Modified polyaluminum chloride flocculant and preparation method thereof

Abstract

The invention relates to the technical field of water treatment, and discloses a modified polyaluminum chloride flocculant and a preparation method thereof.The modified polyaluminum chloride flocculant is prepared from, by weight, 50-65 parts of polyaluminum chloride, 8-12 parts of magnesium silicate, 5-8 parts of carboxymethyl chitosan, 15-25 parts of polyaluminum ferric chloride and 3-5 parts of tea polyphenol; the molar ratio of aluminum ions to iron ions in the modified polyaluminum chloride flocculant is (3-4.5): 1. According to the invention, an inorganic-organic dual-modifier synergistic effect mechanism is adopted to construct a'rigid framework-flexible network 'composite structure, and the structure can significantly improve the adsorption capacity of Pb < 2 + >. Meanwhile, the mechanical property of the flocculating agent is improved, so that the flocculating agent can be applied to a high-turbulence environment.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a modified polyaluminium chloride flocculant and a preparation method thereof. Background Art

[0002] Polyaluminium chloride (PAC) is also commonly known as a water purifier or flocculant. It is a water-soluble inorganic high molecular polymer between AlCl3 and Al(OH)3. It is a resinous solid in yellow, light yellow, dark brown or dark grey in colour. The product has strong bridging adsorption properties. During the hydrolysis process, physical and chemical processes such as coagulation, adsorption and precipitation occur. The fundamental difference between polyaluminium chloride and traditional inorganic flocculants is that traditional inorganic flocculants are low molecular crystalline salts, while the structure of polyaluminium chloride is composed of polycarboxyl complexes with various forms. It has a fast flocculation and precipitation speed, a wide range of applicable pH values, is non-corrosive to pipeline equipment, has a significant water purification effect, and can effectively remove SS, COD, BOD and heavy metal ions such as arsenic and mercury in water. The product is widely used in the fields of drinking water, industrial water and sewage treatment.

[0003] However, the polyaluminium chloride currently sold on the market has a relatively simple functionality, a low aluminium content, and the flocculation effect on heavy metal ions needs to be improved. At the same time, polyaluminium chloride also has problems such as low treatment efficiency of low-temperature and low-turbidity water and weak co-precipitation ability of heavy metals. Existing modification technologies mostly use single silicate or polyacrylamide modification, which has defects such as poor compatibility of modifiers and unstable molecular structure. Therefore, how to develop a new type of high-efficiency flocculant is an urgent problem to be solved by technicians in this field. Summary of the invention

[0004] In view of this, the present invention proposes a modified polyaluminium chloride flocculant and a preparation method thereof, aiming to solve the problem of poor flocculation effect when polyaluminium chloride is used as a flocculant in the current technology.

[0005] In one aspect, the present invention provides a modified polyaluminium chloride flocculant, comprising the following raw materials in parts by weight:

[0006] 50-65 parts of polyaluminium chloride, 8-12 parts of magnesium silicate, 5-8 parts of carboxymethyl chitosan, 15-25 parts of polyaluminium ferric chloride and 3-5 parts of tea polyphenols;

[0007] The molar ratio of aluminum ions to iron ions in the modified polyaluminium chloride flocculant is (3-4.5):1.

[0008] Preferably, the modified polyaluminium chloride flocculant comprises the following raw materials in parts by weight:

[0009] 55-60 parts of polyaluminium chloride, 9-11 parts of magnesium silicate, 5-8 parts of carboxymethyl chitosan, 18-22 parts of polyaluminium ferric chloride and 3-5 parts of tea polyphenols;

[0010] The molar ratio of aluminum ions to iron ions in the modified polyaluminium chloride flocculant is (3.5-4):1.

[0011] Preferably, the Al2O3 content in the polyaluminium chloride is ≥28%.

[0012] Preferably, the specific surface area of ​​the magnesium silicate is ≥200m 2 / g.

[0013] Preferably, the degree of substitution of the carboxymethyl chitosan is ≥ 0.8.

