Use method and preparation method of sludge repair film with sandwich structure

Abstract

The invention provides a use method and a preparation method of a sludge repair film with a sandwich structure, the composite sludge repair film comprises a heating conductive layer, an adsorption layer and a capillary layer which are sequentially overlaid, on one hand, the heating conductive layer can convert solar energy into heat energy through photo-thermal conversion to heat a sludge surface layer and enhance the capillary transpiration effect of sludge, and on the other hand, the adsorption layer can adsorb the sludge; the sludge moisture content is reduced, and heavy metal pollutants are promoted to migrate to the sludge surface layer; on the other hand, the heating conductive layer can serve as an electrode material for electrodynamic force in-situ remediation of the heavy metal polluted sludge, electric energy is provided through the solar cell panel, an electric field is formed in the sludge, and directional migration and enrichment of heavy metal in the sludge are accelerated. The film can be used for sludge treatment and removal of heavy metals in sludge, and has the characteristics of good repair effect, environmental protection and high efficiency.

Description

Technical Field

[0001] The present invention relates to the field of harmless treatment of municipal sludge, and particularly relates to a method for using and a method for preparing a sludge repair film with a sandwich structure. Background Art

[0002] Sludge is a semi-solid or solid substance generated in the process of sewage treatment and is the product of sewage treatment. The sludge in urban sewage treatment plants mainly comes from process links such as primary sedimentation tanks and secondary sedimentation tanks.

[0003] Currently, the disposal methods of sludge include land use, landfill, incineration, building material utilization, etc. According to the research report of Weber Consulting, it is expected that by 2025, the proportion of land use will be 20 - 25%, the proportion of landfill will be 30 - 35%, the proportion of incineration will be 25 - 30%, and the proportion of building material utilization will be 10 - 15%. With the increasingly tight land resources, the continuous rise of energy prices and the continuous decline of the building material industry, landfill, incineration and building material utilization cannot fully realize the resource utilization of sludge. Therefore, land use is likely to become the best way to large-scale consume sludge in the future because it conforms to the development direction of pollution reduction, carbon reduction and resource recycling. If the sludge contaminated by heavy metals can be effectively treated, considering that the sludge itself contains rich organic matter, nitrogen, phosphorus, potassium and other fertilizer elements as well as various minerals, the land use of the harmless treated sludge can enhance soil fertility, improve soil structure and promote plant growth. Summary of the Invention

[0004] The main purpose of the present invention is to provide a method for using and a method for preparing a sludge repair film with a sandwich structure to solve the problems in the above background art.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows: The steps are as follows: S1. Uniformly pre-bury multiple columns of electrode rods in the repair site, and connect the electrode rods to the positive pole of the power supply system; S2. Use construction machinery to evenly spread the sludge on the repair site, and on this basis, use a ridging machine to form semi-circular sludge ridges. The center of the bottom of the sludge ridges is the pre-buried electrode rods; S3. Unfold and cover the composite sludge repair film on the sludge ridges. The composite sludge repair film includes a heating and conductive layer, an adsorption layer and a capillary layer stacked in sequence. Both sides of the composite sludge repair film extend along the sludge ridges to the ridge trenches and cover and compact the sludge, so that the bottom capillary layer is closely attached to the sludge; S4. Paste a conductive copper foil at the end of the heating and conductive layer on the composite sludge repair film and connect it to the negative pole of the power supply system; S5. During the repair process, the moisture content of the sludge is continuously monitored. One cycle is 15 to 22 days. After each cycle of repair is completed, the composite sludge repair film is rolled up and stored for use in the next cycle. The specific number of cycles is determined according to the degree of sludge pollution. If the composite sludge repair film is saturated with adsorption and the repair effect is not good, a new composite sludge repair film is replaced to continue repairing the sludge.

[0006] Preferably, the power supply system is a solar power generation system, the output current of the solar power generation system is direct current, the voltage is 24V, the current is 10mA, the positive electrode is connected to the electrode rod, and the negative electrode is connected to the heating conductive layer in the composite sludge remediation film.

