Carbon particle electrode material of modified phosphorus-free epoxy resin as well as preparation method and application of carbon particle electrode material

Abstract

The invention discloses a modified phosphorus-free epoxy resin carbon particle electrode material and a preparation method and application thereof. The preparation method of the material comprises the following steps: crushing waste phosphorus-free epoxy resin particles, carbonizing, and sieving to obtain carbon particles; and grafting hydroxyl and methyl crown groups to the carbon particles for surface modification. According to the electrode material, waste epoxy resin serves as a raw material, the efficient electrode material containing hydroxyl and methyl at the same time is obtained through carbonization and surface modification, and the electrolysis efficiency is greatly improved; when the phosphorus release agent is used in the process of electrolyzing the wet sludge to release phosphorus, the phosphorus release rate of the sludge is greatly improved while the one-step electrolytic phosphorus release of the wet sludge is realized, tests show that the phosphorus release rate of the sludge can reach 86.7%, organic phosphorus in the sludge can be converted into inorganic phosphorus, the conversion efficiency can reach 87.18%, and the subsequent resource utilization of phosphorus-rich liquid is facilitated.

Description

Technical Field

[0001] The present invention relates to a carbon particle electrode material, specifically to a carbon particle electrode material of modified phosphorus-free epoxy resin, its preparation method and application, belonging to the technical field of sludge phosphorus recovery. Background Art

[0002] Phosphorus is an essential element for life and an important fertilizer component in agricultural production. However, global phosphorus resources are facing a crisis of depletion. Data shows that the proven global phosphorus ore reserves are only enough to last for decades. Although China has rich phosphorus ore reserves, the grade is decreasing year by year, and the mining difficulty and cost are constantly rising. Currently, the main source of phosphorus resources is the mining of phosphorus ore, but this non-renewable resource will eventually be exhausted. Therefore, recovering phosphorus resources has become an important way to solve the phosphorus crisis. Recovering phosphorus from sewage and waste can not only alleviate the problem of resource shortage but also reduce environmental pollution. In recent years, with the continuous growth of the demand for phosphorus resources in agriculture and industry and the low phosphorus utilization rate, a large amount of phosphorus has been discharged into water bodies, resulting in increasingly serious water eutrophication. The process of phosphorus removal from sewage is widely used, and a large amount of phosphorus-rich sludge is generated. During the sewage treatment process, 90% of the phosphorus is transferred from the sewage to the solid-phase sludge. In 2022, China's annual sludge output exceeded 70 million tons, and the recovery and utilization of phosphorus in sludge have great potential.

[0003] There are chemical methods, biological methods, physical methods, and electrochemical methods to release phosphorus from sludge. The chemical phosphorus removal process is simple to operate, has a high phosphorus removal rate, but generates a large amount of chemical sludge, is costly, and has poor treatment accuracy and stability. Biological phosphorus removal does not require additional chemical agents, has a low cost, and can remove organic matter and nitrogen at the same time. It has become a very mature technology and has been gradually applied in the sewage phosphorus removal process. However, the phosphorus removal efficiency is low, and the post-biochemical sludge is difficult to treat. The physical method is simple, but the maintenance cost is high, and it is only applicable to sewage with a low phosphorus concentration. The electrochemical method has high efficiency and flexibility, is easy to operate, and is easy to operate and maintain. The electrochemical method is an efficient wastewater treatment technology, especially suitable for removing phosphorus elements in water. It has the advantages of high efficiency, flexibility, selectivity, few by-products, and easy operation.

[0004] Chinese Patent (CN108726837A) discloses a method for promoting phosphorus release in phosphorus-rich sludge. It adopts an electrochemical treatment method to generate an electric field force and hydroxyl radicals between two electrodes, which can hydrolyze sludge and rupture cells to achieve phosphorus release. However, the concentration of the supernatant after sludge phosphorus release is only about 7 mg / L at most, the generation of free radicals is insufficient, and the conductivity is low, resulting in a low phosphorus release rate. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the first object of the present invention is to provide a carbon particle electrode material of modified phosphorus-free epoxy resin. This electrode material uses waste epoxy resin as raw material, and through carbonization and surface modification, a high-efficiency electrode material containing both hydroxyl groups and methyl groups is obtained. This material is in the shape of three-dimensional particles. Compared with two-dimensional planar electrodes, its reaction area is greatly increased, the current distribution is more uniform, effectively avoiding local polarization. In addition, based on the abundant hydroxyl groups and methyl groups on the surface of this material, while promoting the generation of a large number of hydroxyl radicals in the system, it can also destroy the biological tissues in the system, thus greatly improving the electrolysis efficiency.

