A modified flocculant and equipment for rapidly removing microplastics from drinking water

Abstract

This invention discloses a modified flocculant and equipment for rapidly removing microplastics from drinking water. The modified flocculant is a ternary composite flocculant consisting of polyaluminum sulfate, titanium tetrachloride, and polydimethyldiallyl ammonium chloride. Using polyaluminum sulfate and titanium tetrachloride as a matrix, this invention improves the applicable pH range by combining them with polydimethyldiallyl ammonium chloride, enhancing charge neutralization bridging and trapping capabilities, and strengthening adsorption bridging through polymer chains. This results in a flocculant with advantages such as strong flocculation ability, rapid demulsification, fast sedimentation, and small floc volume, exhibiting a strong purification capacity for microplastics and other fine suspended solids in water. Through a special design for flocculant addition, stirring, and sedimentation, the removal rate of microplastics is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a modified flocculant and equipment for rapidly removing microplastics from drinking water. Background Technology

[0002] With the widespread use of plastic products, microplastic pollution has become an increasingly serious problem in the environment. Due to their tiny size, microplastics are easily distributed in environmental media such as water and soil, and can accumulate through the food chain, posing a potential threat to ecosystems and human health. In the field of water treatment, traditional flocculation processes mainly target pollutants such as suspended solids and colloids, and their removal efficiency is limited for microplastics, a special type of pollutant.

[0003] As is well known, inorganic flocculants have advantages such as low price and a wide optimal dosage range, but disadvantages such as weak adsorption and bridging ability and high dosage. Organic flocculants, on the other hand, have advantages such as strong adsorption and bridging ability, low dosage, and good product stability, but also disadvantages such as high water treatment cost, difficulty in biodegradation, and some even have certain toxic side effects. Given the respective advantages and disadvantages of the two types of flocculants and their complementarity in performance and price, research on inorganic-organic composite polymeric flocculants has gradually become a hot topic.

[0004] When treating wastewater containing microplastics, traditional reaction tanks have many limitations due to the small particle size and density of microplastics, which are close to or even less than that of water. For example, conventional flocculant dosing methods cannot ensure uniform distribution throughout the reaction tank, resulting in insufficient flocculation in some areas. Inappropriate stirring methods can also cause microplastics to float and accumulate on the water surface during flocculation, making them difficult to effectively settle and remove. Furthermore, the sedimentation structure design does not fully consider the special properties of microplastics, resulting in low flocculation and sedimentation efficiency and excessive microplastic content in the effluent.

[0005] Furthermore, existing flocculant preparation and dosing processes are often separate operations, with the preparation process typically being cumbersome and fragmented, lacking continuity and efficiency, thus affecting the overall treatment effect and efficiency. Therefore, there is an urgent need for a high-efficiency reaction tank design specifically for microplastic removal. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a modified flocculant and equipment for rapidly removing microplastics from drinking water.

[0007] A modified flocculant for rapidly removing microplastics from drinking water, wherein the modified flocculant is a ternary composite flocculant of polyaluminum sulfate-titanium tetrachloride-polydimethyldiallylammonium chloride; wherein, by weight, the modified flocculant contains polyaluminum sulfate, titanium tetrachloride, and polydimethyldiallylammonium chloride in a ratio of 10-30 parts: 10-20 parts: 0.2-1.6 parts.

[0008] Explanation: The above-mentioned method uses polyaluminum sulfate and titanium tetrachloride as matrices, and through compounding with polydimethyl diallyl ammonium chloride (i.e., modifying the matrices of polyaluminum sulfate and titanium tetrachloride with polydimethyl diallyl ammonium chloride), the good water solubility, long chain structure, and high positive charge density of polydimethyl diallyl ammonium chloride can be utilized. Through the adsorption and bridging effect of the long polymer chains, combined with the colloidal properties of the hydrolysis products of polyaluminum sulfate and titanium tetrachloride, a bridging effect is achieved, enhancing the integrity and stability of the flocs, and further strengthening the polyaluminum sulfate... The positive charge of the aluminum oxide and titanium tetrachloride matrix enhances the neutralization capacity of the entire flocculation system for the surface charge of microplastics, thereby strengthening the charge neutralization bridging and trapping ability, increasing the applicable pH range, and enhancing the adsorption bridging through polymer chains. This allows for the capture and flocculation of fine suspended matter such as microplastics, thus expanding the working range of the flocculant. Furthermore, the flocculant described above has the advantages of strong flocculation ability, rapid demulsification, fast sedimentation speed, and small floc volume. It is a novel flocculant that is equally effective under alkaline and neutral conditions.

