Capacitor composite material prepared from brewing residual sludge and method and application thereof

Abstract

The present application relates to the technical field of composite materials for energy storage devices, and particularly relates to a capacitor composite material prepared from brewing residual sludge, a method and application thereof, wherein the brewing residual sludge is used as raw material to prepare sludge powder; the sludge powder is co-pyrolyzed with a carbonate to form biochar, and the biochar is treated by HF solution to remove ash and form modified biochar; then the modified biochar is mixed with manganese sulfate solution and potassium permanganate solution to load manganese dioxide, thereby obtaining the composite material, which solves the technical defects of complex manufacturing process and high cost caused by the use of non-renewable resources as raw material for traditional supercapacitor electrode composite material, and helps to realize high-value resource utilization of brewing residual sludge. The specific capacitance of the composite material obtained by the present application is 252.7 F / g under the condition of 2A / g.

Description

Technical Field

[0001] This invention relates to the field of composite materials for energy storage devices, and more particularly to composite materials for capacitors prepared using brewing waste sludge, methods, and applications. Background Technology

[0002] Capacitors are energy storage devices. Supercapacitors, compared to traditional capacitors, are a new type of energy storage device with advantages such as high capacity, high power density, and short charge / discharge time. They have been widely used in aerospace, microelectronics, and other fields, and have become a hot topic of interest for those skilled in the art. The performance of supercapacitors mainly depends on the properties of the electrode materials. Commonly used electrode materials for capacitors include transition metal compounds, conductive polymer composites, and carbon nanotubes. These electrode materials all suffer from complex manufacturing processes and high costs, resulting in high production costs for supercapacitors. Therefore, seeking electrode materials with simple manufacturing processes and low costs to reduce the production cost of supercapacitors has become a key research focus for those skilled in the art.

[0003] Brewing waste sludge is a solid sediment produced during the brewing process, containing abundant organic matter, nitrogen, and phosphorus. As a waste product of the brewing industry, its large-scale accumulation can have adverse environmental impacts. Therefore, how to dispose of brewing waste sludge, improve its utilization rate, and realize its high value has become a key issue in the comprehensive utilization of brewing waste sludge. This is also a long-term research direction of our research team, combining teaching work with our work in the Guizhou Baijiu industry, resulting in the development of numerous technical approaches for the high-value utilization of brewing waste sludge. For example, patent number 202310841621.1 discloses a process for preparing sludge-based biochar from brewing waste sludge, then removing ash with HF solution and oxidizing with nitric acid solution to prepare oxidized sludge-based biochar, and dispersing the oxidized sludge-based biochar with distilled water to prepare a biochar suspension. This suspension is used in electrode modification, which makes the modified electrode have good electrocatalytic activity for glucose. When applied to glucose detection, it has high sensitivity and a detection limit of 1.2 μmol / L.

[0004] Furthermore, existing technologies have also developed methods for preparing biochar from sludge and modifying it with slag to create three-dimensional electrode materials. When these three-dimensional electrode materials are applied to the electrochemical oxidation of phosphorus-containing wastewater, they can improve electrolysis efficiency, efficiently oxidize organic phosphorus into phosphate ions, and efficiently precipitate and recover phosphate ions. This method is suitable for phosphorus-containing wastewater of various water quality conditions; for example, the content disclosed in patent number 202111595600.3.

[0005] It is evident that existing technologies regarding the utilization of brewing waste sludge or sludge resources in electrode materials primarily focus on its participation in electrochemical reactions to improve sensitivity and electrolysis efficiency. However, there are no corresponding technical reports in existing literature regarding whether it can bring improvements to the energy storage field. Summary of the Invention

[0006] Based on the above-mentioned technical problems, the present invention provides a composite material for capacitors prepared using brewing waste sludge, as well as a method and application thereof.

[0007] The specific technical solution is as follows:

[0008] One of the objectives of this invention is to provide a method for preparing a composite material for capacitors using brewing waste sludge, comprising the following steps:

[0009] (1) Dry, grind and sieve the remaining sludge from brewing into sludge powder;

[0010] (2) After mixing sludge powder with carbonate, it is pyrolyzed into biochar under an argon atmosphere;

[0011] (3) The biochar was mixed with HF solution to remove ash, and modified biochar was obtained;

[0012] (4) Add the modified biochar to the manganese sulfate solution and mix evenly, then add the potassium permanganate solution to obtain a mixed solution; treat the mixed solution at 120-160℃ for 4-8h, filter, and wash until the pH is 6.6-7.2, then dry at 60℃ for 24h to obtain the final product.