[0007] Preferably, under sunlight, the black composite sludge remediation film converts solar energy into heat energy, heats the sludge, generates transpiration pulling force, thereby driving the capillary water-conducting structure of the capillary layer to continuously supply water upward, generating water power, and at the same time, under the action of the electric field, the heavy metal ions in the sludge move toward the cathode of the composite sludge remediation film, generating electric power; Under the dual effects of hydrodynamics and electrodynamics, heavy metals are captured by the adsorption layer of the composite sludge remediation film, and water evaporates through the composite sludge remediation film, thereby achieving the purpose of removing heavy metals from the sludge and drying the sludge.

[0008] Preferably, the sludge spread on the remediation site is 5 to 10 cm thick, the sludge ridge is 20 cm high, and the electrode rods pre-buried in the sludge ridge are evenly arranged at intervals of 60 to 80 cm.

[0009] A method for preparing a sludge remediation film with a sandwich structure, wherein the composite sludge remediation film comprises a heating conductive layer, an adsorption layer and a capillary layer which are sequentially stacked, the heating conductive layer is a polypyrrole / cotton composite fabric flexible film, the adsorption layer is a modified natural fiber heavy metal adsorption flexible film, and the capillary layer is a capillary enhanced fiber fabric film; The heating conductive layer, the adsorption layer and the capillary layer are stacked in sequence and then welded and fixed into shape by an ultrasonic welding process.

[0010] Preferably, the heating conductive layer is a black porous polypyrrole / cotton composite fabric flexible film made by chemical vapor deposition CVD technology, and the preparation steps are as follows: Pyrrole (>97%) was selected as the polymerization monomer, anthraquinone-2,6-disulfonic acid sodium salt (>97%) was selected as the dopant, and ferric chloride hexahydrate (98%) was selected as the catalyst, and the mass ratio of the three was 1:9:1.67; Prepare a pyrrole monomer solution with a concentration of 0.004 - 0.149 mol / L. Wash the cotton cloth with clean water, soak it in a solution of ferric chloride hexahydrate and anthraquinone-2,6-disulfonic acid sodium salt, and stir (at 130 rpm) for 30 minutes. Then add the prepared pyrrole monomer solution and polymerize at room temperature (27°C) for 15 hours. Take out the cotton cloth after the reaction, fix it on a glass plate, and rinse it with washing water containing 1 g / L detergent prepared with deionized water for 30 minutes to remove the excess polymer on the surface of the cotton cloth, thereby generating a black conductive coating of polypyrrole (PPY) on the surface of the cotton cloth. After drying at room temperature, a polypyrrole / cotton cloth composite fabric flexible film is obtained.

[0011] Preferably, the adsorption layer is a modified natural fiber heavy metal adsorption flexible film prepared by using cheap and easily available agricultural and forestry waste rich in cellulose (such as straw, bagasse, cotton, wood chips, bran, rice husk, rice hull) in nature through a chemical modification method. The preparation steps are as follows: Wash the collected agricultural and forestry waste to remove the surface dust with tap water, dry it, and pass it through a 20-mesh sieve. Then directly pyrolyze and carbonize it in a tubular furnace, where the pyrolysis temperature is set at 600°C, the heating rate is 10°C / min, and the constant temperature time is 2 h to obtain biochar. Grind the biochar prepared in the previous step and pass it through a 30 - 50-mesh nylon sieve. Add the sieved biochar to 1 L of 0.1 mol / L NaOH solution, stir it under the condition of water bath heating at 65°C for 48 h, then filter, wash, and dry it to obtain alkalized biochar. Weigh a certain amount of alkalized biochar and add it to a 1% KMnO4 solution by mass concentration and ultrasonically treat it for 30 minutes. Then weigh a certain amount of FeCl3·6H2O and FeSO4·7H2O respectively and add them to the above mixed solution. Continuously stir at 65°C for 30 minutes, then adjust the pH to 11 with 0.1 mol / L NaOH solution, continuously stir for 2 h, then stand and age at 80°C for 12 h, and then wash, filter, and dry it to obtain modified biochar. Weigh an appropriate amount of modified biochar and evenly scatter it on the backing cloth, where the backing cloth is melt-blown cloth, non-woven fabric, or hot air cotton. Cover the upper layer with the same backing cloth. Align the upper base cloth, modified biochar, and lower base cloth, and perform hot pressing and compounding through a pressure roller to bond and fix each layer into one body. After cooling, a modified natural fiber heavy metal adsorption flexible film is obtained.

