Treatment method of high-salt coal chemical fluorine-containing wastewater

Abstract

The invention relates to a treatment method of high-salt coal chemical fluorine-containing wastewater, which comprises the following steps: (1) adding a fluorine removal agent into wastewater, regulating the pH value to 6.5-7.5, stirring for reaction, regulating the pH value to 5.5-6.4 again, standing after stirring for reaction, and separating out precipitate to obtain primary fluorine-removed wastewater; (2) introducing a flocculant into the primary defluorination wastewater, stirring to react, standing, and separating out precipitate to obtain water; the flocculating agent is a polysilicic acid-based inorganic-organic hybrid flocculating agent. The treatment method disclosed by the invention is high in pollutant removal rate, simple and convenient to operate and relatively low in investment and operation cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of water pollution control, and in particular relates to a method for treating high-salt coal chemical fluoride-containing wastewater. Background Art

[0002] Among the trace elements contained in coal, fluorine is relatively high, typically ranging from 20 to 300 mg / kg. This results in excessive fluoride ion levels in coal chemical wastewater. Excessive fluoride ion levels can cause severe corrosion of equipment and harm the environment, affecting crop growth and human bone health. The first-level standard of the Integrated Wastewater Discharge Standard (GB 8798-1996) stipulates a maximum allowable fluoride discharge concentration of 10 mg / L. Therefore, simple, low-cost, and efficient treatment of fluoride ions in wastewater is of great significance.

[0003] Traditional fluoride removal methods include chemical precipitation, coagulation-sedimentation, adsorption, reverse osmosis, electrodialysis, etc. Among them, reverse osmosis and electrodialysis have high process costs and are difficult to achieve large-scale industrial promotion and application; adsorption is more suitable for the treatment of low-fluoride wastewater and deep treatment of fluoride-containing wastewater; the combined chemical-coagulation-precipitation method is currently the most widely studied and applied in the treatment of fluoride-containing wastewater.

[0004] Chemical precipitation method usually adds calcium-containing reagents such as CaCl2, Ca(OH)2 and CaO to fluoride-containing wastewater. 2+ and F - When the concentration reaches supersaturation, CaF2 precipitates. Because CaF2 is a slightly soluble mineral, homogeneous nucleation and crystallization of CaF2 require a high reaction kinetics. The resulting calcium fluoride sludge is amorphous, has a high water content, and settles poorly, resulting in unsatisfactory fluoride removal. Especially for complex, high-salinity wastewater environments, such as high-salinity coal chemical wastewater, the presence of scale inhibitors, chelating agents, and high concentrations of inorganic salt ions increases the solubility of CaF2, further complicating fluoride removal from such wastewater. Some researchers have proposed adding quartz sand, calcite, apatite, and CaF2 seed crystals to fluoride-containing wastewater to promote heterogeneous nucleation of CaF2, thereby reducing the starting calcium concentration and further lowering the fluoride ion concentration. However, due to the limited solubility of CaF2, chemical precipitation methods can generally reduce the fluoride ion concentration in wastewater to between 20 and 30 mg / L. Deep fluoride removal, i.e., reducing the fluoride ion concentration to below 10 mg / L, often requires further coagulation and sedimentation methods. In addition, the CaF2 precipitate, coagulation precipitate and hardness precipitate produced as newly generated suspended solids also need further turbidity removal treatment.

