Preparation method of polyaluminum magnesium chloride

Abstract

The invention discloses a preparation method of polyaluminum magnesium chloride, and belongs to the technical field of inorganic high-molecular polymer preparation. A preparation method of polyaluminum magnesium chloride comprises the following steps: S1, mixing aluminum-containing waste hydrochloric acid, aluminum-magnesium-containing waste residues and low-degree hydrochloric acid, and stirring until the aluminum-magnesium-containing waste residues react completely to obtain a first mixed solution; s2, adding calcium aluminate into the first mixed solution, and separating after complete reaction to obtain polyaluminum magnesium chloride. The polyaluminum magnesium chloride is synthesized from industrial waste aluminum-containing waste hydrochloric acid, aluminum-magnesium-containing waste residues and low-degree hydrochloric acid through a specific method, on one hand, the industrial waste can be effectively recycled, and resource waste is avoided; on one hand, compared with common polyaluminum magnesium chloride, the polyaluminum magnesium chloride synthesized by the method has better turbidity removal rate and decolorization effect on alkaline printing and dyeing wastewater, pollutants in the wastewater can be efficiently removed, and the treatment cost of the printing and dyeing wastewater is reduced.

Description

Technical Field

[0001] This invention belongs to the field of inorganic polymer preparation technology, specifically relating to a method for preparing polyaluminum magnesium chloride. Background Technology

[0002] Dyeing and printing wastewater is typically alkaline due to its technological characteristics, exhibiting high concentration, complex composition, high color, and poor biodegradability. Traditional methods for treating this wastewater mainly include physicochemical methods (adsorption, flocculation, ion exchange, ultrafiltration, dialysis, etc.), biological methods (activated sludge process, anaerobic process), and biofilm methods. However, these methods often suffer from low treatment efficiency, high sludge production, severe membrane fouling, biological instability, and low overall efficiency. Polyaluminum chloride (PAC) magnesium flocculant is currently mainly prepared by adding magnesium oxide during the PAC preparation process. Its application in treating alkaline dyeing and printing wastewater has shown initial success. Existing technology CN109081412 A discloses a method for preparing PAC magnesium by adding magnesium oxide to PAC, which is then used for treating dyeing and printing wastewater. However, this method has high production costs, and after reducing the wastewater color to 30-179, it is difficult to further reduce the color.

[0003] Furthermore, the production of methane and chlor-alkali chemicals in chemical plants often produces low-grade hydrochloric acid as a byproduct. Due to its low acidity, low-grade hydrochloric acid is considered substandard. The preparation of electrolytic foil generates a large amount of aluminum-containing waste hydrochloric acid, and the production of calcium ammonium nitrate (compound fertilizer) produces a large amount of aluminum-containing waste slag. With the gradual upgrading of national environmental protection policies, the requirements for the treatment of waste are becoming increasingly stringent, and waste disposal often incurs huge costs and results in resource waste. Therefore, it is essential to achieve comprehensive utilization of the aforementioned waste products. Summary of the Invention

[0004] To address the problems existing in the prior art, the primary objective of this invention is to provide a method for preparing polyaluminum magnesium chloride.

[0005] Another object of the present invention is to provide a polyaluminum magnesium chloride.

[0006] Another object of the present invention is to provide an application of polyaluminum magnesium chloride in the treatment of alkaline dyeing and printing wastewater.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing polyaluminum magnesium chloride includes the following steps: S1. Mix aluminum-containing waste hydrochloric acid, aluminum-magnesium waste residue, and low-temperature hydrochloric acid, and stir until the aluminum-magnesium waste residue reacts completely to obtain the first mixture. S2. Add calcium aluminate to the first mixture, and after the reaction is complete, separate to obtain polyaluminum magnesium chloride; The acidity of the first mixture is 1-3%; The composition of the aluminum-magnesium waste residue, by mass percentage of oxides, includes 12-14 wt% aluminum oxide, 3-5 wt% calcium oxide, and 3-8 wt% magnesium oxide. The aluminum-containing waste hydrochloric acid comprises, by mass percentage, 8.5-9.5 wt% aluminum oxide. The silica content in the calcium aluminate, expressed as an oxide by mass percentage, is 2-5%.

