Preparation method and application of fluorine-containing wastewater treatment material

Abstract

The invention provides a preparation method and application of a fluorine-containing wastewater treatment material, and the preparation method comprises the following steps: repeatedly cleaning shrimp shells with deionized water, drying in a drying oven to constant weight, crushing with a crusher, and sieving. In order to ensure more effective heat transfer, complete carbonization and high biochar yield in the shrimp shell powder and avoid the influence of the change of the heating rate on the biochar pore structure, under the protection of nitrogen, high-temperature firing is performed in a tubular furnace, cooling is performed, washing is performed with deionized water and ethanol in sequence, and drying, grinding and sieving are performed in a drying oven. By adopting the technical scheme designed by the invention, the temperature of Ca < 2 + > released by the biochar is higher than that of conventional acid pickling and conventional firing, and the shrimp shell biochar is relatively low in cost, small in environmental pollution, high in safety coefficient and relatively good in fluorine ion removal effect, and shows relatively great potential in treatment application of fluorine-containing wastewater.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a preparation process of a fluorine chemical wastewater treatment material and its application in actual fluorine chemical wastewater and laboratory simulated fluorine-containing solution. Background Art

[0002] The pollution caused by fluorine-containing wastewater produced by fluorine chemical industry and photovoltaic industry to human beings and ecological environment cannot be underestimated. The efficient removal of fluoride ions in wastewater by using waste materials is of great significance to clean production and circular economy. At present, the main technical methods for treating fluorine-containing wastewater are: physical method, chemical method, biological method and comprehensive method. Among them, the chemical method involves the use of chemical principles to treat fluorine-containing wastewater, including ion exchange method and precipitation method. The ion exchange method exchanges fluoride ions in wastewater through ion exchange resin, adsorbs fluoride ions on the resin, and thus removes fluoride ions. Among them, the representative of precipitation method is calcium salt precipitation method, that is, adding precipitants such as calcium hydroxide and sodium hydroxide to wastewater, so that fluoride ions in wastewater react with precipitants to form precipitates, thereby achieving the treatment of fluoride-containing wastewater. This method is similar to lime precipitation method, but the precipitant used is different. It also has the advantages of convenient treatment and low cost, but it may also face the problem of difficult effluent to meet standards and difficult sludge treatment.

[0003] Physical treatment methods include precipitation, filtration, adsorption, membrane separation and ultraviolet irradiation. Among them, precipitation and filtration are common traditional physical treatment methods. The precipitation method mainly uses the different specific gravity of the material to achieve separation. It is simple to operate and has high treatment efficiency, but it cannot completely remove all fluoride ions; the filtration method mainly uses the adsorption of fluoride ions by the filter medium, which can remove some fluoride ions, but the filter medium needs to be replaced frequently, and the operation is relatively cumbersome. However, physical treatment methods such as adsorption, membrane separation and ultraviolet irradiation have limited effects on the treatment of fluoride-containing wastewater. Chemical precipitation is to add chemical precipitants to fluoride-containing wastewater, so that fluoride ions react with the precipitants to generate water-insoluble fluoride precipitates, and separate the wastewater by precipitation, but it also faces problems such as high treatment cost, large amount of chemical addition, and difficult treatment of reaction products. Biological treatment methods include biological adsorption, biofilm reactor, biological treatment-chemical precipitation, etc. Among them, biological adsorption and biofilm reactor are commonly used biological treatment methods. Biological adsorption is to remove fluoride ions by attaching fluoride ions in fluoride-containing wastewater to the surface of the material through microorganisms. The biofilm reactor degrades fluoride ions in the wastewater into harmless substances through the growth of microorganisms, and at the same time adsorbs fluoride ions on the surface of microorganisms, eventually forming a biofilm in the water. The biological treatment method faces problems such as unstable treatment effect, difficult operation, and long-term operation. Summary of the invention

[0004] In view of the above technical problems, the present invention proposes a preparation process of a fluorine chemical wastewater treatment material and its application in laboratory simulated fluorine-containing solutions and actual fluorine-containing wastewater, which can efficiently remove fluoride ions in wastewater and reduce the cost of use, and can be used in the treatment of wastewater containing high concentrations of fluoride ions.

[0005] To this end, the technical solution adopted by the present invention is: A method for preparing a fluorine-containing wastewater treatment material comprises the following steps: Step S1: repeatedly washing the shrimp shells with deionized water, drying them to constant weight, crushing them with a grinder, and sieving them to obtain shrimp shell powder.

