A method for simultaneously remediation of organically contaminated soil and groundwater by electrokinetic coupled multiphase extraction

Abstract

The application discloses a method for simultaneously repairing organic contaminated soil and underground water by electric coupling and multi-phase extraction. Cathode and anode wells are arranged in the area to be repaired in a staggered manner, electrolyte-filled tubes are inserted into the cathode and anode wells, an extraction tube is inserted into the cathode well, the electrodes are connected to an electric repair system, and the extraction tube is connected to a multi-phase extraction system. Through the electric repair, persulfate anions in the cathode electrolyte are injected into the stratum from the cathode well, and are migrated to the anode through the electromigration effect. Iron ions released from the sacrificial anode in the anode electrolyte are migrated to the cathode through the electromigration and electrodialysis effects. In the "opposite" migration, the persulfate in the soil and underground water is activated. Then, the electric field direction is switched, and electrolyte is added into the corresponding electrode wells to perform the "opposite" migration. The repair is performed according to the above electrode repair and electrode repair with the electrode direction switched. The application can realize the simultaneous and efficient repair and detoxification of the composite organic contaminated soil and underground water.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of in-situ remediation of organic contaminated soil, and particularly relates to a method for simultaneously remediating organic contaminated soil and groundwater by electrically coupling multiphase extraction. BACKGROUND

[0002] The vacuum enhanced extraction technology, i.e., the multiphase extraction technology (MPE), is an in-situ remediation technology that can simultaneously extract underground gas and liquid. Under vacuum conditions, the fluid in the stratum continuously flows into the extraction well in response to the pressure gradient, and the dissolved pollutants and the oil layer (light non-aqueous phase liquid) in the groundwater are extracted and removed. Meanwhile, the soil pore gas pressure drops, accelerating the transfer of volatile organic pollutants (VOCs) and semi-volatile organic pollutants (SVOCs) to the soil gas phase, and the VOCs and SVOCs are extracted from the soil together with the airflow. In addition, the improvement of soil aeration and the increase of pore oxygen content can effectively promote the degradation of aerobic microorganisms. Furthermore, the vacuum dewatering effect can also reduce the groundwater level around the extraction well and improve the air permeability of the stratum, so that the VOCs and SVOCs remaining in the soil are redistributed to the gas phase, thereby improving the remediation efficiency.

[0003] The MPE technology has the advantages of small site disturbance and simultaneous removal of vadose zone and aquifer pollutants, but its application effect is greatly affected by the hydrogeological conditions of the site, mainly in terms of the extraction flow of soil gas and groundwater. The applicable permeability coefficient (K) of the MPE technology ranges from 10 -5 -10 -3 cm·s -1 , which corresponds to a low-to-moderately permeable soil layer (sand-silty clay layer). When applied to clay layers (K<10 -6 cm·s - ), it is difficult to achieve ideal remediation results, and the concentration of pollutants tends to change slowly in the later remediation period (the "tail phenomenon"), which seriously affects the remediation effect. The MPE technology can effectively remove organic pollutants with small molecular weight, good volatility and good water solubility, but it is less effective for organic pollutants with large molecular weight, low volatility and poor water solubility. Generally, the MPE technology is suitable for the removal of organic pollutants with a saturated vapor pressure of >0.133 kPa (20℃), a Henry coefficient of >0.01 (20℃), and a boiling point of 250-300℃. SUMMARY

[0004] The present application aims to solve the problems of limited application of MPE technology in low permeability strata, low remediation efficiency of macromolecular organic pollutants, and serious "tail" in the later remediation period, and proposes a method for simultaneously remediating organic contaminated soil and groundwater by electrically coupling multiphase extraction.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] A method for simultaneously remediation of organic contaminated soil and groundwater by electrokinetic coupled multi-phase extraction, in which cathode and anode wells are arranged in staggered distribution in the area to be remediated, pipes filled with electrolyte are inserted into the cathode and anode wells, electrodes are connected to an electrokinetic remediation system, and extraction pipes are connected to a multi-phase extraction system. Electrokinetic remediation is used to inject persulfate anions from the cathode well into the stratum, which migrate to the anode by electromigration. Iron ions released from the sacrificial anode in the anode electrolyte migrate to the cathode by electromigration and electroosmosis. In the process of "counter migration", persulfate in the soil and groundwater is activated. Then, the direction of the electric field is switched, and electrolyte is added to the corresponding electrode wells for "counter migration". The above electrode remediation and electrode direction switching are repeated until the organic contaminated soil and groundwater in the area to be treated are completely remediated. After the electrode remediation, the multi-phase extraction system is started to deplete the electrolyte in the electrode wells.

[0007] The electrodes in the cathode and anode wells are made of iron or stainless steel. The electrolyte in the cathode well is an aqueous solution of persulfate salt, and the concentration of the aqueous solution of persulfate salt is 50-100 g / L, preferably 50-100 g / L, and more preferably 50 g / L or 100 g / L. The electrolyte in the anode well is water.

