Ozone-Based Advanced Oxidation Processes for the Decomposition of N-Methyl-2-Pyrolidone in Aqueous Medium

The present study investigates the decomposition of N-Methyl-2-Pyrolidone (NMP) using conventional ozonation (O₃), ozonation in the presence of UV light (UV/O₃), hydrogen peroxide (O₃/H₂O₂), and UV/H₂O₂ processes under various experimental conditions. The influence of solution pH, ozone gas flow dosage, and H₂O₂ dosage on the degradation of NMP was studied. All ozone-based advanced oxidation processes (AOPs) were efficient in alkaline medium, whereas the UV/H₂O₂ process was efficient in acidic medium. Increasing ozone gas flow dosage would accelerate the degradation of NMP up to certain level beyond which no positive effect was observed in ozonation as well as UV light enhanced ozonation processes. Hydrogen peroxide dosage strongly influenced the degradation of NMP and a hydrogen peroxide dosage of 0.75 g/L and 0.5 g/L was found to be the optimum dosage in UV/H₂O₂ and O₃/H₂O₂ processes, respectively. The UV/O₃ process was most efficient in TOC removal. Overall it can be concluded that ozonation and ozone-based AOPs are promising processes for an efficient removal of NMP in wastewater.     

Microstructure and its relationship to deformation processes in amorphous polymer glasses

The microdeformation morphology of a number of vinyl polymers with bulky side chains (type I) and arylene polymers with flexible oxygen linkages (type II) was studied by electron microscopy. The polyarylenes crazed only near the glass transition while the polyvinyls exhibited a crazing regime that extended to liquid nitrogen temperatures. In addition significantly less plastic strain was localized in type II glass crazes relative to those in type I glasses. In compatible blends of polystyrene (PS) and 2,6-dimethyl poly(phenylene oxide) (2MPPO), ca. 30% 2MPPO was sufficient to induce a transition from type I to type II crazing behavior. Small amounts of PS suppressed the low-temperature 2MPPO β relaxation but enhanced the intermediate transition of 2MPPO at higher temperatures. Blending increased the conformational energy of the 2MPPO chain and improved interchain packing. The propensity for the polymer glass to form sharp shear bands at the expense of diffuse bands was increased by a decrease in the conformation energy of the polymer chain and an improvement in the glassy state packing.     

Characterisation of the neutral oil from a low-temperature coal tar

Tar resulting from fluidised-bed, low-temperature carbonisation of coal was treated to yield a neutral oil from which a series of six other samples was extracted. These were examined by proton magnetic resonance (p.m.r.) spectroscopy, low-ionising-voltage (11 eV) mass spectroscopy (m.s.), gel chromatography followed by fluorescent indicator analysis, and cryoscopy. Aliphatic fractions separated chromatographically were also examined by infra-red spectroscopy. Distributions of hydrogen between chemical types were found for the several fractions from 60 MHz p.m.r. spectra and presented in terms of average structural parameters. M.s. analysis indicated negligible cracking of paraffin components, and the average molecular weight of 197 agreed well with cryoscopic determinations. For the carbon ratio, f_a, between aromatic and total, agreement between m.s. and p.m.r. depends on the p.m.r. structural analysis scheme adopted. P.m.r. and m.s. structural analyses of the aromatics emphasise the predominance of di- and tri-nuclears, with about 40% of available sites substituted, and the importance of acenes in lowtemperature carbonisation material. Gas and gel chromatography showed urea-adductable paraffins to be largely straight-chain C₁₀-C₂₆, much as for tars from carbonisation at higher temperature.     

Function of sulfur dioxide in the kinetic mechanism of oxidation of carbon

Retardation of the gasification reaction of carbon with oxygen by SO₂ was observed. Rates of oxidation were determined by thermal gravimetric analysis (TGA) of a nuclear graphite in the temperature range of 550–700°C, and of a coconut charcoal in the temperature range of 400–505°C. The oxidant gases were dry air containing 0–6% SO₂. Reduction of the rate by SO₂ varied with burn-off. Differential thermal analysis (DTA) was also applied to detect the retardation effect of SO₂. The technique of infrared internal reflection spectroscopy (IRS) was used to examine the surface species of reacted charcoal samples. Absorption bands were assigned to surface carbonyls, lactones, and a chemisorbed SO₂ in the form of sulfate. Chemisorption of SO₂ was attributed to cause the retardation of the oxidation reaction.     

