Composite polyaluminium chloride water treatment agent and preparation method thereof

Abstract

The invention discloses a composite polyaluminium chloride water treatment agent and a preparation method thereof, and belongs to the technical field of water treatment agent preparation. The preparation steps are as follows: placing a polyaluminium chloride solution in a reactor, adding a KH-570 coupling agent hydrolyzate and stirring evenly, adjusting the pH to 10 with a 0.1 mol / L sodium hydroxide solution, stirring and reacting for 4-6 hours, then adding modified octavinyl-POSS, modified chitosan and a composite emulsifier, stirring, slowly dripping ammonium persulfate under nitrogen protection, sealing the reactor, stirring and reacting for 3-4 hours at 60-65° C., and obtaining the composite polyaluminium chloride water treatment agent. The composite polyaluminium chloride water treatment agent has stable performance, large surface area, and a spatial network structure inside. The spatial network structure has better flocculation small particles and bridging adsorption performance than a branched structure. The composite polyaluminium chloride is used as a water treatment agent, and not only has a strong adsorption capacity, but also has stable flocs formed.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment agent preparation, and specifically relates to a composite polyaluminium chloride water treatment agent and a preparation method thereof. Background Art

[0002] Polyaluminium chloride water treatment agent, also known as polyaluminium chloride water purifier, abbreviated as PAC, has a molecular formula of [Al2(OH ) n Cl 6-n ] m It is a polyhydroxy, polynuclear complex cationic inorganic polymer flocculant, also commonly known as basic aluminum chloride or coagulant. The solid product has a light yellow appearance.

[0003] At present, polyaluminium chloride is widely used in water treatment and sludge dewatering. Compared with traditional aluminum salt flocculants, it has the advantages of wide water quality applicability, low price, good treatment effect on low-temperature and low-turbidity water, easy sedimentation and sludge dewatering, etc. However, its morphology, degree of polymerization and corresponding coagulation and flocculation effect are still inferior to organic polymer flocculants. Its molecular weight and adsorption and bridging ability for colloidal substances are much worse than those of organic polymer flocculants. Due to the lack of chelating groups coordinated with heavy metal ions, the removal efficiency of heavy metal ions is not good. In addition, single polyaluminium chloride often increases the solubility of aluminum ions in water during water treatment, and excessive aluminum ion concentration in water can cause human health problems such as Alzheimer's disease.

[0004] In view of the above problems, composite polyaluminium chloride water treatment agent is often used to improve the purification performance of polyaluminium chloride. For example, Chinese patent CN109231387B discloses a straw / polyaluminium chloride composite water treatment material and a preparation method thereof, which adopts a liquid phase method to prepare aluminium chloride powder with fly ash as raw material, and then composites the aluminium chloride powder with rice straw to obtain a composite material with good water treatment effect. The material has a high specific surface area and good adsorption and flocculation ability, but the straw and polyaluminium chloride are only combined by hydrogen bonding, and the interaction between the two is weak, resulting in poor shear resistance of the composite material during water treatment, and flocculation is easily broken, and small flocs can enter the filtered water through the filter layer, resulting in poor treatment effect. Therefore, it is necessary to improve a composite polyaluminium chloride water treatment agent with higher performance. Summary of the invention

[0005] The object of the present invention is to provide a composite polyaluminium chloride water treatment agent and a preparation method thereof, so as to solve the problems in the background technology.

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

[0007] The preparation method of the composite polyaluminium chloride water treatment agent comprises the following steps:

[0008] Put the polyaluminium chloride solution in a reactor, add KH-570 coupling agent hydrolyzate and stir evenly, adjust the pH to 10 with 0.1 mol / L sodium hydroxide solution, stir and react for 4-6 hours, then add modified octavinyl-POSS, modified chitosan and compound emulsifier, stir for 20-30 minutes, slowly add ammonium persulfate dropwise under nitrogen protection, seal the reactor, stir and react at 60-65°C for 3-4 hours, after the reaction, precipitate the product with ethanol, wash with acetone, and dry at 50°C to constant weight to obtain a composite polyaluminium chloride water treatment agent.