[0008] The electrode well is a cavity drilled in the area to be remediated. A support screen pipe is inserted into the cavity. An electrode, an electrolyte injection pipe, and an extraction pipe are inserted into the screen pipe. The depth of the electrode well is 0.5-1.5 m below the depth of groundwater pollution and 10-30 cm above the ground surface as a well platform. The well mouth is sealed with a valve.

[0009] The electrode well wall and the outer wall of the support screen pipe are filled with conductive particles.

[0010] Further, the diameter of the electrode well is 45-108 mm, and the well wall is supported by a porous PVC screen pipe with an outer diameter of 40-98 mm (10 mm smaller than the diameter of the electrode well) and a screen hole diameter of 3-5 mm. The screen pipe and the well wall are filled with conductive particles such as iron-carbon and petroleum coke (6-15 mm in diameter).

[0011] The electrode is made of iron or stainless steel and has a diameter of 27-42 mm. The extraction pipe is made of PVC or HDPE and has a diameter of 22-34 mm. The filter pipe (with a slit of 0.2-0.4 mm) covers the depth of groundwater pollution. The electrolyte injection pipe is made of PVC or HDPE and has a diameter of 18-27 mm. A pipe valve is installed outside the well mouth to control the sealing of the pipeline.

[0012] Specifically,

[0013] 1) Electrode wells are arranged in a matrix-like staggered distribution in the remediation area. Electrodes, extraction pipes, and electrolyte injection pipes are fixed in the electrode wells, and the well mouth is sealed.

[0014] 2) Water and aqueous persulfate solution are pumped into the anode well and the cathode well as electrolyte respectively, the electrodes are connected to the output end of the electric remediation system, and the extraction pipe is connected to the multi-phase extraction system;

[0015] 3) The working voltage is set and the electric remediation system is started, after the delivery of the persulfate in the cathode well and the iron ions released by the electrodes in the anode well is completed, the multi-phase extraction system of the cathode well is started;

[0016] 4) After the electrolyte in the cathode well is extracted, the electric remediation device and the extraction device are disconnected, the electrolyte in the anode well is pumped to the cathode well, and then the aqueous persulfate solution is supplemented;

[0017] 5) The direction of the electric field is switched, at this time the initial anode well becomes the cathode well, and the initial cathode well becomes the anode well, and the multi-phase extraction system of the cathode well is started;

[0018] 6) Repeat steps 3) to 5) until the target of remediation is reached.

[0019] The well mouth is sealed with rubber pads combined with cement and bentonite, the rubber pads are provided with a plurality of reserved through holes for the electrodes, electrolyte injection pipes and extraction pipes to be inserted, and then the ground part of the electrode well is sealed with cement and bentonite to ensure the airtightness of the extraction system.

[0020] The electric remediation system is composed of a direct current power supply (constant voltage output, 0-220V), a relay (coil voltage 240V), a digital voltmeter (DC 0-500V), a digital ammeter (DC 0-10A), and a time control switch (DC 220V) connected in sequence by wires, which can realize the setting of working voltage and the automatic switching of electrode polarity.

[0021] The working voltage of the electric remediation system in step 3) is 15-150V, and the corresponding potential gradient is 0.1-1V / cm, preferably 0.5V / cm or 1V / cm; the delivery time of the persulfate in the cathode well and the iron ions released by the sacrificial anode in the anode well is 7-30d, preferably 15d;

[0022] The multi-phase extraction system is a single-pump system, which is composed of a high vacuum degree vacuum pump (maximum vacuum degree -101kPa), a gas-liquid separator (DN150-200), a waste gas treatment device (activated carbon adsorption tank), and a waste water treatment device (Fenton oxidation tower) connected in sequence by connecting pipes, wherein the vacuum pump is connected to the extraction pipe through the connecting section.

[0023] The pressure parameter of the vacuum pump of the multi-phase extraction system in step 4) is set to -20-90kPa; the influence radius of the extraction system is 0.5-1.5m, the vacuum degree of the well head is -0.01-0.06MPa, preferably -0.04MPa, and the single-well gas extraction amount is 0.5-10m 3 / h, preferably 3m 3 / h, single well liquid extraction amount 0.005-0.1m 3 / h, preferably 0.02m 3 / h; extraction system running time 5-7d, preferably 5d;

[0024] Activated carbon adsorption tank filling amount 10-50kg; wastewater treatment capacity of Fenton oxidation tower 0.05-0.2m 3 / h, hydrogen peroxide (≥27.5%) addition amount 0.5-5L, iron ion dosage 40-500g;

[0025] The step 5) switches the electric field direction, and the voltage parameters of the electric repair control system are the same as those in the step 3), and the switching period is set to 7-30d, preferably 15d.

[0026] After the switching of the electrode direction, the electrolyte (water) in the original anode well is pumped to the original cathode well, and the self-priming pump (head 10-40m, flow 0.5-2m 3 / h) is connected to the extraction pipe to complete the emptying of the electrode well, and the concentration of the supplemented persulfate aqueous solution is 50-100g / L.

[0027] The application of a kind of EK-MPE coupling technology to the in-situ remediation of organic contaminated soil.

