Modified polyaluminum chloride flocculant and preparation method thereof

Abstract

The application 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 contains the following raw materials in parts by weight: polyaluminum chloride 50-65 parts, magnesium silicate 8-12 parts, carboxymethyl chitosan 5-8 parts, polyaluminum ferric chloride 15-25 parts and tea polyphenol 3-5 parts; and the molar ratio of aluminum ions to iron ions in the modified polyaluminum chloride flocculant is (3-4.5):1.The inorganic-organic double modifier synergistic mechanism is adopted to construct a "rigid skeleton-flexible network" composite structure, and the structure can significantly improve the adsorption amount of Pb 2+ . Meanwhile, the mechanical properties of the flocculant are improved, so that the flocculant can be applied in a high-turbulence environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a modified polyaluminum chloride flocculant and a preparation method thereof. BACKGROUND

[0002] Poly aluminum chloride (Poly aluminum Chloride) code PAC. It is also commonly known as water purifying agent or flocculant, it is a water-soluble inorganic polymer between AlCl3 and Al(OH)3. Color is yellow or light yellow, dark brown, dark gray resin-like solid. The product has strong bridging adsorption performance, in the hydrolysis process, accompanied by condensation, adsorption and precipitation and other physical and chemical processes. The fundamental difference between polyaluminum chloride and traditional inorganic flocculant is that the traditional inorganic flocculant is a low molecular crystalline salt, and the structure of polyaluminum chloride is composed of morphologically variable polycarboxylate complex, the flocculation and precipitation speed is fast, the PH value range is wide, the pipeline equipment is not corrosive, the water purification effect is obvious, the heavy metal ions such as arsenic, mercury and other heavy metal ions in water can be effectively removed. The product is widely used in drinking water, industrial water and sewage treatment field.

[0003] However, the polyaluminum chloride currently sold on the market has relatively single function, low aluminum content, and the flocculation effect of heavy metal ions needs to be improved. At the same time, the polyaluminum chloride also has problems such as low water treatment efficiency at low temperature and low turbidity, and weak heavy metal co-precipitation capacity. The existing modification technology mainly uses single silicate or polyacrylamide modification, which has defects such as poor compatibility of modifier and unstable molecular structure. Therefore, how to develop a new type of high-efficiency flocculant is a problem to be solved by those skilled in the art. SUMMARY

[0004] In view of this, the present application provides a modified polyaluminum chloride flocculant and a preparation method thereof, aiming at solving the problem of poor flocculation effect of polyaluminum chloride as a flocculant in the prior art.

[0005] On one hand, the present application provides a modified polyaluminum chloride flocculant, which comprises the following raw materials in parts by weight:

[0006] Polyaluminum chloride 50-65 parts, magnesium silicate 8-12 parts, carboxymethyl chitosan 5-8 parts, polyaluminum ferric chloride 15-25 parts and tea polyphenol 3-5 parts;

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

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

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

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

[0011] Preferably, the Al2O3 content in the polyaluminum 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] In another aspect, the present application also provides a preparation method of the modified polyaluminum chloride flocculant described above, comprising the following preparation steps:

[0015] (1) mixing polyaluminum chloride, polyaluminum ferric chloride with water, adjusting the pH to 3-3.5 to obtain an inorganic polymer mixture solution;

[0016] (2) mixing magnesium silicate with water to obtain a magnesium silicate dispersion solution, mixing the magnesium silicate dispersion solution with the inorganic polymer mixture solution, modifying reaction to obtain a modified solution;

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

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

[0019] Mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution to obtain a mixed solution;

[0020] Under a protective atmosphere, dropping the mixed solution into the modified solution, grafting reaction to obtain a grafted solution;

[0021] (4) mixing the grafted solution with a sodium citrate solution, low-temperature curing, and spray drying to obtain the modified polyaluminum chloride flocculant.