[0014] On the other hand, the present invention also provides a method for preparing the above-mentioned modified polyaluminium chloride flocculant, comprising the following preparation steps:

[0015] (1) Mixing polyaluminium chloride, polyaluminium ferric chloride and water, adjusting the pH to 3-3.5, and obtaining an inorganic polymer mixed solution;

[0016] (2) mixing magnesium silicate with water to obtain a magnesium silicate dispersion, mixing the magnesium silicate dispersion with an inorganic polymer mixed solution, performing a modification reaction, and obtaining a modified solution;

[0017] (3) mixing carboxymethyl chitosan with acetic acid-sodium acetate buffer to obtain carboxymethyl chitosan buffer;

[0018] Mixing tea polyphenols with water to obtain a tea polyphenol solution;

[0019] After mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution, a mixed solution is obtained;

[0020] Under a protective atmosphere, the mixed solution is added dropwise to the modified solution to undergo a grafting reaction to obtain a grafted solution;

[0021] (4) The grafting solution is mixed with the sodium citrate solution, aged at low temperature, and spray-dried to obtain the modified polyaluminium chloride flocculant.

[0022] Preferably, in step (1), the mixing temperature is 70-80° C., and the mixing time is 1-2 h.

[0023] Preferably, in step (2), the specific steps of the modification reaction include:

[0024] (a) Mixing the magnesium silicate dispersion and the inorganic polymer mixed solution, heating to 60-65°C, and keeping the temperature for 25-35 minutes;

[0025] (b) cooling the reaction solution obtained in step (a) to 50-55° C., and then keeping the temperature for 1-1.5 hours;

[0026] The cooling rate is 0.5-1°C / min;

[0027] (c) cooling the reaction solution obtained in step (b) to 40-45° C., adding polyethylene glycol solution, and ultrasonically treating for 10-20 min;

[0028] The mass fraction of the polyethylene glycol solution is 5%-10%, and the frequency of the ultrasonic treatment is 150-200W.

[0029] Preferably, in step (3), the protective atmosphere is nitrogen, the temperature of the grafting reaction is 35-45° C., and the time of the grafting reaction is 1-2 h.

[0030] Preferably, in step (4), the mass fraction of the sodium citrate solution is 5%-10%; the temperature of the low-temperature aging is 3-5°C, and the time of the low-temperature aging is 40-50h;

[0031] The inlet air temperature of the spray drying is 170-190°C, and the outlet air temperature is 80-90°C.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention provides a modified polyaluminium chloride flocculant, comprising the following raw materials in parts by weight: 50-65 parts of polyaluminium chloride, 8-12 parts of magnesium silicate, 5-8 parts of carboxymethyl chitosan, 15-25 parts of polyaluminium chloride iron and 3-5 parts of tea polyphenols; the molar ratio of aluminium ions to iron ions in the modified polyaluminium chloride flocculant is (3-4.5): 1. The present invention adopts the synergistic action mechanism of inorganic-organic dual modifiers: the Lewis acid sites in magnesium silicate form coordination bonds with the amino groups in carboxymethyl chitosan to construct a "rigid skeleton-flexible network" composite structure. The rigid skeleton (magnesium silicate) provides a high specific surface area and fixed adsorption sites to capture pollutants through ion exchange. The long-chain molecules of the flexible network (carboxymethyl chitosan) unfold in the solution, exposing more chelating groups (-NH2 / -COOH) to dynamically supplement the adsorption sites. After the two are combined, they can significantly increase the Pb 2+ Moreover, in the "rigid skeleton-flexible network" composite structure, the magnesium silicate skeleton bears the main stress and inhibits structural collapse, while the carboxymethyl chitosan network dissipates energy through chain segment slippage, preventing crack propagation, and improving the mechanical properties of the flocculant, so that it can be used in high turbulence environments.

[0034] The trivalent iron ions in polyaluminium ferric chloride can catalyze the oxidation of catechol groups in tea polyphenols into semiquinone free radicals, enhance the reducing ability of the flocculant to Cr(VI), and thus improve the flocculation effect of the flocculant.

[0035] 2. The present invention further limits the Al2O3 content in the polyaluminium chloride to ≥ 28%. Polyaluminium chloride is the main component of the flocculant, which can provide a large amount of aluminium ions and generate positively charged hydroxyaluminium polymers through hydrolysis, which have strong electrical neutralization and adsorption bridging effects and can effectively capture suspended particles in water.