[0009] Further, the KH-570 coupling agent hydrolyzate is obtained by the following steps:

[0010] The silane coupling agent KH-570 was adjusted to pH 3-4 with 5 wt % hydrochloric acid solution and hydrolyzed for 12 h to obtain a KH-570 coupling agent hydrolyzate.

[0011] Furthermore, the mass fraction of polyaluminium chloride solution is 10-20%, the amount of KH-570 is 8-10% of the mass of polyaluminium chloride, the mass ratio of polyaluminium chloride, octavinyl-POSS and modified chitosan is 100:20-23:3-10, the amount of compound emulsifier is 1% of the total mass of octavinyl-POSS and modified chitosan, and the amount of ammonium persulfate is 0.6-0.7% of the total mass of octavinyl-POSS and modified chitosan.

[0012] Further, the preparation steps of modified octavinyl-POSS are as follows:

[0013] Step S11, octavinyl-POSS, mercaptoethylamine, benzoin dimethyl ether and DMF are mixed, and irradiated with ultraviolet light at a wavelength of 365nm for 1-2h, and DMF is removed by rotary evaporation to obtain bifunctional POSS, wherein the amount ratio of octavinyl-POSS, mercaptoethylamine, benzoin dimethyl ether and DMF is 3mmol:12mmol:20mg:40-50mL;

[0014] Step S12, mixing the bifunctional POSS and dimethyl sulfoxide, stirring to dissolve, then adding dibutyltin dilaurate dropwise, then adding 4-carboxyphenylisothiocyanate, stirring for 5-10 minutes, stirring and reacting at 50°C for 4 hours, cooling to room temperature for 48 hours, and after the reaction is completed, removing dimethyl sulfoxide by reduced pressure distillation to obtain modified octavinyl-POSS, the amount ratio of bifunctional POSS, dimethyl sulfoxide, dibutyltin dilaurate and 4-carboxyphenylisothiocyanate is 10.5-11.3g:80-100mL:0.3g:7.3-8.5g.

[0015] Octaveenyl-POSS and mercaptoethylamine are used as raw materials, the dosage ratio between the raw materials is controlled, and a bifunctional POSS containing an active amino group and an unsaturated double bond is obtained through a mercapto-ene click reaction. Then, the active amino group is reacted with the isothiocyanate of 4-carboxyphenyl isothiocyanate to obtain a POSS containing a thiourea structure, a carboxyl group, a benzene ring and an unsaturated double bond, namely, a modified octavinyl-POSS.

[0016] Further, the preparation steps of modified chitosan are as follows:

[0017] Step S21, adding allyl chloride, triethanolamine and deionized water into a flask, sealing the flask mouth with a rubber stopper and tape, heating to 40° C., reacting with magnetic stirring for 24 hours, and removing deionized water and unreacted allyl chloride by rotary evaporation to obtain a trihydroxyallyl quaternary ammonium salt compound;

[0018] Step S22, dispersing chitosan and phthalic anhydride in DMF, heating to 120°C under nitrogen protection, stirring for 8 hours, then cooling to room temperature, pouring the reaction product into ice water, stirring for 20-30 minutes, filtering, washing the filter cake with methanol for 3-5 times, and freeze-drying to obtain amino-protected chitosan;

[0019] Step S23, placing pyridine in a flask, adding amino-protected chitosan at 0°C, stirring and dissolving, slowly adding thionyl chloride, stirring and reacting at 80°C for 0.5h under nitrogen protection, pouring into ice water after cooling to room temperature, filtering after stirring, and vacuum drying the filter cake to obtain an intermediate product; placing tetrahydrofuran in a flask, adding trihydroxyallyl quaternary ammonium salt compound at 0°C, stirring evenly, adding NaH, stirring at 60°C for 1h under nitrogen protection, cooling to 0°C, adding the intermediate product, stirring for 0.5h, stirring at 60°C for 12h, after the reaction is completed, pouring the reaction product into methanol, filtering, and freeze-drying the filter cake to obtain quaternary ammonium salt etherified chitosan;

