showed that the surface cerium modification was responsible for the development of the catalytic activity of RM and this was influenced by the cerium source and the synthesis method. Catalyst prepared from cerium (IV) by precipitation was found to show the best catalytic activity in BZF degradation and detoxification. Reactive oxygen species including peroxides, hydroxyl radicals, and super oxide ions were identified in all reactions and we proposed the corresponding catalytic reaction mechanism for each catalyst that prepared from different cerium source and method. This was supported by the intermediates profiles that were generated upon BZF degradation. The surface and the structural properties of cerium-modified RM were characterized in detail by several analytical methods. Two interesting findings were made: (1) the surface texture (specific surface area and mesoporous volume) influenced the catalytic reaction pathway; and (2) Ce(III) species and oxygen vacancies were generated on the surface of the catalyst after cerium modification. This plays an important role in the development of the catalytic activity.

H2S photocatalytic oxidation over WO3/TiO2 Hombikat UV100

Hydrogen sulfide (H2S) is a toxic, corrosive and malodorous compound with damaging effects even when present at a low concentration in air. Consequently, the development of efficient and environmentally friendly remediation technologies as an alternative to conventional techniques is justified for environmental reasons and public concern over human health and well-being. In the context of indoor air quality control, the use of photocatalysis over semi-conductor oxides could be a valuable alternative purification technology due to its wide-ranging effect and its easy way of implementation. The superiority of the TiO2 Hombikat UV100 photocatalyst in comparison with the Aeroxide© TiO2 P25 standard was already apparent in the UV-A photocatalytic oxidation of H2S. We report here on the first use of WO3/TiO2 UV100 photocatalysts for this reaction. Associating WO3 to TiO2 UV100 was not beneficial in terms of semiconductor coupling and of charge transfer between both phases. Even if such coupled wide band-gap oxide semi-conductor photocatalysts suffered from on-flow deactivation due to the formation of poisoning sulfates as ultimate reaction products continuously stored at the surface, by contrast, their ability to strongly lower and delay the release of SO2 to the gas phase was very positive for maintaining a weak selectivity into the unwanted SO2 by-product.

Design and study of a cost-effective solar photoreactor for pesticide removal from water

In order to remove pesticides from water, a basic photoreactor has been built. We evaluated the performance of this photoreactor using two commercial photocatalytic materials from Ahlstrom group and from Saint-Gobain, with solar and artificial UV-lamps. We compared the kinetics of photocatalytic degradation and mineralization of Diuron in the same reactor with of both photocatalyst supports. We showed that Diuron is easily degraded under solar or artificial irradiation, while the kinetics of mineralization in the same condition are very slow. The behaviour of these commercial materials has been studied after several uses in the same conditions. We showed the effectiveness of this basic and cheap photoreactor for the elimination of pesticide in water.

Removal of atrazine and its by-products from water using electrochemical advanced oxidation processes

Atrazine (ATZ) is one of the most common pesticides detected in surface water in Quebec (Canada). The present study was mainly focused on the degradation of ATZ and its by-products using electrochemical advanced oxidation processes such as photo-electro-Fenton (PEF), electro-Fenton (EF) and anodic-oxidation with simultaneous H2O2 formation (AO - H2O2). The comparison of these processes showed that PEF process was found to be the most effective process in removing ATZ and its by-products from both synthetic solution (ATZ0xa0=xa0100xa0μgxa0L-1) and real agricultural surface water enriched with ATZ (ATZ0xa0=xa010xa0μgxa0L-1). Different operating parameters, including wavelength of the light, pH, current density and the presence of natural organic matter (humic acids) were investigated for PEF process using boron-doped diamond (BDD) anode and graphite cathode. The current density and the wavelength of the light were the most important parameters in the ATZ degradation efficiency. The best operating conditions were recorded for the synthetic samples at a current density of 18.2xa0mAxa0cm-2, a pH of 3.0 and treatment time of 45xa0min. Results showed that atrazine-desethyl-desisopropyl (DEDIA) was the most important by-product recorded. More than 99% of ATZ oxidation was recorded after 15xa0min of treatment and all the concentrations of major by-products were less than the limit of detection after 45xa0min of treatment. The PEF process was also tested for real surface water contaminated by ATZ: i) with and without addition of iron; ii) without pH adjustment (pHxa0∼xa06.7) and with pH adjustment (pHxa0∼xa03.1). In spite of the presence of radical scavenger and iron complexation the PEF process was more effective to remove ATZ from real surface water when the pH value was adjusted near to 3.0. The ATZ removal was 96.0% with 0.01xa0mM of iron (kappxa0=xa00.13xa0min-1) and 100% with 0.1xa0mM of iron (kappxa0=xa00.17xa0min-1).

Degradation of atrazine in aqueous solution with electrophotocatalytic process using TiO2−x photoanode.

