Method for treating fluorine-containing wastewater and treating agent thereof

Abstract

The present application relates to a kind of fluorine-containing wastewater treatment method and its treating agent, it relates to fluorine-containing wastewater treatment technical field, including as follows by weight parts of each raw material composition: MOFs / organic nanocrystal / rare earth titanium dioxide composite material 40-50 parts, synergic carrier 20-25 parts, flocculation function 15-20 parts, auxiliary agent 10-15 parts;The auxiliary agent is that nanometer zero-valent iron, montmorillonite is mixed into by mass ratio (5-8):100.It is strong to the treating agent except fluorine ability, and fluorine removal efficiency is high, and fluorine removal effect is stable;The method of fluorine-containing wastewater treatment using the treating agent is efficient, economic, environmental protection.

Description

Technical Field

[0001] This invention relates to the field of fluoride-containing wastewater treatment technology, and in particular to a method for treating fluoride-containing wastewater and a treatment agent thereof. Background Technology

[0002] Fluoride-containing wastewater mainly originates from industries such as chemical, metallurgical, electronics, and electroplating. Direct discharge without effective treatment can cause serious harm to the environment and human health. Fluoride ions are difficult to degrade in the environment and can accumulate in organisms through the food chain, leading to various symptoms of fluorosis, such as affecting the normal development of bones and teeth, causing dental fluorosis and skeletal fluorosis. Therefore, timely treatment of fluoride-containing wastewater to meet discharge standards is a challenge that fluoride-containing wastewater production enterprises must face.

[0003] Currently, methods for treating fluoride-containing wastewater include precipitation, adsorption, electrocoagulation, electrodialysis, reverse osmosis, and ion exchange. Precipitation uses chemical reactions to induce the formation of insoluble fluoride ions, offering simple operation but potentially generating large amounts of chemical sludge, and its efficiency is limited under high fluoride concentrations. Adsorption utilizes the adsorption properties of specific materials such as activated carbon and zeolite to remove fluoride ions; while flexible and highly efficient, the regeneration and treatment costs of these materials are high, and their adsorption capacity is limited. Electrocoagulation uses electrochemical reactions to generate flocculants, promoting the flocculation and precipitation of fluoride ions, offering high efficiency but high energy consumption, and the wear and cost of electrode materials must be considered. Electrodialysis uses an electric field and selectively permeable membranes to remove fluoride ions, suitable for treating high-concentration fluoride wastewater, but equipment investment and maintenance costs are high. Reverse osmosis, driven by high pressure, uses semi-permeable membranes to remove fluoride ions with high selectivity, offering high efficiency, but it has strict requirements for membrane materials and high operating costs. Ion exchange involves exchanging fluoride ions with ion exchange resins. It is simple to operate, but the regeneration and treatment costs of the resin are relatively high.

[0004] To address the aforementioned issues, Chinese invention patent application CN117247092A discloses a defluoridating agent for treating fluoride-containing wastewater and its preparation method. The defluoridating agent uses chitosan as its biomolecular framework and is prepared by blending magnesium salts, titanium salts, zirconium salts, aluminum salts, iron salts, rare earth materials, and organic materials. The mass ratio of magnesium salt:titanium salt:zirconium salt:aluminum salt:iron salt:rare earth materials:organic materials:chitosan is 1–30:1–30:2–20:2–10:2–10:20–50:2–10:1–10. This invention, based on existing composite defluoridating agents, adds magnesium salts, titanium salts, zirconium salts, and organic materials to prepare a new defluoridating agent. This defluoridating agent exhibits good stability, a wide range of applications, and is suitable for large-scale application. However, its ability to treat high-fluoride-concentration wastewater is insufficient, and its tolerance to complex coexisting ions is poor. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art by providing an efficient, economical, and environmentally friendly method and agent for treating fluoride-containing wastewater. This agent has strong fluoride removal capacity, high fluoride removal efficiency, and stable fluoride removal effect.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a fluoride-containing wastewater treatment agent, comprising the following raw materials in parts by weight: 40-50 parts of MOFs / organic nanocrystals / rare earth titanium dioxide composite material, 20-25 parts of synergistic carrier, 15-20 parts of flocculation function, and 10-15 parts of additives; wherein the additives are nano-zero valent iron and montmorillonite mixed in a mass ratio of (5-8):100.

[0007] Preferably, the preparation method of the MOFs / organic nanocrystals / rare earth titanium dioxide composite material includes the following steps:

[0008] Step D1, Preparation of rare earth titanium dioxide: First, slowly add tetrabutyl titanate to anhydrous ethanol and stir magnetically for 25-35 minutes to form a homogeneous solution A; in another beaker, add glacial acetic acid, deionized water, and a mixed solution of lanthanum nitrate and cerium nitrate, and stir until homogeneous to form solution B; add solution B dropwise to solution A while stirring magnetically, and continue stirring for 1-2 hours until the addition is complete, forming a stable sol; allow the sol to stand at room temperature for 24 hours to form a gel, then place the gel in an oven and dry at 60-70℃ for 10-14 hours; finally, raise the temperature to 500-550℃ at a rate of 3-5℃ / min, hold for calcination for 2-4 hours, and allow to cool naturally to room temperature to obtain rare earth titanium dioxide;

[0009] Step D2, Preparation of organic nanocrystal / rare earth titanium dioxide composite material: Cellulose nanocrystals were dispersed in deionized water, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added as activators. The mixture was stirred at room temperature for 0.8-1.2 h. Then, rare earth titanium dioxide prepared in step S1 was added, and the mixture was stirred at 60 °C for 4 h. After centrifugation and washing, the mixture was vacuum dried at 60 °C for 12 h to obtain the organic nanocrystal / rare earth titanium dioxide composite material.

