Iron-based micro-electrolysis filler, preparation method and application thereof

Abstract

The application relates to the field of water treatment materials, and particularly discloses an iron-based micro-electrolysis filler as well as a preparation method and application thereof. The preparation method comprises the following steps: using aromatic diacid and aliphatic diol as raw materials, and preparing polyester raw materials through an ester exchange method; heating and melting the polyester raw materials under nitrogen protection, rapidly water-cooling, cutting to obtain spherical haydite, and drying to obtain porous haydite; preparing modified haydite loaded with nano-iron: through atomic layer deposition treatment, nano-iron is evaporated and deposited on the porous haydite to prepare the modified haydite; preparing the iron-based micro-electrolysis filler: spraying a silicon dioxide modified polyaniline solution on the modified haydite, and solidifying to obtain the iron-based micro-electrolysis filler; and the application also discloses the iron-based micro-electrolysis filler prepared by using the above preparation method and application of the iron-based micro-electrolysis filler in water treatment. The filler prepared by the application solves the problems that the current iron-carbon micro-electrolysis filler is prone to rusting and hardening during operation, and the water treatment effect is reduced, and the treatment effect of the micro-electrolysis on wastewater is improved.

Description

Technical Field

[0001] This application relates to the field of water treatment technology, and more specifically, to an iron-based micro-electrolysis packing material, its preparation method, and its application. Background Technology

[0002] With the rapid development of industry, various industrial wastewater treatment problems have become increasingly prominent. In the field of wastewater treatment, my country's water treatment process is mainly based on biological methods. However, toxic and recalcitrant organic matter in industrial wastewater is often difficult to treat to meet discharge standards using biological methods. Even with chemical oxidation, it is difficult to completely degrade some large molecular organic matter into inorganic matter.

[0003] Currently, micro-electrolysis technology, based on the synergistic treatment effect of oxidation-reduction reactions, achieves the breaking of large molecular organic compounds and the reduction of oxidizing substances in wastewater, thereby degrading or removing organic pollutants and improving the biodegradability coefficient of wastewater, thus achieving the purpose of wastewater pretreatment. Due to its simple process and convenient operation, it is a widely researched and applied wastewater treatment technology. Currently, the iron-carbon micro-electrolysis method is a relatively mature chemical reduction process both domestically and internationally. Its mechanism mainly includes the electrochemical catalysis of the cathode, direct reduction of iron, reduction of nascent hydrogen, and polymerization and precipitation of hydroxyl iron complexes. Engineering applications have shown that this method has a good effect on removing recalcitrant organic pollutants from industrial wastewater such as dye wastewater, printing and dyeing wastewater, papermaking wastewater, and chemical wastewater.

[0004] However, with the development of iron-carbon micro-electrolysis technology, its shortcomings in wastewater treatment engineering applications have gradually become apparent. Currently, iron-carbon micro-electrolysis packing mainly consists of iron powder and carbon powder in a specific ratio, along with auxiliary raw materials such as pore-forming agents, binders, and catalysts. After operating in wastewater engineering for a period of time, the iron materials in direct contact with the packing are prone to rusting and caking, reducing the wastewater treatment effect and hindering the widespread application of micro-electrolysis technology. Summary of the Invention

[0005] To address the problem that current iron-carbon micro-electrolysis packing materials are prone to rusting and caking during operation, thus reducing wastewater treatment efficiency, and to improve the wastewater treatment effect of micro-electrolysis, this application provides an iron-based micro-electrolysis packing material, its preparation method, and its application.

[0006] In a first aspect, this application provides a method for preparing iron-based micro-electrolysis fillers, employing the following technical solution: A method for preparing an iron-based micro-electrolysis filler includes the following steps: S1. Preparation of polyester raw materials: Polyester raw materials are prepared by transesterification using aromatic diacids and aliphatic diols as raw materials. S2. Preparation of porous ceramsite: Polyester raw material is heated and melted to 200-240℃ under nitrogen protection, and then rapidly cooled in water at 0-5℃. After water cooling and solidification, it is cut into spherical ceramsite and dried to obtain porous ceramsite. S3. Preparation of modified ceramic particles loaded with nano-iron: Nano-iron is evaporated and deposited onto porous ceramic particles through atomic layer deposition to obtain modified ceramic particles. S4. Preparation of iron-based micro-electrolysis filler: Spray silica-modified polyaniline solution onto the modified ceramic particles obtained in step S3, and cure to obtain iron-based micro-electrolysis filler.

[0007] By adopting the above technical solution, this application uses polyester raw material as a reference, and after water-cooled pore-inducing treatment, a large number of micro cracks and pores are generated inside the polyester raw material through rapid high and low temperature conversion, so as to produce porous ceramic particles. Moreover, by controlling the water cooling temperature, the water cooling rate can be controlled, thereby obtaining porous ceramic particles with better pore structure. Then, nano-iron is loaded on the surface of the porous ceramic particles by atomic layer deposition. Finally, a silica-modified polyaniline conductive polymer solution is sprayed onto its surface to form a conductive polymer coating. This conductive polymer coating solves the problem of rusting and caking caused by direct contact between the iron material and wastewater in iron-based micro-electrolysis fillers. Furthermore, the conductive polymer coating does not affect the micro-electrolysis function of the iron-based micro-electrolysis filler. The use of silica-modified polyaniline solution also improves the conductivity of the iron-based micro-electrolysis filler, better transmitting current and accelerating the electrolysis reaction, resulting in better wastewater treatment.

