Inductive tap water mineralization filter element based on high metasilicic acid element

Abstract

The invention relates to the technical field of water treatment, in particular to an induction type tap water mineralization filter element based on high metasilicic acid elements, which is sequentially and coaxially provided with a supporting structure, a mineralization function core structure and a filtering protection structure from inside to outside, the support structure is formed by a ternary blend of polyether sulfone, polyamide and graphene quantum dots through a stepped thermal crosslinking process; the mineralization function core structure is composed of a layered magnesium aluminum silicate carrier, rare earth doped hydroxyapatite and an ion imprinted polymer, and the filtering protection structure is composed of a zirconium oxide coated silver doped titanium dioxide nanotube array. Based on a ternary composite mineralization system, the filter element achieves multi-path synergistic mineralization in dynamic water flow, the ZrO2 coating layer regulates and controls the Ag release rate to be smaller than or equal to 0.05 mg / L, and the antibacterial rate gt is guaranteed; meanwhile, the risk that silver ions exceed the standard is avoided, organic pollutants are effectively repelled, diffusion of inorganic ions is promoted, and the compressive strength of the polyether sulfone-polyamide-graphene quantum dot ternary matrix reaches 8-12 MPa.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly relates to a tap water mineralization filter element based on high metasilicate element induction. Background Art

[0002] Traditional mineralization filter elements mostly use single-component silicate materials as mineralization media. Although such materials have a certain ability to dissolve calcium and magnesium ions, their specific surface area is usually limited to the range of 50-120 m² / g, resulting in the mineralization rate being difficult to break through the threshold of 60 mg Moreover, the magnesium aluminum silicate material prepared by the conventional sintering method is prone to delamination of the layered structure under the impact of dynamic water flow. After 60-90 days of use, the mineralization efficiency attenuation rate can reach 35%-50%, and the nano-scale particles generated by the delamination will cause the risk of secondary pollution.

[0003] In terms of filtration and antibacterial, the existing technologies mostly directly load silver-based antibacterial agents on activated carbon or ceramic substrates. This simple composite method has two major defects: First, the silver ion release rate is uncontrollable. The initial high concentration may exceed the drinking water safety standard, and the antibacterial efficiency drops sharply due to the agglomeration of silver particles in the later stage; Second, the pore structure of the traditional filter layer is single. When treating water bodies containing organic pollutants or heavy metals, the micropores are easily blocked, resulting in an increase in water flow resistance of 8-12 kPa per month, seriously restricting the service life of the filter element. The test data of the mainstream products in the market show that the 24-hour antibacterial rate of such filter elements against Gram-negative bacteria is generally lower than 95%, and the interception rate of heavy metal ions such as lead and cadmium is less than 80%.

[0004] Existing filter elements mostly adopt a homogenized support structure. The mechanical strength of traditional polymer matrices such as polypropylene and polyethylene is difficult to withstand the expansion stress of the mineralization layer, and microcracks are easily generated under the working conditions of temperature and humidity changes. More critically, such materials lack functional modification and cannot achieve the directional transport of mineralization elements, resulting in 40%-60% of the mineralization components remaining inside the filter element and unable to be effectively released. Hydrodynamic simulation shows that the traditional straight-through pore design will cause more than 30% of the water flow short-circuit phenomenon, significantly reducing the mineral contact efficiency.

[0005] Although there have been research attempts to introduce nanomaterials for improvement in recent years, they often fall into the dilemma of technical imbalance: either over-pursuing a high specific surface area leads to deterioration of the mechanical strength of the material, or focusing on improving the antibacterial performance at the expense of the mineralization function. For example, a certain type of carbon nanotube composite filter element can achieve a 99% antibacterial rate, but its calcium ion dissolution amount is only 35-40 mg / L, and the manufacturing cost increases by more than 300%. These technical defects make it difficult for existing mineralization filter elements to meet the dual requirements of balanced mineral supplementation and microbial safety in the "Healthy Direct Drinking Water Quality Standard".

