Preparation method of multifunctional composite reagent for micro-polluted water body and reagent

Abstract

The application relates to the field of water treatment, and particularly discloses a preparation method of a multifunctional composite medicament suitable for micro-polluted water bodies and the medicament, which comprises the following steps: preparing modified aluminum-iron chloride: mixing active aluminum oxide, iron chloride, lanthanum chloride and a hydrochloric acid solution, and performing a warming reaction to obtain modified aluminum-iron chloride; performing a polymerization reaction: after the active silicon acid and the modified aluminum-iron chloride are mixed and reacted in advance, a sufficient amount of ferrous sulfate is added for continuous reaction, and finally the composite medicament is obtained through aging; the aluminum content in the composite medicament is 1%-5%, the silicon content is 0.1%-0.5%, the iron content is 0.5%-1%, the ferrous iron content is 0.5%-1%, and the lanthanum content is 1‰-3‰. The composite medicament prepared by the application has excellent removal effect on various pollution factors, reduces the medicament dosage, and improves the treatment effect on the micro-polluted water bodies.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water treatment, more particularly, it relates to a preparation method of a multifunctional composite agent suitable for micro-polluted water bodies and the agent. BACKGROUND

[0002] At present, most of the tail water of sewage treatment plants in China is discharged in accordance with the national standard level A, which is higher than the environmental quality requirement of surface water. The concentration of pollution factors such as organic matter, phosphorus, fluorine and arsenic in water bodies is low, which is called micro-polluted water bodies. With the promotion of sustainable development strategy, the treatment of micro-polluted water bodies has become a topic of concern worldwide.

[0003] For micro-polluted water bodies containing phosphorus and / or arsenic and / or fluorine, adsorption, ion exchange and extraction methods are generally used for deep purification, but the treatment cost of these methods is high. For the treatment of slightly polluted rivers and lakes, the method of adding agents for coagulation sedimentation or air flotation deep purification is still the mainstream choice in the industry. However, the traditional agents have high removal efficiency for water bodies with high concentration of pollution factors, but when treating micro-polluted water bodies, the removal effect is poor due to the low concentration of pollution factors, and the dosage is large, resulting in large amount of waste residue. SUMMARY

[0004] The present application provides a preparation method of a multifunctional composite agent suitable for micro-polluted water bodies and the agent. The composite agent prepared by the present application has excellent removal effect on various pollution factors, reduces the dosage of the agent and improves the treatment effect of micro-polluted water bodies.

[0005] In the first aspect, the present application provides a preparation method of a multifunctional composite agent suitable for micro-polluted water bodies, which adopts the following technical scheme:

[0006] A preparation method of a multifunctional composite agent suitable for micro-polluted water bodies, comprising the following steps: preparing modified aluminum iron chloride: mixing active alumina, ferric chloride, lanthanum chloride and hydrochloric acid solution, and reacting under heating to obtain modified aluminum iron chloride;

[0007] Polymerization reaction: after the pre-mixed reaction of active silicic acid and modified aluminum iron chloride, a sufficient amount of ferrous sulfate is added for further reaction, and finally the composite agent is obtained after aging;

[0008] The aluminum content in the composite agent is 1%-5%, the silicon content is 0.1%-0.5%, the iron content is 0.5%-1%, the ferrous content is 0.5%-1%, and the lanthanum content is 1‰-3‰.

[0009] First, the active aluminum oxide, iron chloride, lanthanum chloride and hydrochloric acid solution are reacted to form a modified aluminum iron chloride polyhydroxy complex with lanthanum as the catalytic active center, aluminum and iron as the complex center in a polymerization form, then polymerized with active silicic acid, and in the reaction process, aluminum and iron are preferentially polymerized with Si on the active silicic acid, the base degree is adjusted, and a poly-silicon aluminum iron with good polymerization form is obtained, then ferrous sulfate is added, and ferrous iron is polymerized with Si on the active silicic acid, avoiding the oxidation of free ferrous iron, further improving the quality of the reagent, and then improving the removal effect of the reagent on the pollution factors in the slightly polluted water body.

