Composite gel microspheres capable of efficiently adsorbing fluorine ions as well as preparation method and application of composite gel microspheres

Abstract

The invention discloses composite gel microspheres capable of efficiently adsorbing fluorine ions and a preparation method and application of the composite gel microspheres, and belongs to the technical field of removal of fluorine ions from tea soup. Then mixing with equivalent hydroxyapatite to form carboxymethyl cellulose / hydroxyapatite suspension, extruding the carboxymethyl cellulose / hydroxyapatite suspension into an aluminum chloride aqueous solution by a disposable syringe at a constant speed through a peristaltic pump to form white hydrogel beads, soaking the white hydrogel beads in an aluminum chloride coagulating bath, washing, performing freeze-forming, and performing freeze-drying to obtain the hydrogel. The hydroxyapatite / carboxymethyl cellulose / aluminum chloride composite aerogel microspheres are prepared. According to the invention, a good adsorption effect on fluorides in tea soup crude substances can be realized, and the flavor and nutrient substances of brick tea soup can be effectively retained.

Description

Technical Field

[0001] The present invention discloses a composite gel microsphere capable of efficiently absorbing fluoride ions, a preparation method and an application thereof, and specifically relates to a carboxymethyl cellulose / aluminum chloride / hydroxyapatite composite aerogel microsphere capable of efficiently absorbing fluoride ions in tea soup, a preparation method thereof, and an application thereof in removing fluoride ions in tea soup, belonging to the technical field of removing fluoride ions from tea soup. Background Art

[0002] Tea is a beverage consumed worldwide. Mature leaves of the tea plant accumulate fluoride excessively, and its effects on human health are concentration-dependent, with the lowest intake (0.4-1.0 mg / L) promoting bone and tooth development. It is generally considered safe for tea to contain fluoride at levels below 300 mg / kg. However, some types of tea, such as brick tea, may contain higher fluoride levels. Excessive intake of fluoride can lead to fluorosis, which includes diseases such as arthritis, osteoporosis, and skeletal muscle problems.

[0003] Hydroxyapatite is a calcium phosphate mineral that is known to specifically adsorb fluoride. The interaction between hydroxyapatite and fluoride primarily involves the hydroxyl groups within the hydroxyapatite lattice, which undergo ion exchange with fluoride ions. In addition, surface functional groups can participate in chemical reactions during adsorption or precipitation. Although it is effective in certain fluoride removal situations, unmodified hydroxyapatite often has limited ability to adsorb fluoride. This limitation has inspired the development of hydroxyapatite composites, however, the application of hydroxyapatite-based nanoparticles as adsorbents faces the challenge of recovery from solution after removal. Therefore, immobilizing these particles in a polymer matrix is ​​considered a potential solution to facilitate adsorbent recovery. For example, Chinese patent CN117923446A discloses a hydroxyapatite with high efficiency in adsorbing fluoride ions and its preparation method. The method modifies nano-hydroxyapatite with a mixture of stearic acid and arginine to solve the crystal agglomeration problem of hydroxyapatite, then adds calcium nitrate tetrahydrate, diammonium hydrogen phosphate and ferrous chloride tetrahydrate to obtain hydroxyapatite composite powder through polymerization reaction, and then adds pore-forming agent and adhesive to make spherical particles, which can be used for the adsorption of fluoride ions, heavy metal ions and organic pollutants in mine water. However, whether the hydroxyapatite composite material prepared by the patented method can be used to remove fluoride ions in tea soup while ensuring that the flavor and nutrients of the tea soup are not lost remains to be verified.

[0004] In order to reduce the content of fluorine compounds in brick tea soup, Chinese patent CN106472958B discloses a method for efficiently and selectively reducing fluorine ions in high-fluorine foods. The method uses MOFs materials (i.e. metal-organic framework materials, in which metal ions can be aluminum ions and organic ligands can be heterocyclic compounds with alkyl groups) as adsorbents for high-fluorine food tea, which can effectively remove fluorine ions from food. When adsorbing fluorine ions in brick tea soup, the fluorine content of the tea soup can be reduced from 8.45 mg / L to 5.91 mg / L, and the fluorine reduction reaches 30%, which will hardly affect the original flavor substances / active substances / nutrients in the food. The total content loss rate of caffeine, catechins and polyphenols in the tea soup is small.