[0008] The aluminum-containing waste hydrochloric acid, aluminum-magnesium-containing waste residue, and low-concentration hydrochloric acid used in this invention are all industrial wastes from aluminum foil production. These are first mixed and reacted to obtain a first mixed solution. This first mixed solution is then reacted with calcium aluminate to prepare polyaluminum magnesium chloride. In this invention, the acidity of the first mixed solution must be controlled between 1% and 3% to ensure that the prepared polyaluminum magnesium chloride has good turbidity removal and decolorization effects. If the acidity of the first mixed solution is too high, silicic acid will be generated in the reaction system. Silicic acid will cause difficulties in subsequent solid-liquid separation, resulting in a high content of insoluble matter in the polyaluminum magnesium chloride.

[0009] Specifically, S1 also includes testing the acidity of aluminum-containing waste hydrochloric acid and the acidity of low-grade hydrochloric acid.

[0010] This invention calculates the dosage of aluminum-magnesium waste residue based on the acidity of aluminum-containing waste hydrochloric acid and low-acid hydrochloric acid to ensure complete reaction of the aluminum-magnesium waste residue.

[0011] Specifically, S1 also includes testing the content of aluminum oxide and magnesium oxide in the first mixture by mass percentage as oxides, as well as the acidity.

[0012] Preferably, the acidity of the first mixture is 1 to 2.5%.

[0013] By controlling the acidity of the first mixture within this range, the comprehensive utilization of aluminum-magnesium waste residue and low-level hydrochloric acid can be maximized.

[0014] Preferably, in S1, the mass ratio of aluminum-containing waste hydrochloric acid, aluminum-magnesium waste slag, and low-grade hydrochloric acid is (1~1.5):1:(2~2.5), the acidity of the aluminum-containing waste hydrochloric acid is 0.5~1.5%, the acidity of the low-grade hydrochloric acid is 10%~20%, and the composition of each substance in the aluminum-magnesium waste slag by mass percentage as oxides includes an aluminum oxide content of 12~14wt%, a calcium oxide content of 3~5wt%, and a magnesium oxide content of 3~8wt%.

[0015] More preferably, in S1, the mass ratio of aluminum-containing waste hydrochloric acid, aluminum-magnesium waste slag, and low-grade hydrochloric acid is (1~1.2):1:(2~2.3), the acidity of the aluminum-containing waste hydrochloric acid is 0.5%~1.5%, the acidity of the low-grade hydrochloric acid is 10~20%, and the composition of each substance in the aluminum-magnesium waste slag by mass percentage as oxides includes an aluminum oxide content of 12~14wt%, a calcium oxide content of 3~5wt%, and a magnesium oxide content of 3~8wt%.

[0016] More preferably, in S1, the mass ratio of aluminum-containing waste hydrochloric acid, aluminum-magnesium waste slag, and low-grade hydrochloric acid is 1:1:2, the acidity of the aluminum-containing waste hydrochloric acid is 0.5%~1.5%, the acidity of the low-grade hydrochloric acid is 10~20%, and the composition of each substance in the aluminum-magnesium waste slag by mass percentage as oxides includes an aluminum oxide content of 12~14wt%, a calcium oxide content of 3~5wt%, and a magnesium oxide content of 3~8wt%.

[0017] Preferably, in S1, the reaction temperature is 80~90℃.

[0018] Preferably, the components in the first mixture, by mass percentage based on oxides, include an alumina content of 5-7 wt% and an acidity of 1-3%.

[0019] More preferably, the components in the first mixture, by mass percentage based on oxides, include an alumina content of 5-6 wt% and an acidity of 1-3%.

[0020] Preferably, the magnesium oxide content in the first mixture, expressed as an oxide by mass percentage, is 0.75~2wt%.

[0021] More preferably, the magnesium oxide content in the first mixture, expressed as an oxide by mass percentage, is 1 to 2 wt%.

[0022] Preferably, the mass ratio of calcium aluminate to the first mixed solution is (1~1.25):10.

[0023] The mass ratio of calcium aluminate to the first mixed solution in this invention can be adjusted according to the required basicity of polyaluminum magnesium chloride.