[0028] Compared with the prior art, the application has the following advantages and technical effects:

[0029] The application realizes the transportation of persulfate in the cathode well to the soil and groundwater in the anode direction based on electromigration, and the iron ions released by the sacrificial anode are transported to the soil and groundwater in the cathode direction under the dual action of electrodialysis and electromigration, which can effectively activate the persulfate and realize the oxidative degradation of pollutants; at the same time, the weak direct current electric field can stimulate the biodegradation of indigenous microorganisms in the soil and groundwater, further improving the removal efficiency of pollutants; under the strengthening effect of stable electrodialysis flow, the extraction efficiency of MPE for low permeability stratum groundwater is further improved; the alternative operation of the electric field not only avoids the drastic change of soil acid-base conditions caused by water electrolysis, but also eliminates the differences in activation efficiency and pollutant removal efficiency caused by the differences in the transportation efficiency of persulfate ions and iron ions, significantly improving the spatial uniformity of pollutant removal. In addition, the desorption and mass transfer of pollutants promoted by the direct current electric field can further improve the pollutant extraction efficiency of MPE. The EK-MPE coupling technology can effectively solve the application bottleneck of MPE technology in low permeability stratum and effectively solve the "tail" problem in the later stage of extraction, realizing the synchronous and efficient remediation and detoxification of composite organic contaminated soil and groundwater. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of this application, and the drawings that illustrate them, are for purposes of explanation only and not limitation, as the full scope of the application will be set forth in the claims. In the drawings:

[0031] Figure 1 The amount of iron ion released from the sacrificial anode of the present application over time;

[0032] Figure 2 The simulated injection experimental device for the persulfate and the iron ion released from the sacrificial anode of the present application; in the figure, 1-direct current power supply; 2-cathode chamber electrolyte recovery tank; 3-cathode chamber; 4-cathode; 5-multi-hole screen plate; 6-soil chamber; 7-anode; 8-anode chamber; 9-peristaltic pump; 10-anode chamber electrolyte storage tank; 11-soil sampling point position;

[0033] Figure 3 The distribution of the persulfate in the soil when the cathode injection method is used in the present application;

[0034] Figure 4 The distribution of the iron ion released from the sacrificial anode in the soil in the present application;

[0035] Figure 5 The laboratory verification device for the electromotive coupling multi-phase extraction method of the present application; in the figure, (a) laboratory simulation verification device; (b) sampling point arrangement;

[0036] Figure 6 The electrode well schematic diagram provided by the embodiments of the present application; in the figure, (a) anode well; (b) cathode well;

[0037] Figure 7 The laboratory verification results of the electromotive coupling multi-phase extraction method of the present application; in the figure, (a) spatial distribution of benzene pollutants; (b) spatial distribution of petroleum hydrocarbon pollutants;

[0038] Figure 8 The method schematic diagram for the specific implementation when the site is actually applied in the present application; in the figure, (a) field layout schematic diagram of the implementation process; (b) plane layout schematic diagram;

[0039] Figure 9 The soil remediation results of the electromotive coupling multi-phase extraction method of the present application in the field application; in the figure, (a) chloroform residual amount in the soil; (b) cis-1,2-dichloroethylene residual amount in the soil; (c) benzene residual amount in the soil; (d) petroleum hydrocarbon residual amount in the soil;

[0040] Figure 10 The groundwater remediation results of the electromotive coupling multi-phase extraction method of the present application in the field application; in the figure, (a) chloroform residual amount in the groundwater; (b) cis-1,2-dichloroethylene residual amount in the groundwater; (c) benzene residual amount in the groundwater. DETAILED DESCRIPTION

[0041] Various exemplary embodiments of the present application will now be described in detail, with reference to the figures. Such description, however, is to be considered in all respects only as illustrative, and not restrictive.

[0042] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. In addition, where particular ranges of values are given, understand that each intervening value, to the upper or lower limit of the ranges is also specifically included. Each smaller range that falls within the broader ranges is also specifically included in the present application. The upper and lower limits of these smaller ranges can independently be included or excluded in the range.

[0043] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All patents, patent applications, publications, and descriptions mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the patents, patent applications, publications, and descriptions are cited.

[0044] Many modifications and variations of this application can be made in the light of the above teachings without departing from the spirit and scope thereof, and it is to be understood that all such modifications and variations warrant patent protection herein to the full extent provided by the above disclosure and claimed, accordingly. Further, it is the intention that any additional claims coming into the applicant's or its assignee's possession after the filing date of this application will be incorporated into this application by reference as part of this original disclosure.

[0045] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional elements or steps.

[0046] The starting materials used in the following examples of the present application are commercially available.

