Pt Modified Heterogeneous Catalysts Combined with Ozonation for the Removal of Diclofenac from Aqueous Solutions and the Fate of by-Products

The degradation of the pharmaceutical compound diclofenac in an aqueous solution was studied with an advanced oxidation method, catalytic ozonation. Diclofenac was destroyed in a few minutes by ozonation but several long-lasting degradation by-products were formed. For this reason, the combination of heterogeneous catalysts and ozonation was applied to eliminate them completely. The kinetics of the diclofenac degradation and the formation of by-products were thoroughly investigated. Loading of Pt on the catalysts resulted in an improvement of the activity. The Mesoporous Molecular Sieves (MCM) were one of the promising catalysts for the degradation of organic pollutants. In this study, six heterogeneous catalysts were screened, primarily MCM-22-100 catalysts with different Pt concentrations loaded via the evaporation-impregnation (EIM) method, and they were applied on the degradation of diclofenac. It was found that the presence of Pt improved the degradation of diclofenac and gave lower concentrations of by-products. The 2 wt % Pt-H-MCM-22-100-EIM demonstrated the highest degradation rate compared to the proton form, 1% or 5 wt % Pt concentration, i.e., an optimum was found in between. Pt-H-Y-12-IE and Pt-gamma-Al2O3 (UOP)-IMP catalysts were applied and compared with the MCM-22 structure. Upon use of both of these catalysts, an improvement in the degradation of diclofenac and by-products was observed, and the 2 wt % Pt-H-MCM-22-100-EIM illustrated the maximum activity. All important characterization methods were applied to understand the behavior of the catalysts (X-ray powder diffraction, transmission electron microscopy, nitrogen physisorption, scanning electron microscopy, energy dispersive X-ray micro-analyses, pyridine adsorption-desorption with FTIR spectroscopy, X-ray photoelectron spectroscopy). Finally, leaching of Pt and Al were analyzed by inductively coupled optical emission spectrometry

Hydrodeoxygenation of Isoeugenol over Carbon-Supported Pt and Pt-Re Catalysts for Production of Renewable Jet Fuel

A series of monometallic platinum and bimetallic platinum-rhenium catalysts supported on mesoporous carbon Sibunit, which is a type of mesoporous, microcrystalline carbon, were investigated for hydrodeoxygenation (HDO) of isoeugenol (IE) at 200-300 degrees C and 30 bar of H-2, using dodecane as a solvent. Catalytic activity was tested in a batch reactor to screen the catalysts and, for comparison, also in the continuous mode. For batch experiments, complete conversion, and a high yield of the desired product, propylcyclohexane (PCH), were obtained for all bimetallic PtRe/Sibunit in 240 min, with the highest yield of PCH when Pt:Re ratio was 1:1 or 1:3. The results for Pt-Re (1:1) were reproducible, in terms of catalytic activity and reusability of catalysts, which showed no deactivation. Monometallic Pt catalysts displayed low activity. Continuous experiments were performed with PtRe(1:1)/Sibunit at 30 bar H-2, 0.5 mL/min of the liquid flow, and temperatures between 75 degrees C and 200 degrees C. The distribution of products showed deoxygenation at higher temperatures, while at lower temperatures, mainly oxygenated products were formed. XPS results confirmed the presence of ReOx species, where an increase in the platinum loading resulted in a decrease in the fraction of ReOx species and subsequently lower PCH yield

XPS spectra from nucleobases, DNA, and RNA

X-ray photoelectron spectroscopy was used to analyze commercially available powders of thymine, uracil, cytosine, guanine, adenine, as well as DNA isolated from salmon testes and RNA from torula yeast. The powders were pressed onto a sample holder and analyzed as received from the manufacturer. Survey spectra and high-resolution spectra of O 1s, N 1s, C 1s of all nucleobases are reported, including a small Na 1s contamination in cytosine. Spectra of DNA and RNA are also included for comparison. Furthermore, the presented data are compared with previously published results, as well as theoretical values, and differences are discussed

Cryo-XPS spectra from bacterial reference strain Pseudomonas fluorescens DSM50090

Cryogenic x-ray photoelectron spectroscopy was used to analyze the cell envelope of intact and hydrated Gram-negative bacteria of the species Pseudomonas fluorescens. We used a reference strain, DSM50090, from the German microbial culture collection, which we previously have suggested would function well as a reference strain for future XPS analyses of Gram-negative bacteria. Bacteria were grown on nutrient agar plates at room temperature, collected with a cultivation loop, and washed using phosphate buffered saline. An aliquot of the cell pellet was fast-frozen on the sample holder in the sample introduction chamber to a temperature of 103 K and kept frozen throughout the measurement. Survey spectra and high-resolution spectra of Na 1s, O 1s, N 1s, C 1s, Cl 2p, S 2p, and P 2p are reported. The spectra obtained from the analyzed cells represent a combined signal from O, N, C, and S atoms in proteins, lipids, and polysaccharides at the cell surface. Furthermore, signal from P, Na, K, and Cl atoms was present both originating from processes in the cell envelope and remnants from the wash buffer

