Modified modeling of the effect of pH and viscosity on the mass transfer in hydrophobic hollow fiber membrane contactors

This paper studied the effect of pH and the viscosity of feed solution on the mass transfer in two different specifications of hydrophobic hollow fiber membrane contactors. Experimental results showed that the pH of the feed had a significant effect on the rate of mass transfer, the flux and the removal efficiency of easily ionized volatile compounds (VCs), such as ammonia. In unbuffered feed solutions, both the resistance of membrane and the resistance of feed side were affected by the pH of feed and both of them had contributions to the overall mass transfer. A model, , was proposed to predict the effect of pH and gave good agreement with the experimental data for the two contactors. The relationship between viscosities and the mass transfer coefficient could be described by . Based on our experiments, the change of the viscosities in the concentration range of ammonia from 50 to 10,000 mg l⁻¹ caused about 3–4% variation of the mass transfer coefficients. Moreover, it may be more suitable to use the equilibrium concentrations of volatile species instead of the total concentrations of VCs to estimate mass transfer coefficients, removal efficiency and flux. Experimental results also revealed that the choice of the pH of feed might be one of the most crucial factors for removing easily ionized VCs, such as ammonia, from water and wastewater.     

C9‐Iridoids from Scrophularia buergeriana

Four new iridoids, buergerinins B–E ( 1 – 4 ), along with three known iridoids, were isolated from the roots of Scrophularia buergeriana. Their structures were identified on the basis of spectroscopic analysis.     

An Efficient Synthesis of Pyrazolo[3,4‐b]Pyridine Derivatives in Aqueous Media

A series of pyrazolo[3,4‐b]pyridines was synthesized by the reaction of 5‐aminopyrazole with benzylidenemalononitrile in aqueous media. The structures were characterized by IR, ¹H NMR, and elemental analysis and were further confirmed by X‐ray diffraction analysis.     

1－芳氧乙酰氧基－1－（1H－1，2，4－三唑－1－基）－3，3－二甲基－2－丁酮衍生物的研究

以三乙胺为缚酸剂，用芳氧乙酸同ω－溴代－ω－（１Ｈ－１，２，４－三唑－１－基）频哪酮反应，合成了一系列三唑类新化合物，探讨了化合物的合成方法。通过ＩＲ￣１ＨＮＭＲ、ＭＳ分析及元素分析确定了化合物的结构，生物活性测定结果表明，部分化合物具有良好的除草活性，同时表现出一定程度的植物生长调节活性及杀菌活性．     

反相高效液相色谱法的多波长同时测定预混合饲料中的脂溶性维生素A，α－E，D_3，K_3

反相高效液相色谱法的多波长同时测定预混合饲料中的脂溶性维生素Ａ，α－Ｅ，Ｄ＿３，Ｋ＿３李桂凤，李缙扬，郝征红，聂燕，孟兆宏，李学春（山东省农业科学院中心实验室济南２５０１００）１前言对脂溶性维生素的分析，被许多国内外分析专家认为是高难度的分析项目。本...     

Comparative X-ray photoelectron spectroscopic study on the desulfurization of thiophene by Raney nickel and rapidly quenched skeletal nickel

The desulfurization of thiophene on Raney Ni and rapidly quenched skeletal Ni (RQ Ni) has been studied in ultrahigh vacuum (UHV) by X-ray photoelectron spectroscopy (XPS). The Raney Ni or RQ Ni can be approximated as a hydrogen-preadsorbed polycrystalline Ni-alumina composite. It is found that thiophene molecularly adsorbs on Raney Ni or RQ Ni at 103 K. At 173 K, thiophene on alumina is desorbed, while thiophene in direct contact with the metallic Ni in Raney Ni undergoes C-S bond scission, leading to carbonaceous species most probably in the metallocycle-like configuration and atomic sulfur. On RQ Ni, the temperature for thiophene dissociation is about 100 K higher than that on Raney Ni. The lower reactivity of RQ Ni toward thiophene is tentatively attributed to lattice expansion of Ni crystallites in RQ Ni due to rapid quenching. The existence of alumina and hydrogen may block the further cracking of the metallocycle-like species on Raney Ni and RQ Ni at higher temperatures, which has been the dominant reaction pathway on Ni single crystals. By 473 K, the C 1s peak has disappeared, leaving nickel sulfide on the surface.     

Co-immobilization of polymeric luminol,iron(II) tris(5-aminophenanthroline) and glucose oxidase at an electrode surface,and its application as a glucose optrode

The anodic polymerization of 3-aminophthalhydrazide (luminol) and iron(II) tris 5-aminophenanthroline (Fe(phen-NH2)3(2+)) has been reported in this paper. A bilayer electrode was developed based on these polymers and the ITO conductive glass (denoted ITO[Fe(phen-NH2)3(2+)]luminol electrode). This electrode emitted light (lambdaem: 430 nm) as it was brought into contact with H2O2. At pH 10, the resulting electrochemiluminescence (ECL) showed a linear relationship with the concentration of H2O2 in the range of 10 microM(-1) mM. This bilayer electrode also showed an application potential for the detection of glucose after being further modified with glucose oxidase (denoted ITO[Fe(phen-NH2)3(2+)]luminol]GOx electrode). Although the resulting ECL decayed more rapidly in concentrated glucose solutions (e.g., I M) because of the consumption of luminol during use, the decay became less severe in diluted glucose solutions (e.g., 10 mM). According to the flow injection analysis, a linear relationship existed between the ECL and the concentration of glucose from 10(-5)-10(-3) M at pH 9. The detection limit could reach a level of 5 x 10(-5) M at this pH.     

Determination of N-Methylpyrrolidine in Cefepime for Injection by Capillary Electrophoresis with Indirect UV Detection

N-Methylpyrrolidine in cefepime for injection was determined by capillary electrophoresis with indirect UV detection. Best results were achieved with background electrolyte consisting of 10 mM creatinine adjusted to pH 3.8 with formic acid and an applied voltage of 30 kV in a bare fused-silica capillary. Indirect UV detection was performed at a wavelength of 225 nm. The application of a small amount of inlet pressure during the separation assisted the attainment of a stable baseline. The optimized method was validated regarding selectivity, linearity, accuracy, precision, ruggedness, repeatability and detection limits. Careful control of capillary conditioning enabled migration time precision values of <0.2% RSD. The use of an internal standard enabled precision values of <1% RSD to be obtained for peak area ratios.     

Crystal Structure of Dimethylamine 3,5-Dinitrobenzoic Acid Organic Adduct

1 INTRODUCTION Nonlinear optics (NLO) is at the forefront of cur- rent researches because of its importance in provi- ding the key functions of frequency shifting, optical modulation, optical switching, optical logic and op- tical memory for the emerging …     

催化燃烧去除VOCs污染物的最新进展

催化燃烧是目前最有效的处理挥发性有机物(VOCs)技术之一. 本文从催化剂活性组分、催化剂载体、有效组分颗粒大小、水蒸汽的影响及催化燃烧反应中的积碳等几个方面, 对近年来催化燃烧处理VOCs的研究进行了总结. 分析表明: 贵金属催化剂的研究主要着重于选择有效的载体和双组分贵金属催化剂; 非贵金属催化剂的研究主要集中在高活性的过渡金属复合氧化物、钙钛矿和尖晶石型等催化剂的研制, 还有这些活性组分粒径大小及载体对催化燃烧VOCs反应活性的影响;此外, 在实际应用中,水蒸汽和催化剂积碳失活等问题对催化燃烧VOCs的反应也有很大影响. 本文的评述将为选择合适的催化燃烧技术处理VOCs污染物提供一定参考.