[0010] Strictly control the content of aluminum, silicon, iron, ferrous iron and lanthanum in the reagent, and cooperate with specific process conditions, not only can form a mutual conjugate system in the product, ensure the stability of Fe 3+ Coexist with Fe 2+ , and complement each other between elements, form a product with excellent polymerization form and suitable base degree, and promote the effect of the reagent together, so that the prepared reagent has excellent removal effect on pollution factors in slightly polluted water body with low pollution factor concentration, while reducing the dosage of the reagent.

[0011] The above prepared composite reagent can form lanthanum phosphate, lanthanum arsenate and lanthanum fluoride which are insoluble in water when treating slightly polluted water body, and the generated water-insoluble compounds can be used as crystal of coagulation floc to induce rapid formation of floc of aluminum iron hydrolysis product in the reagent, and then through the compression double electric layer adsorption-electric neutralization adsorption-bridge of floc, sediment net capture and other actions, excellent removal effect on phosphorus, arsenic and fluorine is achieved. Active aluminum can quickly complex with fluorine to generate various complexes such as AlF2 + , AlF3 to AlF6 3- , etc., and F - is removed by complex precipitation; under the condition of supersaturation and oxygen enrichment, Fe(II) can be oxidized to Fe(III), and hydroxyl radicals will be released during the oxidation of Fe(II) to catalyze the oxidation of arsenic(III) to arsenic(V), and arsenic(V) will coagulate with Fe(III) and aluminum in the composite reagent to generate floc rich in arsenic, thereby effectively removing various pollution factors, reducing the dosage of the reagent and improving the treatment effect on slightly polluted water body.

[0012] Further, in the step of preparing modified aluminum iron chloride, the temperature rising reaction is specifically as follows: the temperature is raised to 80-95℃ and kept constant for 1.6-2.5h.

[0013] Further, in the step of preparing modified aluminum iron chloride, the mass concentration of the hydrochloric acid solution is 5-10%.

[0014] Optimizing the process conditions of the temperature rising reaction and the concentration of hydrochloric acid solution in the step of preparing modified aluminum iron chloride further helps to form the modified aluminum iron chloride polyhydroxy complex with lanthanum as the catalytic active center and aluminum and iron as the complex center in a polymerization form, which is convenient for forming the medicament product with better quality with active silicic acid polymerization.

[0015] Further, the active silicic acid is prepared by activating the sodium silicate solution with an acidic solution, adjusting the pH to 1-3 to obtain the active silicic acid.

[0016] Further, the mass concentration of the sodium silicate solution is preferably 40-60%, and most preferably 50%.

[0017] Further, the SiO2 concentration in the active silicic acid is 0.5-2.5 mol / L. It is found through research experiments that the medicament has better treatment effect on the water body when the SiO2 concentration in the active silicic acid is 1.5 mol / L.

[0018] Further, the acidic solution is one of a hydrochloric acid solution and a sulfuric acid solution.

[0019] As a further preferred acidic solution, the acidic solution is a hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 1.5-2.5 mol / L. The concentration of the hydrochloric acid solution is most preferably 2 mol / L.

[0020] The hydrochloric acid solution is selected to activate the sodium silicate, which has good activation effect and does not introduce new impurity ions, and can further improve the quality of the medicament product.

[0021] Further, the acidic solution needs to be added slowly and uniformly to the sodium silicate aqueous solution. If the acidic solution is added too fast, the reaction with the sodium silicate solution is too fast, the local temperature rises rapidly, and colloidal particles are formed. Therefore, the dropping speed of the acidic solution is reasonably controlled to avoid the formation of solid colloidal particles. When the pH approaches 7, the adding speed of the acidic solution can be appropriately accelerated to prevent a large amount of silicic acid gel from being generated in the neutral system.

[0022] Further, in the step of the polymerization reaction, the active silicic acid and the modified aluminum iron chloride are pre-mixed at 40-60°C for 1.5-3h, and then a sufficient amount of ferrous sulfate is added for further reaction for 0.5-1h.

[0023] Maintaining the appropriate temperature reaction conditions and time ensures that aluminum and iron preferentially polymerize with silicon in the active silicic acid, further improving the polymerization form of the product.

[0024] Further, in the step of the polymerization reaction, aging is performed at room temperature, and the aging time is 20-30h.

[0025] During the aging process, hydrolysis of iron, aluminum, etc. occurs to generate Fe(OH) nor Al(OH) n The complex can further improve the internal structure of the system and improve the quality of the pharmaceutical product.

