A water purifier based on polyaluminium chloride and preparation method thereof

Abstract

The present invention relates to the technical field of polyaluminium chloride water purifiers, specifically discloses a water purifier based on polyaluminium chloride and a preparation method thereof, the water purifier is made by mixing polyaluminium chloride magnesium silicate composite solution, modified starch modified chitosan composite solution and magnetized active kaolin, ultrasonic dispersion, slaking and drying; wherein polyaluminium chloride magnesium silicate composite solution is made of aluminium chloride, magnesium chloride hexahydrate and trichloroethylsilane; modified starch modified chitosan composite solution is made of starch modified by dimethyl diallyl ammonium chloride and acrylamide, and chitosan modified by diethyltriamine pentaacetic acid; magnetized active kaolin is made of ferric chloride hexahydrate, sodium silicate and acidified kaolin. The water purifier of the present invention contains a variety of efficient flocculation adsorption components, not only has the function of traditional polyaluminium chloride mesh sweeping, but also can synchronously and efficiently remove pollutants such as ammonia nitrogen, total phosphorus, COD and suspended matter in water.

Description

Technical Field

[0001] The present invention relates to the technical field of polyaluminium chloride water purifiers, in particular to a polyaluminium chloride-based water purifier and a preparation method thereof. Background Art

[0002] Polyaluminum chloride, abbreviated as PAC, is a water-soluble inorganic polymer intermediate between AlCl3 and Al(OH)3. It typically appears as a white, yellow, or tan resinous solid and can be used in drinking water, industrial water, and wastewater treatment. Compared to traditional inorganic coagulants, PAC, composed of a diverse array of polycarboxyl complexes, exhibits rapid flocculation and sedimentation, a wide pH range, is non-corrosive to pipeline equipment, and exhibits significant water purification effectiveness. However, with technological advancements, the types and concentrations of pollutants in industrial and municipal wastewater are increasing. The presence of high concentrations of ammonia nitrogen, total phosphorus, and heavy metal ions in conventional PACs can lead to poor water purification results. Furthermore, the decolorization rate of wastewater during flocculation and sedimentation is low, requiring additional treatment equipment and increasing wastewater treatment costs. Therefore, the development of new, highly efficient water purifiers is needed to address this issue. Summary of the Invention

[0003] The present invention aims to provide a polyaluminium chloride-based water purifier and a preparation method thereof. The water purifier is added with high-efficiency water purification ingredients such as nano-iron oxide, magnesium salt, modified starch, modified chitosan and activated kaolin, and can effectively remove high-concentration ammonia nitrogen, total phosphorus and heavy metal ions in sewage, thereby decolorizing the sewage. In addition, the water purifier of the present invention has strong adsorption capacity and a wide range of applications.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] A method for preparing a water purifier based on polyaluminium chloride, the preparation method of the water purifier is specifically as follows:

[0006] The polyaluminium chloride-magnesium silicate composite solution, the modified starch-modified chitosan composite solution and the magnetised active kaolin are mixed, stirred evenly, ultrasonically dispersed, aged and dried to obtain a water purifier.

[0007] As a limitation of the present invention, the mass ratio of the polyaluminium chloride-magnesium silicate composite solution, the modified starch-modified chitosan composite solution and the magnetically activated kaolin is (24-26):(98-102):(6-8).

[0008] As a limitation of the present invention, during the ultrasonic dispersion treatment, the ultrasonic frequency is 34 to 60 kHz, the ultrasonic power is 600 to 1200 W, and the ultrasonic dispersion treatment time is 80 to 200 min.

[0009] As a limitation of the present invention, the preparation of the polyaluminium chloride-magnesium silicate composite solution is specifically as follows:

[0010] Aluminum chloride and deionized water were mixed and stirred in a mass ratio of 1:(20-24) to fully dissolve, and sodium hydroxide solution was slowly added at 30-40°C and 480-520rpm to react for 2-4h to obtain a polyaluminum chloride solution;

[0011] Mix magnesium chloride hexahydrate, trichloroethylsilane, and deionized water in a mass ratio of 1:(1.5-2.5):(19-23), stir evenly, and irradiate with low-temperature plasma to obtain a magnesium chloride silicate solution;

[0012] The polyaluminium chloride solution and the magnesium aluminium silicate solution are mixed in a volume ratio of (4-6):1, reacted at 40-50°C and 50-60 rpm for 20-40 minutes, and allowed to stand and mature for 2-6 hours to obtain a polyaluminium chloride-magnesium silicate composite solution.

