Method for producing high-purity polyaluminum chloride

Abstract

The embodiment of the invention provides a method for producing high-purity polyaluminum chloride, which comprises the following steps: mixing an aluminum-containing compound with an acid solution, and carrying out dissolution reaction to obtain an aluminum-containing intermediate solution; adding a polymerization additive into the aluminum-containing intermediate solution, and carrying out polymerization reaction without external heating to obtain a high-purity polyaluminum chloride solution; part of the high-purity polyaluminum chloride solution serves as the aluminum-containing compound to be recycled, and the other part of the high-purity polyaluminum chloride solution serves as a finished product. According to the embodiment of the invention, by optimizing the reaction raw materials, controlling the reaction conditions and adopting a cyclic utilization mode, the technical problem of improving the purity and the quality stability of the PAC is solved, and meanwhile, green and efficient production is realized.

Description

Technical Field

[0001] This application relates to the field of light metal metallurgy technology, and in particular to a method for producing high-purity polyaluminum chloride. Background Technology

[0002] With the acceleration of industrialization and urbanization, water pollution has become increasingly serious, leading to a growing demand for efficient water treatment agents. Polyaluminum chloride (PAC), a classic inorganic polymeric flocculant, is widely used in drinking water purification, industrial wastewater treatment, and domestic sewage treatment due to its advantages such as rapid hydrolysis, large floc size, and rapid sedimentation. However, traditional PAC production processes have several shortcomings: firstly, the use of low-quality aluminum ore as raw material results in high impurity content, low effective components, and excessive insoluble matter in the product; secondly, the reaction process is relatively crude, with insufficient precision in controlling key parameters such as temperature, pressure, and time, leading to large fluctuations in product basicity and inconsistent quality. Furthermore, traditional production processes are lengthy, energy-intensive, and have low yields, generating large amounts of waste residue and waste liquid, resulting in resource waste and serious environmental pollution. Summary of the Invention

[0003] This application provides a method for producing high-purity polyaluminum chloride to solve the following technical problem: how to improve the purity and quality stability of polyaluminum chloride (PAC).

[0004] This application provides a method for producing high-purity polyaluminum chloride, including:

[0005] An aluminum-containing compound is mixed with an acidic solution to undergo a dissolution reaction, yielding an aluminum-containing intermediate solution.

[0006] A polymerization aid is added to the aluminum-containing intermediate solution, and a polymerization reaction is carried out under conditions without external heating to obtain a high-purity polyaluminum chloride solution.

[0007] A portion of the high-purity polyaluminum chloride solution is recycled as the aluminum-containing compound, while the remainder is used as the finished product.

[0008] Optionally, the aluminum-containing compound is selected from one or more of aluminum hydroxide, sodium aluminate, calcium aluminate, aluminum oxide, aluminum powder, aluminum shavings, aluminum ash, aluminum hydroxide gel, potassium aluminate, and magnesium aluminate.

[0009] Optionally, the acidic solution is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, oxalic acid, citric acid, and lactic acid, and the mass concentration of the acidic solution is 10-40%.

[0010] Optionally, the polymerization aid is selected from one or more of the following: mother liquor from sintered alumina, carbonic acid mother liquor, polyacrylamide, polyvinyl alcohol, polyethylene glycol, chitosan, gelatin, starch, cellulose, and lignin.

[0011] Optionally, the temperature of the dissolution reaction is from room temperature to 120°C, and the reaction time is from 1 to 8 hours.

[0012] Optionally, the polymerization reaction is carried out at a temperature of room temperature to 100°C, for a reaction time of 0.1 to 2 hours, and at a pH value of 3.0 to 5.0 at the reaction endpoint.

[0013] Optionally, the mass ratio of the aluminum-containing compound to the acidic solution is 1:2 to 1:10.

[0014] Optionally, the mass of the polymerization aid is 1% to 10% of the mass of the aluminum-containing intermediate solution.

[0015] Optionally, a portion of the high-purity polyaluminum chloride solution accounts for 10% to 30% of the total mass of the high-purity polyaluminum chloride solution.

[0016] Optionally, the aluminum-containing compound is aluminum hydroxide, the acidic solution is hydrochloric acid with a concentration of 20% to 30%, the polymerization aid is a mother liquor of sintered alumina seed solution, and the temperature of the mother liquor of sintered alumina seed solution is 40 to 90°C.

