Electrokinetic-aeration-liquid injection combined remediation method for compound contaminated soil containing heavy metals and organic substances

An electrokinetic-aeration-liquid injection combined remediation method for compound contaminated soil containing heavy metals and organic substances, comprising the following steps:

• (1) laying a double-channel porous electro kinetic geosynthetics (EKG electrode at a bottom of compound contaminated soil, wherein the double-channel porous EKG electrode is provided with a liquid injection transmission channel and a bubble transmission channel inside, and an upper surface of the electrode is provided with a plurality of liquid injection holes connected to the liquid injection transmission channel and a plurality of bubble emission holes connected to the bubble transmission channel;
• a conventional EKG electrode and an isolation layer are laid in turn at a top of the contaminated soil, and a pumping well is buried;
• (2) connecting the dual-channel porous EKG electrode at the bottom to an anode of a power supply, connecting the conventional EKG electrode at the top to a cathode of the power supply, powering on to start electrokinetic remediation;
• (3) injecting micro-nano bubbles through the bubble emission holes in the dual-channel porous EKG electrode at the bottom, starting an aeration process, opening the pumping well at the top, and collecting toxic gases;
• an electrolyte is injected through the liquid injection holes in the double-channel porous EKG electrode at the bottom to start a liquid injection process;
• discharged liquid is collected at the cathode;
• the electrolyte is natural surfactant, glycerin, sodium bicarbonate or a mixed solution, and is used for remediating heavy metals and organic pollutants in the contaminated soil;
• the whole remediation process is carried out from bottom to top, so that heavy metals and organic pollutants are enriched in top soil.
• (4) carrying out in-situ or ectopic treatment on a surface soil enriched with pollutants by leaching or solidification/stabilization after finishing the processes of electrokinetic remediation and aeration-liquid injection;
• wherein by using the electrokinetic remediation method, water in the soil moves from the bottom to the top, which drives the pollutants to be enriched to the top, which has a better treatment effect on heavy metals;
• at the same time, an electroosmotic flow is configured to generate more diffusion channels and driving forces for bubbles;
• the aeration method is used to generate bubbles, and a large number of hydroxyl radicals are generated when the bubbles burst;
• redox potentials of the bubbles is capable of oxidizing and reducing the pollutants that are difficult to remove in the contaminated soil, which has a better treatment effect on organic pollutants and is capable of enhancing the remediation effect of the electrokinetic remediation method;
• in the process of electrokinetic remediation, a slightly acidic environment is produced near the anode, and the electrolyte is capable of alleviating the strong acidity near the anode and keep the pH of the soil stable;
• higher temperature near the anode causes the electrolyte decomposing into gases, and the generated gases near anode promotes the bubbles generated by the aeration method to further expand in the process of moving from the bottom to the top, so as to increase a contact force with the soil and take away more pollutants;
• the isolation layer adopts an impermeable geomembrane for preventing the gases carrying toxic substances generated by the aeration method and the liquid carrying toxic substances generated during remediation from being discharged into the external environment.