A carbon-based pumice and its preparation method

Abstract

This invention provides a carbon-based pumice and its preparation method, belonging to the field of new material preparation technology in water treatment. The invention uses a base material and / or a silicon-aluminum ratio adjuster as the main raw material. During foaming, a foaming agent and foaming aid generate a large number of bubbles, forming numerous open pores and gaps within the material, thereby increasing the effective porosity. An air-retaining agent is used to encapsulate the material, preventing the generated bubbles from escaping rapidly, further improving the effective porosity. Sintering under sealed conditions deoxygenates the CO produced by organic carbon and biochar into pure elemental carbon molecules. Simultaneously, these molecules self-assemble in pre-made gaps to form a honeycomb-like channel bundle structure composed of carbon molecules, exhibiting excellent adsorption and flow properties. Using sludge or organic sludge and a small amount of auxiliary carbon source, a structure with silicon oxide as the main component and honeycomb-like carbon molecule channel bundles connected by numerous pores is obtained, greatly improving the material's performance while reducing the use of a large amount of wood material, thus saving raw material costs.

Description

Technical Field

[0001] This invention belongs to the field of new material preparation technology in water treatment, specifically relating to a carbon-based pumice and its preparation method. Background Technology

[0002] In water treatment projects, filter beds are a common process technology, and the filter media in the filter bed is a very important part. Commonly used porous materials for filter media are pumice and activated carbon.

[0003] Most filter media used in current water treatment processes have porous surfaces, which absorb organic matter in the water by utilizing the specific surface area of ​​the pores. However, the effective porosity is relatively low, and the liquid only flows in the gaps between the materials, which can easily lead to clogging due to impermeability or poor permeability.

[0004] The porosity of pumice and activated carbon is mostly calculated by mass ratio, which has a very high upper limit, sometimes reaching 200% to 400%. However, in actual water treatment, the effective porosity (volume ratio) is often obtained by volume calculation (Equation I).

[0005] The formula for calculating the effective porosity of filter media at room temperature is shown in Equation I, which uses volume ratio for description:

[0006]

[0007] In the formula, m1 is the mass of the material when dry, m2 is the mass of the material after absorbing water and becoming saturated, and V1 is the volume of the material.

[0008] The theoretical upper limit of the volume ratio is 100%. The effective porosity, which is more reflected in real-world projects, can be truly used to test the water storage capacity and pollutant adsorption of materials in projects.

[0009] In addition, pumice has a certain porosity and a large specific surface area. Its internal pores can store some water. Pumice is divided into natural pumice and artificial pumice. Artificial pumice has a higher effective porosity, reaching 20-30%; natural pumice has an effective porosity of 5-20%. Activated carbon commonly used in water treatment is coconut shell activated carbon (effective porosity 30-40%) and coal-based activated carbon (effective porosity 20-30%), both of which have relatively low effective porosity. Pumice and activated carbon have closed pores, preventing liquid flow and resulting in clogging. Furthermore, the high cost of raw materials for producing activated carbon leads to an overall high cost, thus limiting its widespread use. Therefore, improving the adsorption performance and flowability of filter media while reducing costs has become a pressing technical challenge in this field. Summary of the Invention

[0010] The purpose of this invention is to provide a carbon-based pumice and its preparation method. Compared with conventional activated carbon materials, the carbon-based pumice provided by this invention has better effective porosity, adsorption performance, and conductivity, while significantly reducing manufacturing costs.

[0011] Traditional carbon-based materials are basically made from a large amount of wood and coal-based materials using various methods to produce finished products with carbon as the main component. Typical examples include wood-based activated carbon, coconut shell / fruit shell activated carbon, and coal-based activated carbon.

[0012] This invention is a hybrid of silicon-based and carbon-based materials. It uses silicon oxide from sludge as the primary base material, supplemented by a silicon-aluminum blending agent to form the main body. Specialized foaming agents and gas-retaining agents are used to create numerous pores and gaps within the material. Organic matter from the sludge serves as the primary carbon source, with the addition of a small amount of auxiliary carbon source. In a sealed space, carbon molecules are reduced, and after deposition, they self-assemble within the pre-made gaps to form a honeycomb-like, channel-like structure. These channel-like structures give the material excellent adsorption and flow properties, as well as good electrical conductivity, while the silicon oxide molecules provide good stability and strength.

[0013] The carbon-based pumice prepared by the method provided by this invention has a honeycomb-like channel bundle structure, which is different from the structure of existing filter media. This structure enables the material to have excellent adsorption performance and conductivity, both of which exceed those of conventional activated carbon materials currently on the market. At the same time, by using sludge or organic sludge as the base material and a small amount of auxiliary carbon source, a structure with silicon oxide as the main body containing honeycomb carbon molecular channel bundles connected by a large number of pores is prepared. While improving performance, it reduces the use of a large amount of wood material, saves raw material costs, and makes its manufacturing cost far lower than that of conventional activated carbon materials.