[0012] Preferably, the capillary layer is a capillary enhanced fiber fabric film processed by a blending process using waste absorbent cotton fabric. The preparation steps are as follows: Wash the waste cotton fabric to remove stains and impurities, crush the washed cotton fabric to make it fibrous, and use a carding machine to further loosen the fibers to ensure that the fibers are loose. The opened cotton fibers are mixed with polyvinyl alcohol fibers and polyacrylamide superabsorbent materials in a certain proportion, and then combed by a carding machine to form a uniform fiber web; The fiber web is subjected to hot pressing treatment by a hot press to obtain a capillary enhanced fiber fabric film.

[0013] The present invention provides a method for using and preparing a sludge repair film with a sandwich structure, and the beneficial effects are as follows: 1. It provides a new path for the repair of heavy metal contaminated sludge, solves the problem of heavy metal pollution in sludge, broadens the sludge disposal path, and fully reduces the potential risk of sludge land use; 2. The composite film has a special sandwich structure and has good electrical conductivity, good adsorption, good water permeability, good heat preservation and good moisture retention; 3. By enhancing the capillary phenomenon of sludge and increasing the electric field effect, the composite film can achieve the dual effects of sludge drying and heavy metal removal from sludge, and has the characteristics of large treatment area, high repair efficiency, simple construction and easy retraction; 3. The main materials of the composite film are recycled and reused from natural agricultural and forestry waste and waste cotton fabrics, and have the characteristics of low repair cost, low carbon and environmental protection; 4. The composite film is applicable to the repair of various heavy metal contaminated sludges and has a wide application range. Description of the Drawings

[0014] The present invention will be further described below with reference to the drawings and embodiments: Figure 1 is the structural diagram of the composite sludge repair film of the present invention; Figure 2 is the working principle diagram of the present invention; In the figure: composite sludge repair film 1; heating and conductive layer 101; adsorption layer 102; capillary layer 103; solar power generation system 2; electrode rod 3; sludge ridge 4. Detailed Embodiments

[0015] Embodiment 1 As Figures 1 - 2 shown, a method for using a sludge repair film with a sandwich structure is as follows: S1. A plurality of electrode rods 3 are uniformly embedded in the repair site, and the electrode rods 3 are connected to the positive pole of the power supply system; the electrode rods 3 can be selected from graphite electrodes or other metal electrodes. The electrode rods 3 are arranged in parallel, with a spacing of 60 - 80 cm, and the electrode rods 3 are uniformly connected to the positive pole of a solar panel with an output voltage of 24V and a direct current output current; S2. Use construction machinery to evenly spread the sludge on the remediation site, and on this basis, use a ridger to form semi-circular sludge ridges 4. The center of the bottom of the sludge ridge 4 is the pre-buried electrode rod 3. The sludge treated by the sludge plant to a moisture content of 70% - 80% is evenly spread on the remediation site to a thickness of 5 - 10 cm. On this basis, use a ridger to form semi-circular sludge ridges 4 with a ridge height of 20 cm. The length of the sludge ridge 4 can be set according to the actual situation, generally set to 10 - 100 m. S3. Unroll the composite sludge remediation film 1 and cover it on the sludge ridge 4. The composite sludge remediation film 1 includes a heating and conductive layer 101, an adsorption layer 102, and a capillary layer 103 stacked in sequence. Both sides of the composite sludge remediation film 1 extend along the sludge ridge 4 to the ridge ditch and cover the sludge and compact it, so that the bottom capillary layer 103 is in close contact with the sludge. S4. Paste a conductive copper foil at the end of the heating and conductive layer 101 on the composite sludge remediation film 1 and connect it to the negative pole of the power supply system. Set the output voltage of the solar panel to 24V and the output current to 10mA, and start remediating the sludge. S5. During the remediation process, continuously monitor the moisture content of the sludge. One cycle is 15 - 22 days. After each cycle of remediation is completed, roll up and store the composite sludge remediation film 1 for use in the next cycle. The specific number of implementation cycles is determined according to the pollution degree of the sludge. If the composite sludge remediation film 1 is saturated with adsorption and the remediation effect is not good, replace the new composite sludge remediation film 1 and continue to remediate the sludge.

[0016] The power supply system is a solar power generation system 2. The output current of the solar power generation system 2 is direct current, the voltage is 24V, and the current is 10mA. The positive pole is connected to the electrode rod 3, and the negative pole is connected to the heating and conductive layer 101 in the composite sludge remediation film 1.