[0036] 3. The present invention further limits the specific surface area of ​​the magnesium silicate to ≥ 200 m 2 / g. As a coagulant, magnesium silicate can increase the density and mechanical strength of flocs, making them easier to settle. At the same time, the silanols on the surface of magnesium silicate can adsorb organic matter in pollutants, further improving the removal effect. In addition, the layered structure of magnesium silicate can provide intercalation sites, load Al-Fe hydroxy polymers to form multi-level adsorption channels. And when the specific surface area of ​​magnesium silicate is ≥200m 2 / g, it has a larger adsorption capacity, which further improves the flocculation effect of the flocculant.

[0037] 4. The present invention further limits the degree of substitution of carboxymethyl chitosan to ≥ 0.8. Carboxymethyl chitosan carries a large amount of negative charge and can combine with the positively charged flocs generated by polyaluminium chloride to form more stable flocs and enhance the flocculation effect. Carboxymethyl chitosan can also aggregate small flocs into larger flocs through the bridging effect of its polymer chains, which is convenient for sedimentation and filtration. Carboxymethyl chitosan with a degree of substitution ≥ 0.8 is selected, and its chelating site density reaches 3.2 mmol / g (potentiometric titration method), and the shear strength of the flocs is increased by 50%, thereby satisfying the use of flocculants in more turbulent conditions.

[0038] 5. The modified polyaluminium chloride flocculant provided by the present invention also includes polyaluminium chloride ferric. Polyaluminium chloride ferric contains iron ions. Compared with aluminium ions, iron ions have a stronger flocculation effect and can further improve the ability to remove suspended matter in water. At the same time, the synergistic effect of aluminium ions and iron ions can enable the flocculant to maintain a good flocculation effect in a wider pH range. And the Fe-O-Al bond energy in polyaluminium chloride ferric reaches 418 kJ / mol (DFT calculation), which further strengthens the flocculent skeleton strength and satisfies the use of the flocculant in a high-intensity environment.

[0039] 6. The modified polyaluminium chloride flocculant provided by the present invention also includes tea polyphenols. Tea polyphenols have antioxidant and microbial growth inhibition effects, which can improve the storage stability of the flocculant. At the same time, it is also a good organic flocculant, which can complex with organic matter and metal ions in water through its polyphenol groups to promote the flocculation process. The catechol group (C6H3(OH)2) in tea polyphenols can form a stable five-membered ring chelate with heavy metals (stability constant logK>16). In addition, the antioxidant property of tea polyphenols can also protect Fe 2+ Not over-oxidized.

[0040] 7. The present invention also provides a preparation method of the above-mentioned modified polyaluminium chloride flocculant, comprising the following preparation steps: (1) mixing polyaluminium chloride, polyaluminium chloride iron and water, adjusting the pH to 3-3.5, and obtaining an inorganic polymer mixed solution; (2) mixing magnesium silicate with water to obtain a magnesium silicate dispersion, mixing the magnesium silicate dispersion with the inorganic polymer mixed solution, and performing a modification reaction to obtain a modified solution; (3) mixing carboxymethyl chitosan with acetic acid-sodium acetate buffer to obtain a carboxymethyl chitosan buffer; mixing tea polyphenol with water to obtain a tea polyphenol solution; mixing the carboxymethyl chitosan buffer with the tea polyphenol solution to obtain a mixed solution; under a protective atmosphere, dropping the mixed solution into the modified solution, performing a grafting reaction, and obtaining a grafted solution; (4) mixing the grafted solution with a sodium citrate solution, aging at low temperature, and spray drying to obtain the modified polyaluminium chloride flocculant.

[0041] The preparation method provided by the present invention is simple, suitable for large-scale production, and does not produce toxic substances during the production process, which conforms to the concept of green environmental protection technology. The grafting reaction process of step (3) of the present invention is carried out under a protective atmosphere, which can ensure the stable formation of the coordination bond between the amino group and the metal ion.

[0042] 8. The present invention further defines the preparation method of the modified polyaluminium chloride flocculant. In step (2), the specific steps of the modification reaction include: (a) mixing the magnesium silicate dispersion with the inorganic polymer mixed solution, heating to 60-65°C, and keeping warm for 25-35 minutes; (b) cooling the reaction solution obtained in step (a) to 50-55°C, and then keeping warm for 1-1.5 hours; the cooling rate is 0.5-1°C / min; (c) cooling the reaction solution obtained in step (b) to 40-45°C, adding polyethylene glycol solution, and ultrasonic treatment for 10-20 minutes; the mass fraction of the polyethylene glycol solution is 5%-10%, and the frequency of the ultrasonic treatment is 150-200W. In the modification reaction of the present invention, the temperature is controlled in stages, and the bonding mode of magnesium silicate and Al-Fe hydroxy complex (edge ​​hydroxyl → interlayer insertion → interface modification) is regulated in stages. This achieved the directional assembly of inorganic-organic components, and the Alb morphology retention rate was increased by 28% (the traditional process is prone to structural collapse due to sudden temperature changes). DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0044] The present invention provides a modified polyaluminium chloride flocculant, comprising the following raw materials in parts by weight:

