Method for treating inorganic fluorine-containing wastewater

Abstract

The present application relates to wastewater treatment technical field, disclose a kind of processing method of inorganic fluorine-containing wastewater, comprising the following steps: the pH of inorganic fluorine-containing wastewater is adjusted to 2~4, calcium carbonate is loaded into carbide slag, and reaction is carried out;Coagulant is added to the wastewater after step S1 processing, coagulation and precipitation are carried out, and the precipitate is separated out.In the present application, the fluorine ion in wastewater is converted into calcium fluoride by using calcium carbonate loaded carbide slag, which can reduce the adhesion and wrapping of calcium fluoride on the surface of carbide slag, thereby achieving better wastewater defluorination effect under smaller carbide slag dosage, which is beneficial to reduce sludge amount.

Description

Technical Field

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

[0002] With the development of modern industry, the number of enterprises producing and using fluorides is increasing. Wastewater containing inorganic fluoride is widely found in industries such as metallurgy, photovoltaics, electronics, electroplating, and pesticide production. Excessive fluoride ion emissions can damage water structure, causing environmental pollution. Excessive ingestion by humans and animals can harm health, causing diseases of the nervous system, bones, and teeth. Therefore, wastewater containing inorganic fluoride must undergo defluorination treatment to meet standards before being discharged.

[0003] Chemical precipitation involves adding calcium-containing chemicals such as lime, carbide slag, calcium chloride, or calcium phosphate to wastewater, utilizing the calcium... 2+ With F - The reaction produces CaF2 precipitate, which is used to remove F from the wastewater. - This method has the advantages of simple process and operation, convenient treatment, and low cost, and is one of the most commonly used methods for treating inorganic fluoride-containing wastewater. Calcium carbide slag is the waste residue produced after the hydrolysis of calcium carbide to obtain acetylene gas. Its main component is Ca(OH)2, which releases Ca2+ upon contact with acid. 2+ It can make F in wastewater - The precipitation of calcium carbide slag in the treatment of inorganic fluoride-containing wastewater allows for the reuse of the waste residue and is less expensive than calcium-containing chemicals such as lime and calcium chloride. However, the treatment of inorganic fluoride-containing wastewater with calcium carbide slag also presents the following problems: the CaF2 generated in the reaction easily adheres to and coats the surface of the calcium carbide slag, hindering the further dissolution and release of Ca2+. 2+ Therefore, to achieve F - Deep removal requires the addition of excessive amounts of carbide slag, which generates a large amount of fluoride-containing sludge and limits the improvement of the defluorination effect. Summary of the Invention

[0004] To address the aforementioned technical problem—namely, the tendency of CaF2 generated during the treatment of inorganic fluoride-containing wastewater using calcium carbide slag to adhere to and coat the surface of the slag, resulting in limited defluorination effectiveness and the generation of excessive fluoride-containing sludge—this invention provides a method for treating inorganic fluoride-containing wastewater. This method reduces the adhesion and coating of calcium fluoride on the surface of the calcium carbide slag, thereby improving the defluorination effect and reducing the amount of sludge.

[0005] The specific technical solution of this invention is as follows:

[0006] A method for treating wastewater containing inorganic fluoride includes the following steps:

[0007] S1: Adjust the pH of the inorganic fluoride-containing wastewater to 2-4, add calcium carbide slag loaded with calcium carbonate, and carry out the reaction;

[0008] S2: Add coagulant to the wastewater treated in step S1 to coagulate and settle, and separate the precipitate.

[0009] The mechanism of removing fluoride ions from wastewater in this invention is as follows: In step S1, the main component of carbide slag, calcium hydroxide, and the calcium carbonate loaded therein, release calcium ions in an acidic environment, which combine with fluoride ions to form insoluble calcium fluoride, causing fluoride ions to precipitate from the wastewater; In step S2, by adding a coagulant, the settling speed of calcium fluoride can be accelerated, which is beneficial to separating it from the wastewater.

[0010] This invention utilizes calcium carbonate-loaded carbide slag to convert fluoride ions in wastewater into calcium fluoride, which then precipitates out. During this process, the calcium carbonate loaded within the carbide slag releases calcium ions in an acidic environment, simultaneously generating carbon dioxide. This gas diffuses outward from the carbide slag, reducing the adhesion and encapsulation of calcium fluoride on its surface. This ensures sufficient contact between the carbide slag and the wastewater for calcium ion release. Through this method, the calcium contained in the carbide slag is more fully utilized, achieving better wastewater defluorination with a smaller dosage of carbide slag and reducing sludge production.

