Preparation method of 3D printing activated carbon rod based on coffee grounds, product and water purification and adsorption application of 3D printing activated carbon rod

Abstract

The invention relates to the technical field of water treatment, in particular to a preparation method of a 3D printing activated carbon rod based on coffee grounds, a product and water purification and adsorption application of the 3D printing activated carbon rod based on the coffee grounds, and the preparation method comprises the steps that 1, the coffee grounds are collected, washed, dried to constant weight, smashed and sieved, and coffee grounds fine powder is obtained; step 2, mixing sodium carboxymethyl cellulose with polylactic acid to prepare a binder, then adding deionized water into the binder, stirring until the deionized water is completely dissolved, and cooling to room temperature to form a binder solution; step 3, uniformly mixing the coffee residue fine powder, the binder solution, a pore forming agent and a reinforcing agent to prepare a 3D printing material; wherein the pore forming agent is a mixture of sodium bicarbonate and starch, and the reinforcing agent is nano silicon dioxide; 4, the 3D printing material is formed through a 3D printing technology, a carbon rod precursor is prepared, and then the carbon rod precursor is dried and cured; the adsorbent has high-efficiency adsorption performance and good structural stability, and meets actual application requirements.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a method for preparing 3D-printed activated carbon rods based on coffee grounds, the product, and its application in water purification and adsorption. Background Technology

[0002] Activated carbon, due to its well-developed pore structure, large specific surface area, and excellent adsorption performance, is widely used in drinking water purification, industrial wastewater treatment, and gas purification. Currently, the raw materials for industrial production of activated carbon are still mainly coconut shells, wood, and coal. However, these traditional raw materials suffer from limited resources, rising costs, and the need for logging or mining, leading to increasing pressure on the ecological environment. Meanwhile, global coffee consumption is growing rapidly, resulting in a large amount of coffee grounds waste. Statistics show that approximately 0.9 kg of coffee grounds are generated for every 1 kg of instant coffee produced, and the vast majority of these grounds are directly landfilled or incinerated, wasting carbon resources and posing a risk of secondary pollution. Therefore, the resource recovery and high-value utilization of coffee grounds has become an urgent need for waste management and the circular economy.

[0003] In terms of activated carbon forming technology, although traditional sintering or extrusion molding processes are mature, the activated carbon products prepared are generally limited by mold structure and processing technology, resulting in defects such as uncontrollable pore distribution, single fluid channels, and low specific surface area utilization. These defects make it difficult to meet the personalized requirements of activated carbon geometry for complex working conditions (such as high flux, low pressure drop, and high selective adsorption). Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing 3D-printed activated carbon rods based on coffee grounds, the product, and its application in water purification and adsorption.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The first aspect of this invention provides a method for preparing 3D-printed activated carbon rods based on coffee grounds, comprising the following steps:

[0007] Step 1: Collect coffee grounds, wash and dry them to constant weight, grind them and sieve them to obtain fine coffee ground powder;

[0008] Step 2: Mix sodium carboxymethyl cellulose and polylactic acid to prepare an adhesive. Then add deionized water to the adhesive, stir until completely dissolved, and cool to room temperature to form an adhesive solution.

[0009] Step 3: Mix coffee grounds powder, binder solution, pore-forming agent and reinforcing agent evenly to obtain 3D printing material;

[0010] The pore-forming agent is a mixture of sodium bicarbonate and starch, and the reinforcing agent is nano-silica.

[0011] Step 4: The 3D printing material is formed using 3D printing technology to obtain a carbon rod precursor, which is then dried and cured.

[0012] Step 5: The dried and cured carbon rod precursor is carbonized under inert gas protection. The temperature is raised to the set temperature and held, and then cooled in the furnace to obtain the carbonized carbon rod.

[0013] Step 6: Activate the carbonized carbon rods using either physical or chemical activation. Then, clean the activated carbon rods until they are neutral and dry them to a constant weight to obtain 3D printed activated carbon rods based on coffee grounds.