[0017] Under sunlight irradiation, the black composite sludge remediation film 1 converts solar energy into heat energy to heat the sludge, generating a transpiration pull to drive the capillary water-conducting structure of the capillary layer 103 to continuously supply water upward, generating a water power. At the same time, under the action of the electric field, the heavy metal ions in the sludge move towards the cathode of the composite sludge remediation film 1, generating an electric power. Under the dual action of the water power and the electric power, the heavy metals are captured by the adsorption layer 102 of the composite sludge remediation film 1, and the water evaporates through the composite sludge remediation film 1, so as to achieve the purpose of removing heavy metals from the sludge and drying the sludge.

[0018] Example 2 Further described in conjunction with Embodiment 1, a method for preparing a sludge repair film with a sandwich structure, the method is as follows: The composite sludge repair film includes a heating conductive layer, an adsorption layer, and a capillary layer stacked in sequence. The heating conductive layer is a polypyrrole / cotton fabric composite flexible film, the adsorption layer is a modified natural fiber heavy metal adsorption flexible film, and the capillary layer is a capillary enhanced fiber fabric film; After the heating conductive layer, the adsorption layer, and the capillary layer are stacked in sequence, they are welded and fixed into shape through an ultrasonic welding process.

[0019] Preferably, the heating conductive layer is a black porous polypyrrole / cotton fabric composite flexible film made by using chemical vapor deposition (CVD) technology. The preparation steps are as follows: Select pyrrole (>97%) as the polymerization monomer, anthraquinone-2,6-disulfonic acid sodium salt (>97%) as the dopant, and ferric chloride hexahydrate (98%) as the catalyst. The mass ratio of the three is 1:9:1.67; Prepare a pyrrole monomer solution with a concentration of 0.004~0.149 mol / L. Wash the cotton cloth with clean water, soak it in a solution of ferric chloride hexahydrate and anthraquinone-2,6-disulfonic acid sodium salt, stir (130 rpm) for 30 minutes, and then add the prepared pyrrole monomer solution. Polymerize at room temperature (27°C) for 15 hours; Take out the reacted cotton cloth, fix it on a glass plate, and rinse it with washing water containing 1 g / L detergent prepared with deionized water for 30 minutes to remove the excess polymer on the surface of the cotton cloth, thereby generating a black conductive polypyrrole (PPY) coating on the surface of the cotton cloth. After drying at room temperature, a polypyrrole / cotton fabric composite flexible film is obtained.

[0020] Preferably, the adsorption layer 102 is a modified natural fiber heavy metal adsorption flexible film prepared by using cheap and easily available agricultural and forestry waste rich in cellulose (straw, bagasse, cotton, wood chips, bran, rice husk, rice hull) in nature through a chemical modification method. The preparation steps are as follows: Wash the collected agricultural and forestry waste to remove the surface dust with tap water, dry it, and pass it through a 20-mesh sieve. Then directly pyrolyze and carbonize it in a tubular furnace, where the pyrolysis temperature is set at 600°C, the heating rate is 10°C / min, and the constant temperature time is 2 h to obtain biochar; Grind the biochar prepared in the previous step, pass it through a 30~50-mesh nylon sieve, add the sieved biochar to 1 L of 0.1 mol / L NaOH solution, stir it in a water bath at 65°C for 48 h, then filter, wash, and dry it to obtain alkalized biochar; Weigh a certain amount of alkalized biochar and add it to a 1% KMnO4 solution by mass, then perform ultrasonic treatment for 30 min. Next, weigh a certain amount of FeCl3·6H2O and FeSO4·7H2O respectively and add them to the above mixed solution. Continuously stir at 65 °C for 30 min. Then, use 0.1 mol / L NaOH solution to adjust the pH to 11. After continuously stirring for 2 h, stand and age at 80 °C for 12 h, and then wash, filter and dry to obtain modified biochar; Weigh an appropriate amount of modified biochar and evenly scatter it on the backing cloth. The backing cloth is melt-blown cloth, non-woven fabric or hot air cotton. The upper layer is also covered with a backing cloth. Align the upper base cloth, modified biochar, and lower base cloth, and perform hot pressing and compounding through a pressure roller to bond and fix each layer into one body. After cooling, a modified natural fiber heavy metal adsorption flexible film is obtained.