The present study investigates the efficiency of a sustainable treatment technology, the electrophotocatalytic (EPC) process using innovative photoanode TiO2-x prepared by a magnetron sputter deposition process to remove the herbicide atrazine (ATZ) from water. The coexistence of anatase and rutile were identified by X-ray diffraction (XRD) and the presence of oxygen vacancies reduce the value of the observed bandgap to 3.0xa0eV compared to the typical 3.2xa0eV TiO2, this reduction is concomitant with a partial phase transition which is probably responsible for the increase in photoactivity. The experimental results with an initial concentration of ATZ (100xa0μgxa0L(-1)) show that more than 99% of ATZ oxidation was obtained after 30xa0min of treatment and reaction kinetic constant was about 0.146 min(-1). This good efficiency indicates that EPC process is an efficient, simple and green technique for degradation of pesticides such as ATZ in water. The analysis with liquid chromatography technique permits to identify, quantify and see the evolution of ATZ by-products which are generated by dechlorination, dealkylation and alkylic-oxidation mechanisms. Finally, the possible pathways of ATZ degradation by hydroxyl radicals were proposed.

Nitrogen-containing organic compounds: Origins, toxicity and conditions of their photocatalytic mineralization over TiO2.

Sustainable water management remains a global concern to meet the food needs of industrial and agricultural activities. Therefore, pollution abatement techniques, cheap and environmentally, are highly desired and recommended. The present review is devoted to the origin and the toxicity of nitrogen-containing organic compounds in water. The progress made in removing these pollutants, in recent years, is addressed. However, a prominent place is given to the photocatalytic degradation process using the TiO2 as a semiconductor, the conditions for good mineralization and especially the factors influencing it. The parameters that impact the performance of this method are the pH, the temperature, the reactor used, the light, the concentration of the pollutant, the amount of catalyst, etc. Up to now, the importance of one parameter relative to another has not been established because in the context of the photocatalytic degradation, certain parameters are often tightly coupled. Consequently, the mineralization is dependent on the initial degree of oxidation of nitrogen atom contained in the pollutant to be degraded. The hydroxyl nitrogen is primarily converted into nitrate ions (NO3-), while the amides and the primary amines are converted into ammonium ions (NH4+).

Photocatalytic Oxidation of Carbamazepine: Application of an Experimental Design Methodology

Carbamazepine is one of the pharmaceutical compounds frequently detected in the receiving waters and water bodies. The main objective of this study was to develop a quadratic model to predict carbamazepine (CBZ) photocatalytic removal through a response surface methodology. A factorial plan (linear model; 24 experiments) was used to determine the contribution of individual factors (pH, CBZ concentration, photocatalyst concentration, and treatment time) and interactions among the factors. Pollutant concentration and treatment time were found to be the most important parameters influencing the oxidation rate, with respective contributions of 19.22 and 71.55xa0%. Central composite methodology was then applied to determine the optimal experimental parameters for CBZ oxidation. The highest percentage of CBZ removed was 94.67u2009±u20090.51xa0%, recorded using a pH of 5, a minimal CBZ concentration of 10xa0mg/L, a photocatalyst concentration of 1.14xa0g/L, and a treatment time of 90xa0min. The effects of different anions (NO3− and SO42−) and cations (Cu2+, Cr3+, Zn2+) were also studied. Copper was found to have both catalytic and inhibitory effects on CBZ removal rate.

Solar Photocatalytic Decolorization and Degradation of Methyl Orange Using Supported TiO2

Abstract The photocatalytic degradation of Methyl orange has been investigated on dynamic solar pilot plant using nonwoven fibers coated with TiO2 as photocatalyst. The operational parameters, such as initial dye concentration and pH, were studied. Disappearance of color and substrate together with decreases in chemical oxygen demand (COD) and total organic carbon (TOC) content were observed. The photo-decomposition followed pseudo-firstorder kinetics. In addition, the toxicity of some by-products was tested using the earthworm (Eisenia andrei) avoidance test. High sensitivity of E. andrei towards soil wetted with MO solution was observed, while no effects were seen for the same solution after photocatalytic oxidation.

Effect of W doping level on TiO2 on the photocatalytic degradation of Diuron

In the present study, three compositions of W-doped titania nano-photocatalyst are synthesized via the sol-gel method. The powders obtained were characterized by X-ray diffraction, Raman spectroscopy and UV-visible diffuse reflectance spectroscopy. The photocatalytic performances of the different photocatalysts are tested with respect to the degradation of Diuron in water solutions under simulated solar light and visible light irradiation. The W0.03Ti0.97O2 catalyst exhibits better photoactivity than the pure TiO2 even under simulated solar light and visible light. This improvement in activity was attributed to photoelectron/hole separation efficiency.