A method for fluoride ion crystallization recovery based on a PCR pellet reactor

Abstract

The present application relates to the field of environmental engineering technology, and more particularly to a fluorine ion crystallization recovery method based on a PCR pellet reactor, comprising the following steps: (1) measuring the concentration of fluorine ions in the wastewater to be treated, recording, and then adding calcium salt reagents and special seeds according to the concentration of fluorine ions in the wastewater to be treated; (2) after adding the calcium salt reagents and special seeds, stirring and mixing uniformly, and then adjusting the pH value of the wastewater to 6.0-7.5; (3) the reaction time is controlled to be 10-30 minutes; (4) after the wastewater treatment is completed, the fluorine-containing pellet crystals are recovered; the present application provides a fluorine ion crystallization recovery method based on a PCR pellet reactor, which adds calcium-containing composite chemical reagents and seeds into fluorine-containing wastewater to induce fluorine element crystallization to form microcrystals, and with the passage of time, fluorite-like layers are formed by layer-by-layer crystallization, thereby realizing the recovery and reuse of fluorine resources.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental engineering and chemical engineering, in particular to a fluorine ion crystallization recovery method based on a PCR pellet reactor. BACKGROUND

[0002] Fluorine-containing wastewater mainly comes from the electrolytic aluminum, glass etching, fluorine chemical industry and other chemical manufacturing industries. The fluorine-containing wastewater not only has a great impact on the environment, but also can cause chronic inflammation of the upper respiratory tract, damage to bones and teeth, such as dental fluorosis, fluorosis, kidney, liver and brain damage, etc. The discharge of fluorine-containing wastewater in China is about 1 billion tons / year. The treatment and control of fluorine-containing wastewater are very important for protecting human health and the ecological environment.

[0003] The traditional chemical defluorination and water softening is to convert fluorine and calcium ions into calcium fluoride and other chemical precipitates with the help of chemical agents and flocculants. However, the process often produces amorphous precipitates with random particle arrangement, loose structure, and a large amount of water and impurities. The process has the problems of large volume, complex process including coagulation, precipitation, and clarification, high operation cost, difficulty in meeting the 1.0 discharge standard, and no economic value of the recovered precipitate. In addition, the defluorination effect is not ideal when using RO membrane or resin, and the problems of clogging and stability are difficult to solve.

[0004] In view of the challenges of serious fluorine pollution and insufficient reserves of fluorite ore, a PCR (Pelletized Crystal Reactor) pellet technology is developed to solve the problem of fluorine pollution, and to realize the recovery and efficient resource utilization of high-purity calcium fluoride (artificial fluorite) and solve the problem of insufficient reserves of fluorite ore. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a fluorine ion crystallization recovery method based on a PCR pellet reactor.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0007] A fluorine ion crystallization recovery method based on a PCR pellet reactor, comprising the following steps:

[0008] (1) measuring the concentration of fluorine ions in the wastewater to be treated, recording, and then adding calcium salt reagents and special seeds according to the concentration of fluorine ions in the wastewater to be treated;

[0009] (2) After adding the calcium salt reagents and special seeds, stirring and mixing uniformly, and then adjusting the pH value of the wastewater to 6.0-7.5;

[0010] (3) The reaction time is controlled within 10-30 minutes;

[0011] (4) After the wastewater treatment is completed, the fluorine-containing pellet crystal is recovered.

[0012] As a further technical solution, the calcium salt agent is formed by mixing calcium hydroxide, calcium chloride and calcium sulfate.

[0013] Among them, the mass ratio of calcium hydroxide, calcium chloride and calcium sulfate is 3-4:100-120:15-18.

[0014] As a further technical solution, when adding, the molar ratio of calcium ions in the calcium salt agent to fluorine ions in the wastewater to be treated is 1:2.

[0015] As a further technical solution, the amount of special seed crystal added is 1 / 5-1 / 6 of the effective volume of the PCR pellet reactor.

[0016] As a further technical solution, the special seed crystal is made of quartz sand, tourmaline powder, dolomite powder and fluorite powder.

[0017] As a further technical solution, the mass ratio of quartz sand, tourmaline powder, dolomite powder and fluorite powder is 80:1:2:1.

