CN113231460B

CN113231460B - Three-dimensional electric remediation device and method for contaminated soil

Info

Publication number: CN113231460B
Application number: CN202110600613.9A
Authority: CN
Inventors: 徐海音; 张宏伟; 王平; 吴红辉; 龚绘林; 彭创新; 罗远玲; 黄兢; 李琳; 彭添威
Original assignee: Central South University of Forestry and Technology
Current assignee: Central South University of Forestry and Technology
Priority date: 2021-05-31
Filing date: 2021-05-31
Publication date: 2022-08-19
Anticipated expiration: 2041-05-31
Also published as: CN113231460A

Abstract

The invention discloses a three-dimensional electric remediation device for polluted soil, which comprises an anode rotating shaft, an anode cover, a cathode wall, an adsorption ring, a rotating blade, a cathode bottom, a first power supply and a second power supply, wherein the three-dimensional electric remediation device comprises: the three-dimensional electric field is formed by the anode rotating shaft, the anode cover, the cathode wall and the cathode bottom, the anode rotating shaft and the anode cover are anodes, the cathode wall and the cathode bottom are cathodes, and the electro-catalyst dispersed in the three-dimensional electric field restoration area forms an induction third pole. The invention also discloses an electric restoration method by adopting the three-dimensional electric restoration device, which has the advantages of low energy consumption, high restoration efficiency and short restoration time for the composite polluted soil and strong practicability.

Description

Three-dimensional electric restoration device and method for polluted soil

Technical Field

The invention relates to the technical field of soil treatment, in particular to a three-dimensional electric restoration device and an electric restoration method for polluted soil.

Background

From the release of action for preventing and treating soil pollution in 2016 to the implementation of a method for preventing and treating soil pollution in 2019, a road for quickly starting soil environment protection, which is mainly based on administrative supervision measures and matched with necessary relevant technical guidelines, is developed rapidly in China, so that the treatment and the restoration of the composite polluted soil are enhanced.

At present, the remediation of the composite contaminated soil is mainly carried out in a stabilizing and migrating manner as follows:

the composite pollutants of the soil are mainly stabilized by stabilizers, plants, microorganisms and the like. The stabilizing by adopting the stabilizer is to mix the soil polluted by the heavy metal with the stabilizer according to a certain proportion, and finally form a solid mixture with low permeability after curing, the treatment effect of the stabilizing by adopting the stabilizer is related to the components and proportion of the stabilizer, the total concentration of the heavy metal in the soil and interference substances influencing the stability in the soil, the engineering quantity of the stabilizing treatment by adopting the stabilizer is large, the fertility of the soil can be damaged, pollutants are still in the soil, and the risk of re-release exists; plant and microorganism stabilization is adopted, although secondary damage to soil is less, the repair period is longer, the influence of the external environment on the repair effect is larger, pollutants are still in the soil, and the risk of re-release exists.

The migration methods of the composite pollutants comprise leaching repair, bioremediation, electric repair and the like. In the leaching repair process, such as a surfactant reinforced leaching process, although the solubility of organic pollutants in the polluted soil and the desorption of heavy metals can be improved by adding the surfactant, the artificially synthesized surfactant has high cost, is toxic to soil organisms and is easy to cause secondary pollution to the environment. The biological method comprises phytoremediation and microbial remediation, the bioremediation is relatively economic and does not cause secondary pollution to soil, but the remediation period is relatively long, and the remediation effect is easily influenced by factors such as external environment change and the like. The electrokinetic remediation technology is a technology for migrating and enriching pollutants to an electrode area by using the action of electromigration, electroosmotic flow, electrophoresis and the like of electrodynamics so as to carry out concentrated separation or treatment, and has the advantages of being suitable for low-permeability soil, and having various types of pollutants for rapid remediation and treatment. Therefore, the electrokinetic remediation technology is a green remediation technology and is a research hotspot of the remediation technology of the compound contaminated soil.

Because the traditional electric restoration technology lacks oxidation capacity, heavy metals are difficult to be converted into ionic states from oxidation states and reduction states, and organic matters are difficult to be oxidized and degraded, so that the effect of restoring the heavy metal-organic matter combined polluted soil by using the traditional electric method is limited. In the electric repairing process, the type and the spatial configuration of the electrode have important influence on the repairing effect, the traditional electric repairing method mostly adopts parallel plate-shaped electrodes, the mode has good uniformity of soil repairing, but the concentration polarization phenomenon can occur to cause a large amount of electric energy to be consumed in the surface area of the electrode. In practical application, the traditional electric repairing method also has the problems of large engineering quantity and the like during field repairing.

Therefore, the method has great significance in finding the composite polluted soil remediation technology which is high in efficiency, low in energy consumption and friendly to ecological environment.

Disclosure of Invention

The invention provides a three-dimensional electric field electric restoration device and an electric restoration method for composite polluted soil, aiming at the defects of high energy consumption, poor restoration efficiency and long restoration time of the composite polluted soil and the like of the traditional electric restoration technology, and the specific technical scheme is as follows:

a three-dimensional electric remediation device for contaminated soil comprises an anode rotating shaft, an anode cover, a cathode wall, an adsorption ring, a rotating blade, a cathode bottom, a first power supply and a second power supply;

the anode cover and the cathode bottom are respectively positioned at the end parts of two ends of the cathode wall, and the anode cover, the cathode bottom and the cathode wall enclose a three-dimensional electric field repairing region; an adsorption ring is arranged on the outer side of the cathode wall;

the anode rotating shaft and the cathode wall are coaxially and axially arranged, and the anode rotating shaft penetrates through the mounting through hole in the anode cover to be movably arranged; the rotating blade is arranged on the anode rotating shaft and is positioned in the three-dimensional electric field repairing area;

the anode rotating shaft is connected with the anode of a first power supply, and the cathode wall is connected with the cathode of the first power supply; the anode cover is connected with the anode of a second power supply, and the cathode bottom is connected with the cathode of the second power supply.