[0006] The second object of the present invention is to provide a preparation method of a carbon particle electrode material of modified phosphorus-free epoxy resin. This method first controls the carbonization of the raw material by programmed heating, and then uses a three-step method to ensure the qualitative and quantitative grafting of hydroxyl groups and methyl groups on the surface of carbon particles, realizing the surface modification of carbon particles; the raw materials required by this method are widely sourced, the operation is simple, the cost is low, and the resource utilization of waste organic matter is realized.

[0007] The third object of the present invention is to provide an application of a carbon particle electrode material of modified phosphorus-free epoxy resin as a three-dimensional electrode for electrolyzing wet sludge to release phosphorus. Based on the excellent performance of the above carbon particle electrode material, using it as a three-dimensional electrode for electrolyzing wet sludge to release phosphorus can, while realizing the one-step electrolytic phosphorus release of wet sludge, greatly improve the phosphorus release rate of sludge. After testing, the phosphorus release rate of sludge using the technical solution of the present invention can reach 86.7%, and the organic phosphorus in the sludge can be converted into inorganic phosphorus, and its conversion efficiency can reach 87.18%, which is convenient for the subsequent resource utilization of the phosphorus-rich liquid.

[0008] To achieve the above technical objects, the present invention provides a preparation method of a carbon particle electrode material of modified phosphorus-free epoxy resin, which crushes waste phosphorus-free epoxy resin particles and then carbonizes them, and obtains carbon particles after sieving; grafts hydroxyl groups and methyl crown groups onto the carbon particles for surface modification, and that's it.

[0009] As a preferred scheme, the carbonization process is as follows: Place the waste phosphorus-free epoxy resin in a tube furnace, under a protective atmosphere, heat from room temperature to 400 - 600 °C at a rate of 3 - 10 °C / min, and cool to room temperature with the furnace, then it is obtained.

[0010] The carbonization process must be carried out strictly in accordance with the above requirements. The carbonization process is mainly a process of graphitization of the raw material organic matter, and its carbonization temperature is a key parameter for precisely controlling the degree of graphitization. If the temperature is too low, effective carbonization cannot be achieved, while if the temperature is too high, the pores will collapse.

[0011] As a preferred scheme, the particle size of the carbon particles is -100 mesh.

[0012] As a preferred solution, the surface modification process of the carbon particles is as follows: treating the carbon particles with hydrogen peroxide to increase the hydroxyl groups on their surface to obtain hydroxyl carbon particles, then treating the hydroxyl carbon particles with concentrated thionyl chloride to replace some of the hydroxyl groups on their surface with chlorine to obtain hydroxyl chlorinated carbon particles, then treating the hydroxyl chlorinated carbon particles with methylmagnesium chloride to replace all the chlorine with methyl groups, and then washing to obtain the product.

[0013] The present invention uses a three-step method of "oxidation-chlorination-methylation" to modify the surface of carbon particles, and its modification sequence must be strictly carried out according to the above requirements. If chlorination is carried out first and then oxidation, hydrogen peroxide will react with Cl⁻ to generate ClO⁻, destroying the carbon skeleton structure; if methylation is directly carried out after oxidation, due to the absence of Cl⁻ as an intermediate bridge, the methyl grafting rate will drop significantly, and it cannot be effectively grafted onto the surface of carbon particles.

[0014] As a preferred solution, the process of treating carbon particles with hydrogen peroxide is as follows: treating carbon particles with 20-30 wt% hydrogen peroxide, with a volume-mass ratio of 15-25 mL / g between the two, ultrasonicating for 30 min, and then magnetically stirring and refluxing at 90-110 °C for 3-6 h.

[0015] The main function of hydrogen peroxide is to oxidize carbon particles, and its parameters must be strictly carried out according to the above requirements. The oxidation process is mainly to increase the hydroxyl groups on its surface. Therefore, hydrogen peroxide needs to be in a high concentration range. However, excessive hydrogen peroxide will cause over-oxidation of carbon particles, resulting in a significant loss of specific surface area. Only within the above requirements can rich and uniform hydroxyl groups be obtained on the material surface.

