Method for preparing multifunctional composite flocculants by using pyrolytic carbonized slag

Abstract

The application provides a method for preparing multifunctional composite flocculants by using pyrolysis carbonized slag, and relates to the technical field of solid waste treatment. The method comprises three steps of magnetic separation, catalytic activation and acid dissolution oxidation. First, impurities in the pyrolysis carbonized slag are removed through magnetic separation; then, an activator zinc chloride solution and a catalyst are added, and a high-temperature reaction is carried out under an inert atmosphere to obtain iron-containing activated carbon; finally, acid dissolution oxidation is carried out, iron-containing waste hydrochloric acid and an oxidizing agent are added, and multifunctional composite flocculants are prepared. The flocculants have the dual effects of adsorption and flocculation, and are particularly suitable for treating high-COD and high-color wastewater, can effectively improve the COD removal rate and the decolorization effect, and have obvious advantages compared with the removal effect of conventional ferric chloride water treatment agents. The method provided by the application is low-energy and high-efficiency, and a water treatment flocculant that can be directly applied is prepared, and efficient and clean utilization of solid waste is realized.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, and more specifically, to a method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag. Background Technology

[0002] With the acceleration of industrialization, a large amount of industrial waste is generated in production activities such as machining, metal surface treatment, equipment maintenance and replacement, and dismantling. Among them, iron-rich oily sludge, a highly emulsified, viscous semi-solid waste consisting of water, oil, and slag, has attracted much attention due to its high concentration of toxic and harmful components, including petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), heavy metals, bacteria, suspended solids, and chemical agents, as well as large amounts of aged crude oil and iron. Iron-rich oily sludge not only poses a serious threat to the environment but is also a renewable resource with extremely high potential for resource utilization and industrial recycling value.

[0003] It is estimated that my country's annual production of iron-rich oily sludge reaches as high as 3 million tons. Given its resource value and hazardous nature, efficient and clean treatment and resource utilization technologies have become a research hotspot in the energy and environmental fields. Low-temperature anaerobic pyrolysis technology for oily sludge, as an emerging treatment method, has advantages such as low energy consumption, clean combustion, environmentally friendly emissions (no dioxin production), and heavy metal solidification. In an oxygen-free closed system, iron-rich oily sludge is indirectly heated and carbonized, converting into pyrolysis oil, pyrolysis carbon, and pyrolysis gas. The pyrolysis gas can be used as fuel, the pyrolysis oil can be used as fuel oil or a raw material for organic feedstock production, and the pyrolysis carbon contains high levels of carbon and magnetite (Fe3O4), making it valuable for recycling.

[0004] However, current methods for recovering iron and carbon resources from pyrolysis carbonization slag of iron-rich oily sludge mainly employ magnetic separation technology. Because the distribution of carbon and iron elements in pyrolysis carbonization slag is interwoven and encapsulated, magnetic separation is not ideal for separating and recovering iron and carbon resources. Existing methods for recovering metallic iron from pyrolysis carbon slag utilize high-temperature carbothermal reduction, adding reducing carbon powder and slagging agents. However, due to the ultra-high temperature calcination, energy consumption is high, and the resulting crude iron product is difficult to directly recycle and requires further refining.

[0005] Therefore, developing a low-energy, high-efficiency method that can directly recycle and utilize iron and carbon resources in pyrolysis carbonization slag is of great research significance. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of traditional methods for treating pyrolysis carbonization slag, such as high energy consumption and difficulty in recycling the products, and provides a method for preparing multifunctional composite flocculants using pyrolysis carbonization slag.

[0007] Therefore, the primary objective of this invention is to provide a method for preparing a multifunctional composite flocculant using pyrolytic carbonized slag.

[0008] Another object of the present invention is to provide a multifunctional composite flocculant prepared by the above preparation method.