[0006] Therefore, the development of new filter elements with bionic mineralization pathways, intelligent antibacterial mechanisms, and integrated structural functions has become an urgent need in the industry. Summary of the Invention

[0007] (I) Technical Problems to be Solved In view of the deficiencies of the prior art, the present invention provides a tap water mineralization filter element based on high metasilicate element induction.

[0008] (II) Technical Solutions A tap water mineralization filter element based on high metasilicate element induction is coaxially provided with a support structure, a mineralization functional core structure, and a filtering and protective structure from the inside out; The support structure is formed by a stepwise thermal crosslinking process of a ternary blend of polyethersulfone, polyamide, and graphene quantum dots, wherein the mass ratio of polyethersulfone is 55%-65%, polyamide is 25%-35%, and graphene quantum dots are 5%-10%. The chemical structural formula of the polyethersulfone is: wherein the typical degree of polymerization n is 50-100, and the molecular weight range Mw is 25000-50000 Da. The chemical structural formula of the polyamide is: wherein m is 100-200, corresponding to Mw of 10000-20000 Da. The particle size of the graphene quantum dots is 2-5 nm and the surface carboxylation modification degree is greater than 0.8 functional groups per square nanometer; The thermal crosslinking process is specifically divided into three stages: the first stage is preheating treatment at 120-140 °C for 1-1.5 h to plasticize the material, the second stage is the main crosslinking reaction at 180-200 °C for 2-3 h, and the third stage is post-curing treatment at 220-230 °C for 0.5-1 hour. The finally formed porous matrix has a porosity of 38%-42%, a pore size distribution of 50-200 nm, and a compressive strength of 8-12 MPa; The mineralization functional core structure is composed of three components: a layered magnesium aluminum silicate carrier, rare earth-doped hydroxyapatite, and an ion-imprinted polymer. The chemical composition of the layered magnesium aluminum silicate is Mg3Al2Si4O 12 (OH)4·2H2O, the specific surface area measured by the BET method is 220-250 m² / g, and the layer spacing measured by X-ray diffraction is 1.2-1.5 nm; the chemical formula of the rare earth-doped hydroxyapatite is Ca 9.8 Eu 0.2 (PO4)6(OH)2, wherein the molar doping amount of europium ions is 0.8%-1.0%, and the grain size is 35-45 nm; The filtering and protective structure is composed of zirconia-coated silver-doped titanium dioxide nanotube arrays. The diameter of the nanotubes is 80-120 nm, the wall thickness is 8-12 nm, the atomic doping concentration of silver element is 0.8%-1.2%, the zirconia coating layer is formed by atomic layer deposition technology and the thickness is 5-8 nm. The porosity of the nanotube arrays is measured by mercury intrusion method to be 65%-75%. Based on the ternary composite mineralization system, the filter element realizes multi-path collaborative mineralization in dynamic water flow. The surface-modified magnesium aluminum silicate carrier makes the dissolution rate reach 1.2-1.5 mg / (cm³·min), which is 50%-70% higher than that of traditional silicate materials; The doped hydroxyapatite reduces the mineral dissolution activation energy to 28-32 kJ / mol through lattice distortion effect, promoting the continuous release of calcium ions.

[0009] Preferably, the hyperbranched polyamide-amine crosslinking promoter added in the support structure has a three-generation branched structure, its molecular weight is 1200-1500 Da, the content of terminal amino groups is greater than 2.5 mmol / g, and the addition amount in the blend is 1.0%-1.8% of the mass of polyethersulfone. The addition method is to ultrasonically disperse it with graphene quantum dots in N,N-dimethylacetamide solvent for 30-45 minutes to form a composite colloid, and then melt-blend it with polyethersulfone and polyamide. The compressive strength of the polyethersulfone-polyamide-graphene quantum dot ternary matrix reaches 8-12 MPa, which is 160%-240% higher than that of the traditional PP matrix.

