CN111514846B - Preparation method of defluorination filter material - Google Patents
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- CN111514846B CN111514846B CN202010309403.XA CN202010309403A CN111514846B CN 111514846 B CN111514846 B CN 111514846B CN 202010309403 A CN202010309403 A CN 202010309403A CN 111514846 B CN111514846 B CN 111514846B
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Abstract
The invention discloses a preparation method of a defluorination filter material, which is improved on the basis of the traditional acid-base reaction method and comprises the following steps: respectively adding phosphoric acid and alkali into the pasty liquid in the reaction kettle, adding an interfacial reaction catalyst, stirring simultaneously, and preparing hydroxyapatite by an acid-base reaction method; discharging reaction products after the reaction is finished, carrying out filter pressing dehydration and granulation on the reaction products, putting the hydroxyapatite balls into a sintering furnace for sintering, putting the hydroxyapatite balls into a positive charge molecular solution, soaking for 20-60 min, fishing out and draining to obtain the charged defluorination filter material. The reaction process is accelerated by adding the interface catalyst during the reaction, so that the production efficiency is greatly improved; when the ball-shaped filter material is soaked in the positive charge solution, the filter material is charged with positive charges and can absorb F in water ‑ Better adsorption effect and stronger action.
Description
Technical Field
The invention belongs to the technical field of water treatment materials, and relates to a preparation method of a defluorination filter material.
Background
Fluorine is one of indispensable trace elements for human bodies, but high-fluorine water can cause fluorosis of people and seriously affect human health if the high-fluorine water is drunk for a long time, so that the world health organization publishes the regulation that the fluoride content of drinking water cannot exceed 1.5mg/L, and the limit value of the conventional index fluoride of water quality is 1mg/L according to the sanitary Standard for Drinking Water (GB 5749-2006) in China. A large amount of calcium-aluminum plasma can be left by a chemical precipitation method and a coagulation sedimentation method in the water treatment defluorination method, and the method is mainly used for industrial wastewater treatment; because high-fluorine water is mainly distributed in regions with severe environment, complex terrain or water and electricity shortage, the effect of removing fluorine by using an electrodialysis method, an electrocoagulation method, a reverse osmosis method, a nanofiltration method and the like is excellent, but the popularization and the application are difficult due to the defects of complex devices, expensive equipment, high use cost and the like. The ion exchange resin method is difficult to be widely applied due to low anti-interference capability. The adsorption method is the most common drinking water defluorination treatment method at present, but the filter material needs to be regenerated, and the problems of use cost, defluorination efficiency and the like exist, so that the practical application of the adsorption method is limited.
Hydroxyapatite (HAP) with molecular formula of Ca 10 (PO 4 ) 6 (OH) 2 Density of 3.16g/cm 3 And the refractive index is 1.64-1.65. Slightly soluble in pure water, weakly alkaline, easily soluble in acid and hardly soluble in alkali. Hydroxyapatite (HAP) is a currently recognized ceramic material with good biocompatibility and osteoconductivity, i.e., bioactivity. It is the main inorganic component of human and animal bones and teeth. With the progress of science and technology and the continuous improvement of people's understanding, many research results show that hydroxyapatite is a biological active material which is non-toxic, non-carcinogenic, free of side effects and good in biocompatibility; people also find that the hydroxyapatite has solid alkali performance and stronger ion exchange capacity, so the hydroxyapatite is widely applied to the fields of catalytic carriers and ion exchange; meanwhile, the paint can adsorb toxic ions and has temperature-sensitive and humidity-sensitive effects, so that the paint is a green environment-friendly material and an intelligent material.
HAPs are prepared in a number of ways, and can be roughly classified into three categories: dry (solid phase reaction), hydrothermal, and wet (solution reaction). 1) The dry process (solid phase reaction) is generally carried out by using Ca 3 (PO 4 ) 2 Or CaCO 3 And Ca 4 P 2 O 9 HAP was synthesized by solid-phase reaction by introducing steam at a high temperature of 1200 ℃. The temperature of the reaction must be strictly controlled because at the sintering temperature of 1200 ℃, the crystalline phase of the reaction product is HAP; and at the sintering temperature of 1250 ℃, the crystal phase is a mixture of HAP and TCP. During the reaction, steam must be introduced at a high temperature to suppress decomposition of HAP. The method has the advantage that HAP crystals free of lattice defects and having a high degree of crystallinity can be obtained. The disadvantages are that the raw material powder needs to be mixed and ground for a long time, the pollution is easy, the reaction speed is slow, the particle size of the product is large, and the activity of the product is poor.