[0006] Step S2: To ensure more effective heat transfer, complete carbonization and high biochar yield inside the shrimp shell powder, and to avoid the influence of changes in the heating rate on the pore structure of the biochar, the shrimp shell powder is placed in a tubular furnace under nitrogen protection and heated to 700°C-1100°C for calcination. After cooling, it is repeatedly immersed and washed with deionized water and ethanol for more than 5 times, dried, ground and sieved.

[0007] This technical solution uses discarded shrimp shells as raw materials. After high-temperature calcination and immersion washing, more water-soluble Ca(OH)2 is produced on the surface, releasing more Ca into the water. 2+ , and then fully react with fluoride ions in water to generate CaF2, thereby reducing the concentration of fluoride ions in water. This bio-based material has a high efficiency in removing fluoride ions in water and has no secondary pollution to the environment, because it is a chemical reaction, and its pores are filled with CaF2. 2+ The release pore size is further enlarged, and it still has a certain regeneration ability after removal.

[0008] As a further improvement of the present invention, in step S1, the drying temperature is preferably 105°C, and the mixture is dried to a constant weight.

[0009] As a further improvement of the present invention, in step S1, the dried shrimp shells are crushed by a crusher and passed through a 200-150 mesh sieve. Furthermore, the shrimp shells are passed through a 150 mesh sieve.

[0010] As a further improvement of the present invention, in step S2, the heating rate is 10°C / min.

[0011] As a further improvement of the present invention, in step S2, under the protection of nitrogen, the temperature of the tubular furnace is raised to 700°C-1100°C. Furthermore, the calcination temperature is preferably 800°C and kept at this temperature for 2 hours.

[0012] As a further improvement of the present invention, in step S2, after cooling, the product is washed with deionized water and then with ethanol. Furthermore, after cooling, the product is repeatedly washed with deionized water and then with ethanol for more than 5 times.

[0013] As a further improvement of the present invention, in step S2, drying, grinding and sieving are further performed in an oven at 60° C. for 10 hours, and after drying, the mixture is ground and sieved through a 60-mesh sieve.

[0014] The present invention also discloses a fluorine chemical wastewater treatment material, which is prepared by the preparation method of the bio-based fluorine-containing wastewater treatment material with shrimp shell as the main body carbonized as described in any one of the above items.

[0015] The invention also discloses a fluorine chemical wastewater treatment material as described above and its application, which is used for treating fluorine-containing wastewater.

[0016] Compared with the prior art, the present invention has the following beneficial effects: By adopting the technical scheme of the present invention, fluoride ions in wastewater can be efficiently removed, and the effluent can reach the industrial emission standard for inorganic fluorine compounds (GB 31573-2015). In addition, the recycling of discarded shrimp shells reduces the use cost, which is in line with the concept of circular economy and green environmental protection. It can be used in the treatment of wastewater containing high-concentration fluoride ions, has strong adaptability to the environment, does not have high requirements on the pH value of the solution, and has a simple preparation method, low cost, and regeneration performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a preparation flow chart of a fluorine chemical wastewater treatment material of the present invention; Figure 2 is a transmission electron micrograph of the fluorine-containing wastewater treatment material prepared in Example 1; Figure 3 is a transmission electron micrograph of the material after treatment in Example 5; Figure 4 is a graph of calcium fluoride crystals formed during the treatment of the present material in Example 5; Figure 5 This is a diagram showing the removal effect of the material in the presence of ion interference in Example 2; Figure 6 This is the removal effect of the material in Example 3 under acidic and alkaline conditions. DETAILED DESCRIPTION

[0018] The preferred embodiments of the present invention are described in further detail below.

[0019] A method for preparing a fluorine chemical wastewater treatment material, such as Figure 1 As shown, the following steps are included: Step S1: repeatedly wash the shrimp shells with deionized water, place them in an oven at 105° C. and dry them to constant weight, crush them with a grinder, and sieve them to obtain shrimp shell powder.

[0020] Step S2 is to ensure more effective heat transfer, complete carbonization and high biochar yield inside the shrimp shell powder, and avoid the influence of changes in heating rate on the pore structure of biochar. Under nitrogen protection, the shrimp shell powder is placed in a tubular furnace and heated to 700°C-1100°C for calcination. After cooling, it is placed in water and ethanol and washed repeatedly for more than 5 times, dried, ground and sieved.