[0010] Step D3: Preparation of MOFs / organic nanocrystals / rare earth titanium dioxide composite material: ZrCl4 and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide, and the organic nanocrystal modified / rare earth titanium dioxide composite material prepared in step S2 was added. After ultrasonic dispersion for 25-35 min, the mixture was transferred to a hydrothermal reactor and reacted at 118-122℃ for 22-25 h. The product was washed three times alternately with N,N-dimethylformamide and ethanol, and then vacuum dried at 70-80℃ for 10-15 h to obtain the MOFs / organic nanocrystals / rare earth titanium dioxide composite material.

[0011] Preferably, the volume ratio of tetrabutyl titanate, anhydrous ethanol, glacial acetic acid, and deionized water in step D1 is 4:10:1:1.

[0012] Preferably, the molar ratio of tetrabutyl titanate, lanthanum nitrate, and cerium nitrate in step D1 is 1:0.02:0.04.

[0013] Preferably, the mass ratio of cellulose nanocrystals, deionized water, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, and rare earth titanium dioxide in step D2 is 1:200:0.2:0.2:10.

[0014] Preferably, the cellulose nanocrystals in step D2 have a diameter of 10-50 nm and a length of 200-500 nm.

[0015] Preferably, the ratio of ZrCl4, 2-aminoterephthalic acid, N,N-dimethylformamide, and organic nanocrystal modified / rare earth titanium dioxide composite material in step D3 is 0.5 mmol:0.5 mmol:50 mL:1 g.

[0016] Preferably, the synergistic carrier is a mixture of attapulgite and hydroxyapatite in a mass ratio of (2-3):1.

[0017] Preferably, the average particle size of the hydroxyapatite is 1-5 μm; and the average particle size of the attapulgite is 5-20 μm.

[0018] Preferably, the flocculation function is achieved by mixing polyaluminum ferric chloride and modified starch acrylamide copolymer at a mass ratio of 1:(0.8-1.2).

[0019] Preferably, the polyaluminum ferric chloride is SJ-601 polyaluminum ferric chloride PAFC-A2 type; the source of the modified starch acrylamide copolymer is not particularly required. In one embodiment of the present invention, the modified starch acrylamide copolymer is prepared according to the method of Example 11 of Chinese Invention Patent No. CN102936318B.

[0020] Preferably, the particle size of the nano-zero valent iron is 20-30 nm; the particle size of the montmorillonite is 1-5 μm.

[0021] Another objective of this invention is to provide a method for treating fluoride-containing wastewater using the aforementioned fluoride-containing wastewater treatment agent, comprising the following steps: collecting fluoride-containing wastewater into a reaction tank, adjusting the pH value of the wastewater to 6-8 by adding sodium hydroxide solution; after adding the treatment agent, performing two-stage stirring: the first stage is rapid stirring at a speed of 300-400 r / min for 5-10 min to ensure thorough mixing of the agent and wastewater; the second stage is slow stirring at a speed of 50-100 r / min for 20-30 min to promote floc formation; sending the reacted mixture into an inclined tube sedimentation tank for a residence time of 1-2 h, the supernatant being the treated water, and the bottom sludge being dewatered by a plate and frame filter press and then transported for disposal.

[0022] Preferably, the ratio of the mass of the treatment agent added to the mass of fluoride ions in the wastewater is (1.2-2.0):1.

[0023] Due to the application of the above technical solution, the present invention has the following beneficial effects:

[0024] (1) The fluoride-containing wastewater treatment method disclosed in this invention is simple in process, convenient in construction, efficient, and has low dependence on equipment, and has high promotion and application value.

[0025] (2) The fluoride-containing wastewater treatment agent disclosed in this invention comprises the following raw materials in parts by weight: 40-50 parts of MOFs / organic nanocrystals / rare earth titanium dioxide composite material, 20-25 parts of synergistic carrier, 15-20 parts of flocculation function, and 10-15 parts of additives; the additives are nano-zero valent iron and montmorillonite mixed in a mass ratio of (5-8):100. Through the mutual cooperation and synergistic effect of the raw materials, the prepared treatment agent has strong defluorination ability, high defluorination efficiency, and stable defluorination effect; the method of treating fluoride-containing wastewater using this treatment agent is efficient, economical, and environmentally friendly.

[0026] (3) The fluoride-containing wastewater treatment agent disclosed in this invention is the first to feature a three-in-one reinforced structure of "organic nanocrystals-MOFs-rare earth". The introduction of organic nanocrystals not only increases the specific surface area of ​​the material, but also allows the abundant hydroxyl groups on its surface to react with F. - Additional hydrogen bonds are formed, synergistically with the adsorption sites of MOFs and rare earth ions, significantly improving the saturated adsorption capacity. Simultaneously, the organic nanocrystals act as a bridge, enhancing the bonding force between MOFs and rare earth titanium dioxide, making the material more structurally stable during recycling.