[0017] The technical solutions provided in this application have the following advantages compared with the prior art:

[0018] This application provides a method for producing high-purity polyaluminum chloride (PAC). First, this method involves mixing an aluminum-containing compound with an acidic solution for a leaching reaction to generate an aluminum-containing intermediate solution. This process, through precise control of reaction conditions, avoids the problem of impurities introduced by the use of low-quality aluminum ore in traditional processes, thereby improving the purity of PAC from the source. Second, during the polymerization reaction stage, polymerization auxiliaries are added, and polymerization is carried out using the heat of the reaction system itself, eliminating the need for external heating. This heat-free polymerization method not only reduces energy consumption but also reduces fluctuations in product basicity through stable reaction conditions, improving quality stability. Simultaneously, the rapid reaction characteristics of liquid-phase polymerization further enhance production efficiency. Finally, by recycling a portion of the high-purity PAC solution, the production process is made continuous and stable. The recycled PAC solution, as a supplement to the aluminum-containing compound, further optimizes the composition of the reaction system, ensuring consistent product quality. This recycling method not only improves resource utilization but also reduces production costs. In summary, the embodiments of this application have solved the technical problems of improving the purity and quality stability of PAC by optimizing the reaction raw materials, controlling the reaction conditions, and adopting a recycling approach, while achieving green and efficient production. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings required in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other related drawings can be derived from these drawings without creative effort.

[0021] Figure 1 This is a flowchart illustrating a method for producing high-purity polyaluminum chloride, provided as an embodiment of this application. Detailed Implementation

[0022] To more clearly illustrate the purpose, technical solutions, and advantages of the embodiments of this application, the technical solutions of this embodiment will be described in detail below with reference to the accompanying drawings. Please note that the mentioned embodiments are merely examples and not all possible implementations. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0023] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1 to 6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "comprise" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0024] Figure 1 This is a flowchart illustrating a method for producing high-purity polyaluminum chloride, provided as an embodiment of this application.

[0025] Please see Figure 1 This application provides a method for producing high-purity polyaluminum chloride, comprising:

[0026] S1. Mix the aluminum-containing compound with an acidic solution to carry out a dissolution reaction, and obtain an aluminum-containing intermediate solution;

[0027] S2. Add a polymerization aid to the aluminum-containing intermediate solution and carry out a polymerization reaction under conditions without external heating to obtain a high-purity polyaluminum chloride solution.

[0028] S3. A portion of the high-purity polyaluminum chloride solution is recycled as the aluminum-containing compound, and the remaining portion of the high-purity polyaluminum chloride solution is used as the finished product.

[0029] Aluminum-containing compounds: These are compounds containing aluminum and are one of the raw materials for producing high-purity polyaluminum chloride (PAC). Commonly used aluminum-containing compounds include aluminum hydroxide, sodium aluminate, and calcium aluminate. Acidic solutions: These are solutions with acidic properties used to react with aluminum-containing compounds and promote the dissolution of aluminum. Commonly used acidic solutions include hydrochloric acid, sulfuric acid, and nitric acid. Polymerization aids: These are substances that promote polymerization reactions and help improve the degree of polymerization and stability of polyaluminum chloride. Commonly used polymerization aids include mother liquor from sintering alumina and carbonic acid mother liquor.

[0030] Aluminum-containing compounds undergo a chemical reaction in acidic solutions, dissolving aluminum from the compounds to form an aluminum-containing intermediate solution. This process requires controlled reaction temperature and time to ensure complete aluminum dissolution while avoiding the introduction of impurities. A polymerization aid is added to the aluminum-containing intermediate solution, and aluminum ions polymerize under the action of the aid without external heating, forming a high-purity polyaluminum chloride solution. The polymerization aid promotes the polymerization of aluminum ions by providing a reaction site or regulating the reaction environment. A portion of the high-purity polyaluminum chloride solution is recycled as a supplement to the aluminum-containing compounds, achieving material recycling while ensuring product quality stability. This process reduces raw material consumption and lowers production costs. The high-purity polyaluminum chloride produced by this method can be widely used in drinking water treatment, industrial wastewater treatment, and domestic sewage treatment.

[0031] In some embodiments, the aluminum-containing compound is selected from one or more of aluminum hydroxide, sodium aluminate, calcium aluminate, aluminum oxide, aluminum powder, aluminum shavings, aluminum ash, aluminum hydroxide gel, potassium aluminate, and magnesium aluminate.

[0032] Different aluminum-containing compounds exhibit varying reaction characteristics and product quality under acidic conditions. For example, aluminum hydroxide readily dissolves under acidic conditions, producing intermediate solutions with high purity; while sodium aluminate is suitable for specific chemical reaction pathways and can provide different reaction mechanisms. Different aluminum-containing compounds are suitable for different water quality conditions and treatment requirements. For instance, aluminum hydroxide is suitable for applications requiring high product purity, while calcium aluminate is suitable for applications requiring high reaction rates.

[0033] In some embodiments, the acidic solution is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, oxalic acid, citric acid, and lactic acid, and the mass concentration of the acidic solution is 10-40%.

[0034] Acidic solutions provide an acidic environment for the dissolution of aluminum, allowing it to be released from aluminum-containing compounds. Different acidic solutions have different acidity and reaction characteristics. For example, hydrochloric acid has a fast reaction rate and is suitable for rapid dissolution, while sulfuric acid has a high solubility and is suitable for handling sparingly soluble aluminum-containing compounds. Different acidic solutions are suitable for different reaction conditions and applications. For example, hydrochloric acid is suitable for situations requiring high reaction rates, while phosphoric acid is suitable for situations requiring high product stability.

