Method for producing carbon material from straw and carbon material

Abstract

The application provides a method for generating carbon material by using straw and the carbon material, and relates to the field of comprehensive utilization of solid waste. The method comprises the following steps: mixing and reacting straw powder and sulfuric acid, washing to neutral, drying, and obtaining a pretreated straw product; uniformly mixing the pretreated straw product and a zinc-iron mixture to obtain a straw zinc-iron mixture, wherein the zinc-iron mixture is iron-vanadium slag or iron-vanadium solid; performing thermal plasma reaction on the straw zinc-iron mixture under the conditions of 0.3-0.7 atm of air pressure, 50-100 A of current and 0.85-4.6 kW of power, and collecting solid matter to obtain the carbon material. The straw powder and the zinc-iron mixture have a synergistic effect, part of the carbon in the pretreated straw product reduces iron and zinc elements in the zinc-iron mixture, and the iron and zinc elements will reversely catalyze the ordered arrangement of the remaining carbon in the straw, so that high-value flaky graphene and carbon nanotubes are formed, and the carbon material is obtained.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization of solid waste, and in particular to a method for generating carbon materials from straw and the carbon materials themselves. Background Technology

[0002] Agricultural solid waste constitutes the largest category of waste. On-site landfilling poses health risks to residents, causes severe environmental pollution, and is increasingly costly. Currently, straw treatment primarily involves low-value methods such as reactor composting, fermentation, and vermicomposting. High-value conversion of straw solid waste is becoming the inevitable path for future agricultural solid waste treatment and disposal. Summary of the Invention

[0003] The main objective of this invention is to provide a method for generating carbon materials from straw and the carbon materials themselves, in order to solve the technical problem of low straw value.

[0004] To achieve the above objectives, the present invention provides a method for generating carbon materials from straw, comprising the following steps: Straw powder and sulfuric acid are mixed and reacted, washed until neutral, and dried to obtain pretreated straw products.

[0005] The pretreated straw product and the zinc-iron mixture are mixed evenly to obtain a straw zinc-iron mixture, wherein the zinc-iron mixture is iron-vanadium slag or iron-vanadium solid.

[0006] A mixture of straw, zinc, and iron is subjected to a thermal plasma reaction under conditions of 0.3-0.7 atm pressure, 50-100 A current, and 0.85-4.6 kW power, and the solid material is collected to obtain carbon materials. The duration of the thermal plasma reaction is 10-25 min.

[0007] According to an embodiment of this application, the conditions for the thermal plasma reaction are a gas pressure of 0.5 atm, a current of 50 A, and a power of 0.85 kW.

[0008] According to embodiments of this application, the method also includes collecting the metallic gas generated during the thermal plasma reaction.

[0009] According to an embodiment of this application, the mass ratio of the pretreated straw product to the zinc-iron mixture is 1:(0.5~2).

[0010] According to the embodiments of this application, in the steps of mixing and reacting straw powder and sulfuric acid, washing until neutral, and drying, the drying step involves exposing the washed material to a constant temperature of 80°C for 6 hours and then allowing it to cool naturally.

[0011] According to an embodiment of this application, the concentration of sulfuric acid is 2M, and the straw powder and sulfuric acid are mixed in a solid-liquid ratio of 1:10 and reacted for 8-12 hours.

[0012] According to an embodiment of this application, the step of mixing the pretreated straw product and the zinc-iron mixture includes: Pretreated straw products, zinc-iron solution, NaOH, and Na₂SO₄ are mixed and reacted at pH 2 to obtain a straw zinc-iron suspension. The total Na content in the NaOH and Na₂SO₄ is in a molar ratio of 1:3 to the Fe content in the zinc-iron solution. The zinc-iron solution contains Fe. 3+ Zn 2+ and SO4 2- The zinc-iron solution is a zinc-iron ore leaching solution or a prepared solution.

[0013] The solids in the straw zinc-iron suspension were separated, dried, and ground to obtain a straw zinc-iron mixture.

[0014] According to an embodiment of this application, the zinc-iron solution is a prepared solution, and the preparation method of the zinc-iron solution includes: A zinc-iron solution is prepared by mixing ZnSO4 solution and Fe2(SO4)3 solid with Zn and Fe in a molar ratio of 3:1.

[0015] According to the embodiments of this application, in the steps of separating the solids from the zinc-iron suspension of straw, drying, and grinding, the grinding step includes grinding with a mortar and pestle, then using a 100-mesh filter sieve, shaking three times, with each shaking time lasting 10 minutes, and collecting powder with a mesh size greater than 100.