[0027] (4) The fluoride-containing wastewater treatment agent disclosed in this invention establishes a multi-stage purification model of "multiple adsorption-enhanced coordination-high-efficiency flocculation". The small size effect of organic nanocrystals allows them to enter the pores of MOFs, forming an adsorption network and improving the capture efficiency of F⁻; rare earth ions, through coordination, bind the adsorbed F⁻.- The composite material provides a strong fixation to prevent desorption; the attapulgite-hydroxyapatite carrier provides a flocculation framework; and the synergistic effect of these three components significantly improves the defluorination efficiency compared to materials without organic nanocrystals. Compared to using MOFs or organic nanocrystals alone, the solid-liquid separation efficiency of the composite material is significantly improved, solving the problem of the difficulty in recycling nanomaterials.

[0028] (5) The fluoride-containing wastewater treatment agent disclosed in this invention uses a composite system of nano-zero valent iron and montmorillonite (mass ratio 5-8:100) as the auxiliary phase (10-15 parts). The nano-zero valent iron (particle size 20-30nm) not only removes oxidizing interfering substances (such as Cr) in the water through reduction. 6+ ), its surface Fe 2+ It can also form complexes with fluoride ions, while the layered structure of montmorillonite (particle size 1-5 μm) can fix nano-zero valent iron, reducing agglomeration loss. This combination significantly reduces sludge production and substantially lowers sludge disposal costs. Detailed Implementation

[0029] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0030] Example 1

[0031] A fluoride-containing wastewater treatment agent comprises the following raw materials in parts by weight: 40 parts of MOFs / organic nanocrystals / rare earth titanium dioxide composite material, 20 parts of synergistic carrier, 15 parts of flocculation function, and 10 parts of additives; wherein the additives are nano-zero valent iron and montmorillonite mixed in a mass ratio of 5:100.

[0032] The preparation method of the MOFs / organic nanocrystals / rare earth titanium dioxide composite material includes the following steps:

[0033] Step D1, Preparation of rare earth titanium dioxide: First, tetrabutyl titanate is slowly added to anhydrous ethanol and magnetically stirred for 25 minutes to form a homogeneous solution A. In another beaker, glacial acetic acid, deionized water, and a mixed solution of lanthanum nitrate and cerium nitrate are added and stirred until homogeneous to form solution B. Solution B is added dropwise to solution A while magnetically stirring. The addition is completed in 1 hour, and stirring is continued for 2 hours after the addition is completed to form a stable sol. The sol is allowed to stand at room temperature for 24 hours to form a gel. The gel is then placed in an oven and dried at 60°C for 10 hours. Finally, the temperature is increased to 500°C at a rate of 3°C / min and calcined for 2 hours. The mixture is then naturally cooled to room temperature to obtain rare earth titanium dioxide.

[0034] Step D2, Preparation of organic nanocrystal / rare earth titanium dioxide composite material: Cellulose nanocrystals were dispersed in deionized water, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added as activators. The mixture was stirred at room temperature for 0.8 h. Then, rare earth titanium dioxide prepared in step S1 was added, and the mixture was stirred at 60 °C for 4 h. After centrifugation and washing, the mixture was vacuum dried at 60 °C for 12 h to obtain the organic nanocrystal / rare earth titanium dioxide composite material.

[0035] Step D3: Preparation of MOFs / organic nanocrystals / rare earth titanium dioxide composite material: ZrCl4 and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide, and the organic nanocrystal modified / rare earth titanium dioxide composite material prepared in step S2 was added. After ultrasonic dispersion for 25 min, the mixture was transferred to a hydrothermal reactor and reacted at 118 °C for 22 h. The product was washed three times alternately with N,N-dimethylformamide and ethanol, and then vacuum dried at 70 °C for 10 h to obtain the MOFs / organic nanocrystals / rare earth titanium dioxide composite material.

[0036] In step D1, the volume ratio of tetrabutyl titanate, anhydrous ethanol, glacial acetic acid, and deionized water is 4:10:1:1; the molar ratio of tetrabutyl titanate, lanthanum nitrate, and cerium nitrate in step D1 is 1:0.02:0.04; in step D2, the mass ratio of cellulose nanocrystals, deionized water, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, and rare earth titanium dioxide is 1:200:0.2:0.2:10; the diameter of the cellulose nanocrystals in step D2 is 10-50 nm, and the length is 200-500 nm; in step D3, the molar ratio of ZrCl4, 2-aminoterephthalic acid, N,N-dimethylformamide, and organic nanocrystal-modified / rare earth titanium dioxide composite material is 0.5 mmol:0.5 mmol:50 mL:1 g.

[0037] The synergistic carrier is a mixture of attapulgite and hydroxyapatite in a mass ratio of 2:1; the average particle size of the hydroxyapatite is 1 μm; the average particle size of the attapulgite is 5 μm; the flocculation function is a mixture of polyaluminum ferric chloride and modified starch acrylamide copolymer in a mass ratio of 1:0.8; the polyaluminum ferric chloride is SJ-601 polyaluminum ferric chloride PAFC-A2 type; the modified starch acrylamide copolymer is prepared according to the method of Example 11 of Chinese Invention Patent No. CN102936318B; the particle size of the nano-zero valent iron is 20-30 nm; the particle size of the montmorillonite is 1-5 μm.