[0047] The application couples and integrates the MPE technology and the EK-ISCO technology, mainly adopts the direct current field to realize the efficient "opposite" transportation of the oxidant (persulfate, cathode→anode) and the activator (iron ions released from the sacrificial anode, anode→cathode) in the soil, activates the persulfate by the iron ions, and realizes the effective degradation of the pollutants; the direction of the electric field is switched at a specific time, which can not only avoid the dramatic fluctuation of the pH of the remediated soil and groundwater, but also effectively avoid the loss of the oxidant caused by the pH increase of the electrolyte during the cathode injection process, and the uniform spatial distribution of the iron ions and the persulfate can further improve the uniformity of the pollutant removal; after the persulfate-iron ion-pollutant is fully reacted, the cathode well extraction system is started, and the stable electroosmosis flow (anode→cathode) can effectively improve the groundwater extraction efficiency; at the same time, the weakly bound water in the soil becomes free water under the action of the electric field and can escape from the double electric layer, which can accelerate the mass transfer process of the pollutants and improve the pollutant extraction efficiency of the MPE technology; in addition, the vacuum negative pressure effectively improves the air and water permeability of the soil, which is beneficial to the mass transfer process and the electric field stimulated biodegradation process in the next EK-ISCO stage, effectively improves the remediation efficiency and shortens the remediation period. The application realizes the synchronous and efficient remediation and detoxification of the composite organic contaminated soil and groundwater based on the synchronous electrokinetic transportation of the oxidant and the activator, the electric field stimulated biodegradation, and the negative pressure extraction to improve the mass transfer efficiency.

[0048] In the following preferred embodiments of the application, the electrode well can be constructed by selecting Geoprobe, Powerprobe or a 30-type drilling machine, etc., the electrode well aperture is 45-108 mm, and the well wall is supported by a porous PVC screen pipe (screen aperture 3-5 mm) with an outer diameter of 40-98 mm (less than the electrode well aperture by 10 mm).

[0049] The electrode is made of iron or stainless steel and has a diameter of 27-42 mm; the extraction pipe is made of PVC or HDPE and has a pipe diameter of 22-34 mm; the filter pipe (slit 0.2-0.4 mm) length covers the groundwater pollution depth; the electrolyte injection pipe is made of PVC or HDPE and has a pipe diameter of 18-27 mm, and a pipe valve is installed outside the well mouth to control the pipeline sealing.

[0050] The electrokinetic remediation system is composed of a direct current power supply (constant voltage output, 0-220 V), a relay (coil voltage 240 V), a digital voltage meter (DC 0-500 V), a digital ammeter (DC 0-10 A), a time control switch (DC 220 V), etc., which can realize the working voltage setting and the automatic switching of the electrode polarity; the multi-phase extraction system is a single pump system, which is composed of a high vacuum degree vacuum pump (maximum vacuum degree -101 kPa), a gas-liquid separator (DN150-200), a waste gas treatment device (activated carbon adsorption tank), a waste water treatment device (Fenton oxidation tower), etc.

[0051] The following examples are further illustrations of the technical solutions of the present application.

[0052] Example 1

[0053] (1) Sacrificial anode iron ion release amount over time

[0054] In three 1 L beakers (14 cm in diameter), 100 g / L aqueous sodium sulfate solution was added, covered with a plexiglass plate with holes (hole spacing 12 cm for placing electrodes), and a stainless steel anode (12 cm long, 1.5 cm in diameter), a graphite cathode (12 cm long, 1.5 cm in diameter) were inserted into the holes of the cover plate and connected to the output terminals of a direct current power supply, and the power supply voltage was set to 6 V, 12 V, and 24 V (corresponding to potential gradients of 0.5 V / cm, 1 V / cm, and 2 V / cm, respectively). The iron ion content of the electrolyte was periodically collected and tested to investigate the change of the iron ion release amount of the anode over time. The results are shown in Table 1. Figure 1 As shown in Table 1, the ferrous ion content increased with increasing applied voltage and prolonged power-on time. Within 1 day, the iron ion release amount was small due to limited electrode corrosion. With prolonged power-on time, the water electrolysis reaction of the anode led to gradual acidification of the electrolyte, and the iron ion release amount of the sacrificial anode increased continuously.

[0055] (2) Persulfate cathode injection efficiency based on polarity switching operation

[0056] The experimental device Figure 2 consists of a numerical control direct current power supply, electrode connecting wires, electrodes, electrode wells, soil chambers, electrolyte storage tanks, electrolyte recovery tanks, peristaltic pumps, etc. Viscous soil was loaded into the soil chamber (50 cm long x 10 cm wide x 10 cm high) using a wet filling method, and the soil moisture content was adjusted to the saturated moisture content (40.0%, w / w), with a loading height of 8.0 cm and a soil density of 1.96 g / cm 3 (about 7.9 kg). To prevent soil from entering the electrode well through the holes, the outer wall of the electrode well in contact with the soil was covered with a 100-mesh nylon mesh, and the electrode (graphite material, 12 cm long, 1.5 cm in diameter) was installed in the electrode well (10 cm long x 10 cm wide).

[0057] The first running stage: the initial anode and the initial cathode are connected to the corresponding output ports of the direct current power supply respectively; the voltage of the direct current power supply is set to 25 V (corresponding to a potential gradient of 0.5 V / cm); tap water is injected into the initial anode well as the electrolyte (liquid level of 8.0 cm), and the persulfate solution (100 g / L) is pumped into the initial cathode well as the electrolyte (liquid level of 8.0 cm); the direct current power supply is started, and the duration is 15 days. The second running stage: the initial anode is connected to the cathode output of the direct current power supply, and the initial cathode is connected to the anode output of the direct current power supply (switching the direction of the electric field, initial anode→cathode, initial cathode→anode); the electrolyte in the electrode well in the last stage is emptied, and tap water is injected into the anode well and the persulfate solution (100 g / L) is injected into the cathode well; the direct current power supply is started, and the duration is 15 days.

