Composite polyaluminum chloride water purifying agent and preparation method thereof

Abstract

The application belongs to the technical field of water purifying agent preparation, and provides a composite polyaluminum chloride water purifying agent and a preparation method thereof; first, polyaluminum chloride mother liquor with high polymerization degree is prepared by a high-temperature and high-pressure hydrothermal method as an inorganic skeleton, ferrous sulfide / magnetic iron oxide composite nanocrystal cores are hydrothermally synthesized by using ferrous sulfate heptahydrate, thiourea and trisodium citrate, and a cationic / anionic polymer composite template is constructed by using sodium lignosulfonate and cationic polyacrylamide, further, calcium and magnesium ions chelated by glycine are introduced to form a chemical precipitation precursor which can be released in water, and the above functional modules are sequentially added to the polyaluminum chloride mother liquor according to an optimized adding sequence, so that the nanocrystal cores, the polymer template and the calcium and magnesium precursor are orderly self-assembled in the mother liquor, and an integrated composite coagulant with coagulation, adsorption and chemical precipitation phosphorus removal functions is obtained.

Description

Technical Field

[0001] This invention belongs to the field of water purification agent preparation technology, and relates to a composite polyaluminum chloride water purification agent and its preparation method. Background Technology

[0002] Eutrophication is one of the major challenges facing the water environment today, primarily due to the long-term excessive levels of nutrients such as nitrogen and phosphorus in water bodies. Therefore, achieving efficient phosphorus removal has become a key technological aspect and an essential requirement in the treatment of municipal sewage and various industrial wastewaters. Chemical precipitation is currently one of the most widely used phosphorus removal technologies. Its basic principle is to add metal salt coagulants to the water, causing soluble phosphates to be converted into insoluble precipitates and separated from the water along with the flocs. Polyaluminum chloride (PAC), as a high-performance inorganic polymeric coagulant, has advantages such as low dosage, wide applicable pH range, and large, dense flocs, leading to its widespread application in water treatment. Traditional PAC mainly relies on the positive charge of its polynuclear aluminum hydroxyl complex to neutralize negatively charged colloidal pollutants in the water, thereby removing suspended solids and simultaneously removing some inorganic phosphates.

[0003] However, under conditions of deep phosphorus removal and complex water quality, the limitations of traditional polyaluminum chloride (PAC) are becoming increasingly apparent. On the one hand, it mainly removes phosphorus by generating aluminum phosphate precipitate, but aluminum phosphate has a relatively high solubility product, making it difficult to stably control the phosphorus concentration in the effluent at extremely low levels. On the other hand, its mechanism of action is relatively simple, making it sensitive to fluctuations in influent water quality. Its phosphorus removal efficiency is prone to fluctuations when dealing with complex forms of phosphorus or changes in water quality conditions, and its ability to remove complex forms of phosphorus such as organic phosphorus is also limited. To improve phosphorus removal efficiency, existing technologies have attempted to physically blend or simply copolymerize PAC with iron salts, but these composite methods are mostly mechanical superpositions of the functions of each component, with limited synergy between structure and function. The overall performance improvement of the product remains small, making it difficult to meet the requirements of deep phosphorus removal and stable operation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a composite polyaluminum chloride water purifier and its preparation method. The method involves preparing polyaluminum chloride using a high-temperature, high-pressure process, introducing a composite dispersion, a synergistic network template composed of anionic and cationic polymers, and an organic acid-chelated calcium and magnesium ion precursor capable of chemical precipitation for phosphorus removal. Through a specific self-assembly pathway, these functional modules are systematically composited onto a polyaluminum chloride matrix to construct a composite polyaluminum chloride, thereby meeting the needs of actual production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a composite polyaluminum chloride water purification agent, specifically comprising the following components: a composite dispersion, a sodium lignosulfonate solution, a glycine chelated calcium magnesium precursor solution, a polyacrylamide solution, and a polyaluminum chloride mother liquor.

[0007] In some optional embodiments, the mass ratio of the composite dispersion, sodium lignosulfonate solution, glycine chelated calcium magnesium precursor solution, polyacrylamide solution and polyaluminum chloride mother liquor is (3-6):(1-3):(15-25):(3-6):(65-75).

[0008] Secondly, the present invention provides a method for preparing a composite polyaluminum chloride water purification agent, the preparation method comprising:

[0009] S1, mix hydrochloric acid solution with deionized water to obtain dilute hydrochloric acid solution, then mix aluminum hydroxide with dilute hydrochloric acid solution to react and obtain polyaluminum chloride mother liquor;

[0010] S2, ferrous sulfate heptahydrate, thiourea and trisodium citrate are sequentially dispersed in deionized water to react and obtain a composite solid. The composite solid is then dispersed in fresh deionized water to obtain a composite dispersion.

[0011] S3, Sodium lignosulfonate is dispersed in deionized water to obtain a sodium lignosulfonate solution, and cationic polyacrylamide is dispersed in deionized water to obtain a polyacrylamide solution;

[0012] S4, calcium chloride dihydrate, magnesium chloride hexahydrate and glycine are sequentially dispersed in deionized water and reacted to obtain glycine chelated calcium magnesium precursor solution.

