Soil remediation device and application thereof

Abstract

The invention relates to the technical field of soil remediation, and discloses a soil remediation device and application thereof. The soil remediation device comprises an anode chamber (1), a cathode chamber (2), a proton exchange membrane (3) and an external circuit, a substrate in the anode chamber (1) contains oxidizing bacteria, the cathode chamber (2) contains reducible substances, the proton exchange membrane (3) is used for separating the anode chamber (1) and the cathode chamber (2), and the external circuit is connected with the anode chamber (1) and the cathode chamber (2). Power lines at two ends of the external circuit are respectively connected with electrodes in the anode chamber (1) and the cathode chamber (2) to form a closed circuit. The device can be used for remediation treatment of organic pollutant and heavy metal contaminated soil, and is high in remediation efficiency, low in treatment cost and free of secondary pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a soil remediation device and application thereof. Background Art

[0002] Heavy metals refer to metals with a specific gravity greater than 5, mainly including copper, lead, zinc, tin, nickel, cobalt, antimony, mercury, cadmium and bismuth. The degree of harm caused by heavy metals depends on their concentration and chemical form. Due to the rapid development of industries such as machinery manufacturing, ore mining, chemical industry, and instrumentation, the current form of soil heavy metal pollution is severe. Heavy metals in the soil will be absorbed by plants, enriched by livestock, and eventually enter the human body through the food chain, thereby inducing various diseases and endangering human health. In addition, heavy metal pollutants will also be discharged into the ocean through river runoff, resulting in excessive levels of heavy metals such as mercury, cadmium, lead, and zinc in the bottom mud, which in turn leads to excessive levels of heavy metals in aquatic products, ultimately affecting human health.

[0003] With the rapid development of agricultural planting, crops are harmed by many pests during their growth, and pesticides are usually sprayed to eliminate pests. However, the large-scale use of pesticides has caused the accumulation of heavy metals in the soil, affecting the balance of the ecological environment for crop growth. Based on the characteristics of insects being phototactic, insecticidal lamps are used to clean up pests, which can effectively kill insects and reduce the pest index.

[0004] In response to the current status of soil pollution, a variety of remediation technologies such as biological, physical and chemical have been developed. In actual applications, physical remediation is affected by factors such as soil heterogeneity and permeability, and chemical remediation will produce more toxic byproducts. However, due to the oxidizing nature of heavy metal wastewater, the existing soil remediation equipment has low remediation efficiency and unsatisfactory remediation effects. Microbial fuel cells (MFCs) are devices that convert chemical energy in organic or inorganic matter into electrical energy. They are a new method of biomass power generation that uses the biocatalytic action of microorganisms to oxidize substrates and release electrons to form current output. The main problem currently is that its output power density is too low. Therefore, there is an urgent need for a new type of soil remediation device to improve the remediation effect of heavy metal contaminated soil. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of high treatment cost, secondary pollution and low soil remediation efficiency in the prior art, and to provide a soil remediation device and its application. The device can be used for the remediation of organic pollutants and heavy metal contaminated soil, with high remediation efficiency, low treatment cost and no secondary pollution.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a soil remediation device, which includes an anode chamber, a cathode chamber, a proton exchange membrane and an external circuit. The substrate in the anode chamber contains oxidizing bacteria, and the cathode chamber contains reducible substances. The proton exchange membrane is used to separate the anode chamber and the cathode chamber. The power lines at both ends of the external circuit are respectively connected to the electrodes in the anode chamber and the cathode chamber to form a closed circuit.

[0007] Preferably, the substrate of the anode chamber is soil containing oxidizing bacteria; the oxidizing bacteria are selected from at least one of Shewanella, Geobacter and Geobacter sulfur-reducing.

[0008] Further preferably, the reducible substance in the cathode chamber is a compound containing reducing metal ions.

[0009] Further preferably, the metal ion is a reducing metal ion, more preferably at least one selected from Cr(VI), Hg(II), Pb(II) and Cd(II);

[0010] The substrate in the cathode chamber is soil containing heavy metal ions.

[0011] Preferably, the electrode in the anode chamber is a carbon felt electrode.

[0012] Preferably, the electrode in the anode chamber is a carbon felt electrode modified with lignin-based carbon nitride; the content of the lignin-based carbon nitride in the carbon felt electrode is 0.1-3wt%, preferably 0.9-1wt%.

[0013] Further preferably, the content of nitrogen atoms in the lignin-based carbon nitride is 0.02-0.04 wt%.

[0014] Preferably, the method for preparing the lignin-based carbon nitride comprises the following steps:

[0015] S1, mixing lignin and urea and calcining to obtain powder I;

[0016] S2, under hydrothermal reaction conditions, mixing the powder I obtained in step S1 with water, and washing and drying to obtain powder II;

[0017] S3, mixing the powder II obtained in step S2 with zinc chloride and carbonizing them to obtain powder III.

[0018] Preferably, in step S1, the calcination conditions at least include: a temperature of 240-260° C. and a time of 6-8 h.

[0019] Further preferably, the mass ratio of lignin to urea is 1:0.1-0.6, preferably 1:0.2-0.3.

[0020] Further preferably, in step S2, the mass ratio of the powder I to water is 0.2-0.5:1; and the conditions of the hydrothermal reaction at least include: a temperature of 120-180°C and a time of 12-14h.

