C2 Fraction Research Articles

Coprecipitation preparation of copper -cobalt based catalysts for higher alcohol production

A series of K modified coppercobalt based catalysts were prepared using step by step continuous coprecipitation method, and the catalytic performance of the catalysts was investigated. The experimental results showed that the catalyst exhibited the best activity, CO conversion, the yield of C₂+OH in liquid products and the mass fraction of C₂+OH was 65.74%,0.062 g·(mL·h)-I and 18.95%, respectively, under the condition as follows: mass ratio of cobalt to copper 1:1, K₂CO₃ loading mass fraction 1%, pH=7.2 and reaction temperature 310 ℃.

Direct OC-CHO coupling towards highly C2+ products selective electroreduction over stable Cu0/Cu2+ interface

Electroreduction of CO2 to valuable multicarbon (C2+) products is a highly attractive way to utilize and divert emitted CO2. However, a major fraction of C2+ selectivity is confined to less than 90% by the difficulty of coupling C-C bonds efficiently. Herein, we identify the stable Cu0/Cu2+ interfaces derived from copper phosphate-based (CuPO) electrocatalysts, which can facilitate C2+ production with a low-energy pathway of OC-CHO coupling verified by in situ spectra studies and theoretical calculations. The CuPO precatalyst shows a high Faradaic efficiency (FE) of 69.7% towards C2H4 in an H-cell, and exhibits a significant FEC2+ of 90.9% under industrially relevant current density (j = −350 mA cm−2) in a flow cell configuration. The stable Cu0/Cu2+ interface breaks new ground for the structural design of electrocatalysts and the construction of synergistic active sites to improve the activity and selectivity of valuable C2+ products.

Monoisotopic targets production from atomic and molecular positive ion implantation in a tandem accelerator at low energies

We produced monoisotopic targets of 13C and 28,29Si with 1015−16 atoms/cm2 areal density by ion implantation in different matrices at the Accelerator Mass Spectrometry (AMS) facility in Mexico. The tandem accelerator terminal voltage was set at the lowest achievable value (200 kV) that yield beams with energy of 435 keV. It is possible to do ion implantation at lower energies in our facility through the use of molecular beams, so in this work we looked for, and successfully found, bound positively charged molecular beams, although with very low intensity. We inject 235 keV molecules into the charge of exchange canal (argon) of our tandem accelerator and detected the survival fraction of C2,3,4 molecules in 1+ and 2+ charge states or above. Our results showed that some molecules remain bound, with one or more electrons missing, after being forced through a low density gas stripper at relatively high energy. In the production process of negative molecular fluxes in the Source of Negative Ions by Cesium Sputtering (SNICS) we found an odd-even effect in their intensity that we understand as the coupling between the fragment size distribution of a dynamic fragmentation of graphite by cesium impact and the electron affinity of the molecules with n-carbon atoms. The availability of these kind of high energy molecular beams opens the door for discovery both in the study of the physics of negative and positive molecular ions.

Patient-specific transfer learning for auto-segmentation in adaptive 0.35 T MRgRT of prostate cancer: a bi-centric evaluation.

