Ke-Long Huang

Rapid Reaction‐Diffusion Model for the Enantioseparation of Phenylalanine across Hollow Fiber Supported Liquid Membrane

Abstract This paper deals with the rapid reaction‐diffusion model of the transport and enantioseparation factor of (d/l)‐phenylalanine across hollow fiber supported liquid membranes. Mass transfer resistance of the boundary layer in the tube side and the boundary layer in the shell‐side, diffusion in the membrane phase, and interfacial chemical reactions at the liquid membrane interfaces are taken into account in the model equations. The experimental results show that the proposed model can simulate the concentration of the (d/l)‐phenylalanine and the separation factor of the enantioselective process satisfactorily. It is simply a mathematical model which can be easily used to predict the concentration of the enantiomers and the separation factor of the enantioseparation process.

Rapid microwave synthesis of chitosan modified carbon nanotube composites.

Chitosan modified multi-walled carbon nanotube composites were synthesized under microwave irradiation. The resultant chitosan modified multi-walled carbon nanotube composites were purified by twice adjusting of pH value of the solution and centrifugating in succession. The surface functional groups of chitosan modified multi-walled carbon nanotube composites are confirmed by Fourier transform infrared spectroscopy and UV-vis spectroscopy. Transmission electron microscopic images further show the morphologic changes of the carbon nanotubes. Thermal gravimetric analysis shows that the chitosan content in the chitosan modified multi-walled carbon nanotube composites is much higher than conventional methods. The whole reaction procedure can be completed in 1 h under microwave irradiation.

Cross-Linking of Multi-Walled Carbon Nanotubes with Polyethylene Glycol

In this paper a new approach to cross-link two individual multi-walled carbon nanotubes (MWCNTs) by a nucleophilic substitution of brominated MWCNTs using polyethylene glycol anion was introduced. The functionalized MWCNTs were characterized using thermogravimetric analysis (TGA), energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. It is found that polyethylene glycol act as cross-linking agents to interconnect or cross-link the MWCNTs within and among the bundles, as demonstrated by TEM analysis, and few defects will be induced to the nanotube sidewalls. After cross-linking of PEG, the functionalized MWCNTs are still insoluble in any solvent; however, the morphologies of the cross-linked MWCNTs were largely intact, undoubtedly which will provide a useful way to construct nanoscale devices with MWCNTs in the future.

Enantioseparation of racemic alpha-cyclohexyl-mandelic acid across hollow fiber supported liquid membrane

This paper deals with the enantioseparation of racemic a-cyclohexyl-mandelic acid containing copper(II) N-dodecyl-(L)-hydroxyproline (CuN2) as a chiral carrier using hollow fiber supported liquid membrane. A mathematical model of transport and enantioseparation of chiral compounds was deduced, the observed partition coefficient between the feed phase and the membrane phase, the stripping phase and the membrane phase, mass transfer resistance of boundary layer in strip phase inside the hollow fibers, boundary layer in feed phase and the diffusion in the membrane phase are taken into account in the model equations. Using the experimental results, several parameters of the proposed model have been achieved by nonlinear fitting method. It is a simply mathematical model which can be easily used to predict the concentration of the enantiomers and the separation factor of the enantioseparation process, and it can also be used to design and scale up the enantioseparation process.

Improvement of electrochemical performance of LiMn2O4 composite cathode by ox-MWCNT addition for Li-ion battery

Oxidized multi-walled carbon nanotubes (ox-MWCNT) were used as conducting addition to prepare a novel network composite cathode for lithium ion battery. The morphology was analyzed by scanning electron microscope, LiMn2O4 active particles were connected by ox-MWCNT with the formation of three-dimensional networking wiring. Electron transport and electrochemical activity were improved effectively. Galvanostatic charge-discharge tests of LiMn2O4/ox-MWCNT cathode showed that the initial discharge capacities are 119.4, 110.6, 105.5 and 91.4 mAh g-1 at the rate of 0.1, 0.5, 1 and 2 C, respectively, which were much higher than LiMn2O4/acetylene black (AB) at the same content. The electrochemical AC impedance spectroscopy showed that the charge transfer resistance (Rct) of the composite electrode reduced obviously contrasting to 34.32xa0Ω for LiMn2O4/ox-MWCNT and 53.2 Ω for LiMn2O4/AB. Overall, it is found that a conductive network to facilitate electron transfer and good connection of the active-material particle to the network were playing an important role to rate capability and cycle efficiency.

Effects of metal oxides addition on the electrochemical performance of M1Ni3.5Co0.6Mn0.4Al0.5 hydrogen storage alloy

The AB5-type M1Ni3.5Co0.6Mn0.4Al0.5 alloy (where M1 denotes mixed lanthanide) was modified with different additives (ZnO and MnO2), and the effects of metal oxides on the electrochemical properties of the M1Ni3.5Co0.6Mn0.4Al0.5xa0−xa0x% M (xxa0=xa05, 10; Mxa0=xa0ZnO, MnO2) alloy were studied. The results showed that the addition of metal oxides had a positive effect on the activation property of the alloy electrode. With the addition of ZnO, the maximum discharge capacity of the alloy increased from 315 to 334xa0mAh/g (xxa0=xa05) and 341xa0mAh/g (xxa0=xa010) with good cycle capability (C30/Cmax) (87% for xxa0=xa05 and 85% for xxa0=xa010), while the maximum discharge capacity remained invariable and the cyclic stability was deteriorated by the addition of MnO2. Linear polarization (LP), cycle voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements were also performed to investigate the electrochemical kinetics of alloy electrodes.