[0013] S5, the composite dispersion, sodium lignosulfonate solution, glycine chelated calcium magnesium precursor solution and polyacrylamide solution are added sequentially to the polyaluminum chloride mother liquor to obtain a composite polyaluminum chloride water purification agent.

[0014] Specifically, it includes:

[0015] S1, mix hydrochloric acid solution with deionized water to obtain dilute hydrochloric acid solution, then mix aluminum hydroxide with dilute hydrochloric acid solution and transfer to reaction vessel, adjust temperature to the first temperature, control pressure and carry out reaction, after the reaction is completed, polyaluminum chloride mother liquor is obtained;

[0016] S2, ferrous sulfate heptahydrate, thiourea and trisodium citrate are sequentially dispersed in deionized water and subjected to hydrothermal reaction. After the reaction is completed, the mixture is centrifuged and washed until the washing solution is neutral to obtain a composite solid. The composite solid is then dispersed in fresh deionized water and ultrasonically dispersed to obtain a composite dispersion.

[0017] S3, Sodium lignosulfonate is dispersed in deionized water and stirred to obtain a sodium lignosulfonate solution. Cationic polyacrylamide is dispersed in deionized water and dispersed evenly to obtain a polyacrylamide solution.

[0018] S4, calcium chloride dihydrate, magnesium chloride hexahydrate and glycine are sequentially dispersed in deionized water, the temperature is adjusted to the second temperature and the reaction is stirred to obtain glycine chelated calcium magnesium precursor solution.

[0019] S5. Through orthogonal experiments, a composite dispersion, sodium lignosulfonate solution, glycine chelated calcium magnesium precursor solution, and polyacrylamide solution were sequentially added to the polyaluminum chloride mother liquor to obtain a composite polyaluminum chloride water purification agent.

[0020] First, via a high-temperature, high-pressure hydrothermal method, aluminum hydroxide undergoes depolymerization and repolymerization in an acidic medium, forming an inorganic polymer framework primarily composed of polynuclear hydroxyl aluminum complexes. Aluminum ions hydrolyze and polymerize to generate aluminum polymers with high positive charge and excellent spatial conformation. These aluminum polymers disrupt the stability of colloidal particles in the water through charge neutralization and connect microparticles into initial flocculant nuclei through adsorption bridging. Then, ferrous sulfide / magnetic iron oxide composite nanocrystals are prepared via a hydrothermal method. The magnetic iron oxide component provides a large specific surface area and abundant surface hydroxyl groups, serving as efficient phosphate adsorption sites and anchoring points for heterogeneous nucleation and ordered growth of the aluminum polymers. The ferrous sulfide component endows the system with potential reducing and heavy metal capture capabilities. During the subsequent slow reaction with the main acidic medium, ferrous ions are continuously released. The in-situ generated ferrous ions are oxidized in the water treatment environment, forming new ferric hydroxide colloids, producing a secondary coagulation effect and enhancing the capture capacity of pollutants.

[0021] In step S3, a synergistic template system of anionic and cationic polymers was used. Lignosulfonate, as a natural anionic polymer, first forms a polyelectrolyte complex with the positively charged polyaluminum chloride mother liquor through electrostatic interaction during the preparation of composite polyaluminum chloride. The formation of the polyelectrolyte complex not only stabilizes the colloid and prevents it from over-polymerizing and gelling, but more importantly, it constructs a hybrid network framework with a denser structure and a more uniform charge distribution. Subsequently, the long-chain cationic polyacrylamide is introduced, which simultaneously adsorbs multiple polyelectrolyte complexes through its flexible long chains. This results in the final flocs having both high density and large size, thereby increasing the sedimentation rate and achieving efficient solid-liquid separation.

[0022] Finally, by pre-chelating calcium and magnesium ions with glycine, divalent cations are introduced into the acidic polyaluminum chloride mother liquor in a stable form. Glycine, as an amphoteric ligand, effectively shields the free activity of calcium and magnesium ions, preventing adverse side reactions with the main polymer during product storage. When the product is added to the wastewater for dilution, the equilibrium of the chelate is disrupted, allowing calcium and magnesium ions to be slowly released. The released magnesium ions, in the presence of ammonia nitrogen, can form a precipitate with phosphate ions; while calcium ions, in the slightly alkaline environment formed by hydroxide ion enrichment within the flocs, can form hydroxyapatite precipitate with phosphate ions. These two chemical precipitation mechanisms, complementing the coagulation and precipitation of polyaluminum chloride and the adsorption of nanonuclei, together constitute a multi-pathway removal system for phosphate ions, ensuring extremely high removal efficiency even at low concentrations.

[0023] Regarding orthogonal experiments, the orthogonal experiment scheme table (Table 1) will now be explained in detail.