[0024] Preferably, in S2, the reaction temperature is 80~90℃. For example, it can be 80℃, 82℃, 84℃, 85℃, 86℃, 88℃, 90℃, etc., but is not limited to the values ​​listed.

[0025] More preferably, in S2, the temperature is raised to 82~88°C.

[0026] More preferably, in S2, the temperature is raised to 85°C.

[0027] It should be noted that in step S1, the temperature of the reaction system decreases during the reaction of aluminum-containing waste hydrochloric acid, aluminum-magnesium-containing waste slag, and low-concentration hydrochloric acid. Therefore, it is necessary to raise the temperature again in step S2. Since calcium aluminate powder contains calcium oxide, the reaction of calcium oxide with the acid in the first mixture releases a large amount of heat, which causes the temperature to rise rapidly. Therefore, controlling the temperature at 80-90℃ ensures complete dissolution of calcium aluminate while preventing boiling over caused by temperature rise during the dissolution process.

[0028] This invention also protects the polyaluminum magnesium chloride prepared by the above preparation method.

[0029] Preferably, the polyaluminum magnesium chloride contains 10-10.5 wt% alumina, 1-2 wt% magnesium oxide, and 60-70% basicity.

[0030] This invention also protects the application of the above-mentioned polyaluminum magnesium chloride in the treatment of alkaline dyeing and printing wastewater.

[0031] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes aluminum-containing waste hydrochloric acid, aluminum-magnesium waste residue, and low-concentration hydrochloric acid to prepare polyaluminum magnesium chloride. The polyaluminum magnesium chloride is prepared using hydroxylated aluminum (Al₂O₃). 3+ ) and magnesium (Mg 2+ Using [aluminum-magnesium alloy] as the core, a multinucleated polymer is formed through bridging. The process of this invention is simple and easy to operate. The aluminum-magnesium waste residue itself contains magnesium oxide, eliminating the need for additional magnesium oxide or magnesium chloride. The introduction of aluminum-containing waste hydrochloric acid significantly reduces the amount of calcium aluminate required, improving production efficiency and lowering costs.

[0032] This invention comprehensively utilizes aluminum-containing waste hydrochloric acid and aluminum-magnesium waste residue to convert them into polyaluminum magnesium chloride flocculant with high added value. It integrates existing resources, realizes the comprehensive utilization of waste resources, improves resource utilization rate, and reduces the environmental protection treatment pressure on enterprises for solid waste and waste liquid.

[0033] Compared to ordinary polyaluminum magnesium chloride, the polyaluminum magnesium chloride prepared by the method of this invention exhibits superior coagulation enhancement, turbidity removal rate, and decolorization effects on alkaline dyeing and printing wastewater. Using the polyaluminum magnesium chloride of this invention can efficiently remove pollutants from wastewater, reducing water treatment costs for dyeing and printing enterprises. Attached Figure Description

[0034] Figure 1 This is a structural diagram of the apparatus corresponding to the preparation method of the present invention.

[0035] Attached image captions: 1-Low-grade hydrochloric acid tank, 2-Aluminum-containing waste hydrochloric acid tank, 3-Reaction vessel, 4-Belt conveyor, 5-Aluminum slag storage area, 6-Plate and frame filter press, 7-Finished product tank. Detailed Implementation

[0036] The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0037] The aluminum-magnesium waste residue used in this invention comes from the affiliated production unit, Ruyuan Dongyangguang Chemical Foil Company. During the production of calcium ammonium nitrate (compound fertilizer), a large amount of neutralization residue is generated. First, the neutralization residue is added to a slurry tank, and lime slurry (containing magnesium) is added to remove phosphorus from the residue. Then, liquid alkali is added, controlling the caustic ratio of liquid alkali to aluminum hydroxide to be 1.6-2.5. After stirring, the neutralization residue is fully dissolved. The slurry from the slurry tank is then pumped to a plate and frame filter press. After thorough filtration, the filtrate is pumped into a filtrate buffer tank. The filtrate then enters a crystallization tank via a heat exchanger, where aluminum hydroxide is added and thoroughly mixed before being pumped into a decomposition tank. Under the action of aluminum hydroxide seed crystals, decomposition begins, yielding aluminum hydroxide crystals. The decomposition liquid is pumped back into the plate and frame filter press, and the filter residue is the aluminum hydroxide semi-finished product, which is the aluminum-magnesium waste residue used in this invention.

