Properties of food grade (edible) surfactants affecting subsurface remediation of chlorinated solvents.
ABSTRACT In this research, several food grade (edible) surfactants are systematically evaluated for various loss mechanisms: precipitation, adsorption, and coacervation (for nonionic surfactants). Cloud points for the polyethoxylate sorbitan (T-MAZ) surfactants are much higher than aquifer temperatures, and the effects on surfactant losses should be minimum. Precipitation boundaries of bis(2-ethylhexyl) sodium sulfosuccinate (AOT) and sodium mono- and dimethylnaphthalene sulfonate (SMDNS) were established. Existing precipitation models successfully predicted precipitation boundaries for SMDNS but showed minor deviations for AOT results. AOT was more susceptible to precipitation than the cosurfactant evaluated, SMDNS. Nonionic polyethoxylate (POE = 20) sorbitan monostearate (T-MAZ-60) and POE(80) sorbitan monolaurate (T-MAZ-28) formed liquid crystal phases at high surfactant concentrations (> 0.5 wt %) white POE(20) sorbitan monolaurate (T-MAZ-20) and POE(20) sorbitan monooleate (T-MAZ-80) remained in aqueous solution at concentrations up to 5 wt %. T-MAZ-60 and T-MAZ-28 also showed a continuous increase of ''adsorption'' at high surfactant concentrations (likely due to liquid crystal formation). Other surfactants showed Langmuirian-shaped isotherms at high concentration, while the cosurfactant SMDNS experienced negligible adsorption. On a mass basis, the maximum adsorption (q(max) in mu mol/g) was higher for T-MAZ surfactants than for alkylphenol ethoxylates, AOT, and disulfonated surfactants.
- SourceAvailable from: Venkateswarlu Kadiyala[Show abstract] [Hide abstract]
ABSTRACT: Due to human activities to a greater extent and natural processes to some extent, a large number of organic chemical substances such as petroleum hydrocarbons, halogenated and nitroaromatic compounds, phthalate esters, solvents and pesticides pollute the soil and aquatic environments. Remediation of these polluted sites following the conventional engineering approaches based on physicochemical methods is both technically and economically challenging. Bioremediation that involves the capabilities of microorganisms in the removal of pollutants is the most promising, relatively efficient and cost-effective technology. However, the current bioremediation approaches suffer from a number of limitations which include the poor capabilities of microbial communities in the field, lesser bioavailability of contaminants on spatial and temporal scales, and absence of bench-mark values for efficacy testing of bioremediation for their widespread application in the field. The restoration of all natural functions of some polluted soils remains impractical and, hence, the application of the principle of function-directed remediation may be sufficient to minimize the risks of persistence and spreading of pollutants. This review selectively examines and provides a critical view on the knowledge gaps and limitations in field application strategies, approaches such as composting, electrobioremediation and microbe-assisted phytoremediation, and the use of probes and assays for monitoring and testing the efficacy of bioremediation of polluted sites.Environment international 06/2011; 37(8):1362-75. DOI:10.1016/j.envint.2011.06.003 · 5.66 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The effectiveness of four food-grade and two industrial surfactants to remove toluene or 1,2,4-trichlorobenzene added to an Iowa soil was evaluated in batch and column experiments. One of the anionic food-grade surfactants, disodium n-hexadecyl diphenyloxide disulfonate (Dowfax 8390), was more effective than the other surfactants in shaken batch experiments. The maximum recoveries of the added toluene (57%) or 1,2,4-trichlorobenzene (71%) were obtained with one surfactant wash plus two water rinses. Dowfax 8390 also yielded the highest recovery of toluene (75%) or 1,2,4-trichlorobenzene (83%) in columns of soil flushed with 1250 mL of 4% surfactant solutions. Synergism in a mixture of 2% Dowfax 8390 (anionic) and 2% T-Maz 60 (nonionic) did not occur, in contrast to enhanced recoveries exhibited by a similar mixture of the two industrial surfactants, Sandopan JA36 (anionic) and Pluronic L44 (nonionic).Key words: surfactants, toluene, 1,2,4-trichlorobenzene, recoveries, synergism.Canadian Geotechnical Journal 01/2011; 38(6):1329-1334. DOI:10.1139/cgj-38-6-1329 · 1.21 Impact Factor
- Environment International 01/2011; 37:1362-1375. · 5.66 Impact Factor