[0024] Table 1 L9(3) 4 Orthogonal Experimental Design Table

[0025]

[0026] To systematically optimize the formulation and preparation process of composite polyaluminum chloride and explore the synergistic effect among its components, this invention employs an orthogonal experimental design method. Considering the multiple key variables involved in the system, orthogonal experiments can significantly reduce the number of experiments by rationally selecting representative experimental points while ensuring the scientific validity of the results. This invention selects four key factors that have a decisive impact on product performance: firstly, the mass ratio of the "dry solids" (msolid) in the composite dispersion of step S2 to the mass of Al2O3 contained in the polyaluminum chloride mother liquor of step S1, msolid... 固 / m Al2O3 The objective is to explore the optimal dosage of the composite solid as both an adsorption center and a reaction nucleus, balancing performance gain with product stability and cost; secondly, the mass ratio of sodium lignosulfonate to cationic polyacrylamide in step S3, m 木质素磺酸钠 :m 聚丙烯酰胺 The aim is to optimize the synergistic effect of anionic / cationic polymers to construct a polyelectrolyte complex template with a dense network framework; furthermore, the molar ratio of calcium and magnesium to aluminum, n (Ca+Mg) / n Al The optimal molar ratio of calcium and magnesium ions as auxiliary chemical precipitation phosphorus removal agents was determined to enhance deep phosphorus removal capability. Finally, the order of material addition was studied to investigate the influence of the synthesis process on the microstructure of the final product. By controlling the order of reactant addition, the synergistic effect was maximized, and three investigation levels were set for each factor. Based on this, L9(3) was selected. 4Orthogonal arrays were used to guide the construction of experimental schemes. Through nine representative experiments, the primary and secondary factors affecting the coagulation and phosphorus removal performance of the product were efficiently screened, and the optimal parameter combination was determined.

[0027] The order of addition is detailed below. In order 1, the sodium lignosulfonate solution, glycine chelated calcium-magnesium precursor solution, composite dispersion, and polyacrylamide solution are sequentially added to the polyaluminum chloride mother liquor. The aim is to construct a layered core-shell structure, maximizing functionality through alternating polymer and ionic layer coating. In order 2, the glycine chelated calcium-magnesium precursor solution, composite dispersion, and a mixture of sodium lignosulfonate and polyacrylamide solutions are sequentially added to the polyaluminum chloride mother liquor. The aim is to examine the integration effect of the premixed polyelectrolyte template on the entire system. In order 3, the composite dispersion, sodium lignosulfonate solution, glycine chelated calcium-magnesium precursor solution, and polyacrylamide solution are sequentially added to the polyaluminum chloride mother liquor. Starting with the composite solid, subsequent components grow and assemble on its surface sequentially, aiming to form structurally stable and functionally integrated composite particles.

[0028] According to L9(3) 4 An orthogonal array was used to construct a specific scheme containing 9 independent experiments. Under constant reaction conditions (temperature 55℃, stirring speed 350rpm), and strictly following the factor levels and order specified in Table 1, 9 composite coagulant samples were synthesized. All samples were matured under sealed conditions for 24 hours. The water samples used were simulated wastewater with a total phosphorus concentration of 5mg / L, turbidity of 100 NTU, and alkalinity of 120mg / L (calculated as CaCO3). The dosage of all samples was set at 15 mg / L based on Al2O3. The coagulation program was rapid stirring (250 rpm, 60s), slow stirring (40 rpm, 900s), and settling (1200s).

[0029] Further analysis of the "total phosphorus removal rate" and "turbidity removal rate" indicators reveals that this invention employs an intuitive analysis method to process the data obtained from orthogonal experiments, quantifying the impact of various process factors on product performance and determining the optimal parameter combination. The K value, the average value of a specific factor at a specific level, is obtained by arithmetically averaging all experimental results in the orthogonal table that include the combination of that factor and that level. Specifically, it involves calculating the K value of a factor at a certain level and selecting all experimental numbers that satisfy this combination from the orthogonal experimental results table. Subsequently, the performance index values ​​corresponding to these experimental numbers are summed and divided by the total number of times that level appears in the entire experimental design. Due to the balance characteristic of the orthogonal table, the number of times each level of each factor appears is equal. In this invention, L9(3) 4In the design, all factors are calculated three times. By performing the above calculations on all levels of all factors one by one, a set of K values ​​can be obtained. Each K value represents the comprehensive average performance of its corresponding factor level under the background of changes in the levels of all other factors. The magnitude of the K value directly reflects the contribution of the factor level to the performance index. When the removal rate is used as the evaluation index, the higher the K value, the more beneficial the factor level is to performance improvement. Therefore, by comparing the K values ​​of different levels under the same factor, the local optimal level of the factor can be determined. Combining the local optimal levels of all factors constitutes the theoretically global optimal technical solution. Range calculation (R value): The R value is calculated based on the K value set obtained in the previous step. For each factor, the maximum and minimum values ​​in its corresponding K value set are found, and the difference between the two is calculated to obtain the R value of the factor. The magnitude of the R value is positively correlated with the influence of the factor on the result. The larger the R value, the more dominant the level change of the factor is on the fluctuation of the final performance, and it is a key variable or sensitive parameter in process control. Conversely, the smaller the R value, the less significant the impact of the level change on the result.