2) Hydrothermal method, hydrothermal synthesis method is in a closed pressure vessel, using water solution as reaction medium, by heating the reaction vessel, make under normal conditions difficult to dissolve or insoluble material dissolved and recrystallized. Mixing Ca (NO) 3 ) 2 And H 3 PO 4 Mixing uniformly according to the calcium phosphorus ratio Ca/P =1.67, putting into a specially-made closed pressure cooker, and adding distilled water. Heating to different temperatures (200-400 deg.C) at a heating rate of 7 deg.C/min, and performing hydrothermal reaction at specified temperature to obtain [ OH ]]Adding into crystal lattice to generate HAP. The method has the greatest advantage that the product is directly in a crystalline state, does not need to be sintered and crystallized, and can reduce the difficult-to-avoid agglomeration in the sintering process. The granularity is uniform, and the form is relatively regular; moreover, the reaction conditions are changed to obtain products with different crystal structures and crystal forms. With the increase of the hydrothermal synthesis temperature and the prolonging of the time, the more complete the crystal grain development and the larger the grain size. However, this method requires a high level of equipment and is also costly.
3) Wet reaction including acid-base reaction, hydrolysis, electrochemical deposition, sol-gel process, microemulsion process, etc. The acid-base reaction is based on the neutralization of an acid or base to form HAP, e.g. with Ca (OH) 2 And H 3 PO 4 The reaction produces HAP. Firstly, a certain amount of Ca (OH) 2 The powder is mixed with water to form a paste, and the paste Ca (OH) is added into a beaker which is added with distilled water and heated to about 70 DEG C 2 Stirring, slowly adding H dropwise 3 PO 4 Adjusting the pH value to generate HAP. The method is simple and convenient to operate, is most economical, does not need complex equipment, and is suitable for industrial production.
The hydrolysis method and the hydrothermal synthesis method have similar principles. In the hydrolysis process, caHPO is generally used 4 And (2) reacting [ OH ] at about 70 ℃ and pH of 8.5]Adding into crystal lattice to generate HAP. In addition, there are electrochemical deposition methods. From Ca, according to the basic principle of electrochemistry 3 (PO 4 ) 2 The HAP particles are electrodeposited in an aqueous solution on a cathode. The chemical precipitation method comprises mixing phosphorus-containing compound and calcium-containing compound water solution at certain concentration, stirring, reacting under controlled pH to generate colloid HAP precipitate, and calcining to obtain HAP crystal powder. The reaction temperature of the method is not high, the purity of the synthesized powder is high, the particles are fine, but the pH value of the solution and other process conditions need to be strictly controlled. Otherwise, the Ca/P atomic ratio is not in accordance with the theoretical value of HAP.
The hydrothermal synthesis method is characterized in that under higher pressure and temperature, calcium salt and phosphate react in an aqueous solution in a closed container to synthesize large-grain HAP powder. The hydrothermal synthesis method has high requirements on equipment. A high-temperature and high-pressure resistant closed container is required. Generally, the synthesized particle size is large, and the method is suitable for producing HAP powder or single crystal HAP with large crystal grains. The microemulsion method is to form a uniform emulsion by using two solvents which are not mutually soluble under the action of a surfactant, and to precipitate a solid phase from the emulsion.
Disclosure of Invention
The invention aims to provide a preparation method of a defluorination filter material, which is improved on the basis of preparing HAP by an acid-base method so as to improve the production efficiency and the product performance.
The invention is realized by the following technical scheme:
a preparation method of a defluorination filter material comprises the following operations:
1) Adding water into a reaction kettle, sequentially adding sieved calcium hydroxide or calcium oxide and ammonium bicarbonate into the water, and fully stirring to prepare a pasty liquid;
2) Respectively adding phosphoric acid and alkali into the pasty liquid in the reaction kettle, adding an interfacial reaction catalyst, stirring simultaneously, and preparing hydroxyapatite by an acid-base reaction method; adjusting the dropping speed of phosphoric acid and alkali to ensure that the pH of the feed liquid in the reaction kettle is not lower than 9.0, completing the addition of the acid and the alkali simultaneously, and then continuously stirring for reaction for 1-3 h;
the interface reaction catalyst comprises sodium polyacrylate and aluminum chloride, wherein the weight ratio of sodium polyacrylate: aluminum chloride: the mass ratio of the calcium hydroxide is (0.005-0.010): (0.05-0.10): 1;
3) Discharging reaction products after the reaction is finished, carrying out filter pressing dehydration on the reaction products, and washing the reaction products with water until the effluent water is neutral; obtaining hydroxyapatite with water content of 50-75%;
4) Uniformly stirring the prepared hydroxyapatite and attapulgite powder, and preparing hydroxyapatite balls with the particle size of 2-5 mm by using a granulator;
5) Putting the prepared hydroxyapatite balls into a sintering furnace, sintering at 300-400 ℃ for 1.5-2 h, taking out and cooling;
6) And putting the sintered hydroxyapatite balls into a positive charge molecular solution, soaking for 20-60 min, fishing out and draining to obtain the charged defluorination filter material.
