A method for the efficient recovery of carbon resources from electrolytic aluminum waste carbon blocks and the preparation of carbon nanomaterials.

Abstract

This invention proposes a method for the efficient recovery of carbon resources from electrolytic aluminum waste carbon blocks and the preparation of nano-carbon materials, belonging to the field of solid waste resource utilization technology. The method includes the following steps: placing the electrolytic aluminum waste carbon blocks within a confined space to form an electrode; placing the electrode in an electrolyte as the working electrode, using a platinum sheet as the counter electrode, and applying a positive bias voltage for electrochemical treatment until the confined space is fully expanded; adding a platinum sheet electrode to form a new working electrode, using a platinum sheet as the counter electrode, and applying a positive bias voltage for electrochemical treatment until the electrolyte turns dark brown; performing ultrasonic and centrifugal treatment; collecting the upper suspension; and then washing and drying to obtain the product. This invention can achieve deep removal of fine particulate impurities from electrolytic aluminum waste carbon blocks, effectively reducing the ash content of the product. The process is simple and efficient, eliminating the need for pretreatment steps such as crushing and grinding, and avoiding problems such as low processing efficiency and difficulty in achieving nanoscale refinement.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically to a method for the efficient recovery of carbon resources from electrolytic aluminum waste carbon blocks and the preparation of nano-carbon materials. Background Technology

[0002] The electrolytic aluminum industry generates a large amount of waste carbon blocks during production, mainly including waste anode carbon slag salvaged from electrolytic cells and waste cathode carbon blocks produced during electrolytic cell overhauls. These waste carbon blocks are mostly disposed of through stockpiling or landfilling, which not only occupies significant land resources but also causes serious soil, water, and air pollution problems due to their high fluoride content. Waste cathode carbon blocks contain a large amount of highly graphitized carbon. Therefore, waste carbon blocks from electrolytic aluminum production are a high-quality and inexpensive precursor for the preparation of high-performance carbon materials.

[0003] Currently, methods for recovering carbon resources from electrolytic aluminum waste char blocks mainly include flotation, acid leaching, roasting, and high-temperature treatment. Patent CN121423357A involves crushing electrolytic aluminum char slag into particles of 0.1-1 cm, mixing it with a flotation agent, wet-milling it, and then separating it by flotation to obtain carbon powder. However, the purity of the obtained carbon powder is low (fixed carbon content ≤85%). Patent CN118106331A first crushes and screens the electrolytic aluminum waste char blocks to below 1 cm, then mixes them with molten salt doped with alkali and places them in a reactor. Recovery is achieved under an inert atmosphere at 500-700℃, combined with microwave heating and ultrasonic vibration. The fluoride removal rate of the product reaches 90-96%, but this process requires harsh reaction conditions and sophisticated equipment. Patent CN114749465B discloses a method for purifying carbon from aluminum electrolysis waste cathodes and preparing porous carbon adsorbents. Through multiple steps such as crushing, sieving, ball milling, high-temperature roasting with alkaline substances, acid leaching, and hydrogen peroxide treatment, porous carbon materials with high purity (ash content <3%) are prepared. However, this method has a complex process, and the use of a large amount of strong alkali and strong oxidizing reagents can easily cause environmental pollution.

[0004] Traditional recycling methods generally suffer from complex processes and difficulties in producing high-purity carbon materials. This is mainly because the long-term electrolysis process causes a large number of inorganic impurities to be tightly encapsulated within the carbon matrix. Therefore, traditional methods struggle to deeply remove the fine impurities embedded between carbon layers and in the gaps between carbon microcrystals. Furthermore, existing methods all require pretreatment of the waste carbon blocks, such as crushing and grinding. Due to the long-term penetration and erosion of the high-temperature electrolyte, the waste carbon blocks become denser and their hardness significantly increases, making the pretreatment process cumbersome and limiting the particle size of the resulting product.

