Method for preparing activated carbon based on waste mask and PCB nonmetal powder and application

Abstract

The invention belongs to the technical field of carbon material preparation, and particularly relates to a method for preparing activated carbon based on waste masks and PCB nonmetal powder and application. After metal wires and rubber belts are removed from the non-woven fabric waste mask, the remaining part is smashed; and grinding the non-metal part of the waste circuit board, mixing with the mask chippings, pickling, filtering, washing filter residues to be neutral, mixing with Ca (OH) 2 and a second activating agent to obtain slurry, and sintering the slurry to obtain the activated carbon material. The prepared activated carbon material has developed pores, high specific surface area and excellent adsorption performance, and can synergistically utilize the PCB nonmetal components and the waste masks to prepare the carbon material, thereby providing a low-cost, high-benefit, environment-friendly and energy-saving technical solution for realizing resource utilization of the PCB nonmetal components and the waste masks; wide application prospects are realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional carbon material preparation, and particularly relates to a method for preparing activated carbon based on waste masks and PCB non-metallic powder and application. BACKGROUND

[0002] With the frequent occurrence of public health events, the recycling of waste disposable masks has become a focus in the field of solid waste treatment. Waste masks are mainly composed of polypropylene (PP) melt-blown non-woven fabric, which has considerable organic carbon resource potential. However, at present, they are mainly treated by incineration or landfill, which not only causes resource waste, but also produces secondary pollution hazards.

[0003] Waste printed circuit boards (PCBs) are one of the most challenging parts in electronic waste recycling. Traditional PCB recycling processes mainly focus on the recovery of metal parts, and common methods include mechanical crushing and sorting, thermal treatment, chemical leaching, etc. to extract precious metals such as copper, gold, silver, and palladium. The non-metallic part of PCB (mainly composed of thermosetting resin and glass fiber) accounts for more than 60% of the total mass of PCB, which has the characteristics of high stability and difficult degradation. If not properly treated, it can easily cause resource waste and environmental pollution.

[0004] Currently, the research on PCB non-metallic components or waste polymers mainly focuses on separate resource utilization, such as pyrolysis to recover carbon materials, doping concrete materials, or landfilling. Among them, both PCB non-metallic components and waste polymers have the potential to be used as carbon resources. If PCB non-metallic components and waste masks can be used together to prepare carbon materials, not only can the efficient conversion of carbon resources and the synchronous reduction of composite solid waste be achieved, but also the process limitations can be broken through to obtain activated carbon materials with better functionality and expand their application potential in the field of environmental purification. SUMMARY

[0005] To solve the above problems, one of the purposes of the present application is to provide a method for preparing activated carbon based on waste masks and PCB non-metallic powder.

[0006] The present application adopts the following technical solutions:

[0007] A method for preparing activated carbon based on waste masks and PCB non-metallic powder, comprising the following steps:

[0008] S1. After removing the metal wire and rubber belt from the non-woven fabric waste mask, the remaining part is crushed for use;

[0009] S2. After crushing the waste PCB, separate the metal part and the non-metallic part, grind the non-metallic part, and mix it with the debris obtained in step S1, grind and pass through an 80-mesh sieve;

[0010] S3. The undersize obtained in step S2 is subjected to acid washing, filtration, and washing of the filter residue until neutral to obtain a precursor;

[0011] S4. The precursor is mixed with a first activator, a second activator, and water in a set mass ratio to obtain a slurry, the first activator being Ca(OH)2, and the second activator being any one of KOH, K2CO3, NaOH, and Na2CO3;

[0012] S5. The slurry is subjected to temperature rising sintering under a nitrogen atmosphere to obtain the desired activated carbon material.

[0013] Preferably, in step S2, the non-metallic part grinding product is mixed with the debris obtained in step S1 in a mass ratio of 2:(0-1), and the mass of the debris is not 0.

[0014] Preferably, in step S3, the acid washing method is to add the undersize to a 2M HCl solution at a concentration of 100 g / L, heat the system to 80°C, and stir for at least 12 h.

[0015] Preferably, in step S4, the set mass ratio is 5:(0-2):(3-5.5):(8-14), and the amount of the first activator is not 0.

[0016] Preferably, in step S6, the temperature rising sintering procedure is to place the slurry in a nitrogen atmosphere, heat to 100°C at a heating rate of 5°C / min and maintain for 2 h, then heat to 600-800°C at a heating rate of 10°C / min and maintain for 1-2 h.

[0017] Preferably, in step S6, the sintered product further includes a cleaning and drying step, and the cleaning and drying method is to sequentially use 0.1M HCl and clean water to ultrasonically clean the sintered product for 30 min after cooling to room temperature, then wash with water until neutral, and dry at 80°C for 24 h to obtain the desired activated carbon material.

