Bacteriostatic sintered activated carbon filter element and preparation method thereof

Abstract

This invention discloses an antibacterial sintered activated carbon filter element and its preparation method, belonging to the technical field of water treatment functional materials. The method uses biomass-derived activated carbon as the main adsorbent phase, combined with activated carbon loaded with zinc components formed by zinc acetate impregnation and a chitosan-zinc phytate composite antibacterial agent. After uniform mixing with a hydrophilic bonding system constructed from ultra-high molecular weight polyethylene and polyvinyl alcohol, the filter element is formed by pressing and segmented temperature-controlled sintering. The chitosan-zinc phytate forms a stable composite network through multi-toothed coordination. The zinc components in the activated carbon loaded with zinc components are distributed in a fixed state on the carbon skeleton surface, synergistically interacting with the micro-mesoporous structure of the activated carbon to achieve a combination of adsorption and antibacterial functions. The filter element forms a three-dimensional interconnected pore structure, maintaining low flow resistance while ensuring structural stability.

Description

Technical Field

[0001] This invention belongs to the field of water treatment functional materials technology, specifically, it relates to an antibacterial sintered activated carbon filter element and its preparation method. Background Technology

[0002] Activated carbon, due to its large specific surface area, well-developed pore structure, rapid adsorption kinetics, and good thermal and chemical stability, has been widely used in water purification, air filtration, heavy metal removal, and bioremediation, and is a commonly used adsorption medium in existing filter material systems. Relevant literature has reported that activated carbon materials with both microporous and mesoporous structures and containing oxygen and nitrogen functional groups on their surface can be prepared by using green tea as a precursor and activating it with potassium hydroxide; such materials have application potential in water treatment adsorption.

[0003] However, activated carbon alone still has shortcomings in practical applications. On the one hand, although activated carbon can adsorb organic pollutants and some microbial nutrients, bacteria easily accumulate and multiply within its pores, leading to pore blockage, reduced service life, and even the risk of secondary pollution. To address this issue, existing technologies typically employ composite modification of activated carbon using metals, metal oxides, or polymers. However, there is still room for improvement in existing solutions. Existing literature has pointed out that while silver nanomaterials or silver ion systems possess strong antimicrobial activity, they may also present challenges such as the toxicity risks from residual silver precursor ions, high raw material costs, and the need for further optimization of preparation conditions. Meanwhile, current research on biomass-based activated carbon focuses more on adsorption performance or single antibacterial modification, lacking systematic solutions for composite systems that balance adsorption performance, antibacterial stability, molding strength, and suitability for low-temperature sintering filter cartridge preparation.

[0004] Therefore, it is still necessary to provide an antibacterial sintered activated carbon filter element and its preparation method, so as to improve the antibacterial stability, structural integrity and practical application adaptability of the filter element while maintaining the adsorption performance of activated carbon. Summary of the Invention

[0005] To address the issues that existing activated carbon filter cartridges, while possessing certain adsorption and purification capabilities, suffer from insufficient antibacterial ability, are prone to microbial growth and potential secondary pollution with prolonged use, and have problems such as difficulty in simultaneously achieving structural strength, water flow resistance, and antibacterial durability in the filter cartridge molding system, this invention provides an antibacterial sintered activated carbon filter cartridge and its preparation method.

[0006] The present invention adopts the following technical solution: a method for preparing an antibacterial sintered activated carbon filter element, comprising the following steps by weight: (1) green tea is boiled and washed with water, dried at 80°C, pulverized and sieved, mixed with potassium hydroxide, impregnated and carbonized at 600-800°C under nitrogen protection, washed to neutral and dried to obtain the first activated carbon; (2) peach shells are mixed with potassium hydroxide and activated and carbonized, washed to neutral to obtain the second activated carbon; the second activated carbon is pre-wetted and contacted with zinc acetate dihydrate, impregnated, dried at 80°C and heat-treated at 350-360°C to obtain activated carbon loaded with zinc components; (3) shell polymerase is added to the activated carbon. Sugar is dissolved in an acidic aqueous solution and then reacted with a zinc phytate complex solution. The solid and liquid are separated and dried and pulverized to obtain a chitosan-zinc phytate composite antibacterial agent; (4) Ultra-high molecular weight polyethylene and polyvinyl alcohol are physically blended to obtain a hydrophilic binder; (5) By mass, 60-70 parts of the first activated carbon and activated carbon loaded with zinc components, 3-6 parts of the chitosan-zinc phytate composite antibacterial agent, 22-30 parts of the hydrophilic binder and 2-5 parts of natural silicate ore powder are mixed, compacted at 3.0-5.0 MPa, and preheated at 105-115℃ and sintered at 165-175℃ to obtain an antibacterial sintered activated carbon filter element.