[0021] Further preferably, in step S3, the mass ratio of the powder II to zinc chloride is 1:1-5; and the mixed carbonization conditions at least include: a temperature of 600-900°C and a time of 2-4h.

[0022] Preferably, the method for preparing the lignin-based carbon nitride modified carbon felt electrode comprises the following steps: mixing the powder III obtained in step S3 and polytetrafluoroethylene with a solvent to prepare a suspension, and then contacting the carbon felt with the suspension.

[0023] Further preferably, the concentration of the powder III in the suspension is 8-10 g / L.

[0024] Further preferably, the concentration of the polytetrafluoroethylene is 0.04-0.05 g / L.

[0025] Further preferably, the contacting conditions at least include: a temperature of 30-40° C. and a time of 0.5-1 h.

[0026] Preferably, the substrate of the anode chamber is soil containing oxidizing bacteria; the oxidizing bacteria are selected from at least one of Shewanella, Geobacter and Geobacter sulfur-reducing.

[0027] Preferably, the reducible substance in the cathode chamber is a compound containing a reducing metal ion. Further preferably, the metal ion is a reducing metal ion, more preferably at least one selected from Cr(VI), Hg(II), Pb(II) and Cd(II); and the substrate in the cathode chamber is soil containing heavy metal ions.

[0028] The second aspect of the present invention provides application of the soil remediation device described in the first aspect in power generation equipment.

[0029] Preferably, the power generation device is a microbial fuel cell.

[0030] Preferably, the power generation equipment is a power source for supplying insecticidal lamps.

[0031] The third aspect of the present invention provides the use of the soil remediation device described in the first aspect in removing heavy metals and / or organic pollutants in soil and / or water.

[0032] Preferably, the soil is water sediment containing heavy metal ions.

[0033] Preferably, the heavy metal ion is selected from at least one of Cr(VI), Hg(II), Pb(II) and Cd(II), and the organic pollutant is phenol.

[0034] Through the above technical solution, the beneficial effects of the present invention are:

[0035] The anode chamber of the soil remediation device provided by the present invention utilizes the rich oxidizing bacteria microorganisms in the substrate to degrade organic matter, and releases electrons during the decomposition process. The electrons are effectively transferred between the organic matter and the electrode, and are transferred to the cathode through the external circuit to form an electric current, that is, a microbial fuel cell is formed; the reducible substances in the cathode chamber receive electrons to undergo a reduction reaction, and the electric energy generated during the conversion process is used to strengthen or comprehensively optimize the soil remediation device. High-efficiency treatment of organic matter and reducible substances is achieved, with high remediation efficiency, low treatment cost, and no secondary pollution.

[0036] The above-mentioned soil remediation device can also be used as a power generation equipment to provide electricity. As a renewable clean energy for soil remediation / power generation, it is of great significance to the treatment and remediation of heavy metal contaminated soil, the protection of the ecological environment and the protection of human health. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0038] Figure 1 It is a structural schematic diagram of an implementation mode of the soil remediation device of the present invention;

[0039] Figure 2 It is a structural schematic diagram of an implementation method of an external voltage for the soil remediation device of the present invention;

[0040] Figure 3 It is a schematic diagram of the principle of the soil remediation device of the present invention for degrading phenol;

[0041] Figure 4 It is a comparison diagram of phenol degradation under different applied voltage conditions of the soil remediation device of the present invention;

[0042] Figure 5 It is a schematic diagram of the structure of the soil remediation device of the present invention for removing Cr(VI) from sewage;

[0043] Figure 6 It is a schematic diagram of an implementation of the soil remediation device of the present invention as a power generation device;

[0044] Figure 7 is a SEM image of the lignin-based carbon nitride prepared by the present invention.

[0045] Description of Reference Numerals

[0046] 1. Anode chamber; 2. Cathode chamber; 3. Proton exchange membrane; 4. Applied voltage; 5. Constant temperature water bath; 6. Insecticidal lamp. DETAILED DESCRIPTION

[0047] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0048] A first aspect of the present invention provides a soil remediation device, such as Figure 1 As shown, the soil remediation device includes an anode chamber 1, a cathode chamber 2, a proton exchange membrane 3 and an external circuit. The substrate in the anode chamber 1 contains oxidizing bacteria, the cathode chamber 2 contains reducible substances, the proton exchange membrane 3 is used to separate the anode chamber 1 and the cathode chamber 2, and the power lines at both ends of the external circuit are respectively connected to the electrodes in the anode chamber 1 and the cathode chamber 2 to form a closed circuit.

[0049] When the soil remediation device provided by the present invention is working, the anode chamber 1 utilizes the rich oxidizing bacteria microorganisms in the substrate to degrade organic matter, and releases electrons during the decomposition process. The electrons are effectively transferred between the organic matter and the electrode, and are transferred to the cathode through the external circuit to form a current, that is, a microbial fuel cell is formed; the reducible substances in the cathode chamber 2 receive electrons to undergo a reduction reaction, and the electrical energy generated during the conversion process is used to strengthen or comprehensively optimize the soil remediation device. High-efficiency treatment of organic matter and reducible substances is achieved, with high remediation efficiency, low treatment cost, and no secondary pollution.