[0018] As a further technical solution, the preparation method of the special seed crystal is:

[0019] Mix the quartz sand, tourmaline powder, dolomite powder and fluorite powder with chitosan adhesive solution as the adhesive, and then vacuum dry to obtain the special seed crystal.

[0020] The mixing ratio of quartz sand and chitosan adhesive solution is 30-35g:100mL.

[0021] As a further technical solution, the preparation method of the chitosan adhesive solution is:

[0022] Dissolve 5g of chitosan in 1% acetic acid solution to obtain a 5%(w / v) preliminary chitosan solution.

[0023] Weigh dopamine and prepare an alkaline aqueous solution, add dopamine to the alkaline aqueous solution, stir and mix for 20min to obtain a dispersion, and store in an ice bath for standby;

[0024] Mix the preliminary chitosan solution and the dispersion according to a mass ratio of 5:1 to obtain a chitosan adhesive solution.

[0025] As a further technical solution, the alkaline aqueous solution is a sodium hydroxide solution, and the pH of the sodium hydroxide solution is 11.

[0026] The mass ratio of dopamine to alkaline aqueous solution is 10g:180mL.

[0027] As a further technical solution, the vacuum drying temperature is 50 DEG C, and the time is 20 hours.

[0028] Compared with the prior art, the present application has the following advantages:

[0029] The present application provides a method for recovering fluorine ion crystallization based on PCR pellet reactor, which comprises adding calcium-containing composite chemical agent and crystal seeds into the fluorine-containing wastewater to induce fluorine element crystallization to form microcrystals.

[0030] The core of the method is to combine chemical reaction precipitation method and generalized nucleation-growth-aggregation theory, adjust the pH value of the wastewater, control the appropriate supersaturation, inhibit homogeneous nucleation, promote the combination of fluorine ion and calcium ion to form calcium fluoride crystals, and induce large particle seeds to accelerate the precipitation process through electrostatic interaction force and other intermolecular interaction forces.

[0031] The technical solution of the present application is mainly formed by combining chemical reaction precipitation method and seed induction method.

[0032] Ca 2+ +2F-=CaF2

[0033] After the reaction of the generated calcium fluoride microcrystals, the pH of the wastewater is controlled between 6.0-7.5 to weaken the hydrogen proton ion strength, adjust the reaction equilibrium, and reduce the concentration of fluorine ions in the system.

[0034] Seed induction method: by adding special crystal seeds (such as micro-particles made of quartz sand, tourmaline powder, dolomite powder, and fluorite powder) into the wastewater, the nucleation and crystallization process of calcium fluoride is accelerated.

[0035] The formation of precipitates is a complex process, usually involving two key stages: nucleation and growth. In a supersaturated solution, the nucleation stage includes one-step nucleation and two-step nucleation. One-step nucleation can occur homogeneously in a pure solution without foreign particles, requiring a higher degree of supersaturation. In addition, foreign particles can reduce the degree of supersaturation required for nucleation. Two-step nucleation systems do not directly form the most stable phase, but first form the closest metastable phase, which serves as a precursor and eventually transforms into the target crystal, which occurs in the presence of existing crystal seeds, caused by fluid shear or contact between seeds.

[0036] However, in industrial crystallization processes, one-step nucleation can be effectively inhibited and the ordered growth of crystals can be promoted by fine-tuning the supersaturation of the reaction and the promotion of fluidization in the fluidized bed. The introduction of an appropriate amount of seed crystals during precipitation not only reduces the degree of supersaturation and inhibits one-step nucleation, but also provides more secondary nucleation sites and increases the contact area for crystal growth, thereby promoting the crystallization and growth of small particles. The entire system needs to overcome an initial free energy barrier, then a shallow minimum (saddle point) appears on the free energy curve, and further overcome an energy barrier to transform into the final crystalline state, the overall energy is less than one-step nucleation. After the formation of the crystal nucleus, it will grow in the supersaturated solution through diffusion and surface reaction processes, which consist of the migration of solute from the solution to the crystal surface and the embedding of solute on the crystal surface.