[0007] Preferably, in step (1), the green tea is first boiled and washed with deionized water, then dried at 80°C and passed through a 150μm sieve; the carbonization conditions of the first activated carbon are: under nitrogen protection, the temperature is raised to 700-800°C at 10°C / min and kept at that temperature for 1 hour, and after washing, it is dried at 110°C for 24 hours.

[0008] Preferably, in step (2), the immersion temperature is 25°C and the immersion time is 24-72h; the heat treatment temperature is 360°C and the time is 8h.

[0009] Preferably, in the activated carbon loaded with zinc components obtained in step (2), zinc exists in the form of zinc particles and / or zinc ions fixed on the surface, and its carbon skeleton has a hierarchical pore structure in which micropores, mesopores and macropores coexist.

[0010] Preferably, in step (3), the pH of the acidic aqueous solution is 3.5-4.0, which is adjusted by glacial acetic acid; the mass ratio of effective solids of phytic acid in the chitosan to zinc phytate complex solution is 1.25-3:1; the dropping rate of the zinc phytate complex solution is 1-3 mL / min; the reaction temperature is 55-65℃, and the reaction time is 3-5 h.

[0011] Preferably, zinc phytate is prepared in situ by the following method: phytic acid is mixed with water to form a phytic acid solution, and then zinc acetate dihydrate is added to it and stirred for 30-60 min to obtain a zinc phytate complex solution, which is then used in step (3).

[0012] Preferably, the weight-average molecular weight of the ultra-high molecular weight polyethylene in step (4) is 3.0 × 10⁻⁶. 6 -5.0×10 6 The degree of alcoholysis of polyvinyl alcohol is 87-89%, and the mass ratio of the two is (5-12.5):1.

[0013] Preferably, the natural silicate ore powder in step (5) is maifanite powder, with a D50 particle size ≤10μm, and the total mass of silicon dioxide and aluminum oxide accounts for more than 60% of the total mass of the ore powder.

[0014] Preferably, the filter element has a three-dimensional interconnected pore network composed of a first activated carbon, activated carbon loaded with zinc components, a chitosan-zinc phytate composite antibacterial agent, and a hydrophilic binder.

[0015] Compared to existing technologies, this invention has at least the following beneficial effects: This invention utilizes biomass-derived activated carbon, activated carbon loaded with zinc components, and a chitosan-zinc phytate composite antibacterial agent to construct a composite functional system. This system can significantly improve the antibacterial performance and stability of the filter element while maintaining high adsorption performance, thereby reducing the risk of microbial growth and secondary pollution during the use of the activated carbon filter element. Simultaneously, this invention forms a hydrophilic bonding system between ultra-high molecular weight polyethylene and polyvinyl alcohol, combined with specific pressing and segmented temperature-controlled sintering processes, to create a three-dimensional interconnected pore structure inside the filter element, thus balancing the filter element's molding strength, porosity, water flow performance, and low pressure drop. The results of the examples and comparative examples show that this invention achieves a good balance between adsorption performance, antibacterial performance, mechanical strength, and operational stability, and has good practical application value. Attached Figure Description

[0016] Figure 1 This is a transmission electron microscope (TEM) image of the first activated carbon prepared in Example 1.

[0017] Figure 2 This is a transmission electron microscope (TEM) image of the zinc-loaded activated carbon prepared in Example 1.

[0018] Figure 3 This is a transmission electron microscope image of the chitosan-zinc phytate composite antibacterial agent prepared in Example 1.

[0019] Figure 4 This is the infrared spectrum of the hydrophilic binder prepared in Example 1.

[0020] Figure 5 This is a photograph of the antibacterial sintered activated carbon filter element prepared in Example 1. Detailed Implementation

[0021] The present invention will be further described below with reference to embodiments. It should be noted that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. For those skilled in the art, equivalent substitutions or conventional adjustments made to the source of raw materials, equipment models, operating sequences, and process details without departing from the concept of the present invention should be considered to fall within the scope of protection of the present invention.