[0008] In summary, the iron-based micro-electrolysis filler provided in this application represents a change in the current form of iron addition to the anode. The iron-based micro-electrolysis filler uses a porous structure formed from polyester as a carrier to load nano-iron, and then a conductive polymer protective coating protects the iron, solving the problem of reduced treatment efficiency due to viscosity surrounding the iron upon direct contact with water. In the conductive polymer protective coating, silica acts as a dispersant and polyaniline as a continuous conductive phase, improving conductivity through their electron transport channels. Combined with the porous structure and hydrophilicity of silica in the protective coating, it possesses water permeability, enabling micro-electrolysis with the carbon source, while simultaneously blocking impurities such as clay, thus solving the problem of reduced treatment efficiency caused by direct contact between iron and water.

[0009] Optionally, in step S1, the aromatic diacid is a mixture of terephthalic acid and isophthalic acid, and the mass ratio of terephthalic acid to isophthalic acid is 60:(30-50). The aliphatic diol is a mixture of 1,4-butanediol and 1,6-hexanediol, and the mass ratio of 1,4-butanediol to 1,6-hexanediol is 55:(40-50). The mass ratio of the aromatic diacid to the aliphatic diol is 1:(1-1.2).

[0010] By adopting the above technical solution, the addition of aromatic diacid isophthalic acid improves the toughness and flexibility of polyester raw material molecules, which is beneficial for preventing microcracks in the subsequent processing of polyester raw materials. The addition of 1,4-butanediol and 1,6-hexanediol increases the flexibility of the polyester main chain. The final polyester has a molecular weight greater than 35,000, a molecular weight distribution index of 1.8-2.2, a melt index of 220-240℃, high thermoplasticity, and crystallinity of less than 30%. After subsequent water-cooling pore-forming treatment, the porous ceramic particles have better pore distribution and better loading capacity and uniformity of nano-iron. The final iron-based micro-electrolysis filler has a better effect on the removal of organic matter from wastewater.

[0011] Optionally, in step S1, the specific operation of transesterification is as follows: The raw material is heated and melted to 180±20℃, then an acidic catalyst is added, and the temperature is raised to 220±20℃. The reaction is carried out under reduced pressure of 0.08±0.02MPa for 2-3 hours, the reaction is terminated, and the temperature is lowered to obtain polyester raw material.

[0012] By adopting the above technical solution and controlling the reaction temperature, time, and raw material ratio, the desired high molecular weight polyester raw material can be obtained. The addition of acid catalyst can significantly increase the transesterification reaction rate.

[0013] Optionally, the amount of acidic catalyst added is 0.1-0.5 wt% of the raw material.

[0014] By employing the above technical solution and selecting the acidic catalyst added in the above proportion, the transesterification reaction rate can be significantly increased. When the amount of acidic catalyst added is too small, the increase in reaction rate is not significant; when the amount added is too large, the content of acidic catalyst in the reaction system is too high, leading to the formation of distilled products by side reactions, which inhibits the formation of the target product and is not conducive to obtaining the desired high molecular weight polyester. When adding the catalyst in the above proportion, its catalytic effect can be fully utilized without excessively inhibiting the reaction.

[0015] Optionally, in step S2, after heating and melting the polyester raw material to 200-240°C, the resulting melt is extruded in multiple stages into extrusion strips with a diameter of 5-10 mm, and then water-cooled in a nitrogen environment.

[0016] By adopting the above technical solution, the polyester raw material is subjected to multi-stage extrusion to obtain small-diameter extrusion strips, followed by water-cooling to induce pores. This process is more favorable for constructing the pore structure of the final spherical ceramsite, resulting in porous ceramsite with a porosity ≥50% and a specific surface area >500 m². 2 / g, further improving the loading effect of porous ceramsite on nano-iron, and further improving the treatment effect of iron-based micro-electrolysis packing on wastewater.

[0017] Optionally, in step S3, during atomic layer deposition, the pressure is 0.01-0.05 MPa and the temperature is controlled at 100-150℃, so that the nano-iron is evaporated and deposited onto the porous ceramic particles, wherein the amount of nano-iron particles added is 8-10% of the mass of the porous ceramic particles.

[0018] By adopting the above technical solution, this application uses atomic layer deposition (ALD) to load nano-iron onto porous ceramic particles. ALD is a self-limiting growth mode, allowing iron to be highly released and deeply penetrate into the ceramic particles, achieving a higher iron loading capacity. The iron loading capacity in this application is 3-5 times that of traditional loading processes. Moreover, this process can strictly control the iron loading capacity, ensuring high dispersion of iron in the porous ceramic particles. Regarding the pressure and temperature control during ALD, under these conditions, the effective release of nano-iron and its full reaction with the porous ceramic particles are achieved, allowing the nano-iron to be efficiently and uniformly deposited on the surface of the porous ceramic particles, thus achieving a high loading capacity and dispersion effect. Too low a pressure and temperature are detrimental to the release of nano-iron, while too high a pressure and temperature can cause some nano-iron to aggregate, hindering dispersion.

[0019] Optionally, in step S3, the nano-iron is obtained by the following method: Ferric nitrate is dissolved in water to obtain a ferric nitrate solution. The pH of the ferric nitrate solution is adjusted to 3-5, and the concentration of the ferric nitrate solution is 0.05-0.2 mol / L. A reduction reaction is initiated by introducing hydrogen gas into a ferric nitrate solution. The hydrogen gas flow rate is 50-100 mL / min, the reaction temperature is 60-80℃, and the reaction time is 2-4 h. After the reaction was completed, the particles were centrifuged, washed, and dried to obtain nano-iron particles with a particle size of 20-50 nm.

