Study On Remediation Of PCBs' Contaminated Soils Using Surfactants

Polychlorinated biphenyls are important environmental organic pollutants due to their carcinogenicity. They are physically and chemically stable, and resistant to degradation. Their strongly hydrophobic nature make them bind to soil tightly, resulting in remediation of PCB contaminated soils a challenge problem.Remediation of PCBs contaminated soils by surfactants was studied in the thesis. When an anionic surfactant, sodium dodecyl sulfate (SDS), was applied at 10000mg/L, 67.8% and 54.1% PCBs were washed out from a laboratory contaminated soil and a field contaminated soil, respectively, while 70.5% and 12.7% PCBs were washed out from the same soils, respectively, using an nonionic surfactant, TritonX-100 at 10000mg/L. These results indicate that the laboratory contaminated soil was easier to remediate than the field contaminated soil which has been polluted over 10 years. The SDS is better than the TritonX-100, in general, for washing PCBs from soils. Further, factors such as organic carbon fraction of soil, volume, temperature, and times of surfactant solvent applied, which affect on surfactant desorbing PCB from the soils were tested. It was found that the higher the organic carbon fraction of the soil, the lower the PCB washing efficiency; In the range of 10-30°C, temperature did not show definitely influence on the soil washing; Increasing volume of surfactant as well as the repeat washings leaded to increasing amount of PCB washed from soils, and 20(ml):l (g) ratio of surfactant to soil, and 2-3 repeat washings were the most effective for the soil washing under the test conditions. Ultrasonification could also improve surfactant soil washing efficiency and reduce the quantity of surfactant adsorbed by soil. Based on the results, it may conclude that surfactant soil washing is a viable way for remediation of PCBs contaminated soils.