[0014] Physical activation uses water vapor or carbon dioxide as an activating agent;

[0015] Chemical activation uses one or more of potassium hydroxide solution, zinc chloride solution, and phosphoric acid solution as activating agents.

[0016] Furthermore, in step one, the drying temperature is 80℃-100℃, and the sieve mesh size is 100-200 mesh.

[0017] Furthermore, in step two, the mass ratio of sodium carboxymethyl cellulose to polylactic acid is 1:1-3:1; the mass ratio of binder to deionized water is 1:10-1:15; and the mixing of binder and deionized water is carried out in a water bath at 50℃-70℃ for 30min-60min.

[0018] Furthermore, in step three,

[0019] The mass ratio of fine coffee grounds to binder solution is 3:1-5:1; the mass ratio of sodium bicarbonate to starch in the pore-forming agent is 1:1-2:1.

[0020] The total mass of the pore-forming agent accounts for 8%-12% of the mass of the coffee grounds powder;

[0021] The enhancer accounts for 2%-5% of the mass of the finely ground coffee grounds;

[0022] The stirring speed for mixing coffee grounds powder, binder solution, pore-forming agent and reinforcing agent is 400r / min-600r / min, and the stirring time is 20min-30min.

[0023] Furthermore, in step four, the 3D printing technology involves printing using a 3D printer and employing fused deposition modeling (FDM) technology.

[0024] The printing parameters for the 3D printer are as follows: printing temperature 200℃-220℃, heated bed temperature 40℃-60℃, printing speed 20mm / s-60mm / s, layer thickness 0.1mm-0.4mm, nozzle diameter 0.4mm-0.6mm, and extrusion pressure 0.2MPa-0.6MPa.

[0025] Drying and curing involves natural drying at room temperature for 24-48 hours.

[0026] Furthermore, in step five, the heating rate of the carbonization treatment is 5℃ / min-10℃ / min, the set temperature of the carbonization treatment is 400℃-600℃, and the holding time of the carbonization treatment is 1h-3h.

[0027] Furthermore, physical activation includes the following steps: placing the carbonized carbon rods into a high-temperature tube furnace, then introducing steam or carbon dioxide gas as an activating agent, and carrying out the activation reaction at a temperature of 700℃-900℃ for 1-2 hours, and finally drying to constant weight;

[0028] The final drying temperature to constant weight is 80℃-100℃.

[0029] Further, chemical activation includes the following steps: immersing the carbonized carbon rod in an activating agent, removing the carbon rod after immersion, drying the carbon rod and placing it in a tube furnace for activation reaction, rinsing the activated carbon rod repeatedly with deionized water until the rinsing solution is neutral, and finally drying it to constant weight;

[0030] The mass ratio of activator to carbon rod is 1:1 to 1:4.

[0031] The carbon rods are immersed in the activator for 12-24 hours;

[0032] The activation temperature in the tube furnace is 700℃-900℃;

[0033] The activation reaction takes 1-2 hours.

[0034] The final drying temperature to constant weight is 80℃-100℃.

[0035] A second aspect of the present invention provides a 3D-printed activated carbon rod based on coffee grounds prepared by the method described above, wherein the activated carbon rod is cylindrical.

[0036] The activated carbon rod has a first groove in its center, which extends through the top and bottom surfaces of the activated carbon rod.

[0037] The activated carbon rod has several second grooves along its radial direction. The second grooves penetrate the side wall of the activated carbon rod but are not connected to the first grooves. The second grooves do not penetrate the top and bottom surfaces of the activated carbon rod.

[0038] Several third grooves are provided in the area between adjacent second grooves. The third grooves penetrate the top and bottom surfaces of the activated carbon rod, and at least some of the third grooves are not connected to the second grooves.