[0020] Step S24, dissolving the quaternary ammonium salt etherified chitosan in N-methyl-2-pyrrolidone, then adding a 4 mol / L hydrazine hydrate solution, reacting at 100° C. for 4-6 hours under argon protection, and removing water from the reaction solution by rotary evaporation after the reaction is completed. The rotary evaporation product is placed in anhydrous ethanol for precipitation and centrifugation. The obtained solid is washed with anhydrous ethanol, then placed in a dialysis bag for 2 days, and freeze-dried to obtain modified chitosan.

[0021] Firstly, allyl chloride and triethanolamine are used as raw materials, and a trihydroxyallyl quaternary ammonium salt compound is obtained through a quaternization reaction, and then phthalic anhydride is used to protect the active amino groups on the chitosan molecular chain, and then thionyl chloride is used to make the hydroxyl groups of the chitosan molecular chain undergo HCl elimination reaction, and the trihydroxyallyl quaternary ammonium salt compound is grafted onto the chitosan molecular chain through an ether bond, and finally the quaternary ammonium salt etherified chitosan is subjected to a hydrazine hydrate solution to remove the amino protecting group, so as to obtain a modified chitosan containing an active amino group, a quaternary ammonium salt structure and an unsaturated double bond. Compared with introducing a functional compound into the chitosan molecular chain through an acylation reaction or an esterification reaction, the ether bond has higher stability, better acid and alkali resistance, and can ensure the stability of the modified chitosan molecule.

[0022] Furthermore, in step S21, the dosage ratio of allyl chloride, triethanolamine and deionized water is 0.1 mol: 0.11 mol: 150-200 mL.

[0023] Furthermore, in step S22, the usage ratio of chitosan, phthalic anhydride and DMF is 4.5-4.8 g:13.32 g:200 mL.

[0024] Furthermore, in step S23, the usage ratio of pyridine, amino-protected chitosan, dithionyl chloride, tetrahydrofuran, trihydroxyallyl quaternary ammonium salt compound and NaH is 100 mL: 2 g: 0.5 mL: 50-60 mL: 2.3-2.5 g: 1 g.

[0025] Furthermore, in step S24, the dosage ratio of quaternary ammonium salt etherified chitosan, N-methyl-2-pyrrolidone and hydrazine hydrate solution is 2.5-3.0 g: 100 mL: 100 mL.

[0026] Furthermore, the compound emulsifier is composed of anionic emulsifier and nonionic emulsifier in a mass ratio of 0.5-3:1, the anionic emulsifier is selected from one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium fatty alcohol ether sulfate, and sodium secondary alkyl sulfonate; the nonionic emulsifier is selected from one of Tween 80, Span 80, alkylphenol polyoxyethylene ether, and fatty alcohol polyoxyethylene ether.

[0027] The composite polyaluminium chloride water treatment agent is prepared by the above preparation method.

[0028] Beneficial effects of the present invention:

[0029] The invention provides a composite polyaluminium chloride water treatment agent. The composite polyaluminium chloride is used as a base material, and is pre-treated by a KH-570 coupling agent. Then, unsaturated double bonds of the KH-570 coupling agent and modified octaethylene-POSS and modified chitosan are used to generate a polymerization reaction. KH-570 builds a "molecular bridge" between inorganic hydroxyl polyaluminium chloride and an organic polymer, so that the polyaluminium chloride is connected with the modified octaethylene-POSS and the modified chitosan through chemical bonds. The obtained composite polyaluminium chloride has more stable performance and a larger surface area, and has a spatial network structure inside. The spatial network structure has better flocculation small particles and bridging adsorption performance than a branched structure. Therefore, the composite polyaluminium chloride is used as a water treatment agent, and not only has a strong adsorption capacity, but also has stable flocs.