[0058] After the experiment is completed, the content of persulfate in the soil is tested by ultraviolet spectrophotometry. Specifically, deionized water, NaHCO3 and KI are mixed in a ratio of 40:0.2:4 (mL:g:g) to configure reagent A; the persulfate in the soil (soil:water = 1:10) is extracted by deionized water (room temperature, 150 r / min, oscillation for 30 min), and the supernatant after centrifugation (6000 rpm, 3 min) of the extraction solution is used as the test solution; 100 μL of the test solution is mixed with 40 mL of reagent A, and the absorbance value is measured at a wavelength of 352 nm after standing for 15 min. The absorbance values of persulfate solutions with different concentrations mixed with reagent A are measured to draw a standard curve.

[0059] The results show that Figure 3 , the cathode well injection method based on polarity switching operation can realize the relatively uniform distribution of persulfate in low-permeability soil, and the persulfate concentration in the soil S1-S5 profile at the end of the experiment (30 days) is between 16.8-19.2 g / kg, with an average content of 17.88 g / kg, and the injection efficiency is about 70%.

[0060] (3) Distribution of iron ions released by sacrificial anode based on polarity switching operation in soil

[0061] The experimental device, soil filling and experimental parameters are the same as in (2), except that the graphite electrode is replaced by an iron electrode (length 12 cm, diameter 1.5 cm). The results show that Figure 4 , the electrokinetic transport method of iron ions released by the sacrificial anode based on polarity switching operation can realize efficient production and spatial distribution of ferrous ions, and the iron ion content in the soil S1-S5 profile at the end of the experiment (30 days) is between 10.2-11.9 g / kg, with an average content of 10.96 g / kg.

[0062] Example 2

[0063] Based on the parameters of the electrically driven transport of the ferric ions released from the sacrificial anode and the injected persulfate under the conditions of the polarity switching operation obtained in Example 1, the laboratory verification of the effect of the electrically coupled multi-phase extraction method was carried out.

[0064] The device is composed of a numerical control direct current power supply, an electric wire, a PVC soil tank, an electrode well, an electrode, a peristaltic pump, a water electrolyte storage tank, a persulfate electrolyte storage tank, an electrolyte injection pipeline, an extraction pipeline, a vacuum pump, and the like.

[0065] The specific simulation device Figure 5 is provided with anode and cathode wells (see Figure 6 ) staggered and distributed in the area to be repaired (soil chamber), that is, one column of cathode wells is arranged between two columns of symmetrically distributed anode wells, the spacing between the anode wells and the opposite cathode wells is equal, the cathode wells and the anode wells are inserted with electrolyte injection pipes, the cathode wells are inserted with extraction pipes, the electrodes are connected to the electric remediation system, and the extraction pipes are connected to the multi-phase extraction system.

[0066] The above-mentioned electrodes are respectively connected to the anode and cathode output ports of the numerical control direct current power supply. The artificial simulation of the composite contaminated cohesive soil (benzene content 7.8 mg / kg, petroleum hydrocarbon content 1570.6 mg / kg) is filled into the soil chamber (length 120 cm x width 120 cm x height 50 cm) by using the wet filling method, the water content of the soil is adjusted to the saturated water content (40.0%, w / w), the filling height is 45 cm, and the soil density is 1.96 g / cm 3 (about 1412 kg); in order to avoid the soil entering the electrode well through the hole, the electrode well (height 50 cm, inner diameter 6 cm) is wrapped with a 100-mesh nylon net at the outer wall of the contact end with the soil; the well wall is supported by a porous PVC screen pipe (screen hole diameter 3 mm) with an outer diameter of 5 cm (less than the electrode well aperture 1 cm); the screen pipe and the well wall are filled with petroleum coke conductive particles (diameter 6 mm); the electrode (iron material, length 52 cm, diameter 2 cm), the electrolyte injection pipe (diameter 1 cm), and the extraction pipe (diameter 2 cm) are inserted into the electrode well through the hole of the rubber sealing cover.

[0067] The extraction pipe is connected to the vacuum pump, and the vacuum pump is connected in turn to the gas-liquid separator (DN15-DN25, rated flow 0.3-0.5 m 3 / min, the capacity of this embodiment is set to 0.3 m 3 / min), the activated carbon adsorption purifier (treatment air volume 5-20 m 3 / h, the capacity of this embodiment is set to 5 m 3 / h, and the addition amount of activated carbon is 30 kg), and the Fenton reactor (wastewater treatment capacity 0.05-0.5 m 3The extracted waste gas and waste water are connected to a further treatment device, such as an activated carbon adsorption purifier with a loading capacity of 30-60 kg and a Fenton reactor with a H2O2(≥27.5%) addition amount of 0.5 L and an iron ion amount of 40 g.