[0022] Unless otherwise specified, all raw materials used in this invention can be obtained commercially. The green tea (dehydrated tea residue mainly derived from the screenings and residual leaves during the processing of suitable green tea varieties such as Longjing 43) is selected after dehydration treatment. Specifically, the moisture content ranges from 4.6-5.1 wt%, the water activity (aw) ranges from 0.25-0.32, the total ash content is approximately 6.2 wt%, the average soluble polyphenol content is 7.46 wt%, the average total phenol content is 22.6 g GAE / 100g, and the particle size ranges from 100-200 μm. The peach shells used are dried, hard peach shells after washing and impurity removal (mainly taken from the outer shell of the pit, a byproduct of wild peach processing). Their specific physicochemical parameters meet the following conditions: moisture content: 8.5-10.5 wt%, ash content: ≤2.5 wt%, lignin content: 38.0-42.0 wt%, cellulose content: 28.0-32.0 wt%, average shell wall thickness: 4.0 mm, and average particle size: 0.1 mm. Ultra-high molecular weight polyethylene (UHMWPE) is a powdered resin, CAS number: 9002-88-4, with a weight-average molecular weight of 3.0. 10 6 -5.0 10 6 The median particle size (D50) is 80-120 μm, and the loose packing density is 0.45-0.50 g / cm³. 3The melting point is 130-135℃. Commercially available products meeting the above requirements can be used, such as Celanese's GUR4150 product. Polyvinyl alcohol is a partially alcoholyzed powder, CAS number: 9002-89-5. It is a slightly milky white powder, soluble in water, with a degree of polymerization of 1000-2000 and a degree of alcoholysis of 88%. It is completely soluble in water at 25℃. Commercially available 17-88 (PVA1788) type polyvinyl alcohol powder can be used, such as the aforementioned product from Sichuan Chuanwei Chemical Co., Ltd. "Zinc phytate" is a zinc-containing coordination system formed by the reaction of phytic acid and zinc acetate dihydrate in an aqueous phase. Specifically, it is a slightly acidic, homogeneous zinc-containing coordination aqueous solution formed by stirring in deionized water for 30-60 minutes. Its main raw materials can be commercially available 50wt% phytic acid aqueous solution (CAS number: 83-86-3) and zinc acetate dihydrate with a purity ≥99%. All amounts listed in the examples are by mass (g). For ease of comparison, Example 1 is set as the preferred implementation method; the other examples are based on Example 1, with single-factor or small-factor adjustments to the proportion of key components or key process parameters; the comparative examples focus on the absence, substitution, out-of-bounds, and process defects of key components.

[0023] I. Raw Materials and Equipment

[0024] Main ingredients: green tea, peach shells, potassium hydroxide (CAS No.: 1310-58-3), chitosan (CAS No.: 9012-76-4, degree of deacetylation 88.0%, light yellow powder, commercially available with a molecular weight of 1) 10 5 -1.5 10 5 The following ingredients are used: powdered chitosan with a viscosity of 100-300 mPa·s (1% acetic acid aqueous solution, 25℃); glacial acetic acid (CAS No.: 64-19-7); phytic acid aqueous solution (mass fraction 50.0%); zinc acetate dihydrate (CAS No.: 5970-45-6); ultra-high molecular weight polyethylene; polyvinyl alcohol; and maifanite powder (natural silicate mineral powder, silicon dioxide: 55.0-68.0%, alumina: 13.0-17.0%, calcium oxide: 3.0-8.0%, iron oxide: 1.5-4.5%, magnesium oxide: 1.0-3.0%, with potassium oxide as the remainder; particle size range 1250-2000 mesh; loose density 0.8-1.2 g / cm³). 3 ), deionized water.

[0025] Main equipment: Box drying oven (DHG-9140A, Shanghai Yiheng), tube furnace (OTF-1200X, Hefei Kejing), vacuum drying oven (DZF-6090), planetary mixer (MSK-SFM-7), hydraulic press (YLJ-15T), programmable temperature controlled sintering furnace (KSL-1100X), electronic universal testing machine (5967, Instron), scanning electron microscope (SU8020, Hitachi), BET surface area analyzer (ASAP2460, Micromeritics), inductively coupled plasma atomic emission spectrometer (5110ICP-OES, Agilent).