Online adaptive radiation therapy (RT) using hybrid magnetic resonance linear accelerators (MR-Linacs) can administer a tailored radiation dose at each treatment fraction. Daily MR imaging followed by organ and target segmentation adjustments allow to capture anatomical changes, improve target volume coverage, and reduce the risk of side effects. The introduction of automatic segmentation techniques could help to further improve the online adaptive workflow by shortening the re-contouring time and reducing intra- and inter-observer variability. In fractionated RT, prior knowledge, such as planning images and manual expert contours, is usually available before irradiation, but not used by current artificial intelligence-based autocontouringapproaches. The goal of this study was to train convolutional neural networks (CNNs) for automatic segmentation of bladder, rectum (organs at risk, OARs), and clinical target volume (CTV) for prostate cancer patients treated at 0.35 T MR-Linacs. Furthermore, we tested the CNNs generalization on data from independent facilities and compared them with the MR-Linac treatment planning system (TPS) propagated structures currently used in clinics. Finally, expert planning delineations were utilized for patient- (PS) and facility-specific (FS) transfer learning to improve auto-segmentation of CTV and OARs on fractionimages. In this study, data from fractionated treatments at 0.35T MR-Linacs were leveraged to develop a 3D U-Net-based automatic segmentation. Cohort C1 had 73 planning images and cohort C2 had 19 planning and 240 fraction images. The baseline models (BMs) were trained solely on C1 planning data using 53 MRIs for training and 10 for validation. To assess their accuracy, the models were tested on three data subsets: (i) 10 C1 planning images not used for training, (ii) 19 C2 planning, and (iii) 240 C2 fraction images. BMs also served as a starting point for FS and PS transfer learning, where the planning images from C2 were used for network parameter fine tuning. The segmentation output of the different trained models was compared against expert ground truth by means of geometric metrics. Moreover, a trained physician graded the network segmentations as well as the segmentations propagated by the clinicalTPS. The BMs showed dice similarity coefficients (DSC) of 0.88(4) and 0.93(3) for the rectum and the bladder, respectively, independent of the facility. CTV segmentation with the BM was the best for intermediate- and high-risk cancer patients from C1 with DSC=0.84(5) and worst for C2 with DSC=0.74(7). The PS transfer learning brought a significant improvement in the CTV segmentation, yielding DSC=0.72(4) for post-prostatectomy and low-risk patients and DSC=0.88(5) for intermediate- and high-risk patients. The FS training did not improve the segmentation accuracy considerably. The physician's assessment of the TPS-propagated versus network-generated structures showed a clear advantage of thelatter. The obtained results showed that the presented segmentation technique has potential to improve automatic segmentation for MR-guidedRT.

Metal-organic framework (MOF) derived porous NiCo2O4 and ZnCo2O4 spinels with high microwave absorption performance for environmentally friendly EMI shielding applications

Sheet-like NiCo2O4 and ZnCo2O4 spinels were prepared by metal-organic framework (MOF) as sacrificial template to derive into porous microwave absorber materials. The NiCo and ZnCo MOFs obtained by using 2-methylimidazole linker were decomposed to the sheet-like NiCo2O4 and ZnCo2O4 powders, respectively, with the similar specific surface area of 75 m2/g and the pore volume of 0.31 cm3/g. However, the NiCo2O4 and ZnCo2O4 absorbers had the distinct microwave absorption performance on account of their various physicochemical properties caused by the nature of Ni and Zn elements. From the practical viewpoint, the MOF-derived NiCo2O4 sample had the broader effective absorption bandwidth (>3 GHz) at smaller thicknesses (<3 mm) in the Ku and X bands, whereas a significant fraction of C2, C1, and S bands could be absorbed by the MOF-derived ZnCo2O4 sample.

Tuning chemical environment and synergistic relay reaction to promote higher alcohols synthesis via syngas conversion

Higher alcohols synthesis (HAS) from syngas with high selectivity attracts great attention but remains challenging. Herein, we reported an effective strategy by tuning chemical environment and synergistic relay reaction to promote the production of higher alcohols. CO insertion rate was greatly enhanced by introducing Rh or Ru component to CoMn oxides. The catalytic activity and oxygenates selectivity increased dramatically over the as-obtained Rh-CoMn or Ru-CoMn catalyst, while the fraction of C2+OH in oxygenates maintained >92 %. Multiple studies demonstrated the highly dispersed Rhδ+ or Ruδ+ species not only effectively tuned the chemical environment and facilitated the stable existence of Co2C, but also catalyzed the coupling of syngas and in-situ generated olefins to produce extra oxygenates via hydroformylation route. The synergistic effect of Co0, Co2C and Rhδ+ (or Ruδ+) species, as well as the promotional effect of olefins relay reaction contributed to the enhancement in both higher alcohols selectivity and CO conversion.