Further, the mass ratio of the calcium hydroxide to the ammonium bicarbonate is 55-65: 1;
when calcium hydroxide is replaced by calcium oxide, the molar weight of the calcium oxide is the same as that of the calcium hydroxide;
the phosphoric acid is phosphoric acid with the volume concentration of 30 percent, and the acid adding flow is 0.8-1.0L/h;
the alkali is NaOH with the mass concentration of 30% or ammonia water with the mass concentration of 25%.
The acid adding flow is 0.8-1.0L/h; acid and alkali are continuously dripped for 1.5h.
Specifically, the molecular weight of the sodium polyacrylate in the interfacial reaction catalyst is 2500-2800.
Further, the positive charge molecule solution comprises 0.05-0.35 mol/L of Al 2 (SO 4 ) 3 0.8-1 mol/L NaOH and 0.8-1 mol/L MgCl 2 。
The filter-pressing dehydration is to filter-press and dehydrate the reaction product discharged from the reaction kettle by adopting a plate-and-frame filter press; a plurality of sets of reaction kettles are matched with a plate-and-frame filter press to carry out continuous preparation of hydroxyapatite;
the hydroxyapatite is washed by water until the effluent is neutral, crushed by a mechanical crusher, then evenly mixed with the attapulgite powder, and pelletized and granulated by a round pot granulator.
The mass ratio of the hydroxyapatite powder to the attapulgite powder is 1.5-2.5.
The charged defluorination filter material is placed in a storage yard for airing after being fished out, and the finished product is packaged after being aired for 2 to 5 days.
Compared with the prior art, the invention has the following beneficial technical effects:
the preparation process of the hydroxyapatite is an improvement of the traditional acid-base reaction method, and the interface catalyst is added during the reaction of the raw materials, so that the reaction process is accelerated by adding the interface catalyst, and the production efficiency is greatly improved; soaking the granulated product in positive charge solution for 30min, and soaking the pelletized filter material in the positive charge solution to remove F in water due to the positive charge of the filter material - Better adsorption effect and stronger action.
Drawings
FIG. 1 is a schematic view of the preparation process of the present invention.
Fig. 2 is a detection result of raw water containing fluoride after being filtered by a fluorine removal filter.
Detailed Description
The present invention will now be described in further detail with reference to the following examples, which are intended to be illustrative, but not limiting, of the invention.
The invention provides a preparation method of hydroxyapatite, which is an improvement of the traditional acid-base reaction method and comprises the following steps:
(1) the interface catalyst is added during the reaction of the raw materials, so that the reaction process is accelerated by adding the interface catalyst, and the production efficiency is greatly improved; the reaction equation is expressed as follows:
(2) soaking the granulated product in positive charge solution, soaking the pelletized filter material in positive charge solution to make it charged, and carrying out positive charge on F in water - The adsorption effect is better, and the effect is stronger; the reaction equation is expressed as follows:
referring to fig. 1, the preparation method of the defluorination filter material provided by the invention comprises the following operations:
1) Adding water into a reaction kettle, sequentially adding sieved calcium hydroxide or calcium oxide and ammonium bicarbonate into the water, and fully stirring to prepare a pasty liquid;
2) Respectively adding phosphoric acid and alkali into the pasty liquid in the reaction kettle, adding an interfacial reaction catalyst, stirring simultaneously, and preparing hydroxyapatite by an acid-base reaction method; adjusting the dropping speed of phosphoric acid and alkali to ensure that the pH of the feed liquid in the reaction kettle is not lower than 9.0, completing the addition of the acid and the alkali simultaneously, and then continuously stirring for reaction for 1-3 h;
the interface reaction catalyst comprises sodium polyacrylate and aluminum chloride, wherein the weight ratio of sodium polyacrylate: aluminum chloride: the mass ratio of the calcium hydroxide is (0.005-0.010): (0.05-0.10): 1;
3) Discharging reaction products after the reaction is finished, carrying out filter pressing dehydration on the reaction products, and washing the reaction products with water until the effluent water is neutral; obtaining hydroxyapatite with water content of 50-75%;
4) Uniformly stirring the prepared hydroxyapatite and attapulgite powder, and preparing hydroxyapatite balls with the particle size of 2-5 mm by using a granulator;
5) Putting the prepared hydroxyapatite balls into a sintering furnace, sintering for 1.5-2 h at 300-400 ℃, taking out and cooling;
6) And putting the sintered hydroxyapatite balls into a positive charge molecular solution, soaking for 20-60 min, fishing out and draining to obtain the charged defluorination filter material.