[0045] 50-65 parts of polyaluminium chloride, 8-12 parts of magnesium silicate, 5-8 parts of carboxymethyl chitosan, 15-25 parts of polyaluminium ferric chloride and 3-5 parts of tea polyphenols;

[0046] The molar ratio of aluminum ions to iron ions in the modified polyaluminium chloride flocculant is (3-4.5):1.

[0047] The invention controls the weight portion of polyaluminium chloride to 50-65 parts. When the weight portion of polyaluminium chloride is less than 50 parts, the electrical neutralization capacity is insufficient. The invention controls the weight portion of magnesium silicate to 8-12 parts. When the weight portion of magnesium silicate is greater than 12 parts, the viscosity of the initiating system is too high. The invention controls the weight portion of carboxymethyl chitosan to 5-8 parts. When the weight portion of carboxymethyl chitosan is less than 5 parts, the floc strength decreases by 40%. The invention controls the weight portion of polyaluminium ferric chloride to 15-25 parts. When the weight portion of polyaluminium ferric chloride is greater than 30 parts, pH fluctuation is caused to be greater than 1.5. The invention controls the weight portion of tea polyphenol to 3-5 parts. When the weight portion of tea polyphenol is greater than 6 parts, brown colour development interference is easily generated in the system.

[0048] In some embodiments of the present invention, the modified polyaluminium chloride flocculant comprises the following raw materials in parts by weight:

[0049] 55-60 parts of polyaluminium chloride, 9-11 parts of magnesium silicate, 5-8 parts of carboxymethyl chitosan, 18-22 parts of polyaluminium ferric chloride and 3-5 parts of tea polyphenols;

[0050] The molar ratio of aluminum ions to iron ions in the modified polyaluminium chloride flocculant is (3.5-4):1.

[0051] In some embodiments of the present invention, the Al2O3 content in the polyaluminium chloride is ≥28%.

[0052] In some embodiments of the present invention, the specific surface area of ​​the magnesium silicate is ≥200m 2 / g.

[0053] In some embodiments of the present invention, the degree of substitution of the carboxymethyl chitosan is ≥ 0.8.

[0054] The present invention also provides a method for preparing the modified polyaluminium chloride flocculant, comprising the following preparation steps:

[0055] (1) Mixing polyaluminium chloride, polyaluminium ferric chloride and water, adjusting the pH to 3-3.5, and obtaining an inorganic polymer mixed solution;

[0056] (2) mixing magnesium silicate with water to obtain a magnesium silicate dispersion, mixing the magnesium silicate dispersion with an inorganic polymer mixed solution, performing a modification reaction, and obtaining a modified solution;

[0057] (3) mixing carboxymethyl chitosan with acetic acid-sodium acetate buffer to obtain carboxymethyl chitosan buffer;

[0058] Mixing tea polyphenols with water to obtain a tea polyphenol solution;

[0059] After mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution, a mixed solution is obtained;

[0060] Under a protective atmosphere, the mixed solution is added dropwise to the modified solution to undergo a grafting reaction to obtain a grafted solution;

[0061] (4) The grafting solution is mixed with the sodium citrate solution, aged at low temperature, and spray-dried to obtain the modified polyaluminium chloride flocculant.

[0062] In some embodiments of the present invention, in step (1), the mixing temperature is 70-80° C., and the mixing time is 1-2 h.

[0063] In some embodiments of the present invention, in step (2), the specific steps of the modification reaction include:

[0064] (a) Mixing the magnesium silicate dispersion and the inorganic polymer mixed solution, heating to 60-65°C, and keeping the temperature for 25-35 minutes;

[0065] (b) cooling the reaction solution obtained in step (a) to 50-55° C., and then keeping the temperature for 1-1.5 hours;

[0066] The cooling rate is 0.5-1°C / min;

[0067] (c) cooling the reaction solution obtained in step (b) to 40-45° C., adding polyethylene glycol solution, and ultrasonically treating for 10-20 min;

[0068] The mass fraction of the polyethylene glycol solution is 5%-10%, and the frequency of the ultrasonic treatment is 150-200W.

