Aluminum-based hybrid flocculants and methods for their preparation

Abstract

The application relates to the technical field of water treatment, in particular to an aluminum-based hybrid flocculant and a preparation method thereof. The preparation method of the aluminum-based hybrid flocculant comprises the following steps: (1) mixing an ammonium carbonate solution and an aluminum chloride solution to obtain an aluminum hydroxide colloid; (2) uniformly mixing the aluminum hydroxide colloid, dimethyl diallyl ammonium chloride, part of acrylamide and a solubilizing agent to obtain a mixed solution; (3) mixing the mixed solution, an initiator and butyl acrylate to react, and obtaining a product system; and (4) adding the rest of the acrylamide into the product system obtained in the step (3) to continue the reaction and obtaining the aluminum-based hybrid flocculant. The removal rates of the turbidity and emulsified oil in the mine water with high turbidity and trace emulsified oil reach 98.8% and 62.2% respectively, and the turbidity and the emulsified oil are reduced to 8.4 NTU and 0.2646 mg / L respectively.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to an aluminum-based hybrid flocculant and a preparation method thereof. BACKGROUND

[0002] A flocculant is an inorganic or organic substance that can make different particle sizes of fine particles in water bodies gather to produce flocculent material and then settle to achieve the purpose of separation from water bodies. Different classification standards correspond to different classification methods. From the chemical composition, flocculants are divided into four categories: inorganic, organic, microbial, and composite flocculants. Throughout the development history of flocculants, from small molecules to macromolecules, from single-component type to composite type, it has undergone a series of development processes.

[0003] Composite flocculants can overcome many shortcomings of single flocculants, especially when treating complex wastewater systems, and can achieve more satisfactory results compared to single flocculants. Therefore, research on composite flocculants has been more active in recent years, and the integration and functional diversification of flocculants are the main development trend. Among the many categories of composite flocculants, inorganic-organic composite flocculants have received widespread attention, mainly because they combine the characteristics of inorganic coagulants and organic flocculants. However, the development and application of inorganic-organic composite flocculants are limited due to macroscopic phase separation and other phenomena during preparation.

[0004] Therefore, how to provide a hybrid flocculant to solve the defects of existing composite flocculants is a problem to be solved by those skilled in the art. SUMMARY

[0005] The purpose of the present application is to provide an aluminum-based hybrid flocculant and a preparation method thereof to solve the defects of the prior art.

[0006] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0007] The present application provides a preparation method of an aluminum-based hybrid flocculant, comprising the following steps:

[0008] (1) mixing an ammonium carbonate solution and an aluminum chloride solution to obtain an aluminum hydroxide colloid;

[0009] (2) mixing the aluminum hydroxide colloid, dimethyl diallyl ammonium chloride, part of acrylamide, and a solubilizing agent to obtain a mixed solution;

[0010] (3) mixing the mixed solution, an initiator, and butyl acrylate to react and obtain a product system;

[0011] (4) adding the remaining acrylamide to the product system obtained in step (3) to continue the reaction to obtain an aluminum-based hybrid flocculant.

[0012] Preferably, the mass concentration of the aluminum chloride solution is 8-12%, the mass concentration of the ammonium carbonate solution is 10-20%, and the volume ratio of the ammonium carbonate solution to the aluminum chloride solution is 4-5:100.

[0013] The temperature when the ammonium carbonate solution is mixed with the aluminum chloride solution is 28-32℃.

[0014] The mass ratio of aluminum chloride, dimethyl diallyl ammonium chloride, acrylamide, initiator and butyl acrylate in the aluminum chloride solution is 18-22:20-28:40-56:0.1-0.3:6.4-11.2.

[0015] The solubilizing agent accounts for 0.5%-2% of the total volume of the reactants.

[0016] Preferably, the reaction time of the step (3) is 30-50 min, and the reaction temperature is 42-47℃.

[0017] Preferably, the reaction time of the step (4) is 5.5-6.5 h, and the reaction temperature is 42-47℃.

[0018] Preferably, the steps (3) and (4) are both carried out in a nitrogen atmosphere.

[0019] Preferably, the step (1) is to drop the ammonium carbonate solution into the aluminum chloride solution, and the dropping speed is 8-10 s / drop.