[0010] Preferably, the 2-aminoethylphosphonic acid monolayer surface-modified on the layered magnesium aluminum silicate carrier is formed by a self-assembly process. Specifically, the purified carrier material is immersed in a 2-aminoethylphosphonic acid ethanol solution with a concentration of 0.05-0.1 mol / L, magnetically stirred and reacted at 50-60 °C for 6-8 h, then centrifugally washed with absolute ethanol 3-5 times, and finally freeze-dried under a vacuum of less than 10 Pa for 12-24 h. The thickness of the formed monolayer is measured by atomic force microscopy to be 0.8-1.2 nm, and the surface concentration of phosphorus element is analyzed by X-ray photoelectron spectroscopy to be 2.5-3.0 atomic percentage.

[0011] Preferably, the zirconia-coated silver-doped titanium dioxide nanotube arrays are prepared by anodic oxidation method, photochemical reduction method and atomic layer deposition technology. The anodic oxidation method uses titanium foil as the raw material, oxidizes it in an ethylene glycol solution containing 0.5%-1.0% ammonium fluoride and an electrolyte with an oxidation voltage of 30-50 V for 2-4 h to form a titanium dioxide nanotube substrate; the photochemical reduction method immerses the substrate in a 0.01-0.05 mol / L silver nitrate solution, and under an ultraviolet light intensity of 50-80 mW / cm 2Reduce for 10 - 30 minutes in the environment to form silver - loaded nanoparticles; for the atomic layer deposition technology, zirconium tetrachloride and deionized water are used as precursors, and at a temperature of 200 - 250 °C, the number of cycles is 50 - 100 times, and the single - cycle deposition thickness is 0.05 - 0.1 nanometers to form a zirconia - coated layer.

[0012] Preferably, a gradient doping structure is provided in the tube wall of the nanotube array, where the silver concentration decreases linearly from the tube orifice to the tube bottom. The percentage of silver atoms at the tube orifice is 1.0% - 1.2%, and at the tube bottom is 0.3% - 0.5%. The gradient change rate is measured by the slope of the energy spectrum line scan to be 0.05% - 0.08% per nanometer.

[0013] Preferably, the rare - earth - doped hydroxyapatite is prepared by mixing calcium nitrate, diammonium hydrogen phosphate and europium nitrate in a molar ratio of calcium:phosphorus:europium of 9.8:6:0.2, and adding 1.0 - 2.0 mol / L sodium citrate as a morphology - controlling agent; Perform hydrothermal reaction for 24 - 48 h at a reaction temperature of 160 - 180 °C under the condition of pH being 10.5 - 11.0.

[0014] Preferably, disperse the calcined hydroxyapatite in a Tris buffer solution containing 0.1 - 0.3 g / L graphene oxide, add dopamine hydrochloride to a final concentration of 1.0 - 2.0 g / L, and magnetically stir and react for 12 - 24 hours to finally form a polydopamine - graphene oxide composite layer with a thickness of 15 - 25 nanometers. The carbon - oxygen atomic ratio is measured by elemental analysis to be 2.3:1 - 2.8:1.

[0015] Preferably, the pore size distribution of the ion - imprinted polymer is a bimodal structure. The first peak is 1.2 - 1.5 nm corresponding to the calcium ion transport channel, and the second peak is 3.0 - 4.0 nm corresponding to the silicate ion diffusion channel.

[0016] Preferably, under the condition of an influent calcium ion concentration of 20 mg / L, after treatment by the filter element, the effluent calcium ion concentration reaches 85 - 115 mg / L, the metasilicic acid concentration is 30 - 45 mg / L, and the magnesium ion concentration is 5 - 8 mg / L; the antibacterial rate against Escherichia coli ATCC 25922 is greater than 99.99%, and the antibacterial rate against Staphylococcus aureus ATCC 6538 is greater than 99.95%; after continuously operating for 200 days at a flux of 10 L / h, the attenuation rate of the calcium ion dissolution efficiency is less than 7.5%, and the attenuation rate of the metasilicic acid concentration is less than 9.2%.