Preferably, the three-dimensional electric field repairing region is filled with an electrocatalyst.

Preferably, the preparation method of the electrocatalyst comprises the following steps:

the vitrification treatment of the biochar specifically comprises the following steps:

the preparation of the biochar specifically comprises the following steps: crushing, carbonizing, grinding and sieving biological straws to obtain straw biochar;

suspension i was prepared specifically as follows: mixing silicon dioxide and water according to the weight ratio of 15-25 g: 100 ml of the mixture is mixed and stirred to prepare suspension I;

the biological carbon vitrification specifically comprises the following steps: adding straw biochar into the suspension I, stirring, drying, and burning to obtain vitrified biochar, wherein the burning temperature is 1750-2150 ℃;

the preparation method of the vitrified biochar with the electrocatalytic performance specifically comprises the following steps:

preparation of suspension II: mixing polyethylene glycol and water according to a volume ratio of 1: 0.7-0.8, mixing to prepare a polyethylene glycol solution, adding ferric oxide into the polyethylene glycol solution, and stirring to prepare a suspension II; wherein the mass of the ferric oxide is as follows: the volume ratio of the polyethylene glycol solution is 1 g: 90-110 ml;

adding the obtained vitrified biochar into the suspension II, and firing at the constant temperature of 600-800 ℃ to obtain vitrified biochar with electrocatalytic performance, wherein: quality of vitrified biochar: the volume of suspension ii was 1 g: 10-60 ml.

Preferably, the biomass charcoal preparation method specifically comprises the following steps: crushing biological straws, soaking in an oxidizing solution, cleaning, and drying to obtain treated straws; carbonizing the treated straws under the protection of nitrogen, cooling, grinding and sieving to obtain straw biochar; wherein: the mass content of the hydrogen peroxide in the oxidizing solution is 15-30%, the soaking time is 0.5-2 hours, the drying temperature is 50-60 ℃, and the drying time is 8-12 hours; the purity of nitrogen is 95-99%, the heating rate is 12-17 ℃ per minute, the carbonization temperature is 300-500 ℃, the carbonization time is 0.5-1 hour, and the number of sieving meshes is 10-16 meshes;

suspension I was prepared specifically as follows: mixing silicon dioxide with the diameter of 2-10 microns with water, ultrasonically oscillating for 1-2 hours, and magnetically stirring for 0.5-1 hour at the speed of 200-240 revolutions per minute to prepare a suspension I;

the biological carbon vitrification specifically comprises the following steps: after adding straw biochar into the prepared suspension I, carrying out ultrasonic oscillation, magnetic stirring, filtering and drying, and firing at constant temperature for 0.25-0.5 h under the protection of argon to prepare vitrified biochar, wherein: the ultrasonic oscillation time is 0.5-1 hour, the magnetic stirring speed is 160-180 revolutions per minute, the magnetic stirring time is 0.5-1 hour, the drying temperature is 50-60 ℃, and the drying time is 8-12 hours;

adding the vitrified biochar into the suspension II, performing ultrasonic oscillation for 0.25-0.5 hour, filtering, drying, and firing at constant temperature for 0.4-0.6 hour under the protection of nitrogen to prepare vitrified biochar with electrocatalysis performance; the drying temperature is 50-60 ℃, and the drying time is 8-12 hours;

among the vitrified biochar with electrocatalytic properties: the grain diameter of the biochar is 1 mm-2 mm, the loading capacity of ferric oxide is 0.4 mol/g-0.8 mol/g, the loading capacity of silicon dioxide is 0.6 mol/g-1.2 mol/g, and the volume weight is 0.15g/cm ³ ～0.21g/cm ³ The total porosity is 37-57%.

Preferably, the anode rotating shaft and the cathode wall are both arranged along the vertical direction, and the anode cover and the cathode bottom are both arranged along the horizontal direction; the rotating blades are detachably arranged on the anode rotating shaft; the anode cover is movably arranged on the anode rotating shaft and can move up and down along the vertical direction; the cathode wall is of a porous structure; the first power supply is arranged along the horizontal direction, and the second power supply is arranged along the vertical direction.

Preferably, the anode rotating shaft, the anode cover, the cathode wall and the cathode bottom form a three-dimensional electric field; the anode rotating shaft and the anode cover are anodes, the cathode wall and the cathode bottom are cathodes, and the electro-catalyst dispersed in the three-dimensional electric field repairing area forms an induction third pole.

Preferably, the anode rotating shaft is a titanium-based material, wherein the mass fraction of titanium is 86% -99%; the rotating blades are made of stainless steel; the cathode wall is made of stainless steel, the pore density of the cathode wall is 20-70%, and the pore size is 0.05-0.18 cm; the anode cover is made of a titanium-based material, the titanium-based material is a titanium plate, and the mass fraction of titanium in the titanium plate is 86% -99%; the cathode bottom is made of stainless steel; sponge and adsorption liquid are filled in the adsorption ring; the first power supply and the second power supply are both one of a direct current power supply and a programmable direct current power supply, and the voltage provided by the programmable direct current power supply is square wave pulse voltage.

Preferably, the adsorption solution is at least one of a nitric acid solution of 0.01mol/L to 0.1mol/L, an acetic acid solution of 0.01mol/L to 0.2mol/L, ethylenediamine tetraacetic acid of 4mmol/L to 7mmol/L, N-dicarboxymethylalanine trisodium salt of 4mmol/L to 7mmol/L, citric acid of 0.1mol/L to 0.4mol/L and oxalic acid of 0.1mol/L to 0.5 mol/L;

the maximum current of the direct current power supply is less than or equal to 1.5A; the pulse amplitude of the square wave pulse voltage is + 0.5V- +2.5V, the pulse width is 1 s-4 s, and the pulse period is 2 s-9 s.

