Solvent Extraction of Uranium (VI) from Chloride Solutions using Cyphos IL-101

The solvent extraction of uranium (VI) from chloride solutions by Cyphos IL-101 in xylene has been studied. Distribution coefficients were found to increase with aqueous chloride concentration and extractant concentration. The enthalpy of extraction is endothermic with ΔH = +24 ± 2 kJ·mol^?1. Based upon slope analysis, an anion exchange extraction mechanism is proposed, with formation of a UO₂Cl₄ ^2- complex in association with 4 Cyphos IL-101 ligands. The extraction kinetics were fast, with complete equilibration occurring within 30 seconds. An isotherm for uranium extraction from 1.0 mol·L^?1 chloride solution by 0.1 mol·L^?1 Cyphos IL-101 in xylene shows that 45 mmol·L^?1 uranium can be loaded into the organic phase in equilibrium with 2.1 mmol·L^?1 in the aqueous phase. The absorption spectrum of the uranium loaded solvent between 350 and 550 nm is indicative of the UO₂Cl₄ ^2- complex with only chlorides present in the inner coordination sphere, unlike the more strongly hydrogen bonded Alamine 336 extracted uranium complex. Subject to the same experimental conditions, distribution coefficients for Cyphos IL-101 were significantly greater than for Alamine 336 or Aliquat 336.     

Preparation of nanosize Pt clusters using ion exchange of Pt(NH3) 4 2+ inside mesoporous channel of MCM-41

Mesoporous molecular sieve MCM-41 with a Si/Al ratio of 35 was obtained by hydrothermal synthesis using a gel mixture with a molar composition of 6 SiO₂0.1 Al₂O₃1 hexadecyltrimethylammonium chloride 0.25 dodecyltrimethylammonium bromide 0.25 tetrapropylammonium bromide0.15 (NH₄)₂O1.5 Na₂O300 H₂O. The MCM-41 sample was calcined in O₂ flow at 813 K and subsequently ion exchanged with Ca²⁺. A small Pt cluster has been supported on the MCM-41 sample following a procedure using ion exchange of Pt(NH₃) ₄ ²⁺ . The Pt(NH₃) ₄ ²⁺ ion supported on MCM-41 has been activated in O₂ flow at 593 K and subsequently reduced with Fh flow at 573 K, in the same way used for the preparation of a Pt cluster entrapped inside the supercage of zeolite NaY. The resulting Pt cluster supported on the MCM-41 shows hydrogen chemisorption oftotal two H atoms per Pt at 296 K (based on the total amount of Pt) and high catalytic activity for hydrogenolysis of ethane. The chemical shift in¹²⁹Xe NMR spectroscopy of adsorbed xenon indicates that the Pt cluster is located inside the mesoporous molecular sieve.     

Initial stages of Pt deposition on Au(111) and Au(100)

The deposition of Pt onto unreconstructed Au(111) and Au(100) was studied with cyclic voltammetry and in-situ STM. The latter revealed that in [PtCl₄]²⁻ containing electrolytes, both surfaces are covered by an ordered adlayer of the complex. For the adsorbed [PtCl₄]²⁻ a slightly compressed (√7×√7) R19.1°-structure was assumed for Au(111) and a (3×√10) for Au(100). In both cases, a rather high overpotential for Pt deposition was observed, most probably due to the high stability of the [PtCl₄]²⁻ complex. Nucleation of Pt starts mainly at defects like step edges for low deposition rates and three-dimensional clusters are formed. Due to the high overpotential, some nuclei appear also on terraces at random sites. Higher coverages of Pt lead to a cauliflower like appearance. It is not possible to dissolve the platinum clusters at positive potentials without severely roughening the gold surface. The [PtCl₄]²⁻ complex is oxidized to the [PtCl₆]²⁻ complex at about 0.7 V, when metallic Pt is on the surface.     

