[Show abstract][Hide abstract] ABSTRACT: White-rot fungi are known to degrade a wide variety of recalcitrant pollutants. In this work, three white-rot fungi were used to degrade a mixture of PCBs at high initial concentrations from 600 to 3000 mg/l, in the presence of a non-ionic surfactant (Tween 80). The PCBs were extracted from a historically PCB-contaminated soil. Preliminary experiments showed that Tween 80 exhibited the highest emulsification index of the three surfactants tested (Tergitol NP-10, Triton X-100 and Tween 80). Tween 80 had no inhibitory effect on fungal radial growth, whereas the other surfactants inhibited the growth rate by 75–95%. Three initial PCB concentrations (600, 1800 and 3000 mg/l) were assayed with three fungi for the PCB degradation tests. The extent of PCB modification was found to depend on PCB concentration (P
Advances in Environmental Research 01/2002; 6(4):559-568.
[Show abstract][Hide abstract] ABSTRACT: Surfactant micellar solubilization is under investigation as a promising method for significantly increasing the efficiency of remediation of aquifers contaminated with nonaqueous phase liquids (NAPLs). In this study, the influence of three parameters on the micellar solubilization of NAPLs by a mixture of ethoxylated dodecyl alcohol surfactants was investigated: Presence of model aquifer materials, extent of equilibrium partitioning of surfactant into the nonaqueous phase, and sample mixing regime. The micellar solubilization of two NAPLs, hexane, representative of nonbranched alkanes, and 1,2-dichlorobenzene, representative of polar and aromatic compounds, was studied. Batch experiments indicated that surfactant losses to sorption on organic-coated silica were relatively small for these experimental systems. Surfactant partitioning into hexane was not significant, but there was significant surfactant partitioning into the 1,2-DCB phase, resulting in a total surfactant dose required to achieve 1,2-DCB micellar solubilization greater than that predicted from the surfactant critical micelle concentration. Partitioning of surfactant into 1,2-DCB was selective, with the more hydrophobic surfactant molecules favoring the 1,2-DCB phase, resulting in an aqueous phase surfactant mixture with different solubilization properties than the original. Mixing conditions had a significant effect on the extent of solubilization of 1,2-DCB, attributed to the greater tendency of 1,2-DCB versus hexane to form emulsions. Results indicate that partitioning may be significant for certain nonionic surfactant/NAPL systems and should be investigated prior to remedial activities. Total surfactant concentration, aqueous to nonaqueous phase volume ratio, and surfactant formulation should be chosen to minimize losses to nonaqueous phases.
Water Research - WATER RES. 01/1998; 32(5):1345-1354.
[Show abstract][Hide abstract] ABSTRACT: Oil-in-water (o/w) nano-emulsions with paraffin as an oil phase and Sorbitan monooleate (Span 20)/polyoxyethylene sorbitan monooleate (Tween 20) as emulsifiers were prepared using the emulsion inversion phase (EIP) method at 25 ℃. The properties of the nano-emulsions were investigated in detail as a function of emulsifier content and the addition of ionic surfactants including cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). The droplets of the nano-emulsions become smaller with the increasing concentration of Tween 20/Span 20 and the polydispersity of the droplets decreases. Similarly, the mean droplet size also decreases with the addition of both CTAB and SDS. The zeta potential of the nano-emulsion droplet without SDS or CTAB was found to be negative. Upon the addition of SDS, a more negative value was obtained which leads to an increased electrostatic interactions between droplets and improves the stability of the nano-emulsions via lowering the Ostwald ripening rate. Upon the addition of CTAB, however, a less negative zeta potential was induced which weakens the electrostatic interactions between droplets and lowers the stability of the nano-emulsions. These results indicate that electrostatic interaction is the main factor determining the stability of the nano-emulsions. Interfacial rheological measurements indicated that the maximum values of dilational moduli of both Tween 20/SDS and Tween 20/CTAB mixed adsorption layers at paraffin oil/water interface are lower than that of single adsorption layer of Tween 20. Our results give new insights of the nano-emulsions containing mixed surfactants and may serve as guidelines for preparation of new nano-emulsion systems for practical applications.
Colloids and Surfaces A Physicochemical and Engineering Aspects 02/2013; 418:60–67. · 2.11 Impact Factor
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