Bisphenol A degradation and mineralization by the Fenton and the Photo-Fenton process

The performance of the Fenton and photo-Fenton processes for the degradation and mineralization of Bisphenol A was investigat-ed. A parameterized kinetic model was suitably fitted to the exper-imental data in order to determine two performance parameters related to the global equilibrium conversion and kinetic rate of the process. Further analysis allowed selecting those process condi-tions (iron and hydrogen peroxide load) that maximize the process performance. The Fenton process clearly proved to more efficient-ly degrade Bisphenol A under irradiation. The highest conversion rates were achieved with only the stoichiometric hydrogen perox-ide load and the appropriate iron load (i.e. total Bisphenol A elimination and 90 % TOC decay).Postprint (published version

Abatement of the fluorinated antidepressant fluoxetine (Prozac) and its reaction by-products by electrochemical advanced methods

The degradation of the fluorinated antidepressant fluoxetine, as hydrochloride, was comparatively studied in sulfate medium at pH 3.0 by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF). Experiments were performed with 100 mL solutions in an undivided tank reactor equipped with a Pt, RuO2-based or boron-doped diamond (BDD) anode and an air-diffusion cathode for continuous H2O2 production. The BDD anode showed higher mineralization rate due to the great production of physisorbed BDD(¿OH), which has larger reactivity to oxidize the drug and intermediates. The degradation rate was enhanced by EF with 0.50 mM Fe2+ due to the additional production of ¿OH in the bulk from Fenton's reaction. The degradation was even faster using PEF owing to the additional photolytic action of UVA radiation. The most effective process was PEF with a BDD anode achieving 94% mineralization at 300 min. The fluoxetine decay followed a pseudo-first-order kinetics, being quicker in the order: AO-H2O2 < EF < PEF. The effect of the current density and drug concentration on the mineralization rate and fluoxetine decay was clarified. Oxidation of fluoxetine by hydroxyl radicals yielded four aromatic by-products, as found by GC-MS. Additionally, a chloroaromatic compound was identified as a result of the reaction of active chlorine, which was formed in situ from the oxidation of chloride ion at the BDD anode. Four short-chain linear carboxylic acids, being oxalic and formic acid more abundant, were identified. In PEF, fluorine atoms of fluoxetine were completely released as fluoride ion, whereas the initial nitrogen was converted to nitrate ion in all cases. A reaction pathway for fluoxetine mineralization by the electrochemical advanced methods is finally proposed

Sonochemical synthesis of CuO nanostructures and their morphology dependent optical and visible light driven photocatalytic properties

A controlled synthesis of CuO nanostructures with various morphologies were successfully achieved by presence/absence of low frequency (42 kHz) ultrasound with two different methods. The size, shape and morphology of the CuO nanostructures were tailored by altering the ultrasound, mode of addition and solvent medium. The crystalline structure and molecular vibrational modes of the prepared nanostructures were analysed through X-ray diffraction and FTIR measurement, respectively which confirmed that the nanostructures were phase pure high-quality CuO with monoclinic crystal structure. The morphological evaluation and elemental composition analysis were done using TEM and EDS attached with SEM, respectively. Furthermore, we demonstrated that the prepared CuO nanostructures could be served as an effective photocatalyst towards the degradation of methyl orange (MO) under visible light irradiation. Among the various nanostructures, the spherical shape CuO nanostructures were found to have the better catalytic activities towards MO dye degradation. The catalytic degradation performance of MO in the presence of CuO nanostructures showed the following order: spherical\nanorod \layered oval \nanoleaf \triangular \shuttles structures. The influence of loading and reusability of catalyst revealed that the efficiency of visible light assisted degradation of MO was effectively enhanced and more than 95 % of degradation was achieved after 3 cycle

