Preparation method and process of high-conductivity flowing electrode for adsorbing and separating nitrogen and phosphorus in sewage

Abstract

The invention belongs to the field of sewage treatment, and particularly relates to a preparation method of a high-conductivity flowing electrode for adsorption and separation of nitrogen and phosphorus in sewage, the method comprises the following steps: firstly, carbonizing pig manure under a protective atmosphere, then carrying out alkali activation to obtain pig manure-based porous carbon with a hierarchical porous structure and a graphite-like domain, and adding the pig manure-based porous carbon into a high-conductivity flowing electrode for adsorption and separation of nitrogen and phosphorus in the sewage. According to the invention, a semi-solid flowing electrode suspension liquid is prepared by fully mixing with ultrapure water, a supporting electrolyte and a conductive additive, and an electrochemical nitrogen and phosphorus adsorption separation process is constructed based on the flowing electrode. Compared with a common commercial active carbon flow electrode, the pig manure-based porous carbon-based flow electrode prepared by the invention has the characteristics of high conductivity and low resistance, so that a more efficient charge seepage network can be formed, and electron transmission and ion diffusion separation are promoted. In addition, the flowing electrode particles provided by the invention have relatively high hydrophilicity, the viscosity of the flowing electrode is relatively low, the flowability is good, and the system is not easy to block.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and specifically relates to a preparation method and process of a high-conductivity mobile electrode for nitrogen and phosphorus adsorption separation in sewage. Background Art

[0002] As global water environmental problems become increasingly serious, nitrogen and phosphorus pollution has become one of the main causes of water eutrophication, especially in agriculture and animal husbandry. Excessive discharge of nitrogen and phosphorus has had a serious impact on aquatic ecosystems and human health. Nitrogen and phosphorus pollution not only leads to eutrophication of water bodies and produces algal blooms, but may also cause environmental problems such as odor emissions, seriously damaging the ecological balance and threatening public health. Nitrogen and phosphorus are the main pollutants in wastewater, especially nitrogen, which is an important component of livestock and poultry manure and often exists in the form of ammonia nitrogen (NH3) and ammonium ions (NH4⁺). Ammonia is not only an important source of water pollution, but also an important raw material for synthetic nitrogen fertilizers. However, traditional wastewater treatment methods, such as physical and chemical methods and biological methods, are often difficult to recover nitrogen and phosphorus resources efficiently and at low cost, and there is a risk of unstable treatment effects and secondary pollution. Therefore, developing a technology that can effectively remove nitrogen and phosphorus from sewage and achieve resource recovery has become a difficult problem that needs to be solved in the current environmental field.

[0003] In recent years, electrochemical separation technology has gradually become a cutting-edge method for recovering nutrients such as nitrogen and phosphorus from wastewater due to its advantages such as ion selectivity, reversibility and sustainability. As an emerging electrochemical separation method, the electrochemical separation process based on flow electrodes combines ion exchange membranes with semi-solid electrodes and utilizes the dual effects of electrodialysis and electrosorption to remove nitrogen and phosphorus from water while achieving the goal of continuous and efficient recovery of nitrogen and phosphorus. However, the existing commercial activated carbon (AC) flow electrodes are limited in their application in the efficient removal of nitrogen and phosphorus pollution due to their poor electrical conductivity and ion adsorption capacity.

[0004] Therefore, exploring new highly conductive materials as active materials for flow electrodes has become a hot topic in current research. Livestock and poultry waste (such as animal manure) is rich in nitrogen, oxygen and minerals. After high-temperature carbonization and subsequent activation, it can form hierarchical porous structures and graphite-like domains in situ that are difficult to achieve through artificial synthesis. Therefore, it not only has a larger specific surface area, but also has excellent electrical conductivity. It is expected to solve the problems of poor electrical conductivity and insufficient ion capture capacity of traditional carbon materials. Due to the rich oxygen functional groups on the surface, this type of porous carbon is also hydrophilic, which makes its flow electrode have ideal fluidity, which is crucial for the long-term stable operation of the flow electrode electrochemical separation process.

[0005] The invention uses pig manure, a renewable biomass resource, to prepare a semi-solid flow electrode with high conductivity and low viscosity, and constructs an electrochemical nitrogen-phosphorus adsorption separation process based on this flow electrode, providing an efficient solution for the recovery of nitrogen and phosphorus in sewage. At the same time, this process conforms to the principle of circular economy, can realize the resource utilization of waste, and is a low-cost, sustainable, green and environmentally friendly technology. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a highly conductive mobile electrode and an efficient electrochemical nitrogen-phosphorus adsorption separation process based thereon. The mobile electrode provided by the present invention, compared with the mobile electrode based on commonly used commercial activated carbon, has the advantages of high electronic conductivity, fast ion diffusion, low viscosity, high nitrogen-phosphorus adsorption separation efficiency and low energy consumption.