[0013] As a limitation of the present invention, the preparation of the modified starch-modified chitosan composite solution is specifically as follows:

[0014] Starch and deionized water are mixed in a mass ratio of 1:(42-48), stirred evenly, gelatinized at 80-90°C for 40-60 minutes, cooled to room temperature to obtain a starch solution, dimethyldiallylammonium chloride, acrylamide, and starch solution are mixed in a mass ratio of 1:(0.6-1):(200-220), adjusted to pH 2 with dilute hydrochloric acid, reacted for 2-3 hours, and then added with sodium hydroxide solution until the pH is neutral to obtain a modified starch solution;

[0015] Chitosan, acetic acid, glutaraldehyde, and deionized water are mixed in a mass ratio of (8-12):(5-6):(4-5):(490-510), and reacted at 30-50°C and 35-45 rpm for 2-4 hours to obtain a cross-linked chitosan solution. Diethylenetriamine pentaacetic acid, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, a sodium hydroxide solution with a molar volume of 1 mol / L, and deionized water are mixed in a mass ratio of (9-11):(11-12). :(12-16):(12-16):(480-500) are mixed evenly, reacted at 30-50°C and 35-45rpm for 2-4h to obtain an activated group solution, the cross-linked chitosan solution and the activated group solution are mixed in a volume ratio of (1-3):1, and reacted at 50-70°C for 2-4h, and then 1.2%-1.3% tetrahydrofuran of the mixed solution volume and an equal volume of modified starch solution are added to the mixed solution, and the reaction is continued for 1-3h to obtain a modified starch-modified chitosan composite solution.

[0016] As a limitation of the present invention, the preparation of magnetically activated kaolin is specifically as follows:

[0017] Ferric chloride hexahydrate and ethylene glycol are mixed uniformly in a mass ratio of 1:(44-45), stirred until the solution is clear to obtain a ferric chloride hexahydrate solution, polyethylene glycol and sodium acetate are mixed in a mass ratio of 1:(3-4), added to the ferric chloride hexahydrate solution, reacted at 180-220° C. and 20-40 rpm for 16-24 hours, cooled after completion of the reaction, washed with ethanol, and vacuum dried to obtain magnetic iron oxide nanoparticles;

[0018] The magnetic iron oxide nanoparticles, deionized water, and sodium silicate are uniformly mixed in a mass ratio of (7-9):(120-130):(18-22), and the pH of the mixture is adjusted to 1 with a sulfuric acid solution and a sodium hydroxide solution. The mixture is reacted at 35-45° C. and 20-40 rpm for 2-3 hours. After the reaction is completed, the mixture is aged at 45-55° C. for 5-7 hours to obtain a magnetic iron oxide silicate solution.

[0019] The kaolin is calcined at 500-700°C for 3-5 hours, cooled to room temperature, and then a 40wt% sulfuric acid solution of 0.25-0.28 times the weight of the kaolin is added, and the mixture is reacted at 85-95°C for 3-5 hours. After the reaction, the filtrate is washed with deionized water until the pH value of the filtrate is neutral, and a magnetic silicate iron oxide solution of 4-6 times the weight of the kaolin is added. The mixture is dried at 70-90°C for 20-28 hours, crushed, sieved, and the magnetized active kaolin is separated using a magnet.

[0020] As a limitation of the present invention, the low-temperature plasma irradiation time is 40 to 80 minutes, the low-temperature plasma irradiation voltage is 4 to 6 kV, and the low-temperature plasma atmosphere is oxygen.

[0021] The beneficial effects achieved by the present invention are as follows: Compared with conventional polyaluminum chloride water purifiers, the present invention incorporates magnesium salts, modified starch, modified chitosan, and magnetized activated kaolin. The magnesium salts can rapidly form large, dense flocs when treating wastewater, increasing the sedimentation rate of fine particles and improving the sedimentation efficiency. The modified starch and chitosan structures contain abundant active adsorption sites such as amino and hydroxyl groups, resulting in strong anion adsorption capacity. Furthermore, the modified starch and chitosan are environmentally friendly, non-toxic, and highly degradable. The magnetized activated kaolin, with its unique layered structure, abundant surface siloxy groups, and strong ion exchange capacity, forms flocs with good dispersibility and chemical stability when treating wastewater, making them easily separable from the solution by an external magnetic field. DETAILED DESCRIPTION

[0022] The following describes preferred implementations of the present invention. Obviously, the described embodiments are only a portion of the embodiments of the present invention, not all of them. It will be apparent to those skilled in the art that all other implementations derived without inventive effort, without departing from the principles of the present invention, are within the scope of protection of the present invention.

[0023] Diethylenetriaminepentaacetic acid (D807203), 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (N808856), N-hydroxysuccinimide (H6231), kaolin (K812211), sodium silicate (S871946), magnesium chloride hexahydrate (M813913) were provided by Shanghai MacLean; aluminum chloride (A433483), trichloroethylsilane (E156100), starch (S16 4486), dimethyldiallylammonium chloride (D110133), acrylamide (A108465), chitosan (C434551), acetic acid (A11616), glutaraldehyde (G359127), tetrahydrofuran (T103259), ferric chloride hexahydrate (F102742), ethylene glycol (E103318), polyethylene glycol (P432430), and sodium acetate (S299552) were provided by Shanghai Aladdin.

[0024] Example 1: A water purifier based on polyaluminium chloride, prepared by:

[0025] Step 1: Prepare polyaluminium chloride solution

[0026] Aluminum chloride and deionized water were mixed and stirred in a mass ratio of 1:22 to fully dissolve. 0.18 mol / L sodium hydroxide solution (3 times the weight of aluminum chloride) was slowly added at 35°C and 500 rpm, and the mixture was reacted for 3 hours to obtain a polyaluminum chloride solution.