Sonophotocatalytic mineralization of Norflurazon in aqueous environment

Norflurazon (4-chloro-5-(methylamino)-2-[3- trifluoromethyl)phenyl]pyridazin-3(2H)-one; C12H9ClF3N3O) is an excellent weed controlling agent being practiced in the agricultural lands. The excessive addition or the undissolved Norflurazon (maximum solubility 28 mg/L at 25 C) enters into the aquatic environment and causes the adverse effects associated with its high concentration. To avoid the perilous effects, visible light assisted photocatalysis set-up coupled with the 42 kHz ultrasound producing bath type sonicator is used to completely mineralize the Norflurazon. TiO2, ZnO and gold loaded zinc oxide nanocatalysts were utilized to study the mineralization of Norflurazon. AueZnO shows the greater efficiency for the sonophotocatalytic removal of Norflurazon among the various nanocatalysts employed to study the mineralization. The order of Norflurazon mineralization was sonophotocatalysis > sonocatalysis > photocatalysis. The additive effect was achieved for the sonophotocatalytic degradation. The high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometric (LCMS) analyses were employed to identify the various intermediates produced during the mineralization. The identification of four pseudo molecular ions and various intermediates using the LCMS analysis evidently suggests the sonophotocatalytic degradation was preceded in various decay pathways. A suitable mechanism has been proposed for the sonophotocatalytic mineralization of Norflurazo

Microstructure, vibrational and visible emission properties of low frequency ultrasound (42 kHz) assisted ZnO nanostructures

Size and shape tuneable ZnO nanostructures were prepared by a low frequency ultrasound (42 kHz) route using various organic solvents as the reaction media. The crystalline nature, lattice parameters and microstructural parameters such as microstrain, stress and energy density of the prepared ZnO nanostructures were revealed through X-ray diffraction (XRD) analysis. The organic solvents influenced the size and morphology of the ZnO nanostructures, and interesting morphological changes involving a spherical to triangular shaped transition were observed. The visible emission properties and lattice vibrational characteristics of the nanostructures were drastically modified by the changes in size and shape. Raman spectral measurements revealed the presence of multiphonon processes in the ZnO nanostructures. The intensity of the visible emission band was found to vary with the size and morphology of the structures. The strongest visible emission band corresponded to the structure with the largest surface/volume ratio and could be attributed to surface oxygen vacancies. The control over the size and morphology of ZnO nanostructures has been presented as a means of determining the intensity of the visible emission ban

Experimental and computational investigation of the substituent effects on the reduction of Fe³⁺ by 1,2-dihydroxybenzenes

This study reports on the kinetics of the early steps that mediate the reactions of substituted 1,2-dihydroxybenzenes (1,2-DHB) with Fe³⁺. The rate constants of the three processes identified by means of the stopped-flow technique are affected by the electron-withdrawing or electron-donating abilities of the substituent. The fastest process is assigned to the formation of a 1 : 1 complex between Fe³⁺ and the 1,2-DHB, which is accompanied by proton loss. The second process involves the inner-sphere electron transfer from the ligand to Fe³⁺ and the slowest step is related to the deprotonation of one of the oxygen atoms bonded to the metal. A reaction mechanism is proposed on the basis of the experimental data and density functional theory (DFT) calculations on mono- and bidentate species with different degrees of protonation.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Automated lumen segmentation using multi-frame convolutional neural networks in Intravascular Ultrasound datasets