[0020] Preferably, the part of acrylamide added in the step (2) accounts for 45-55% of the total mass of acrylamide.

[0021] Preferably, the initiator is a mixture of potassium persulfate and sodium bisulfite, and the mass ratio of potassium persulfate to sodium bisulfite is 1:1-2.5.

[0022] The application further provides an aluminum-based hybrid flocculant prepared by the preparation method.

[0023] The technical principle of the application is as follows:

[0024] In aluminum-based hybrid flocculants, the charge neutralization effect of positively charged aluminum hydroxide nanonuclei and the cationic monomer dimethyl diallyl ammonium chloride (DMDAAC) effectively neutralizes the high negative potential ultrafine particles in mine water, reducing their electrostatic repulsion and facilitating the subsequent adsorption and bridging effects of the flocculant. Furthermore, the -C=O and -NH2 groups carried by amide and ester groups on the organic molecular chains form hydrogen bonds with the -OH or -O- groups on the surfaces of coal powder particles and organic matter, bridging the ultrafine particles and causing them to aggregate into flocs that continuously grow and become denser, ultimately settling rapidly. This process reduces the distance between particles, further promoting charge neutralization.

[0025] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0026] On the one hand, aluminum-based hybrid flocculants disperse long polymer chains in a branched form, which effectively reduces the steric hindrance effect compared with traditional linear organic polymer flocculants, making it more conducive to the functional groups on the polymer chains to fully contact with fine particulate matter and organic matter in the water. On the other hand, the hydrophobic association between molecules enables synergistic flocculation between molecules.

[0027] This invention achieves turbidity removal rates of 98.8% and 62.2% for mine water with high turbidity and trace amounts of emulsified oil, respectively, reducing the turbidity and emulsified oil levels to 8.4 NTU and 0.2646 mg / L. Attached Figure Description

[0028] Figure 1 This is a diagram illustrating the synthesis mechanism of the aluminum-based hybrid flocculant of the present invention;

[0029] Figure 2 The Fourier transform infrared (FT-IR) spectrum of the aluminum-based hybrid flocculant of Example 1 of the present invention;

[0030] Figure 3 (a) and (b) are respectively the aluminum-based hybrid flocculant of Example 1 of the present invention. 1 H-NMR and 13 C NMR spectrum;

[0031] Figure 4 The images shown are scanning electron microscope (SEM) images of the aluminum-based hybrid flocculant of Example 1 of the present invention, where (a) is observed at 5000x magnification and (b) is observed at 10000x magnification.

[0032] Figure 5 The thermogravimetric analysis (TG) diagram of the aluminum-based hybrid flocculant of Example 1 of the present invention is shown. Detailed Implementation

[0033] This invention provides a method for preparing an aluminum-based hybrid flocculant, comprising the following steps:

[0034] (1) Mix ammonium carbonate solution with aluminum chloride solution to obtain aluminum hydroxide colloid;

[0035] (2) A mixed solution is obtained by mixing aluminum hydroxide colloid, dimethyl diallyl ammonium chloride, a portion of acrylamide, and solubilizer;

[0036] (3) Mix the mixed solution, initiator, and butyl acrylate to react and obtain the product system;

[0037] (4) Add the remaining acrylamide to the product system obtained in step (3) and continue the reaction to obtain an aluminum-based hybrid flocculant.

[0038] In this invention, the mass concentration of the aluminum chloride solution is 8-12%, preferably 9-11%, the mass concentration of the ammonium carbonate solution is 10-20%, preferably 12-18%, and the volume ratio of the ammonium carbonate solution to the aluminum chloride solution is 4-5:100, preferably 4.2-4.8:100.

[0039] The temperature at which the ammonium carbonate solution and aluminum chloride solution are mixed is 28~32℃, preferably 29~30℃;

[0040] The mass ratio of aluminum chloride, dimethyl diallyl ammonium chloride, acrylamide, initiator, and butyl acrylate in the aluminum chloride solution is 18~22:20~28:40~56:0.1~0.3:6.4~11.2, preferably 19~20:22~24:44~50:0.15~0.25:7~10;

[0041] The solubilizer accounts for 0.5-2% of the total volume of the reactants, preferably 1-1.5%.