[0020] By adopting the above technical solution, when preparing nano-iron, if the pH value is too low, it will inhibit the subsequent hydrogen reduction reaction, while if the pH value is too high, it will lead to the precipitation of iron ions. If the concentration of ferric nitrate is too low, it will not be conducive to the reduction reaction, while if the concentration is too high, it will lead to excessive aggregation of nano-iron. During the subsequent hydrogen reduction reaction, the hydrogen flow rate needs to be controlled. If the hydrogen flow rate is too low, the supply of reducing agent will be insufficient and the reaction will be slow, while if the flow rate is too high, it will lead to uneven mixing of the reaction system. If the temperature is too low, the reaction rate will be slow, and if the temperature is too high, it will lead to product aggregation. If the reaction time is too short, the yield will be high, while if it is too long, the product will grow excessively. In this application, the control of the pH and concentration of the ferric nitrate solution ensures the smooth progress of the nano-iron synthesis reaction, while the control of the flow rate, temperature and time in the hydrogen reduction process ensures the excellent synthesis effect of nano-iron, so that it has a higher loading capacity with porous ceramic particles, and ultimately a better wastewater treatment effect.

[0021] Optionally, in step S4, the specific curing operation is as follows: the modified ceramic particles coated with silica-modified polyaniline solution are microwave cured at a curing temperature of 150±10℃ and a holding time of 5-10 min, and then cooled to obtain iron-based micro-electrolysis filler.

[0022] By adopting the above technical solution, the modified ceramic particles coated with silica-modified polyaniline solution are microwave-cured, which efficiently completes the cross-linking and curing of the coating, enhances the bonding force between the conductive polymer coating and the modified ceramic particle matrix, and avoids the oxidative degradation of the conductive polymer under high temperature conditions.

[0023] Optionally, in step S4, the silica-modified polyaniline solution is prepared by the following method: Silica sol and hydrochloric acid solution were mixed at a volume ratio of 1:(5-8) and ultrasonically dispersed to obtain diluted silica sol. An ethanol solution of aniline was added under stirring, and the temperature was controlled to be less than 5±2℃. The amount of aniline added was 1.2-1.5 times that of silica sol, and the amount of ethanol solution added was 3-5 times that of aniline. At the same time, ammonium persulfate solution was added, with an amount of 3-8%. The pH was adjusted to 1-2, and the reaction was stirred for 1.5-2.5 hours. After the reaction was stopped, the mixture was allowed to stand, filtered, washed with water, and dried to obtain silica-modified polyaniline. The prepared silica-modified polyaniline was mixed with ethanol at a mass ratio of 1:(10-15) to obtain a silica-modified polyaniline solution.

[0024] By adopting the above technical solution, when preparing silica-modified polyaniline, the control of raw material ratio and reaction conditions ensures that silica and polyaniline are effective tools to generate modified polyaniline with excellent electrical conductivity. The addition of ammonium persulfate is also to regulate the reaction process and improve product performance, ultimately obtaining silica-modified polyaniline with better electrical conductivity. This polyaniline can then be used as a conductive coating for subsequent iron-based micro-electrolysis fillers to improve product conductivity, accelerate the electrolysis reaction process, and further improve the removal rate of pollutants from wastewater by iron-based micro-electrolysis fillers.

[0025] The subsequent control of the ratio of silica-modified polyaniline to ethanol is crucial for preparing a silica-modified polyaniline solution with appropriate concentration and viscosity for use as a coating material for the outer layer of the iron-based micro-electrolysis filler. If the mass ratio is too low, the resulting solution concentration will be too small, making it difficult to form a uniform coating. If the ratio is too high, the solution viscosity will be too large, which is not conducive to the spraying operation. The mass ratio used in this application is selected to ensure that the solution content is high enough to form a uniform conductive coating, while also ensuring that it has sufficient low viscosity and good spraying performance.

[0026] Secondly, this application provides an iron-based micro-electrolysis filler, which adopts the following technical solution: An iron-based microelectrolysis filler is prepared by the aforementioned method.

[0027] By adopting the above technical solution, the iron-based micro-electrolysis filler prepared by the method in this application is coated with a conductive polymer coating, which solves the problem of rusting and caking caused by direct contact between the iron material and wastewater in the iron-based micro-electrolysis filler. At the same time, the coating is a conductive polymer, which will not affect the micro-electrolysis function of the iron-based micro-electrolysis filler. When used in industrial wastewater treatment, it has a better treatment effect on wastewater.

[0028] Thirdly, this application provides an application of an iron-based micro-electrolysis filler, employing the following technical solution: The application of an iron-based micro-electrolysis packing material in wastewater treatment, as described above.

[0029] By adopting the above technical solution, the iron-based micro-electrolysis filler in this application is used as the anode iron material and is directly applied in conjunction with the external carbon plate. By changing the current form of anode iron element addition, the problem of reduced treatment effect caused by iron element directly contacting water is solved.

[0030] In summary, this application has the following beneficial effects: 1. The iron-based micro-electrolysis filler in this application is coated with a silica-modified polyaniline solution and then microwave-cured to form a strong conductive polymer protective coating. It is used for the pretreatment of industrial wastewater, which improves the wastewater treatment effect of the micro-electrolysis filler, prevents the iron-based filler from rusting and clumping, improves the conductivity of the iron-based micro-electrolysis filler, and better transmits current, thereby accelerating the electrolysis reaction and achieving better wastewater treatment effect. 2. In this application, polyester raw materials are rapidly water-cooled after high-temperature melting, generating numerous micro-cracks and pores within the polyester raw materials to form porous ceramic particles with superior pore structure. Then, nano-iron is loaded onto the surface of the porous ceramic particles using atomic layer deposition. Compared to the prior art where iron powder and carbon powder are directly physically mixed with adhesives and other auxiliary materials, resulting in the consumption of iron on the surface of the filler and the iron inside being surrounded by clay, thus reducing the reaction effect of the filler, the polyester in this application forms a pore-forming skeleton structure and is then loaded with nano-iron through atomic layer deposition, avoiding the above-mentioned problems and achieving a superior wastewater treatment effect.