[0038] The semi-finished aluminum hydroxide product (containing aluminum and magnesium waste residue) mainly consists of calcium sulfate (CaSO4), aluminum hydroxide (Al(OH)3), calcium phosphate (Ca3(PO4)2), and aluminum phosphate (AlPO4). After slurrying and alkali dissolution of the neutralized residue, most of the calcium and phosphorus are removed. Following crystallization, decomposition, and pressure filtration, the semi-finished aluminum hydroxide product (containing aluminum waste residue) is obtained. Therefore, the main components of the aluminum waste residue are aluminum hydroxide (containing water of crystallization) and small amounts of calcium and phosphorus. ICP testing was used to determine the composition and content of the aluminum-magnesium waste residue. The composition of each substance in the aluminum-magnesium waste residue, by mass percentage of oxides, includes 12-14 wt% aluminum oxide, 3-5 wt% calcium oxide, 3-8 wt% magnesium oxide, and the remainder being bound water.

[0039] The aluminum-containing waste hydrochloric acid used in this invention comes from Ruyuan Dongyangguang Chemical Foil Company. The composition content of the aluminum-containing waste hydrochloric acid, calculated as the mass percentage of oxides, was tested using the national standard GB / T22627-2022. The Al2O3 content in the aluminum-containing waste hydrochloric acid is 9.0~9.2wt%, and the acidity of the aluminum-containing waste hydrochloric acid is 1.5%.

[0040] Calcium aluminate: Manufacturer: Guiyang Xiuwen County Suda New Environmental Protection Materials Co., Ltd., Brand: YuDC2107. The tested silica content, calculated as oxides by mass percentage, is 3.64%.

[0041] Low-grade hydrochloric acid is a byproduct of the methane industry, with an acidity of 10% to 20%.

[0042] In this invention, the methods for testing alumina and basicity in aluminum-containing waste hydrochloric acid, the first mixed solution, and the product polyaluminum magnesium chloride are as follows: The test method for alumina content is as follows: The analysis method for the corresponding indicators in the national standard "GB / T22627-2022 Water Treatment Agents Polyaluminum Chloride" is used for testing. Alumina testing method: Refer to the analytical steps described in section 6.3.1.3 of the national standard "GB / T22627-2022 Polyaluminum Chloride for Water Treatment". The calculation formula is the same as the formula used in section 6.3.1.4 of the national standard "GB / T22627-2022 Polyaluminum Chloride for Water Treatment".

[0043] Basicity test method: Refer to the analytical steps described in section 6.5.3 of the national standard "GB / T22627-2022 Polyaluminum Chloride for Water Treatment", wherein the preparation of test solution A refers to section 6.3.1.3.1 of the standard. The calculation formula refers to the formula in section 6.5.4 of the national standard "GB / T22627-2022 Polyaluminum Chloride for Water Treatment".

[0044] In this invention, the methods for determining and calculating the acidity of low-grade hydrochloric acid, aluminum-containing waste hydrochloric acid, and the first mixed solution are as follows, or refer to the national standard "GB / T320-2025 Industrial Synthetic Hydrochloric Acid": Test method: Pipette approximately 3 mL of the sample into a conical flask containing 15 mL of water and weigh it (accurate to 0.0001 g). Mix well and weigh again, accurate to 0.0001 g. Add (2-3) drops of bromocresol green indicator solution (1 g / L) to the sample, and titrate with 1 mol / L sodium hydroxide standard solution until the solution changes from yellow to blue, which is the endpoint.

[0045] Total acidity, expressed as a mass fraction (%), is calculated using the following formula: =

[0046] In the formula: V is the volume of the sodium hydroxide standard titration solution in milliliters (mL); c is the accurate concentration of the sodium hydroxide standard titration solution in moles per liter (mol / L); m0 is the mass of the sample in grams (g); M is the molar mass of hydrogen chloride in grams per mole (g / mol) (M=36.46).

[0047] It should be noted that, in this invention, the magnesium oxide content in the first mixture and polyaluminum magnesium chloride was obtained by ICP testing.