[0068] Specifically,

[0069] 1) Setting up electrode wells in a matrix staggered distribution in the repair area (soil chamber), fixing the electrodes, extraction pipes and electrolyte injection pipes in the electrode wells, and sealing the wellheads;

[0070] 2) Pumping water and aqueous persulfate solution as electrolyte into the anode well and the cathode well respectively, connecting the electrodes to the output end of the electric repair system, and connecting the extraction pipe to the multiphase extraction system;

[0071] 3) Setting the working voltage and starting the electric repair system, and after completing the delivery of persulfate in the cathode well and the release of iron ions from the electrodes in the anode well, starting the multiphase extraction system in the cathode well;

[0072] 4) After the electrolyte in the cathode well is extracted, disconnecting the electric repair device and the extraction device, pumping the electrolyte in the anode well to the cathode well, and supplementing the aqueous persulfate solution;

[0073] 5) Switching the electric field direction, at this time the initial anode well becomes the cathode well and the initial cathode well becomes the anode well, and starting the multiphase extraction system in the cathode well;

[0074] 6) Repeating steps 3) to 5) until the repair target is reached.

[0075] The step 3) is the first running stage: the initial anode and the initial cathode are connected to the corresponding output ports of the direct current power supply; the voltage of the direct current power supply is set to 25 V (corresponding to a potential gradient of 0.5 V / cm); tap water is injected into the initial anode well as electrolyte (liquid level height 45 cm), and aqueous persulfate solution (100 g / L) is pumped into the initial cathode well as electrolyte (liquid level height 45 cm); the direct current power supply is started, and the duration is 15 d.

[0076] The extraction system parameters in step 4) are: the influence radius of the extraction well is set to 0.5 m, the vacuum degree at the well head is -0.01 MPa, the gas extraction amount of a single well is 0.5 m 3 / h, and the liquid extraction amount is 0.005 m 3 / h; the running time of the extraction system is 5 d.

[0077] The step 5), i.e., the second running stage: the initial anode is connected to the cathode output end of the direct current power supply, and the initial cathode is connected to the anode output end of the direct current power supply (switching the electric field direction, initial anode→cathode, initial cathode→anode); the electrolyte in the electrode well in the last stage is emptied, tap water (liquid level height 45 cm) is injected into the current anode well, and the persulfate solution (100 g / L) is injected into the current cathode well (liquid level height 45 cm); the direct current power supply is started, and the duration is 15 d. The extraction system parameters are as follows: the influence radius of the extraction well is set to 0.5 m, the vacuum degree at the well head is -0.01 MPa, the gas extraction amount of a single well is 0.5 m 3 / h, and the liquid extraction amount is 0.005 m 3 / h; and the running time of the extraction system is 5 d.

[0078] After the running is completed (40 d), the average contents of benzene (0.41-0.72 mg / kg) and petroleum hydrocarbon (539.8-624.8 mg / kg) in the soil at different sampling points are 0.56 mg / kg and 584.6 mg / kg Figure 7 , respectively, which are lower than the first type of land screening values (benzene 1 mg / kg, petroleum hydrocarbon C10-C40: 826 mg / kg) in the “Soil Environmental Quality Risk Control Standards for Construction Land (Trial)” (GB 36600-2018).

[0079] Example 3

[0080] The field application of the electrokinetic coupling multiphase extraction method is carried out. A certain chemical plant site is selected, the production history mainly includes pesticides and other chemical reagents, and the test area soil is complexly contaminated by chloroform (4.7-12.5 mg / kg), cis-1,2-dichloroethylene (105.8-620.3 mg / kg), benzene (1.7-23.9 mg / kg), and petroleum hydrocarbon (975.4-1986.5 mg / kg); the groundwater is complexly contaminated by chloroform (783.9-4657.2 μg / L), cis-1,2-dichloroethylene (83.7-143.8 μg / L), and benzene (650.4-9806.1 μg / L); and the maximum pollution depth reaches 7 m.

[0081] The specific implementation method is shown in Figure 8 . The cathode well and the anode well are staggered and distributed in the area to be repaired (soil chamber) (see Figure 6 ), that is, one column of cathode wells is arranged between two columns of symmetrically distributed anode wells, the spacing of the anode well and the opposite cathode well is equal, the cathode well and the anode well are inserted with the electrolyte-filled pipe, the cathode well is inserted with the extraction pipe, the electrodes are connected to the electrokinetic remediation system, and the extraction pipe is connected to the multiphase extraction system.

[0082] First, in the selected test range with 30 drillers electrode wells (hole diameter 108 mm) construction, well spacing 1.5 m, well depth 8 m; well wall with porous PVC screen pipe (hole diameter 98 mm, screen hole diameter 5 mm) support, exposed to the ground 20 cm; screen pipe and well wall filled with diameter 10 mm iron-carbon particles; stainless steel (pipe) electrode (DN25, diameter 3.4 cm), PVC extraction tube (pipe diameter 3.4 cm, 0.4 mm slit filter tube length 5 m), PVC electrolyte injection tube (pipe diameter 1.8 cm) through the rubber pad (diameter 113 mm, thickness 40 mm) reserved hole inserted into the electrode well fixed; with cement and bentonite masonry well platform, sealing the electrode well above ground.