[0030] This invention calculates the K and R values ​​for two indicators: total phosphorus removal rate and turbidity removal rate. For total phosphorus removal rate, the K values ​​for factor A are 89.73, 95.83, and 97.63; for factor B, they are 92.93, 95.33, and 94.93; for factor C, they are 93.20, 94.60, and 95.40; and for factor D, they are 93.83, 93.73, and 95.63. Therefore, the optimal combination of K values ​​for each factor is 97.63, 95.33, 95.40, and 95.63. The R values ​​for each factor are R(A) 7.90, R(B) 2.40, R(C) 2.20, and R(D) 1.90. Therefore, for total phosphorus removal rate, the order of influence of the factors is: Factor A > Factor B > Factor C > Factor D. For turbidity removal rate, the K values ​​for factor A are 98.70, 98.93, and 99.20; for factor B, they are 99.10, 99.20, and 98.53; for factor C, they are 98.93, 99.10, and 98.80; and for factor D, they are 98.90, 98.93, and 99.00. Therefore, the optimal combination for the maximum K value of each factor is 99.20, 99.20, 99.10, and 99.00. The R values ​​for each factor are R(A) 0.5, R(B) 0.67, R(C) 0.30, and R(D) 0.10. Therefore, for turbidity removal rate, the order of influence of the factors is: Factor B > Factor A > Factor C > Factor D. Based on the analysis of the orthogonal experiment results, the optimal combination is: factor A = 5%, factor B = 1:1, factor C = 10%, and factor D = sequence 3, i.e., m. 固 / mAl2O3 =5%, m 木质素磺酸钠 :m 聚丙烯酰胺 =1:1,n (Ca+Mg) / n Al =10%, the order of addition is to add the composite dispersion, sodium lignosulfonate solution, glycine chelated calcium magnesium precursor solution and polyacrylamide solution to the polyaluminum chloride mother liquor in sequence.

[0031] In a preferred embodiment of the present invention, in S1, the mass fraction of the hydrochloric acid solution is 31 wt.%.

[0032] In some optional embodiments, the mass ratio of the hydrochloric acid solution, deionized water, and aluminum hydroxide is (26-30):(68-76):(12-22), for example, it can be (26, 26.4, 26.8, 27.2, 27.6, 28, 28.4, 28.8, 29.2, 29.6 or 30):(68, 68.8, 69.6, 70.4, 71.2, 72, 72.8, 73.6, 74.4, 75.2 or 76):(12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22), but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] In some alternative embodiments, the first temperature is 160-175°C, for example, it can be 160°C, 161.5°C, 163°C, 164.5°C, 166°C, 167.5°C, 169°C, 170.5°C, 172°C, 173.5°C or 175°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0034] In some alternative embodiments, the control pressure is 0.7-0.9 MPa, for example, it can be 0.7 MPa, 0.72 MPa, 0.74 MPa, 0.76 MPa, 0.78 MPa, 0.8 MPa, 0.82 MPa, 0.84 MPa, 0.86 MPa, 0.88 MPa or 0.9 MPa, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the reaction time is 100-120 min, for example, 100 min, 102 min, 104 min, 106 min, 108 min, 110 min, 112 min, 114 min, 116 min, 118 min or 120 min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0036] In some optional embodiments, the polyaluminum chloride mother liquor has an Al2O3 mass fraction of 10 wt.% and a basicity of 70%.

[0037] As a preferred embodiment of the present invention, in S2, the mass ratio of ferrous sulfate heptahydrate, thiourea, trisodium citrate, and deionized water is (45-55):(25-30):(0.8-1.2):(190-210), for example, it can be (45, 46, 47, 48, 49, 50, 51, 52, 53, 54 or 55):(25, 25.5, 26, 26.5, 27, 27.5, 2...). 8, 28.5, 29, 29.5 or 30: (0.8, 0.84, 0.88, 0.92, 0.96, 1.0, 1.04, 1.08, 1.12, 1.16 or 1.2): (190, 192, 194, 196, 198, 200, 202, 204, 206, 208 or 210), but not limited to the listed values, other unlisted values ​​within this range also apply.

[0038] In some optional embodiments, the hydrothermal reaction temperature is 170-190°C and the reaction time is 10-12 h. For example, the temperature can be (170, 172, 174, 176, 178, 180, 182, 184, 186, 188 or 190)°C and the reaction time can be (10.0, 10.2, 10.4, 10.6, 10.8, 11.0, 11.2, 11.4, 11.6, 11.8 or 12.0) h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] In some optional embodiments, the solid content of the composite dispersion is 10%.