[0005] CN111439865A proposes a method for defluoridating coal gasification wastewater. The method first pre-oxidizes the coal gasification wastewater to remove scale inhibitors. Reflux adsorption sludge is then added to the pre-oxidized wastewater for a first-stage defluoridation process, yielding first-stage defluoridated wastewater. Wastewater, representing 10% to 20% of the total first-stage defluoridated wastewater, is injected into a seeding tank, and a composite defluoridant is added to the tank. The wastewater reacts with the composite defluoridant to form metal fluoride crystals, forming wastewater containing metal fluoride nuclei. This replaces the externally added seeds with in-situ generated seeds, promoting heterogeneous nucleation of CaF2. The remaining first-stage fluoridated wastewater and wastewater containing metal fluoride nuclei are then introduced into a reaction tank. The composite defluoridant continues to react with fluoride ions in the first-stage defluoridated wastewater, enriching the metal fluoride nuclei and causing crystal growth to form metal fluoride crystals. Polyaluminum chloride, a coagulant, is then added for coagulation, yielding second-stage defluoridated wastewater. The fluoride ion concentration of the secondary defluoridation wastewater is reduced to 10-15 mg / L. This invention uses a combined process of pre-oxidation + pre-adsorption + in-situ seed-induced defluoridation + coagulation to defluoridate coal gasification wastewater, but the process flow is still relatively lengthy.

[0006] CN210764753U discloses a zero-emission pretreatment system for high-salt wastewater from coal coking. In the fluoride removal process, calcium chloride, ferric chloride, polyacrylamide, and other reagents must be added in two steps. The introduction of calcium chloride also necessitates a hardness removal process, requiring the stepwise addition of liquid caustic soda, sodium carbonate, ferric chloride, polyacrylamide, and other reagents. This results in high reagent consumption and a complex process flow. Furthermore, because an acidic pH is suitable for fluoride removal and an alkaline pH is suitable for hardness removal, the invention involves the addition of both alkali and acid, resulting in high acid and alkali consumption and increasing the burden of subsequent membrane desalination.

[0007] Therefore, a simple, efficient and suitable treatment method for fluoride-containing wastewater from coal chemical industry in high-salinity scenarios remains to be developed. Summary of the Invention

[0008] To address the shortcomings of existing treatment technologies for high-salt coal chemical fluoride wastewater, such as complex processes and high reagent consumption, the present invention provides a method for treating high-salt coal chemical fluoride wastewater. This method not only achieves a high pollutant removal rate, but also is simple to operate and has low investment and operating costs.

[0009] To achieve the purpose of the present invention, the present invention provides a method for treating high-salt coal chemical fluoride-containing wastewater, comprising the following steps:

[0010] (1) adding a defluoridating agent to the wastewater, adjusting the pH to 6.5-7.5, stirring the reaction, and adjusting the pH again to 5.5-6.4, stirring the reaction, and allowing the reaction to stand, separating the precipitate, and obtaining primary defluoridated wastewater;

[0011] (2) introducing a flocculant into the primary defluoridation wastewater, stirring the reaction and then allowing it to stand, separating the precipitate to obtain water; the flocculant is a polysilicic acid-based inorganic-organic hybrid flocculant.

[0012] In step (1), the fluoride ion concentration in the high-salt coal chemical fluoride-containing wastewater is higher than 10 mg / L, generally 20-100 mg / L; the TDS concentration is greater than 10000 mg / L, and the pH is 8-10.

[0013] In step (1), the defluoridating agent is a calcified substance, preferably at least one of calcium chloride, calcium hydroxide, calcium oxide, etc., and the dosage of the defluoridating agent is 300-800 mg / L in terms of calcium.

[0014] In step (1), the pH of the wastewater is adjusted from the initial pH to 6.5-7.5; the stirring reaction rate is 300-500 rpm, and the stirring time is 10-30 min.

[0015] In step (1), after adjusting the pH to 5.5-6.4 again, the stirring reaction rate is 200-400 rpm, the stirring time is 10-30 min, and the standing time is 30-60 min.

[0016] In step (2), the introduced flocculant is a polysilicic acid-based inorganic-organic hybrid flocculant, and its preparation method is as follows:

[0017] (a) preparing a sodium silicate solution, adjusting the pH to 3-6, and activating the solution to obtain a mixed solution I;

[0018] (b) preparing an organic monomer solution, wherein the organic monomers are carboxylic acid monomers and sulfonic acid monomers, and adjusting the pH to 3-6 to obtain a mixed solution II;

[0019] (c) Mixing the mixed solutions I and II, placing the mixed solutions in a constant temperature water bath, adding an initiator under an inert atmosphere, and carrying out a polymerization reaction to obtain a polysilicic acid-based inorganic-organic hybrid flocculant.

