| Electrokinetic?EK?repair technology is an emerging in-situ soil remediation technology.At present,some combination technologies of EK technology are gradually attracting people's attention.In this paper,the physicochemical processes of phenanthrene migration and transformation in soil were studied firstly,and the main factors affecting migration and transformation of phenanthrene were selected,namely electroosmotic flow,electromigration,convection and dispersion.According to the principle of mass conservation,the control equation of phenanthrene migration and transformation in soil were deduced.Combining with COMSOL Multiphysics software,the migration model of phenanthrene in soil under EK and the migration and transformation model of phenanthrene in soil under EK/laccase were constructed.The main conclusions were as follows.?1?Under the EK system,a new model,M4EKR,was developed based on the principle of mass conservation and charge conservation.Combined with the literature,the relevant parameters,boundary conditions and initial conditions of the model were determined.Numerical simulations of soil phenanthrene migration were performed using fluid flow,chemical transfer,and electrochemical modules in COMSOL Multiphysics 5.3.It was found that the concentration distribution of phenanthrene was bowl-shaped.Under the optimal conditions that EK voltage was 2 V·cm-1 and soil porosity was 0.48,the maximum mobility of phenanthrene was 44.35%.The model results and experimental results were obtained.Comparing the model results with the experimental results,the trends were basically the same,which proved that the model was feasible for EK to repair phenanthrene contaminated soil.?2?Under the EK/laccase system,a new module-chemical reaction engineering was added based on the migration model.And three control factors of voltage,porosity and laccase concentration were selected to repair the phenanthrene-contaminated soil.The migration transformation was numerically simulated.It was found that the experimental results and numerical simulation results were similar to the concentration distribution of phenanthrene in the EK system,both of them were bowl-shaped.Under the optimal conditions,the maximum conversion rates of phenanthrene in the experimental results and simulation results were 61.1%and 54.15%,respectively.The experimental results showed that the concentration of laccase contributed a lot to the conversion part of the migration and transformation model of phenanthrene.The experimental results were compared with the simulations,and the trends were generally consistent.It was proved that the model was applied to EK/laccase to repair phenanthrene-contaminated soil.?3?Combining the results of the two systems,it was found that the dominant role of phenanthrene conversion was the catalytic oxidation of laccase,independent of the electrolysis near the two poles in EK.GC-MS analysis and comparison with the mass spectrometry library confirmed that the conversion product and conversion pathway of phenanthrene were as follow.Phenanthrene first produced 9,10-phenanthrenequinone,then converted into 2,2'-diphenyl phthalate,and then changed to phthalic acid. |
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