The electric remediation method for the polluted soil by adopting the three-dimensional electric remediation device comprises the following steps:

step one, preparing composite contaminated soil to be repaired; the type of the composite contaminated soil to be repaired is heavy metal-organic matter composite contamination, wherein: the heavy metal contaminants include at least one of manganese, zinc, cadmium, thallium, arsenic, lead and copper; the organic pollutant comprises at least one of pyrene, dichlorodiphenyl, chlordane, toxaphene, hexachlorobenzene and polychlorinated biphenyl;

step two, taking down the anode cover, and installing a rotating blade at the bottom end of the anode rotating shaft; putting the composite polluted soil to be restored prepared in the step one into a three-dimensional electric field restoration area; driving a rotating blade to stir through an anode rotating shaft to obtain a mixture I, so that the composite soil to be treated and the electrocatalyst are uniformly mixed, and the mass of the added electrocatalyst accounts for 2% -15% of the sum of the dry weight of the electrocatalyst and the dry weight of the composite polluted soil to be repaired; taking the rotating blade and the anode rotating shaft out of the three-dimensional electric field repairing area, and detaching the rotating blade from the anode rotating shaft;

step three, adjusting the water content of the mixture I obtained in the step two to obtain a mixture II; compacting the mixture II by using an anode cover; inserting an anode rotating shaft into the three-dimensional electric field repairing area through an anode cover; respectively connecting the anode rotating shaft, the anode cover, the cathode wall and the cathode bottom with a first power supply and a second power supply;

step four, adding adsorption liquid into the adsorption rings filled with the sponge, starting the first power supply and the second power supply simultaneously, and repairing to obtain soil after repairing, wherein: the ratio of the average voltage of the first power supply to the average voltage of the second power supply is 1: (0.2-0.8).

Preferably, in the second step, the stirring speed of the rotating blade driven by the anode rotating shaft is 60-80 rpm, and the stirring time is 0.2-0.3 hour; the water content of the mixture II in the third step is 25-35 percent; when repairing is carried out in the fourth step: the electric field intensity of the first power supply and the second power supply is 1V/cm-3V/cm; the repair time is 3-5 days.

The technical scheme of the invention has the following beneficial effects:

1. the three-dimensional electric repairing device comprises an anode rotating shaft, an anode cover, a cathode wall, an adsorption ring, a rotating blade, a cathode bottom, a first power supply and a second power supply, wherein the anode rotating shaft, the anode cover, the cathode wall and the cathode bottom form a three-dimensional electric field, the anode rotating shaft and the anode cover are anodes, the cathode wall and the cathode bottom are cathodes, and an electrocatalyst dispersed in a three-dimensional electric field repairing region forms an induction third pole (specifically, the electrocatalyst dispersed in the three-dimensional electric field repairing region is a good conductor and forms a third pole with the cathode and anode properties in an electrostatic induction mode), so that the three-dimensional electric repairing device is a special three-dimensional electric repairing device, and the oxidation-reduction capability of soil can be greatly improved under the action of the electric field, and the removal rate is improved; the invention adopts the combination of a unique three-dimensional electric repairing device and a unique electrocatalyst (vitrified biochar with electrocatalysis performance), and the electrocatalyst generates hydroxyl free radicals under the electrified condition, so that the removal rate of the composite pollutants is increased. Under the action of an electric field, a positive electrode and a negative electrode are formed on the surface of the biochar, and a catalyst loaded on the surface of the anode biochar catalyzes to generate hydroxyl radicals (OH); the cathode biochar indirectly catalyzes hydrogen peroxide to generate hydroxyl free radicals (. OH), once the hydroxyl free radicals are formed, a series of free radical chain reactions are induced, organic substances are oxidized and decomposed, and finally the organic substances are degraded into water, carbon dioxide and trace inorganic salts, and the reaction rate is high; meanwhile, the heavy metal in the soil can be catalyzed to be converted from an oxidizable state and a reducible state to an ionic state, the oxidation-reduction capability of the soil is obviously improved, and the removal rate of the heavy metal is improved.

2. According to the invention, the electrode is expanded from the outside of the soil to the inside of the soil after the electrocatalyst is added, and the electrified anode rotating shaft and cathode wall form an electric field in the horizontal direction, so that the biochar forms a negative and positive electrode in the horizontal direction of the soil, and has the capability of direct oxidation reduction; the electrified anode cover and the electrified cathode bottom form an electric field in the vertical direction, so that electrode blind areas above and below the biochar are reduced, the redox capability of the biochar is improved, and pollutants can be directly and rapidly oxidized and reduced; in addition, under the action of an electric field and electrocatalysis biochar, the conductivity of soil is increased, the resistance is reduced, and the migration rate of pollutants is improved, so that the repair rate of composite pollution is accelerated.

3. In the invention, electrokinetic remediation is realized by one cathode chamber. The device is provided with an anode rotating shaft, an anode cover, a cathode wall and a cathode bottom as four electrodes. On the basis, only the cathode wall is provided with the adsorption ring to form a cathode chamber, so that cathode chambers and anode chambers in other directions are saved, and the structure of the electric repairing device is optimized.

In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. In the drawings:

FIG. 1 is a schematic view showing the construction of a three-dimensional electrokinetic remediation device for contaminated soil according to example 1;

FIG. 2 is a top view of FIG. 1 (without illustrating the first and second power supplies);

FIG. 3 is a schematic view showing the construction of the electromotive repairing device in comparative example 1;

FIG. 4 is a top view of FIG. 3;

FIG. 5 is a schematic view showing the construction of an electromotive repairing device in comparative example 2;

FIG. 6 is a distribution diagram of the adsorption column of FIG. 5;

FIG. 7 is a top view of FIG. 5;

FIG. 8 is a schematic view showing the construction of an electromotive repairing device in comparative example 3;

the device comprises an anode rotating shaft 1, an anode cover 2, an anode cover 3, a cathode wall 4, an adsorption ring 5, a three-dimensional electric field repair area 6, a rotating blade 7, a cathode bottom 8, a first power supply 9, a second power supply 10, an insulating layer 11 and an adsorption column.