[0039] A third aspect of the present invention provides an application of a 3D-printed activated carbon rod based on coffee grounds as an adsorption unit in water purification treatment, as described above.

[0040] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0041] This invention uses 3D printing technology to precisely design the internal structure of activated carbon rods, significantly increasing the contact area with water and improving the adsorption efficiency of pollutants in water. Complex structures that are difficult to achieve using traditional molding methods can be completed at low cost.

[0042] By optimizing the material formulation (a composite binder of sodium carboxymethyl cellulose and polylactic acid, a composite pore-forming agent of sodium bicarbonate and starch, and a nano-silica reinforcing agent, etc.), while ensuring the plasticity of the material and its applicability to 3D printing, the pore-forming agent can regulate the pore structure, increase the specific surface area of ​​activated carbon, and enhance the adsorption capacity; the reinforcing agent effectively improves the mechanical strength of the activated carbon rod and extends its service life; thus, this invention combines high-efficiency adsorption performance with good structural stability, meeting the needs of practical applications. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the axial side structure of the 3D-printed activated carbon rod based on coffee grounds prepared in Example 1 of the present invention;

[0044] Figure 2 This is a cross-sectional view of the 3D-printed activated carbon rod based on coffee grounds prepared in Example 1 of the present invention.

[0045] Figure 3 This is a cross-sectional view of the 3D-printed activated carbon rod based on coffee grounds prepared in Example 2 of the present invention.

[0046] Figure 4 This is a schematic diagram of the axial side structure of the 3D-printed activated carbon rod based on coffee grounds prepared in Example 2 of the present invention;

[0047] The reference numerals in the attached figures are:

[0048] First slot, 1; Second slot, 2; Third slot, 3. Detailed Implementation

[0049] 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 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.

[0050] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0051] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0052] Example 1

[0053] This embodiment 1 provides a method for preparing a 3D printed activated carbon rod based on coffee grounds, the preparation steps of which include:

[0054] Step 1: Coffee grounds pretreatment:

[0055] The collected coffee grounds were rinsed with deionized water at least three times to remove coffee oils, sugars and other impurities from their surface. They were then dried in a 90°C oven to constant weight to remove moisture and facilitate subsequent processing. After drying, they were pulverized with a high-speed grinder and passed through a 150-mesh sieve to obtain fine coffee grounds with uniform particle size.

[0056] Step 2: Preparation of adhesive solution:

[0057] Weigh 4.5g of sodium carboxymethyl cellulose (CMC) and 4.5g of polylactic acid (PLA) at a 1:1 mass ratio, mix thoroughly, and use as a binder. Add 90g of deionized water to the binder (binder to water mass ratio 1:10), and place in a 60℃ water bath. Stir at 300 rpm for 45 minutes until completely dissolved. Cool to room temperature to obtain a binder solution with good adhesion. This binder solution can effectively bind coffee grounds powder with other components, while ensuring that the material has the plasticity and flowability required for 3D printing, avoiding breakage or collapse during the printing process.

[0058] Step 3: 3D Printing Material Preparation

[0059] Weigh out the coffee grounds powder from step one, the binder solution from step two, the pore-forming agent and the reinforcing agent, and then add all the components to a high-speed mixer for mixing. Stir at 500 r / min for 25 minutes to obtain the 3D printing material.

[0060] The pore-forming agent is a mixture of sodium bicarbonate and starch, and the reinforcing agent is nano-silica.

[0061] The mass ratio of fine coffee grounds to binder solution is 5:1, wherein in this embodiment, the mass of fine coffee grounds is 150g and the mass of binder solution is 30g.

[0062] The mass ratio of sodium bicarbonate to starch in the pore-forming agent is 1:1. In this embodiment, the mass of sodium bicarbonate in the pore-forming agent is 6g and the mass of starch is 6g. These two components will decompose or volatilize during the subsequent carbonization and activation process to form a rich pore structure, thereby increasing the specific surface area of ​​activated carbon and improving its adsorption capacity.