[0021] Preferably, the capillary layer 103 is a capillary enhanced fiber fabric film processed by a blending process using waste absorbent cotton fabric. The preparation steps are as follows: Wash the waste cotton fabric to remove stains and impurities. Crush the washed cotton fabric to make it fibrous, and use a carding machine to further loosen the fibers to ensure that the fibers are loose; Mix the carded cotton fibers with polyvinyl alcohol fibers and polyacrylamide superabsorbent materials in a certain proportion, and comb through a carding machine to form a uniform fiber web; Perform hot pressing treatment on the fiber web through a hot press to obtain a capillary enhanced fiber fabric film.

[0022] Example 3 Simulate the remediation of heavy metal contaminated sludge under natural conditions: Collect an appropriate amount of surplus sludge from a municipal sewage treatment plant, add heavy metal ions for poisoning, and age for 7 days to configure and form simulated heavy metal contaminated sludge (with a water content of about 80%). At the same time, take samples to test the heavy metal content in the simulated heavy metal contaminated sludge.

[0023] Weigh an appropriate amount of simulated heavy metal contaminated sludge, use a mold to ridge the simulated heavy metal contaminated sludge to form a semi-cylindrical ridge block with a radius of 20 cm and a length of 20 cm. Lay a water-proof cloth at the bottom of the ridge block (to prevent the water and pollutants in the sludge from migrating downward). Then, insert a graphite electrode rod along the axis of symmetry direction of the semi-cylinder into the center of the bottom of the ridge block, and connect the graphite electrode to the positive pole of a DC regulated power supply to form an electric field anode.

[0024] Unroll the composite sludge repair film and cover it on the surface of the sludge ridge blocks. The two sides of the film extend along the sludge ridge blocks to the water-proof cloth, and are compacted on both sides to make the repair film closely adhere to the sludge, and the capillary layer of the film is in full contact with the sludge. Then, conductive copper foils with a width of 10 mm are pasted at both ends of the repair film extending to the water-proof cloth, and connected to the negative pole of a DC regulated power supply to form the cathode of the electric field.

[0025] Turn on the full-spectrum solar lamp with a power of 48 W, and set the height of the solar lamp from the top of the sludge ridge blocks to be 50 - 60 cm, and irradiate the simulated heavy metal contaminated sludge ridge blocks covered by the repair film. Turn on the DC regulated power supply, and set the working voltage to 24 V and the working current to 10 mA.

[0026] Set the daily power-on time to 12 h, and the light illumination time is the same as the power-on time. Samples are taken every two days to test the heavy metal content and sludge moisture content in the simulated heavy metal contaminated sludge.

[0027] Through a 16-day indoor simulation experiment, the changes in the heavy metal content in the simulated heavy metal contaminated sludge are as follows in the table:

[0028] In addition, through regular testing of the moisture content in the simulated heavy metal contaminated sludge, the results show that through the 16-day experiment, the moisture content of the simulated sludge has decreased from 85% initially to 72%.

[0029] The above experimental results show that this repair film can effectively reduce the heavy metal content in the simulated heavy metal contaminated sludge, and at the same time, the moisture content of the sludge is also decreasing synchronously.

[0030] Example 4 Repair of heavy metal contaminated sludge under natural conditions: The outdoor experiment was carried out in a certain sunlight drying shed, and the sludge also came from the surplus sludge produced by the factory. After preliminary testing, the cadmium content in this municipal sludge was 3.74 mg / kg, exceeding the requirement of the total cadmium limit of <3 mg / L for Class A sludge products in the "Control Standards for Pollutants in Sludge Used in Agriculture" (GB4284 - 2018) in China. Therefore, the sludge repair film was used to repair it for 15 days, and the specific process is as follows: First, pre-bury aluminum metal electrode bars in the repair site as the repair anode. The electrode bars can be graphite electrodes or other metal electrodes. The electrode bars need to be arranged in parallel, with a spacing of 60 - 80 cm, and the electrode bars are uniformly connected to the positive pole of a solar panel with an output voltage of 24 V and a DC output current.

[0031] Next, use a forklift to evenly spread the sludge processed by the sludge plant to a thickness of about 10 cm with a moisture content of 70% - 80%. On this basis, use a ridging machine to ridge the sludge (ridge height 20 cm) to form semi-circular ridge strips. The center of the bottom of the ridge strip is a pre-buried aluminum metal electrode strip. The length of the ridge strip is set to 10 m, and a total of 5 groups are set.