[0026] II. Implementation Examples

[0027] Example 1

[0028] This embodiment is a preferred embodiment of the present invention.

[0029] Step (1) Preparation of the first activated carbon: Take 100.0g of green tea, boil and wash it twice with deionized water, adding 1500.0g of water each time, and keep it boiling gently for 20min; after filtration, dry it at 80℃ for 12h. After pulverizing the dried material, pass it through a 150μm sieve to obtain 92.0g of pretreated green tea powder. Mix 92.0g of pretreated green tea powder with 92.0g of potassium hydroxide evenly, add 184.0g of deionized water and soak for 2h, dry at 80℃ and place it in a tube furnace, under nitrogen flow rate of 0.8L / min protection, heat it to 700℃ at 10℃ / min and keep it at that temperature for 1h. After cooling, take it out, wash it repeatedly with deionized water until the pH of the filtrate is 7, and dry it at 110℃ for 24h to obtain the first activated carbon, the microstructure of which is as follows. Figure 1 As shown.

[0030] Step (2) Preparation of activated carbon loaded with zinc component: Take 100.0g of peach shell, crush it and pass it through a 250μm sieve, mix it with 100.0g of potassium hydroxide, add 200.0g of deionized water and soak for 2h, dry it, and then heat it to 750℃ at 10℃ / min under nitrogen protection and keep it at that temperature for 1h. Wash it until neutral, and dry it at 110℃ for 12h to obtain 43.8g of second activated carbon. Weigh 25.0g of the second activated carbon, pre-wet it with 12.5g of deionized water for 30min, and then add an aqueous solution of zinc acetate dihydrate. The aqueous solution of zinc acetate dihydrate is prepared by mixing 2.0g of zinc acetate dihydrate and 23.0g of deionized water. After impregnation at 25℃ in the dark for 72 hours, the sample was filtered, dried at 80℃ for 8 hours, and then heat-treated at 360℃ in air for 8 hours. After heat treatment, the sample was naturally cooled to room temperature. The resulting material was repeatedly washed with deionized water and dried to obtain activated carbon loaded with zinc components. Its microstructure is as follows. Figure 2As shown, the heat treatment time and air atmosphere are controlled to prevent significant ablation of the activated carbon, thereby promoting the transformation, anchoring, or partial reduction of zinc species under the influence of oxygen-containing functional groups on the activated carbon surface and the carbon-based reducing environment.

[0031] Step (3) Preparation of chitosan-zinc phytate composite antibacterial agent: First, prepare the zinc phytate complexation solution: Mix 12.0 g of phytic acid aqueous solution (50 wt%) with 68.0 g of deionized water and stir at room temperature for 5 min; then add 8.0 g of zinc acetate dihydrate and continue stirring for 45 min to obtain 88.0 g of zinc phytate complexation solution. Take another 10.0 g of chitosan, add 186.0 g of deionized water, and add 4.0 g of glacial acetic acid dropwise while stirring to adjust the pH to 3.8. Stir at 500 rpm in a 60℃ water bath until the chitosan (degree of deacetylation 88.0%) is fully dissolved. Then, add the above zinc phytate complexation solution 88.0 g dropwise to the acidic chitosan solution at a rate of 2 mL / min and continue the reaction at 60℃ for 4 h. After the reaction was complete, the mixture was filtered. The filter cake was washed with deionized water until the pH of the filtrate reached 6.5. It was then vacuum-dried at 60℃ for 12 hours, pulverized, and passed through a 100-mesh sieve to obtain the chitosan-zinc phytate composite antibacterial agent. Its microstructure is shown below. Figure 3 As shown.

[0032] Step (4) Preparation of hydrophilic adhesive: Weigh 23.6g of ultra-high molecular weight polyethylene, 2.9g of polyvinyl alcohol, and 58.0g of deionized water, and mix them at 1500rpm for 15min in a high-speed mixer at 90℃ to obtain the hydrophilic adhesive. Its infrared spectrum is shown below. Figure 4 As shown. The weight-average molecular weight of the ultra-high molecular weight polyethylene is 4.0 × 10⁻⁶. 6 The degree of alcoholysis of polyvinyl alcohol is 88.0%.

