Adsorption of fluoride on synthetic siderite from aqueous solution

The study has investigated the feasibility of using synthetic siderite for F⁻ removal from aqueous solution. Batch experiments were performed to test effects of adsorbent dosage, contact time, initial F⁻ concentration, temperature, solution pH, and coexisting anions on F⁻ removal. Results show that the kinetic rate of F⁻ adsorption was high in the first 2 h, and thereafter significantly decreased. The kinetic data was better fitted to the pseudo-second order kinetic model than the pseudo-first order kinetic model. In comparison with Langmuir isotherm, both Freundlich and Redlich-Peterson isotherms better described the adsorption process, which indicates that the multilayer adsorption should be involved in the process of F⁻ removal. Thermodynamic study manifests that F⁻ adsorption on synthetic siderite was spontaneous and exothermic in nature. The synthetic siderite had high adsorption capacity for F⁻ removal, which was up to 1.775 mg/g in the batch with an adsorbent dosage of 5 g/L and an initial F⁻ concentration of 20 mg/L at 25 °C. The adsorption was relatively independent on solution pH between 4 and 9. The presence of Cl⁻ and NO₃⁻ had less impact on F⁻ adsorption, while PO₄³⁻ significantly affected F⁻ removal from aqueous solution. Results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) suggest that the high adsorption capacity possibly arose from both coprecipitation of ferric hydroxide with F⁻ and adsorption of F⁻ on the fresh goethite.     

Direct cross-coupling of aryl alkynyliodines with arylsulfinic acids leading to alkynyl sulfones under catalyst-free conditions

A facile and efficient one-pot method has been developed for the construction of alkynyl sulfones via direct cross-coupling reaction of aryl alkynyliodines and arylsulfinic acids. The present transformation could be accomplished under catalyst- and additive-free conditions, providing a series of alkynyl sulfones in moderate to good yields with favorable functional group tolerance.     

A novel strategy for in situ maskless synthesis of biochips： Self-driving micro-fluid porous type printing （SMPTP）

A novel maskless technique,self-driving micro-fluid porous type printing(SMPTP),was reported to in situ synthesize oligonucleotide arrays on glass slide,which has the merits of low cost,high quality and simple craft.In SMPTP for fabricating gene- chips,porous fiber tubes with a number of nanometric or micron channels functioned as“active letters”and were assembled in designed patterns,which are identical to the distribution of monomers in each layer of the array,and four patterns were needed for each layer.By means of capillarity,the synthesis solution was automatically taken into porous tubes assembled in a printing plate and reached the surface.An oligonucleotide array of 160 features with four different 15-mer probes was in situ synthesized using this technique.The four specific oligonucleotide probes,including the matched and the mismatched by the fluorescent target sequence,gave obviously different hybridization fluorescent signals.     

Molecular simulation study of adsorption and diffusion on silicalite for a benzene/CO2 mixture

The adsorption and diffusion of a binary mixture of supercritical CO2 and benzene on silicalite (MFI-type) have been studied through the grand canonical Monte Carlo and molecular dynamics (MD) simulations. The adsorption behavior of pure CO2 on silicalite was discussed in detail from the adsorption isotherms, adsorption sites, interaction energies, and isosteric heats of adsorption. For the mixture, the influences of temperature, pressure and composition on the adsorption isotherms have been examined. The adsorption site behavior of the mixture has been analyzed, and benzene molecules get adsorbed preferentially in the more spacious channel intersection positions. These simulation results suggest that SC-CO2 fluid can be used as an efficient desorbent of larger aromatics in the zeolite material. The diffusion characteristic for the benzene/CO2 mixture was studied on the basis of MD simulation. It was found that the large coadsorbed benzene molecule has a pronounced effect on the CO2 diffusion in the mixture, while the mobility of benzene molecules is very small due to geometrical restrictions.     

High-performance thin-layer chromatographic analysis of selected organophosphorous pesticide residues in tea

The separation of 9 organophosphates (monocrotophos, quinalphos, triazophos, parathion-methyl, isofenphos-methyl, temephos, parathion, phoxim-ethyl, and chlorpyrifos) by high-performance thin-layer chromatography (HPTLC) with automated multiple development was studied. The HPTLC method was developed and validated for analysis of residues of phoxim-ethyl and chlorpyrifos in tea. The sample was extracted with acetonitrile and cleaned up by ENVI-CARB solid-phase extraction. The extract was directly applied as bands to glass-backed silica gel 60F254 HPTLC plates. The plates were developed with dichloromethane-hexane (1 + 1, v/v) in a glass twin-trough chamber. Evaluation of the developed HPTLC plates was performed densitometrically. The results indicated that the detection limits of phoxim and chlorpyrifos were 5.0 x 10(-9) and 1.0 x 10(-8) g, respectively. Recoveries of the pesticides from tea by this analytical method were 90.7-105.5%, and relative standard deviations were 7.3-13.5%. The precision and accuracy of the method were generally satisfactory for analysis of pesticide residues in tea.     