[0031] 3. The iron-based micro-electrolysis filler provided in this application changes the current form of anode iron addition. In this application, the iron-based micro-electrolysis filler uses a porous structure formed by polyester as a carrier to load nano-iron. The iron-based micro-electrolysis filler is used as the anode iron material and is applied in conjunction with an external carbon plate to form a micro-electrolysis effect for wastewater treatment. The conductive polymer protective coating protects the iron element, solving the problem that direct contact with water and the surrounding viscosity reduce the treatment effect. The conductive polymer protective coating, through its electron transfer channel, combined with the porous structure and hydrophilicity of silica in the protective coating, makes it permeable and can form a micro-electrolysis effect with the carbon source. At the same time, it blocks impurities such as clay, solving the problem that direct contact between iron and water leads to a reduction in treatment effect. Detailed Implementation

[0032] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0033] The nano-iron particles used in this application can be derived from commercially available sources or obtained through the following methods. The nano-iron particles used in the following examples are prepared using the nano-iron particles prepared in the following preparation examples.

[0034] Unless otherwise specified, all percentages in the following preparation examples and embodiments are mass percentages.

[0035] Preparation Example 1 A method for preparing nano-iron particles includes the following steps: Ferric nitrate was dissolved in water to obtain a ferric nitrate solution. The pH of the ferric nitrate solution was adjusted to 4, and the concentration of the ferric nitrate solution was 0.1 mol / L. Hydrogen gas was introduced into a ferric nitrate solution to induce a reduction reaction. The hydrogen gas flow rate was 80 mL / min, the reaction temperature was 70 °C, and the reaction time was 3 h. After the reaction was completed, the particles were centrifuged, washed, and dried to obtain nano-iron particles with a particle size of 20-50 nm.

[0036] Preparation Example 2 A method for preparing nano-iron particles includes the following steps: Ferric nitrate was dissolved in water to obtain a ferric nitrate solution. The pH of the ferric nitrate solution was adjusted to 3, and the concentration of the ferric nitrate solution was 0.05 mol / L. Hydrogen gas was introduced into a ferric nitrate solution to induce a reduction reaction. The hydrogen gas flow rate was 50 mL / min, the reaction temperature was 60 °C, and the reaction time was 4 h. After the reaction was completed, the particles were centrifuged, washed, and dried to obtain nano-iron particles with a particle size of 20-50 nm.

[0037] Preparation Example 3 A method for preparing nano-iron particles includes the following steps: Ferric nitrate was dissolved in water to obtain a ferric nitrate solution. The pH of the ferric nitrate solution was adjusted to 5, and the concentration of the ferric nitrate solution was 0.2 mol / L. Hydrogen gas was introduced into a ferric nitrate solution to induce a reduction reaction. The hydrogen gas flow rate was 100 mL / min, the reaction temperature was 80 °C, and the reaction time was 2 h. After the reaction was completed, the particles were centrifuged, washed, and dried to obtain nano-iron particles with a particle size of 20-50 nm.

[0038] The following preparation examples 4-6 are examples of the preparation of silica-modified polyaniline solutions. In preparation examples 4-6, the mass fraction of silica sol is 10%, the hydrochloric acid solution is a hydrochloric acid solution with a molar concentration of 1 mol / L, and the mass fraction of ammonium persulfate solution is 2%.

[0039] Preparation Example 4 Silica sol and hydrochloric acid solution were mixed at a volume ratio of 1:6 and ultrasonically dispersed to obtain diluted silica sol. An ethanol solution of aniline was added under stirring, with the temperature controlled at 5°C. The amount of aniline added was 1.3 times the mass of silica sol, and the amount of ethanol added was 4 times the mass of aniline. At the same time, ammonium persulfate solution was added, with the amount of ammonium persulfate solution being 5 wt% of the mass of aniline. The pH was adjusted to 2, and the reaction was stirred for 2 hours. After the reaction was stopped, the mixture was allowed to stand, filtered, washed with water, and dried to obtain silica-modified polyaniline. The obtained silica-modified polyaniline was mixed with ethanol at a mass ratio of 1:12 to obtain a silica-modified polyaniline solution.

[0040] Preparation Example 5 Silica sol and hydrochloric acid solution were mixed at a volume ratio of 1:5 and ultrasonically dispersed to obtain diluted silica sol. An ethanol solution of aniline was added under stirring, and the temperature was controlled at 5°C. The amount of aniline added was 1.2 times the amount of silica sol added, and the amount of ethanol added was 3 times the amount of aniline added. At the same time, ammonium persulfate solution was added, and the amount of ammonium persulfate solution added was 3 wt% of the mass of aniline. The pH was adjusted to 1, and the reaction was stirred for 1.5 h. After the reaction was stopped, the mixture was allowed to stand, filtered, washed with water, and dried to obtain silica-modified polyaniline. The prepared silica-modified polyaniline was mixed with ethanol at a mass ratio of 1:10 to obtain a silica-modified polyaniline solution.