[0033] Step (5) Filter element molding and sintering: Weigh 45.2g of the first activated carbon, 20.8g of activated carbon loaded with zinc components, 4.5g of chitosan-zinc phytate composite antibacterial agent, 26.5g of hydrophilic binder, and 3.0g of maifan stone powder, and mix them in a planetary mixer for 25 minutes to obtain a molding mixture. Place the mixture into a cylindrical mold with an inner diameter of 30mm and a length of 125mm, and press it under 4.0MPa for 3 minutes. After demolding, preheat at 110℃ for 30 minutes, then sinter at 170℃ for 3 minutes, and allow it to cool naturally to room temperature to obtain an antibacterial sintered activated carbon filter element. Its physical image is shown below. Figure 5 As shown.

[0034] The sintering temperature was set at 170℃, higher than the melting point of ultra-high molecular weight polyethylene (UHMWPE), causing it to soften and partially melt and bond, forming the main adhesive skeleton of the filter element. Actual experimental observations revealed polyethylene-based adhesive neck structures on the pore walls of the sintered filter element, indicating that the UHMWPE had fixed and connected the activated carbon and inorganic powder particles; simultaneously, discontinuous dot-like or thin-layered hydrophilic micro-regions were visible on the pore walls.

[0035] According to the test results, the filter element obtained in Example 1 has a continuous through-hole structure, and a discontinuous hydrophilic layer formed by polyvinyl alcohol can be observed on the surface. Moreover, there are no obvious cracks or powder shedding after molding.

[0036] Example 2

[0037] This embodiment illustrates that when the total amount of activated carbon is near the lower limit of the claims, the filter element can still achieve both adsorption and antibacterial performance. Compared with Example 1, only the formulation of step (5) and the carbonization temperature of step (1) are adjusted. All other conditions not listed are the same as in Example 1, as shown in Table 1.

[0038] Table 1 Adjustment parameters for Example 2

[0039]

[0040] In step (4), the mass ratio of ultra-high molecular weight polyethylene to polyvinyl alcohol is adjusted to 7.5:1, that is, 25.6g of ultra-high molecular weight polyethylene and 3.4g of polyvinyl alcohol. In step (5), the pressing pressure is 3.5MPa, the preheating temperature is 105℃, and the sintering temperature is 168℃.

[0041] Example 3

[0042] This example illustrates the effect of increasing the proportion of activated carbon loaded with zinc components and decreasing the ratio of zinc phytate to chitosan. Compared with Example 1, the only differences are as follows: the impregnation time of the activated carbon loaded with zinc components in step (2) is 48 h; the mass ratio of chitosan to zinc phytate solids in step (3) is 1.5:1; and the formula in step (5) is 38.5 g of first activated carbon, 28.5 g of activated carbon loaded with zinc components, 4.0 g of chitosan-zinc phytate composite antibacterial agent, 26.0 g of hydrophilic binder, and 3.0 g of maifanite powder. The pressing pressure is 4.5 MPa, the preheating temperature is 112 °C, and the sintering temperature is 172 °C.

[0043] Example 4

[0044] This embodiment illustrates the situation when the carbonization temperature of the first activated carbon is at its upper limit and the proportion of the hydrophilic binder is near its lower limit. Compared with Example 1, the only differences are as follows: the carbonization temperature of the green tea in step (1) is 800℃; in step (2), 25.0g of the second activated carbon is weighed, pre-wetted with 12.5g of deionized water for 30min, and then an aqueous solution of zinc acetate dihydrate prepared by 1.5g of zinc acetate dihydrate and 23.5g of deionized water is added; the remaining zinc loading treatment conditions are the same as in Example 1. The amount of zinc acetate dihydrate used is equivalent to 6.0g zinc acetate dihydrate / 100.0g of the second activated carbon. In step (3), the dropping rate is 1 mL / min; in step (4), the mass ratio of ultra-high molecular weight polyethylene to polyvinyl alcohol is 12.0:1, i.e., 24.0 g and 2.0 g; in step (5), the formula is 49.0 g of first activated carbon, 18.0 g of activated carbon loaded with zinc components, 4.0 g of chitosan-zinc phytate composite antibacterial agent, 26.0 g of hydrophilic binder, and 3.0 g of maifanite powder. The pressing pressure is 5.0 MPa, the preheating temperature is 115℃, and the sintering temperature is 175℃.

