Fluorine adsorbent and its preparation method and application

Abstract

The present invention provides a fluorine adsorbent and its preparation method and application, which relates to the field of adsorbent technology. The structural formula of the fluorine adsorbent is: Sn(OH) 4‑x Cl x / PVC-PVB, wherein: 0.8≤x≤1.0; the PVC-PVB is a dual binder. In the above fluorine adsorbent structural formula, Sn(OH) 4‑x Cl x The powder has the advantages of stable structure and high adsorption capacity. At the same time, the PVC-PVB dual binder can make the Sn(OH) 4‑x Cl x The PVC-PVB adsorbent beads form a network of adsorption channels, significantly improving the adsorption capacity and stability of the fluorine adsorbent. This fluorine adsorbent, when used in the treatment of fluorine-containing wastewater, offers the advantages of large adsorption capacity, stable adsorption performance, high regeneration efficiency, and efficient, harmless treatment of high-concentration fluoride ions in the regenerated liquid.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorbents, and in particular to a fluorine adsorbent and a preparation method and application thereof. Background Art

[0002] Excessive fluoride in wastewater not only causes serious environmental pollution but also has profound impacts on human health. Therefore, effective prevention and control measures and treatment technologies are essential. Currently, the treatment of low-concentration fluoride-excessive wastewater primarily relies on adsorption. The core material in this adsorption method is the adsorbent, and its performance directly affects the treatment of fluoride-containing wastewater.

[0003] For example, CN113842871A discloses an anti-interference defluorination adsorbent and its preparation method. This defluorination adsorbent can resist the interference of bicarbonate in water, but the adsorption capacity of this defluorination material is relatively low, only about 10 mg / g. CN112547021A discloses a biomass-based hydroxyapatite composite material, its preparation method, and its application. This composite material can reduce the concentration of fluoride ions in a certain amount of fluorine-contaminated water to below 1.5 mg / L. However, after adsorbing fluoride ions, the adsorbent of this invention is eluted using an alkaline salt mixture of 5wt% sodium hydroxide and 5wt% sodium chloride for 12 hours. The elution time is too long and the regeneration efficiency is extremely low. CN112755972A discloses the preparation and application of a silicon-based resin as a defluorination adsorbent. When used as a defluorination adsorbent, this silicon-based resin has high adsorption selectivity for fluoride ions, large adsorption capacity, and is recyclable. However, the synthesis process of this invention's fluoride adsorbent uses a large amount of toxic and harmful organic raw materials or solvents, which can easily cause harm to humans or the environment. CN112520811A discloses a manganese-loaded activated alumina defluoridation adsorbent and its preparation method. The provided manganese-loaded activated alumina defluoridation adsorbent and its preparation method enhance the adsorption capacity of fluoride ions, making the treated water more suitable for drinking. However, the defluoridation material of this invention cannot be regenerated and recycled. CN114082407A discloses a method for preparing a defluoridation adsorption resin. The defluoridation resin cannot achieve a fluoride ion concentration of less than 1 mg / L in the defluoridated water produced, and the high concentration of fluoride ions in the regenerated liquid is not rendered harmless.

[0004] As can be seen from the above, the existing commercially available fluorine adsorbents have the following disadvantages: low adsorption capacity, unstable adsorption performance, low regeneration efficiency, and the high concentration of fluoride ions in the regeneration liquid cannot be efficiently and harmlessly treated.

[0005] Therefore, it is necessary and urgent to research and develop a fluorine adsorbent with the advantages of large adsorption capacity, stable adsorption performance, high regeneration efficiency, and efficient and harmless treatment of high concentrations of fluoride ions in the regeneration liquid, so as to alleviate the technical problems of low adsorption capacity and unstable adsorption performance of existing fluorine adsorbents.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The first object of the present invention is to provide a fluorine adsorbent having the advantages of large adsorption capacity, stable adsorption performance, high regeneration efficiency, and efficient and harmless treatment of high-concentration fluoride ions in the regeneration liquid.

[0008] The second object of the present invention is to provide a method for preparing the above-mentioned fluorine adsorbent.

[0009] The third object of the present invention is to provide an application of the above-mentioned fluorine adsorbent in the treatment of fluorine-containing wastewater.

[0010] The fourth object of the present invention is to provide a method for treating fluorine-containing wastewater based on the above-mentioned fluorine adsorbent.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0012] The present invention provides a fluorine adsorbent, the structural formula of the fluorine adsorbent is: Sn(OH) 4-x Cl x / PVC-PVB, where: 0.8≤x≤1.0;

[0013] The PVC-PVB is a dual binder, and the fluorine adsorbent is prepared by using PVC and PVB as binders.

[0014] Furthermore, the fluorine adsorbent has a spherical structure, and the particle size of the fluorine adsorbent is 0.5 to 2 mm.

[0015] The present invention provides a method for preparing a fluorine adsorbent, the preparation method comprising:

[0016] S1 precipitation reaction: NaF-Na2CO3 solution is added dropwise to SnCl2-citric acid solution to perform precipitation reaction to obtain Sn(OH) 2-x F x slurry;

[0017] S2 oxidation reaction: Sn(OH) 2-x F x The slurry is oxidized to make Sn(OH) 2-x F x Converted to Sn(OH) 4-x F x , obtaining Sn(OH) 4-x F x slurry;

[0018] S3 drying and powdering: Sn(OH) 4-x Fx The slurry was filtered to obtain Sn(OH) 4-x F x The filter cake is then dried and crushed to obtain Sn(OH) with a particle size of 0.5 to 20 μm. 4-x F x powder;

[0019] S4 powder granulation: Sn(OH) 4-x F x Powder, PVC and PVB are added to the solvent to obtain a granulation solution; then drop ball granulation is performed to obtain Sn(OH) with a particle size of 0.5 to 2 mm. 4-x F x / PVC-PVB balls;

[0020] S5 Fluorine-chlorine replacement: using NaCl-NaHCO3 solution to Sn(OH) 4-x F x / PVC-PVB beads were subjected to fluorine-chlorine replacement to obtain spherical fluorine adsorbent.

[0021] Furthermore, the dropping speed of the NaF-Na2CO3 solution in step S1 is 10 to 50 L / h;

[0022] and / or, the oxidation in step S2 is carried out by aeration;

[0023] Preferably, the oxidation is carried out by aeration at a rate of 10 to 30 L / min to Sn(OH) 2-x F x Air is introduced into the slurry.

[0024] Furthermore, the drying temperature in step S3 is 50-80°C, and after drying, Sn(OH) 4-x F x The moisture content of the powder is less than 5%.

[0025] And / or, the solvent in step S4 is N,N-dimethylacetamide;

[0026] And / or, the mass of the solvent in step S4 is 75-150% of the total mass of the granulation raw materials; the total mass of the granulation raw materials is Sn(OH) 4-x F x The sum of the mass of powder, PVC and PVB;

[0027] And / or, the pH value of the NaCl-NaHCO3 solution in step S5 is 7.5-8.5.

[0028] Furthermore, in step S4, the mass of PVC and PVB accounts for 8 to 25% of the total mass of the granulation raw materials;

[0029] And / or, in step S4, the mass ratio of PVC to PVB is 1:1-5.

[0030] The present invention provides an application of the above-mentioned fluorine adsorbent in the treatment of fluorine-containing wastewater.

[0031] The present invention provides a method for treating fluorine-containing wastewater based on the above-mentioned fluorine adsorbent, the method comprising:

[0032] (A) Fluoride removal from wastewater;

[0033] (B) Fluorine adsorbent regeneration;

[0034] (C) Regeneration fluid is reused.

[0035] Furthermore, the wastewater defluoridation comprises: filling a fluorine adsorbent into an adsorption column, then flowing the fluorine-containing wastewater into the adsorption column for defluoridation, and when the fluoride ion concentration is greater than 1 mg / L, stopping the flow of the fluorine-containing wastewater and regenerating the fluorine adsorbent;

[0036] And / or, the fluorine adsorbent regeneration includes: using MgCl2 solution as a regeneration liquid to circulate and elute the fluorine adsorbent adsorbed with fluoride ions, completing the regeneration of the fluorine adsorbent and obtaining an eluent containing MgCl2 solution and MgF2 precipitate;

[0037] Preferably, the concentration of the MgCl2 solution is 0.5 to 3 mol / L.

[0038] Furthermore, the regeneration liquid reuse includes:

[0039] (C1) performing solid-liquid separation on the eluate containing the MgCl2 solution and the MgF2 precipitate to obtain a MgCl2 solution and a MgF2 precipitate;

[0040] (C2) adjusting the concentration of the MgCl2 solution to 0.5-3 mol / L for recycling as a regeneration solution;

[0041] and, drying the MgF2 precipitate to obtain MgF2 powder.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The structural formula of the fluorine adsorbent provided by the present invention is: Sn(OH) 4-x Cl x / PVC-PVB, wherein: 0.8≤x≤1.0; the PVC-PVB is a dual binder, and the fluorine adsorbent is prepared using PVC and PVB as binders. In the structural formula of the above fluorine adsorbent, Sn(OH) 4-x Cl xThe powder has the properties of stable physical and chemical structure and high adsorption capacity. At the same time, the soft and hard skeleton of the PVC-PVB dual binder can make the Sn(OH) 4-x Cl x / PVC-PVB adsorbent beads form extensive adsorption channels, greatly improving the adsorption capacity and adsorption stability of the fluorine adsorbent.

[0044] The present invention provides a preparation method for a fluorine adsorbent, wherein the preparation method uses NaF-Na2CO3 solution, SnCl2-citric acid solution and NaCl-NaHCO3 solution as raw materials, and carries out precipitation reaction, oxidation reaction, drying and pulverization, powder granulation and fluorine and chlorine replacement steps to prepare Sn(OH) 4-x Cl x / PVC-PVB fluorine adsorbent. The above preparation method has the advantages of simple synthesis process and easy operation.

[0045] The fluorine adsorbent provided by the present invention can be widely used in the treatment process of fluorine-containing wastewater.