[0005] It can be seen that there is no report on carboxymethyl cellulose / aluminum chloride / hydroxyapatite composite aerogel microspheres that are specifically used for removing fluoride ions from brick tea and can ensure that the flavor and nutrients of the tea soup are not lost. Summary of the invention

[0006] The purpose of the present invention is to provide a composite gel microsphere for efficiently absorbing fluoride ions and a preparation method and application thereof, which can efficiently absorb fluoride in tea soup and retain flavor and nutrients.

[0007] The present invention is achieved through the following technical solution: a method for preparing composite gel microspheres for efficiently adsorbing fluoride ions, comprising the following steps:

[0008] S1. Dissolve 1-2% carboxymethyl cellulose in water and stir until transparent to obtain a carboxymethyl cellulose solution;

[0009] S2. Mixing an equal amount of 1-2% hydroxyapatite and carboxymethyl cellulose solution and stirring to form a carboxymethyl cellulose / hydroxyapatite suspension;

[0010] S3. The carboxymethyl cellulose / hydroxyapatite suspension is uniformly extruded into a 0.5-1% aluminum chloride aqueous solution using a disposable syringe through a peristaltic pump to form white hydrogel beads, which are then immersed in an aluminum chloride coagulation bath for 12-16 hours;

[0011] S4. The soaked hydrogel beads are washed, freeze-formed, and freeze-dried to obtain hydroxyapatite / carboxymethyl cellulose / aluminum chloride composite aerogel microspheres.

[0012] In step S2, the mixing and stirring time is controlled within 1 to 2 hours.

[0013] In step S3, the rate of the peristaltic pump is controlled to be 2-3 mL / min.

[0014] In the step S4, the hydrogel beads are washed with deionized water.

[0015] In the step S4, the molding is performed by freezing at -80°C.

[0016] In the step S4, freeze drying is performed using a vacuum freeze dryer.

[0017] A composite gel microsphere with high efficiency in adsorbing fluoride ions prepared by the above preparation method, wherein the composite gel microsphere has an adsorption and removal efficiency of more than 95% for a fluoride ion solution with an initial concentration of 11.36 mg / L.

[0018] The composite gel microspheres can absorb fluoride ions in tea soup, and the tea soup adsorbed by the composite gel microspheres contains at least the following components:

[0019] Volatile substances such as methyl heptenone, acetophenone, camphor, tea ketone, β-dihydroionone, hexanal, safranal, decanal, β-cyclocitral, 2-ethylhexanol, linalool, cedarwood, eucalyptol and (E)-linalool oxide, caffeine (CAF), catechins such as epigallocatechin gallate (EGCG), epicatechin gallate (ECG), epigallocatechin (EGC), epicatechin (EC) and catechin (C).

[0020] Furthermore, the tea soup after adsorption by the composite gel microspheres meets the following indicators: methyl heptenone ≥55%, acetophenone ≥50%, camphor ≥85%, tea ketone ≥95%, β-dihydroionone ≥50%, hexanal ≥50%, safranal ≥65%, decanal ≥70%, β-cyclocitral ≥75%, 2-ethylhexanol ≥75%, linalool ≥75%, cedarwood ≥70%, eucalyptol ≥60%, (E)-linalool oxide ≥50%, caffeine content ≥90%, epigallocatechin gallate content ≥90%, epicatechin gallate content ≥75%, epigallocatechin content ≥70%, epicatechin content ≥85% and catechin content ≥75%.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] (1) In the present invention, equal amounts of hydroxyapatite and carboxymethyl cellulose solution are mixed and stirred to form a carboxymethyl cellulose / hydroxyapatite suspension, which is beneficial to the formation of an aerogel structure. By controlling the amount of hydroxyapatite and carboxymethyl cellulose solution, the mechanical properties of the aerogel can be effectively maintained, the aerogel is not easy to break, and has good adsorption performance.

[0023] (2) The present invention can promote gel formation by using a crosslinking agent. In the gel preparation process, the structure of the aerogel can be made more stable by reasonably controlling the extrusion rate of the carboxymethyl cellulose / hydroxyapatite suspension, thereby avoiding the problems of unstable aerogel structure and slow preparation efficiency. At the same time, by reasonably controlling the mass concentration of aluminum chloride, immersion time and other parameters, not only can the effective crosslinking reaction be ensured, but also the leakage hazard easily caused by excessive Al3+ adsorption can be avoided (excessive Al ingestion by the human body) 3+ can lead to neurological diseases).