[0027] Step 2: Preparation of polyaluminium chloride-magnesium silicate composite solution

[0028] Magnesium chloride hexahydrate, trichloroethylsilane, and deionized water were mixed in a mass ratio of 1:2:21, stirred evenly, and irradiated with low-temperature plasma for 60 minutes to obtain a magnesium chloride silicate solution;

[0029] The polyaluminium chloride solution and the magnesium chloride silicate solution were mixed in a volume ratio of 5:1, reacted at 45°C and 55 rpm for 30 minutes, and allowed to stand and mature for 4 hours to obtain a polyaluminium chloride-magnesium silicate composite solution.

[0030] Step 3: Prepare modified starch solution

[0031] Starch and deionized water were mixed in a mass ratio of 1:45, stirred evenly, gelatinized at 85°C for 50 minutes, and cooled to room temperature to obtain a starch solution. Dimethyldiallylammonium chloride, acrylamide, and starch solution were mixed in a mass ratio of 1:0.8:210, and the pH was adjusted to 2 with 0.1 mol / L dilute hydrochloric acid. After reacting for 2.5 hours, 30 wt% sodium hydroxide solution was added until the pH was neutral to obtain a modified starch solution.

[0032] Step 4: Preparation of modified starch-modified chitosan composite solution

[0033] Chitosan, acetic acid, glutaraldehyde, and deionized water were mixed in a mass ratio of 10:5.5:4.5:500 and reacted at 40°C and 40 rpm for 3 h to obtain a cross-linked chitosan solution. Diethylenetriaminepentaacetic acid, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, a sodium hydroxide solution with a molar volume of 1 mol / L, and deionized water were mixed in a mass ratio of 10:11.5:14:14:490 and reacted at 40°C and 40 rpm for 3 h to obtain an activated group solution. The cross-linked chitosan solution and the activated group solution were mixed in a volume ratio of 2:1 and reacted at 60°C for 3 h. Then, tetrahydrofuran (1.25% by volume of the mixed solution) and a modified starch solution (equal to the volume of the mixed solution) were added and the reaction was continued for 2 h to obtain a modified starch-modified chitosan composite solution.

[0034] Step 5: Preparation of magnetic iron oxide nanoparticles

[0035] Ferric chloride hexahydrate and ethylene glycol were mixed uniformly in a mass ratio of 1:44.5, stirred until the solution was clear, and a ferric chloride hexahydrate solution was obtained. Polyethylene glycol and sodium acetate were mixed in a mass ratio of 1:3.5, added to the ferric chloride hexahydrate solution, and reacted at 200°C and 30 rpm for 20 hours. After the reaction was completed, the mixture was cooled, washed with ethanol, and vacuum dried to obtain magnetic iron oxide nanoparticles.

[0036] Step 6: Preparation of magnetically activated kaolin

[0037] Magnetic iron oxide nanoparticles, deionized water, and sodium silicate were uniformly mixed in a mass ratio of 8:125:20, and the pH of the mixture was adjusted to 1 with 30 wt% sulfuric acid and 0.1 mol / L sodium hydroxide solution. The mixture was reacted at 40°C and 30 rpm for 2.5 hours. After the reaction was completed, the mixture was aged at 50°C for 6 hours to prepare a magnetic iron oxide silicate solution.

[0038] The kaolin was calcined at 600°C for 4 hours, cooled to room temperature, and then a 40wt% sulfuric acid solution (0.26 times the weight of the kaolin) was added, and the mixture was reacted at 90°C for 4 hours. After the reaction, the filtrate was washed with deionized water until the pH value of the filtrate was neutral. A magnetic silicate iron oxide solution (5 times the weight of the kaolin) was added, and the mixture was dried at 80°C for 24 hours. The mixture was crushed, sieved, and the magnetized active kaolin was separated using a magnet.

[0039] Step 7: Prepare water purifier

[0040] The polyaluminum chloride-magnesium silicate composite solution, the modified starch-modified chitosan composite solution, and the magnetized active kaolin were mixed in a mass ratio of 25:100:7, magnetically stirred at 27°C and 300 rpm for 25 minutes, and ultrasonically dispersed and mixed after the stirring was completed. After the ultrasonic dispersion treatment was completed, the mixture was aged at 75°C for 24 hours and freeze-dried to obtain a water purifier.

[0041] Example 2: A water purifier based on polyaluminium chloride, prepared by:

[0042] Step 1: Prepare polyaluminium chloride solution

[0043] Aluminum chloride and deionized water were mixed and stirred in a mass ratio of 1:24 to fully dissolve. 0.18 mol / L sodium hydroxide solution (3 times the weight of aluminum chloride) was slowly added at 35°C and 500 rpm, and the mixture was reacted for 3 hours to obtain a polyaluminum chloride solution.