[0030] The invention introduces modified octavinyl-POSS into composite polyaluminium chloride, which not only acts together with modified chitosan to form a spatial network structure on the surface of polyaluminium chloride, but also introduces a porous cage-type siloxane structure, which is beneficial to the interaction with inorganic heavy metal ions and organic pollutants in water. Combined with the thiourea structure, benzene ring and active carboxyl group in the modified octavinyl-POSS molecule, the modified octavinyl-POSS can interact with inorganic heavy metal ions and organic pollutants through coordination and π-π adsorption, thereby improving the adsorption and removal effect.

[0031] The invention introduces modified chitosan into the composite polyaluminium chloride, not only utilizing the abundant amino groups and hydroxyl groups in the chitosan molecules to adsorb organic pollutants, metal ions and protein molecules through adsorption and coordination, but also overcoming the harm of excessive aluminium ion solubility in water caused by the release of aluminium ions by polyaluminium chloride through the coordination between the active amino groups and the aluminium ions. In addition, the modified chitosan in the invention has a quaternary ammonium salt structure, which can adsorb pollutants through electrostatic action. DETAILED DESCRIPTION

[0032] 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment provides a modified octavinyl-POSS, and the preparation steps are as follows:

[0035] Step S11, 3 mmol of octavinyl-POSS, 12 mmol of mercaptoethylamine, 20 mg of benzoin dimethyl ether and 40 mL of DMF were mixed, and the mixture was irradiated with ultraviolet light at a wavelength of 365 nm for 1 h, and the DMF was removed by rotary evaporation to obtain bifunctional POSS;

[0036] Step S12, 10.5 g of bifunctional POSS and 80 mL of dimethyl sulfoxide were mixed, and after stirring to dissolve, 0.3 g of dibutyltin dilaurate was added dropwise, followed by adding 7.3 g of 4-carboxyphenyl isothiocyanate, stirring for 5 min, and reacting at 50 ° C for 4 h, then cooling to room temperature for 48 h. After the reaction was completed, the dimethyl sulfoxide was removed by vacuum distillation to obtain modified octavinyl-POSS.

[0037] Example 2

[0038] This embodiment provides a modified octavinyl-POSS, and the preparation steps are as follows:

[0039] Step S11, 3 mmol of octavinyl-POSS, 12 mmol of mercaptoethylamine, 20 mg of benzoin dimethyl ether and 50 mL of DMF were mixed, and the mixture was irradiated with ultraviolet light at a wavelength of 365 nm for 2 h, and the DMF was removed by rotary evaporation to obtain bifunctional POSS;

[0040] Step S12, 11.3 g of bifunctional POSS and 100 mL of dimethyl sulfoxide were mixed, 0.3 g of dibutyltin dilaurate was added dropwise after stirring to dissolve, and then 8.5 g of 4-carboxyphenyl isothiocyanate was added, stirred for 10 min, stirred and reacted at 50 ° C for 4 h, cooled to room temperature and reacted for 48 h. After the reaction was completed, the dimethyl sulfoxide was removed by vacuum distillation to obtain modified octavinyl-POSS.

[0041] Comparative Example 1

[0042] This comparative example is octavinyl-POSS.

