Method for preparing substitute alkali for sewage treatment by using industrial waste alkali

Abstract

The application discloses a method for preparing substitute alkali for sewage treatment by industrial waste alkali, and belongs to the technical field of sewage treatment and the technical field of solid waste resource utilization. The method comprises the following steps: waste alkali collection and component analysis; pretreatment; adding calcium-based and / or magnesium-based alkaline substances and active silico-aluminate mineral powder into the pretreated waste alkali liquid to perform component allocation and crystallization inhibition modification, and stirring and reacting to perform activation modification; adding stabilizers and dispersants to perform composite stabilization; drying and forming or directly filling to obtain substitute alkali products. In the application, the active silico-aluminate mineral and free calcium ions in the system generate calcium silicate hydrate gel in situ, the formed calcium carbonate and calcium sulfate microcrystals are three-dimensionally wrapped and suspended, the further growth and agglomeration and settlement of the calcium carbonate and calcium sulfate microcrystals are inhibited, the crystallization settlement and caking problems of calcium-based composite substitute alkali are solved, and the pH adjustment efficiency and flocculation adsorption performance of the products are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and specifically to a method for preparing a substitute alkali for wastewater treatment using industrial waste alkali. Background Technology

[0002] Industrial waste alkali is widely generated in various alkaline washing and impregnation processes in industries such as petrochemicals, textile printing and dyeing, and metal processing. It is usually highly alkaline and contains a large amount of pollutants, and direct discharge will cause serious environmental pollution. At present, the mainstream disposal methods for industrial waste alkali include high-temperature incineration, acid neutralization, and wet air oxidation. These methods generally have drawbacks such as high treatment costs, high energy consumption, easy generation of secondary pollution, or only solving the disposal problem without achieving effective resource utilization of alkali components, resulting in resource waste.

[0003] On the other hand, in the field of wastewater treatment, sodium hydroxide is a commonly used alkali agent for adjusting pH, promoting flocculation and sedimentation, and removing pollutants. However, it is expensive and classified as a hazardous chemical, posing safety risks during storage and use. Compound alkalis, with calcium hydroxide as the main component, can replace sodium hydroxide in wastewater treatment, significantly reducing costs while achieving comparable or even better treatment results. However, existing compound alkali products are mostly processed from natural minerals, failing to realize the resource utilization of industrial waste alkali.

[0004] Existing technologies include methods for preparing alternative alkalis by mixing industrial waste alkali with calcium-based alkaline substances. This approach can achieve waste-to-waste treatment and reduce processing costs. However, industrial waste alkali typically contains carbonate and sulfate ions. Upon addition of calcium-based alkaline substances, it rapidly reacts to form fine calcium carbonate and calcium sulfate crystals. These microcrystals are prone to agglomeration and sedimentation during storage, leading to product clumping and reduced flowability. When used in wastewater treatment, they can clog dosing pipes and metering pumps, severely affecting dosing accuracy and operational stability. Furthermore, these alternative alkalis have a relatively limited function in wastewater treatment, primarily acting as pH adjusters and lacking the ability to synergistically remove pollutants such as heavy metals and suspended solids. Therefore, this invention provides a method for preparing alternative alkalis for wastewater treatment using industrial waste alkali. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the present invention aims to provide a method for preparing a substitute alkali for wastewater treatment using industrial waste alkali. This method solves the agglomeration problem, produces a loose and porous powder, significantly improves the product's efficiency in removing heavy metals and suspended solids in wastewater treatment, and achieves synergistic effects of pH adjustment and flocculation adsorption.

[0006] This invention employs a combination of industrial waste alkali and calcium-based alkaline substances as its basic approach, addressing the issues of resource utilization of industrial waste alkali and cost reduction of alkali agents in wastewater treatment. To address the problems of product sedimentation, agglomeration, and pipe blockage caused by the crystallization of carbonate and sulfate ions in this combination, this invention introduces active aluminosilicate minerals as crystallization inhibitors and performance enhancers. These active aluminosilicate minerals react with calcium ions in the system to form a hydrated calcium silicate gel with a three-dimensional network structure. This gel not only encapsulates and suspends the already formed microcrystals of calcium carbonate and calcium sulfate, inhibiting their further growth and agglomeration, but also synergistically enhances the pH buffering capacity and flocculation adsorption performance of the substitute alkali, significantly improving the wastewater treatment effect of the product. This invention has advantages such as wide availability of raw materials, simple preparation process, excellent product performance, and low processing cost.