Cu-Promoted Iron Catalysts Supported on Nanorod-Structured Mn-Ce Mixed Oxides for Higher Alcohol Synthesis from Syngas

A series of supports were prepared through the method of hydrothermal synthesis, and copper–iron catalysts supported on ceria nanorods modified by different amounts of manganese were prepared by the liquid phase co-reduction method. The effect of the catalytic performance after Mn addition mainly on higher alcohols synthesis (HAS) was evaluated. Different techniques, such as BET, ICP-AES, XRD, H2-TPR, CO-TPD, TEM, FESEM, XPS and MES, were performed for catalyst characterization. The results indicated that the abilities of CO chemical desorption and carbon chain growth were promoted with appropriate Mn addition, and higher ratio of Cu0/Cu+ species facilitated the methanol homologous reaction and the C2+OH formation. The Ce4+ species were reduced into Ce3+ species during HAS process, providing a large amount of oxygen vacancies. Proper Mn content promoted the formation of χ-Fe5C2 and leaded to the Fe 2p binding energy shift, causing the electron transformation between Fe and Mn species. The largest weight selectivity of C2+OH appeared in the reaction over CuFe/3.6MnCe catalyst with CO conversion 41.43%, and weight fraction of C2+OH 84.41 wt% in the alcohols distribution.

Attapulgite supported Cu-Fe-Co based catalyst combination system for CO hydrogenation to lower alcohols

Attapulgite (ATP) and ATP mixed with SiO2 microspheres (ATPS) supported Cu-Fe-Co modified Fischer-Tropsch (F-T) catalysts were prepared by impregnation method (IM) and impregnation-solution combustion method (IMSC). The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), hydrogen temperature-programmed reduction (H2-TPR) and CO2-temperature programmed desorption (CO2-TPD). The catalysts were also applied to lower alcohols synthesis from CO hydrogenation. Results show that the IMSC method is much beneficial for the loading, dispersion and reduction of CuO on the prepared catalyst than IM method, which promotes the touch of H2 and CO with Cu active site. The optimum reaction temperature for lower alcohols synthesis is 280°C for the catalysts prepared by both methods. Through the optimization of catalyst combination system between ATP and ATPS supported Cu-Fe-Co based catalysts (CFCK/ATP, CFCK/ATPS) and Cu/ZnO/Al2O3 catalyst (CZA) for methanol synthesis, the ideal catalyst combination system, CZA||CFCK/ATPS-IMSC, is obtained for lower alcohols synthesis. For the dual-bed configuration, a lower alcohols selectivity of 39.6% with the fraction of C2+ alcohols of 22.7% in oxygenates is achieved at CO conversion of 46.3% via the product conversion coupling effect.

Non-isothermal kinetics of biomass-pyrolysis-derived-tar (BPDT) thermal decomposition via thermogravimetric analysis

Thermal decomposition kinetics of biomass-pyrolysis-derived-tar (BPDT) was studied via non-isothermal thermogravimetric analysis. Single-step kinetics results from iso-conversional procedure showed the kinetic of BPDT thermal decomposition had apparent activation energy of E0=79.6kJ/mol, pre-exponential factor of A0=2.42E7s−1, and reaction order of n=4.6. Single-step reaction was not suitable for BPDT thermal decomposition, since the apparent activation energy varied largely with the conversion. The first step was controlled by diffusion with activation energy of E1=36.6kJ/mol. The second step which was main contributed step (fraction of c2=0.93) followed a reaction order mechanism of f(α)=(1−α)2.26 with activation energy of E2=44.6kJ/mol. Distributed activation energy model (DAEM) was also investigated using Gaussian, Gamma, Weibull, Logistic, Rayleigh and Log-normal distributions. According to calculated results different DAEMs, energy compensation effect was found to be reasonable. Although the fitting goodness of different DAEMs were very well, Akaike Information Criteria (AIC) test showed that the Rayleigh DAEM was the most suitable kinetic model for BPDT thermal decomposition.