[0043] Example 3

[0044] A modified chitosan, the preparation steps are as follows:

[0045] Step S21, adding 0.1 mol of allyl chloride, 0.11 mol of triethanolamine and 150 mL of deionized water into a flask, sealing the flask mouth with a rubber stopper and tape, heating to 40° C., reacting with magnetic stirring for 24 h, and removing the deionized water and unreacted allyl chloride by rotary evaporation to obtain a trihydroxyallyl quaternary ammonium salt compound;

[0046] Step S22, dispersing 4.5 g of chitosan and 13.32 g of phthalic anhydride in 200 mL of DMF, heating to 120° C. under nitrogen protection, stirring for reaction for 8 h, then cooling to room temperature, pouring the reaction product into ice water, stirring for 20, filtering, washing the filter cake with methanol 3 times, and freeze-drying to obtain amino-protected chitosan;

[0047] Step S23, placing 100mL of pyridine in a flask, adding 2g of amino-protected chitosan at 0°C, stirring and dissolving, slowly adding 0.5mL of dichlorothionyl, stirring and reacting at 80°C for 0.5h under nitrogen protection, pouring into ice water after cooling to room temperature, filtering after stirring, and vacuum drying the filter cake to obtain an intermediate product; placing 50mL of tetrahydrofuran in a flask, adding 2.3g of trihydroxyallyl quaternary ammonium salt compound at 0°C, stirring evenly, adding 1g of NaH, stirring at 60°C for 1h under nitrogen protection, cooling to 0°C, adding the intermediate product, stirring for 0.5h, stirring at 60°C for 12h, after the reaction is completed, pouring the reaction product into methanol, filtering, and freeze-drying the filter cake to obtain quaternary ammonium salt etherified chitosan;

[0048] Step S24, dissolving 2.5 g of quaternary ammonium salt etherified chitosan in 100 mL of N-methyl-2-pyrrolidone, then adding 100 mL of 4 mol / L hydrazine hydrate solution, reacting at 100 ° C for 4 h under argon protection, and removing water from the reaction solution by rotary evaporation after the reaction is completed. The rotary evaporation product is placed in anhydrous ethanol for precipitation and centrifugation. The obtained solid is washed with anhydrous ethanol, and then placed in a dialysis bag for 2 d, and freeze-dried to obtain modified chitosan.

[0049] Example 4

[0050] A modified chitosan, the preparation steps are as follows:

[0051] Step S21, adding 0.1 mol of allyl chloride, 0.11 mol of triethanolamine and 200 mL of deionized water into a flask, sealing the flask mouth with a rubber stopper and tape, heating to 40° C., reacting with magnetic stirring for 24 h, and removing the deionized water and unreacted allyl chloride by rotary evaporation to obtain a trihydroxyallyl quaternary ammonium salt compound;

[0052] Step S22, dispersing 4.8 g of chitosan and 13.32 g of phthalic anhydride in 200 mL of DMF, heating to 120° C. under nitrogen protection, stirring for reaction for 8 h, then cooling to room temperature, pouring the reaction product into ice water, stirring for 30 min, filtering, washing the filter cake with methanol 5 times, and freeze-drying to obtain amino-protected chitosan;

[0053] Step S23, placing 100mL of pyridine in a flask, adding 2g of amino-protected chitosan at 0°C, stirring and dissolving, slowly adding 0.5mL of dichlorothionyl, stirring and reacting at 80°C for 0.5h under nitrogen protection, pouring into ice water after cooling to room temperature, filtering after stirring, and vacuum drying the filter cake to obtain an intermediate product; placing 60mL of tetrahydrofuran in a flask, adding 2.5g of trihydroxyallyl quaternary ammonium salt compound at 0°C, stirring evenly, adding 1g of NaH, stirring at 60°C for 1h under nitrogen protection, cooling to 0°C, adding the intermediate product, stirring for 0.5h, stirring at 60°C for 12h, after the reaction is completed, pouring the reaction product into methanol, filtering, and freeze-drying the filter cake to obtain quaternary ammonium salt etherified chitosan;

[0054] Step S24, dissolving 3.0 g of quaternary ammonium salt etherified chitosan in 100 mL of N-methyl-2-pyrrolidone, then adding 100 mL of 4 mol / L hydrazine hydrate solution, reacting at 100 ° C for 6 h under argon protection, and removing water from the reaction solution by rotary evaporation after the reaction is completed. The rotary evaporation product is placed in anhydrous ethanol for precipitation and centrifugation. The obtained solid is washed with anhydrous ethanol, and then placed in a dialysis bag for 2 d, and freeze-dried to obtain modified chitosan.