[0007] In a first aspect, the present invention provides a method for preparing a substitute alkali for wastewater treatment using industrial waste alkali, characterized by comprising the following steps: S1. Waste Alkali Collection and Composition Analysis: Collect industrial waste alkali and analyze the effective alkali content (calculated as NaOH), heavy metal content, suspended solids content and organic matter content in the waste alkali; S2. Pretreatment: The collected industrial waste alkali is subjected to solid-liquid separation to remove large particulate suspended solids and insoluble impurities; the separated waste alkali liquid is filtered to remove fine suspended solids. S3. Component Adjustment: Based on the component analysis results of step S1, calcium-based and / or magnesium-based alkaline substances are added to the pretreated waste alkaline solution to ensure that the final solid substitute alkali product contains OH-. - The effective alkali content reaches 25-45%; and active aluminosilicate mineral powder is added, the amount of which is 5-15% of the mass of the waste alkali solution; the components are fully mixed under stirring conditions; S4. Activation and Modification: The mixture obtained in step S3 is stirred and reacted at 50-90℃ for 30-120 minutes to fully activate the calcium-based alkaline substances and the effective components in the waste alkali. At the same time, the active aluminosilicate minerals and the free calcium ions in the system undergo a hydration-volcanic ash reaction to generate a calcium silicate hydration product gel with a three-dimensional network structure. This gel encapsulates and suspends the formed calcium carbonate and calcium sulfate microcrystals in a three-dimensional manner, inhibiting their further growth and agglomeration and sedimentation, thus obtaining an activated and modified alkali solution. S5. Composite stabilization: Add stabilizer and dispersant to the activated modified alkaline solution obtained in step S4, and continue stirring for 15-40 minutes to ensure that the stabilizer and dispersant are fully and evenly mixed with the alkaline solution; S6. Drying and molding: The composite alkali solution obtained in step S5 is dried to obtain a solid substitute alkali product; or the composite alkali solution obtained in step S5 is directly filled to obtain a liquid substitute alkali product.

[0008] Preferably, in step S1, the industrial waste alkali is selected from one or more of the following: petrochemical waste alkali solution, textile printing and dyeing mercerizing waste alkali solution, chemical fiber production waste alkali solution, hydrogen peroxide production waste alkali solution, and metal processing waste alkali solution.

[0009] Preferably, in step S3, the calcium-based alkaline substance is one or more of quicklime (CaO), hydrated lime (Ca(OH)2), or limestone powder; the magnesium-based alkaline substance is magnesium oxide (MgO) or magnesium hydroxide (Mg(OH)2); and the active aluminosilicate mineral is selected from one or more of metakaolin, zeolite powder, or diatomaceous earth.

[0010] Preferably, in step S5, the stabilizer is one or more of sodium carboxymethyl cellulose, xanthan gum, and polyvinyl alcohol; and the dispersant is one or more of sodium polyacrylate and sodium hexametaphosphate.

[0011] Preferably, in step S5, the amount of stabilizer added is 0.5-3% of the mass of the activated and modified alkali solution, and the amount of dispersant added is 0.2-2% of the mass of the activated and modified alkali solution.

[0012] Preferably, in step S6, the drying method is spray drying, drum drying or fluidized bed drying, the drying temperature is 80-200℃, and the product moisture content is ≤5%.

[0013] The present invention also provides a wastewater treatment substitute alkali prepared by the above method, wherein the wastewater treatment substitute alkali is a solid substitute alkali and comprises the following components by mass percentage: effective alkali (in OH-) - (Total) 25-45%; Calcium / magnesium active ingredients 15-35%; Active aluminosilicate minerals and their hydration products 5-15%; Stabilizer 0.5-3%; Dispersant 0.2-2%; Water and impurities as the balance, the sum of the above components is 100%.

[0014] Preferably, the pH value (1% aqueous solution) of the substitute alkali is 11.0-13.0, and the effective alkali content (as OH) is... - (Calculated) ≥25%.

[0015] This invention also provides the application of the above-mentioned substitute alkali for wastewater treatment in the treatment of acidic wastewater, wherein the substitute alkali is added to the acidic wastewater for pH adjustment, and the dosage is 0.4-2.0 kg / m³. 3 After stirring and reacting for 15-60 minutes, proceed to the subsequent processing steps.