[0017] (III) Beneficial technical effects Compared with the existing technology, the beneficial effects of the present invention are: 1. Significantly improved mineralization efficiency. Based on the ternary composite mineralization system, the filter element achieves multi-path collaborative mineralization in dynamic water flow. The surface-modified magnesium aluminum silicate carrier enables the dissolution rate to reach 1.2 - 1.5 mg / (cm³·min), which is 50% - 70% higher than that of traditional silicate materials; Doped hydroxyapatite reduces the activation energy of mineral dissolution to 28 - 32 kJ / mol through the lattice distortion effect, promoting the continuous release of calcium ions; The ion-imprinted polymer selectively adsorbs water to promote the supersaturated precipitation of CaCO3, stabilizing the calcium ion concentration in the effluent at 85 - 115 mg / L and metasilicic acid at 30 - 45 mg / L, meeting the standards of high-quality mineral water.

[0018] 2. Enhanced antibacterial performance. The ZrO2 coating regulates the release rate ≤ 0.05 mg / L, while ensuring an antibacterial rate > 99.99% and avoiding the risk of silver ion over-standard; The TiO2 nanotube array generates reactive oxygen species under visible light, producing a surface plasmon resonance effect with Ag nanoparticles, increasing the sterilization efficiency by 3 - 5 times; The contact angle of the pH-responsive coating reaches 120° at pH 6.0, effectively repelling organic pollutants, and drops to 35° at pH 8.0, promoting the diffusion of inorganic ions and reducing the fouling rate by 62%.

[0019] 3. Breakthrough in structural stability and lifespan. The compressive strength of the polyethersulfone - polyamide - graphene quantum dot ternary matrix reaches 8 - 12 MPa, which is 160% - 240% higher than that of the traditional PP matrix; The supramolecular coating achieves self-healing within 48 hours through host-guest interactions at microcracks less than 50 μm, restoring more than 90% of its mechanical properties; 4. Improved environmental adaptability. The zwitterionic polymer coating maintains a mineralization efficiency fluctuation < 5% within the pH range of 5.5 - 8.5, adapting to water quality differences in different regions; The glass transition temperature of the support structure reaches 215 - 225 °C, and the deviation of mineralization efficiency is < 3% at water temperatures of 40 - 80 °C.

[0020] 5. Advantages in industrial application. The stepwise thermal cross-linking and ALD deposition processes match the existing injection molding production line, reducing the transformation cost by 40%; The dosage of the hyperbranched polyamidoamine cross-linking agent is only 0.8% - 1.5%, promoting the directional distribution of graphene quantum dots; The entire process is free of cyanide and heavy metal catalysts, and the COD emission in the wastewater is < 50 mg / L. Description of the Drawings

[0021] Figure 1 is a three-dimensional structural schematic diagram of the self-induced tap water mineralization filter element based on high metasilicic acid elements proposed by the present invention; Figure 2 is the attenuation rate and the effluent after 180 days in the examples and comparative examples Test results of concentration; Figure 3 It is the mineralization attenuation fitting curve of Example 1 within 180 days. Specific implementation method

[0022] Example 1 Preparation of support structure: Polyethersulfone (PES), polyamide (PA) and carboxylated graphene quantum dots (GQD) are mixed in a mass ratio of 60:30:10. Among them, the particle size D50 of PES is 45μm, PA is of the BASF Ultramid® B3S model with a melt index of 12g / 10min, and GQD of the Nanjing Xianfeng Company GQD-COOH-5nm specification is selected. The mixed material is ultrasonically dispersed in N,N-dimethylacetamide solvent for 2 hours, and then injected into a mold to implement three-stage thermal cross-linking: Plasticization stage: Process at 130°C ± 5°C and a pressure of 0.8MPa for 1 hour to form a primary pore network; Main cross-linking stage: Process at 190°C ± 5°C and a pressure of 2.5MPa for 2.5 hours, with a cross-linking degree of 85%; Post-curing stage: Process at 225°C ± 5°C and a pressure of 5.0MPa for 0.7 hours, with a final porosity of 38% - 42% and a compressive strength of 10.5MPa.

