Deep deoxygenation of water with a metal-ion exchanger nanocomposite in closed system

Kinetics and dynamics of the reduction of oxygen dissolved in water by metal-ion exchanger nanocomposites differing in the nature (Ag, Cu, Bi, Ni), quantitative content of the introduced metal, and ionic form of the matrix were studied. It is shown that the process of oxygen absorption occurs to the fullest extent with the copper-containing nanocomposite. As the content of the metal increases, the amount of oxygen reduced by a single grain and granular bed grows and reaches the limiting values. It was found on this basis that the material with a copper capacity of 5.0 ± 0.5 mequiv cm^?3 in the H⁺ form is the most efficient for deep removal of molecular oxygen from water. The advisability of using the nanocomposite with the suggested parameters for deep deoxygenation of water in a closed system was confirmed by experiments and calculations.     

Low‐Temperature Solid‐State Microwave Reduction of Graphene Oxide for Transparent Electrically Conductive Coatings on Flexible Polydimethylsiloxane (PDMS)

Microwaves (MWs) are applied to initialize deoxygenation of graphene oxide (GO) in the solid state and at low temperatures (～165 °C). The Fourier‐transform infrared (FTIR) spectra of MW‐reduced graphene oxide (rGO) show a significantly reduced concentration of oxygen‐containing functional groups, such as carboxyl, hydroxyl and carbonyl. X‐ray photoelectron spectra confirm that microwaves can promote deoxygenation of GO at relatively low temperatures. Raman spectra and TGA measurements indicate that the defect level of GO significantly decreases during the isothermal solid‐state MW‐reduction process at low temperatures, corresponding to an efficient recovery of the fine graphene lattice structure. Based on both deoxygenation and defect‐level reduction, the resurgence of interconnected graphene‐like domains contributes to a low sheet resistance (～7.9×10⁴ Ω per square) of the MW‐reduced GO on SiO₂‐coated Si substrates with an optical transparency of 92.7 % at ～547 nm after MW reduction, indicating the ultrahigh efficiency of MW in GO reduction. Moreover, the low‐temperature solid‐state MW reduction is also applied in preparing flexible transparent conductive coatings on polydimethylsiloxane (PDMS) substrates. UV/Vis measurements indicate that the transparency of the thus‐prepared MW‐reduced GO coatings on PDMS substrates ranges from 34 to 96 %. Correspondingly, the sheet resistance of the coating ranges from 10⁵ to 10⁹ Ω per square, indicating that MW reduction of GO is promising for the convenient low‐temperature preparation of transparent conductors on flexible polymeric substrates.     

Porous Pd-containing polypropylene membranes for catalytic water deoxygenation

Water deoxygenation has been studied in a catalytic membrane reactor in which oxygen is reduced with hydrogen fed into the hollow fiber of a porous polypropylene membrane containing palladium metal on its outer surface. Palladized fibers obtained by different methods and the initial fibers have been characterized by dynamic desorption porosimetry, gas permeability measurements, X-ray structure determination, and light microscopy. The possibility of efficient water deoxygenation at room temperature is demonstrated.     

Fabrication of catalyst-coated membrane by modified decal transfer technique

A decal transfer method based on colloidal ink was developed for the fabrication of membrane electrode assemblies (MEAs). The new method requires fewer steps and utilizes H⁺ form of membrane compared to conventional decal method based on solution ink utilizing Na⁺ form of membrane. The structural features of the electrodes made by the modified decal method were investigated by scanning electron microscopy (SEM). The performance of fabricated electrode was evaluated for oxygen reduction reaction in a proton exchange membrane fuel cell. The results indicate that the modified decal method has the potential to be a facile method of fabricating electrodes with high performance.     

Effective gas-phase deoxygenation of alcohols and ketones on iron catalyst

A method of gas-phase deoxygenation of alcohols and ketones into hydrocarbons on iron catalyst at 600 K and 1–2·10⁵ Pa is discussed.     