[0041] Preparation Example 6 Silica sol and hydrochloric acid solution were mixed at a volume ratio of 1:8 and then ultrasonically dispersed to obtain diluted silica sol. An ethanol solution of aniline was added under stirring, and the temperature was controlled at 5°C. The amount of aniline added was 1.5 times the amount of silica sol added, and the amount of ethanol added was 5 times the amount of aniline added. At the same time, ammonium persulfate solution was added, and the amount of ammonium persulfate solution added was 8 wt% of the mass of aniline. The pH was adjusted to 1, and the reaction was stirred for 2.5 h. After the reaction was stopped, the mixture was allowed to stand, filtered, washed with water, and dried to obtain silica-modified polyaniline. The prepared silica-modified polyaniline was mixed with ethanol at a mass ratio of 1:15 to obtain a silica-modified polyaniline solution.

[0042] Example 1 A method for preparing an iron-based micro-electrolysis filler includes the following steps: S1. Preparation of polyester raw materials: using aromatic diacids and aliphatic diols as raw materials, the aromatic diacids are selected as a mixture of terephthalic acid and isophthalic acid with a mass ratio of 60:40, and the aliphatic diols are selected as a mixture of 1,4-butanediol and 1,6-hexanediol with a mass ratio of 55:45. The polyester raw materials are obtained by transesterification. The specific operation of the transesterification method is as follows: Aromatic diacid and aliphatic diol are mixed at a mass ratio of 1:1.1 and added as raw materials, heated to melt, and the temperature is raised to 180°C; then an acidic catalyst, specifically p-toluenesulfonic acid, is added, with the amount of acidic catalyst added being 0.5 wt% of the raw materials; the temperature is raised to 220°C, and the pressure is reduced to 0.08 MPa. During the pressure reduction process, the generated low-boiling alcohols are removed, and the reaction is carried out under the pressure reduction condition of 0.08 MPa for 2.5 h. The reaction is then terminated, and the temperature is lowered to room temperature to obtain polyester raw materials; S2. Preparation of porous ceramsite: The polyester raw material in step S1 is heated and melted to 220°C under nitrogen protection. The melt obtained by heating and melting is extruded into extrusion strips with a diameter of 5-10 mm through a multi-stage extruder. The extrusion strips are then rapidly water-cooled in a water-cooling tank at 3°C ​​under nitrogen environment. After water-cooling and solidification, spherical ceramsite is cut and dried to obtain porous ceramsite. S3. Preparation of modified ceramic particles loaded with nano-iron: The nano-iron particles obtained in Preparation Example 1 and the porous ceramic particles obtained in step S2 are placed in a low-pressure reactor, and the pressure is controlled at 0.03 MPa and the temperature at 120°C. Atomic layer deposition is used to evaporate and deposit the nano-iron particles onto the porous ceramic particles to obtain modified ceramic particles. The amount of nano-iron particles added is 9 wt% of the mass of the porous ceramic particles. S4. Preparation of iron-based micro-electrolysis filler: Spray the modified ceramic particles prepared in step S3 with the silica-modified polyaniline solution prepared in Example 4, and then transfer it to a microwave curing oven (equipment power 2 kW), heat it to 150°C for microwave curing, hold it at that temperature for 8 min, and then let it cool naturally to obtain an iron-based micro-electrolysis filler with a silica-modified polyaniline conductive polymer film formed on its surface. The thickness of the conductive polymer film on the surface of the micro-electrolysis filler is 100 nm.

[0043] Example 2 A method for preparing an iron-based micro-electrolysis filler includes the following steps: S1. Preparation of polyester raw materials: using aromatic diacids and aliphatic diols as raw materials, the aromatic diacids are selected as a mixture of terephthalic acid and isophthalic acid with a mass ratio of 60:30, and the aliphatic diols are selected as a mixture of 1,4-butanediol and 1,6-hexanediol with a mass ratio of 55:40, and polyester raw materials are obtained by transesterification. The specific operation of the transesterification method is as follows: Aromatic diacid and aliphatic diol are mixed in a mass ratio of 1:1 and added as raw materials, heated to melt, and the temperature is raised to 160°C; then an acidic catalyst, specifically p-toluenesulfonic acid, is added, with the amount of acidic catalyst added being 0.1 wt% of the raw materials; the temperature is raised to 200°C, and the pressure is reduced to 0.06 MPa. During the pressure reduction process, the generated low-boiling alcohols are removed, and the reaction is carried out under the pressure reduction condition of 0.06 MPa for 2 hours. The reaction is then terminated, and the temperature is lowered to room temperature to obtain polyester raw materials; S2. Preparation of porous ceramsite: The polyester raw material in step S1 is heated and melted to 200°C under nitrogen protection. The melt obtained by heating and melting is extruded into extrusion strips with a diameter of 5-10 mm through a multi-stage extruder. The extrusion strips are then rapidly water-cooled in a water-cooling tank at 1°C under nitrogen environment. After water-cooling and solidification, spherical ceramsite is cut and dried to obtain porous ceramsite. S3. Preparation of modified ceramic particles loaded with nano-iron: The nano-iron particles obtained in Preparation Example 2 and the porous ceramic particles obtained in step S2 are placed in a low-pressure reactor, and the pressure is controlled at 0.01 MPa and the temperature at 100°C. Atomic layer deposition is used to evaporate and deposit the nano-iron particles onto the porous ceramic particles to obtain modified ceramic particles. The amount of nano-iron particles added is 8 wt% of the mass of the porous ceramic particles. S4. Preparation of iron-based micro-electrolysis filler: Spray the modified ceramic particles prepared in step S3 with the silica-modified polyaniline solution prepared in Example 5, and then transfer it to a microwave curing oven (equipment power 2 kW), heat it to 140°C for microwave curing, hold it for 5 min, and then let it cool naturally to obtain an iron-based micro-electrolysis filler with a silica-modified polyaniline conductive polymer film formed on its surface. The thickness of the conductive polymer film on the surface of the micro-electrolysis filler is 100 nm.