[0005] Therefore, how to achieve efficient recycling of waste carbon from electrolytic aluminum, obtain deeply purified carbon resources, and collaboratively complete their high-value modification is a key technical problem that urgently needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to propose a method for the efficient recovery of carbon resources from electrolytic aluminum waste carbon blocks and the preparation of nano-carbon materials. This method can achieve deep removal of fine particulate impurities from electrolytic aluminum waste carbon blocks, effectively reduce the ash content of the product, and synergistically achieve functional modification of the product carbon materials. At the same time, this technology does not require pretreatment processes such as crushing and grinding, avoiding problems such as low processing efficiency and difficulty in achieving nanoscale refinement. The process is simple and efficient, and can realize the direct conversion of electrolytic aluminum waste carbon blocks into high-end nano-carbon materials.

[0007] The technical solution of this invention is implemented as follows:

[0008] This invention provides a method for the efficient recovery of carbon resources from electrolytic aluminum waste carbon blocks and the preparation of nano-carbon materials, comprising the following steps:

[0009] (1) Placing the waste carbon blocks from electrolytic aluminum within a confined space constitutes an electrode;

[0010] The electrolytic aluminum waste carbon blocks include anode carbon slag and waste cathode carbon blocks, with a fixed carbon content of over 40% and a low resistivity that ensures the smooth implementation of the electrochemical recovery process.

[0011] Preferably, the size of the electrolytic aluminum waste carbon block is 0.5-10 dm. 3 .

[0012] (2) Place the electrode obtained in step (1) in the electrolyte as the working electrode, use a platinum sheet as the counter electrode, apply a positive bias voltage to perform electrochemical treatment until the confined space is fully expanded; the fully expanded working electrode refers to the waste carbon block being destroyed under electrochemical action, and the size of the fine carbon particles in the confined space is between 100-200 mesh; this process also promotes the leaching of some impurity ions, causing the electrolyte to change from colorless and transparent to transparent light yellow.

[0013] The full expansion is characterized by a confined space exhibiting a distinct bulge state, which ceases to increase further, while the internal blocky waste carbon transforms into granular carbon.

[0014] (3) Place the platinum sheet electrode in the fully expanded confined space in step (2) to form a new working electrode. Use the platinum sheet as the counter electrode and apply a positive bias voltage to perform electrochemical treatment until the electrolyte turns blackish-brown.

[0015] (4) The dark brown product obtained in step (3) is subjected to ultrasonic and centrifugal treatment, the upper suspension is collected, and then washed and dried to obtain the product. The washing is performed by repeatedly washing the above suspension with deionized water until it is neutral.

[0016] This invention achieves the direct conversion of electrolytic aluminum waste carbon blocks into high-purity nano-carbon materials through electrochemical technology. Utilizing the directional migration and intercalation behavior of electrolyte ions during the electrochemical process, combined with the expansion and peeling effect of bubbles generated during the reaction on the carbon sheets within the electrolytic aluminum waste carbon blocks, the tightly embedded fine impurity particles are fully dissociated and released. Simultaneously, hydroxyl radicals (OH•) and oxygen radicals (O•) released during hydrolysis synergistically decompose the impurity phase with the acidic electrolyte, converting them into soluble ions. After multiple washing processes, highly efficient purification of electrolytic aluminum waste carbon can be achieved, with a simple process flow. Furthermore, under the combined action of oxygen radicals and electrolyte additives, the functional modification of high-purity nano-carbon materials can be simultaneously realized.

[0017] Preferably, low-frequency ultrasound is applied simultaneously in step (2), with an ultrasound frequency of 20-40 kHz and an ultrasound duration of 5-10 min. This process can accelerate the penetration of electrolyte and promote the initial dissolution of surface impurities.

[0018] As a further improvement of the present invention, the confined space described in step (1) is made of a sieve or sieve plate with a sieve opening of 600-1000 mesh.

[0019] As a further improvement of the present invention, the confined space in step (1) is a double-layer gradient structure consisting of an inner coarse sieve or sieve plate with 100-200 mesh openings and an outer fine sieve or sieve plate with 600-1000 mesh openings. In the first electrochemical treatment, the electrolytic aluminum waste carbon block is placed in the inner coarse sieve space. After expansion and crushing, the fine particles pass through the inner sieve and enter the outer fine sieve space. In the second electrochemical treatment, the platinum sheet is inserted into the outer fine sieve space to contact the refined carbon particles. The inner layer allows the electrolyte and small molecules to enter and exit freely, but prevents large particles from escaping. The outer layer further confines the fine particles and acts as an electrode current collector. This design solves the problems of uneven particle size during crushing in a single-layer confined space and uneven electrolyte penetration caused by large particles blocking the sieve openings. The product particle size distribution is narrower, the second electrochemical contact is more sufficient, the current distribution uniformity is improved, the current efficiency is increased, and local overheating is avoided. At the same time, the diffusion loss of nano-products in the electrolyte is reduced.