[0023] Construction of mineralization functional layer: Magnesium aluminum silicate carrier: Synthesize Mg3Al2Si4O 12 (OH)4·2H2O precursor with a molar ratio of magnesium to aluminum of 1.8:1. The hydrothermal crystallization conditions are 180°C / 72h. After selective etching with 0.1M HCl for 4 hours, the surface is modified with 0.08M 2-aminoethylphosphonic acid ethanol solution, and the modification density is 1.6 molecules / nm²; Rare earth hydroxyapatite: Hydrothermally synthesized according to the molar ratio of Ca:PO4:Eu = 9.8:6:0.2, adding 1.5M sodium citrate as a morphology control agent, and calcined in an argon atmosphere at 550°C for 3 hours, with a grain size of 38 ± 5nm; Ion imprinted polymer: Using as a template, 4-vinylbenzeneboronic acid and N,N'-methylenebisacrylamide are cross-linked in a molar ratio of 4:1, and a bimodal pore size structure of 1.5nm / 3.8nm is formed after dynamic elution.

[0024] Preparation of filter protection layer: ZrO2@Ag-TiO2 nanotube array: Prepare a TiO2 nanotube substrate by anodizing a titanium foil, photoreductively load Ag nanoparticles, and deposit a 5nm thick ZrO2 coating by ALD; MXene / GO Hybrid Membrane: Ti3C2Tx MXene was prepared by HF etching of Ti3AlC2 and ultrasonically compounded with graphene oxide at a mass ratio of 1:1, with an interlayer spacing of 1.2 nm.

[0025] Performance Data: The initial calcium ion dissolution amount was 108.3 mg / L, and the metasilicic acid was 38.5 mg / L; After 180 days, the calcium ion dissolution amount was 89.7 mg / L (attenuation rate 17.2%), and the antibacterial rate was 99.99%.

[0026] Example 2 Improvements: Mineralized layer enhancement: On the basis of Example 1, the interlayer spacing of the magnesium aluminum silicate carrier layer was expanded to 1.5 nm, The doping amount was increased to 1.0 mol%; Filtration layer optimization: 0.5% Ti3C2Tx@GO composite membrane was added, and ZrO2 was deposited by gradient ALD process, with 1.2 at% Ag at the pipe orifice and 0.5 at% Ag at the pipe bottom; Support structure strengthening: The addition amount of hyperbranched polyamidoamine was increased to 1.5%, and the molecular weight was 1500 Da.

[0027] Performance improvement: The initial calcium ion dissolution amount was 112.5 mg / L, and the attenuation rate after 180 days was reduced to 13.5%; The Pb²⁺ rejection rate was 99.92%, an increase of 0.09 percentage points compared with Example 1.

[0028] Example 3 Material adjustment: The dosage of GQD was reduced to 8%, PA was increased to 32%, and the MXene / GO composite membrane was replaced with a single-layer GO membrane; Process simplification: The number of ALD cycles was reduced from 80 to 60, and the ZrO2 layer thickness was 6.5 nm; Mineralized layer optimization: The doping amount was reduced to 0.8 mol%, and the ratio of the ion-imprinted polymer cross-linking agent was adjusted to 3:1.

[0029] Performance performance: The initial calcium ion dissolution amount was 103.6 mg / L, and the attenuation rate after 180 days was 17.8%; The production cost was reduced by 12.3% compared with Example 1, and the antibacterial rate of 99.95% was still maintained.

[0030] Control Example Structure and materials: Support structure: Homogeneous polypropylene (PP) was injection-molded, with a porosity of 25% and a compressive strength of 4.2 MPa; Mineralization layer: Ordinary magnesium aluminum silicate (Mg3Al2Si3O 10 (OH)2), specific surface area 92 m² / g, without surface modification; Filter layer: Mechanical mixture of activated carbon / silver particles (Ag content 0.5 wt%), without coating structure.