[0014] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0015] This invention provides a method for preparing carbon-based pumice, comprising the following steps:

[0016] (1) Mix the main material, foaming agent, foaming aid and water to obtain a slurry; the main material includes basic materials and / or silicon-aluminum ratio adjuster; the basic materials include sludge or organic sludge;

[0017] (2) Granulate the slurry obtained in step (1) to obtain spherical particles;

[0018] (3) Spray the aqueous solution of the gas-retaining agent onto the surface of the spherical particles obtained in step (2), and then foam and dry them in sequence to obtain the blank;

[0019] (4) The blank obtained in step (3) is subjected to a first sintering under sealed conditions to obtain a first sintered product;

[0020] (5) The first sintered product obtained in step (4) is subjected to a second sintering under a nitrogen atmosphere to obtain a second sintered product;

[0021] (6) Activate the second sintered product obtained in step (5) to obtain carbon-based pumice.

[0022] Preferably, the silicon-aluminum ratio modifier in step (1) is Al4[Si4O] 10 [OH]8, the purity of the silicon-aluminum ratio modifier is above 95%, and the particle size of the silicon-aluminum ratio modifier is 200-300 mesh.

[0023] Preferably, in step (1), the foaming agent is azodicarbonamide and / or polyurethane, and the foaming agent accounts for 0.5 to 1.5% of the main material mass.

[0024] Preferably, the foaming agent in step (1) is at least one of calcium carbonate, calcium bicarbonate, aluminum trichloride and phosphate starch, and the mass ratio of the foaming agent to the foaming agent is 1:1.

[0025] Preferably, the gas-retaining agent in step (3) is sodium silicate and / or methylcellulose, and the mass concentration of the aqueous solution of the gas-retaining agent is 1-3%.

[0026] Preferably, the foaming temperature in step (3) is 150-200°C and the foaming time is 30-60 minutes.

[0027] Preferably, the temperature of the first sintering in step (4) is 1000-1200℃, and the time of the first sintering is 90-120min.

[0028] Preferably, the temperature of the second sintering in step (5) is 1000–1200°C, and the sintering time is 30–60 min.

[0029] Preferably, the activator used in step (6) is an aqueous solution of at least one of bio-acid, sodium dodecyl sulfate, fatty alcohol polyoxyethylene ether, and alkyl glycoside.

[0030] The present invention also provides carbon-based pumice prepared by the preparation method described in the above technical solution.

[0031] This invention provides a method for preparing carbon-based pumice, comprising the following steps: mixing a main material, a foaming agent, a foaming aid, and water to obtain a slurry; the main material includes a base material and / or a silicon-aluminum ratio adjuster; the base material includes sludge or organic sludge; granulating the slurry to obtain spherical particles; spraying an aqueous solution of an air-retaining agent onto the surface of the spherical particles, and then sequentially foaming and drying to obtain a blank; subjecting the blank to a first sintering under sealed conditions to obtain a first sintered product; subjecting the first sintered product to a second sintering under a nitrogen atmosphere to obtain a second sintered product; and activating the second sintered product to obtain carbon-based pumice. This invention uses basic materials and / or silicon-aluminum ratio modifiers as main ingredients. The addition of foaming agents and foaming aids generates a large number of bubbles during foaming, forming numerous open pores and gaps within the material, thereby increasing the effective porosity of the carbon-based pumice. By employing a gas-retaining agent, the material is encapsulated, preventing the rapid escape of bubbles generated during foaming, further enhancing the effective porosity of the carbon-based pumice. Utilizing the principle of vapor deposition, sintering under sealed conditions allows the CO produced by organic carbon and biochar to be deoxygenated into pure elemental carbon molecules. Simultaneously, these molecules self-assemble in pre-made gaps to form a honeycomb-like channel bundle structure composed of carbon molecules. These bundle-like channels possess excellent adsorption and flow properties. Activation further strengthens the honeycomb-like micron-sized channel bundles, increasing the effective porosity and thus improving fluidity and significantly reducing the probability of clogging. Using sludge or organic sludge as the basic material and a small amount of auxiliary carbon source, a structure with silicon dioxide as the main component and honeycomb-like carbon molecule channel bundles connected by numerous pores is prepared. This improves performance while reducing the use of a large amount of wood material, saving raw material costs. Experimental results show that the effective porosity of the carbon-based pumice prepared by this invention is 35-50%, the compressive strength is 0.5-2.8 MPa, and the electrical conductivity is 3.5-5 S / m. Attached Figure Description

[0032] Figure 1 A photograph of the carbon-based pumice prepared in Example 1;

[0033] Figure 2 SEM image of the carbon-based pumice prepared in Example 1;

[0034] Figure 3 SEM image of the carbon-based pumice prepared in Example 1;

[0035] Figure 4 The image shows a comparison of the effluent from the carbon-based pumice prepared in Example 1 and the coconut shell activated carbon in Comparative Example 2 after 1 hour of adsorption of domestic sewage.