[0040] As a preferred technical solution of the present invention, in S3, the mass ratio of sodium lignosulfonate to deionized water in the sodium lignosulfonate solution is (4.5-5.5):(94.5-95.5), for example, it can be (4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4 or 5.5):(94.5, 94.6, 94.7, 94.8, 94.9, 95.0, 95.1, 95.2, 95.3, 95.4 or 95.5), but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0041] In some optional embodiments, the mass ratio of cationic polyacrylamide to deionized water in the polyacrylamide solution is (0.45-0.55):(99.45-99.55), for example, it can be (0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, 0.54 or 0.55):(99.45, 99.46, 99.47, 99.48, 99.49, 99.50, 99.51, 99.52, 99.53, 99.54 or 99.55), but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0042] In a preferred embodiment of the present invention, in S4, the mass ratio of calcium chloride dihydrate, magnesium chloride hexahydrate, glycine, and deionized water is (20-24):(14-17):(35-40):(420-430), for example, it can be (20, 20.4, 20.8, 21.2, 21.6, 22.0, 22.4, 22.8, 23.2, 23.6, or 24):(14, 14.3, 14.6, 14). 9, 15.2, 15.5, 15.8, 16.1, 16.4, 16.7 or 17: (35, 35.5, 36, 36.5, 37, 37.5, 38, 38.5, 39, 39.5 or 40): (420, 421, 422, 423, 424, 425, 426, 427, 428, 429 or 430), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0043] In some alternative embodiments, the second temperature is 60-65°C, for example, it can be 60°C, 60.5°C, 61°C, 61.5°C, 62°C, 62.5°C, 63°C, 63.5°C, 64°C, 64.5°C or 65°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0044] In some alternative embodiments, the reaction time is 60-70 min, for example, 60 min, 61 min, 62 min, 63 min, 64 min, 65 min, 66 min, 67 min, 68 min, 69 min or 70 min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] In some optional embodiments, the total molar concentration of calcium and magnesium in the glycine chelated calcium-magnesium precursor solution is 0.44-0.46 mol / kg, and the total solids content is 15.0 wt.%, for example, the total molar concentration of calcium and magnesium can be (0.44, 0.442, 0.444, 0.446, 0.448, 0.45, 0.452, 0.454, 0.456, 0.458 or 0.46) mol / kg, and the total solids content is 15.0 wt.%, but it is not limited to the values ​​listed, and other unlisted values ​​within this range are also applicable.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Based on the inorganic framework of polyaluminum chloride, ferrous sulfide / magnetic iron oxide composite nanocrystal nuclei and glycine-chelated calcium and magnesium ion precursors are introduced to form a multi-phosphorus removal mechanism with the synergistic effect of physical adsorption, coagulation sedimentation, chemical precipitation and in-situ secondary flocculation. A high total phosphorus removal rate can be obtained at a low dosage, and a relatively stable deep phosphorus removal performance can be maintained under low influent phosphorus concentration and complex water quality conditions; (2) Sodium lignosulfonate and cationic polyacrylamide are used to form an anion / cationic synergistic template, so that the composite coagulant forms a structure with uniform charge distribution and spatial network structure. The polyelectrolyte skeleton generates flocs with both large particle size and high density. Through the combined action of charge neutralization and adsorption bridging, it accelerates floc growth and sedimentation, reduces effluent turbidity, and is conducive to obtaining sludge with low water content and good dewatering performance, thereby improving solid-liquid separation efficiency. (3) By systematically optimizing key parameters such as the amount of composite dispersion, the ratio of anion / cation templates, the molar ratio of calcium, magnesium and aluminum and the order of addition, a reasonable ratio and process window between each functional module is given, so that the obtained composite polyaluminum chloride can still maintain high and repeatable coagulation and phosphorus removal performance within a certain water quality fluctuation range, which is suitable for engineering scale-up and stable production control. Detailed Implementation

[0047] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in this application, including technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0048] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0049] Example 1

[0050] This embodiment provides a composite polyaluminum chloride water purification agent and its preparation method, the preparation method specifically including the following steps:

[0051] S1, 28g of hydrochloric acid solution with a mass fraction of 31wt.% was mixed with 72g of deionized water to obtain a dilute hydrochloric acid solution. Then, 20g of aluminum hydroxide was mixed with the dilute hydrochloric acid solution and transferred to a reaction vessel. The temperature was adjusted to 165℃, the pressure was controlled at 0.8MPa, and the reaction was carried out for 110min. After the reaction was completed, a polyaluminum chloride mother liquor was obtained. The mass fraction of Al2O3 in the polyaluminum chloride mother liquor was 10wt.%, and the basicity was 70%.

[0052] S2, 50g of ferrous sulfate heptahydrate, 28g of thiourea, and 1.0g of trisodium citrate were sequentially dispersed in 200g of deionized water and subjected to a hydrothermal reaction at 180℃ for 11 hours. After the reaction, the mixture was centrifuged and washed until the washing liquid was neutral to obtain a composite solid. The composite solid was then dispersed in fresh deionized water and ultrasonically dispersed to obtain a composite dispersion with a solid content of 10%.

[0053] S3, 5.0g sodium lignosulfonate was dispersed in 95.0g deionized water and stirred to obtain a sodium lignosulfonate solution. 0.5g cationic polyacrylamide was dispersed in 99.5g deionized water and dispersed evenly to obtain a polyacrylamide solution.

[0054] S4, 22g calcium chloride dihydrate, 15g magnesium chloride hexahydrate and 38g glycine were sequentially dispersed in 425g deionized water, the temperature was adjusted to 62℃ and the mixture was stirred for 65min to obtain glycine chelated calcium magnesium precursor solution.

[0055] S5. Through orthogonal experiments, 4.5g of composite dispersion, 2.0g of sodium lignosulfonate solution, 20g of glycine chelated calcium magnesium precursor solution and 4.5g of polyacrylamide solution were added sequentially to 70g of polyaluminum chloride mother liquor to obtain a composite polyaluminum chloride water purification agent.