[0037] In the PCR pellet reactor, the chemical precipitation method and the seed crystal induction method are used to reduce the concentration of fluoride ions, reduce the zeta potential, promote secondary nucleation and inhibit primary nucleation, agglomeration between small particles, adsorption of small particles on seed crystals, and adsorption and agglomeration between seed crystals. The comprehensive effect ultimately realizes the preparation of artificial fluorite and the recovery of fluoride ions, and artificial fluorite is finally recovered. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0039] Figure 1 Mechanism diagram for particle precipitation and growth;

[0040] Figure 2 Zeta (ζ) potential relationship diagram of seed crystal surface under different environmental pH. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of the present application.

[0042] A fluorine ion crystallization recovery method based on a PCR pellet reactor, comprising the following steps:

[0043] (1) measuring the concentration of fluorine ions in the wastewater to be treated, recording, and then adding calcium salt reagents and special seeds according to the concentration of fluorine ions in the wastewater to be treated;

[0044] (2) After adding the calcium salt reagents and special seeds, stirring and mixing uniformly, and then adjusting the pH value of the wastewater to 6.0-7.5;

[0045] (3) The reaction time is controlled at 10-30 minutes;

[0046] (4) After the wastewater treatment is completed, the fluorine-containing pellet crystals are recovered.

[0047] The calcium salt reagent is a mixture of calcium hydroxide, calcium chloride and calcium sulfate;

[0048] Among them, the mass ratio of calcium hydroxide, calcium chloride and calcium sulfate is 3-4:100-120:15-18.

[0049] When adding, the molar ratio of calcium ions in the calcium salt reagent to fluorine ions in the wastewater to be treated is 1:2.

[0050] The addition amount of the special seed is 1 / 5-1 / 6 of the effective volume of the PCR pellet reactor.

[0051] The special seed is made of quartz sand, tourmaline powder, dolomite powder and fluorite powder.

[0052] The mass ratio of quartz sand, tourmaline powder, dolomite powder and fluorite powder is 80:1:2:1.

[0053] The preparation method of the special seed is:

[0054] The quartz sand, tourmaline powder, dolomite powder and fluorite powder are mixed with chitosan adhesive solution as an adhesive, and then vacuum dried to obtain the special seed.

[0055] The mixing ratio of quartz sand and chitosan adhesive solution is 30-35g:100mL.

[0056] The preparation method of the chitosan adhesive solution is:

[0057] 5 g of chitosan is dissolved in 1% acetic acid solution to obtain a 5% (w / v) primary chitosan solution;

[0058] Dopamine is weighed, an alkaline aqueous solution is prepared, the dopamine is added to the alkaline aqueous solution, and stirring and mixing are performed for 20 min to obtain a dispersion, which is prepared in an ice bath and kept ready for use;

[0059] The primary chitosan solution and the dispersion are mixed in a mass ratio of 5:1 to obtain a chitosan bonding solution.

[0060] The alkaline aqueous solution is a sodium hydroxide solution, and the pH of the sodium hydroxide solution is 11;

[0061] The mass ratio of the dopamine to the alkaline aqueous solution is 10 g:180 mL.

[0062] The vacuum drying temperature is 50℃, and the time is 20 hours.

[0063] In order to further improve the treatment effect of wastewater and improve the recovery of fluoride ions, after step (4) is completed, the treated wastewater is subjected to a secondary PCR pellet crystallization reactor, and a special seed crystal, sodium phosphate and a calcium salt medicament are added in an amount of 1 / 5-1 / 6 of the effective volume of the reactor, and the PCR pellet is crystallized for 20 min, and then the fluoride-containing pellet crystal is recovered.

[0064] The mechanism of particle precipitation growth includes the following three main ways: A, agglomeration between small particles; B, adsorption of small particles on the seed; C, adsorption and agglomeration between the seeds, as shown in Figure 1 .

[0065] The following is a specific embodiment:

[0066] Embodiment 1

[0067] A fluoride ion crystallization recovery method based on a PCR pellet reactor, comprising the following steps:

[0068] (1) The concentration of fluoride ions in the wastewater to be treated is measured and recorded, and then the calcium salt medicament and the special seed crystal are added according to the concentration of fluoride ions in the wastewater to be treated;

[0069] (2) After the calcium salt medicament and the special seed crystal are added, stirring and mixing are performed until they are uniform, and then the pH value of the wastewater is adjusted to 6.0;

[0070] (3) The reaction time is controlled to be 10 minutes;

[0071] (4) After the wastewater treatment is completed, the fluoride-containing pellet crystal is recovered.