Hydrothermal Deoxygenation of Graphene Oxide: Chemical and Structural Evolution

A green and facile approach for the partial deoxygenation of graphene oxide (GO) at moderate temperature (100 °C) and under atmospheric pressure, catalyzed by acidic conditions in water is reported. The chemical and structural changes in GO as a function of hydrothermal time were probed to understand the deoxygenation events. The brown GO dispersion in water was found to gradually turn black over the hydrothermal‐treatment time on account of the increasing graphitic content. FTIR, thermogravimetric (TG), Raman, and XRD analyses revealed that the labile oxygen functionalities are progressively eliminated, thereby partially restoring the π‐conjugated network. This was further corroborated by X‐ray photoelectron spectroscopy (XPS) studies based on quantitative analysis of each carbon component associated with the different chemical functionalities. Carbonyl, carboxyl, ether, and phenolic groups were found to be thermally stable, which hinders complete deoxygenation of GO and makes their dispersion in water stable, as monitored by the ζ potential. It is worth noting that deoxygenation events are expedited under acid‐catalyzed hydrothermal treatment relative to thermal deoxygenation in air.     

The impact of in-line coagulant addition on fouling potential of secondary effluent at a pilot-scale immersed ultrafiltration plant

The impact of in-line coagulation pre-treatment of secondary effluent on the operation of an immersed hollow-fibre ultrafiltration membrane pilot was evaluated as part of a larger study on optimising phosphorus removal. The efficacy of alum and ferric chloride was investigated, with an emphasis on alum use. Both coagulants were found to shift the particle-size distribution of organic matter in the feed towards larger fractions, with a notable reduction in colloidal matter. This was reflected in a reduction of both average daily transmembrane pressure increases, as well as a reduction of transmembrane pressure increases within backpulse intervals. Fouling reduction was observed with both lower and higher membrane packing density modules (membrane surface areas of 55.7 and 62.7 m²/module). The results of one-way analysis of variance (ANOVA) testing indicate that for this pilot system, chemical pre-treatment and solids concentrations in the feed water played a statistically significant role in determining transmembrane pressure variations. Membrane packing density and membrane production method did not exhibit a statistically significant effect on transmembrane pressure under the conditions of this study.     

A study of the electret state of polyethylene formulations with a ferroelectric

A method for simultaneous desalting and deoxygenation of feed and extra water was developed for through steam generators using ion-exchange mixed bed filters and the fi lter with ferrous hydroxide electron ion exchanger which eliminates the stage of thermal deaeration.     

Polarographic Determination of Glycyrrhizic Acid Based on Double Enhancement Action of Surfactant and Dissolved Oxygen

ABSTRACT

A method for the determination of glycyrrhizic acid (GA) is described based on polarographic current of GA enhanced doubly by both cation surfactant (cetyl trimethyl ammonium bromide (CTMAB)), and dissolved oxygen (including oxygen-derived species). The doubly enhanced current of GA includes two additional currents. One is the increased reduction current of adsorbed GA induced by CTMAB. The other is the catalytic current of GA caused by the dissolved oxygen molecule and its derived species. In 0.1 M NaAc-Hac (pH4.7±0.1) ～ 1x10^?5 M CTMAB supporting electrolyte without deoxygenation, the enhanced current of GA is linearly proportional to its concentration in the range of 4x10^?7 M ～ 4.0x10^?6 M. The detection limit is 1.8x10^?7 M. The double enhanced current of GA in sensitivity is about 15 times higher than its reduction wave in the same acetate buffer solution.     

Water treatment for steam generators with the aid of ion exchangers

A method for simultaneous desalting and deoxygenation of feed and extra water was developed for through steam generators using ion-exchange mixed bed filters and the filter with ferrous hydroxide electron ion exchanger which eliminates the stage of thermal deaeration.     