[0031] Performance defects: The initial calcium ion dissolution amount is only 58.3 mg / L, and the attenuation rate is as high as 63.1% after 180 days; The release of silver ions is uncontrollable. The release amount is 0.12 → 0.03 mg / L from 0 to 30 days, and the antibacterial rate drops to 82.7% after 90 days; The pressure drop increases at a rate of 1.2 kPa / month, and the service life is less than 90 days.

[0032] Comprehensive comparison table: Data for generating the mineralization attenuation curve in Example 1: Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A tap water mineralization filter element based on high metasilicic acid element induction, characterized by: From the inside to the outside, a support structure, a mineralization function core structure and a filtering protection structure are coaxially arranged in sequence; The support structure is formed by a ternary blend of polyethersulfone, polyamide and graphene quantum dots through a step-by-step thermal crosslinking process, wherein the mass proportion of polyethersulfone is 55%-65%, the mass proportion of polyamide is 25%-35%, and the mass proportion of graphene quantum dots is 5%-10%. The chemical structure of the polyethersulfone is: The typical degree of polymerization n is 50-100, the molecular weight range Mw is 25000-50000Da, and the chemical structure of the polyamide is: Wherein m is 100-200, corresponding to Mw of 10000-20000Da, the particle size of the graphene quantum dots is 2-5nm and the surface carboxylation modification degree is greater than 0.8 functional groups per square nanometer; The thermal cross-linking process is specifically divided into three stages: the first stage is preheating at 120-140°C for 1-1.5h to plasticize the material, the second stage is performing the main cross-linking reaction at 180-200°C for 2-3h, and the third stage is post-curing at 220-230°C for 0.5-1h. The porous matrix finally formed has a porosity of 38%-42%, a pore size distribution of 50-200nm, and a compressive strength of 8-12MPa. The mineralization functional core structure is composed of three components: a layered magnesium aluminum silicate carrier, rare earth doped hydroxyapatite and an ion imprinted polymer, wherein the chemical composition of the layered magnesium aluminum silicate is Mg3Al2Si4O 12 (OH)4·2H2O, the specific surface area is 220-250㎡ / g as determined by the BET method, and the interlayer spacing is 1.2-1.5nm as determined by X-ray diffraction; the chemical formula of rare earth-doped hydroxyapatite is Ca 9.8 Eu 0.2 (PO4)6(OH)2, wherein the molar doping amount of europium ions is 0.8%-1.0% and the grain size is 35-45nm; The filtering protection structure is composed of a zirconium oxide-coated silver-doped titanium dioxide nanotube array, wherein the nanotube diameter is 80-120 nm, the tube wall thickness is 8-12 nm, the atomic doping concentration of the silver element is 0.8%-1.2%, the zirconium oxide coating layer is formed by an atomic layer deposition process and has a thickness of 5-8 nm, and the porosity of the nanotube array is 65%-75% as measured by mercury intrusion.

2. The high metasilicic acid element-based induction tap water mineralization filter element according to claim 1, characterized in that: The hyperbranched polyamide-amine cross-linking promoter added to the support structure has a three-generation branched structure, a molecular weight of 1200-1500Da, an end group amine content of more than 2.5mmol / g, and an addition amount in the blend of 1.0%-1.8% of the mass of polyethersulfone. The addition method is to pre-ultrasonic disperse it with graphene quantum dots in N,N-dimethylacetamide solvent for 30-45min to form a composite colloid, and then melt-blended with polyethersulfone and polyamide.

3. The high metasilicic acid element-based induction tap water mineralization filter element according to claim 1, characterized in that: The 2-aminoethylphosphonic acid monolayer modified on the surface of the layered magnesium aluminum silicate carrier is formed by a self-assembly process, specifically, the purified carrier material is immersed in a 2-aminoethylphosphonic acid ethanol solution with a concentration of 0.05-0.1 mol / L, and reacted for 6-8 hours under magnetic stirring at 50-60° C., and then centrifugally washed with anhydrous ethanol for 3-5 times, and finally freeze-dried for 12-24 hours under a vacuum degree of less than 10 Pa. The thickness of the formed monolayer is measured to be 0.8-1.2 nm by atomic force microscopy, and the surface concentration of phosphorus is 2.5-3.0 atomic percent by X-ray photoelectron spectroscopy analysis.

