Product analysis and mechanism of toluene degradation by low temperature plasma with single dielectric barrier discharge

A single dielectric barrier discharge (DBD) low-temperature plasma reactor was set up, and toluene was selected as the representative substance for volatile organic compounds (VOCs), to study the reaction products and degradation mechanism of VOCs degradation by low-temperature plasma. Different parameters effect on the concentration of O₃ and NO_x during the degradation of toluene were studied. The exhaust in the process of toluene degradation was continuously detected and analyzed, and the degradation mechanism of toluene was explored. The results showed that the concentration of O₃ increased with the increase of the power density and discharge voltage of the plasma device. However, as the initial concentration of toluene increased, the concentration of O₃ basically keep steady. The concentration of NO_x in the by-products increased with the discharge voltage, power density, and initial concentration of toluene in the plasma device, and the concentration of NO₂ was much higher than the concentration of NO. The degradation process of toluene was detected and analyzed. The results showed that the degradation mechanism of toluene by plasma includes high energy electron bombardment reaction, active radical reaction and ion molecule reaction. Among them, the effect of high-energy electrons on toluene degradation is the largest, followed by the effect of free radicals, in which oxygen radicals participated in the reaction mainly through the formation of C–O bond, CO bond, (CO)–O– bond and –OH radical, while nitrogen radicals participate in the reaction mainly through the formation of C–NH₂, (CNH)- bond, CN bond and C–NO₂ bond. The results can provide some data supports for the study of low-temperature plasma degradation of VOCs.     

Intrinsically flame retardant epoxy resin - Fire performance and background - Part I

The flame retardant effect of newly synthesized phosphorus-containing reactive amine, which can be used both as crosslinking agent in epoxy resins and as a flame retardant, was investigated. The effect of montmorillonite and sepiolite additives on the fire induced degradation was compared to pristine epoxy resin. The effect of combining the organophosphorous amine with clay minerals was also studied. It could be concluded that the synthesized phosphorus-containing amine, TEDAP can substitute the traditional epoxy resin curing agents providing additionally excellent flame retardancy: the epoxy resins flame retarded this way reach 960 °C GWFI value, 33 LOI value and V-0 UL-94 rating - compared to the 550 °C GWFI value, 21 LOI value and “no rate” UL-94 classification of the reference epoxy resin. The peak of heat release was reduced to 1/10 compared to non-flame retarded resin, furthermore a shift in time was observed, which increases the time to escape in case of fire. The flame retardant performance can be further improved by incorporating clay additives: the LOI and the HRR results showed that the optimum of flame retardant effect of clay additives is around 1 mass% filler level in AH-16-TEDAP system. Applying a complex method for mechanical and structural characterization of the intumescent char it was determined that the flame retarded system forms significantly more and stronger char of better uniformity with smaller average bubble size. Incorporation of clay additives (owing to their bubble nucleating activity) results in further decrease in average bubble diameter.     

1‐Oxa‐nido‐dodecaborate [OB11H12]− from the Controlled Oxidation of the closo‐Borates [B11H11]2− and [B12H12]2−

The closo‐dodecaborate [B₁₂H₁₂]^2? is degraded at room temperature by oxygen in an acidic aqueous solution in the course of several weeks to give B(OH)₃. The degradation is induced by Ag²⁺ ions, generated from Ag⁺ by the action of H₂S₂O₈. Oxa‐nido‐dodecaborate(1?) is an intermediate anion, that can be separated from the reaction mixture as [NBzlEt₃][OB₁₁H₁₂] after five days in a yield of 18 %. The action of FeCl₃ on the closo‐undecaborate [B₁₁H₁₁]^2? in an aqueous solution gives either [B₂₂H₂₂]^2? (by fusion) or nido‐B₁₁H₁₃(OH)^? (by protonation and hydration), depending on the concentration of FeCl₃. In acetonitrile, however, [B₁₁H₁₁]^2? is transformed into [OB₁₁H₁₂]^? by Fe³⁺ and oxygen. The radical anions [B₁₂H₁₂] ^{˙ ?} and [B₁₁H₁₁] ^{˙ ?} are assumed to be the primary products of the oxidation with the one‐electron oxidants Ag²⁺ and Fe³⁺, respectively. These radical anions are subsequently transformed into [OB₁₁H₁₂]^? by oxygen. The crystal structure analysis shows that the structure of [OB₁₁H₁₂]^? is derived from the hypothetical closo‐oxaborane OB₁₂H₁₂ by removal of the B3 vertex, leaving a non‐planar pentagonal aperture with a three‐coordinate O vertex, as predicted by NMR spectra and theory.     