[0048] Example 1 A method for preparing polyaluminum magnesium chloride includes the following steps: S1. After mixing low-grade hydrochloric acid with aluminum-containing waste hydrochloric acid, the acidity of the mixture was tested. Based on the acidity, the dosage of aluminum-magnesium waste residue was calculated. Aluminum-containing waste hydrochloric acid, aluminum-magnesium waste residue, and low-grade hydrochloric acid were added to a reaction vessel in a mass ratio of 1:1:2. Steam was turned on, and the temperature was raised to 85°C. The mixture was stirred until the aluminum-magnesium waste residue was completely dissolved, yielding the first mixture. Samples were taken to test the content of aluminum chloride and magnesium oxide, as well as the acidity. The first mixture contained 6 wt% aluminum oxide, 1.65 wt% magnesium oxide, and had an acidity of 1.5%.

[0049] S2. Raise the temperature to 85℃, add calcium aluminate to the first mixed solution, with a mass ratio of calcium aluminate to the first solution of 1:10. Turn on the steam, maintain the temperature at 100℃, and stir the reaction for 1 hour. Filter the mixture through a plate and frame filter press, and collect the liquid phase to obtain polyaluminum magnesium chloride. The polyaluminum magnesium chloride has an alumina content of 10.5 wt%, a magnesium oxide content of 1.5 wt%, and a basicity of 70%.

[0050] Example 2 This embodiment provides a method for preparing polyaluminum magnesium chloride, which differs from Example 1 in that the mass ratio of aluminum-containing waste hydrochloric acid, aluminum-magnesium waste residue, and low-degree hydrochloric acid is 1.1:1:2.2. The first mixed solution contains 5.5 wt% alumina, 1.5 wt% magnesium oxide, and has an acidity of 2.1%. The polyaluminum magnesium chloride contains 10.5 wt% alumina, 1.4 wt% magnesium oxide, and has a basicity of 65.5%.

[0051] Example 3 This embodiment provides a method for preparing polyaluminum magnesium chloride, which differs from Example 1 in that the mass ratio of aluminum-containing waste hydrochloric acid, aluminum-magnesium waste residue, and low-concentration hydrochloric acid is 1.1:1:2.3. The first mixed solution contains 5.4 wt% alumina, 1.5 wt% magnesium oxide, and has an acidity of 2.4%. The polyaluminum magnesium chloride contains 10.5 wt% alumina, 1.3 wt% magnesium oxide, and has a basicity of 60%.

[0052] Example 4 This embodiment provides a method for preparing polyaluminum magnesium chloride, which differs from Example 1 in that the mass ratio of aluminum-containing waste hydrochloric acid, aluminum-magnesium waste residue, and low-concentration hydrochloric acid is 1.1:1.1:2.1. The first mixed solution contains 5.8 wt% alumina, 1.5 wt% magnesium oxide, and has an acidity of 1.4%. The polyaluminum magnesium chloride contains 10.5 wt% alumina, 1.4 wt% magnesium oxide, and has a basicity of 70%.

[0053] Example 5 This embodiment provides a method for preparing polyaluminum magnesium chloride, which differs from Example 1 in that the mass ratio of aluminum-containing waste hydrochloric acid, aluminum-magnesium waste residue, and low-degree hydrochloric acid is 1.1:1:2. The first mixed solution contains 5.9 wt% alumina, 1.4 wt% magnesium oxide, and has an acidity of 1.3%. The polyaluminum magnesium chloride contains 10.5 wt% alumina, 1.3 wt% magnesium oxide, and has a basicity of 70%.

[0054] Comparative Example 1 Commercially available polyaluminum chloride: Polyaluminum chloride contains 10.2 wt% alumina and has a basicity of 60%.

[0055] Comparative Example 2 Commercially available ordinary polyaluminum magnesium chloride: Its production method is to add magnesium chloride solution to polyaluminum chloride, and the resulting liquid polyaluminum magnesium chloride has an alumina content of 10.5 wt%, a magnesium oxide content of 1.5 wt%, and a basicity of 60%.