[0009] Another object of the present invention is to provide an application of the above-mentioned multifunctional composite flocculant.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] This invention protects a method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag, characterized by comprising the following steps:

[0012] S1. Magnetic separation: The pyrolysis carbonization slag is separated by magnetic separation to remove non-magnetic impurities and obtain iron-carbon particles;

[0013] S2. Catalytic activation: Add zinc chloride solution and catalyst to the iron-carbon particles and react at 500℃~900℃ for 3~7h under an inert atmosphere to obtain iron-containing activated carbon;

[0014] S3. Acid dissolution and oxidation: Iron-containing waste hydrochloric acid is added to the iron-containing activated carbon for reaction, and then an oxidant is added for reaction to obtain a multifunctional composite flocculant;

[0015] The catalyst is one or more of magnesium oxide, calcium oxide, cobalt oxide, or manganese dioxide.

[0016] The mass ratio of zinc chloride to pyrolytic carbonization slag in S2 is (0.3-0.5):(1-5);

[0017] The mass of catalyst added in S2 is 0.1 to 2.0% of the mass content of the pyrolysis carbonization slag.

[0018] This invention processes pyrolysis carbonization slag into a multifunctional composite flocculant liquid containing activated carbon, ferric chloride, and small amounts of magnesium, calcium, cobalt, manganese, and zinc ions through magnetic separation, catalytic activation, and acid dissolution oxidation reactions. This liquid can remove COD and color from wastewater through efficient adsorption and flocculation.

[0019] Specifically, the present invention first obtains iron-carbon particles with non-magnetic impurities removed by magnetic separation. The impurities include non-magnetic mineral particles, ash, unreacted raw materials, and other non-iron, non-carbon residues, which are derived from the original components of iron-rich oily sludge or by-products generated by chemical reactions during pyrolysis.

[0020] Secondly, iron-carbon particles are catalyzed and activated to obtain iron-containing activated carbon:

[0021] The catalyst used is one or more of magnesium oxide, calcium oxide, cobalt oxide, or manganese dioxide. On one hand, it acts as a catalyst during the activation process, increasing the reaction rate, reducing the activation temperature and time, and altering the chemical reaction mechanism. This causes carbides that previously could not form pores to undergo chemical reactions and form pores, thereby effectively increasing the specific surface area of ​​the carbon matrix, improving the pore structure, and enhancing adsorption performance to prepare iron-containing activated carbon. On the other hand, it introduces small amounts of calcium, magnesium, and manganese ions into the subsequently prepared flocculant, effectively promoting the flocculation and sedimentation of organic matter to the bottom of the water. Specifically, ionized positive ions in the water (such as Ca2+, calcium oxide, and manganese dioxide)... 2+ Mg 2+ Catalysts (such as those for neutralizing or reducing the negative charge on the surface of colloids, decreasing uncompensated bond energies, weakening the repulsive forces between them, disrupting the stable state of the colloids, and promoting their collision and contact under intermolecular interactions, destabilizing them to form flocs, which then settle down. In summary, catalysts play a catalytic role, having a dual function of aiding coagulation and enhancing adsorption performance. Adding too little will significantly reduce the removal rate of color and COD, but it should not be excessive either, because the catalyst is mainly an alkaline earth metal oxide, and adding too much will cause the flocculant system to become unstable and deteriorate, which will in turn affect the color and COD removal rate of the water.

[0022] The activator used is zinc chloride, which can activate the carbon matrix, giving it a larger micropore volume, increasing the adsorption specific surface area, adsorption porosity, and adsorption sites, thereby improving the yield and adsorption capacity of iron-containing activated carbon. In addition, zinc chloride has a catalytic dehydration effect at high temperatures; it can dehydrate and condense with oxygen-containing functional groups, causing hydrogen and oxygen atoms in the raw material to separate as water, forming a loose, porous, and permeable structure—that is, iron-containing activated carbon. This also allows more carbon to be retained in the raw material, improving the yield and adsorption capacity of iron-containing activated carbon. In summary, zinc chloride acts as an activator, improving the carbon matrix yield and adsorption capacity of the flocculant. A small amount is insufficient to activate the transformation of iron-carbon particles into iron-containing activated carbon, while a large amount reduces the flocculation performance of the flocculant (e.g., affecting its adsorption charge neutralization capacity) and can cause the zinc content in the water to rise excessively.