Synthesis of persulfate containing poly (N-vinyl-2-pyrrolidone) (PVP) hydrogels in aqueous solutions by γ-induced radiation

The effect of ⁶⁰Co γ-irradiation on aqueous solutions of poly(N-vinyl-2-pyrrolidone) (PVP) in the presence of persulfate anion has been investigated. The gelation dose of PVP and persulfate containing PVP aqueous solutions has been determined. At low concentrations of persulfate (1.00–3.50%), gelation percentages exhibited a decreasing trend by increasing persulfate content in aqueous solutions of the polymer. The gelation doses of persulfate containing polymer solutions were calculated by the Charlesby–Pinner equation. It was observed that the gelation dose values were shifted to higher values by increasing persulfate concentration in solution. The ratio of the chain scission and crosslinking yields (G(s)/G(x)) was also determined. The results showed that the G(s)/G(x) ratios were smaller than one for PVP aqueous solution system, whereas those obtained for persulfate containing PVP aqueous solutions were higher than unity. The results implied that the chain scission of polymer is more effective than crosslinking in the presence of persulfate. Mechanism of the crosslinking and/or degradation and structure–property relationship of PVP and PVP/persulfate hydrogel systems were investigated by Fourier transformation infeared and thermal analysis (differential scanning calorimetry, thermal gravimetric analysis and differential thermai analysis) methods.     

Photocatalytic degradation of sulfadiazine in suspensions of TiO2 nanosheets with exposed (001) facets

Antibiotics such as sulfonamides are widely used in agriculture as growth promoters and medicine in treatment of infectious diseases. However, the release of these antibiotics has caused serious environmental problems. In this paper, photocatalytic oxidation technology was used to degrade sulfadiazine (SDZ), one of the typical sulfonamides antibiotics, in UV illuminated TiO₂ suspensions. It was found that TiO₂ nanosheets (TiO₂-NSs) with exposed (001) facets exhibit much higher photoreactivity towards SDZ degradation compared to TiO₂ nanoparticles (TiO₂-NPs) with a rate constant increases from 0.017 min⁻¹ to 0.035 min⁻¹, improving by a factor of 2.1. Under the attacking of reactive oxygen species (ROSs) such as superoxide radicals (O₂^–) and hydroxyl radicals (OH), SDZ was steady degraded on the surface of TiO₂-NSs. Based on the identification of the produced intermediates by LC–MS/MS, possible degradation pathways of SDZ, which include desulfonation, oxidation and cleavage, were put forwards. After UV irradiation for 4 h, nearly 90% of the total organic carbon (TOC) can be removed in suspensions of TiO₂-NSs, indicating the mineralization of SDZ. TiO₂-NSs also exhibits excellent stability in photocatalytic degradation of SDZ in wide range of pH. Even after recycling used for 7 times, more than 91.3% of the SDZ can be efficiently removed, indicating that they are promising to be practically used in treatment of wastewater containing antibiotics.     

DNA microarray: a high throughput approach for methylation detection

We described a DNA microarray-based method combined with bisulphite treatment of DNA and regular PCR to examine hyper-methylation in promoter 1A of APC gene. A set of oligonucleotide probes were designed and immobilized on the aldehyde-coated glass slides for detecting the methylation pattern of 15 selected CpG sites in the region. The methylation status of 30 colorectal tumor samples have been examined by both of methylation-specific PCR (MS-PCR) and the present microarray method. The methylation pattern of the 15 CpG sites for the samples have been obtained with the microarray. A total of 19 samples out of 30 were methylated by microarray, in which five samples cannot be detected by MS-PCR due to the methylated CpG patterns not accordant to the MS-PCR primers. The detecting ratio for methylation of APC gene of colorectal tumor samples increased from 46.7% with MS-PCR to 63.3% with the microarray, which successfully demonstrated that DNA microarray-based method not only can obtained the methylation patterns for the related genes, but also decrease the false-negative results of methylation status by the conventional MS-PCR for the investigated genes.     