[0018] The second object of the present application is to provide an activated carbon material prepared by the method described above, which has the characteristics of low impurity content, high composite efficiency of different materials, uniform particles, and good pore size distribution.

[0019] Specifically, the activated carbon material is in the form of a loose porous agglomerate, the surface of the activated carbon material has mesoscale wrinkles, and the inside has a sponge-like multi-level pore structure, the multi-level pore structure includes macropores with a diameter of 50-200 nm and micropores with a diameter of 0.35-2 nm. The specific surface area of the activated carbon material can reach 1077-2712 m2 / g, the pore volume is 0.7-2 cm3 / g, and the adsorption capacity for methylene blue is as high as 425 mg / g.

[0020] A third objective of this invention is to provide an application of the activated carbon material described above as an adsorption material.

[0021] The fourth objective of this invention is to provide an application of the activated carbon material described above in wastewater treatment and / or removal of organic pollutants and / or preparation of electrochemical energy storage materials.

[0022] The beneficial effects of this invention are as follows:

[0023] This application provides a method for preparing carbon materials by synergistically utilizing non-metallic components of PCBs and discarded face masks. In this method:

[0024] The main component of the mask is polypropylene nonwoven fabric, while the non-metallic components of PCBs are rich in phenolic resin and a large amount of glass fiber. The mask can serve as a supplementary carbon source, optimizing the specific surface area and pore distribution of the material after activation. Moreover, both the non-metallic components of PCBs and discarded masks are waste products, which aligns with the environmental protection strategy of "treating waste with waste," resulting in a synergistic effect of 1+1>2.

[0025] By using ball milling to homogenize raw materials from different solid waste sources, not only can efficient composite of different components at the microscale be achieved, but also the particle size can be further refined, enabling better synergistic activation during heat treatment. Acid washing can remove residual inorganic impurities (such as metal impurities such as Cu, Sn, and Al) from recycled PCB non-metallic powder, as well as dissolve any inorganic salts (such as a small amount of carbonates) and oxides that may be present, thereby improving the purity and pore structure stability of the resulting carbon material.

[0026] A synergistic wet activation process using Ca(OH)₂ and KOH (or their alkaline salts) allows the activator to penetrate the particle interior more effectively, and the generation of intermediate activating substances at low temperatures increases the reaction rate. Calcium hydroxide, as an additive in the heat treatment of carbon materials, can inhibit tar formation. On one hand, calcium hydroxide is an alkaline substance with a strong affinity for acidic gases and certain organic components, enabling them to combine and undergo chemical reactions. On the other hand, the calcium oxide generated during the heating process of calcium hydroxide has a porous structure, which can physically adsorb tar precursor gases. Simultaneously, Ca(OH)₂ decomposes at high temperatures to generate CaO and water. Water vapor participates in physical activation, contributing to the formation of pores on the carbon material surface, while CaO, as a filler and supporting phase, can prevent the collapse of the carbon framework structure. Furthermore, at even higher temperatures, the combined use of Ca(OH)₂ with KOH, K₂CO₃, NaOH, and Na₂CO₃ can enhance the etching of the carbon material surface.

[0027] Finally, the generated product is washed with water with ultrasound assistance until neutral to accelerate the dissolution of alkaline substances and avoid the reverse reaction of residual Na2SiO3 and other dissolved substances that would otherwise be generated into glass fibers due to the use of acid in traditional methods.

[0028] In this method, the total mass ratio of the activator is significantly lower than that commonly used in existing literature (e.g., patent CN102923702A uses an activator ratio of 1:(1-4.5), which effectively reduces costs and the pressure of alkaline post-treatment. Furthermore, experimental results show that the prepared activated carbon material has well-developed pores and a specific surface area exceeding 2700 m². 2 / g, with an adsorption capacity of 425mg / g for methylene blue, far exceeding the performance of premium grade products in the industry standard.

[0029] The porous carbon composite material prepared in this application maintains a high specific surface area and a well-developed pore structure while also possessing excellent adsorption properties, making it suitable for efficient water treatment, deep removal of organic pollutants, and electrochemical energy storage. Attached Figure Description

[0030] Figure 1 The following are the analysis results of the non-metallic components of the PCB used in the example, where (a) is the composition analysis diagram and (b) is the thermogravimetric analysis result;

[0031] Figure 2 The results of testing the activated carbon material prepared in Example 1 are shown in Figure (a), which is a pore size distribution diagram, and Figure (b) is a SEM image of the activated carbon material.

