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Soil Surfactant Flushing/Washing
Published in David J. Wilson, Ann N. Clarke, Hazardous Waste Site Soil Remediation, 2017
David J. Wilson, Ann N. Clarke
Aqueous surfactant solutions with surfactant concentrations substantially above the CMC contain a significant volume of nonpolar phase in the interiors of the micelles. This nonpolar phase is able to dissolve relatively nonpolar solutes—hydrophobic compounds such as PCBs, organic solvents, chlorinated pesticides, and the like. This phenomenon, known as micellar solubilization, is illustrated in Figure 3. The solubilities of these hydrophobic compounds in water are typically quite small, on the order of 1 mg/L for PCBs, for instance. In surfactant solutions, on the other hand, their solubilities are increased manyfold by micellar solubilization. Cleanups that might require hundreds of years if simple water flushing were used may be complete within a year or two if surfactants are employed, due to the ability of surfactant solutions to dissolve perhaps 100-fold to 1000-fold more contaminant per unit volume than can be dissolved in water. Two early but very useful references on solubilization are McBain and Hutchinson’s book (1955) and a review article by Klevens (1950). The thermodynamics of solubilization (or mixed micelle formation) has been discussed by Hall and Pethica (1967), Mukerjee (1971a,b), and Wayt and Wilson (1989), among others.
Simultaneously enhanced surfactant flushing of diesel contaminated soil column and qualified emission of effluent
Published in Journal of Environmental Science and Health, Part A, 2020
Zhaolu Huang, Daoyuan Wang, Indu Tripathi, Zhao Chen, Juan Zhou, Quanyuan Chen
In the same CMC-fold concentration range, seven kinds of surfactants were used to select the flushing agent solution (Figure 2). SDS has shown an excellent diesel removal rate, even for remediation of loamy soils contaminated with 12% oil (30 d aging). This is because the CMC of SDS is more than 10 times that of nonionic surfactants. In the same concentration range, TX 100, Tw 80, and saponin showed similar diesel removal ability. At the same time, between 0.2 and 2 times, saponin showed a slight advantage, and the growth rate was faster compared with other surfactants. Brij 35 and tannin showed similar diesel removal curves, and the Brij 35 diesel removal curve was higher than tannin in the concentration range of 0.6 to 1.8 folds of the CMC. However, the CMC of saponin was 0.15 g L−1 when tested at room temperature, which was about four times that of Brij 35 (0.035 g L−1). However, under this condition, the surface tension of the saponin solution ranged from 62.1 ± 0.3 mN m−1 to 67.5 ± 0.4 m Nm−1, while the surface tension of the Brij 35 solution reaches from 50.1 ± 0.1 mN m−1 to 59.4 ± 0.2 mN m−1. The Brij 35 solution showed a lower surface tension; therefore, under this condition, the saponin removed more diesel due to its micellar solubilization. Saponin showed superiority on the contaminant removal rate because of its excellent hydrophobic compounds solubilization capacity. Brij 35 showed a lower surface tension compared to the other four nonionic surfactants.
Remediation of phenanthrene contaminated soils by nonionic surfactants enhanced soil washing coupled with ozone oxidation
Published in Ozone: Science & Engineering, 2018
The PHE removal efficiencies of TX-100 and Brij-35 were 80.2% and 73.8%, respectively. As reported in a literature review, the removal efficiencies from aged contaminated soil had a range of 81.1–94.5% with different types of surfactants (Chong et al. 2014). These results can be attributed to aqueous surfactant solutions that promote the solubilization of the PHE and the desorption of PHE from the soil particles. It is well known that surfactants can increase the solubility of PAH in water through micellar solubilization and then improve PAH mobilization due to the reduction of interfacial tension between water and contaminant above critical micelle concentration. TX-100 had a greater effect than Brij-35, which may be because TX-100 is adsorbed by the soil to a lesser degree (Chang et al. 2015). Unlike for aged contaminated soil, there was a smaller amount of bound PHE in the soil; therefore, the artificially polluted soil was washed only once.
Adsorption of anionic dye by anionic surfactant modified chitosan beads: Influence of hydrophobic tail and ionic head-group
Published in Journal of Dispersion Science and Technology, 2018
Cuiying Lin, Shuo Wang, Haoqi Sun, Rong Jiang
The adsorption capacity of modified CS beads also depends on the micellar solubilization of dyes,[25,27] and ionic head-group of surfactant can be involved in the micelle formation and micelle characteristics. Figure 3 shows the effect of ionic head-group type of surfactants (i.e., SDOS, SDS, and SDBS, respectively) on the adsorption of CR. The initial CR concentration was fixed at 1000 mg · L−1, and surfactant concentration was 0.5% (wt%). It is found that the obviously increased adsorption capacity of the modified CS beads regardless of the ionic head-group type used in this study. As mentioned in the section On CR Adsorption, the enhancement of adsorption capacity of modified CS beads can be explained by (i) the hydrophobic interaction between CR molecules and hydrophobic part surfactant, (ii) solubilization of CR in the surfactant micelle. Figure 3 also shows that the adsorption capacity slightly increases in order from SDBS/CS beads to SDOS/CS beads to SDS/CS beads. Three surfactants have the same length of alkyl tails, so the difference of adsorption capacity might be due to micellar solubilization. The location of CR molecules solubilization was generally considered to be the micelle palisade layer. The large inter-space of the micelle palisade layer may be in favor of the adsorption of CR molecule. For ionic surfactants, besides the hydrophobic tails, the electrostatic repulsion between ionic head-groups also affects the micelle size. Considering the difference of three ionic head-groups (i.e., the aromatic groups on the head-groups of SDBS molecules and the larger partial charge on the α -methylene group of SDOS molecules), it is not surprising that SDBS/CS beads have the highest adsorption capacity followed by SDOS/CS beads. But Figure 3 also shows the difference is modest and indicates the ionic head-group only has a minor effect.