[0055] Comparative Example 2

[0056] This comparative example is the trihydroxyallyl quaternary ammonium salt compound prepared in step S21 of Example 3.

[0057] Example 5

[0058] A method for preparing a composite polyaluminium chloride water treatment agent comprises the following steps:

[0059] The pH value of the silane coupling agent KH-570 was adjusted to 3 with 5wt% hydrochloric acid solution, and the mixture was hydrolyzed for 12h to obtain a KH-570 coupling agent hydrolyzate. A 10% polyaluminium chloride solution was placed in a reactor, and the KH-570 coupling agent hydrolyzate was added and stirred evenly. The pH value was adjusted to 10 with 0.1mol / L sodium hydroxide solution, and the mixture was stirred for 4h. Then, the modified octavinyl-POSS of Example 1, the modified chitosan of Example 3 and the compound emulsifier were added, and the mixture was stirred for 20min. Under nitrogen protection, ammonium persulfate was slowly added dropwise, and the reactor was sealed. The mixture was stirred for 3h at 60°C. After the reaction was completed, the product was precipitated with ethanol, washed with acetone, and dried at 50°C to constant weight to obtain a composite polyaluminium chloride water treatment agent.

[0060] Among them, the amount of KH-570 is 8% of the mass of polyaluminium chloride, the mass ratio of polyaluminium chloride, octavinyl-POSS and modified chitosan is 100:20:3, the amount of compound emulsifier is 1% of the mass of octavinyl-POSS and modified chitosan, and the amount of ammonium persulfate is 0.6% of the mass of octavinyl-POSS and modified chitosan.

[0061] Wherein, the compound emulsifier is composed of sodium lauryl sulfate and Tween 80 in a mass ratio of 0.5:1.

[0062] Example 6

[0063] A method for preparing a composite polyaluminium chloride water treatment agent comprises the following steps:

[0064] The pH value of the silane coupling agent KH-570 was adjusted to 4 with 5wt% hydrochloric acid solution, and the mixture was hydrolyzed for 12h to obtain a KH-570 coupling agent hydrolyzate. A 15% polyaluminium chloride solution was placed in a reactor, and the KH-570 coupling agent hydrolyzate was added and stirred evenly. The pH value was adjusted to 10 with 0.1mol / L sodium hydroxide solution, and the mixture was stirred for 5h. Then, the modified octavinyl-POSS of Example 1, the modified chitosan of Example 4 and the compound emulsifier were added, and the mixture was stirred for 20min. Under nitrogen protection, ammonium persulfate was slowly added dropwise, and the reactor was sealed. The mixture was stirred for 3.5h at 64°C. After the reaction, the product was precipitated with ethanol, washed with acetone, and dried at 50°C to constant weight to obtain a composite polyaluminium chloride water treatment agent.

[0065] Among them, the amount of KH-570 is 9% of the mass of polyaluminium chloride, the mass ratio of polyaluminium chloride, octavinyl-POSS and modified chitosan is 100:22:6, the amount of compound emulsifier is 1% of the total mass of octavinyl-POSS and modified chitosan, and the amount of ammonium persulfate is 0.6% of the total mass of octavinyl-POSS and modified chitosan.

[0066] Wherein, the compound emulsifier is composed of sodium dodecylbenzene sulfonate and Span 80 in a mass ratio of 1:1.