[0038] A method for treating fluoride-containing wastewater using the aforementioned fluoride-containing wastewater treatment agent includes the following steps: collecting the fluoride-containing wastewater in a reaction tank, adjusting the pH value of the wastewater to 6 by adding sodium hydroxide solution; after adding the treatment agent, performing two-stage stirring: the first stage is rapid stirring at a speed of 300 r / min for 5 min to ensure thorough mixing of the agent and wastewater; the second stage is slow stirring at a speed of 50 r / min for 20 min to promote floc formation; the mixed liquid after reaction is sent to an inclined tube sedimentation tank for a retention time of 1 h, the supernatant is the treated water, and the bottom sludge is dewatered by a plate and frame filter press and then transported for disposal; the ratio of the mass of the treatment agent added to the mass of fluoride ions in the wastewater is 1.2:1.

[0039] Example 2

[0040] A fluoride-containing wastewater treatment agent comprises the following raw materials in parts by weight: 43 parts of MOFs / organic nanocrystals / rare earth titanium dioxide composite material, 21 parts of synergistic carrier, 16 parts of flocculation function, and 11 parts of additives; wherein the additives are nano-zero valent iron and montmorillonite mixed in a mass ratio of 6:100.

[0041] The preparation method of the MOFs / organic nanocrystals / rare earth titanium dioxide composite material includes the following steps:

[0042] Step D1, Preparation of rare earth titanium dioxide: First, tetrabutyl titanate is slowly added to anhydrous ethanol and magnetically stirred for 27 minutes to form a homogeneous solution A. In another beaker, glacial acetic acid, deionized water, and a mixed solution of lanthanum nitrate and cerium nitrate are added and stirred until homogeneous to form solution B. Solution B is added dropwise to solution A while magnetically stirring, and the addition is completed in 1.2 hours. After the addition is complete, stirring is continued for 2.3 hours to form a stable sol. The sol is allowed to stand at room temperature for 24 hours to form a gel. The gel is then placed in an oven and dried at 63°C for 11 hours. Finally, the temperature is increased to 520°C at a rate of 3.5°C / min and calcined at that temperature for 2.5 hours. The mixture is then naturally cooled to room temperature to obtain rare earth titanium dioxide.

[0043] Step D2, Preparation of organic nanocrystal / rare earth titanium dioxide composite material: Cellulose nanocrystals were dispersed in deionized water, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added as activators. The mixture was stirred at room temperature for 0.9 h. Then, rare earth titanium dioxide prepared in step S1 was added, and the mixture was stirred at 60 °C for 4 h. After centrifugation and washing, the mixture was vacuum dried at 60 °C for 12 h to obtain the organic nanocrystal / rare earth titanium dioxide composite material.

[0044] Step D3: Preparation of MOFs / organic nanocrystals / rare earth titanium dioxide composite material: ZrCl4 and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide, and the organic nanocrystal modified / rare earth titanium dioxide composite material prepared in step S2 was added. After ultrasonic dispersion for 27 min, the mixture was transferred to a hydrothermal reactor and reacted at 119 °C for 23 h. The product was washed three times alternately with N,N-dimethylformamide and ethanol, and then vacuum dried at 73 °C for 12 h to obtain the MOFs / organic nanocrystals / rare earth titanium dioxide composite material.

[0045] In step D1, the volume ratio of tetrabutyl titanate, anhydrous ethanol, glacial acetic acid, and deionized water is 4:10:1:1; the molar ratio of tetrabutyl titanate, lanthanum nitrate, and cerium nitrate in step D1 is 1:0.02:0.04; in step D2, the mass ratio of cellulose nanocrystals, deionized water, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, and rare earth titanium dioxide is 1:200:0.2:0.2:10; the diameter of the cellulose nanocrystals in step D2 is 10-50 nm, and the length is 200-500 nm; in step D3, the molar ratio of ZrCl4, 2-aminoterephthalic acid, N,N-dimethylformamide, and organic nanocrystal-modified / rare earth titanium dioxide composite material is 0.5 mmol:0.5 mmol:50 mL:1 g.

[0046] The synergistic carrier is a mixture of attapulgite and hydroxyapatite in a mass ratio of 2.3:1; the average particle size of the hydroxyapatite is 2 μm; the average particle size of the attapulgite is 8 μm; the flocculation function is a mixture of polyaluminum ferric chloride and modified starch acrylamide copolymer in a mass ratio of 1:0.9; the polyaluminum ferric chloride is SJ-601 polyaluminum ferric chloride PAFC-A2 type; the modified starch acrylamide copolymer is prepared according to the method of Example 11 of Chinese Invention Patent No. CN102936318B; the particle size of the nano-zero valent iron is 20-30 nm; the particle size of the montmorillonite is 1-5 μm.

[0047] A method for treating fluoride-containing wastewater using the aforementioned fluoride-containing wastewater treatment agent includes the following steps: collecting the fluoride-containing wastewater into a reaction tank, adjusting the pH value of the wastewater to 6.5 by adding sodium hydroxide solution; after adding the treatment agent, performing two-stage stirring: the first stage is rapid stirring at a speed of 330 r / min for 7 min to ensure thorough mixing of the agent and wastewater; the second stage is slow stirring at a speed of 70 r / min for 23 min to promote floc formation; the mixed liquid after reaction is sent to an inclined tube sedimentation tank for a retention time of 1.2 h, the supernatant is the treated water, and the bottom sludge is dewatered by a plate and frame filter press and then transported for disposal; the ratio of the mass of the treatment agent added to the mass of fluoride ions in the wastewater is 1.2:1.