[0056] Comparative Example 3 The difference between this comparative example and Example 1 is that the mass ratio of aluminum-containing waste hydrochloric acid, aluminum-magnesium-containing waste slag, and low-degree hydrochloric acid is 1:1:3. The first mixed solution contains 5.1% alumina, 1.3% magnesium oxide, and has an acidity of 6.45%. The polyaluminum magnesium chloride contains 9.6% alumina, 1.0 wt% magnesium oxide, and has a basicity of 54%.

[0057] Comparative Example 4 The difference between this comparative example and Example 1 is that the mass ratio of aluminum-containing waste hydrochloric acid, aluminum-magnesium-containing waste slag, and low-degree hydrochloric acid is 0.95:1:1. The first mixed solution contains 7.8% alumina, 2.1% magnesium oxide, and has an acidity of 0.23%. The polyaluminum magnesium chloride contains 10.65% alumina, 0.68% magnesium oxide, and has a basicity of 71.2%.

[0058] Performance testing Test Method: Take 1L of alkaline dyeing wastewater from a textile dyeing company in Dongguan (9 groups). The pH of the alkaline dyeing wastewater is 12, the COD is 1269, the color is 120, and the turbidity is 100. Take 1g of each of the products from Examples 1-5 and Comparative Examples 1-4 and dilute to 100mL in a volumetric flask. These test solutions are X1-X9 respectively. Take 1g of polyacrylamide (PAM) and dilute to 1 / 1000, then dilute to 1000mL. This is test solution A. Add 3mL of each of test solutions X1-X9 to the wastewater and stir at 500r / min for 30s. Then add 1mL of test solution A and stir at 100r / min for 5min. Let it stand for 10min to settle, and take the supernatant for testing. The results are shown in Table 1.

[0059] Colorimetric testing method: Take 50 mL of clear water sample into a colorimetric tube. If the water sample is turbid, centrifuge it first and take the supernatant for measurement. If the water sample color is too high, take a smaller amount of water sample, dilute it with pure water, and then measure the color. Multiply the result by the dilution factor to obtain the water sample colorimetric value. Separately, take 11 colorimetric tubes and add 0, 0.50, 1.00, 1.50, 2.00, 2.50, 3.00, 3.50, 4.00, 4.50, and 5.00 mL of platinum-cobalt standard solution, respectively. Add pure water to the mark and shake well. Prepare a standard color series with colorimetric values ​​of 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 degrees. This standard color series can be used for a long time, but evaporation and contamination of the solution should be prevented. In a well-lit area, place the water sample and the standard colorimetric tube side by side, using white paper as a background. Allow light to pass through the colorimetric tube from the bottom up, and observe the colorimetric reading vertically downwards from the tube opening. Record the corresponding colorimetric value of the standard tube. If the water sample used for testing is diluted, multiply the result by the dilution factor to obtain the original water sample colorimetric value.

[0060] COD testing method: Under strongly acidic conditions (sulfuric acid medium) and with a silver sulfate catalyst, potassium dichromate oxidizes the reducing substances (mainly organic matter) in the water sample. The remaining potassium dichromate is then back-titered with ferrous ammonium sulfate, and the COD value is calculated based on the consumption.

[0061] Turbidity testing method: Add the sample to the sample cell up to the graduation mark (approximately 30 mL), carefully holding the top of the sample cell during operation. Then close the sample cell lid. Holding the lid, wipe the outside of the sample cell clean of water droplets and fingerprints with a soft paper towel. Holding the lid, place the sample cell containing the sample into the instrument's sample cell holder and close the lid of the sample cell holder. The instrument will display a reading; once the reading stabilizes, this is the turbidity of the sample. Record the measurement data.

[0062] Table 1 Wastewater treatment results of the examples and comparative examples

[0063] Table 2. Coagulation results of the examples and comparative examples.

[0064] During the above processing, the coagulation speed of each embodiment and comparative example is as follows: Embodiment 1 > Embodiment 4 > Embodiment 5 > Embodiment 2 > Embodiment 3 > Comparative Example 4 > Comparative Example 2 > Comparative Example 3 > Comparative Example 1.