[0016] This application also provides a carbon material prepared by the above method, wherein the carbon material includes at least one of graphene and carbon nanotubes.

[0017] The above-described method for generating carbon materials from straw involves treating the straw powder to prevent it from reacting with the iron and zinc in the zinc leaching solution. In the thermal plasma reaction, the straw powder and the zinc-iron mixture have a synergistic effect. Part of the carbon in the pretreated straw product reduces the iron and zinc elements in the zinc-iron mixture, and these elements, in turn, catalyze the ordered arrangement of the remaining carbon in the straw, forming high-value-added sheet-like graphene and carbon nanotubes, thus yielding carbon materials. This method for generating carbon materials from straw is fast, uses inexpensive raw materials, and produces high-value-added carbon materials. Attached Figure Description

[0018] 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 the structures shown in these drawings without creative effort.

[0019] Figure 1 This is a flowchart of a method for generating carbon materials from straw according to an embodiment of this application; Figure 2 This is the Raman spectrum of a carbon material according to an embodiment of this application; Figure 3(a) is a SEM image of a one-dimensional carbon nanotube product according to an embodiment of this application; Figure 3(b) is a SEM image of a two-dimensional graphene product according to an embodiment of this application; Figure 3(c) is a SEM image of a three-dimensional graphite microparticle product according to an embodiment of this application; Figure 4 This is a SEM image of a pair of thermal plasma reaction products of this application.

[0020] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0022] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0023] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0024] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0025] This invention provides a method for generating carbon materials from straw, see [link to relevant documentation]. Figure 1 This includes the following steps: S100: Mix straw powder and sulfuric acid, wash until neutral, and dry to obtain pretreated straw product.

[0026] Straw powder is the small particulate matter formed after straw is crushed. Straw powder includes one or more common crop straw powders such as rice straw powder, wheat straw powder, corn straw powder, and sorghum straw powder.

[0027] To increase the reaction rate, in some embodiments, the straw powder is 200-mesh straw powder. Exemplarily, the straw powder is vibrated and filtered through a 200-mesh filter to obtain the desired straw powder.

[0028] Straw powder and sulfuric acid are mixed and stirred to react. The sulfuric acid is used to decompose the carbonates, bicarbonates, and other minerals in the straw, preventing these substances from reacting with the iron and zinc in the zinc-iron mixture.

[0029] In some embodiments, the mass ratio of the pretreated straw product to the zinc-iron mixture is 1:1:(0.5~2). This ratio is set according to the equivalence ratio of the carbon content of the straw to the zinc content of the iron slag so that a reduction reaction can occur.

[0030] In some embodiments, the concentration of sulfuric acid is 2M, and the straw powder and sulfuric acid are mixed in a solid-liquid ratio of 1:10 and reacted for 8-12 hours.

[0031] In this reaction, the concentration of sulfuric acid is 2M, the solid-liquid ratio of straw powder and sulfuric acid is 1:10, the mixing and stirring time is 8-12 hours, and the stirring is carried out at room temperature.

[0032] After the straw powder and sulfuric acid have reacted, they are washed. Washing methods include washing with deionized water, or, for example, using a vacuum filtration pump to filter multiple times until the pH of the filtrate is around 7.

[0033] After washing to neutrality, the material is dried. In some embodiments, the drying step involves exposing the washed material to a constant temperature of 80°C for 6 hours, followed by natural cooling.

[0034] For example, drying is carried out by a drying method using an 80°C low-temperature constant temperature drying oven, without covering the film, for 6 hours, followed by natural cooling.

[0035] S200: Mix the pretreated straw product and the zinc-iron mixture to obtain a straw zinc-iron mixture, wherein the zinc-iron mixture is iron-vanadium slag or iron-vanadium solid.

[0036] A zinc-iron mixture is a solid comprising iron and zinc. In some embodiments, the molar ratio of zinc to iron in the zinc-iron mixture is approximately 3:1, such as 3:1. Zinc-iron mixtures include various types; exemplary, the metal ions in the zinc-iron mixture mainly comprise iron and zinc in a solid form. For example, it can be a prepared solution obtained by mixing Fe2(SO4)3 solid with ZnSO4 solution, followed by the addition of NaOH and Na2SO4.

[0037] For example, in addition to iron and zinc, the zinc-iron mixture also contains other metal elements such as Cr and Hg, which are highly mobile heavy metals, meaning the zinc-iron mixture is an iron-vanadium slag.