[0016] As a preferred solution, the process of treating hydroxyl carbon particles with concentrated thionyl chloride is as follows: treating hydroxyl carbon particles with concentrated thionyl chloride at 70-90 °C, with a volume-mass ratio of 2-3 mL / g between the two, refluxing for 20-30 h, and filtering, then washing with deionized water in a Soxhlet apparatus until the pH value is neutral.

[0017] The main function of concentrated thionyl chloride is to replace some of the hydroxyl groups with chlorine, using chlorine as a bridge to facilitate the subsequent methylation of the material. If its addition amount is too low, the hydroxyl chlorination rate will be insufficient, and the subsequent methylation efficiency will also decrease accordingly. If its addition amount is too high, it will cause over-chlorination of hydroxyl groups, resulting in a decrease in the number of hydroxyl groups on the material surface, and then leading to a decrease in the hydrophilicity and free radical adsorption ability of carbon particles.

[0018] As a preferred solution, the process of treating hydroxyl chlorinated carbon particles with methylmagnesium chloride is as follows: under a protective atmosphere, first rinsing the hydroxyl chlorinated carbon particles with an organic solvent, and then immediately placing them in a 1-2 M methylmagnesium chloride solution, and standing at 50-60 °C for 20-30 h.

[0019] During the methylation process, if the concentration of methylmagnesium chloride is too low, not all chlorine can be replaced by methyl groups, and the remaining chlorine will trigger side reactions during subsequent electrolysis, resulting in the reaction of Cl⁻ to form ClO⁻, which will corrode the electrodes.

[0020] As a preferred solution, the cleaning process is as follows: The materials treated with methylmagnesium chloride are collected and ultrasonically cleaned in an organic solvent and ultrapure water for 10 - 20 min in sequence.

[0021] As a preferred solution, the organic solvent is at least one of chlorobenzene, tetrahydrofuran, and ethanol.

[0022] The present invention also provides a carbon particle electrode material for modified phosphorus - free epoxy resin, which is obtained by the preparation method described in any one of the above.

[0023] The present invention also provides an application of the carbon particle electrode material for modified phosphorus - free epoxy resin as a three - dimensional electrode for electrolyzing wet sludge to release phosphorus; the process of electrolyzing sludge to release phosphorus is as follows: The obtained carbon particle electrode material is mixed evenly with wet sludge, placed in an electrolytic cell, electrified for electrolysis, left to stand for 10 - 14 h after electrolysis, and then sulfuric acid is added for acidolysis to obtain the product; the volume - mass ratio of the carbon particles to the sewage sludge is 3 - 10 g / L.

[0024] As a preferred solution, the conditions for electrolysis are: the current density is 0.5 - 1.5 mA / cm 2 , and the time is 0.5 - 1.5 h.

[0025] As a preferred solution, the addition amount of sulfuric acid is 1 - 10% of the volume of the wet sludge.

[0026] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are as follows:

[0027] 1) The carbon particle electrode material provided by the present invention uses waste epoxy resin as a raw material, and through carbonization and surface modification, a high - efficiency electrode material containing both hydroxyl and methyl groups is obtained. This material is in the form of three - dimensional particles. Compared with two - dimensional planar electrodes, its reaction area increases significantly, the current distribution is more uniform, effectively avoiding local polarization. In addition, based on the abundant hydroxyl and methyl groups on the surface of this material, while promoting the generation of a large number of hydroxyl radicals in the system, it can also destroy the biological tissues in the system, thereby greatly improving the electrolysis efficiency.

[0028] 2) The preparation method provided by the present invention first controls the carbonization of the raw material by programmed temperature rise, and then uses a three - step method to ensure the qualitative and quantitative grafting of hydroxyl and methyl groups on the surface of the carbon particles, realizing the surface modification of the carbon particles; this method has wide sources of raw materials, is simple to operate, has low cost, and realizes the resource utilization of waste organic substances.