[0021] As a further improvement of the present invention, in step S1, the drying temperature is selected to be 105°C, and the mixture is dried to a constant weight.

[0022] As a further improvement of the present invention, in step S1, the dried shrimp shells are crushed by a crusher and passed through a 200-150 mesh sieve. Furthermore, the shrimp shells are passed through a 150 mesh sieve.

[0023] As a further improvement of the present invention, in step S2, the heating rate is 10°C / min.

[0024] As a further improvement of the present invention, in step S2, under the protection of nitrogen, the temperature of the tubular furnace is raised to 700°C-1100°C, and further, the calcination temperature is selected to be 800°C and kept at this temperature for 2 hours.

[0025] As a further improvement of the present invention, in step S2, after cooling, the product is washed with deionized water and then with ethanol. Furthermore, after cooling, the product is repeatedly washed with water and ethanol for more than 5 times.

[0026] As a further improvement of the present invention, in step S2, drying, grinding and sieving are further performed in an oven at 60° C. for 10 hours, and after drying, the mixture is ground and sieved through a 60-mesh sieve.

[0027] The following describes it in conjunction with specific embodiments.

[0028] Example 1 A fluorine chemical wastewater treatment material is prepared by the following steps: The shrimp shells were repeatedly washed with deionized water, dried in an oven at 105°C to constant weight, crushed with a grinder, and passed through a 150-mesh sieve.

[0029] In order to ensure more effective heat transfer, complete carbonization and high biochar yield inside the shrimp shell powder, and avoid the influence of changes in heating rate on the pore structure of biochar, the shrimp shell powder was placed in a tubular furnace under nitrogen protection and heated to 800°C at a heating rate of 10°C / min and maintained for 2 hours. After cooling, it was repeatedly washed in deionized water and ethanol for more than 5 times, placed in a 60°C oven for drying for 10 hours, ground, passed through a 60-mesh sieve, and the biochar was obtained and placed in a medicine bottle for later use.

[0030] Accurately weigh 221 mg of anhydrous sodium fluoride and dissolve it in 1 L of deionized water to prepare a fluoride stock solution (100.5 mg / L); weigh 0.06 g of biochar and add it to 20 ml of the fluoride stock solution in a polyethylene tube, then place the mixture in a shaker at 20°C; after 24 hours of contact, filter the mixed solution with a 0.45 μm syringe; place the filtered solution in a conical flask and continue to shake it in a shaker to allow the calcium ions and fluoride ions to fully react. After 24 hours of reaction, filter the suspended precipitate with a 0.45 μm syringe and measure the fluoride concentration in the solution. It was found that the fluoride ion concentration in the solution was between 1.8 mg and 3 mg at this time, and the removal rate could reach 97% to 98.2%.

[0031] Example 2 A fluorine chemical wastewater treatment material is prepared by the following steps: The shrimp shells were repeatedly washed with deionized water, dried in an oven at 105°C to constant weight, crushed with a grinder, and passed through a 150-mesh sieve.

[0032] In order to ensure more effective heat transfer, complete carbonization and high biochar yield inside the shrimp shell powder, and avoid the influence of changes in heating rate on the pore structure of biochar, the shrimp shell powder was placed in a tubular furnace and heated to 800°C at a heating rate of 10°C / min and maintained for 2 hours under nitrogen protection. After cooling, it was washed repeatedly in deionized water and ethanol for more than 5 times, placed in a 60°C oven for drying for 10 hours, ground, passed through a 60-mesh sieve, and the biochar was obtained and placed in a medicine bottle for later use.

[0033] The removal effect of this material under the condition of ion interference was investigated; 221 mg of anhydrous sodium fluoride was accurately weighed and dissolved in 1 L of deionized water to obtain a fluoride stock solution (100.5 mg / L); 12 g of NH4Fe(SO4)2·12H2O was accurately weighed, 5 mL of concentrated sulfuric acid and deionized water were added to dissolve in a 250 mL volumetric flask to the mark, and 2.5 mL of the solution was transferred to a 250 mL volumetric flask after shaking, and diluted to the mark with deionized water to obtain Fe 3＋ solution (55.85 mg / L); accurately weigh 0.585 g of sodium chloride, add deionized water to the mark in a 1 L volumetric flask while stirring, and prepare a sodium chloride solution (0.01 mol / L); weigh two portions of 0.06 g of biochar and add 20 ml of fluorine stock solution to polyethylene tubes respectively; add 1 mL of Fe 3＋solution (55.85 mg / L), and another one was added with 1 mL of sodium chloride solution (0.01 mol / L), and then the mixture was shaken in a shaker at 20°C; after 24 hours of contact, the mixed solution was filtered with a 0.45 μm syringe; the filtered solution was placed in a conical flask and continued to be shaken in a shaker to allow the calcium ions and fluoride ions to fully react, and after 24 hours of reaction, the suspended precipitate was filtered with a 0.45 μm syringe, and the fluoride concentration in the solution was measured. It was found that the fluoride ion concentration in the solution was still between 1.8 mg and 3 mg, and the removal rate could still reach 97% to 98.2%.