[0050] According to the present invention, preferably, the substrate of the anode chamber 1 is soil containing oxidizing bacteria. The oxidizing bacteria in the anode chamber 1 can be indigenous microorganisms in the environment, or functional microbial strains (groups) with high electrical activity can be added exogenously. Preferably, the oxidizing bacteria are selected from at least one of Shewanella, Geobacter and Geobacter metallireducens. The inventors have found that the mixed bacteria in the soil to be repaired can decompose organic matter to release electrons and protons, which are then transferred to the cathode through an external circuit to form an electric current, thereby improving the degradation efficiency of pollutants in the soil to be repaired.

[0051] According to the present invention, preferably, the reducible substance in the cathode chamber 2 is a compound containing reducing metal ions. Further preferably, the metal ions are reducing metal ions, more preferably at least one selected from Cr(VI), Hg(II), Pb(II) and Cd(II), and specifically may contain two, three or four of the above heavy metal ions at the same time. Other reducible heavy metal ions other than the above heavy metal ions may also be included. The substrate in the cathode chamber 2 is soil containing heavy metal ions. The inventors have found that when the soil substrate in the cathode chamber 2 contains reducing metal ions, the heavy metal pollutants in the cathode chamber 2 can be reduced while degrading the organic pollutants in the anode chamber 1, and the reduced metal ions can be recycled and reused, which can significantly improve the efficiency of soil remediation.

[0052] According to the present invention, preferably, the electrode in the anode chamber 1 is a carbon felt electrode. The inventors found that when the above preferred embodiment is adopted, oxidizing bacteria will adhere to the surface of the carbon felt electrode, which will enhance the electron intensity generated by the oxidizing bacteria to decompose organic matter and enhance the interaction between electrons and electrodes, thereby improving the degradation efficiency.

[0053] According to the present invention, preferably, the electrode in the anode chamber 1 is a carbon felt electrode modified with lignin-based carbon nitride; the content of the lignin-based carbon nitride in the carbon felt electrode is 0.1-3wt%, specifically 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, or any value between the above two values; preferably 0.9-1wt%, specifically 0.9wt%, 1wt%; or any value between the above two values. The inventors found that lignin-based carbon nitride can provide more suitable conditions for the attachment and growth of oxidizing bacteria microorganisms in the substrate. When the above preferred embodiment is adopted, more oxidizing bacteria will be attached to the surface of the anode electrode modified with lignin-based carbon nitride, which enhances the electron intensity generated by the oxidizing bacteria decomposing organic matter and enhances the interaction between electrons and electrodes, thereby improving the degradation efficiency.

[0054] According to the present invention, further preferably, the content of nitrogen atoms in the lignin-based carbon nitride is 0.02-0.04wt%, specifically 0.02wt%, 0.03wt%, 0.04wt%, or any value between the above two values. The inventors found that when the above preferred embodiment is adopted, more oxidizing bacteria will adhere to the surface of the anode electrode modified by lignin-based carbon nitride, which enhances the electron intensity generated by the oxidizing bacteria to decompose organic matter and enhances the interaction between electrons and electrodes, thereby improving the degradation efficiency.

[0055] According to the present invention, preferably, the method for preparing lignin-based carbon nitride comprises the following steps:

[0056] S1, mixing lignin and urea and calcining to obtain powder I;

[0057] S2, under hydrothermal reaction conditions, mixing the powder I obtained in step S1 with water, and washing and drying to obtain powder II;

[0058] S3, mixing the powder II obtained in step S2 with zinc chloride and carbonizing to obtain powder III. The inventors found that the lignin-based carbon nitride prepared by the above method has a porous structure, which can increase the surface area of ​​the electrode, so that more oxidizing bacteria are attached to the surface of the anode electrode modified by the lignin-based carbon nitride, further enhancing the electron intensity generated by the oxidizing bacteria to decompose organic matter and enhancing the interaction between the electrons and the electrode, thereby improving the degradation efficiency.

[0059] According to the present invention, preferably, in step S1, the calcination conditions at least include: a temperature of 240-260°C, specifically 240°C, 250°C, 260°C, or any value between the above two values; a time of 6-8h, specifically 6h, 7h, 8h, or any value between the above two values. Further preferably, the mass ratio of lignin to urea is 1:0.1-0.6, specifically 1:0.1, 1:0.3, 1:0.6, or any value between the above two values; preferably 1:0.2-0.3, specifically 1:0.2, 1:0.3, or any value between the above two values. The inventors found that when the above preferred embodiment is adopted, the porosity of the prepared lignin-based carbon nitride is high, which can further increase the electrode surface area, so that more oxidizing bacteria are attached to the surface of the anode electrode modified by lignin-based carbon nitride, further enhancing the electron intensity generated by the oxidizing bacteria to decompose organic matter while enhancing the interaction between electrons and electrodes, thereby improving the degradation efficiency.

[0060] According to the present invention, preferably, in step S2, the mass ratio of the powder I to water is 0.2-0.5:1, specifically 0.3:1, 0.5:1, or any value between the above two values; the conditions of the hydrothermal reaction at least include: the temperature is 120-180°C, specifically 120°C, 140°C, 160°C, 180°C, or any value between the above two values; the time is 12-14h, specifically 12h, 13h, 14h, or any value between the above two values. The inventors found that when the above preferred embodiment is adopted, the porosity of the prepared lignin-based carbon nitride is high, which can further increase the surface area of ​​the electrode, so that more oxidizing bacteria are attached to the surface of the anode electrode modified by the lignin-based carbon nitride, further enhancing the electron intensity generated by the oxidizing bacteria to decompose organic matter while enhancing the interaction between electrons and electrodes, thereby improving the degradation efficiency.