[0038] Iron vanadium slag is a type of precipitated iron slag produced during hydrometallurgical zinc smelting, and its treatment is a major challenge in the industry. This precipitated iron slag, also known as iron alum slag, contains not only highly mobile heavy metals such as Pb, Zn, Cr, and Hg, but also precious and rare metals, exhibiting strong toxicity. Direct stockpiling not only occupies large amounts of land but also poses a potential pollution risk to soil and water bodies. The technical solution presented in this application provides a method for treating iron alum slag.

[0039] The methods for mixing the pretreated straw product and the zinc-iron mixture include at least two types. For example, if the zinc-iron mixture has already been prepared, the pretreated straw product and the zinc-iron mixture, such as iron vanadium slag or iron vanadium solid, can be directly mixed and stirred until homogeneous.

[0040] Another example is the mixing of zinc-iron mixtures with pretreated straw products, such as during iron precipitation, where the pretreated straw products are mixed in.

[0041] For example, in the process of preparing iron-vanadium solid, pretreated straw products are mixed in. Specifically, in some embodiments, according to the implementation of this application, the step of mixing the pretreated straw products and the zinc-iron mixture includes: S210: Pretreated straw product, zinc-iron solution, NaOH, and Na₂SO₄ are mixed and reacted at pH=2 to obtain a straw zinc-iron suspension. The total molar ratio of Na in the NaOH and Na₂SO₄ to Fe in the zinc-iron solution is 1:3. The zinc-iron solution contains Fe. 3+ Zn 2+ and SO4 2- The zinc-iron solution is a zinc-iron ore leaching solution or a prepared solution.

[0042] The prepared solution corresponds to the formation of the aforementioned iron-vanadium solid. Its composition and Zn-iron element ratio are similar to those of zinc-iron ore leaching solution, but it mainly lacks highly mobile heavy metal ions such as Cr and Hg. Therefore, on the one hand, the iron-vanadium solid formed by the prepared solution can be used in methods for generating carbon materials from straw. On the other hand, the prepared solution can also simulate zinc-iron ore leaching solution (hence, the prepared solution is also called an industrial simulated hydrometallurgical zinc leaching solution) to study the application of zinc-iron ore leaching solution or iron ore slag in the generation of carbon materials from straw. This will be illustrated below as an example.

[0043] This step primarily simulates the mature synthesis process of ferrous sulfate. NaOH is added to raise the pH, ensuring the solution's pH is 2. Na₂SO₄ is added to maintain the Na:Fe ratio in the ferrous sulfate phase, ensuring a Na:Fe molar ratio of 1:3. In some embodiments, NaOH is added first to adjust the solution pH to 2, then Na₂SO₄ is added to adjust the Na:Fe molar ratio to 1:3.

[0044] In this step, the main component of the iron-vanadium solid is NaFe3(SO4)2(OH)6 (which can also be called simulated iron alum slag), which is formed in the suspension of zinc leaching solution and straw powder. In this way, the iron-vanadium solid will grow at the solid-liquid interface of straw powder, enhancing the mass transfer of subsequent plasma reactions.

[0045] In some embodiments, the zinc-iron solution is a prepared solution, and the method for preparing the zinc-iron solution includes: A zinc-iron solution was prepared by mixing ZnSO4 solution and Fe2(SO4)3 solid with Zn in a molar ratio of 3:1 to Fe. This solution was prepared according to industrial standards to better study the application of zinc-iron ore leaching solutions or iron ore slag in the generation of carbon materials from straw. For example, a 0.45M ZnSO4 solution was used.

[0046] S220: Separate the solids from the straw zinc-iron suspension, dry and grind to obtain a straw zinc-iron mixture.

[0047] In this step, solid-liquid separation can be performed using conventional methods such as filtration and centrifugation. In some embodiments, the separation is performed by vacuum filtration. Vacuum filtration is performed using a vacuum pump, with the filtration pressure adjusted until the filtrate falls at a rate of 0.5-4 drops per minute. The filtration is then stopped, and the filtered product is placed in a petri dish.

[0048] In some embodiments, drying is performed using an oven drying method. For example, the drying is performed using a constant temperature oven at 80°C.

[0049] In some embodiments, the dried product is manually ground using a mortar and pestle, filtered through a 100-mesh sieve, and shaken three times for 10 minutes each time. Powder with a mesh size greater than 100 is collected to obtain a straw zinc-iron mixture (also known as a thermal plasma pretreated product).