[0007] In order to achieve the above object, the present invention provides the following technical solutions: The present invention provides a method for preparing a high-conductivity mobile electrode for nitrogen and phosphorus adsorption separation in sewage, comprising a mobile electrode, wherein the mobile electrode is made of livestock and poultry breeding waste pig manure as a raw material, and the preparation method of the mobile electrode using pig manure as a raw material comprises the following steps: S1. Dry the fresh pig manure in an oven to remove moisture until the quality no longer decreases; S2, crushing, grinding and screening the dried pig manure; S3, pre-carbonizing the sieved pig manure powder in an inert gas; S4, fully mixing the pre-carbonized pig manure, strong alkali and ultrapure water; S5, drying the mixture in an oven, and then activating it in an inert gas to obtain pig manure-based porous carbon; S6, repeatedly washing the pig manure-based porous carbon with hydrochloric acid and ultrapure water; S7, uniformly mixing the pig manure-based porous carbon, carbon black, ultrapure water and supporting electrolyte sodium chloride, ultrasonically treating at room temperature, and then magnetically stirring to obtain a highly conductive semi-solid mobile electrode suspension; Preferably, the carbonization temperature is 500-600°C, and the pre-carbonization holding time is 2-3 h; Preferably, the temperature of the alkali activation is 700-900°C, and the holding time of the alkali activation is 1-2 h; Preferably, the mass fraction of the pig manure-based porous carbon in the high-conductivity mobile electrode is 5-10 wt.%, the mass fraction of carbon black is greater than 0.5 wt.%, and the concentration of supporting electrolyte sodium chloride is 1-2 g / L; Preferably, the ultrasonic treatment temperature of the high-conductivity mobile electrode is 25°C, the time is 0.5-1 h, and the magnetic stirring time is at least 24 h; Preferably, the pig manure-based porous carbon has an electronic conductivity of 17.10 S / cm at a pressure of 1 MPa; The specific surface area of ​​the pig manure-based porous carbon rice is 766.51 m 2 / g; The pig manure-based porous carbon has abundant mesopores, and the volume percentage of mesopores is greater than 50%; The surface of the pig manure-based porous carbon contains hydrophilic functional groups, and the hydrophilic functional groups mainly include hydroxyl groups; The water contact angle of the pig manure-based porous carbon is 19.4°. The viscosity of the high-conductivity mobile electrode is 1.53 mPa·s; The electrochemical nitrogen-phosphorus adsorption separation system based on the electrode of pig manure flow has an overall resistance of 26.61 Ω when the electrolyte is 1000 mgN / L ammonium chloride solution.

[0008] A high-efficiency flow electrode electrochemical nitrogen-phosphorus adsorption separation process, the high-efficiency electrochemical nitrogen-phosphorus adsorption separation process comprises the flow electrode, a direct current power supply, a current sensor, a conductivity sensor, a multi-channel data recorder, an electrochemical workstation, a flow electrode electrochemical cell, and a peristaltic pump. The power supply mode of the direct current power supply is constant voltage power supply. The flow electrode is the high-conductivity flow electrode based on pig manure-based porous carbon. Preferably, the flow electrode electrochemical cell is composed of a current collector having a serpentine flow electrode flow channel, an ion exchange membrane, a water inlet flow channel, and a gasket, and the operation mode of the high-efficiency electrochemical nitrogen-phosphorus adsorption separation process is a short-circuit closed cycle mode; Preferably, the working voltage of the constant voltage power supply is 1-1.6 V, the flow electrode and the water inlet flow rate are controlled by a peristaltic pump and are 10-30 mL / min, the ammonia nitrogen content in the water body is ≥100 mgN / L, the phosphorus content in the water body is ≥1 mgP / L, and the effective contact area between the ion exchange membrane and the serpentine flow electrode flow channel in the flow electrode electrochemical cell is 15-30 cm 2 .

