Resourceful Treatment Of Oil-bearing Soil By Microemulsion Method And Its Effect Evaluation

In the process of oil exploitation,transportation and processing,a large amount of oil-bearing soil will be produced,resulting in environmental damage and waste of resources.Therefore,it is the key to find a harmless and resource-based treatment method to treat oil-bearing soil.Microemulsion has unique advantages in remediation of oily soil due to its ultra-low interfacial tension and strong solubilization ability.The crude oil contaminated soil was taker as the research object,the anionic sodium dodecylbenzene sulfonate(SDBS)and non-ionic biological sophorolipid were selected as the surfactants of microemulsion,aiming at realizing the resourceful and harmless treatment of oil-contaminated soil.In order to achieve better industrial application effect,SDBS microemulsion was prepared with formula of w(SDBS)=10%、w(n-butnaol)=4.8%、w(Na Cl)=0.8%、w(diesel)=13.6%.The deoiling effect of batch operation and continuous operation on oil-bearing soil was studied respectively.The process parameters of batch operation were optimized.The optimum operating conditions were determined as follows,liquid-solid ratio3:1,cleaning temperature 35℃,stirring rate 500 r/min and stirring time 10 min.The removal rate of crude oil reached 95.05%after treatment.The optimal continuous operating conditions were determined as follows,stirring rate 1200 r/min,cleaning temperature 55℃and liquid-solid ratio 2:1.Under these operating conditions,the removal rate of crude oil could reach 93.4%.Microemulsions were prepared using bio-surfactant,sophorolipid,and the simulation experiments of innocuous treatment and resource recovery of soil polluted by crude oil were carried out.By comparison,it was found that the effect of microemulsion of sophorolipid is better than its aqueous solution on the removal of crude oil from oily soil,and it was determined that the removal of crude oil was the result of the synergistic effect of sophorolipid and diesel oil.The effects of the addition amount of sophorolipid,diesel oil and Na Cl on the removal of crude oil were investigated,and the parameters of oily soil cleaning were optimized.Results showed that the optimal microemulsion formula was w(sophorolipid)=6%,w(Na Cl)=1%and w(diesel)=13.36%.The optimized cleaning conditions were as follows,liquid solid ratio of 2:1,temperature of 35℃,stirring rate of 600r/min,and cleaning time of 20 min.Under these conditions,the oil removal efficiency reached the highest value of 95.95%.Comparison between the original and the recovered crude oil and soil samples was done.It was found that the saturated alkanes content in the recovered oil became higher,while the content of aromatic,resin and asphaltene were lower than the original crude oil,and at the same time,the ash content and the density of the recovered oil were higher,while the viscosity was lower.The recovered oil showed certain economic value.The p H of the treated soil and total salinity decreased,while the organic matter content increased,and the soil was changed from heavy saline-alkali type to mildly saline-alkali type.Finally,the corrosion properties and biotoxicity of the two different microemulsions were evaluated.The results showed that Q235 steel or 45~#steel should be selected as the equipment material for SDBS microemulsion system.For the sophorolipid microemulsion system,the equipment material should be 316L or 304 stainless steel with corrosion resistance.At the same time,the soil treated with sophorolipid was more suitable for plant growth,and its biological toxicity was much lower than that treated with SDBS.