[0026] In a second aspect, the application provides a multifunctional composite agent suitable for micro-polluted water bodies, which adopts the following technical solution:

[0027] A composite agent is prepared by the above-mentioned preparation method of the multifunctional composite agent suitable for micro-polluted water bodies.

[0028] The prepared composite agent has excellent removal effect on various pollution factors, reduces the dosage of the agent, improves the treatment effect on micro-polluted water bodies, and can be effectively applied to the tail water upgrading of the existing treatment site and the treatment of micro-polluted rivers and lakes.

[0029] In summary, the application has the following beneficial effects:

[0030] 1. The active aluminum oxide, iron chloride and lanthanum chloride are reacted with hydrochloric acid solution to form a modified aluminum iron chloride polyhydroxy complex in a polymerization form with lanthanum as a catalytic active center and aluminum and iron as a complex center. Then, the active silicic acid is polymerized. In the reaction process, aluminum and iron are preferentially polymerized with Si on the active silicic acid, the basicity is adjusted, and a poly-silicon aluminum iron with good polymerization form is obtained. Then, ferrous sulfate is added, and ferrous iron is polymerized with Si on the active silicic acid to avoid oxidation of free ferrous iron, further improve the quality of the agent, reduce the dosage of the agent, and improve the treatment effect on micro-polluted water bodies.

[0031] 2. The content of elements such as aluminum, silicon, iron, ferrous iron and lanthanum in the agent is strictly controlled, and the corresponding preparation method is adopted. Not only can a system that is mutually conjugated be formed to ensure the stability of Fe 3+ and Fe 2+ coexist, but also the elements complement each other to form a product with excellent polymerization form and suitable basicity, which can promote the effect of the agent and make the prepared agent have excellent removal effect on various low-concentration pollution factors while reducing the dosage of the agent. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The preparation flowchart of the composite agent of the application is shown in the figure. DETAILED DESCRIPTION

[0033] The embodiments of the application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only for illustration of the application and should not be regarded as limiting the scope of the application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not mentioned by the manufacturer are conventional products that can be purchased on the market.

[0034] In the process of the treatment of micro-polluted water bodies, and according to the researches at home and abroad and the treatment experiences of river and lake water bodies, reducing the concentration of total phosphorus (TP) in water bodies is a key measure to alleviate eutrophication and control the outbreak of blue-green algae. According to the researches, the TP < 0.05 mg / L entering the receiving water body can effectively control the eutrophication of the water body.

[0035] At present, the tail water of most domestic sewage treatment plants is discharged in accordance with the national standard of level A, which is much higher than the requirement of the third class water in the lake and reservoir surface water (TP≤0.05 mg / L). In the traditional deep purification and phosphorus removal, the phosphorus removal efficiency of the conventional iron / aluminum salt coagulant is limited, and it is difficult to meet the requirements and the dosage of the reagent is large.

[0036] In the process of mineral resource exploitation and processing, the tail water discharged and the water bodies such as lakes located in the basin of the mineral processing area often have an arsenic concentration exceeding the discharge limit value of arsenic concentration in surface water (the fifth class water in surface water, arsenic≤0.1 mg / L). These wastewaters contain trivalent arsenic (III) and pentavalent arsenic (V). The conventional coagulant deep purification treatment can effectively remove arsenic (V), but the removal effect of arsenic (III) is poor.

[0037] After the treatment of high-concentration fluorine-containing wastewater, the fluorine concentration still reaches 10 mg / L, which is much higher than the requirement of the discharge limit of fluorine in surface water (fluorine < 1.0 mg / L). The dosage of aluminum / iron salt defluorination reagent and the method of coagulation sedimentation or flotation are used to remove fluorine, and in this process, several tens of times of reagent needs to be added, the dosage of the reagent is large, the cost is high, and the amount of slag produced is also large.