[0009] The present invention proposes a preparation method and process for a high-conductivity flow electrode for nitrogen and phosphorus adsorption separation in sewage. In the flow electrode electrochemical adsorption separation process, the high-conductivity flow electrode uses pig manure-based porous carbon as the active material. The preparation method of the flow electrode is as follows: drying, crushing, grinding and screening the raw material pig manure, carbonizing the screened pig manure powder in an inert gas, fully mixing the carbonized pig manure powder with a strong base, deionized water and a supporting electrolyte, and drying the mixture, sintering the mixture at a high temperature in an inert gas to achieve alkali activation of the carbonized pig manure powder to obtain pig manure-based porous carbon; fully mixing the pig manure-based porous carbon with carbon black, ultrapure water and a supporting electrolyte, and then subjecting the pig manure-based porous carbon to ultrasonic and magnetic stirring treatment to obtain a uniform high-conductivity flow electrode. The present invention converts livestock and poultry waste into a high-conductivity flow electrode through carbonization, activation and ultrasonic treatment. Compared with commercial activated carbon, the electronic conductivity of the pig manure-based porous carbon is several orders of magnitude higher, and the overall resistance of the pig manure-based porous carbon-based flow electrode is low. In addition, the porous carbon surface prepared in this way contains abundant hydrophilic groups, showing strong hydrophilicity and small contact angle, so the highly conductive flow electrode also has the characteristics of low viscosity and high fluidity, thereby ensuring the robustness of performance. The electrochemical nitrogen-phosphorus adsorption separation process based on the highly conductive flow electrode provided by the present invention can efficiently transmit ammonium ions and phosphate ions, and realize efficient adsorption, separation and recovery of nitrogen and phosphorus in sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a SEM image of the pig manure-based porous carbon prepared in Example 1 of the present invention; Figure 2 TEM image of the pig manure-based porous carbon prepared in Example 1 of the present invention; Figure 3 This is the FTIR characterization image of the pig manure-based porous carbon prepared in Example 1 of the present invention; Figure 4 The nitrogen adsorption-desorption curve and pore size distribution diagram of the pig manure-based porous carbon prepared in Example 1 of the present invention; Figure 5 The water contact angles of the pig manure-based porous carbon and commercial activated carbon prepared in Example 1 of the present invention; Figure 6 The electronic conductivity of the pig manure-based porous carbon and commercial activated carbon prepared in Example 1 of the present invention is measured by a four-point probe method; Figure 7 This is a graph showing the viscosity test results of the pig manure-based porous carbon and commercial activated carbon prepared in Example 1 of the present invention; Figure 8 A schematic diagram of an electrochemical nitrogen and phosphorus adsorption separation process system constructed in Example 2 of the present invention; Fig. 9A schematic diagram of the internal structure of a mobile electrode electrochemical cell in the process constructed in Example 2 of the present invention; Fig.10 The electrochemical impedance spectrum of the electrochemical nitrogen and phosphorus adsorption separation process system constructed in Example 2 of the present invention; Fig.11 A comparison chart of the ammonia nitrogen adsorption and separation performance of the high-conductivity mobile electrode prepared in Example 2 of the present invention and the commercial activated carbon mobile electrode prepared in Comparative Example 2 in the electrochemical nitrogen-phosphorus adsorption and separation process system constructed in Example 2 for simulated sewage; Fig.12 This is a result diagram of the adsorption and separation performance of phosphorus in water by the high-conductivity mobile electrode prepared in Example 2 of the present invention when simulating sewage treatment at different initial phosphorus concentrations; Fig.13 This is a graph showing the performance of the simultaneous adsorption and separation rate of nitrogen and phosphorus by the highly conductive mobile electrode prepared in Example 2 of the present invention in actual pig farm wastewater treatment. DETAILED DESCRIPTION

[0011] refer to Figure 1-Figure 13 The present invention provides a method for preparing a high-conductivity mobile electrode for nitrogen and phosphorus adsorption separation in sewage, comprising a mobile electrode, wherein the mobile electrode is made of pig manure, which is livestock and poultry breeding waste, and the method for preparing the mobile electrode using pig manure as raw material comprises the following steps: S1. Dry the fresh pig manure in an oven to remove moisture until the quality no longer decreases; S2, crushing, grinding and screening the dried pig manure; S3, pre-carbonizing the sieved pig manure powder in an inert gas; S4, fully mixing the pre-carbonized pig manure, strong alkali and ultrapure water; S5, drying the mixture in an oven, and then activating it in an inert gas to obtain pig manure-based porous carbon; S6, repeatedly washing the pig manure-based porous carbon with hydrochloric acid and ultrapure water; S7, uniformly mixing the pig manure-based porous carbon, carbon black, ultrapure water and supporting electrolyte sodium chloride, ultrasonically treating at room temperature, and then magnetically stirring to obtain a highly conductive semi-solid mobile electrode suspension; In the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art. In the present invention, fresh livestock and poultry breeding waste pig manure is dried, crushed, ground and sieved to obtain pig manure powder.