[0044] Example 3 A method for preparing an iron-based micro-electrolysis filler includes the following steps: S1. Preparation of polyester raw materials: using aromatic diacids and aliphatic diols as raw materials, the aromatic diacids are selected as a mixture of terephthalic acid and isophthalic acid with a mass ratio of 60:50, and the aliphatic diols are selected as a mixture of 1,4-butanediol and 1,6-hexanediol with a mass ratio of 55:50, and polyester raw materials are obtained by transesterification. The specific operation of the transesterification method is as follows: Aromatic diacid and aliphatic diol are mixed at a mass ratio of 1:1.2 and added as raw materials, heated to melt, and the temperature is raised to 200℃; then an acidic catalyst, specifically p-toluenesulfonic acid, is added, with the amount of acidic catalyst added being 0.5wt% of the raw materials; the temperature is raised to 240℃, and the pressure is reduced to 0.1MPa. During the pressure reduction process, the generated low-boiling alcohols are removed, and the reaction is carried out under the pressure reduction condition of 0.1MPa for 3 hours. The reaction is then terminated, and the temperature is lowered to room temperature to obtain polyester raw materials; S2. Preparation of porous ceramsite: The polyester raw material in step S1 is heated and melted to 240°C under nitrogen protection. The melt obtained by heating and melting is extruded into extrusion strips with a diameter of 5-10 mm through a multi-stage extruder. The extrusion strips are then rapidly water-cooled in a water-cooling tank at 5°C under nitrogen environment. After water-cooling and solidification, spherical ceramsite is cut and dried to obtain porous ceramsite. S3. Preparation of modified ceramic particles loaded with nano-iron: The nano-iron particles obtained in Preparation Example 3 and the porous ceramic particles obtained in step S2 are placed in a low-pressure reactor, and the pressure is controlled at 0.05 MPa and the temperature at 150°C. Atomic layer deposition is used to evaporate and deposit the nano-iron particles onto the porous ceramic particles to obtain modified ceramic particles. The amount of nano-iron particles added is 10 wt% of the mass of the porous ceramic particles. S4. Preparation of iron-based micro-electrolysis filler: Spray the modified ceramic particles prepared in step S3 with the silica-modified polyaniline solution prepared in Example 6, and then transfer it to a microwave curing oven (equipment power 2 kW), heat it to 160°C for microwave curing, hold it at that temperature for 10 min, and then let it cool naturally to obtain an iron-based micro-electrolysis filler with a silica-modified polyaniline conductive polymer film formed on its surface. The thickness of the conductive polymer film on the surface of the micro-electrolysis filler is 100 nm.

[0045] Example 4 A method for preparing an iron-based microelectrolysis filler is carried out according to the method in Example 1, except that in step S1, the aromatic diacid is terephthalic acid.

[0046] Example 5 A method for preparing an iron-based microelectrolysis filler is carried out according to the method in Example 1, except that the aromatic diacid in step S1 is isophthalic acid.

[0047] Example 6 A method for preparing an iron-based microelectrolysis filler is carried out according to the method in Example 1, except that the aliphatic diol in step S1 is 1,4-butanediol.

[0048] Example 7 A method for preparing an iron-based microelectrolysis filler is carried out according to the method in Example 1, except that the aliphatic diol in step S1 is 1,6-hexanediol.

[0049] Example 8 A method for preparing an iron-based micro-electrolysis filler is carried out according to the method in Example 1, except that in step S2, the polyester raw material is heated and melted, and then directly enters the water cooling tank for rapid water cooling without undergoing multiple extrusion stages.

[0050] Comparative Example 1 A method for preparing an iron-based micro-electrolysis filler is carried out according to the method in Example 1, except that step S4 is not performed, that is, the surface of the modified ceramic particles is not sprayed with silica-modified polyaniline solution, and the obtained modified ceramic particles are directly used for wastewater treatment.

[0051] Comparative Example 2 A method for preparing an iron-based microelectrolysis filler is carried out according to the method in Example 1, except that the specific operation of modifying the ceramic particles and loading nano-iron in step S3 is as follows: Ferric nitrate was dissolved in water to prepare a ferric nitrate solution with a molar concentration of 0.1 mol / L. The porous ceramsite obtained in step S2 was immersed in the above-mentioned ferric nitrate solution for 40 minutes. Then, the immersed porous ceramsite was dried to remove moisture and then calcined at a temperature of 110°C for 1 hour to obtain iron-loaded modified ceramsite.

[0052] Comparative Example 3 A method for preparing an iron-based microelectrolysis filler is carried out according to the method in Example 1, except that the specific operation of modifying the ceramic particles and loading nano-iron in step S3 is as follows: The nano-iron particles obtained in Preparation Example 1 were ball-milled and mixed with the porous ceramic particles obtained in step S2. Then, they were calcined at 110°C for 20-30 min and cooled to obtain modified ceramic particles loaded with nano-iron.

[0053] Performance testing First, the porosity and specific surface area of ​​the porous ceramic particles prepared in step S2 of the examples and comparative examples were tested. The test results are shown in Table 1 below.

[0054] Table 1: As shown in Table 1 above, the porous ceramsite prepared by the method described in this application has high porosity (≥50%) and a specific surface area greater than 500 m². 2 / g, combined with the test results of Examples 1 and Examples 4-7, it can be seen that when isophthalic acid was not added to the aromatic diacid in Example 4, the porosity and specific surface area of ​​the final porous ceramic particles were reduced. The addition of isophthalic acid helped to induce cracks during the water-cooling pore-forming process, thus increasing its porosity. When only isophthalic acid was used as the aromatic diacid in Example 5, its porosity and specific surface area were slightly reduced. When only one type of aliphatic diol was used in Examples 6 and 7, the porosity and specific surface area of ​​the final porous ceramic particles were both reduced. Combined with the test results of Examples 1 and 8, it can be seen that when the polyester raw material was heated and melted in step S2 and then directly water-cooled, the porosity and specific surface area of ​​the resulting porous ceramic particles were significantly reduced.