[0034] Example 3 A fluorine chemical wastewater treatment material is prepared by the following steps: The shrimp shells were repeatedly washed with deionized water, dried in an oven at 105°C to constant weight, crushed with a grinder, and passed through a 150-mesh sieve.

[0035] In order to ensure more effective heat transfer, complete carbonization and high biochar yield inside the shrimp shell powder, and avoid the influence of changes in heating rate on the pore structure of biochar, the shrimp shell powder was placed in a tubular furnace under nitrogen protection and heated to 800°C at a heating rate of 10°C / min and maintained for 2 hours. After cooling, it was repeatedly washed in deionized water and ethanol for more than 5 times, placed in a 60°C oven for drying for 10 hours, ground, passed through a 60-mesh sieve, and the biochar was obtained and placed in a medicine bottle for later use.

[0036] The treatment effect of bio-based fluorine-containing wastewater treatment materials carbonized with shrimp shells as the main body in water bodies with different pH values ​​was investigated; 221 mg of anhydrous sodium fluoride was accurately weighed and dissolved in 1 L of deionized water to prepare a fluoride stock solution (100.5 mg / L); 4.5 mL of hydrochloric acid was accurately transferred into a 500 ml conical flask and stirred, and the volume was adjusted to the mark to prepare a hydrochloric acid pH adjustment solution (0.1 mol / L); 2 g of sodium hydroxide was accurately transferred into a 500 ml conical flask and stirred to dissolve, and the volume was adjusted to the mark to prepare a sodium hydroxide pH adjustment solution (0.1 mol / L); take two 50mL polyethylene tubes, accurately transfer 20mL of fluorine stock solution (100.5mg / L) into the polyethylene tubes, measure the pH values ​​respectively, and the pH is 6.55±0.05, adjust them to pH=3 and pH=9 respectively, then add 0.06g of shrimp shell biochar (800℃), and then shake the mixture at 20℃; after contacting for 24h, filter the mixed solution with a 0.45 μm syringe; place the filtered solution in a conical flask and continue to shake it in a shaker to allow calcium ions and fluoride ions to fully react, filter the suspended precipitate with a 0.45 μm syringe after 24h of reaction, and measure the fluorine concentration in the solution. The fluoride ion concentrations at pH=3 and pH=9 are both between 1.8mg-3mg, and the removal rate can still reach 97% to 98.2%. It can be concluded that this material is not affected by the acidity and alkalinity of the treated solution.

[0037] Example 4 A fluorine chemical wastewater treatment material is prepared by the following steps: The shrimp shells were repeatedly washed with deionized water, dried in an oven at 105°C to constant weight, crushed with a grinder, and passed through a 150-mesh sieve.

[0038] In order to ensure more effective heat transfer, complete carbonization and high biochar yield inside the shrimp shell powder, and avoid the influence of changes in heating rate on the pore structure of biochar, the shrimp shell powder was placed in a tubular furnace under nitrogen protection and heated to 800°C at a heating rate of 10°C / min and maintained for 2 hours. After cooling, it was repeatedly washed with deionized water and ethanol solution for more than 5 times, placed in a 60°C oven for drying for 10 hours, ground, passed through a 60-mesh sieve, and the biochar was obtained and placed in a medicine bottle for later use.