[0069] In some embodiments of the present invention, in step (3), the protective atmosphere is nitrogen, the temperature of the grafting reaction is 35-45° C., and the time of the grafting reaction is 1-2 h.

[0070] In some embodiments of the present invention, in step (4), the mass fraction of the sodium citrate solution is 5%-10%, the temperature of the low-temperature aging is 3-5°C, and the time of the low-temperature aging is 40-50h;

[0071] The inlet air temperature of the spray drying is 170-190°C, and the outlet air temperature is 80-90°C.

[0072] In some embodiments of the present invention, in step (4), the low-temperature aging is carried out under phosphate buffer conditions with a pH of 6.

[0073] Example 1

[0074] A modified polyaluminium chloride flocculant comprises the following raw materials in parts by weight:

[0075] 50 parts of polyaluminium chloride, 8 parts of magnesium silicate, 5 parts of carboxymethyl chitosan, 15 parts of polyaluminium ferric chloride and 3 parts of tea polyphenols;

[0076] The molar ratio of aluminum ions to iron ions in the modified polyaluminium chloride flocculant is 3:1.

[0077] A method for preparing a modified polyaluminium chloride flocculant comprises the following preparation steps:

[0078] (1) Mixing polyaluminium chloride, polyaluminium chloride iron and water at 70°C for 1 hour, then adding hydrochloric acid to adjust the pH of the reaction system to 3 to obtain an inorganic polymer mixed solution;

[0079] (2) mixing magnesium silicate with water to obtain a magnesium silicate dispersion having a mass fraction of 1%;

[0080] (a) Mixing the magnesium silicate dispersion with the inorganic polymer mixed solution, heating the reaction system to 60°C and keeping the temperature for 35 minutes; (b) then cooling the reaction solution to 55°C at a cooling rate of 1°C / min and keeping the temperature for 1 hour; (c) cooling the reaction solution obtained in step (b) to 40°C, adding a polyethylene glycol solution with a mass fraction of 5%, and ultrasonically treating the solution at a frequency of 150W for 10 minutes to obtain a modified solution;

[0081] (3) mixing carboxymethyl chitosan with acetic acid-sodium acetate buffer (pH=5) to obtain carboxymethyl chitosan buffer;

[0082] Mixing tea polyphenols with water to obtain a tea polyphenol solution;

[0083] After mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution, a mixed solution is obtained;

[0084] Under nitrogen atmosphere, the mixed solution was added dropwise to the modified solution, and the grafting reaction was carried out at a temperature of 35°C for 1 hour to obtain a grafting solution;

[0085] (4) After the grafting solution is mixed with a sodium citrate solution with a mass fraction of 10%, low-temperature aging is carried out in a phosphate buffer solution with a pH of 6 at a temperature of 3°C for 40 hours, followed by spray drying at an inlet air temperature of 170°C and an outlet air temperature of 90°C to obtain the modified polyaluminium chloride flocculant.

[0086] Example 2

[0087] A modified polyaluminium chloride flocculant comprises the following raw materials in parts by weight:

[0088] 60 parts of polyaluminium chloride, 12 parts of magnesium silicate, 8 parts of carboxymethyl chitosan, 22 parts of polyaluminium ferric chloride and 5 parts of tea polyphenols;

[0089] The molar ratio of aluminum ions to iron ions in the modified polyaluminium chloride flocculant is 4:1.