[0048] Example 3

[0049] A fluoride-containing wastewater treatment agent comprises the following raw materials in parts by weight: 45 parts of MOFs / organic nanocrystals / rare earth titanium dioxide composite material, 23 parts of synergistic carrier, 18 parts of flocculation function, and 13 parts of additives; wherein the additives are nano-zero valent iron and montmorillonite mixed in a mass ratio of 6.5:100.

[0050] The preparation method of the MOFs / organic nanocrystals / rare earth titanium dioxide composite material includes the following steps:

[0051] Step D1, Preparation of rare earth titanium dioxide: First, tetrabutyl titanate is slowly added to anhydrous ethanol and magnetically stirred for 30 minutes to form a homogeneous solution A. In another beaker, glacial acetic acid, deionized water, and a mixed solution of lanthanum nitrate and cerium nitrate are added and stirred until homogeneous to form solution B. Solution B is added dropwise to solution A while magnetically stirring, and the addition is completed in 1.5 hours. After the addition is completed, stirring is continued for 2.5 hours to form a stable sol. The sol is allowed to stand at room temperature for 24 hours to form a gel. The gel is then placed in an oven and dried at 65°C for 12.5 hours. Finally, the temperature is increased to 530°C at a rate of 4°C / min and calcined for 3 hours. The calcined gel is then allowed to cool naturally to room temperature to obtain rare earth titanium dioxide.

[0052] Step D2, Preparation of organic nanocrystal / rare earth titanium dioxide composite material: Cellulose nanocrystals were dispersed in deionized water, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added as activators. The mixture was stirred at room temperature for 1 h. Then, rare earth titanium dioxide prepared in step S1 was added, and the mixture was stirred at 60 °C for 4 h. After centrifugation and washing, the mixture was vacuum dried at 60 °C for 12 h to obtain the organic nanocrystal / rare earth titanium dioxide composite material.

[0053] Step D3: Preparation of MOFs / organic nanocrystals / rare earth titanium dioxide composite material: ZrCl4 and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide, and the organic nanocrystal modified / rare earth titanium dioxide composite material prepared in step S2 was added. After ultrasonic dispersion for 30 min, the mixture was transferred to a hydrothermal reactor and reacted at 120℃ for 23.5 h. The product was washed three times alternately with N,N-dimethylformamide and ethanol, and then vacuum dried at 75℃ for 13 h to obtain the MOFs / organic nanocrystals / rare earth titanium dioxide composite material.

[0054] In step D1, the volume ratio of tetrabutyl titanate, anhydrous ethanol, glacial acetic acid, and deionized water is 4:10:1:1; the molar ratio of tetrabutyl titanate, lanthanum nitrate, and cerium nitrate in step D1 is 1:0.02:0.04; in step D2, the mass ratio of cellulose nanocrystals, deionized water, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, and rare earth titanium dioxide is 1:200:0.2:0.2:10; the diameter of the cellulose nanocrystals in step D2 is 10-50 nm, and the length is 200-500 nm; in step D3, the molar ratio of ZrCl4, 2-aminoterephthalic acid, N,N-dimethylformamide, and organic nanocrystal-modified / rare earth titanium dioxide composite material is 0.5 mmol:0.5 mmol:50 mL:1 g.

[0055] The synergistic carrier is a mixture of attapulgite and hydroxyapatite in a mass ratio of 2.5:1; the average particle size of the hydroxyapatite is 3.5 μm; the average particle size of the attapulgite is 13 μm; the flocculation function is a mixture of polyaluminum ferric chloride and modified starch acrylamide copolymer in a mass ratio of 1:1; the polyaluminum ferric chloride is SJ-601 polyaluminum ferric chloride PAFC-A2 type; the modified starch acrylamide copolymer is prepared according to the method of Example 11 of Chinese Invention Patent No. CN102936318B; the particle size of the nano-zero valent iron is 20-30 nm; the particle size of the montmorillonite is 1-5 μm.

[0056] A method for treating fluoride-containing wastewater using the aforementioned fluoride-containing wastewater treatment agent includes the following steps: collecting the fluoride-containing wastewater in a reaction tank, adjusting the pH value of the wastewater to 7 by adding sodium hydroxide solution; after adding the treatment agent, performing two-stage stirring: the first stage is rapid stirring at a speed of 350 r / min for 7 min to ensure thorough mixing of the agent and wastewater; the second stage is slow stirring at a speed of 80 r / min for 25 min to promote floc formation; the mixed liquid after reaction is sent to an inclined tube sedimentation tank for a retention time of 1.5 h, the supernatant is the treated water, and the bottom sludge is dewatered by a plate and frame filter press and then transported for disposal; the ratio of the mass of the treatment agent added to the mass of fluoride ions in the wastewater is 1.6:1.

[0057] Example 4

[0058] A fluoride-containing wastewater treatment agent comprises the following raw materials in parts by weight: 48 parts of MOFs / organic nanocrystals / rare earth titanium dioxide composite material, 24 parts of synergistic carrier, 19 parts of flocculation function, and 14 parts of additives; wherein the additives are nano-zero valent iron and montmorillonite mixed in a mass ratio of 7.5:100.