[0024] (3) The composite gel microspheres of the present invention form an aerogel structure through cross-linking of hydroxyapatite, carboxymethyl cellulose and aluminum chloride to achieve effective adsorption of fluoride ions in tea soup. In particular, due to the specific adsorption ability of hydroxyapatite for fluoride ions, fluoride ions can occupy the binding sites of hydroxyapatite first, so that the tea soup can still retain volatile substances, caffeine and catechins in the tea soup after the fluoride ions are adsorbed. This can be distinguished from the existing fluoride ion adsorbents for tea soup. It is a new fluoride ion aerogel product with a simple preparation method, economical cost and strong adsorption effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the adsorption efficiency diagram of Examples 1 to 5 and Comparative Examples 1-2.

[0026] Figure 2 These are images of Examples 1 to 3 and Comparative Example 2.

[0027] Figure 3 The SEM images of Example 2 and Comparative Example 2 are shown.

[0028] Figure 4 The thermogravimetric diagrams of Examples 1 to 3 and Comparative Example 2 are shown.

[0029] Figure 5 It is the infrared spectra of Example 2 and Comparative Example 1 and Comparative Example 2.

[0030] Figure 6 This is the adsorption efficiency diagram of fluoride ion, catechin and caffeine. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto, and the "%" in the present invention refers to mass concentration.

[0032] Example 1: CMC-Al / HAP-1

[0033] This embodiment relates to the specific preparation process of carboxymethyl cellulose / aluminum chloride / hydroxyapatite composite aerogel microspheres (CMC-Al / HAP-1).

[0034] First, 2% carboxymethyl cellulose was dissolved in deionized water and stirred until transparent to obtain a carboxymethyl cellulose solution; an equal amount of 1% hydroxyapatite and the above carboxymethyl cellulose solution were mixed and stirred for 1 hour to form a carboxymethyl cellulose / hydroxyapatite suspension; the carboxymethyl cellulose / hydroxyapatite suspension was taken and pumped by a peristaltic pump using a disposable syringe. 2 mL / min at a uniform speed to extrude into a 1% aluminum chloride aqueous solution to form white hydrogel beads, which were then immersed in the aluminum chloride coagulation bath for 12 hours; the immersed beads were taken out, washed with deionized water to completely remove the residual reactants, and then placed in a -80°C environment for freezing and forming, and then dried using a vacuum freeze dryer (the vacuum degree was adjusted to 0.8Pa , the temperature is -50℃ ) Freeze-dried 24 h, to obtain CMC-Al / HAP-1.

[0035] Example 2: CMC-Al / HAP-2

[0036] This example relates to the specific preparation process of carboxymethyl cellulose / aluminum chloride / hydroxyapatite composite aerogel microspheres (CMC-Al / HAP-2). However, the preparation process of this example is exactly the same as that of Example 1, and the only difference is that 2% hydroxyapatite is used when forming the carboxymethyl cellulose / hydroxyapatite suspension.

[0037] Example 3: CMC-Al / HAP-3

[0038] This example relates to the specific preparation process of carboxymethyl cellulose / aluminum chloride / hydroxyapatite composite aerogel microspheres (CMC-Al / HAP-2). However, the preparation process of this example is exactly the same as that of Example 1, and the only difference is that 4% hydroxyapatite is used when forming the carboxymethyl cellulose / hydroxyapatite suspension.

[0039] Example 4: CMC-Al / HAP-4

[0040] This embodiment relates to the specific preparation process of carboxymethyl cellulose / aluminum chloride / hydroxyapatite composite aerogel microspheres (CMC-Al / HAP-4).