[0056] Example 2

[0057] This embodiment provides a composite polyaluminum chloride water purification agent and its preparation method, the preparation method specifically including the following steps:

[0058] S1, 27g of hydrochloric acid solution with a mass fraction of 31wt.% was mixed with 70g of deionized water to obtain a dilute hydrochloric acid solution. Then, 12g of aluminum hydroxide was mixed with the dilute hydrochloric acid solution and transferred to a reaction vessel. The temperature was adjusted to 172℃, the pressure was controlled at 0.75MPa, and the reaction was carried out for 105min. After the reaction was completed, a polyaluminum chloride mother liquor was obtained. The mass fraction of Al2O3 in the polyaluminum chloride mother liquor was 10wt.%, and the basicity was 70%.

[0059] S2, 48g of ferrous sulfate heptahydrate, 26g of thiourea, and 0.9g of trisodium citrate were sequentially dispersed in 195g of deionized water and subjected to a hydrothermal reaction at 175℃ for 10.5h. After the reaction, the mixture was centrifuged and washed until the washing liquid was neutral to obtain a composite solid. The composite solid was then dispersed in fresh deionized water and ultrasonically dispersed to obtain a composite dispersion with a solid content of 10%.

[0060] S3, 4.8g of sodium lignosulfonate was dispersed in 94.8g of deionized water and stirred to obtain a sodium lignosulfonate solution. 0.48g of cationic polyacrylamide was dispersed in 99.48g of deionized water and dispersed evenly to obtain a polyacrylamide solution.

[0061] S4, 21g calcium chloride dihydrate, 16g magnesium chloride hexahydrate and 36g glycine were sequentially dispersed in 422g deionized water, the temperature was adjusted to 61℃ and the mixture was stirred for 62min to obtain glycine chelated calcium magnesium precursor solution.

[0062] S5. Through orthogonal experiments, 3.5g of composite dispersion, 1.5g of sodium lignosulfonate solution, 18g of glycine chelated calcium magnesium precursor solution and 3.5g of polyacrylamide solution were added sequentially to 68g of polyaluminum chloride mother liquor to obtain a composite polyaluminum chloride water purification agent.

[0063] Example 3

[0064] This embodiment provides a composite polyaluminum chloride water purification agent and its preparation method, the preparation method specifically including the following steps:

[0065] S1, 29g of hydrochloric acid solution with a mass fraction of 31wt.% was mixed with 75g of deionized water to obtain a dilute hydrochloric acid solution. Then, 21g of aluminum hydroxide was mixed with the dilute hydrochloric acid solution and transferred to a reaction vessel. The temperature was adjusted to 168℃, the pressure was controlled at 0.85MPa, and the reaction was carried out for 115min. After the reaction was completed, a polyaluminum chloride mother liquor was obtained. The mass fraction of Al2O3 in the polyaluminum chloride mother liquor was 10wt.%, and the basicity was 70%.

[0066] S2, 52g of ferrous sulfate heptahydrate, 29g of thiourea, and 1.1g of trisodium citrate were sequentially dispersed in 205g of deionized water and subjected to a hydrothermal reaction at 185℃ for 11.5h. After the reaction, the mixture was centrifuged and washed until the washing solution was neutral to obtain a composite solid. The composite solid was then dispersed in fresh deionized water and ultrasonically dispersed to obtain a composite dispersion with a solid content of 10%.

[0067] S3, 5.2g of sodium lignosulfonate was dispersed in 95.2g of deionized water and stirred to obtain a sodium lignosulfonate solution. 0.52g of cationic polyacrylamide was dispersed in 99.52g of deionized water and dispersed evenly to obtain a polyacrylamide solution.

[0068] S4, 23g calcium chloride dihydrate, 14.5g magnesium chloride hexahydrate and 39g glycine were sequentially dispersed in 428g deionized water, the temperature was adjusted to 64℃ and the mixture was stirred for 68min to obtain glycine chelated calcium magnesium precursor solution.

[0069] S5. Through orthogonal experiments, 5.5g of composite dispersion, 2.5g of sodium lignosulfonate solution, 22g of glycine chelated calcium magnesium precursor solution and 5.5g of polyacrylamide solution were added sequentially to 72g of polyaluminum chloride mother liquor to obtain a composite polyaluminum chloride water purification agent.

[0070] Example 4

[0071] This embodiment provides a composite polyaluminum chloride water purification agent and its preparation method, the preparation method specifically including the following steps:

[0072] S1, 30g of hydrochloric acid solution with a mass fraction of 31wt.% was mixed with 76g of deionized water to obtain a dilute hydrochloric acid solution. Then, 22g of aluminum hydroxide was mixed with the dilute hydrochloric acid solution and transferred to a reaction vessel. The temperature was adjusted to 175℃, the pressure was controlled at 0.9MPa, and the reaction was carried out for 120min. After the reaction was completed, a polyaluminum chloride mother liquor was obtained. The mass fraction of Al2O3 in the polyaluminum chloride mother liquor was 10wt.%, and the basicity was 70%.

[0073] S2, 55g of ferrous sulfate heptahydrate, 30g of thiourea, and 1.2g of trisodium citrate were sequentially dispersed in 210g of deionized water and subjected to a hydrothermal reaction at 190℃ for 12 hours. After the reaction, the mixture was centrifuged and washed until the washing liquid was neutral to obtain a composite solid. The composite solid was then dispersed in fresh deionized water and ultrasonically dispersed to obtain a composite dispersion with a solid content of 10%.