[0013] Using brewing waste sludge as raw material, sludge powder is prepared. The sludge powder is then pyrolyzed with carbonates to form biochar. After ash removal using HF solution, modified biochar is obtained. The modified biochar is then mixed with manganese sulfate solution and potassium permanganate solution and loaded with manganese dioxide to obtain a composite material. This method solves the technical defects of traditional supercapacitor electrode composite materials, which require non-renewable resources as raw materials, resulting in complex manufacturing processes and high costs. It also helps to realize the high-value resource utilization of brewing waste sludge.

[0014] To reduce moisture content and thus viscosity, the drying of the brewing residue sludge is preferably carried out at a constant temperature of 105°C until constant weight; the grinding and sieving is done through an 80-mesh sieve.

[0015] To increase the pore size of the sludge-based biochar, the carbonate is preferably potassium carbonate and / or potassium bicarbonate, and the carbonate content, based on the mass of K2O, is 1-2 times that of the sludge powder. Preferably, the pyrolysis is performed at a temperature of 400-600°C for 2 hours.

[0016] To enhance the performance of biochar in composite materials for supercapacitor electrodes and improve specific capacitance, step (3) is preferably to weigh 3-6g of biochar, add 5-10mL of HF and 30mL of distilled water, mix, stir and heat for 30min, centrifuge and wash until the pH of the supernatant is 6, add water, stir and heat for 20min, centrifuge, and dry.

[0017] To achieve uniform loading of manganese dioxide, preferably, the molar concentration of the manganese sulfate solution is 10 mmol / L, and the molar concentration of the potassium permanganate solution is 100 mmol / L; the amount of manganese sulfate solution is 35 mL, the amount of potassium permanganate solution is 15-30 mL, and the amount of modified biochar is 0.1-0.3 g; and / or the manganese sulfate solution is preheated to 60°C before the modified biochar is added.

[0018] The second objective of this invention is to provide a composite material prepared by the above method.

[0019] The third objective of this invention is to provide the application of the composite material prepared by the above method in the fabrication of working electrodes for capacitors.

[0020] The working electrode used in the specific capacitance test process of this invention is a nickel foam-based electrode. The method for manufacturing the nickel foam-based electrode is to mix the composite material with conductive carbon black and polytetrafluoroethylene in a mass ratio of 8:1:1, then add anhydrous ethanol to prepare an electrode slurry, and then uniformly coat the electrode slurry onto the nickel foam, dry and press it into shape to obtain the electrode.

[0021] Compared with the prior art, the technical effects of this invention are reflected in:

[0022] By using brewing waste sludge as raw material, and mixing it with carbonates and / or potassium bicarbonate for pyrolysis, the formation of biochar pore structure is facilitated. Combined with HF solution treatment, the specific surface area is increased, achieving a specific surface area of ​​406.7 m². 2 / g will help promote ion transport and diffusion; the brewing waste sludge itself is rich in organic matter and elements such as nitrogen and phosphorus. After pyrolysis, it can achieve in-situ heteroatom doping of biochar, which helps to improve the pseudocapacitive effect; at the same time, manganese dioxide is loaded with a specific process to form a composite material for capacitor working electrode, which makes it low cost and effectively solves the technical defects of unstable working process structure when manganese dioxide is used alone as a composite material for capacitor working electrode.

[0023] This invention creates a composite material obtained by loading manganese dioxide. This composite material forms a petal-like structure, which can expose more active sites and effectively shorten the ion diffusion path. When applied to the preparation of capacitors, the specific capacitance is 252.7 F / g under the condition of 2 A / g. Attached Figure Description

[0024] In order to enable those skilled in the art to fully understand the technical solution of the present invention, the following description is made in conjunction with the technical solution content and the accompanying drawings.

[0025] Figure 1 A process flow diagram is provided for this invention.

[0026] Figure 2 The BET diagram of the modified biochar obtained in Example 1 of this invention.

[0027] Figure 3 The BET diagram of the biochar obtained in Example 2 of this invention.

[0028] Figure 4 The electron microscope scan image of the composite material obtained in Example 1 of this invention.

[0029] Figure 5 The SEM-mapping image of the composite material obtained in Example 1 of this invention is shown.