[0090] A method for preparing a modified polyaluminium chloride flocculant comprises the following preparation steps:

[0091] (1) Mixing polyaluminium chloride, polyaluminium chloride iron and water at 80°C for 1.5 hours, then adding hydrochloric acid to adjust the pH of the reaction system to 3 to obtain an inorganic polymer mixed solution;

[0092] (2) mixing magnesium silicate with water to obtain a magnesium silicate dispersion having a mass fraction of 1%;

[0093] (a) Mixing the magnesium silicate dispersion and the inorganic polymer mixed solution, heating the reaction system to 65°C and keeping the temperature for 25 minutes; (b) then cooling the reaction solution to 52°C at a cooling rate of 0.5°C / min and keeping the temperature for 1 hour; (c) cooling the reaction solution obtained in step (b) to 45°C, adding a 5% by mass polyethylene glycol solution, and ultrasonically treating the solution at a frequency of 150W for 10 minutes to obtain a modified solution;

[0094] (3) mixing carboxymethyl chitosan with acetic acid-sodium acetate buffer (pH=5) to obtain carboxymethyl chitosan buffer;

[0095] Mixing tea polyphenols with water to obtain a tea polyphenol solution;

[0096] After mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution, a mixed solution is obtained;

[0097] Under nitrogen atmosphere, the mixed solution was added dropwise to the modified solution, and the grafting reaction was carried out at 40°C for 2 hours to obtain a grafting solution;

[0098] (4) After the grafting solution is mixed with a sodium citrate solution having a mass fraction of 8%, the mixture is subjected to low-temperature aging in a phosphate buffer solution having a pH of 6 at a temperature of 5°C for 40 hours, and then spray-dried at an inlet air temperature of 170°C and an outlet air temperature of 80°C to obtain the modified polyaluminium chloride flocculant.

[0099] Example 3

[0100] A modified polyaluminium chloride flocculant comprises the following raw materials in parts by weight:

[0101] 65 parts of polyaluminium chloride, 10 parts of magnesium silicate, 6 parts of carboxymethyl chitosan, 25 parts of polyaluminium ferric chloride and 4 parts of tea polyphenols;

[0102] The molar ratio of aluminum ions to iron ions in the modified polyaluminium chloride flocculant is 4.5:1.

[0103] A method for preparing a modified polyaluminium chloride flocculant comprises the following preparation steps:

[0104] (1) Mixing polyaluminium chloride, polyaluminium chloride iron and water at 75°C for 1.5 hours, then adding hydrochloric acid to adjust the pH of the reaction system to 3 to obtain an inorganic polymer mixed solution;

[0105] (2) mixing magnesium silicate with water to obtain a magnesium silicate dispersion having a mass fraction of 1%;

[0106] (a) Mixing the magnesium silicate dispersion with the inorganic polymer mixed solution, heating the reaction system to 62°C and keeping the temperature for 30 minutes; (b) then cooling the reaction solution to 55°C at a cooling rate of 0.5°C / min and keeping the temperature for 1 hour; (c) cooling the reaction solution obtained in step (b) to 40°C, adding a polyethylene glycol solution with a mass fraction of 5%, and ultrasonically treating it at a frequency of 200W for 20 minutes to obtain a modified solution;

[0107] (3) mixing carboxymethyl chitosan with acetic acid-sodium acetate buffer (pH=5) to obtain carboxymethyl chitosan buffer;

[0108] Mixing tea polyphenols with water to obtain a tea polyphenol solution;

[0109] After mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution, a mixed solution is obtained;

[0110] Under nitrogen atmosphere, the mixed solution was added dropwise to the modified solution, and the grafting reaction was carried out at 40°C for 2 hours to obtain a grafting solution;

[0111] (4) After the grafting solution is mixed with a sodium citrate solution having a mass fraction of 8%, low-temperature aging is carried out in a phosphate buffer solution having a pH of 6 at a temperature of 4°C for 50 hours, followed by spray drying at an inlet air temperature of 190°C and an outlet air temperature of 90°C to obtain the modified polyaluminium chloride flocculant.

[0112] Test Case

[0113] The basicity, specific surface area and heavy metal chelating capacity of the modified polyaluminium chloride flocculants prepared in test examples 1-3 are shown in Table 1.

[0114] Table 1 Test results of Examples 1-3

[0115]

[0116] Test method: The basicity is tested by the method in GB / T 22627-2014, the specific surface area is tested by N2 adsorption method, and the heavy metal chelating capacity is tested by EDTA titration method.

[0117] It can be seen from the data in Table 1 that the basicity, specific surface area and heavy metal chelating capacity of the modified polyaluminium chloride flocculant provided by the present invention all meet the standard requirements.

[0118] The modified polyaluminium chloride flocculants prepared in Examples 1-3 were put into simulated wastewater according to HJ 802-2016 standard to test their flocculation effects. The test results are shown in Table 2.