[0020] In step (a) of the above method, the sodium silicate solution has a SiO2 molar concentration of 0.1-0.5 mol / L.

[0021] In step (a) of the above method, the pH is adjusted using an inorganic or organic acid. The inorganic acid may be at least one of hydrochloric acid, sulfuric acid, phosphoric acid, or hydrobromic acid, preferably phosphoric acid; the organic acid may be at least one of citric acid, oxalic acid, formic acid, or acetic acid, preferably acetic acid. The inorganic or organic acid is used at a concentration of 0.1-1 mol / L. After pH adjustment, the activation reaction is carried out at room temperature for 0.5-1 hour.

[0022] In step (b) of the above method, the carboxylic acid monomer may be at least one of acrylic acid, methacrylic acid or maleic acid, and the concentration of the carboxylic acid monomer solution is 0.5-2.0 mol / L.

[0023] In step (b) of the above method, the sulfonic acid monomer may be at least one of vinyl sulfonic acid or 2-acrylamido-2-methylpropanesulfonic acid, and the mass ratio of the sulfonic acid monomer to the carboxylic acid monomer is 1:9-1:1.

[0024] In step (b) of the above method, an alkali solution is added dropwise to adjust the pH while stirring at a rate of 200-500 rpm and a dropwise addition rate of 0.1-0.5 mL / min. The alkali solution may be at least one of NaOH, KOH, or NH3·H2O, and the concentration of the alkali solution may be 0.1-1.0 mol / L.

[0025] In step (c) of the above method, the mixed solutions I and II are mixed at a volume ratio of 5:1 to 50:1. The temperature of the constant temperature water bath is 40-90°C.

[0026] In step (c) of the above method, the inert atmosphere is in the presence of nitrogen or an inert gas, and the inert gas is at least one of helium, argon, etc.

[0027] In step (c) of the above method, the initiator may be at least one of a redox initiator or an azo initiator. The redox initiator may be at least one of ammonium persulfate and sodium bisulfite, potassium persulfate and sodium bisulfite, etc. The azo initiator may be at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, etc., with azo initiators being preferred.

[0028] In step (c) of the above method, the mass ratio of the initiator to the organic monomer is 1:1000-1:50. The polymerization reaction time is 8-24 hours.

[0029] In step (2), the dosage of the polysilicic acid-based inorganic-organic hybrid flocculant is 10-200 mg / L.

[0030] In step (2), after adding the flocculant, the stirring reaction rate is 100-500 rpm, and the stirring time is 10-30 minutes. More preferably, after adding the flocculant, the mixture is first stirred at a high speed of 300-500 rpm for 1-10 minutes, and then stirred at a low speed of 100-295 rpm for 10-20 minutes.

[0031] In step (2), after the stirring reaction is completed, the standing time is 30-60 minutes.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) In response to the shortcomings of high-salt fluoride-containing wastewater in coal chemical industry and the use of calcium-containing defluoridation agents, the present invention uses two-stage pH adjustment. The first pH adjustment breaks the complex between calcium ions and complexing agents, scale inhibitors or hydroxide ions, releases some free calcium ions, and forms calcium fluoride seed crystals; the second pH adjustment further releases calcium ions, promotes the reaction of remaining fluoride ions with calcium ions, and enriches them on calcium fluoride crystals, thereby promoting crystal growth; on this basis, the polysilicic acid-based inorganic-organic hybrid flocculant described in the present invention is added to achieve adsorption, coagulation and rapid separation of fluoride ions. After treatment, the fluoride ion concentration in the wastewater is lower than 10 mg / L, and the effluent water quality can meet the first-level standard of the "Integrated Sewage Discharge Standard" (GB 8798-1996).

[0034] (2) The present invention can induce the production of seed crystals in situ by means of two-stage pH adjustment, saving the consumption of external seed crystals and facilitating the recycling and reuse of CaF2 crystals.

