Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Isothermal surface distillation

Osmotic distillation (OD), sometimes called isothermal membrane distillation, is a membrane process in which a liquid phase (usually an aqueous solution) containing one or more volatile components flows across one surface of a microporous membrane whose pores are not wetted by the hquid, while the opposing surfece is in contact with a second nonwetting liquid phase (usually an aqueous solution) in which the volatile components are soluble or miscible [35]. The device is similar to the membrane contactor (MC) discussed in Chapter 1, which contains hollow fibre membranes that are hydrophobic (non-wetting. [Pg.203]

Vapor-phase decomposition and collection (Figs 4.16 to 4.18) is a standardized method of silicon wafer surface analysis [4.11]. The native oxide on wafer surfaces readily reacts with isothermally distilled HF vapor and forms small droplets on the hydrophobic wafer surface at room temperature [4.66]. These small droplets can be collected with a scanning droplet. The scanned, accumulated droplets finally contain all dissolved contamination in the scanning droplet. It must be dried on a concentrated spot (diameter approximately 150 pm) and measured against the blank droplet residue of the scanning solution [4.67-4.69]. VPD-TXRF has been carefully evaluated against standardized surface analytical methods. The user is advised to use reliable reference materials [4.70-4.72]. [Pg.192]

Figure 34. Surface pressure - area isotherms for monolayers of Ci 8TCNQ (a), the mixture of the dihydrothiophene and G 8TCNQ (b), and the complex (c), spread on distilled water, as compared with that on the aqueous subphase with 10 5M LiTCNQ (c ). Figure 34. Surface pressure - area isotherms for monolayers of Ci 8TCNQ (a), the mixture of the dihydrothiophene and G 8TCNQ (b), and the complex (c), spread on distilled water, as compared with that on the aqueous subphase with 10 5M LiTCNQ (c ).
As pointed out by Sposito (1984) this equation initiated the surface chemistry of naturally occurring solids. Maarten van Bemmelen published this equation (now referred to as the Freundlich isotherm) more than 100 years ago and distilled from his results, that the adsorptive power of ordinary soils depends on the colloidal silicates, humus, silica, and iron oxides they contain. [Pg.95]

Rust samples scraped off from exposed AISI 1019 steel surfaces were ground to fine size in a morter with a pestle. A fraction of the samples was subjected to a salts extraction process using distilled water to determine the concentration of most common ions by chemical analysis and to study changes in adsorption isotherm after elimination of hygroscopic salts. Samples were obtained from AISI 1019 steel coupons, exposed for up to six months at coastal and rural locations. [Pg.87]

Material balance calculations on separation processes follow the same procedures used in Chapters 4 and 5. If the product streams leaving a unit include two phases in equilibrium, an equilibrium relationship for each species distributed between the phases should be counted in the degree-of-freedom analysis and included in the calculations. If a species is distributed between gas and liquid phases (as in distillation, absorption, and condensation), use tabulated vapor-liquid equilibrium data, Raoult s law, or Henry s law. If a solid solute is in equilibrium with a liquid solution, use tabulated solubility data. If a solute is distributed between two immiscible liquid phases, use a tabulated distribution coefficient or equilibrium data. If an adsorbate is distributed between a solid surface and a gas phase, use an adsorption isotherm. [Pg.280]

The same amoimt of work may be obtained reversibly in a different manner, viz. by the isothermal distillation of the amount dm from the small sphere to the plane surface. Let jp be the ordinary vapour pressure of the liquid at the plane surface and jf its vapour pressure at the small sphere. If the vapour obeys the gas laws, the work done in the transference is... [Pg.375]

Work is done when any solution is diluted in a reversible manner. Let v be the volume and tt the osmotic pressure of the solution. The maximum work done when the solution is diluted isothermally by d-y is tt dv. If we now allow for the fact that the surface of the solution is increased by da during the dilution (which we may suppose to be performed by isothermal distillation from a large volume of the solvent), we must subtract the work yda due to the surface tension. Hence the free energy of the solution diminishes during dilution by... [Pg.378]