Pilot plant studies of novel membranes and devices for direct contact membrane distillation-based desalination

A small pilot plant for direct contact membrane distillation (DCMD) based desalination was built and operated successfully on a daily basis for 3 months. The operation employed hot brine at 64–93 °C and distillate at 20–54 °C. The hot brine was either city water, city water containing salt at the level of 3.5, 6 or 10%, or sea water trucked in from Long Island Sound, CT. One to ten horizontal crossflow hollow fiber membrane modules each having either 2448 or 2652 hollow fibers and 0.61 or 0.66 m² surface area were combined in various configurations to study the plant performance. The highest water vapor flux of 55 kg/(m² h) was achieved with two modules in series; the flux varied between 15 and 33 kg/(m² h) for configurations employing 6–10 modules. The highest distillate production rate achieved was 0.62 gallons per minute (gpm). The membrane modules never showed any sign of distillate contamination by salt. The plant operated successfully with a very limited flux reduction at salt concentrations up to 19.5% from sea water. A mathematical model was successfully developed to describe the performance of the pilot plant with multiple crossflow modules in different test configurations.     

A Graphene Oxide Membrane with Highly Selective Molecular Separation of Aqueous Organic Solution

A graphene oxide (GO) membrane is supported on a ceramic hollow fiber prepared by a vacuum suction method. This GO membrane exhibited excellent water permeation for dimethyl carbonate/water mixtures through a pervaporation process. At 25 °C and 2.6 wt % feed water content, the permeate water content reached 95.2 wt % with a high permeation flux (1702 g m^?2 h^?1).     

Perovskite membrane reactor for continuous and isothermal redox hydrogen production from the dissociation of water

The redox water splitting is one of the most promising routes for sustainable hydrogen production. Towards this goal, serious technological obstacles are set: (i) by the non-isothermal operation of the redox process, that causes serious reactor construction problems, and (ii) by the need for efficient high temperature oxygen/hydrogen separation technology which is a very challenging development. In this paper, perovskite materials having the formula La_0.3Sr_0.7FeO₃ were synthesized and subsequently tested for their high temperature oxidation/reduction behavior. The redox activity of the materials in relation to the water splitting reaction has been also investigated. Dense, disc shaped membranes of the materials were synthesized and placed in a membrane reactor. Experiments at 1133 K revealed the possibility of performing the reduction and oxidation steps simultaneously and isothermally on each side of the membrane reactor. A steady-state situation was thereby achieved where hydrogen was continuously produced on one side while the material was simultaneously regenerated on the other side. The created oxygen vacancy gradient formed the driving force for a continuous flux of vacancies from the membrane reduction surface to the membrane oxidation surface. The hydrogen production rate under the particular experimental conditions estimated to be ∼47.5 cm³ H₂ (STP) m⁻² min⁻¹. It could be increased by a factor of approximately 3, up to ∼145 cm³ H₂ (STP) m⁻² min⁻¹, if the membrane reduction was enhanced with a reductant such as carbon monoxide. This approach resulted in an efficient execution of the water gas shift reaction towards high purity hydrogen production.     

Reaction of polyperoxides with triphenylphosphine

The triphenylphosphine deoxygenation of the polyperoxides, poly(styrene peroxide), poly(methyl methacrylate peroxide), and poly(α-methylstyrene peroxide) proceed via the phosphorane intermediates, which in the presence of moisture hydrolyze to give the respective diols. At higher temperatures and under dry conditions the phosphorane decomposes into epoxide and triphenylphosphine oxide. The reaction has been studied by ¹H-, ¹³C-, and ³¹P-NMR spectroscopy. The results obtained are consistent with a concerted insertion of the biphile, triphenylphosphine, into the peroxy bond and this reaction pathway seems to be new as far as the chemistry of polyperoxides is concerned. Though the aim of this investigation was to test the selective deoxygenation of polyperoxide by triphenylphosphine as a method of preparing polyethers, it turned out to be a fruitful method of synthesis of stereospecific diols. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1167–1172, 1997     

Quantification of partial structures of aquatic humic substances by 1H-NMR under WATR conditions