[0035] As an example:

[0036] Example 1: Using 10% hydrochloric acid is suitable for scenarios where the rate of aluminum dissolution is less critical and impurity control is important.

[0037] Example 2: Using sulfuric acid with a mass concentration of 15% is suitable for medium-requirement scenarios where a balance needs to be struck between dissolution rate and impurity content.

[0038] Example 3: Using nitric acid with a mass concentration of 20% is suitable for scenarios that require a certain level of dissolution efficiency and can tolerate a slightly higher level of impurities.

[0039] Example 4: Using phosphoric acid with a mass concentration of 25% is suitable for scenarios where product stability is required and a slower dissolution rate is acceptable.

[0040] Example 5: Using hydrobromic acid with a mass concentration of 30% is suitable for scenarios where the dissolution rate is critical and impurity control is generally not a priority.

[0041] Example 6: Using hydrofluoric acid with a mass concentration of 35% is suitable for special scenarios where the dissolution rate of aluminum is required to be extremely high, but its strong corrosiveness should be noted.

[0042] Example 7: Using oxalic acid with a mass concentration of 40% is suitable for scenarios with high requirements for product environmental friendliness and who can accept a slower dissolution rate.

[0043] Example 8: Citric acid with a mass concentration of 12% is suitable for scenarios with high requirements for product biocompatibility, but the dissolution rate is relatively slow.

[0044] Example 9: Using lactic acid with a mass concentration of 18% is suitable for scenarios where the product's gentleness is required and a slightly slower dissolution rate is acceptable.

[0045] Example 10: Using acetic acid with a mass concentration of 22% is suitable for scenarios with high requirements for product environmental friendliness and a moderate dissolution rate.

[0046] In some embodiments, the polymerization aid is selected from one or more of the following: mother liquor from sintered alumina, carbonic acid mother liquor, polyacrylamide, polyvinyl alcohol, polyethylene glycol, chitosan, gelatin, starch, cellulose, and lignin.

[0047] Polymerization aids act as bridging agents in polymerization reactions, promoting the polymerization of aluminum ions. Different polymerization aids possess different chemical properties and mechanisms of action. For example, the mother liquor from sintered alumina seed solution can provide a stable source of aluminum ions, promoting the polymerization reaction; while polyacrylamide can increase the degree of polymerization of polyaluminum chloride through adsorption and bridging effects. Different polymerization aids are suitable for different polymerization reaction conditions and application scenarios. For instance, the mother liquor from sintered alumina seed solution is suitable for applications requiring high product stability, while polyacrylamide is suitable for applications requiring a high degree of polymerization.

[0048] In some embodiments, the dissolution reaction is carried out at a temperature ranging from room temperature to 120°C for a reaction time of 1 to 8 hours.

[0049] Leaching reaction: This refers to the process in which aluminum-containing compounds react in an acidic solution, causing aluminum to dissolve from the compounds. The leaching reaction is a crucial step in the production of high-purity polyaluminum chloride (PAC), dissolving aluminum from the compounds into the acidic solution to form an aluminum-containing intermediate solution. The efficiency and effectiveness of this process directly affect the quality of subsequent polymerization reactions and the purity of the product. Temperature, ranging from room temperature to 120°C, significantly impacts the rate and efficiency of the leaching reaction. At lower temperatures (e.g., room temperature), the reaction rate is slower, but this reduces the dissolution of impurities and improves product purity. As the temperature increases, the reaction rate accelerates, and the leaching efficiency of aluminum improves; however, excessively high temperatures may lead to the dissolution of impurities, affecting product quality. The reaction time, ranging from 1 to 8 hours, determines the degree of aluminum dissolution. Shorter reaction times (e.g., 1 hour) may not completely dissolve aluminum, resulting in an incomplete reaction; while longer reaction times (e.g., 8 hours) ensure sufficient aluminum dissolution, but excessively long times increase production costs and energy consumption. The synergistic effect of temperature and time: At lower temperatures (e.g., 40-60°C), extending the reaction time (e.g., 6-8 hours) ensures sufficient aluminum dissolution while reducing the introduction of impurities. At higher temperatures (e.g., 80-120°C), shortening the reaction time (e.g., 1-3 hours) can improve production efficiency, but strict temperature control is required to avoid impurity dissolution. As an example:

[0050] Example 1: Reaction at 40℃ for 8 hours results in sufficient aluminum dissolution and low impurity content, suitable for high-purity products. Example 2: Reaction at 50℃ for 6 hours results in high dissolution efficiency and moderate impurities, suitable for general water treatment. Example 3: Reaction at 60℃ for 5 hours results in rapid dissolution but a slight increase in impurities, suitable for medium-purity requirements. Example 4: Reaction at 70℃ for 4 hours results in significant dissolution efficiency and good impurity control, suitable for high-efficiency production scenarios. Example 5: Reaction at 80℃ for 3 hours results in rapid dissolution but slightly more impurities, suitable for rapid production needs. Example 6: Reaction at 90℃ for 2.5 hours results in high-efficiency dissolution but slightly more impurities, suitable for high-efficiency production. Example 7: Reaction at 100℃ for 2 hours results in extremely rapid dissolution but more impurities, suitable for rapid processing where purity requirements are not high. Example 8: Reaction at 110℃ for 1.5 hours results in rapid dissolution but more impurities, suitable for emergency treatment scenarios. Example 9: Reacting at 120℃ for 1 hour results in the fastest dissolution and the most impurities, suitable for ultra-fast processing needs. Example 10: Reacting at room temperature for 8 hours results in slow dissolution and the fewest impurities, suitable for scenarios requiring extremely high purity.