Pharmacokinetics in Wistar Rats of 5-[(4-Carboxybutanoyl)Amino]-2-Hydroxybenzoic Acid: A Novel Synthetic Derivative of 5-Aminosalicylic Acid (5-ASA) with Possible Anti-Inflammatory Activity.

5-[(4-carboxybutanoyl)amino]-2-hydroxybenzoic acid (C2) is a novel synthetic derivative of 5-aminosalicylic acid (5-ASA), which is currently being evaluated ex vivo as an anti-inflammatory agent and has shown satisfactory results. This study aimed to obtain the pharmacokinetic profiles, tissue distribution and plasma protein binding of C2 in Wistar Rats. Additionally, an HPLC method was developed and validated to quantify C2 in rat plasma. The pharmacokinetic profiles of intragastric, intravenous and intraperitoneal administration routes at singles doses of 100, 50, and 100 mg/kg, respectively, were studied in Wistar rats. The elimination half-life of intravenously administered C2 was approximately 33 min. The maximum plasma level of C2 was reached approximately 24 min after intragastric administration, with a Cmax value of 2.5 g/mL and an AUCtot value of 157 μg min-1/mL; the oral bioavailability was approximately 13%. Following a single intragastric or oral dose (100 mg/kg), C2 was distributed and detected in all examined tissues (including the brain and colon). The results showed that C2 accumulates over time. The plasma protein binding results indicated that the unbound fraction of C2 at concentrations of 1 to 20 μg/mL ranged from 89.8% to 92.5%, meaning that this fraction of C2 is available to cross tissues. Finally, the blood-plasma partitioning (BP ratio) of C2 in rat plasma was 0.71 and 0.6 at concentrations of 5 and 10 μg/mL, respectively, which indicates that C2 is free in the plasmatic phase and not inside blood cells. The results of this study suggest that a fraction of the administered C2 dose is absorbed in the stomach, and the fraction that is not absorbed reaches the small intestine and colon. This distribution constitutes the main advantage of C2 compared with 5-ASA for the treatment of ulcerative colitis (UC) and Crohn's disease (CD).

Engineering of a Synthetic Metabolic Pathway for the Assimilation of (d)-Xylose into Value-Added Chemicals.

A synthetic pathway for (d)-xylose assimilation was stoichiometrically evaluated and implemented in Escherichia coli strains. The pathway proceeds via isomerization of (d)-xylose to (d)-xylulose, phosphorylation of (d)-xylulose to obtain (d)-xylulose-1-phosphate (X1P), and aldolytic cleavage of the latter to yield glycolaldehyde and DHAP. Stoichiometric analyses showed that this pathway provides access to ethylene glycol with a theoretical molar yield of 1. Alternatively, both glycolaldehyde and DHAP can be converted to glycolic acid with a theoretical yield that is 20% higher than for the exclusive production of this acid via the glyoxylate shunt. Simultaneous expression of xylulose-1 kinase and X1P aldolase activities, provided by human ketohexokinase-C and human aldolase-B, respectively, restored growth of a (d)-xylulose-5-kinase mutant on xylose. This strain produced ethylene glycol as the major metabolic endproduct. Metabolic engineering provided strains that assimilated the entire C2 fraction into the central metabolism or that produced 4.3 g/L glycolic acid at a molar yield of 0.9 in shake flasks.

Conformational study of some 4′-substituted 2-(phenylselanyl)-2-(ethylsulfanyl)-acetophenones

