Preparation method of polyaluminum chloride water purifying agent

Abstract

The invention discloses a preparation method of a polyaluminum chloride water purifying agent. Comprising the following steps: step 1, dissolving aluminum trichloride hexahydrate in deionized water, raising the temperature to 70-80 DEG C, slowly dropwise adding a sodium hydroxide solution, reacting for 1-2 hours, and then curing for 24 hours to obtain a polyaluminum chloride solution; and 2, adding the modified chitosan into glacial acetic acid, carrying out ultrasonic stirring for 30-40 min, raising the temperature to 70-80 DEG C, slowly adding a polyaluminum chloride solution, dropwise adding a sodium hydroxide solution, carrying out a reaction for 1-2 h, and after the reaction is completed, carrying out static curing for 24 h to obtain the polyaluminum chloride water purifying agent. The water purifying agent has the beneficial effects that the chitosan is modified and compounded with the polyaluminum chloride, so that the water purifying capability is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of water purifiers, and in particular relates to a method for preparing a polyaluminium chloride water purifier. Background Art

[0002] In the field of water treatment, polyaluminium chloride (PAC), as a common inorganic polymer flocculant, is widely used in sewage and drinking water treatment due to its advantages such as fast hydrolysis rate and strong floc formation ability.

[0003] However, traditional polyaluminium chloride still has some limitations in practical applications. First, its flocculation effect is greatly affected by water quality conditions (such as pH value and temperature), and its stability is insufficient in complex water quality environments, resulting in loose flocs and slow sedimentation rate, especially limited removal efficiency of organic pollutants and colloidal particles. Secondly, traditional polyaluminium chloride mainly destroys colloid stability through charge neutralization, but its adsorption capacity for soluble organic pollutants (such as humic acid) is weak, making it difficult to achieve an efficient comprehensive purification effect. In addition, when polyaluminium chloride is used alone, the flocs are easily broken and secondary dispersion occurs, affecting subsequent treatment processes. Although chitosan has been tried to be compounded with polyaluminium chloride due to its biocompatibility and adsorption properties, unmodified chitosan has poor water solubility, low utilization rate of active groups, and weak synergistic effect with polyaluminium chloride, resulting in limited improvement in water purification effect.

[0004] Therefore, in order to solve the above problems, the present invention provides a method for preparing a polyaluminum chloride water purifier. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a method for preparing a polyaluminium chloride water purifier.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a polyaluminium chloride water purifier comprises the following steps:

[0008] Step 1: Dissolve aluminum chloride hexahydrate in deionized water, raise the temperature to 70-80°C, slowly add sodium hydroxide solution dropwise, react for 1-2 hours, and then mature for 24 hours to obtain a polyaluminum chloride solution;

[0009] Step 2: Add the modified chitosan to glacial acetic acid, ultrasonically stir for 30-40 minutes, then raise the temperature to 70-80°C, slowly add the polyaluminum chloride solution, and then add the sodium hydroxide solution dropwise, react for 1-2 hours, and after the reaction is completed, let it stand for 24 hours to obtain the polyaluminum chloride water purifier.

[0010] More optimally, the raw materials of the polyaluminium chloride solution include the following substances: by weight, 10-12 parts of aluminium chloride hexahydrate, 60-80 parts of deionised water, and 1-2 parts of sodium hydroxide solution; wherein the concentration of the sodium hydroxide solution is 1 mol / L.

[0011] More optimally, the raw materials of the polyaluminum chloride water purifier include the following substances: by weight, 10-12 parts of modified chitosan, 5-8 parts of glacial acetic acid, 20-30 parts of polyaluminum chloride solution, and 0.5-1 part of sodium hydroxide solution; wherein the concentration of the sodium hydroxide solution is 1 mol / L.

[0012] More optimally, the preparation process of the modified chitosan is:

[0013] S1: Mix 4-(chloromethyl)benzoic acid, 4-aminopyridine, and ethyl acetate, raise the temperature to 80-90°C, and reflux for 8-10 hours. After the reaction is complete, cool to room temperature, filter, wash, and vacuum dry to obtain intermediate A;

[0014] S2: Add chitosan to an aqueous acetic acid solution, stir and dissolve to obtain a chitosan solution; add intermediate A to methanol, stir and dissolve, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide, and continue stirring at room temperature for 30-40 minutes to obtain an intermediate solution; slowly add the intermediate solution dropwise to the chitosan solution, stir and react at room temperature for 24 hours, and post-treat to obtain modified chitosan.