[0012] In the present invention, the drying temperature is preferably 105°C, and the specific implementation method of drying is preferably oven drying. The present invention has no special requirements for the drying time, and the pig manure can be dried until the weight is constant. There are no special requirements for the specific implementation process of crushing and grinding. In the present invention, screening is preferably through a 100 mesh sieve. In the present invention, the particle size of the pig manure is preferably ≤149 μm.

[0013] The present invention carbonizes the sieved pig manure powder in a protective gas atmosphere, the carbonization temperature is preferably 500-600°C, more preferably 500°C, the carbonization holding time is preferably 2-3 h, more preferably 2 h, and the inert protective gas during carbonization is preferably nitrogen.

[0014] The method comprises fully mixing and drying carbonized pig manure powder, a strong base and ultrapure water, and activating the dried mixture in an inert gas to obtain pig manure-based porous carbon.

[0015] In the present invention, the strong base is preferably potassium hydroxide, and the mass ratio of the carbonized pig manure powder to the strong base is preferably 1:3. The present invention has no special requirements on the amount of water used, and it is sufficient to ensure that the inorganic strong base is completely dissolved and evenly mixed with the carbonized pig manure powder.

[0016] The present invention preferably further comprises drying the mixed liquid obtained by mixing the pig manure biochar, the inorganic strong base and water before activation. In the present invention, the drying temperature is preferably 105°C, the drying insulation time is preferably 24 h, and the specific implementation method of drying is preferably oven drying.

[0017] In the present invention, the activation temperature is preferably 700-900°C, more preferably 800°C, the activation holding time is preferably 1-2 h, more preferably 1 h, and the activation protective gas is preferably nitrogen.

[0018] In the present invention, activation is performed to obtain an activated material. In the present invention, the activated material is preferably post-treated to obtain a pig manure-based porous carbon. In the present invention, the post-treatment preferably includes the following steps: the activated material is placed in a hydrochloric acid solution and washed until the pH value is 7, and then membrane filtered to obtain a solid material; the solid material is dried to obtain a pig manure-based porous carbon. In the present invention, the concentration of the hydrochloric acid solution is preferably 1 mol / L. In the present invention, the pore size of the filter membrane used in membrane filtration is preferably 45 mm. In the present invention, the drying temperature is preferably 105°C, the drying insulation time is preferably 24 h, and the specific implementation method of drying is preferably drying.

[0019] The invention uniformly mixes pig manure-based porous carbon with carbon black, ultrapure water and supporting electrolyte sodium chloride to obtain a highly conductive semi-solid flow electrode suspension.

[0020] In the present invention, the mass fraction of the pig manure-based porous carbon in the high-conductivity mobile electrode is preferably 5 wt.%, the mass fraction of carbon black is preferably 0.5 wt.%, and the concentration of the supporting electrolyte sodium chloride is preferably 1 g / L.

[0021] In the present invention, the pig manure-based porous carbon is uniformly mixed with carbon black, ultrapure water and supporting electrolyte sodium chloride. The present invention preferably subjects the mixture to ultrasonic treatment and magnetic stirring. The frequency of the ultrasonic treatment is preferably 53 kHz, and the time of the ultrasonic treatment is preferably 1 h; the rotor speed of the magnetic stirring treatment is preferably 300 rpm, and the magnetic stirring treatment time is preferably 24 h.

[0022] The electronic conductivity of the pig manure-based porous carbon at 1 MPa pressure is 17.10 S / cm; The specific surface area of ​​the pig manure-based porous carbon rice is 766.51 m 2 / g; Pig manure-based porous carbon has abundant mesopores, with a volume percentage of mesopores greater than 50%, an average pore size of less than 2 nm, and a volume percentage of micropores greater than or equal to 90%; The surface of pig manure-based porous carbon contains hydrophilic functional groups, which mainly include hydroxyl groups. The water contact angle of pig manure-based porous carbon is 19.4°, the high conductive mobile electrode viscosity is 1.53 mPa·s, and the mesopores are pores with a pore size greater than 2 nm and less than 50 nm.

[0023] The high-conductivity flow electrode provided by the present invention has better conductivity, better hydrophilicity, stronger fluidity and better ion transmission performance than the common commercial activated carbon flow electrode. In addition, in a high-efficiency electrochemical nitrogen-phosphorus adsorption separation process provided by the present invention, the use of the high-conductivity flow electrode can significantly improve the nitrogen-phosphorus removal efficiency, showing many significant advantages over the common commercial activated carbon flow electrode.

[0024] The high-conductivity mobile electrode provided by the present invention has outstanding fluidity (rheological properties) due to its good hydrophilicity (water contact angle is 19.4°, and there are a large number of hydrophilic functional groups on the surface) and extremely low viscosity (almost equal to the viscosity of deionized water, much lower than the viscosity of the activated carbon mobile electrode).