[0051] In some embodiments, the polymerization reaction is carried out at a temperature ranging from room temperature to 100°C, for a reaction time ranging from 0.1 to 2 hours, and at a final pH value ranging from 3.0 to 5.0.

[0052] Polymerization reaction: refers to the process by which aluminum ions polymerize under the action of polymerization aids to form a high-purity polyaluminum chloride solution. pH value at the reaction endpoint: refers to the acidity or alkalinity of the solution when the polymerization reaction is complete, usually measured using a pH meter.

[0053] The temperature of the polymerization reaction has a significant impact on the reaction rate and product stability. Lower temperatures (e.g., room temperature) can reduce side reactions and improve product purity; higher temperatures (e.g., 100°C) can accelerate the reaction rate and shorten the reaction time, but may lead to decreased product stability. The reaction time determines the degree of polymerization of aluminum ions. Shorter reaction times (e.g., 0.1 hours) may lead to incomplete polymerization, affecting product performance; longer reaction times (e.g., 2 hours) ensure sufficient polymerization, but increase energy consumption and production costs. The pH value at the reaction endpoint has a significant impact on the degree of polymerization and stability of polyaluminum chloride. The polymerization reaction is most effective when the pH value is between 3.0 and 5.0, resulting in a higher degree of polymerization and greater product stability. Too low a pH value may lead to incomplete polymerization, while too high a pH value may lead to product decomposition. Example support:

[0054] The reaction time is as follows: 0.1 hours at room temperature, pH 3.0, suitable for rapid production. 0.5 hours at 30°C, pH 3.5, suitable for medium-efficiency production. 1 hour at 50°C, pH 4.0, suitable for general production. 1.5 hours at 70°C, pH 4.5, suitable for high-efficiency production. 2 hours at 100°C, pH 5.0, suitable for high-efficiency production. 0.8 hours at 40°C, pH 3.2, suitable for applications requiring high purity. 1.2 hours at 60°C, pH 3.8, suitable for applications requiring high stability. 1.8 hours at 80°C, pH 4.8, suitable for applications requiring high degree of polymerization. 0.3 hours at 20°C, pH 3.1, suitable for applications requiring low energy consumption. 1.0 hour at 90°C, pH 4.2, suitable for applications requiring both high production efficiency and high product quality.

[0055] By precisely controlling the polymerization reaction conditions, high-purity polyaluminum chloride suitable for different water treatment needs can be produced. For example, lower temperature and shorter reaction time conditions are suitable for drinking water treatment, while higher temperature and longer reaction time conditions are suitable for industrial wastewater treatment.

[0056] In some embodiments, the mass ratio of the aluminum-containing compound to the acidic solution is 1:2 to 1:10.

[0057] Mass ratio: This refers to the mass ratio of the aluminum-containing compound to the acidic solution. It is used to control the amount of reactants to ensure the completeness of the reaction and the quality of the product. The mass ratio of the aluminum-containing compound to the acidic solution has a significant impact on the efficiency of the dissolution reaction and the purity of the product. A lower mass ratio (e.g., 1:10) ensures an excess of acidic solution, improving the dissolution efficiency of aluminum, but may lead to waste of acidic solution; a higher mass ratio (e.g., 1:2) can reduce the amount of acidic solution used, lowering costs, but may result in incomplete dissolution of aluminum, affecting product quality. Example support:

[0058] A 1:2 mass ratio of aluminum compound to acidic solution is suitable for scenarios with high cost control requirements. A 1:3 mass ratio is suitable for medium cost control needs. A 1:4 mass ratio is suitable for scenarios with certain leaching efficiency requirements. A 1:5 mass ratio is suitable for scenarios with high leaching efficiency requirements. A 1:6 mass ratio is suitable for scenarios with high product quality requirements. A 1:7 mass ratio is suitable for scenarios with high impurity control requirements. A 1:8 mass ratio is suitable for scenarios with high production efficiency requirements. A 1:9 mass ratio is suitable for scenarios with low energy consumption requirements. A 1:10 mass ratio is suitable for scenarios with extremely high purity requirements. A 1:2.5 mass ratio is suitable for scenarios requiring a balance between cost and efficiency.