[0044] Step 2: Preparation of polyaluminium chloride-magnesium silicate composite solution

[0045] Magnesium chloride hexahydrate, trichloroethylsilane, and deionized water were mixed in a mass ratio of 1:2.5:23, stirred evenly, and irradiated with low-temperature plasma for 60 minutes to obtain a magnesium chloride silicate solution;

[0046] The polyaluminium chloride solution and the magnesium aluminium silicate solution were mixed in a volume ratio of 6:1, reacted at 45°C and 55 rpm for 30 minutes, and allowed to stand and mature for 4 hours to obtain a polyaluminium chloride-magnesium silicate composite solution.

[0047] Step 3: Prepare modified starch solution

[0048] Starch and deionized water were mixed in a mass ratio of 1:48, stirred evenly, gelatinized at 85°C for 50 minutes, and cooled to room temperature to obtain a starch solution. Dimethyldiallylammonium chloride, acrylamide, and starch solution were mixed in a mass ratio of 1:1:220, and the pH was adjusted to 2 with 0.1 mol / L dilute hydrochloric acid. After reacting for 2.5 hours, 30 wt% sodium hydroxide solution was added until the pH was neutral to obtain a modified starch solution.

[0049] Step 4: Preparation of modified starch-chitosan composite solution

[0050] Chitosan, acetic acid, glutaraldehyde and deionized water were mixed in a mass ratio of 12:6:5:510, and reacted at 40°C and 40 rpm for 3 h to obtain a cross-linked chitosan solution. N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide and deionized water were mixed in a mass ratio of (11-12):(12-16):(480-500), and diethylenetriamine (1-1.5 times the mass of N-hydroxysuccinimide) was added. Amine pentaacetic acid, at 30-50 ° C, 35-45 rpm, slowly add sodium hydroxide solution of equal mass to N-hydroxysuccinimide, react for 2-4 hours to obtain an activated group solution, the cross-linked chitosan solution and the activated group solution are mixed in a volume ratio of 2:1, react at 60 ° C for 3 hours, add tetrahydrofuran (1.25% times the volume of the mixture) and a modified starch solution of equal volume to the mixture, and continue to react for 2 hours to obtain a modified starch-modified chitosan composite solution.

[0051] Step 5: Preparation of magnetic iron oxide nanoparticles

[0052] Ferric chloride hexahydrate and ethylene glycol were mixed uniformly in a mass ratio of 1:45, stirred until the solution was clear, and a ferric chloride hexahydrate solution was obtained. Polyethylene glycol and sodium acetate were mixed in a mass ratio of 1:4, added to the ferric chloride hexahydrate solution, and reacted at 200°C and 30 rpm for 20 hours. After the reaction was completed, the mixture was cooled, washed with ethanol, and vacuum dried to obtain magnetic iron oxide nanoparticles.

[0053] Step 6: Preparation of magnetically activated kaolin

[0054] Magnetic iron oxide nanoparticles, deionized water, and sodium silicate were uniformly mixed in a mass ratio of 9:130:22, and the pH of the mixture was adjusted to 1 with 30 wt% sulfuric acid and 0.1 mol / L sodium hydroxide solution. The mixture was reacted at 40°C and 30 rpm for 2.5 hours. After the reaction was completed, the mixture was aged at 50°C for 6 hours to prepare a magnetic iron oxide silicate solution.

[0055] The kaolin was calcined at 600°C for 4 hours, cooled to room temperature, and then a 40wt% sulfuric acid solution (0.28 times the weight of the kaolin) was added. The mixture was reacted at 90°C for 4 hours. After the reaction, the filtrate was washed with deionized water until the pH value of the filtrate was neutral. A magnetic silicate iron oxide solution (6 times the weight of the kaolin) was added, and the mixture was dried at 80°C for 24 hours. The mixture was crushed, sieved, and the magnetized active kaolin was separated using a magnet.

[0056] Step 7: Prepare water purifier

[0057] The polyaluminum chloride-magnesium silicate composite solution, the modified starch-modified chitosan composite solution, and the magnetized active kaolin were mixed in a mass ratio of 26:102:8, magnetically stirred at 27°C and 300 rpm for 25 minutes, and ultrasonically dispersed and mixed after the stirring was completed. After the ultrasonic dispersion treatment was completed, the mixture was aged at 75°C for 24 hours and freeze-dried to obtain a water purifier.

[0058] Example 3: A water purifier based on polyaluminium chloride, prepared by:

[0059] Step 1: Prepare polyaluminium chloride solution

[0060] Aluminum chloride and deionized water were mixed and stirred in a mass ratio of 1:20 to fully dissolve. 0.18 mol / L sodium hydroxide solution (3 times the weight of aluminum chloride) was slowly added at 35°C and 500 rpm, and the mixture was reacted for 3 hours to obtain a polyaluminum chloride solution.

[0061] Step 2: Preparation of polyaluminium chloride-magnesium silicate composite solution

[0062] Magnesium chloride hexahydrate, trichloroethylsilane, and deionized water were mixed in a mass ratio of 1:1.5:19, stirred evenly, and irradiated with low-temperature plasma for 60 minutes to obtain a magnesium chloride silicate solution;

[0063] The polyaluminium chloride solution and the magnesium aluminium silicate solution were mixed in a volume ratio of 4:1, reacted at 45°C and 55 rpm for 30 minutes, and allowed to stand and mature for 4 hours to obtain a polyaluminium chloride-magnesium silicate composite solution.