[0046] The fluorine-containing wastewater treatment method based on the above-mentioned fluorine adsorbent not only has the advantages of large adsorption capacity and stable adsorption performance in the treatment process of fluorine-containing wastewater; at the same time, the adsorbent has high regeneration efficiency, and the high concentration of fluoride ions in the regeneration liquid can be harmlessly treated to obtain high-value-added MgF2 powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0048] Figure 1 A schematic diagram of the preparation process of the fluorine adsorbent provided by the present invention;

[0049] Figure 2 Schematic diagram of the application process of the fluorine adsorbent of the present invention in the treatment process of fluorine-containing wastewater;

[0050] Figure 3a This is a physical picture of the fluorine adsorbent pellet product prepared in Example 1 of the present invention;

[0051] Figure 3b This is a surface scanning electron microscope image of the fluorine adsorbent pellet product prepared in Example 1 of the present invention;

[0052] Figure 4Example 1 of the present invention provides a fluorine adsorbent Sn (OH) 3.2 Cl 0.8 / The regular curve diagram of the fluoride concentration in the inlet and outlet water during the fluoride removal operation of PVC-PVB balls in real fluoride-containing groundwater;

[0053] Figure 5a This is a physical picture of the fluorine adsorbent pellet product prepared in Example 2 of the present invention;

[0054] Figure 5b This is a surface scanning electron microscope image of the fluorine adsorbent pellet product prepared in Example 2 of the present invention;

[0055] Figure 6 Example 2 of the present invention provides a fluorine adsorbent Sn (OH) 3.1 Cl 0.9 / PVC-PVB balls show the regularity of fluoride concentration in influent and outfluent water during the defluorination process in real fluoride-containing industrial wastewater;

[0056] Figure 7a This is a physical picture of the fluorine adsorbent pellet product prepared in Example 3 of the present invention;

[0057] Figure 7b This is a surface scanning electron microscope image of the fluorine adsorbent pellet product prepared in Example 3 of the present invention;

[0058] Figure 8 Example 3 of the present invention provides a fluorine adsorbent Sn (OH) 3.0 Cl 1.0 / The regular curve diagram of the fluorine concentration in the inlet and outlet water during the defluorination operation of PVC-PVB balls in real fluorine-containing industrial wastewater. DETAILED DESCRIPTION

[0059] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0060] According to one aspect of the present invention, a fluorine adsorbent has the structural formula: Sn(OH) 4-x Cl x / PVC-PVB, where: 0.8≤x≤1.0;

[0061] The PVC-PVB is a dual binder, and the fluorine adsorbent is prepared by using PVC and PVB as binders.

[0062] The structural formula of the fluorine adsorbent provided by the present invention is: Sn(OH) 4-x Cl x / PVC-PVB, wherein: 0.8≤x≤1.0; the PVC-PVB is a dual binder, and the fluorine adsorbent is prepared using PVC and PVB as binders. In the structural formula of the above fluorine adsorbent, Sn(OH) 4-x Cl x The powder has the properties of stable physical and chemical structure and high adsorption capacity, and is matched with the soft and hard skeleton granulation method of PVC-PVB dual binder, which can make the Sn(OH) 4-x Cl x / PVC-PVB adsorbent beads form extensive adsorption channels, greatly improving the adsorption capacity and adsorption stability of the fluorine adsorbent.

[0063] In a preferred embodiment of the present invention, the fluorine adsorbent is a spherical structure, and the particle size of the fluorine adsorbent is 0.5 to 2 mm.

[0064] According to one aspect of the present invention, a method for preparing a fluorine adsorbent comprises:

[0065] S1 precipitation reaction: NaF-Na2CO3 solution is added dropwise to SnCl2-citric acid solution to perform precipitation reaction to obtain Sn(OH) 2-x F x slurry;

[0066] S2 oxidation reaction: Sn(OH) 2-x F x The slurry is oxidized to make Sn(OH) 2-x F x Converted to Sn(OH) 4-x F x , obtaining Sn(OH) 4-x F x slurry;

[0067] S3 drying and powdering: Sn(OH) 4-x F x The slurry was filtered to obtain Sn(OH) 4-x F x The filter cake is then dried and crushed to obtain Sn(OH) with a particle size of 0.5 to 20 μm. 4-x F x powder;

[0068] S4 powder granulation: Sn(OH) 4-x F x Powder, PVC and PVB are added to the solvent to obtain a granulation solution; then drop ball granulation is performed to obtain Sn(OH) with a particle size of 0.5 to 2 mm.4-x F x / PVC-PVB balls;

[0069] S5 Fluorine-chlorine replacement: using NaCl-NaHCO3 solution to Sn(OH) 4-x F x / PVC-PVB beads were subjected to fluorine-chlorine replacement to obtain spherical fluorine adsorbent.

[0070] The present invention provides a preparation method for a fluorine adsorbent, wherein the preparation method uses NaF-Na2CO3 solution, SnCl2-citric acid solution and NaCl-NaHCO3 solution as raw materials, and carries out precipitation reaction, oxidation reaction, drying and pulverization, powder granulation and fluorine and chlorine replacement steps to prepare Sn(OH) 4-x Cl x / PVC-PVB fluorine adsorbent. The above preparation method has the advantages of simple synthesis process and easy operation. The fluorine adsorbent prepared by this method not only has the performance of physical and chemical stable structure and high adsorption capacity, but also the soft and hard skeleton granulation method of PVC-PVB dual binder makes Sn(OH) 4-x Cl x / PVC-PVB beads form extensive adsorption channels, greatly improving the adsorption capacity and adsorption stability of the fluorine adsorbent.

[0071] Figure 1 This is a schematic diagram of the preparation process of the fluorine adsorbent provided by the present invention.

[0072] See also Figure 1 The preparation method of the fluorine adsorbent of the present application can be described as follows:

[0073] (1) Solution preparation:

[0074] 1. Preparation of SnCl2-citric acid solution: Add a certain amount of deionized water to a stirring tank, then add citric acid powder to prepare a citric acid solution with a mass fraction of 40%-60%. Then add SnCl2·2H2O powder to the citric acid solution so that the concentration of SnCl2 in the prepared SnCl2-citric acid solution is 1-2.5 mol / L to obtain a SnCl2-citric acid solution for later use.

[0075] 2. Preparation of NaF-Na2CO3 solution: Add Na2CO3 powder to deionized water to prepare a saturated Na2CO3 solution, then add NaF powder to the saturated Na2CO3 solution so that the concentration of NaF in the prepared NaF-Na2CO3 solution is 0.1-0.25 mol / L to obtain a NaF-Na2CO3 solution for later use.

[0076] 3. Preparation of NaCl-NaHCO3 solution: Add NaCl powder to deionized water to prepare 1-4 mol / L NaCl solution, then add NaHCO3 powder to the 1-4 mol / L NaCl solution, adjust the pH of the NaCl-NaHCO3 solution to 7.5-8.5, and obtain a NaCl-NaHCO3 solution for later use.

[0077] (2) Precipitation reaction:

[0078] In an enameled stirring tank, add 50-100L of SnCl2-citric acid solution and heat the solution to 50-90°C. Then, at a speed of 100-300rpm, add the above-prepared NaF-Na2CO3 solution to the enameled kettle at a dropwise rate of 10-50L / h. The dropwise volume of the NaF-Na2CO3 solution is 75-150L. After the reaction, Sn(OH) 2-x F x White slurry.

[0079] The reaction equation in this process is: 3SnCl2+3xNaF+(6-3x)Na2CO3+(2-x)C3H4OH(COOH)3=3Sn(OH) 2-x F x +6NaCl+(6-3x)CO2+(2-x)C3H4OH(COONa)3.

[0080] It should be noted that during the above precipitation reaction, the NaF-Na2CO3 solution should be added dropwise to the SnCl2-citric acid solution, but the SnCl2-citric acid solution should not be added dropwise to the NaF-Na2CO3 solution. This is because when the SnCl2-citric acid is excessive, the OH in the reaction solution will - Very little, OH - Unable to communicate with Sn 2+ The reaction occurs, and the F in the added NaF-Na2CO3 solution - It will quickly and Sn 2+ A complexation reaction occurs, first forming [SnF a ] 2-a Complex ions; With the addition of NaF-Na2CO3 solution, the pH value of SnCl2-citric acid solution becomes higher and higher, OH - As the concentration increases, [SnF a ] 2-a The complex ions begin to react with OH in the solution - React to generate Sn(OH) 2-x F x White precipitate.

[0081] In addition, it should be emphasized that during the above precipitation reaction, the target Sn(OH) 2-x F x The synthesis is carried out in two steps. Under strong acidity, F - and Sn 2+ A complex reaction occurs, and the fluoride ion F - Smoothly introduced into Sn-containing 2+ In the compound system, under weak acidic or weak alkaline conditions, the hydroxide OH - Introduced into Sn-containing 2+ In the compound system, the reaction is carried out in two steps to avoid F - With OH - Competition for Sn 2+ The target Sn(OH) 2-x F x This is a major improvement of the present application over the prior art.

[0082] (3) Oxidation reaction:

[0083] At a speed of 100-300 rpm, insert the aeration tube into the above slurry and aerate Sn(OH) at a rate of 10-30 L / min. 2-x F x Air is introduced into the white slurry, and oxygen in the air is used as a cheap and readily available oxidant to make Sn(OH) 2-x F x The white slurry turns into Sn(OH) 4-x F x Light yellow slurry.

[0084] The reaction equation in this process is: 2Sn(OH) 2-x F x +O2+2H2O=2Sn(OH) 4-x F x .

[0085] (4) Drying and pulverization:

[0086] The Sn(OH) 4-x F x The light yellow slurry is pumped into a plate and frame filter press to filter out the liquid and obtain Sn(OH) 4-x F x Light yellow filter cake; Sn(OH) 4-x F x The light yellow filter cake is placed in a crawler drying kiln, the temperature is controlled at 50-80℃, and dried until the moisture content is less than 5% to obtain Sn(OH) 4-x F x Light yellow dry block solid; Sn(OH)4-x F x The light yellow dry block solid was crushed with an impact mill to obtain Sn(OH) with a particle size of 0.5-20 μm. 4-x F x Light yellow dry powder.

[0087] (5) Powder granulation:

[0088] Sn(OH) with a particle size of 0.5-20 μm 4-x F x Light yellow dry powder, polyvinyl chloride (PVC), polyvinyl butyral (PVB), and N,N-dimethylacetamide (DMAC) are mixed in a certain mass ratio, wherein:

[0089] The total mass of binder PVC and binder PVB accounts for the total powder mass (Sn(OH) 4-x F x +PVC+PVB) 8%-25%, the mass of solvent DMAC accounts for the total powder mass (Sn(OH) 4-x F x +PVC+PVB) is 75%-150%, and the mass ratio of the adhesive PVC to the adhesive PVB is 1:1-1:5.

[0090] Add the materials to the stirred tank in this order: first add the solvent DMAC, heat to 50-90℃, add the adhesive PVC and adhesive PVB while stirring, after the adhesive PVC and adhesive PVB are dissolved, add Sn(OH) 4-x F x Light yellow dry powder, continue stirring for 1-4h. Transfer the liquid to the ball dropping equipment for ball dropping, and the small balls fall into deionized water for phase conversion to obtain Sn(OH) with a particle size of 0.5-2mm. 4-x F x / PVC-PVB balls.

