共查询到20条相似文献,搜索用时 9 毫秒
1.
Deductions from phenomenological thermodynamics and schematic molecular-kinetic concepts are compared with experiment to explain the constancy of partial molar quantities and of the relative fugacity in the Henry region. The result is of considerable importance to purification by rectification. 相似文献
2.
H. A. El-Naggar A. S. Abdel-Gawad H. H. Someda 《Journal of Radioanalytical and Nuclear Chemistry》1988,128(3):233-243
The extraction of Co/III/ by benzoylacetone solutions has been carried out from acetateacetic acid solutions. The effect of different parameters affecting the distribution coefficient of Co/III/ have been determined. Lg D for Co was found to be a third order dependent on extractant concentration and a negative first order with respect to [H+]. From the thermodynamic parameters and the data of distribution ratios, the extraction mechanism has been suggested. Addition of some electron donor compounds shows no possibility for the increase of coordination number. 相似文献
3.
Extraction by benzene solutions of TBP of carrier-free90Y(III) from mixed aqueous-organic nitrate and perchlorate solutions was studied with special respect to the S-shaped DY versus acid concentration plots observed in aqueous systems. The presence of organic solvents in the aqueous phase enhanced
the extraction of Y(III) and also influenced the shape of the DY vs. acid concentration plots in that the minimum was shifted towards lower acid concentration, became less pronounced, and
eventually vanished completely. 相似文献
4.
A new apparatus for the extraction of organic compounds from sea water is described. With this apparatus it is possible to extract 54 standard compounds with high recovery percentages from 9 1 of sea water with 3 ml ofn-hexane. The analysis time (about 1 h) is appreciably lower than those of the extraction methods based on RP-18 and Carbopack-B adsorption (about 15 h). Furthermore, it is possible to analyze samples without filtration. An application of this method to the analysis of Tirreno sea water is reported. 相似文献
5.
《Journal of the Less Common Metals》1985,105(2):255-261
The distribution of lanthanum(III) between aqueous H2SO4 solutions and Primene JMT in the organic phase is described. The dependence of the extraction on acidity, extractant concentration and type of diluent was investigated. Aggregation numbers are calculated and a mechanism for the extraction is suggested. The separation of thorium(IV) from lanthanum(III), cerium(III) and cerium(IV) is outlined. 相似文献
6.
The role of citric acid in the demineralization of dental enamel, which is mainly constituted by hydroxyapatite, is important for periodontal regeneration and in the conditioning of enamel or dentin for bonding restorative resins. The adsorption of citric acid from aqueous solutions onto synthetic hydroxyapatite at 278, 288, 298, and 308 K and pH 4.8 has been studied by means of UV spectroscopy. The adsorption reaction, which takes place by an interaction between phosphate groups and citrate anions at the solid-solution interface, yields an adsorbate-adsorbent complex of high stability. The adsorption isotherms fit the Langmuirian shape. The proposed adsorption model, where citrate species interact in a bidentate manner (one citrate ion links two phosphate sites), is coherent with the experimental data. The activation standard heat and activation standard entropy were calculated. All the thermodynamic and kinetic parameters were in concordance with the adsorption reaction proposed in this work. 相似文献
7.
A. V. Reddy G. S. Reddy Y. K. Reddy 《Journal of Radioanalytical and Nuclear Chemistry》1986,103(3):167-175
The solvent extraction of silver/I/ has been carried out in 0.5M nitric acid in presence of cyanide by 2,4-dihydroxyacetophenone thiosemicarbazone /DATS/. Ethyl acetate has been used as a solvent and quantitative recovery is made possible with 12.5-fold excess of the reagent in a single extraction. In this medium silver/I/ forms a 22 complex /metal:ligand/ with DATS. The effect of diverse ions on the extraction of silver/I/ has been investigated. 相似文献
8.
A. V. Terekhov G. S. Dmitriev S. N. Khadzhiev L. N. Zanaveskin 《Russian Journal of Applied Chemistry》2016,89(4):639-643
The extraction of solketal from aqueous glycerol with AI-92 gasoline, toluene, hexane, and 1-hexene was studied. Aromatic compounds and mixtures containing them exhibit the best extracting properties. A flowsheet was suggested for recovering solketal from reaction products by extraction. 相似文献
9.
