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21.
Equilibrium, FTIR, scanning electron microscopy and small wide angle X-ray scattering studies of chromates adsorption on modified bentonite 总被引:5,自引:0,他引:5
Marek Majdan Oksana Maryuk Stanisaw Pikus Elzbieta Olszewska Ryszard Kwiatkowski Henryk Skrzypek 《Journal of Molecular Structure》2005,740(1-3):203-211
The study presents a discussion about the adsorption mechanism of chromate anions on bentonite modified by hexadecyltrimethylammonium bromide (HDTMA-Br). The formation of alkylammonium chromates: HDTMAHCrO4, (HDTMA)2Cr2O7 and to the lesser extent (HDTMA)2CrO4 at the water–bentonite interface is examined based on the Scanning Electron Microscopy and surface tension measurements. The histograms of HDTMA/Cr(VI) molar ratio on the bentonite surface, found from Scanning Electron Microscopy (SEM) measurements, show that for the majority of points of bentonite surface the value of this ratio is in 1–2 range. FTIR spectra of modified bentonite samples show the change from gauche to trans conformation in the surfactant arrangement in the clay interlayer accompanying its concentration increase.
In turn Small Wide Angle X-Ray Scattering (SWAXS) patterns evidently suggest incorporation of chromate anions into the interlamellar space of bentonite structure. 相似文献
22.
Majdan M Pikus S Kowalska-Ternes M Głdysz-Płaska A Staszczuk P Fuks L Skrzypek H 《Journal of colloid and interface science》2003,262(2):321-330
The objective of the presented study was to investigate the adsorption of Cu, Co, Mn, Zn, Cd and Mn on A-type zeolite. The isotherms for adsorption of metals from their nitrates were registered. The following adsorption constants K of metals were found: 162,890, 124,260, 69,025, 16,035, 10,254, and 151 [M(-1)] for Cu, Co, Mn, Zn, Cd, and Ni, respectively, for the concentration range 10(-4)-10(-3) M. On the other hand, the investigation of pH influence on the distribution constants of metals showed that the adsorption of metals proceeds essentially through an ion-exchange process, surface hydrolysis, and surface complexation. The supplementary results from DRIFT, scanning electron microscopy, and X-ray diffraction methods confirmed the presumption about the possible connection between the electronic structure of divalent ions and their adsorption behavior, showing that ions with d5 and d10 configurations such as Mn2+, Zn2+, Cd2+, with much weaker hydrolytic properties than Cu2+ and Ni2+, strongly interact with the zeolite framework and therefore their affinity to the zeolite phase is much stronger when compared with that of the Ni2+ ion, but at the same time not as strong as the affinity of the Cu2+ ion, the latter forming a new phase during the interaction with zeolite framework. For Zn2+, during inspection of the correlation between the proton concentration H/Al and zinc concentration Zn/Al on the zeolite surface, the formation of the surface complex [triple bond]S-OZn(OH) was proposed. A correlation between the heterogeneity of proton concentrations H/Al on Me-zeolite surfaces and the hydrolysis constants pKh of Me2+ ions was found. 相似文献
23.
P. Staszczuk M. Majdan S. Pikus D. Sternik M. Błachnio 《Journal of Thermal Analysis and Calorimetry》2008,94(3):655-662
Complex studies of physicochemical properties of pure and modified of aluminia oxides samples are presented. The presence
of Mn2+ and Ni2+ modifiers on the aluminium oxide surface causes increase in water adsorption capacity and decrease in benzene and n-octane adsorption. This is due to decrease of specific surface area, volume and radius of pores as a result of surface impregnation
and microcrystal formation during modification with manganese and nickel chlorides. Microcrystal formation on the surface
and porosity decrease as confirmed by AFM, EDX and powder diffraction studies using automated diffractometer by step scanning.