[0032] Slightly unfold the composite sludge repair film with a special sandwich structure and cover it on the sludge ridge strips. The two sides of the film extend along the sludge ridge strips to the ground furrows and are compacted on both sides to make the repair film closely fit with the sludge (the capillary layer of the film is in full contact with the sludge).

[0033] Paste conductive copper foils with a width of 20 mm at both ends of the composite sludge repair film extending to the furrows, and uniformly connect them to the negative pole of the solar panel to form a repair cathode. Adjust the rectifier, set the output voltage of the solar panel to 24 V, and the output current to 10 mA, and start repairing the sludge.

[0034] Set the daily power-on time to 12 h, regularly take samples, and test the content of heavy metal cadmium in the sludge and the moisture content of the sludge.

[0035] Through 15 days of repair, the content of heavy metals in the sludge decreased from the initial 3.74 mg / L to 0.94 mg / L, and the moisture content of the sludge decreased from the initial 81% to 63%.

[0036] The above results show that the present invention has achieved good results in both removing heavy metals from municipal sludge and reducing the moisture content of sludge.

[0037] The above embodiments are only the preferred technical solutions of the present invention and should not be regarded as limitations on the present invention. The protection scope of the present invention should be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for using a sandwich structure sludge repair film, the method comprising the following steps: S1. Pre-burying multiple rows of electrode rods (3) evenly at the restoration site, and connecting the electrode rods (3) to the positive electrode of the power supply system; S2, using engineering machinery to evenly spread the sludge on the restoration site, and on this basis, using a ridging machine to ridge a semicircular sludge ridge (4), the bottom center of the sludge ridge (4) being the pre-buried electrode rod (3); S3, unfolding the composite sludge remediation film (1) and covering it on the sludge ridge strip (4), the composite sludge remediation film (1) comprising a heating conductive layer (101), an adsorption layer (102) and a capillary layer (103) stacked in sequence, and extending both sides of the composite sludge remediation film (1) along the sludge ridge strip (4) to the ridge ditch and covering the sludge and compacting it, so that the capillary layer (103) at the bottom is closely attached to the sludge; S4, pasting a conductive copper foil on the end of the heating conductive layer (101) on the composite sludge remediation film (1), and connecting it to the negative electrode of the power supply system; S5. During the repair process, the moisture content of the sludge is continuously monitored. A cycle lasts for 15 to 22 days. After each cycle of repair is completed, the composite sludge repair film (1) is rolled up and stored for use in the next cycle. The specific number of cycles is determined according to the degree of sludge contamination. If the composite sludge repair film (1) is saturated with adsorption and the repair effect is poor, a new composite sludge repair film (1) is replaced to continue repairing the sludge.

2. The method for using the sandwich structure sludge remediation film according to claim 1 is characterized by: The power supply system is a solar power generation system (2). The output current of the solar power generation system (2) is direct current, the voltage is 24V, and the current is 10mA. The positive electrode is connected to the electrode rod (3), and the negative electrode is connected to the heating conductive layer (101) in the composite sludge remediation film (1).

3. The method for using the sandwich structure sludge remediation film according to claim 1 is characterized by: Under sunlight, the black composite sludge remediation film (1) converts solar energy into heat energy, heats the sludge, generates transpiration pulling force, and drives the capillary water-conducting structure of the capillary layer (103) to continuously supply water upward, generating hydrodynamic force. At the same time, under the action of the electric field, the heavy metal ions in the sludge move toward the cathode of the composite sludge remediation film (1), generating electrodynamic force. Under the dual effects of hydrodynamic force and electrodynamic force, heavy metals are captured by the adsorption layer (102) of the composite sludge remediation film (1), and water evaporates through the composite sludge remediation film (1), thereby achieving the purpose of removing heavy metals from the sludge and drying the sludge.

4. The method for using the sandwich structure sludge remediation film according to claim 1 is characterized by: The sludge spread on the restoration site is 5 to 10 cm thick, the sludge ridge (4) is 20 cm high, and the sludge ridge (4) is 10 to 100 m long.

5. The method for using the sandwich structure sludge remediation film according to claim 1 is characterized by: The electrode rod (3) is a graphite electrode or a metal electrode.

6. The method for using the sandwich structure sludge remediation film according to claim 1, characterized in that: The electrode rods (3) are evenly arranged at intervals of 60 to 80 cm.