[0059] The preparation method of the MOFs / organic nanocrystals / rare earth titanium dioxide composite material includes the following steps:

[0060] Step D1, Preparation of rare earth titanium dioxide: First, tetrabutyl titanate is slowly added to anhydrous ethanol and magnetically stirred for 33 minutes to form a homogeneous solution A. In another beaker, glacial acetic acid, deionized water, and a mixed solution of lanthanum nitrate and cerium nitrate are added and stirred until homogeneous to form solution B. Solution B is added dropwise to solution A while magnetically stirring, and the addition is completed in 1.8 hours. After the addition is complete, stirring is continued for 2.8 hours to form a stable sol. The sol is allowed to stand at room temperature for 24 hours to form a gel. The gel is then placed in an oven and dried at 68°C for 13.5 hours. Finally, the temperature is increased to 540°C at a rate of 4.5°C / min and calcined at this temperature for 3.5 hours. The mixture is then naturally cooled to room temperature to obtain rare earth titanium dioxide.

[0061] Step D2, Preparation of organic nanocrystal / rare earth titanium dioxide composite material: Cellulose nanocrystals were dispersed in deionized water, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added as activators. The mixture was stirred at room temperature for 1.1 h. Then, rare earth titanium dioxide prepared in step S1 was added, and the mixture was stirred at 60 °C for 4 h. After centrifugation and washing, the mixture was vacuum dried at 60 °C for 12 h to obtain the organic nanocrystal / rare earth titanium dioxide composite material.

[0062] Step D3: Preparation of MOFs / organic nanocrystals / rare earth titanium dioxide composite material: ZrCl4 and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide, and the organic nanocrystal modified / rare earth titanium dioxide composite material prepared in step S2 was added. After ultrasonic dispersion for 33 min, the mixture was transferred to a hydrothermal reactor and reacted at 121℃ for 24.5 h. The product was washed three times alternately with N,N-dimethylformamide and ethanol, and then vacuum dried at 78℃ for 14 h to obtain the MOFs / organic nanocrystals / rare earth titanium dioxide composite material.

[0063] In step D1, the volume ratio of tetrabutyl titanate, anhydrous ethanol, glacial acetic acid, and deionized water is 4:10:1:1; the molar ratio of tetrabutyl titanate, lanthanum nitrate, and cerium nitrate in step D1 is 1:0.02:0.04; in step D2, the mass ratio of cellulose nanocrystals, deionized water, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, and rare earth titanium dioxide is 1:200:0.2:0.2:10; the diameter of the cellulose nanocrystals in step D2 is 10-50 nm, and the length is 200-500 nm; in step D3, the molar ratio of ZrCl4, 2-aminoterephthalic acid, N,N-dimethylformamide, and organic nanocrystal-modified / rare earth titanium dioxide composite material is 0.5 mmol:0.5 mmol:50 mL:1 g.

[0064] The synergistic carrier is a mixture of attapulgite and hydroxyapatite in a mass ratio of 2.8:1; the average particle size of the hydroxyapatite is 4 μm; the average particle size of the attapulgite is 18 μm; the flocculation function is a mixture of polyaluminum ferric chloride and modified starch acrylamide copolymer in a mass ratio of 1:1.1; the polyaluminum ferric chloride is SJ-601 polyaluminum ferric chloride PAFC-A2 type; the modified starch acrylamide copolymer is prepared according to the method of Example 11 of Chinese Invention Patent No. CN102936318B; the particle size of the nano-zero valent iron is 20-30 nm; the particle size of the montmorillonite is 1-5 μm.

[0065] A method for treating fluoride-containing wastewater using the aforementioned fluoride-containing wastewater treatment agent includes the following steps: collecting the fluoride-containing wastewater into a reaction tank, adjusting the pH value of the wastewater to 7.5 by adding sodium hydroxide solution; after adding the treatment agent, performing two-stage stirring: the first stage is rapid stirring at a speed of 390 r / min for 9 min to ensure thorough mixing of the agent and wastewater; the second stage is slow stirring at a speed of 90 r / min for 28 min to promote floc formation; the mixed liquid after reaction is sent to an inclined tube sedimentation tank for a retention time of 1.8 h, the supernatant is the treated water, and the bottom sludge is dewatered by a plate and frame filter press and then transported for disposal; the ratio of the mass of the treatment agent added to the mass of fluoride ions in the wastewater is 1.2:1.

[0066] Example 5

[0067] A fluoride-containing wastewater treatment agent comprises the following raw materials in parts by weight: 50 parts of MOFs / organic nanocrystals / rare earth titanium dioxide composite material, 25 parts of synergistic carrier, 20 parts of flocculation function, and 15 parts of additives; wherein the additives are nano-zero valent iron and montmorillonite mixed in a mass ratio of 8:100.