[0041] First, 1% carboxymethyl cellulose was dissolved in deionized water and stirred until transparent to obtain a carboxymethyl cellulose solution; an equal amount of 2% hydroxyapatite and the above carboxymethyl cellulose solution were mixed and stirred for 2 hours to form a carboxymethyl cellulose / hydroxyapatite suspension; the carboxymethyl cellulose / hydroxyapatite suspension was taken and pumped by a peristaltic pump using a disposable syringe. 1mL / min at a uniform speed to extrude into a 0.5% aluminum chloride aqueous solution to form white hydrogel beads, which were then immersed in the aluminum chloride coagulation bath for 16 hours; the immersed beads were taken out, washed with deionized water to completely remove the residual reactants, and then placed in a -80°C environment for freezing and forming, and then dried using a vacuum freeze dryer (the vacuum degree was adjusted to 0.8Pa , the temperature is -50℃ ) Freeze-dried 24 h, to obtain CMC-Al / HAP-4.

[0042] Example 5: CMC-Al / HAP-5

[0043] This embodiment relates to the specific preparation process of carboxymethyl cellulose / aluminum chloride / hydroxyapatite composite aerogel microspheres (CMC-Al / HAP-5).

[0044] First, 1.8% carboxymethyl cellulose was dissolved in deionized water and stirred until transparent to obtain a carboxymethyl cellulose solution; an equal amount of 2% hydroxyapatite and the above carboxymethyl cellulose solution were mixed and stirred for 1.5 hours to form a carboxymethyl cellulose / hydroxyapatite suspension; the carboxymethyl cellulose / hydroxyapatite suspension was taken and pumped by a peristaltic pump using a disposable syringe. 1.5 mL / min at a uniform speed to extrude into a 1% aluminum chloride aqueous solution to form white hydrogel beads, which were then immersed in the aluminum chloride coagulation bath for 14 hours; the immersed beads were taken out, washed with deionized water to completely remove the residual reactants, and then placed in a -80°C environment for freezing and forming, and then dried using a vacuum freeze dryer (the vacuum degree was adjusted to 0.8Pa , the temperature is -50℃ ) Freeze-dried 24 h, to obtain CMC-Al / HAP-5.

[0045] Comparative Example 1:

[0046] This comparative example involves adsorbent hydroxyapatite particles, which can be directly used for fluoride adsorption.

[0047] Comparative Example 2:

[0048] This comparative example involves carboxymethyl cellulose aerogel microspheres, and the specific preparation process is as follows:

[0049] First, 2% carboxymethyl cellulose was dissolved in deionized water and stirred until transparent to obtain a carboxymethyl cellulose solution; then the carboxymethyl cellulose solution was taken and pumped by a peristaltic pump using a disposable syringe. 2mL / min at a uniform speed to extrude into a 1% aluminum chloride aqueous solution to form white hydrogel beads, which were then immersed in the aluminum chloride coagulation bath for 12 hours; the immersed beads were taken out, washed with deionized water to completely remove the residual reactants, and then placed in a -80°C environment for freezing and forming, and then dried using a vacuum freeze dryer (the vacuum degree was adjusted to 0.8Pa , the temperature is -50℃ ) Freeze-dried 24 h, carboxymethyl cellulose / aluminum chloride composite aerogel microspheres were prepared.

[0050] The hydroxyapatite / carboxymethyl cellulose / aluminum chloride composite aerogel microspheres of Examples 1 to 5, the hydroxyapatite particles of Comparative Example 1, and the carboxymethyl cellulose / aluminum chloride composite aerogel microspheres of Comparative Example 2 were respectively used to carry out the following experiments.

[0051] (I) Comparison of fluoride adsorption performance

[0052] The determination of fluoride in the solution refers to NY / T 838-2004 "Determination of fluoride content in tea - fluoride ion selective electrode method".

[0053] Taking 20 mg / L sodium fluoride solution as the initial solution, the adsorption performance of sodium fluoride in Examples 1 to 3, Comparative Example 1 and Comparative Example 2 was investigated. The addition amount was 10 mg / mL and the adsorption time was 1 hour. The results are as follows: Figure 1 shown.

[0054] The results show that the fluoride adsorption efficiency is proportional to the hydroxyapatite content, and the higher the hydroxyapatite concentration, the stronger the adsorption effect. This trend can be attributed to the increased availability of functional groups on hydroxyapatite for fluorine binding. However, the fluorine adsorption capacity of Example 3 decreased significantly, probably due to excessive hydroxyapatite aggregation that offsets the advantage of high concentration. In summary, Example 2 was selected as the best adsorbent to study the fluoride adsorption behavior, which achieved a balance between hydroxyapatite loading and maintaining good aerogel properties for efficient ion removal.

