| Soils often contain several pollutants and compound pollution of heavy metals and organic matter is a common and serious pollution phenomenon. The combination of electric technology and PRB technology was proposed to deal with the multiplex pollutants in soils. The most critical aspect of PRB technology was the selection of medium. Firstly, the chitosan nano fiber membrane was prepared by electrospinning and the preparation conditions were optimized, on this basis, combined electrokinetics(EK) and nano fiber membrane were used to repair multiplex pollutants in soils.In this paper, the effects of solution properties on the electrospinning process were studied and the spinning solution was prepared by blending chitosan with polyvinyl alcohol. The effects of the mass ratio of chitosan and polyvinyl alcohol, the mass fraction of the mixed solution and the concentration of acetic acid on the spinning were explored. The optimum conditions for the preparation of nano fiber membrane were as follows: the weight ratio of chitosan: polyvinyl alcohol was 20:80, the concentration of acetic acid concentration was 20% and the mixed solution concentration was 8%; the average diameter of the prepared nano fiber membrane was 294.69 nm and the adsorption equilibrium of CS /PVA on metal ions was 4 hours and PAHs was 3 hours; the adsorption capacities of the nano fiber membrane on two metals were 151.8 and 127.2 mg.g-1, phe and pyr were 75.15 and 69.39 mg.g-1, respectively; adsorption kinetics of heavy metals and polycyclic aromatic hydrocarbons on the chitosan nano fibrous membrane were better conform to pseudo first-order and pseudo second-order model at the same time; the adsorption isotherms of nano fiber membrane was more suitable to the Freundlich model and the adsorption was an endothermic reaction.In order to explore the optimal conditions for the repair of complex pollutants by electrokinetic remediation, the experiments were carried out on the EK for the remediation of heavy metals and polycyclic aromatic hydrocarbons individually. The experiment results show that using 0.1M citric acid sodium citrate buffer to control cathode pH at 6~7 can greatly improve the repair efficiency of heavy metals; using 0.1M NaOH solution to control anode pH value at 4 ~ 5 as well adding nonionic surfactant Tween80 can greatly improve the repair efficiency of PAHs. Under the optimized experimental conditions, the experiments of EK-PRB were carried out with the pH control of cathode and anode, which could keep soil pH changed between 4~7. Not only this ensured the unchanged of flow of electricity direction, but also ensured that the heavy metals in soils wound not form a large amount of precipitation, The removal efficiencies of heavy metals(Cu, Cr) were 88.3% and 85.3%, respectively, and the removal efficiencies of PAHs(phenanthrene and pyrene) were 75.3% and 65.7%, respectively. The removal efficiency of heavy metals was increased by 53.4% and 73.6 respectively and PAHs was 28.1% and 48% respectively compared with the single electrokinetic remediation.In this paper, the GMS simulation software was adopted to simulate the movement of pollutants in soils after 1 years and 5 years before and after treatment under the action of underground water.. The simulation results show that the pollution area continued to expand to the level of X and Y axis direction over time and the pollution range was larger in the downstream direction of groundwater flow. Concentration of pollutants in soil were higher and exceed the value of the ―soil environmental quality standard‖ before EK remediation and the simulation showed that, concentration of heavy metals in the soil were exceed the standard in coal gangue yard less than 60 m and PAHs less than 20 m after 5 years. After the end of the EK-PRB repair, concentration of pollutants were greatly reduced and within the scope of the standard which would not cause pollution to underground water and soil. |
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