[0015] In the scheme, the amino group of 4-aminopyridine acts as a nucleophile to attack the benzyl carbon in 4-(chloromethyl)benzoic acid to obtain intermediate A. The specific synthesis process is shown below:

[0016]

[0017] More optimally, the intermediate A raw material includes the following components: 17-18 parts of 4-(chloromethyl)benzoic acid, 10-12 parts of 4-aminopyridine, and 80-100 parts of ethyl acetate, by weight.

[0018] In this scheme, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide system are used to activate the carboxyl group in intermediate A to generate an active ester, which then undergoes a nucleophilic reaction with the amino group on chitosan to form a stable amide bond, thereby achieving graft modification of chitosan. The specific synthesis process is shown below:

[0019]

[0020] More optimally, the modified chitosan raw material includes the following components: by weight, 1-2 parts of chitosan, 50-60 parts of acetic acid aqueous solution, 2-3 parts of intermediate A, 40-50 parts of methanol, 1-2 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 1-2 parts of N-hydroxysuccinimide.

[0021] More optimally, the concentration of the acetic acid aqueous solution is 2 vol%.

[0022] Beneficial effects of the present invention:

[0023] The present invention effectively improves the efficiency of water purification by modifying chitosan and compounding it with polyaluminium chloride. The details are as follows:

[0024] Polyaluminum chloride preferentially destabilizes colloidal particles through charge neutralization, forming primary flocs. Modified chitosan, however, utilizes its high density of quaternary ammonium groups and long-chain structure to exert an adsorption bridging effect, cross-linking tiny flocs into larger, dense aggregates. The electrostatic attraction between the quaternary ammonium groups and the hydrolysis products of polyaluminum chloride may strengthen internal cross-linking within the flocs, reducing secondary dispersion after floc breakage. Furthermore, the amino and quaternary ammonium groups of chitosan can coordinate with the aluminum-hydroxy complex formed by polyaluminum chloride, forming an organic-inorganic composite network that enhances the density and sedimentation rate of the flocs. For organic pollutants, the synergistic effect of the hydrophobic regions of modified chitosan and the quaternary ammonium groups allows for the simultaneous adsorption of polar and non-polar pollutants, while the metal centers provided by polyaluminum chloride may further immobilize specific pollutants (such as phosphates) through coordination or coprecipitation, achieving multifunctional purification. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] Example 1: A method for preparing a polyaluminium chloride water purifier, comprising the following steps:

[0027] Step 1: Dissolve 10 parts of aluminum chloride hexahydrate in 60 parts of deionized water, raise the temperature to 70°C, slowly add 1 part of sodium hydroxide solution (concentration of 1 mol / L), react for 1 hour, and then mature for 24 hours to obtain a polyaluminum chloride solution;

[0028] Step 2: Add 10 parts of modified chitosan to 5 parts of glacial acetic acid, stir ultrasonically for 30 minutes, then raise the temperature to 70°C, slowly add 20 parts of polyaluminum chloride solution, and then add 0.5 parts of sodium hydroxide solution (concentration of 1 mol / L) dropwise, react for 1 hour, and after the reaction is completed, let it stand for 24 hours to obtain a polyaluminum chloride water purifier;

[0029] Wherein, the preparation process of modified chitosan is:

[0030] S1: Mix 17 parts of 4-(chloromethyl)benzoic acid, 10 parts of 4-aminopyridine, and 80 parts of ethyl acetate, raise the temperature to 80°C, and reflux for 8 hours. After the reaction is complete, cool to room temperature, filter, wash, and vacuum dry to obtain intermediate A;

[0031] S2: Add 1 part of chitosan to 50 parts of acetic acid aqueous solution, stir and dissolve to obtain a chitosan solution; add 2 parts of intermediate A to 40 parts of methanol, stir and dissolve, add 1 part of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1 part of N-hydroxysuccinimide, and continue stirring at room temperature for 30 minutes to obtain an intermediate solution; slowly add the intermediate solution dropwise to the chitosan solution, stir and react at room temperature for 24 hours, and post-treat to obtain modified chitosan.