Cryo-XPS analysis reveals surface composition of microalgae

Green microalgae are widely used for wastewater treatment, food/feed and pigment production, as well as for aquaculture. However, very little is known about their surface composition, which can determine algae behavior in nature and influence their processing. In this work, we use cryo-XPS to characterize the surface chemical composition of three different microalgae species. We investigate the applicability of a data treatment method, developed for bacteria, deconvoluting C 1s with respect to protein, lipid and polysaccharide. We discuss how substances unique to algae contribute to the C 1s spectra and how this affects the transferability of the method to microalgae. Two species of green microalgae isolated from Northern Sweden, Chlorella vulgaris 13-1 and Coelastrella sp. 3-4, were compared to reference culture collection strain, Scenedesmus obliquus RISE (UTEX 417). Cryo-XPS data indicate that surfaces of Coelastrella sp. 3-4 and C. vulgaris 13-1 cells are dominated by protein and carbohydrates. However, the carbohydrate content was higher for C. vulgaris. The reference strain shows the highest content of proteins and has an increased amount of lipids compared to the other two. Estimation of the cell surface hydrophobicity suggests that the hydrophobicity increases in the order: C. vulgaris < Coelastrella sp. < S. obliquus

Kinetics and Mechanisms of Ciprofloxacin Oxidation on Hematite Surfaces

International audienceAdsorption of antibiotics at mineral surfaces has been extensively studied over the past 20 years, yet much remains to be learned on their interfacial properties and transformation mechanisms. In this study, interactions of Ciprofloxacin (CIP), a fluoroquinolone antibiotic with two sets of synthetic nanosized hematite particles, with relatively smooth (H10, 10-20 nm in diam.) and roughened (H80, 80-90 nm in diam.) surfaces, were studied by means of liq. chromatog. (LC), mass spectrometry (MS), and spectroscopy (vibration and X-ray photoelectron). Attenuated Total Reflectance Fourier Transform IR (ATR-FTIR) spectroscopy provides evidence for inner-sphere bidentate complex formation of CIP at hematite surfaces in 0.01 M NaCl, irresp. of pH and particle size. ATR-FTIR spectroscopy also revealed that the sorbed mother CIP mol. decayed to other surface species over a period of at least 65 h. This was supported by the detection of three daughter products in the aq. phase by LC/MS. The appearance of NH3+ groups during the course of these expts., revealed by cryogenic XPS, provides further evidence that CIP oxidn. proceeds through an opening of piperazine ring via N-dealkylation. Addnl. in vacuo FTIR expts. under temp.-programmed desorption also showed that oxidn. of sorbed byproducts were effectively degraded beyond 450 °C, a result denoting considerably strong (inter)mol. bonds of both mother and daughter products. This work also showed that rougher, possibly multidomainic particles (H80) generated slower rates of CIP decompn. but occurring through more complex schemes than at smoother particle surfaces (H10). This work thus uncovered key aspects of the binding of an important antibiotic at iron oxide surfaces, and therefore provided addnl. constraints to our growing understanding of the fate of emerging contaminants in the environment

Competing commercial catalysts: Unprecedented catalyst activity and stability of Mizoroki-Heck reaction in a continuous packed bed reactor

Main obstacle for adopting continuous processes as a standard technology for Mizoroki-Heck reaction usually lies in its specific reaction mechanism. Here we present an important step forward answering the challenges unraveled through a comprehensive study that provides deeper understanding on the Mizoroki-Heck reaction, in particular the case when iodobenzene and butyl acrylate react in a continuous packed bed reactor in the presence of a Pd Supported Ionic Liquid Catalyst (SILCA). On-line UV–VIS spectrometry supported by ICP-OES, TEM and XPS measurements were carried out and the catalyst leaching was minimized. Finally, simple continuous flow process was proposed resulting in a high catalytic activity (up to 1470 molArI molPd−1h−1) and reaching productivity in the range of 12,000 to 16,000 molArI molPd−1 thus competing with the performance of commercial catalysts.Volume 433, Part 1.</p

Cobalt- doped hematite thin films for electrocatalytic water oxidation in highly acidic media

Earth-abundant cobalt-doped hematite thin-film electrocatalysts were explored for acidic water oxidation. The strategically doped hematite produced a stable geometric current density of 10 mA cm(-2) for up to 50 h at pH 0.3, as a result of Co-enhanced intrinsic catalytic activity and charge transport properties across the film matrix