[0091] It should be noted that in the molding process of the powder of this application, PVC and PVB are used as joint binders, wherein: the skeleton of PVC is a rigid skeleton, and the particles after molding are relatively hard, which is beneficial to improve the Sn(OH) 4-x F x / PVC-PVB balls have high pressure and wear resistance; the skeleton of PVB is flexible and the particles after molding are relatively soft, which is beneficial to Sn(OH) 4-x F x Powder entanglement and interception to avoid Sn(OH) 4-x F x / Loss of effective powder in PVC-PVB balls;

[0092] In addition, the chemical formula of the above PVB (C8H 14 O2) n There are a lot of oxygen atoms in it, which can react with Sn(OH) 4-x F x The hydrogen atoms in the powder form hydrogen bonds, which are beneficial to the mutual traction between the powder and the organic skeleton, and are beneficial to the uniform dispersion and stable attraction of the powder, thus avoiding the loss of the powder.

[0093] (6) Fluorine-chlorine replacement:

[0094] 100-200L of Sn(OH) 4-x F x / PVC-PVB balls are loaded into the adsorption column, and the above-prepared NaCl-NaHCO3 solution with a pH of 7.5-8.5 is added from the bottom of the adsorption column at a flow rate of 1-3BV / h. The amount of NaCl-NaHCO3 solution used is 150-300L to fully soak the Sn(OH) 4-x F x / PVC-PVB small balls, making Sn(OH) 4-x F x / The fluorine element on the PVC-PVB ball is replaced by the chlorine element in the NaCl--NaHCO3 solution, Sn(OH) 4-x F x / PVC-PVB beads transformed into Sn(OH) 4-x Cl x / PVC-PVB balls.

[0095] The ion exchange reaction that occurs in this process is: Sn(OH) 4-x F x / PVC-PVB+xNaCl=Sn(OH) 4-x Cl x / PVC-PVB+xNaF. Sn(OH) 4-x Cl x / PVC-PVB beads are the prepared fluorine adsorbent.

[0096] It should be emphasized that in the fluorine-chlorine replacement process of this application, a NaCl-NaHCO3 solution with a pH of 7.5-8.5 is used instead of a pure NaCl solution. That is, the fluorine-chlorine replacement process of this application utilizes the appropriate concentration of hydroxide ions OH in the weak alkaline solution. - Sn(OH) 4-x F x The Sn-F chemical bond on the - Concentration (≈10 - 4mol / L) and Cl in NaCl-NaHCO3 solution - Compared with the concentration (1~4mol / L), OH - The concentration is at an extremely low concentration, so after the Sn-F chemical bond breaks, a Sn-Cl chemical bond is formed instead of a Sn-OH chemical bond, achieving fluorine-chlorine replacement and obtaining the effective component of the fluorine adsorbent, Sn(OH). 4-x Cl x This is also a major innovation of this application compared to the prior art.

[0097] According to one aspect of the present invention, the above-mentioned fluorine adsorbent is used in the treatment of fluorine-containing wastewater.

[0098] The fluorine adsorbent provided by the present invention can be widely used in the treatment process of fluorine-containing wastewater. The above-mentioned fluorine adsorbent not only has the advantages of large adsorption capacity, stable adsorption performance, high regeneration efficiency, and high concentration of fluoride ions in the regeneration liquid can be efficiently and harmlessly treated in the treatment process of fluorine-containing wastewater, but also the MgF2 precipitate formed in the regeneration process is a useful material with high added value.

[0099] Therefore, the treatment process of the fluorine adsorbent of the present invention can convert the toxic and harmful fluoride ions exceeding the standard in sewage into salable, high-value-added, and widely used MgF2 powder, truly turning waste into treasure and efficiently utilizing resources.

[0100] According to one aspect of the present invention, a method for treating fluorine-containing wastewater based on the above-mentioned fluorine adsorbent comprises:

[0101] (A) Fluoride removal from wastewater;

[0102] (B) Fluorine adsorbent regeneration;

[0103] (C) Regeneration fluid is reused.

[0104] Figure 2 This is a schematic diagram of the application process of the fluorine adsorbent of the present invention in the treatment of fluorine-containing wastewater.

[0105] See also Figure 2 The present invention relates to a method for treating fluorine-containing wastewater based on the above-mentioned fluorine adsorbent, which can be described as follows:

[0106] (A) Wastewater defluoridation process:

[0107] Sn(OH) 4-x Cl x / PVC-PVB balls are loaded into the adsorption column. The fluoride ion concentration of the fluoride-containing wastewater is 5-200 mg / L. The fluoride-containing wastewater flows into the adsorption column from bottom to top at a flow rate of 5-20BV. The fluoride ion concentration in the produced water after fluoride removal is less than 1 mg / L.

[0108] The ionic equation of the defluorination process is: Sn(OH) 4-x Cl x / PVC-PVB+xF - =Sn(OH) 4-x F x / PVC-PVB+xCl - .

[0109] Preferably, a fluoride ion sensor is installed at the water outlet to monitor the fluoride ion concentration of the produced water in real time online. Once the fluoride ion concentration of the produced water is greater than 1 mg / L, the adsorption of water is stopped and regeneration is prepared.

[0110] (B) Fluorine adsorbent regeneration process:

[0111] When the fluoride ion concentration of the adsorption column reaches >1mg / L, the 0.5-3mol / L MgCl2 solution in regeneration liquid storage tank A is used as the regeneration liquid to regenerate the fluoride adsorbent from bottom to top at a flow rate of 15-25BV / h. The regeneration liquid storage tank A and the adsorption column form a circulation system. The upper effluent of the adsorption column is returned to the regeneration liquid storage tank A. The regeneration liquid volume is 2-4BV. The circulation lasts for 10-20 minutes to complete the regeneration of the fluoride adsorbent. After regeneration is complete, all the remaining regeneration liquid in the adsorption column is pumped back to the regeneration liquid storage tank A.

[0112] The ionic equation for the regeneration process is: Sn(OH) 4-x F x / PVC-PVB+xCl - =Sn(OH) 4-x Cl x / PVC-PVB+xF - Mg 2+ +2F - =MgF2↓. During the regeneration process of fluorine adsorbent, magnesium ions Mg 2+ Will react with the eluted fluoride ion F - The precipitation reaction is carried out to quickly reduce the concentration of fluoride ions in the regeneration liquid, thereby preventing the fluoride adsorbent from continuing to adsorb fluoride ions in the regeneration liquid, facilitating the elution of fluoride ions from the fluoride adsorbent, and achieving a fast and efficient regeneration process.

[0113] It should be noted that, using MgCl2 solution as regeneration solution, magnesium ions and fluoride ions can form precipitated MgF2. 2+ +2F - =MgF2↓, a large amount of Mg in the regeneration solution 2+ , which can induce Sn(OH) 4-x F xThe Sn-F chemical bonds on the PVC-PVB beads break, and immediately Sn-Cl chemical bonds form. However, because the bond energy of the Sn-Cl chemical bond is lower than that of the Sn-F chemical bond, the tendency to form Sn-F chemical bonds is higher than that of Sn-Cl chemical bonds. Once the concentration of fluoride ions released from the regeneration liquid increases, the regeneration process will experience reverse adsorption, that is, the fluoride ions in the regeneration liquid will be re-adsorbed onto the fluoride adsorbent.

[0114] The present application solves this problem by using a 0.5-3 mol / L MgCl2 solution as the regeneration liquid, because the fluoride ions in the regeneration liquid will undergo precipitation reaction with the magnesium ions in the regeneration liquid, which greatly reduces the fluoride ion concentration in the regeneration liquid, improves the regeneration rate and regeneration time, and the regeneration of the fluoride adsorbent can be completed in only 10-20 minutes.

[0115] It should also be noted that during the regeneration process of the fluorine adsorbent of the present invention, the fluorine adsorbent is regenerated from bottom to top at a flow rate of 15-25BV / h, and the regeneration liquid storage tank A and the adsorption column serve as a circulation system. The innovation of this step compared to the prior art is that the regeneration liquid is pumped into the adsorption column at a high flow rate, which is conducive to breaking up the formed MgF2 precipitate into extremely small particles and avoiding the formation of large flocculent precipitation. The high flow rate is also conducive to preventing the precipitate from being deposited on the Sn(OH) 4-x Cl x / PVC-PVB balls to avoid clogging of adsorption channels and adsorption sites; in addition, the regeneration liquid storage tank A and the adsorption column are regenerated as a circulation system instead of using a one-time overflow regeneration, which is beneficial to reduce the amount of regeneration liquid used, reduce the volume of the liquid storage tank, reduce the floor space, and facilitate engineering applications.

[0116] (C) Regeneration liquid reuse process: After the fluorine adsorbent is regenerated with the regeneration liquid (0.5-3 mol / L MgCl2 solution), an eluent (a mixture of MgCl2 solution and MgF2 precipitate, wherein the MgCl2 concentration is less than 0.5-3 mol / L) is obtained. The eluent is pumped into a plate and frame filter press to perform solid-liquid separation of the MgCl2 solution and the MgF2 precipitate to obtain a MgCl2 solution (filtrate) and a MgF2 filter cake.

[0117] The MgCl2 solution (filtrate) is pumped back to the regeneration liquid storage tank B. After all the eluent in the regeneration liquid storage tank A has flowed through the plate and frame filter press, the slightly lower concentration MgCl2 solution (filtrate) in the regeneration liquid storage tank B is pumped into the regeneration liquid storage tank A, and an appropriate amount of MgCl2·6H2O solid is added to the regeneration liquid storage tank A to obtain a 0.5-3 mol / L MgCl2 solution as a new regeneration liquid for recycling.

[0118] After the MgF2 filter cake is dried and crushed, MgF2 powder is obtained, which can be sold as a chemical. As an important inorganic compound, magnesium fluoride has shown wide application potential and unlimited possibilities in the electronics industry. Its excellent physical and chemical properties make it a key material in high-power and high-frequency electronic devices, chip manufacturing, solar cells and other fields.