[0016] In summary, the present invention has the following beneficial effects: First, this invention uses industrial waste alkali as the main raw material to prepare a substitute alkali for wastewater treatment, transforming industrial waste alkali, which originally required costly disposal, into a valuable wastewater treatment agent, thus achieving "waste treatment with waste" and resource recycling. The substitute alkali prepared by this invention can replace sodium hydroxide for wastewater treatment, reducing raw material costs by more than 50%, effectively lowering the agent procurement costs for wastewater treatment plants.

[0017] Secondly, this invention introduces active aluminosilicate minerals, causing them to react in situ with free calcium ions in the system to form a hydrated calcium silicate gel with a three-dimensional network structure. This gel encapsulates and suspends the already formed microcrystals of calcium carbonate and calcium sulfate, inhibiting their further growth and aggregation, thus fundamentally preventing the formation of large crystals. The product exhibits no sedimentation or clumping during long-term storage, maintaining good fluidity and solving the problem of existing calcium-based compound alkali substitutes easily clogging pipes and metering pumps.

[0018] Third, the substitute alkali prepared by this invention not only possesses stable alkalinity and good storage stability, but also, due to the abundant surface hydroxyl groups and large specific surface area of ​​the hydrated calcium silicate gel, endows the product with excellent proton buffering capacity. Under the premise of achieving the same wastewater treatment effect, the dosage of the substitute alkali of this invention is reduced by 18-25% compared to similar products without added active aluminosilicate minerals, and the pH adjustment efficiency is significantly improved.

[0019] Fourth, the substitute alkali prepared by this invention not only has excellent pH adjustment ability, but the hydrated calcium silicate gel and its negatively charged active sites can also bridge and adsorb suspended colloidal particles and heavy metal cations in sewage, forming a "flocculation-adsorption" co-precipitate with the gel as the core. Under the same dosage conditions, the suspended solids removal rate is 30-40% higher than that of conventional substitute alkali, and the heavy metal removal rate is 15-25% higher, achieving a synergistic effect of pH adjustment and flocculation adsorption.

[0020] Fifth, the preparation method of this invention has a simple process route, requires little equipment investment, and can treat industrial waste alkali from various sources, thus possessing good industrial application value. By selecting different drying methods such as spray drying, drum drying, or fluidized bed drying, both solid alkali substitute products and liquid alkali substitute products can be prepared, adapting to different needs. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The present invention will be further described in detail below with reference to the embodiments.

[0022] Example 1

[0023] This embodiment provides a method for preparing a substitute alkali for wastewater treatment using petrochemical waste alkali solution.

[0024] Weigh each raw material according to the following quantities: Industrial waste alkaline solution: Waste alkaline solution generated from the alkaline washing process of ethylene cracking gas in a petrochemical enterprise. After testing, the waste alkaline solution contained 8.5% NaOH, 3.2% Na2CO3, 0.5% sulfide, and 1.2% suspended solids.

[0025] Quicklime (CaO): Industrial grade, with an effective CaO content of ≥85%.

[0026] Quicklime (Ca(OH)2): Industrial grade, with an effective Ca(OH)2 content ≥90%.

[0027] Activated aluminosilicate mineral: 100 kg of metakaolin. The preparation method is as follows: 200 mesh kaolin is calcined at 800℃ for 2 hours for activation treatment. After calcination, the product is taken out and naturally cooled to room temperature in the air.

[0028] Stabilizer: Sodium carboxymethyl cellulose (CMC-Na), industrial grade.

[0029] Dispersant: Sodium hexametaphosphate, industrial grade.

[0030] The preparation steps of the above-mentioned substitute alkali are as follows: The substitute alkali in this embodiment is prepared according to the following steps: S1. Waste Alkali Collection and Composition Analysis: Collect 1000 kg of petrochemical waste alkali liquid, take samples for testing and analysis, and obtain the composition data of the waste alkali liquid; S2. Pretreatment: The collected waste alkaline solution is allowed to settle in a settling tank for 4 hours to remove large suspended solids and insoluble impurities; then the supernatant is filtered through a plate and frame filter press to remove fine suspended solids, resulting in pretreated waste alkaline solution. S3. Composition Adjustment: Based on the composition analysis results of step S1, add 120 kg of quicklime, 80 kg of hydrated lime, and 100 kg of metakaolin to the pretreated waste alkaline solution. Mix thoroughly under stirring conditions to adjust the alkalinity of the system to the target value, so that the effective alkali content (expressed as OH-) in the final solid substitute alkali product is achieved.- (Calculation) reached 32%; S4. Activation and modification: The mixture obtained in step S3 is stirred at 75°C for 60 minutes at a stirring speed of 80 rpm to promote the full reaction and activation of calcium-based alkaline substances and effective components in waste alkali. At the same time, metakaolin reacts with free calcium ions in the system to undergo a hydration-volcanic ash reaction, thereby generating calcium silicate hydration product gel, and finally obtaining activated and modified alkali solution. S5. Composite Stabilization: Add 8 kg of sodium carboxymethyl cellulose and 5 kg of sodium hexametaphosphate to the activated modified alkaline solution obtained in step S4, and continue stirring for 30 minutes to ensure that the stabilizer and dispersant are fully and evenly mixed with the alkaline solution; S6. Drying and Shaping: The composite alkali solution obtained in step S5 is dried in a spray drying tower with an inlet temperature of 180℃ and an outlet temperature of 85℃ until the product moisture content is ≤5%, yielding approximately 490 kg of solid substitute alkali product.