[0030] Figure 6 EDS diagram of the composite material obtained in Example 1 of this invention.

[0031] Figure 7 The specific capacitance diagram is obtained at a current density of 2A / g after the composite material obtained in Example 1 of this invention is prepared into a working electrode and assembled into an electrode system. Detailed Implementation

[0032] To facilitate a correct understanding of the present invention by those skilled in the art, and to enable them to fully understand the technical content of the present invention, the technical solution of the present invention will be further described below in conjunction with specific embodiments. However, this description does not limit the scope of protection claimed by the present invention. Those skilled in the art should not limit the scope of protection of the present invention to the following description. Any equivalent substitutions or changes made by those skilled in the art or those familiar with the art based on the present invention, and based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0033] like Figure 1 As shown, in some embodiments, the method for preparing a composite material for capacitors using brewing waste sludge includes the following steps:

[0034] (1) The remaining sludge from brewing is dried, ground and sieved into sludge powder; the drying of the remaining sludge from brewing is carried out at a constant temperature of 105°C until constant weight; the grinding and sieving is carried out through an 80-mesh sieve.

[0035] (2) After mixing the sludge powder with carbonate, the mixture is pyrolyzed for 2 hours under an argon atmosphere at temperatures ranging from 400-600℃, for example: 400℃, 430℃, 450℃, 480℃, 500℃, 520℃, 540℃, 570℃, 600℃, etc., to obtain biochar. The carbonate is 1-2 times the mass of the sludge powder, for example, 1 time, 1.5 times, 2 times, etc., based on the mass of potassium oxide. In this invention, the carbonate used is a mixture of one or two of potassium carbonate and potassium bicarbonate in any mass ratio.

[0036] (3) The biochar is mixed with HF solution to remove ash, thereby obtaining modified biochar; the HF solution is a mixture of 5-10 mL of anhydrous hydrogen fluoride (e.g., 5 mL, 6 mL, 7 mL, 8 mL, 9 mL, 10 mL, etc.) and 30 mL of distilled water, and the biochar added is 3-6 g (e.g., 3 g, 4 g, 5 g, 6 g, etc.); the ash removal treatment is performed after mixing, stirring and heating at 100 r / min for 30 min, centrifuging and washing until the pH of the supernatant is 6, then adding water, stirring and heating for 20 min, centrifuging, and drying. For details, refer to the ash removal process in the prior art, such as the technical content disclosed in patent number 202310841621.1.

[0037] (4) Add the modified biochar to the manganese sulfate solution and mix evenly, then add the potassium permanganate solution to obtain a mixed solution; treat the mixed solution at 120-160℃ (e.g., 120℃, 130℃, 140℃, 150℃, 160℃, etc.) for 4-8 hours (e.g., 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc.), filter, and wash until the pH is 6.6-7.2 (neutral), then dry at 60℃ for 24 hours to obtain the final product. The manganese sulfate solution has a molar concentration of 10 mmol / L, and the potassium permanganate solution has a molar concentration of 100 mmol / L; the manganese sulfate solution is 35 mL, the potassium permanganate solution is 15-30 mL (e.g., 15 mL, 16 mL, 17 mL, 18 mL, 19 mL, 20 mL, 21 mL, 22 mL, 23 mL, 24 mL, 25 mL, 26 mL, 27 mL, 28 mL, 29 mL, 30 mL, etc.), and the modified biochar is 0.1-0.3 g, e.g., 0.1 g, 0.2 g, 0.3 g, etc., thus obtaining the product.

[0038] In some embodiments, the manganese sulfate solution is preheated to 60°C before the modified biochar is added.

[0039] In order to better verify the technical effects that this invention can bring, the research team of this invention conducted the following experimental studies:

[0040] I. Sample Preparation

[0041] Example 1

[0042] The residual sludge from brewing was dried at 105℃ to constant weight, ground and passed through an 80-mesh sieve to obtain sludge powder. The sludge powder was mixed with potassium carbonate at a mass ratio of 1:1 and pyrolyzed at 500℃ for 2 hours under an argon atmosphere to obtain biochar. 4g of biochar, 8mL of anhydrous hydrogen fluoride, and 30mL of distilled water were mixed and stirred and heated at 100r / min for 30min. The mixture was centrifuged and washed until the pH of the supernatant reached 6. Water was then added, and the mixture was stirred and heated for 20min, centrifuged, and dried to obtain modified... Modified biochar was prepared by heating 10 mmol and 35 mL of manganese sulfate solution to 60 °C, adding 0.2 g of modified biochar and mixing thoroughly, then slowly adding 100 mmol and 20 mL of potassium permanganate solution until the potassium permanganate solution was completely added to obtain a mixed solution. The mixed solution was transferred to a hydrothermal reactor and treated at 140 °C for 5 h. After filtration and washing until the pH was neutral (approximately 6.6-7.2), the solution was dried at 60 °C for 24 h to obtain the composite material.