[0083] The above extraction tube is connected to a vacuum pump, which is connected in turn to a gas-liquid separator (DN15-DN25, rated flow 0.3-0.5 m 3 / min, the capacity of this embodiment is set to 0.5 m 3 / min), activated carbon adsorption purifier (treatment air volume 5-20 m 3 / h, the capacity of this embodiment is set to 5 m 3 / min, the amount of activated carbon added is 50 kg), Fenton reactor (wastewater treatment capacity 0.05-0.5 m 3 / h), H2O2(≥27.5%) addition amount 1.5 L, iron ion dosage 120 g) connected, so that the extracted waste gas and wastewater are further treated. The activated carbon adsorption purifier is filled with 30-60 kg; the H2O2(≥27.5%) addition amount of the Fenton reactor is 1.5 L, and the iron ion dosage is 120 g.

[0084] Specifically:

[0085] 1) Set up electrode wells in the repair area (soil chamber) in a matrix staggered distribution, fix the electrode, extraction tube, and electrolyte injection tube in the electrode well, and seal the well mouth;

[0086] 2) Pump water and persulfate aqueous solution into the anode well and cathode well respectively as electrolyte, connect the electrode to the output end of the electric repair system, and connect the extraction tube to the multi-phase extraction system;

[0087] 3) Set the working voltage and start the electric repair system, after completing the delivery of persulfate in the cathode well and the release of iron ions from the electrode in the anode well, start the multi-phase extraction system of the cathode well;

[0088] 4) After the electrolyte in the cathode well is extracted, disconnect the electric repair device and the extraction device, pump the electrolyte in the anode well to the cathode well, and then supplement the persulfate aqueous solution;

[0089] 5) Switch the direction of the electric field, at this time the initial anode well becomes the cathode well, and the initial cathode well becomes the anode well, and start the multi-phase extraction system of the cathode well;

[0090] 6) Repeat steps 3) to 5) until the repair target is reached.

[0091] The step 3), i.e. the first running stage: the initial anode and the initial cathode are respectively connected to the corresponding output ports of the direct current power supply of the electric repair system; water is pumped into the initial anode well, and the initial cathode well is pumped with aqueous persulfate solution (100 g / L) as electrolyte; the potential gradient of the electric field is set to 0.5 V / cm (the working voltage of the direct current power supply is set to 75 V), and the transport time is 15 d.

[0092] The step 4) extraction system parameters: the influence radius of the extraction well is set to 1.5 m, the vacuum degree at the well head is -0.04 MPa, the gas extraction amount of a single well is 3 m 3 / h, and the liquid extraction amount is 0.02 m 3 / h; the running time of the extraction system is 5 d.

[0093] The step 5), i.e. the second running stage: switch the direction of the electric field (initial anode→cathode, initial cathode→anode); empty the electrolyte in the electrode well of the previous stage, and inject tap water into the present anode well and inject persulfate solution (100 g / L) into the present cathode well; start the direct current power supply, and the duration is 15 d. The extraction system parameters: the influence radius of the extraction well is set to 1.5 m, the vacuum degree at the well head is -0.04 MPa, the gas extraction amount of a single well is 3 m 3 / h, and the liquid extraction amount is 0.02 m 3 / h; the running time of the extraction system is 5 d.

[0094] Repeat the first and second running stages, and after the running ends (the overall running time is 80 d), the average contents of chloroform (0.16-0.24 mg / kg), cis-1,2-dichloroethylene (37.8-57.4 mg / kg), benzene (0.52-0.85 mg / kg), and petroleum hydrocarbon (632.8-705.0 mg / kg) in the soil of the repair area are 0.21 mg / kg, 49.5 mg / kg, 0.74 mg / kg, and 680.3 mg / kg Figure 9 , respectively, which are all lower than the first type of land screening values (chloroform 0.3 mg / kg, cis-1,2-dichloroethylene 66 mg / kg, benzene 1 mg / kg, and petroleum hydrocarbon C10-C40: 826 mg / kg) in the Soil Environmental Quality Risk Control Standard for Construction Land (Trial) (GB 36600-2018); the average contents of chloroform (111.5-167.5 μg / L) and benzene (51.2-83.9 μg / L) in the groundwater are 149.5 μg / L and 70.7 μg / L Figure 9), reaching the IV water quality standard (chloroform ≤ 300 μg / L, benzene ≤ 120 μg / L) of the Groundwater Quality Standard (GB / T 14848-2017); the average content of cis-1,2-dichloroethylene (22.7-42.8 μg / L) was 33.4 μg / L ( Figure 10 ), reaching the III water quality standard (cis-1,2-dichloroethylene ≤ 60 μg / L) of GB / T 14848-2017.