The conformational analysis of some 4′-substituted 2-(phenylselanyl)-2-(ethylsulfanyl)-acetophenones bearing the substituents NO2 (1), Br (2), H (3), Me (4) and OMe (5) was performed by νCO IR analysis, B3LYP/6-31+G(d,p) and single point polarisable continuum model (PCM) calculations, along with NBO analysis for 1, 3 and 5. Calculations for 1–5 indicate the existence of three stable conformations, c1, c2 and c3, whose stability depends on the balance between electrostatic and orbital interactions that are strictly related to the geometrical arrangement. The comparison between the experimental IR spectra in solution and the computed data in gas phase for 1–5 allows the c1 conformer to be assigned to the less intense component at higher frequency of the carbonyl doublet and both the c2 and c3 ones to the more intense lower frequency component. The sum of the calculated molar fraction of c2 and c3 conformers decreases from 95% to 63% on going from 1 to 5 (in gas phase), and this trend compares well with the PCM calculations and the IR experimental data for the majority of the solvents for all compounds 1–5. The NBO analysis for 1, 3 and 5 shows that the sum of the relevant orbital delocalization energies for the c1, c2 and c3 conformers is almost constant and does not match the computed stability order. The lowest stability of the c1 conformer for 1–3 can be related to the small value of the α dihedral angle that enables a strong electrostatic destabilizing repulsion between the OCOδ−…Sδ− atoms. The relative stability of the c1 conformer increases for 4 and 5 as the α dihedral angle enlarges and the repulsion is minimized. Moreover, the strong repulsive field effect between the Cδ+Oδ− and Cδ+Sδ− dipoles exerted to a greater extent on the c1 conformers of 1–3 with respect to 4 and 5, causes a major increase of the corresponding CO bond orders and related carbonyl frequencies. For the c2 conformer, the electrostatic destabilizing repulsion between the Oδ−…Seδ− atoms is weaker than that involving the Oδ−…Sδ− atoms in the c1 conformer and therefore has negligible effects on the conformer stability that is mainly determined by the sum of the orbital interactions. The c3 conformer has the shortest Sδ−…Seδ− contact for all compounds and thus the related electrostatic repulsion seems to be the most important factor that affects its stability. In conclusion, the computed order of stability of the three conformers for 1–5 depends on the electrostatic repulsions between close charged atoms rather than on the sum of the orbital delocalization energies that are quite similar for all the conformers.

The genetic algorithm based back propagation neural network for MMP prediction in CO2-EOR process

In this study, a genetic algorithm based back propagation artificial neural network model was developed and used to predict the minimum miscibility pressure, i.e. MMP, for both pure and impure CO2 injection cases. Ten parameters that affecting the MMP were chosen as input variables, while the MMP was selected as output parameter. These parameters were reservoir temperature-TR, mole fraction of volatile oil components-xvol, mole fraction of intermediate oil components-xint, mole fraction of C5–C6 oil components-xC5-C6, molecular weight of C7+ components-MWC7+, mole fraction of CO2 in solvent-xCO2, mole fraction of C1 in solvent-xC1, mole fraction of N2 in solvent-xN2, mole fraction of H2S in solvent-xH2S, and mole fraction of C2–C4 in solvent-xC2–C4. The performance of the newly developed model was evaluated by calculating the deviations between the predicted and the target values, and was compared with four well known correlations in published literature. Through the comparison, it can be found that our new model outperformed those four correlations with the lowest average absolute relative error of 5.51% and mean square error of 7.01%. The influence degrees of each factor on MMP were also analyzed qualitatively and quantitatively by sensitivity analysis. It was found that xint, xC5–C6, and xH2S have positive effects on MMP, while TR, xvol, MWC7+, xCO2, xC1, and xN2 have negative effects on MMP. In addition, the effect of xC2–C4 on MMP can be neglected. Furthermore, the variations of MMP with the increase of each factor were also considered, and it can be found that the slopes of these curves are not constant all the time and change with the variations of the influence factors.

Catalytic gasification of tars from a dumping site

The work deals with catalytic gasification, pyrolysis and non-catalytic gasification of tar from an industrial dumping site. All experiments were carried out in a vertical stainless steel gasification reactor at 800 °C. Crushed calcined dolomite was used as the gasification catalyst. Parameters such as addition of water and air, and the influence of the catalyst in regard to the composition of the process gas were investigated. The catalytic gasification experiment in the steady state produced process gas with the composition: 56 % of H2, 9 % of CO, 11 % of CH4 and 12 % of CO2 (mol.%). Concentration of the C2 fraction was lower than 1 mol.%. Volume flow of air was later changed from 120 to 230 ml min−1 reducing the amount of hydrogen to 51 mol.% and that of methane to 10 mol.%. Process gas created in a non-catalytic gasification process contained 26–30 mol.% of methane, 13–15 mol.% of carbon monoxide and 15–17 mol.% of the C2 fraction and lower amounts of hydrogen (20 mol.%) and carbon dioxide (2–3 mol.%). The highest apparent conversion of tar was reached in the catalytic gasification processes. A higher rate of catalyst deactivation can be observed when water or air is not added.