[0032] Figure 3 The image shows the pore size distribution of the activated carbon material prepared in Example 2.

[0033] Figure 4 The pore size distribution diagram is for the activated carbon material prepared in Comparative Example 1.

[0034] Figure 5 The image shows a SEM image of the activated carbon material prepared in Comparative Example 1. Detailed Implementation

[0035] The technical solution of the present invention will be described in more detail below with reference to the embodiments.

[0036] Unless otherwise stated, the terms used herein have the meanings commonly understood by those skilled in the art.

[0037] The masks used in this embodiment are recycled medical waste masks. The recycled waste circuit boards are provided by an environmental protection company. The non-metallic components obtained after the recycled waste circuit boards are crushed, pulverized, and sorted have an average particle size D. 50 It is approximately 20 μm. See also... Figure 1 It contains approximately 60% glass fiber, 30% resin, and about 10% impurities.

[0038] Example 1

[0039] A method for preparing activated carbon based on waste masks and PCB non-metallic powder includes the following steps:

[0040] S1. After removing the metal wires and rubber bands from the waste non-woven fabric masks, cut the remaining part into small pieces and process it in a shredder for 2 minutes;

[0041] S2. After the waste circuit board is crushed, the metal and non-metal parts are separated. After grinding the non-metal part, 10g of it is mixed with 5g of mask fragments obtained in step S1, processed in a ball mill for 30 minutes, and then passed through an 80-mesh sieve.

[0042] S3. Mix the sieve residue obtained in step S2 with 150 mL of 2 M HCl and heat to 80 °C for 12 hours; after cooling, separate the filter residue and filtrate. Wash the filter residue with water until neutral to obtain the precursor;

[0043] S4. The precursor (dry weight) is mixed with the first activator and the second activator in a mass ratio of 5:1:3, and 27g of water is added and stirred at room temperature for 1 hour to obtain a slurry, wherein the first activator is Ca(OH)2 and the second activator is KOH;

[0044] S5. The slurry is placed in a nitrogen atmosphere, heated to 100°C at a heating rate of 5°C / min and dried for 2 hours, then heated to 700°C at a heating rate of 10°C / min and held for 1 hour.

[0045] After the product was cooled to room temperature, it was ultrasonically washed with 1M HCl and water until it reached neutral conditions (pH = 7-8) and then dried in an oven for 12 hours to obtain activated carbon product.

[0046] In this embodiment, two activators were used simultaneously, and the presence of Ca(OH)₂ optimized the pore distribution ratio. The product was tested, and its pore volume distribution is shown in [reference needed]. Figure 2 In the middle (a) region, macropores account for approximately 17% and micropores for approximately 50%, which is beneficial for the adsorption of both large organic molecules and small molecules. Its morphology is shown in [reference needed]. Figure 2 (b) Compared to the control sample without masks ( Figure 5 The proportion of glass fiber is reduced, and the surface exhibits an uneven texture with abundant pores. The specific surface area of ​​the activated carbon product reaches 1537 m². 2 / g, average pore size is 2.6nm, and total pore volume is 1.03cm. 3 / g. Using GB / T12496.10 Test Methods for Wood-based Activated Carbon – Determination of Methylene Blue Adsorption Value, the adsorption value of the sample for methylene blue reached 370 mg / g.

[0047] Example 2

[0048] A method for preparing activated carbon based on waste masks and PCB non-metallic powder includes the following steps:

[0049] S1. After removing the metal wires and rubber bands from the waste non-woven fabric masks, cut the remaining part into small pieces and process it in a shredder for 2 minutes;

[0050] S2. After the waste circuit board is crushed, the metal and non-metal parts are separated. After grinding the non-metal part, 4g of it is mixed with 1g of mask fragments obtained in step S1, processed in a ball mill for 30 minutes, and then passed through an 80-mesh sieve.

[0051] S3. Mix the undersize obtained in step S2 with 50 mL of 2 M HCl and heat to 80 °C for 12 hours; after cooling, separate the filter residue and filtrate. Wash the filter residue with water until neutral to obtain the precursor;

[0052] S4. The precursor (dry weight) is mixed with the first activator and the second activator in a mass ratio of 5:2:5.5, and 12.5g of water is added and stirred at room temperature for 1 hour to obtain a slurry, wherein the first activator is Ca(OH)2 and the second activator is NaOH;

[0053] S5. The slurry is placed in a nitrogen atmosphere, heated to 100°C at a heating rate of 5°C / min and dried for 2 hours, then heated to 700°C at a heating rate of 10°C / min and held for 1 hour.