[0031] Test Example: Product Performance Testing The performance of the alkali substitute product prepared in this embodiment was tested, and the results are as follows:

[0032] Application example: Verification of the effect of wastewater treatment application The substitute alkali product prepared in this embodiment was used for pH adjustment treatment of acidic wastewater from a wastewater treatment plant in an electroplating industrial park. The raw water had a pH of 2.5-3.5, a COD of 300-500 mg / L, and contained Cu. 2+ Ni 2+ Heavy metal ions.

[0033] Treatment process: The substitute alkali prepared in this embodiment is added to the wastewater equalization tank at a dosage of 0.7-1.0 kg / m³. 3 After stirring and reacting for 30 minutes, the mixture is transferred to a flocculation sedimentation tank, where PAM flocculant is added to assist sedimentation.

[0034] Treatment results: The pH value of the effluent stabilized between 7.0 and 8.5, and Cu... 2+ The removal rate reached over 97%, Ni 2+ The removal rate reaches over 94%, the COD removal rate reaches over 68%, and the effluent quality meets the requirements of the "Electroplating Pollutant Discharge Standard" (GB21900-2008).

[0035] Compared with the control group using industrial-grade sodium hydroxide (caustic soda), the reagent cost of the alkali substitute in this embodiment was reduced by approximately 58% while achieving the same treatment effect.

[0036] Example 2

[0037] The difference between this embodiment and Embodiment 1 lies in the source of raw materials and the preparation conditions.

[0038] Weigh each raw material according to the following quantities: Industrial waste alkali solution: Mercerizing waste alkali solution from a textile printing and dyeing enterprise. After testing, the waste alkali solution contained 6.8% NaOH, 1.5% hemicellulose, and 0.8% suspended solids.

[0039] Quicklime (CaO): Industrial grade, with an effective CaO content of ≥85%.

[0040] Magnesium oxide (MgO): Industrial grade, with an effective MgO content of ≥80%.

[0041] Active aluminosilicate minerals: zeolite powder, fineness 200 mesh.

[0042] Stabilizer: Xanthan gum, industrial grade.

[0043] Dispersant: Sodium polyacrylate, number average molecular weight 8 million-12 million, industrial grade.

[0044] The preparation steps of the above-mentioned substitute alkali are as follows: S1. Waste alkali collection and composition analysis: Collect 1000 kg of mercerizing waste alkali liquid, take samples for testing and analysis; S2. Pretreatment: The collected waste alkaline solution is pretreated by sedimentation-filtration process. First, it is allowed to stand for 3 hours to settle, and then filtered through a bag filter. S3. Composition Adjustment: Add 150 kg of quicklime, 30 kg of magnesium oxide, and 120 kg of zeolite powder to the pretreated waste alkaline solution, and mix thoroughly under stirring conditions to ensure that the effective alkali content (expressed as OH⁻) in the final solid substitute alkali product is high. - (Calculation) reached 30%; S4. Activation and modification: The mixture obtained in step S3 is stirred at 80°C for 90 minutes at a stirring speed of 60 rpm. S5. Composite stabilization: Add 5 kg of xanthan gum and 3 kg of sodium polyacrylate to the activated modified alkaline solution obtained in step S4, and continue stirring for 25 minutes; S6. Drying and Shaping: The composite alkali solution obtained in step S5 is dried in a drum dryer at a temperature of 120°C to obtain approximately 430 kg of solid substitute alkali product.

[0045] Upon testing, the effective alkali content (expressed as OH-) of the substitute alkali product prepared in this embodiment was found to be... - The product has a content of 30.8% (calculated), a pH value (1% aqueous solution) of 12.3, and a water content of 4.0%. After 90 days of storage under sealed conditions at room temperature, the product showed no clumping or stratification and exhibited good fluidity.