[0050] S300: A mixture of straw, zinc, and iron is subjected to a thermal plasma reaction under conditions of 0.3-0.7 atm pressure, 50-100 A current, and 0.85-4.6 kW power, and the solid matter is collected to obtain carbon materials. The duration of the thermal plasma reaction is 10-25 min.

[0051] In this step, a vacuum arc plasma reactor is used to irradiate the straw-zinc-iron mixture, causing a thermal plasma reaction. The settings of the vacuum arc plasma reactor are: pressure 0.3-0.7 atm, current 50-100 A, and power 0.85-4.6 kW. In some embodiments, the thermal plasma reaction conditions are: pressure 0.5 atm, current 50 A, and power 0.85 kW.

[0052] Plasma heat treatment is characterized by high thermal efficiency and rapid heat treatment, enabling materials to be heated quickly to the desired temperature. Under the aforementioned conditions, thermal plasma reactions can generate a temperature range exceeding 3000℃. Within this temperature range, the straw-zinc-iron mixture reacts, with straw powder exhibiting a synergistic effect with the zinc-iron mixture. Pretreatment of the straw products involves the partial reduction of iron and zinc elements in the zinc-iron mixture by some carbon, producing elemental iron and zinc. These elemental iron and zinc then catalyze the ordered arrangement of the remaining carbon in the straw, forming high-value sheet-like graphene and carbon nanotubes, thus yielding carbon materials.

[0053] Because the reaction temperature is high, elemental iron and zinc will evaporate as iron vapor and zinc vapor, leaving only carbonaceous material as solid matter. In some embodiments, the reaction also includes collecting the metallic gases generated during the thermal plasma reaction.

[0054] In some embodiments, the carbon material includes one-dimensional carbon nanotubes, two-dimensional graphene, and three-dimensional graphite microparticles. The one-dimensional carbon nanotubes have a particle size of approximately 84.24 nm. The two-dimensional graphene has a particle size of approximately 84.18 nm. The three-dimensional graphite microparticles have a particle size of approximately 21.92 nm, a peak D / G ratio of 0.125, and a carbon content of 100%. They are in the form of graphene, carbon nanotubes, or graphite microparticles, and the material is black. Carbon nanotubes cost approximately 10,000 yuan / kg, and two-dimensional graphene costs approximately 6,000 yuan / kg, while simple carbon black nanospheres cost approximately 800 yuan / kg, making their value far lower than that of carbon nanotubes and two-dimensional graphene.

[0055] The above-described method for generating carbon materials from straw involves treating the straw powder to prevent it from reacting with the iron and zinc in the zinc leaching solution. In the thermal plasma reaction, the straw powder and the zinc-iron mixture have a synergistic effect. Part of the carbon in the pretreated straw product reduces the iron and zinc elements in the zinc-iron mixture, and these elements, in turn, catalyze the ordered arrangement of the remaining carbon in the straw, forming high-value-added sheet-like graphene and carbon nanotubes, thus yielding carbon materials. This method for generating carbon materials from straw is fast, uses inexpensive raw materials, and produces high-value-added carbon materials.

[0056] Compared with existing technologies, the above-mentioned method for generating carbon materials from straw has the following advantages: The plasma thermal treatment method used in this invention can obtain high-value carbon materials in a short time. The plasma treatment time is only 10-25 minutes, and the carbon material product has a carbon content of up to 95%. The straw organic matter is completely decomposed, the overall reaction is fast and thorough, and the iron and zinc recovery rate in non-ferrous solid waste is also high.

[0057] The plasma thermal treatment method used in this invention does not require the use of chemical reagents or solvents, has a high resource utilization rate, can generate syngas from straw organic matter to recover heat energy, and can rapidly heat up solid waste in the presence of metal components without producing secondary pollutants (dioxins), achieving zero emissions and zero landfill, and greatly reducing pollution and harm to the environment.

[0058] The plasma thermal treatment method employed in this invention enables the transformation of inexpensive agricultural solid waste into high-value carbon materials. This method converts the organic carbon elements in straw into one-dimensional or two-dimensional high-value carbon materials with superior microscopic physical and chemical properties. These materials can be widely applied in high-tech fields such as medicine, magnetic recording materials, electromagnetic shielding materials, lithium battery electrode materials, and catalytic materials, resulting in high added value. The high-value carbon materials produced through this invention can generate greater profit margins and have broad industrialization prospects.

[0059] The plasma thermal treatment method employed in this invention features high thermal efficiency and rapid heat treatment, quickly raising the material temperature to the required level and directly bypassing the side reaction generation temperature, thereby reducing the generation of secondary pollutants and meeting national environmental protection requirements. Furthermore, this invention can achieve the desired heat treatment effect in a short time, enabling rapid start-up and shutdown, and handling large quantities within a small footprint, improving material processing and production efficiency, meeting the demand for large-volume agricultural solid waste treatment, and possessing high commercial value.