[0063] The total mass of the pore-forming agent accounts for 8% of the mass of the fine coffee grounds;

[0064] The mass of nano-silica accounts for 2% of the mass of coffee grounds powder. In this embodiment, the mass of nano-silica is 3g. Nano-silica acts as a reinforcing agent, which can effectively improve the mechanical strength of the material and prevent the activated carbon rod from breaking during printing, carbonization and use.

[0065] Step 4: 3D printing to form the shape:

[0066] The 3D printing material prepared in step three is loaded into the barrel of the 3D printer and printed using fused deposition modeling (FDM) technology;

[0067] The printing parameters of the 3D printer were set as follows: printing temperature 210℃, heated bed temperature 50℃, printing speed 40mm / s, layer thickness 0.25mm, nozzle diameter 0.5mm, and extrusion pressure 0.4MPa. After printing, the resulting carbon rod precursor was placed in a room temperature environment to dry naturally for 36 hours to solidify and set.

[0068] Step 5: Carbonization treatment:

[0069] The dried and cured charcoal rod precursor was placed in a tube furnace, and nitrogen was introduced as a protective gas. The temperature was raised to 500°C at a rate of 7°C / min and held at this temperature for 2 hours for carbonization. During the carbonization process, the organic matter in the coffee grounds gradually decomposed (lignin pyrolysis), forming a carbonized product with a preliminary porous structure. After carbonization, the heating was turned off and the furnace was cooled to room temperature to obtain the carbonized charcoal rod.

[0070] Step Six: Chemical Activation Treatment

[0071] The carbonized carbon rods were immersed in a potassium hydroxide (KOH) solution (KOH to carbonized carbon rod mass ratio of 1:2.5) and soaked at room temperature for 18 hours. After soaking, the carbon rods were dried at 90°C to constant weight and then placed in a tube furnace. Under nitrogen protection, the temperature was raised to 800°C and activated at 800°C for 1.5 hours. After activation, the carbon rods were repeatedly rinsed with deionized water until the rinsing solution was neutral. Then, they were dried in a 90°C oven to constant weight to obtain 3D printed activated carbon rods based on coffee grounds.

[0072] The 3D-printed activated carbon rod based on coffee grounds prepared according to the preparation method in Example 1 is cylindrical;

[0073] As attached Figure 1-2 As shown, its specific structure is as follows: a first groove 1 is opened in the center of the 3D printed activated carbon rod based on coffee grounds, and the first groove 2 penetrates through the top surface and bottom surface of the 3D printed activated carbon rod based on coffee grounds.

[0074] The first groove 1 has a circular cross-section;

[0075] The 3D printed activated carbon rod based on coffee grounds has several second grooves 2 opened in its radial direction. The second grooves 2 penetrate the side wall of the 3D printed activated carbon rod based on coffee grounds, but do not communicate with the first groove 1, and the second grooves 2 do not penetrate the top surface and bottom surface of the 3D printed activated carbon rod based on coffee grounds.

[0076] The second groove 2 has a rectangular cross-section, and its transverse direction extends along the radius of the cylinder. The second groove 2 is parallel to the axis of the first groove 1.

[0077] Several third grooves 3 are provided in the area between adjacent second grooves 2. The third grooves 3 penetrate the top and bottom surfaces of the 3D printed activated carbon rod based on coffee grounds. At least part of the third grooves 3 are not connected to the second grooves 2.

[0078] The third groove 3 consists of multiple concentric arc-shaped channels, nested at equal intervals outward from the center of the activated carbon rod, forming a multi-layered arc structure; furthermore, according to the attached diagram... Figure 2 As shown, every other arc-shaped channel is connected to the second channel 2. The above structure increases the contact area between water and activated carbon rod, thereby increasing the adsorption effect of activated carbon.