[0036] Figure 5 The image shows a comparison of the effluent from the carbon-based pumice prepared in Example 1 and the coconut shell activated carbon in Comparative Example 2 after 1 hour of adsorption of dyeing and printing wastewater.

[0037] Figure 6 Five positions of elemental detection were obtained from the carbon molecular tube bundle of carbon-based pumice prepared in Example 1.

[0038] Figure 7 The EDS spectrum of position 1 of the carbon molecular tube bundle in carbon-based pumice prepared in Example 1;

[0039] Figure 8 The EDS spectrum of position 2 of the carbon molecular tube bundle in carbon-based pumice prepared in Example 1;

[0040] Figure 9 The EDS spectrum of position 3 of the carbon molecular tube bundle in the carbon-based pumice prepared in Example 1;

[0041] Figure 10 The EDS spectrum of position 4 of the carbon molecular tube bundle in the carbon-based pumice prepared in Example 1;

[0042] Figure 11 The EDS spectrum of position 5 of the carbon molecular tube bundle in the carbon-based pumice prepared in Example 1;

[0043] Figure 12 The diagram shows the test results of the carbon-based pumice prepared in Examples 1-3.

[0044] Figure 13 The data show the flowability of the carbon-based pumice prepared in Examples 1-3. Detailed Implementation

[0045] This invention provides a method for preparing carbon-based pumice, comprising the following steps:

[0046] (1) Mix the main material, foaming agent, foaming aid and water to obtain a slurry; the main material includes basic materials and / or silicon-aluminum ratio adjuster; the basic materials include sludge or organic sludge;

[0047] (2) Granulate the slurry obtained in step (1) to obtain spherical particles;

[0048] (3) Spray the aqueous solution of the gas-retaining agent onto the surface of the spherical particles obtained in step (2), and then foam and dry them in sequence to obtain the blank;

[0049] (4) The blank obtained in step (3) is subjected to a first sintering under sealed conditions to obtain a first sintered product;

[0050] (5) The first sintered product obtained in step (4) is subjected to a second sintering under a nitrogen atmosphere to obtain a second sintered product;

[0051] (6) Activate the second sintered product obtained in step (5) to obtain carbon-based pumice.

[0052] This invention does not impose any special restrictions on the source of the raw materials; commercially available products familiar to those skilled in the art can be used.

[0053] This invention mixes the main ingredient, foaming agent, foaming aid and water to obtain a slurry.

[0054] In this invention, the main ingredients include base materials and / or silicon-aluminum ratio modifiers.

[0055] In this invention, the base material includes sludge or organic sludge; the particle size of the sludge is preferably 300 mesh; and the silicon-aluminum ratio modifier is preferably Al4[Si4O] 10 [OH]8; the purity of the silicon-aluminum ratio modifier is preferably above 95%; the particle size of the silicon-aluminum ratio modifier is preferably 200-300 mesh. In this invention, the main material is a matrix material.

[0056] In this invention, the slurry preferably also contains an auxiliary carbon source; the auxiliary carbon source is preferably coal powder, weeds, or sawdust particles; the purity of the coal powder is preferably ≥95%; the particle size of the coal powder is preferably >200 mesh; the particle size of the weeds and sawdust particles is independently preferably >100 mesh; the auxiliary carbon source is preferably 1-10 wt% of the main material, more preferably 5-8 wt%. In this invention, the auxiliary carbon source is used to provide a carbon source.

[0057] In this invention, the auxiliary carbon source is preferably added simultaneously with the main material.

[0058] In this invention, when the main material is a base material and a silicon-aluminum ratio modifier, the base material is preferably 50-60% of the main material's mass, more preferably 50-55%, and the silicon-aluminum ratio modifier is preferably 40-50% of the main material's mass, more preferably 45-50%. This invention can further improve the effective porosity of carbon-based pumice by controlling the mass of the base material and the silicon-aluminum ratio modifier.

[0059] In this invention, the foaming agent is preferably azodicarbonamide and / or polyurethane; the foaming agent is preferably 0.5-1.5% of the main material mass, more preferably 0.6-1.2%, and even more preferably 0.8-1.0%. By limiting the amount of foaming agent within the above range, this invention can further improve the adsorption performance of carbon-based pumice.

[0060] In this invention, the foaming aid is preferably at least one of calcium carbonate, calcium bicarbonate, aluminum trichloride, and phosphate starch; the mass ratio of the foaming aid to the foaming agent is preferably 1:1. Limiting the mass ratio of the foaming aid to the foaming agent to 1:1 in this invention further improves the adsorption performance of carbon-based pumice.

[0061] The present invention does not have a special limitation on the amount of water used, as long as the raw materials are dissolved.

[0062] In this invention, the mixing of the main material, foaming agent, foaming aid, and water is preferably performed using the following steps:

[0063] 1) The foaming agent and foaming aid are ball-milled and mixed to obtain a mixture;

[0064] 2) Mix the mixture obtained in step 1) with water to obtain a mixed solution;

[0065] 3) Mix the mixed solution obtained in step 2) with the main material.