[0095] As can be seen from the above, the persulfate anion can be injected into the stratum from the cathode well through electromigration (cathode→anode), and the iron ions released by the sacrificial anode migrate to the cathode through electromigration and electrodialysis (anode→cathode), which can effectively activate the persulfate in the soil and groundwater; at the same time, the microbial degradation of pollutants can be further improved under the stimulation of the weak direct current field. After the delivery of persulfate and iron ions and the activation of persulfate, the MPE device of the cathode well is started, and the stable electrodialysis flow (anode→cathode) can further improve the extraction efficiency of the groundwater in the low permeability stratum. The VOCs in the soil gas, the incompletely degraded organic pollutants in the groundwater, and the degradation products dissolved in the water can be extracted for deep disposal under the action of MPE, realizing the synchronous and efficient remediation and detoxification of the compound organic contaminated soil and groundwater.

[0096] The above merely describes the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for the simultaneous remediation of organically contaminated soil and ground water by electrokinetic coupled multiphasic extraction, characterized in that, The cathode well is inserted with an extraction pipe, the electrodes are connected to an electric remediation system, and the extraction pipe is connected to a multi-phase extraction system. The electric remediation makes the persulfate anion in the cathode electrolyte injected into the stratum from the cathode well, migrates to the anode through the electromigration effect, and the iron ions released by the sacrificial anode in the anode electrolyte migrate to the cathode through the electromigration and electrodialysis effect. In the "opposite" migration, the persulfate in the soil and groundwater is activated. Then, the direction of the electric field is switched, and electrolyte is added to the corresponding electrode well for "opposite" migration. The electrode remediation and the electrode remediation with the switching of the electrode direction are performed according to the above-mentioned method until the organic contaminated soil and groundwater in the treatment area are completely remediated. After the electrode remediation, the multi-phase extraction system is started, and the electrolyte in the electrode well is depleted. Specifically, 1) electrode wells are arranged in a matrix staggered distribution in the remediation area, and the electrodes, extraction pipes, and electrolyte injection pipes are fixed in the electrode wells, and the wellheads are sealed; 2) water and persulfate aqueous solution are pumped into the anode well and the cathode well as electrolyte, the electrodes are connected to the output end of the electric remediation system, and the extraction pipe is connected to the multi-phase extraction system; 3) the working voltage is set and the electric remediation system is started, and after the transportation of persulfate in the cathode well and the release of iron ions from the electrode in the anode well is completed, the multi-phase extraction system of the cathode well is started; 4) after the electrolyte in the cathode well is extracted, the electric remediation device and the extraction device are disconnected, the electrolyte in the anode well is pumped into the cathode well, and the persulfate aqueous solution is supplemented; 5) the direction of the electric field is switched, at this time the initial anode well becomes the cathode well, and the initial cathode well becomes the anode well, and the multi-phase extraction system of the cathode well is started; 6) steps 3) to 5) are repeated until the remediation target is reached. The electrodes in the cathode well and the anode well are made of iron or stainless steel; the electrolyte in the cathode well is a persulfate aqueous solution with a concentration of 50-100 g / L; and the electrolyte in the anode well is water. The electrode well is a hollow hole drilled in the area to be remediated, a support screen pipe is inserted into the hollow hole, and the electrode, electrolyte injection pipe, and extraction pipe are inserted into the screen pipe. The depth of the electrode well is 0.5-1.5 m below the depth of groundwater pollution and 10-30 cm above the ground as a well platform, and the wellhead is sealed. The electrode well wall and the outer wall of the support screen pipe are filled with conductive particles. The wellhead sealing is completed with rubber pads combined with cement and bentonite. The rubber pads are provided with multiple reserved through holes for the electrodes, electrolyte injection pipes, and extraction pipes to be inserted, and then cement and bentonite are used for masonry to seal the above-ground part of the electrode well, so as to ensure the airtightness of the extraction system.

6. Application of the method for electrically coupled multi-phase extraction and synchronous remediation of organic contaminated soil and groundwater in claim 1 in the in-situ remediation of organic contaminated soil. ​ 2. The method of electrokinetically coupled multiphasic extraction simultaneous remediation of organic contaminated soil and groundwater according to claim 1, wherein, ​ 3. The method of electrokinetically coupled multiphasic extraction and simultaneous remediation of organic contaminated soil and groundwater according to claim 2, wherein, ​ 4. The method of electrokinetically coupled multiphasic extraction and simultaneous remediation of organic contaminated soil and groundwater according to claim 1, wherein, ​ 5. The method of electrokinetically coupled multiphasic extraction and simultaneous remediation of organic contaminated soil and groundwater of claim 1, wherein, The working voltage range of the electromotive remediation system in the step 3) is 15-150 V, and the corresponding potential gradient is 0.1-1 V / cm; the transport time of persulfate in the cathode well and the iron ion released by the sacrificial anode in the anode well is 7-30 d; the vacuum pump pressure parameter of the multi-phase extraction system in the step 4) is set to-20~-90 kPa; the influence radius of the extraction system is 0.5-1.5 m, the well head vacuum degree is-0.01~-0.06 MPa, the single well gas extraction amount is 0.5-10 m 3 / h, the single well liquid extraction amount is 0.005-0.1 m 3 / h; the extraction system operation time is 5-7 d; the switching electric field direction in the step 5) has the same voltage parameter as the electromotive remediation control system in the step 3), and the switching cycle is set to 7-30 d. ​

Images