[0038] Therefore, it is crucial to develop a composite reagent for the treatment of micro-polluted water bodies, which can reduce the dosage of the reagent while improving the treatment effect on the water body. In the process of developing the reagent for the treatment of the above-mentioned micro-polluted water bodies containing phosphorus and / or arsenic and / or fluorine, the inventors found that the content of the elements aluminum, silicon, iron, ferrous and lanthanum in the reagent is crucial, and under the cooperation of the corresponding preparation method, a system can be formed, which ensures the stability of Fe 3+ and Fe 2+ coexistence, the elements can complement each other, form a product with excellent polymerization form and suitable base degree, and jointly promote the effect of the reagent, which can reduce the dosage of the reagent while improving the treatment effect on the micro-polluted water body.

[0039] Embodiment

[0040] Embodiment 1

[0041] A preparation method of a multifunctional composite reagent suitable for micro-polluted water bodies, comprising the following steps:

[0042] Preparation of modified aluminum iron chloride: mix active alumina, iron chloride, lanthanum chloride with hydrochloric acid solution, the mass concentration of the hydrochloric acid solution is 10%, heat to 95℃ in the polymerization reactor, and keep the temperature constant for 1.6h to obtain modified aluminum iron chloride;

[0043] Preparation of active silicic acid: under the condition of high shear stirring, activate the sodium silicate solution with a mass concentration of 40% in the reactor with a 5% hydrochloric acid solution, and adjust the pH to 3 to obtain active silicic acid; the SiO2 concentration in the active silicic acid is 2.5mol / L; the sulfuric acid solution is slowly and uniformly added to the sodium silicate aqueous solution, and when the pH approaches 7, the addition speed of the sulfuric acid solution can be appropriately accelerated;

[0044] Polymerization reaction: mix the active silicic acid obtained above with the modified aluminum iron chloride in the polymerization reactor, react at 60℃ for 1.5h, then add sufficient ferrous sulfate to continue the reaction for 0.5h, and finally age at room temperature for 30h to obtain the composite agent;

[0045] The aluminum content in the above composite agent is 5%, the silicon content is 0.5%, the iron content is 0.5%, the ferrous content is 0.5%, and the lanthanum content is 3 ‰.

[0046] Example 2

[0047] A method for preparing a multifunctional composite agent suitable for micro-polluted water bodies, comprising the following steps:

[0048] Preparation of modified aluminum iron chloride: mix active alumina, iron chloride, lanthanum chloride with hydrochloric acid solution, the mass concentration of the hydrochloric acid solution is 5%, heat to 80℃ in the polymerization reactor, and keep the temperature constant for 2.5h to obtain modified aluminum iron chloride;

[0049] Preparation of active silicic acid: under the condition of high shear stirring, activate the sodium silicate solution with a mass concentration of 60% in the reactor with a 1.5mol / L hydrochloric acid solution, and adjust the pH to 1 to obtain active silicic acid; the SiO2 concentration in the active silicic acid is 0.5mol / L; the hydrochloric acid solution is slowly and uniformly added to the sodium silicate aqueous solution, and when the pH approaches 7, the addition speed of the hydrochloric acid solution can be appropriately accelerated;

[0050] Polymerization reaction: mix the active silicic acid obtained above with the modified aluminum iron chloride in the polymerization reactor, react at 40℃ for 3h, then add sufficient ferrous sulfate to continue the reaction for 1h, and finally age at room temperature for 20h to obtain the composite agent;

[0051] The aluminum content in the above composite agent is 2.5%, the silicon content is 0.1%, the iron content is 1%, the ferrous content is 1%, and the lanthanum content is 1 ‰.

[0052] Example 3

[0053] The difference from example 1 is that the aluminum content in the composite agent is 4.5%, the silicon content is 0.4%, the iron content is 0.8%, the ferrous content is 0.8%, and the lanthanum content is 2 ‰; the rest is the same as example 1.

[0054] Example 4

[0055] The difference from example 3 is that a multifunctional composite agent suitable for micro-polluted water bodies is prepared by the following steps:

[0056] Preparation of modified aluminum chloride iron: mix active aluminum oxide, iron chloride, lanthanum chloride with hydrochloric acid solution, the mass concentration of the hydrochloric acid solution is 7%, heat to 90℃ in the polymerization reactor for 2h to obtain modified aluminum chloride iron;

[0057] Preparation of active silicon acid: under high shear stirring conditions, sodium silicate solution with a mass concentration of 50% is activated by 2 mol / L hydrochloric acid solution in the reactor and the pH is adjusted to 2 to obtain active silicon acid; the SiO2 concentration in the active silicon acid is 1.5 mol / L; the hydrochloric acid solution is slowly and uniformly added to the sodium silicate aqueous solution at multiple points, and when the pH approaches 7, the addition speed of the hydrochloric acid solution can be appropriately accelerated;

[0058] Polymerization reaction: mix the active silicon acid obtained above with the modified aluminum chloride iron in the polymerization reactor, react at 50℃ for 2h, then add sufficient ferrous sulfate and continue to react for 0.5h, and finally age at room temperature for 24h to obtain the composite agent; the rest is the same as example 3.