[0066] The present invention preferably involves ball milling and mixing the foaming agent and the foaming aid to obtain a mixture.

[0067] The present invention does not have any special limitations on the ball milling operation, as long as the mixture is processed to <100 mesh.

[0068] After obtaining the mixture, the present invention preferably mixes the mixture with water to obtain a mixed solution.

[0069] The present invention does not impose any special limitations on the operation of mixing the mixture with water, as long as the raw materials are mixed evenly.

[0070] After obtaining the mixed solution, the present invention preferably mixes the mixed solution with the main material.

[0071] The present invention does not impose any special limitations on the operation of mixing the mixed solution with the main material; any technical solution for preparing the mixed material that is well known to those skilled in the art can be used.

[0072] After mixing, the present invention preferably ages the product obtained by mixing to obtain a slurry.

[0073] In this invention, the aging temperature is preferably room temperature; the aging time is preferably 12–24 hours, more preferably 15–24 hours. This invention achieves thorough immersion through aging.

[0074] After obtaining the slurry, the present invention granulates the slurry to obtain spherical particles.

[0075] The present invention does not impose any special limitations on the granulation operation; any operation known to those skilled in the art can be used.

[0076] In this invention, the particle size of the spherical particles is preferably 0.5 to 1.0 cm.

[0077] After obtaining spherical particles, the present invention sprays an aqueous solution of a gas-retaining agent onto the surface of the spherical particles, and then performs foaming and drying in sequence to obtain a blank.

[0078] In this invention, the gas-retaining agent is preferably sodium silicate and / or methylcellulose. By employing a gas-retaining agent, this invention can encapsulate the material, preventing the rapid escape of bubbles generated during foaming, thereby further improving the effective porosity of carbon-based pumice.

[0079] In this invention, the concentration of the aqueous solution of the gas-retaining agent is preferably 1-3 wt%, more preferably 1.5-2 wt%; the mass of water in the gas-retaining agent is preferably 30-40% of the mass of the main material. By limiting the amount of gas-retaining agent to the above range, this invention can further improve the effective porosity of carbon-based pumice.

[0080] The present invention does not have any special limitations on the operation of spraying the aqueous solution of the gas-retaining agent onto the surface of the spherical particles; any operation known to those skilled in the art can be used.

[0081] In this invention, the foaming temperature is preferably 150–200°C, more preferably 160–180°C; the foaming time is preferably 30–60 min, more preferably 40–50 min, and most preferably 45 min. This invention, by foaming at high temperatures, can rapidly increase the temperature, allowing the foaming agent to react fully in a short time, generating a large amount of oxygen, carbon monoxide, carbon dioxide, and some water vapor forming pores and gaps. By controlling the foaming temperature and time, the adsorption performance of carbon-based pumice can be further improved.

[0082] The present invention does not impose any special limitations on the drying operation, as long as the moisture content of the raw material is controlled below 10%.

[0083] After obtaining the blank, the present invention performs a first sintering on the blank under sealed conditions to obtain a first sintered product.

[0084] In this invention, the first sintering is preferably carried out in a reduction sintering furnace. This invention does not specify the type of reduction sintering furnace; any instrument or equipment well-known to those skilled in the art can be used.

[0085] In this invention, the temperature of the first sintering is preferably 1000–1200°C, more preferably 1050–1150°C, and most preferably 1100°C; the time of the first sintering is preferably 90–120 min, more preferably 100 min. Sintering under sealed conditions in this invention allows organic carbon to undergo deoxidation and enter the reduction reaction stage, generating free carbon molecules, CO, and CO2 gas.

[0086] After obtaining the first sintered product, the present invention performs a second sintering on the first sintered product under a nitrogen atmosphere to obtain the second sintered product.

[0087] In this invention, the second sintering temperature is preferably 1000–1200°C, more preferably 1050–1150°C, and most preferably 1100°C; the second sintering time is preferably 30–60 min, more preferably 40–50 min. This invention performs the second sintering in a nitrogen atmosphere, which enables the CO generated during the first sintering to decompose, CO bonds to break, and CO to decompose into C and O atoms, further forming a large number of carbon molecules and CO2 gas. The carbon molecules can self-assemble in the pre-made gaps to form a honeycomb-like tubular structure composed of carbon molecules. These tubular bio-carbon tubular structures give the material excellent adsorption, flow, and electrical conductivity.

[0088] After obtaining the second sintered product, the present invention activates the second sintered product to obtain carbon-based pumice.

[0089] In this invention, the activator used for activation is preferably an aqueous solution of at least one of a bio-acid, sodium dodecyl sulfate, fatty alcohol polyoxyethylene ether, and alkyl glycoside; the bio-acid is preferably citric acid, polylactic acid, or tufted acid.

[0090] In this invention, the mass concentration of the activator is preferably 3-5%, more preferably 3.5-4.0%. This invention does not impose any particular limitation on the amount of the activator; it is sufficient to completely immerse the second sintered product in the activator.