[0060] This application also provides a carbon material prepared by the above method, wherein the carbon material includes at least one of graphene and carbon nanotubes. In some embodiments, the carbon material includes one-dimensional carbon nanotubes, two-dimensional graphene, and three-dimensional graphite particles. The one-dimensional carbon nanotubes have a particle size of approximately 84.24 nm. The two-dimensional graphene has a particle size of approximately 84.18 nm. The three-dimensional graphite particles have a particle size of approximately 21.92 nm, a D / G peak ratio of 0.125, a carbon content of 100%, and are in the form of graphene, carbon nanotubes, or graphite particles; the material is black.

[0061] In this embodiment of the invention, the method for analyzing the degree of graphitization is to use the Roman test.

[0062] Example 1 Corn straw powder (200 mesh fineness) was mixed with 2M sulfuric acid and stirred for 8-12 hours at a solid-liquid ratio of 1:10. The mixture was washed until neutral, dried at 80°C for 6 hours, and allowed to cool naturally to obtain the pretreated straw product. Fe2(SO4)3 solid was mixed with 0.45M ZnSO4 to obtain an industrial simulated wet zinc smelting leaching solution, ensuring a Fe:Zn ratio of 1:3. The pretreated straw product was mixed with the industrial simulated wet zinc smelting leaching solution at a 2:1 ratio. NaOH solid was added to adjust the pH to 2, followed by Na2SO4 solid to adjust the Na:Fe ratio to 1:3. The mixture was stirred for 8-12 hours. The suspension was then filtered until the filtrate fell at a rate of 0.5-4 min / drop. The solution was dried at 80°C for 6 hours, and the powder product (greater than 100 mesh) was collected by grinding to obtain the thermal plasma pretreated product. The thermal plasma pretreatment product was placed into a vacuum arc plasma reactor, the furnace pressure was adjusted to 0.5 atm, the reaction current to 50 A, the reaction time to 10 min, and the product was allowed to cool naturally to obtain a high-value carbon material product.

[0063] Example 2 Corn straw powder (200 mesh fineness) was mixed with 2M sulfuric acid and stirred for 8-12 hours, with a solid-liquid ratio of 1:10. The mixture was washed until neutral, dried at 80°C for 6 hours, and allowed to cool naturally to obtain the pretreated straw product. Fe2(SO4)3 solid was mixed with 0.45M ZnSO4 to obtain an industrial-scale simulated wet zinc smelting leaching solution, ensuring a Fe:Zn ratio of 1:3. The pretreated straw product was mixed with the industrial-scale simulated wet zinc smelting leaching solution at a 1:1 ratio. NaOH solid was added to adjust the pH to 2, followed by Na2SO4 solid, adjusting the Na:Fe ratio to 1:3. The mixture was stirred for 8-12 hours. The suspension was then filtered until the filtrate fell at a rate of 0.5-4 min / drop. The solution was dried at 80°C for 6 hours, and the powder product (greater than 100 mesh) was collected by grinding to obtain the thermal plasma pretreated product. The thermal plasma pretreatment product was placed into a vacuum arc plasma reactor, the furnace pressure was adjusted to 0.5 atm, the reaction current to 50 A, the reaction time to 10 min, and the product was allowed to cool naturally to obtain a high-value carbon material product.

[0064] Example 3 Corn straw powder (200 mesh fineness) was mixed with 2M sulfuric acid and stirred for 8-12 hours, with a solid-liquid ratio of 1:10. The mixture was washed until neutral, dried at 80°C for 6 hours, and allowed to cool naturally to obtain the pretreated straw product. Fe2(SO4)3 solid was mixed with 0.45M ZnSO4 to obtain an industrial-scale simulated wet zinc smelting leaching solution, ensuring a Fe:Zn ratio of 1:3. The pretreated straw product was mixed with the industrial-scale simulated wet zinc smelting leaching solution at a 1:1 ratio. NaOH solid was added to adjust the pH to 2, followed by Na2SO4 solid, adjusting the Na:Fe ratio to 1:3. The mixture was stirred for 8-12 hours. The suspension was then filtered until the filtrate fell at a rate of 0.5-4 min / drop. The solution was dried at 80°C for 6 hours, and the powder product (greater than 100 mesh) was collected by grinding to obtain the thermal plasma pretreated product. The thermal plasma pretreatment product was placed into a vacuum arc plasma reactor, the furnace pressure was adjusted to 0.5 atm, the reaction current was 125 A, the reaction time was 15 min, and the product was allowed to cool naturally to obtain a high-value carbon material product.

