Photocatalytic, sonocatalytic and sonophotocatalytic degradation of Rhodamine B using ZnO/CNTs composites photocatalysts

A series of ZnO nanoparticles decorated on multi-walled carbon nanotubes (ZnO/CNTs composites) was synthesized using a facile sol method. The intrinsic characteristics of as-prepared nanocomposites were studied using a variety of techniques including powder X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), transmission electron microscope (TEM), scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET) surface area analyzer and X-ray photoelectron spectroscopy (XPS). Optical properties studied using UV–Vis diffuse reflectance spectroscopy confirmed that the absorbance of ZnO increased in the visible-light region with the incorporation of CNTs. In this study, degradation of Rhodamine B (RhB) as a dye pollutant was investigated in the presence of pristine ZnO nanoparticles and ZnO/CNTs composites using photocatalysis and sonocatalysis systems separately and simultaneously. The adsorption was found to be an essential factor in the degradation of the dye. The linear transform of the Langmuir isotherm curve was further used to determine the characteristic parameters for ZnO and ZCC-5 samples which were: maximum absorbable dye quantity and adsorption equilibrium constant. The natural sunlight and low power ultrasound were used as an irradiation source. The experimental kinetic data followed the pseudo-first order model in photocatalytic, sonocatalytic and sonophotocatalytic processes but the rate constant of sonophotocatalysis is higher than the sum of it at photocatalysis and sonocatalysis process. The sonophotocatalysis was always faster than the respective individual processes due to the more formation of reactive radicals as well as the increase of the active surface area of ZnO/CNTs photocatalyst. Chemical oxygen demand (COD) of textile wastewater was measured at regular intervals to evaluate the mineralization of wastewater

Vaccine breakthrough hypoxemic COVID-19 pneumonia in patients with auto-Abs neutralizing type I IFNs

Life-threatening `breakthrough' cases of critical COVID-19 are attributed to poor or waning antibody response to the SARS- CoV-2 vaccine in individuals already at risk. Pre-existing autoantibodies (auto-Abs) neutralizing type I IFNs underlie at least 15% of critical COVID-19 pneumonia cases in unvaccinated individuals; however, their contribution to hypoxemic breakthrough cases in vaccinated people remains unknown. Here, we studied a cohort of 48 individuals ( age 20-86 years) who received 2 doses of an mRNA vaccine and developed a breakthrough infection with hypoxemic COVID-19 pneumonia 2 weeks to 4 months later. Antibody levels to the vaccine, neutralization of the virus, and auto- Abs to type I IFNs were measured in the plasma. Forty-two individuals had no known deficiency of B cell immunity and a normal antibody response to the vaccine. Among them, ten (24%) had auto-Abs neutralizing type I IFNs (aged 43-86 years). Eight of these ten patients had auto-Abs neutralizing both IFN-a2 and IFN-., while two neutralized IFN-omega only. No patient neutralized IFN-ss. Seven neutralized 10 ng/mL of type I IFNs, and three 100 pg/mL only. Seven patients neutralized SARS-CoV-2 D614G and the Delta variant (B.1.617.2) efficiently, while one patient neutralized Delta slightly less efficiently. Two of the three patients neutralizing only 100 pg/mL of type I IFNs neutralized both D61G and Delta less efficiently. Despite two mRNA vaccine inoculations and the presence of circulating antibodies capable of neutralizing SARS-CoV-2, auto-Abs neutralizing type I IFNs may underlie a significant proportion of hypoxemic COVID-19 pneumonia cases, highlighting the importance of this particularly vulnerable population

Étude de l'élimination de bleu de méthylène dans l'eau par le charbon actif commercial CECA40


The removal of methylene blue(BM) through adsorption over the commercial actived charcoal ( CECA 40) was studied in a static batch reactor. At constant pH and temperature the adsorption equilibrium time is equal to 5 hours regardless of the initial concentration of metylene blue (BM). The adsorption in this case follows a Langmuir isotherm of the first type with an ultimate adsorption capacity of about 367,6 mg of methylene blue for each gram of CECA 40. Moreover, we observed no significant influence of temperature on the adsorption equilibrium. The adsorption and the Intraparticular diffusion kinectics were studied. Adsorption is clearly higher in an alcaline environment than in the acid one. This adsorption is further improved by the use of finer granulometry

Experimental investigation of the propagation of a planar shock wave through a two-phase gas-liquid medium

