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31.
Optimization of reduction potential for electroseparation was studied for the recovery of gold, copper, and lead from acidic
solution. A linear sweep voltammetric method enabled us to determine characteristic reduction potentials for each metal and
the kinetics of the metal deposition indicated by current-voltage curves. In order to precipitate the metal species sequentially,
reduction potentials were examined for the individual and mixed solutions of Au(III), Cu(II), and Pb(II). The three metals
were reasonably well isolated from the mixed solutions such as Cu(II)/ Pb(II) and Au(III)/Cu(II)/Pb(II) in the order of the
corresponding reduction potentials, in particular, the mass transfer controlled reduction potentials, obtained from linear
sweep voltammetry (LSV) measurement. 相似文献
32.
Jung Joon Lee Heeyeon Kim Jae Hyun Koh Ara Jo Sang Heup Moon 《Applied catalysis. B, Environmental》2005,61(3-4):274-280
The performance of a new type of CoMoS/Al2O3 catalyst, with added fluorine and prepared by sonochemical and chemical vapor deposition (CVD) methods, was investigated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The catalyst, which was designed to contain optimum amounts of fluorine and cobalt, exhibited a higher activity, ca. 4.6 times higher activity particularly in the HDS of 4,6-DMDBT, than a fluorine-free catalyst prepared by a conventional impregnation method. The enhanced activity of the new catalyst can be attributed to the cumulative effects of individual factors involved in the catalyst preparation. That is, the use of a sonochemical synthesis led to a high dispersion of small MoS2 crystallites on the alumina, and the addition of the Co species to the catalyst by CVD caused a close interaction between the Co species and the MoS2 crystallites to produce numerous CoMoS species, which are the catalytically active species for HDS. The addition of fluorine increased the amounts of acidic sites in the catalyst, which promoted hydrogenation (HYD) route to a greater extent than the direct desulfurization (DDS) route in DBT HDS and both HYD and DDS routes to similar extents in the case of 4,6-DMDBT HDS. Accordingly, the addition of fluorine led to a greater increase in catalytic activity for 4,6-DMDBT HDS than for DBT HDS. 相似文献
33.
Neung‐Ju Lee Ja‐Chul Koo Sung‐Suk Ju Seong‐Bae Moon Won‐Jei Cho In‐Cheol Jeong Song‐Jae Lee Moo‐Youn Cho Emmanuel A Theodorakis 《Polymer International》2002,51(7):569-576
The attachment of anticancer agents to polymers is a promising approach towards reducing the toxic side‐effects and retaining the potent antitumour activity of these agents. A new tetrahydrophthalimido monomer containing 5‐fluorouracil (ETPFU) and its homopolymer and copolymers with acrylic acid (AA) and with vinyl acetate (VAc) have been synthesized and spectroscopically characterized. The ETPFU contents in poly(ETPFU‐co‐AA) and poly(ETPFU‐co‐VAc) obtained by elemental analysis were 21 mol% and 20 mol%, respectively. The average molecular weights of the polymers determined by gel permeation chromatography were as follows: Mn = 8900 g mol?1, Mw = 13 300 g mol?1, Mw/Mn = 1.5 for poly(ETPFU); Mn = 13 500 g mol?1, Mw = 16 600 g mol?1, Mw/Mn = 1.2 for poly(ETPFU‐co‐AA); Mn = 8300 g mol?1, Mw = 11 600 g mol?1, Mw/Mn = 1.4 poly(ETPFU‐co‐VAc). The in vitro cytotoxicity of the compounds against FM3A and U937 cancer cell lines increased in the following order: ETPFU > 5‐FU > poly(ETPFU) > poly(ETPFU‐co‐AA) > poly(ETPFU‐co‐VAc). The in vivo antitumour activities of all the polymers in Balb/C mice bearing the sarcoma 180 tumour cell line were greater than those of 5‐FU and monomer at the highest dose (800 mg kg?1). © 2002 Society of Chemical Industry 相似文献
34.
Inorganic–organic hybrid materials for the optical waveguide were synthesized by the sol–gel process starting from the acid-catalyzed solutions of phenyltrimethoxysilane, methyltriethoxysilane, and tetraethylorthosilicate. The control of the refractive index in the organically modified silicate films was achieved by varying the content of phenyltrimethoxysilane incorporated as a refractive index modifier. A single spin-coating with the precursor solution produced a crack-free buffer layer of 22-μm thickness with a dense microstructure. For the fabrication of the patterned guiding layer on top of the buffer layer, the microfluidic lithography method was used. The patterned microlines of the linewidth of 20–35 μm with a sharp edge definition could form by filling the precursor solutions into the microchannels associated with the polydimethylsiloxane microfluidic device. The patterned guiding layer was optically transparent as similar as the bare quartz glass at the wavelength above 500 nm and had a low propagation loss of 0.77 dB/cm at 1310 nm. 相似文献
35.