Aquatic humic substances (HS) isolated from surface water, leakage water and ground water have been investigated by ¹H-NMR. The overlapping HOD signal was eliminated by adding ammonium chloride and applying the multiecho method CPMG (Carr, Purcell, Meiboom, Gill) under WATR conditions (water attenuation by transverse relaxation) permitting quantification of partial structures of HS. The proportion of carbohydrates/alcohols/ethers decreases and the proportion of alkyl moieties increases with increasing water or soil depth and thus microbial diagenesis. Also, increasing deoxygenation of aromatic substituents is observed with increasing water or soil depth. In some cases, elimination of the NMR signal of HOD is accompanied by the appearance of another HOD signal which is slightly shifted and much smaller in intensity; this signal probably results from water strongly bound by hydrogen bonding within the HS macromolecules.     

Copper‐Catalyzed Reduction of Alkyl Triflates and Iodides: An Efficient Method for the Deoxygenation of Primary and Secondary Alcohols

We describe an effective method for catalytic reduction of 1° alkyl sulfonates, and 1° and 2° iodides in the presence of a wide range of functional groups. This Cu‐catalyzed reaction provides a means for the effective deoxygenation of alcohols, as demonstrated by the highly selective reduction of 1° alcohols using a triflation/reduction sequence. A preliminary study of the reaction mechanism suggests that the reduction does not involve free‐radical intermediates.     

A Sulfoxide Reduction Method Using Low Valent Molybdenum Acetates

It has been demonstrated that molybdenum(III) ion is effective for deoxygenation of sulfoxides.¹ However, since this reagent was generated by treatment of molybdenyl chloride with zinc dust, the role of some suspended metal in the sulfoxide reduction cannot be assessed. In order to conclusively establish the reducing capability of low-valent molybdenum ions for sulfoxides we have carried out experiments with Mo species obtained in a manner that the suspicion of active metal participation is exonerated.     

Deoxygenation of tertiary amine N-oxides under metal free condition using phenylboronic acid

A simple and efficient method for the deoxygenation of amine N-oxides to corresponding amines is reported using the green and economical reagent phenylboronic acid. Deoxygenation of N,N-dialkylaniline N-oxides, trialkylamine N-oxides and pyridine N-oxides were achieved in good to excellent yields. The reduction susceptible functional groups such as ketone, amide, ester and nitro groups are well tolerated with phenylboronic acid during the deoxygenation process even at high temperature. In addition, an indirect method for identification and quantification of tert-amine N-oxide is demonstrated using UV–Vis spectrometry which may be useful for drug metabolism studies.     

A method for the analysis of sucralose with electrospray LC/MS in recipient waters and in sewage effluent subjected to tertiary treatment technologies

A method for the analysis of the artificial sweetener sucralose in sewage water and recipient water was developed. Extraction and clean up was performed with solid-phase extraction utilising Oasis HLB columns. Detection was made by liquid chromatography electrospray mass spectrometry (LC/MS). The triple-quadrupole mass spectrometer was operated in multiple reaction monitoring (MRM) mode. However, ‘pseudo MRM’ was used, a technique where the two quadrupoles monitor the same m/z. The sodium adduct of sucralose was used for quantification, since lower detection limits were obtained as compared to the sucralose quasi-molecular ion in negative ion mode. The two ions with highest intensity in the chlorine isotope pattern were monitored. The reduction of matrix effects with this approach is discussed. The method limit of quantification (MLOQ) for sewage water was 0.2?µg?L^?1, whereas for recipient water MLOQ was 0.02?µg?L^?1. The method was used to analyse effluent samples from an experimental sewage treatment plant (STP) to assess the efficiency of tertiary treatment techniques for removal of sucralose. Filtration through activated carbon was shown to be efficient, while ozonation, advanced oxidation techniques and membrane bioreactors were less efficient. Analyses of receiving waters showed low dilution of sucralose emitted from the STPs.