[0059] By adjusting the mass ratio of the aluminum compound to the acidic solution, high-purity polyaluminum chloride suitable for different water treatment needs can be produced. For example, a higher mass ratio is suitable for scenarios with high cost control requirements, while a lower mass ratio is suitable for scenarios with high purity requirements.

[0060] In some embodiments, the polymerization aid is 1% to 10% of the mass of the aluminum-containing intermediate solution.

[0061] The mass ratio of polymerization auxiliaries has a significant impact on the efficiency of the polymerization reaction and the stability of the product. A lower mass ratio (e.g., 1%) can reduce the amount of polymerization auxiliaries used, lowering costs, but may lead to incomplete polymerization and affect product stability; a higher mass ratio (e.g., 10%) can improve the efficiency of the polymerization reaction and ensure product stability, but will increase costs. Example support:

[0062] The polymerization aid is 1% of the aluminum-containing intermediate solution by mass, suitable for scenarios with high cost control requirements. 2% of the aluminum-containing intermediate solution by mass, suitable for medium cost control needs. 3% of the aluminum-containing intermediate solution by mass, suitable for scenarios with certain polymerization efficiency requirements. 4% of the aluminum-containing intermediate solution by mass, suitable for scenarios with high polymerization efficiency requirements. 5% of the aluminum-containing intermediate solution by mass, suitable for scenarios with high product quality requirements. 6% of the aluminum-containing intermediate solution by mass, suitable for scenarios with high impurity control requirements. 7% of the aluminum-containing intermediate solution by mass, suitable for scenarios with high production efficiency requirements. 8% of the aluminum-containing intermediate solution by mass, suitable for scenarios with low energy consumption requirements. 9% of the aluminum-containing intermediate solution by mass, suitable for scenarios with extremely high purity requirements. 10% of the aluminum-containing intermediate solution by mass, suitable for scenarios with the highest requirements for stability and efficiency.

[0063] By adjusting the mass ratio of polymerization aids, high-purity polyaluminum chloride suitable for different water treatment needs can be produced. For example, a lower mass ratio is suitable for scenarios with high cost control requirements, while a higher mass ratio is suitable for scenarios with high stability and efficiency requirements.

[0064] In some embodiments, a portion of the high-purity polyaluminum chloride solution accounts for 10% to 30% of the total mass of the high-purity polyaluminum chloride solution.

[0065] Recycling ratio: This refers to the proportion of the mass of a portion of the high-purity polyaluminum chloride solution to the total mass of the high-purity polyaluminum chloride solution. It is used to control the amount recycled, ensuring material recycling efficiency and product quality. The recycling ratio has a significant impact on material recycling efficiency and product quality. A lower recycling ratio (e.g., 10%) can reduce the amount recycled and lower operational complexity, but may lead to material waste; a higher recycling ratio (e.g., 30%) can improve material recycling efficiency and reduce waste, but will increase operational complexity and energy consumption. Example support:

[0066] A recycling rate of 10% is suitable for scenarios with low operational complexity requirements. A recycling rate of 12% is suitable for medium operational complexity requirements. A recycling rate of 15% is suitable for scenarios with certain requirements for material utilization efficiency. A recycling rate of 18% is suitable for scenarios with high requirements for material utilization efficiency. A recycling rate of 20% is suitable for scenarios with high requirements for product quality. A recycling rate of 22% is suitable for scenarios with high requirements for impurity control. A recycling rate of 25% is suitable for scenarios with high requirements for production efficiency. A recycling rate of 28% is suitable for scenarios with low energy consumption requirements. A recycling rate of 30% is suitable for scenarios with the highest requirements for material utilization efficiency. A recycling rate of 13% is suitable for scenarios that balance cost and efficiency requirements.

[0067] By adjusting the recycling ratio, high-purity polyaluminum chloride suitable for different water treatment needs can be produced. For example, a lower recycling ratio is suitable for scenarios with lower operational complexity requirements, while a higher recycling ratio is suitable for scenarios with higher material utilization efficiency requirements.

[0068] In some embodiments, the aluminum-containing compound is aluminum hydroxide, the acidic solution is hydrochloric acid with a concentration of 20% to 30%, the polymerization aid is a mother liquor of sintered alumina seed solution, and the temperature of the mother liquor of sintered alumina seed solution is 40 to 90°C.

[0069] Aluminum hydroxide undergoes a dissolution reaction in the presence of hydrochloric acid, generating an aluminum-containing intermediate solution. The concentration of hydrochloric acid significantly affects the dissolution efficiency; a concentration range of 20% to 30% ensures sufficient dissolution of aluminum while minimizing the introduction of impurities. The mother liquor from the sintering alumina seed solution acts as a bridging agent in the polymerization reaction, promoting the polymerization of aluminum ions. Temperature significantly affects the efficiency of the polymerization reaction and the stability of the product; a temperature range of 40 to 90°C ensures complete polymerization while preventing side reactions. Example support:

[0070] Using 20% ​​hydrochloric acid and a sintering mother liquor at 40℃ is suitable for scenarios with low energy consumption requirements. Using 22% hydrochloric acid and a sintering mother liquor at 50℃ is suitable for medium energy consumption requirements. Using 24% hydrochloric acid and a sintering mother liquor at 60℃ is suitable for scenarios with certain production efficiency requirements. Using 26% hydrochloric acid and a sintering mother liquor at 70℃ is suitable for scenarios with high production efficiency requirements. Using 28% hydrochloric acid and a sintering mother liquor at 80℃ is suitable for scenarios with high product quality requirements. Using 30% hydrochloric acid and a sintering mother liquor at 90℃ is suitable for scenarios with the highest degree of polymerization requirements. Using 21% hydrochloric acid and a sintering mother liquor at 45℃ is suitable for scenarios requiring a balance between cost and efficiency. Using 23% hydrochloric acid and a sintering mother liquor at 55℃ is suitable for scenarios with high impurity control requirements. Using 25% hydrochloric acid and a sintering-grade alumina seed mother liquor at 65℃ is suitable for scenarios where a balance between energy consumption and efficiency is required. Using 27% hydrochloric acid and a sintering-grade alumina seed mother liquor at 75℃ is suitable for scenarios with higher requirements for production efficiency and product quality.

[0071] By adjusting the dosage and conditions of aluminum hydroxide, hydrochloric acid, and the mother liquor from the sintering process of alumina, high-purity polyaluminum chloride suitable for different water treatment needs can be produced. For example, lower concentrations of hydrochloric acid and lower temperatures of the mother liquor from the sintering process are suitable for scenarios with lower energy consumption requirements, while higher concentrations of hydrochloric acid and higher temperatures of the mother liquor from the sintering process are suitable for scenarios with higher requirements for production efficiency and product quality.

[0072] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0073] Example 1

[0074] Dissolution process: Take 100g of aluminum hydroxide and mix it with hydrochloric acid at a [Al] / [Cl] molar ratio of 3.0, controlling the hydrochloric acid concentration to 25%. Add a portion of polyaluminum chloride solution, the proportion of which is 20% of the volume of hydrochloric acid solution. Control the reaction temperature to 95℃ and the reaction time to 3 hours.

[0075] Polymerization process: After the reaction is complete, sintered alumina seed mother liquor is added as a polymerization aid. The temperature of the aid is controlled at 65℃, the polymerization temperature is controlled at 80℃, the pH value at the reaction endpoint is controlled at 4.0, and the polymerization reaction time is 0.2 hours.

[0076] Recycling: 1030 grams of high-purity polyaluminum chloride solution was obtained, of which 150 grams were returned to the leaching process and mixed with new aluminum hydroxide and hydrochloric acid to continue the leaching reaction; the remaining 880 grams were used as the finished product.

[0077] Example 2

[0078] Dissolution process: Take 100g of aluminum hydroxide and mix it with hydrochloric acid at a [Al] / [Cl] molar ratio of 2.8, controlling the hydrochloric acid concentration to 22%. Add a portion of polyaluminum chloride solution, the proportion of which is 25% of the volume of the hydrochloric acid solution. Control the reaction temperature to 90℃ and the reaction time to 3.5 hours.

[0079] Polymerization process: After the reaction is complete, add carbonic acid mother liquor as a polymerization aid, control the aid temperature at 70℃, the polymerization temperature at 75℃, control the pH value at the reaction endpoint at 4.2, and the polymerization reaction time at 0.3 hours.

[0080] Recycling: 1035 grams of high-purity polyaluminum chloride solution was obtained, of which 160 grams were returned to the leaching process and mixed with new aluminum hydroxide and hydrochloric acid to continue the leaching reaction; the remaining 875 grams were used as the finished product.

[0081] Example 3

[0082] Dissolution process: Take 100g of aluminum hydroxide and mix it with hydrochloric acid at a [Al] / [Cl] molar ratio of 3.2, controlling the hydrochloric acid concentration to 28%. Add a portion of polyaluminum chloride solution, which is 15% of the volume of the hydrochloric acid solution. Control the reaction temperature at 100℃ and the reaction time to 2.5 hours.

[0083] Polymerization process: After the reaction is complete, sintered alumina seed mother liquor is added as a polymerization aid. The temperature of the aid is controlled at 55℃, the polymerization temperature is controlled at 85℃, the pH value at the reaction endpoint is controlled at 3.8, and the polymerization reaction time is 0.4 hours.

[0084] Recycling: 1040 grams of high-purity polyaluminum chloride solution was obtained, of which 170 grams were returned to the leaching process and mixed with new aluminum hydroxide and hydrochloric acid to continue the leaching reaction; the remaining 870 grams were used as the finished product.

[0085] Example 4

[0086] Dissolution process: Take 100g of aluminum hydroxide and mix it with hydrochloric acid at a [Al] / [Cl] molar ratio of 2.6, controlling the hydrochloric acid concentration to 24%. Add a portion of polyaluminum chloride solution, the proportion of which is 18% of the volume of the hydrochloric acid solution. Control the reaction temperature to 85℃ and the reaction time to 4 hours.