Young Tae Moon Do Kyung Kim Chong Hee Kim 《Journal of the American Ceramic Society》1995,78(4):1103-1106
Based on the principle that the solubility of a salt decreases as the dielectric constant of the solvent decreases, zirconia powders were prepared by heating a zirconyl chloride solution with a 2-PrOH-water mixture as the solvent. The morphology, size, and size distribution of the resulting particles were highly sensitive to the heating method used on the starting solution. Particles formed under conventional heating methods were polydisperse, agglomerated spherical, or irregularly shaped because of inhomogeneous precipitation through the temperature gradient, the shear force induced by stirring, compositional nonuniformity, and the low heating rate. The present study demonstrated that microwaves provide an excellent means of heating uniformly and rapidly without stirring. The particles resulting from microwave treatment were monodisperse and spherical, with a mean diameter of 0.28 μm. 相似文献
36.
Electrochemical cell current requirements for toxic organic waste destruction in Ce(IV)-mediated electrochemical oxidation process 总被引:1,自引:0,他引:1
Vasily V. Kokovkin Sang Joon Chung Subramanian Balaji Manickam Matheswaran Il-Shik Moon 《Korean Journal of Chemical Engineering》2007,24(5):749-756
The electrochemical cell for cerium oxidation and reactor for organic destruction are the most important operation units for
the successful working mediated electrochemical oxidation (MEO) process. In this study, electrochemical cells with DSA electrodes
of two types, single stack and double stack connected in series, were used. The performances towards the electrochemical generation
of Ce(IV) in nitric acid media at 80 °C were studied. The current-voltage curves and cerium electrolysis kinetics showed the
dependence on number of cell stacks needed to be connected in series for the destruction of a given quantity of organic pollutant.
The presence of an optimum region for Ce(III) oxidation with a contribution of oxygen evolution, especially at low Ce(III)
concentration (high conversion ratios), was found. The cells were applied for the Ce(IV) regeneration during the organic destruction.
The cell and reactor processes were fitted in a simple model proposed and used to calculate the current needed in terms of
Ce(III) oxidation rate and the number of cell stacks required for maintaining Ce(IV)/Ce(III) ratio at the same level during
the organic destruction. This consideration was based on the kinetic model previously developed by us for the organic destruction
in the MEO process. 相似文献
37.
A numerical solution of the pseudo-steady state governing equations on the basis of the Langmuir-Hinshelwood type rate equation
was obtained by the approximate finite difference method in packed bed reactors for gas-solid reaction system. It was proved
that the numerical method has good accuracy compared with the strict solution in the special case that the reaction rate can
be represented by the first-order kinetics in terms of gaseous reactant and the effectiveness factor is unity druing the reaction.
The numerical method is proposed to predict the transient of exit-gas compositions of a packed bed reactor used for gas-solid
reaction systems. The exit-gas composition can be predicted from the conversion data of a single particle with varying reaction
time. The present method can be easily applied to the systems involving adsorptive gaseous reactants and complex reaction
behavior with structural changes of particles. 相似文献
38.
The effect of adsorptive species on non-isothermal gas-solid reactions is studied on the basis of Langmuir-Hinshelwood kinetics. The concept of an effectiveness factor provides good information to ascertain the effect of adsorptive species and the transition of the rate controlling regime, in connection with the parameters, generally used in the analysis of non-isothermal behavior. For highly exothermic reactions, the effectiveness factor-Thiele modulus curves with multiple solutions are presented with respect to the modified adsorption equilibrium constant. The variations of the rate-controlling regime by the effect of adsorptive species are also discussed. 相似文献
39.
A new characterization procedure for aqueous solutions with unknown composition was proposed based on the binomial distribution
of TOC (total organic carbon) fraction in terms of a characterizing variable, the Freundlich coefficient, k, so that the solution
in question can be described by a finite number of pseudo.species identified with a certain k value. The validity and computational
accuracy of this procedure has been demonstrated by characterizing three sets of experimental data chosen from different sources.
Predictions based on this procedure yielded acceptable results that agreed closely with experimental data. 相似文献
40.
A surface diffusion mocel with diffusional interference has been presented for the analysis of multicomponent adsorption of
phenols by activated carbon. Surface diffusion coefficients for multicomponent adsorptions were estimated from the relationship
between. the surface diffusion coefficient of each species and the surface coverage. The diffusional interference coefficients,
Wij, was determined from experimental counter-adsorption data. The numerical values of Wij were in the range of 0.4–0.9, which show that the introduction of diffusional interference is necessary to analyze multicomponent
counter-adsorptions properly. The proposed model successfully simulates the behaviour of phenols-activated carbon system in
a batch adsorber. 相似文献