Surfactant screening results

Surfactant Screening. Partial results from the surfactant serening tests are presented in Table IV. (For complete results s Peters et al. [15]) Surfactants 13 (nonionic), 15, and 18 (both anionic) were cht n for column-flooding studies on the basis of their high level of perfmmance in removing TPH from soil during the screening process. 

A comparistxi of TPH removal values obtained by leaching columns with water alone and with surfactant solution (Table VIII) shows that the only substantial increase in amounts of TPH remove was observed in the 26.2-m column (S-13) a dramatic decrease was observed in the 23.2-m column, and only slight differences were observed in the 6.3-m and 17.1-m columns. These results indicate that the use of surfactants 15 and 18 did not yield an improvement over using water alone, but surfactant 13 was quite successful in enhancing the diesel fuel mobilization. The generally poor performance of these surfactants is in contrast to the screening results (Table IV) and the results of other studies (6-9). 

Barry and Russell explain At the viscosity maximum the concentration of surfactant required to reach reversal of charge point has just been exceeded and the excess surfactant acts as added salt and suppresses the coacervation by screening the charges on the reacting species. With further addition of surfactant, the ( -potential progressively rises, colloidal particles repel each other and the solutions become more mobile. In the limit, the viscosities approach those of the dye-free surfactant solutions. Results above and below the CMC indicate that surfactant micelles are not necessary for interaction to occur between the dye and surfactant. ... 

These results obtained from the analyses of industrial blends proved that the identification of the constituents of the different surfactant blends in the FIA-MS and MS-MS mode can be performed successfully in a time-saving manner only using the product ion scan carried out in mixture analysis mode. The applicability of positive ionisation either using FIA-MS for screening and MS-MS for the identification of these surfactants was evaluated after the blends examined before were mixed resulting in a complex surfactant mixture (cf. Fig. 2.5.7(a)). Identification of selected mixture constituents known to belong to the different blends used for mixture composition was performed by applying the whole spectrum of analytical techniques provided by MS-MS such as product ion, parent ion and/or neutral loss scans. 

In a screening approach, non-ionic surfactants were monitored in the form of their [M + NH4]+ ions, equally spaced with Am/z 44 and identified by FIA-MS-MS(+) in combination with APCI or ESI interface [34,35]. Ci8-SPE was performed prior to selective elution by diethyl ether [35]. Ions of the non-ionics of AE type at m/z 350-570 (Am/z 44) were identified as surfactants with the general formula Ci3H27-0(CH2CH20)mH (m = 3-7). The complexity of the mixture confirmed the results using the diagnostic parent scans m/z 89 for aliphatic non-ionic surfactants of ethoxylate type necessary [35]. 

Because the inverse Debye length is calculated from the ionic surfactant concentration of the continuous phase, the only unknown parameter is the surface potential i/io this can be obtained from a fit of these expressions to the experimental data. The theoretical values of FeQx) are shown by the continuous curves in Eig. 2.5, for the three surfactant concentrations. The agreement between theory and experiment is spectacular, and as expected, the surface potential increases with the bulk surfactant concentration as a result of the adsorption equilibrium. Consequently, a higher surfactant concentration induces a larger repulsion, but is also characterized by a shorter range due to the decrease of the Debye screening length. 

Shea and colleagues [109-111] added an exciting contribution to this field They created molecular imprints for the peptide melittin, the main component of bee venom, in polymer nanoparticles, resulting in artificial antibody mimics that can be used for the in vivo capture and neutralization of melittin. Melittin is a peptide comprising 26 amino acids which is toxic because of its cytolytic activity. Shea and colleagues strategy was to synthesize cross-linked, acrylamide-based MIP nanoparticles by a process based on precipitation polymerization using a small amount of surfactant. To maximize the specificity and the affinity for melittin, a number of hydrophilic monomers were screened for complementarity with the template. The imprinted nanoparticles were able to bind selectively the peptide with an apparent dissociation constant of Ax>app > 1 nM [109]. 

SDS and kaolinite (i.e., at pH 4.6 both the kaolinite surface and SDS have net negative charges). The initial enhancement of sorption that occurs with increasing NaCl at low SDS concentrations most likely results from a screening effect between SDS and kaolinite that allows SDS molecules to first sorb enhancement at higher SDS concentrations most likely results from decreasing repulsions between sorbed SDS headgroups when hydrophobic forces become more important. For the nonionic Tween 80 surfactant, isotherms for 0 and 0.1 M NaCl show that differences in sorption are minor for these conditions, consistent with results from Brownawell et al. (1997). 

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