[0042] In this invention, the solubilizer is one of urea, sodium alkylbenzene sulfonate, polysorbate, and polyoxyethylene fatty acid ester.

[0043] In this invention, step (1) involves dropping an ammonium carbonate solution into an aluminum chloride solution at a rate of 8-10 s / drop, preferably 9 s / drop.

[0044] In this invention, the amount of acrylamide added in step (2) is 45-55% of the total mass of acrylamide, preferably 48-52%.

[0045] In this invention, the initiator is a mixture of potassium persulfate and sodium bisulfite, wherein the mass ratio of potassium persulfate to sodium bisulfite is 1:1 to 2.5, preferably 1:1.5 to 2.

[0046] In this invention, the reaction time in step (3) is 30-50 min, preferably 35-45 min, and the reaction temperature is 42-47°C, preferably 43-46°C.

[0047] In this invention, the reaction time in step (4) is 5.5~6.5h, preferably 5.8~6.2h, and the reaction temperature is 42~47℃, preferably 43~46℃.

[0048] In this invention, steps (3) and (4) are both performed under a nitrogen atmosphere.

[0049] The present invention also provides an aluminum-based hybrid flocculant prepared by the above preparation method.

[0050] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0051] Example 1

[0052] The first step involves injecting a 10 wt% aluminum chloride solution into a 250 mL three-necked flask and placing it in a constant-temperature magnetic water bath at 30°C. The aluminum chloride accounts for 20% of the total reactant mass.

[0053] The second step involves slowly adding a 15% ammonium carbonate solution (at a rate controlled at one drop every 9 seconds) to a 100 mL constant pressure dropping funnel under a stirring speed of 1800 rpm to obtain aluminum hydroxide colloid. The volume ratio of the ammonium carbonate solution to the aluminum chloride solution is 4.5:100.

[0054] The third step involves dissolving DMDAAC and acrylamide (AM) in a colloidal system and adding a small amount of urea as a solubilizer. Simultaneously, the water temperature in the water bath is increased to 45°C, and nitrogen gas is introduced for about 30 minutes to purge the oxygen from the apparatus. At this point, the amount of DMDAAC added is 24% of the total mass of the reactants, AM is 23.1% of the total mass of the reactants, and 0.5 ml (0.5% of the reaction volume) of urea is added as a solubilizer.

[0055] In the fourth step, the initiator solution is slowly added dropwise to the three-necked flask at a ratio of m(K2S2O8) / m(NaHSO3)=2 to initiate the polymerization of acrylamide monomer. The amount of initiator added is 0.2% of the total mass of the reactants. At the same time, butyl acrylate (BA) is added at a rate of 9.6% of the total mass of the reactants. The reaction is carried out for 40 minutes under continuous nitrogen purging.

[0056] Fifth step: Using a constant pressure dropping funnel, AM is slowly added dropwise to the reaction system in solution form. The reaction is continued for 6 hours and then stopped. The amount of AM added is 23.1% of the total mass of the reactants.

[0057] Step 6: Dilute the viscous gel obtained from the reaction with a small amount of deionized water, add acetone for extraction, filter under negative pressure, wash the precipitate multiple times with anhydrous ethanol to dissolve and remove acrylamide monomers that did not participate in the polymerization reaction, place the obtained product in a constant temperature vacuum drying oven, dry at 45°C for 48 h, and then seal and store.

[0058] The obtained aluminum-based hybrid flocculant (S1) has an characteristic viscosity of 1492.93 mL / g and a corresponding average relative molecular mass of 7.44 × 10⁻⁶. 6 Da, the cationicity of the product is 16.97%.

[0059] Example 2

[0060] The preparation steps are the same as in Example 1, and the reagent dosages are as follows:

[0061] The main raw materials and reagents are: aluminum chloride 20%, AM 53.4%, DMDAAC 20%, initiator 0.2%, and BA 6.4%;

[0062] The obtained aluminum-based hybrid flocculant (S2) has an characteristic viscosity of 1311.46 mL / g and a corresponding average relative molecular mass of 6.33 × 10⁻⁶. 6 The cationicity of the product is 15.89%.