[0065] Example 4 Corn straw powder (200 mesh fineness) was mixed with 2M sulfuric acid and stirred for 8-12 hours. The solid-liquid ratio of the straw powder to sulfuric acid was 1:10. The mixture was washed until neutral, dried at 80°C for 6 hours, and allowed to cool naturally to obtain the pretreated straw product. Fe2(SO4)3 solid was mixed with 0.45M ZnSO4 to obtain an industrial simulated wet zinc smelting leaching solution, ensuring a Fe:Zn ratio of 1:3. The pretreated straw product was mixed with the industrial simulated wet zinc smelting leaching solution at a ratio of 1:2. NaOH solid was added to adjust the pH of the solution to 2, and then Na2SO4 solid was added to adjust the Na:Fe ratio to 1:3. The mixture was stirred for 8-12 hours. The suspension was filtered until the filtrate fell at a rate of 0.5-4 min / drop. The solution was dried at 80°C for 6 hours, and the powder product larger than 100 mesh was collected by grinding to obtain the thermal plasma pretreated product. The thermal plasma pretreatment product was placed into a vacuum arc plasma reactor, the furnace pressure was adjusted to 0.5 atm, the reaction current was 125 A, the reaction time was 15 min, and the product was allowed to cool naturally to obtain a high-value carbon material product.

[0066] Example 5 Corn straw powder (200 mesh fineness) was mixed with 2M sulfuric acid and stirred for 8-12 hours. The solid-liquid ratio of the straw powder to sulfuric acid was 1:10. The mixture was washed until neutral, dried at 80°C for 6 hours, and allowed to cool naturally to obtain the pretreated straw product. Fe2(SO4)3 solid was mixed with 0.45M ZnSO4 to obtain an industrial simulated wet zinc smelting leaching solution, ensuring a Fe:Zn ratio of 1:3. The pretreated straw product was mixed with the industrial simulated wet zinc smelting leaching solution at a ratio of 1:2. NaOH solid was added to adjust the pH of the solution to 2, and then Na2SO4 solid was added to adjust the Na:Fe ratio to 1:3. The mixture was stirred for 8-12 hours. The suspension was filtered until the filtrate fell at a rate of 0.5-4 min / drop. The solution was dried at 80°C for 6 hours, and the powder product larger than 100 mesh was collected by grinding to obtain the thermal plasma pretreated product. The pretreated product of thermal plasma was placed into a vacuum arc plasma reactor, the gas pressure inside the furnace was adjusted to 0.5 atm, the reaction current was 200 A, the reaction time was 20 min, and the product was allowed to cool naturally to obtain a high-value carbon material product.

[0067] Example 6 Corn straw powder (200 mesh fineness) was mixed with 2M sulfuric acid and stirred for 8-12 hours, with a solid-liquid ratio of 1:10. The mixture was washed until neutral, dried at 80°C for 6 hours, and allowed to cool naturally to obtain the pretreated straw product. Fe2(SO4)3 solid was mixed with 0.45M ZnSO4 to obtain an industrial simulated wet zinc smelting leaching solution, ensuring a Fe:Zn ratio of 1:3. The pretreated straw product was mixed with the industrial simulated wet zinc smelting leaching solution at a 1:2 ratio. NaOH solid was added to adjust the solution pH to 2, followed by Na2SO4 solid, adjusting the Na:Fe ratio to 1:3. The mixture was stirred for 8-12 hours. The suspension was then filtered until the filtrate fell at a rate of 0.5-4 min / drop. The solution was dried at 80°C for 6 hours, and the powder product (greater than 100 mesh) was collected by grinding to obtain the thermal plasma pretreated product. The thermal plasma pretreatment product was placed into a vacuum arc plasma reactor, the furnace pressure was adjusted to 0.5 atm, the reaction current was 200 A, the reaction time was 25 min, and the product was allowed to cool naturally to obtain a high-value carbon material product.