[0072] The calcium salt medicament is a mixture of calcium hydroxide, calcium chloride and calcium sulfate;

[0073] The mass ratio of calcium hydroxide, calcium chloride and calcium sulfate is 3:100:15.

[0074] The molar ratio of calcium ions in the calcium salt medicament to fluoride ions in the wastewater to be treated is 1:2 during the feeding.

[0075] The amount of the special seed crystal added is 1 / 6 of the effective volume of the PCR pellet reactor.

[0076] The special seed crystal is made of quartz sand, tourmaline powder, dolomite powder and fluorite powder.

[0077] The mass ratio of quartz sand, tourmaline powder, dolomite powder and fluorite powder is 80:1:2:1.

[0078] The preparation method of the special seed crystal is as follows:

[0079] The quartz sand, tourmaline powder, dolomite powder and fluorite powder are mixed with a chitosan bonding solution as a bonding agent, and then vacuum dried to obtain the special seed crystal.

[0080] The mixing ratio of quartz sand and chitosan bonding solution is 30g:100mL.

[0081] The preparation method of the chitosan bonding solution is as follows:

[0082] 5g of chitosan is dissolved in 1% acetic acid solution to obtain a 5% (w / v) preliminary chitosan solution.

[0083] Dopamine is weighed and an alkaline aqueous solution is prepared, the dopamine is added to the alkaline aqueous solution, stirred and mixed for 20 minutes to obtain a dispersion, and the dispersion is prepared for use in ice bath;

[0084] The preliminary chitosan solution and the dispersion are mixed in a mass ratio of 5:1 to obtain the chitosan bonding solution.

[0085] The alkaline aqueous solution is a sodium hydroxide solution, and the pH of the sodium hydroxide solution is 11.

[0086] The mass ratio of dopamine to alkaline aqueous solution is 10g:180mL.

[0087] The vacuum drying temperature is 50℃, and the time is 20 hours.

[0088] Example 2

[0089] A fluorine ion crystallization recovery method based on a PCR pellet reactor, comprising the following steps:

[0090] (1) The concentration of fluoride ions in the wastewater to be treated is measured and recorded, and then calcium salt medicament and special seed crystal are added according to the concentration of fluoride ions in the wastewater to be treated.

[0091] (2) After adding calcium salt medicament and special crystal seeds, stirring and mixing uniformly, adjusting the pH value of the wastewater to 6.6;

[0092] (3) The reaction time is controlled to 15 minutes;

[0093] (4) After the wastewater treatment is completed, the fluorine-containing pellet crystal is recovered.

[0094] The calcium salt medicament is obtained by mixing calcium hydroxide, calcium chloride and calcium sulfate;

[0095] The mass ratio of calcium hydroxide, calcium chloride and calcium sulfate is 3.2:110:16.

[0096] When the medicament is added, the molar ratio of calcium ions in the calcium salt medicament to fluorine ions in the wastewater to be treated is 1:2.

[0097] The special crystal seed is added in an amount of 1 / 5 of the effective volume of the PCR pellet reactor.

[0098] The special crystal seed is made of quartz sand, tourmaline powder, dolomite powder and fluorite powder.

[0099] The mass ratio of quartz sand, tourmaline powder, dolomite powder and fluorite powder is 80:1:2:1.

[0100] The preparation method of the special crystal seed is:

[0101] The quartz sand, tourmaline powder, dolomite powder and fluorite powder are mixed with chitosan adhesive solution as an adhesive, and then vacuum dried to obtain the special crystal seed.

[0102] The mixing ratio of quartz sand and chitosan adhesive solution is 35g:100mL.

[0103] The preparation method of the chitosan adhesive solution is:

[0104] 5g of chitosan is dissolved in 1% acetic acid solution to obtain a 5%(w / v) preliminary chitosan solution;

[0105] Dopamine is weighed and an alkaline aqueous solution is prepared. The dopamine is added to the alkaline aqueous solution and stirred and mixed for 20 minutes to obtain a dispersion, which is prepared for use in ice bath;

[0106] The preliminary chitosan solution and the dispersion are mixed in a mass ratio of 5:1 to obtain the chitosan adhesive solution.

[0107] The alkaline aqueous solution is a sodium hydroxide solution, and the pH of the sodium hydroxide solution is 11;

[0108] The mass ratio of dopamine to alkaline aqueous solution is 10g:180mL.