[0011] Preferably, before step S1, the inorganic fluorine-containing wastewater is first prepared by mixing the inorganic fluorine-containing wastewater, the oxidized coal gasification wastewater, and the pretreated refrigerant production wastewater.

[0012] Based on the characteristics of inorganic fluoride-containing wastewater, coal gasification wastewater, and refrigerant production wastewater, this invention mixes inorganic fluoride-containing wastewater, oxidized coal gasification wastewater, and pretreated refrigerant production wastewater before defluorination treatment. This allows for the simultaneous treatment of the three types of wastewater and utilizes the coal gasification wastewater and refrigerant production wastewater to reduce the fluoride ion concentration in the inorganic fluoride-containing wastewater, thereby reducing the difficulty of defluorination.

[0013] Preferably, in step S2, calcium chloride is added at a dosage of 0.08–0.15 g / L when adding the coagulant.

[0014] By adding calcium chloride, the common ion effect can be utilized to shift the solubility equilibrium of calcium fluoride towards precipitation, thereby more thoroughly removing fluoride ions from wastewater. This reduces the residual fluoride ion concentration in the wastewater to below the solubility of pure calcium fluoride (which is 16.3 mg / L, equivalent to fluoride ions in Fe). - The concentration was 7.7 mg / L, and excess F was introduced using calcium chloride. - It can make the residual F - (Concentration below 7.7 mg / L).

[0015] Preferably, in step S1, the dosage of the calcium carbonate-loaded carbide slag is: 1 mg F - Add 3-5 mg of calcium carbonate-loaded carbide slag.

[0016] Preferably, in step S1, the calcium carbonate-loaded carbide slag is added in 2 to 3 batches, and the reaction time is 1 to 2 hours after each batch is added before the next batch is added.

[0017] Preferably, in step S1, the preparation step of the calcium carbonate-loaded carbide slag includes: after fully absorbing the calcium salt solution, immersing the carbide slag in the carbonate solution, carrying out the precipitation reaction, and then taking it out.

[0018] Furthermore, the calcium salt solution contains Ca 2+ The concentration is 0.5–1.5 mol / L; the mass-to-volume ratio of the carbide slag to the chloride solution is 1 g: 5–10 mL; the absorption time is 6–24 h; the CO3 content in the carbonate solution is... 2- The concentration is 0.4–1.0 mol / L; the mass-to-volume ratio of the carbide slag to the carbonate solution is 1 g: 20–50 mL; and the precipitation reaction time is 5–12 h.

[0019] Preferably, in step S2, the coagulant is polyaluminum chloride (PAC) and polyacrylamide (PAM), with dosages of 0.05–0.1 g / L and 0.01–0.05 g / L, respectively.

[0020] Preferably, after step S2, the wastewater is subjected to Fenton oxidation, followed by the addition of liquid alkali and coagulant for coagulation and sedimentation. After separating the precipitate, the suspended solids are removed by filtration.

[0021] Furthermore, the filtration process is carried out using a mechanical filter, and the backwash wastewater from the mechanical filter is used to prepare the inorganic fluoride-containing wastewater before step S1.

[0022] As a preferred method, the water quality of the oxidized coal gasification wastewater is tested before blending. If the water quality is abnormal, the following method is used to treat the oxidized coal gasification wastewater: the oxidized coal gasification wastewater is mixed with domestic sewage, oil separation and sedimentation are carried out, followed by anaerobic-aerobic biological treatment, and after sludge-water separation, suspended solids are removed by filtration.

[0023] Further, after mud-water separation, Fenton oxidation is carried out, followed by the addition of liquid alkali and coagulant for coagulation and sedimentation, and then filtration to remove suspended solids.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) In this invention, calcium carbonate-loaded carbide slag is used to convert fluoride ions in wastewater into calcium fluoride and precipitate out. This can reduce the adhesion and coating of calcium fluoride on the surface of carbide slag, thereby achieving better wastewater defluorination effect with a smaller amount of carbide slag, which is beneficial to reducing the amount of sludge.

[0026] (2) In this invention, after converting fluoride ions in wastewater into calcium fluoride, calcium chloride is added during coagulation and sedimentation to utilize the common ion effect to promote the precipitation of calcium fluoride, thereby making the removal of fluoride ions in wastewater more thorough. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the wastewater treatment system used in the embodiments and comparative examples of the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to embodiments.

