GC-MS法用于苯二甲酸酐催化氯化过程的研究

将ＧＣ－ＭＳ用于以氯磺酸为介质（在Ｆｅ和Ｉ２存在的情况下）苯二甲酸酐催化氯化合成四氯苯酐的反应过程研究,对反应物中间体产物（一,二,三氯苯二甲酸酐及异构体）进行了定性和相对百分含量分析,找出了提高收率的最佳工艺条件。     

Synthesis and photoluminescence properties of ZnO nanowire arrays

In this paper we report a chemical method named coordination reaction method to synthesize ZnO nanowire arreys. ZnO nanowires with the diameter about 80nm were successfully fabricated in the channels of the porous anodic alumina (PAA) template by the above coordination reaction method. The microstructures of ZnO/PAA assembly were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The results showed that the ZnO nanowires can be uniformly assembled into the nanochannels of PAA template. The growth mechanism of ZnO nanowires and the conditions of the coordination reaction are discussed. Photoluminescence (PL) measurement shows that the ZnO/PAA assembly system has a blue emission band caused by the various defects of ZnO. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Comparison of methodologies for determination of residual peracetic acid in wastewater disinfection

The use of peracetic acid (PAA) in the disinfection of sanitary effluents provides an opportunity for the study of analytic methods that permit the determination of the residual concentration of the disinfectant in the effluent. The object of the present study is to compare different methodologies for the determination of residual PAA in concentrations recommended for disinfection of wastewater. The methodologies adopted in this study include three redox titration methods and one spectrophotometric method. Preliminary tests were performed by adding PAA (0.1; 0.5; 1.0; 5.0 and 10.0?mg?L^?1) to distilled water, and later reevaluated by applying the same concentrations of the disinfectant in wastewater. The results obtained were statistically evaluated and showed that the concentrations between 0.5 and 10?mg?L^?1 of PAA could be determined both by the cerimetric/iodometric titration method and by the spectrophotometric method using DPD chromophore with catalase. For concentrations between 0.1 and 0.5?mg?L^?1, only the spectrophotometric method provided satisfactory results.     

Removal of heavy metal ions from aqueous solutions by filtration with a novel complexing membrane containing poly(ethyleneimine) in a poly(vinyl alcohol) matrix

A novel complexing membrane was used for the removal of heavy metal ions such as Pb(II), Cd(II) and Cu(II) from aqueous solutions. The membrane consists in a semi-interpenetrating polymer network of crosslinked poly(vinyl alcohol) as the matrix and poly(ethyleneimine) as the complexing polymer. The absorption reactions followed pseudo-first-order kinetics with similar rate constants for the three cations. A model is proposed for the absorption–desorption process in order to rationalize the data obtained for the retention ratio and the retention efficiency ratio. The corresponding equilibrium constants were determined for the three metal ions, showing that the affinity order of the membrane is Pb > Cu > Cd. This sequence is consistent with the order of maximum uptake of the ions per gram of membrane: 0.59, 0.47 and 0.33 mmol g⁻¹, respectively. On the other hand, the uptake order is different on a mass basis: 123, 30 and 37 mg g⁻¹, respectively. Regeneration of the membrane and metal recovery were studied with HCl and HNO₃ at different concentrations. Filtration of solutions of each metal ion showed large elimination ratios (96–99.5%) with a retention sequence Cd > Cu > Pb. The membrane remained efficient until complete saturation of its sites. Moreover, Cu retention is larger than expected, indicating possible additional chelation by the PVA matrix. Better retention ratios were observed when the concentration of the feed solution was kept constant. Filtration of a mixture of the three cations (all at 100 ppm concentration) resulted in the same retention sequence, but the elimination ratios were smaller and Pb was eventually displaced by Cu and Cd that were present in larger molar concentrations.     

Lysozyme purification from tobacco extract by polyelectrolyte precipitation

Tobacco is widely used as a model plant for feasibility studies of recombinant protein production from transgenic plants. However, dealing with large quantities of biomass to recover recombinant proteins is a challenge for down-stream processing. In this study, the effect of isoelectric precipitation on native tobacco protein was first studied. Among the three acids studied, hydrochloric acid is shown to be more effective than acetic or citric acid, and at pH 4, 60% of native tobacco protein was precipitated by HCl. Egg white lysozyme was used as the model protein to test the feasibility of polyelectrolyte precipitation in protein recovery from tobacco extract. Precipitation of lysozyme at pH 7 was shown ineffective probably because of the interference of polyphenolic acids. However, after isoelectric precipitation at pH 5 poly(acrylic) acid (PAA) was shown to precipitate 85% of the soluble lysozyme when the polymer dosage was increased to 1.5 mg polymer/mg lysozyme, while negligible amounts of native tobacco protein was co-precipitated. Lysozyme precipitation by PAA in tobacco extract obtained at pH 5 was also studied, and lysozyme yield was significant improved.     