[0043] Example 2

[0044] The residual sludge from brewing was dried at 105℃ to constant weight, ground and passed through an 80-mesh sieve to obtain sludge powder. The sludge powder and potassium carbonate were mixed evenly at a mass ratio of 1:1 and pyrolyzed at 500℃ for 2 hours under an argon atmosphere to obtain biochar. 10 mmol and 35 mL of manganese sulfate solution were heated to 60℃, and 0.2 g of biochar was added and mixed evenly. Then, 100 mmol and 20 mL of potassium permanganate solution were slowly added until the potassium permanganate solution was completely added to obtain a mixed solution. The mixed solution was transferred to a hydrothermal reactor and treated at 140℃ for 5 hours. After filtration and washing until the pH was neutral (about 6.6-7.2), it was dried at 60℃ for 24 hours to obtain the composite material.

[0045] Example 3

[0046] The residual sludge from brewing was dried at 105℃ to constant weight, ground and passed through an 80-mesh sieve to obtain sludge powder. The sludge powder was pyrolyzed at 500℃ for 2 hours under an argon atmosphere to obtain biochar. 4g of biochar, 8mL of anhydrous hydrogen fluoride and 30mL of distilled water were mixed and heated at 100r / min for 30min. After centrifugation and washing until the pH of the supernatant was 6, water was added, and the mixture was stirred and heated for 20min. After centrifugation and drying, modified biochar was obtained. 10mmol and 35mL of manganese sulfate solution were heated to 60℃, and 0.2g of modified biochar was added and mixed evenly. Then, 100mmol and 20mL of potassium permanganate solution were slowly added until the potassium permanganate solution was completely added to obtain a mixed solution. The mixed solution was transferred to a hydrothermal reactor and treated at 140℃ for 5 hours. After filtration and washing until the pH was neutral (approximately 6.6-7.2), it was dried at 60℃ for 24 hours to obtain the composite material.

[0047] II. Sample Testing

[0048] 1. Effect of HF solution treatment on comparative surface area

[0049] The specific surface area of ​​the composite materials obtained in Examples 1 and 2 was tested, and the results are as follows: Figure 2 (BET plot of the sample obtained in Example 1) and Figure 3 (The BET plot of the sample obtained in Example 2 is shown.) It can be seen that the specific surface area of ​​the composite material obtained in Example 1 is 406.7 m². 2 / g, the specific surface area of ​​the composite material obtained in Example 2 is 108.6m². 2 / g, which shows that pyrolysis of sludge powder mixed with carbonate, followed by treatment with HF solution, will help increase the specific surface area.

[0050] 2. Specific capacitance test results of different samples at corresponding current densities

[0051] The composite material obtained in Example 1 was used as sample 1, the composite material obtained in Example 2 was used as sample 2, the modified biochar obtained in Example 1 was used as sample 3, manganese dioxide was used as sample 4, and the composite material obtained in Example 3 was used as sample 5.

[0052] Samples 1, 2, 3, 4, and 5 were taken and mixed with conductive carbon black and polytetrafluoroethylene at a mass ratio of 8:1:1. Anhydrous ethanol was then added to prepare an electrode slurry. The electrode slurry was then evenly coated onto nickel foam, dried, and pressed to form the working electrode. A platinum electrode was used as the counter electrode, a silver chloride electrode as the reference electrode, and a 6 mol / L potassium hydroxide solution as the electrolyte to assemble an electrode system. The specific capacitance was then measured at current densities of 1 A / g and 2 A / g, and the results are recorded in Table 1 below.