International audienceWe conducted a series of shock tube experiments to study the influence of a cloud of water droplets on the propagation of a planar shock wave. In a vertically oriented shock tube, the cloud of droplets was released downwards into the air at atmospheric pressure while the shock wave propagated upwards. Two shock wave Mach numbers, 1.3 and 1.5, and three different heights of clouds, 150 mm, 400 mm, and 700 mm, were tested with an air-water volume fraction and a droplet diameter fixed at 1.2% and 500 mu m, respectively. From high-speed visualization and pressure measurements, we analyzed the effect of water clouds on the propagation of the shock wave. It was shown that the pressure histories recorded in the two-phase gas-liquid mixture are different from those previously obtained in the gas-solid case. This different behavior is attributed to the process of atomization of the droplets, which is absent in the gas-solid medium. Finally, it was observed that the shock wave attenuation was dependent on the exchange surface crossed by the shock combined with the breakup criterion. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3657083

Fate of nitrogen atoms in the photocatalytic degradation of industrial (congo red) and alimentary (amaranth) azo dyes. Evidence for mineralization into gaseous dinitrogen

The photocatalytic degradation of two azo-dyes–an industrial one (Congo Red (CR)), and an alimentary one (Amaranth (AM))–has been investigated in TiO2/UV aqueous suspensions. In addition to a prompt removal of the colors, TiO2/UV-based photocatalysis was simultaneously able to fully oxidize the dyes, with a complete mineralization of organic carbon into CO2. In particular, the aromatic rings were submitted to successive attacks by photogenerated OH∘ radicals leading to hydroxylated metabolites before the ring opening and the final evolution of CO2 induced by repeated subsequent “photo-Kolbe” reactions with carboxylic intermediates. Simultaneously, sulfur heteroatoms were converted into innocuous SO42− ions. The mineralization of nitrogen was more complex to analyze. Nitrogen atoms in the -3 oxidation state, such as in the amino-groups of CR, initially remained at this reduction degree and produced NH4+ cations, subsequently and very slowly converted into NO3− anions. For both azo-dyes (CR and AM) degradation, the overall mass balance in nitrogen was always found incomplete. Various experiments performed in pure oxygen in a vacuum-tight cell and then in an air-free photoreactor (but filled with pure oxygen) enabled us to put in evidence the formation of N2. Quantitative measurements clearly indicated that gaseous dinitrogen evolved stoichiometrically corresponded to the mineralization of the central –N=N– azo-group. This constitutes the ideal issue for the elimination of nitrogen-containing pollutants, not only for environmental photocatalysis but also for any other physicochemical method. These results suggest that TiO2/UV photocatalysis may be envisaged as a method for treatment of diluted colored waste waters not only for decolorization but also for total detoxification, in particular in textile industries in semi-arid countries

Experimental and numerical investigations of a shock wave propagation through a bifurcation

International audienceThe propagation of a planar shock wave through a split channel is both experimentally and numerically studied. Experiments were conducted in a square cross-section shock tube having a main channel which splits into two symmetric secondary channels, for three different shock wave Mach numbers ranging from about 1.1 to 1.7. High-speed schlieren visualizations were used along with pressure measurements to analyze the main physical mechanisms that govern shock wave diffraction. It is shown that the flow behind the transmitted shock wave through the bifurcation resulted in a highly two dimensional unsteady and non-uniform flow accompanied with significant pressure loss. In parallel , numerical simulations using a personal code based on the solution of the Euler equations with a second-order Go-dunov scheme confirmed the experimental results with a good agreement. Finally, a parametric study was carried out using numerical analysis where the angular displacement of the two channels that define the bifurcation was changed from 90 • ,45 • , 20 • and 0 •. We found that the angular displacement does not significantly affect the overpressure experience in either of the two channels and that the area of the expansion region is the important variable affecting overpressure; the effect being, in the present case, a decrease of almost one half

Experimental and numerical investigations of a shock wave propagation through a bifurcation

International audienceThe propagation of a planar shock wave through a split channel is both experimentally and numerically studied. Experiments were conducted in a square cross-section shock tube having a main channel which splits into two symmetric secondary channels, for three different shock wave Mach numbers ranging from about 1.1 to 1.7. High-speed schlieren visualizations were used along with pressure measurements to analyze the main physical mechanisms that govern shock wave diffraction. It is shown that the flow behind the transmitted shock wave through the bifurcation resulted in a highly two dimensional unsteady and non-uniform flow accompanied with significant pressure loss. In parallel , numerical simulations using a personal code based on the solution of the Euler equations with a second-order Go-dunov scheme confirmed the experimental results with a good agreement. Finally, a parametric study was carried out using numerical analysis where the angular displacement of the two channels that define the bifurcation was changed from 90 • ,45 • , 20 • and 0 •. We found that the angular displacement does not significantly affect the overpressure experience in either of the two channels and that the area of the expansion region is the important variable affecting overpressure; the effect being, in the present case, a decrease of almost one half