[0032] Example 2: A method for preparing a polyaluminium chloride water purifier, comprising the following steps:

[0033] Step 1: Dissolve 12 parts of aluminum chloride hexahydrate in 80 parts of deionized water, raise the temperature to 80°C, slowly add 2 parts of sodium hydroxide solution (concentration is 1 mol / L), react for 2 hours, and then mature for 24 hours to obtain a polyaluminum chloride solution;

[0034] Step 2: Add 12 parts of modified chitosan to 8 parts of glacial acetic acid, stir ultrasonically for 40 minutes, then raise the temperature to 80°C, slowly add 30 parts of polyaluminum chloride solution, and then add 1 part of sodium hydroxide solution (concentration of 1 mol / L) dropwise, react for 2 hours, and after the reaction is completed, let it stand for 24 hours to obtain a polyaluminum chloride water purifier;

[0035] Wherein, the preparation process of modified chitosan is:

[0036] S1: Mix 18 parts of 4-(chloromethyl)benzoic acid, 12 parts of 4-aminopyridine, and 100 parts of ethyl acetate, raise the temperature to 90°C, and reflux for 10 hours. After the reaction is complete, cool to room temperature, filter, wash, and vacuum dry to obtain intermediate A;

[0037] S2: Add 2 parts of chitosan to 60 parts of acetic acid aqueous solution, stir and dissolve to obtain a chitosan solution; add 3 parts of intermediate A to 50 parts of methanol, stir and dissolve, add 2 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 2 parts of N-hydroxysuccinimide, and continue stirring at room temperature for 40 minutes to obtain an intermediate solution; slowly add the intermediate solution dropwise to the chitosan solution, stir and react at room temperature for 24 hours, and post-treat to obtain modified chitosan.

[0038] Example 3: A method for preparing a polyaluminium chloride water purifier, comprising the following steps:

[0039] Step 1: Dissolve 11 parts of aluminum chloride hexahydrate in 70 parts of deionized water, raise the temperature to 75°C, slowly add 1.5 parts of sodium hydroxide solution (concentration is 1 mol / L), react for 1.5 hours, and then mature for 24 hours to obtain a polyaluminum chloride solution;

[0040] Step 2: Add 11 parts of modified chitosan to 6.5 parts of glacial acetic acid, stir ultrasonically for 35 minutes, then raise the temperature to 75°C, slowly add 25 parts of polyaluminum chloride solution, and then add 0.75 parts of sodium hydroxide solution (concentration of 1 mol / L) dropwise, react for 1.5 hours, and after the reaction is completed, let it stand for 24 hours to obtain a polyaluminum chloride water purifier;

[0041] Wherein, the preparation process of modified chitosan is:

[0042] S1: Mix 17.5 parts of 4-(chloromethyl)benzoic acid, 11 parts of 4-aminopyridine, and 90 parts of ethyl acetate, raise the temperature to 85°C, and reflux for 9 hours. After the reaction is complete, cool to room temperature, filter, wash, and vacuum dry to obtain intermediate A;

[0043] S2: Add 1.5 parts of chitosan to 55 parts of acetic acid aqueous solution, stir and dissolve to obtain a chitosan solution; add 2.5 parts of intermediate A to 45 parts of methanol, stir and dissolve, add 1.5 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1.5 parts of N-hydroxysuccinimide, and continue stirring at room temperature for 35 minutes to obtain an intermediate solution; slowly add the intermediate solution dropwise to the chitosan solution, stir and react at room temperature for 24 hours, and post-treat to obtain modified chitosan.

[0044] Comparative Example 1: Without adding modified chitosan, a separate polyaluminum chloride water purifier was prepared, as follows:

[0045] Step 1: Dissolve 11 parts of aluminum chloride hexahydrate in 70 parts of deionized water, raise the temperature to 75°C, slowly add 1.5 parts of sodium hydroxide solution (concentration is 1 mol / L), react for 1.5 hours, and then mature for 24 hours to obtain a polyaluminum chloride water purifier.

[0046] Comparative Example 2: Chitosan is not modified, specifically as follows:

[0047] Step 1: Dissolve 11 parts of aluminum chloride hexahydrate in 70 parts of deionized water, raise the temperature to 75°C, slowly add 1.5 parts of sodium hydroxide solution (concentration is 1 mol / L), react for 1.5 hours, and then mature for 24 hours to obtain a polyaluminum chloride solution;

[0048] Step 2: Add 11 parts of chitosan to 6.5 parts of glacial acetic acid, ultrasonically stir for 35 minutes, then raise the temperature to 75°C, slowly add 25 parts of polyaluminum chloride solution, and then add 0.75 parts of sodium hydroxide solution (concentration is 1 mol / L) dropwise, react for 1.5 hours, and after the reaction is completed, let it stand for 24 hours to obtain a polyaluminum chloride water purifier.