Preparation of polyelectrolyte multilayer membranes by dynamic layer-by-layer process for pervaporation separation of alcohol/water mixtures

In the past decades, the layer-by-layer (LBL) adsorption of oppositely charged polyelectrolytes has proven to be a promising method for the preparation of polyelectrolyte multilayer membranes. However, to obtain a good separation capability, LBL adsorption involved relatively long periods because 50–60 bilayers were normally required. The aim of this study was to develop such a new method that would allow simplification of the LBL procedure. LBL adsorption was proposed to proceed under a dynamic condition to prepare polyelectrolyte multilayer membranes. The polyacrylic acid (PAA) and polyethyleneimine (PEI) were alternatively deposited on polyethersulfone (PES) ultrafiltration support membrane under a pressure of 0.1 MPa. The polyelectrolyte multilayer membranes prepared by dynamic LBL process were compared with those prepared by the static LBL process for the pervaporation separation of water–ethanol mixture. The results suggested that a relatively high separation factor could be obtained with only four composite bilayers by using dynamic LBL process. The preparative conditions including bilayer number, filtration time of the first PAA layer, reaction time, ratio between polayanion and polycation concentrations, PAA molecular weight and salt addition were investigated. The pervaporation conditions such as feed temperature and water concentration in the feed were also evaluated. Under the temperature of 40 °C, the separation factor and the permeate flux of the polyelectrolyte multilayer membranes were about 1207 and 140 g/(m² h), respectively.     

吸附聚丙烯酸对纳米碳管表面特征影响的研究

利用低温氮气吸附法系统研究了吸附聚丙烯酸 (PAA)的量对纳米碳管表面特征的影响 .分析结果表明 :当PAA吸附量增加到 2 68 98mg·g-1时 ,纳米碳管的比表面积下降了 46 97% ;虽然吸附PAA后的纳米碳管在 1 8nm以上的孔径分布特征基本上与原样一致 ,但孔容减少 ,这部分孔对比表面的贡献明显降低 ,同时出现 1 8nm以下的孔 ;通过氮气吸附等温线利用热力学方法计算的纳米碳管的表面分维值 (surfacefractaldimension)dSF由原样的 2 5 4下降至吸附后的 2 48,表明吸附PAA分子能够降低纳米碳管的粗糙度 .这些说明堵孔效应和屏蔽效应是纳米碳管表面特征改变的主要因素 ,这一研究对纳米碳管在吸附、催化等方面的应用有着非常重要的意义 .     

PVA/PAA水凝胶纤维的电刺激响应性能

以过硫酸胺为引发剂,在PVA水溶液中原位聚合丙烯酸单体,得到的PVA／PAA混合水溶液在凝固浴硫酸胺饱和水溶液中纺丝制备了物理缠结和氢固定网络形式的PVA／PAA水凝胶纤维。该纤维于NaCl溶液中在直流电场作用下具有电流－刺激敏感性,表现为溶胀、收缩、弯曲行为。纤维的弯曲速度和最大弯曲度随电场强度和凝胶网络中PAA含量的增加而增大,随电解质溶液离子强度的变化出现临界最大值。纤维向负极弯曲的过程中,在电场下自由离子和反庆子迁移引起的渗透压主导作用,弯曲过程主要是溶胀弯曲;向正极弯曲过程中,由于电化学反应和电场作用下产生的PH梯度导致凝胶网络构像变化主导作用,弯曲主要是收缩弯曲;弯曲由负极向正极转化过程中,两种机理对弯曲的影响相对平衡。     

STUDIES ON REVERSE OSMOSIS SEPARATION OF AQUEOUS ORGANIC SOLUTIONS BY PAA/PSF COMPOSITE MEMBRANE

The reverse osmosis (RO) separation of aqueous organic solutions, such as alcohols, amines, aldehydes, acids,ketones, and esters etc., by PAA (polyacrylic acid)/PSF (polysulfone) composite membrane has been studied. It was foundthat the separation results for aliphatic alcohols, amines and aldehydes are satisfactory, the solute rejection (R_a) and thevolume fluxes of solutions (J_v) for 1000 ppm ethanol, ethylamine and ethyl aldehyde are 66.2%, 61.0%, 84.0% and 0.90×10~(-6), 0.35×10~(-6), 0.40×10~(-6) m~3/m~2·s, respectively, at 5.0 MPa and 30℃. R_a increased with increasing molecular weights ofalcohols, amines and aldehydes, and the R_a for n-amyl alcohol, n-butylamine and n-butyl aldehyde reached 94.3%, 88.6%and 96.0%, respectively. Satisfactory separation results (R_a>70%) for ketones, esters, phenols and polyols have beenobtained with the PAA/PSF composite membrane. The effect of operating pressure on the properties of reverse osmosis hasalso been investigated. Analysis of experimental data with Spiegler-Kedem's transport model has been carried out and themembrane constants such as reflection coefficient σ, solute and hydraulic permeabilities ω and L_p for several organic soluteshave been obtained.