Static ultrasonic oscillations induced degradation and its effect on the linear rheological behavior of novel propylene based plastomer melts

The ultrasonic degradation of novel propylene based plastomer (DP) melts with different melt viscosities was conducted in a “static” ultrasonic device where the samples were taken from various distances from the tip of an ultrasonic probe. The effects of ultrasonic time, oscillation temperature, ultrasonic intensity and the distance from the ultrasonic probe tip on the degradation behavior of DP melts as well as the ultrasonic degradation effect on the linear rheological behavior of DP melts were studied. The results show that the increase of initial melt viscosity of DP (higher molecular weight) has greater impact on the ultrasonic degradation of DP melt. The molecular weight and intrinsic viscosity of DP decrease with the increase of ultrasonic oscillation time and they approach to a limiting value. The molecular weight distribution of DP increases after ultrasonic degradation. Decreasing oscillation temperature and distance from probe tip and increasing ultrasonic intensity lead to an increase in the degradation of DP melt. The linear rheological behavior measurements of the samples obtained near the ultrasonic probe tip show that ultrasonic oscillations decrease the complex viscosity, zero shear viscosity, viscoelastic moduli, cross modulus, relaxation time and the slope of log G′ − log G″ for DP melts.     

Dissipative structures formed in the course of drying the colloidal crystals of silica spheres on a cover glass

Macroscopic and microscopic dissipative structural patterns formed in the course of drying the deionized aqueous colloidal crystal suspensions of silica spheres (diameter: 103 nm) on a cover glass have been observed. Spoke-like and ring-like patterns are formed in the macroscopic scale; the former is the crack in the sphere film and the latter is the hill accumulated with spheres formed around the outside edge. The neighbored inter-spoke angle, thickness of the film, and other morphological parameters have been discussed as a function of sphere concentration, concentration of sodium chloride, and the inclined angle of the cover glass. Fractal patterns of the mud cracks are observed in the microscopic scale. Capillary forces between spheres at the air-liquid surface and the relative rates between the water flow at the drying front and the convection flow of spheres are important for the pattern formation. Electronic Publication     

Ti基IrO2＋Ta2O5阳极在H2SO4溶液中的电解时效行为

研究了450 ℃制备所得Ti/70％IrO2 30％Ta2O5（摩尔分数）高寿命阳极在H2SO4溶液电解过程中电极的物理、化学及电化学性能的时效行为.结果发现，整个电解过程可分为“活化”、“稳定”及“失效”三个阶段.在“活化”及“稳定”区内主要发生电极表面活性氧化物的溶解，涂层中IrO2金红石相的（110）、（101）晶面择优取向随电解时间延长而减弱，而（002）晶面择优增强.但是在“失效区”内，各晶面的择优程度却不随电解时间的变化而变化，这表明在“失效区”内氧化物的损失机制发生了变化.电化学阻抗谱测试表明，电极的析氧电化学反应电阻随电解时间的延长发生缓慢而连续的上升，而整个电极的物理阻抗在“失效区”内却发生突升现象.X射线衍射分析（XRD）表明，随电解时间的延长TiO2金红石相的衍射强度增大，达“失效区”时衍射强度发生突升.根据实验现象特别是“失效区”内阳极的时效行为提出高寿命Ti基氧化物涂层阳极的失效机制.     

微波无极紫外光助双氧水处理活性艳红X-3B染料废水研究

活性艳红X-3B(C.I.ReactionRed 2)是一种单偶氮染料,其应用范围广泛,可用于棉、粘纤、涤/棉、锦纶、蚕丝、羊毛、锦/粘等织物的染色和丝绸的印花,因此其废水量大且色度深。目前染料废水的生物处理方法脱色效果差、占地面积大、处理周期长,传统的物理法和化学法也存在着成本高、不能彻底矿化染料分子等缺点。近年来发展起来的光化学处理染料废水的方法及各种光化学组合技术日益受到人们关注,但其中使用的普通紫外灯存在使用寿命短、启动慢、发光不稳定、电极材料易损等缺点[1],致使光化学方法处理废水的成本很高。本文利用微波产生的高频…