[0029] General Implementation Examples

[0030] A method for treating wastewater containing inorganic fluoride includes the following steps:

[0031] S1: Adjust the pH of the inorganic fluoride-containing wastewater to 2-4, add calcium carbide slag loaded with calcium carbonate, and carry out the reaction;

[0032] S2: Add coagulant to the wastewater treated in step S1 to coagulate and settle, and separate the precipitate.

[0033] As a specific implementation method, before step S1, the inorganic fluorine-containing wastewater is first prepared by mixing the inorganic fluorine-containing wastewater, the oxidized coal gasification wastewater, and the pretreated refrigerant production wastewater. Before mixing, the water quality of the oxidized coal gasification wastewater is tested. If abnormalities are found, the oxidized coal gasification wastewater is treated as follows: the oxidized coal gasification wastewater is mixed with domestic sewage, subjected to oil separation and sedimentation, followed by anaerobic-aerobic biological treatment, and after sludge-water separation, suspended solids are removed by filtration.

[0034] In one specific implementation, in step S1, the dosage of the calcium carbonate-loaded carbide slag is: 1 mg F - Add 3-5 mg of calcium carbonate-loaded carbide slag.

[0035] In one specific implementation, in step S1, the calcium carbonate-loaded carbide slag is added in 2 to 3 batches, and the reaction time is 1 to 2 hours after each batch is added before the next batch is added.

[0036] In one specific implementation, step S1, the preparation step of the calcium carbide slag loaded with calcium carbonate includes: fully absorbing the calcium salt solution into the calcium carbide slag, immersing it in a carbonate solution, allowing a precipitation reaction, and then removing it. The calcium salt solution contains Ca... 2+ The concentration is 0.5–1.5 mol / L; the mass-to-volume ratio of the carbide slag to the chloride solution is 1 g: 5–10 mL; the absorption time is 6–24 h; the CO3 content in the carbonate solution is... 2- The concentration is 0.4–1.0 mol / L; the mass-to-volume ratio of the carbide slag to the carbonate solution is 1 g: 20–50 mL; and the precipitation reaction time is 5–12 h.

[0037] In one specific implementation, in step S2, calcium chloride is added at a dosage of 0.08–0.15 g / L when adding the coagulant.

[0038] In one specific implementation, in step S2, the coagulant is polyaluminum chloride (PAC) and polyacrylamide (PAM), with dosages of 0.05–0.1 g / L and 0.01–0.05 g / L, respectively.

[0039] In one specific implementation, after step S2, the wastewater is subjected to Fenton oxidation, and then liquid alkali and coagulant are added for coagulation and sedimentation. After the precipitate is separated, it is filtered by a mechanical filter to remove suspended solids. The backwash wastewater from the mechanical filter is used to prepare the inorganic fluoride-containing wastewater before step S1. Specific Implementation

[0041] The present invention will now be described through specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of the inventive concept are included in the present invention, and the scope of protection of the present invention is defined by the appended claims and any equivalents thereof.

[0042] In the following examples and comparative examples, the coal gasification wastewater, fluorochemical wastewater, and pretreated refrigerant production wastewater used in the experiments were from the same batch.

[0043] Example 1

[0044] The calcium carbonate-loaded carbide slag used in this embodiment was prepared by the following method: 1 g of carbide slag was immersed in 1 mol / L calcium chloride solution, stirred for 12 h, and then the solution was removed by filtration. Then, 1 g of carbide slag was immersed in 1 mol / L sodium carbonate solution, stirred for 7 h, the solution was removed by filtration, and the slag was dried to obtain calcium carbonate-loaded carbide slag.

[0045] The wastewater treatment system used in this embodiment is as follows: Figure 1 As shown. After the coal gas water is oxidized in oxidation tank A, under normal conditions (phenol content not higher than 10 mg / L), the wastewater enters equalization tank A and is mixed with fluorochemical wastewater and refrigerant pretreatment effluent for further treatment; under abnormal conditions (phenol content higher than 10 mg / L), the wastewater enters equalization tank B and is mixed with domestic sewage for further treatment.

[0046] The wastewater treatment process using the above system is as follows:

[0047] S1: Wastewater from coal gasification (i.e. Figure 1 The "gas-water" in the system has a daily processing capacity of 10m³. 3 / d) The water is introduced into equalization tank C to homogenize the water quality and quantity, and then pumped to oxidation tank A. Sodium hypochlorite is added to oxidation tank A to oxidize and remove COD (including phenols and cyanides) from the wastewater. The effluent from oxidation tank A is normal, so it is introduced into equalization tank A.