[0059] Example 5

[0060] A multifunctional composite agent suitable for micro-polluted water bodies is prepared by the following steps:

[0061] Preparation of modified aluminum chloride iron: mix active aluminum oxide, iron chloride, lanthanum chloride with hydrochloric acid solution, the mass concentration of the hydrochloric acid solution is 12%, heat to 85℃ and react for 3h to obtain modified aluminum chloride iron;

[0062] Preparation of active silicon acid: under high shear stirring conditions, sodium silicate solution with a mass concentration of 65% is activated by 0.8 mol / L hydrochloric acid solution and the pH is adjusted to 4 to obtain active silicon acid; the SiO2 concentration in the active silicon acid is 1 mol / L; the hydrochloric acid solution is slowly and uniformly added to the sodium silicate aqueous solution at multiple points, and when the pH approaches 7, the addition speed of the hydrochloric acid solution can be appropriately accelerated;

[0063] Polymerization: the active silicic acid obtained above was mixed with modified aluminum-iron chloride at 65°C for 3.2h, then sufficient ferrous sulfate was added to continue the reaction for 1.5h, and finally the mixture was aged at room temperature for 24h to obtain the composite agent;

[0064] The aluminum content in the composite agent above was 1.4%, the silicon content was 0.2%, the iron content was 0.6%, the ferrous content was 0.9%, and the lanthanum content was 1.2‰.

[0065] Comparative Example

[0066] Comparative Example 1

[0067] The difference from Example 4 was that the aluminum content in the composite agent was 0.5%, the silicon content was 3%, the iron content was 0.2%, the ferrous content was 0.1%, and the lanthanum content was 3.5‰, and the rest was the same as Example 4.

[0068] Comparative Example 2

[0069] The difference from Example 4 was that no lanthanum chloride was added in the step of preparing modified aluminum-iron chloride, i.e. the composite agent did not contain lanthanum element, and the rest was the same as Example 4.

[0070] Comparative Example 3

[0071] The difference from Example 4 was that no ferrous sulfate was added in the step of polymerization, i.e. the composite agent did not contain ferrous, and the rest was the same as Example 4.

[0072] Performance detection test

[0073] Micro-polluted water treatment experiment 1:

[0074] For the high-hardness wastewater containing fluorine, arsenic and phosphorus in the polysilicon industry, the initial water body had the pollution factor concentrations as shown in Table 1. After entering the spore transfer all-in-one machine, the wastewater was treated by the composite agents prepared by Examples 1-5 and Comparative Examples 1-3, respectively, and the dosing concentration of the composite agents was equal, which was 30ppm. The conditions of the effluent after treatment were detected and shown in Table 2 as follows:

[0075] Table 1 Initial conditions of water body

[0076]

[0077] Table 2 Conditions of effluent after treatment

[0078]

[0079] Micro-polluted water treatment experiment 2:

[0080] For the effluent from sewage treatment plants and slightly polluted water bodies such as rivers and lakes, after entering the spore transfer integrated machine, the composite agents prepared in Examples 1-5 and Comparative Examples 1-3 are used for treatment to control the concentration of pollutants in the effluent. The amount of each agent required is recorded. The initial conditions of the water body and the effluent requirements are shown in Table 3. The results of the required amount of each agent are recorded in Table 4.

[0081] Table 3 Initial water conditions and effluent requirements

[0082]

[0083] Table 4 Required Dosage for Drug Samples

[0084] Pharmaceutical agent sample Dosage concentration (ppm) Example 1 25 Example 2 23 Example 3 17 Example 4 28 Example 5 30 Comparative Example 1 300 Comparative Example 2 93 Comparative Example 3 85

[0085] As can be seen from Examples 1-5 and Tables 1-4, the composite agent prepared in this application has excellent removal effect on a variety of pollutants, reducing the dosage of the agent while improving the treatment effect on slightly polluted water bodies.