[0068] Comparative Example 1 Fe2(SO4) solid was mixed with 0.45M ZnSO4 to obtain an industrial-scale simulated wet zinc smelting leaching solution, ensuring an Fe:Zn ratio of 1:3. NaOH solid was added to the industrial-scale simulated wet zinc smelting leaching solution to adjust the pH to 2, followed by Na2SO4 solid, adjusting the Na:Fe ratio to 1:3. The mixture was stirred for 8-12 hours. The suspension was then filtered until the filtrate fell at a rate of 0.5-4 min / drop. The solution was dried at 80°C for 6 hours, and the powder product (greater than 100 mesh) was collected by grinding to obtain the thermal plasma pretreated product. The thermal plasma pretreated product was placed in a vacuum arc plasma reactor, with the furnace pressure adjusted to 0.5 atm, the reaction current to 50 A, and the reaction time to 10 min. The mixture was then allowed to cool naturally to obtain the final product.

[0069] Comparative Example 2 Corn straw powder (200 mesh fineness) was mixed with 2M sulfuric acid and stirred for 8-12 hours at a solid-liquid ratio of 1:10. The mixture was washed until neutral, dried at 80°C for 6 hours, and allowed to cool naturally to obtain a pretreated straw product. NaOH solid was added to the pretreated straw product to adjust the pH to 2, followed by Na2SO4 solid, and the mixture was stirred for 8-12 hours. The suspension was then filtered until the filtrate fell at a rate of 0.5-4 min / drop, dried at 80°C for 6 hours, and ground to collect a powder product larger than 100 mesh to obtain a thermal plasma pretreated product. This thermal plasma pretreated product was placed in a vacuum arc plasma reactor, with the furnace pressure adjusted to 0.5 atm, the reaction current to 50 A, and the reaction time to 10 min. After natural cooling, a high-value carbon material product was obtained.

[0070] Table 1. Iron-zinc conversion rate and power of each example and comparative example The conversion rates of elemental iron and elemental zinc were determined by collecting the volatilized metal powder using a volatilization collection device, performing digestion-ICP detection, and calculating the conversion rate.

[0071] The data in the table show that this method has the ability to efficiently convert carbon into high-value carbon. Through the thermal plasma reaction in this experiment, agricultural solid waste straw powder and industrial solid waste iron and vanadium slag can be co-processed to achieve solid waste reuse and prepare high-value materials. The reaction effect is optimal under fixed conditions.

[0072] Based on Examples 1, 1, and 2, it can be seen that in Example 1, the conversion rate of elemental iron was 95% and the conversion rate of elemental zinc was 82%. Comparative Example 1 produced iron oxide and sodium hydroxide, while Comparative Example 2 did not contain iron or zinc. This indicates that pretreatment of the straw products is crucial for the conversion of metal elements into elemental metals during the reaction.

[0073] Based on Examples 1, 3, and 5, it can be seen that in Example 1, the mixing ratio of pretreated straw product to industrial simulated wet zinc smelting leachate is 2:1, resulting in a 90% conversion rate of elemental iron and a 75% conversion rate of elemental zinc. In Example 3, the mixing ratio is 1:1, with a 95% conversion rate of elemental iron and an 82% conversion rate of elemental zinc. In Example 5, the mixing ratio is 1:2, with a 73% conversion rate of elemental iron and a 53% conversion rate of elemental zinc. Within a certain range, the higher the proportion of straw in the suspension, the higher the conversion rate of elemental iron and zinc. The optimal ratio of the two raw materials is 1:1. This indicates that by further controlling the ratio of pretreated straw product to industrial simulated wet zinc smelting leachate within a specific range, the carbon content of straw and the iron, vanadium, and zinc content in the straw undergo a reduction reaction during the reaction process, thus increasing both the consumption of straw solid waste and the conversion rate of elemental metals.

[0074] Based on Examples 2, 4, and 6, it can be seen that in Example 2, the vacuum arc plasma reactor reaction process with a reaction current of 50A achieved a 95% conversion rate for elemental iron and an 82% conversion rate for elemental zinc. In Example 4, the reaction process with a vacuum arc plasma reactor reaction current of 125A achieved a 77% conversion rate for elemental iron and a 66% conversion rate for elemental zinc. In Example 6, the reaction process with a vacuum arc plasma reactor reaction current of 200A achieved a 67% conversion rate for elemental iron and a 56% conversion rate for elemental zinc. As the reaction current gradually increases, the conversion rates of elemental iron and zinc gradually decrease. This indicates that the present invention, by controlling the thermal plasma reaction current within a specific range, both improves the conversion rate of elemental metals and controls experimental costs.