[0061] According to the present invention, the cleaning process uses acetone and water in a volume ratio of 0.1-0.5:1 for cleaning, and the specific volume ratio can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, or any value between the above two values; the drying conditions at least include: a temperature of 60-65°C, specifically 60°C, 62°C, 65°C, or any value between the above two values; a time of 12-24h, specifically 12h, 14h, 16h, 18h, 20h, 22h, 24h, or any value between the above two values. The inventors found that when the above preferred embodiment is adopted, the porosity of the prepared lignin-based carbon nitride is high, which can further increase the surface area of ​​the electrode, so that more oxidizing bacteria are attached to the surface of the anode electrode modified by the lignin-based carbon nitride, further enhancing the electron intensity generated by the oxidizing bacteria to decompose organic matter while enhancing the interaction between the electrons and the electrode, thereby improving the degradation efficiency.

[0062] According to the present invention, preferably, in step S3, the mass ratio of the powder II to zinc chloride is 1:1-5, specifically 1:1, 1:3, 1:5, or any value between the above two values; the mixed carbonization conditions at least include: the temperature is 600-900°C, specifically 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, or any value between the above two values; the time is 2-4h, specifically 2h, 3h, 4h, or any value between the above two values. The prepared lignin-based carbon nitride has a higher porosity, which can further increase the electrode surface area, so that more oxidizing bacteria are attached to the surface of the anode electrode modified by lignin-based carbon nitride, further enhancing the electron intensity generated by the oxidizing bacteria decomposing organic matter while enhancing the interaction between electrons and electrodes, thereby improving the degradation efficiency.

[0063] According to the present invention, preferably, the method for preparing the carbon felt electrode modified with lignin-based carbon nitride comprises the following steps: mixing the powder III obtained in step S3 with polytetrafluoroethylene and a solvent to prepare a suspension, and then contacting the carbon felt with the suspension. The inventors have found that the carbon felt electrode modified by the above method can better attach the lignin-based carbon nitride to the carbon felt electrode, so that the modified carbon felt electrode has better biocompatibility, can attract more oxidizing bacteria microorganisms to gather on the modified carbon felt electrode, further enhance the electron intensity generated by the oxidizing bacteria decomposing organic matter, and enhance the interaction between the electrons and the electrode, thereby improving the degradation efficiency.

[0064] According to the present invention, further preferably, the concentration of the powder III in the suspension is 8-10 g / L, specifically 8 g / L, 9 g / L, 10 g / L, or any value between the above two values; further preferably, the concentration of polytetrafluoroethylene is 0.04-0.05 g / L, specifically 0.04 g / L, 0.045 g / L, 0.05 g / L, or any value between the above two values; further preferably, the contact conditions at least include: temperature of 30-40°C, specifically 30°C, 35°C, 40°C, or any value between the above two values; time of 0.5-1h, specifically 0.5h, 0.8h, 1h, or any value between the above two values. The inventors have found that the modified carbon felt electrode prepared using the above-mentioned preferred embodiment can better attach lignin-based carbon nitride to the carbon felt electrode, making the modified carbon felt electrode have better biocompatibility, and can attract more oxidizing bacteria and microorganisms to gather on the modified carbon felt electrode, further enhancing the electron intensity generated by the oxidizing bacteria in decomposing organic matter while enhancing the interaction between electrons and electrodes, thereby improving the degradation efficiency.

[0065] According to the present invention, the preparation method of the lignin-based carbon nitride modified carbon felt electrode also includes the pretreatment of the carbon felt electrode. Preferably, the pretreatment includes: slicing the carbon felt electrode, cleaning and drying it for standby use. The inventors found that the carbon felt obtained by the above pretreatment can be better composite-modified with lignin-based carbon nitride, thereby improving the degradation efficiency of pollutants in the soil to be repaired. Exemplarily, the pretreatment method of the carbon felt electrode is as follows: cut the carbon felt into 1-2mm thick square slices of 3cm×3cm-6cm×6cm, rinse it with deionized water several times, and then perform ultrasonic cleaning. Change the water every 10-20min of ultrasonic cleaning, repeat 3-5 times, place it in a beaker filled with ethanol or acetone and soak it for 10-20min, and then place it in an ultrasonic cleaning machine for 30-40min. Then use 40-50℃ hot water to soak and clean it, and then place it in a 60-65℃ vacuum drying oven for heating for 8-10h. The treated carbon felt is the required electrode substrate, which is placed in a dryer for standby use.

[0066] As a relatively preferred embodiment of the present invention, the method for preparing the lignin-based carbon nitride-modified carbon felt electrode comprises the following steps:

[0067] (1) Carbon felt pretreatment: Cut the carbon felt into slices with a thickness of 1-2 mm and a size of 3 cm×3 cm-6 cm×6 cm, rinse with deionized water for 20-30 times, and then perform ultrasonic cleaning. Change the water every 10-20 minutes of ultrasonic cleaning. Repeat 3-5 times, soak the carbon felt in ethanol for 10-20 minutes, and then place it in an ultrasonic cleaning machine for 30-40 minutes; then soak it in 40-50℃ hot water and heat it in a 60-65℃ vacuum drying oven for 8-10 hours. The treated carbon felt is the required electrode substrate and is placed in a desiccator for later use.