[0065] As shown in Tables 1 and 2, the polyaluminum chloride produced by this invention using aluminum-containing waste hydrochloric acid, aluminum-magnesium-containing waste residue, and low-concentration hydrochloric acid is of high quality because it contains Mg. 2+ Mg 2+ With Al 3+ Synergistically forming a composite flocculant, it is added to alkaline dyeing wastewater, Mg 2+ With OH - Rapid formation of magnesium hydroxide precipitate, Mg 2+ The higher the basicity, the more precipitate is formed, and the faster the coagulation speed of polyaluminum magnesium chloride. This invention provides enhanced coagulation, superior turbidity removal, and decolorization effects for alkaline dyeing wastewater. Using the polyaluminum magnesium chloride of this invention can efficiently remove pollutants from wastewater, reducing water treatment costs for dyeing and printing enterprises.

[0066] As shown in Table 1, when the polyaluminum magnesium chloride prepared according to this invention is used as a water treatment agent to treat alkaline dyeing and printing wastewater, with a dosage of 30 mg / L, stirring at 100 r / min for 5 min, and settling for 10 min, the decolorization rate is ≥94.58% and the COD removal rate is ≥88.17%. Furthermore, the polyaluminum magnesium chloride prepared according to this invention can reduce the color of wastewater to single digits, demonstrating excellent decolorization effects. Compared to commercially available polyaluminum chloride and polyaluminum magnesium chloride, the polyaluminum magnesium chloride prepared according to this invention exhibits superior treatment effects for alkaline dyeing and printing wastewater.

[0067] It should be noted that, due to the acidity of the first mixture not being within the acceptable range, the products prepared in Comparative Examples 3 and 4 had a higher content of insoluble matter. Such products with a high content of insoluble matter can cause pipe blockage or pipe corrosion during actual use, and will not be able to form effective flocs during flocculation, resulting in poor quality flocs and slower settling speed.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for producing a polyaluminum magnesium chloride, characterized by, The method comprises the following steps: S1. mixing aluminum-containing waste hydrochloric acid, aluminum-magnesium-containing waste residue and low-grade hydrochloric acid, stirring until the aluminum-magnesium-containing waste residue is completely reacted to obtain a first mixed solution; S2. adding calcium aluminate to the first mixed solution, and separating to obtain polyaluminum magnesium chloride after the reaction is completed; The acidity of the first mixed solution is 1-3%; The composition of the aluminum-magnesium-containing waste residue in terms of mass percentage of oxides includes 12-14wt% of aluminum oxide content, 3-5wt% of calcium oxide content, and 3-8wt% of magnesium oxide content; The aluminum-containing waste hydrochloric acid contains 8.5-9.5wt% of aluminum oxide; The calcium aluminate contains 2-5% of silicon dioxide in terms of mass percentage of oxides.

2. The preparation method according to claim 1, characterized in that, In S1, the mass ratio of the aluminum-containing waste hydrochloric acid, the aluminum-magnesium-containing waste residue and the low-grade hydrochloric acid is (1-1.5):1:(2-2.5); the acidity of the aluminum-containing waste hydrochloric acid is 0.5-1.5%, the acidity of the low-grade hydrochloric acid is 10-20%, and the composition of the aluminum-magnesium-containing waste residue in terms of mass percentage of oxides includes 12-14wt% of aluminum oxide content, 3-5wt% of calcium oxide content, and 3-8wt% of magnesium oxide content.

3. The preparation method according to claim 1, characterized in that, In S1, the reaction temperature is 80-90℃.

4. The preparation method according to claim 1, characterized in that, The acidity of the first mixed solution is 1-2.5%.

5. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The magnesium oxide content in the first mixed solution is 0.75-2wt%.

6. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The aluminum oxide content in the first mixed solution is 5-7wt%.

7. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. In S2, the reaction temperature is 80-90℃.

8. The polyaluminum magnesium chloride prepared by the preparation method of any one of claims 1-7.

9. The polyaluminum magnesium chloride according to claim 8, characterized in that, The aluminum oxide content in the polyaluminum magnesium chloride is 10-10.5wt%, the magnesium oxide content is 1-2wt%, and the basicity is 60-70%.

10. The polyaluminum magnesium chloride of claim 8 or 9 for treating alkaline printing and dyeing wastewater.

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