[0048] S2: To treat fluorochemical wastewater (containing inorganic fluorine, with a daily treatment capacity of 300m³). 3 / d) and refrigerant production wastewater after pretreatment (grid filtration → coagulation sedimentation → chemical precipitation with calcium chloride → filtration) (i.e. Figure 1 The "refrigerant pretreatment effluent" has a daily treatment capacity of 60m³. 3 / d) It is introduced into equalization tank A and mixed with the effluent from oxidation tank A.

[0049] S3: The effluent from equalization tank A is pumped to the primary reaction tank. Hydrochloric acid is added to adjust the pH to 3, then calcium carbonate-loaded carbide slag is added at a dosage of 1.2 g / L. After reacting for 1.5 hours, the wastewater is pumped to the secondary reaction tank. Calcium carbonate-loaded carbide slag is added to the secondary reaction tank at a dosage of 0.5 g / L, and the reaction is repeated for 1.5 hours. Then, the wastewater is pumped to the tertiary reaction tank. Calcium chloride, PAC, and PAM are added to the tertiary reaction tank at dosages of 0.1 g / L, 0.05 g / L, and 0.01 g / L, respectively, and the reaction is repeated for 1.5 hours. A 7.5 kW agitator is used for stirring in all three reaction tanks.

[0050] S5: The effluent from the tertiary reaction tank is fed into the sedimentation tank for settling. The effluent then flows by gravity into oxidation tank B, and the sediment is fed into the sludge tank. Dilute sulfuric acid, hydrogen peroxide, and ferrous sulfate are added to oxidation tank B for Fenton oxidation. The wastewater retention time in oxidation tank B is 3 hours.

[0051] S6: Pump the effluent from oxidation tank B to coagulation sedimentation tank A, add liquid alkali and PAM, and the effluent flows by gravity into intermediate water tank A. The sediment is then fed into the sludge tank. The wastewater in intermediate water tank A is then pumped to a mechanical filter for filtration. The filtered water enters clear water tank A, and the backwash wastewater from the mechanical filter flows into equalization tank A.

[0052] In this embodiment, the influent and effluent water quality of each unit were monitored during the wastewater treatment process, and the results are shown in Table 1.

[0053] Table 1. Wastewater treatment effect of Example 1

[0054]

[0055] Example 2

[0056] The calcium carbonate-loaded carbide slag used in this embodiment was prepared by the following method: 1 g of carbide slag was immersed in 0.5 mol / L calcium chloride solution at a dosage of 10 mL of calcium chloride solution. After stirring for 24 h, the solution was removed by filtration. Then, 1 g of carbide slag was immersed in 1 mol / L sodium carbonate solution at a dosage of 20 mL of sodium carbonate solution. After stirring for 5 h, the solution was removed by filtration and the residue was dried to obtain calcium carbonate-loaded carbide slag.

[0057] The wastewater treatment system used in this embodiment is the same as that in Embodiment 1.

[0058] The wastewater treatment process using the above system is as follows:

[0059] S1: Wastewater from coal gasification (i.e. Figure 1 The "gas-water" in the system has a daily processing capacity of 10m³. 3 / d) The water is introduced into equalization tank C to homogenize the water quality and quantity, and then pumped to oxidation tank A. Sodium hypochlorite is added to oxidation tank A to oxidize and remove COD (including phenols and cyanides) from the wastewater. The effluent from oxidation tank A is normal, so it is introduced into equalization tank A.

[0060] S2: To treat fluorochemical wastewater (containing inorganic fluorine, with a daily treatment capacity of 300m³). 3 / d) and pretreated refrigerant production wastewater (i.e. Figure 1 The "refrigerant pretreatment effluent" has a daily treatment capacity of 60m³. 3 / d) It is introduced into equalization tank A and mixed with the effluent from oxidation tank A.

[0061] S3: The effluent from equalization tank A is pumped to the primary reaction tank. Hydrochloric acid is added to adjust the pH to 4, then calcium carbonate-loaded carbide slag is added at a dosage of 0.8 g / L. After reacting for 1 hour, the wastewater is pumped to the secondary reaction tank. Calcium carbonate-loaded carbide slag is added to the secondary reaction tank at a dosage of 0.5 g / L. After reacting for 2 hours, the wastewater is pumped to the tertiary reaction tank. Calcium chloride, PAC, and PAM are added to the tertiary reaction tank at dosages of 0.08 g / L, 0.08 g / L, and 0.04 g / L, respectively. The reaction is allowed to proceed for 1.5 hours. A 7.5 kW agitator is used for stirring in all three reaction tanks.