[0068] (2) The preparation method of lignin-based carbon nitride comprises the following steps:

[0069] S1. Grind lignin and urea in a ball mill at a mass ratio of 1:0.1-0.6 and mix them evenly, and then calcine them under inert gas at 240-260° C. for 6-8 hours to obtain powder I;

[0070] S2. Under hydrothermal reaction conditions at a temperature of 120-180° C., the powder I obtained in step S1 and water are mixed in a mass ratio of 0.2-0.5:1, heated for 12-14 hours, cooled to room temperature, washed with acetone and water in a volume ratio of 0.1-0.5:1, and after washing, dried in a vacuum drying oven at 60-65° C. to obtain powder II;

[0071] S3. The powder II obtained in step S2 and zinc chloride are uniformly mixed in a mass ratio of 1:1-5, stably carbonized for 2-4 hours at a temperature of 600-900°C in a tube furnace vacuum environment, and naturally cooled to room temperature to obtain a black powder, which is soaked in 1-2 mol / L hydrochloric acid overnight, then washed with water until the pH value is stable and unchanged, and then transferred to a vacuum drying oven, and vacuum dried at 80-90°C overnight to obtain powder III, i.e., lignin-based carbon nitride.

[0072] (3) The preparation method of the lignin-based carbon nitride-modified carbon felt electrode comprises the following steps:

[0073] 60-100 mL of anhydrous ethanol and a predetermined mass of PTFE (polytetrafluoroethylene) are mixed to obtain a mixed solution, wherein the concentration of PTFE in the mixed solution is 0.04-0.05 g / L. The mixed solution is ultrasonicated for 0.5-1 h to uniformly disperse the PTFE in the ethanol to form a suspension, and then mixed and contacted with the powder III obtained in the above step S3, and ultrasonicated for 0.5-1 h at a temperature of 30-40° C., and the concentration of lignin-based carbon nitride in the suspension is 8-10 g / L. Finally, the mixture is mixed with the carbon felt pretreated in the above step (1), and ultrasonicated for 0.5-1 h. After the ultrasonication is completed, the modified carbon felt is taken out and transferred to a vacuum drying oven, and dried in a vacuum oven at 80-85° C. overnight. Then, the dried modified carbon felt is placed in a muffle furnace, calcined at 350-400° C. for 1-1.5 h, cooled to room temperature, washed with water, and dried in a vacuum oven at 80-85° C. overnight to obtain a lignin-based carbon nitride modified carbon felt electrode.

[0074] According to the present invention, preferably, Figure 2 As shown, the external circuit includes a power switch, a resistor, a capacitor, an inductor, a charging power supply and a power line connecting the above devices; further preferably, an external voltage 4 can be applied to the external circuit, and the range of the external voltage 4 is 0.5-2V. The inventors found that when the external voltage 4 is applied to the external circuit, the degradation efficiency of organic pollutants can be further improved.

[0075] According to the present invention, preferably, Figure 5 As shown, the soil remediation device also includes a heating device, which can be a hot water bath heating device, and the heating temperature is 30-35°C, which can be 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, or any value between the above two values. The inventors have found that when the above preferred embodiment is adopted, the degradation efficiency of organic pollutants can be further improved.

[0076] As a relatively preferred embodiment of the present invention, Figure 2-Figure 3 As shown, taking the degradation of phenol in soil as an example, the soil remediation device includes: an anode chamber 1, a cathode chamber 2, a proton exchange membrane 3 and an external circuit, wherein an external voltage 4 is also provided in the external circuit, the substrate in the anode chamber 1 contains oxidizing bacteria, the cathode chamber 2 contains reducible substances, the proton exchange membrane 3 is used to separate the anode chamber 1 and the cathode chamber 2, and the power lines at both ends of the external circuit are respectively connected to the electrodes in the anode chamber 1 and the cathode chamber 2 to form a closed circuit; the electrode in the anode chamber 1 is a carbon felt electrode modified with lignin-based carbon nitride, and the electrode in the cathode chamber 2 is a graphite electrode.

[0077] The above substances are commercially available.

[0078] The second aspect of the present invention provides the use of the soil remediation device described in the first aspect in a power generation device. Figure 6 As shown, the electric energy generated by the power generation equipment can be used by low-power electrical appliances, specifically insecticidal lamps 6, street lamps, etc.

[0079] According to the present invention, preferably, the power generation equipment is a microbial fuel cell. The power generation equipment is designed according to the principle of microbial fuel cells, and can utilize microorganisms in the soil to be repaired to decompose organic pollutants, while reducing heavy metal ions in the cathode chamber to improve the efficiency of soil remediation. Further preferably, the power generation equipment is a power supply for insecticidal lamps. The soil remediation device is used as a microbial fuel cell to generate electricity to supply insecticidal lamps to lure and kill pests of crops, thereby reducing the production of pesticides and other substances, protecting the environment, and protecting human health. In addition, the insecticidal lamp can provide lighting for people while eliminating pests, making the insecticidal lamp more practical.