[0025] In the present invention, a high-conductivity mobile electrode is provided with excellent electronic conductivity and ion transport properties due to the hierarchical porous structure and graphite-like domains introduced by carbonization and alkali activation.

[0026] In the present invention, the provided high-conductivity mobile electrode has a high nitrogen and phosphorus removal efficiency. This is because the long-range disordered and short-range ordered graphite-like domains in its structure significantly improve its electronic conductivity, and the reasonable hierarchical porous structure is conducive to the diffusion and transmission of ions therein. In addition, its excellent hydrophilicity and fluidity are also conducive to the formation of a charge permeation network and the diffusion of ions, thereby improving its nitrogen and phosphorus adsorption and separation performance.

[0027] The present invention provides a high-efficiency electrochemical nitrogen-phosphorus adsorption separation process, which includes a flow electrode, a direct current power supply, a current sensor, a conductivity sensor, a multi-channel data recorder, an electrochemical workstation, a flow electrode electrochemical cell, and a peristaltic pump. The power supply mode of the direct current power supply is constant voltage power supply, and the flow electrode is a high-conductivity flow electrode based on pig manure-based porous carbon.

[0028] In the present invention, the flowing electrode electrochemical cell is composed of a current collector having a serpentine flowing electrode flow channel, an ion exchange membrane, a water inlet flow channel, and a gasket.

[0029] In the present invention, the effective contact area between the serpentine flow electrode flow channel and the ion exchange membrane is preferably 22.8 cm 2 .

[0030] The operating mode of the high-efficiency electrochemical nitrogen-phosphorus adsorption separation process is preferably a short-circuit closed cycle mode.

[0031] In the present invention, the working voltage of the constant voltage power supply is preferably 1~1.6 V. In the present invention, the flow electrode and the water inlet flow are controlled by a peristaltic pump, the flow rate is preferably 10~30 mL / min, the ammonia nitrogen content in the inlet water body is ≥100 mgN / L, and the phosphorus content in the inlet water body is ≥1 mgP / L.

[0032] The present invention preferably collects the conductivity of the influent water body and the current data flowing through the system through a data recorder connected to the conductivity sensor and the current sensor. The preferred time interval for data collection is 30 s. An influent water sample is taken every 30 minutes for ammonia nitrogen concentration detection. The detection method is Nessler's reagent spectrophotometry. Specifically refer to the "National Environmental Protection Standard of the People's Republic of China (HJ 535-2009)", and then the ammonia nitrogen adsorption separation performance and energy consumption of the high-conductivity flow electrode are investigated; an influent water sample is taken every 20 minutes for phosphorus concentration detection. The detection method is molybdenum antimony spectrophotometry. Specifically refer to the "Water and Wastewater Detection and Analysis Methods (Fourth Edition)", which is equivalent to GB 11893-89. Then the phosphorus adsorption separation performance and energy consumption of the high-conductivity flow electrode are investigated.

[0033] In order to further illustrate the present invention, the technical solution provided by the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0034] Example 1 First, fresh pig manure from livestock and poultry farms was placed in an oven and dried at 105 °C until the quality no longer decreased. The dried pig manure was crushed with a pulverizer and then ground into powder. The pig manure powder was sieved through a 200-mesh sieve and placed in a tubular furnace. The temperature was raised to 500 °C at a rate of 5 °C / min under a nitrogen atmosphere. After keeping the temperature for 2 hours and cooling naturally, carbonized pig manure powder was obtained. The carbonized pig manure powder was fully mixed with potassium hydroxide in deionized water at a mass ratio of 1:3, and then treated at 105 °C for 24 hours. The resulting mixture was placed in a tubular furnace, and the temperature was raised to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere. After keeping the temperature for 1 hour and cooling naturally, potassium hydroxide-activated pig manure-based porous carbon was obtained. The obtained pig manure-based porous carbon material was washed with 1 M hydrochloric acid until the pH was 7, then filtered with a 45 mm filter membrane, and treated in an oven at 105 °C for 24 hours.

[0035] Test Example 1 The morphology, structure and elements of the pig manure-based porous carbon particles provided in Example 1 were characterized by using a variety of testing techniques. Among them, the morphology of the pig manure-based porous carbon was observed by scanning electron microscopy (SEM); the microstructure and graphite-like domains of the pig manure-based porous carbon were observed by high-resolution transmission electron microscopy (TEM); and the surface functional groups of the pig manure-based porous carbon were characterized by Fourier transform infrared spectroscopy (FTIR); Figure 1 This is a SEM image of the pig manure-based porous carbon prepared in Example 1 of the present invention. Figure 1 It can be seen that the pig manure-based porous carbon prepared in Example 1 of the present invention has a porous structure; Figure 2 TEM image of the pig manure-based porous carbon prepared in Example 1 of the present invention. Figure 2 It can be seen that the pig manure-based porous carbon prepared in the embodiment of the present invention has short-range ordered graphite-like domains; Figure 3 This is the FTIR characterization diagram of the pig manure-based porous carbon prepared in Example 1 of the present invention. Figure 3 It can be seen that the surface of pig manure-based porous carbon has hydrophilic functional groups hydroxyl and carboxyl.