[0091] In this invention, the activation temperature is preferably room temperature; the activation time is preferably 15-30 minutes. This invention, through activation, can wash out impurities (nitrogen, phosphorus, potassium, calcium oxide, and dust, etc.) from the material, further activate the carbon microtubes, improve adsorption efficiency, and form a honeycomb-shaped carbon microtube bundle composed of pure silicon oxide and carbon microtubes.

[0092] This invention uses basic materials and / or silicon-aluminum ratio modifiers as the main ingredients. The addition of foaming agents and foaming aids generates a large number of bubbles during foaming, forming numerous open pores and gaps within the material, thereby increasing the effective porosity of the carbon-based pumice. By employing a gas-retaining agent, the material is encapsulated, preventing the rapid escape of bubbles generated during foaming, further enhancing the effective porosity of the carbon-based pumice. Utilizing the principle of vapor deposition, sintering under sealed conditions allows the CO produced by organic carbon and biochar to be deoxygenated into pure elemental carbon molecules. Simultaneously, these molecules self-assemble in pre-made gaps to form a honeycomb-like channel bundle structure composed of carbon molecules. These bundle-like channels possess excellent adsorption and flow properties. Activation further strengthens the honeycomb-like micron-sized channel bundles, increasing the effective porosity and thus improving fluidity and significantly reducing the probability of clogging. Using sludge or organic sludge as the basic material and a small amount of auxiliary carbon source, a structure with silicon dioxide as the main component and honeycomb-like carbon molecule channel bundles connected by numerous pores is prepared. This improves performance while reducing the use of a large amount of wood material, saving raw material costs.

[0093] The main raw material of this invention is sludge or organic sludge, with Al4[Si4O] as the main component. 10 [OH]8 is a silicon-aluminum blending agent. Organic carbon in sludge or organic sludge is the main carbon source, with the addition of auxiliary carbon sources. The final product is a porous material with silicon dioxide as the main material, alumina as the auxiliary material, and containing bio-carbon microtubes as conduits and a large number of micropores. Since the raw material silicon dioxide is a very readily available basic material, and a large number of carbon microtube bundles are produced by reducing organic carbon in nature, the cost is greatly reduced, while achieving higher adsorption and conductivity than common activated carbon.

[0094] The present invention also provides carbon-based pumice prepared by the preparation method described in the above technical solution.

[0095] The carbon-based pumice provided by this invention has electrical conductivity of 3.5 to 5 S / m, which is several to tens of times higher than that of coconut shell activated carbon (0.1 to 1 S / m). It is a semiconductor non-metallic material with good electrical conductivity. It contains honeycomb-shaped carbon micron channel bundles of about 5% by mass and 20 to 25% by volume. It also contains a large number of micropores, accounting for 40 to 50% by volume.

[0096] In this invention, the carbon-based pumice is preferably porous blocky, breccia, spherical, or columnar in shape; the carbon-based pumice is preferably dark gray or black in color.

[0097] The carbon-based pumice provided by this invention has a much higher short-term adsorption capacity for various organic substances in water than coconut shell activated carbon; it has good stability under natural conditions, possessing both high-intensity water adsorption and slow release of adsorbed water; its internal structure is characterized by a honeycomb-like bundle of carbon microtubes combined with a large number of pores; the pore diameter is 0.2-2 mm, densely distributed; the pore shape is mainly polygonal, with a small number of elliptical pores; the pores are completely sealed by the outer wall to form closed pores; it has strong resistance to weathering and no aging phenomenon.

[0098] The performance parameters of the carbon-based pumice provided by this invention are as follows:

[0099] Bulk density: 0.33–0.67 tons / cubic meter

[0100] Electrical conductivity: 3.5~5S / m

[0101] Specific surface area: ≥50cm² 2 / g

[0102] Effective porosity: 35-50%

[0103] Compressive strength of cylinder: 0.5~2.8MPa / cm 2

[0104] Particle size: 5-10 mm or 10-15 mm.

[0105] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0106] The silt used in the examples was bottom mud (200-300 mesh) from natural lakes in Huizhou, Guangdong Province, and the organic carbon content was found to be about 5-10 wt%.

[0107] Example 1

[0108] A method for preparing carbon-based pumice comprises the following steps:

[0109] (1) Mix sludge and a silicon-aluminum ratio modifier at a mass ratio of 1:1 to obtain ingredient 1; wherein, the silicon-aluminum ratio modifier is Al4[Si4O] 10 [OH]8; The purity of the silicon-aluminum ratio modifier is above 95%, and the particle size is 200-300 mesh;

[0110] (2) Mix 5% by mass of auxiliary carbon source wood chips of 200 mesh or larger with ingredient 1 to obtain ingredient 2;

[0111] (3) Mix 1% by mass of azodicarbonamide and 1% by mass of phosphate starch in ingredient 1 and process them in a ball mill to <100 mesh to obtain ingredient 3;

[0112] (4) Prepare an aqueous solution by placing ingredient 3 in water at 30% of the mass of ingredient 1, then mix it with ingredient 2 to form a slurry, and then age it at room temperature for 24 hours. After that, place it in a disc granulator to form spherical particles with a diameter of 0.5 to 1.5 cm.

