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31.
粉煤灰与几种酸固相反应特性的表面分析 总被引:1,自引:0,他引:1
用扫描电镜.能量色散谱研究了粉煤灰与酸的固相反应过程中表面形貌和化学组成变化特性。室温下粉煤灰分别与HCI、HNO3、H2SO4、HCIO4固相反应后,表面产生直径20—200nm的结晶颗粒或晶柱。反应生成的水溶物结晶体的扫描电镜图像分别呈手指状、龟背形、蛛蛛状、蝙蝠态,分别为氯化铝铁混晶、硝酸铝铁混晶、硫酸铝铁混晶和高氯酸铝铁混晶。粉煤灰是硅、铝、铁等元素的氧化物聚集体,铁铝等氧化物主要分布在颗粒表面,氧化硅主要分布在颗粒内层。用少量酸进行固相反应这些氧化物聚集体可相互剥离,用H2SO4处理粉煤灰优先将铁铝氧化物转化成可溶性硫酸盐。 相似文献
32.
P. Ubbriaco 《Journal of Thermal Analysis and Calorimetry》1996,47(1):7-16
A lime-pozzolan cement was used to make pastes containing different quantities of MSW fly ash. After setting, the pastes were cured in water at room temperature from 1 h to 260 days. The hydration characteristics and the nature of the hydration products of the various pastes were studied by simultaneous TG/DSC thermal analysis and X-ray diffractometry. The MSW fly ash was found to induce a slowing of the hydration process in lime-pozzolan pastes, and after some days an evident acceleration of hydration reactions occurred. Sulphate and chloride in the MSW fly ash yield hydration products forming a cementitious matrix.The author is grateful to D. Calabrese for assistance with the thermal and XRD analyses. 相似文献
33.
Utilization of one waste material to control pollution caused by another is of high significance in the remediation of environmental
problems. Rice husk, an abundantly available agricultural waste, can be used as a low cost adsorbent for dyes and heavy metals
in effluent streams. The possible utilization of rice husk ash as an adsorbent for methylene blue dye from aqueous solutions
has been investigated. Ash samples from husks of two origins were prepared at different temperatures and their physical, chemical
spectroscopic and morphological properties were determined. XRD, FTIR and SEM were some of the techniques adopted for the
characterization. The samples were also analyzed for bulk density, pH, nitrogen adsorption properties and lime reactivity.
Experiments of methylene blue adsorption on the ash samples were conducted using batch technique and a comparative study was
made. Results were analyzed using linear, Langmuir and Freundlich isotherms. The values of separation factor indicate that
most of the ash samples do adsorb the dye molecules, but in varying quantities. Calcination at 900∘C reduces the adsorption capacity of the ash to a great extent. Regression analysis shows that the experimental data fits
both Langmuir and Freundlich isotherms for certain concentration limits. The adsorbate species are most probably transported
from the bulk of the solution into the solid phase through intra-particle diffusion process. Kinetics of adsorption was found
to follow pseudo second order rate equation with R
2∼ 0.99. The highest adsorption capacity (Q
0) achieved is found to be ∼690 mg/g, which is even higher than the values reported for activated carbon from rice husk. The
adsorption capacity of the ash samples are in good agreement with their surface area and pore volume. 相似文献
34.
Barry R. Lentz 《Journal of fluorescence》1995,5(1):29-38
An important process in the life of a cell is fusion between cellular membranes. This is the process by which two cellular compartments surrounded by different membranes join to become a single compartment surrounded by a single membrane, without significant loss of compartment contents. To demonstrate fusion, the cell biophysicist must demonstrate all three critical aspects of the process: (1) mixing of membrane components, (2) mixing of compartment contents; and (3) retention of compartment contents. Most commonly, accomplishing this involves the use of fluorescence probes. The general theme to the methods described involves some form of concentration-dependent quenching. An unique method developed in our laboratory utilizes the concentration dependence of the fluorescence lifetime of a phosphatidylcholine containing carboxyethyl diphenylhexatriene at position 2 and palmitic acid at position 1 of glycerol (DPHpPC). The fluorescence lifetime of this molecule and that of its parent fluorophore diphenylhexatriene (DPH) shorten dramatically as their two-dimensional concentrations in a membrane increase. This lifetime quenching can be described by dimer formation that reduces the symmetry of the DPH excited state. This phenomenon allows one to use the fluorescence lifetime to gain insight into the local concentration of probe in microscopic regions of a membrane. One application of this is in distinguishing lipid transfer between the outer leaflets of two contacting membrane bilayers from fusion between these membranes that leads to mixing of lipids in both the inner and outer leaflets of the membrane bilayers. This allows a single measurement to demonstrate fusion between membrane pairs.Abbreviations PEG
poly(ethylene glycol)
- Na2EDTA
ethyiene-diamine-tetraacedic acid, disodium salt
- LUV
large, unilamellar vesicles made by rapid extrusion technique
- DPH
1,6-diphenyl-trans-1,3,5-hexatriene
- DPHpPC
1-palmitoyl-2-[[[2-[4- (phenyl-trans-1,3,5-hexatrienyl)phenyl]ethyl]oxy]carbonyl]-3-sn-phosphatidylcholine
- DPPC
1,2-dipalmitoyl-3-sn-phosphatidylcholine
- PA
palmitic acid
- NBD-PE
N-(7-nitro-2,1,3-benzoxadiazol-4-yl)-PE
- Rh-PE
N-(lissamine Rhodamine B sulfoyl)-PE
- R18
octadecyl Rhodamine B chloride
- ANTS
1-aminonaphthalene-3,6,8-trisulfonic acid
- DPX
N,N-p-xylylene-bis(pyradinium bromide) 相似文献
35.