[0053] Table 1

[0054]

[0055] As shown in Table 1, this invention utilizes brewing waste sludge as raw material. After doping with carbonates (potassium carbonate and / or potassium bicarbonate), it helps to improve the pore structure of biochar. Combined with HF solution treatment, it increases the specific surface area of ​​the modified biochar. Furthermore, by combining the organic matter, nitrogen, phosphorus and other elements naturally abundant in brewing waste sludge, it achieves in-situ heteroatom doping of biochar, which enhances the pseudocapacitive effect of the composite material. Compared with manganese dioxide alone as a capacitor electrode material, it has stable working performance and better specific capacitance, resulting in a specific capacitance of 252.7 F / g under a current density of 2 A / g.

[0056] like Figure 5 and Figure 6 As shown in Table 2, the atomic composition of Ca, K, Mn, P, O, N, and C in the composite material obtained in Example 1 was analyzed, and the results are shown below:

[0057] Table 2

[0058] Ca K Mn P O C Percentage of mass, % 0.89 8.48 50.66 1.35 35.21 3.41

[0059] It is evident that the modified biochar obtained by this invention can provide sufficient sites for the attachment of Mn atoms, which helps to enhance the pseudocapacitive effect of the composite material after it is used to fabricate the working electrode.

[0060] like Figure 4 As shown, the composite material obtained in Embodiment 1 of the present invention has a petal-like structure.

[0061] For any other matters not covered in this invention, conventional technical means can be used to implement them, referring to existing technologies or common knowledge known to those skilled in the art. For example, the brewing waste sludge selected is the brewing waste sludge disclosed in patent number 202310841621.1. Another example: the process of mixing biochar with HF solution is based on the content disclosed in patent number 202310841621.1. Yet another example: in the fabrication of the working electrode, the drying-pressing process after uniformly coating the electrode slurry onto nickel foam is prepared according to common knowledge in the field of electrode fabrication technology. Furthermore, the conductive carbon black, polytetrafluoroethylene, and manganese dioxide are all purchased from the market.

Claims

1. A method for preparing composite materials for capacitors using brewing waste sludge, characterized in that, Includes the following steps: (1) Dry, grind and sieve the remaining sludge from brewing into sludge powder; (2) After mixing sludge powder with carbonate, it is pyrolyzed into biochar under an argon atmosphere; (3) The biochar was mixed with HF solution to remove ash, and modified biochar was obtained; (4) Add the modified biochar to the manganese sulfate solution and mix evenly, then add the potassium permanganate solution to obtain a mixed solution; treat the mixed solution at 120-160℃ for 4-8h, filter, and wash until the pH is 6.6-7.2, then dry at 60℃ for 24h to obtain the final product.

2. The method as described in claim 1, characterized in that, The drying of the brewing residue sludge is carried out at a constant temperature of 105°C until constant weight; the grinding and sieving is done by passing it through an 80-mesh sieve.

3. The method as described in claim 1, characterized in that, The carbonate is potassium carbonate and / or potassium bicarbonate, and the carbonate is 1-2 times the mass of the sludge powder based on K2O.

4. The method as described in claim 1, characterized in that, The pyrolysis is performed at a temperature of 400-600℃ for 2 hours.

5. The method as described in claim 1, characterized in that, Step (3) involves weighing 3-6g of biochar, adding 5-10mL of HF and 30mL of distilled water, mixing, stirring and heating, centrifuging and washing until the pH of the supernatant is 6, adding water, stirring and heating for 20min, centrifuging, and drying.

6. The method as described in claim 1, characterized in that, The manganese sulfate solution has a molar concentration of 10 mmol / L, and the potassium permanganate solution has a molar concentration of 100 mmol / L; the manganese sulfate solution is 35 mL, the potassium permanganate solution is 15-30 mL, and the modified biochar is 0.1-0.3 g; and / or the manganese sulfate solution is preheated to 60°C before the modified biochar is added.

7. The composite material prepared by the method according to any one of claims 1-6.

8. The composite material prepared by the method of any one of claims 1-6 or the composite material of claim 7 is used in the fabrication of a working electrode for a capacitor.

9. The application as described in claim 8, characterized in that, The working electrode is a nickel foam-based electrode.

10. The application as described in claim 9, characterized in that, The method for manufacturing the foamed nickel-based electrode involves mixing the composite material with conductive carbon black and polytetrafluoroethylene in a mass ratio of 8:1:1, then adding anhydrous ethanol to prepare an electrode slurry. The electrode slurry is then evenly coated onto the foamed nickel, dried, and pressed into shape to obtain the electrode.

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