[0055] In addition, the iron loading of the modified ceramic particles loaded with nano-iron in step S3 of the examples and comparative examples was detected, and the conductivity of the iron-based micro-electrolysis filler prepared in step S4 was statistically analyzed. The test results are shown in Table 2 below: Table 2: As can be seen from the test results in Table 2 above, the porous ceramic particles in this embodiment have an iron loading of 8-10% and an electrical conductivity of 80-120 S / cm, which are excellent in terms of nano-iron loading and electrical conductivity, and are more conducive to the subsequent wastewater treatment effect.

[0056] The iron-based micro-electrolysis packing material prepared in the embodiments and comparative examples of this application was used to treat wastewater. During wastewater treatment, the iron-based micro-electrolysis packing material of this application was placed on a carbon plate (carbon fiber plate). The carbon plate served as the cathode carbon source, and the iron-based micro-electrolysis packing material served as the anode iron source. The amount of iron-based micro-electrolysis packing material added was 5 wt% of the wastewater, and the mass ratio of carbon plate to iron-based micro-electrolysis packing material was 1:2. The initial COD concentration of the wastewater was 2500 mg / L. The COD removal rate of the iron-based micro-electrolysis packing material on the wastewater was tested, and the test results are shown in Table 3 below.

[0057] Table 3: Combining the test results in Tables 1, 2, and 3, it can be seen that when isophthalic acid was not added to the aromatic diacid in Example 4, the porosity and specific surface area of ​​the final porous ceramsite were significantly reduced, the iron loading was also reduced, the final conductivity was also significantly reduced, and the final COD removal rate of the wastewater was also lower. In Examples 5-7, when only one of the aromatic diacid and fatty alcohol diacid was selected, the porosity and specific surface area were also reduced, the iron loading was also reduced, the final conductivity was also reduced, and the COD removal rate of the wastewater was also lower than that of Example 1. In Example 8, when the porosity and specific surface area of ​​the porous ceramsite were significantly reduced, its iron loading and conductivity were significantly reduced, and the wastewater treatment effect was significantly reduced.

[0058] In Comparative Example 1, the modified ceramsite was the same as in Example 1, with the same loading amount of nano-iron. However, the surface of the modified ceramsite in Comparative Example 1 was not coated with a conductive polymer coating, resulting in a significant decrease in the conductivity of the filler and a low COD removal rate from the wastewater. Referring to the test results of Examples 1, 2, and 3, it can be seen that when the modified ceramsite was loaded with nano-iron using other methods, the iron loading amount was much lower than that in Example 1 of this application, and the conductivity was also significantly reduced, resulting in a poor wastewater treatment effect. In Comparative Example 2, the loading method of impregnating porous ceramsite with iron oxide precursors and then calcining showed a relatively higher iron loading amount, but its conductivity was low, which may be related to the distribution of iron.

[0059] In addition, to consider the service life of the iron-based micro-electrolysis packing material in this application, that is, the treatment stability after contact with water in the subsequent wastewater treatment process, the micro-electrolysis packing material prepared in Example 1 and the comparative example of this application was subjected to 10 cycles of wastewater treatment according to the above wastewater treatment method (iron-based micro-electrolysis packing material as the anode iron source and carbon plate as the cathode carbon source). The COD removal rate of the wastewater after the 3rd, 5th, 8th and 10th cycles is shown in Table 4 below.

[0060] Table 4: Example 1: COD removal rate after cycle / % 85 83 79 77 73 Comparative Example 1: COD removal rate after cycle / % 53 48 43 40 31 Comparative Example 2: COD removal rate after cycle / % 63 60 54 47 40 Comparative Example 3: COD removal rate after cycle / % 62 58 53 45 37 Referring to the test results in Table 4 above, it can be seen that the iron-based micro-electrolysis filler prepared in Example 1 of this application still maintains a good COD removal rate after 10 cycles of wastewater treatment, with minimal decrease in treatment capacity and a long service life. Moreover, no obvious rusting or caking was observed after 10 cycles, indicating good rust prevention performance. However, referring to the test results of Comparative Example 1, the modified ceramsite in Comparative Example 1 was not coated with a conductive polymer coating. With more cycles of wastewater treatment, the wastewater treatment effect significantly decreased, and noticeable rusting and caking occurred after 5 cycles, resulting in a significant decrease in subsequent wastewater treatment effectiveness.

[0061] Referring to the test results of Comparative Examples 2 and 3, the iron-based micro-electrolysis filler obtained by loading nano-iron in Comparative Example 2 with other loading methods also showed a significant decrease in the effect of wastewater treatment after 5 cycles. Moreover, rusting occurred after 5 cycles, and the rusting was obvious after 8 cycles.