[0045] III. Comparative Example

[0046] Comparative Example 1

[0047] Compared with Example 1, only the chitosan-zinc phytate composite antibacterial agent in step (3) was removed, and replaced with the first activated carbon in equal mass. That is, the formula in step (5) is 49.7g of the first activated carbon, 20.8g of activated carbon loaded with zinc components, 26.5g of hydrophilic binder, and 3.0g of maifan stone powder. The other conditions are the same as in Example 1.

[0048] Comparative Example 2

[0049] Compared with Example 1, only the activated carbon loaded with zinc components in step (2) was replaced with a second activated carbon without zinc loading. The formula in step (5) was 45.2g of the first activated carbon, 20.8g of the second activated carbon, 4.5g of chitosan-zinc phytate composite antibacterial agent, 26.5g of hydrophilic binder, and 3.0g of maifanite powder. The other conditions were the same as in Example 1.

[0050] Comparative Example 3

[0051] Compared to Example 1, only the polyvinyl alcohol in step (4) is removed, and the hydrophilic binder is replaced by 26.5g of ultra-high molecular weight polyethylene alone. The remaining components in step (5) remain unchanged. This setup is equivalent to omitting the key hydrophilic component in the hydrophilic adhesive system.

[0052] Comparative Example 4

[0053] Compared with Example 1, only the sintering temperature in step (5) is increased to 185°C, which exceeds the upper limit of the claim; the other conditions remain unchanged.

[0054] IV. Testing Methods

[0055] Iodine adsorption value: Refer to GB / T12496.8-2015. Take 0.500g of a pulverized filter element sample that has passed through a 40-mesh sieve, add it to a standard iodine solution and hydrochloric acid system, shake to adsorb, and back-titrate with sodium thiosulfate to calculate the iodine adsorption value. The unit is mg / g. Each group is tested in triplicate, and the average value is taken.

[0056] Compressive strength: Refer to GB / T1041-2008. Cut the filter element into cylindrical specimens with a length of 20.0 mm, load them on an electronic universal testing machine at a speed of 2 mm / min, record the maximum load at which the specimen fails, and calculate the compressive strength in MPa. Test 5 samples in each group and take the average value.

[0057] Antibacterial rate: *Escherichia coli* (ATCC25922) and *Staphylococcus aureus* (ATCC6538) were selected as test bacteria. The shaking contact method according to GB / T21866-2008 was adjusted based on the characteristics of the filter media sample. 1.0 g of the pulverized filter element sample was weighed and 50.0 g of bacterial suspension was added, with the bacterial concentration controlled at 1.0 × 10⁻⁶. 5 CFU / mL, after contacting at 37℃ with shaking for 2 hours, samples were taken, diluted, and plated. The antibacterial rate was calculated according to the blank control.

[0058] Water flux and pressure drop: The filter element was installed in a small water purification test device, and deionized water was introduced at 25℃. The inlet pressure was set to 0.20MPa. After stable operation for 10 minutes, the water mass produced within 1 minute was recorded and the flux was calculated in L / h. At the same time, the inlet and outlet pressure difference was recorded in kPa. Each group was repeated in triplicate.

[0059] Porosity: A dried filter element sample was taken and determined using the n-butanol immersion method. The dry mass, wetted mass, and geometric volume of the sample were recorded, and the open porosity was calculated in percentages (%).

[0060] V. Test Results

[0061] Table 2 Performance test results of the examples and comparative examples

[0062]

[0063] Table 3. Operational stability results of the examples and comparative examples

[0064]

[0065] VI. Results Analysis

[0066] As can be seen from Tables 2 and 3, the antibacterial sintered activated carbon filter elements prepared in Examples 1-4 of this invention all exhibit good comprehensive performance, indicating that the composite adsorption-antibacterial system and molding sintering process adopted in this invention can effectively achieve a balance between adsorption performance, antibacterial performance, mechanical strength, and water flow performance. Specifically, the iodine adsorption value of Examples 1-4 is 846.3-926.8 mg / g, the compressive strength is 14.7-16.5 MPa, the antibacterial rate against Escherichia coli is 99.3%-99.8%, the antibacterial rate against Staphylococcus aureus is 99.1-99.6%, the water flow rate is 17.4-19.2 L / h, the pressure drop is 11.2-12.5 kPa, and the porosity is 39.6%-42.4%, indicating that the filter elements of this invention, while ensuring high adsorption capacity and excellent antibacterial effect, still have good structural stability and low flow resistance.