[0035] (3) The present invention uses a polysilicic acid-based inorganic-organic hybrid flocculant as a flocculant, which acts on suspended matter and free metal ions at the same time to form flocs with larger particle sizes, which can effectively shorten the separation time of pollutants, reduce turbidity to below 3NTU, and reduce the total hardness to below 200mg / L, ultimately achieving efficient wastewater treatment.

[0036] (4) Compared with existing processes, the process of the present invention shortens the process flow, reduces reagent consumption and slag production. Therefore, the method has low operating costs, simple operation, and good application prospects. DETAILED DESCRIPTION

[0037] The technical solution of the present invention and its effects are further illustrated below with reference to specific examples. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the scope of protection of the present invention is not limited to the following examples.

[0038] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores.

[0039] In the present invention, the concentration of fluoride ions in the wastewater was measured by means of a multi-parameter water quality analyzer (Seven Excellence, Mettler Toledo, Switzerland), the total hardness of the wastewater was measured by means of an EDTA complexometric titration method, and the turbidity of the wastewater was measured by means of a turbidimeter (TL2300EPA, Hach, USA).

[0040] Example 1

[0041] The high-salt coal chemical industry fluoride-containing wastewater treated in this example has a pH of 8.0, a TDS concentration of 12000 mg / L, and a fluoride ion concentration of 80 mg / L. The treatment was performed using the following steps:

[0042] (1) 500 mg / L (calcium) calcium chloride was added to the wastewater, the pH of the wastewater was adjusted to 7.0, and the mixture was stirred at 500 rpm for 10 minutes. The pH was then adjusted to 6.0, and the mixture was stirred at 400 rpm for 10 minutes. Testing revealed that the total hardness of the wastewater was 1095 mg / L and the turbidity was 924 NTU. After the reaction, the mixture was allowed to settle for 1 hour, and the precipitate was separated to obtain primary defluoridated wastewater.

[0043] (2) Add 70 mg / L of polysilicic acid-based inorganic-organic hybrid flocculant to the primary defluoridation wastewater, stir at 400 rpm for 5 minutes, then stir at 200 rpm for 15 minutes, let it stand for 30 minutes, separate the precipitate, and obtain effluent.

[0044] The preparation method of a polysilicic acid-based inorganic-organic hybrid flocculant is as follows: (a) preparing a sodium silicate solution with a SiO2 molar concentration of 0.2 mol / L, adjusting the pH value to 4 with the help of a 0.5 mol / L hydrochloric acid solution, and performing an activation reaction at room temperature for 1 hour to obtain a mixed solution I; (b) preparing acrylic acid and vinyl sulfonic acid solutions, controlling the concentration of the acrylic acid solution to 0.5 mol / L and the mass ratio of vinyl sulfonic acid to acrylic acid to be 1:5, slowly adding a 0.5 mol / L NaOH solution dropwise at a rate of 0.3 mL / min under stirring at 300 rpm, until the pH value at the end of the addition is 4, to obtain a mixed solution II; (c) mixing the mixed solutions I and II in a volume ratio of 10:1, placing the mixed solutions in a constant temperature water bath at 70°C, passing nitrogen for 0.5 hour, adding azobisisobutylamidine hydrochloride as an initiator, controlling the mass ratio of the initiator to the organic monomer to be 1:200, and performing a polymerization reaction for 10 hours to obtain a polysilicic acid-based inorganic-organic hybrid flocculant.

[0045] After testing, the fluoride ion concentration in the outlet water was 9.87 mg / L, the total hardness was 176 mg / L, and the turbidity was 2.03 NTU.