[0020] Preferably, the sieve or sieve plate is a sieve or sieve plate with polytetrafluoroethylene as the supporting structure and carbon nanotubes self-assembled and deposited on its surface. This structure reduces contact resistance, improves current efficiency, allows voltage to be applied more evenly to the interior of the waste carbon block, and enhances the impurity removal effect.

[0021] The preparation method is as follows:

[0022] S1. Add multi-walled carbon nanotubes to concentrated acid, heat and stir to react, filter, wash and dry to obtain carboxylated multi-walled carbon nanotubes.

[0023] Concentrated acid is a mixed acid prepared by mixing concentrated sulfuric acid and concentrated nitric acid in a ratio of 2-4:1.

[0024] The temperature for heating and stirring the reaction is 60-80℃, and the time is 3-5 hours.

[0025] S2. Carboxylated multi-walled carbon nanotubes were added to thionyl chloride, heated under reflux and stirred, filtered, and the product was added to ethylenediamine, heated under reflux and stirred, filtered, washed, and dried to obtain aminated multi-walled carbon nanotubes.

[0026] The heating, reflux, and stirring reaction time is 24-48 hours.

[0027] S3. Prepare 3-5 wt% aqueous dispersions of carboxylated multi-walled carbon nanotubes and 3-5 wt% aqueous dispersions of aminated multi-walled carbon nanotubes, respectively.

[0028] S4. Wash and dry the polytetrafluoroethylene sieve or sieve plate, treat it under plasma glow discharge for 80-100 seconds to activate its surface, add it to an ionic solution of diethylene glycol diacrylate phthalate (molecular weight 200,000-350,000, concentration 10-20 mg / mL) with a NaCl content of 0.5-1 mol / L, remove it, wash it, dry it, soak it in an aqueous dispersion of carboxylated multi-walled carbon nanotubes for 0.5-1 h, remove it, wash it, dry it, soak it in an aqueous dispersion of aminated multi-walled carbon nanotubes for 0.5-1 h, remove it, wash it, repeat the soaking process in the aqueous dispersions of carboxylated and aminated multi-walled carbon nanotubes 2-5 times, finally remove it, wash it, dry it to obtain a sieve or sieve plate with self-assembled carbon nanotubes deposited on the surface.

[0029] As a further improvement of the present invention, the electrolyte in steps (2) and (3) is 10-30 wt% dilute sulfuric acid. Too low an electrolyte concentration will result in insufficient acid leaching, while too high a concentration will reduce the content of OH• and O• free radicals released by water electrolysis, thus weakening the decomposition effect of reactive oxygen free radicals on impurities.

[0030] As a further improvement of the present invention, the electrolyte in step (2) is 10-30 wt% dilute sulfuric acid, and the electrolyte in step (3) is 10-30 wt% dilute sulfuric acid with added additives, the concentration of the additives being 2-5 wt%, and the additives being selected from one or more of ammonium sulfate, sodium tetraborate, and ammonium fluoride.

[0031] As a further improvement of the present invention, the working voltage of the electrochemical process in step (2) is 2-5V and the working current is 0.1-0.5A. If the working voltage is too high, it will easily cause the working electrode to release a large number of bubbles, thereby corroding the electrode clip; if the working voltage is too low, it will affect the crushing efficiency of the waste carbon block.

[0032] As a further improvement of the present invention, the electrochemical process in step (2) uses pulsed voltage, with a 2-5V pulse for 0.5-1s and a 0V pause for 0.5-1s. The pulsed mode can promote the detachment of bubbles from the electrode surface, reduce concentration polarization, and avoid excessive oxidation.

[0033] As a further improvement of the present invention, the electrochemical process in step (2) first adopts a constant current mode, and automatically switches to a constant voltage mode when the voltage reaches a preset value. This precisely controls the reaction rate and prevents local overheating or excessive current from causing excessive breakage of carbon particles.