[0067] Example 1, as a preferred embodiment, has an iodine adsorption value of 901.6 mg / g, a compressive strength of 15.8 MPa, antibacterial rates of 99.6% and 99.4% against Escherichia coli and Staphylococcus aureus, respectively, a water flux of 18.7 L / h, a pressure drop of 11.8 kPa, and a porosity of 41.2%. Based on the observations of the filter element molding state in Example 1, the resulting filter element has a continuous through-pore structure, and a discontinuous hydrophilic layer formed by polyvinyl alcohol can be observed on the surface. Furthermore, there are no obvious cracks or powder shedding after molding, indicating that the hydrophilic bonding system and segmented sintering process constructed in this invention are beneficial for forming a filter element structure that combines strength and water permeability.

[0068] In Comparative Example 1, after removing the chitosan-zinc phytate composite antibacterial agent, the antibacterial rate of *E. coli* decreased to 93.2%, and the antibacterial rate of *Staphylococcus aureus* decreased to 91.8%, while the corresponding values ​​in Example 1 were 99.6% and 99.4%, respectively. This indicates that the chitosan-zinc phytate composite antibacterial agent plays an important role in improving the overall antibacterial ability of the filter element. In Comparative Example 2, after replacing the zinc-loaded activated carbon with a second activated carbon without zinc loading, the antibacterial rates of *E. coli* and *Staphylococcus aureus* further decreased to 90.5% and 89.7%, respectively. This indicates that the zinc-loaded activated carbon can form a synergistic antibacterial effect with the chitosan-zinc phytate composite antibacterial agent, thereby significantly improving the antibacterial effect and antibacterial stability of the filter element.

[0069] In Comparative Example 3, after removing polyvinyl alcohol, although the antibacterial rates against Escherichia coli and Staphylococcus aureus remained at 99.1% and 98.8% respectively, the compressive strength decreased to 13.2 MPa, the water flux decreased to 14.6 L / h, the pressure drop increased to 18.4 kPa, and the porosity decreased to 31.8%. This indicates that using ultra-high molecular weight polyethylene alone as a binder is not conducive to forming a molding system with both hydrophilicity and interconnected pore structures. This shows that polyvinyl alcohol in this invention not only participates in constructing a hydrophilic binder system but also helps improve the internal pore connectivity of the filter element and reduce water flow resistance, thereby improving operational stability.

[0070] In Comparative Example 4, when the sintering temperature was increased to 185℃, the compressive strength decreased to 12.5 MPa, the water flux decreased to 13.9 L / h, the pressure drop increased to 19.6 kPa, and the porosity was only 29.7%, significantly worse than Examples 1-4. This indicates that exceeding the sintering temperature limit of this invention will destroy the optimal pore structure and balanced bonding state inside the filter element, which is detrimental to improving overall performance. Therefore, this invention controls the sintering temperature within the range of 165-175℃, which helps to ensure the softening and bonding of ultra-high molecular weight polyethylene while avoiding excessive densification of the structure, thereby achieving a better match between mechanical properties and water flow performance.

[0071] Furthermore, even with adjustments to the raw material ratio and some process parameters, Examples 2-4 still maintained a high antibacterial rate, good iodine adsorption value, and low pressure drop, indicating that the technical solution of the present invention has a certain degree of process adaptability and composition tolerance. For example, Example 2 still achieved a dual-bacterial antibacterial rate of 99.8% and 99.6% and a compressive strength of 16.5 MPa when the total activated carbon amount was near the lower limit. Example 4 still achieved an iodine adsorption value of 926.8 mg / g, a water flux of 19.2 L / h, and a pressure drop of 11.2 kPa when the sintering temperature was near the upper limit, demonstrating that the present invention can stably achieve excellent comprehensive performance within the scope defined by the claims.

[0072] In summary, the results in Tables 2 and 3 demonstrate that this invention, through the synergistic combination of a first activated carbon, activated carbon loaded with zinc components, a chitosan-zinc phytate composite antibacterial agent, and a hydrophilic binder, along with appropriate pressing and low-temperature sintering processes, can produce an antibacterial sintered activated carbon filter element that possesses high adsorption capacity, high antibacterial properties, high mechanical strength, low pressure drop, and a good pore structure. These results prove that this invention effectively solves the problems of insufficient antibacterial capacity, easy microbial growth during long-term use, and the difficulty in simultaneously achieving structural strength, water flow resistance, and antibacterial durability in existing activated carbon filter elements, thus possessing significant practical application value.