From the Q-TG and Q-DTG data, the energies of liquid desorption from the surface of the samples and the functions of desorption,
energy distribution were calculated. High degree of nonlinearity of the functions resulting from great heterogeneity of the
studied surface was found. Adsorption of cations creates more homogeneous surface in aluminium oxide, and it is responsible
for the change in adsorbate molecule interaction energy and changes mechanism of adsorption and desorption as well as thickness
and structure of the adsorbed film. From the experimental data some parameters characterizing adsorption properties and porosity
of the studied samples were determined using the complex measuring methods (thermal analysis, sorptometry, porosimetry, AFM
and EDX). 相似文献
24.
Z. Rzączyńska M. Woźniak W. Wołodkiewicz A. Ostasz S. Pikus 《Journal of Thermal Analysis and Calorimetry》2008,91(3):951-956
The complexes of yttrium(III) and lanthanides(III) with 2-aminoterephthalic acid form the isostructural series of triclinic
compounds with a space group P from La to Lu and they have the general formula of Ln2(C8H5O4N)3·8H2O. On heating in air or inert gas atmosphere they lose all water molecules in the temperature range 50–200°C in one or two
steps. The anhydrous compounds are stable from 360 to 435°C and then decompose to oxides. 相似文献
25.
A theory of weak localization responsible for the negative magnetoresistance effect is developed for quantum wells at the
tellurium surface, which retains, in contrast to the
surface considered earlier, a trigonal spectrum distortion with opposite signs near the M and P extrema, with the latter playing the part of states with opposite spins. It is shown that as a result of the motion in momentum
and spin spaces being correlated the spin relaxation due to this distortion is smaller than that for the (0001) surface.
Fiz. Tverd. Tela (St. Petersburg) 39, 1659–1664 (September 1997) 相似文献
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Mariusz Barczak Andrzej Dąbrowski Stanisław Pikus Janusz Ryczkowski Piotr Borowski Maciej Kozak 《Adsorption》2010,16(4-5):457-463
SBA-15 organosilicas containing amine, thiol, vinyl and phenyl pendant groups were synthesized by co-condensation of tetraethoxysilane and appropriate alkoxysilanes in the presence of Pluronic P123 surfactant. The obtained materials have usually well-developed porous structure—values of specific surface area are in the range 820–950 m2/g. Sizes of the ordered mesopores are in the range 7.5–9.1 nm while the interconnecting pores are 2.3–3.1 nm in size. It was establish that size of the mesopores strongly depends even on small amounts of co-monomers co-condensing with tetraethoxysilane. Several instrumental techniques such as infrared spectroscopy, X-ray diffraction, nitrogen sorption measurements, elemental analysis, transmission electron microscopy. FT-IR photoacoustic spectroscopy (FT-IR/PAS) was used to determine chemical composition of the final materials and to monitor the efficiency of the template removal. 相似文献
29.
A series of mesoporous silica materials were synthesized by applying Pluronic type polymers as pore creating agents. In order to differentiate the characteristics of porous structure of the obtained sorbents the temperature of aging process was changed in the synthesis. The parameters characterizing the pore structure were estimated from nitrogen adsorption/desorption isotherms. The changes of pore arrangement of the obtained materials being a result of different synthesis conditions were investigated by using a small angle X-ray scattering method. Correlations between the values of structure parameters and aging temperature were found. 相似文献
30.
WAXS, DSC and AFM methods were employed to compare phase structures of the coatings obtained from waterborne polyurethane cationomers which had been synthesised in the reaction of some diisocyanates (MDI, IPDI, TDI and HDI) with polyoxyethylene glycols (M?=?600 and 2,000) and butane1,4-diol or N-methyl- or N-butyldiethanolamine and 2,2,3,3-tetrafluoro-1,4-butanediol. The structures were also analysed of the coatings derived from linear polyurethanes which had been synthesised on the basis of similar raw materials. Better rigidity was found for generally amorphous cationomer coats. Changes were discussed in the surface free energy (SFE) values and in their components, as calculated independently with the use of the van Oss-Good and Owens-Wendt methods. Polyurethane coats turned out more hydrophobic as compared to cationomer ones. In both coat types, fluorine incorporated into cationomers contributed to lower SFE values: from 50 down to about 30?mJ/m(2). 相似文献