Oxide ion conduction in the sintered oxides of MoO3-doped Bi2O3

In order to examine the conduction behaviour in the sintered oxides of MoO₃-doped Bi₂O₃, the electrical conductivity in air and the EMF of oxygen gas concentration cell were measured with respect to the phase relation determined by X-ray diffraction.The tetragonal single phase oxide containing 22 mol% MoO₃ was found to be a high oxide ion conductor, the conductivity of which was comparable to those of stabilized zirconias. The partial electronic conduction in this phase was negligibly small at relatively high oxygen pressure. The oxide ion conduction was considered to be attributable to an appreciable amount of oxygen vacancies present in the crystal. In the monoclinic compound 3Bi₂O₃·2MoO₃, the oxide ion conduction was also observed. Although the conductivity of this phase was somewhat lower than that of the tetragonal phase, the activation energy for conduction (53·5 kJ mol^–1) was much lower than the values for usual oxide ion conductors.     

Softening phenomenon by remilling of styrene–butadiene copolymer rubber–general-purpose polystyrene resin blend

The softening phenomenon by remilling of uncured blends of various commercia styrene—butadiene copolymer rubber (styrene content, 23.5 to 48 wt-%, styrene block 0 to 18 wt-%) with general-purpose polystyrene resin was mainly studied by examining the blend ratio dependence of hardness and compression modulus (in logarithmic form), with special attention to the state of dispersion of the polymers. It was found that the blend of styrene—butadiene copolymer rubber with general-purpose polystyrene resin forms a microheterogeneous polymer blend system and that the hardness and the compression modulus change in S-shaped curves versus blend ratio. However, the degree of softening phenomenon by remilling (roll surface temperature, 70°–90°C) was found to be different for the two blend systems, i.e., random styrene—butadiene copolymer rubber and block styrene—butadiene copolymer rubber. The softening phenomenon is more pronounced in random-type rubbers; and in some block-type rubbers, no softening phenomenon was observed. The influence of the styrene content of the polymer is small. Further discussions have shown us that the strong interaction between the polystyrene block of the copolymer and the styrene homopolymer of the general-purpose polystyrene resin controls the state of dispersion of polymers thereby causing this difference in the softening phenomena among the different kinds of styrene—butadiene copolymer rubbers.     

Origin of Grain-Boundary Diffusion in MgO

Preferential diffusion of Ni²⁺ and Co²⁺ along grain boundaries was observed in certain bicrystals of MgO. This enhancement is attributed to impurity segregation at the boundary. The identified impurities responsible for the effect are the principal impurities in the single-crystal MgO: Ca, Si, and Fe. No enhancement was observed in any bicrystal prepared above 1300°C, a temperature similar to that at which studies of the mechanical properties of MgO have implied a reabsorption of impurity precipitates into solid solution. It is concluded that enhanced grain-boundary diffusion of cations in MgO is an extrinsic, rather than an intrinsic, property of the boundary.     

Refractories with a Boron nitride base

Conclusions A technique for the reaction sintering of a new refractory made of 82–83% boron nitride and 17–18% graphite has been developed.The refractory possesses high specific resistance up to 1500–1800°, a low coefficient of thermal expansion, a moderative evaporation rate in a vacuum, satisfactory strength and machinability, as well as high resistance to cryolite-aluminum melts, borate, chloride and also silicide and boron-silicon alloy melts (at between 900 and 2000°).     

Control of neutral delay linear systems using feedback with dynamic structure

To solve the problem of modal controllability of linear autonomous systems of neutral type, a new class of linear difference-differential controllers with feedback of dynamic structure is proposed. The construction principle of these controllers is based on the use of aftereffect in the control action. The domain of application of such controllers includes systems that do not possess the modal controllability property in the class of conventional classes of feedback controllers of constant structure.     

Preparation of 6FDA-based polyimide composite membrane by CVDP process

Preparation of polyimide composite membranes by a chemical vapor deposition and polymerization process (CVDP) was studied for the development of pervaporation or gas separation membranes. Hexafluoroisopropylidene-2,2-bis [phethalic acid anhydride] (6F-dianhydride) (6FDA) and 4,4′-diaminodiphenyl ether (ODA) were used as monomers and were simultaneously deposited on an asymmetric polyimide membrane in vacuum of 10⁻⁶ Torr. The deposited layer of the monomers was converted to polyimide by heating at 250°C at 3 h in an ordinary vacuum oven, and its separation performance for water-ethanol and CO₂−N₂ systems was characterized.