[0119] It should be noted that the present application uses a plate and frame filter press for solid-liquid separation of MgCl2 solution and MgF2 precipitate, which is more efficient and energy-saving than centrifugation or evaporation, and is more conducive to continuous operation; at the same time, in addition to allowing the MgCl2 solution (filtrate) to be reused during the reuse of the above-mentioned regenerated liquid, a high-value-added MgF2 powder can also be obtained. The powder has a wide range of uses and high added value and can be widely used in the optical field, electronics industry, photovoltaic field, ion conductive materials and raw materials for electronic devices, manufacturing high-power electronic devices and integrated circuits, catalyst carriers, biomedical field, bulletproof and protective materials, metallurgical industry, ceramics and glass industry, and nuclear energy and many other fields.

[0120] The technical solution of the present invention will be further described below with reference to embodiments.

[0121] Example 1

[0122] A method for preparing a fluorine adsorbent, comprising:

[0123] (1) Solution preparation: Preparation of SnCl2-citric acid solution: Add a certain amount of deionized water to a stirring tank, then add citric acid powder to prepare a citric acid solution with a mass fraction of 40%, and then add SnCl2·2H2O powder to the citric acid solution so that the concentration of SnCl2 in the prepared SnCl2-citric acid solution is 1 mol / L to obtain a SnCl2-citric acid solution.

[0124] Preparation of NaF-Na2CO3 solution: Na2CO3 powder is added to deionized water to prepare a saturated Na2CO3 solution, and then NaF powder is added to the saturated Na2CO3 solution so that the concentration of NaF in the prepared NaF-Na2CO3 solution is 0.1 mol / L to obtain a NaF-Na2CO3 solution.

[0125] Preparation of NaCl-NaHCO3 solution: Add NaCl powder to deionized water to prepare a 1 mol / L NaCl solution, then add NaHCO3 powder to the 1 mol / L NaCl solution and adjust the pH of the NaCl-NaHCO3 solution to 7.5 to obtain a NaCl-NaHCO3 solution.

[0126] (II) Precipitation reaction: Add 50 L of SnCl2-citric acid solution to an enameled stirring tank and heat the solution to 50°C. Then, add the above-prepared NaF-Na2CO3 solution to the enameled kettle at a speed of 10 L / h at a rate of 100 rpm. The volume of the NaF-Na2CO3 solution added is 75 L. After the reaction, Sn(OH) 2-x F x White slurry.

[0127] (III) Oxidation reaction: insert the aeration tube into the above slurry at a speed of 100 rpm, and aerate Sn(OH) 2-x F x Air is introduced into the white slurry, and oxygen in the air is used as a cheap and readily available oxidant to make Sn(OH) 2-x F x The white slurry turns into Sn(OH) 4-x F x Light yellow slurry.

[0128] (IV) Drying and powdering: Sn(OH) 4-x F x The light yellow slurry is pumped into a plate and frame filter press to filter out the liquid and obtain Sn(OH) 4-x F x Light yellow filter cake; Sn(OH) 4-x F x The light yellow filter cake was placed in a crawler drying kiln, the temperature was controlled at 50°C, and dried to a moisture content of 1% to obtain Sn(OH) 4-x F x Light yellow dry block solid; Sn(OH) 4-x F x The light yellow dry block solid was crushed with an impact mill to obtain Sn(OH) with a particle size of 0.5-5 μm. 4-x F x Light yellow dry powder.

[0129] (5) Powder granulation: Sn(OH) with a particle size of 0.5-5μm 4-x F x Light yellow dry powder, polyvinyl chloride (PVC), polyvinyl butyral (PVB), and N,N-dimethylacetamide (DMAC) are mixed in a certain mass ratio, wherein the total mass of the binder PVC and the binder PVB accounts for the total powder mass (Sn(OH) 4-x F x +PVC+PVB) 8%, the mass of solvent DMAC accounts for 8% of the total powder mass (Sn(OH) 4-x F x+PVC+PVB), and the mass ratio of the adhesive PVC to the adhesive PVB is 1:1.

[0130] Add the materials to the stirred tank in this order: first add the solvent DMAC, heat to 50 ° C, add the adhesive PVC and adhesive PVB while stirring, after the adhesive PVC and adhesive PVB are dissolved, add Sn(OH) 4-x F x The light yellow dry powder was stirred for 1 hour. The liquid was transferred to the ball dropping device for ball dropping. The small balls fell into deionized water for phase conversion to obtain Sn(OH) with a particle size of 0.5 mm. 4-x F x / PVC-PVB balls.

[0131] (6) Fluorine-chlorine replacement: 100L of Sn(OH) 4-x F x / PVC-PVB balls were loaded into the adsorption column, and the above-prepared NaCl-NaHCO3 solution with a pH of 7.5 was added from the bottom of the adsorption column at a flow rate of 1BV / h. The amount of NaCl-NaHCO3 solution used was 150L, ​​and the Sn(OH) 4-x F x / PVC-PVB small balls, making Sn(OH) 4-x F x / The fluorine element on the PVC-PVB ball is replaced by the chlorine element in the NaCl--NaHCO3 solution, Sn(OH) 4-x F x / PVC-PVB beads transformed into Sn(OH) 4-x Cl x / PVC-PVB balls.

[0132] (VII) Fluorine adsorbent property testing:

[0133] Figure 3a This is a physical picture of the fluorine adsorbent pellet product prepared in this example.

[0134] Figure 3b This is a surface scanning electron microscope image of the fluorine adsorbent pellet product prepared in this example.

[0135] from Figure 3a 、 Figure 3b As can be seen from the figure, the fluorine adsorbent beads have a very uniform particle size of approximately 0.5 mm. The fluorine adsorbent powder is encapsulated by the PVC and PVB resins, preventing it from falling off. Furthermore, the figure shows that the PVC and PVB resins form a rich pore structure. This interconnected pore network facilitates the adsorption and elution of fluoride ions, improving ion exchange efficiency.

[0136] Table 1 is the fluorine adsorbent Sn(OH) prepared in this example 4-x Cl x / PVC-PVB pellets are produced by heating and dissolving Sn(OH) with 4 mol / L sodium hydroxide 4-x Cl x Afterwards, the contents of Sn and Cl in the solution were tested with an instrument, and it was inferred that Sn(OH) 4-x Cl x The chemical formula is Sn(OH) 3.2 Cl 0.8 .

[0137] Table 1 Chemical formula and adsorption capacity analysis of fluorine adsorbent in Example 1:

[0138]

[0139] Passed the test Sn(OH) 3.2 Cl 0.8 / PVC-PVB beads have a saturated adsorption capacity of fluoride ions of 115 mg / g, which is much higher than the 31 mg / g of the fluoride adsorbent (TFR-93) on the market. 3.2 Cl 0.8 / PVC-PVB beads have the performance advantage of high adsorption capacity. In addition, Sn(OH) 3.2 Cl 0.8 / PVC-PVB ball after 1000 cycles of powder loss rate is only 0.5%, proving that the soft and hard skeleton of the PVC-PVB dual binder can make the Sn(OH) 4- x Cl x / PVC-PVB adsorbent beads form an extensive adsorption channel, while also avoiding Sn(OH) 3.2 Cl 0.8 / The loss of effective powder in the PVC-PVB beads greatly improves the adsorption capacity and adsorption stability of the fluorine adsorbent.

[0140] Application Example 1

[0141] The fluorine adsorbent Sn(OH) prepared in Example 1 was 3.2 Cl 0.8 / PVC-PVB balls were used for application tests.

[0142] See also Figure 2 Schematic diagram of the application process of the fluorine adsorbent of the present invention in the treatment of fluorine-containing wastewater. The application process of the fluorine adsorbent in this application example based on Example 1 for treating fluorine-containing wastewater includes:

[0143] (1) Wastewater defluoridation process: The fluorine adsorbent beads prepared in Example 1 were loaded into an adsorption column. The fluorine ion concentration of the fluorine-containing wastewater was 5 mg / L. The fluorine-containing wastewater flowed into the adsorption column from bottom to top at a flow rate of 5 BV. The fluorine ion concentration in the produced water after defluoridation was less than 1 mg / L.

[0144] A fluoride ion sensor is installed at the water outlet to monitor the fluoride ion concentration of the produced water in real time. Once the fluoride ion concentration of the produced water is greater than 1 mg / L, the adsorption of water will be stopped and regeneration will be prepared.

[0145] (2) Fluorine adsorbent regeneration process: When the fluorine ion concentration of the water produced by the adsorption column of the fluorine adsorbent is greater than 1mg / L, the 0.5mol / L MgCl2 solution in the regeneration liquid storage tank A is used as the regeneration liquid to regenerate the fluorine adsorbent from bottom to top at a flow rate of 15BV / h. The regeneration liquid storage tank A and the adsorption column are used as a circulation system. The upper water of the adsorption column is returned to the regeneration liquid storage tank A. The regeneration liquid volume is 2BV. The circulation is 10 minutes to complete the regeneration of the fluorine adsorbent. After the regeneration is completed, all the residual regeneration liquid in the adsorption column is pumped back to the regeneration liquid storage tank A.

[0146] (3) Regeneration liquid reuse process: After the fluorine adsorbent is regenerated with the regeneration liquid (0.5 mol / L MgCl2 solution), an eluent (a mixture of MgCl2 solution and MgF2 precipitate, wherein the MgCl2 concentration is less than 0.5 mol / L) is obtained. The eluent is pumped into a plate-and-frame filter press to perform solid-liquid separation of the MgCl2 solution and the MgF2 precipitate, and the obtained MgCl2 solution (filtrate) is pumped back into the regeneration liquid storage tank B. After all the eluent in the regeneration liquid storage tank A has flowed through the plate-and-frame filter press, the slightly lower concentration MgCl2 solution (filtrate) in the regeneration liquid storage tank B is pumped into the regeneration liquid storage tank A, and an appropriate amount of MgCl2·6H2O solid is added to the regeneration liquid storage tank A to obtain a 0.5 mol / L MgCl2 solution that is recycled as a new regeneration liquid. The MgF2 filter cake is dried and crushed to obtain MgF2 powder, which can be sold as a chemical.

[0147] Figure 4 Example 1 fluorine adsorbent Sn(OH) provided for this application example 3.2 Cl 0.8 / The regular curve diagram of the fluoride concentration in the inlet and outlet water during the fluoride removal operation of PVC-PVB balls in real fluoride-containing groundwater.

[0148] from Figure 4It can be seen that the fluoride ion concentration of the produced water of the fluoride adsorbent during the fluoride removal process is very stable. The fluoride ion concentration in the fluoride-containing groundwater inlet is about 5 mg / L. Before the column adsorption is saturated, the fluoride ion concentration of the produced water is always less than 0.5 mg / L. China's "National Drinking Water Quality Standard" (GB5749-2022) stipulates that the limit of fluoride in drinking water is 1.0 mg / L, which proves that the fluoride adsorbent can meet the national standard requirements for groundwater fluoride removal and also meet engineering needs. It has the advantages of large adsorption capacity and stable adsorption performance, and is expected to be able to be applied on a large scale. In addition, the purity of the MgF2 powder product obtained by the application method of the above-mentioned fluoride adsorbent for the defluorination of fluoride-containing groundwater is 99.6%, which can be sold as a high-value-added product. It proves that the fluoride adsorbent can realize the resource utilization of sewage and turn waste into treasure.