[0113] (5) Add methylcellulose to 30% of the water in ingredient 1 to prepare an aqueous solution of gas-retaining agent with a concentration of 1.5%. Then spray the gas-retaining agent solution onto the surface of the spherical particles, then foam at 180°C for 30 minutes, and then dry to obtain a raw material with a moisture content of less than 10%.

[0114] (6) The blank is conveyed to a reduction sintering furnace via a conveyor belt and sintered at 1100℃ under sealed conditions for 100 min to obtain the first sintered product;

[0115] (7) Nitrogen gas is introduced into the furnace and sintered at 1100℃ for 30 minutes to obtain the second sintered product.

[0116] (8) The second sintered product was activated by immersing it in a 5% citric acid aqueous solution to obtain carbon-based pumice. The activation temperature was room temperature and the activation time was 15 min.

[0117] Example 2

[0118] A method for preparing carbon-based pumice comprises the following steps:

[0119] (1) Mix the silicon-aluminum ratio modifier with 10% by mass of auxiliary carbon source coal powder of 300 mesh or higher to obtain ingredient 1; wherein, the silicon-aluminum ratio modifier is Al4[Si4O] 10 [OH]8; The purity of the silicon-aluminum ratio modifier is above 95%, and the particle size is 200-300 mesh; the purity of the coal powder is 95%;

[0120] (2) Polyurethane with a silicon-aluminum ratio modifier of 0.5% by mass and calcium bicarbonate with a silicon-aluminum ratio modifier of 0.5% by mass are mixed and processed in a ball mill to <100 mesh to obtain ingredient 2;

[0121] (4) Prepare an aqueous solution by placing ingredient 2 in water with a silicon-aluminum ratio of 30% by mass of the conditioning agent, then mix it with ingredient 1 to form a slurry, and then age it at room temperature for 24 hours. After that, place it in a disc granulator to form spherical particles with a diameter of 0.5 to 1.5 cm.

[0122] (5) Sodium silicate is added to water with a silica-alumina ratio of 30% by mass to prepare a 2% concentration of gas-retaining agent aqueous solution. Then, the gas-retaining agent solution is atomized and sprayed onto the surface of spherical particles. Then, it is foamed at 180°C for 60 minutes and then dried to obtain a blank with a moisture content of less than 10%.

[0123] (6) The blank is conveyed to a reduction sintering furnace via a conveyor belt and sintered at 1200℃ under sealed conditions for 120 minutes to obtain the first sintered product;

[0124] (7) Nitrogen gas was introduced into the furnace and sintered at 1200℃ for 30 min to obtain the second sintered product;

[0125] (8) The second sintered product was activated by immersing it in an aqueous solution of sodium dodecyl sulfate with a mass concentration of 5% to obtain carbon-based pumice. The activation temperature was room temperature and the activation time was 20 min.

[0126] Example 3

[0127] (1) Mix 0.5% by weight of azodicarbonamide and 0.5% by weight of phosphate starch in a ball mill and process to <100 mesh to obtain ingredient 1;

[0128] (2) Prepare an aqueous solution by placing ingredient 1 in water with 30% of the sludge mass, then mix it with the sludge to form a slurry, and then age it at room temperature for 24 hours. After that, place it in a disc granulator to form spherical particles with a diameter of 0.5 to 1.5 cm.

[0129] (3) Add methylcellulose to water with a mass of 30% of the sludge to prepare an aqueous solution of air-retaining agent with a concentration of 1.0%. Then spray the air-retaining agent solution onto the surface of spherical particles, then foam at 180°C for 45 minutes, and then dry to obtain a raw material with a moisture content of less than 10%.

[0130] (4) The blank is conveyed to a reduction sintering furnace via a conveyor belt and sintered at 1100℃ under sealed conditions for 90 minutes to obtain the first sintered product;

[0131] (5) Nitrogen gas is introduced into the furnace and sintered at 1100℃ for 30 minutes to obtain the second sintered product.

[0132] (6) The second sintered product is activated by immersing it in a 3% citric acid aqueous solution to obtain carbon-based pumice. The activation temperature is room temperature and the activation time is 30 min.

[0133] Comparative Example 1

[0134] Artificial pumice, using common standards selected from other companies' artificial pumice, has a particle size of 10-20mm and a market price of approximately 6000 RMB / cubic meter.

[0135] Comparative Example 2

[0136] Coconut shell activated carbon is a commonly used activated carbon for water treatment by other companies. It has a particle size of 5-15mm and a market price of 12,000 RMB / cubic meter.

[0137] The materials prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests, and the results are shown in Tables 1 and 2. Among them, the carbon content was detected by standard elemental analysis; the effective porosity was tested by standard impregnation method (measured with water at room temperature and pressure, and the formula for calculating the effective porosity is shown in Equation I); the compressive strength was tested by the national standard GB2842-81 "Test Methods for Lightweight Aggregates"; and the electrical conductivity was tested by ST2258C four-probe tester.