[0063] Example 3

[0064] The preparation steps are the same as in Example 1, and the reagent dosages are as follows:

[0065] The main raw materials and reagents are: aluminum chloride 20%, AM 49.5%, DMDAAC 24%, initiator 0.1%, and BA 6.4%;

[0066] The obtained aluminum-based hybrid flocculant (S3) has an characteristic viscosity of 1352.44 mL / g and a corresponding average relative molecular mass of 6.58 × 10⁻⁶. 6 Da, the cationicity of the product is 18.04%.

[0067] Example 4

[0068] The preparation steps are the same as in Example 1, and the reagent dosages are as follows:

[0069] The main raw materials and reagents are: aluminum chloride 20%, AM 45.3%, DMDAAC 28%, initiator 0.3%, and BA 6.4%;

[0070] The obtained aluminum-based hybrid flocculant (S4) has an characteristic viscosity of 1321.84 mL / g and a corresponding average relative molecular mass of 6.39 × 10⁻⁶. 6 The cationicity of the product is 19.94%.

[0071] Example 5

[0072] The preparation steps are the same as in Example 1, and the reagent dosages are as follows:

[0073] The main raw materials and reagents are: aluminum chloride 20%, AM 47.8%, DMDAAC 24%, initiator 0.2%, and BA 8%;

[0074] The obtained aluminum-based hybrid flocculant (S5) has an characteristic viscosity of 1401.84 mL / g and a corresponding average relative molecular mass of 6.88 × 10⁻⁶. 6 Da, the cationicity of the product is 17.43%.

[0075] Example 6

[0076] The preparation steps are the same as in Example 1, and the reagent dosages are as follows:

[0077] The main raw materials and reagents are: aluminum chloride 20%, AM 44.6%, DMDAAC 24%, initiator 0.2%, and BA 11.2%;

[0078] The obtained aluminum-based hybrid flocculant (S6) has an characteristic viscosity of 1511.93 mL / g and a corresponding average relative molecular mass of 7.56 × 10⁻⁶. 6 The cationicity of the product is 15.41%.

[0079] Analysis of the aluminum-based hybrid flocculant prepared in Example 1

[0080] FTIR spectrum analysis

[0081] Depend on Figure 2 It can be seen that after introducing the cationic monomer DMDAAC and the hydrophobic monomer BA into the hybrid flocculant Al-PAM, the peak shape and position of most of the absorption peaks in the infrared spectrum of the product do not change significantly. This is because the main chain of the macromolecule is mainly composed of methylene (-CH2-) and methine (-CH-) before and after the introduction.

[0082] Due to the grafting of quaternary ammonium groups and ester groups, shifts in absorption peak positions and changes in peak area, as well as new absorption peaks, also occurred at a few locations, such as 3411.5 cm⁻¹ in Al-PAM. -1The characteristic absorption peak generated by free -NH2 in the amide is red-shifted to 3398.7 cm⁻¹ in Al-P(AM-DMDAAC) and Al-P(AM-DMDAAC-BA), respectively. -1 and 3396.6 cm -1 Place;

[0083] 3194 cm in Al-PAM -1 The characteristic absorption peak generated by associated -NH2 is red-shifted to 3166.5 cm⁻¹ in Al-P(AM-DMDAAC) and Al-P(AM-DMDAAC-BA), respectively. -1 and 3378 cm -1 At 1608 cm in Al-PAM -1 The absorption peaks generated by the bending vibrations of NH in the amide also red-shifted to 1616 cm⁻¹. -1 and 1620.3 cm -1 Place;

[0084] Meanwhile, in Al-PAM, 1221.6 cm -1 The characteristic absorption peak generated by the stretching vibration of the CN bond is redshifted to 1226 cm⁻¹ in Al-P(AM-DMDAAC). -1 The increased peak area is due to the presence of CN bond stretching vibrations in the newly grafted quaternary ammonium groups.

[0085] For Al-P(AM-DMDAAC-BA), due to the addition of the ester group, its infrared spectrum is at 1259 cm⁻¹. -1 and 1734.5cm -1 The new characteristic absorption peaks with low intensity were generated at the point, which can be attributed to the stretching vibrations of COC and C=O in the ester group, respectively.