[0149] Example 2

[0150] A method for preparing a fluorine adsorbent, comprising:

[0151] (1) Solution preparation: Preparation of SnCl2-citric acid solution: Add a certain amount of deionized water to a stirring tank, then add citric acid powder to prepare a citric acid solution with a mass fraction of 50%, and then add SnCl2·2H2O powder to the citric acid solution so that the concentration of SnCl2 in the prepared SnCl2-citric acid solution is 1.75 mol / L to obtain a SnCl2-citric acid solution.

[0152] Preparation of NaF-Na2CO3 solution: Na2CO3 powder is added to deionized water to prepare a saturated Na2CO3 solution, and then NaF powder is added to the saturated Na2CO3 solution so that the concentration of NaF in the prepared NaF-Na2CO3 solution is 0.175 mol / L to obtain a NaF-Na2CO3 solution.

[0153] Preparation of NaCl-NaHCO3 solution: Add NaCl powder to deionized water to prepare a 2.5 mol / L NaCl solution, then add NaHCO3 powder to the 2.5 mol / L NaCl solution, and adjust the pH of the NaCl-NaHCO3 solution to 8 to obtain a NaCl-NaHCO3 solution.

[0154] (II) Precipitation reaction: Add 75 L of SnCl2-citric acid solution into an enameled stirring tank and heat the solution to 70°C. Then, add the prepared NaF-Na2CO3 solution into the enameled kettle at a rate of 30 L / h at a speed of 200 rpm. The added volume of NaF-Na2CO3 solution is 112.5 L. After the reaction, Sn(OH) 2-x F x White slurry.

[0155] (III) Oxidation reaction: insert the aeration tube into the above slurry at a speed of 200 rpm, and aerate Sn(OH) 2-x F x Air is introduced into the white slurry, and oxygen in the air is used as a cheap and readily available oxidant to make Sn(OH) 2-x F x The white slurry turns into Sn(OH) 4-x F x Light yellow slurry.

[0156] (IV) Drying and powdering: Sn(OH) 4-x F x The light yellow slurry is pumped into a plate and frame filter press to filter out the liquid and obtain Sn(OH) 4-x F x Light yellow filter cake; Sn(OH) 4-x F x The light yellow filter cake was placed in a crawler drying kiln, the temperature was controlled at 65°C, and dried to a moisture content of 2.5% to obtain Sn(OH) 4-x F x Light yellow dry block solid; Sn(OH) 4-x F x The light yellow dry block solid was crushed with an impact mill to obtain Sn(OH) with a particle size of 0.5-10 μm. 4-x F x Light yellow dry powder.

[0157] (5) Powder granulation: Sn(OH) with a particle size of 0.5-10μm 4-x F x Light yellow dry powder, polyvinyl chloride (PVC), polyvinyl butyral (PVB), and N,N-dimethylacetamide (DMAC) are mixed in a certain mass ratio, wherein the total mass of the binder PVC and the binder PVB accounts for 1% of the total powder mass (Sn(OH) 4-x F x +PVC+PVB) accounts for 16.5% of the total powder mass (Sn(OH) 4-x F x +PVC+PVB) is 112.5%, and the mass ratio of the adhesive PVC to the adhesive PVB is 1:3.

[0158] Add the materials to the stirred tank in this order: first add the solvent DMAC, heat to 70℃, add the adhesive PVC and adhesive PVB while stirring, after the adhesive PVC and adhesive PVB are dissolved, add Sn(OH) 4-x F xLight yellow dry powder, continue stirring for 2.5h. Transfer the liquid to the ball dropping equipment for ball dropping, and the small balls fall into deionized water for phase conversion to obtain Sn(OH) with a particle size of about 1mm 4-x F x / PVC-PVB balls.

[0159] (6) Fluorine-chlorine replacement: 150L of Sn(OH) 4-x F x / PVC-PVB balls were loaded into the adsorption column, and the above-prepared NaCl-NaHCO3 solution with a pH of 8 was added from the bottom of the adsorption column at a flow rate of 2BV / h. The amount of NaCl-NaHCO3 solution used was 225L, and the Sn(OH) 4-x F x / PVC-PVB small balls, making Sn(OH) 4-x F x / The fluorine element on the PVC-PVB ball is replaced by the chlorine element in the NaCl--NaHCO3 solution, Sn(OH) 4-x F x / PVC-PVB beads transformed into Sn(OH) 4-x Cl x / PVC-PVB beads, Sn(OH) 4-x Cl x / PVC-PVB beads are the prepared fluorine adsorbent.

[0160] (VII) Fluorine adsorbent property testing:

[0161] Figure 5a This is a physical picture of the fluorine adsorbent pellet product prepared in this example.

[0162] Figure 5b This is a surface scanning electron microscope image of the fluorine adsorbent pellet product prepared in this example.

[0163] from Figure 5a 、 Figure 5b It can be seen that the particle size of the fluorine adsorbent beads is very uniform, about 1mm in size, and the fluorine adsorbent powder is wrapped by PVC and PVB resin to prevent the fluorine adsorbent powder from falling off. Figure 5a 、 Figure 5b It can be seen that PVC and PVB resins form a rich pore structure, and the interconnected network pore structure is conducive to the adsorption and elution of fluoride ions, thereby improving the ion exchange efficiency.

[0164] Table 2 is the fluorine adsorbent Sn(OH) prepared in this example 4-x Cl x / PVC-PVB pellets are produced by heating and dissolving Sn(OH) with 4 mol / L sodium hydroxide 4-x Cl x Afterwards, the contents of Sn and Cl in the solution were tested with an instrument, and it was inferred that Sn(OH) 4-x Cl x The chemical formula is Sn(OH) 3.1 Cl 0.9 .

[0165] Table 2 Chemical formula and adsorption capacity analysis of fluorine adsorbent in Example 2:

[0166]

[0167] Passed the test Sn(OH) 3.1 Cl 0.9 The saturated adsorption capacity of fluoride ions of the PVC-PVB beads is 139 mg / g, which is much higher than the 31 mg / g of the fluoride adsorbent (TFR-93) on the market. 3.1 Cl 0.9 / PVC-PVB beads have the performance advantage of high adsorption capacity. In addition, Sn(OH) 3.1 Cl 0.9 The powder loss rate of the PVC-PVB ball after 1000 cycles is only 0.42%, proving that the soft and hard skeleton of the PVC-PVB dual binder can make the Sn(OH) 3.1 Cl 0.9 / PVC-PVB adsorbent beads form an extensive adsorption channel, while also avoiding Sn(OH) 3.1 Cl 0.9 / The loss of effective powder in the PVC-PVB beads greatly improves the adsorption capacity and adsorption stability of the fluorine adsorbent.

[0168] Application Example 2

[0169] The fluorine adsorbent Sn(OH) prepared in Example 2 was 3.1 Cl 0.9 / PVC-PVB balls were used for application tests.

[0170] See also Figure 2 The fluorine-containing wastewater treatment application process based on the fluorine adsorbent of Example 2 includes:

[0171] (1) Wastewater defluoridation process: The fluorine adsorbent beads prepared in Example 2 were loaded into an adsorption column. The fluorine ion concentration of the fluorine-containing industrial wastewater was approximately 100 mg / L. The fluorine-containing wastewater flowed into the adsorption column from bottom to top at a flow rate of 12.5 BV. The fluorine ion concentration in the defluorinated water was less than 1 mg / L. A fluorine ion sensor was installed at the water outlet to monitor the fluorine ion concentration of the water in real time. Once the fluorine ion concentration of the water was greater than 1 mg / L, adsorption of the water was stopped and regeneration was prepared.

[0172] (2) Fluorine adsorbent regeneration process: After the fluorine ion concentration of the adsorption column of the fluorine adsorbent is greater than 1mg / L, the 1.75mol / L MgCl2 solution in the regeneration liquid storage tank A is used as the regeneration liquid to regenerate the fluorine adsorbent from bottom to top at a flow rate of 20BV / h. The regeneration liquid storage tank A and the adsorption column are used as a circulation system. The upper water of the adsorption column is returned to the regeneration liquid storage tank A. The regeneration liquid volume is 3BV. The circulation is 15 minutes to complete the regeneration of the fluorine adsorbent. After the regeneration is completed, all the residual regeneration liquid in the adsorption column is pumped back to the regeneration liquid storage tank A.

[0173] (3) Regeneration liquid reuse process: After the fluorine adsorbent is regenerated with the regeneration liquid (1.75 mol / L MgCl2 solution), an eluent (a mixture of MgCl2 solution and MgF2 precipitate, wherein the MgCl2 concentration is less than 1.75 mol / L) is obtained. The eluent is pumped into a plate-and-frame filter press to perform solid-liquid separation of the MgCl2 solution and the MgF2 precipitate, and the obtained MgCl2 solution (filtrate) is pumped back into the regeneration liquid storage tank B. After all the eluent in the regeneration liquid storage tank A has flowed through the plate-and-frame filter press, the slightly lower concentration MgCl2 solution (filtrate) in the regeneration liquid storage tank B is pumped into the regeneration liquid storage tank A, and an appropriate amount of MgCl2·6H2O solid is added to the regeneration liquid storage tank A to obtain a 1.75 mol / L MgCl2 solution that is recycled as a new regeneration liquid. The MgF2 filter cake is dried and crushed to obtain MgF2 powder, which can be sold as a chemical.

[0174] Figure 6 Example 2 fluorine adsorbent Sn(OH) provided for this application example 3.1 Cl 0.9 / The regular curve diagram of the fluorine concentration in the inlet and outlet water during the defluorination operation of PVC-PVB balls in real fluorine-containing industrial wastewater.

[0175] from Figure 6It can be seen that the fluoride ion concentration in the water produced by the fluoride adsorbent during the fluoride removal process is very stable. The fluoride ion concentration in the fluoride-containing groundwater inlet is about 100 mg / L, and the fluoride ion concentration in the water produced is always less than 0.5 mg / L before the column adsorption is saturated. China's "National Drinking Water Quality Standard" (GB5749-2022) stipulates that the limit value of fluoride in drinking water is 1.0 mg / L, which proves that the fluoride adsorbent can meet the national standard requirements for groundwater fluoride removal and also meet engineering needs. It has the advantages of large adsorption capacity and stable adsorption performance, and is expected to be able to be applied on a large scale.