Detailed Description

Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways as defined and covered by the claims.

Example 1:

referring to fig. 1 and 2, a three-dimensional electric remediation device for contaminated soil, the three-dimensional electric remediation device comprises an anode rotating shaft 1, an anode cover 2, a cathode wall 3, an adsorption ring 4, a rotating blade 6, a cathode bottom 7, a first power supply 8 and a second power supply 9;

the anode cover 2 and the cathode bottom 7 are respectively positioned at the end parts of two ends of the cathode wall 3, and the anode cover 2, the cathode bottom 7 and the cathode wall 3 enclose a three-dimensional electric field repairing region 5. In this embodiment: the anode rotating shaft 1 and the cathode wall 3 are both arranged along the vertical direction, and the anode cover 2 and the cathode bottom 7 are both arranged along the horizontal direction; the cathode wall 3 is of a porous structure, and an adsorption ring 4 is arranged on the outer side of the cathode wall 3. The outer side of the anode cover is provided with an insulating layer 10, and the specific material of the insulating layer refers to the prior art.

The positive pole pivot 1 with 3 concentric axial settings of negative pole wall, just positive pole pivot 1 runs through installation through-hole activity on the positive pole lid 2 sets up, specifically is: the anode cover 2 is movably arranged on the anode rotating shaft 1 and can move up and down along the vertical direction.

The rotating blades 6 are arranged on the anode rotating shaft 1 and are positioned in the three-dimensional electric field repairing area 5, and specifically comprise: the rotating blades 6 are detachably arranged on the anode rotating shaft 1;

the first power supply 8 is a power supply arranged in the horizontal direction, and the second power supply 9 is a power supply arranged in the vertical direction. The anode rotating shaft 1 is connected with the anode of a first power supply 8, and the cathode wall 3 is connected with the cathode of the first power supply 8; the anode cover 2 is connected with the anode of a second power supply 9, and the cathode bottom 7 is connected with the cathode of the second power supply 9.

In this embodiment, the three-dimensional electric field repairing region 5 is filled with an electrocatalyst, and the preparation method of the electrocatalyst includes the following steps:

suspension i was prepared, specifically: mixing silica and water according to a ratio of 20 g: 100 ml of the mixture is mixed and stirred to prepare suspension I;

the biological carbon vitrification specifically comprises the following steps: adding straw biochar into the suspension I, stirring, drying, and burning to obtain vitrified biochar at 1750 ℃;

preparation of suspension II: mixing polyethylene glycol and water according to a volume ratio of 1: 0.7, mixing to prepare a polyethylene glycol solution, adding ferric oxide into the polyethylene glycol solution, and stirring to prepare a suspension II; wherein the mass of the ferric oxide is as follows: the volume ratio of the polyethylene glycol solution is 1 g: 100 ml of the solution;

adding the obtained vitrified biochar into the suspension II, and firing at the constant temperature of 800 ℃ to obtain vitrified biochar with electrocatalytic performance, wherein: quality of vitrified biochar: the volume of suspension ii was 1 g: 50 ml.

This embodiment is further preferredThe preparation of the biomass charcoal comprises the following steps: crushing biological straws, soaking in an oxidizing solution, cleaning, and drying to obtain treated straws; carbonizing the treated straws under the protection of nitrogen, cooling, grinding and sieving to obtain straw biochar; wherein: the mass content of hydrogen peroxide in the oxidizing solution is 20%, the soaking time is 1 hour, the drying temperature is 60 ℃, and the drying time is 10 hours; the purity of nitrogen is 96 percent, the heating rate is 15 ℃ per minute, the carbonization temperature is 400 ℃, the carbonization time is 1 hour, and the number of sieving meshes is 12 meshes; suspension I was prepared specifically as follows: mixing silicon dioxide with the diameter of 8 microns with water, ultrasonically oscillating for 2 hours, and magnetically stirring for 1 hour at the speed of 240 revolutions per minute to prepare suspension I; the biological carbon vitrification specifically comprises the following steps: after adding straw biochar into the prepared suspension I, carrying out ultrasonic oscillation, magnetic stirring, filtering and drying, and firing at constant temperature for 0.5 hour under the protection of argon to prepare vitrified biochar, wherein: the ultrasonic oscillation time is 1 hour, the magnetic stirring speed is 180 revolutions per minute, the magnetic stirring time is 1 hour, the drying temperature is 60 ℃, and the drying time is 12 hours; adding the vitrified biochar into the suspension II, performing ultrasonic oscillation for 0.5 hour, filtering, drying, and firing at constant temperature for 0.6 hour under the protection of nitrogen to prepare vitrified biochar with electrocatalysis performance; the drying temperature is 60 ℃, and the drying time is 10 hours; among the vitrified biochar having electrocatalytic properties: the particle diameter of the biochar is 1mm, the loading capacity of ferric oxide is 0.6mol/g, the loading capacity of silicon dioxide is 1.0mol/g, and the volume weight is 0.20g/cm ³ The total porosity was 45%.

In this embodiment, the anode rotating shaft 1, the anode cover 2, the cathode wall 3 and the cathode bottom 7 form a three-dimensional electric field; the anode rotating shaft, the anode cover, the cathode wall and the cathode bottom form a three-dimensional electric field; the anode rotating shaft and the anode cover are anodes, the cathode wall and the cathode bottom are cathodes, and the electro-catalyst dispersed in the three-dimensional electric field repairing area forms an induction third pole.