[0086] This demonstrates that the cationic monomer DMDAAC and the hydrophobic monomer BA have been successfully incorporated into the organic macromolecular chain of the hybrid flocculant.

[0087] Nuclear magnetic resonance (NMR) spectrum analysis:

[0088] from Figure 3 As shown in (a) of the 1H NMR spectrum, after the addition of DMDAAC and BA, the chemical shifts corresponding to the proton peaks of hydrogen atoms on the methylene (-CH2-) and methine (-CH-) atoms in the main chain (-CH2-CH-) remain essentially unchanged at δ=1.598 ppm and δ=2.106 ppm, respectively. The integral value of the peak area decreases slightly. This is due to the increased proportion of hydrogen protons at other chemical shifts in the molecule. Figure 3 This is also reflected in the carbon NMR spectrum shown in (b);

[0089] At the same time, the proton peak of the hydrogen atom in amino (-NH2) showed a more obvious splitting phenomenon due to the addition of new organic monomers;

[0090] In the 1H resonance spectra of Al-P(AM-DMDAAC) and Al-P(AM-DMDAAC-BA), the proton peaks that appear near the chemical shift δ=3.0 ppm are generated by hydrogen atoms in the methyl (-CH3) and methylene (-CH2-) groups of the quaternary ammonium groups, respectively. In addition, the new proton peaks that appear at δ=4.31 ppm correspond to hydrogen atoms on the non-carbonyl carbon atoms attached to the ester group in Al-P(AM-DMDAAC-BA).

[0091] The chemical shift at δ = 4.802 ppm corresponds to the solvent proton peak of heavy water. Figure 3 In (b), it can be clearly seen that the proton peak generated by the carbon atom of the carbonyl group (-C=O) in the amide group at the chemical shift δ=175.159 ppm in Al-PAM and Al-P(AM-DMDAAC) has shifted to δ=179.51 ppm in Al-P(AM-DMDAAC-BA) due to the addition of the ester group;

[0092] Furthermore, due to the introduction of new organic monomers, some new proton peaks with lower heights appeared in the chemical shift δ=30-50 ppm, which correspond to the proton peaks of hydrogen atoms of the terminal methyl groups in macromolecular chains of different lengths;

[0093] Comparison of carbon NMR spectra of Al-P(AM-DMDAAC) and Al-P(AM-DMDAAC-BA) Figure 3 (b) It was found that the proton peak heights of hydrogen atoms on the methylene (-CH2-) and methine (-CH-) groups in the main chain of the former were higher than those of the latter. This indicates that for a single flocculant molecule, the introduction of the hydrophobic ester group did not increase the chain length of its carbon chain. This further suggests that the increase in the characteristic viscosity of the product after the introduction of BA is caused by the hydrophobic association between molecules.

[0094] The above phenomena also indicate that the cationic group DMDAAC and the hydrophobic group BA have been successfully introduced into the hybrid flocculant molecular chain, and the hybrid product Al-P (AM-DMDAAC-BA) has a relatively complete structure and high purity.

[0095] Scanning electron microscopy analysis:

[0096] Depend on Figure 4 It can be seen that the surface of Al-P(AM-DMDAAC-BA) exhibits an uneven and intricately interwoven network structure, which is caused by the different sizes of organic macromolecular chains regularly coating the surface of inorganic aluminum hydroxide particles.

[0097] Meanwhile, in addition to the opening of carbon-carbon double bonds and polymerization with AM, the cationic monomer DMDAAC and hydrophobic monomer BA introduced during the polymerization process also promote the formation of this complex structure by the quaternary ammonium groups and ester groups on their side chains approaching each other due to hydrogen bonds or van der Waals forces.

[0098] This structure helps increase the surface area of ​​flocculant molecules and provides enough contact sites for ultrafine particles, thereby enhancing the adsorption bridging performance of flocculants and their sweeping and trapping effect during sedimentation.