[0036] Test Example 2 Using the standard degassing station of the Mac Instrument, the carbonized pig manure and the alkali-activated pig manure-based porous carbon in Example 1 were pretreated for 12 h under vacuum at 200 °C, and then the samples were subjected to nitrogen adsorption and desorption tests respectively using the 4-station fully automatic specific surface area analyzer of the American Micromeritics APSP 2460 model under 77K liquid nitrogen conditions. After the instrument analysis was completed, the isothermal adsorption and desorption curve was obtained, and the total specific surface area of ​​the material was obtained by the (BET) specific surface area test method, and the pore size distribution of the material was obtained by the (NL-DFT) model. Table 1 is a comparison of the pore structures of the pig manure-based porous carbon prepared in Example 1 and the commercial activated carbon. Figure 4 The nitrogen adsorption-desorption curve and pore size distribution diagram of the pig manure-based porous carbon prepared in Example 1 are shown in Table 1 and Figure 4 It can be seen that the pig manure-based porous carbon prepared in Example 1 of the present invention has a hierarchical porous structure, in which there are more mesopores (pore diameter greater than 2 nm and less than 50 nm).

[0037] Table 1 is a comparison of the specific surface area, pore volume and average pore size of the pig manure-based porous carbon prepared in Example 1 and the unactivated carbonized pig manure

[0038] Test Example 3 (1) Take appropriate amounts of the pig manure-based porous carbon prepared in Example 1 and commercial activated carbon powder, press them into sheets using an infrared tablet press, place them in a JY-82 contact angle test platform, drop water on them using the automatic titration system of the equipment, shoot a test video, and measure the contact angle using the high titration method. Figure 5 The water contact angles of the pig manure-based porous carbon and commercial activated carbon prepared in Example 1 of the present invention; Figure 5 It can be seen that compared with commercial activated carbon, the water contact angle of the pig manure-based porous carbon prepared in Example 1 of the present invention is significantly smaller, indicating that the pig manure-based porous carbon prepared in Example 1 of the present invention has good hydrophilicity.

[0039] (2) Four-point probe resistivity test: The electronic conductivity of the pig manure-based porous carbon prepared in Example 1 and the commercial activated carbon was measured using a four-point probe method. Figure 6 For the test results. Figure 6 It can be seen that compared with commercial activated carbon, pig manure-based porous carbon exhibits very high electronic conductivity, and the surface pig manure-based porous carbon has strong electron transmission ability.

[0040] (3) Take the pig manure-based porous carbon and commercial activated carbon prepared in Example 1 and prepare them into a semi-solid flow electrode suspension with a mass fraction of 5 wt.% using deionized water. Place 25 mL of the flow electrode slurry in the test tube of the viscometer, keep the viscometer in a horizontal state, and install the protective frame. Refer to the range table, select rotor No. 0 for testing, select rotor No. 0 into the viscometer rotor connector, slowly adjust the viscometer lifting knob, and adjust the height of the rotor in the measured liquid until the liquid level mark of the rotor is level with the liquid surface. Start the viscometer and start measuring the viscosity of the flow electrode at a speed of 60 rpm. Figure 7 is the viscosity test result. Figure 7 It can be seen that compared with the flow electrode based on commercial activated carbon, the flow electrode based on the pig manure-based porous carbon prepared in Example 1 of the present invention has a lower viscosity. This flow electrode with low viscosity characteristics reduces the possibility of blockage during the operation of the flow electrode electrochemical system, ensuring the robust performance of the system.

[0041] Example 2 4.5 g of the swine manure-based porous carbon prepared in Example 1, 0.5 g of carbon black, and 95 g of deionized water were mixed, and 0.1 g of sodium chloride was added as a supporting electrolyte. After mixing evenly, the mixture was treated with 53 kHz ultrasound for 1 hour, and then magnetically stirred at 300 rpm for 24 hours to obtain a flow electrode based on swine manure-based porous carbon, i.e., a high-conductivity flow electrode provided by this patent. A set of electrochemical nitrogen and phosphorus adsorption separation process was constructed. The system composition and internal structure diagram of this process are shown in FIG. Figure 8 and Fig. 9 As shown, the high conductivity flow electrode provided by this patent is pumped into the positive electrode chamber and the negative electrode chamber of the electrochemical cell at a flow rate of 10 mL / min, the constant voltage power supply is 1.2V, and then the NH4Cl simulated wastewater with an initial concentration of 1000 mgN / L is pumped in at a flow rate of 10 mL / min as the influent, and the operation is carried out in a short-circuit closed circulation mode.