[0176] Furthermore, the MgF2 powder product obtained by using the above-mentioned fluorine adsorbent method to remove fluorine from fluorinated groundwater has a purity of 99.8%, which can be sold as a high-value-added product. This proves that the fluorine adsorbent can realize the resource utilization of wastewater, turning waste into treasure.

[0177] Example 3

[0178] A method for preparing a fluorine adsorbent, comprising:

[0179] (1) Solution preparation: Preparation of SnCl2-citric acid solution: Add a certain amount of deionized water to a stirring tank, then add citric acid powder to prepare a citric acid solution with a mass fraction of 60%, and then add SnCl2·2H2O powder to the citric acid solution so that the concentration of SnCl2 in the prepared SnCl2-citric acid solution is 2.5 mol / L to obtain a SnCl2-citric acid solution.

[0180] Preparation of NaF-Na2CO3 solution: Na2CO3 powder is added to deionized water to prepare a saturated Na2CO3 solution, and then NaF powder is added to the saturated Na2CO3 solution so that the concentration of NaF in the prepared NaF-Na2CO3 solution is 0.25 mol / L to obtain a NaF-Na2CO3 solution.

[0181] Preparation of NaCl-NaHCO3 solution: Add NaCl powder to deionized water to prepare a 4 mol / L NaCl solution, then add NaHCO3 powder to the 4 mol / L NaCl solution, and adjust the pH of the NaCl-NaHCO3 solution to 8.5 to obtain a NaCl-NaHCO3 solution.

[0182] (II) Precipitation reaction: Add 100 L of SnCl2-citric acid solution to an enameled stirring tank and heat the solution to 90°C. Then, add the above-prepared NaF-Na2CO3 solution to the enameled kettle at a speed of 50 L / h at a speed of 300 rpm. The dropwise addition volume of the NaF-Na2CO3 solution is 150 L. After the reaction, Sn(OH) 2-x Fx White slurry.

[0183] (III) Oxidation reaction: insert the aeration tube into the above slurry at a speed of 300 rpm, and aerate Sn(OH) 2-x F x Air is introduced into the white slurry, and oxygen in the air is used as a cheap and readily available oxidant to make Sn(OH) 2-x F x The white slurry turns into Sn(OH) 4-x F x Light yellow slurry.

[0184] (IV) Drying and powdering: Sn(OH) 4-x F x The light yellow slurry is pumped into a plate and frame filter press to filter out the liquid and obtain Sn(OH) 4-x F x Light yellow filter cake; Sn(OH) 4-x F x The light yellow filter cake was placed in a crawler drying kiln, the temperature was controlled at 80°C, and dried to a moisture content of 5% to obtain Sn(OH) 4-x F x Light yellow dry block solid; Sn(OH) 4-x F x The light yellow dry block solid was crushed with an impact mill to obtain Sn(OH) with a particle size of 0.5-20 μm. 4-x F x Light yellow dry powder.

[0185] (5) Powder granulation: Sn(OH) with a particle size of 0.5-20 μm 4-x F x Light yellow dry powder, polyvinyl chloride (PVC), polyvinyl butyral (PVB), and N,N-dimethylacetamide (DMAC) are mixed in a certain mass ratio, wherein the total mass of the binder PVC and the binder PVB accounts for 1% of the total powder mass (Sn(OH) 4-x F x +PVC+PVB) 25%, the mass of solvent DMAC accounts for the total powder mass (Sn(OH) 4-x F x +PVC+PVB), and the mass ratio of the adhesive PVC to the adhesive PVB is 1:5.

[0186] Add the materials to the stirred tank in this order: first add the solvent DMAC, heat to 90℃, add the adhesive PVC and adhesive PVB while stirring, after the adhesive PVC and adhesive PVB are dissolved, add Sn(OH) 4-x Fx The light yellow dry powder was stirred for 4 hours. The liquid was transferred to the ball dropping device for ball dropping. The small balls fell into deionized water for phase conversion to obtain Sn(OH) with a particle size of about 2 mm. 4-x F x / PVC-PVB balls.

[0187] (6) Fluorine-chlorine replacement: 200L of Sn(OH) 4-x F x / PVC-PVB balls were loaded into the adsorption column, and the above-prepared NaCl-NaHCO3 solution with a pH of 8.5 was added from the bottom of the adsorption column at a flow rate of 3BV / h. The amount of NaCl-NaHCO3 solution used was 300L, and the Sn(OH) 4-x F x / PVC-PVB small balls, making Sn(OH) 4-x F x / The fluorine element on the PVC-PVB ball is replaced by the chlorine element in the NaCl--NaHCO3 solution, Sn(OH) 4-x F x / PVC-PVB beads transformed into Sn(OH) 4-x Cl x / PVC-PVB beads, Sn(OH) 4-x Cl x / PVC-PVB beads are the prepared fluorine adsorbent.

[0188] (VII) Fluorine adsorbent property testing:

[0189] Figure 7a This is a physical picture of the fluorine adsorbent pellet product prepared in this example.

[0190] Figure 7b This is a surface scanning electron microscope image of the fluorine adsorbent pellet product prepared in this example.

[0191] from Figure 7a 、 Figure 7b It can be seen that the particle size of the fluorine adsorbent beads is very uniform, about 2mm in size, and the fluorine adsorbent powder is wrapped by PVC and PVB resin to prevent the fluorine adsorbent powder from falling off. Figure 7a 、 Figure 7b It can be seen that PVC and PVB resins form a rich pore structure, and the interconnected network pore structure is conducive to the adsorption and elution of fluoride ions, thereby improving the ion exchange efficiency.

[0192] Table 3 is the fluorine adsorbent Sn(OH) prepared in this example 4-x Cl x / PVC-PVB pellets are produced by heating and dissolving Sn(OH) with 4 mol / L sodium hydroxide 4-x Cl x Afterwards, the contents of Sn and Cl in the solution were tested with an instrument, and it was inferred that Sn(OH) 4-x Cl x The chemical formula is Sn(OH) 3.0 Cl 1.0 .

[0193] Table 3 Chemical formula and adsorption capacity analysis of fluorine adsorbent in Example 3:

[0194]

[0195]

[0196] Passed the test Sn(OH) 3.0 Cl 1.0 / PVC-PVB beads have a saturated adsorption capacity of fluoride ions of 162 mg / g, which is much higher than the 31 mg / g of the fluoride adsorbent (TFR-93) on the market. 3.0 Cl 1.0 / PVC-PVB beads have the performance advantage of high adsorption capacity. In addition, Sn(OH) 3.0 Cl 1.0 The powder loss rate of the PVC-PVB ball after 1000 cycles is only 0.53%, proving that the soft and hard skeleton of the PVC-PVB dual binder can make the Sn(OH) 3.0 Cl 1.0 / PVC-PVB adsorbent beads form an extensive adsorption channel, while also avoiding Sn(OH) 3.0 Cl 1.0 / The loss of effective powder in the PVC-PVB beads greatly improves the adsorption capacity and adsorption stability of the fluorine adsorbent.

[0197] Application Example 3

[0198] The fluorine adsorbent Sn(OH) prepared in Example 3 was 3.0 Cl 1.0 / PVC-PVB balls were used for application tests.

[0199] See also Figure 2 The fluorine-containing wastewater treatment application process based on the fluorine adsorbent of Example 3 includes:

[0200] (1) Wastewater defluoridation process: The fluorine adsorbent beads prepared in Example 3 were loaded into an adsorption column. The fluorine ion concentration of the fluorine-containing wastewater was approximately 200 mg / L. The fluorine-containing wastewater flowed into the adsorption column from bottom to top at a flow rate of 20 BV. The fluorine ion concentration in the produced water after defluoridation was less than 1 mg / L. A fluorine ion sensor was installed at the water outlet to monitor the fluorine ion concentration of the produced water in real time. Once the fluorine ion concentration of the produced water was greater than 1 mg / L, adsorption of the water was stopped and regeneration was prepared.

[0201] (2) Fluorine adsorbent regeneration process: When the fluorine ion concentration of the adsorption column of the fluorine adsorbent is greater than 1mg / L, the 3mol / L MgCl2 solution in the regeneration liquid storage tank A is used as the regeneration liquid to regenerate the fluorine adsorbent from bottom to top at a flow rate of 25BV / h. The regeneration liquid storage tank A and the adsorption column are used as a circulation system. The upper water of the adsorption column is returned to the regeneration liquid storage tank A. The regeneration liquid volume is 4BV. The circulation is 20 minutes to complete the regeneration of the fluorine adsorbent. After the regeneration is completed, all the residual regeneration liquid in the adsorption column is pumped back to the regeneration liquid storage tank A.

[0202] (3) Regeneration liquid reuse process: After the fluorine adsorbent is regenerated with the regeneration liquid (3 mol / L MgCl2 solution), an eluent (a mixture of MgCl2 solution and MgF2 precipitate, wherein the MgCl2 concentration is less than 3 mol / L) is obtained. The eluent is pumped into a plate-and-frame filter press to perform solid-liquid separation of the MgCl2 solution and the MgF2 precipitate, and the obtained MgCl2 solution (filtrate) is pumped back into the regeneration liquid storage tank B. After all the eluent in the regeneration liquid storage tank A has flowed through the plate-and-frame filter press, the slightly lower concentration MgCl2 solution (filtrate) in the regeneration liquid storage tank B is pumped into the regeneration liquid storage tank A, and an appropriate amount of MgCl2·6H2O solid is added to the regeneration liquid storage tank A to obtain a 3 mol / L MgCl2 solution that is recycled as a new regeneration liquid. The MgF2 filter cake is dried and crushed to obtain MgF2 powder, which can be sold as a chemical.

[0203] Figure 8 Example 3 fluorine adsorbent Sn(OH) provided for this application example 3.0 Cl 1.0 / The regular curve diagram of the fluorine concentration in the inlet and outlet water during the defluorination operation of PVC-PVB balls in real fluorine-containing industrial wastewater.

[0204] from Figure 8It can be seen that the fluoride ion concentration in the water produced by the fluoride adsorbent during the fluoride removal process is very stable. The fluoride ion concentration in the fluoride-containing groundwater inlet is about 200 mg / L, and the fluoride ion concentration in the water produced is always less than 0.5 mg / L before the column adsorption is saturated. China's "National Drinking Water Quality Standard" (GB5749-2022) stipulates that the limit value of fluoride in drinking water is 1.0 mg / L, which proves that the fluoride adsorbent can meet the national standard requirements for groundwater fluoride removal and also meet engineering needs. It has the advantages of large adsorption capacity and stable adsorption performance, and is expected to be able to be applied on a large scale.