[0054] After the product was cooled to room temperature, it was ultrasonically washed with 1M HCl and water until it reached neutral conditions (pH = 7-8) and then dried in an oven for 12 hours to obtain activated carbon product.

[0055] Compared to Example 1, this example increases the amount of activator, allowing for a more complete reaction between the activator and carbon, creating more developed pores. The product was tested, and the specific surface area of ​​the activated carbon product reached 2712 m². 2 / g, average pore size is 2.9nm, total pore volume is 2cm. 3 / g. See also Figure 3 The pore volume showed a stable distribution of macropores at 17% and micropores at 46%. The adsorption value of methylene blue was determined using the GB / T 12496.10 standard for wood-based activated carbon, employing a UV spectrophotometer. The sample's adsorption value for methylene blue reached 425 mg / g.

[0056] Comparative Example 1

[0057] A method for preparing activated carbon based on waste masks and PCB non-metallic powder includes the following steps:

[0058] S1. After removing the metal wires and rubber bands from the waste non-woven fabric masks, cut the remaining part into small pieces and process it in a shredder for 2 minutes;

[0059] S2. After the waste circuit board is crushed, the metal and non-metal parts are separated. After grinding the non-metal part, 4g of it is mixed with 2g of mask fragments obtained in step S1, processed in a ball mill for 30 minutes, and then passed through an 80-mesh sieve.

[0060] S3. Mix the undersize obtained in step S2 with 50 mL of 2 M HCl and heat to 80 °C for 12 hours; after cooling, separate the filter residue and filtrate. Wash the filter residue with water until neutral to obtain the precursor;

[0061] S4. The precursor (dry weight) is mixed with the first activator, the second activator, and water in a mass ratio of 5:0:4:9 and stirred at room temperature for 1 hour to obtain a slurry, wherein the first activator is Ca(OH)2 and the second activator is KOH;

[0062] S5. The slurry is placed in a nitrogen atmosphere, heated to 100°C at a heating rate of 5°C / min and dried for 2 hours, then heated to 800°C at a heating rate of 10°C / min and held for 1 hour.

[0063] After the product was cooled to room temperature, it was ultrasonically washed with 1M HCl and water until it reached neutral conditions (pH = 7-8) and then dried in an oven for 12 hours to obtain activated carbon product.

[0064] Test the product, such as Figure 4 The proportion of macropores was reduced to only 10% compared to Examples 1 and 2, where the first activator Ca(OH)2 was not zero, and the specific surface area of ​​the activated carbon product reached 1077 m². 2 / g, average pore size is 2.8nm, and total pore volume is 0.76cm. 3 The adsorption value of methylene blue was reduced compared to Example 1. The same method was used to test the adsorption value of methylene blue, which was 275 mg / g.

[0065] Comparative Example 2

[0066] Comparative Example 2 does not add any components from discarded masks. The steps are as follows:

[0067] S1. After the waste circuit board is crushed, the metal and non-metal parts are separated. After grinding the non-metal part, take 5g and continue to process it in a ball mill for 30 minutes, and then pass it through an 80-mesh sieve.

[0068] S2. The undersize obtained in step S1 is mixed with 50 mL of 2 M HCl and heated to 80 °C for 12 hours. After cooling, the filter residue and filtrate are separated. The filter residue is washed with water until neutral to obtain the precursor.

[0069] S3. The precursor (dry weight) is mixed with the first activator, the second activator, and water in a mass ratio of 5:1:3:9 and stirred at room temperature for 1 hour to obtain a slurry, wherein the first activator is Ca(OH)2 and the second activator is KOH;

[0070] S4. The slurry is placed in a nitrogen atmosphere, heated to 100°C at a heating rate of 5°C / min and dried for 2 hours, then heated to 700°C at a heating rate of 10°C / min and held for 1 hour.

[0071] After the product was cooled to room temperature, it was ultrasonically washed with 1M HCl and water until it reached neutral conditions (pH = 7-8) and then dried in an oven for 12 hours to obtain activated carbon product.

[0072] See Figure 5 Exposed glass fibers were visible on the surface of the product. Testing revealed that the specific surface area of ​​the activated carbon product reached 607 m². 2 / g, average pore size is 3.2nm, and total pore volume is 0.4cm. 3 / g, with an adsorption value of 189 mg / g for methylene blue. Without the addition of a mask, both the specific surface area and total pore volume were significantly reduced compared to Example 1.

[0073] Comparative Example 3

[0074] Comparative Example 3 does not use any activator; the steps are as follows:

[0075] S1. After removing the metal wires and rubber bands from the waste non-woven fabric masks, cut the remaining part into small pieces and process it in a shredder for 2 minutes;

[0076] S2. After the waste circuit board is crushed, the metal and non-metal parts are separated. After grinding the non-metal part, 4g of it is mixed with 2g of mask fragments obtained in step S1, processed in a ball mill for 30 minutes, and then passed through an 80-mesh sieve.