[0074] S3, 5.5g of sodium lignosulfonate is dispersed in 95.5g of deionized water and stirred to obtain a sodium lignosulfonate solution. 0.55g of cationic polyacrylamide is dispersed in 99.55g of deionized water and dispersed evenly to obtain a polyacrylamide solution.

[0075] S4, 24g calcium chloride dihydrate, 17g magnesium chloride hexahydrate and 40g glycine were sequentially dispersed in 430g deionized water, the temperature was adjusted to 65℃ and the reaction was stirred for 70min to obtain glycine chelated calcium magnesium precursor solution.

[0076] S5. Through orthogonal experiments, 6g of composite dispersion, 3g of sodium lignosulfonate solution, 25g of glycine chelated calcium magnesium precursor solution and 6g of polyacrylamide solution were added sequentially to 75g of polyaluminum chloride mother liquor to obtain a composite polyaluminum chloride water purification agent.

[0077] Comparative Example 1

[0078] This comparative example provides a composite polyaluminum chloride water purifier and its preparation method. The difference between this example and Example 1 is that the mass of the composite dispersion in S5 is 0, while the other process parameters and operating conditions are exactly the same as in Example 1.

[0079] Comparative Example 2

[0080] This comparative example provides a composite polyaluminum chloride water purifier and its preparation method. The difference between this example and Example 1 is that the mass of sodium lignosulfonate solution in S5 is 0, while other process parameters and operating conditions are exactly the same as in Example 1.

[0081] Comparative Example 3

[0082] This comparative example provides a composite polyaluminum chloride water purifier and its preparation method. The difference between this example and Example 1 is that the mass of the glycine chelate calcium magnesium precursor solution in S5 is 0, while other process parameters and operating conditions are exactly the same as in Example 1.

[0083] Comparative Example 4

[0084] This comparative example provides a composite polyaluminum chloride water purification agent and its preparation method. The difference between this example and Example 1 is that the mass of the polyacrylamide solution in S5 is 0, while the other process parameters and operating conditions are exactly the same as in Example 1.

[0085] Comparative Example 5

[0086] This comparative example provides a composite polyaluminum chloride water purifier and its preparation method. The difference between this example and Example 1 is that in S5, equal masses of the composite dispersion, sodium lignosulfonate solution, glycine chelated calcium magnesium precursor solution, and polyacrylamide solution are added to the polyaluminum chloride mother liquor at one time for mixing. Other process parameters and operating conditions are exactly the same as in Example 1.

[0087] The water samples used were all simulated wastewater with a total phosphorus concentration of 5 mg / L, turbidity of 100 NTU, and alkalinity of 120 mg / L (calculated as CaCO3). The dosage for all samples was set at 15 mg / L, calculated as Al2O3. The coagulation program was rapid stirring (250 rpm, 60 s), slow stirring (40 rpm, 900 s), and settling (1200 s). The total phosphorus concentration was measured using spectrophotometry, and the phosphorus removal efficiency was calculated as follows: Total phosphorus removal rate = (phosphate standard water sample phosphorus concentration - supernatant phosphorus concentration) / phosphate standard water sample phosphorus concentration × 100%. Flocculation performance was tested by sequentially performing rapid stirring, slow stirring, and settling. The supernatant was collected, and its turbidity was measured using a turbidimeter. The turbidity removal rate was calculated as follows: Turbidity removal rate = (standard water sample turbidity - supernatant turbidity) / standard water sample turbidity × 100%.

[0088] The test results are shown in Table 2.

[0089] Table 2 Test Results of Composite Polyaluminum Chloride Water Purifier in Examples 1-4 and Comparative Examples 1-5

[0090]

[0091] Table 2 shows that, compared to Example 1, the total phosphorus removal rate and turbidity removal rate decreased in Comparative Example 1; the total phosphorus removal rate and turbidity removal rate decreased in Comparative Example 2; the total phosphorus removal rate and turbidity removal rate decreased in Comparative Example 3; the total phosphorus removal rate and turbidity removal rate decreased in Comparative Example 4; and the total phosphorus removal rate and turbidity removal rate decreased in Comparative Example 5. In Comparative Example 1, the lack of a composite dispersion resulted in the disappearance of physical adsorption, secondary flocculation from in-situ generation of ferric hydroxide, and heavy metal capture. Phosphorus removal relied solely on the coagulation and precipitation of polyaluminum chloride and the chemical precipitation of calcium and magnesium, thus leading to a decrease in the total phosphorus removal rate and turbidity removal rate. In Comparative Example 2, the lack of sodium lignosulfonate solution resulted in a heterogeneous and unstable product structure, and the poor strength of the floc structure formed by long-chain cationic polyacrylamide, thus decreasing the total phosphorus removal rate and turbidity removal rate. In Comparative Example 3, the lack of glycine-chelated calcium and magnesium precursor solution prevented the formation of chemical precipitates of phosphate, thus decreasing the total phosphorus removal rate and turbidity removal rate. In Comparative Example 4, the lack of polyacrylamide solution prevented the adsorption of tiny flocs, resulting in poor solid-liquid separation and high turbidity in the effluent. In Comparative Example 5, a one-step mixing process was used. When components with different charges and reactivity were mixed at once, they preferentially neutralized each other to form ineffective precipitates. The resulting composite coagulant had an uneven, disordered, and inefficient microstructure.