[0064] Step 3: Prepare modified starch solution

[0065] Starch and deionized water were mixed in a mass ratio of 1:42, stirred evenly, gelatinized at 85°C for 50 minutes, and cooled to room temperature to obtain a starch solution. Dimethyldiallylammonium chloride, acrylamide, and starch solution were mixed in a mass ratio of 1:0.6:200, and the pH was adjusted to 2 with 0.1 mol / L dilute hydrochloric acid. After reacting for 2.5 hours, 30 wt% sodium hydroxide solution was added until the pH was neutral to obtain a modified starch solution.

[0066] Step 4: Preparation of modified starch-modified chitosan composite solution

[0067] Chitosan, acetic acid, glutaraldehyde, and deionized water were mixed in a mass ratio of 8:5:4:490 and reacted at 40°C and 40 rpm for 3 h to obtain a cross-linked chitosan solution. Diethylenetriaminepentaacetic acid, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, a sodium hydroxide solution with a molar volume of 1 mol / L, and deionized water were mixed in a mass ratio of 9:11:12:12:480 and reacted at 40°C and 40 rpm for 3 h to obtain an activated group solution. The cross-linked chitosan solution and the activated group solution were mixed in a volume ratio of 3:1 and reacted at 60°C for 3 h. Then, 1.25% times the volume of the mixed solution of tetrahydrofuran and an equal volume of modified starch solution to the mixed solution were added, and the reaction was continued for 2 h to obtain a modified starch-modified chitosan composite solution.

[0068] Step 5: Preparation of magnetic iron oxide nanoparticles

[0069] Ferric chloride hexahydrate and ethylene glycol were mixed uniformly in a mass ratio of 1:44, stirred until the solution was clear, and a ferric chloride hexahydrate solution was obtained. Polyethylene glycol and sodium acetate were mixed in a mass ratio of 1:3, added to the ferric chloride hexahydrate solution, and reacted at 200°C and 30 rpm for 20 hours. After the reaction was completed, the mixture was cooled, washed with ethanol, and vacuum dried to obtain magnetic iron oxide nanoparticles.

[0070] Step 6: Preparation of magnetically activated kaolin

[0071] Magnetic iron oxide nanoparticles, deionized water, and sodium silicate were uniformly mixed in a mass ratio of 7:120:18, and the pH of the mixture was adjusted to 1 with 30 wt% sulfuric acid and 0.1 mol / L sodium hydroxide solution. The mixture was reacted at 40°C and 30 rpm for 2.5 hours. After the reaction was completed, the mixture was aged at 50°C for 6 hours to prepare a magnetic iron oxide silicate solution.

[0072] The kaolin was calcined at 600°C for 4 hours, cooled to room temperature, and then a 40wt% sulfuric acid solution with a weight of 0.25 times that of the kaolin was added. The mixture was reacted at 90°C for 4 hours. After the reaction, the filtrate was washed with deionized water until the pH of the filtrate was neutral. A magnetic silicate iron oxide solution with a weight of 4 times that of the kaolin was added, and the mixture was dried at 80°C for 24 hours. The mixture was crushed, sieved, and the magnetized active kaolin was separated using a magnet.

[0073] Step 7: Prepare water purifier

[0074] The polyaluminum chloride-magnesium silicate composite solution, the modified starch-modified chitosan composite solution, and the magnetized active kaolin were mixed in a mass ratio of 24:98:6, magnetically stirred at 27°C and 300 rpm for 25 minutes, and ultrasonically dispersed and mixed after the stirring was completed. After the ultrasonic dispersion treatment was completed, the mixture was aged at 75°C for 24 hours and freeze-dried to obtain a water purifier.

[0075] Based on Example 1, control experiments were conducted, specifically Comparative Example 1 and Comparative Example 2, as described below:

[0076] Comparative Example 1: The amount of the polyaluminium chloride-magnesium silicate composite solution was reduced, and the other conditions were the same as those in Example 1.

[0077] A water purifier based on polyaluminium chloride, the preparation method is as follows:

[0078] Step 1: Prepare polyaluminium chloride solution

[0079] Aluminum chloride and deionized water were mixed and stirred in a mass ratio of 1:22 to fully dissolve. 0.18 mol / L sodium hydroxide solution (3 times the weight of aluminum chloride) was slowly added at 35°C and 500 rpm, and the mixture was reacted for 3 hours to obtain a polyaluminum chloride solution.

[0080] Step 2: Preparation of polyaluminium chloride-magnesium silicate composite solution

[0081] Magnesium chloride hexahydrate, trichloroethylsilane, and deionized water were mixed in a mass ratio of 1:2:21, stirred evenly, and irradiated with low-temperature plasma for 60 minutes to obtain a magnesium chloride silicate solution;

[0082] The polyaluminium chloride solution and the magnesium aluminium silicate solution were mixed in a volume ratio of 5:1, reacted at 45°C and 55 rpm for 30 minutes, and allowed to stand and mature for 4 hours to obtain a polyaluminium chloride-magnesium silicate composite solution.