[0067] Example 7

[0068] A method for preparing a composite polyaluminium chloride water treatment agent comprises the following steps:

[0069] The pH value of the silane coupling agent KH-570 was adjusted to 4 with 5wt% hydrochloric acid solution, and the mixture was hydrolyzed for 12h to obtain a KH-570 coupling agent hydrolyzate. A 20% polyaluminium chloride solution was placed in a reactor, and the KH-570 coupling agent hydrolyzate was added and stirred evenly. The pH value was adjusted to 10 with 0.1mol / L sodium hydroxide solution, and the mixture was stirred for 6h. Then, the modified octavinyl-POSS of Example 2, the modified chitosan of Example 4 and the compound emulsifier were added, and the mixture was stirred for 30min. Under nitrogen protection, ammonium persulfate was slowly added dropwise, and the reactor was sealed. The mixture was stirred for 4h at 65°C. After the reaction was completed, the product was precipitated with ethanol, washed with acetone, and dried at 50°C to constant weight to obtain a composite polyaluminium chloride water treatment agent.

[0070] Among them, the amount of KH-570 is 10% of the mass of polyaluminium chloride, the mass ratio of polyaluminium chloride, octavinyl-POSS and modified chitosan is 100:23:10, the amount of compound emulsifier is 1% of the total mass of octavinyl-POSS and modified chitosan, and the amount of ammonium persulfate is 0.7% of the total mass of octavinyl-POSS and modified chitosan.

[0071] Wherein, the compound emulsifier is composed of sodium dodecylbenzene sulfonate and fatty alcohol polyoxyethylene ether in a mass ratio of 3:1.

[0072] Comparative Example 3

[0073] Compared with Example 5, the modified octavinyl-POSS in Example 5 is replaced by the substance in Comparative Example 1, and the remaining raw materials and preparation process are the same as in Example 5.

[0074] Comparative Example 4

[0075] Compared with Example 5, the modified chitosan in Example 5 is used as the material in Comparative Example 2, and the other raw materials and preparation process are the same as in Example 5.

[0076] The composite polyaluminium chloride prepared in Examples 5-7 and Comparative Examples 3-4 was subjected to performance tests, and the test items were as follows:

[0077] Wastewater from a company was collected. The contents of various substances in the wastewater were as follows: methylene blue 55.8 mg / L, Cu 2+ 50.3mg / mL, COD 312.9mg / mL;

[0078] (I) Aluminum ion dissolution performance test:

[0079] The composite polyaluminium chloride of the embodiment and the comparative example was added to the collected wastewater in a 500 mL conical flask (the addition amount was 0.5 g / L), shaken for 5 min, allowed to stand for 30 min, and the supernatant was taken to measure the residual aluminium ion content;

[0080] (II) Purification capacity:

[0081] The composite polyaluminium chloride of the embodiment and the comparative example was added to the collected wastewater in a 500mL conical flask (the addition amount was 0.5g / L), shaken for 5min, and allowed to stand for 30min. The supernatant was taken to test the methylene blue content, COD content, Cu 2+ content, and calculate the removal rate of methylene blue, COD removal rate, Cu 2+ Removal rate;

[0082] The test results are shown in Table 1:

[0083] Table 1

[0084] project Example 5 Example 6 Example 7 Comparative Example 3 Comparative Example 4 Aluminum ion residual (mg / L) 1.2 1.1 0.9 1.7 2.4 Methylene blue removal rate (%) 96.4 96.9 97.8 95.9 94.2 COD removal rate (%) 88.1 88.7 89.2 87.1 84.2 <![CDATA[Cu 2+ Removal rate (%)]]> 95.3 95.9 96.5 91.4 88.3

[0085] It can be seen from Table 1 that, compared with Comparative Examples 3-4, the composite polyaluminum chloride prepared in Examples 5-7 has low residual aluminum ion content after wastewater treatment and high removal rate for polluting dyes, COD, and metal ions, and has a very high purification effect.