[0046] The substitute alkali prepared in this embodiment was used for pH adjustment and decolorization treatment in a dyeing and printing wastewater treatment plant, with a dosage of 0.5-0.9 kg / m³. 3 The effluent pH value is stable at 7.0-8.0, the color removal rate reaches over 83%, and the reagent cost is reduced by about 52% compared to using caustic soda.

[0047] Example 3

[0048] This embodiment provides a method for preparing liquid substitute alkali.

[0049] Weigh each raw material according to the following quantities: Industrial waste alkali solution: Waste alkali solution generated during the production of viscose fiber by a chemical fiber production enterprise. After testing, the waste alkali solution contained 5.5% NaOH and 2.0% hemicellulose.

[0050] Quicklime (Ca(OH)2): Industrial grade, with an effective Ca(OH)2 content ≥90%.

[0051] Active aluminosilicate mineral: diatomaceous earth, fineness 250 mesh.

[0052] Stabilizer: Polyvinyl alcohol (PVA), type 2488, industrial grade.

[0053] Dispersant: Sodium hexametaphosphate, industrial grade.

[0054] The preparation steps of the above-mentioned substitute alkali are as follows: S1. Waste Alkali Collection and Composition Analysis: Collect 1000 kg of waste alkali liquid from chemical fibers, take samples for testing and analysis; S2. Pretreatment: The collected waste alkaline solution is filtered through a precision filter to remove suspended solids; S3. Composition Adjustment: Add 200 kg of slaked lime and 80 kg of diatomaceous earth to the pretreated waste alkaline solution, and mix thoroughly under stirring conditions to ensure that the effective alkali content (expressed as OH⁻) in the final liquid substitute alkali product is high. - (Calculation) reached approximately 8.9%; S4. Activation and modification: The mixture obtained in step S3 is stirred at 70°C for 50 minutes at a stirring speed of 100 rpm. S5. Composite Stabilization: Add 6 kg of polyvinyl alcohol and 4 kg of sodium hexametaphosphate to the activated modified alkaline solution obtained in step S4, and continue stirring for 20 minutes; S6. Product filling: After cooling the composite alkali solution obtained in step S5 to room temperature, it is directly filled and sealed to obtain the liquid substitute alkali product.

[0055] Testing revealed that the effective alkali content (expressed as OH⁻) of the liquid alkali substitute product prepared in this embodiment was [data missing]. -The concentration (calculated) was 8.9%, the pH value was 12.5, and the density was 1.25 g / cm³. 3 When stored at room temperature and in a sealed environment for 90 days, the product showed no stratification or sedimentation, demonstrating good storage stability.

[0056] Example 4

[0057] The difference between this embodiment and Embodiment 1 is that a functional additive is added to improve the wastewater treatment effect of the alkali substitute.

[0058] Weigh each raw material according to the following quantities: The same petrochemical waste alkaline solution as in Example 1 was used.

[0059] Active aluminosilicate mineral: metakaolin, fineness 300 mesh.

[0060] Functional additives: polyaluminum chloride (PAC, CAS No.: 1327-41-9) and ferrous sulfate (FeSO4·7H2O).

[0061] The preparation steps of the above-mentioned substitute alkali are as follows: Steps S1-S4 are the same as in Example 1.

[0062] S5. Composite Stabilization and Functionalization: Add 8 kg of sodium carboxymethyl cellulose, 5 kg of sodium hexametaphosphate, 10 kg of polyaluminum chloride and 5 kg of ferrous sulfate to the activated modified alkaline solution obtained in step S4, and continue stirring for 40 minutes to ensure that all components are fully mixed and homogeneous. S6. Drying and shaping: The composite alkali solution obtained in step S5 is spray-dried to obtain a functional substitute alkali product.

[0063] Testing revealed that the effective alkali content (expressed as OH⁻) of the functional alkali substitute product prepared in this embodiment was [data missing]. - The product has a total effective rate of 32.2% and combines multiple functions such as pH adjustment, flocculation and sedimentation, and heavy metal removal. When used to treat acidic wastewater containing heavy metals, under the same dosage conditions, the heavy metal removal rate is increased by 10-15 percentage points compared with the product in Example 1, and the COD removal rate is increased by 8-12 percentage points.

[0064] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. 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 are within the scope of the claims of the present invention.