Aims: Assessment of minimum lumen areas in intravascular ultrasound (IVUS) pullbacks is time-consuming and demands adequately trained personnel. In this work, we introduce a novel and fully automated pipeline to segment the lumen boundary in IVUS datasets. Methods and results First, an automated gating is applied to select end-diastolic frames and bypass saw-tooth artefacts. Second, within a machine learning (ML) environment, we automatically segment the lumen boundary using a multi-frame (MF) convolutional neural network (MFCNN). Finally, we use the theory of Gaussian processes (GPs) to regress the final lumen boundary. The dataset consisted of 85 IVUS pullbacks (52 patients). The dataset was partitioned at the pullback-level using 73 pullbacks for training (20 586 frames), 6 pullbacks for validation (1692 frames), and 6 for testing (1692 frames). The degree of overlapping, between the ground truth and ML contours, median (interquartile range, IQR) systematically increased from 0.896 (0.874–0.933) for MF1 to 0.925 (0.911–0.948) for MF11. The median (IQR) of the distance error was also reduced from 3.83 (2.94–4.98)% for MF1 to 3.02 (2.25–3.95)% for MF11-GP. The corresponding median (IQR) in the lumen area error remained between 5.49 (2.50–10.50)% for MF1 and 5.12 (2.15–9.00)% for MF11-GP. The dispersion in the relative distance and area errors consistently decreased as we increased the number of frames, and also when the GP regressor was coupled to the MFCNN output. Conclusion: These results demonstrate that the proposed ML approach is suitable to effectively segment the lumen boundary in IVUS scans, reducing the burden of costly and time-consuming manual delineation.Fil: Ziemer, Paulo G. P.. Laboratorio Nacional de Computacao Cientifica; BrasilFil: Bulant, Carlos Alberto. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Orlando, José Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; ArgentinaFil: Maso Talou, Gonzalo D.. University of Auckland; Nueva ZelandaFil: Mansilla Álvarez, Luis A.. Laboratorio Nacional de Computacao Cientifica; BrasilFil: Guedes Bezerra, Cristiano. Universidade de Sao Paulo; BrasilFil: Lemos, Pedro A.. Universidade de Sao Paulo; BrasilFil: García García, Héctor M.. Georgetown University School of Medicine; Estados UnidosFil: Blanco, Pablo J.. Laboratorio Nacional de Computacao Cientifica; Brasi

Bisphenol A degradation and mineralization by the Fenton and the Photo-Fenton process

The performance of the Fenton and photo-Fenton processes for the degradation and mineralization of Bisphenol A was investigat-ed. A parameterized kinetic model was suitably fitted to the exper-imental data in order to determine two performance parameters related to the global equilibrium conversion and kinetic rate of the process. Further analysis allowed selecting those process condi-tions (iron and hydrogen peroxide load) that maximize the process performance. The Fenton process clearly proved to more efficient-ly degrade Bisphenol A under irradiation. The highest conversion rates were achieved with only the stoichiometric hydrogen perox-ide load and the appropriate iron load (i.e. total Bisphenol A elimination and 90 % TOC decay)

Solvothermal synthesis of BiOI microspheres: Effect of the reaction time on the morphology and photocatalytic activity

International audienceBiOI microspheres were synthesized by a solvothermal synthesis route from Bi(NO3)3*5H2O, using ethylene glycol in the presence of the ionic liquid 1-butyl-3-methylimidazolium iodide. The autoclave temperature was maintained constant at 120 °C and the reaction time was varied from 2 to 48 h. The obtained materials were characterized by XRD, SEM, TEM, EDS, nitrogen adsorption, FTIR and DRS. In addition, the photocatalytic activity of synthesized BiOI was evaluated in the oxidation of caffeic acid under simulated solar irradiation. Samples obtained between 12 and 24 h of synthesis present microsphere shapes and higher photocatalytic activity. All materials exhibit higher activities than TiO2 Evonik P25 used as standard catalyst

Bisphenol A degradation and mineralization by the Fenton and the Photo-Fenton process

The performance of the Fenton and photo-Fenton processes for the degradation and mineralization of Bisphenol A was investigat-ed. A parameterized kinetic model was suitably fitted to the exper-imental data in order to determine two performance parameters related to the global equilibrium conversion and kinetic rate of the process. Further analysis allowed selecting those process condi-tions (iron and hydrogen peroxide load) that maximize the process performance. The Fenton process clearly proved to more efficient-ly degrade Bisphenol A under irradiation. The highest conversion rates were achieved with only the stoichiometric hydrogen perox-ide load and the appropriate iron load (i.e. total Bisphenol A elimination and 90 % TOC decay)