[0080] The third aspect of the present invention provides the use of the soil remediation device described in the first aspect in removing heavy metals and / or organic pollutants from soil and / or water. Preferably, the soil is water sediment containing heavy metal ions; further preferably, the heavy metal ions are selected from at least one of Cr(VI), Hg(II), Pb(II) and Cd(II), and specifically can contain two, three or four of the above heavy metal ions at the same time. Other reducible heavy metal ions other than the above heavy metal ions can also be included. The organic pollutant is phenol. The inventors have found that when heavy metal-contaminated water sediment is used as a substrate for the cathode chamber 2 and the anode chamber 1, the organic pollutants can be degraded by microorganisms in the water sediment, and the heavy metal ions in the water can be reduced in the cathode chamber 2, which can greatly improve the soil remediation efficiency.

[0081] As a relatively preferred embodiment of the present invention, taking the reduction of heavy metal ions Cr(VI) in the soil to be repaired as an example, the soil remediation device includes: an anode chamber 1, a cathode chamber 2, a proton exchange membrane 3, an external circuit and a constant temperature water bath 5; a measuring cylinder with a volume of 2.0-3L is used as the chamber body of the soil remediation device; 800-1000mL of moist sediment rich in oxidizing bacteria is added to the bottom as a substrate in the anode chamber 1, and a carbon felt electrode modified with lignin-based carbon nitride is used as an anode embedded in the middle of the sediment; simulated wastewater with a Cr(VI) concentration of 5-8mg / L is used as the cathode electrolyte, and the proton exchange membrane 3 is arranged between the anode chamber 1 and the cathode chamber 2 to separate the substrate in the anode chamber 1 from the substrate in the cathode chamber 2, and the electrode in the cathode chamber 2 is a graphite electrode; the power lines at both ends of the external circuit are respectively connected to the electrodes in the anode chamber 1 and the cathode chamber 2 to form a closed circuit.

[0082] The present invention will be described in detail below through examples.

[0083] In the following examples, lignin is derived from agricultural and forestry biomass; urea is purchased from Aladdin Biochemical Technology Co., Ltd.; zinc chloride is purchased from Sinopharm Reagent Chemical Co., Ltd.; carbon felt electrodes are purchased from Jingtan Technology Co., Ltd.; polytetrafluoroethylene is purchased from Zhejiang Juhua Co., Ltd., product number JF-G90; unless otherwise specified, the remaining reagents or raw materials are conventional biochemical reagent grade products.

[0084] In the following examples, the preparation process of the lignin-based carbon nitride-modified carbon felt electrode 1 is as follows:

[0085] (1) Carbon felt pretreatment: Cut the carbon felt into slices with a thickness of 1 mm and a size of 3 cm × 3 cm, rinse with deionized water 20 times, and then perform ultrasonic cleaning. Change the water every 10 minutes of ultrasonic cleaning. Repeat 3 times, transfer the carbon felt to a beaker filled with ethanol and soak it for 10 minutes. Then place the beaker in an ultrasonic cleaner for 30 minutes; then soak and clean it with 40°C hot water and heat it in a 60°C vacuum drying oven for 8 hours. The treated carbon felt is the required electrode substrate and is placed in a desiccator for later use.

[0086] (2) The preparation method of lignin-based carbon nitride comprises the following steps:

[0087] S1, grinding and mixing lignin and urea in a ball mill at a mass ratio of 1:0.2, and then calcining them under nitrogen at 260° C. for 6 h to obtain powder I;

[0088] S2. Under the hydrothermal reaction condition of 180°C, the powder I obtained in step S1 and water were mixed in a mass ratio of 0.2:1, heated for 12 hours, cooled to room temperature, and then heated with acetone in a volume ratio of 0.2:1.

[0089] and water, and then transferred to a 60°C vacuum drying oven for drying to obtain powder II;

[0090] S3, the powder II obtained in step S2 and zinc chloride were mixed in a mass ratio of 1:1, and stably carbonized for 2 hours at 600°C in a vacuum environment of a tube furnace, and naturally cooled to room temperature to obtain a black powder, which was soaked in 1 mol / L hydrochloric acid overnight, and then washed with water until the pH value was stable and unchanged, and then transferred to a vacuum drying oven, and vacuum dried at 80°C overnight to obtain powder III, i.e., lignin-based carbon nitride. The SEM image is as follows Figure 7 shown.

[0091] (3) The preparation method of the lignin-based carbon nitride-modified carbon felt electrode comprises the following steps:

[0092] A predetermined amount of PTFE (polytetrafluoroethylene) was added to 60 mL of anhydrous ethanol to make its concentration 0.05 g / L, and ultrasonicated for 0.5 h to make the PTFE evenly dispersed in the ethanol to form a suspension. Then, a certain amount of the powder III obtained in the above step S3, i.e., lignin-based carbon nitride, was added to contact the above suspension. Ultrasonication was continued for 0.5 h at a temperature of 30 ° C. The concentration of lignin-based carbon nitride in the suspension was 8 g / L. Finally, the carbon felt pretreated in the above step (1) was added and ultrasonication was continued for 30 min. After the ultrasonication was completed, the modified carbon felt was taken out and transferred to a vacuum drying oven, dried in a vacuum oven at 80 ° C overnight, and then the dried modified carbon felt was placed in a muffle furnace, calcined at 350 ° C for 1 h, cooled to room temperature, washed with water, and dried in a vacuum oven at 80 ° C overnight to obtain a lignin-based carbon nitride modified carbon felt electrode 1.