In this work, nickel oxides are prepared by dehydration under vacuum (10 torr) at moderate temperatures (200-300 ) of a pure nickel hydroxide. The hydroxide itself is prepared by the steam distillation of a solution of reagent grade Ni(NOs)2 in an excess of aqueous ammonia (22). As has been shown (22), this method yields Ni(OH)2 containing less than 0.08% of NHs and N2O6. When dried at about 60°, the product has the composition NiO, 1.05 H2O and its BET surface area amounts to 34 m /gm. The external aspect is that of a fine crystalline powder and not of a gel. There are no small-diameter pores in the hydroxide particles since the adsorption-desorption isotherm of nitrogen at —195° does not present an hysteresis loop. The X-ray diagram is that of a well-crystalized nickel hydroxide. [Pg.171]

A second apparatus originally developed by Abribat, Rosano, and Vaillet (5) for studying the transfer of film (distillation isotherme super-ficielle) was used to determine if the subphase was also being dragged with the surface film. A cathetometer was used to measure the change in height of the substrate. [Pg.269]

Figure 4. Surface pressure and change in substrate height vs. time using the distillation isotherme superficielle technique. Trough area—201 cm2. Bridge—four glass rods, ody = 4 mm, length = 6.94 cm. OA (oleic acid) spread on 0.01N HCly pH == 1.9, 25°C COH (decyl alcohol) spread on water, pH 6.45> 22°C ME (methyl laurate) spread on water, pH 6.45, 22°C BSA (bovine serum albumin) spread on water, pH 6.45, 22°C. Figure 4. Surface pressure and change in substrate height vs. time using the distillation isotherme superficielle technique. Trough area—201 cm2. Bridge—four glass rods, ody = 4 mm, length = 6.94 cm. OA (oleic acid) spread on 0.01N HCly pH == 1.9, 25°C COH (decyl alcohol) spread on water, pH 6.45> 22°C ME (methyl laurate) spread on water, pH 6.45, 22°C BSA (bovine serum albumin) spread on water, pH 6.45, 22°C.
The water used as a substrate was twice distilled and had a pH slightly below 7.0 and a specific conductivity of about 0.5 jumho. Because the pH was always below 7.0, its variation had a negligible effect on the lecithin isotherm. Thorough testing of the water surface on the film balance ensured freedom from significant capillary-active contamination. [Pg.296]

The water was distilled twice from glass (initially from alkaline permanganate). It was subsequently twice distilled from quartz. Surface areas at most pressures were reproducible within 0.5 A2/molecule however, at low pressures, for gaseous isotherms, the error was somewhat greater. Surface potentials were also obtained but are not reported here. Surface potential values, however, confirm observations made with surface pressure measurements (8). [Pg.305]

The porous alumina catalyst was supplied by B. I. Parsons, Department of Energy, Mines and Resources, Ottawa, Canada. It had a measured surface area of 220 m2/g (one-point isotherm), and a slurry of the material in distilled water had a pH of 10.0. The pore size varied between 1000 and 400A, and the pore volume was 1.9 ml/g (5). The active alumina was manufactured by the Aluminum Co. of America, Portland, Ore. [Pg.86]

The silicagel supports were obtained from Merck and Grace. Some were treated with 2n H(31 (3h, 25 C), then washed 15 times with a large excess of distilled water and finally dried under vacuum, first at 80 C (2h) and then at 350 C (12 h) (Table 1). The BET surface areas were determined from adsorption isotherms [181 and the pore size distribution [191 by standard methods from the desorption isotherm of N2 at 77K (apparatus Omicron, Omnisorp joO). The mean pore size calculated according to [201. The number of surface... [Pg.112]

The enthalpies of reactions (2), (3), and (5) were determined in a variable temperature calorimeter with an isothermal jacket (Fig. 1). The calorimeter was constructed in accordance with the recommendations given in [24, 26]. A cylindrical calorimeter casing was made of 0.2-mm-thick nickel sheet. The calorimeter liquid was 2 kg of distilled water. The evaporation of the water was prevented by pouring 8.4 g of vaseline oil on its surface. [Pg.165]

