Study On The Preparation Of Microemulsion And Its Remediation Performance To Phenanthrene Contaminated Soil

With the accelerated development of China's industry,the emissions of polycyclic aromatic compounds(PAHs)in the environment have increased dramatically.PAHs can exist in the soil for a long time,enter the food chain directly or indirectly,and pose a threat to the life and health of human beings due to its characteristics of "triple effect"(mutagenesis ? carcinogenesis ? teratogenesis),difficulty in degradation,easy accumulation and low water solubility.Therefore,PAHs-contaminated soil need restoration urgently.Soil leaching is a repair method with high treatment efficiency,short-term repair and low cost.At present,surfactant,humic acid,microemulsion,cyclodextrin were used widely in the research of soil remediation.Microemulsion is a transparent and stable system formed by water,surfactant,co-surfactant,oil and other components at an appropriate ratio.It has the advantages of good wetting ability,ultra-low interfacial tension,and high solubility in hydrophobic compounds.It is widely used in the areas of pollution remediation,oil displacement and pharmaceutical.However,the solubilizing ability of microemulsions depend on their composition.Therefore,it is crucial to study the influence of each component on the phase behavior of the microemulsion,select and prepare a suitable microemulsion system for remediation of PAHs contaminated soil.In this paper,phenanthrene was selected as the target pollutant.Microemulsion with vegetable oil as the oil phase,surfactant solution as the polar phase and pentanol as the co-surfactant was successfully constructed.This paper explored the effects of oil phase types and mixed surfactant types on the phase behavior and phase forming ability of microemulsion systems,and determined the best microemulsion formula which was suitable for soil leaching based on their solubilizing ability and desorption efficiency for phenanthrene.The effects of different eluents,injection rates,and soil types on remediation efficiency of contaminated soil were compared by a one-dimensional simulation column experiment.The main conclusions are as follows:(1)Soybean oil,sunflower oil and palm kernel oil were successfully used to construct microemulsion as the oil phase.Among them,the microemulsion constructed by palm kernel oil has the largest phase forming ability and dilution ability.The solubilization ability of the three vegetable oil-microemulsions to phenanthrene increased with the increase of the oil content(O/S)in the system.Taking into the phase forming ability,dilution ability and solubilizing ability of the microemulsions constructed by three vegetable oils,sunflower oil was chosen as the best oil phase.(2)Tween80-SDBS,Tween80-Triton X-100 and Tween80-Cremophor EL can be successfully used to construct microemulsions.Among them,the microemulsion with Tween80:Cremophor EL = 4: 6 had the largest phase forming ability and dilution ability.The solubilization ability of three mixed surfactant microemulsions to phenanthrene increased with the increase of oil content in the system.When S/O=8:1,the Tween80-Cremophor(4:6)microemulsion had the best solubilization effect for phenanthrene,which was 851.62 mg/L.(3)The desorption efficiency of the three mixed surfactant microemulsions on phenanthrene had different degrees of improvement.Among them,Tween80-SDBS microemulsion had the best desorption efficiency on phenanthrene in soil.The desorption efficiency of phenanthrene by three mixed surfactant microemulsions decreased slightly with the increase of oil content in the system.When Tween80:SDBS = 9:1 and S/O = 15:1,the desorption efficiency was best,83.22%.Therefore,Tween80-SDBS(9:1)was selected as the best mixed surfactant.(4)Within the scope of the experiment,the removal ability of several eluents to phenanthrene in soil was Tween80-SDBS microemulsion > Tween80 microemulsion > Tween80-SDBS solution;compared with high injection rate,Tween80-SDBS microemulsion had better removal efficiency for phenanthrene in soil at low injection rate;the worse leaching efficiency of Tween80-SDBS microemulsion in the soil which had higher organic carbon.