Simulation Of Migration Of Heavy Metals In Electrokinetic Remediation Of Soil

With the development of Chinese industrialization and urbanization, the problem of soil contamination by heavy metals has been getting worse. The electrokinetic remediation technique has became one of effective remediation techniques to solve soil pollution by heavy metals. Its remediation effect mainly depends on heavy metal migration during the remediation process. This paper mainly studies the migration and distribution of heavy metals in electrokinetic remediation of soils through modeling, and the main factors that influence the migration behavior.Firstly, this paper analyses the main mechanism of the migration of pollutants in electrokinetic remediation of soils, as well as the factors that influence the migration of pollutants. A migration model of heavy metals is established and the impact of electrolysis and permeable reactive barrier (PRB) are considered, through the four main factors that influence the migration of pollutants:electric convection, dispersion, migration, seepage migration. Through consulting literature materials, the parameters of the model are obtained. Finally, through the COMSOL Multiphysics software, combing with migration model and selected parameters, the simulation calculation on migration of heavy metals in electrokinetic remediation of soil is conducted. The results of heavy metals’ migration and distribution through simulation are similar with results of experiment which has relative conditions, and the trends in the concentration are consistent between them, which preliminarily verifies the applicability of the model used for electrokinetic remediation of soil pollution by heavy metals.The pH on electrokinetic remediation system, the distribution of pollutant concentration and changes in fluxes, the influence which made by voltage and distribution of concentration on pollutant concentration, and EK-PRB combined remediation are studied through simulation used by the model. The results show that:(1)the PH of the system has changed, pH drops to3close to anode and increases to10near cathode of which most of soil is acid;(2) the electro-migration contaminant fluxes, electroosmosis fluxed and liquidity gradually increase form the anode to the cathode, on the contrary, diffusion flux dramatically increases at the cathode, which leads the amount of contamination near the cathode sharply reduced instead of increasing;(3) with the increasing of system’s voltage, the rate of heavy metals migration increases, as well as heavy metals’ enrichment to the cathode is getting higher;(4) with the increase of the porosity, however,the degree of enrichment of heavy metals decreases, thus the main reason for this result is a given total concentration which leads pollutant concentration of unit pore volume smaller with the higher porosity;(5) finally we simulate the situation of EK-PBR combined remediation which uses activated carbon as PRB filler, where the PRB existed pollutant concentration reaches2200mg/kg, while the system without PRB in the same position,the concentration reaches1480mg/kg, so activated carbon shows obvious adsorption of pollutants and the feasibility of the EK-PRB combined remediation was confirmed. This model can be used to optimize indoor soil remediation and design for soil test program and electrical repair project parameters, further study of soil electrical repair process synergy effects of various factors.