[0086] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0087] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a composite polyaluminium chloride water treatment agent, characterized in that: The following steps are involved: The first step is to mix the bifunctional POSS and dimethyl sulfoxide, stir and dissolve, then add dibutyltin dilaurate dropwise, then add 4-carboxyphenyl isothiocyanate, stir, react at 50°C for 4h, then cool to room temperature for 48h to obtain modified octavinyl-POSS; Step 2: Add KH-570 coupling agent hydrolyzate to the polyaluminium chloride solution, stir evenly, adjust the pH to 10 with 0.1 mol / L sodium hydroxide solution, stir and react for 4-6 hours, then add modified octavinyl-POSS, modified chitosan and compound emulsifier, stir, add ammonium persulfate dropwise under nitrogen protection, stir and react for 3-4 hours at 60-65°C to obtain a composite polyaluminium chloride water treatment agent; The preparation steps of bifunctional POSS are as follows: Octavinyl-POSS, mercaptoethylamine, benzoin dimethyl ether and DMF were mixed and irradiated with ultraviolet light at a wavelength of 365 nm for 1-2 h to obtain bifunctional POSS; The preparation steps of modified chitosan are as follows: Step S21, mixing allyl chloride, triethanolamine and deionized water, stirring and reacting at 40° C. for 24 hours to obtain a trihydroxyallyl quaternary ammonium salt compound; Step S22, dispersing chitosan and phthalic anhydride in DMF, stirring and reacting at 120° C. for 8 h under nitrogen protection to obtain amino-protected chitosan; Step S23, placing pyridine in a flask, adding amino-protected chitosan at 0°C, stirring to dissolve, slowly adding thionyl chloride, stirring and reacting at 80°C for 0.5h under nitrogen protection to obtain an intermediate product; placing tetrahydrofuran in a flask, adding trihydroxyallyl quaternary ammonium salt compound at 0°C, stirring evenly, adding NaH, stirring at 60°C for 1h under nitrogen protection, cooling to 0°C, adding the intermediate product, stirring for 0.5h, stirring at 60°C for 12h, and obtaining quaternary ammonium salt etherified chitosan; Step S24, dissolving the quaternary ammonium salt etherified chitosan in N-methyl-2-pyrrolidone, then adding a 4 mol / L hydrazine hydrate solution, and reacting at 100° C. for 4-6 hours under argon protection to obtain modified chitosan.

2. The method for preparing a composite polyaluminium chloride water treatment agent according to claim 1, characterized in that: The usage ratio of bifunctional POSS, dimethyl sulfoxide, dibutyltin dilaurate and 4-carboxyphenyl isothiocyanate is 10.5-11.3 g: 80-100 mL: 0.3 g: 7.3-8.5 g.

3. The preparation method of the composite polyaluminium chloride water treatment agent according to claim 1, characterized in that: KH-570 coupling agent hydrolyzate is obtained by the following steps: The silane coupling agent KH-570 was adjusted to pH 3-4 with 5wt% hydrochloric acid solution and hydrolyzed for 12h to obtain a KH-570 coupling agent hydrolyzate.

4. The method for preparing a composite polyaluminium chloride water treatment agent according to claim 1, characterized in that: The mass ratio of polyaluminium chloride, modified octavinyl-POSS and modified chitosan is 100:20-23:3-10, and the amount of ammonium persulfate is 0.6-0.7% of the total mass of modified octavinyl-POSS and modified chitosan.

5. The method for preparing a composite polyaluminium chloride water treatment agent according to claim 1, characterized in that: The mass fraction of polyaluminium chloride solution is 10-20%, and the amount of KH-570 used is 8-10% of the mass of polyaluminium chloride.

6. The method for preparing a composite polyaluminium chloride water treatment agent according to claim 1, characterized in that: In step S23, the dosage ratio of pyridine, amino-protected chitosan, dithionyl chloride, tetrahydrofuran, trihydroxyallyl quaternary ammonium salt compound and NaH is 100 mL: 2 g: 0.5 mL: 50-60 mL: 2.3-2.5 g: 1 g.

7. Composite polyaluminium chloride water treatment agent, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6.