[0029] 3) In the technical solution provided by the present invention, based on the excellent performance of the above carbon particle electrode material, it is used as a three-dimensional electrode for electrolyzing phosphorus release from wet sludge. While realizing the one-step electrolytic phosphorus release from wet sludge, the phosphorus release rate of the sludge is greatly improved. After testing, the phosphorus release rate of the sludge using the technical solution of the present invention can reach 86.7%, and the organic phosphorus in the sludge can be converted into inorganic phosphorus, and the conversion efficiency can reach 87.18%, which is convenient for the subsequent resource utilization of the phosphorus-rich liquid. Description of the Drawings

[0030] Figure 1 Schematic diagram of electrolyzing phosphorus release from wet sludge by the carbon particle electrode material provided by the present invention;

[0031] Figure 2 Graph of the carbon particle electrode material provided by the present invention for electrolyzing wet sludge;

[0032] Figure 3 Graph of the change in the phosphorus release rate of the electrode materials obtained in Examples 1-3 and Comparative Example 1 of the present invention for electrolyzing wet sludge;

[0033] Figure 4 Graph of the change in the conversion rate of organic phosphorus in the electrode materials obtained in Examples 1-3 and Comparative Example 1 of the present invention for electrolyzing wet sludge. Detailed Embodiments

[0034] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to specific implementation cases. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0035] Example 1

[0036] This example provides a carbon particle electrode material of modified phosphorus-free epoxy resin, which is used as a three-dimensional electrode for electrolyzing phosphorus release from wet sludge. The wet sludge comes from a sewage treatment plant in a certain place in Hunan, with a total phosphorus content of 370.36 ± 90.16 mg / L and a sewage sludge volume mass ratio of 15.07 ± 4.93 g / L. The specific treatment process is as follows:

[0037] 1) Hammer the waste phosphorus-free epoxy resin into small pieces and put them into a tubular furnace. Under a nitrogen atmosphere, heat from room temperature to 500 °C at a rate of 5 °C / min, keep the temperature constant for two hours, cool to room temperature with the furnace, take out and crush with a crusher, and pass through a 100-mesh sieve to obtain waste phosphorus-free epoxy resin carbon particles.

[0038] 2) Take 5 g of carbon particles and 100 ml of H 2 O 2 (30 wt% solution) and mix them in a 250 mL round-bottom flask. Ultrasonic for 30 min, then stir magnetically and reflux at 105 °C for 5 h. After cooling, collect the solid, centrifuge at 8000 rpm for 10 min, then wash with deionized water and repeat the above process five times. Then dry overnight under vacuum at 60 °C to obtain hydroxyl carbon particles; Treat 10 g of hydroxyl carbon with 25 ml of concentrated thionyl chloride at 84 °C, reflux for 24 h, filter and wash with deionized water in a Soxhlet apparatus until the pH value is neutral to obtain hydroxyl carbon chloride particles; Place the hydroxyl carbon chloride particles in a glove box. Under a nitrogen atmosphere, first rinse with dry chlorobenzene and dry tetrahydrofuran, and then immediately place them in 1.5 M CH 3 MgCl solution (THF diluted with 3.0 M CH 3 MgCl in THF, Sigma-Aldrich), place at 55 °C for 24 h to complete methylation; The substrate obtained after methylation is collected in a glass funnel, rinsed with THF, and then sonicated in THF, ethanol, and 18 MΩ water for 10 min respectively to obtain carbon rich in hydroxyl and methyl groups, and pass through a 100-mesh sieve for standby.

[0039] 3) Retrieve sewage sludge from a sewage treatment plant and divide it into two equal parts. Mix one part with the obtained carbon particle material, and use the other part to measure the solid content rate and phosphorus content of the sewage sludge; The mass-volume ratio of the carbon particle material to the wet sludge is 5 g / L. After mixing, add it to the device and electrolyze at a current density of 1 mA / cm 2 for 60 min, let it stand for 12 h, add 5% concentrated sulfuric acid for acidolysis, stir evenly, then let it stand for 12 h, and measure the total phosphorus, inorganic phosphorus, and organic phosphorus in the supernatant and sludge.

[0040] Example 2

[0041] This example is exactly the same as Example 1, except that the electrolysis time is 40 min.

[0042] Example 3

[0043] This example is exactly the same as Example 1, except that the electrolysis time is 80 min.

[0044] Comparative Example 1

[0045] This comparative example is exactly the same as Example 1, except that the waste phosphorus-free epoxy resin carbon particles are directly used as the three-dimensional electrode.

[0046] As Figure 3 and Figure 4As shown, compared with the use of the granular carbon electrode without functional groups, for the electrode provided by the present invention, when electrolysis is carried out for 60 min, the phosphorus release rate of the sludge increases from 71.68% to 86.71%, and the conversion rate of organic phosphorus in the sludge also increases from 73.43% to 86.74%. Further, the effect of electrolysis for 40 min is lower than that of electrolysis for 60 min, and the effect of electrolysis for 80 min is slightly lower than that of electrolysis for 60 min. It can be seen therefrom that the efficiency is higher and the effect is the best when electrolysis is carried out for 60 min.

