Surfactants toxicity reduction

Association of surfactant molecules onto humic substances is also termed sorption and has been given some attention. In the case of cationic alkyl trimethyl and dimeth-yldioctadecyl ammonium surfactants (Versteeg and Shorter, 1992), the presence of dissolved organic carbon in the water significantly reduced the toxicity of these compounds to fathead minnows. The effect of toxicity reduction increased with increasing hydrophobicity. For the anionic surfactant LAS, this mitigating effect was less pronounced (Traina et al., 1996). 

A number of batch and column studies have sought to enhance the solubilization and desorption of PAHs from soil. Surfactants are commonly used to remediate PAH-contaminated soil. Two methods are employed micellar solubilization and PAH mobilization by reduction of interfacial tension (West and Harwell, 1992). As surfactant toxicity became a significant issue, biodegradable and biocompatible surfactants have been more widely examined. For example, food-grade surfactants such as Tergitol 15-S-X (X = 7,9, and 12) (Li and Chen, 2002) and other surfactants with indirect food additive status, such as alkyl diphenyl disulfonate (DOWFAX) (Deshpande et /., 2000), have been investigated for use in solubilization/desorption of single PAHs or PAHs mixtures from contaminated soils. 

Toxic compounds are frequently rendered less toxic by electrochemical treatment, for instance dehalogenation of chlorinated derivatives such as PCBs or AOX (performed in a divided cell or in the absence of Cl ions in a monocell) odors are eliminated or greatly reduced, i.e. reduction of nitrotoluene which can be a serious odor nuisance biodegradability is improved. Elimination of colloids and surfactants is possible. 

The mitochondrial respiratory parameters have also been employed to determine the toxicity of surfactants, including anionic (LAS), nonionic (NPEO) and their metabolites, sulfophenyl carboxylates (SPCs), NP and nonylphenoxy carboxylate (NPECi) [37]. The system employed was the in vitro response of submitochondrial particles from beef heart. The EC50 toxicity calculated as the reduction rate of NAD+ ranged from 0.61 mg L-1 for a commercial LAS mixture to 18 000 mg L-1 for SPCs, and 1.3 mg L-1, 8.2 and 1.8mgL 1 for NPEOio, NPECi and NP, respectively. These results indicate that from the toxicity perspective, LAS is the compound demanding increased attention, while for NPEO, the parental compound and the metabolites must be quantified. 

Surfactants are selected based primarily on the degree of solubilization. Other factors to be considered include toxicity, biodegradability, surfactant sorption, and surfactant solubility and compatibility with the separation process. Surfactants have the ability to lower the interfacial tension between water and the contaminant by as little as a factor of three to four orders of magnitude. Combined with a sufficient reduction in capillary forces, this allows pumped groundwater theoretically to move the DNAPL toward the recovery or extraction well. This is accomplished by injecting surfactant solution into the contaminated zone. Impacted groundwater characterized by an increase in the concentration of the contaminant is then recovered and treated. 

Table X shows similar results for anionic surfactants, in which no reduction in toxicity of LAS was observed but some reduction was found in the case of SAE(3E0) sulfate and C ...

Gas hydrate inhibitors. Gas hydrates, solid water clathrates containing small hydrocarbons, are problematic for oil and gas production because they can precipitate and cause line blockage. Simple cationic surfactants containing at least two butyl groups were previously developed to inhibit formation of gas hydrate precipitates in gas production lines [87]. However, similar to the situation with cationic drag reduction additives, poor toxicity profiles prevent widespread commercial acceptance. Ester quaternaries with structures somewhat similar to those used in fabric care have been claimed as hydrate inhibitors [88 ]. Additionally, certain alkylether quaternary compounds, e.g. C12-C14 alkyl polyethoxy oxypropyl tributyl ammonium bromide, were shown to have hydrate inhibition properties [89]. 

Another area of unmet need is in the identification of surfactants in textile wastewater. The effects of surfactants can be readily measured in terms of reduction of surface energy, foaming, aquatic toxicity, turbidity, and the like. However, it is often desirable to identify the exact concentration and identity of surfactants in wastewater. This is helpful, for example, in efforts to evaluate waste treatment system removal efficiency, or to reduce the detrimental effects of surfactants on the environment by pollution prevention (or cleaner production as it is called outside the USA). At present, there is no reasonable scheme for surfactant identification in textile wastewater. 

It is important to keep in mind that cytotoxic effects of surfactants differ depending on the cell line used because of metabolic abilities (e.g., the presence special of enzymes) and capabilities (e.g., phagocytosis) of the cells [30]. In experiments with murine peritoneal macrophages the viability was, in comparison with the pure surfactant solution, slightly reduced when incubated with the SLN [5]. On HL-60, and human peripheral blood granulocytes, a severe reduction of toxicity of the surfactants when incorporated in SLN was observed [24]. Here the cytotoxicity of... 

An important aspect in all drug delivery is the toxicity of the drug as well as that of the drug carrier. Therefore, toxicity has to be assessed also for microemulsion formulations. In microemulsion systems, the main concern regarding toxicity has to do with the cosurfactants used. For example, the majority of the work on the pharmaceutical application of microemulsions has involved the use of short- or medium-chain alcohols, e.g., butanol. In a range of studies it has been shown that these cause toxic side effects. For example, inhalation studies of the toxicity of 1-butanol, 2-butanol, and / -butanol in rats showed a dose-dependent reduction in fetal weight [56]. Furthermore, aqueous solutions of ethanol, propanol, and butanol were shown to result in elongated mitochondria in hepatocytes after 1 month of exposure [57]. (In addition to the toxicity aspects of these alcohols, microemulsions formed in their presence are often destabilized on dilution of the continuous phase.) Furthermore, many studies so far have involved aliphatic or aromatic oils, such as hexane or benzene, which obviously are unsuitable for pharmaceutical use. Moreover, ionic surfactants could in themselves be toxic and irritant [58]. 

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