In the preferred embodiment, the anode rotating shaft 1 is a titanium-based material, wherein the mass fraction of titanium is 92%, the diameter is 2cm, and the height is 100 cm; the rotating blades 6 are made of stainless steel materials, and the radius of the rotating blades is 45 cm; the cathode wall 3 is made of stainless steel, the radius is 50cm, the height is 80cm, the pore density of the cathode wall 3 is 70%, and the pore diameter is 0.18 cm; the anode cover 2 is made of a titanium-based material, the titanium-based material is a titanium plate, the mass fraction of titanium in the titanium plate is 92%, and the radius is 49 cm; the cathode bottom 7 is made of stainless steel and has a radius of 59 cm; the thickness of adsorption ring 4 is 10cm, and the height is 80cm, and the adsorption ring is filled with sponge and adsorption liquid, and further preferred: the adsorption solution is at least one of 0.06mol/L nitric acid solution, 0.1mol/L acetic acid solution, 6mmol/L ethylene diamine tetraacetic acid, 5mmol/L N, N-dicarboxymethylalanine trisodium salt, 0.4mol/L citric acid and 0.5mol/L oxalic acid (here, 0.06mol/L nitric acid solution is preferred); the first power supply 8 and the second power supply 9 are both one of a direct current power supply and a programmable direct current power supply, and the voltage provided by the programmable direct current power supply is a square wave pulse voltage, and further preferably: the maximum current of the direct current power supply is less than or equal to 1.5A; the pulse amplitude of the square wave pulse voltage is + 0.5V- +2.5V, the pulse width is 1 s-4 s, and the pulse period is 2 s-9 s.

The electric remediation device for the polluted soil comprises the following steps:

step one, preparing composite contaminated soil to be repaired, specifically sieving the composite contaminated soil to be repaired for later use, wherein the diameter of a sieved sieve pore is 2 cm; the heavy metal-organic matter combined polluted soil to be repaired is clay artificially added with heavy metals and organic matters, wherein: the heavy metal pollutants added in the embodiment are manganese, zinc, cadmium and lead; the organic pollutant is pyrene;

step two, taking down the anode cover 2, and installing the rotating blade 6 at the bottom end of the anode rotating shaft 1; placing the composite polluted soil to be repaired prepared in the first step into a three-dimensional electric field repairing area 5; the anode rotating shaft 1 drives the rotating blades 6 to stir to obtain a mixture I, so that the composite soil to be treated and the electrocatalyst are uniformly mixed, and the mass of the added electrocatalyst accounts for 10% of the sum of the dry weight of the electrocatalyst and the composite polluted soil to be repaired; taking out the rotating blade 6 and the anode rotating shaft 1 from the three-dimensional electric field repairing area 5 to rotateThe blade 6 is dismounted from the anode rotating shaft 1; the particle size of the electrocatalyst is 1-2 mm (after the electrocatalyst is sieved by a 10-mesh sieve, undersize is taken out, the obtained undersize is sieved by a 18-mesh sieve, and the screened contents are taken), the loading capacity of the ferric oxide is 0.6mol/g, the loading capacity of the silicon dioxide is 0.9mol/g, and the volume weight is 0.19g/cm ³ Total porosity 46%;

step three, adjusting the water content of the mixture I obtained in the step two to obtain a mixture II; compacting the mixture II (filling height 50cm) by means of an anode cap 2; inserting the anode rotating shaft 1 into the three-dimensional electric field repairing area 5 through the anode cover 2; connecting the anode rotating shaft 1, the anode cover 2, the cathode wall 3 and the cathode bottom 7 with a first power supply 8 and a second power supply 9 respectively;

step four, adding an adsorption liquid into the adsorption ring 4 filled with the sponge, starting the first power supply 8 and the second power supply 9 simultaneously, and repairing to obtain the soil after repairing, wherein: the ratio of the average voltage of the first power supply 8 to the average voltage of the second power supply 9 is 1: 0.4.

preferably, in the second step, the stirring speed of the rotating blade 6 driven by the anode rotating shaft 1 is 70 revolutions per minute, and the stirring time is 0.25 hour; the water content of the mixture II in the third step is 30 percent; when repairing is carried out in the fourth step: the first power supply 8 and the second power supply 9 are both of sandisk HSPY-120-01 type, the electric field intensity of a vertical electric field is 1V/cm, and the repair time is 4 days.

Examples 2 to 3:

example 2 differs from example 1 only in that: the mass of the added electrocatalyst accounts for 2% of the sum of the dry weight of the electrocatalyst and the dry weight of the composite contaminated soil to be repaired; the ratio of the average voltage of the first power supply 8 to the average voltage of the second power supply 9 is 1: 0.2.

example 3 differs from example 1 only in that: the mass of the added electrocatalyst accounts for 15% of the sum of the dry weight of the electrocatalyst and the composite contaminated soil to be repaired; the ratio of the average voltage of the first power supply 8 to the average voltage of the second power supply 9 is 1: 0.8.

comparative example 1:

the two-dimensional electric repairing device filled with the traditional charcoal adsorption column in the comparative example.

The basic components and dimensions of the device are the same as in example 1, except that: the device of the embodiment does not have an anode cover 2, an adsorption ring 4, a rotating blade 6, a second power supply 9 and an insulating layer 10, only soil to be treated is added in an electric field restoration area, an adsorption column 11 filled with traditional biochar is placed in the electric field restoration area, the adsorption column is made of stainless steel, six groups of adsorption columns are arranged in the device of the embodiment, the center of each group of adsorption columns is 20cm away from the center of the bottom of the device, and six adsorption columns are arranged in a plum blossom shape; the radius of the adsorption column is 3cm, and the height of the adsorption column is consistent with the soil filling height, which is shown in detail in figures 3-4.

Comparative example 2:

the three-dimensional electric repairing device filled with the traditional charcoal adsorption column in the comparative example.