[0092] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A composite polyaluminum chloride water purification agent, characterized in that, Specifically, it includes the following components: Composite dispersion, sodium lignosulfonate solution, glycine chelated calcium magnesium precursor solution, polyacrylamide solution and polyaluminum chloride mother liquor; The preparation method of the composite polyaluminum chloride water purification agent includes: S1, mix hydrochloric acid solution with deionized water to obtain dilute hydrochloric acid solution, then mix aluminum hydroxide with dilute hydrochloric acid solution to react and obtain polyaluminum chloride mother liquor; S2, ferrous sulfate heptahydrate, thiourea and trisodium citrate are sequentially dispersed in deionized water and subjected to hydrothermal reaction to obtain a composite solid. The composite solid is then dispersed in fresh deionized water to obtain a composite dispersion. S3, Sodium lignosulfonate is dispersed in deionized water to obtain a sodium lignosulfonate solution, and cationic polyacrylamide is dispersed in deionized water to obtain a polyacrylamide solution; S4, calcium chloride dihydrate, magnesium chloride hexahydrate and glycine are sequentially dispersed in deionized water and reacted to obtain glycine chelated calcium magnesium precursor solution. S5, the composite dispersion, sodium lignosulfonate solution, glycine chelated calcium magnesium precursor solution and polyacrylamide solution are added sequentially to the polyaluminum chloride mother liquor to obtain a composite polyaluminum chloride water purification agent.

2. The composite polyaluminum chloride water purification agent according to claim 1, characterized in that, The mass ratio of the composite dispersion, sodium lignosulfonate solution, glycine chelated calcium magnesium precursor solution, polyacrylamide solution and polyaluminum chloride mother liquor is (3-6):(1-3):(15-25):(3-6):(65-75).

3. A method for preparing the composite polyaluminum chloride water purification agent as described in any one of claims 1-2, characterized in that, The preparation method includes: S1, mix hydrochloric acid solution with deionized water to obtain dilute hydrochloric acid solution, then mix aluminum hydroxide with dilute hydrochloric acid solution to react and obtain polyaluminum chloride mother liquor; S2, ferrous sulfate heptahydrate, thiourea and trisodium citrate are sequentially dispersed in deionized water and subjected to hydrothermal reaction to obtain a composite solid. The composite solid is then dispersed in fresh deionized water to obtain a composite dispersion. S3, Sodium lignosulfonate is dispersed in deionized water to obtain a sodium lignosulfonate solution, and cationic polyacrylamide is dispersed in deionized water to obtain a polyacrylamide solution; S4, calcium chloride dihydrate, magnesium chloride hexahydrate and glycine are sequentially dispersed in deionized water and reacted to obtain glycine chelated calcium magnesium precursor solution. S5, the composite dispersion, sodium lignosulfonate solution, glycine chelated calcium magnesium precursor solution and polyacrylamide solution are added sequentially to the polyaluminum chloride mother liquor to obtain a composite polyaluminum chloride water purification agent.

4. The preparation method of the composite polyaluminum chloride water purification agent according to claim 3, characterized in that, In S1: The mass ratio of the hydrochloric acid solution, deionized water and aluminum hydroxide is (26-30):(68-76):(12-22).

5. The preparation method of the composite polyaluminum chloride water purification agent according to claim 3, characterized in that, In S1: The mass fraction of Al2O3 in the polyaluminum chloride mother liquor is 10 wt.%, and the basicity is 70%.

6. The preparation method of the composite polyaluminum chloride water purification agent according to claim 3, characterized in that, In S2: The mass ratio of ferrous sulfate heptahydrate, thiourea, trisodium citrate, and deionized water is (45-55):(25-30):(0.8-1.2):(190-210).

7. The preparation method of the composite polyaluminum chloride water purification agent according to claim 3, characterized in that, In S2: The solid content of the composite dispersion is 10%.

8. The preparation method of the composite polyaluminum chloride water purification agent according to claim 3, characterized in that, In S3: In the sodium lignosulfonate solution, the mass ratio of sodium lignosulfonate to deionized water is (4.5-5.5):(94.5-95.5).

9. The preparation method of the composite polyaluminum chloride water purification agent according to claim 3, characterized in that, In S3: In the polyacrylamide solution, the mass ratio of cationic polyacrylamide to deionized water is (0.45-0.55):(99.45-99.55).

10. The preparation method of the composite polyaluminum chloride water purification agent according to claim 3, characterized in that, In S4: The mass ratio of calcium chloride dihydrate, magnesium chloride hexahydrate, glycine and deionized water is (20-24):(14-17):(35-40):(420-430). The total molar concentration of calcium and magnesium in the glycine chelated calcium-magnesium precursor solution is 0.44-0.46 mol / kg, and the total mass fraction of solids is 15.0 wt.%.

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