精氨酸的溶剂浮选分离技术及其分离机制

以表面活性剂十二烷基苯磺酸为捕收剂(DBSA),二(2-乙基己基)磷酸酯(P204)为萃取剂,正庚烷为有机溶剂,采用溶剂浮选法对水溶液中精氨酸进行分离富集,并与气浮络合萃取法、泡沫浮选法和溶剂萃取法进行了比较.结果表明,在常温下,0.09 g/L精氨酸水溶液250 mL、初始pH 7.0,DBSA浓度0.15 g/L,正庚烷体积10 mL, P204体积4.5 mL,气体流量200 mL/min,溶剂浮选法分离水溶液中精氨酸的富集比为16.2,回收率为97.2%.溶剂浮选法分离精氨酸的动力学实验结果表明,精氨酸的溶剂浮选过程阶段性明显,大致可分为3个阶段,第一阶段和第二阶段都符合一级动力学方程,第三阶段符合零级动力学方程,探索了溶剂浮选法分离精氨酸的分离机制.     

Phase composition and phase transformation in Bi(Sb,Nb,Ta)O4 system

In this work Bi(Sb_xNb_yTa_z)O₄ (x + y + z = 1) samples are prepared using mixed-oxide method. A pseudo-ternary phase diagram of Bi(Sb,Nb,Ta)O₄ system is given below the melting point. It is composed of a monoclinic phase region, an orthorhombic phase region and a monoclinic–orthorhombic co-existing phase region. In the orthorhombic phase region, the transformation from orthorhombic to triclinic phase is found to be sensitive to the composition and sintering temperature. Both the transformation from monoclinic to orthorhombic structure and the transformation from orthorhombic to triclinic structure have been studied by the cell parameters.     

Evaluation of lipid peroxidation inhibition and free radical scavenging abilities of 5,6,7-trimethoxy dihydroflavonols

Four naturally rare 5,6,7-trimethoxy-2,3-cis-dihydroflavonols(3-6) and two 5,6,7-trimethoxy-2,3-trans-dihydroflavonols(7-8) were designed and synthesized.Their antioxidative properties were evaluated by way of examining their scavenging capacities towards DPPH and O_2~(·-) free radicals,as well as by measuring their inhibitory ability against LPO.Both the 2,3-trans and the 2,3- cis conformers exhibited certain quenching abilities to DPPH and O_2~(·-) radicals,while most of the synthetic dihydroflavonols ...     

通过加成反应制备纳米材料的新方法

通过加成反应,结合再沉淀法,制备得到Ni(DMG)₂的单晶纳米结构,并且通过调节反应物浓度可实现不同形貌的可控生长,在浓度低的条件下,可得到六方纳米管材,而随着浓度的升高,逐渐变为实心的六方纳米棒,这种制备方法提供了一种潜在的新方法——即通过加成反应来制备纳米材料。     

水热法可控制备铋铁系化合物材料

本文以Fe(NO₃)₃·9H₂O和Bi(NO₃)₃·5H₂O为反应原料,以NaOH为矿化剂, 利用水热方法制备出几种纯相的铋铁系化合物材料,通过调节NaOH的浓度范围可以很容易的控制铋铁系化合物的物相。在NaOH浓度为0.1~0.4 mol·L^-1区间,可以得到立方相的软铋矿Bi₂₅FeO₄₀,当NaOH浓度提高到0.8~2.0 mol·L^-1区间,可以得到六方钙钛矿结构的BiFeO₃,再提高NaOH浓度至8.0 mol·L^-1以上可以得到正交相的Bi₂Fe₄O₉,在NaOH浓度为12.0 mol·L^-1时可以获得纳米片状Bi₂Fe₄O₉。同时探讨了铋铁系化合物的生长机理。     

花状Cu2O/Cu的水热合成及其光催化性能

以硝酸铜为前驱体, 不采用任何模板, 通过逐步水热法合成了花状Cu2O/Cu复合纳米材料. 用扫描电镜(SEM)、X射线衍射(XRD)和紫外-可见漫反射光谱(DRS)对样品进行表征. 结果表明, 花状纳米Cu2O/Cu材料是由长为300-500 nm, 宽为30-70 nm的带状花瓣构成, 在可见光区域有很强的吸收. 复合材料中Cu的含量可以通过反应时间进行调控. 对染料Procion Red MX-5B(PR)的可见光催化降解, Cu能明显提高Cu2O的光催化性能. 当Cu质量分数为27%-71%时, 复合材料Cu2O/Cu的催化活性明显高于单相Cu2O. 与立方体形貌的Cu2O/Cu复合材料相比, 花状纳米Cu2O/Cu复合材料对染料PR有更高的催化降解性能. 且该复合材料有较高的循环回收利用率.     

氢键诱导的聚吡咯/苯磺酸功能化多壁碳纳米管的制备及其电化学行为

采用原位芳基重氮化反应对碳纳米管进行苯磺酸功能化, 进而制备了聚吡咯/苯磺酸化碳纳米管复合材料(PPy/f-MWCNTs), 通过透射电镜(TEM)及扫描电镜(SEM)测试发现, 氢键诱导使聚吡咯成功地包覆在碳纳米管表面. 循环伏安和恒流充放电测试结果表明, 复合材料具有良好的电化学电容性能, 当聚吡咯与苯磺酸化碳纳米管质量比为1:1时, 复合材料在1.0 A·g-1的电流密度下的比容量达266 F·g-1, 而且聚吡咯利用率比未功能化聚吡咯/碳纳米管(PPy/p-MWCNTs)和纯聚吡咯(PPy)提高了1倍以上.     

Effects of nonionic sugar surfactants on the phase transition of DPPC membranes

The influence of newly synthesized N-alkanoyl-N-methyllactitolamines (decanoyl [C₁₀MELA], lauoroyl [C₁₂MELA] and miristoyl [C₁₄MELA]) on the thermotropic phase transition of phosphatidylcholine bilayer was compared with common sugar-based surfactants N-dodecyl-β-d-glucopyranoside [C12G1] and decanoyl-N-methyl glucamide [MEGA-10]. The results indicate that C_nMELA are very active at the membrane surface and disturb the phospholipid bilayer structure less than commercially used MEGA-10 and C12G1.     

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.     

Ab initio study on structure and phase transition of A- and B-type rare-earth sesquioxides Ln2O3 (Ln=La-Lu, Y, and Sc) based on density function theory

Ab initio energetic calculations based on the density functional theory (DFT) and projector augmented wave (PAW) pseudo-potentials method were performanced to determine the crystal structural parameters and phase transition data of the polymorphic rare-earth sesquioxides Ln₂O₃ (where Ln=La-Lu, Y, and Sc) with A-type (hexagonal) and B-type (monoclinic) configurations at ground state. The calculated results agree well with the limited experimental data and the critically assessed results. A set of systematic and self-consistent crystal structural parameters, energies and pressures of the phase transition were established for the whole series of the A- and B-type rare-earth sesquioxides Ln₂O₃. With the increase of the atomic number, the ionic radii of rare-earth elements Ln and the volumes of the sesquioxides Ln₂O₃ reflect the so-called “lanthanide contraction”. With the increase of the Ln³⁺-cation radius, the bulk modulus of Ln₂O₃ decreases and the polymorphic structures show a degenerative tendency.