Further, the mass ratio of the calcium hydroxide to the ammonium bicarbonate is 55-65: 1;
when calcium hydroxide is replaced by calcium oxide, the molar weight of the calcium oxide is the same as that of the calcium hydroxide;
the phosphoric acid is 30% in volume concentration, and the acid adding flow is 0.8-1.0L/h;
the alkali is NaOH with the mass concentration of 30% or ammonia water with the mass concentration of 25%.
The acid adding flow is 0.8-1.0L/h; acid and alkali are continuously dripped for 1.5h.
Specifically, the molecular weight of the sodium polyacrylate in the interfacial reaction catalyst is 2500-2800.
Further, the positive charge molecule solution comprises 0.05-0.35 mol/L of Al 2 (SO 4 ) 3 、0.8NaOH of 1mol/L and MgCl of 0.8-1 mol/L 2 。
Specifically, the filter-pressing dehydration is to filter-press and dehydrate a reaction product discharged from the reaction kettle by adopting a plate-and-frame filter press; a plurality of sets of reaction kettles are matched with a plate-and-frame filter press to carry out continuous preparation of hydroxyapatite;
the hydroxyapatite is washed by water until the effluent is neutral, crushed by a mechanical crusher, then evenly mixed with the attapulgite powder, and pelletized and granulated by a round pot granulator.
The mass ratio of the hydroxyapatite powder to the attapulgite powder is 1.5-2.5.
The charged defluorination filter material is piled up after being fished out and is placed in a storage yard for airing, and the finished product is packaged after 2 to 5 days of airing.
Specific examples are given below.
Example 1
A preparation method of a defluorination filter material comprises the following operations:
1. the calcium hydroxide is sieved by a 400-mesh vibrating screen.
2. 4L of deionized water is added into a reaction kettle with the effective volume of 6L, 592g of calcium hydroxide which is sieved by a 400-mesh sieve is weighed and added, 9.6g of ammonium bicarbonate is added, and a stirrer is started to prepare pasty liquid.
3. And starting a metering pump to add phosphoric acid with the volume concentration of 30% into the pasty liquid of the reaction kettle, wherein the acid adding flow is 0.892L/h, 1.34L is added after 1.5h is continuously performed, and a stirrer of the reaction kettle is started while the phosphoric acid is added.
4. Adding phosphoric acid, starting a metering pump, and dropwise adding NaOH with the mass concentration of 30% or ammonia water with the mass concentration of 25% into the reaction kettle at a speed that ensures that the pH value of the feed liquid in the reaction kettle is not lower than 9.0; simultaneously, interface reaction catalyst is added into the reaction kettle to accelerate the calcium phosphate and OH - Generating HAP catalytic reaction.
The interfacial reaction catalyst comprises sodium polyacrylate (molecular weight 2500) and aluminum chloride, wherein the weight ratio of sodium polyacrylate: aluminum chloride: the mass ratio of the calcium hydroxide is 0.005:0.10:1;
5. after the acid and the alkali are added simultaneously, the reaction kettle stirrer is continuously started to react for 1.5h.
6. Stopping the reaction kettle stirrer, discharging reaction products, performing filter pressing dehydration, and washing with deionized water until effluent is neutral.
Two sets of the same reaction production lines are arranged in parallel to ensure continuous reaction, one set of reaction is dehydrated after the completion of the dehydration, and the other set of reaction is reacted after the completion of the dehydration. The product was dried after dehydration to give a powder of product with a single batch yield of about 800g (no more than 75% water content after filter pressing).