[0087] Polymerization process: After the reaction is complete, add carbonic acid mother liquor as a polymerization aid, control the aid temperature at 60℃, the polymerization temperature at 70℃, control the pH value at the reaction endpoint at 4.1, and the polymerization reaction time at 0.25 hours.

[0088] Recycling: 1032 grams of high-purity polyaluminum chloride solution was obtained, of which 155 grams were returned to the leaching process and mixed with new aluminum hydroxide and hydrochloric acid to continue the leaching reaction; the remaining 877 grams were used as the finished product.

[0089] Example 5

[0090] Dissolution process: Take 100g of aluminum hydroxide and mix it with hydrochloric acid at a [Al] / [Cl] molar ratio of 3.1, controlling the hydrochloric acid concentration to 26%. Add a portion of polyaluminum chloride solution, the proportion of which is 22% of the volume of the hydrochloric acid solution. Control the reaction temperature to 92℃ and the reaction time to 3.2 hours.

[0091] Polymerization process: After the reaction is complete, sintered alumina seed mother liquor is added as a polymerization aid. The temperature of the aid is controlled at 68℃, the polymerization temperature is controlled at 82℃, the pH value at the reaction endpoint is controlled at 4.0, and the polymerization reaction time is 0.35 hours.

[0092] Recycling: 1038 grams of high-purity polyaluminum chloride solution was obtained, of which 165 grams were returned to the leaching process and mixed with new aluminum hydroxide and hydrochloric acid to continue the leaching reaction; the remaining 873 grams were used as the finished product.

[0093] Example 6

[0094] Dissolution process: Take 100g of aluminum hydroxide and mix it with hydrochloric acid at a [Al] / [Cl] molar ratio of 2.7, controlling the hydrochloric acid concentration to 23%. Add a portion of polyaluminum chloride solution, the proportion of which is 28% of the volume of the hydrochloric acid solution. Control the reaction temperature to 98℃ and the reaction time to 2.8 hours.

[0095] Polymerization process: After the reaction is complete, add carbonic acid mother liquor as a polymerization aid, control the aid temperature at 72℃, the polymerization temperature at 78℃, control the pH value at the reaction endpoint at 4.3, and the polymerization reaction time at 0.45 hours.

[0096] Recycling: 1042 grams of high-purity polyaluminum chloride solution was obtained, of which 180 grams were returned to the leaching process and mixed with new aluminum hydroxide and hydrochloric acid to continue the leaching reaction; the remaining 862 grams were used as the finished product.

[0097] Comparative Example 1

[0098] Dissolution process: Take 100g of aluminum hydroxide and mix it with hydrochloric acid at a [Al] / [Cl] molar ratio of 3.0, controlling the hydrochloric acid concentration to 25%. No polyaluminum chloride solution was added. The reaction temperature was controlled at 95℃, and the reaction time was 3 hours.

[0099] Polymerization process: After the reaction is complete, sintered alumina seed mother liquor is added as a polymerization aid. The temperature of the aid is controlled at 65℃, the polymerization temperature is controlled at 80℃, the pH value at the reaction endpoint is controlled at 4.0, and the polymerization reaction time is 0.2 hours.

[0100] No recycling was carried out: 980 grams of polyaluminum chloride solution was obtained, and all of it was used as the finished product.

[0101] Comparative Example 2

[0102] Dissolution process: Take 100g of aluminum hydroxide and mix it with hydrochloric acid at a [Al] / [Cl] molar ratio of 3.0, controlling the hydrochloric acid concentration to 25%. Add a portion of polyaluminum chloride solution, the proportion of which is 20% of the volume of hydrochloric acid solution. Control the reaction temperature to 95℃ and the reaction time to 3 hours.

[0103] Polymerization process: After the reaction is complete, no polymerization aids are added, and the polymerization reaction is carried out directly. The polymerization temperature is controlled at 80℃, the pH value at the reaction endpoint is controlled at 4.0, and the polymerization reaction time is 0.2 hours.

[0104] No recycling was carried out: 970 grams of polyaluminum chloride solution was obtained, and all of it was used as the finished product.

[0105] Comparative Example 3

[0106] Dissolution process: Take 100g of aluminum hydroxide and mix it with hydrochloric acid at a [Al] / [Cl] molar ratio of 3.0, controlling the hydrochloric acid concentration to 25%. Add a portion of polyaluminum chloride solution, the proportion of which is 20% of the volume of hydrochloric acid solution. Control the reaction temperature to 95℃ and the reaction time to 3 hours.

[0107] Polymerization process: After the reaction is complete, sintered alumina seed mother liquor is added as a polymerization aid. The temperature of the aid is controlled at 65℃, the polymerization temperature is controlled at 80℃, the pH value at the reaction endpoint is controlled at 4.0, and the polymerization reaction time is 0.2 hours.

[0108] No recycling was carried out: 990 grams of polyaluminum chloride solution was obtained, and all of it was used as the finished product.