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

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

[0024] (a) mixing the magnesium silicate dispersion solution with the inorganic polymer mixture solution, heating to 60-65°C, and keeping for 25-35min;

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

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

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

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

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

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

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

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

[0033] 1. The present application provides a modified polyaluminum chloride flocculant, comprising the following raw materials in parts by weight: polyaluminum chloride 50-65 parts, magnesium silicate 8-12 parts, carboxymethyl chitosan 5-8 parts, polyaluminum ferric chloride 15-25 parts, and tea polyphenol 3-5 parts; the molar ratio of aluminum ions to iron ions in the modified polyaluminum chloride flocculant is (3-4.5):1. The present application adopts the synergistic mechanism of inorganic-organic double modifiers: the Lewis acid sites in magnesium silicate form coordinate bonds with the amino groups in carboxymethyl chitosan, constructing a "rigid skeleton-flexible network" composite structure. The rigid skeleton (magnesium silicate) provides a high specific surface area and fixed adsorption sites, capturing 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, the adsorption capacity of Pb 2+ can be significantly improved. Moreover, in the "rigid skeleton-flexible network" composite structure, the magnesium silicate skeleton bears the main stress, inhibiting the collapse of the structure, and the carboxymethyl chitosan network dissipates energy through chain segment slipping to prevent crack propagation, improving the mechanical properties of the flocculant, so that it can be applied in high-turbulence environments.

[0034] The trivalent iron ion in the polymeric aluminum ferric chloride can catalyze the oxidation of the catechol group of tea polyphenols into semiquinone free radicals, enhance the reduction capacity of the flocculant on Cr(VI), and further improve the flocculation effect of the flocculant.

[0035] 2. The application further limits the Al2O3 content in the polyaluminum chloride to be greater than or equal to 28%. The polyaluminum chloride is the main component of the flocculant and can provide a large number of aluminum ions, which can generate positively charged hydroxy aluminum polymers through hydrolysis, have strong electric neutralization and adsorption bridging effect, and can effectively capture suspended particles in water.

[0036] 3. The application further limits the specific surface area of the magnesium silicate to be greater than or equal to 200 m 2 / g. As a coagulant aid, magnesium silicate can increase the density and mechanical strength of the floc, making the floc more easily settle. At the same time, the silicon hydroxyl groups on the surface of magnesium silicate can adsorb organic matter in the pollutants, further improving the removal effect. In addition, the layered structure of magnesium silicate can provide intercalation sites to load Al-Fe hydroxyl polymers to form a multi-level adsorption channel. When the specific surface area of magnesium silicate is greater than or equal to 200 m 2 / g, it has a larger adsorption capacity, further improving the flocculation effect of the flocculant.

[0037] 4. The application further limits the degree of substitution of carboxymethyl chitosan to be greater than or equal to 0.8. Carboxymethyl chitosan has a large number of negative charges, which can combine with the positively charged floc generated by polyaluminum chloride to form more stable floc and enhance the flocculation effect. Carboxymethyl chitosan can also aggregate small flocs into larger flocs through the bridging effect of its polymer chain, facilitating settling and filtration. The chelation site density of carboxymethyl chitosan with a degree of substitution greater than or equal to 0.8 reaches 3.2 mmol / g (potentiometric titration method), and the floc shear strength is increased by 50%, thereby meeting the use of the flocculant in more turbulent conditions.

[0038] 5. The modified polyaluminum chloride flocculant provided by the application also includes polyaluminum ferric chloride. Polyaluminum ferric chloride contains iron ions, and compared with aluminum ions, the flocculation effect of iron ions is stronger, which can further improve the removal capacity of suspended solids in water. At the same time, the synergistic effect of aluminum ions and iron ions can make the flocculant maintain good flocculation effect in a wider pH range. And the Fe-O-Al bond energy in polyaluminum ferric chloride reaches 418 kJ / mol (DFT calculation), further strengthening the floc skeleton strength, meeting the use of the flocculant in high-strength environment.

[0039] 6. The modified polyaluminum chloride flocculant provided by the present application further comprises tea polyphenol. Tea polyphenol has the effects of antioxidation and inhibition of microbial growth, and can improve the storage stability of the flocculant. Meanwhile, tea polyphenol is a good organic flocculant, and can promote the flocculation process by forming complexes with organic matters and metal ions in water through its polyphenol groups. The catechol group (C6H3(OH)2) in tea polyphenol can form stable five-membered ring chelates with heavy metals (stability constant logK>16). In addition, the antioxidation of tea polyphenol can also protect Fe 2+ from being excessively oxidized.

