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The Role Of Surfactant In Soil Organic Pollutant Remediation And Its Mechanisms

Posted on:2005-08-22Degree:DoctorType:Dissertation
Country:ChinaCandidate:B L ChenFull Text:PDF
GTID:1101360122971917Subject:Environmental Science
Abstract/Summary:PDF Full Text Request
The widespread occurrence of many persistent toxic organic compounds, such as polycyclic aromatic hydrocarbons (PAHs), in soils and groundwater has become a serious environmental concern, which has led to intensive studies of the transport, bioavailability, fate and potential remediation technology of these contaminants in subsurface environment. The ability of surfactants to enhance the aqueous solubility of nonionic organic compounds (NOCs) or to promote immobilization of NOCs offers a potential means of remediating contaminated soils and groundwater by use of surfactant solutions. There has a great interest in surfactant-enhanced remediation (SER) in recent years.In this dissertation, the application of surfactant to soil organic pollution remediation and its mechanisms were reviewed. Based on the influence of surfactant on interface behavior of organic contaminants between soil and water, the multiprocess among multimedia including surfactant-soil-water-organic pollution was investigated. The influential factors of myristylpyridinium bromide (MPB), a cationic surfactant, on enhanced-immobilization of nonpolar and polar organic contaminants onto soils and bentonites and their mechanisms were studied; sorption mechanisms of mineral-sorbed surfactant and critical immobilization concentration of surfactant were discussed. Solubility enhancement in aqueous solution and desorption enhancement from soil by anionic and nonionic surfactant were also studied; the critical desorption concentrations (CDC) and its influential factors were discussed. Through simulating desorption solution with organic pollutant and surfactant, removal efficiency of organic pollutant and recovery efficiency of surfactant from the simulated solution by air-stripping and liquid-liquid extraction methods were elementarily researched. The observations in this work will provide a reference to use of surfactants for remediation of contaminated soils or groundwater in engineered surfactant-enhanced washing/immobilization, and offer a theoretical gist for guaranteeing quality of the agricultural products in organic contaminated regions. The main original conclusions of this work are drawn.(1) The sorption capacities of naphthalene, phenol, and p-nitrophenol on MPB-sorbed solids are much higher than on MPB-free solids. The Kd* values, the ratio of bound NOC to mobile NOC, for naphthalene, phenol, and p-nitrophenol were calculated. Kd* = Kocfoc + Koc*foc*, which indicated that sorption mechanisms of NOC on MPB-sorbed solid was dual-partition into soil organic matter (SOM) andMPB-derived organic matter. The enhanced-sorption of NOCs was contributed to increasing both soil total organic carbons contents (foc*) and partition capability (Koc*). The ratio of Koc* to Koc for NOCs are approximately to 10-25. The optimal immobilization (Kdmax*/Kd ratio) was positive relative to MPB saturated sorption amount, and negative relative to soil organic carbon contents (foc).(2) Contaminant sorption coefficients with mineral-adsorbed surfactants, Kss, show a strong dependence on surfactant loading in the solid. At low surfactant levels, the Kss values increased with increasing sorbed surfactant mass, reached a maximum, and then decreased with increasing surfactant loading. At low sorbed-surfactant levels, the resulting mineral- adsorbed surfactant via the cation-exchange process appears to form a thin organic film, which effectively "adsorbs" the contaminants, resulting in very high Kss values. At high surfactant levels, the sorbed surfactant on minerals appears to form a bulk-like medium that behaves essentially as a partition phase (rather than an adsorptive surface), with the resulting Kss being significantly decreased and less dependent on the MPB loading. The structure transition of mineral-sorbed MPB was verified by XRD and FTIR.(3) A "Tetragonal" distribution model was suggested to discuss multiprocess of PAHs among multimedia including soil-surfactant-water. The surfactant dissolved in water enhances contaminant solubility, favoring...
Keywords/Search Tags:Soil, Organic Pollution, Surfactant-Enhanced Remediation, Sorption, Solubility-Enhancement
PDF Full Text Request
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