[0034] As a further improvement of the present invention, the electrochemical process in step (3) is performed under the following conditions: working voltage 5-20V and working current 1-3A. This step achieves deep stripping and doping. If the working voltage is too high, a large amount of heat will be released, causing the electrolyte level to drop rapidly, requiring frequent replenishment of electrolyte and increasing material consumption; if the voltage is too low, it will affect the purification efficiency of the waste carbon blocks.

[0035] As a further improvement of the present invention, the ultrasonic power in step (4) is 100-400W, the ultrasonic frequency is 20-50kHz, the ultrasonic time is 1-12h, the centrifugation speed is 5000-8000rpm, and the centrifugation time is 10-20min.

[0036] The present invention has the following beneficial effects:

[0037] Electrolytic aluminum waste char blocks are hard and difficult to crush. This invention achieves in-situ transformation of electrolytic aluminum waste char blocks into nano-sized particles, overcoming the technical bias that waste char blocks must undergo pretreatment for effective processing. The process is simple and efficient, avoiding the problems of mechanical crushing, which is difficult to achieve nanoscale and has low processing efficiency. At the same time, this invention achieves efficient separation of difficult-to-remove fine particulate impurities in electrolytic aluminum waste char, with significant removal effects on impurities such as sodium, aluminum, and calcium in the waste char, and a significant reduction in the ash content of the product.

[0038] Furthermore, by adding additives such as ammonium sulfate, sodium tetraborate, and ammonium fluoride to the acidic electrolyte, nitrogen doping and boron doping are simultaneously achieved under the action of high voltage in the second step. In existing technologies, doping is usually a post-processing step, while this patent establishes a synergistic mechanism among impurity removal, stripping, and doping. The OH• / O• free radicals released by electrochemical hydrolysis decompose impurities, and then the acidic electrolyte dissolves the impurity ions, while the additives simultaneously achieve doping under the action of an electric field. This electrochemical system can synergistically achieve functional modification of carbon materials, preparing high-performance nano-carbon materials such as graphene oxide, nitrogen-doped graphene, and boron-doped graphene, expanding the high-value utilization path of electrolytic aluminum waste carbon, and promoting the technological upgrading of related industries. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a process flow diagram of the method for deep impurity removal and synergistic preparation of nano-carbon materials from electrolytic aluminum waste carbon blocks according to the present invention.

[0041] Figure 2 The image shows the XRD pattern of carbon residue from the anode of electrolytic aluminum.

[0042] Figure 3 The image shows the XRD pattern of the nano-carbon material prepared in Example 1.

[0043] Figure 4 The image shows the XPS spectrum of the nano-carbon material prepared in Example 1.

[0044] Figure 5 This is a morphology diagram of the nano-carbon material obtained in Example 2.

[0045] Figure 6 These are photos of the physical objects before and after processing in Example 3.

[0046] Figure 7 The image shows the TG spectrum of the carbon material after treatment in Comparative Example 1. Detailed Implementation

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Diethylene glycol diacrylate phthalate, molecular weight 200,000-350,000.

[0049] The anode carbon slag has an ash content of approximately 22.89%, and its elemental composition is shown in Table 1. Figure 2 The image shows the XRD pattern of carbon slag from the anode of electrolytic aluminum. As can be seen from the image, the impurities are tightly embedded in the carbon matrix in a crystalline form. Traditional mechanical crushing cannot destroy the interfacial bond between these crystalline phases and carbon, which explains why Comparative Example 1 could not remove impurities to a deep extent even after ball milling to 200 mesh.

[0050] Table 1 Elemental Analysis of Electrolytic Aluminum Anode Carbon Slag

[0051]

[0052] Preparation Example 1: Surface Self-Assembled Carbon Nanotube Deposited Screen

[0053] The preparation method is as follows:

[0054] S1. Add multi-walled carbon nanotubes to concentrated acid, heat to 70°C, stir for 4 hours, filter, wash, and dry to obtain carboxylated multi-walled carbon nanotubes.

[0055] The concentrated acid is a mixture of concentrated sulfuric acid and concentrated nitric acid in a 3:1 ratio.