[0109] Effect data: The effect data of Examples 1 to 6 and Comparative Examples 1 to 4 are shown in Table 1.

[0110] Experimental methods for obtaining effect data:

[0111] 1. Product purity test

[0112] Instrumentation: A high-precision atomic absorption spectrometer (AAS) was used. Method: A high-purity polyaluminum chloride solution was diluted to an appropriate concentration, and the aluminum content was determined by AAS to calculate the product purity. The purity is expressed as a percentage; higher purity indicates better product quality.

[0113] 2. Basicity test

[0114] Instruments: A pH meter and conductivity meter were used. Method: A high-purity polyaluminum chloride solution was diluted to a 1% aqueous solution, and its pH value and conductivity were measured. The basicity was calculated using a formula. The result is expressed as a percentage; the higher the basicity, the better the flocculation effect of the product.

[0115] 3. Stability Test

[0116] Instrument: UV-Vis spectrophotometer. Method: High-purity polyaluminum chloride solution was allowed to stand at different temperatures (20℃, 40℃, 60℃) for 24 hours, and the absorbance changes at different time points were measured. Qualitative descriptions such as "good," "excellent," "fair," and "poor" were used; higher stability indicates more stable performance during storage and use.

[0117] 4. Cost Reduction Test

[0118] Method: Calculate the amount of raw materials used, energy consumed, and waste generated during the production process, and compare it with traditional processes. Express the results as a percentage; the greater the cost reduction, the better the economic efficiency of the process.

[0119] 5. Waste Reduction Test

[0120] Method: Weigh the amount of waste generated during the production process and compare it with that of traditional processes. The percentage reduction indicates a greater reduction in waste, signifying better environmental friendliness of the process.

[0121] Table 1

[0122]

[0123] The above effect data table provides a clear comparison of the differences between various embodiments and comparative examples. The following conclusions can be drawn:

[0124] This application provides a method for producing high-purity polyaluminum chloride (PAC). By optimizing reaction conditions and process flow, it significantly improves product quality, reduces production costs, and minimizes environmental pollution. Experimental data shows that the products from Examples 1 to 6 all have a purity of over 99.3%, a basicity between 65% and 72%, and good to excellent stability, making them suitable for various water treatment scenarios. By recycling a portion of the high-purity PAC solution back to the leaching process, production costs are reduced by 20% to 26%, and waste residue is reduced by 30% to 36%.

[0125] In contrast, Comparative Examples 1 to 3, due to the lack of recycling or the absence of polymerization aids, had lower product purity and basicity, poorer stability, and their effects on cost reduction and waste reduction were not significant.

[0126] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for producing high-purity polyaluminum chloride, comprising: An aluminum-containing compound is mixed with an acidic solution to carry out a dissolution reaction, yielding an aluminum-containing intermediate solution. A polymerization aid is added to the aluminum-containing intermediate solution, and a polymerization reaction is carried out under conditions without external heating to obtain a high-purity polyaluminum chloride solution. A portion of the high-purity polyaluminum chloride solution is recycled as the aluminum-containing compound, while the remainder is used as the finished product.

2. The method according to claim 1, characterized in that, The aluminum-containing compound is selected from one or more of aluminum hydroxide, sodium aluminate, calcium aluminate, aluminum oxide, aluminum powder, aluminum shavings, aluminum ash, aluminum hydroxide gel, potassium aluminate, and magnesium aluminate.

3. The method according to claim 1, characterized in that, The acidic solution is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, oxalic acid, citric acid, and lactic acid, and the mass concentration of the acidic solution is 10-40%.

4. The method according to claim 1, characterized in that, The polymerization aid is selected from one or more of the following: mother liquor from sintering alumina, carbonic acid mother liquor, polyacrylamide, polyvinyl alcohol, polyethylene glycol, chitosan, gelatin, starch, cellulose, and lignin.

5. The method according to claim 1, characterized in that, The dissolution reaction is carried out at temperatures ranging from room temperature to 120°C, and for a reaction time of 1 to 8 hours.

6. The method according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature ranging from room temperature to 100°C, for a reaction time of 0.1 to 2 hours, and at a final pH value of 3.0 to 5.

0.

7. The method according to claim 1, characterized in that, The mass ratio of the aluminum-containing compound to the acidic solution is 1:2 to 1:

10.

8. The method according to claim 1, characterized in that, The mass of the polymerization aid is 1% to 10% of the mass of the aluminum-containing intermediate solution.

9. The method according to claim 1, characterized in that, The mass of the high-purity polyaluminum chloride solution accounts for 10% to 30% of the total mass of the high-purity polyaluminum chloride solution.

10. The method according to claim 1, characterized in that, The aluminum-containing compound is aluminum hydroxide, the acidic solution is hydrochloric acid with a concentration of 20% to 30%, the polymerization aid is a mother liquor of sintered alumina seed solution, and the temperature of the mother liquor of sintered alumina seed solution is 40 to 90°C.

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