7. 435g of attapulgite powder (sieved by a 400-mesh sieve) is added into the HAP product containing 75 percent of water after filter pressing, and the mixture is stirred and mixed evenly to be made into pellets of about 3mm by a granulator.
8. And (3) putting the prepared pellets into a sintering furnace, sintering for 2 hours at 350 ℃, taking out and cooling.
9. And (3) putting the sintered filter material balls into the positively charged molecular solution, soaking for 30min, fishing out and draining to obtain the charged defluorination filter material, wherein the weight of the product is about 3.2kg.
Example 2
A preparation method of a defluorination filter material comprises the following operations:
1. the calcium oxide is sieved by a 400-mesh vibrating screen.
2. 4L of deionized water is added into a reaction kettle with an effective volume of 6L, 568g of calcium oxide sieved by a 400-mesh sieve is weighed and added, 9.6g of ammonium bicarbonate is added, and a stirrer is started to prepare pasty liquid.
3. And starting a metering pump to add 30 volume percent phosphoric acid into the pasty liquid in the reaction kettle, wherein the acid adding flow is 0.928L/h, 1.34L of phosphoric acid is continuously added for 1.5h, and a stirrer of the reaction kettle is started while the phosphoric acid is added.
4. Starting a metering pump to add NaOH with the mass concentration of 30% or ammonia water with the mass concentration of 25% into the reaction kettle while adding phosphoric acid, wherein the adding speed ensures that the pH value of the feed liquid in the reaction kettle is not lower than 9.0; simultaneously, interface reaction catalyst is added into the reaction kettle to accelerate the calcium phosphate and OH - Generating HAP catalytic reaction.
The interfacial reaction catalyst comprises sodium polyacrylate (molecular weight 2800) and aluminum chloride, wherein the weight ratio of sodium polyacrylate: aluminum chloride: the mass ratio of the calcium hydroxide is 0.010:0.05:1;
5. after the acid and the alkali are added simultaneously, the reaction kettle stirrer is continuously started to react for 1.5 hours.
6. Stopping the reaction kettle stirrer, discharging reaction products, performing filter pressing dehydration, and washing with deionized water until effluent is neutral.
Specifically, the filter-pressing dehydration is to filter-press and dehydrate a reaction product discharged from the reaction kettle by adopting a plate-and-frame filter press; two sets of reaction kettles are matched with a plate-and-frame filter press to carry out continuous preparation of hydroxyapatite: one set of reaction is dehydrated after completion, and the other set of reaction is dehydrated after completion; drying the dehydrated product to obtain product powder with single batch yield of about 800g (the water content after filter pressing is not more than 75%)
7. The hydroxyapatite is washed by water until the effluent is neutral, crushed by a mechanical crusher, then evenly stirred with the attapulgite powder (the mass ratio is 1.5-2.5), and pelletized and granulated by a round pot pelletizer to be made into pellets of about 3mm by the pelletizer.
8. And (3) putting the prepared pellets into a sintering furnace, sintering at 400 ℃ for 1.5 hours, taking out and cooling.
9. Putting the sintered filter material balls into a positively charged molecular solution, soaking for 30min, fishing out and draining to obtain a charged defluorination filter material;
then the charged defluorination filter material is piled up and placed in a storage yard for airing, and the finished product is packaged after 2 to 5 days of airing.
The filter material adsorption experiments and data of the present invention are given below:
sodium fluoride (NaF) 500mg was added to 10L of tap water to dissolve it to 22.6mgF/L.
100mL of fluorine-containing water is added into 6 plastic bottles with 250mL, 200.0mg of the defluorination filter material prepared by the invention is added, and the plastic bottles are covered with bottle caps and put into an air constant temperature oscillator for oscillation reaction. Setting the temperature of the oscillator at 25 ℃, rotating speed of 180r/min, carrying out adsorption reaction for 10min, 0.5, 1.0, 2.0, 4.0, 6, 12, 24h, 48h and 72h, and respectively taking out 1 conical flask and 10 flasks in total. Performing solid-liquid separation, collecting supernatant, and measuring F - And (4) concentration. The obtained adsorption capacities were respectively:
| serial number | Adsorption capacity (mg/g) |
| 1# | 5.0794 |
| 2# | 5.3470 |
| 3# | 4.9484 |
| 4# | 5.3923 |
| 5# | 8.1032 |
| 6# | 7.9224 |
| 7# | 8.7511 |
| 8# | 8.8573 |
| 9# | 8.9377 |
| 10# | 9.9359 |
The results show that the adsorption capacity is continuously increased until the limit value is about 10mgF/L along with the continuous progress of the adsorption reaction, and the results show that the defluorination filter material prepared by the invention has good adsorption capacity.