[0056] S2. Carboxylated multi-walled carbon nanotubes were added to thionyl chloride, heated and stirred under reflux for 36 h, filtered, and the product was added to ethylenediamine, heated and stirred under reflux for 48 h, filtered, washed, and dried to obtain aminated multi-walled carbon nanotubes.

[0057] S3. Prepare 4 wt% carboxylated multi-walled carbon nanotube aqueous dispersion and 4 wt% aminated multi-walled carbon nanotube aqueous dispersion, respectively.

[0058] S4. Wash and dry the polytetrafluoroethylene (PTFE) sieve, treat it under plasma glow discharge for 90 seconds to activate its surface, add it to an ionic solution of diethylene glycol diacrylate (15 mg / mL) with 0.5 mol / L NaCl, remove it, wash and dry it, soak it in an aqueous dispersion of carboxylated multi-walled carbon nanotubes for 0.5 h, remove it, wash and dry it, then soak it in an aqueous dispersion of aminated multi-walled carbon nanotubes for 0.5 h, remove it, wash it, repeat the soaking process in the aqueous dispersions of carboxylated and aminated multi-walled carbon nanotubes 5 times, finally remove it, wash it and dry it to obtain a sieve with self-assembled carbon nanotubes deposited on its surface.

[0059] Example 1

[0060] refer to Figure 1 This embodiment provides a method for the efficient recovery of carbon resources from electrolytic aluminum waste carbon blocks and the preparation of nano-carbon materials, including the following steps:

[0061] (1) Select a volume of approximately 0.5 dm 3 The anode carbon slag is used to form an electrode by wrapping the anode carbon slag in a 1000-mesh polytetrafluoroethylene screen as a confined space.

[0062] (2) Using the above electrode as the working electrode and a platinum sheet as the counter electrode, 30 mL of 20 wt% dilute sulfuric acid was selected as the electrolyte. Electrochemical treatment was carried out for 3 hours under a DC voltage of 2 V to obtain carbon particles that were broken and refined in the confined space.

[0063] (3) Insert the platinum electrode into the above confined space and make close contact with the carbon particles to form a new working electrode.

[0064] (4) The above-mentioned new electrode was selected as the working electrode and a platinum sheet was used as the counter electrode. Electrochemical treatment was carried out for 6 hours in the same electrolyte system under a DC voltage of 5V to obtain a dark brown electrolyte.

[0065] (5) Take the above electrolyte and sonicate it at 100W and 40kHz for 1h. Then transfer it into a centrifuge tube and centrifuge at 8000rpm for 20min. Collect the upper suspension.

[0066] (6) The above suspension was repeatedly washed with deionized water until pH=7, and then dried in a 70℃ forced-air oven for 24h to obtain high-purity nano-carbon materials. Figure 3 The XRD pattern of the high-purity nano-carbon material is shown in the figure. As can be seen from the figure, the impurity peak regions have completely disappeared. Figure 4 The XPS spectrum of the high-purity nano-carbon material obtained is shown. The figure reveals characteristic peaks such as CO and C=O, indicating that the product contains oxygen-containing functional groups.

[0067] Example 2

[0068] refer to Figure 1 This embodiment provides a method for the efficient recovery of carbon resources from electrolytic aluminum waste carbon blocks and the preparation of nano-carbon materials, including the following steps:

[0069] (1) Select a volume of approximately 10 dm 3 The anode carbon slag was used as a confined space. The anode carbon slag was wrapped in the sieve plate to form the electrode.

[0070] (2) Using the above-mentioned electrode as the working electrode and the platinum sheet as the counter electrode, 500 mL of 10 wt% dilute sulfuric acid was selected as the electrolyte, and ammonium sulfate was added as an electrolyte additive with a concentration of 5 wt%. Electrochemical treatment was carried out for 8 hours under a DC voltage of 5 V to obtain carbon particles that were broken and refined in the confined space.

[0071] (3) Select a platinum sheet electrode, insert it into the above confined space and bind it tightly with the waste carbon particles to prepare a new electrode.

[0072] (4) The above-mentioned new electrode was selected as the working electrode and a platinum sheet was used as the counter electrode. Electrochemical treatment was carried out for 9 hours in the same electrolyte system under a DC voltage of 10V to obtain a dark brown electrolyte.