[0093] Example 1

[0094] Reference Figure 1 The soil remediation device includes an anode chamber 1, a cathode chamber 2, a proton exchange membrane 3 and an external circuit. The substrate in the anode chamber 1 is soil containing Shewanella, Geobacter and Soilbacter sulphur-reducing. The cathode chamber 2 contains the reducible substance Cr(VI). The proton exchange membrane 3 is used to separate the anode chamber 1 and the cathode chamber 2. The power lines at both ends of the external circuit are respectively connected to the electrodes in the anode chamber 1 and the cathode chamber 2 to form a closed circuit; the electrode in the anode chamber 1 is a lignin-based carbon nitride modified carbon felt electrode 1, and the electrode in the cathode chamber 2 is a graphite electrode.

[0095] Reference Figure 2-Figure 3 The soil remediation device includes an anode chamber 1, a cathode chamber 2, a proton exchange membrane 3 and an external circuit. Different external voltages 4 are applied to the external circuit, and phenol is added to the soil in the anode chamber 1 to determine the degradation of phenol pollutants in the soil under different external voltages 4. The initial phenol concentration in the soil substrate of the anode chamber 1 is 80 mg / mL. The concentration of phenol in the soil substrate of the anode chamber 1 is measured when the external voltage 4 is 2.0V, 1.0V, 0.5V and the circuit is open. The degradation of phenol in the soil substrate of the anode chamber 1 under different external voltages 4 is shown in Figure 2. Figure 4 The degradation rate of phenol was determined by photodegradation method.

[0096] from Figure 4It can be seen that in the first 7 days, the phenol concentration in the soil substrate of the anode chamber 1 of the soil remediation device decreased rapidly. After the 7th day, the degradation rate of phenol slowed down, and the degradation rates of phenol from fast to slow were: 2.0V, 1.0V, 0.5V and open circuit. On the 11th day, the degradation rates of phenol were 98.5%, 95.7%, 81.7% and 48.9%, respectively.

[0097] Example 2

[0098] Reference Figure 5 The soil remediation device includes an anode chamber 1, a cathode chamber 2, a proton exchange membrane 3, an external circuit and a constant temperature water bath 5; a measuring cylinder with a volume of 2.0L is used as the chamber body of the soil remediation device; 800mL of moist sediment rich in oxidizing bacteria is added to the bottom as a substrate in the anode chamber 1, and a carbon felt electrode is used as an anode embedded in the middle of the sediment; simulated wastewater with a Cr(VI) concentration of 8mg / L is used as a cathode electrolyte, and a proton exchange membrane 3 is arranged between the anode chamber 1 and the cathode chamber 2 to separate the substrate in the anode chamber 1 from the substrate in the cathode chamber 2, and the electrode in the cathode chamber 2 is a graphite electrode; power lines at both ends of the external circuit are respectively connected to the electrodes in the anode chamber 1 and the cathode chamber 2 to form a closed circuit.

[0099] Example 3

[0100] Reference Figure 5 The soil remediation device includes an anode chamber 1, a cathode chamber 2, a proton exchange membrane 3, an external circuit and a constant temperature water bath 5; a measuring cylinder with a volume of 2.0L is used as the chamber body of the soil remediation device; 800mL of moist sediment rich in oxidizing bacteria is added to the bottom as a substrate in the anode chamber 1, and a carbon felt electrode modified with lignin-based carbon nitride is used as an anode embedded in the middle of the sediment; simulated wastewater with a Cr(VI) concentration of 8mg / L is used as a cathode electrolyte, a proton exchange membrane 3 is arranged between the anode chamber 1 and the cathode chamber 2 to separate the substrate in the anode chamber 1 from the substrate in the cathode chamber 2, and the electrode in the cathode chamber 2 is a graphite electrode; power lines at both ends of the external circuit are respectively connected to the electrodes in the anode chamber 1 and the cathode chamber 2 to form a closed circuit.

[0101] The soil remediation devices of Example 2 and Example 3 were used to conduct a heavy metal pollutant removal experiment. Before the experiment, the lignin-based carbon nitride-modified carbon felt electrode and the carbon felt electrode were immersed in activated activated sludge for 36 hours, and the bacterial flora was inoculated on the electrode surface. After the electrode was taken out, it was placed about 5 cm from the liquid surface as an anode, and a 1000Ω external resistor was provided in the external circuit and connected between the two electrodes to form a closed circuit.

[0102] The temperature of the constant temperature water bath 5 of the above two soil remediation devices was set to 30°C for constant temperature operation. The voltage generated in the soil remediation device was collected in real time by an external voltmeter and recorded once per minute. When the Cr(VI) concentration in the cathode liquid dropped to 0, the cathode liquid was replaced. After 14 days of normal operation, the Cr(VI) in the simulated wastewater treated by the soil remediation device using the carbon felt electrode modified with lignin-based carbon nitride in Example 3 can be completely removed (reduced), and the time for complete removal of Cr(VI) in the simulated wastewater treated by the soil remediation device using the carbon felt electrode in Example 2 is doubled compared with the soil remediation device in Example 3.

[0103] Application Example 1

[0104] See also Figure 6 The soil remediation device in Example 1 to Example 3 is used as a power generation device to provide electric energy to the insecticidal lamp 6, and the insecticidal lamp 6 can meet the working requirements of insecticide and lighting at night.