The basic components and dimensions of the device are the same as in example 1, except that: the device of the embodiment does not have the adsorption rings 4 and the rotating blades 6, only soil to be treated is added in the three-dimensional electric field restoration area 5, the adsorption columns 11 filled with traditional biochar are placed in the three-dimensional electric field restoration area, the adsorption columns are made of stainless steel materials, six groups of adsorption columns are arranged in the device, the center of each group of adsorption columns is 20cm away from the circle center of the bottom of the device, and each group of adsorption columns is provided with six adsorption columns which are all arranged in a plum blossom shape; the radius of the adsorption column is 3cm, and the height of the adsorption column is consistent with the soil filling height; the top and the bottom of the adsorption column are provided with insulating rubber to prevent direct connection with the anode cover and the cathode bottom after being electrified, which is detailed in figures 5, 6 and 7.

Comparative example 3:

the two-dimensional electric field electric repairing device for uniformly dispersing the electrocatalytic biochar in the comparative example.

The basic components and dimensions of the device are the same as in example 1, except that: the device of this example does not have an anode cover 2, a second power supply 9 and an insulating layer 10, see in detail fig. 8; the filling height of the soil to be treated was 50 cm.

Comparative examples 4 to 6:

comparative example 4 differs from example 1 only in that: the ratio of the average voltage of the first power supply 8 to the average voltage of the second power supply 9 is 1: 0.1.

comparative example 5 differs from example 1 only in that: the ratio of the average voltage of the first power supply 8 to the average voltage of the second power supply 9 is 1: 0.9.

comparative example 6 differs from example 1 only in that: the ratio of the average voltage of the first power supply 8 to the average voltage of the second power supply 9 is 1: 1.1.

the tests were carried out using examples 1 to 3 and comparative examples 1 to 6, as follows:

the soil used in the experiment is artificial composite contaminated soil, and in the contaminated soil: the manganese content is 400mg/kg, the cadmium content is 400mg/kg, the zinc content is 400mg/kg, the lead content is 400mg/kg, and the pyrene content is 20 mg/kg.

Extracting heavy metals in different forms in soil by adopting a BCR four-step continuous extraction method to extract weak acid in an extraction state, an oxidizable state, a reducible state and a residue state, wherein the specific extraction method is shown in Table 1; then, the measurement was carried out by the ICP-OES method.

TABLE 1 BCR four-step continuous extraction method

The contaminated soil is filled into examples 1 to 3 and comparative examples 1 to 6 for remediation, and the concrete filling method is shown in example 1.

The contents of manganese, cadmium, zinc, lead and pyrene in the repaired soil are shown in the following tables 2-3.

Table 2 Total amount of heavy metals and content of each form

TABLE 3 contaminant removal Rate for each example

The heavy metal in the ionic state can be directly removed through the action of an electric field, but the relatively stable oxidizable state and the reducible state are difficult to directly remove under the action of the electric field, and the aim of quickly removing the heavy metal can be achieved only by converting the oxidizable state and the reducible state into the ionic state, so that the key for quickly converting the oxidizable state and the reducible state into the ionic state becomes heavy metal pollution treatment. According to the study of the invention, the following were:

as can be seen from tables 2 and 3, the soil treated in example 1 has a significantly reduced C2 state and a significantly improved C3 state of Mn, Cd, Zn, and Pb, and the removal rate of each metal is significantly improved, as compared with the soil treated in comparative example 1, and it is seen that the electric repairing apparatus according to the present invention has a significantly improved effect as compared with the conventional two-dimensional electric repairing apparatus.

As can be seen from Table 2: the soil treated in the example 1 has obviously reduced C2 state and C3 state compared with the soil treated in the comparative example 2. The results show that, although example 1 and comparative example 2 are three-dimensional electric fields, the biochar added to the metal adsorption column in comparative example 2 cannot exert a catalytic effect due to the electrostatic shielding effect, and can only adsorb heavy metals. Although the oxidizable state and the reducible state can be converted into the ionic state under the energization condition, the amount of conversion at the same time is small as can be seen from table 2. The surface of the electrocatalytic biochar dispersed in the soil forms a negative and positive bipolar under the action of an electric field, and a catalyst loaded on the surface of the anode biochar catalyzes and generates hydroxyl radicals (. OH); the cathode biochar indirectly catalyzes hydrogen peroxide to generate hydroxyl radicals (. OH). The hydroxyl free radical (. OH) can activate metals and catalyze the heavy metals in the soil to rapidly convert from an oxidizable state and a reducible state to an ionic state, thereby improving the remediation efficiency.

As can be seen from table 2: compared with the soil treated by the comparative example 3, the soil treated by the embodiment 1 has obviously reduced C2 state and C3 state of Mn, Cd, Zn and Pb. The results show that although the electrocatalysts are uniformly mixed in the composite soil to be treated in the example 1 and the comparative example 3, the electric field in the vertical direction is formed between the anode cover and the cathode bottom after the electrification in the example 1, the electrode blind areas above and below the biochar are reduced, the generation of hydroxyl radicals is increased, once the hydroxyl radicals are formed, a series of radical chain reactions are induced, organic substances are oxidatively decomposed, and finally, the hydroxyl radicals are degraded into water, carbon dioxide and trace inorganic salts, and the reaction rate is high; meanwhile, the heavy metal in the soil can be catalyzed to be converted from an oxidizable state and a reducible state to an ionic state, and the removal rate of the heavy metal is improved.

As can be seen from Table 3, compared with the soil treated in the comparative example 1, the removal rate of Mn, Cd, Zn and Pb in the soil of the comparative example 2 is improved by 8-9.33%, and the removal rate of pyrene is improved by 15%, and the result shows that the three-dimensional electric field can accelerate the conversion and migration of pollutants in the soil by using the adsorption column filled with common biochar in the same time, so that the removal rate of the pollutants in the soil is improved; compared with the soil treated by the comparative example 3, the removal rate of Mn, Cd, Zn and Pb in the soil in the embodiment 1 is improved by 12.15-20.42%, and the removal rate of pyrene is improved by 2.5%.

