Chloroform,adsorption isotherm

Figure 5. Langmuir Adsorption Isotherms for Benzene, Butyl Chloride and Chloroform...

Examples of mono-layer adsorption isotherms obtained for chloroform and butyl chloride are shown in Figure 5. The adsorption isotherms of the more polar solvents, ethyl acetate, isopropanol and tetrahydro-furan from -heptane solutions on silica gel were examined by Scott and Kucera [4]. Somewhat surprisingly, it was found that the experimental results for the more polar solvents did not fit the simple mono-layer... 

It is seen that at high concentrations (a) becomes unity and the surface is completely covered with the more strongly adsorbed solvent. The adsorption isotherm of chloroform on silica gel, determined by Scott and Kucera (5) is shown in figure 1. It is seen that the monolayer of chloroform collects on the surface continuously until the chloroform content of the mobile phase is about 50%. At this concentration the monolayer appears complete. Thus, between 0 and 50% chloroform in the n-heptane, the interactions between the solute and the chloroform in the mobile phase are continuously increasing. 

Chlorofluorocarbon (CFC) replacements have recently been used for their lower stability and because they have carbon-hydrogen bonds, which means that their atmospheric lifetime is expected to be much shorter than those of CFCs. The adsorption properties of l,l,2-trichloro-l,2,2-trifluoroethane (CFC 113) and its replacement compounds, l,l-dichloro-2,2,2-trifluoroethane (HCFC123), 1,1-dichloro-l-fluoroethane (HCFC141b), and l,l-dichloro-l,2,2,3,3-pentafluoropropane (HCFC225ca) on four kinds of activated carbons were investigated. The adsorption isotherms of inhalational anesthetics (halothane, chloroform, enflurane, isoflurane, and methoxyflurane) on the activated carbon were measured to evaluate the action mechanism of inhalational anesthesia. The anesthesia of CFC replacements can be estimated by the Freundlich constant N of the adsorption isotherms (Tanada et al., 1997). 

The surface was actually a film of native aluminum oxide it did not adsorb pyridine but did adsorb chloroform showing the oxide to have no acid sites, but basic sites. Treatment of the aluminum oxide with aqueous carbonate solutions clearly enhanced the basicity, as evidenced by stronger adsorption of chloroform. By observing the temperature coefficient of adsorption isotherms with ellipsometry one can actually determine heats of adsorption on a square centimeter of flat surface. 

In Fig.S, experimental adsorption isotherms for chloroform in PQ-USY at 303 K are shown. Initial slopes for 303 K are also shown. This whole range of adsorption isotherm at 303 K could be compared with simulation. 

Fig.5 Comparison between exp. and simulations for adsorption isotherms ofPQ-USY-Chloroform system...

Figure 13. The adsorption isotherms of chloroform on CPG heated at 700 C for different periods of time. The values at curves mean the period of time heating in hrs.

Figure 8. Absolute adsorption isotherms of chloroform. Symbols are the same as in Fig. 7.

Figure 14. Absolute adsorption isotherm of chloroform for adsorbents listed in Table 5.

Applying modification of substances having different chemical nature and different methods to deposit their pyrolysis products one can obtain adsorbents with differentiated surface properties and thus showing different chromatographic resolution abilities. The data in Table 7 and Figs. 17 20 confirm this statement. Figs. 17-20 show adsorption isotherms while Table 7 lists characteristic data of n-heptane and chloroform adsorption on Adsorbent Y as well as on the same adsorbent but modified with n-heptanol in an autoclave and in a rotary reactor. Similarly to the experiments described in papers... 

The concentrations of chloroform and oxygen on the Ti02 catalyst can be derived from Langmuir adsorption isotherms and it is of interest to note that with chloro-... 

Fig. 6.2. A plot of the Langmuir adsorption isotherm for three non-polar solvents (chloroform, butyl chloride and benzene) in n-heptane. It can be seen that the data fit very closely to the monolayer function y = x/(A + Bx). Reproduced from Scott and...

For adsorption isotherm determination, the accurate knowledge of the dead volume is required. In most cases, the dead volume tracer method produces appropriate results. When a cross-check of the dead volume value is necessary, the density method can be used. First, the column is carefiiUy flushed and filled with methanol which has a density of 0.7914 g/cm at 20°C. It is disconnected fi om the pump and its two sides are closed to avoid evaporation. The column is weighted. Its mass is W eon- Next, the coluirm is similarly flushed and filled with chloroform, d=1.483 g/cm at 20°C, and weighted. The second mass, Wchcijj higher than the first one, allows to obtain the dead volume with a high accuracy using ... 