[0040] 7. The present application further provides a preparation method of the modified polyaluminum chloride flocculant, comprising the following steps: (1) mixing polyaluminum chloride and polyaluminum ferric chloride with water, and adjusting the pH to 3-3.5 to obtain an inorganic polymer mixture solution; (2) mixing magnesium silicate with water to obtain a magnesium silicate dispersion solution, mixing the magnesium silicate dispersion solution with the inorganic polymer mixture solution, and performing modification reaction to obtain a modified solution; (3) mixing carboxymethyl chitosan with acetic acid-sodium acetate buffer solution to obtain a carboxymethyl chitosan buffer solution, mixing tea polyphenol with water to obtain a tea polyphenol solution, mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution to obtain a mixed solution, and adding the mixed solution dropwise into the modified solution in a protective atmosphere to perform grafting reaction and obtain a grafted solution; and (4) mixing the grafted solution with a sodium citrate solution, performing low-temperature curing, and performing spray drying to obtain the modified polyaluminum chloride flocculant.

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

[0042] 8. The application further limits the preparation method of the modified polyaluminum chloride flocculant, and in step (2), the specific steps of the modification reaction include: (a) mixing the magnesium silicate dispersion liquid and the inorganic polymer mixed solution, heating to 60-65 DEG C, and keeping for 25-35 min; (b) cooling the reaction liquid obtained in step (a) to 50-55 DEG C, and then keeping for 1-1.5 h; the cooling rate is 0.5-1 DEG C / min; (c) cooling the reaction liquid obtained in step (b) to 40-45 DEG C, adding a polyethylene glycol solution, and ultrasonic treatment for 10-20 min; the mass fraction of the polyethylene glycol solution is 5%-10%, and the ultrasonic treatment frequency is 150-200 W. In the modification reaction, the temperature is controlled in stages, the bonding mode of the magnesium silicate and the Al-Fe hydroxyl complex is regulated in stages (edge hydroxyl -> interlayer insertion -> interface modification), and then the directional assembly of the inorganic-organic components is realized, and the Alb form retention rate is increased by 28% (the structure is prone to collapse due to temperature mutation in the traditional process). DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0044] The application provides a modified polyaluminum chloride flocculant, which comprises the following raw materials in parts by weight:

[0045] 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.

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

[0047] In the application, the weight fraction of polyaluminum chloride is controlled to be 50-65 parts, when the weight fraction of polyaluminum chloride is <50 parts, the electric neutralization capacity is insufficient; the weight fraction of magnesium silicate is controlled to be 8-12 parts, when the weight fraction of magnesium silicate is >12 parts, the viscosity of the system is too high; the weight fraction of carboxymethyl chitosan is controlled to be 5-8 parts, when the weight fraction of carboxymethyl chitosan is <5 parts, the floc strength is decreased by 40%; the weight fraction of polyaluminum ferric chloride is controlled to be 15-25 parts, when the weight fraction of polyaluminum ferric chloride is >30 parts, the pH fluctuation is >1.5; and the weight fraction of tea polyphenol is controlled to be 3-5 parts, when the weight fraction of tea polyphenol is >6 parts, brown color development interference is prone to occur in the system.

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

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

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

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

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

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

[0054] The present application also provides a preparation method of the modified polyaluminum chloride flocculant, comprising the following preparation steps:

[0055] (1) mixing polyaluminum chloride, polyaluminum ferric chloride, and water, adjusting the pH to 3-3.5 to obtain an inorganic polymer mixture solution;

[0056] (2) mixing magnesium silicate with water to obtain a magnesium silicate dispersion solution, mixing the magnesium silicate dispersion solution with the inorganic polymer mixture solution, and modifying to obtain a modified solution;

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

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

[0059] mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution to obtain a mixed solution;

[0060] under a protective atmosphere, dropping the mixed solution into the modified solution, and grafting to obtain a grafted solution;

[0061] (4) mixing the grafted solution with a sodium citrate solution, low-temperature curing, and spray drying to obtain the modified polyaluminum chloride flocculant.