Studies on a synthetic sitinakite-type silicotitanate cation exchanger. Part 2. Effect of alkaline earth and alkali metals on the uptake of Cs and Sr radioisotopes

A commercially available synthetic silicotitanate (IONSIV^® IE-911), with a sitinakite-like structure, is a candidate material for the remediation of aqueous nuclear waste streams. These streams often vary in both cation composition and cation concentration. Commonly Na, K, Mg, Ca and Ba are present, and sodium is the most prevalent with barium present at much lower concentrations. Batch experiments to measure distribution coefficients (K_d) have been carried out to monitor the effect of these cations on the removal of the fission products Cs and Sr from simulated aqueous waste streams relevant to their remediation prior to release to the environment.     

Sulfate radical-based ferrous–peroxymonosulfate oxidative system for PCBs degradation in aqueous and sediment systems

Polychlorinated biphenyls (PCBs) in the environment pose long-term risk to public health because of their persistent and toxic nature. This study investigates the degradation of PCBs using sulfate radical-based advanced oxidation processes (SR-AOPs). These processes are based on the generation of sulfate radicals through iron (Fe(II), Fe(III)) mediated activation of peroxymonosulfate (KHSO₅, PMS) or persulfate (Na₂S₂O₈, PS). This study is the first instance for coupling of Fe(II)/Fe(III) with PMS for PCB degradation in aqueous and sediment systems. The high oxidation efficiencies of the free radicals (SO₄⁻), in combination with the slow rate of consumption of the oxidants, make these processes very effective for the degradation of recalcitrant organic compounds. The effectiveness of the process was evaluated based on the degradation of a model polychlorinated biphenyl, 2-chlorobiphenyl and total organic carbon (TOC) removal. The kinetics of 2-chlorobiphenyl degradation along with the effect of oxidant and catalyst concentrations on the degradation efficiency was studied. Near complete removal of 2-chlorobiphenyl was observed when Fe(II) was used with PMS or PS. Fe(II) acts as a sulfate radical scavenger at higher concentrations indicating that there is an optimum concentration of Fe(II) that leads to most effective degradation of the target contaminant. A chelating agent, sodium citrate, was used to control the quantity of iron in the solution for activation of the oxidant. For the first time, we studied the feasibility of the activation of PMS using iron citrate complexes for PCB degradation. In the presence of sodium citrate, increase in degradation efficiency was observed up to a metal:ligand ratio of 1:2, after which the increase in citrate concentration led to a decrease in removal efficiency. Fe(II)/PMS systems were found to be very effective in degrading PCB in a sediment-slurry system with more than 90% PCB removal being observed within 24 h.     

Preparation and characterization of titanium suboxides as conductive supports of IrO2 electrocatalysts for application in SPE electrolysers

A novel chemical route for the preparation of titanium suboxides (Ti_nO_2n−1) with Magneli phase was developed. The ceramic powders were prepared from TiCl₄ by complexation of Ti ions and successive decomposition of the complex to form an amorphous oxide. A high temperature reduction (1050 °C) of the amorphous oxide was carried out by using diluted hydrogen. IrO₂ electrocatalysts supported on Ti-suboxides were prepared by incipient wetness. The chemistry, morphology and structure of the materials were studied by TPR, XRF, XPS, BET, TEM and XRD. The electrochemical activity for oxygen evolution in a solid polymer electrolyte (SPE) electrolyser of IrO₂ catalysts supported on a commercial titanium suboxide (Ebonex^®) and Ti_nO_2n−1 prepared in-house was investigated by ac-impedance spectroscopy, linear sweep and cyclic voltammetry. The results showed proper electronic conductivity for both electrocatalysts and superior electrocatalytic activity of the catalyst based on the Ti-suboxides prepared in-house compared to the commercial support. In situ cyclic voltammetry and ac-impedance analyses showed larger voltammetric charge and double layer capacitance for the catalyst based on the Ti-suboxides prepared in-house with respect to the catalyst supported on Ebonex^®. These results were attributed to the better dispersion and larger occurrence of active catalytic sites on the surface of the suboxide prepared in-house based anode compared to the anode based on the commercial support.     