[0068] The preparation method of the MOFs / organic nanocrystals / rare earth titanium dioxide composite material includes the following steps:

[0069] Step D1, Preparation of rare earth titanium dioxide: First, tetrabutyl titanate is slowly added to anhydrous ethanol and magnetically stirred for 35 minutes to form a homogeneous solution A. In another beaker, glacial acetic acid, deionized water, and a mixed solution of lanthanum nitrate and cerium nitrate are added and stirred until homogeneous to form solution B. Solution B is added dropwise to solution A while magnetically stirring. The addition is completed in 2 hours, and stirring is continued for 3 hours afterward to form a stable sol. The sol is allowed to stand at room temperature for 24 hours to form a gel. The gel is then placed in an oven and dried at 70°C for 14 hours. Finally, the temperature is increased to 550°C at a rate of 5°C / min and calcined for 4 hours. The mixture is then naturally cooled to room temperature to obtain rare earth titanium dioxide.

[0070] Step D2, Preparation of organic nanocrystal / rare earth titanium dioxide composite material: Cellulose nanocrystals were dispersed in deionized water, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added as activators. The mixture was stirred at room temperature for 1.2 h. Then, rare earth titanium dioxide prepared in step S1 was added, and the mixture was stirred at 60 °C for 4 h. After centrifugation and washing, the mixture was vacuum dried at 60 °C for 12 h to obtain the organic nanocrystal / rare earth titanium dioxide composite material.

[0071] Step D3: Preparation of MOFs / organic nanocrystals / rare earth titanium dioxide composite material: ZrCl4 and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide, and the organic nanocrystal modified / rare earth titanium dioxide composite material prepared in step S2 was added. After ultrasonic dispersion for 35 min, the mixture was transferred to a hydrothermal reactor and reacted at 122℃ for 25 h. The product was washed three times alternately with N,N-dimethylformamide and ethanol, and then vacuum dried at 80℃ for 15 h to obtain the MOFs / organic nanocrystals / rare earth titanium dioxide composite material.

[0072] In step D1, the volume ratio of tetrabutyl titanate, anhydrous ethanol, glacial acetic acid, and deionized water is 4:10:1:1; the molar ratio of tetrabutyl titanate, lanthanum nitrate, and cerium nitrate in step D1 is 1:0.02:0.04; in step D2, the mass ratio of cellulose nanocrystals, deionized water, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, and rare earth titanium dioxide is 1:200:0.2:0.2:10; the diameter of the cellulose nanocrystals in step D2 is 10-50 nm, and the length is 200-500 nm; in step D3, the molar ratio of ZrCl4, 2-aminoterephthalic acid, N,N-dimethylformamide, and organic nanocrystal-modified / rare earth titanium dioxide composite material is 0.5 mmol:0.5 mmol:50 mL:1 g.

[0073] The synergistic carrier is a mixture of attapulgite and hydroxyapatite in a mass ratio of 3:1; the average particle size of the hydroxyapatite is 5 μm; the average particle size of the attapulgite is 20 μm; the flocculation function is a mixture of polyaluminum ferric chloride and modified starch acrylamide copolymer in a mass ratio of 1:1.2; the polyaluminum ferric chloride is SJ-601 polyaluminum ferric chloride PAFC-A2 type; the modified starch acrylamide copolymer is prepared according to the method of Example 11 of Chinese Invention Patent No. CN102936318B; the particle size of the nano-zero valent iron is 20-30 nm; the particle size of the montmorillonite is 1-5 μm.

[0074] A method for treating fluoride-containing wastewater using the aforementioned fluoride-containing wastewater treatment agent includes the following steps: collecting the fluoride-containing wastewater into a reaction tank, adjusting the pH value of the wastewater to 8 by adding sodium hydroxide solution; after adding the treatment agent, performing two-stage stirring: the first stage is rapid stirring at a speed of 400 r / min for 10 min to ensure thorough mixing of the agent and wastewater; the second stage is slow stirring at a speed of 100 r / min for 30 min to promote floc formation; the mixed liquid after reaction is sent to an inclined tube sedimentation tank for a retention time of 2 h, the supernatant is the treated water, and the bottom sludge is dewatered by a plate and frame filter press and then transported for disposal; the ratio of the mass of the treatment agent added to the mass of fluoride ions in the wastewater is 1.2:1.

[0075] Comparative Example 1

[0076] This example provides a method and agent for treating fluoride-containing wastewater, which is basically the same as that in Example 1, except that an equal amount of rare earth titanium dioxide is used instead of the MOFs / organic nanocrystals / rare earth titanium dioxide composite material.

[0077] Comparative Example 2

[0078] This example provides a method for treating fluoride-containing wastewater and its treatment agent, which is basically the same as that in Example 1, except that an equal amount of polyaluminum ferric chloride is used instead of the modified starch acrylamide copolymer.

[0079] To further illustrate the beneficial technical effects of the fluoride-containing wastewater treatment methods and treatment agents involved in the various embodiments of the present invention, the following experiments were conducted on the products and usage methods of each example:

[0080] Fluoride-containing wastewater from an electronic component manufacturing workshop in Inner Mongolia was collected. The fluoride ion concentration was measured to be 300 mg / L, and the pH was 4. The wastewater was treated according to the methods in Examples 1-5 and Comparative Examples 1-2. The fluoride ion concentration in the treated water was measured in each example, and the fluoride removal rate was calculated. The fluoride ion concentration was determined according to HJ 84-2016 "Determination of Inorganic Anions in Water - Ion Chromatography". The test results are shown in Table 1.