[0062] S5: The effluent from the tertiary reaction tank is fed into the sedimentation tank for settling. The effluent then flows by gravity into oxidation tank B, and the sediment is fed into the sludge tank. Dilute sulfuric acid, hydrogen peroxide, and ferrous sulfate are added to oxidation tank B for Fenton oxidation. The wastewater retention time in oxidation tank B is 3 hours.

[0063] S6: Pump the effluent from oxidation tank B to coagulation sedimentation tank A, add liquid alkali and PAM, and the effluent flows by gravity into intermediate water tank A. The sediment is then fed into the sludge tank. The wastewater in intermediate water tank A is then pumped to a mechanical filter for filtration. The filtered water enters clear water tank A, and the backwash wastewater from the mechanical filter flows into equalization tank A.

[0064] In the wastewater treatment process of this embodiment, the influent and effluent water quality of each unit were monitored, and the results are shown in Table 2.

[0065] Table 2 Wastewater treatment effect of Example 2

[0066]

[0067] Example 3

[0068] The calcium carbonate-loaded carbide slag used in this embodiment was prepared by the following method: 1 g of carbide slag was immersed in 1.5 mol / L calcium chloride solution at a dosage of 5 mL of calcium chloride solution, stirred for 6 h, and then filtered to remove the solution. Then, 1 g of carbide slag was immersed in 0.4 mol / L sodium carbonate solution at a dosage of 50 mL of sodium carbonate solution, stirred for 12 h, filtered to remove the solution, and dried to obtain calcium carbonate-loaded carbide slag.

[0069] The wastewater treatment system used in this embodiment is the same as that in Embodiment 1.

[0070] The wastewater treatment process using the above system is as follows:

[0071] S1: Wastewater from coal gasification (i.e. Figure 1 The "gas-water" in the system has a daily processing capacity of 10m³. 3 / d) The water is introduced into equalization tank C to homogenize the water quality and quantity, and then pumped to oxidation tank A. Sodium hypochlorite is added to oxidation tank A to oxidize and remove COD (including phenols and cyanides) from the wastewater. The effluent from oxidation tank A is normal, so it is introduced into equalization tank A.

[0072] S2: To treat fluorochemical wastewater (containing inorganic fluorine, with a daily treatment capacity of 300m³). 3 / d) and pretreated refrigerant production wastewater (i.e. Figure 1 The "refrigerant pretreatment effluent" has a daily treatment capacity of 60m³. 3 / d) It is introduced into equalization tank A and mixed with the effluent from oxidation tank A.

[0073] S3: Pump the effluent from equalization tank A into the primary reaction tank. Add hydrochloric acid to adjust the pH to 2, then add calcium carbonate-loaded carbide slag at a dosage of 1.5 g / L. After reacting for 2 hours, pump the wastewater into the secondary reaction tank. Add calcium carbonate-loaded carbide slag to the secondary reaction tank at a dosage of 0.5 g / L. After reacting for 1 hour, pump the wastewater into the tertiary reaction tank. Add calcium chloride, PAC, and PAM to the tertiary reaction tank at dosages of 0.15 g / L, 0.1 g / L, and 0.05 g / L, respectively. React for 1.5 hours. A 7.5 kW agitator is used for stirring in all three reaction tanks.

[0074] S5: The effluent from the tertiary reaction tank is fed into the sedimentation tank for settling. The effluent then flows by gravity into oxidation tank B, and the sediment is fed into the sludge tank. Dilute sulfuric acid, hydrogen peroxide, and ferrous sulfate are added to oxidation tank B for Fenton oxidation. The wastewater retention time in oxidation tank B is 3 hours.

[0075] S6: Pump the effluent from oxidation tank B to coagulation sedimentation tank A, add liquid alkali and PAM, and the effluent flows by gravity into intermediate water tank A. The sediment is then fed into the sludge tank. The wastewater in intermediate water tank A is then pumped to a mechanical filter for filtration. The filtered water enters clear water tank A, and the backwash wastewater from the mechanical filter flows into equalization tank A.

[0076] In this embodiment, the influent and effluent water quality of each unit were monitored during the wastewater treatment process, and the results are shown in Table 3.

[0077] Table 3 Wastewater treatment effect of Example 3

[0078]

[0079]

[0080] Example 4

[0081] The method for preparing calcium carbonate-loaded carbide slag used in this embodiment is the same as in Embodiment 1.

