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171.
Alginate Properties and Heavy Metal Biosorption by Marine Algae 总被引:10,自引:0,他引:10
The physical properties of the alginate component in four different brown seaweeds (Sargassumfluitans, Ascophyllum nodosum, Fucus vesiculo-sus, andLaminaria japonica) were characterized using potentiometric titration,13C-nuclear magnetic resonance (NMR), chemical analysis, and viscosity measurements. The heavy metal binding capacities of the
corresponding seaweeds were directly proportional to their respective total carboxyl group content, and related to the electronegativity
of the elements investigated (Ca, Zn, Cd, Cu, and Pb). The uronic acid composition or sequence of the alginate component did
not affect the metal uptake properties of the biosorbents studied here. However, the alginate leaching owing to its solubilization
by Na ions was observed to decrease with increasing intrinsic viscosity of the extracted alginate, related to its molecular
weight, and with increasing apparent acidic dissociation constant, related to the alginate density inside the biomass. 相似文献
172.
T. Al Adlouni F. Meyer C. Meyer A. Fayt 《International Journal of Infrared and Millimeter Waves》1986,7(3):405-419
The perpendicularv
8 band lying in the 1000–1100 cm–1 region has been studied from infrared and laser Stark, spectra. We were interested in the part of spectrum corresponding to the spectral range of the 9 m CO2 laser lines. Assignments of rovibrational lines with J'<40 and K'<6 have been made. About 100 Stark resonances have been assigned to 12 rovibrational transitions. Effective molecular constants and dipole moment have been determined with high accuracy. A list of close resonances with CO2 laser lines is given and may be used for optical pumping experiments. 相似文献
173.
The recombination kinetics of spin-correlated radical pairs (RPs) with three nonequivalent magnetic nuclei were calculated
under conditions of enforced encounters between radicals at time-independent frequency ndif. The simplest two-position model of a RP was used, which includes two states (contact state and distance-separated state)
of the RP, differing in magnitude of isotropic spin-spin exchange interaction between radicals. The calculated kinetic curves
were treated in terms of a three-exponential model. The dependences of corresponding rate constants (k
rec) on ndif, external magnetic field strength (B
0), and intensity, A
eff, of isotropic hyperfine coupling (HFC) were obtained. The k
rec-vs.-ndif or k
rec-vs.-viscosity (ndif varies simultaneously with the inverse lifetime of the contact state) plots pass through maxima whose positions are shifted
from the ndif region near the A
eff value at B
0 = 0.5 G toward high ndif values with an increase in B
0. At ndif ≫ A
eff, the k
rec-vs.-B
0 plots pass through maxima in the region B
0 = A
eff. The calculated dependences are compared with experimental data on recombination of biradicals. The results of calculations
show that the experimentally observed maxima on the k
rec-vs.-B
0 or k
rec-vs.-ndif plots can be due to peculiar features of the spin dynamics induced by the hyperfine coupling rather than the exchange interaction
effects, as is commonly accepted.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1103–1110, May, 2005. 相似文献
174.
A series of Ln(tmtaa)(Htmtaa)·CH_2Cl_2(Ln=Sm,Tb,Er and Yb)complexes were prepared and characterized byinfrared spectra,mass spectra and molecular electronic spectroscopy as well as DSC measurement.A sandwichstructure containing all the eight nitrogen atoms of tmtaa and Htmtaa was proposed for these complexes.X-rayphotoelectron spectra(XPS)of these complexes revealed that four nitrogen atoms of both tmtaa and Htmtaa werechemically equivalent to each other,respectively.The acidic hydrogen of Htmtaa did not bind specifically to any ni-trogen atom of Htmtaa,but was shared by all the four nitrogen atoms.The magnetic properties of these complexeswere found to be in good agreement with their theoretical values. 相似文献
175.
Chihiro Kachi‐Terajima Dr. Takamasa Akatsuka Masa‐aki Kohbara Satoshi Takamizawa Dr. 《化学:亚洲杂志》2007,2(1):40-50
The crystalline one‐dimensional compound, [RhII2(bza)4(pyz)]n ( 1 ) (bza=benzoate, pyz=pyrazine) demonstrates gas adsorbency for N2, NO, NO2, and SO2. These gas‐inclusion crystal structures were characterized by single‐crystal X‐ray crystallography as 1 ?1.5 N2 (298 K), 1 ?2.5 N2 (90 K), and 1 ?1.95 NO (90 K) under forcible adsorption conditions and 1 ?2 NO2 (90 K) and 1 ?3 SO2 (90 K) under ambient pressure. Crystal‐phase transition to the P space group that correlates with gas adsorption was observed under N2, NO, and SO2 conditions. The C2/c space group was observed under NO2 conditions without phase transition. All adsorbed gases were stabilized by the host lattice. In the N2, NO, and SO2 inclusion crystals at 90 K, short interatomic distances within van der Waals contacts were found among the neighboring guest molecules along the channel. The adsorbed NO molecules generated the trans‐NO???NO associated dimer with short intermolecular contacts but without the conventional chemical bond. The magnetic susceptibility of the NO inclusion crystal indicated antiferromagnetic interaction between the NO molecules and paramagnetism arising from the NO monomer. The NO2 inclusion crystal structure revealed that the gas molecules were adsorbed in the crystal in dimeric form, N2O4. 相似文献
176.
A new μ3-O triiron(III) complex [Fe3O(OBz)6(CH3OH)3](NO3)(CH3OH)2 (HOBZ = benzoic acid) has been synthesized, its structure has been determined and variable temperature magnetic susceptility has also been measured. In the molecule, three iron atoms formed an equilateral triangle with μ3-O in center. The fitting to the magnetic susceptibility showed that an intramolecular antiferromagnetic exchange interaction occurred between iron atoms with J=-25.51 cm?1, and a weaker intermolecular autiferromagnetic exchange interaction occurred with zJ' = ?2.30 cm?1. 相似文献
177.
178.
179.
The applicability of pulsed field gradient nuclear magnetic resonance spectroscopy to nanocapsule systems is demonstrated on dispersed poly-n-butylcyanoacrylate nanocapsules as a model system. Spectroscopic data are presented that allow for the structural characterization of the inner cavities, the observation of Brownian motion of the capsules and the detection of rapid molecular exchange through the capsule walls. An analytical formula is proposed that yields equilibrium populations and average residence times of a given tracer molecule, thus leading to crucial information regarding the permeability of the capsule walls. Based on these analytical methods, two varieties of nanocapsules are compared that derive from two different preparation procedures. It is found that thinner capsule walls obtained under acidic conditions of the organic phase during interfacial polymerization lead to correspondingly higher exchange rates of benzene as a tracer molecule. 相似文献
180.
The structure of CsPd2F5 has been confirmed from neutron diffraction data on powdered sample. CsPd2F5 crystallizes in the orthorhombic Imma space group. At 100 K, the unit-cell constants are a = 6.473(2) Å, b = 7.853(5) Å, c = 10.718(3) Å and the calculation carried out using the Rietveld method leads to R1 = 0.020. The network is formed of PdF6 octahedra chains containing half of Pd in high-spin configuration, connected one to each other by square planes containing the other half of Pd in low-spin configuration. CsPd2F5 orders antiferromagnetically below TN = 38 K. In the ordered state a weak ferromagnetic component occurs (σ0 = 0.098 μB at 2 K). The magnetic structure determined at 4 K is consistent with the magnetization data and can be described in the Im′m′a′ magnetic group without any doubling of the unit-cell parameters. Within the chains, Pd2+ are coupled antiparallel. The magnetic moments are located in the (x0z) plane, the angle between the moments and the z axis being 18°. 相似文献