单层平面索网幕墙结构的几何非线性问题研究

单层平面索网支承式玻璃幕墙结构是近年来在国内外应用较为广泛的一种新型幕墙结构形式,由于单层平面索网不具有负高斯曲面形式,结构在平面外方向的刚度偏柔,表现出较明显的几何非线性特征.本文采用连续化方法建立了单层平面索网结构考虑几何非线性影响的静力平衡方程和振动方程,得到了结构刚度的解析表达式,并采用谐波平衡法求得非线性频率的简化解析表达式,以此为基础研究了单层平面索网结构的静力非线性和动力非线性问题.研究结果表明:结构的非线性和结构的初始位置密切相关;结构的非线性频率主要取决于索的初始应变、结构振动幅值与跨度的比值,几何非线性对于结构动力性能的影响要小于对结构静力性能的影响;本文得到的结构在地震荷载和平均风荷载作用下的非线性振动方程和非线性频率为结构在地震荷载和脉动风荷载作用下动力响应的求解奠定了基础.     

Thiazolidine Derivatives as Chiral Catalysts in the Enantioselective Addition of Diethylzinc to Benzaldehyde

Enantioselective addition ofdialkylzinc to aldehydes in the presence of catalytic amountsof chiral catalysts is one of the most important asymmetric C-C bond formation reactions.In most cases chiral fi -amino alcohols or their analogies were used as efficient catalystsin this reactionl.Several chiral catalysts based on the thiazolidine ring have been reported, whichshowed moderate enantioselectivity'. While esters or their derivatives were seldom usedas efficient catalysts. But in our previou…     

Lewis酸对杂多酸催化异丁烷/丁烯烷基化反应的作用Ⅰ.SbCl5的修饰作用

考察了SbCl5对杂多酸 (HPA)催化i C4 H10 /C4 H8烷基化反应的修饰作用 ,用Hammett指示剂测定了SbCl5/HPA催化剂的酸强度 .结果表明 ,经SbCl5修饰的HPA的酸强度有所提高 ,SbCl5的加入量、反应温度及反应时间对烷基化油收率及产物分布均有不同的影响 .     

Characterization of Lignin Compounds at the Molecular Level: Mass Spectrometry Analysis and Raw Data Processing

Lignin is the second most abundant natural biopolymer, which is a potential alternative to conventional fossil fuels. It is also a promising material for the recovery of valuable chemicals such as aromatic compounds as well as an important biomarker for terrestrial organic matter. Lignin is currently produced in large quantities as a by-product of chemical pulping and cellulosic ethanol processes. Consequently, analytical methods are required to assess the content of valuable chemicals contained in these complex lignin wastes. This review is devoted to the application of mass spectrometry, including data analysis strategies, for the elemental and structural elucidation of lignin products. We describe and critically evaluate how these methods have contributed to progress and trends in the utilization of lignin in chemical synthesis, materials, energy, and geochemistry.     

小肽修饰的PAMAM树枝状化合物的生物活性

合成了甘氨酸 (Gly) 天冬氨酸 (Asp)组成的肽链Gly Asp、Gly Asp Gly Asp、Gly Asp (Gly Asp) 2 .分别将天冬氨酸及上述合成的肽链引入到聚酰胺 胺型树枝状化合物 (PAMAM)的表面 .对所得化合物进行了分子模拟 ,结果表明Gly Asp (Gly Asp) 2 肽链在PAMAM表面可形成接近于 β sheet的构象 .由实验得知 ,经Asp、Gly Asp、Gly Asp Gly Asp、Gly Asp (Gly Asp) 2 修饰的PAMAM树枝状化合物对抗坏血酸还原FeⅢ 细胞色素C(cytc)的反应有干扰作用 ,导致该反应速率下降 .这说明所合成的化合物与cytc有较好的结合能力 .特别是Gly Asp (Gly Asp) 2 修饰的PAMAM ,其与cytc的结合常数为 1 6ⅹ 1 0 5.