The overall rate of crystallization of isotactic polystyrene from dilute solutions, 1% by weight, in trans-decalin and benzyl alcohol was studied as a function of temperature using dilatometry. These solvents were chosen because the dissolution temperatures of crystalline isotactic polystyrene are practically the same in both solvents. The overall rate of crystallization as a function of crystallization temperature showed a maximum in both solvents at about 50°C. At lower crystallization temperatures the rate of crystallization is much lower. The overall rate of crystallization of isotactic polystyrene in benzyl alcohol is far larger than in trans-decalin at the same undercooling throughout the temperature range, which is in apparent contradiction to present crystallization theories. At very large undercooling (Tc lower than about 0°C) the solutions of isotactic polystyrene in both solvents quickly become “rigid” gels. Surface replicas of freeze-etched gels indicate that a fringed micelle type of crystallization takes place at these low temperatures. The transition from folded chain crystallization to fringed micelle crystallization may be due to a stiffening of the polymer chain below about 50°C, with a reduced rotational mobility of the phenyl groups on the chain. If very dilute solutions, below 0.5% by weight, are crystallized at these low temperatures no gels were formed but fibrous crystals are produced which could be observed under the polarizing microscope. 相似文献
10.
V. N. Bekhterev 《Journal of Analytical Chemistry》2008,63(10):950-953
A procedure was developed for the recovery of phenol from aqueous solutions into acetonitrile using extraction freezing. Experimental results and the revealed regularities were discussed in the context of the proposed theoretical model. The low temperature used in the sample preparation advantageously distinguishes this procedure from the conventional versions of the extraction recovery of organic compounds from water. Moreover, the procedure does not require special glassware or expendable materials. 相似文献
11.
溶剂萃取法回收固体废渣中的N-甲基吡咯烷酮 总被引:1,自引:0,他引:1
研究了溶剂萃取法从工业固体废渣中回收N-甲基吡咯烷酮,考察了萃取剂的种类、溶剂比、萃取温度、萃取时间以及萃取原液中NMP的含量等因素对萃取效果的影响,同时也探索了超声波对萃取效果的影响。研究结果表明,对于N-甲基吡咯烷酮的含盐水溶液体系,三氯甲烷的萃取效果最好。最适宜的萃取条件为:萃取原液中NMP的含量为9.14%、萃取温度40℃、萃取时间3h、溶剂比2:1、通过三级萃取,N-甲基吡咯烷酮的萃取回收率达到98.6%。在超声波存在的条件下,可明显地改善萃取效果,提高N-甲基吡咯烷酮回收率。 相似文献
12.
D. E. Chirkst T. E. Litvinova V. S. Starshinova G. S. Roshchin 《Russian Journal of Applied Chemistry》2007,80(2):185-188
Cerium(III) extraction with oleic acid in o-xylene from nitrate solutions was studied. The extraction mechanism and the dependence of the distribution ratio on pH and composition of the organic and aqueous phases were examined. The thermodynamic characteristics of extraction were calculated. 相似文献
13.
Uranium concentrations were analyzed in the Syrian phosphate deposits. Mean concentrations were found between 50 and 110 ppm.
As a consequence, an average phosphate dressing of 22 kg/ha phosphate would charge the soil with 5–20 g/ha uranium when added
as a mineral fertilizer. Fine grinding phosphate produced at the Syrian mines was used for uranium recovery by carbonate leaching.
The formation of the soluble uranyl tricarbonate anion UO2(CO3)3
4− permits using alkali and sodium bicarbonate salts for the nearly selective dissolution of uranium from phosphate. Separation
of iron, aluminum, titanium, etc., from uranium during leaching was carried out. Formation of some small amounts of molybdates,
vanadates, phosphates, aluminates, and some complex metals was investigated. This process could be used before the manufacture
of Tri-Super Phosphate (TSP) fertilizer, and the final products would contain less uranium quantities. 相似文献
14.