Claims

1. A method for preparing a carbon particle electrode material of a modified phosphorus-free epoxy resin, characterized in that: The waste phosphorus-free epoxy resin particles are crushed and then carbonized, and then sieved to obtain carbon particles; hydroxyl and methyl cap groups are grafted to the carbon particles for surface modification to obtain the obtained carbon particles.

2. The method for preparing a carbon particle electrode material of a modified phosphorus-free epoxy resin according to claim 1, characterized in that: The carbonization process is as follows: placing the waste phosphorus-free epoxy resin in a tubular furnace, heating it from room temperature to 400-600°C at 3-10°C / min under a protective atmosphere, and cooling it to room temperature along with the furnace to obtain the carbon particles; the particle size of the carbon particles is -100 mesh.

3. The method for preparing a carbon particle electrode material of a modified phosphorus-free epoxy resin according to claim 1, characterized in that: The surface modification process of the carbon particles is as follows: treating the carbon particles with hydrogen peroxide to increase the hydroxyl groups on their surface to obtain hydroxy carbon particles; then treating the hydroxy carbon particles with concentrated thionyl chloride to replace part of the hydroxyl groups on their surface with chlorine to obtain hydroxyl carbon chloride particles; then treating the hydroxyl carbon chloride particles with methyl magnesium chloride to replace all the chlorine with methyl; and then washing to obtain the obtained particles.

4. The method for preparing a carbon particle electrode material of a modified phosphorus-free epoxy resin according to claim 3, characterized in that: The process of treating carbon particles with hydrogen peroxide is as follows: treating carbon particles with 20-30wt% hydrogen peroxide, with a volume mass ratio of 15-25 mL / g, ultrasonicating for 30 min, and then refluxing with magnetic stirring at 90-110° C. for 3-6 h.

5. The method for preparing a carbon particle electrode material of a modified phosphorus-free epoxy resin according to claim 3, characterized in that: The process of treating the hydroxy carbon particles with concentrated thionyl chloride is as follows: treating the hydroxy carbon particles with concentrated thionyl chloride at 70-90° C., with a volume mass ratio of 2-3 mL / g, refluxing for 20-30 hours, filtering, and washing with deionized water in a Soxhlet apparatus until the pH value is neutral.

6. The method for preparing a carbon particle electrode material of a modified phosphorus-free epoxy resin according to claim 3, characterized in that: The process of treating hydroxychlorocarbon particles with methylmagnesium chloride is as follows: under a protective atmosphere, the hydroxychlorocarbon particles are firstly washed with an organic solvent, and then immediately placed in a 1-2M methylmagnesium chloride solution and allowed to stand at 50-60°C for 20-30 hours.

7. The method for preparing a carbon particle electrode material of a modified phosphorus-free epoxy resin according to claim 3, characterized in that: The cleaning process is as follows: collecting the material treated with methylmagnesium chloride and then ultrasonically cleaning it in an organic solvent and ultrapure water in turn for 10 to 20 minutes; the organic solvent is at least one of chlorobenzene, tetrahydrofuran and ethanol.

8. A carbon particle electrode material modified with phosphorus-free epoxy resin, characterized in that: Obtained by the preparation method according to any one of claims 1 to 7.

9. The use of a carbon particle electrode material modified with phosphorus-free epoxy resin as claimed in claim 8, characterized in that: As a three-dimensional electrode for electrolyzing wet sludge to release phosphorus; the process of electrolyzing sludge to release phosphorus is: the obtained carbon particle electrode material is evenly mixed with wet sewage, placed in an electrolytic cell, powered on for electrolysis, left to stand for 10 to 14 hours after the electrolysis is completed, and then sulfuric acid is added for acid hydrolysis to obtain; the volume mass ratio of the carbon particles to sewage sludge is 3 to 10 g / L.

10. The use of a carbon particle electrode material modified with phosphorus-free epoxy resin according to claim 8, characterized in that: The electrolysis conditions are: current density of 0.5-1.5 mA / cm 2 , time is 0.5~1.5h; the amount of sulfuric acid added is 1~10% of the volume of wet sludge.

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