Alkyl sulfonate, adsorption

Somasundaran, P and D. W. Fuerstenau (1966), "Mechanisms of Alkyl Sulfonate Adsorption at the Alumina-Water Interface", J. of Physical ChemistrylQ, 90-96. 

Somasundaran, P. and Furstenau, D.W., Mechanisms of alkyl sulfonate adsorption at the alumina-water interface, J. Phys. Chem., 70, 91, 1966. 

Giles, C.H. and Nakhwa, S.N. (1962). Adsorption XVI The measurement of specific surface areas of finely divided solids by solution adsorption. J. Appl. Chem., 12, 266-73. Lopez-Gonzalez, J., de, D., Valenzuela-Calahorro, C., et al. (1988). Adsorption of p-nitrophenol by active carbons prepared from obve wood. An. Quim., 84B, 47—51. Femandez-Cobnas, J., Denoyel, R., and Rouquerol, J. (1991). Characterization of activated charcoals by adsorption from solution. Stud. Surf. Sci. Catal., 62, 399—408. Somasundaran, P. and Fuerstenau, D.W. (1966). Mechanisms of alkyl sulfonate adsorption at the alumina-water interface. J. Phys. Chem., 70, 90-6. 

Since sulfonate groups have been used in other ground-water tracers, the goal of this work was to synthesize several N-substi-tuted pyridone alkyl sulfonates which might be less susceptible to adsorption as well as more soluble. Alkyl sulfonates of varying chain lengths would be unique in a water system and separately identifiable by HPLC analysis. Two series of compounds were synthesized (Vla-c and Vlla-c). These compounds could be prepared by treating compounds III and IV with the appropriate lu-bromoalkyl sulfonate. 

Adsorption of a surfactant on solids is dependent, among other things, on the structure of both the hydro-phobic and hydrophilic portions of it. There are a number of mechanisms proposed for surfactant adsorption and an understanding of the effects of the structure of the surfactant can help in elucidating the role of these mechanisms. In this study, the effect on adsorption on alumina of some structure variations of sulfonates (chain length and the branching and the presence of ethyoxyl, phenyl, disulfonate and dialkyl groups) is examined above and below CMC as a function of surfactant concentration, pH and salinity. Co-operative action between an ionic alkyl sulfonate and a nonionic ethoxylated alcohol is also studied. 

Aryl Addition. Surfactants having an aryl group added between the sulfonate and alkyl chain are studied using the standard adsorption procedure, and compared with an alkyl sulfonate. Figure... 

While surface charge is by no means the only factor responsible for electrolyte adsorption (94), particularly organic electrolytes (9, 27), the extent of adsorption of the less specifically adsorbed species, such as the simple aquo ions and, for example, primary amines and alkyl sulfonates, decreases rapidly when the sign of the oxides surface charge is changed to that of the sorbing species (6, 10). 

The molecular architecture and the chain length of the IPR greatly affect analyte retention enhancement. At constant eluent composition, log k of an analyte oppositely charged to the IPR raises linearly with the number of carbon atoms in the chain of the alkyl sulfonate [2,3]. The shorter the IPR side chain, the lower its adsorption onto the stationary phase. This involves a lower potential difference between the electrified stationary phase and bulk eluent that in turn results in a lower driving force for analyte retention [4-7]. To attain comparable retention, the effect played by a higher concentration of a less hydrophobic IPR is tantamount to that of a lower concentration of a more lipophilic IPR [8-10]. However, the relationship between adsorbophilicity and chain length of the IPR is only part of the story. 

Chemical interactions The chemical contribution may result from interactions such as covalent or complex bond formation between the surfactants and the surface sites. Surfactants such as fatty acids, alkyl sulfates, alkyl sulfonates, amines and alkylhydroxa-mates have been proposed to adsorb by means of chemical interactions on a variety of particles. In addition, surfactants containing hydroxyl, phenolic, carboxylic and amine groups can hydrogen-bond with the surface sites. Infrared spectroscopy has been used to understand the chemisorption of surfactants at the surface, by examining the shift in the characteristic peaks of the surfactants upon adsorption. 

Hoeft [44] also studied the cooperative and competitive adsorption of ionic surfactant mixtures onto hydrophobic surfaces. When shorter alkyl chain surfactants (sodium octyl sulfonate and sodium decyl sulfonate) are adsorbed, the decyl will displace the octyl surfactant. For mixtures of sodium dodecyi sulfonate and sodium octyl sulfonate, however, there appears to be an association between the surfactant molecules leading to enhanced adsorption of the sodium dodecyi sulfonate with no depletion of the octyl sulfonate adsorption. This is shown in Fig, 2, where the lines indicate the expected adsorption determined using a two-component Langmuir adsorption isotherm with the adsorption parameters determined analyzing the data from adsorption of each species individually. Also shown in Fig. 2 is the concentration of surface-active materials in the aqueous phase at equilibrium. In each of these experiments the total molar concentration and amount of surfactant solution added to the latex was a constant, as was the amount of latex. Thus a lower value for the bulk concentration corresponds to greater adsorption. 

Trogus et al. (2) have also found that the adsorption of alkyl aryl sulfonates from brine on Berea and kaolinite increased with surfactant molecular weight. Lawson and Dilgren (3) have noted that sulfonate adsorption increased with brine salinity and therefore with decreased solubility. These results are in agreement with the theory that adsorption from solution depends in part on the magnitude of the solute-solvent interactions in the solution (4) in general, weak interactions, as manifested by low solubility, lead to large solute adsorption. 

Yet, the reality is complex and sometimes ambiguous. For example, at a certain low level of residual ionic calcium, around 0.5 mmol of calcimn per liter, the detergent effect of such anionic surfactants as sodium alkylbenzene sulfonate is enhanced [4,5]. Several explanations have been suggested for his phenomenon, but, so far, it has been impossible to settle the question. It is certain that divalent cations help increase the size of the micelles of anionic surfactants, which may improve cleaning power. Calcium in very substoichio-metric amoimts with respect to an alkyl sulfonate will cause no precipitation but will rather lower the critical micelle concentration or possibly the existence of surfactant units with two hydrophobic heads. Finally, free calcium may increase the adsorption of anionic surfactants on textiles like cotton, and such adsorption as the fiber-water interfaces is well known as a mechanism that explains soil removal. 

Alkyl ether sulfates are/after alkyl benzene sulfonates(LAS),the group of technically important anionic surfactants with the largest production voluJne and product value. They have in comparison with other anionic surfactants special properties which are based on the particular structure of the molecule. These are expressed,for example,in the general adsorption properties at different interfaces, and in the Krafft-Point. Alkyl ether sulfates may be used under conditions, at which the utilization of other surfactant classes is very limited. They possess particularly favorable interfacial and application properties in mixtures with other surfactants. The paper gives a review of all important mechanisms of action and properties of interest for application. 

Comparison of these adsorption isotherms with those obtained for the linear alkyl aryl sulfonates (Figure 6) reveals the behavior of the 2 ( ) HDBS to be close to that which would be expected for a 1 (t> HDBS and that of the 8 ( ) HDBS to be equivalent to that of a tridecyl benzene sulfonate. Development of a cguantitative model that can account for the effect of the position of the benzene group on the chain warrants additional data for a variety of surfactants with branched chains. 

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