Properties of fast carbon cluster microbeams produced with a tapered capillary

We study the transmission properties of fast cluster ions (Cn+ (n=2–4) with velocities ranging from 0.89 to 1.79a.u.) through a single tapered capillary with an outlet diameter of 13.7μm. We investigate the projectile-velocity dependence of the transmission fraction from the measurements of transmitted particle energy spectra. It is found that the non-fragmentation fraction of C2+ projectiles increases with decreasing velocity, indicating that fragmentation occurs mainly via close collisions with the surfaces of the capillary wall. For Cn+ (n=2–4) ions with the same incident velocity, the cluster-size dependence of the non-fragmentation fraction shows even–odd alternation, implying that the fraction includes contributions from stable clusters surviving the grazing scattering process at the capillary surface. We also find that the angular distribution of transmitted particles is narrower for cluster projectiles compared with atomic projectiles.

A novel bioactive peptide from yoghurts modulates expression of the gel-forming MUC2 mucin as well as population of goblet cells and Paneth cells along the small intestine

Several studies demonstrated that fermented milks may provide a large number of bioactive peptides into the gastrointestinal tract. We previously showed that beta-casomorphin-7, an opioid-like peptide produced from bovine β-casein, strongly stimulates intestinal mucin production in ex vivo and in vitro models, suggesting the potential benefit of milk bioactive peptides on intestinal protection. In the present study, we tested the hypothesis that the total peptide pool (TPP) from a fermented milk (yoghurt) may act on human intestinal mucus-producing cells (HT29-MTX) to induce mucin expression. Our aim was then to identify the peptide(s) carrying the biological activity and to study its impact in vivo on factors involved in gut protection after oral administration to rat pups (once a day, 9 consecutive days). TPP stimulated MUC2 and MUC4 gene expression as well as mucin secretion in HT29-MTX cells. Among the four peptide fractions that were separated by preparative reversed-phase high-performance liquid chromatography, only the C2 fraction was able to mimic the in vitro effect of TPP. Interestingly, the sequence [94-123] of β-casein, present only in C2 fraction, also regulated mucin production in HT29-MTX cells. Oral administration of this peptide to rat pups enhanced the number of goblet cells and Paneth cells along the small intestine. These effects were associated with a higher expression of intestinal mucins (Muc2 and Muc4) and of antibacterial factors (lysozyme, rdefa5). We conclude that the peptide β-CN(94-123) present in yoghurts may maintain or restore intestinal homeostasis and could play an important role in protection against damaging agents of the intestinal lumen.

Rheological properties of pectin-enriched products isolated from butternut (Cucurbita moschata Duch ex Poiret)

Abstract Rheological behavior of five different pectin-enriched products obtained from a cell wall enriched powder of butternut (Cucurbita moschata Duch ex Poiret) was evaluated through flow and oscillatory assays. The product SE was obtained through treatment with citrate buffer; C1 and C2 were obtained using cellulase and different enzyme–substrate ratios while H1 and H2 resulted from hemicellulase treatment at different levels. SE- and H1-pectin-enriched fractions showed the best performance as thickeners as indicated by their highest Newtonian viscosities and time constants on shear-thinning along the flow. These fractions showed a structure with the highest density of interactions between the hydrated macromolecules when solutions were evaluated at rest. Fractions obtained with a higher activity of hemicellulase (H2) or with the lowest activity of cellulase assayed (C1) showed the same degree of structure when evaluated at rest, while C2-fraction presented the lowest density of macromolecular interactions in water, behaving as a diluted hydrocolloid solution as confirmed by its fitting to the Cox–Merz rule. Molecular weight distribution of polysaccharide fractions along with chemical composition helped to explain the rheological behavior of these isolated fractions which contained between 39 and 78 g of galacturonic acid per 100 g of product. With the exception of C2 fraction, pectin-enriched products isolated from butternut showed an interesting range of thickening properties and can be used as thickeners in the food industry.