[0055] (II) Material Characterization

[0056] (1) Macrostructure

[0057] In the synthesis of microspheres, the mass fraction of hydroxyapatite has an important influence on the mechanical strength and adsorption capacity of the prepared aerogel spheres.

[0058] like Figure 2 As shown in Figure 2, the increase in hydroxyapatite content leads to the expansion of the microspheres, which may be due to the destruction of the coordination bond between aluminum and hydroxyl groups. However, when the mass ratio is 1:2, the hollow structure is destroyed and a powdery structure is formed, indicating that the structural integrity of the microspheres will be seriously damaged when the hydroxyapatite concentration exceeds this threshold.

[0059] (2) Scanning electron microscope

[0060] The prepared composite aerogels were characterized by SEM.

[0061] Figure 3 The SEM photos of Comparative Example 2 and Example 2 are shown. It can be seen from the photos that the prepared composite aerogel exhibits a rich and porous three-dimensional fiber structure. Due to the presence of hydroxyapatite, the aerogel presents a porous sheet structure, which is conducive to the adsorption of the target substance.

[0062] (3) Thermogravimetry

[0063] Thermal stability is a key property of aerogel materials.

[0064] like Figure 4 As shown, after testing, comparative example 2 only retained 32.36% of its mass, while the addition of hydroxyapatite significantly improved the thermal stability of the microspheres, and the final residual mass was 48.76%, 51.97% and 64.30%, respectively. With the increase of hydroxyapatite content, the mass loss rate in the temperature range of 200-600°C decreased, and the temperature for reaching mass balance also increased. The results show that the addition of hydroxyapatite effectively inhibits the decomposition of the microsphere skeleton and improves the thermal stability of the composite aerogel beads.

[0065] (4) Infrared spectroscopy

[0066] Figure 5 It shows that the comparative example 1, comparative example 2 and embodiment 2 have a range of 500-4000 cm -1 FT-IR spectrum in the range.

[0067] Depend on Figure 5 Visible, 3426cm -1 The broad and strong peak at 1614cm corresponds to the OH vibration absorption peak characteristic of carboxymethyl cellulose. -1 、1399cm -1 and 1054cm -1 The peaks at 1650cm-1 belong to the asymmetric and symmetric stretching vibrations of COO- and the stretching vibration of CO. -1 The band at 604cm is related to the bending vibration of water molecules in aluminum chloride cations. -1 and 564cm -1 The peaks at 900–1100 cm -1 The peaks in the range are related to the stretching vibration of the PO bond in hydroxyapatite. The coordination interaction between the -COOH group and Al(III) in Comparative Example 2 is at 1741 cm -1However, in Example 2, 1742 cm -1 The peak at 3400-3500 cm-1 was shifted and decreased after HAP modification, which may be due to the destruction of the coordination bond between the carboxyl group and Al(III), indicating that Example 2 was transformed into a hollow structure after hydroxyapatite modification. -1 The broad absorption band centered at indicates enhanced hydrogen bonding between components.

[0068] (III) Tea Soup Adsorption Experiment (Determination of Fluoride, Catechins and Caffeine before and after Adsorption of Tea Soup in Experimental Example 2 and Comparative Example 2)

[0069] Adsorption test of fluoride and catechins was carried out using brick tea extract. Pingwu Fu brick tea was extracted at 80°C for 30 minutes with a solid-liquid ratio of 1:10 (m / v) and then cooled. The extract was then centrifuged at high speed to separate the tea residue from the supernatant. 1% (m / v) of comparative example 2 or 0.5% (m / v) of example 2 was added to the diluted tea brewing liquid and adsorbed for 40 minutes. After the adsorption was completed, the suspension was centrifuged and the supernatant was filtered through a 0.2μm PTFE membrane filter to obtain a clear filtrate for subsequent analysis.

[0070] The determination of fluoride ion concentration in tea soup refers to NY / T 838-2004 "Determination of fluoride content in tea - fluoride ion selective electrode method". The determination of caffeine (CAF) and catechin compounds in tea soup, including epigallocatechin gallate (EGCG), epicatechin gallate (ECG), epigallocatechin (EGC), epicatechin (EC), and catechin (C) refers to GB / T 8313-2018 "Determination of tea polyphenols and catechins in tea". The experimental results are shown in Table 1 and Figure 6 shown.

