Toluene degradation by a water/silicone oil mixture for the design of two phase partitioning bioreactors

Toluene degradation performances were studied in a 10 L Two-Phase Partitioning Bioreactor (TPPB).The liquid phase consisted of a mixture of water and PDMS 50 (PolyDiMethylSiloxane,i.e.silicone oil,viscosity of 46 maa·s) in the volume ratio of 75％/25％.Two series of experiments were carried out:in the first,the reactor was sequentially supplied with toluene whereas in the second,toluene was continuously supplied.Activated sludge from the wastewater treatment plant of Beaurade (Rennes,France) was used at an initial concentration of 0.5 dry mass g· (mixture L)-1.The elimination capacity (EC) was investigated as well as the change in biomass concentration over time.Toluene biodegradation was very efficient (removal efficiency,RE =100％) for toluene flows ranging from 0.2 to 1.2 ml· h-1,corresponding to elimination capacities of up to 104 g· m-3· h-1.For a toluene flow of 1.2 ml·h-1,the biomass concentration measured at the end of the experiment was 4.7 dry mass g.(mixture L)-1.The oxygen concentration in the liquid phase was clearly not a limiting factor in these operating conditions.Based on these results,an extrapolation leading to the design of a large-scale pilot TPPB can now be considered to study toluene degradation performances in industrial conditions.     

碾磨力场作用下聚丙烯结构变化的研究

本文研究了磨盘碾磨过程中聚丙烯 (PP)的粉碎、降解、交联、氧化和晶型转化等结构变化 ,考察了不同液体介质及不同填料与PP共碾磨时对PP降解和粉碎的影响。     

Inquire into degradation process of Ni-Co coating in 3.5% NaCl solution by EIS北大核心CSCD

The degradation process of Ni-Co coating on plate of Kovar alloy 4J42 in 3.5%NaCl solution was studied by means of electrochemical impedance spectroscope (EIS). Four distinguished electrical equivalent circuits (EEC) were proposed to simulate the degradation process. At the very beginning of immersion, the coating exhibited excellent corrosion resistance, which could be treated as a barrier layer with a high resistance in parallel with a low capacitance. After a short time of immersion, a double-layer capacitance Cdl and a charge-transfer resistance Rct were introduced, indicating that the electrochemical reactions at the metal/coating interface may take place. In the late stage of immersion, Warburg impedance was adopted to characterize the corrosion products. With the accumulation of the corrosion products, the diffusion process of corrosive medium was affected, and the EEC comprising a diffusion capacitance (Cdiff) and a diffusion resistance (Rdiff) was then introduced to fit the impedance spectra. The evolution of coating resistance and coating capacitance were investigated to illuminate the Ni-Co coating degradation process. The results showed that the degradation process of Ni-Co coating could be described by three stages: the permeation of corrosive medium, the corrosion of metal at the interface of coating/substrate and finally the failure of coating. © 2016, Corrosion Science and Protection Technology. All rights reserved.     

聚氨酯弹性体的降解及其稳定剂

评述了聚氨酯弹性体所经历的热氧降解、水解,光降解和微生物降解等降解过程。介绍了用于抑制这些降解的多种稳定剂以及它们的稳定机理。     

Synthesis, characterization and degradation of poly(dl-lactide)-block-polyvinylpyrrolidone-block-poly(dl-lactide) copolymers

A new kind of A-B-A block copolymers with good biocompatibility and adjustable degradability was synthesized by ring-opening polymerization, in which DL-lactide polymerized and grew from the two ends of polyvinylpyrrolidone (PVP). The well-defined triblock structures of copolymers were characterized by GPC, ¹H NMR, FTIR and DSC. There were two pronounced glass transition temperatures which showed apparent microphase separations between hydrophilic PVP segment and hydrophobic poly(dl-lactide) (PDLLA) segments. The hydrolytic degradation of PDLLA and copolymers in phosphate buffer solution (PBS, pH = 7.4) showed that the degradation rate of copolymers apparently became faster in comparison with that of PDLLA homopolymer, and increased with increasing PVP content. The measurements through ¹H NMR and FTIR showed that the degraded fragments contained PDLLA oligomers, lactates and soluble chains composed of PVP blocks attached with short PDLLA ones.     