[0023] Finally, iron-containing waste hydrochloric acid and an oxidant are added to react with the obtained iron-containing activated carbon to prepare a multifunctional composite flocculant liquid. The waste hydrochloric acid dissolves the iron in the iron-containing activated carbon, achieving iron-carbon separation. Using the iron-containing waste hydrochloric acid serves two purposes: firstly, it utilizes the iron-containing waste acid after industrial pickling; secondly, the iron ions in the waste hydrochloric acid supplement the iron source, which is beneficial for increasing the iron content in the composite flocculant. The oxidant converts the ferrous ions generated after dissolving iron in the waste hydrochloric acid into ferric ions. The resulting multifunctional composite flocculant liquid contains activated carbon, ferric chloride, and small amounts of magnesium, calcium, cobalt, manganese, and zinc ions, which can work together to efficiently adsorb and flocculate COD and color in wastewater, thus removing them in a water treatment process.

[0024] Preferably, the catalyst is magnesium oxide, calcium oxide, cobalt oxide, and manganese dioxide. More preferably, the mass ratio of magnesium oxide, calcium oxide, cobalt oxide, and manganese dioxide is 1:1:1:1.

[0025] Preferably, the magnetic force intensity of the magnetic separation in S1 is 100-500 Gs.

[0026] Specifically, the pyrolysis carbonization slag is obtained by indirect heating and carbonization decomposition of iron-rich oily sludge in an oxygen-free closed system, and contains high levels of carbon and magnetite (Fe3O4). Preferably, the carbon content of the pyrolysis carbonization slag in S2 is 10-20% by mass.

[0027] Preferably, the iron content (calculated as Fe3O4) of the pyrolytic carbonization slag in S2 is 20-30%.

[0028] Preferably, the mass ratio of the activator zinc chloride solution to the pyrolytic carbonization slag in S2 is 1:(1-5).

[0029] Preferably, the concentration of the zinc chloride solution as an activator in S2 is 3-5 mol / L.

[0030] Preferably, the inert gas in S2 is one or more of nitrogen, argon, or helium.

[0031] Preferably, the inert gas flow rate in step S2 is 2–4 m³ / s. 3 / h.

[0032] Preferably, the hydrochloric acid content of the iron-containing waste hydrochloric acid in S3 is 15-20% by mass.

[0033] Preferably, the iron content of the iron-containing waste hydrochloric acid in S3 is 5% to 10% by mass.

[0034] Preferably, the mass ratio of iron-containing waste hydrochloric acid to iron-containing activated carbon in S3 is (3-4):1.

[0035] Preferably, the oxidant in S3 is one or both of sodium chlorate and hydrogen peroxide.

[0036] More preferably, the oxidant in S3 is sodium chlorate.

[0037] Preferably, the amount of oxidant added in S3 is 1.5% to 2.5% of the total mass of iron-containing waste hydrochloric acid and iron-containing activated carbon.

[0038] This invention protects a multifunctional composite flocculant, which is prepared by the above-described preparation method.

[0039] This invention also protects the application of the above-mentioned multifunctional composite flocculant in water treatment.

[0040] More preferably, the application of the multifunctional composite flocculant in the treatment of high COD and high color wastewater is also within the scope of protection of this invention.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] 1. This invention provides a method for preparing a multifunctional composite flocculant using pyrolytic carbonized slag. The pyrolytic carbonized slag is treated with mild catalytic activation to prepare iron-containing activated carbon, avoiding the energy consumption caused by ultra-high temperature calcination in the prior art.

[0043] 2. The method of preparing multifunctional composite flocculant using pyrolysis carbonization slag of the present invention prepares iron and carbon particles in pyrolysis carbonization slag into multifunctional composite flocculant, which can be directly used to treat COD and color in wastewater.

[0044] 3. This invention provides a multifunctional composite flocculant with dual functions of adsorption and flocculation. It is suitable for the treatment of wastewater with high COD and high color. Compared with conventional ferric chloride water treatment agents, it has advantages in COD removal and decolorization capabilities, and the dosage is only 0.8‰, making it highly efficient and durable. Detailed Implementation

[0045] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0046] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0047] 1. Experimental Methods

[0048] Example 1: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0049] S1. Magnetic separation: Magnetic separation is used to remove impurities from the pyrolysis carbonization slag.