Secondary Reactions of Ethylene As Studied in a Laboratory-Scale Recycle Slurry Reactor

Data from a recycle laboratory slurry reactor were considered to investigate the secondary reactions of ethylene in Sasol’s commercial iron-based low-temperature Fischer–Tropsch synthesis. In particular, the behavior of ethylene was compared to that of propylene. No evidence could be found for significant reincorporation of either of these two olefins. Propylene was hydrogenated to a very small extent, whereas ethylene was substantially hydrogenated. The estimated primary olefin/paraffin ratio for the C2 fraction was higher than for the C3 fraction, in line with the prediction of our recently proposed chain length dependent desorption model.

Size-Based Speciation of Natural Colloidal Particles by Flow Field Flow Fractionation, Inductively Coupled Plasma-Mass Spectroscopy, and Transmission Electron Microscopy/X-ray Energy Dispersive Spectroscopy: Colloids−Trace Element Interaction

Flow field flow fractionation (FIFFF), inductively coupled plasma-mass spectroscopy (ICP-MS), and transmission electron microscopy (TEM) coupled to X-ray energy dispersive spectrometry (X-EDS) are used in series for the first time to characterize colloids. Results demonstrate the utility of FIFFF-ICP-MS-TEM/X-EDS to relate physical properties (size) of colloids to their chemical properties (chemical composition, surface chemical composition, and colloids-trace elements association). Results suggest that the major part of natural organic matter (NOM) is concentrated in the fraction < 0.01 microm (C2). Aluminum, iron, and manganese are the main colloidal components in the fraction 0.01-0.45 microm (C1). Aluminum occurs as aluminum oxides or aluminosilicates in the whole size range, while iron and manganese occur as individual oxyhydroxides in the size range < 0.20 microm. Within the C2 fraction, Al, Mn, Cu, and Ni elements are complexed to NOM (e.g., humic substances). Iron is complexed to NOM in some samples and probably free in other samples. Lead is totally free in all samples. Within the C1 fraction, Cu and Pb are mostly associated to Fe and Mn oxyhydroxides. Consequently, NOM with Fe and Mn oxyhydroxides are the main colloidal carriers of trace elements in the Loire watershed system.

Electrochemical reduction of carbon dioxide at various series of copper single crystal electrodes

Abstract Electrochemical reduction of carbon dioxide was studied with various series of copper single crystal electrodes in 0.1 M KHCO3 aqueous solution at constant current density 5 mA cm−2; the electrodes employed are Cu(S)-[n (1 0 0)×(1 1 1) ], Cu(S)-[n (1 0 0)×(1 1 0) ], Cu(S)-[n (1 1 1)×(1 0 0) ], Cu(S)-[n (1 1 1)×(1 1 1) ] and Cu(S)-[n (1 1 0)×(1 0 0) ]. The electrodes based on (1 0 0) terrace surface give ethylene as the major product. The ethylene formation is further promoted by the introduction of (1 1 1) or (1 1 0) steps to the (1 0 0) basal plane. The highest C2H4 to CH4 formation ratio amounts to 10 in terms of the current efficiency for the (7 1 1) (=4(1 0 0) − (1 1 1)) surface as compared with the value 0.2 for the (1 1 1) electrode. The n(1 1 1)−(1 1 1) surfaces favor the formations of acetic acid, acetaldehyde and ethyl alcohol with the increase of the (1 1 1) step atom density. CH4 formation at the n(1 1 1)−(1 1 1) electrodes decreases with the increase of the (1 1 1) step atom density. The n(1 1 1)−(1 0 0) surfaces give higher gaseous products; the major product is CH4 with lower fraction of C2+ compounds.