[0042] Comparative Example 1 The method is basically the same as that in Example 2, except that commercial activated carbon is used to replace the pig manure-based porous carbon to obtain a flow electrode based on commercial activated carbon.

[0043] Test Example 4 In the two-electrode system, an electrochemical impedance spectroscopy (EIS) test was performed on the electrochemical cell constructed in Example 2 using an electrochemical workstation. In the test, the amplitude of the alternating current signal applied to the flow electrode electrochemical cell system in Example 2 was 5 mV, and the test frequency range was 10 -3 ~ 10 5Hz, the equivalent circuit model was established and fitted using Zview software to obtain the resistance value at each frequency distribution. The results are shown in Fig.10 shown. Fig.13 It shows that the electrochemical cell with the high-conductivity flow electrode provided by this patent being circulated and pumped has a lower overall resistance and has a better charge percolation network and ion transport performance.

[0044] Test Example 5 The conductivity meter and current sensor collect the conductivity of the simulated wastewater and the current data flowing through the system every 30 seconds, and a water sample is taken every hour for ammonia nitrogen concentration detection. The detection method is Nessler's reagent spectrophotometry, with specific reference to the "National Environmental Protection Standards of the People's Republic of China (HJ 535-2009)", and then examine the adsorption and separation performance of ammonia nitrogen in water by the high conductivity flow electrode provided by this patent in the process constructed by this patent. Fig.11 The graph of the variation of ammonia nitrogen removal rate over time when the high-conductivity flow electrode prepared in Example 2 of the present invention and the commercial activated carbon flow electrode prepared in Comparative Example 2 are used to treat ammonia nitrogen in water in the electrochemical nitrogen-phosphorus adsorption separation process system constructed in Example 2. Fig.11 It can be seen that the removal rate of ammonia nitrogen in water by the high-conductivity flowing electrode prepared in Example 2 of the present invention is better than the removal rate of ammonia nitrogen by the commercial activated carbon flowing electrode prepared in Comparative Example 2.

[0045] Example 3 The operation is basically the same as that of Example 2, except that the influent water is a simulated phosphorus-containing sewage of an equimolar mixture of Na2HPO4 and NaH2PO4, and the initial phosphorus concentrations are 20 mgP / L, 10 mgP / L, and 5 mgP / L, respectively.

[0046] Test Example 6 The conductivity meter and current sensor collect the conductivity of the simulated wastewater and the current data flowing through the system every 30 seconds, and a water sample is taken every 20 minutes for phosphorus concentration detection. The detection method is molybdenum antimony anti-spectrophotometry. For specific reference, the "Water and Wastewater Detection and Analysis Methods (Fourth Edition)", which is equivalent to GB 11893-89, and then the high conductivity flow electrode provided by this patent is examined in the process constructed by this patent. The adsorption and separation performance of phosphorus in water bodies. Fig.12 The highly conductive flow electrode based on pig manure-based porous carbon prepared in Example 2 of the present invention has adsorption and separation performance for phosphorus in water when treating influent water containing different initial phosphorus concentrations in the process provided in Example 2.

[0047] Comparative Example 2 The method is basically the same as that of Example 3 and Example 4, except that the influent water body is real pig farm sewage, and its initial ammonia nitrogen concentration is about 212.26 mgN / L, and its initial phosphorus concentration is about 31.65 mgP / L.

[0048] Test Example 7 The conductivity meter and current sensor collect the conductivity of the simulated wastewater and the current data flowing through the system every 30 seconds, and a water sample is taken every 20 minutes to detect the ammonia nitrogen concentration and phosphorus concentration. The detection method of ammonia nitrogen concentration and phosphorus concentration is the same as that of Test Example 5 and Test Example 6. Fig.13 The high-conductivity flow electrode prepared in Example 2 demonstrated the simultaneous adsorption and separation rate performance of nitrogen and phosphorus in actual pig farm wastewater in the electrochemical nitrogen-phosphorus adsorption and separation process constructed in Example 2. The results showed that the high-conductivity flow electrode and electrochemical nitrogen-phosphorus adsorption and separation process provided in Example 2 had excellent electrochemical nitrogen-phosphorus adsorption and separation performance for both simulated and actual wastewater.