The water filtered by the filter material is detected mainly according to GB/T5750.6-2006, the comparison result of raw water and the water filtered by the filter material is shown in figure 2, and the result shows that the fluoride content of the raw water with the fluoride content of 2.7mg/L is less than 0.1mg/L after the raw water is filtered by the filter material, which shows that the filter material has good purification effect.
The embodiments given above are preferable examples for implementing the present invention, and the present invention is not limited to the above-described embodiments. Any non-essential addition and replacement made by the technical characteristics of the technical scheme of the invention by a person skilled in the art belong to the protection scope of the invention.
Claims (8)
1. The preparation method of the defluorination filter material is characterized by comprising the following operations:
1) Adding water into a reaction kettle, sequentially adding sieved calcium hydroxide or calcium oxide and ammonium bicarbonate into the water, and fully stirring to prepare a pasty liquid;
2) Respectively adding phosphoric acid and alkali into the pasty liquid in the reaction kettle, adding an interfacial reaction catalyst, stirring simultaneously, and preparing hydroxyapatite by an acid-base reaction method; adjusting the dropping speed of phosphoric acid and alkali to ensure that the pH of the feed liquid in the reaction kettle is not lower than 9.0, completing the addition of the acid and the alkali simultaneously, and then continuously stirring for reaction for 1-3 h;
the interface reaction catalyst comprises sodium polyacrylate and aluminum chloride, wherein the weight ratio of sodium polyacrylate: aluminum chloride: the mass ratio of the calcium hydroxide is (0.005-0.010): (0.05-0.10): 1;
3) Discharging reaction products after the reaction is finished, carrying out filter pressing dehydration on the reaction products, and washing the reaction products with water until the effluent is neutral; obtaining hydroxyapatite with water content of 50-75%;
4) Uniformly stirring the prepared hydroxyapatite and attapulgite powder, and preparing hydroxyapatite balls with the particle size of 2-5 mm by using a granulator;
5) Putting the prepared hydroxyapatite balls into a sintering furnace, sintering for 1.5-2 h at 300-400 ℃, taking out and cooling;
6) And putting the sintered hydroxyapatite balls into a positive charge molecular solution, soaking for 20-60 min, fishing out and draining to obtain the charged defluorination filter material.
2. The method for preparing the defluorination filter material of claim 1, wherein the mass ratio of the calcium hydroxide to the ammonium bicarbonate is 55-65: 1;
when calcium hydroxide is replaced by calcium oxide, the molar weight of the calcium oxide is the same as that of the calcium hydroxide;
the phosphoric acid is 30% in volume concentration, and the acid adding flow is 0.8-1.0L/h;
the alkali is NaOH with the mass concentration of 30% or ammonia water with the mass concentration of 25%.
3. The method for preparing the defluorination filter material of claim 2, wherein the acid adding flow rate is 0.8-1.0L/h; acid and alkali are continuously dripped for 1.5h.
4. The method for preparing the defluorination filter material of claim 1, wherein the molecular weight of the sodium polyacrylate in the interfacial reaction catalyst is 2500-2800.
5. The method of claim 1, wherein the solution of positively charged molecules comprises 0.05 to 0.35mol/L Al 2 (SO 4 ) 3 0.8 to 1mol/L NaOH and 0.8 to 1mol/L MgCl 2 。
6. The method for preparing a defluorinating filter material of claim 1, wherein the filter-pressing dehydration is carried out by adopting a plate-and-frame filter press to filter-press and dehydrate the reaction product discharged from the reaction kettle; a plurality of sets of reaction kettles are matched with a plate-and-frame filter press to carry out continuous preparation of hydroxyapatite;
the hydroxyapatite is washed by water until the effluent is neutral, crushed by a mechanical crusher, then evenly mixed with the attapulgite powder, and pelletized by a round pot pelletizer.
7. The method for preparing the defluorinating filter material of claim 1 or 6, wherein the mass ratio of the hydroxyapatite to the attapulgite powder is 1.5-2.5.
8. The method for preparing the defluorinating filter material of claim 1 or 6, wherein the defluorinating filter material with electric charge is placed in a storage yard for airing after being fished out, and the finished product is packaged after being aired for 2-5 days.
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