[0071] Table 1 Caffeine and catechins content

[0072] Compound Name Tea Comparative Example 2 Example 2 Fluoride ion 11.36±0.28a 0.61±0.01b 0.58±0.07b caffeine 491.22±19.99a 482.22±9.78a 452.99±20.3b Epigallocatechin gallate 311.28±16.85a 298.26±9.28a 288.19±10.07b Epicatechin gallate 97.32±1.23a 82.39±6.79b 75.2±5.32c Epigallocatechin 53.2±2.87a 47.23±3.33b 38.23±4.32c Epicatechin 43.27±2.67a 39.22±5.39b 37.2±1.59b Catechins 19.7±1.11a 14.3±0.29b 15.22±0.22b

[0073] From the above table 1 and Figure 6 It can be seen that the catechin and caffeine content in tea did not decrease significantly, indicating that Example 2 has good selectivity for the adsorption and removal of fluoride in brick tea. The small reduction in catechins in the sample treated in Example 2 compared with the treatment in Comparative Example 2 can be attributed to the presence of a large number of hydroxyl groups in the catechin molecules, especially adjacent hydroxyl groups. These groups can interact with other functional groups on the aerogel, such as carboxyl and amine groups, through hydrogen bonds.

[0074] (IV) Determination of volatile components

[0075] This experiment uses headspace solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) to test the volatile components in the sample, and uses the internal standard method to semi-quantitate the main components (the internal standard is ethyl decanoate, and the concentration of the internal standard solution is 20 mg / L). The concentration content of all substances is equivalent to ethyl decanoate. Specifically, the sample pretreatment and analysis conditions in the determination method are as follows:

[0076] A 5 mL aliquot of the tea solution was placed in a sealed headspace vial (20 mL) and equilibrated at 60 °C for 30 min. The volatile compounds were extracted using a 50 μm DVB / CAR / PDMS fiber needle at 60 °C for 30 min. The fiber needle was inserted into the gas chromatograph injector and thermal desorption was performed at 240 °C for 5 min. GC-MS instrument parameter settings: chromatographic column: DB-5ms (30m×0.25mm×0.25μm); helium flow rate: 1.0mL / min; heating program: 40℃ for 3min, increase to 85℃ at a rate of 3℃ / min, increase to 160℃ at a rate of 3℃ / min and maintain for 3min, then increase to 240℃ at a rate of 10℃ / min and maintain for 5min; carrier gas control mode: linear speed; carrier gas helium flow rate: 1.0mL / min; injection mode: non-divided; injection time: 1min; ion source temperature: 230℃; interface temperature: 240℃; acquisition mode: Scan.

[0077] The main volatile components and contents of Example 2 are shown in Table 2.

[0078] The main volatile components and contents of the tea soup after treatment in the tea soup, Example 2 and Comparative Example 2 are shown in Table 2.

[0079] Table 2 Main volatile components and contents

[0080]

[0081]

[0082]

[0083] Common adsorbents are known to reduce the aromatic characteristics of tea infusions. To evaluate the effect of Example 2 on the volatile components of tea infusions during fluorine adsorption, a comparative analysis of the volatile components of untreated tea infusions and tea infusions treated with the two adsorbents was performed. A total of 66 volatile compounds were identified in the control brick tea infusion, including alcohols, ketones, aldehydes, esters, alkanes, and others. The treatment of Example 2 reduced the number of volatile compounds to 50, while the treatment of Example 2 retained more volatile compounds, with 54 compounds remaining. It is noteworthy that the key flavor compounds of brick tea in the treatment of Example 2 were significantly preserved, especially those with high concentrations and low odor thresholds, such as methylheptenone, acetophenone, camphor, tea ketone, β-dihydroionone, hexanal, safranal, decanal, β-cyclocitral, 2-ethylhexanol, linalool, cedarwood, eucalyptol, and (E)-linalool oxide.