Claims

1. A method for preparing a substitute alkali for wastewater treatment using industrial waste alkali, characterized in that, Includes the following steps: S1. Waste Alkali Collection and Composition Analysis: Collect industrial waste alkali and analyze the effective alkali content, heavy metal content, suspended solids content and organic matter content in the waste alkali; S2. Pretreatment: The collected industrial waste alkali is subjected to solid-liquid separation to remove large particulate suspended solids and insoluble impurities; the separated waste alkali liquid is filtered to remove fine suspended solids. S3. Component Adjustment: Based on the component analysis results of step S1, calcium-based and / or magnesium-based alkaline substances are added to the pretreated waste alkaline solution to ensure that the final solid substitute alkali product contains OH-. - The effective alkali content reaches 25-45%; and active aluminosilicate mineral powder is added, the amount of which is 5-15% of the mass of the waste alkali solution; the components are fully mixed under stirring conditions; S4. Activation and modification: The mixture obtained in S3 is stirred and reacted at 50-90℃ for 30-120 minutes to allow all components to react and be activated, thus obtaining an activated and modified alkaline solution; S5. Composite Stabilization: Add stabilizer and dispersant to the activated modified alkaline solution obtained in S4, and continue stirring to ensure that the stabilizer and dispersant are fully and evenly mixed with the alkaline solution; S6. Drying and molding: The composite alkali solution obtained in S5 is dried to obtain a solid substitute alkali product; or the composite alkali solution obtained in S5 is directly filled to obtain a liquid substitute alkali product.

2. The method for preparing a substitute alkali for wastewater treatment using industrial waste alkali according to claim 1, characterized in that, In S1, industrial waste alkali includes one or more of the following: petrochemical waste alkali solution, textile printing and dyeing mercerizing waste alkali solution, chemical fiber production waste alkali solution, hydrogen peroxide production waste alkali solution, and metal processing waste alkali solution.

3. The method for preparing a substitute alkali for wastewater treatment using industrial waste alkali according to claim 1, characterized in that, In S3, the calcium-based alkaline substance includes one or more of quicklime, hydrated lime, or limestone powder; the magnesium-based alkaline substance is magnesium oxide or magnesium hydroxide; and the active aluminosilicate mineral is selected from one or more of metakaolin, zeolite powder, or diatomaceous earth.

4. The method for preparing a substitute alkali for wastewater treatment using industrial waste alkali according to claim 1, characterized in that, In step S5, the stabilizer includes one or more of sodium carboxymethyl cellulose, xanthan gum, and polyvinyl alcohol; the dispersant includes one or more of sodium polyacrylate and sodium hexametaphosphate.

5. The method for preparing a substitute alkali for wastewater treatment using industrial waste alkali according to claim 1, characterized in that, In step S5, the amount of stabilizer added is 0.5-3% of the mass of the activated and modified alkali solution, and the amount of dispersant added is 0.2-2% of the mass of the activated and modified alkali solution.

6. The method for preparing a substitute alkali for wastewater treatment using industrial waste alkali according to claim 1, characterized in that, In step S6, the drying method is spray drying, drum drying or fluidized bed drying, the drying temperature is 80-200℃, and the product moisture content is ≤5%.

7. The method for preparing a substitute alkali for wastewater treatment using industrial waste alkali according to claim 1, characterized in that, In step S5, a functional additive is also added. The functional additive is one or more of polyaluminum chloride, ferrous sulfate, and polyferric sulfate, and the amount added is 1-8% of the mass of the activated and modified alkali solution.

8. A substitute alkali for wastewater treatment prepared by the method according to any one of claims 1-6, characterized in that, The alkali substitute for wastewater treatment is a solid alkali substitute, and contains the following components by mass percentage: With OH - The effective alkali content is 25-45%; Calcium / magnesium active ingredients 15-35%; 5-15% active aluminosilicate minerals; Stabilizer 0.5-3%; Dispersant 0.2-2%; Water and impurities are the balance; the sum of the above components is 100%.

9. The alternative alkali for wastewater treatment according to claim 8, characterized in that, The substitute alkali is prepared as a 1% aqueous solution with a pH value of 11.0-13.

0.

10. The application of the substitute alkali for wastewater treatment as described in claim 8 or 9 in the treatment of acidic wastewater, characterized in that, The substitute alkali is added to acidic wastewater for pH adjustment at a dosage of 0.4-2.0 kg / m³. 3 After stirring and reacting for 15-60 minutes, proceed to the subsequent processing steps.

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