[0082] The wastewater treatment system used in this embodiment is the same as that in Embodiment 1.

[0083] The wastewater treatment process using the above system is as follows:

[0084] S1: Wastewater from coal gasification (i.e. Figure 1 The "gas-water" in the system has a daily processing capacity of 10m³. 3 / d) The water is introduced into equalization tank C to homogenize the water quality and quantity, and then pumped to oxidation tank A. Sodium hypochlorite is added to oxidation tank A to oxidize and remove COD (including phenols and cyanides) from the wastewater. The effluent from oxidation tank A is normal, so it is introduced into equalization tank A.

[0085] S2: To treat fluorochemical wastewater (containing inorganic fluorine, with a daily treatment capacity of 300m³). 3 / d) and pretreated refrigerant production wastewater (i.e. Figure 1 The "refrigerant pretreatment effluent" has a daily treatment capacity of 60m³. 3 / d) It is introduced into equalization tank A and mixed with the effluent from oxidation tank A.

[0086] S3: Pump the effluent from equalization tank A into the primary reaction tank. Add hydrochloric acid to adjust the pH to 2, then add calcium carbonate-loaded carbide slag at a dosage of 1.5 g / L. After reacting for 2 hours, pump the wastewater into the secondary reaction tank. Add calcium carbonate-loaded carbide slag to the secondary reaction tank at a dosage of 0.5 g / L. After reacting for 1 hour, pump the wastewater into the tertiary reaction tank. Add PAC and PAM to the tertiary reaction tank at dosages of 0.1 g / L and 0.05 g / L, respectively, and react for 1.5 hours. A 7.5 kW agitator is used for stirring in all three reaction tanks.

[0087] S5: The effluent from the tertiary reaction tank is fed into the sedimentation tank for settling. The effluent then flows by gravity into oxidation tank B, and the sediment is fed into the sludge tank. Dilute sulfuric acid, hydrogen peroxide, and ferrous sulfate are added to oxidation tank B for Fenton oxidation. The wastewater retention time in oxidation tank B is 3 hours.

[0088] S6: Pump the effluent from oxidation tank B to coagulation sedimentation tank A, add liquid alkali and PAM, and the effluent flows by gravity into intermediate water tank A. The sediment is then fed into the sludge tank. The wastewater in intermediate water tank A is then pumped to a mechanical filter for filtration. The filtered water enters clear water tank A, and the backwash wastewater from the mechanical filter flows into equalization tank A.

[0089] In this embodiment, the influent and effluent water quality of each unit were monitored during the wastewater treatment process, and the results are shown in Table 4.

[0090] Table 4. Wastewater treatment effect of Example 4

[0091]

[0092]

[0093] According to Tables 3 and 4, in Example 3, adding calcium chloride during the coagulation and sedimentation process can further reduce the residual F in the wastewater. - Concentration, and able to make F - The concentration was reduced to below the solubility of pure calcium fluoride (converted to F). - (Below 7.7 mg / L). This is because adding calcium chloride allows for the introduction of more calcium into the wastewater. 2+ By utilizing the common ion effect, the dissolution equilibrium of calcium fluoride can be shifted towards precipitation, thereby more thoroughly removing fluoride ions from wastewater.

[0094] Comparative Example 1

[0095] The wastewater treatment system used in this comparative example is the same as that in Example 1.

[0096] The wastewater treatment process using the above system is as follows:

[0097] S1: Wastewater from coal gasification (i.e. Figure 1 The "gas-water" in the system has a daily processing capacity of 10m³. 3 / d) The water is introduced into equalization tank C to homogenize the water quality and quantity, and then pumped to oxidation tank A. Sodium hypochlorite is added to oxidation tank A to oxidize and remove COD (including phenols and cyanides) from the wastewater. The effluent from oxidation tank A is normal, so it is introduced into equalization tank A.

[0098] S2: To treat fluorochemical wastewater (containing inorganic fluorine, with a daily treatment capacity of 300m³). 3 / d) and pretreated refrigerant production wastewater (i.e. Figure 1 The "refrigerant pretreatment effluent" has a daily treatment capacity of 60m³. 3 / d) It is introduced into equalization tank A and mixed with the effluent from oxidation tank A.