As can be seen from tables 2 and 3, the removal rates of Mn, Cd, Zn and Pb in the soils treated in examples 1 to 3 are different from 0.07% to 0.32%, and the relative standard deviation is 0.06% to 0.28% (standard deviation/mean); the difference of the removal rate of pyrene is 1%, and the relative standard deviation is 0.7%. The C2 state difference of Mn, Cd, Zn and Pb in the treated soil accounts for 0.175-0.3% of the total amount of the original soil, and the relative standard deviation is 1.45-2.68% (standard deviation/mean); the difference of the C3 state accounts for 0.175-0.55% of the total amount of the original soil, and the relative standard deviation is 0.65-1.51% (standard deviation/mean). The results show that the soil treated by the soil treatment methods of the examples 1 to 3 has no obvious difference in the removal rate of heavy metals and organic matters and the conversion of the heavy metal forms, and the ratio of the average voltage of the first power supply 8 to the average voltage of the second power supply 9 is (1: 0.2) - (1: 0.8), and has no obvious influence on the removal of the heavy metals and the organic matters and the conversion of the heavy metal forms.

As can be seen from tables 2 and 3, the difference of the removal rates of Mn, Cd, Zn and Pb in the soil treated by the example 1 and the soil treated by the comparative examples 5-6 is 13.48-21.97%, and the difference of the removal rates of pyrene is 2.5%; the C2 state difference of Mn, Cd, Zn and Pb in the treated soil accounts for 8.2-12.35% of the total amount of the original soil, and the C3 state difference accounts for 3.68-9.58% of the total amount of the original soil. The results show that since the ratio of the average voltage of the first power source 8 to the average voltage of the second power source 9 in comparative examples 5 to 6 exceeds 1: 0.8, the migration speed of heavy metals and organic matters in the vertical direction is too high, and the heavy metals and the organic matters are concentrated at the bottom of the device, so that the removal of the heavy metals and the organic matters and the transformation of the forms of the heavy metals are not facilitated.

As can be seen from tables 2 and 3, the removal rates of Mn, Cd, Zn and Pb in the soil treated by the example 1 and the soil treated by the comparative example 4 are different from 10.58 to 16.77 percent, and the removal rate of pyrene is different from 1.5 percent; the C2 state difference of Mn, Cd, Zn and Pb in the treated soil accounts for 6.05-9.7% of the total amount in the original soil, and the C3 state difference accounts for 2.23-7.15% of the total amount in the original soil. The results show that since the ratio of the average voltage of the first power supply 8 to the average voltage of the second power supply 9 in comparative example 4 is less than 1: 0.2, the migration speed of heavy metals and organic matters in the vertical direction is too slow, and the heavy metals and the organic matters are concentrated on the upper part of the device, so that the removal of the heavy metals and the organic matters and the transformation of the forms of the heavy metals are not facilitated.

By combining examples 1 to 3 and comparative examples 4 to 6, it can be seen that: the ratio of the average voltage of the first power supply 8 to the average voltage of the second power supply 9 is (1: 0.2) - (1: 0.8) to promote the migration of the pollutants, thereby improving the removal efficiency and the conversion efficiency of the pollutants; the ratio of the average voltage of the first power supply 8 to the average voltage of the second power supply 9 is too high or too low to facilitate the removal and conversion of the contaminants.

In conclusion, by adopting the technical scheme of the invention, the electrified anode rotating shaft and the electrified cathode wall form an electric field in the horizontal direction, so that the biochar forms a negative and positive pole in the horizontal direction in the soil, and has the capability of direct oxidation and reduction; the electrified anode cover and the electrified cathode bottom form an electric field in the vertical direction, so that the defect that upper and lower parts of the biochar have blind areas is overcome, the redox capability of the biochar is improved, and pollutants can be directly and rapidly oxidized and reduced; in addition, under the action of an electric field and electrocatalysis biochar, the conductivity of soil is increased, the resistance is reduced, and the migration rate of pollutants is improved, so that the repair rate of composite pollution is accelerated.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The three-dimensional electric remediation device for the polluted soil is characterized by comprising an anode rotating shaft (1), an anode cover (2), a cathode wall (3), an adsorption ring (4), a rotating blade (6), a cathode bottom (7), a first power supply (8) and a second power supply (9);

the anode cover (2) and the cathode bottom (7) are respectively positioned at the end parts of two ends of the cathode wall (3), the anode cover (2), the cathode bottom (7) and the cathode wall (3) enclose a three-dimensional electric field repairing region (5), and an electrocatalyst is filled in the three-dimensional electric field repairing region (5); an adsorption ring (4) is arranged on the outer side of the cathode wall (3); the electrocatalyst is vitrified biological charcoal with electrocatalysis performance, and in the vitrified biological charcoal with electrocatalysis performance: the grain diameter of the biochar is 1 mm-2 mm, the loading capacity of ferric oxide is 0.4 mol/g-0.8 mol/g, the loading capacity of silicon dioxide is 0.6 mol/g-1.2 mol/g, and the volume weight is 0.15g/cm ³ ～0.21g/cm ³ The total porosity is 37% -57%;

the anode rotating shaft (1) and the cathode wall (3) are concentrically and axially arranged, and the anode rotating shaft (1) penetrates through the mounting through hole in the anode cover (2) to be movably arranged; the rotating blade (6) is arranged on the anode rotating shaft (1) and is positioned in the three-dimensional electric field repairing region (5);

the anode rotating shaft (1) is connected with the anode of a first power supply (8), and the cathode wall (3) is connected with the cathode of the first power supply (8); the anode cover (2) is connected with the anode of a second power supply (9), and the cathode bottom (7) is connected with the cathode of the second power supply (9); the ratio of the average voltage of the first power supply (8) to the average voltage of the second power supply (9) is 1: (0.2-0.8);

the anode rotating shaft (1), the anode cover (2), the cathode wall (3) and the cathode bottom (7) form a three-dimensional electric field; the anode rotating shaft (1) and the anode cover (2) are anodes, the cathode wall (3) and the cathode bottom (7) are cathodes, and the electrocatalysts dispersed in the three-dimensional electric field repairing area (5) form an induction third pole with cathode and anode properties.