[0046] Example 2

[0047] The high-salt coal chemical industry fluoride-containing wastewater treated in this example has a pH of 8.3, a TDS concentration of 10500 mg / L, and a fluoride ion concentration of 30 mg / L. The treatment was performed using the following steps:

[0048] (1) Add 300 mg / L (calcium) calcium chloride to the wastewater, adjust the pH of the wastewater to 7.5, and stir at 300 rpm for 30 minutes. Then adjust the pH to 6.4 and stir at 300 rpm for 20 minutes. After testing, the total hardness of the wastewater is 705 mg / L and the turbidity is 463 NTU. After the reaction, let it stand for 1 hour, separate the precipitate, and obtain primary defluoridation wastewater;

[0049] (2) Add 40 mg / L of polysilicic acid-based inorganic-organic hybrid flocculant to the primary defluoridation wastewater, stir at 500 pm for 5 minutes, then stir at 150 rpm for 20 minutes, let it stand for 30 minutes, separate the precipitate, and obtain the effluent.

[0050] The preparation method of the polysilicic acid-based inorganic-organic hybrid flocculant is as follows: (1) preparing a sodium silicate solution with a SiO2 molar concentration of 0.5 mol / L, adjusting the pH value to 3 with the help of a 1 mol / L sulfuric acid solution, and performing an activation reaction at room temperature for 45 minutes to obtain a mixed solution I; (2) preparing a maleic acid and vinyl sulfonic acid solution, controlling the concentration of the maleic acid solution to 2 mol / L, the mass ratio of vinyl sulfonic acid to maleic acid to 1:9, stirring at 500 rpm, and stirring at 0 1 mol / L KOH solution was slowly added dropwise at a rate of 0.5 mL / min, and the pH at the end point of the addition was controlled to be 6 to obtain a mixed solution II; (3) the mixed solutions I and II were mixed in a volume ratio of 50:1, placed in a constant temperature water bath at 90°C, and nitrogen was introduced for 0.5 h. Azobisisobutylimidazoline hydrochloride initiator was added, and the mass ratio of the initiator to the organic monomer was controlled to be 1:1000. The polymerization reaction was carried out for 8 h to obtain a polysilicic acid-based inorganic-organic hybrid flocculant.

[0051] After testing, the fluoride ion concentration in the effluent was 9.63 mg / L, the total hardness was 195 mg / L, and the turbidity was 2.52 NTU.

[0052] Example 3

[0053] The high-salt coal chemical industry fluoride-containing wastewater treated in this example has a pH of 7.8, a TDS concentration of 13200 mg / L, and a fluoride ion concentration of 50 mg / L. The treatment was performed using the following steps:

[0054] (1) 500 mg / L (calcium) calcium chloride was added to the wastewater, the pH of the wastewater was adjusted to 6.5, and the mixture was stirred at 400 rpm for 20 minutes. The pH was then adjusted to 5.8, and the mixture was stirred at 200 rpm for 30 minutes. Testing revealed that the total hardness of the wastewater was 1182 mg / L and the turbidity was 732 NTU. After the reaction, the wastewater was allowed to settle for 1 hour, and the precipitate was separated to obtain primary defluoridated wastewater.

[0055] (2) Add 45 mg / L of polysilicic acid-based inorganic-organic hybrid flocculant to the primary defluoridation wastewater, stir at 300 rpm for 10 min, then stir at 200 rpm for 15 min, let it stand for 30 min, separate the precipitate, and obtain secondary defluoridation wastewater.

[0056] The preparation method of the polysilicic acid-based inorganic-organic hybrid flocculant is as follows: (a) preparing a sodium silicate solution with a SiO2 molar concentration of 0.1 mol / L, adjusting the pH value to 6 with the help of a 0.1 mol / L formic acid solution, and performing an activation reaction at room temperature for 0.5 h to obtain a mixed solution I; (b) preparing a mixed solution of methacrylic acid and vinyl sulfonic acid, controlling the concentration of the methacrylic acid solution to 1 mol / L and the mass ratio of vinyl sulfonic acid to methacrylic acid to 1:1, and stirring at 200 rpm. , slowly adding 0.1 mol / L NH3·H2O solution at a rate of 0.1 mL / min, controlling the pH at the end point of the addition to be 3, to obtain a mixed solution II; (c) mixing the mixed solutions I and II in a volume ratio of 30:1, placing the mixed solutions in a constant temperature water bath at 40°C, passing argon for 0.5 h, adding azobisisobutylamidine hydrochloride initiator, controlling the mass ratio of the initiator to the organic monomer to be 1:50, and carrying out a polymerization reaction for 24 h to obtain a polysilicic acid-based inorganic-organic hybrid flocculant.