[0109] The vacuum drying temperature is 50℃, and the time is 20 hours.

[0110] Example 3

[0111] A fluorine ion crystallization recovery method based on a PCR pellet reactor includes the following steps:

[0112] (1) The concentration of fluorine ions in the wastewater to be treated is measured and recorded, and then calcium salt reagents and special seeds are added according to the concentration of fluorine ions in the wastewater to be treated;

[0113] (2) After adding the calcium salt reagents and special seeds, the mixture is stirred uniformly, and then the pH value of the wastewater is adjusted to 6.8;

[0114] (3) The reaction time is controlled at 20 minutes;

[0115] (4) After the wastewater treatment is completed, fluorine-containing pellet crystals are recovered;

[0116] (5) The treated wastewater is then passed through a secondary PCR pellet crystallization reactor, and special seeds, sodium dihydrogen phosphate, and calcium salt reagents are added at 1 / 5 of the effective volume of the reactor. The PCR pellet crystallization reaction is carried out for 20 minutes, and then fluorine-containing pellet crystals are recovered;

[0117] The amount of sodium dihydrogen phosphate added is 50% of the mass of the calcium salt reagent, and the molar ratio of calcium in the calcium salt reagent to fluorine ions in the treated wastewater is 1:2.

[0118] The calcium salt reagent is a mixture of calcium hydroxide, calcium chloride, and calcium sulfate;

[0119] Among them, the mass ratio of calcium hydroxide, calcium chloride and calcium sulfate is 4:115:16.

[0120] When adding the calcium salt reagent, the molar ratio of calcium ions in the calcium salt reagent to fluorine ions in the wastewater to be treated is 1:2.

[0121] The amount of special seed added is 1 / 6 of the effective volume of the PCR pellet reactor.

[0122] The special seed is made of quartz sand, tourmaline powder, dolomite powder, and fluorite powder.

[0123] The mass ratio of quartz sand, tourmaline powder, dolomite powder, and fluorite powder is 80:1:2:1.

[0124] The preparation method of the special seed is:

[0125] The quartz sand, tourmaline powder, dolomite powder, and fluorite powder are mixed with chitosan adhesive solution as an adhesive, and then vacuum dried to obtain the special seed.

[0126] The mixing ratio of the quartz sand and the chitosan binding solution is 35 g: 100 mL.

[0127] The preparation method of the chitosan binding solution is as follows:

[0128] 5 g of chitosan is dissolved in a 1% acetic acid solution to obtain a 5% (w / v) primary chitosan solution;

[0129] Dopamine is weighed and an alkaline aqueous solution is prepared, the dopamine is added to the alkaline aqueous solution, stirred and mixed for 20 min to obtain a dispersion, and the dispersion is prepared and stored in an ice bath;

[0130] The primary chitosan solution and the dispersion are mixed in a mass ratio of 5:1 to obtain the chitosan binding solution.

[0131] The alkaline aqueous solution is a sodium hydroxide solution, and the pH of the sodium hydroxide solution is 11;

[0132] The mixing mass ratio of the dopamine and the alkaline aqueous solution is 10 g: 180 mL.

[0133] The vacuum drying temperature is 50°C, and the time is 20 hours.

[0134] Comparative Example 1: This comparative example is basically the same as Example 1, except that no calcium salt medicament is added.

[0135] Comparative Example 2: This comparative example is basically the same as Example 1, except that no special crystal seeds are added.

[0136] Based on Example 1, the surface Zeta (ζ) potential of the crystal seeds at different pH values is tested

[0137] The surface Zeta (ζ) potential characterization of the crystal seeds includes the following steps:

[0138] The surface ζ potential of the crystal seeds under different environmental pH values is analyzed by dynamic light scattering analysis (DLS). 10 mg of ground crystal seed powder is weighed, and 1 mL of pH=2, pH=4, pH=6, pH=7, pH=8, pH=10, and pH=12 phosphate buffer solution is added respectively. After standing at room temperature for 1 day, when the suspension is stable, 750 uL of the solution is taken for detection, and the surface ζ potential is measured.