[0075] Based on Examples 2, 3, and 5, it can be seen that in Example 1, with a vacuum arc plasma reactor reaction time of 10 min, the conversion rate of elemental iron was 90% and the conversion rate of elemental zinc was 75%; in Example 3, with a reaction time of 15 min, the conversion rate of elemental iron was 82% and the conversion rate of elemental zinc was 72%; and in Example 5, with a reaction time of 20 min, the conversion rate of elemental iron was 73% and the conversion rate of elemental zinc was 53%. As the reaction time gradually increases, the conversion rates of elemental iron and elemental zinc gradually decrease. This indicates that the present invention, by controlling the thermal plasma reaction time within a specific range, both improves the conversion rate of elemental metals and controls experimental costs.

[0076] Analysis example The high-value carbon material product from Example 2 was subjected to Raman spectroscopy. The detection results are as follows: Figure 2 As shown, Figure 2 The high-value carbon powder D / G ratio is shown, with the peak intensity ratio of D peak to G peak being I(D):I(G)=0.13, proving that the layered graphene crystals have few defects and are of high quality.

[0077] The high-value carbon material product from Example 2 was subjected to SEM analysis, and the results are shown in Figure 3(a). Figure 4 As shown, Figure 3(a) shows the one-dimensional carbon nanotube product generated by thermal plasma reaction in Example 2 of the present invention, which is the morphology of the carbon nanotube product; Figure 3(b) shows the two-dimensional graphene product generated by thermal plasma reaction in Example 2 of the present invention, which is the morphology of ordered stacked layered graphene; Figure 3(c) shows the three-dimensional graphite microparticle product generated by thermal plasma reaction in Example 2 of the present invention, which is the morphology of the composite structure of carbon nanospheres and carbon nanotubes. Figure 4 The product of the thermal plasma reaction in Comparative Example 1 of this invention includes only relatively large carbon nanospheres, excluding carbon nanotubes and layered graphene. This demonstrates that without the presence of a zinc-iron mixture, the pretreated straw product alone cannot yield carbon nanotubes and two-dimensional graphene under thermal plasma reaction.

[0078] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for generating carbon materials from straw, characterized in that, Includes the following steps: Straw powder and sulfuric acid are mixed and reacted, washed until neutral, and dried to obtain pretreated straw product; Pretreated straw products, industrial simulated wet zinc smelting leaching solution, NaOH and Na2SO4 were mixed and reacted under pH=2 conditions to obtain straw zinc-iron suspension; The solids in the straw zinc-iron suspension were separated, dried, and ground to obtain a straw zinc-iron mixture; The total Na content of NaOH and Na₂SO₄ and the molar ratio of Fe in the industrial simulated hydrometallurgical zinc leaching solution are 1:3; the industrial simulated hydrometallurgical zinc leaching solution contains Fe. 3+ Zn 2+ and SO4 2- The industrial simulated wet zinc smelting leaching solution is a prepared solution; The preparation method of the industrial simulated wet zinc smelting leaching solution is as follows: Fe2(SO4)3 solid is mixed with 0.45M ZnSO4 solution to obtain the industrial simulated wet zinc smelting leaching solution, ensuring that the molar ratio of Fe to Zn is 1:

3. The mass ratio of the pretreated straw product to the industrial simulated wet zinc smelting leaching solution is 1:(0.5~2). A mixture of straw, zinc, and iron is subjected to a thermal plasma reaction under conditions of 0.3-0.7 atm air pressure, 50-100 A current, and 0.85-4.6 kW power, and the solid matter is collected to obtain carbon materials; wherein the duration of the thermal plasma reaction is 10-25 min.

2. The method according to claim 1, characterized in that, The conditions for the thermal plasma reaction are: gas pressure 0.5 atm, current 50 A, and power 0.85 kW.

3. The method according to claim 1, characterized in that, It also includes collecting the metallic gases produced during thermal plasma reactions.

4. The method according to claim 1, characterized in that, In the steps of mixing and reacting straw powder and sulfuric acid, washing until neutral, and drying, the drying step involves exposing the washed material to a constant temperature of 80°C for 6 hours and then allowing it to cool naturally.

5. The method according to claim 1, characterized in that, The sulfuric acid concentration is 2M, and the straw powder and sulfuric acid are mixed in a solid-liquid ratio of 1:10 and reacted for 8-12 hours.

6. The method according to claim 5, characterized in that, In the steps of separating the solids from the zinc-iron suspension of straw, drying, and grinding, the grinding step includes grinding with a mortar and pestle, then filtering with a 100-mesh sieve, shaking three times for 10 minutes each time, and collecting powder larger than 100 mesh.

7. A carbon material prepared by the method according to any one of claims 1 to 6, characterized in that, The carbon material includes at least one of graphene and carbon nanotubes.

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