[0205] Furthermore, the MgF2 powder product obtained by using the above-mentioned fluorine adsorbent method to remove fluorine from fluorinated groundwater has a purity of 99.75%, which can be sold as a high-value-added product. This proves that the fluorine adsorbent can realize the resource utilization of wastewater, turning waste into treasure.

[0206] Comparative Example 1

[0207] A method for preparing a fluorine adsorbent, comprising:

[0208] (1) Solution preparation: same as in Example 1.

[0209] (2) Precipitation reaction: Same as Example 1.

[0210] (3) Oxidation reaction: Same as Example 1.

[0211] (4) Drying and pulverization: Same as Example 1.

[0212] (5) Powder granulation:

[0213] Sn(OH) with a particle size of 0.5-5 μm 4-x F x Light yellow dry powder, polyvinyl chloride (PVC), and N,N-dimethylacetamide (DMAC) are mixed in a certain mass ratio, wherein the mass of the binder PVC accounts for 1% of the total powder mass (Sn(OH) 4-x F x +PVC) 8%, the mass of solvent DMAC accounts for 8% of the total powder mass (Sn(OH) 4-x F x + 75% of PVC).

[0214] Add the materials to the stirred tank in this order: first add the solvent DMAC, heat to 50 ° C, add the binder PVC while stirring, and after the binder PVC is dissolved, add Sn(OH) 4-x F x The light yellow dry powder was stirred for 1 hour. The liquid was transferred to the ball dropping device for ball dropping. The small balls fell into deionized water for phase conversion to obtain Sn(OH) with a particle size of 0.5 mm. 4-x F x / PVC balls.

[0215] (6) Fluorine-chlorine replacement: 100L of Sn(OH) 4-x F x / PVC balls were loaded into the adsorption column, and the above-prepared NaCl-NaHCO3 solution with a pH of 7.5 was added from the bottom of the adsorption column at a flow rate of 1BV / h. The amount of NaCl-NaHCO3 solution used was 150L, ​​and the Sn(OH) 4-x F x / PVC balls, making Sn(OH) 4-x F x / The fluorine element on the PVC ball is replaced by the chlorine element in the NaCl--NaHCO3 solution, Sn(OH) 4-x F x / PVC balls transformed into Sn(OH) 4-x Cl x / PVC balls.

[0216] Table 4 Analysis of adsorption capacity and powder loss rate of fluorine adsorbents in Example 1 and Comparative Example 1:

[0217] Saturated adsorption capacity of Example 1 (mg / g) 115 Powder loss rate after 1000 cycles of use of Example 1 0.5％ Saturated adsorption capacity of comparative example 1 (mg / g) 107 Powder loss rate of comparative example 1 after 1000 cycles of use 35.6％

[0218] Through testing, this comparative example Sn(OH) 4-x Cl x The powder loss rate of the PVC pellets after 1000 cycles is as high as 35.6%, which is 71 times that of Example 1. This proves that using only PVC as a single binder cannot avoid the Sn(OH) 4- x Cl x / The loss of effective powder in the PVC balls greatly reduces the adsorption stability of the fluorine adsorbent.

[0219] The difference between the fluorine adsorbent synthesis method of this comparative example and that of Example 1 is that a single PVC binder is used for powder granulation.

[0220] Comparative Example 2

[0221] A method for preparing a fluorine adsorbent, comprising:

[0222] (1) Solution preparation: same as in Example 1.

[0223] (2) Precipitation reaction: Same as Example 1.

[0224] (3) Oxidation reaction: Same as Example 1.

[0225] (4) Drying and pulverization: Same as Example 1.

[0226] (5) Powder granulation:

[0227] Sn(OH) with a particle size of 0.5-5 μm 4-x F x Light yellow dry powder, polyvinyl butyral (PVB), and N,N-dimethylacetamide (DMAC) are mixed in a certain mass ratio, wherein the total mass of the binder PVB accounts for 1% of the total powder mass (Sn(OH) 4-x F x +PVB) 8%, the mass of solvent DMAC accounts for 8% of the total powder mass (Sn(OH) 4-x F x +PVB).

[0228] Add the materials to the stirred tank in this order: first add the solvent DMAC, heat to 50 ° C, add the binder PVB while stirring, and after the binder PVB is dissolved, add Sn(OH) 4-x F x The light yellow dry powder was stirred for 1 hour. The liquid was transferred to the ball dropping device for ball dropping. The small balls fell into deionized water for phase conversion to obtain Sn(OH) with a particle size of 0.5 mm. 4- x F x / PVB balls.

[0229] (6) Fluorine-chlorine replacement: 100L of Sn(OH) 4-x F x PVB beads were loaded into the adsorption column, and the above-prepared NaCl-NaHCO3 solution with a pH of 7.5 was added from the bottom of the adsorption column at a flow rate of 1 BV / h. The amount of NaCl-NaHCO3 solution used was 150 L, and the Sn(OH) 4-x F x / PVB beads, making Sn(OH) 4-x F x / The fluorine element on the PVB ball is replaced by the chlorine element in the NaCl--NaHCO3 solution, Sn(OH) 4-x F x / PVB beads transformed into Sn(OH) 4-x Cl x / PVB balls.

[0230] Table 5 Analysis of adsorption capacity and powder loss rate of fluorine adsorbents in Example 1 and Comparative Example 2:

[0231] Saturated adsorption capacity of Example 1 (mg / g) 115 Powder loss rate after 1000 cycles of use of Example 1 0.5％ Saturated adsorption capacity of comparative example 2 (mg / g) 102 Powder loss rate of comparative example 2 after 1000 cycles of use 45.7％

[0232] Through testing, this comparative example Sn(OH) 4-x Cl xThe powder loss rate of the PVB pellets after 1000 cycles is as high as 45.7%, which is 91 times that of Example 1. This proves that using only PVB as a single binder cannot avoid the Sn(OH) 4- x Cl x / The loss of effective powder in the PVB beads greatly reduces the adsorption stability of the fluorine adsorbent.

[0233] The difference between the fluorine adsorbent synthesis method of this comparative example and that of Example 1 is that a single PVB binder is used for powder granulation.

[0234] Comparative Example 3

[0235] This comparative example is the same as Example 1 except that the "NaCl-NaHCO3 solution with a pH of 7.5-8.5" in step (six) is replaced by "pure NaCl solution".

[0236] Comparison of the adsorption test between this comparative example and Example 1 shows that in the "fluorine-chlorine replacement" stage, the use of pure NaCl solution instead of the NaCl-NaHCO3 solution with a pH of 7.5 to 8.5 results in Sn(OH) 4-x F x Cannot be converted into Sn(OH) 4-x Cl x , resulting in an adsorption capacity of only 37 mg / g, which is only 32% of that in Example 1.

[0237] Table 6 Analysis of adsorption capacity of fluorine adsorbents in Example 1 and Comparative Example 3:

[0238]

[0239]

[0240] Comparative Example 4

[0241] A method for preparing a fluorine adsorbent, comprising:

[0242] (1) Solution preparation:

[0243] Preparation of SnCl2-citric acid solution: same as in Example 1.

[0244] Preparation of NaF-Na2CO3 solution: Na2CO3 powder is added to deionized water to prepare a saturated Na2CO3 solution, and then NaF powder is added to the saturated Na2CO3 solution so that the concentration of NaF in the prepared NaF-Na2CO3 solution is 0.02 mol / L to obtain a NaF-Na2CO3 solution.

[0245] Preparation of NaCl-NaHCO3 solution: same as in Example 1.

[0246] (2) Precipitation reaction: Same as Example 1.

[0247] (3) Oxidation reaction: Same as Example 1.

[0248] (4) Drying and pulverization: Same as Example 1.

[0249] (5) Powder granulation: same as Example 1.

[0250] (6) Fluorine-chlorine replacement: same as Example 1.

[0251] Comparison of the adsorption test between Comparative Example 4 and Example 1 shows that in the "solution preparation" stage, the concentration of NaF in the prepared NaF-Na2CO3 solution is 0.02 mol / L, resulting in Sn(OH) 4-x Cl x The x in Example 1 is 0.2, resulting in an adsorption capacity of only 19 mg / g, which is only 16.5% of that in Example 1.

[0252] Table 7 Analysis of adsorption capacity of fluorine adsorbents in Example 1 and Comparative Example 4:

[0253] Chemical formula of the fluorine adsorbent of Example 1 <![CDATA[Sn(OH) 3.2 Cl 0.8 ]]> Saturated adsorption capacity of Example 1 (mg / g) 115 Chemical formula of the fluorine adsorbent of Comparative Example 4 <![CDATA[Sn(OH) 3.8 Cl 0.2 ]]> Saturated adsorption capacity of Comparative Example 4 (mg / g) 19

[0254] The difference between the synthesis method of the fluorine adsorbent in this comparative example and that in Example 1 is that Sn(OH) 4-x Cl x where x is 0.2.

[0255] Comparative Application Example 1

[0256] The fluorine adsorbent Sn(OH) prepared in Example 1 was 3.2 Cl 0.8 / PVC-PVB balls were used for application tests.

[0257] See also Figure 2 The fluorine-containing wastewater treatment application process based on the fluorine adsorbent of Example 1 includes:

[0258] (1) Wastewater defluorination process: same as application example 1.

[0259] (2) Fluorine adsorbent regeneration process: When the fluorine ion concentration of the adsorption column of the fluorine adsorbent is greater than 1mg / L, the 0.1mol / L MgCl2 solution in the regeneration liquid storage tank A is used as the regeneration liquid to regenerate the fluorine adsorbent from bottom to top at a flow rate of 15BV / h. The regeneration liquid storage tank A and the adsorption column are used as a circulation system. The upper water of the adsorption column is returned to the regeneration liquid storage tank A. The regeneration liquid volume is 2BV. The circulation is 10 minutes to complete the regeneration of the fluorine adsorbent. After the regeneration is completed, all the residual regeneration liquid in the adsorption column is pumped back to the regeneration liquid storage tank A.

[0260] (3) Regeneration liquid reuse process: same as application example 1.

[0261] The difference between this comparative example and the example is that this comparative example uses a 0.1 mol / L MgCl solution as the regeneration solution. As shown in Table 8, when the MgCl solution concentration is too low, the fluorine adsorbent is incompletely regenerated. Incomplete regeneration makes it difficult to achieve the same performance as the initial adsorption capacity in the next adsorption process, resulting in a low cycle adsorption capacity of only 51% of that in Example 1.