[0139] As shown in Figure 2 , the surface ζ potential of the crystal seeds decreases with the increase of pH, and when pH≥6, the surface ζ potential of the crystal seeds is stable at-20 mV. The above data shows that when pH≥6, the surface ζ potential of the crystal seeds is effectively reduced, which indicates that the environment with pH≥6 can effectively promote two-step nucleation and inhibit one-step nucleation.

[0140] The photovoltaic panel wastewater was used as a sample and treated by the method of the examples and the comparative examples.

[0141] The photovoltaic panel wastewater had a fluorine ion concentration of 1000 mg / L, a water volume of 5000 m 3 / d, and a pH value of 5.0.

[0142] The fluorine ion concentration of the treated photovoltaic panel wastewater was detected, and the weight (dry weight) of the fluorine-containing pellets recovered per day was counted.

[0143] Table 1

[0144]

[0145] As shown in Table 1, the method can greatly reduce the fluorine ion concentration of the photovoltaic panel wastewater and recover more fluorine-containing pellets.

[0146] The chip wastewater was used as a sample and treated by the method of Example 3.

[0147] The chip wastewater had a fluorine ion concentration of 300 mg / L, a water volume of 3000 m 3 / d, and a pH value of 2.0. After the treatment of the previous steps (1)-(4), the fluorine ion concentration of the wastewater was 4.5 mg / L, and more than 1.9 tons of fluorine-containing pellets were recovered per day. After the treatment of step (5), the fluorine ion concentration of the wastewater was 0.5 mg / L, and more than 400 kg of fluorine-containing pellets were recovered per day.

[0148] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details and do not limit the present application to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the present application. The present application selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and use the present application. The present application is limited only by the claims and their entire scope and equivalents.

Claims

1. A method for fluoride ion crystallization recovery based on a PCR pellet reactor, characterized by, It comprises the following steps: (1) measuring the concentration of fluoride ions in the wastewater to be treated, recording, and then adding calcium salt reagent and special seed according to the concentration of fluoride ions in the wastewater to be treated; (2) After adding calcium salt reagent and special seed, stirring and mixing uniformly, and then adjusting the pH value of the wastewater to 6.0-7.5; (3) The reaction time is controlled within 10-30 minutes; (4) After the wastewater treatment is completed, the fluorine-containing pellet crystals are recovered; the calcium salt reagent is made by mixing calcium hydroxide, calcium chloride and calcium sulfate; Among them, the mass ratio of calcium hydroxide, calcium chloride and calcium sulfate is 3-4:100-120:15-18; the special seed is made of quartz sand, tourmaline powder, dolomite powder and fluorite powder; the mass ratio of quartz sand, tourmaline powder, dolomite powder and fluorite powder is 80:1:2:1; the preparation method of the special seed is: Mixing quartz sand, tourmaline powder, dolomite powder and fluorite powder with chitosan adhesive solution as adhesive, and then vacuum drying, to obtain the special seed; The mixing ratio of quartz sand and chitosan adhesive solution is 30-35g:100mL; the preparation method of the chitosan adhesive solution is: Dissolve 5g of chitosan in 1% acetic acid solution to obtain a 5%(w / v) preliminary chitosan solution; Weigh dopamine, prepare an alkaline aqueous solution, add dopamine to the alkaline aqueous solution, stir and mix for 20 minutes to obtain a dispersion, and store in an ice bath for standby; Mix the preliminary chitosan solution and the dispersion in a mass ratio of 5:1 to obtain the chitosan adhesive solution.

2. A method for fluorine ion crystallization recovery based on a PCR pellet reactor according to claim 1, characterized in that, When feeding, the molar ratio of calcium ions in the calcium salt reagent to fluoride ions in the wastewater to be treated is 1:

2.

3. A method for fluorine ion crystallization recovery based on a PCR pellet reactor according to claim 1, characterized in that, The addition amount of the special seed is 1 / 5-1 / 6 of the effective volume of the PCR pellet reactor.

4. A method for fluorine ion crystallization recovery based on a PCR pellet reactor according to claim 1, characterized in that, The alkaline aqueous solution is a sodium hydroxide solution, and the pH of the sodium hydroxide solution is 11; The mass ratio of dopamine to alkaline aqueous solution is 10g:180mL.

5. A method for fluorine ion crystallization recovery based on a PCR pellet reactor according to claim 1, characterized in that, The vacuum drying temperature is 50℃, and the time is 20 hours.

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