Unique Regulation of Intestinal Villus Epithelial Cl−/HCO3− Exchange by Cyclooxygenase Pathway Metabolites of Arachidonic Acid in a Mouse Model of Spontaneous Ileitis

Electrolytes (NaCl) and fluid malabsorption cause diarrhea in inflammatory bowel disease (IBD). Coupled NaCl absorption, mediated by Na⁺/H⁺ and Cl⁻/HCO₃⁻ exchanges on the intestinal villus cells brush border membrane (BBM), is inhibited in IBD. Arachidonic acid metabolites (AAMs) formed via cyclooxygenase (COX) or lipoxygenase (LOX) pathways are elevated in IBD. However, their effects on NaCl absorption are not known. We treated SAMP1/YitFc (SAMP1) mice, a model of spontaneous ileitis resembling human IBD, with Arachidonyl Trifluoro Methylketone (ATMK, AAM inhibitor), or with piroxicam or MK-886, to inhibit COX or LOX pathways, respectively. Cl⁻/HCO₃⁻ exchange, measured as DIDS-sensitive ³⁶Cl uptake, was significantly inhibited in villus cells and BBM vesicles of SAMP1 mice compared to AKR/J controls, an effect reversed by ATMK. Piroxicam, but not MK-886, also reversed the inhibition. Kinetic studies showed that inhibition was secondary to altered K_m with no effects on V_max. Whole cell or BBM protein levels of Down-Regulated in Adenoma (SLC26A3) and putative anion transporter-1 (SLC26A6), the two key BBM Cl⁻/HCO₃⁻ exchangers, were unaltered. Thus, inhibition of villus cell Cl⁻/HCO₃⁻ exchange by COX pathway AAMs, such as prostaglandins, via reducing the affinity of the exchanger for Cl⁻, and thereby causing NaCl malabsorption, could significantly contribute to IBD-associated diarrhea.     

Optimization of caustic current efficiency in a zero-gap advanced chlor-alkali cell with application of genetic algorithm assisted by artificial neural networks

The effects of various process parameters on caustic current efficiency (CCE) in a zero-gap oxygen-depolarized chlor-alkali cell employing a state-of-the-art silver plated nickel screen electrode (ESNS^®) were studied. For doing a thorough research, we selected the process parameters from both cathodic and anodic compartments. Seven process parameters were studied including anolyte pH, temperature, flow rate and brine concentration from the anode side, oxygen temperature and flow rate from the cathode side and the applied current density. The effect of these parameters on CCE was determined quantitatively. A feed forward neural network model with the Levenberg–Marquardt (LM) back propagation training method was developed to predict CCE. Then genetic algorithm (GA) was implemented to neural network model. The highest CCE (98.53%) was found after 20 times running GA at the following conditions: brine concentration (287 g/L), anolyte temperature (80 °C), anolyte pH (2.7), anolyte flow rate (408 cm³/min), oxygen flow rate (841 cm³/min), oxygen temperature (79 °C), and current density (0.33 A/cm²).     

Investigation on V(IV)/V(V) species in a vanadium redox flow battery

Stokes radii of V(IV) and V(V) species in concentrated sulfuric acid solutions were determined from their diffusion limited current densities on a rotating platinum disk electrode and the solution viscosity. In addition, V(IV) and V(V) species were estimated based on their solubility, UV-Vis spectra, and cyclic voltammetric data. The possible ion-pair formation of V(IV) cation with SO₄²⁻ and/or HSO₄⁻ and the spontaneous polymerization of V(V) at a low H₂SO₄ concentration were discussed.     