[0138] Table 1 Performance data of carbon-based pumice prepared in Examples 1-3

[0139] Item (average) Example 1 Example 2 Example 3 Carbon content (mass ratio) 5％ 5.5％ 3％ Effective porosity 50％ 40％ 35％ Cylinder compressive strength 1MPa 2.8MPa 0.5MPa

[0140] Table 2. Performance data of the materials prepared in Example 1 and Comparative Examples 1-2

[0141] project Example 1 Comparative Example 1 Comparative Example 2 Effective porosity 50％ 15％ 35％ electrical conductivity 4.3S / m NA 0.8S / m Cylinder compressive strength 1MPa 1.8MPa 0.6MPa

[0142] The formula for calculating the effective porosity of filter media at room temperature is shown in Equation I, which uses volume ratio for description:

[0143]

[0144] In the formula, m1 is the mass of the material when dry, m2 is the mass of the material after absorbing water and becoming saturated, and V1 is the volume of the material.

[0145] As can be seen from Tables 1 and 2, the effective porosity and electrical conductivity of the carbon-based pumice prepared by this invention are significantly improved, thus resulting in a several-fold improvement in adsorption performance.

[0146] A physical image of the carbon-based pumice prepared in Example 1 is shown below. Figure 1 As shown.

[0147] from Figure 1 As can be seen, the carbon-based pumice prepared in the examples is spherical.

[0148] SEM images of the carbon-based pumice prepared in Example 1 at different magnifications are shown below. Figure 2 and 3 As shown.

[0149] from Figure 2 and 3 It can be seen that the prepared carbon-based pumice is a combination of through-hole carbon nanotubes and pores.

[0150] The adsorption performance of the carbon-based pumice prepared in Example 1 and the coconut shell activated carbon in Comparative Example 2 were tested, and the results are as follows: Figure 4 and 5 As shown, where, Figure 4 The image shows a comparison of the effluent from the carbon-based pumice prepared in Example 1 and the coconut shell activated carbon in Comparative Example 2 after 1 hour of adsorption of domestic sewage. Figure 5 The image shows a comparison of the effluent from the carbon-based pumice prepared in Example 1 and the coconut shell activated carbon in Comparative Example 2 after 1 hour of adsorption of dyeing and printing wastewater (the testing equipment used was a Hach 3900 spectrophotometer and Hach standard reagents; the domestic sewage was sampled from residential areas in Boluo County, Huizhou (COD: 269 mg / L; ammonia nitrogen: 15 mg / L; total phosphorus: 20.25 mg / L; total nitrogen: 84.7 mg / L); the dyeing and printing wastewater was from the internal water tank of a dyeing and printing factory in Boluo County, Huizhou (COD: 549 mg / L, ammonia nitrogen: 5.2 mg / L, total phosphorus: 9.01 mg / L, total nitrogen: 12.4 mg / L); the effluent was obtained by simulating an aerated biological filter, with wastewater entering from the bottom and exiting from the top, and effluent was obtained after 1 hour).

[0151] from Figure 4 and 5 It can be seen that the carbon-based pumice provided by this invention has a short-time adsorption capacity several times that of other products in water treatment, which can greatly improve the effluent effect in water treatment and significantly shorten the water treatment time.

[0152] The carbon-based pumice prepared in Example 1 was subjected to compositional analysis. The instrument used was an ARL Perform'X X-ray fluorescence spectrometer, instrument number 21003415. The test was conducted according to JY / T0569-2020 General Rules for Wavelength Dispersive X-ray Fluorescence Spectroscopy. The test method involved adding carbon-based pumice and boric acid to a tablet press and pressing it into a smooth, flat circular block with a diameter of 40 mm and a thickness of 3 mm. The circular block was then placed in a sample holder and inserted into the instrument's sample inlet. The sample information was entered into the instrument software, the test was started, and the test data was exported after the test was completed. The XRF compositional analysis results showed that the main components were SiO2, Al2O3, K2O, and Fe2O3, with contents of 51.83%, 38.7%, 3.42%, and 2.89%, respectively.

[0153] Five locations (e.g.) in the carbon-based pumice prepared in Example 1 Figure 6 Element detection was performed (as shown), and the results are as follows: Figures 7-11 As shown in Tables 3-7, among which, Figure 7 The EDS spectrum of position 1 of the carbon molecular tube bundle in carbon-based pumice prepared in Example 1; Figure 8 The EDS spectrum of position 2 of the carbon molecular tube bundle in carbon-based pumice prepared in Example 1; Figure 9The EDS spectrum of position 3 of the carbon molecular tube bundle in the carbon-based pumice prepared in Example 1; Figure 10 The EDS spectrum of position 4 of the carbon molecular tube bundle in the carbon-based pumice prepared in Example 1; Figure 11 The image shows the EDS spectrum of position 5 of the carbon molecular tube bundle in the carbon-based pumice prepared in Example 1.