4. The high metasilicic acid element-based induction tap water mineralization filter element according to claim 1, characterized in that: The zirconium oxide-coated silver-doped titanium dioxide nanotube array is prepared by anodization, photochemical reduction, and atomic layer deposition technology. The anodization method uses titanium foil as a raw material, oxidizes it in an electrolyte containing 0.5%-1.0% ammonium fluoride in ethylene glycol solution and an oxidation voltage of 30-50V for 2-4 hours to form a titanium dioxide nanotube substrate; the photochemical reduction method immerses the substrate in a 0.01-0.05 mol / L silver nitrate solution and exposes it to ultraviolet light at an intensity of 50-80 mW / cm 2 The process is carried out in an environment of 10-30 minutes to form loaded silver nanoparticles; the atomic layer deposition technology uses zirconium tetrachloride and deionized water as precursors, cycles 50-100 times at a temperature of 200-250°C, and a single cycle deposition thickness of 0.05-0.1 nanometers to form a coated zirconium oxide layer.

5. The high metasilicic acid element-based induction tap water mineralization filter element according to claim 4, characterized in that: The nanotube array has a gradient doping structure in the tube wall, wherein the silver concentration decreases linearly from the tube mouth to the tube bottom, the silver atomic percentage at the tube mouth is 1.0%-1.2%, and at the tube bottom is 0.3%-0.5%, and the gradient change rate is measured by energy spectrum line scanning and the slope is 0.05%-0.08% per nanometer.

6. The high metasilicic acid element-based induction tap water mineralization filter element according to claim 1, characterized in that: The rare earth doped hydroxyapatite is prepared by mixing calcium nitrate, diammonium hydrogen phosphate and europium nitrate in a calcium-phosphorus-europium molar ratio of 9.8:6:0.2, and adding 1.0-2.0 mol / L sodium citrate as a morphology control agent; The hydrothermal reaction was carried out at a pH of 10.5-11.0 for 24-48 hours and a reaction temperature of 160-180°C.

7. The high metasilicic acid element-based induction tap water mineralization filter element according to claim 6, characterized in that: The calcined hydroxyapatite is dispersed in a Tris buffer containing 0.1-0.3 g / L graphene oxide, dopamine hydrochloride is added to a final concentration of 1.0-2.0 g / L, and the mixture is reacted by magnetic stirring for 12-24 hours. The final composite layer has a thickness of 15-25 nanometers and a carbon-oxygen atomic ratio of 2.3:1-2.8:1 as determined by elemental analysis.

8. The high metasilicic acid element-based induction tap water mineralization filter element according to claim 1, characterized in that: The pore size distribution of the ion-imprinted polymer is a bimodal structure, wherein the first peak value is 1.2-1.5 nm corresponding to the calcium ion transmission channel, and the second peak value is 3.0-4.0 nm corresponding to the silicate ion diffusion channel.

9. The high metasilicic acid element-based induction tap water mineralization filter element according to claim 1, characterized in that: Under the condition of influent calcium ion concentration of 20 mg / L, the effluent calcium ion concentration reaches 85-115 mg / L, the metasilicic acid concentration is 30-45 mg / L, and the magnesium ion concentration is 5-8 mg / L after filter treatment; the antibacterial rate against Escherichia coli ATCC 25922 is greater than 99.99%, and the antibacterial rate against Staphylococcus aureus ATCC 6538 is greater than 99.95%; after continuous operation for 200 days at a flux of 10L / h, the calcium ion dissolution efficiency attenuation rate is less than 7.5%, and the metasilicic acid concentration attenuation rate is less than 9.2%.

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