Ship-in-Bottle synthesis of Pt9-Pt15 carbonyl clusters inside NaY and NaX zeolites,in-situ FTIR and EXAFS characterization and the catalytic behaviors in13CO exchange reaction and NO reduction by CO

[Pt₉(CO)₁₈]^2–/NaY (orange-brown, 2056 and 1798 cm^–1), [Pt₁₂(CO)₂₄]^2–/NaY (dark-green, 2080 and 1824 cm^–1 and [Pt₁₅(CO)₃₀]^2–/NaX (yellow-green, 2100 and 1865 cm^–1) were stoichiometrically synthesized by the reductive carbonylation of [Pt(NH₃)₄]²⁺/NaY, Pt²⁺/NaY and Pt²⁺/NaX, respectively. The IR bands characteristic of their linear carbonyls shift to higher frequencies whereas the bridging CO bands to lower frequencies, compared with those on the external zeolites and in solution. In-situ FTIR studies suggested that the subcarbonyl species such as PtO(CO) and Pt₃(CO)₃(₂ –CO)₃ are formed as the proposed intermediates towards [Pt₁₂(CO)₂₄]^2–/NaY in the reductive carbonylation of Pt²⁺/NaY.¹³CO exchange reaction preceded with the different intrazeolite Pt carbonyl species in the following order of activity at 298–343 K: Pt₃(CO)₃(₂ –CO)₃/NaY PtO(CO)/NaY>[Pt₉(CO)₁₈]^2–/NaY >[Pt₁₂(CO)₂₄]^2–/NaY. Pt-L₃-edge EXAFS measurment for these synthesized samples demonstrated that they are consistent with the Pt carbonyl clusters having trigonal prismatic Pt₉ and Pt₁₂ frameworks infered to a series of the Chini complexes such as [NEt₄]₂[Pt₃(CO)₆] _n ( _n = 3–5). The intrazeolite Pt₉ and Pt₁₂ carbonyl clusters exhibited higher cataytic activity in NO reduction by CO towards N₂ and N₂O at 473 K, compared with those on the conventional Pt/Al₂O₃ catalysts. The mechanism of intrazeolite Pt₉-Pt₁₅ carbonyl cluster formation are discussed in terms of the intrazeolite basicity and acidity.On leave from National Laboratory for Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 129 Street, China.     

Treatment with the Probiotic Product Aviguard® Alleviates Inflammatory Responses during Campylobacter jejuni-Induced Acute Enterocolitis in Mice

Prevalences of Campylobacter (C.) jejuni infections are progressively rising globally. Given that probiotic feed additives, such as the commercial product Aviguard^®, have been shown to be effective in reducing enteropathogens, such as Salmonella, in vertebrates, including livestock, we assessed potential anti-pathogenic and immune-modulatory properties of Aviguard^® during acute C. jejuni-induced murine enterocolitis. Therefore, microbiota-depleted IL-10^−/− mice were infected with C. jejuni strain 81-176 by gavage and orally treated with Aviguard^® or placebo from day 2 to 4 post-infection. The applied probiotic bacteria could be rescued from the intestinal tract of treated mice, but with lower obligate anaerobic bacterial counts in C. jejuni-infected as compared to non-infected mice. Whereas comparable gastrointestinal pathogen loads could be detected in both groups until day 6 post-infection, Aviguard^® treatment resulted in improved clinical outcome and attenuated apoptotic cell responses in infected large intestines during acute campylobacteriosis. Furthermore, less distinct pro-inflammatory immune responses could be observed not only in the intestinal tract, but also in extra-intestinal compartments on day 6 post-infection. In conclusion, we show here for the first time that Aviguard^® exerts potent disease-alleviating effects in acute C. jejuni-induced murine enterocolitis and might be a promising probiotic treatment option for severe campylobacteriosis in humans.     

