Enhanced Soil Washing Of Dichlorobenzene By Biodegradable Surfactants

Dichlorobenzene is a chlorinated aromatic compound, widely used in pesticides, dyes, pharmaceuticals, plastics and chemical products and daily production. Among them, the o-dichlorobenzene (o-DCB) and p-dichlorobenzene (p-DCB) could easily enter the soil environment and endanger biological and human health, because of its high production capacity and wide applications. Therefore, remediation of dichlorobenzene contaminated soil is one of the urgent environmental problems to be solved. The application of surfactants (especially biodegradable surfactants) to enhance the remediation of organic contaminated soil is one of the most promising technology. Solubilization elution is the prerequisite for its implementation.In this study, we compared the ex-situ and in-situ elution effect of o-DCB and p-DCB contaminated soil by biodegradable surfactants saponin and APG0810. We also investigated the impact of the two biodegradable surfactants on soil properties. The results are summarized as follows:(1) The solubilization of o-DCB and p-DCB by saponin, APG0810 and Tween80 was linear with the concentration, front and rear of CMC. The solubilization order was Tween80> APG0810> saponin. The ex-situ elution removal of o-DCB and p-DCB from soil by saponin and APG0810 were better than Tween80. The elution process of o-DCB and p-DCB from mixed contaminated soil with biodegradable surfactant could achieve balance within 360min. The elution process of DCB could be described by a 4-parameter biphasic first-order kinetic model, which obviously showed a rapid elution phase and a slow elution phase.(2) The in-situ elution removal of o-DCB and p-DCB from soil by saponin and APG0810 were also better than Tween80, but the removal rate of in-situ elution was lower than ex-situ elution. After the in-situ elution, the o-DCB and p-DCB concentration in topsoil was lower than bottom layer and middle layer (the highest). With the increasing of surfactants concentration, The o-DCB and p-DCB concentration in eluent decreased while the cumulative amount of o-DCB and p-DCB was increased(3) The saponin and Tween80 could significantly reduce the soil pH while APG0810 could significantly increase the soil pH. The 4g L-1 saponin and Tween80 could increase the soil organic matter content and the 2g L-1 saponin, APG0810 and Tween80 could improve the soil CEC. The 4g L-1 saponin, APG0810 and Tween80 could significantly increase the soil total nitrogen, available phosphorus and available potassium content. The 4g L-1 saponin, APG0810 and Tween80 could significantly improve the soil dehydrogenase and catalase activity. And the 1g L-1 saponin, APG0810 and Tween80 could significantly improve the soil polyphenol oxidase activity.In summary, compared with Tween80, the ex-situ and in-situ elution removal of o-DCB and p-DCB from contaminated soil by biodegradable surfactant saponin and APG0810 were higher. The biodegradable surfactant saponin and APG0810 could better improve the soil fertility, nutrient content and soil enzyme activities. The biodegradable surfactant not only remediate DCB contaminated soil, but also improve soil properties, providing guarantee for reuse of polluted soil.