[0084] (V) Stability test

[0085] Take 5 different batches of Pingwu Fuzhuan tea to obtain tea infusion in the above manner, add 0.5% (m / v) of Example 2 to the tea infusion for adsorption for 40 minutes, centrifuge the suspension after adsorption, filter the supernatant through a 0.2 μm PTFE membrane filter to obtain a clear filtrate for subsequent analysis. Mainly analyze the content of fluorine content, caffeine, catechin compounds (epigallocatechin gallate, epicatechin gallate, epigallocatechin, epicatechin, catechin) and volatile substances (methyl heptenone, acetophenone, camphor, tea ketone, β-dihydroionone, geranylacetone, hexanal, safranal, decanal, β-cyclocitral, 2-ethylhexanol, linalool, cedarwood, eucalyptol, (E)-linalool oxide and (Z)-linalool oxide) in the tea soup before and after adsorption. The specific detection method is the same as above.

[0086] The analysis results are shown in Table 3 below.

[0087] Table 3 Component contents of different batches of tea soup before and after adsorption in Example 2

[0088]

[0089]

[0090] As can be seen from Table 3, when Example 2 is used for adsorption treatment of different batches of tea brick extracts, it can achieve an adsorption removal efficiency of more than 95% for the fluoride ion solution, and can effectively retain the content of volatile substances, caffeine and catechins in the tea soup, and has a stable treatment efficiency and good practical application prospects for tea brick extracts.

[0091] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing composite gel microspheres for efficient adsorption of fluoride ions, characterized in that: The following steps are involved: S1. Dissolve 1-2% carboxymethyl cellulose in water and stir until transparent to prepare a carboxymethyl cellulose solution; S2. Mixing and stirring equal amounts of 1-2% hydroxyapatite and carboxymethyl cellulose solution to form a carboxymethyl cellulose / hydroxyapatite suspension; S3. Using a disposable syringe and a peristaltic pump, the carboxymethyl cellulose / hydroxyapatite suspension is uniformly squeezed into a 0.5-1% aluminum chloride aqueous solution to form white hydrogel beads, which are then immersed in an aluminum chloride coagulation bath for 12-16 hours; S4. The soaked hydrogel beads are washed, freeze-formed, and freeze-dried to obtain hydroxyapatite / carboxymethyl cellulose / aluminum chloride composite aerogel microspheres.

2. The preparation method according to claim 1, characterized in that: In step S2, the mixing and stirring time is controlled within 1 to 2 hours.

3. The preparation method according to claim 1, characterized in that: In step S3, the rate of the peristaltic pump is controlled to be 2-3 mL / min.

4. The preparation method according to claim 1, characterized in that: In the step S4, the hydrogel beads are washed with deionized water.

5. The preparation method according to claim 1, characterized in that: In the step S4, the molding is performed by freezing at -80°C.

6. The preparation method according to claim 1, characterized in that: In the step S4, freeze drying is performed using a vacuum freeze dryer.

7. A composite gel microsphere with high efficiency in adsorbing fluoride ions obtained by the preparation method according to any one of claims 1 to 6, characterized in that: The composite gel microspheres have an adsorption removal efficiency of >95% for a fluoride ion solution with an initial concentration of 11.36 mg / L.

8. Use of the composite gel microspheres as claimed in claim 7 in preparing a fluoride adsorbent for tea, characterized in that: The composite gel microspheres can absorb fluoride ions in tea soup, and the tea soup after adsorption by the composite gel microspheres contains at least the following components: methyl heptenone, acetophenone, camphor, tea ketone, β-dihydroionone, hexanal, safranal, decanal, β-cyclocitral, 2-ethylhexanol, linalool, cedarwood, eucalyptol, (E)-oxidized linalool, caffeine, epigallocatechin gallate, epicatechin gallate, epigallocatechin, epicatechin and catechin.

9. The use according to claim 8, characterized in that: The tea soup after adsorption by composite gel microspheres meets the following indicators: methyl heptenone ≥ 55%, acetophenone ≥ 50%, camphor ≥ 85%, tea ketone ≥ 95%, β-dihydroionone ≥ 50%, hexanal ≥ 50%, safranal ≥ 65%, decanal ≥ 70%, β-cyclocitral ≥ 75%, 2-ethylhexanol ≥ 75%, linalool ≥ 75%, cedarwood ≥ 70%, eucalyptol ≥ 60%, (E)-linalool oxide ≥ 50%, caffeine content ≥ 90%, epigallocatechin gallate content ≥ 90%, epicatechin gallate content ≥ 75%, epigallocatechin content ≥ 70%, epicatechin content ≥ 85% and catechin content ≥ 75%.

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