| Surfactant enhanced remediation (SER) has been suggested as a promising technology for the remediation of contaminated soils and groundwater. It was pointed out that an improved strategy for SER was to enhance the remediation efficiency and reduce the surfactant dose, technique expenditure and ecosystem risk with maintaining remediation efficiency.The application of surfactants in the remediation of contaminated soils and groundwater and the corresponding mechanisms were reviewed. The role and mechanism of anionic-nonionic mixed surfactant to enhance the desorption and biodegradation of contaminated soils were investigated in an aim to enhance the soil remediation efficiency and reduce the loss of surfactant onto soils. The objectives of the present paper are to prospect novel agents and approaches for SER. The main original conclusions of this work are drawn as following.(1) Anionic-nonionic mixed surfactant not only increased the solubilization of phenanthrene, but also reduced the sorption of TX100 onto soils. Both of the results induced that the distribution of phenanthrene in soil-water system with TX100 was reduced with the presence of SDS and then the desorption percentage of phenanthrene from the contaminated soil was enhanced. For example, the apparent solubilites of phenanthrene were increased about 60%, the maximum sorption amount for TX100 was reduced about 70% and the desorption percentage of phenanthrene was improved about 1 times with the SDS-TX100 mixed surfacetants (mohmol, 2:1).(2) Mixed surfactants with relatively low amount of SDS promoted phenanthrene biodegradation. For example, the biodegradation percentage of phenanthrene with 1:9 SDS-TX100 mixed solutions was about 170% of that with the single TX100 solution at the same TX100 concentration of 1.6 mmol/L in 24 h. But the biodegradation was inhibited with larger ratio of SDS in the mixed solutions, which may be due to the preferential utilization of SDS by phenanthrene degraders.
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