[0050] Specifically, the pyrolysis carbonization slag is passed through a magnetic separator to remove non-magnetic impurities from the slag. The magnetic force is 300 Gs, and iron-carbon particles are obtained.

[0051] S2. Catalytic activation: Pyrolysis carbonized slag is treated with activators and catalysts.

[0052] Specifically, the iron-carbon particles after impurity removal from S1 are ground through a 200-mesh sieve, and a 4 mol / L zinc chloride solution is added. The mass ratio of zinc chloride solution to pyrolytic carbonization slag is 0.4:3. Then, magnesium oxide, calcium oxide, cobalt oxide, and manganese dioxide catalysts are added, with a total amount equal to 1.0% of the mass of the pyrolytic carbonization slag. The mass ratio of magnesium oxide, calcium oxide, cobalt oxide, and manganese dioxide is 1:1:1:1. After thorough mixing, the mixture is placed in a tube furnace, nitrogen gas is introduced, and it is calcined at 600℃ for 4 hours to obtain iron-containing activated carbon.

[0053] S3. Acid dissolution and oxidation: Add waste hydrochloric acid and oxidant to prepare a multifunctional composite flocculant.

[0054] Specifically, the iron-containing activated carbon obtained in S2 is ground and passed through a 200-mesh sieve. Iron-containing waste hydrochloric acid is added at a mass ratio of 1:3.5, and the mixture is stirred in a water bath at 70°C for 1.5 hours to form a mixed liquid. Then, 2.0% of the total mass of the mixed liquid is added as an oxidant sodium chlorate for oxidation reaction for 10 minutes to obtain a multifunctional composite flocculant liquid.

[0055] Example 2: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0056] The scheme is the same as in Example 1, except that the mass ratio of zinc chloride to pyrolytic carbonization slag is 0.4:1.

[0057] Example 3: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0058] The scheme is the same as in Example 1, except that the mass ratio of zinc chloride to pyrolytic carbonization slag is 0.4:5.

[0059] Example 4: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0060] The scheme is the same as in Example 1, except that the catalytic activation temperature is 500°C.

[0061] Example 5: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0062] The scheme is the same as in Example 1, except that the catalytic activation temperature is 700°C.

[0063] Example 6: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0064] The scheme is the same as in Example 1, except that the catalytic activation temperature is 900°C.

[0065] Example 7: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0066] The scheme is the same as in Example 1, except that the catalytic activation time is 3 hours.

[0067] Example 8: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0068] The scheme is the same as in Example 1, except that the catalytic activation time is 5 hours.

[0069] Example 9: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0070] The scheme is the same as in Example 1, except that the catalytic activation time is 7 hours.

[0071] Example 10: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0072] The scheme is the same as in Example 1, except that the catalyst is magnesium oxide.

[0073] Example 11: A method for preparing a multifunctional composite flocculant using pyrolytic carbonization slag.

[0074] The scheme is the same as in Example 1, except that the catalyst is calcium oxide.

[0075] Example 12: A method for preparing a multifunctional composite flocculant using pyrolytic carbonization slag.

[0076] The scheme is the same as in Example 1, except that the catalyst is cobalt oxide.

[0077] Example 13: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0078] The scheme is the same as in Example 1, except that the catalyst is manganese oxide.

[0079] Example 14: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0080] The scheme is the same as in Example 1, except that the amount of catalyst added is 0.5% of the pyrolysis carbonization slag.

[0081] Example 15: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0082] The scheme is the same as in Example 1, except that the amount of catalyst added is 0.1% of the pyrolysis carbonization slag.

[0083] Example 16: A method for preparing a multifunctional composite flocculant using pyrolytic carbonization slag.

[0084] The scheme is the same as in Example 1, except that the amount of catalyst added is 2.0% of the pyrolysis carbonization slag.

[0085] Comparative Example 1: A method for preparing a multifunctional composite flocculant using pyrolytic carbonized slag.