[0083] Step 3: Prepare modified starch solution

[0084] Starch and deionized water were mixed in a mass ratio of 1:45, stirred evenly, gelatinized at 85°C for 50 minutes, and cooled to room temperature to obtain a starch solution. Dimethyldiallylammonium chloride, acrylamide, and starch solution were mixed in a mass ratio of 1:0.8:210, and the pH was adjusted to 2 with 0.1 mol / L dilute hydrochloric acid. After reacting for 2.5 hours, 30 wt% sodium hydroxide solution was added until the pH was neutral to obtain a modified starch solution.

[0085] Step 4: Preparation of modified starch-modified chitosan composite solution

[0086] Chitosan, acetic acid, glutaraldehyde, and deionized water were mixed in a mass ratio of 10:5.5:4.5:500 and reacted at 40°C and 40 rpm for 3 h to obtain a cross-linked chitosan solution. Diethylenetriaminepentaacetic acid, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, a sodium hydroxide solution with a molar volume of 1 mol / L, and deionized water were mixed in a mass ratio of 10:11.5:14:14:490 and reacted at 40°C and 40 rpm for 3 h to obtain an activated group solution. The cross-linked chitosan solution and the activated group solution were mixed in a volume ratio of 2:1 and reacted at 60°C for 3 h. Then, 1.25% times the volume of the mixed solution of tetrahydrofuran and an equal volume of modified starch solution to the mixed solution were added, and the reaction was continued for 2 h to obtain a modified starch-modified chitosan composite solution.

[0087] Step 5: Preparation of magnetic iron oxide nanoparticles

[0088] Ferric chloride hexahydrate and ethylene glycol were mixed uniformly in a mass ratio of 1:44.5, stirred until the solution was clear, and a ferric chloride hexahydrate solution was obtained. Polyethylene glycol and sodium acetate were mixed in a mass ratio of 1:3.5, added to the ferric chloride hexahydrate solution, and reacted at 200°C and 30 rpm for 20 hours. After the reaction was completed, the mixture was cooled, washed with ethanol, and vacuum dried to obtain magnetic iron oxide nanoparticles.

[0089] Step 6: Preparation of magnetically activated kaolin

[0090] Magnetic iron oxide nanoparticles, deionized water, and sodium silicate were uniformly mixed in a mass ratio of 8:125:20, and the pH of the mixture was adjusted to 1 with 30 wt% sulfuric acid and 0.1 mol / L sodium hydroxide solution. The mixture was reacted at 40°C and 30 rpm for 2.5 hours. After the reaction was completed, the mixture was aged at 50°C for 6 hours to prepare a magnetic iron oxide silicate solution.

[0091] The kaolin was calcined at 600°C for 4 hours, cooled to room temperature, and then a 40wt% sulfuric acid solution (0.26 times the weight of the kaolin) was added, and the mixture was reacted at 90°C for 4 hours. After the reaction, the filtrate was washed with deionized water until the pH value of the filtrate was neutral. A magnetic silicate iron oxide solution (5 times the weight of the kaolin) was added, and the mixture was dried at 80°C for 24 hours. The mixture was crushed, sieved, and the magnetized active kaolin was separated using a magnet.

[0092] Step 7: Prepare water purifier

[0093] The polyaluminum chloride-magnesium silicate composite solution, deionized water, modified starch-modified chitosan composite solution, and magnetized active kaolin were mixed in a mass ratio of 5:20:100:7, magnetically stirred at 27°C and 300 rpm for 25 minutes, and ultrasonically dispersed and mixed after the stirring was completed. After the ultrasonic dispersion treatment was completed, the mixture was aged at 75°C for 24 hours and freeze-dried to obtain a water purifier.

[0094] Comparative Example 2: The amount of the modified starch-modified chitosan composite solution was reduced, and the remaining conditions were the same as those in Example 1.

[0095] A water purifier based on polyaluminium chloride, the preparation method is as follows:

[0096] Step 1: Prepare polyaluminium chloride solution

[0097] Aluminum chloride and deionized water were mixed and stirred in a mass ratio of 1:22 to fully dissolve. 0.18 mol / L sodium hydroxide solution (3 times the weight of aluminum chloride) was slowly added at 35°C and 500 rpm, and the mixture was reacted for 3 hours to obtain a polyaluminum chloride solution.

[0098] Step 2: Preparation of polyaluminium chloride-magnesium silicate composite solution

[0099] Magnesium chloride hexahydrate, trichloroethylsilane, and deionized water were mixed in a mass ratio of 1:2:21, stirred evenly, and irradiated with low-temperature plasma for 60 minutes to obtain a magnesium chloride silicate solution;

[0100] The polyaluminium chloride solution and the magnesium aluminium silicate solution were mixed in a volume ratio of 5:1, reacted at 45°C and 55 rpm for 30 minutes, and allowed to stand and mature for 4 hours to obtain a polyaluminium chloride-magnesium silicate composite solution.