[0262] Table 8 Analysis of cyclic adsorption capacity of fluorine adsorbent in Example 1 and Comparative Example 1:

[0263]

[0264] Application Comparative Example 2

[0265] The fluorine adsorbent Sn(OH) prepared in Example 1 was 3.2 Cl 0.8 / PVC-PVB balls were used for application tests.

[0266] See also Figure 2 The fluorine-containing wastewater treatment application process based on the fluorine adsorbent of Example 1 includes:

[0267] (1) Wastewater defluorination process: same as application example 1.

[0268] (2) Fluorine adsorbent regeneration process: When the fluorine ion concentration of the adsorption column of the fluorine adsorbent is greater than 1mg / L, the 4mol / L MgCl2 solution in the regeneration liquid storage tank A is used as the regeneration liquid to regenerate the fluorine adsorbent from bottom to top at a flow rate of 15BV / h. The regeneration liquid storage tank A and the adsorption column are used as a circulation system. The upper water of the adsorption column is returned to the regeneration liquid storage tank A. The regeneration liquid volume is 2BV. The circulation is 10 minutes to complete the regeneration of the fluorine adsorbent. After the regeneration is completed, all the residual regeneration liquid in the adsorption column is pumped back to the regeneration liquid storage tank A.

[0269] (3) Regeneration liquid reuse process: same as application example 1.

[0270] The difference between this comparative example and the application example is that this comparative example uses a 4 mol / L MgCl2 solution as the regeneration solution. As shown in Table 9, when the concentration of the MgCl2 solution is too high, the precipitation reaction driving force Mg 2+ +2F - =The presence of MgF2↓, the high concentration of Mg in the regeneration solution 2+, the formed MgF2 precipitate particles will be too large, blocking the adsorption and desorption channels of the fluorine adsorbent, and the MgF2 precipitate particles cannot flow out of the adsorption column with the regeneration liquid flow, making it difficult to carry out the next cycle of adsorption and desorption, resulting in a low cyclic adsorption capacity of only 12.5% ​​of that in Example 1.

[0271] Table 9 Analysis of cyclic adsorption capacity of fluorine adsorbents in Example 1 and Comparative Example 2:

[0272]

[0273] Application Comparative Example 3

[0274] The fluorine adsorbent Sn(OH) prepared in Example 1 was 3.2 Cl 0.8 / PVC-PVB balls were used for application tests.

[0275] See also Figure 2 The fluorine-containing wastewater treatment application process based on the fluorine adsorbent of Example 1 includes:

[0276] (1) Wastewater defluorination process: same as application example 1.

[0277] (2) Fluorine adsorbent regeneration process: After the fluorine ion concentration of the adsorption column of the fluorine adsorbent is greater than 1mg / L, the 0.5mol / L MgCl2 solution in the regeneration liquid storage tank A is used as the regeneration liquid to regenerate the fluorine adsorbent from bottom to top at a flow rate of 10BV / h. The regeneration liquid storage tank A and the adsorption column are used as a circulation system. The upper water of the adsorption column is returned to the regeneration liquid storage tank A. The regeneration liquid volume is 2BV. The circulation is 10 minutes to complete the regeneration of the fluorine adsorbent. After the regeneration is completed, all the residual regeneration liquid in the adsorption column is pumped back to the regeneration liquid storage tank A.

[0278] (3) Regeneration liquid reuse process: same as application example 1.

[0279] The difference between this comparative example and the example is that the fluorine adsorbent in this comparative example was regenerated from bottom to top at a flow rate of 10 BV / h. As shown in Table 10, when the regeneration liquid flow rate is too low, the liquid flow rate between the particles is too low. This prevents the formed MgF2 precipitate from flowing out of the adsorption column with the water flow, blocking the adsorption and desorption channels of the fluorine adsorbent, making it difficult to proceed with the next adsorption and desorption cycle. This results in a low cyclic adsorption capacity of only 28.5% of that in Example 1.

[0280] Table 10 Analysis of cyclic adsorption capacity of fluorine adsorbents in Example 1 and Comparative Example 3:

[0281]

[0282] Comparative Application Example 4

[0283] The fluorine adsorbent Sn(OH) prepared in Example 1 was 3.2 Cl 0.8 / PVC-PVB balls were used for application tests.

[0284] See also Figure 2 The fluorine-containing wastewater treatment application process based on the fluorine adsorbent of Example 1 includes:

[0285] (1) Wastewater defluorination process: same as application example 1.

[0286] (2) Fluorine adsorbent regeneration process: When the fluorine ion concentration of the water produced by the adsorption column of the fluorine adsorbent is greater than 1mg / L, the 0.5mol / L MgCl2 solution in the regeneration liquid storage tank A is used as the regeneration liquid to regenerate the fluorine adsorbent from bottom to top at a flow rate of 30BV / h. The regeneration liquid storage tank A and the adsorption column are used as a circulation system. The upper water of the adsorption column is returned to the regeneration liquid storage tank A. The regeneration liquid volume is 2BV. The circulation is 10 minutes to complete the regeneration of the fluorine adsorbent. After the regeneration is completed, all the residual regeneration liquid in the adsorption column is pumped back to the regeneration liquid storage tank A.

[0287] (3) Regeneration liquid reuse process: same as application example 1.

[0288] The difference between this comparative example and the example is that this comparative example regenerates the fluorine adsorbent from bottom to top at a flow rate of 30 BV / h. As shown in Table 11, when the regeneration liquid flow rate is too high, the water flow causes severe collisions and friction between the fluorine adsorbent particles, resulting in severe powder loss. The effective fluorine adsorbent powder flows out of the adsorption column with the water flow, causing a sharp decrease in the effective fluorine adsorbent content within the column. This results in a low cyclic adsorption capacity of only 24% of that in Example 1.

[0289] Table 11 Analysis of cyclic adsorption capacity of fluorine adsorbents in Example 1 and Comparative Example 4:

[0290]

[0291] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fluorine adsorbent, characterized in that: The structural formula of the fluorine adsorbent is: Sn(OH) 4-x Cl x / PVC-PVB, where: 0.8≤x≤1.0; The PVC-PVB is a dual binder, and the fluorine adsorbent is prepared by using PVC and PVB as binders.

2. The fluorine adsorbent according to claim 1, characterized in that The fluorine adsorbent has a spherical structure and a particle size of 0.5 to 2 mm.

3. A method for preparing the fluorine adsorbent according to claim 1, characterized in that: The preparation method comprises: Step S1: Add NaF-Na2CO3 solution dropwise to SnCl2-citric acid solution to perform precipitation reaction to obtain Sn(OH) 2-x F x slurry; Step S2 oxidation reaction: Sn(OH) 2-x F x The slurry is oxidized to make Sn(OH) 2-x F x Converted to Sn(OH) 4-x F x , obtaining Sn(OH) 4-x F x slurry; Step S3 Drying and Powdering: Sn(OH) 4-x F x The slurry was filtered to obtain Sn(OH) 4-x F x The filter cake is then dried and crushed to obtain Sn(OH) with a particle size of 0.5 to 20 μm. 4-x F x powder; Step S4 powder granulation: Sn(OH) 4-x F x Powder, PVC and PVB are added to the solvent to obtain a granulation solution; then drop ball granulation is performed to obtain Sn(OH) with a particle size of 0.5 to 2 mm. 4-x F x / PVC-PVB balls; Step S5: Fluorine-chlorine replacement: Sn(OH) 4-x F x / PVC-PVB beads were subjected to fluorine-chlorine replacement to obtain spherical fluorine adsorbent.

4. The method for preparing the fluorine adsorbent according to claim 3, characterized in that: The dropping speed of the NaF-Na2CO3 solution in step S1 is 10 to 50 L / h; And / or, the oxidation in step S2 is performed by aeration.

5. The method for preparing the fluorine adsorbent according to claim 4, characterized in that: The oxidation is to aerate Sn(OH) at an aeration rate of 10 to 30 L / min 2-x F x Air is introduced into the slurry.

6. The method for preparing the fluorine adsorbent according to claim 3, characterized in that: The drying temperature in step S3 is 50-80°C, and after drying, Sn(OH) 4-x F x The moisture content of the powder is less than 5%; And / or, the solvent in step S4 is N,N-dimethylacetamide; And / or, the mass of the solvent in step S4 is 75-150% of the total mass of the granulation raw materials; the total mass of the granulation raw materials is Sn(OH) 4-x F x The sum of the mass of powder, PVC and PVB; And / or, the pH value of the NaCl-NaHCO3 solution in step S5 is 7.5-8.

5.

7. The method for preparing a fluorine adsorbent according to claim 6, characterized in that: In step S4, the mass of PVC and PVB accounts for 8-25% of the total mass of the granulation raw materials; And / or, in step S4, the mass ratio of PVC to PVB is 1:1-5.

8. Use of the fluorine adsorbent according to claim 1 or 2 in the treatment of fluorine-containing wastewater.

9. The method for treating fluorine-containing wastewater using the fluorine adsorbent according to claim 1 or 2, characterized in that: The processing method comprises: (A) Fluoride removal from wastewater; (B) Fluorine adsorbent regeneration; (C) Regeneration fluid is reused.

10. The method for treating fluorine-containing wastewater according to claim 9, characterized in that: The wastewater defluoridation comprises: filling the fluorine adsorbent according to claim 1 or 2 into an adsorption column, then flowing the fluorine-containing wastewater into the adsorption column for defluoridation, and when the fluoride ion concentration is greater than 1 mg / L, stopping the flow of the fluorine-containing wastewater and regenerating the fluorine adsorbent; And / or, the fluorine adsorbent regeneration includes: using MgCl2 solution as a regeneration liquid to circulate and elute the fluorine adsorbent adsorbed with fluoride ions, completing the regeneration of the fluorine adsorbent and obtaining an eluent containing MgCl2 solution and MgF2 precipitate.

11. The method for treating fluorine-containing wastewater according to claim 10, characterized in that: The concentration of the MgCl2 solution is 0.5-3 mol / L.

12. The method for treating fluorine-containing wastewater according to claim 10, characterized in that: The regeneration liquid reuse comprises: (C1) performing solid-liquid separation on the eluate containing the MgCl2 solution and the MgF2 precipitate to obtain a MgCl2 solution and a MgF2 precipitate; (C2) adjusting the concentration of the MgCl2 solution to 0.5-3 mol / L for recycling as a regeneration solution; and, drying the MgF2 precipitate to obtain MgF2 powder.

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