[0086] The method is the same as in Example 1, except that the mass ratio of zinc chloride to pyrolytic carbonization slag is 0.4:0.5. Comparative Example 2: A method for preparing a multifunctional composite flocculant using pyrolytic carbonization slag.

[0087] The scheme is the same as in Example 1, except that the mass ratio of zinc chloride to pyrolytic carbonization slag is 0.4:6.

[0088] Comparative Example 3: A method for preparing multifunctional composite flocculants using pyrolytic carbonization slag

[0089] The scheme is the same as in Example 1, except that zinc chloride solution is not added.

[0090] Comparative Example 4: A method for preparing multifunctional composite flocculants using pyrolytic carbonized slag.

[0091] The scheme is the same as in Example 1, except that no catalyst is added.

[0092] Comparative Example 5: A method for preparing a multifunctional composite flocculant using pyrolytic carbonized slag.

[0093] The scheme is the same as in Example 1, except that the amount of catalyst added is 3% of the pyrolysis carbonization slag.

[0094] Comparative Example 6: A method for preparing a multifunctional composite flocculant using pyrolytic carbonization slag.

[0095] The scheme is the same as in Example 1, except that the catalytic activation temperature is 200°C.

[0096] Comparative Example 7: A method for preparing a multifunctional composite flocculant using pyrolytic carbonized slag.

[0097] The scheme is the same as in Example 1, except that the catalytic activation temperature is 1000°C.

[0098] Comparative Example 8: A method for preparing a multifunctional composite flocculant using pyrolysis carbonization slag.

[0099] The scheme is the same as in Example 1, except that the catalytic activation time is 1 hour.

[0100] Comparative Example 9: A method for preparing a multifunctional composite flocculant using pyrolytic carbonized slag.

[0101] The scheme is the same as in Example 1, except that the catalytic activation time is 8 hours.

[0102] Comparative Example 10: A method for preparing a multifunctional composite flocculant using pyrolytic carbonization slag.

[0103] The scheme is the same as in Example 1, except that the reaction gas atmosphere for catalytic activation is oxygen.

[0104] 2. Experimental results of Examples 1-16 and Comparative Examples 1-10

[0105] (1) Evaluation of product performance indicators

[0106] The effectiveness of the multifunctional composite flocculant liquids prepared in the above embodiments and comparative examples was comprehensively evaluated. The evaluation standards and test methods referred to GB / T 4482-2018 "Ferric Chloride for Water Treatment Agents". Specific test results are detailed in Table 1.

[0107] Table 1 Main performance indicators of multifunctional composite flocculant products

[0108]

[0109]

[0110] (2) Evaluation of the effectiveness of chemical wastewater treatment

[0111] Chemical wastewater from a chemical plant was used as a simulated wastewater treatment process, and its water quality is detailed in Table 2. Using the controlled variable method, under the same experimental conditions, the multifunctional composite flocculants prepared in the above examples and comparative examples were added to 200 ml of chemical wastewater at a dosage ratio of 0.8‰. The mixtures were stirred at the same speed for 5–10 min, allowed to stand for 30 min, and then the supernatant was collected to detect COD and color. The wastewater treatment effects of the multifunctional composite flocculants prepared in the examples and comparative examples were compared with those of conventional ferric chloride water treatment agents. The results are detailed in Table 3.

[0112] Table 2 Water Quality Indicators of Chemical Wastewater

[0113]

[0114]

[0115] Table 3 shows the wastewater treatment effects of the examples and comparative examples (dosage of the reagent is 0.8‰).

[0116]

[0117]

[0118] As shown in Table 1, the iron content, HCl content and carbon matrix content of the multifunctional composite flocculant prepared by this invention meet the standard requirements of GB / T 4482-2018 ferric chloride for water treatment, and can be directly applied to water treatment.

