Study On The Soil-washing Of Polycyclic Aromatic Hydrocarbons Contaminated Soil And Regeneration Of The Effluent

Polycyclic aromatic hydrocarbons with "deformed","cancer" and "mutagenic"effect,and low solubility in the aqueous phase,belong to the hydrophobic organic pollutants,so its migration ability in the environment is poorer,and lack of biodegradability.All these characteristics make PAHs contaminated soil remediation more urgent and more difficult.In many soil restoration techniques,soil washing/flushing is the most common and mature technology,and the treatment of the effluent is gradually taken seriously.This research comebined soil washing and the advanced oxidation technology to remediate phenanthrene polluted soil.The effects of liquid to soil ratio,Tween80 concentration and temperature on phenanthrene removal efficiency were discussed.When liquid to soil ratio is 10:1(mL:g),Tween80 concentrations is 20 g/L,and temperature is 20 ?,after 24 h of soil washing,90.7%phenanthrene was brought out of the contaminated soil.However,if the effluent produced by soil washing process has not been properly treated and are discharged directly into natural water,a secondary pollution will be inevitably caused.Many physical,chemical and biological technology is introduced to deal with the effluent,for example:activated carbon adsorption,photodissociation,electrochemical,advanced oxidation and microbial degradation technology.In order to achieve the goal of total degradation of target pollutants and the purpose of recovering surfactants,this study selected advanced oxidation technology to selectively oxidise phenanthrene.The regenerated effluent was re-employed in the soil washing process,and the results showed that the removal efficiency was almost the same as with fresh surfactant solution.The reaction mechanism of the UV/PDS process was also investigated,the possible intermediates were detected by LC-MS and the corresponding degradative pathway of the target contaminant was proposed.Overall,the result indicates that soil washing with TW 80 and the subsequent selective UV/PDS oxidation process may provide a potential option for the remediation of soil contaminated with PAHs.