Claims

1. A method for preparing an antibacterial sintered activated carbon filter element, characterized in that: The steps included by mass are as follows: (1) green tea is boiled and washed with water, dried at 80°C, pulverized and sieved, mixed with potassium hydroxide, impregnated and then carbonized at 600-800°C under nitrogen protection, washed until neutral and dried to obtain the first activated carbon. (2) Peach shells were mixed with potassium hydroxide and activated and carbonized. After washing until neutral, a second activated carbon was obtained. The second activated carbon was pre-wetted and then contacted with zinc acetate dihydrate. After impregnation, drying at 80°C and heat treatment at 350-360°C, activated carbon loaded with zinc components was obtained. (3) Chitosan was dissolved in an acidic aqueous solution and then reacted with a zinc phytate complexation solution. After solid-liquid separation and drying and pulverization, a chitosan-zinc phytate composite antibacterial agent was obtained. (4) Ultra-high molecular weight polymers were mixed with potassium hydroxide and activated and carbonized. Ethylene and polyvinyl alcohol are physically blended to obtain a hydrophilic binder; (5) By mass, 60-70 parts of the first activated carbon and activated carbon loaded with zinc components, 3-6 parts of chitosan-zinc phytate composite antibacterial agent, 22-30 parts of hydrophilic binder and 2-5 parts of natural silicate ore powder are mixed, compacted at 3.0-5.0 MPa, and preheated at 105-115℃ and sintered at 165-175℃ to obtain antibacterial sintered activated carbon filter element.

2. The method for preparing the antibacterial sintered activated carbon filter element according to claim 1, characterized in that: In step (1), the green tea is first boiled and washed with deionized water, then dried at 80℃ and passed through a 150μm sieve; the carbonization conditions of the first activated carbon are: under nitrogen protection, the temperature is raised to 700-800℃ at 10℃ / min and kept at the temperature for 1h, and after washing, it is dried at 110℃ for 24h.

3. The method for preparing the antibacterial sintered activated carbon filter element according to claim 1, characterized in that: In step (2), the immersion temperature is 25℃ and the immersion time is 24-72h; the heat treatment temperature is 360℃ and the time is 8h.

4. The method for preparing the antibacterial sintered activated carbon filter element according to claim 1, characterized in that: In step (2), the zinc in the activated carbon loaded with zinc components exists in the form of zinc particles and / or zinc ions fixed on the surface, and its carbon skeleton has a hierarchical pore structure with micropores, mesopores and macropores coexisting.

5. The method for preparing the antibacterial sintered activated carbon filter element according to claim 1, characterized in that: In step (3), the pH of the acidic aqueous solution is 3.5-4.0, which is adjusted by glacial acetic acid; the mass ratio of effective solids of phytic acid in the chitosan-zinc phytate complex solution is 1.25-3:1; the dropping rate of the zinc phytate complex solution is 1-3 mL / min; the reaction temperature is 55-65℃, and the reaction time is 3-5 h.

6. The method for preparing the antibacterial sintered activated carbon filter element according to claim 1, characterized in that: Zinc phytate is prepared in situ by the following method: phytic acid is mixed with water to form a phytic acid solution, and then zinc acetate dihydrate is added to it and stirred for 30-60 minutes to obtain a zinc phytate complex solution, which is then used in step (3).

7. The method for preparing the antibacterial sintered activated carbon filter element according to claim 1, characterized in that: The weight average molecular weight of the ultra-high molecular weight polyethylene in step (4) is 3.0 x 10 6 -5.0 x 10 6 , the alcoholysis degree of the polyvinyl alcohol is 87-89%, and the mass ratio of the two is (5-12.5):

1.

8. The method for preparing the antibacterial sintered activated carbon filter element according to claim 1, characterized in that: In step (5), the natural silicate ore powder is maifanite powder with a D50 particle size ≤10μm and the total mass of silicon dioxide and aluminum oxide accounts for more than 60% of the total mass of the ore powder.

9. The method for preparing the antibacterial sintered activated carbon filter element according to claim 1, characterized in that: The filter element has a three-dimensional interconnected pore network composed of a first activated carbon, activated carbon loaded with zinc components, chitosan-zinc phytate composite antibacterial agent, and hydrophilic binder.

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