[0086] Combining Example 4 and Comparative Example 1 with Tables 1-4, it can be seen that the aluminum, silicon, iron, ferrous, and lanthanum contents in the composite agent are unbalanced, resulting in poor polymerization morphology of the entire product. This leads to a significant decrease in the removal efficiency of pollutants in slightly polluted water bodies with low pollutant concentrations. Furthermore, combining Example 4 and Comparative Examples 2-3 with Tables 1-4, it can be seen that Comparative Example 3 lacks both lanthanum and ferrous iron. The composite agents obtained in Comparative Examples 2 and 3 show poor treatment effects on slightly polluted water bodies, requiring a significant increase in agent dosage to achieve the same treatment effect. In Comparative Example 3, due to the lack of ferrous iron, although the agent dosage was increased, the removal of arsenic(III) still failed to meet the effluent requirements.

[0087] This demonstrates that the elements in the composite reagent complement each other, and the content of aluminum, silicon, iron, ferrous iron, and lanthanum in the reagent must be strictly controlled during the preparation process. Combined with specific process conditions, this ensures the formation of a mutually conjugated system within the product, guaranteeing the optimal Fe content. 3+ with Fe 2+ The coexistence of these substances creates a stable environment and produces products with excellent polymerization morphology and suitable basicity, which together promote the efficacy of the agents, improve the treatment effect on slightly polluted water bodies, and reduce the amount of agents required.

[0088] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a multifunctional composite agent suitable for slightly polluted water bodies, characterized in that, Includes the following steps: Preparation of modified aluminum ferric chloride: Activated alumina, ferric chloride, lanthanum chloride and hydrochloric acid solution are mixed and heated to 80-95℃ and reacted at a constant temperature for 1.6-2.5h to obtain modified aluminum ferric chloride; Polymerization reaction: Active silica and modified aluminum ferric chloride are premixed and reacted at 40-60℃ for 1.5-3h, then sufficient ferrous sulfate is added and the reaction continues for 0.5-1h. Finally, the composite agent is obtained by aging at room temperature for 20-30h. First, activated alumina, ferric chloride, and lanthanum chloride are reacted with hydrochloric acid solution to form a modified aluminum-iron chloride polyhydroxy complex with lanthanum as the catalytic active center and aluminum and iron as the complex centers. Then, it is polymerized with activated silicic acid. During the reaction, aluminum and iron preferentially polymerize with the Si on the activated silicic acid. While adjusting the basicity, a polysilicon-aluminum-iron complex with good polymerization morphology is obtained. Then, ferrous sulfate is added, and ferrous sulfate polymerizes with the Si on the activated silicic acid. The composite agent contains 1%-5% aluminum, 0.1%-0.5% silicon, 0.5%-1% iron, 0.5%-1% ferrous iron, and 1‰-3‰ lanthanum.

2. The preparation method of the multifunctional composite agent suitable for slightly polluted water bodies according to claim 1, characterized in that: In the step of preparing modified aluminum ferric chloride, the mass concentration of the hydrochloric acid solution is 5-10%.

3. The preparation method of the multifunctional composite agent suitable for slightly polluted water bodies according to claim 1, characterized in that: The active silicic acid is obtained by the following steps: activating a sodium silicate solution with an acidic solution and adjusting the pH to 1-3 to obtain active silicic acid.

4. The method for preparing the multifunctional composite agent suitable for slightly polluted water bodies according to claim 1 or 3, characterized in that: The concentration of SiO2 in the active silicic acid is 0.5-2.5 mol / L.

5. The preparation method of the multifunctional composite agent suitable for slightly polluted water bodies according to claim 4, characterized in that: The acidic solution is either hydrochloric acid or sulfuric acid.

6. The method for preparing the multifunctional composite agent suitable for slightly polluted water bodies according to claim 5, characterized in that: The acidic solution is a hydrochloric acid solution with a concentration of 1.5-2.5 mol / L.

7. A compound agent, characterized in that, It is prepared by the method of any one of claims 1-6 for the preparation of a multifunctional composite agent suitable for slightly polluted water bodies.

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