[0039] The treatment effect of a fluorine chemical wastewater treatment material on actual wastewater - phosphogypsum wastewater was explored; 20g of phosphogypsum powder was accurately weighed, placed in a beaker and added with water to make up to 100ml, and magnetically stirred for 12h to fully release the various elements in the phosphogypsum. After 12h, the fluorine content of the phosphogypsum was measured to be 65-70mg / L. 0.06g of biochar was weighed and added to 20ml of phosphogypsum wastewater in a polyethylene tube, and then the mixture was shaken in a 20℃ shaker; after 24h of contact, the mixed solution was filtered with a 0.45 μm syringe; the filtered solution was placed in a conical flask and continued to shake in a shaker to allow the calcium ions and fluoride ions to fully react. After 24h of reaction, the suspended precipitate was filtered with a 0.45 μm syringe, and the fluoride concentration in the solution was measured. It was found that the fluoride ion concentration in the solution was between 8-10mg / L.

[0040] Example 5 A fluorine chemical wastewater treatment material is prepared by the following steps: The shrimp shells were repeatedly washed with deionized water, dried in an oven at 105°C to constant weight, crushed with a grinder, and passed through a 150-mesh sieve.

[0041] In order to ensure more effective heat transfer, complete carbonization and high biochar yield inside the shrimp shell powder, and avoid the influence of changes in heating rate on the pore structure of biochar, the shrimp shell powder was placed in a tubular furnace under nitrogen protection and heated to 800°C at a heating rate of 10°C / min and maintained for 2 hours. After cooling, it was repeatedly washed in deionized water and ethanol for more than 5 times, placed in a 60°C oven for drying for 10 hours, ground, passed through a 60-mesh sieve, and the biochar was obtained and placed in a medicine bottle for later use.

[0042] The treatment effect of a fluorine chemical wastewater treatment material on fluorine chemical wastewater was investigated; 1 mL of fluorine chemical wastewater with a concentration of about 3000 mg / L was weighed and added to a volumetric flask to make up to 25 mL, 0.06 g of biochar was weighed and added to 20 ml of fluorine chemical wastewater in a polyethylene tube, and then the mixture was shaken in a 20°C shaker; after 24 hours of contact, the mixed solution was filtered with a 0.45 μm syringe; the filtered solution was placed in a conical flask and continued to be shaken in a shaker to allow calcium ions and fluoride ions to fully react, and after 24 hours of reaction, the suspended precipitate was filtered with a 0.45 μm syringe, and the fluoride concentration in the solution was measured. It was found that the fluoride ion concentration in the solution was between 1.8 mg and 3 mg, and the removal rate could still reach 97% to 98.2%.

[0043] from Figure 2 It can be seen that there are large calcium-containing components on the surface of this material; from Figure 3 It can be seen that during the treatment of this material, calcium hydroxide will be released to react with fluoride ions, so after the reaction is completed, the large calcium-containing components on its surface disappear; from Figure 4 The surface structure of the white precipitate generated by the material during the reaction with fluoride ions can be seen in the figure; from Figure 5 It can be seen that this material is not affected by Fe 3＋ and Cl - interference; from Figure 6 It can be seen that the treatment effect of this material is not affected under acidic (pH=3) and alkaline (pH=9) conditions.

[0044] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a fluorine-containing wastewater treatment material, characterized in that: The steps include: Step S1: repeatedly washing the shrimp shells with deionized water, drying to constant weight, crushing with a grinder, and sieving to obtain shrimp shell powder; Step S2: Under nitrogen protection, the shrimp shell powder is placed in a tube furnace and heated to 700° C.-1100° C. for calcination. After cooling, it is repeatedly washed with deionized water and ethanol for more than 5 times. After completion, it is dried, ground and sieved.

2. The preparation method according to claim 1, characterized in that: In step S1, the drying temperature is 105°C.

3. The preparation method according to claim 1, characterized in that: In step S1, sieving specifically refers to sieving through a 200-150 mesh sieve.

4. The preparation method according to claim 1, characterized in that: In step S2, the calcination temperature is 800°C.

5. The preparation method according to claim 1, characterized in that: In step S2, the calcination time is 2 hours.

6. The preparation method according to claim 1, characterized in that: In step S2, the heating rate of the calcination process is 10°C / min.

7. The preparation method according to claim 1, characterized in that: In step S2, the drying temperature is 50-70°C and the drying time is 12-15h.

8. The preparation method according to claim 1, characterized in that: In step S2, sieving specifically refers to sieving through a 60-mesh sieve.

9. A fluorine-containing wastewater treatment material obtained according to the preparation method according to any one of claims 1 to 8.

10. Use of the fluorine-containing wastewater treatment material according to claim 9 in the treatment of fluorine-containing wastewater.

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