[0073] (5) Take the above electrolyte and sonicate it at 500W and 28kHz for 12h. Then transfer it into a centrifuge tube and centrifuge at 5000rpm for 10min. Collect the upper suspension.

[0074] (6) The above suspension was repeatedly washed with deionized water until pH=7, and then dried in an 80℃ oven for 12h to obtain high-purity nano-carbon materials. Figure 5 The image shows the morphology of the high-purity carbon nanomaterial. As can be seen from the image, the product is a large-area, wrinkled, thin, two-dimensional nanosheet, with the sheets in a flexible, curled, and overlapping state; there are no micron-sized particles or blocky residues.

[0075] Example 3

[0076] refer to Figure 1 This embodiment provides a method for the efficient recovery of carbon resources from electrolytic aluminum waste carbon blocks and the preparation of nano-carbon materials, including the following steps:

[0077] (1) Select a volume of approximately 1 dm 3 The anode carbon slag was prepared by using a 600-mesh polytetrafluoroethylene (PTFE) screen as a confined space to wrap the anode carbon slag within the screen to form the electrode.

[0078] (2) Using the above electrode as the working electrode and a platinum sheet as the counter electrode, 100 mL of 30 wt% dilute sulfuric acid was selected as the electrolyte, and sodium tetraborate was added as an electrolyte additive with a concentration of 3 wt%. Electrochemical treatment was carried out for 5 h under a DC voltage of 5 V to obtain carbon particles that were broken and refined in the confined space.

[0079] (3) Select a platinum sheet electrode, insert it into the above confined space and bind it tightly with the waste carbon particles to prepare a new electrode.

[0080] (4) The above-mentioned new electrode was selected as the working electrode, and a platinum sheet was used as the counter electrode. Electrochemical treatment was carried out for 5 hours in the same electrolyte system under a DC voltage of 8V to obtain a dark brown electrolyte.

[0081] (5) Take the above electrolyte and sonicate it at 300W and 40kHz for 5h. Then transfer it into a centrifuge tube and centrifuge at 6000rpm for 15min. Collect the upper suspension.

[0082] (6) The above suspension was repeatedly washed with deionized water until pH=7, and then dried in an 80℃ oven for 12h to obtain high-purity nano-carbon materials. Figure 6 These are actual images showing the anode carbon slag before and after treatment. As can be seen from the images, this invention directly reduces carbon slag from 1 dm³. 3 The anode carbon slag is transformed into fluffy powder without the need for any mechanical crushing equipment, thus achieving in-situ transformation.

[0083] Example 4

[0084] Compared with Example 3, the only difference is that the confined space is a double-layer gradient structure consisting of an inner coarse polytetrafluoroethylene screen with 200 mesh holes and an outer fine polytetrafluoroethylene screen with 600 mesh holes, and in step (3), the platinum electrode is inserted into the outer fine screen space.

[0085] Example 5

[0086] The only difference from Example 4 is that the sieve is made of the sieve material of surface self-assembled deposited carbon nanotubes prepared in Preparation Example 1.

[0087] Example 6

[0088] Compared with Example 3, the only difference is that low-frequency ultrasound is applied simultaneously in step (2), with an ultrasound frequency of 30 kHz and an ultrasound time of 10 min.

[0089] Example 7

[0090] Compared with Example 3, the only difference is that the electrochemical process in step (2) uses pulsed voltage, with a 5V pulse for 1 second and a 0V pause for 1 second.

[0091] Example 8

[0092] Compared with Example 3, the only difference is that in step (2), a constant current of 0.3A is used first, and when the voltage reaches 5V, it automatically switches to a constant voltage mode.

[0093] Comparative Example 1

[0094] (1) Select a volume of approximately 0.5 dm 3 The anode carbon slag was first crushed to a particle size of less than 3 mm using a crusher, and then continuously ground at 500 rpm for 4 hours using a planetary ball mill until the particle size was less than 200 mesh, thus obtaining waste anode carbon powder.

[0095] (2) Place the above-mentioned waste anode carbon powder in 20 mL of 40% dilute sulfuric acid solution, use ammonium sulfate as electrolyte additive, and stir at 400 rpm for 3 hours on a magnetic stirrer.