In very weak brine or in distilled water, the repulsion forces are very high between the COO— groups. As a result of this high repulsion, the adsorption isotherm levels off above a certain polymer concentration a complete monolayer adsorption covers the sand surface. [Pg.294]

For a convex surface, that is, R> 0, as is the case for liquid droplets in vapor, it follows that the saturated vapor pressure is higher than that for a flat surface, causing transport of molecules through the vapor phase from the curved toward the flat surface. As a result, the droplets evaporate and condensation occurs at the flat surface. This process accelerates as the droplets become smaller. If the dispersion is heterodisperse, containing a variety of droplet sizes, the larger droplets grow at the expense of the smaller ones. This phenomenon is called isothermal distillation. [Pg.88]

The experiments were performed by a computer controlled KSV MiniMicro Langmuir balance (KSV Instruments, Finland). The trough (51 x 169 x4 mm) was made of Teflon while the material of the barrier was polyoxymethylene recommended for work with lipid layers [16]. Trough was cleaned with dichloromethane and double distilled water, while the barriers with methanol and double distilled water. Lipid dissolved in chloroform (Ig/L) was spread on the water surface. 15pL of solution was applied dropwise by a Hamilton syringe to form the monolayer. Prior recording the isotherms the solvent was let to evaporate for 10 minutes. [Pg.132]

In addition to analysis, GC may be used to study structure of chemical compounds, determine the mechanisms and kinetics of chemical reactions, and measure isotherms, heats of solution, heats of adsorption, free energy of solution and/or adsorption, activity coefficients, and diffusion constants (see Chapter 12). Another significant application of GC is in the area of the preparation of pure substances or narrow fractions as standards for further investigations. Gas chromatography is also utilized on an industrial scale for process monitoring. In adsorption studies it can be used to determine specific surface areas (4,5). A novel use is its utilization for elemental analyses of organic components (8-10). Distillation curves may also be plotted from gas chromatographic data. [Pg.40]

CF3(CF2)7(CH2)2SiCl3) (Shin-Etsu Chemical Co., Ltd.) were used to prepare the monolayers. NTS and FOETS were purified by vacuum distillation. NTS and FOETS toluene solutions with a concentration of ca. 3 x 10" M were spread on the pure water surface at 293 K. Surface pressure-area (jt-A) isotherms were measured with a computer-controlled home-made Langmuir-trough. In order to fomii the-... [Pg.333]

Fig. 3. The equilibrium surface tension reduction isotherm of 1-monocaproin (broken line) and of 21 pM ovalbumin in 1-monocaproin solution (solid line). The surface tension reduction of ovalbumin without the amphiphile is indicated on the ordinate. Measurements were performed at 23 °C in doubie distilled water, pH adjusted to 5.6 using 1.0 N NaOH... Fig. 3. The equilibrium surface tension reduction isotherm of 1-monocaproin (broken line) and of 21 pM ovalbumin in 1-monocaproin solution (solid line). The surface tension reduction of ovalbumin without the amphiphile is indicated on the ordinate. Measurements were performed at 23 °C in doubie distilled water, pH adjusted to 5.6 using 1.0 N NaOH...

See other pages where Isothermal surface distillation is mentioned: [Pg.272]    [Pg.272]    [Pg.272]    [Pg.272]    [Pg.40]    [Pg.241]    [Pg.174]    [Pg.218]    [Pg.83]    [Pg.86]    [Pg.92]    [Pg.417]    [Pg.1106]    [Pg.691]    [Pg.216]    [Pg.1106]    [Pg.14]    [Pg.111]    [Pg.545]    [Pg.382]    [Pg.515]    [Pg.47]    [Pg.278]    [Pg.545]    [Pg.113]    [Pg.987]    [Pg.99]    [Pg.95]    [Pg.1294]    [Pg.94]   


SEARCH



Isothermic distillation

© 2024 chempedia.info