[0062] In summary, compared to existing technologies such as the micro-electrolysis filler disclosed in patent CN104550939A, which is prepared by physically mixing and calcining iron powder and activated carbon powder, without considering the porosity and conductivity issues of the micro-electrolysis filler during actual wastewater treatment, and the micro-electrolysis filler disclosed in patent CN101838034A, although the porosity problem is solved by creating pores, this method suffers from rapid iron consumption, and the addition of bentonite with a high specific gravity leads to a large amount of sludge generated subsequently. Moreover, after the iron on the surface of the filler is consumed, the iron inside is surrounded by clay, thereby reducing the reaction efficiency of the filler itself. In this application, an organic polyester is first prepared, and then ceramsite with higher porosity and specific surface area is constructed by water cooling and pore creation. Then, a high proportion and high uniformity of nano-iron loading are achieved through atomic layer deposition. Finally, a silica-modified polyaniline conductive polymer coating is applied, and microwave curing is used to form a strong conductive polymer protective coating, which improves the conductivity of the product, accelerates the electrolysis reaction process, and improves the removal rate of pollutants in wastewater.

[0063] In summary, the iron-based micro-electrolysis filler provided in this application represents a change in the current form of iron addition to the anode. The iron-based micro-electrolysis filler uses a porous structure formed from polyester as a carrier to load nano-iron, and then a conductive polymer protective coating protects the iron, solving the problem of reduced treatment efficiency due to viscosity surrounding the iron upon direct contact with water. The conductive polymer protective coating, through its electron transport channels, combined with the porous structure and hydrophilicity of silica in the protective coating, allows for water permeability and enables micro-electrolysis with the carbon source, while simultaneously blocking impurities such as clay. This solves the problem of reduced treatment efficiency caused by direct contact between iron and water. Therefore, the iron-based micro-electrolysis filler in this application, as an anode iron material, can be directly used in conjunction with an external carbon plate.

[0064] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing an iron-based micro-electrolysis filler, characterized in that, Includes the following steps: S1. Preparation of polyester raw materials: Polyester raw materials are prepared by transesterification using aromatic diacids and aliphatic diols as raw materials. S2. Preparation of porous ceramsite: Polyester raw material is heated and melted to 200-240℃ under nitrogen protection, and then rapidly cooled in water at 0-5℃. After water cooling and solidification, it is cut into spherical ceramsite and dried to obtain porous ceramsite. S3. Preparation of modified ceramic particles loaded with nano-iron: Nano-iron is evaporated and deposited onto porous ceramic particles through atomic layer deposition to obtain modified ceramic particles. S4. Preparation of iron-based micro-electrolysis filler: Spray silica-modified polyaniline solution onto the modified ceramic particles obtained in step S3, and cure to obtain iron-based micro-electrolysis filler; In step S1, the aromatic diacid is a mixture of terephthalic acid and isophthalic acid, and the mass ratio of terephthalic acid to isophthalic acid is 60:(30-50). The aliphatic diol is selected as a mixture of 1,4-butanediol and 1,6-hexanediol, and the mass ratio of 1,4-butanediol to 1,6-hexanediol is 55:(40-50); the mass ratio of the aromatic diacid to the aliphatic diol is 1:(1-1.2). In step S2, the polyester raw material is heated and melted to 200-240°C, and the resulting melt is extruded in multiple stages into extrusion strips with a diameter of 5-10 mm, and then water-cooled in a nitrogen environment. In step S3, during atomic layer deposition, the pressure is 0.01-0.05 MPa and the temperature is controlled at 100-150℃, so that nano-iron is evaporated and deposited onto porous ceramic particles, wherein the amount of nano-iron particles added is 8-10% of the mass of porous ceramic particles; In step S4, the specific curing operation is as follows: the modified ceramic particles sprayed with silica-modified polyaniline solution are microwave cured at a curing temperature of 150±10℃ and a holding time of 5-10min. After cooling, iron-based micro-electrolysis filler is obtained. In step S4, the silica-modified polyaniline solution is prepared by the following method: A 10% silica sol (by mass) was mixed with a 1 mol / L hydrochloric acid solution at a volume ratio of 1:(5-8) and then ultrasonically dispersed to obtain a diluted silica sol. An ethanol solution of aniline was then added while stirring, maintaining a temperature of 5°C. The amount of aniline added was 1.2-1.5 times the mass of the silica sol, and the amount of ethanol added was 3-5 times the mass of the aniline. Simultaneously, add a 2% ammonium persulfate solution, the amount of which is 3-8 wt% of the aniline mass, adjust the pH to 1-2, stir the reaction for 1.5-2.5 h, and after the reaction stops, let it stand, filter, wash with water and dry to obtain silica-modified polyaniline. The prepared silica-modified polyaniline was mixed with ethanol at a mass ratio of 1:(10-15) to obtain a silica-modified polyaniline solution.

2. The method for preparing an iron-based micro-electrolysis filler according to claim 1, characterized in that: In step S1, the specific operation of transesterification is as follows: The raw material is heated and melted to 180±20℃, then an acidic catalyst is added, and the temperature is raised to 220±20℃. The reaction is carried out under reduced pressure of 0.08±0.02MPa for 2-3 hours, the reaction is terminated, and the temperature is lowered to obtain polyester raw material.

3. The method for preparing an iron-based micro-electrolysis filler according to claim 1, characterized in that: In step S3, nano-iron is obtained through the following method: Ferric nitrate is dissolved in water to obtain a ferric nitrate solution. The pH of the ferric nitrate solution is adjusted to 3-5, and the concentration of the ferric nitrate solution is 0.05-0.2 mol / L. A reduction reaction is initiated by introducing hydrogen gas into a ferric nitrate solution. The hydrogen gas flow rate is 50-100 mL / min, the reaction temperature is 60-80℃, and the reaction time is 2-4 h. After the reaction was completed, the iron nanoparticles with a particle size of 20-50 nm were obtained by centrifugation, washing and drying.

4. An iron-based micro-electrolysis filler, characterized in that: It is prepared by the preparation method described in any one of claims 1-3.

5. The application of the iron-based micro-electrolysis packing material as described in claim 4 in wastewater treatment.

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