The scattering law S( k ,w) for dilute polymer solutions is obtained from Kirkwood's diffusion equation via the projection operator technique. The width Ω(k) of S( k ,w) is obtained for all k without replacing the Oseen tensor by its average (as is done in the Rouse–Zimm model) using the “spring-bead” model ignoring memory effects. For small (ka\documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt N $ \end{document} ? 1) and large (ka ? 1) values of k we find Ω = 0.195 k2/β α η0 \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt N $ \end{document} and Ω = k2/βξ, respectively, indicating that the width is governed mainly by the viscosity η0 for small k values and by the friction coefficient ξ for large k values. For intermediate k values which are of importance in neutron scattering we find that in the Rouse limit Ω = k4a2/12βξ. When the hydrodynamic effects are included, Ω(k) becomes 0.055 k3/βη0. Using the Rouse–Zimm model, it is seen that the effect of pre-averaging the Oseen tensor is to underestimate the half-width Ω(k). The implications of the theoretical predictions for scattering experiments are discussed. 相似文献
15.
The scattering law S(k, w) for dilute polymer solutions is obtained from Kirkwood's diffusion equation via the projection operator technique. The width Ώ(κ) of S(k, w) is obtained for all k without replacing the Oseen tensor by its average (as is done in the Rouse-Zimm model) using the “spring-bead” model ignoring memory effects. For small $ \left( {ka\sqrt N \ll 1} \right) $ and large (ka >> 1) values of k we find OHacgr; = 0.195 κ2/β aŋo,$ \sqrt N $ and OHacgr; = κ2/βξ respectively, indicating that the width is governed mainly by the viscosity ŋo for small κ values and by the friction coefficient ξ for large κ values. For intermediate κ values which are of importance in neutron scattering we find that in the Rouse limit Ώ = κ4a2/12βξ. When the hydrodynamic effects are included, Ώ(κ) becomes 0.055 κ3/βeng;o. Using the Rouse-Zimm model, it is seen that the effect of pre-averaging the Oseen tensor is to underestimate the half-width Ώ(κ). The implications of the theoretical predictions for scattering experiments are discussed. 相似文献
16.
V. Jedináková J. Cibulková L. Kuča M. Havranová 《Journal of Radioanalytical and Nuclear Chemistry》1979,51(1):47-54
Benzyldimethyldodecylammonium nitrate and benzyltrioctylammonium nitrate were used for the extraction of Am(III) from aqueous
nitrate solutions. The dependence of the extraction performance for Am(III) on the concentration of nitric acid, the kind
and concentration of salting-out agents in the aqueous phase, and the kind of solvent was investigated. Americium is extracted
by the above quarternary salts as a R4NAm(NO3)4 associate. The extraction of Am(III) is compared with the extraction of lanthanides. The high differences in the distribution
coefficients for lanthanides and americium can be utilized for the separation of lanthanides and americium. 相似文献
17.
Faujasite type zeolite CBV-780 was tested as adsorbent for isotactic polypropylene by liquid chromatography. When cyclohexane, cyclohexanol, n-decanol, n-dodecanol, diphenylmethane, or methylcyclohexane was used as mobile phase, polypropylene was fully or partially retained within the column packing. This is the first series of sorbent-solvent systems to show a pronounced retention of isotactic polypropylene. According to the hydrodynamic volumes of polypropylene in solution, macromolecules of polypropylene should be fully excluded from the pore volume of the sorbent. Sizes of polypropylene macromolecules in linear conformations, however, correlate with the pore size of the column packing used. It is presumed that the polypropylene chains partially penetrate into the pores and are retained due to the high adsorption potential in the narrow pores. 相似文献
18.
As biomass hydrolysis, and fermentation technologies approach commercial viability, advancements in product recovery technologies
will be required. For cases in which fermentation products are more volatile than water, recovery by distillation is often
the technology of choice. Distillation technologies that will allow the economic recovery of dilute volatile products from
streams containing a variety of impurities have been developed and commercially demonstrated. Distillation tower and tray
designs, along with specialized heat-exchanger designs, allowing for extended processing intervals on solutions containing
lignocellulosic residues, organic acids, and inorganic salts concentrations >100 g/L are in commerical operation. In the case
of ethanol, distillation energy consumption efficiencies for processing solutions containing <40 g/L of desired product can
approach demonstrated energy consumption efficiencies for solutions containing concentrations >120 g/L. These proprietary
technologies have been applied individually at commercial scale, and designs have been developed that incorporate the combined
technologies with only a marginal increase in capital investment compared to traditional methods. 相似文献
19.