2. The three-dimensional electro-kinetic repair device of claim 1, wherein the method of preparing the electro-catalyst comprises the steps of:

the biological carbon vitrification specifically comprises the following steps: adding the straw biochar into the suspension I, stirring, drying and firing to obtain vitrified biochar, wherein the firing temperature is 1750-2150 ℃;

adding the obtained vitrified biochar into the suspension II, and sintering at the constant temperature of 600-800 ℃ to obtain vitrified biochar with electrocatalysis performance, wherein: quality of vitrified biochar: the volume of suspension ii was 1 g: 10-60 ml.

3. The three-dimensional electro-kinetic repair device of claim 2,

the preparation of the biomass charcoal comprises the following steps: crushing biological straws, soaking in an oxidizing solution, cleaning, and drying to obtain treated straws; carbonizing the treated straws under the protection of nitrogen, cooling, grinding and sieving to obtain straw biochar; wherein: the mass content of the hydrogen peroxide in the oxidizing solution is 15-30%, the soaking time is 0.5-2 hours, the drying temperature is 50-60 ℃, and the drying time is 8-12 hours; the purity of nitrogen is 95-99%, the heating rate is 12-17 ℃ per minute, the carbonization temperature is 300-500 ℃, the carbonization time is 0.5-1 hour, and the number of sieving meshes is 10-16 meshes;

adding the vitrified biochar into the suspension II, performing ultrasonic oscillation for 0.25-0.5 hour, filtering, drying, and firing at constant temperature for 0.4-0.6 hour under the protection of nitrogen to prepare vitrified biochar with electrocatalysis performance; the drying temperature is 50-60 ℃, and the drying time is 8-12 hours.

4. The three-dimensional electro-kinetic repair device according to claim 1, characterized in that the anode shaft (1) and the cathode wall (3) are both arranged in a vertical direction, and the anode cover (2) and the cathode bottom (7) are both arranged in a horizontal direction; the rotating blades (6) are detachably arranged on the anode rotating shaft (1); the anode cover (2) is movably arranged on the anode rotating shaft (1) and can move up and down along the vertical direction; the cathode wall (3) is of a porous structure; the first power supply (8) is arranged along the horizontal direction, and the second power supply (9) is arranged along the vertical direction.

5. The three-dimensional electro-kinetic repair device according to any of the claims 1 to 4, characterized in that the anode rotating shaft (1) is a titanium-based material, wherein the mass fraction of titanium is 86-99%; the rotating blades (6) are made of stainless steel; the cathode wall (3) is made of stainless steel, the pore density of the cathode wall (3) is 20-70%, and the pore size is 0.05-0.18 cm; the anode cover (2) is made of a titanium-based material, the titanium-based material is a titanium plate, and the mass fraction of titanium in the titanium plate is 86-99%; the cathode bottom (7) is made of stainless steel; sponge and adsorption liquid are filled in the adsorption ring (4); the first power supply (8) and the second power supply (9) are both one of a direct current power supply and a programmable direct current power supply, and the voltage provided by the programmable direct current power supply is square wave pulse voltage.

6. The three-dimensional electrokinetic repair device of claim 5, wherein the adsorption solution is at least one of a nitric acid solution of 0.01mol/L to 0.1mol/L, an acetic acid solution of 0.01mol/L to 0.2mol/L, ethylenediaminetetraacetic acid of 4mmol/L to 7mmol/L, N-dicarboxymethylalanine trisodium salt of 4mmol/L to 7mmol/L, citric acid of 0.1mol/L to 0.4mol/L, and oxalic acid of 0.1mol/L to 0.5 mol/L;

7. A method for electrokinetic remediation of contaminated soil using the three-dimensional electrokinetic remediation device of any one of claims 1 to 6, comprising the steps of:

step one, preparing composite contaminated soil to be repaired; the type of the composite contaminated soil to be repaired is heavy metal-organic matter composite contamination, wherein: the heavy metal contaminants include at least one of manganese, zinc, cadmium, thallium, arsenic, lead and copper; the organic pollutant comprises at least one of pyrene, dichlorodiphenyl, chlordane, heptachlor, toxaphenol, hexachlorobenzene and polychlorinated biphenyl;

step two, taking down the anode cover (2), and installing the rotating blade (6) at the bottom end of the anode rotating shaft (1); putting the composite polluted soil to be restored prepared in the step one into a three-dimensional electric field restoration area (5); the anode rotating shaft (1) drives the rotating blades (6) to stir to obtain a mixture I, so that the composite soil to be treated and the electrocatalyst are uniformly mixed, and the mass of the added electrocatalyst accounts for 2% -15% of the sum of the dry weight of the electrocatalyst and the composite polluted soil to be repaired; taking the rotating blade (6) and the anode rotating shaft (1) out of the three-dimensional electric field repairing area (5), and detaching the rotating blade (6) from the anode rotating shaft (1);

step three, adjusting the water content of the mixture I obtained in the step two to obtain a mixture II; compacting the mixture II by using an anode cover (2); inserting the anode rotating shaft (1) into the three-dimensional electric field repairing area (5) through the anode cover (2); the anode rotating shaft (1), the anode cover (2), the cathode wall (3) and the cathode bottom (7) are respectively connected with a first power supply (8) and a second power supply (9);

and step four, adding an adsorption liquid into the adsorption ring (4) filled with the sponge, starting the first power supply (8) and the second power supply (9) at the same time, and repairing to obtain the soil after repairing.

8. The electric restoration method according to claim 7, wherein in the second step, the rotating blade (6) is driven by the anode rotating shaft (1) to rotate at a stirring speed of 60-80 rpm for 0.2-0.3 hours; the water content of the mixture II in the third step is 25-35 percent; when repairing is carried out in the fourth step: the electric field intensity of the first power supply (8) and the second power supply (9) is 1V/cm-3V/cm; the repair time is 3-5 days.