Photocatalytic activity of nanocrystalline mesoporous-assembled TiO2 photocatalyst for degradation of methyl orange monoazo dye in aqueous wastewater

In this work, nanocrystalline mesoporous-assembled TiO₂ photocatalyst was synthesized by a sol–gel process with the aid of a structure-directing surfactant and employed for the photocatalytic degradation of methyl orange azo dye (monoazo dye), as compared to various commercially available non-mesoporous-assembled TiO₂ powders. The experimental results showed that the synthesized mesoporous-assembled TiO₂ nanocrystal calcined at 500 °C provided superior decolorization and degradation performance to the non-mesoporous-assembled commercial TiO₂ powders. In addition, several operational parameters affecting the decolorization and degradation of methyl orange, namely photocatalyst dosage, initial dye concentration, H₂O₂ concentration, and initial solution pH, were systematically investigated, using the mesoporous-assembled TiO₂ nanocrystal. The optimum conditions were a photocatalyst dosage of 7 g/l, an initial dye concentration of 5 mg/l, a H₂O₂ concentration of 0.5 M, and an initial solution pH of 4.7, exhibiting the highest decolorization rate of methyl orange.     

In vitro hydrolytic degradation of poly(para-dioxanone) with high molecular weight

The in vitro hydrolytic degradation of high molecular weight poly (para-dioxanone) was studied by examining the changes of weight retention, water absorption, pH value, tensile strength, break elongation, thermal properties, and morphology of high molecular weight PPDO in phosphate buffered saline (PBS) (pH 7.44) at 37°C for 8 weeks. During the degradation, all samples’ weight retention decreased and water absorption increased significantly, whereas hydrolysis rate of PPDO bars varied with molecular weight. Compared with lower molecular weight samples, higher molecular weight PPDO samples exhibited higher hydrolysis rate. The samples’ glass transition temperature (Tg) decreased notably, while the degrees of crystallinity (Dc) increased. The samples almost totally lost their tensile strengths and breaking elongation after 4 weeks of degradation. The results suggested that the stability of PPDO in vitro hydrolytic degradation increased with the increase of molecular weight.     

Decolorization of methylene blue by heterogeneous Fenton reaction using Fe3−xTixO4 (0 ≤ x ≤ 0.78) at neutral pH values

In this work, a series of Fe_3−xTi_xO₄ (0 ≤ x ≤ 0.78) was synthesized using a new soft chemical method. The synthetic Fe_3−xTi_xO₄ were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy, thermogravimetric and differential scanning calorimetry (TG–DSC) analyses. The results showed that they were spinel structures and Ti was introduced into their structures.Then, decolorization of methylene blue (MB) by Fe_3−xTi_xO₄ in the presence of H₂O₂ at neutral pH values was studied using UV–vis spectra, dissolved organic carbon (DOC) and element C analyses. Furthermore, the degradation products remained in reaction solution after the decolorization were identified using ionic chromatography (IC), ¹³C nuclear magnetic resonance spectra (NMR), liquid chromatography and mass spectrometry (LC–MS). Although small amounts of MB were mineralized, the aromatic rings in MB were destroyed completely after the decolorization. Decolorization of MB by Fe_3−xTi_xO₄ in the presence of H₂O₂ was promoted remarkably with the increase of Ti content in Fe_3−xTi_xO₄ due to the enhancement of both adsorption and degradation of MB on Fe_3−xTi_xO₄.     

环境内分泌干扰物双酚A的降解研究进展

双酚A是一种典型的环境内分泌干扰物,其负面作用随着使用的扩大而日益受到人们的重视。介绍了双酚A的理化性质、应用情况、生物毒性及污染现状,概述了国内外学者对双酚A降解方法与技术（物理法、化学法、生物法等）的研究及影响因素的探讨,并提出了未来研究的主要方向。     

Effects of Some Metals and Chelating Agents on Patulin Degradation by Ozone

The efficiency of ozone treatment for degradation of the mycotoxin patulin in the presence of various metal ions was evaluated in model systems. An initial patulin concentration of 250 μg/L was ozonated and residual ozone concentration was about 0.17±0.01 mg/L at the end of the experiment. Patulin showed a weak resistance to ozone, because up to 98% of this toxin was oxidized in only one minute. Degradation rates in the presence of calcium, aluminum, copper and zinc were almost the same in the absence of these metals. However, degradation of patulin was reduced from 98 to 37% when the concentration of manganese increased from 0 to 3 mg/L. Patulin was almost completely degraded in the absence of iron, while the degradation was only 8.5% in the presence of 0.5 mg/L of iron. These results have revealed that manganese and iron significantly reduce the detoxification of patulin by ozone. Agents such as ethylenediaminetetraacetic acid and sodium polyphosphate effectively chelated iron and increased the degradation rate of patulin. None of the tested agents were able to chelate manganese and to enhance patulin degradation by ozone.