Study On Phase Behavior Of Biodiesel Microemulsion And Remediation Of Petroleum Contaminated Soil By Washing

In the process of oil exploration,exploitation,transportation,processing,storage and transportation,and sales,due to improper management or natural accidents,oil leakage may occur,causing serious harm to the soil and the environment.How to effectively deal with oil-contaminated soil and recover oil resources has become the trend of current research.In this paper,a microemulsion system with good stability and strong solubilization performance was prepared from biodiesel prepared from rapeseed oil,and the microemulsion system was used to remediate oil-contaminated soil,and a magnetic demulsifier was also prepared.Dispose of microemulsions that fail after recycling.The purpose of the research is to provide some basic data for promoting the industrial application of microemulsion washing and remediation of oil-contaminated soil.This paper firstly studies the phase behavior of biodiesel microemulsion.The effects of different oil phases,different surfactants and different co-surfactants on the phase behavior of the microemulsion were investigated,and the microemulsion formulation with large volume and good stability of the microemulsion phase was found.The experimental results show that the microemulsion system with biodiesel as oil phase,SDBS as surface activity,n-butanol as auxiliary agent,and sodium chloride as inorganic salt has the largest volume of microemulsion phase under the same conditions,reaching 58%.After standing for 11 days,the particle size of the microemulsion is always kept at about 30 nm,which has good stability.Therefore,biodiesel as the oil phase,SDBS as the surfactant,n-butanol as the auxiliary agent to prepare the microemulsion system for the treatment of oil-contaminated soil.Then,the simulated oil-contaminated soil was treated with the prepared microemulsion system,and its suitable washing process was explored.The results show that the biodiesel/SDBS/n-butanol/salt microemulsion system（in which the alcohol content is 4%,the salinity is 1%,and the SDBS is 4%）is treated for 30min at a temperature of 35℃,a solid-liquid ratio of 1:5 When the oil removal rate can reach 74%.During the washing process,it is found that the microemulsion has no selectivity for the removal of crude oil through the analysis of crude oil composition.In addition,the reasons for the decrease in the oil removal rate of the recycled microemulsion were explored,and three conjectures were put forward:1)During the cycle washing process,the loss of each component in the microemulsion resulted in the removal rate of crude oil in the soil.decline.2)The microemulsion formed a microemulsion with a solid shell after multiple washings,which reduced the carrying capacity of the microemulsion,resulting in a decrease in the removal rate;3)During the washing process,the asphaltenes and other heavy components washed out of the soil The biodiesel in the oil phase of the microemulsion is replaced and becomes a new oil phase in the microemulsion,which makes the color of the microemulsion deepen and the removal rate decreases.By designing experiments,the conjecture is proved from the side.Finally,four different types of magnetic demulsifiers were prepared to deal with microemulsions that failed after recycling,namely:Fe₃O₄@OA-CS-II,Fe₃O₄@OA-CS-I,Fe₃O₄@OA,Fe₃O₄.Among them,Fe₃O₄@OA-CS-II has nano-sized particle size,large specific surface area,high surface energy,and water contact angle of 80°.Compared with the other three magnetic particles,it is hydrophilic.It shows good dispersibility and adsorption in the liquid,and its demulsification rate is 63.4%,which is the highest efficiency among the four demulsifiers;and experiments show that the maximum efficiency can be reached at room temperature,and the demulsification rate can be broken after 5 cycles.The milk ratio can still reach 56.5%,indicating that Fe₃O₄@OA-CS-II has good recyclability.