[0101] Step 3: Prepare modified starch solution

[0102] Starch and deionized water were mixed in a mass ratio of 1:45, stirred evenly, gelatinized at 85°C for 50 minutes, and cooled to room temperature to obtain a starch solution. Dimethyldiallylammonium chloride, acrylamide, and starch solution were mixed in a mass ratio of 1:0.8:210, and the pH was adjusted to 2 with 0.1 mol / L dilute hydrochloric acid. After reacting for 2.5 hours, 30 wt% sodium hydroxide solution was added until the pH was neutral to obtain a modified starch solution.

[0103] Step 4: Preparation of modified starch-modified chitosan composite solution

[0104] Chitosan, acetic acid, glutaraldehyde, and deionized water were mixed in a mass ratio of 10:5.5:4.5:500 and reacted at 40°C and 40 rpm for 3 h to obtain a cross-linked chitosan solution. Diethylenetriaminepentaacetic acid, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, a sodium hydroxide solution with a molar volume of 1 mol / L, and deionized water were mixed in a mass ratio of 10:11.5:14:14:490 and reacted at 40°C and 40 rpm for 3 h to obtain an activated group solution. The cross-linked chitosan solution and the activated group solution were mixed in a volume ratio of 2:1 and reacted at 60°C for 3 h. Then, 1.25% times the volume of the mixed solution of tetrahydrofuran and an equal volume of modified starch solution to the mixed solution were added, and the reaction was continued for 2 h to obtain a modified starch-modified chitosan composite solution.

[0105] Step 5: Preparation of magnetic iron oxide nanoparticles

[0106] Ferric chloride hexahydrate and ethylene glycol were mixed uniformly in a mass ratio of 1:44.5, stirred until the solution was clear, and a ferric chloride hexahydrate solution was obtained. Polyethylene glycol and sodium acetate were mixed in a mass ratio of 1:3.5, added to the ferric chloride hexahydrate solution, and reacted at 200°C and 30 rpm for 20 hours. After the reaction was completed, the mixture was cooled, washed with ethanol, and vacuum dried to obtain magnetic iron oxide nanoparticles.

[0107] Step 6: Preparation of magnetically activated kaolin

[0108] Magnetic iron oxide nanoparticles, deionized water, and sodium silicate were uniformly mixed in a mass ratio of 8:125:20, and the pH of the mixture was adjusted to 1 with 30 wt% sulfuric acid and 0.1 mol / L sodium hydroxide solution. The mixture was reacted at 40°C and 30 rpm for 2.5 hours. After the reaction was completed, the mixture was aged at 50°C for 6 hours to prepare a magnetic iron oxide silicate solution.

[0109] The kaolin was calcined at 600°C for 4 hours, cooled to room temperature, and then a 40wt% sulfuric acid solution (0.26 times the weight of the kaolin) was added, and the mixture was reacted at 90°C for 4 hours. After the reaction, the filtrate was washed with deionized water until the pH value of the filtrate was neutral. A magnetic silicate iron oxide solution (5 times the weight of the kaolin) was added, and the mixture was dried at 80°C for 24 hours. The mixture was crushed, sieved, and the magnetized active kaolin was separated using a magnet.

[0110] Step 7: Prepare water purifier

[0111] The polyaluminium chloride-magnesium silicate composite solution, modified starch-modified chitosan composite solution, deionized water, and magnetized activated kaolin were mixed in a mass ratio of 25:25:75:7, and magnetically stirred at 27°C and 300 rpm for 25 minutes. After stirring, ultrasonic dispersion and mixing were performed. After ultrasonic dispersion, the mixture was aged at 75°C for 24 hours and freeze-dried to obtain a water purifier. Detection experiment:

[0112] 25L of untreated sewage from a power plant in Jiangsu was taken and divided into 5 parts of equal volume. 10g of the water purifier prepared in Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2 were added respectively. The mixture was fully stirred, allowed to stand for 2h, and its performance was tested.

[0113] Determination of COD concentration: The COD concentration of the solution was determined in accordance with the national standard "Water quality determination of chemical oxygen demand - dichromate method" (GB 11914-1989).

[0114] Determination of suspended matter: The suspended matter in the liquid shall be determined in accordance with the “Water Quality - Determination of Suspended Matter - Gravimetric Method” (GB / T11901-1989).

[0115] Determination of ammonia nitrogen concentration: The concentration of ammonia nitrogen in the liquid is determined in accordance with the "Water quality-Determination of ammonia nitrogen-Salicylic acid spectrophotometry method" (HJ 536-2009).

[0116] Determination of total phosphorus concentration: The concentration of total phosphorus in the liquid was determined in accordance with the "Water Quality - Determination of Total Phosphorus - Flow Injection-Ammonium Molybdate Spectrophotometry" (HJ 671-2013).