[0057] After testing, the fluoride ion concentration in the outlet water was 9.51 mg / L, the total hardness was 188 mg / L, and the turbidity was 1.98 NTU.

[0058] Example 4

[0059] The same method as Example 1 was used, except that calcium hydroxide was used as the defluoridation agent. Purified effluent was obtained. Testing revealed a fluoride ion concentration of 9.57 mg / L, a total hardness of 184 mg / L, and a turbidity of 2.87 NTU.

[0060] Example 5

[0061] The same method as Example 2 was used, except that calcium oxide was used as the defluoridating agent. Purified effluent was obtained. Testing revealed a fluoride ion concentration of 9.13 mg / L, a total hardness of 191 mg / L, and a turbidity of 2.81 NTU.

[0062] Example 6

[0063] The same as Example 1, except that in step (2), the stirring was not staged after the reagent was added, but was continued at 400 rpm for 20 min. The fluoride ion concentration in the effluent was 9.89 mg / L, the total hardness was 190 mg / L, and the turbidity was 2.67 NTU.

[0064] Comparative Example 1

[0065] The same as Example 1, except that in step (1), the pH was adjusted only once to 7.0, and the reaction was stirred at 500 rpm for 20 minutes. The test results showed that the fluoride ion concentration in the effluent was 16.07 mg / L, the total hardness was 552 mg / L, and the turbidity was 5.08 NTU.

[0066] Comparative Example 2

[0067] The same as Example 1, except that in step (1), the pH was adjusted only once to 6.0, and the reaction was stirred at 400 rpm for 20 minutes. The test results showed that the fluoride ion concentration in the effluent was 18.67 mg / L, the total hardness was 480 mg / L, and the turbidity was 6.27 NTU.

[0068] Comparative Example 3

[0069] The same as Example 1, except that polyacrylamide was used instead of the polysilicic acid-based inorganic-organic hybrid flocculant of the present invention. The test results showed that the fluoride ion concentration in the wastewater was 20.6 mg / L, the total hardness was 702 mg / L, and the turbidity was 23.28 NTU.

[0070] Comparative Example 4

[0071] The same as Example 1, except that polyaluminum chloride was used instead of the polysilicic acid-based inorganic-organic hybrid flocculant of the present invention. The test results showed that the fluoride ion concentration in the wastewater was 21.6 mg / L, the total hardness was 756 mg / L, and the turbidity was 32.86 NTU.

Claims

1. A method for treating high-salt coal chemical fluoride wastewater, characterized in that The steps include: (1) Adding a defluoridating agent to the wastewater, adjusting the pH to 6.5-7.5, stirring the reaction, and then adjusting the pH to 5.5-6.4 again. After stirring the reaction, the wastewater is allowed to stand and the precipitate is separated to obtain primary defluoridated wastewater; (2) A flocculant is introduced into the primary defluoridation wastewater, stirred for reaction, and then allowed to stand, and the precipitate is separated to obtain water; the flocculant is a polysilicic acid-based inorganic-organic hybrid flocculant.

2. The method according to claim 1, wherein: In step (1), the fluoride ion concentration in the high-salt coal chemical fluoride-containing wastewater is higher than 10 mg / L, preferably 20-100 mg / L; the TDS concentration is greater than 10,000 mg / L, and the pH is 8-10.

3. The method according to claim 1, wherein: In step (1), the defluoridating agent is a calcified substance, preferably at least one of calcium chloride, calcium hydroxide, and calcium oxide, and the dosage of the defluoridating agent is 300-800 mg / L in terms of calcium.

