Surfactant degradation assessment

With phenanthrene, some indirect evidence for this supposition was demonstrated by adding 100 and 200 mg of glucose (0.13 and 0.25%, w/v) to several phenanthrene and soil-water systems without surfactant to assess whether the presence of a readily degradable substrate would suppress phenanthrene mineralization. In both cases a significant lag period was evident prior to the onset of phenanthrene mineralization. Although not a definitive experiment, this test and the results with nonionic surfactants and phenanthrene (52) and with hexachlorobenzene (66) indicate the need for further investigation. 

Surfactant Chemical Stability. Two approaches were used in assessing surfactant degradation over time. The first consisted of monitoring the pH of surfactant solutions that were in contact with pieces of reservoir rock over several months. Because only commercially available surfactants were tested and almost all of them contained secondary components, the pH data were rather inconclusive. The fact that reservoir solids have some buffering capacity made the interpretation of pH trends even more difficult. 

Photon Correlation Spectroscopy Diameters of Dynasan 114 Solid Lipid Nanoparticles with Different Surfactants (10% Lipid, 1% Surfactant) to Assess the Influence of Different Surfactants on the Enzymatic Degradation (Lipase/Colipase) of Solid Lipid Nanoparticles... 

Routledge, E.J. and Sumpter, J.P. (1996). Estrogenic activity of surfactants and some of their degradation products assessed using a recombinant yeast screen. Environmental Toxicology and Chemistry 15, 241-248. 

Improved risk assessment methodologies regarding surfactants and their degradation products. 

The major part of the biosphere is aerobic and consequently priority has been given to the study and assessment of biodegradability under aerobic conditions. Nevertheless, there are environmental compartments that can be permanently (e.g. anaerobic digesters) or temporarily anaerobic (e.g. river sediments and soils) and surfactants do reach these. The majority of surfactants entering the environment is exposed to and degraded under aerobic conditions. This is the predominant mechanism of removal even in cases of absence of wastewater treatment practices (direct discharge) and it is estimated that less than 20% of the total surfactant mass will potentially reach anaerobic environmental compartments [1]. Only in a few cases, however, will the presence of surfactants in these compartments be permanent. The presence of surfactants in anaerobic zones is not exclusively due to the lack of anaerobic degradation. Physico-chemical factors such as adsorption or precipitation play an important role as well as the poor bioavailability of surfactant derivatives (chemical speciation) in these situations. 

As mentioned before, the presence of surfactants in anaerobic compartments cannot be separated from their physico-chemical characteristics and in fact surfactants which degrade extensively in the laboratory under anaerobic conditions, e.g. soap, are also found in considerable concentrations in anaerobic compartments. Due to their hydrophobic character surfactants are strongly sorbed to sludges and therefore a large amount of the load of these compounds into a sewage treatment plant (reportedly 20-50%) is associated with suspended solids [43,44]. The relevance of the presence of surfactants in the environment should be assessed, therefore, on the basis of their potential impact on the structure and function of the various compartments. In most cases, ionic surfactants are present as insoluble salts and therefore their potential impact is negligible as reflected in the lack of known negative impacts. 

Surfactants and their biotransformation products enter surface waters primarily through discharges from wastewater treatment plants (WWTPs). Depending on their physicochemical properties, surface-active substances may partition between the dissolved phase and the solid phase through adsorption onto suspended particles and sediments [1,2]. Several environmental studies have been dedicated to the assessment of the contribution of surfactant residues in effluents to the total load of surfactants in receiving waters. This contribution reviews the relevant literature describing the presence of linear alkylbenzene sulfonates (LASs) and in particular of their degradation products in surface waters and sediments (Table 6.3.1). 

Hidaka, H., Ajisaka, K., Horikoshi, S., Oyama, T., Takeuchi, K., Zhao, J. and Serpone, N. (2001). Comparative assessment of the efficiency of TiOj/OTE thin film electrodes fabricated by three deposition methods - Photoelectrochemical degradation of the DBS anionic surfactant. J. Photochem. Photobiol. A-Chem. 138(2), 185-192. 

Hi DAKA H, Ajisaka K, Horikoshi S, Oyama T, Takeuchi K, Zhao J, Serpone N (2001) Comparative Assessment of the Efficiency of T102/0TE Thin Eilm Electrodes Fabricated by Three Deposition Methods. Photo-electrochemical Degradation of the DBS Anionic Surfactant, J. Photochem. Photobiol. A Chem. 138 185-192. 

Assessment of Toxicity. Dilution tests were performed to examine a possible toxicity phenomenon. In these tests surfactant solutions were diluted to concentrations below those resulting in micelle formation by addition of water or soil and water. Such dilution was observed to result in the recovery of the phenanthrene-degrading ability in the soil-water systems. This recovery suggested that the presence of surfactant micelles did not result in cell lysis or destruction, and that the inhibition may be attributable to some reversible surfactant-bacteria interaction. 

Note Produced with Dynasan 114 as matrix lipid and poloxamer 407 and sodium cholate as surfactants. The formulations were produced in three sizes (small, medium, large) to assess the influence of the size on the degradation of the nanoparticles. Both 5% lipid and 0.5% surfactant were used. 

FIGURE 6.16 Degradation of different Dynasan 114 formulations to assess the influence of different surfactants. Pbc 188, poloxamer 188 NaCh, sodium cholate Pbc 407, poloxamer 407 SDS, sodium dodecyl sulfate CPC, cetylpyridinium chloride P 908, poloxamine 908. 

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