[0062] In some embodiments of the present application, 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 application, in step (2), the specific steps of the modification reaction include:

[0064] (a) mixing the magnesium silicate dispersion solution with the inorganic high polymer mixed solution, and heating to 60-65℃ for 25-35 min;

[0065] (b) cooling the reaction solution obtained in step (a) to 50-55℃, and then keeping for 1-1.5 h;

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

[0067] (c) cooling the reaction solution obtained in step (b) to 40-45℃, adding the polyethylene glycol solution, and ultrasonic treatment 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 application, in step (3), the protective atmosphere is nitrogen, the temperature of the grafting reaction is 35-45℃, and the time of the grafting reaction is 1-2h.

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

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

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

[0073] Example 1

[0074] A modified polyaluminum chloride flocculant, comprising the following raw materials in parts by weight:

[0075] Polyaluminum chloride 50 parts, magnesium silicate 8 parts, carboxymethyl chitosan 5 parts, polyaluminum ferric chloride 15 parts, and tea polyphenol 3 parts;

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

[0077] A preparation method of a modified polyaluminum chloride flocculant, comprising the following preparation steps:

[0078] (1) mixing polyaluminum chloride, polyaluminum ferric chloride, and water at a temperature of 70℃ for 1h, then adding hydrochloric acid, and adjusting the pH of the reaction system to 3 to obtain an inorganic high polymer mixed solution;

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

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

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

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

[0083] mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution to obtain a mixed solution;

[0084] under a nitrogen atmosphere, dropping the mixed solution into the modified solution, and carrying out grafting reaction at a temperature of 35°C for 1 h to obtain a grafted solution;

[0085] (4) mixing the grafted solution with a sodium citrate solution with a mass fraction of 10%, and then carrying out low-temperature curing in a phosphate buffer solution with a pH of 6, wherein the low-temperature curing is carried out at a temperature of 3°C for 40 h, and then carrying out spray drying at an air inlet temperature of 170°C and an air outlet temperature of 90°C to obtain the modified polyaluminum chloride flocculant.

[0086] Example 2

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

[0088] polyaluminum chloride 60 parts, magnesium silicate 12 parts, carboxymethyl chitosan 8 parts, polyaluminum ferric chloride 22 parts, and tea polyphenol 5 parts;

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

[0090] A preparation method of a modified polyaluminum chloride flocculant comprises the following preparation steps:

[0091] (1) mixing polyaluminum chloride, polyaluminum ferric chloride with water under temperature adjustment at 80°C for 1.5 h, and 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 solution with a mass fraction of 1%;

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

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

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

[0096] Mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution to obtain a mixed solution;

[0097] Under a nitrogen atmosphere, the mixed solution is added dropwise into the modified solution, and a grafting reaction is carried out at a temperature of 40℃ for 2 h to obtain a grafted solution;

[0098] (4) mixing the grafted solution with an 8% sodium citrate solution by mass fraction, and then carrying out low-temperature curing in a phosphate buffer solution with a pH of 6, wherein the low-temperature curing is carried out at a temperature of 5℃ for 40 h, and then carrying out spray drying at an air inlet temperature of 170℃ and an air outlet temperature of 80℃ to obtain the modified polyaluminum chloride flocculant.

[0099] Example 3

[0100] A modified polyaluminum chloride flocculant, comprising the following raw materials by weight fraction:

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

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

[0103] A preparation method of a modified polyaluminum chloride flocculant, comprising the following preparation steps:

[0104] (1) mixing polyaluminum chloride, polyaluminum ferric chloride, and water under temperature adjustment at 75℃ for 1.5 h, and 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 1% magnesium silicate dispersion solution by mass fraction;

[0106] (a) mixing the magnesium silicate dispersion liquid with the inorganic high molecular mixed solution, and heating the reaction system to 62 DEG C and keeping for 30 min; (b) then cooling the reaction liquid to 55 DEG C at a cooling rate of 0.5 DEG C / min and keeping for 1 h; (c) cooling the reaction liquid obtained in step (b) to 40 DEG C, adding a 5% polyethylene glycol solution, and ultrasonic treating at a frequency of 200 W for 20 min to obtain a modified solution;