[0049] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-conductivity mobile electrode for nitrogen and phosphorus adsorption separation in sewage, comprising a mobile electrode, characterized in that: The mobile electrode uses pig manure, a livestock and poultry breeding waste, as a raw material, and the preparation method of the mobile electrode using pig manure as a raw material comprises the following steps: S1. Dry the fresh pig manure in an oven to remove moisture until the quality no longer decreases; S2, crushing, grinding and screening the dried pig manure; S3, pre-carbonizing the sieved pig manure powder in an inert gas; S4, fully mixing the pre-carbonized pig manure, strong alkali and ultrapure water; S5, drying the mixture in an oven, and then activating it in an inert gas to obtain pig manure-based porous carbon; S6, repeatedly washing the pig manure-based porous carbon with hydrochloric acid and ultrapure water; S7. Pig manure-based porous carbon, carbon black, ultrapure water and supporting electrolyte sodium chloride are uniformly mixed, ultrasonically treated at room temperature, and then magnetically stirred to obtain a highly conductive semi-solid flow electrode suspension.

2. The method for preparing a high-conductivity mobile electrode for nitrogen and phosphorus adsorption separation in sewage according to claim 1, characterized in that: The screen size of the screening is 100-200 meshes.

3. The method for preparing a high-conductivity mobile electrode for nitrogen and phosphorus adsorption separation in sewage according to claim 1, characterized in that: The carbonization temperature is 500-600°C, and the pre-carbonization insulation time is 2-3 h.

4. The method for preparing a high-conductivity mobile electrode for nitrogen and phosphorus adsorption separation in sewage according to claim 1, characterized in that: The temperature of the alkali activation is 700-900°C, and the activation holding time is 1-2 h.

5. A method for preparing a high-conductivity mobile electrode for nitrogen and phosphorus adsorption separation in sewage according to claim 1, characterized in that: The mass fraction of pig manure-based porous carbon in the mobile electrode suspension is greater than 4.5 wt.%, the mass fraction of carbon black is greater than 0.5 wt.%, and the concentration of supporting electrolyte sodium chloride is 1~2 g / L.

6. The method for preparing a high-conductivity mobile electrode for nitrogen and phosphorus adsorption separation in sewage according to claim 1, characterized in that: The temperature of the ultrasonic treatment is 25° C., the treatment time is 0.5 to 1 hour, and the magnetic stirring time is at least 24 hours.

7. The method for preparing a high-conductivity mobile electrode for nitrogen and phosphorus adsorption separation in sewage according to any one of claims 1 to 6, characterized in that: The surface of the pig manure-based porous carbon contains hydrophilic functional groups, and the hydrophilic functional groups mainly include hydroxyl groups; The specific surface area of ​​the pig manure-based porous carbon rice is 766.51 m 2 / g; The pig manure-based porous carbon has abundant mesopores, and the volume percentage of mesopores is greater than 50%; The pig manure-based porous carbon has an electronic conductivity of 17.10 S / cm under a pressure of 1 Mpa; The water contact angle of the pig manure-based porous carbon is 19.4°; The viscosity of the pig manure flow electrode is 1.53 mPa·s; The electrochemical nitrogen-phosphorus adsorption separation system based on the electrode of pig manure flow has an overall resistance of 26.61 Ω when the electrolyte is 1000 mgN / L ammonium chloride solution.

8. A flow electrode electrochemical nitrogen-phosphorus adsorption separation process using a method for preparing a high-conductivity flow electrode for nitrogen-phosphorus adsorption separation in sewage, the flow electrode electrochemical nitrogen-phosphorus adsorption separation process comprising a flow electrode, a DC power supply, a current sensor, a conductivity sensor, a multi-channel data recorder, an electrochemical workstation, a flow electrode electrochemical cell, and a peristaltic pump, characterized in that: The DC power supply is a constant voltage power supply.

9. The mobile electrode electrochemical nitrogen and phosphorus adsorption separation process according to claim 8, characterized in that: The flow electrode electrochemical cell is composed of a current collector with a serpentine flow electrode flow channel, an ion exchange membrane, a water flow channel, and a gasket. The effective contact area between the ion exchange membrane and the serpentine flow electrode flow channel is 15-30 cm 2 .

10. The mobile electrode electrochemical nitrogen and phosphorus adsorption separation process according to claim 8, characterized in that: The ion exchange membrane needs to be soaked in ultrapure water for at least 24 hours before use. The flow rate of the flow electrode and the inlet water in the flow electrode electrochemical nitrogen-phosphorus adsorption separation process is 10-30 mL / mi.

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