7. A method for preparing a sandwich structure sludge remediation film according to claim 1, wherein the composite sludge remediation film (1) comprises a heating conductive layer (101), an adsorption layer (102) and a capillary layer (103) stacked in sequence, the heating conductive layer (101) is a polypyrrole / cotton composite fabric flexible film, the adsorption layer (102) is a modified natural fiber heavy metal adsorption flexible film, and the capillary layer (103) is a capillary enhanced fiber fabric film; The heating conductive layer (101), the adsorption layer (102) and the capillary layer (103) are stacked in sequence and then welded and fixed into shape by an ultrasonic welding process.

8. A method for preparing a sandwich structure sludge remediation film according to claim 7, wherein the heating conductive layer (101) is a black porous polypyrrole / cotton composite fabric flexible film made by chemical vapor deposition (CVD) technology, and the preparation steps are as follows: Pyrrole was selected as the polymerization monomer, anthraquinone-2,6-disulfonic acid sodium salt was selected as the dopant, and ferric chloride hexahydrate was selected as the catalyst, and the mass ratio of the three was 1:9:1.67; Prepare 0.004~0.149mol / L pyrrole monomer solution, wash the cotton cloth with clean water, soak it in ferric chloride hexahydrate and sodium anthraquinone-2,6-disulfonate solution and stir for 30 minutes, then add the prepared pyrrole monomer solution and polymerize it at room temperature for 15 hours; The cotton cloth after the reaction was taken out and fixed on a glass plate, and rinsed with deionized water containing 1 g / L detergent for 30 minutes to remove excess polymer on the surface of the cotton cloth, thereby producing a layer of polypyrrole black conductive coating on the surface of the cotton cloth. After drying at room temperature, a polypyrrole / cotton cloth composite fabric flexible film was obtained.

9. A method for preparing a sandwich structure sludge remediation film according to claim 7, wherein the adsorption layer (102) is a modified natural fiber heavy metal adsorption flexible film prepared by a chemical modification method using cellulose-rich agricultural and forestry waste as raw materials, and the preparation steps are as follows: The collected agricultural and forestry waste was washed with tap water to remove dust on the surface, dried, and passed through a 20-mesh sieve, and then directly pyrolyzed and carbonized in a tubular furnace, where the pyrolysis temperature was set to 600°C, the heating rate was 10°C min-1, and the constant temperature time was 2h to obtain biochar; The biochar prepared in the previous step was ground and passed through a 30-50 mesh nylon sieve. The sieved biochar was added to 1 L of 0.1 mol / L NaOH solution, and stirred in a 65°C water bath for 48 h. After that, the mixture was filtered, washed and dried to obtain alkaline biochar. A certain amount of alkalinized biochar was weighed and added to a 1% KMnO4 solution for ultrasonic treatment for 30 minutes. Then, a certain amount of FeCl3·6H2O and FeSO4·7H2O were weighed and added to the mixed solution, and stirred at 65°C for 30 minutes. Then, the pH was adjusted to 11 with 0.1 mol / L NaOH solution, and stirred for 2 hours. After that, the mixture was aged at 80°C for 12 hours, and then washed, filtered, and dried to obtain modified biochar. Weigh an appropriate amount of modified biochar and spread it evenly on the backing cloth, which is meltblown cloth, non-woven fabric or hot air cotton. The upper layer is also covered with the backing cloth. The upper base cloth, modified biochar and lower base cloth are aligned and hot-pressed by a pressure roller to bond and fix the layers together. After cooling, a modified natural fiber heavy metal adsorption flexible film is obtained.

10. The method for preparing a sludge remediation film with a sandwich structure according to claim 7, wherein the capillary layer (103) is a capillary-enhanced fiber fabric film made by blending waste absorbent cotton fabric, and the preparation steps are as follows: Wash the waste cotton fabric to remove stains and impurities, break the washed cotton fabric into pieces to make it fiber-like, and use a loosening machine to further loosen the fibers to ensure that the fibers are loose; The opened cotton fibers are mixed with polyvinyl alcohol fibers and polyacrylamide high water-absorbent materials in a certain proportion, and combed by a carding machine to form a uniform fiber web; The fiber web is subjected to heat pressing treatment by a heat press machine to obtain a capillary-reinforced fiber fabric film.

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