4. The method according to claim 1, wherein: In step (1), the pH of the wastewater is adjusted from the initial pH to 6.5-7.5; the stirring reaction rate is 300-500 rpm, and the stirring time is 10-30 min.

5. The method according to claim 1 or 4, characterized in that: In step (1), after adjusting the pH to 5.5-6.4 again, the stirring reaction rate is 200-400 rpm, the stirring time is 10-30 min, and the standing time is 30-60 min.

6. The method according to claim 1, wherein: In step (2), the preparation method of the polysilicic acid-based inorganic-organic hybrid flocculant is as follows: (a) preparing a sodium silicate solution, adjusting the pH to 3-6, and activating it to obtain a mixed solution I; (b) preparing an organic monomer solution, wherein the organic monomers are carboxylic acid monomers and sulfonic acid monomers, adjusting the pH to 3-6, and obtaining a mixed solution II; (c) mixing the mixed solutions I and II, placing them in a constant temperature water bath, adding an initiator under an inert atmosphere, and conducting a polymerization reaction to obtain a polysilicic acid-based inorganic-organic hybrid flocculant.

7. The method according to claim 6, characterized in that: In step (a), the sodium silicate solution has a SiO2 molar concentration of 0.1-0.5 mol / L.

8. The method according to claim 6, wherein: In step (a), the pH is adjusted by means of an inorganic acid or an organic acid, wherein the inorganic acid is at least one of hydrochloric acid, sulfuric acid, phosphoric acid or hydrobromic acid, preferably phosphoric acid; and the organic acid is at least one of citric acid, oxalic acid, formic acid or acetic acid, preferably acetic acid.

9. The method according to claim 8, characterized in that: In step (a), the inorganic acid or organic acid is prepared to a concentration of 0.1-1 mol / L; after adjusting the pH, the activation reaction is carried out at room temperature for 0.5-1 h.

10. The method according to claim 6, wherein: In step (b), the carboxylic acid monomer is at least one of acrylic acid, methacrylic acid or maleic acid, and the concentration of the carboxylic acid monomer solution is 0.5-2.0 mol / L.

11. The method according to claim 6 or 10, characterized in that: In step (b), the sulfonic acid monomer is at least one of vinyl sulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid; and the mass ratio of the sulfonic acid monomer to the carboxylic acid monomer is 1:9-1:

1.

12. The method according to claim 6, wherein: In step (b), an alkali solution is added dropwise to adjust the pH under stirring conditions at a stirring rate of 200-500 rpm and a dropping rate of 0.1-0.5 mL / min; the alkali is at least one of NaOH, KOH or NH3·H2O, and the concentration of the alkali solution is 0.1-1.0 mol / L.

13. The method according to claim 6, wherein: In step (c), the mixed solutions I and II are mixed in a volume ratio of 5:1-50:1; and the temperature of the constant temperature water bath is 40-90°C.

14. The method according to claim 6, wherein: In step (c), the inert atmosphere is in the presence of nitrogen or an inert gas, and the inert gas is at least one of helium and argon.

15. The method according to claim 6, wherein: In step (c), the initiator is at least one of a redox initiator or an azo initiator; the redox initiator is at least one of ammonium persulfate and sodium bisulfite, or potassium persulfate and sodium bisulfite; the azo initiator is at least one of azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride, preferably an azo initiator.

16. The method according to claim 6, wherein: In step (c), the mass ratio of the initiator to the organic monomer is 1:1000-1:50; and the polymerization reaction time is 8-24 hours.

17. The method according to claim 1, wherein: The dosage of the polysilicic acid-based inorganic-organic hybrid flocculant is 10-200 mg / L.

18. The method according to claim 1, wherein: In step (2), after adding the flocculant, the stirring reaction rate is 100-500 rpm, and the stirring time is 10-30 min. More preferably, after adding the flocculant, the mixture is first stirred at a high speed of 300-500 rpm for 1-10 min, and then stirred at a low speed of 100-295 rpm for 10-20 min.