[0049] Detection test:

[0050] Kaolin was dissolved in deionized water to prepare a suspension with a turbidity of 100 NTU. Humic acid (20 mg / L) was added to simulate COD pollution to obtain simulated sewage. 500 mL of the simulated sewage was placed in a beaker, the pH was adjusted to 7, 50 mg / L of the polyaluminum chloride water purifier obtained in the examples and comparative examples was added, and the mixture was stirred. The following test was conducted:

[0051] (1) Take the supernatant and measure the absorbance at a wavelength of 550 nm using a spectrophotometer, convert it into NTU, and calculate the turbidity removal rate;

[0052] (2) COD removal rate was determined using the potassium dichromate method (GB11914-89);

[0053] The obtained data is shown in the following table:

[0054]

[0055] Conclusion: The present invention significantly improves the performance of the water purifier by compounding modified chitosan with polyaluminum chloride. Experimental data show that the polyaluminum chloride water purifiers prepared in Examples 1, 2, and 3 are superior to those in Comparative Example 1 (without modified chitosan) and Comparative Example 2 (without modified chitosan) in terms of turbidity removal rate and COD removal rate. Specifically, the turbidity removal rate of the embodiment reaches 92.4%-93.8%, and the COD removal rate reaches 88.3%-89.5%, while the turbidity removal rate of Comparative Example 1 is only 70.2%, and the COD removal rate is 64.1%; the turbidity removal rate of Comparative Example 2 is 83.1%, and the COD removal rate is 73.5%. This shows that the introduction of modified chitosan significantly improves the flocculation ability and pollutant removal efficiency of the water purifier. The synergistic effect of its high-density quaternary ammonium group and long-chain structure with polyaluminum chloride enhances the density and sedimentation rate of the flocs, while further fixing the pollutants through electrostatic attraction and coordination, achieving multifunctional purification.

[0056] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0057] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a polyaluminium chloride water purifier, characterized in that: The following steps are involved: Step 1: Dissolve aluminum chloride hexahydrate in deionized water, raise the temperature to 70-80°C, slowly add sodium hydroxide solution dropwise, react for 1-2 hours, and then mature for 24 hours to obtain a polyaluminum chloride solution; Step 2: Add the modified chitosan to glacial acetic acid, ultrasonically stir for 30-40 minutes, then raise the temperature to 70-80°C, slowly add the polyaluminum chloride solution, and then add the sodium hydroxide solution dropwise, react for 1-2 hours, and after the reaction is completed, let it stand for 24 hours to obtain the polyaluminum chloride water purifier.

2. The method for preparing a polyaluminium chloride water purifier according to claim 1, wherein The raw materials of the polyaluminium chloride solution include the following substances: 10-12 parts by weight of aluminium chloride hexahydrate, 60-80 parts by weight of deionised water, and 1-2 parts by weight of sodium hydroxide solution; The concentration of the sodium hydroxide solution is 1 mol / L.

3. The method for preparing a polyaluminium chloride water purifier according to claim 1, wherein The raw materials of the polyaluminum chloride water purifier include the following substances: 10-12 parts by weight of modified chitosan, 5-8 parts by weight of glacial acetic acid, 20-30 parts by weight of polyaluminum chloride solution, and 0.5-1 part by weight of sodium hydroxide solution; wherein the concentration of the sodium hydroxide solution is 1 mol / L.

4. The method for preparing a polyaluminium chloride water purifier according to claim 1, wherein: The preparation process of the modified chitosan is: S1: Mix 4-(chloromethyl)benzoic acid, 4-aminopyridine, and ethyl acetate, raise the temperature to 80-90°C, and reflux for 8-10 hours. After the reaction is complete, cool to room temperature, filter, wash, and vacuum dry to obtain intermediate A; S2: Add chitosan to an aqueous acetic acid solution, stir and dissolve to obtain a chitosan solution; add intermediate A to methanol, stir and dissolve, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide, and continue stirring at room temperature for 30-40 minutes to obtain an intermediate solution; slowly add the intermediate solution dropwise to the chitosan solution, stir and react at room temperature for 24 hours, and post-treat to obtain modified chitosan.

5. The method for preparing a polyaluminium chloride water purifier according to claim 4, wherein: The intermediate A raw material includes the following components: 17-18 parts of 4-(chloromethyl)benzoic acid, 10-12 parts of 4-aminopyridine, and 80-100 parts of ethyl acetate, by weight.

6. The method for preparing a polyaluminium chloride water purifier according to claim 4, wherein: The modified chitosan raw material comprises the following components: by weight, 1-2 parts of chitosan, 50-60 parts of acetic acid aqueous solution, 2-3 parts of intermediate A, 40-50 parts of methanol, 1-2 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 1-2 parts of N-hydroxysuccinimide.

7. The method for preparing a polyaluminium chloride water purifier according to claim 4, wherein: The concentration of the acetic acid aqueous solution is 2 vol%.

Images