Influences of heat treatment on the structure and electrochemical properties of Mg0.9Ti0.1Ni hydrogen storage alloys

Neste trabalho, os efeitos do tratamento termico nas estruturas e propriedades eletroquimicas de ligas para armazenamento de hidrogenio Mg 0.9 Ti 0.1 Ni foram investigadas em detalhe. As analises por difracao de raios-X (XRD) e microscopia eletronica (SEM) mostraram que as amostras exibiram predominantemente uma estrutura amorfa. Estudos eletroquimicos revelaram que o tratamento termico pode melhorar a capacidade maxima de descarga e ciclabilidade dos eletrodos desta liga. O valor de C max a liga Mg 0.9 Ti 0.1 Ni preparada por moagem, foi de apenas 229,9 mAh g -1 ; entretanto, o valor atingiu 331,9 mAh g -1 apos o tratamento termico a 873K por 8 h seguido de moagem. A voltametria ciclica, espectroscopia de impedância eletroquimica e polarizacao potenciodinâmica indicaram que o tratamento termico nao so aumentou a capacidade de descarga, mas tambem melhorou a cinetica de carga/descarga da liga Mg 0.9 Ti 0.1 Ni. In the present study, the effects of heat treatment on the structures and electrochemical properties of Mg 0.9 Ti 0.1 Ni hydrogen storage alloys have been investigated in detail. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses showed that the samples exhibited a predominantly amorphous structure. Electrochemical investigations revealed that heat treatment can improve the maximum discharge capacity and cyclic stability of the alloy electrodes. For Mg 0.9 Ti 0.1 Ni alloy prepare by ball milling, the value of C max was only 229.9 mAh g -1 , however, the value reached 331.9 mAh g -1 after heat treatment at 873K for 8 h and then milling. The cycle voltammetry, electrochemical impedance spectroscopy and potentiodynamic polarization indicated that heat treatment not only increased the discharge capacity but also improved the charge/discharge kinetics of Mg 0.9 Ti 0.1 Ni alloy.

Effect of fluorination treatment on electrochemical properties of M1Ni3.5Co0.6Mn0.4Al0.5 hydrogen storage alloy

The influence of surface treatment by solutions of NH4F, LiF and LiF containing KBH4 on the structure and electrochemical properties of the M1Ni3.5Co0.6Mn0.4Al0.5 hydrogen storage alloy (in which M1 denotes mischmetal) is investigated. The fluorination treatment improves the electrochemical performances of the M1Ni3.5Co0.6Mn0.4Al0.5 alloy. The maximum discharge capacity (Cmax) increases from 314.8 to 325.7 (NH4F), 326.5 (LiF) and 316.4 mAh g-1 (LiF+KBH4). After 60 cycles, the capacity retention rate increases from 83.5 to 84.8% (NH4F), 89.5% (LiF) and 93.9% (LiF+KBH4). The results of the linear polarization and anodic polarization reveal that the exchange current density (I0) and the limiting current density (IL) increase after fluorination treatment, indicating an improvement of the kinetics of the hydrogen absorption/desorption.

Crystal structure of N-(3-hydroxyphenyl)-5-chlorosalicylideneimine, C13H10ClNO2

C13H10ClNO2, monoclinic, P21/n (no. 14), a = 10.149(7) Å, b = 5.925(4) Å, c = 18.27(1) Å, ) = 90.84(1)°, V = 1098.5 Å, Z = 4, Rgt(F) = 0.046, wRref(F) = 0.164, T = 293 K. Source of material To the solution of m-hydroxyaniline (1.09 g, 10 mmol) dissolved in 50 ml ethanol, was added 5-cholosalicylaldehyde (1.57 g, 10 mmol), and the mixture was refluxed for 0.5 h. Then the solution was evaporated slowly at room temperature to obtain orange red prismatic crystals suitable for X-ray structure determination. Experimental details The H atoms were positioned geometrically with d(C—H) = 0.93 0.98 Å and refined as riding with Uiso(H) = 1.2 Ueq(carrier) or 1.5 Ueq(methyl). Discussion Proton tautomerization plays an important role in many fields of chemistry and biochemistry. Schiff bases of salicylaldehyde with amines (anils) comprise a chemical system undergoing hydrogen-atom tautomerism between enol and keto forms and show the phenomena of solid state photochromism and thermochromism [1-3]. In the title compound, the bond length of C4—O1 (1.302(2) Å) is shorter than that of O2—C12 (1.354(2) Å) indicating hydrogenatom tautomerism between O1–H1O–N1. Supposedly, there should be intramolecular proton transfer from the hydroxyl O atom to the imine N atom in the solid state of the compound [4]. The dihedral angle between the plane (N1–C7–C5–C4– O1–H1O) and the plane (C1–C2–C3–C4–C5–C6) is 2.7°, which shows the hydrogen bonded ring is almost coplanar with the adjacent ring. Z. Kristallogr. NCS 226 (2011) 275-276 / DOI 10.1524/ncrs.2011.0123 275