[0099] Thermogravimetric analysis:

[0100] Depend on Figure 5 It can be seen that aluminum-based hybrid flocculants mainly undergo three weight loss stages;

[0101] In the first stage, at 55℃~221℃, the weight loss was 13.3430%, mainly due to the thermal decomposition of ester groups, as well as adsorbed water and some bound water.

[0102] In the second stage, at 221℃~502℃, the weight loss ratio was 40.2770%, mainly consisting of the thermal decomposition of remaining bound water and amide groups, imidization, separation of methyl groups from quaternary ammonium groups, and removal of hydrogen chloride.

[0103] In the third stage, at 502℃~750℃, the weight loss rate was 19.5229%, mainly due to polymer backbone breakage.

[0104] In summary, the aluminum-based hybrid flocculant (S1) exhibits excellent thermal stability.

[0105] Application analysis of Example 1:

[0106] The turbidity and oil content of the high-turbidity well water containing trace amounts of emulsified oil and the treated supernatant in Example 1 were tested using a Hach turbidimeter (instrument model: 2100N) and the method of "Water Quality - Determination of Petroleum Products - Ultraviolet Spectrophotometry (National Standard HJ970-2018)".

[0107] The specific water sample came from mine water in a mine in Yulin City, Shaanxi Province, before it was pumped from an underground water tank to the surface for coagulation treatment. The specific treatment results are shown in Table 1.

[0108] Table 1. Results of Mine Water Treatment

[0109]

[0110] Table 1 shows that with a usage of only 14 mg / L, the removal rate of turbidity in mine water can reach 98.8%, and the removal rate of oil content can reach 62.2%.

[0111] The aluminum-based hybrid flocculant provided by this invention has a good effect on treating high-turbidity, emulsified oil well water, and the treatment process is simple, convenient and efficient, which can avoid the harm to the environment.

[0112] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an aluminum-based hybrid flocculant, characterized in that, Includes the following steps: (1) Mix ammonium carbonate solution with aluminum chloride solution to obtain aluminum hydroxide colloid; (2) A mixed solution is obtained by mixing aluminum hydroxide colloid, dimethyl diallyl ammonium chloride, a portion of acrylamide, and solubilizer; (3) Mix the mixed solution, initiator, and butyl acrylate to react and obtain the product system; (4) Add the remaining acrylamide to the product system obtained in step (3) and continue the reaction to obtain an aluminum-based hybrid flocculant; The aluminum chloride solution contains aluminum chloride, dimethyl diallyl ammonium chloride, acrylamide, initiator, and butyl acrylate in a mass ratio of 18~22:20~28:40~56:0.1~0.3:6.4~11.

2. The solubilizer accounts for 0.5% to 2% of the total volume of the reactants; Step (1) involves adding ammonium carbonate solution dropwise into aluminum chloride solution at a rate of 8-10 s / drop. The amount of acrylamide added in step (2) is 45-55% of the total mass of acrylamide.

2. The method for preparing an aluminum-based hybrid flocculant according to claim 1, characterized in that, The aluminum chloride solution has a mass concentration of 8-12%, the ammonium carbonate solution has a mass concentration of 10-20%, and the volume ratio of the ammonium carbonate solution to the aluminum chloride solution is 4-5:

100. The temperature at which the ammonium carbonate solution and aluminum chloride solution are mixed is 28~32℃.

3. The method for preparing an aluminum-based hybrid flocculant according to claim 1 or 2, characterized in that, The reaction time in step (3) is 30-50 min, and the reaction temperature is 42-47℃.

4. The method for preparing an aluminum-based hybrid flocculant according to claim 3, characterized in that, The reaction time in step (4) is 5.5~6.5h, and the reaction temperature is 42~47℃.

5. A method for preparing an aluminum-based hybrid flocculant according to claim 1, 2, or 4, characterized in that, Both steps (3) and (4) are performed under a nitrogen atmosphere.

6. The method for preparing an aluminum-based hybrid flocculant according to claim 1, characterized in that, The initiator is a mixture of potassium persulfate and sodium bisulfite, wherein the mass ratio of potassium persulfate to sodium bisulfite is 1:1 to 2.

5.

7. The aluminum-based hybrid flocculant prepared by the preparation method according to any one of claims 1 to 6.

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