[0096] (3) Take the above-mentioned acid-soaked mixture and sonicate it for 3 hours at 300W and 20kHz. Transfer the mixture to a centrifuge tube and centrifuge at 8000rpm for 10 minutes. Collect the upper suspension.

[0097] (4) The above suspension was repeatedly washed with deionized water until the pH of the washing solution was 7. The washed product was then placed in a 70°C forced-air oven and dried for 24 hours to obtain the recovered product. Figure 7The TG spectrum of the recovered product is shown in the figure. As can be seen from the figure, the residual mass of 6.06% and the ash content of 6.06% are consistent. This is because the carbon structure is mainly micron-sized blocky and the oxidation rate is low, resulting in a high main weight loss temperature.

[0098] Product Analysis:

[0099] The high-purity nano-carbon materials prepared in Examples 1-8 and Comparative Example 1 were analyzed, and the results are shown in Table 2.

[0100] Table 2

[0101]

[0102] As shown in the table above, the high-purity nano-carbon materials prepared in the embodiments of the present invention have significant effects in removing impurities such as sodium, aluminum, and calcium, and the ash content is significantly reduced. They have achieved doping modification (except for Example 1), have a high recovery rate, and the average size of the materials reaches the nanoscale.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., 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 the efficient recovery of carbon resources from electrolytic aluminum waste carbon blocks and the preparation of nano-carbon materials, characterized in that, Includes the following steps: (1) Placing the waste carbon blocks from electrolytic aluminum within a confined space constitutes an electrode; (2) Place the electrode obtained in step (1) in the electrolyte as the working electrode, use a platinum sheet as the counter electrode, apply a positive bias voltage to perform electrochemical treatment until the confined space is fully expanded; (3) Place the platinum sheet electrode in the fully expanded confined space in step (2) to form a new working electrode. Use the platinum sheet as the counter electrode and apply a positive bias voltage to perform electrochemical treatment until the electrolyte turns blackish-brown. (4) The dark brown product obtained in step (3) is subjected to ultrasonic and centrifugal treatment, the upper suspension is collected, and then washed and dried to obtain the product.

2. The method according to claim 1, characterized in that, The confined space mentioned in step (1) is made of a sieve or sieve plate with a sieve opening of 600-1000 mesh.

3. The method according to claim 1, characterized in that, The confined space described in step (1) is a double-layer gradient structure consisting of an inner coarse screen or sieve plate with 100-200 mesh and an outer fine screen or sieve plate with 600-1000 mesh. In the first electrochemical treatment, the electrolytic aluminum waste carbon block is placed in the inner coarse screen space; in the second electrochemical treatment, the platinum sheet is inserted into the outer fine screen space to contact the refined carbon particles.

4. The method according to claim 1, characterized in that, The electrolyte in steps (2) and (3) is 10-30 wt% dilute sulfuric acid.

5. The method according to claim 1, characterized in that, The electrolyte in step (2) is 10-30 wt% dilute sulfuric acid. The electrolyte in step (3) is 10-30 wt% dilute sulfuric acid with added additives. The concentration of the additives is 2-5 wt%. The additives are selected from one or more of ammonium sulfate, sodium tetraborate, and ammonium fluoride.

6. The method according to claim 1, characterized in that, The working voltage of the electrochemical process in step (2) is 2-5V and the working current is 0.1-0.5A.

7. The method according to claim 6, characterized in that, The electrochemical process in step (2) uses pulsed voltage, with a 2-5V pulse for 0.5-1s and a 0V pause for 0.5-1s.

8. The method according to claim 6, characterized in that, The electrochemical process in step (2) first adopts a constant current mode, and automatically switches to a constant voltage mode when the voltage reaches the preset value.

9. The method according to claim 1, characterized in that, The conditions for the electrochemical process in step (3) are a working voltage of 5-20V and a working current of 1-3A.

10. The method according to claim 1, characterized in that, In step (4), the ultrasonic power is 100-400W, the ultrasonic frequency is 20-50kHz, the ultrasonic time is 1-12h, the centrifugation speed is 5000-8000rpm, and the centrifugation time is 10-20min.

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