A. K. Galwey 《Journal of Thermal Analysis and Calorimetry》2005,82(2):423-437
Summary A representational model, proposed to account for the physical changes that accompany the melting of alkali halides, was described
in Part 1 [1]. The liquid is portrayed as undergoing continual dynamic structural reorganization of its constituent ions between
individual small domains, zones of various regular, crystal-type arrays. These alternative arrangements are stabilized by
the enthalpy of melting, which, in liquids, relaxes the restriction for solids that only the single, most stable, crystal
structure can be present. The dynamic character of the melt accounts for its fluid character and the loss of long-range order
[1, 2]. This model is extended here to consider the phase diagrams of binary, common ion, alkali halide mixtures comprehensively
reviewed in [3]. Factors determining whether each of these yields a eutectic, or a solid solution, on cooling are discussed
and several trends in the 70-phase diagrams are identified. Eutectic formation, involving maintenance of the liquid state
below the melting points of the pure components, is ascribed to the participation, in an extended dynamic equilibrium, of
additional domains having the regular structures characteristic of double salts. The known crystalline double binary halides
[3], Li/Cs or Rb/F, Cl, Br or I, melt at temperatures well below those of the simpler pure component salts. It is concluded
that the set/liq model for melting, proposed in [1, 2], accounts for some important properties of the phase diagrams presented
in [3]. 相似文献
36.
Kim WS Park M Lee DW Moon MH Lim H Lee S 《Analytical and bioanalytical chemistry》2004,378(3):746-752
Fly ash has been regarded as hazardous because of its high adsorption of toxic organic and/or inorganic pollutants. Fly ash is also known to have broad distributions of different chemical and physical properties, such as size and density. In this study, fly ash emitted from a solid waste incinerator was pre-fractionated into six sub-populations by use of gravitational SPLITT fractionation (GSF). The GSF fractions were then analyzed by sedimentation field-flow fractionation (SdFFF) and ICP–AES. SdFFF analysis showed the fly ash has a broad size distribution ranging from a few nanometers up to about 50 µm. SdFFF results were confirmed by electron microscopy. Inductively coupled plasma–atomic emission spectroscopy (ICP–AES) analysis of the GSF fractions showed the fly-ash particles contain a variety of inorganic elements including Ca, Si, Mg, Fe, and Pb. The most abundant in fly ash was Ca, followed by Si then Mg. No correlations were found between trace element concentration and particle size. 相似文献
37.
Differential
scanning calorimetry (DSC) is a thermal analytical tool for preformulation
studies. Extrapolated melting temperature (TP)
and heat of fusion (ΔHf)
can be used as parameters for optimizing the DSC performance. Two model pharmaceuticals
acetaminophen and nicotinamide are used in this study. Using a factorial design
for the experimental model and matrix analysis the results, the effect of
sample mass, heating rate and the nitrogen flow rate were evaluated on the
ΔHf values
and TP values. Two
levels for each of the procedural variables were used as a balanced experimental
design with two sample sizes, two heating rates and two nitrogen flow rates.
It was found that the change in the heating rate caused significant changes
in the ΔHf
values but not the Tp
values for acetaminophen. However, no significant effect was found for the Tp value but ΔHf value was affected to a
certain extent for nicotinamide. 相似文献
38.
The enthalpies of sublimation and fusion and triple-point temperatures of 2-bromo-. 3-bro-mo- and 4-bromobenzoic acids have been determined precisely by sublimation calorimetry, drop calorimetry and differential thermal analysis. The measurements of sublimation enthalpy of the three acids were made at 333, 348 and 363 K, respectively, using a Tian-Calvet microcalorimeter equipped with Knudsen effusion cells. The derived standard molar enthalpies of sublimation at 298.15 K are (95. 94±0. 41), (99. 20± 0.18), and (103. 08±0. 59) kJ · mol-1for the 2-bromo-, 3-bromo- and 4-bromobenzoic acids, respectively. In addition, the saturated vapour pressure of these compounds was also calculated on the basis of the sublimation experiments. The enthalpy of fusion, the triple-point temperatures and the mole fraction purities of the samples of the investigated substances were measured using the mean temperature version DTA apparatus developed by the CTM of the CNRS in Marseille. The triple-point temperature and the 相似文献
39.
40.