[0079] Example 2

[0080] This embodiment 2 provides a method for preparing a 3D printed activated carbon rod based on coffee grounds, the preparation steps of which include:

[0081] Step 1: Coffee grounds pretreatment:

[0082] The collected coffee grounds were rinsed with deionized water at least three times to remove surface oils, sugars and other impurities; then dried in a 90°C oven to constant weight; the dried coffee grounds were pulverized with a high-speed grinder and passed through a 100-mesh sieve to obtain uniformly sized fine coffee grounds powder for later use.

[0083] Step 2: Preparation of adhesive solution:

[0084] Weigh 9g of sodium carboxymethyl cellulose (CMC) and 3g of polylactic acid (PLA) at a mass ratio of 3:1, mix them evenly, and use them as an adhesive. Add 180g of deionized water to the adhesive, controlling the mass ratio of adhesive to deionized water to be 1:15. Place the mixture in a 65℃ water bath and stir at 350r / min for 50min until completely dissolved. Cool to room temperature to obtain a homogeneous and transparent adhesive solution.

[0085] Step 3: 3D Printing Material Preparation

[0086] Weigh the coffee grounds powder obtained in step one, the binder solution obtained in step two, the pore-forming agent and the reinforcing agent, and add them together to a high-speed mixer and mix at 600 r / min for 30 min to obtain a 3D printing material with good flowability.

[0087] The pore-forming agent is a mixture of sodium bicarbonate and starch, and the reinforcing agent is nano-silica.

[0088] The mass ratio of sodium bicarbonate to starch is 2:1, wherein in this embodiment, the mass of sodium bicarbonate is 16g and the mass of starch is 8g.

[0089] The mass ratio of fine coffee grounds to binder solution is 3:1, wherein in this embodiment, the mass of fine coffee grounds is 200g and the mass of binder solution is 67g.

[0090] The total mass of the pore-forming agent accounts for 12% of the mass of the coffee grounds powder;

[0091] The mass of nano-silica accounts for 5% of the mass of coffee grounds powder, and in this embodiment, the mass of nano-silica is 10g.

[0092] Step 4: 3D printing to form the shape:

[0093] The 3D printing material prepared in step three is loaded into the barrel of the 3D printer and printed using fused deposition modeling (FDM) technology;

[0094] The printing parameters of the 3D printer are set as follows: printing temperature 220℃, heated bed temperature 55℃, printing speed 40mm / s, layer thickness 0.3mm, nozzle diameter 0.5mm, and extrusion pressure 0.5MPa.

[0095] After printing, the resulting carbon rod precursor is placed in a room temperature environment to air dry for 40 hours to allow it to fully solidify and set.

[0096] Step 5: Carbonization treatment:

[0097] The dried and cured carbon rod precursor was placed in a tube furnace, and nitrogen was introduced as a protective gas. The temperature was raised to 600°C at a rate of 10°C / min, and held at 600°C for 2.5 hours for carbonization. After carbonization, the heating was turned off, and the furnace was cooled to room temperature to obtain the carbonized carbon rod.

[0098] Step Six: Physical Activation Treatment

[0099] The carbonized charcoal rods were placed in a high-temperature tube furnace, and steam was introduced as an activator under nitrogen protection; the temperature was raised to 850℃, and activated at 850℃ for 1.5 hours.

[0100] After activation, the carbon rod is cooled to room temperature in the furnace, and then dried in a 90°C oven to constant weight to obtain a 3D-printed activated carbon rod based on coffee grounds.

[0101] The 3D-printed activated carbon rod based on coffee grounds prepared according to the preparation method in Example 2 is cylindrical.

[0102] As attached Figure 3-4 As shown, its specific structure is as follows: a first groove 1 is opened in the center of the 3D printed activated carbon rod based on coffee grounds, and the first groove 2 penetrates through the top surface and bottom surface of the 3D printed activated carbon rod based on coffee grounds.