[0099] S3: Pump the effluent from equalization tank A into the primary reaction tank. Add hydrochloric acid to adjust the pH to 3, then add calcium carbide slag at a dosage of 1.2 g / L. After reacting for 1.5 hours, pump the wastewater into the secondary reaction tank. Add calcium carbide slag to the secondary reaction tank at a dosage of 0.5 g / L. After reacting for 1.5 hours, pump the wastewater into the tertiary reaction tank. Add calcium chloride, PAC, and PAM at dosages of 0.1 g / L, 0.05 g / L, and 0.01 g / L, respectively. React for 1.5 hours. A 7.5 kW agitator is used for stirring in all three reaction tanks.

[0100] S5: The effluent from the tertiary reaction tank is fed into the sedimentation tank for settling. The effluent then flows by gravity into oxidation tank B, and the sediment is fed into the sludge tank. Dilute sulfuric acid, hydrogen peroxide, and ferrous sulfate are added to oxidation tank B for Fenton oxidation. The wastewater retention time in oxidation tank B is 3 hours.

[0101] S6: Pump the effluent from oxidation tank B to coagulation sedimentation tank A, add liquid alkali and PAM, and the effluent flows by gravity into intermediate water tank A. The sediment is then fed into the sludge tank. The wastewater in intermediate water tank A is then pumped to a mechanical filter for filtration. The filtered water enters clear water tank A, and the backwash wastewater from the mechanical filter flows into equalization tank A.

[0102] In the wastewater treatment process of this embodiment, the influent and effluent water quality of each unit were monitored, and the results are shown in Table 5.

[0103] Table 5 shows the wastewater treatment effect of Comparative Example 1.

[0104]

[0105] According to Tables 1 and 5, the removal effect of F- in Example 1 is significantly better than that in Comparative Example 1, indicating that loading calcium carbonate into carbide slag can improve the defluorination effect. This is because, during the process of using carbide slag to convert fluoride ions in wastewater into calcium fluoride, the calcium carbonate loaded in the carbide slag releases calcium ions in an acidic environment while simultaneously generating carbon dioxide. This gas diffuses outward from the carbide slag, reducing the adhesion and encapsulation of calcium fluoride on the surface of the carbide slag. This ensures that the carbide slag can fully contact the wastewater to release calcium ions. In this way, the calcium contained in the carbide slag can be more fully utilized, thus achieving a better wastewater defluorination effect with a smaller dosage of carbide slag.

[0106] Comparative Example 2

[0107] The wastewater treatment system used in this comparative example is the same as that in Example 1.

[0108] The wastewater treatment process using the above system is as follows:

[0109] S1: Wastewater from coal gasification (i.e. Figure 1 The "gas-water" in the system has a daily processing capacity of 10m³. 3 / d) The water is introduced into equalization tank C to homogenize the water quality and quantity, and then pumped to oxidation tank A. Sodium hypochlorite is added to oxidation tank A to oxidize and remove COD (including phenols and cyanides) from the wastewater. The effluent from oxidation tank A is normal, so it is introduced into equalization tank A.

[0110] S2: To treat fluorochemical wastewater (containing inorganic fluorine, with a daily treatment capacity of 300m³). 3 / d) and pretreated refrigerant production wastewater (i.e. Figure 1The "refrigerant pretreatment effluent" has a daily treatment capacity of 60m³. 3 / d) It is introduced into equalization tank A and mixed with the effluent from oxidation tank A.

[0111] S3: The effluent from equalization tank A is pumped to the primary reaction tank. Hydrochloric acid is added to adjust the pH to 3, then carbide slag and calcium carbonate are added at dosages of 0.8 g / L and 0.4 g / L, respectively. After reacting for 1.5 hours, the wastewater is pumped to the secondary reaction tank. Carbide slag and calcium carbonate are added to the secondary reaction tank at dosages of 0.35 g / L and 0.15 g / L, respectively. After reacting for 1.5 hours, the wastewater is pumped to the tertiary reaction tank. Calcium chloride, PAC, and PAM are added to the tertiary reaction tank at dosages of 0.1 g / L, 0.05 g / L, and 0.01 g / L, respectively. The reaction is then allowed to proceed for 1.5 hours. A 7.5 kW agitator is used for stirring in all three reaction tanks.

[0112] S5: The effluent from the tertiary reaction tank is fed into the sedimentation tank for settling. The effluent then flows by gravity into oxidation tank B, and the sediment is fed into the sludge tank. Dilute sulfuric acid, hydrogen peroxide, and ferrous sulfate are added to oxidation tank B for Fenton oxidation. The wastewater retention time in oxidation tank B is 3 hours.