FIGURE 1.284 Incremental size distributions of unfrozen structures calculated on the basis of CPMG echo decay envelopes for (a and b) benzene and (c) water adsorbed onto SBA-15 as a mixture at /j=0.16 mL/g and f> = 0.13 mL/g IPSDy based on the nitrogen adsorption isotherm is also shown. (With kind permission from Springer Science+Business Media Central Eur. J. Chem., Behaviour of pure water and water mixture with benzene or chloroform adsorbed onto ordered mesoporous silicas, 5, 2007g, 420-454, Gun ko, V.M., Turov, V.V., Turov, A.V. et ah, Copyright 2007.)... 

Both head- and tail-type cationic vinyl monomers with long methylene chains in THF or chloroform had the maximum adsorption on colloidal silica on the respective adsorption isotherm. Above the monomer concentration giving maximum adsorption, the monomer formed micelles or clusters in bulk solution with removal of adsorbed water molecules from the silica surface. At the monomer concentration giving maximum adsorption, the adsorbed monomer was spontaneously polymerised on the silica surface in THF or chloroform without an initiator at 40C or 60C. The polymerisation mechanism was discussed. Adsorption of an anion-type monomer with a carboxyl group on delta-alumina which showed a positive zeta potential in neutral aqueous solution was higher than that on colloidal silica, but spontaneous polymerisation did not occur on alumina. 19 refs. lAPAN... 

FIGURE 7.3 Adsorption isotherms of chloroform from aqueous solution on carbon before and after outgassing. (Adapted from Ishizaki, C., Marti, I., and Ruiz, M., in Advances in Chemistry, No. 202, I.H. Suffet and M.J. McGuire, Eds., Amer. Chem. Soc., Washington, D.C., 1983, p. 95. With permission.)... 

FIGURE 7.8 Adsorption isotherms of chloroform by different activated carbons. (After Mullins, R.L., Jr, Jogorski, J.S., Hubbs, S.A., and AUgerei, G.D., va Activated Carbon Adsorption, Vol. I, I.H. Suffet and M.J. McGuire, Eds., Ann Arbor Science Pnblishers, Ann Arbor MI, 1981, p. 273. With permission.)... 

Nanoparticles of the semicondnctor titanium dioxide have also been spread as mono-layers [164]. Nanoparticles of TiOi were formed by the arrested hydrolysis of titanium iso-propoxide. A very small amount of water was mixed with a chloroform/isopropanol solution of titanium isopropoxide with the surfactant hexadecyltrimethylammonium bromide (CTAB) and a catalyst. The particles produced were 1.8-2.2 nm in diameter. The stabilized particles were spread as monolayers. Successive cycles of II-A isotherms exhibited smaller areas for the initial pressnre rise, attributed to dissolution of excess surfactant into the subphase. And BAM observation showed the solid state of the films at 50 mN m was featureless and bright collapse then appeared as a series of stripes across the image. The area per particle determined from the isotherms decreased when sols were subjected to a heat treatment prior to spreading. This effect was believed to arise from a modification to the particle surface that made surfactant adsorption less favorable. 

Figure 6.11 Composite (surface excess) isotherms for the adsorption of (a) benzene from solution in methanol on to charcoal177 and (b) chloroform from solution in carbon tetrachloride on to charcoal178 (By courtesy of (a) American Chemical Society, (b) Journal of the Chemical Society)...

The adsorption equilibria were measured using a gravimetric method and were expressed as isotherms. A chromatographic method was used to get the initial slope of the isotherms. In the simulation, GCMC method was used to calculate amounts adsorbed for various conditions. When the experiment result and simulation result of chloroform are compared, the simulation for the acid site model was most agreement with chromatographic data and baratron data. The simulation result of tetrachloroethylene with three models corresponded mostly for the non-polar molecule, and above all the acid site model was the closest to the experiment result. Therefore, to get better coincidence between experimental data and simulation, it was found to be necessary to account for aluminum rather than silanol nest. 

Fig. 21.2. Typical BET isotherm with specific analyte incorporation within the linear slope of the adsorption curve number of moles chloroform n in a QCM layer as a function of the partial pressure p.

According to a multilayer adsorption theory developed by Champion and Halsey such adsorption on a homogeneous surface leads inevitably to step like isotherms and isotherm continuity should be explained by surface heterogeneity [48]. Differences in the relationship course q°( = f(%PEG) between non-polar hexane, polar chloroform, 5r-complexing benzene, acetone and methanol which are capable of hydrogen bonds formation become comprehensible in view of the fact that specific and non-specific interactions, having different adsorption energies, take part in the adsorption process. Formation of distinct extreme on hexane heat of adsorption curve can be explained by hexane non polarity... 

---