| There has been increasing public concern with the problems of waste disposal and contamination of soils in recent years. Organic contaminants in soils may influence the normal function of soils, contaminate ground water, air and food chain, and therefore impact the human health and environmental quality. It is necessary to look into the fate and mobility of organic contaminants in soils in order to assess the soils environmental quality and to control soils pollution. Sorption has a critical effect on the transform, reactivity and bioavailability of organic contaminants in soils and sediments. Nowadays, enormous quantities of surfactants in waste water that are used in industrial and household application can be sorbed by soils and then greatly affect the sorption properties of soils and the transform behaviors of the organic contaminants. A better understanding of the sorption properties and mechanisms of organic contaminants on surfactant-modified soils can get information on surfactants affecting the behaviors of organic contaminants in soils which are important for remediation of contaminated soils. Therefore, the integrated contaminants immobilization with in-situ biodegradation would provide a comprehensive remediation technology to permanently eliminate target contaminants. In this work, we selected ionizable organic contaminants to study their sorption behaviors in surfactant-modified loess soils.Chapter 1.Advances in the Research on the Sorption of Organic Contaminants inNatural Soils Systems and on Surfactants-modified SoilsA review is reported with 68 references about the models of sorption isotherms, the influencing factors and the sorption mechanisms, meantime reviewing the research on the surfactant-modified soils and their applications on the remediation of organic contaminants in groundwater or soils systems.Chapter 2.Influence of Surfactants on the Sorption of 2,4-dichlorophenoI and p-nitroaniline on Loess SoilsIn this study, the loess soils were modified by a series of cation or anion-cationsurfactants, such as the cationic surfactants hexadecyltrimethylammonium (HDTMA) bromide and anionic surfactants sodium dodecylbenzene sulfonate (SDBS). The organic carbon contents of the modified loess soils were proportional to the added quantity of the anionic and cationic surfactants. The sorbed amount of 2,4-dichlorophenol and /?-nitroaniline on the surfactant-modified loess soils was higher than those on the natural loess soils, and the amount of organic contaminants removed from solution depended significantly on the concentrations of HDTMA in the loess soils. The surfactants on the modified loess soils excellently created sorption mediums for organic contaminants in water. 2,4-dichlorophenol and/7-nitroaniline were sorbed to the surfactant-modified loess soils through partition process. The additional anionic surfactants had reduced the sorption capacities of the cation surfactants modified loess soils to 2,4-dichlorophenol andp-nitroaniline.Chapter 3.Sorption of lonizable Organic Contaminants on HDTMA-Modified LoessSoilsThe sorption of ionizable organic contaminants (lOCs), such as 2,4-dichlorophenol (DCP), p-nitroaniline (NA) and benzoic acid (BA) on the loess soils modified with cation surfactant, hexadecyltrimethylammonium (HDTMA) bromide, was determined under different pH conditions. A model describing the sorption of lOCs was developed based on the experimental data. The model represented the sorption of lOCs with two specific Freundlich-type isotherms for ionic and neutral forms, respectively. A synergistic effect on the sorption of DCP, NA and BA in the binary solute systems was also observed. Sorption of NA was decreased in the presence of DCP or BA, while the adding NA increased the sorption of DCP. The neutral forms of DCP had a stronger effect on the sorption of NA than the ionic forms. On the HDTMA-modified loess soils, the sorption mechanisms of lOCs, regardless of the ionic or neutral forms, could be interpreted with a dual-mode model of sorp...
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