[0081] As can be seen from Table 1, the fluoride-containing wastewater treatment methods and treatment agents disclosed in the embodiments of the present invention have better fluoride-containing wastewater treatment effects than the comparative examples. The combined use of MOFs / organic nanocrystals / rare earth titanium dioxide composite materials, polyaluminum ferric chloride and modified starch acrylamide copolymer is beneficial to improving the above performance.

[0082] Table 1

[0083]

[0084] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A fluoride-containing wastewater treatment agent, characterized in that, The product comprises the following raw materials in parts by weight: 40-50 parts of MOFs / organic nanocrystals / rare earth titanium dioxide composite material, 20-25 parts of synergistic carrier, 15-20 parts of flocculation function, and 10-15 parts of additives; the additives are nano-zero valent iron and montmorillonite mixed in a mass ratio of (5-8):100; the synergistic carrier is attapulgite and hydroxyapatite mixed in a mass ratio of (2-3):1; the flocculation function is polyaluminum ferric chloride and modified starch acrylamide copolymer mixed in a mass ratio of 1:(0.8-1.2). The preparation method of the MOFs / organic nanocrystals / rare earth titanium dioxide composite material includes the following steps: Step D1, Preparation of rare earth titanium dioxide: First, tetrabutyl titanate is slowly added to anhydrous ethanol and magnetically stirred for 25-35 minutes to form a homogeneous solution A. In a separate beaker, glacial acetic acid, deionized water, and a mixed solution of lanthanum nitrate and cerium nitrate are added and stirred until homogeneous to form solution B. Solution B is added dropwise to solution A while magnetically stirring, and the addition is completed in 1-2 hours. After the addition is complete, stirring continues for 2-3 hours to form a stable sol. The sol is allowed to stand at room temperature for 24 hours to form a gel. The gel is then placed in an oven and dried at 60-70℃ for 10-14 hours. Finally, the temperature is increased to 500-550℃ at a rate of 3-5℃ / min and calcined for 2-4 hours, then naturally cooled to room temperature to obtain rare earth titanium dioxide. The molar ratio of tetrabutyl titanate, lanthanum nitrate, and cerium nitrate is 1:0.02:0.

04. Step D2, Preparation of Organic Nanocrystal / Rare Earth Titanium Dioxide Composite Material: Cellulose nanocrystals were dispersed in deionized water, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added as activators. The mixture was stirred at room temperature for 0.8-1.2 h. Then, the rare earth titanium dioxide prepared in step S1 was added, and the mixture was stirred at 60 °C for 4 h. After centrifugation and washing, the mixture was vacuum dried at 60 °C for 12 h to obtain the organic nanocrystal / rare earth titanium dioxide composite material. The mass ratio of cellulose nanocrystals, deionized water, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, and rare earth titanium dioxide was 1:200:0.2:0.2:

10. Step D3: Preparation of MOFs / organic nanocrystals / rare earth titanium dioxide composite material: ZrCl4 and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide, and the organic nanocrystal modified / rare earth titanium dioxide composite material prepared in step S2 was added. After ultrasonic dispersion for 25-35 min, the mixture was transferred to a hydrothermal reactor and reacted at 118-122℃ for 22-25 h. The product was washed three times alternately with N,N-dimethylformamide and ethanol, and vacuum dried at 70-80℃ for 10-15 h to obtain the MOFs / organic nanocrystals / rare earth titanium dioxide composite material. The molar ratio of ZrCl4, 2-aminoterephthalic acid, N,N-dimethylformamide, and organic nanocrystal modified / rare earth titanium dioxide composite material was 0.5 mmol:0.5 mmol:50 mL:1 g.

2. The fluoride-containing wastewater treatment agent according to claim 1, characterized in that, The volume ratio of tetrabutyl titanate, anhydrous ethanol, glacial acetic acid, and deionized water in step D1 is 4:10:1:

1.

3. The fluoride-containing wastewater treatment agent according to claim 1, characterized in that, The cellulose nanocrystals described in step D2 have a diameter of 10-50 nm and a length of 200-500 nm.

4. The fluoride-containing wastewater treatment agent according to claim 1, characterized in that, The average particle size of the hydroxyapatite is 1-5 μm; the average particle size of the attapulgite is 5-20 μm.

5. The fluoride-containing wastewater treatment agent according to claim 1, characterized in that, The polyaluminum ferric chloride is SJ-601 polyaluminum ferric chloride PAFC-A2 type; the particle size of the nano-zero valent iron is 20-30nm; and the particle size of the montmorillonite is 1-5μm.

6. A method for treating fluoride-containing wastewater using the fluoride-containing wastewater treatment agent according to any one of claims 1-5, characterized in that, The process includes the following steps: collecting fluoride-containing wastewater into a reaction tank, adjusting the pH of the wastewater to 6-8 by adding sodium hydroxide solution; after adding the treatment agent, performing two-stage stirring, the first stage being rapid stirring at a speed of 300-400 r / min for 5-10 min to ensure thorough mixing of the agent and wastewater; The second stage involves slow stirring at a speed of 50-100 r / min for 20-30 min to promote floc formation. The reacted mixture is then sent to an inclined tube sedimentation tank for 1-2 h. The supernatant is the treated water, and the bottom sludge is dewatered by a plate and frame filter press and then transported off-site for disposal. The ratio of the mass of the treatment agent added to the mass of fluoride ions in the wastewater is (1.2-2.0):1.

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