[0119] Table 3 shows that the flocculants obtained in Examples 1-16 have higher COD and color removal rates than conventional ferric chloride water treatment agents, and are applicable to high-concentration COD and high-color wastewater. Comparative Examples 1-3 illustrate the importance of the activator zinc chloride. Zinc chloride increases the yield of iron-containing activated carbon, enhances adsorption, and improves color removal. Data from Comparative Example 3 shows that without zinc chloride, although the remaining carbon matrix content is high, it is essentially inert carbon that is not activated, lacking usable pores and active sites for adsorption and flocculation, resulting in poor removal. However, excessive zinc chloride addition reduces flocculation. Comparative Examples 4-6 illustrate the importance of the catalyst, which enhances the adsorption and coagulation aid effects of the flocculant, i.e., removing color and COD. Insufficient catalyst addition reduces the removal rates of color and COD. Excessive catalyst addition should be avoided, as it is mainly composed of alkaline earth metal oxides; excessive addition can lead to instability and deterioration of the flocculant system. On the contrary, it will affect the color and COD removal rate of the water. Comparative Examples 6 and 7 illustrate the temperature and time ranges under different conditions and treatment methods. In Comparative Example 6, the reaction temperature of catalytic activation was too low, which could not allow the iron-carbon particles to form sufficient pores, and the active sites required for subsequent adsorption were not sufficient, so the removal effect was poor. In Comparative Example 7, the temperature was too high, which would cause collapse and reduce the adsorption sites of iron-containing activated carbon. In Comparative Example 8, the reaction time of catalytic activation was too short, which made it difficult for the activator and catalyst to react fully with the iron-carbon particles, and the degree of pore formation of the iron-containing activated carbon was also insufficient. In Comparative Example 9, the catalytic activation time was too long. Over-catalytic activation may lead to a decrease in the yield of activated carbon. Prolonged high temperature may cause more carbon to be oxidized, thereby reducing the output of activated carbon. Comparative Example 10 used an oxygen atmosphere. Under high temperature conditions, the reactants are prone to oxidation reaction with oxygen in the air, which leads to the oxidation of iron-carbon particles, reduces carbon content, decreases adsorption and flocculation effects, and poses a safety risk of explosion.

[0120] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a multifunctional composite flocculant using pyrolytic carbonized slag, characterized by, Includes the following steps: S1. Magnetic separation: The pyrolysis carbonization slag is separated by magnetic separation to remove non-magnetic impurities and obtain iron-carbon particles; S2. Catalytic activation: Add zinc chloride solution and catalyst to the iron-carbon particles and react at 500℃~900℃ for 3~7h under an inert atmosphere to obtain iron-containing activated carbon; S3. Acid dissolution and oxidation: Iron-containing waste hydrochloric acid is added to the iron-containing activated carbon described in S2 for reaction, and then an oxidant is added for reaction to obtain a multifunctional composite flocculant; The catalyst is one or more of magnesium oxide, calcium oxide, cobalt oxide, or manganese dioxide. The mass ratio of zinc chloride to pyrolytic carbonization slag in S2 is (0.3-0.5):(1-5). The mass of the catalyst added in S2 is 0.1% to 2.0% of the mass of the pyrolysis carbonization slag.

2. The method of claim 1, wherein, The magnetic force intensity of the magnetic separation in step S1 is 100~500 Gs.

3. The method of claim 1, wherein, In step S2, the concentration of the activator zinc chloride solution is 3~5 mol / L.

4. The method of claim 1, wherein, In step S2, the inert gas is one or more of nitrogen, argon, or helium.

5. The method of claim 1, wherein, In step S3, the oxidant is one or both of sodium chlorate and hydrogen peroxide.

6. The method of claim 1, wherein, In step S3, the amount of oxidant added is 1.5% to 2.5% of the total mass of iron-containing waste hydrochloric acid and iron-containing activated carbon.

7. The method of claim 1, wherein, In step S3, the hydrochloric acid content of the iron-containing waste hydrochloric acid is 15%~20%.

8. The method of claim 1, wherein, The iron content of the iron-containing waste hydrochloric acid in step S3 is 5% to 10%.

9. A multifunctional composite flocculant, characterized by, It is prepared by the method described in any one of claims 1 to 8.

10. The application of the multifunctional composite flocculant according to claim 9 in water treatment.

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