[0103] The first groove 1 has a square cross-section;

[0104] The 3D printed activated carbon rod based on coffee grounds has several second grooves 2 opened in its radial direction. The second grooves 2 penetrate the side wall of the 3D printed activated carbon rod based on coffee grounds, but do not communicate with the first groove 1, and the second grooves 2 do not penetrate the top surface and bottom surface of the 3D printed activated carbon rod based on coffee grounds.

[0105] The second groove 2 has a rectangular cross-section, and its transverse direction extends along the radius of the cylinder. The second groove 2 is parallel to the axis of the first groove 1.

[0106] Several third grooves 3 are provided in the area between adjacent second grooves 2. The third grooves 3 penetrate the top and bottom surfaces of the 3D printed activated carbon rod based on coffee grounds. At least part of the third grooves 3 are not connected to the second grooves 2.

[0107] According to the attached diagram Figure 3-4 It can be seen that the cross-section of the third tank 3 is fan-shaped. The above structure increases the contact area between water and activated carbon rod, thereby increasing the adsorption effect of activated carbon.

[0108] In summary, this invention utilizes 3D printing technology to precisely design the internal structure of activated carbon rods, significantly increasing the contact area with water and improving the adsorption efficiency of pollutants in water. Complex structures that are difficult to achieve using traditional molding methods can be completed at low cost.

[0109] By optimizing the material formulation (a composite binder of sodium carboxymethyl cellulose and polylactic acid, a composite pore-forming agent of sodium bicarbonate and starch, and a nano-silica reinforcing agent, etc.), while ensuring the plasticity of the material and its applicability to 3D printing, the pore-forming agent can regulate the pore structure, increase the specific surface area of ​​activated carbon, and enhance the adsorption capacity; the reinforcing agent effectively improves the mechanical strength of the activated carbon rod and extends its service life; thus, this invention combines high-efficiency adsorption performance with good structural stability, meeting the needs of practical applications.

[0110] The above description of the present invention is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing 3D-printed activated carbon rods based on coffee grounds, characterized in that the steps include... include: Step 1: Collect coffee grounds, wash and dry them to constant weight, grind them and sieve them to obtain fine coffee ground powder; Step 2: Mix sodium carboxymethyl cellulose and polylactic acid to prepare an adhesive. Then add deionized water to the adhesive, stir until completely dissolved, and cool to room temperature to form an adhesive solution. Step 3: Mix the coffee grounds powder, the binder solution, the pore-forming agent, and the reinforcing agent evenly to obtain the 3D printing material; The pore-forming agent is a mixture of sodium bicarbonate and starch, and the reinforcing agent is nano-silica. Step 4: The 3D printing material is formed by 3D printing technology to obtain a carbon rod precursor, and then the carbon rod precursor is dried and cured. Step 5: The dried and cured carbon rod precursor is carbonized under inert gas protection, heated to the set temperature and held at that temperature, and then cooled in the furnace to obtain the carbonized carbon rod. Step 6: Activate the carbonized carbon rods by means of either physical or chemical activation. Then, clean the activated carbonized carbon rods until they are neutral and dry them to a constant weight to obtain 3D printed activated carbon rods based on coffee grounds. The physical activation uses water vapor or carbon dioxide as the activating agent; The chemical activation uses one or more of potassium hydroxide solution, zinc chloride solution, and phosphoric acid solution as activating agents.

2. The method for preparing a 3D-printed activated carbon rod based on coffee grounds according to claim 1, characterized in that, In step one, the drying temperature is 80℃-100℃, and the sieve mesh size is 100-200 mesh.

3. The method for preparing a 3D-printed activated carbon rod based on coffee grounds according to claim 1, characterized in that, In step two, the mass ratio of sodium carboxymethyl cellulose to polylactic acid is 1:1-3:1; the mass ratio of binder to deionized water is 1:10-1:15; the mixing of binder and deionized water is carried out in a water bath at 50℃-70℃ for 30min-60min.