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

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

[0109] Mixing the carboxymethyl chitosan buffer solution with the tea polyphenol solution to obtain a mixed solution;

[0110] Under a nitrogen atmosphere, the mixed solution is added dropwise into the modified solution, and a grafting reaction is carried out at a temperature of 40 DEG C for 2 h to obtain a grafted solution;

[0111] (4) mixing the grafted solution with an 8% sodium citrate solution, and then carrying out low-temperature curing in a phosphate buffer solution with a pH of 6, wherein the low-temperature curing is carried out at a temperature of 4 DEG C for 50 h, and then carrying out spray drying at an air inlet temperature of 190 DEG C and an air outlet temperature of 90 DEG C to obtain the modified polyaluminum chloride flocculant.

[0112] Test Example

[0113] The basicity, specific surface area and heavy metal chelating capacity of the modified polyaluminum 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 method in GB / T 22627-2014 is used for testing the basicity, the N2 adsorption method is used for testing the specific surface area, and the EDTA titration method is used for testing the heavy metal chelating capacity.

[0117] As shown in Table 1, the basicity, specific surface area and heavy metal chelating capacity of the modified polyaluminum chloride flocculants provided by the application all meet the standard requirements.

[0118] The modified polyaluminum chloride flocculants prepared in Examples 1-3 are put into simulated wastewater according to the HJ 802-2016 standard, and the flocculation effect is tested, and the test results are shown in Table 2.

[0119] Water sample: simulated wastewater (water temperature 5℃, turbidity 50 NTU, 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] From the test results in Table 2, the modified polyaluminum chloride flocculant provided by the application has excellent flocculation effect.

[0124] Finally, it should be noted that: the above examples are used to illustrate the technical solutions of the present application rather than limit them, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: the specific embodiments of the present application can still be modified or replaced by the equivalent, without departing from the spirit and scope of the present application, any modification or equivalent replacement, which should be covered within the protection scope of the claims of the present application.

Claims

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

1. The modified polyaluminum chloride flocculant is prepared by the following steps: (1) mixing polyaluminum chloride, polyaluminum ferric chloride and water at 70-80℃ for 1-2h, adjusting pH to 3-3.5 to obtain 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, modifying to obtain a modified solution; (2.1) mixing the magnesium silicate dispersion with the inorganic polymer mixed solution, heating to 60-65℃ and keeping for 25-35min; (2.2) cooling the reaction liquid obtained in step (2.1) to 50-55℃, and then keeping for 1-1.5h; The cooling rate is 0.5-1℃ / min; (2.3) cooling the reaction liquid obtained in step (2.2) to 40-45℃, adding a polyethylene glycol solution, ultrasonic treatment for 10-20min to obtain a modified solution; The mass fraction of the polyethylene glycol solution is 5%-10%, and the ultrasonic treatment frequency is 150-200W; (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; In a protective atmosphere, drop the mixed solution into the modified solution, grafting reaction to obtain a grafted solution; (4) mixing the grafted solution with a sodium citrate solution, low-temperature curing, and spray drying to obtain the modified polyaluminum chloride flocculant.

2. The modified polyaluminum chloride flocculant according to claim 1, characterized in that, The raw materials comprise the following weight parts: Polyaluminum chloride 50-65 parts, magnesium silicate 8-12 parts, carboxymethyl chitosan 5-8 parts, polyaluminum ferric chloride 15-25 parts and tea polyphenol 3-5 parts; The molar ratio of aluminum ions to iron ions in the modified polyaluminum chloride flocculant is (3-4.5):

1.

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

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

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

8.

6. The modified polyaluminum chloride flocculant according to claim 1, characterized in that, In step (3), the protective atmosphere is nitrogen, the grafting reaction temperature is 35-45℃, and the grafting reaction time is 1-2h.

7. The modified polyaluminum chloride flocculant according to claim 1, characterized in that, In step (4), the mass fraction of the sodium citrate solution is 5%-10%, the low-temperature curing temperature is 3-5℃, and the low-temperature curing time is 40-50h; The spray drying inlet temperature is 170-190℃, and the outlet temperature is 80-90℃.

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