[0154] Table 3. Element content of position 1 in the carbon molecular tube bundle of carbon-based pumice prepared in Example 1.

[0155]

[0156]

[0157] Table 4. Element content at position 2 in the carbon molecular tube bundle of carbon-based pumice prepared in Example 1.

[0158] element Wt% At% C 79.21 91.82 O 2.49 2.16 Al 2.24 1.16 Si 2.25 1.12 P 0.37 0.17 S 0.25 0.11 K 1.33 0.47 Ca 0.35 0.12 Fe 11.51 2.87 Total 100.00 100.00

[0159] Table 5. Element content at position 3 in the carbon molecular tube bundle of carbon-based pumice prepared in Example 1.

[0160] element Wt% At% C 91.16 94.60 O 5.60 4.36 Al 0.61 0.28 Si 0.52 0.23 S 0.11 0.04 K 0.42 0.13 Fe 1.58 0.36 Total 100.00 100.00

[0161] Table 6. Element content at position 4 in the carbon molecular tube bundle of carbon-based pumice prepared in Example 1.

[0162]

[0163]

[0164] Table 7. Element content at position 5 in the carbon molecular tube bundle of carbon-based pumice prepared in Example 1.

[0165] element Wt% At% C 54.55 82.03 O 1.10 1.24 Al 2.41 1.61 Si 3.53 2.27 P 0.36 0.21 K 0.58 0.27 Ca 1.99 0.90 Fe 35.48 11.47 Total 100.00 100.00

[0166] from Figures 7-11 As can be seen from Tables 3-7, the main component of the honeycomb carbon molecular channel bundles of the carbon-based pumice prepared by this invention is carbon.

[0167] Flowability test (simulating a BAF aerated biological filter):

[0168] The flowability of the carbon-based pumice prepared in Examples 1-3 was tested using a simulated BAF (Body-Based Float) model. A water pump, operating at the same power, injected water into the bottom of the container from a fixed height using a pipe inserted into the bottom. The total water flow and time taken to reach four standard positions in the container were measured using a weighbridge and timer to calculate the flow velocity of the water within the space when filled with different particle sizes. The two test modes were: no material filling and filling with 5-10mm particles. In the no-fill mode, a 4.15m depth took 1 hour, and the water volume was 302kg. The test method is as follows: Figure 12 As shown.

[0169] The flowability data of the carbon-based pumice prepared in Examples 1-3 are as follows: Figure 13 As shown.

[0170] from Figure 13 It can be seen that the carbon-based pumice prepared by this invention has a significantly reduced probability of clogging; the loss of liquid flowing inside is very small, almost non-existent.

[0171] As can be seen from the above examples and comparative examples, the carbon-based pumice prepared by the preparation method provided by the present invention has excellent adsorption performance, flowability and conductivity, and the cost is significantly reduced.

[0172] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing carbon-based pumice, comprising the following steps: (1) Mix the main material, foaming agent, foaming aid and water to obtain a slurry; the main material includes a base material and a silicon-aluminum ratio adjuster; the base material is sludge or organic sludge; (2) Granulate the slurry obtained in step (1) to obtain spherical particles; (3) Spray the aqueous solution of the gas-retaining agent onto the surface of the spherical particles obtained in step (2), and then foam and dry them in sequence to obtain the blank; (4) The blank obtained in step (3) is subjected to a first sintering under sealed conditions to obtain a first sintered product; (5) The first sintered product obtained in step (4) is subjected to a second sintering under a nitrogen atmosphere to obtain a second sintered product; (6) Activate the second sintered product obtained in step (5) to obtain carbon-based pumice; In step (1), the silicon-to-aluminum ratio adjusting agent is Al4[Si4O] 10 [OH]8, the purity of the silicon-aluminum ratio modifier is above 95%, and the particle size of the silicon-aluminum ratio modifier is 200~300 mesh; In step (1), the foaming agent is azodicarbonamide and / or polyurethane, and the foaming agent accounts for 0.5~1.5% of the main material mass; In step (1), the foaming aid is at least one of calcium carbonate, calcium bicarbonate, aluminum trichloride and phosphate starch, and the mass ratio of the foaming aid to the foaming agent is 1:

1. In step (3), the gas-retaining agent is sodium silicate and / or methylcellulose, and the mass concentration of the aqueous solution of the gas-retaining agent is 1-3%. The activator used in step (6) is an aqueous solution of at least one of sodium dodecyl sulfate, fatty alcohol polyoxyethylene ether, and alkyl glycoside. The temperature of the first sintering in step (4) is 1000~1200℃, and the time of the first sintering is 90~120min; The second sintering temperature in step (5) is 1000~1200℃, and the second sintering time is 30~60min.

2. The preparation method according to claim 1, characterized in that, In step (3), the foaming temperature is 150~200℃ and the foaming time is 30~60min.

3. The carbon-based pumice prepared by the preparation method according to claim 1 or 2.

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