Expression of SLC26A9 in Airways and Its Potential Role in Asthma

SLC26A9 is an epithelial anion transporter with a poorly defined function in airways. It is assumed to contribute to airway chloride secretion and airway surface hydration. However, immunohistochemistry showing precise localization of SLC26A9 in airways is missing. Some studies report localization near tight junctions, which is difficult to reconcile with a chloride secretory function of SLC26A9. We therefore performed immunocytochemistry of SLC26A9 in sections of human and porcine lungs. Obvious apical localization of SLC26A9 was detected in human and porcine superficial airway epithelia, whereas submucosal glands did not express SLC26A9. The anion transporter was located exclusively in ciliated epithelial cells. Highly differentiated BCi-NS1 human airway epithelial cells grown on permeable supports also expressed SLC26A9 in the apical membrane of ciliated epithelial cells. BCi-NS1 cells expressed the major Cl⁻ transporting proteins CFTR, TMEM16A and SLC26A9 in about equal proportions and produced short-circuit currents activated by increases in intracellular cAMP or Ca²⁺. Both CFTR and SLC26A9 contribute to basal chloride currents in non-stimulated BCi-NS1 airway epithelia, with CFTR being the dominating Cl⁻ conductance. In wtCFTR-expressing CFBE human airway epithelial cells, SLC26A9 was partially located in the plasma membrane, whereas CFBE cells expressing F508del-CFTR showed exclusive cytosolic localization of SLC26A9. Membrane localization of SLC26A9 and basal chloride currents were augmented by interleukin 13 in wild-type CFTR-expressing cells, but not in cells expressing the most common disease-causing mutant F508del-CFTR. The data suggest an upregulation of SLC26A9-dependent chloride secretion in asthma, but not in the presence of F508del-CFTR.     

FTIR and electrochemical observation of water content reduction in a thin Nafion film induced by an impregnation of metal complex cations

A thin Nafion^® ion exchange membrane was coated on a graphite electrode, and then impregnated by a metal complex couple of Os(bpy)₃^2+/3+, which served as a typical system to investigate the water content change induced by ion exchange. Cyclic voltammetry and FTIR reflection-adsorption spectroscopic methods were employed to characterize the complex loading, electrochemical behavior of the impregnates inside the film and the water content change. A direct observation of the water content reduction induced by the cation impregnation in the Nafion^® film was achieved. A monotonic relationship between the water reduction percentage and the Os(bpy)₃^2+/3+ loading was also obtained, that is, the heavier the complex loading, the more the water content will be reduced. The FTIR spectroscopic results suggested that the structure of the Nafion^® film could also be changed with water content reduction.     

Continuous transesterification of biodiesel in a helicoidal reactor using recycled oil

The main problem with biodiesel is the high cost of oils made from oleaginous crops. For this reason, various raw materials have been analysed with a view to reducing production costs and obtaining a product that can compete with the price of petrodiesel. Recycled oil is one of the most promising alternatives in the production of biodiesel because not only is the cheapest raw material but it also avoids the expense of treating the oil as a residue.Another way to reduce costs is to make the process more economical. Conventional technology uses sodium hydroxide as the basic catalyst and large-scale batch reactors, whose mechanical agitation requires high energy consumption due to residence times of at least 60 min and temperatures of 60 °C.In this paper we use a recycled pretreated oil to compare conventional transesterification with continuous transesterification in a tubular reactor. In this reactor the reactants (oil, methanol and sodium hydroxide) flow through a helicoidal tube submerged in a heating bath at 60 °C. The reactor has five outlets distributed non-uniformly to enable samples to be taken at different reaction times. This is to reduce the reaction time and avoid the need for mechanical agitation. With the aim of improving the quality of the biodiesel obtained, we varied the helicoidal system by incorporating a static micromixer and supplying energy in the form of ultrasound from the heating bath. This reactor produced biodiesel and glycerine at compositions roughly equal to those obtained in the batch process (89% FAME content at 75 min) but did so continuously (2.5 mL/min) and just 13 min after the reactants were integrated in a single line using a T device. Both the oil and the biodiesel were characterized and analysed in accordance with European standard UNE EN14214 for biodiesel.