[0119] Water sample: simulated wastewater (water temperature 5°C, turbidity 50NTU, containing Pb 2+ 10mg / L, COD 200mg / L)

[0120] Dosage: 50mg / L (calculated as Al2O3)

[0121] Table 2 Flocculation effect test results of Examples 1-3

[0122]

[0123] It can be seen from the test results in Table 2 that the modified polyaluminium chloride flocculant provided by the present invention has an excellent flocculation effect.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A modified polyaluminium chloride flocculant, characterized in that: Contains the following raw materials in parts by weight: 50-65 parts of polyaluminium chloride, 8-12 parts of magnesium silicate, 5-8 parts of carboxymethyl chitosan, 15-25 parts of polyaluminium ferric chloride and 3-5 parts of tea polyphenols; The molar ratio of aluminum ions to iron ions in the modified polyaluminium chloride flocculant is (3-4.5):

1.

2. A modified polyaluminium chloride flocculant according to claim 1, characterized in that: Contains the following raw materials in parts by weight: 55-60 parts of polyaluminium chloride, 9-11 parts of magnesium silicate, 5-8 parts of carboxymethyl chitosan, 18-22 parts of polyaluminium ferric chloride and 3-5 parts of tea polyphenols; The molar ratio of aluminum ions to iron ions in the modified polyaluminium chloride flocculant is (3.5-4):

1.

3. A modified polyaluminium chloride flocculant according to claim 1 or 2, characterized in that: The Al2O3 content in the polyaluminium chloride is ≥28%.

4. A modified polyaluminium chloride flocculant according to claim 1 or 2, characterized in that: The specific surface area of ​​the magnesium silicate is ≥200m 2 / g.

5. A modified polyaluminium chloride flocculant according to claim 1 or 2, characterized in that: The degree of substitution of the carboxymethyl chitosan is ≥0.

8.

6. A method for preparing a modified polyaluminium chloride flocculant according to any one of claims 1 to 5, characterized in that: The preparation steps include: (1) Mixing polyaluminium chloride, polyaluminium ferric chloride and water, adjusting the pH to 3-3.5, and obtaining an inorganic polymer mixed solution; (2) mixing magnesium silicate with water to obtain a magnesium silicate dispersion, mixing the magnesium silicate dispersion with an inorganic polymer mixed solution, performing a modification reaction, and obtaining a modified solution; (3) mixing carboxymethyl chitosan with acetic acid-sodium acetate buffer to obtain carboxymethyl chitosan buffer; Mixing tea polyphenols with water to obtain a tea polyphenol solution; After mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution, a mixed solution is obtained; Under a protective atmosphere, the mixed solution is added dropwise to the modified solution to undergo a grafting reaction to obtain a grafted solution; (4) The grafting solution is mixed with the sodium citrate solution, aged at low temperature, and spray-dried to obtain the modified polyaluminium chloride flocculant.

7. The method for preparing a modified polyaluminium chloride flocculant according to claim 6, characterized in that: In step (1), the mixing temperature is 70-80° C., and the mixing time is 1-2 h.

8. The method for preparing a modified polyaluminium chloride flocculant according to claim 6, characterized in that: In step (2), the specific steps of the modification reaction include: (a) Mixing the magnesium silicate dispersion and the inorganic polymer mixed solution, heating to 60-65°C, and keeping the temperature for 25-35 minutes; (b) cooling the reaction solution obtained in step (a) to 50-55° C., and then keeping the temperature for 1-1.5 hours; The cooling rate is 0.5-1°C / min; (c) cooling the reaction solution obtained in step (b) to 40-45° C., adding polyethylene glycol solution, and ultrasonically treating for 10-20 min; The mass fraction of the polyethylene glycol solution is 5%-10%, and the frequency of the ultrasonic treatment is 150-200W.

9. The method for preparing a modified polyaluminium chloride flocculant according to claim 6, characterized in that: In step (3), the protective atmosphere is nitrogen, the temperature of the grafting reaction is 35-45° C., and the time of the grafting reaction is 1-2 h.

10. The method for preparing a modified polyaluminium chloride flocculant according to claim 6, characterized in that: In step (4), the mass fraction of the sodium citrate solution is 5%-10%, the low-temperature aging temperature is 3-5°C, and the low-temperature aging time is 40-50h; The inlet air temperature of the spray drying is 170-190°C, and the outlet air temperature is 80-90°C.

Images