[0077] S3. Mix the undersize obtained in step S1 with 50 mL of 2 M HCl and heat to 80 °C for 12 hours; after cooling, separate the filter residue and filtrate. Wash the filter residue with water until neutral to obtain the precursor;

[0078] S4. The precursor (dry weight) is directly mixed with an equal mass of water and stirred at room temperature for 1 hour to obtain a slurry;

[0079] S5. The slurry is placed in a nitrogen atmosphere, heated to 100°C at a heating rate of 5°C / min and dried for 2 hours, then heated to 600°C at a heating rate of 10°C / min and held for 1 hour.

[0080] After the product was cooled to room temperature, it was ultrasonically washed with 1M HCl and water until it reached neutral conditions (pH = 7-8) and then dried in an oven for 12 hours to obtain activated carbon product.

[0081] The product was tested, and the specific surface area of ​​the activated carbon product reached 97 m². 2 / g, with an average pore size of 3.9nm and a total pore volume of 0.096cm. 3 / g, with an adsorption value of only 52mg / g for methylene blue.

[0082] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing activated carbon based on waste face masks and PCB non-metallic powder, characterized in that, Includes the following steps: S1. After removing the metal wires and rubber bands from the waste non-woven fabric masks, the remaining part is crushed and set aside for later use; S2. After the waste circuit board is crushed, the metal and non-metal parts are separated. The non-metal parts are ground and mixed with the debris obtained in step S1, ground, and passed through an 80-mesh sieve. S3. The undersize obtained in step S2 is acid-washed, filtered, and the filter residue is washed until neutral to obtain the precursor. S4. The precursor is mixed with a first activator, a second activator and water in a set mass ratio and stirred to obtain a slurry. The first activator is Ca(OH)2 and the second activator is any one of KOH, K2CO3, NaOH and Na2CO3. S5. The slurry is heated and sintered under a nitrogen atmosphere to obtain the desired activated carbon material.

2. The method for preparing activated carbon based on waste masks and PCB non-metallic powder as described in claim 1, characterized in that, In step S2, the non-metallic grinding product is mixed with the debris obtained in step S1 at a mass ratio of 2:(0-1), and the mass of the debris is not 0.

3. The method for preparing activated carbon based on waste masks and PCB non-metallic powder as described in claim 1, characterized in that, In step S3, the acid washing method is to add the sieved material at a concentration of 100 g / L to a 2 M HCl solution, heat the system to 80°C, and stir the reaction for at least 12 hours.

4. The method for preparing activated carbon based on waste masks and PCB non-metallic powder as described in claim 1, characterized in that, In step S4, the mass ratio is set to 5:(0~2):(3~5.5):(8~14), and the amount of the first activator is not 0.

5. The method for preparing activated carbon based on waste masks and PCB non-metallic powder as described in claim 1, characterized in that, In step S6, the heating and sintering procedure is as follows: the slurry is placed in a nitrogen atmosphere, heated to 100°C at a heating rate of 5°C / min and held for 2 hours, and then heated to 600-800°C at a heating rate of 10°C / min and held for 1-2 hours.

6. The method for preparing a three-dimensional network structure porous carbon composite material from waste circuit boards as described in claim 1, characterized in that, In step S6, the sintered product further includes a cleaning and drying step. The cleaning and drying method is as follows: after the sintered product is cooled to room temperature, it is ultrasonically cleaned with 0.1M HCl and water for 30 minutes in sequence, then rinsed with water until neutral, and dried at 80°C for 24 hours to obtain the desired activated carbon material.

7. An activated carbon material, characterized in that, The activated carbon material is prepared by the method described in any one of claims 1-6. The activated carbon material is in the form of an aggregate. The surface of the activated carbon material has a pleated mesoscopic structure with uneven texture, and the interior has a sponge-like hierarchical pore structure. The hierarchical pore structure includes macropores with a diameter of 50-200 nm and micropores with a diameter of 0.35-2 nm.

8. The activated carbon material as described in claim 7, characterized in that, The porous carbon composite material has a specific surface area of ​​1077–2712 m². 2 / g, pore volume is 0.7~2cm³ 3 / g.

9. The application of the activated carbon material as described in claim 7 or 8 as an adsorbent material.

10. The application of an activated carbon material as described in claim 7 or 8 in wastewater treatment and / or removal of organic pollutants and / or preparation of electrochemical energy storage materials.

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