[0105] The soil remediation device provided by the present invention can simultaneously perform deep treatment on organic pollutants and heavy metal ions in the soil, thus solving the existing problem of organic pollutants and heavy metal pollution in the soil. In addition, insect pests are an important factor affecting the growth and harvest of crops. In modern agriculture, the main method of pest control is to spray pesticides, but spraying pesticides is still not enough to eliminate all crop pests. For the control of special or alien species of pests, other auxiliary means are needed to control them. The soil remediation device is used as a microbial fuel cell to generate electricity to supply insecticidal lamps to lure and kill crop pests, thereby reducing the production of pesticides and other substances, protecting the environment, and protecting human health. In addition, the insecticidal lamp can provide lighting for people while eliminating pests, making the insecticidal lamp more practical.

[0106] It can be seen from the above embodiments 1-3 that the lignin-based carbon nitride-modified carbon felt electrode in the soil remediation device as the anode of the microbial fuel cell has better biocompatibility, can attract more oxidizing bacteria microorganisms to gather on the modified carbon felt electrode, further enhance the electron intensity generated by the oxidizing bacteria decomposing organic matter, and at the same time enhance the interaction between electrons and electrodes, thereby improving the degradation efficiency and reaction activity, and can perform efficient deep treatment of organic pollutants and heavy metal ions in the soil, with high remediation efficiency, low treatment cost, and no secondary pollution, thereby solving the problems of high remediation and treatment costs, secondary pollution, and low soil remediation efficiency of existing soil remediation equipment, and at the same time using the electrical energy generated in the remediation process as the power source of the insecticidal lamp to lure and kill insects, thereby reducing the pollution of the soil by harmful substances in various insecticides and pesticides, and protecting the environment.

[0107] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A soil remediation device, characterized in that: The soil remediation device comprises an anode chamber (1), a cathode chamber (2), a proton exchange membrane (3) and an external circuit. The substrate in the anode chamber (1) contains oxidizing bacteria, the cathode chamber (2) contains reducible substances, the proton exchange membrane (3) is used to separate the anode chamber (1) and the cathode chamber (2), and the power lines at both ends of the external circuit are respectively connected to the electrodes in the anode chamber (1) and the cathode chamber (2) to form a closed circuit.

2. The soil remediation device according to claim 1, characterized in that: The substrate of the anode chamber (1) is soil containing oxidizing bacteria; the oxidizing bacteria are selected from at least one of Shewanella, Geobacter and Geobacter sulphur-reducing; Preferably, the reducible substance in the cathode chamber (2) is a compound containing reducing metal ions; Preferably, the metal ion is a reducing metal ion, more preferably at least one selected from Cr(VI), Hg(II), Pb(II) and Cd(II); The substrate in the cathode chamber (2) is soil containing heavy metal ions.

3. The soil remediation device according to claim 1, characterized in that: The electrode in the anode chamber (1) is a carbon felt electrode.

4. The soil remediation device according to claim 1, characterized in that: The electrode in the anode chamber (1) is a carbon felt electrode modified with lignin-based carbon nitride; the content of the lignin-based carbon nitride in the carbon felt electrode is 0.1-3wt%, preferably 0.9-1wt%; Preferably, the content of nitrogen atoms in the lignin-based carbon nitride is 0.02-0.04 wt%.

5. The soil remediation device according to claim 4, characterized in that: The preparation method of the lignin-based carbon nitride comprises the following steps: S1, calcining lignin and urea to obtain powder I; S2, under hydrothermal reaction conditions, mixing the powder I obtained in step S1 with water, and washing and drying to obtain powder II; S3, mixing the powder II obtained in step S2 with zinc chloride and carbonizing them to obtain powder III.

6. The soil remediation device according to claim 5, characterized in that: In step S1, the calcination conditions at least include: a temperature of 240-260° C. and a time of 6-8 h; Preferably, the mass ratio of lignin to urea is 1:0.1-0.6, preferably 1:0.2-0.3; Preferably, in step S2, the mass ratio of the powder I to water is 0.2-0.5:1; The conditions of the hydrothermal reaction include at least: a temperature of 120-180° C. and a time of 12-14 h; Preferably, in step S3, the mass ratio of the powder II to zinc chloride is 1:1-5; the mixed carbonization conditions at least include: a temperature of 600-900°C and a time of 2-4h.

7. The soil remediation device according to claim 5, characterized in that: The method for preparing the lignin-based carbon nitride-modified carbon felt electrode comprises the following steps: mixing the powder III obtained in step S3 and polytetrafluoroethylene with a solvent to prepare a suspension, and then contacting the carbon felt with the suspension; Preferably, the concentration of the powder III in the suspension is 8-10 g / L; Preferably, the concentration of polytetrafluoroethylene is 0.04-0.05 g / L; Preferably, the contacting conditions at least include: a temperature of 30-40° C. and a time of 0.5-1 h.

8. Use of the soil remediation device according to any one of claims 1 to 7 in power generation equipment; Preferably, the power generation device is a microbial fuel cell.

9. The use according to claim 8, characterized in that: The power generation equipment is used to supply power to the insecticidal lamp (6).

10. Use of the soil remediation device according to any one of claims 1 to 7 in removing heavy metals and / or organic pollutants in soil and / or water; Preferably, the soil is water sediment containing heavy metal ions; Preferably, the heavy metal ion is selected from at least one of Cr(VI), Hg(II), Pb(II) and Cd(II), and the organic pollutant is phenol.

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