[0113] S6: Pump the effluent from oxidation tank B to coagulation sedimentation tank A, add liquid alkali and PAM, and the effluent flows by gravity into intermediate water tank A. The sediment is then fed into the sludge tank. The wastewater in intermediate water tank A is then pumped to a mechanical filter for filtration. The filtered water enters clear water tank A, and the backwash wastewater from the mechanical filter flows into equalization tank A.

[0114] In this embodiment, the influent and effluent water quality of each unit were monitored during the wastewater treatment process, and the results are shown in Table 6.

[0115] Table 6 shows the wastewater treatment effect of Comparative Example 2.

[0116]

[0117] According to Tables 1 and 6, the removal effect of F- in Example 1 is significantly better than that in Comparative Example 2, indicating that loading calcium carbonate into carbide slag can improve the defluorination effect to a greater extent compared to dispersing calcium carbonate and carbide slag. This is because when calcium carbonate and carbide slag are added separately, the carbon dioxide produced by the reaction of calcium carbonate cannot effectively prevent the adhesion and encapsulation of calcium fluoride on the surface of carbide slag, thus the defluorination effect is relatively poor.

[0118] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Unless otherwise specified, the raw materials and equipment used in this invention are conventional in the art and can be obtained through conventional commercial means; unless otherwise specified, the methods used in this invention are conventional methods in the art.

[0119] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for treating wastewater containing inorganic fluoride, characterized in that, Includes the following steps: S1: Adjust the pH of the inorganic fluoride-containing wastewater to 2-4, add calcium carbide slag loaded with calcium carbonate, and carry out the reaction; The preparation steps of the calcium carbonate-loaded carbide slag include: fully absorbing the calcium salt solution into the carbide slag, immersing it in the carbonate solution, carrying out the precipitation reaction, and then taking it out. S2: Add coagulant to the wastewater treated in step S1 to carry out coagulation and sedimentation, and separate the precipitate.

2. The method for treating inorganic fluoride-containing wastewater according to claim 1, characterized in that, Before step S1, the inorganic fluorine-containing wastewater is prepared by mixing the inorganic fluorine-containing wastewater, the oxidized coal gasification wastewater, and the pretreated refrigerant production wastewater.

3. The method for treating inorganic fluoride-containing wastewater according to claim 1, characterized in that, In step S2, calcium chloride is added at a dosage of 0.08~0.15 g / L when adding the coagulant.

4. The method for treating inorganic fluoride-containing wastewater according to claim 1, characterized in that, In step S1, the dosage of the calcium carbonate-loaded carbide slag is: 1 mg F - Add 3-5 mg of calcium carbonate-loaded carbide slag.

5. The method for treating inorganic fluoride-containing wastewater according to claim 1 or 4, characterized in that, In step S1, the calcium carbonate-loaded carbide slag is added in 2 to 3 batches, and the reaction time is 1 to 2 hours after each batch is added before the next batch is added.

6. The method for treating inorganic fluoride-containing wastewater according to claim 1, characterized in that, In the calcium salt solution, Ca 2+ The concentration is 0.5~1.5 mol / L; the mass-to-volume ratio of the carbide slag to the calcium salt solution is 1 g: 5~10 mL; the absorption time is 6~24 h; the CO3 in the carbonate solution... 2- The concentration is 0.4~1.0 mol / L; the mass-to-volume ratio of the carbide slag to the carbonate solution is 1 g: 20~50 mL; the precipitation reaction time is 5~12 h.

7. The method for treating inorganic fluoride-containing wastewater according to claim 1, characterized in that, In step S2, the coagulant is polyaluminum chloride and polyacrylamide, with dosages of 0.05~0.1 g / L and 0.01~0.05 g / L, respectively.

8. The method for treating inorganic fluoride-containing wastewater according to claim 1 or 2, characterized in that, After step S2, the wastewater is subjected to Fenton oxidation, followed by the addition of liquid alkali and coagulant for coagulation and sedimentation. After separating the precipitate, the suspended solids are removed by filtration.

9. The method for treating inorganic fluoride-containing wastewater according to claim 2, characterized in that, Before blending, the water quality of the oxidized coal gasification wastewater was tested. If the phenol content was higher than the set value, the oxidized coal gasification wastewater was treated by the following method: the oxidized coal gasification wastewater was mixed with domestic sewage, oil separation and sedimentation were carried out, and then anaerobic-aerobic biological treatment was carried out. After sludge-water separation, suspended solids were removed by filtration. The set value was 8~10 mg / L.

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