[0117] The results are as follows:

[0118] Water purifier performance Experimental Example 1 Experimental Example 2 Experimental Example 3 Comparative Example 1 Comparative Example 2 COD removal rate (%) 88.2％ 88.0％ 88.1％ 82.4％ 88.1％ Suspended matter removal rate (%) 94.2％ 93.9％ 94.0％ 85.2％ 94.1％ Ammonia nitrogen removal rate (%) 89.9％ 90.1％ 89.7％ 89.7％ 84.7％ Total phosphorus removal rate (%) 91.6％ 91.5％ 91.8％ 91.4％ 83.2％

[0119] Conclusion: From the experiment, it can be seen that the performance of Example 1 is better than that of Comparative Example 1 and Comparative Example 2. Compared with Example 1, the water purifier of Comparative Example 2 reduces the proportion of modified starch-modified chitosan composite solution in the water purifier, which is manifested in a decrease in the removal capacity of ammonia nitrogen and total phosphorus in the experiment; Comparative Example 1 reduces the proportion of polyaluminum chloride-magnesium silicate composite solution in the water purifier, which is manifested in a decrease in the removal capacity of COD and suspended solids in the experiment. This shows that the water purifier of the present invention is indeed better than ordinary polyaluminum chloride water purifier in terms of water purification effect. The water purifier of the present invention adds modified starch and modified chitosan, which not only saves costs but is also more environmentally friendly; the added magnetic nanoparticles have relatively stable chemical properties and are easy to separate. At the same time, the magnetic nanoparticles have high reusability and regeneration capacity. Overall, the water purifier of the present invention is superior to ordinary polyaluminum chloride water purifiers.

[0120] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a water purifier based on polyaluminium chloride, characterized in that: The preparation method of the water purifier is specifically as follows: The polyaluminium chloride-magnesium silicate composite solution, the modified starch-modified chitosan composite solution and the magnetised activated kaolin are mixed, stirred evenly, ultrasonically dispersed, aged and dried to obtain a water purifier; The polyaluminium chloride-magnesium silicate composite solution is prepared by the following process: Step 1: fully dissolve aluminum chloride in deionized water, add sodium hydroxide solution, and react to obtain polyaluminum chloride solution; Step 2: Mix magnesium chloride hexahydrate, trichloroethylsilane, and deionized water, stir evenly, and irradiate with low-temperature plasma to obtain a magnesium chloride silicate solution; Step 3: Mix the polyaluminium chloride solution and the magnesium chloride silicate solution, stir evenly, and allow to stand and mature to obtain a polyaluminium chloride-magnesium silicate composite solution.

2. The method for preparing a water purifier based on polyaluminium chloride according to claim 1, wherein: The mass ratio of the polyaluminium chloride-magnesium silicate composite solution, the modified starch-modified chitosan composite solution and the magnetically active kaolin is (24-26):(98-102):(6-8).

3. The method for preparing a water purifier based on polyaluminium chloride according to claim 1, wherein: During the ultrasonic dispersion treatment, the ultrasonic frequency is 34 to 60 kHz, the ultrasonic power is 600 to 1200 W, and the ultrasonic dispersion treatment time is 80 to 200 min.

4. The method for preparing a water purifier based on polyaluminium chloride according to claim 1, wherein: The method for preparing the modified starch-modified chitosan composite solution is: Starch and deionized water are mixed and stirred to obtain a starch solution, dimethyldiallylammonium chloride, acrylamide and the starch solution are mixed, and the pH is adjusted. After the reaction is completed, a modified starch solution is obtained; Chitosan, acetic acid, glutaraldehyde, and deionized water are uniformly mixed and reacted to obtain a cross-linked chitosan solution; N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide are mixed and dissolved in deionized water, and diethylenetriamine pentaacetic acid and sodium hydroxide solution are added to react to obtain an activated group solution; The cross-linked chitosan solution and the activated group solution are mixed, and after the reaction is complete, tetrahydrofuran and the modified starch solution are added and the reaction is continued to obtain a modified starch-modified chitosan composite solution.

5. The method for preparing a water purifier based on polyaluminium chloride according to claim 1, wherein: The method for preparing magnetized activated kaolin is: The ferric chloride hexahydrate and ethylene glycol were mixed, polyethylene glycol and sodium acetate were added to react, the product was washed with ethanol, and vacuum dried to obtain magnetic iron oxide nanoparticles; The magnetic iron oxide nanoparticles, deionized water and sodium silicate are uniformly mixed, the pH of the mixture is adjusted with sulfuric acid solution and sodium hydroxide solution, and the mixture is aged after the reaction is completed to obtain a magnetic iron oxide silicate solution; The kaolin is roasted and then acidified, washed with deionized water, and then added with a magnetic silicate iron oxide solution. The kaolin is dried, crushed, ground, sieved, and the magnetized active kaolin is separated with a magnet.

6. The method for preparing a water purifier based on polyaluminium chloride according to claim 1, wherein: The low-temperature plasma irradiation time is 40 to 80 minutes, the low-temperature plasma irradiation voltage is 4 to 6 kV, and the low-temperature plasma atmosphere is oxygen.

7. The method for preparing a water purifier based on polyaluminium chloride according to claim 4, characterized in that: The mass ratio of diethylenetriamine pentaacetic acid, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide is (9-11):(11-12):(12-16); the volume ratio of cross-linked chitosan solution and activated group solution is (1-3):

1.

8. The method for preparing a water purifier based on polyaluminium chloride according to claim 5, characterized in that: The kaolin is calcined and then acidified at a temperature of 500-700° C. for 3-5 hours. The acid used for the acidification is a 40 wt % sulfuric acid solution.