4. The method for preparing a 3D-printed activated carbon rod based on coffee grounds according to claim 1, characterized in that, In step three The mass ratio of the coffee grounds powder to the binder solution is 3:1-5:1; the mass ratio of the sodium bicarbonate to the starch in the pore-forming agent is 1:1-2:1; The total mass of the pore-forming agent accounts for 8%-12% of the mass of the coffee grounds powder; The enhancer accounts for 2%-5% of the mass of the fine coffee grounds; The stirring speed when mixing the coffee grounds powder, the binder solution, the pore-forming agent and the reinforcing agent is 400 r / min-600 r / min, and the stirring time is 20 min-30 min.

5. The method for preparing a 3D-printed activated carbon rod based on coffee grounds according to claim 1, characterized in that, In step four, the 3D printing technology is to use a 3D printer and employ fused deposition modeling (FDM) technology for printing. The printing parameters of the 3D printer are as follows: printing temperature of 200℃-220℃, heated bed temperature of 40℃-60℃, printing speed of 20mm / s-60mm / s, layer thickness of 0.1mm-0.4mm, nozzle diameter of 0.4mm-0.6mm, and extrusion pressure of 0.2MPa-0.6MPa. The drying and curing process involves natural drying at room temperature for 24-48 hours.

6. The method for preparing a 3D-printed activated carbon rod based on coffee grounds according to claim 1, characterized in that, In step five, the heating rate of the carbonization process is 5℃ / min-10℃ / min, the set temperature of the carbonization process is 400℃-600℃, and the holding time of the carbonization process is 1h-3h.

7. The method for preparing a 3D-printed activated carbon rod based on coffee grounds according to claim 1, characterized in that, The physical activation includes the following steps: placing the carbonized carbon rod into a high-temperature tube furnace, then introducing steam or carbon dioxide gas as an activator, and carrying out the activation reaction at a temperature of 700℃-900℃ for 1-2 hours, and finally drying to constant weight. The final drying temperature to constant weight is 80℃-100℃.

8. The method for preparing a 3D-printed activated carbon rod based on coffee grounds according to claim 1, characterized in that, The chemical activation includes the following steps: immersing the carbonized carbon rod in the activating agent, removing the carbonized carbon rod after immersion, drying the carbonized carbon rod and placing it in a tube furnace for activation reaction, rinsing the activated carbon rod repeatedly with deionized water until the rinsing solution is neutral, and finally drying it to constant weight. The mass ratio of the activator to the carbonized carbon rod is 1:1 to 1:

4. The carbonized carbon rod is immersed in the activator for 12-24 hours; The activation reaction temperature in the tubular furnace is 700℃-900℃; The activation reaction takes 1-2 hours. The final drying temperature to constant weight is 80℃-100℃.

9. A 3D-printed activated carbon rod based on coffee grounds, prepared by the method according to any one of claims 1-8, characterized in that, The 3D-printed activated carbon rod based on coffee grounds is cylindrical; The coffee grounds-based 3D printed activated carbon rod has a first groove (1) in the center, and the first groove (2) extends through the top and bottom surfaces of the coffee grounds-based 3D printed activated carbon rod. The coffee grounds-based 3D printed activated carbon rod has several second grooves (2) along its radial direction. The second grooves (2) penetrate the side wall of the coffee grounds-based 3D printed activated carbon rod, but are not connected to the first groove (1). The second grooves (2) do not penetrate the top and bottom surfaces of the coffee grounds-based 3D printed activated carbon rod. Several third grooves (3) are provided in the area between adjacent second grooves (2). The third grooves (3) penetrate the top surface and bottom surface of the coffee grounds-based 3D printed activated carbon rod. At least part of the third grooves (3) are not connected to the second grooves (2).

10. The application of a 3D-printed activated carbon rod based on coffee grounds as described in claim 9 as an adsorption unit in water purification treatment.

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