Carbon surface tension

Cmde products from organic-based processes contain organic impurities which affect color, odor, surface tension, and stabiUty, and ate normally pretreated to reduce the carbon content before final purification and concentration by various distillation methods. 

K, have been tabulated (2). Also given are data for superheated carbon dioxide vapor from 228 to 923 K at pressures from 7 to 7,000 kPa (1—1,000 psi). A graphical presentation of heat of formation, free energy of formation, heat of vaporization, surface tension, vapor pressure, Hquid and vapor heat capacities, densities, viscosities, and thermal conductivities has been provided (3). CompressibiHty factors of carbon dioxide from 268 to 473 K and 1,400—69,000 kPa (203—10,000 psi) are available (4). 

C,4—C20 AOS surfactants were laboratory-prepared by Tuvell et al. [2]. Table 3 shows the CMC values of these single-carbon-cut AOS surfactants and of reference compounds, their areas per molecule at the water-air interface inferred from plots of surface tension vs. In (concentration), and the surface tension at the CMC, all at 23°C. The area of the molecule is proportional to the equilibrium adsorptivity, which in turn is taken as a comparative measure of the surface activity of the molecule. Tuvell et al. [2] argue that the greater the... 

CMCs of LAS-AOS mixtures in water that contained no calcium or magnesium ions were determined by Suri et al. [3] by means of the surface tension method. The purpose of this work was to study the advantage of LAS-AOS synergism in prototype phosphate-free carbonate-built formulations for use in the Indian market. The authors have used a commercial C10-C14 LAS sample with an average molecular weight of 343 and a commercial C16-C18 AOS sample with an average molecular weight of 350. 

FIG. 1 Critical micelle concentration as a function of the number of carbon atoms in the hydrophobic rest of sodium a-sulfo fatty acid methyl esters. Methods O, surface tension +, conductivity A, solubilization of a dye x, solubility (all without electrolyte) , surface tension with a constant electrolyte concentration of 5 x 10"2 mol/L. (From Ref. 57.)... 

The maximal accessible depression of the surface tension of aqueous solutions of disodium alkanephosphonates is strongly controlled by the length of the carbon chain. There is a similar dependence of foamability on the length of the alkyl chain [188], as is shown in Table 8. 

Activation methods can be divided into two groups. Activation by addition of selected metals (a few wt%), mainly transition metals, e.g., fine powders of Fe, Ni, Co, Cr, Pt, Pd, etc. ", or chlorides of these metals when these are reducible to the metal by hydrogen during presintering. The mechanism of activation is not understood (surface tension, surface diffusion, etc.) but is related to the electronic structure of the metal additive. Activation by carbon is also effective. Alternatively, activation utilizes powders in a specially activated state, e.g., very fine (submicronic) powders. ... 

In a number of general properties, such as viscosity and thermal conductivity, melts differ little from solutions. Their surface tensions are two to three times higher than those of aqueous solutions. This leads to poorer wetting of many solids, including important electrode materials such as carbon and graphite, by the ionic liquids. 

The adsorption action of activated carbon may be explained in terms of the surface tension (or energy per unit surface area) exhibited by the activated particles whose specific surface area is very large. The molecules on the surface of the particles are subjected to unbalanced forces due to unsatisfied bonds and this is responsible for the attachment of other molecules to the surface. The attractive forces are, however, relatively weak and short range, and are called Van der Waals forces, and the adsorption process under these conditions is termed as a physical adsorption (physisorption) process. In this case, the adsorbed molecules are readily desorbed from the surface. Adsorption resulting from chemical interaction with surface molecules is termed as chemisorption. In contrast to the physical process described for the adsorption on carbon, the chemisorption process is characterized by stronger forces and irreversibility. It may, however, be mentioned that many adsorption phenomena involve both physical and chemical processes. They are, therefore, not easily classified, and the general term, sorption, is used to designate the mechanism of the process. 

Quinn, E.L. (1927) The surface tension of liquid carbon dioxide. Journal of the American Chemical Society, 49 (11), 2704-2711. 

It was mentioned previously that the narrow range of concentrations in which sudden changes are produced in the physicochemical properties in solutions of surfactants is known as critical micelle concentration. To determine the value of this parameter the change in one of these properties can be used so normally electrical conductivity, surface tension, or refraction index can be measured. Numerous cmc values have been published, most of them for surfactants that contain hydrocarbon chains of between 10 and 16 carbon atoms [1, 3, 7], The value of the cmc depends on several factors such as the length of the surfactant chain, the presence of electrolytes, temperature, and pressure [7, 14], Some of these values of cmc are shown in Table 2. 

Van der Waals forces between solid/gas interactions and the liquid/gas surface tension forces represent the limiting cases, but in general both the forces competitively affect the adsorption process. Therefore, in determining the surface fractal dimension of the carbon specimen, it is very important to use appropriate relation between C and dFSF. According to Ismail and Pfeifer,111... 

Surface tension is responsible for capillary effects and spreading of the NAPL over the water table. At about 20°C, water has a surface tension of 73.05 dyn/cm, whereas CC14 has a surface tension of only 26.95 dyn/cm. Therefore, water will be held in an unsaturated porous media by surface tension to a much greater degree relative to carbon tetrachloride (i.e., the permeability of porous media will be different with respect to each liquid). The ramifications will be important for contaminant transport of mixed wastes. 

At constant pressure conditions, Quigley, Johnson, and Harris (Ql) find that for higher flow rates, the effect of surface tension on bubble volume is negligible. These authors may not have adequately accounted for the large difference in the densities of the two liquids—water and carbon tetrachloride —used by them. Davidson and Schuler find that under constant pressure conditions, surface tension does appreciably affect the bubble volume. 

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