[0009] Furthermore, the preparation method of the polyaluminum sulfate-titanium tetrachloride-polydimethyldiallylammonium chloride ternary composite flocculant includes:

[0010] S1. Dissolve 10-30 parts of solid polyaluminum sulfate in 100 parts of water to form a polyaluminum sulfate solution. Keep the temperature of the polyaluminum sulfate solution at 60-65°C, start stirring at a speed of 200-400 r / min, then add 1-8 parts of calcium chloride dihydrate and stir until dissolved. Then add 1-8 parts of manganese chloride and stir until dissolved. Keep warm for 30 min to form solution A.

[0011] S2. At a temperature of 60-65℃, add 1-8 parts of 20% polydimethyldiallylammonium chloride to 110-130 parts of solution A, and then stir for 10-20 minutes at a stirring speed of 200-400 r / min to obtain solution C.

[0012] S3. At a temperature of 60-65℃, add 10-20 parts of titanium tetrachloride to 55-65 parts of ethanol to dissolve, and then stir for 10-20 minutes at a stirring speed of 90-110 r / min. While stirring, add 1 part of polyethylene oxide to obtain solution B.

[0013] S4. According to the volume ratio of solution C to solution B of 1:1, add solution C to solution B to obtain a mixture. Then, stir the mixture continuously at 20-25°C for 80-100 minutes. Subsequently, vacuum dry the mixture to obtain a solid powder of polyaluminum sulfate-titanium tetrachloride-polydimethyldiallylammonium chloride ternary composite flocculant.

[0014] Note: The flocculant prepared by the above method combines the advantages of inorganic polymeric flocculants (polyaluminum sulfate) and organic polymeric flocculants. It can specifically capture microplastic particles in water through mechanisms such as adsorption, bridging, and cross-linking. Because the flocculant obtained by the above method can form a stable and dense floc structure with a network structure, this structure is conducive to the encapsulation and sedimentation of microplastic particles, making the combination of microplastic particles and flocs more compact and increasing the sedimentation rate, thereby greatly shortening the treatment time.

[0015] Furthermore, the vacuum drying temperature described in S4 is 35–55°C.

[0016] Note: The above parameters are appropriate. If they are outside this range, it may cause structural damage to the surface of the flocculant, resulting in a decrease in the flocculant's flocculation ability.

[0017] Furthermore, the stirring speed during continuous stirring in S4 is 200–400 r / min.

[0018] Note: The stirring speed mentioned above is appropriate.

[0019] Furthermore, in S3, titanium tetrachloride is added at a rate of 1-2 drops / s, with each drop being 0.5 ml, and is added to ethanol while shaking is performed during the addition process.

[0020] Note: The above-mentioned dropping rate can prevent titanium tetrachloride from being directly introduced into ethanol, which may cause titanium tetrachloride to react rapidly and violently with ethanol, generating a large amount of heat and possibly toxic gases and impurities, thus ensuring the normal progress of subsequent reactions.

[0021] Furthermore, in step S4, the dropping rate of the mixed solution of solution C and solution B is 0.5 to 1 mL / min.

[0022] Note: The above-mentioned mixing and dripping rate is more suitable, which is beneficial to the mixing process of the three raw materials in the composite flocculant of the present invention, resulting in a more preferred structural morphology (a stable, dense, network-like floc structure).

[0023] This invention also provides an application device for rapidly removing microplastics from drinking water. The device includes a reaction tank and a reagent dosing device located above the reaction tank. The reagent dosing device contains the modified flocculant. A discharge vertical pipe for uniformly dispensing the flocculant into the reaction tank is connected below the reagent dosing device via a discharge pipe. The reaction tank contains a stirring component, which includes low-shear wide blades and a drive rod. The bottom of the reaction tank is shaped like an upward-opening cone, and an inclined plate is fixedly provided on the inner wall of the reaction tank. A scraper is provided below the inclined plate and is rotatably connected to the bottom of the reaction tank. The scraper is rotatably in contact with the inclined plate.

[0024] Explanation: The above-mentioned device setup can further improve the removal rate of microplastics, significantly reducing the microplastic content in the treated water and mitigating the environmental pollution risk posed by microplastics. The uniform addition of the discharge vertical pipe and the stirring action of the low-shear wide blades ensure uniform mixing of the flocculant and wastewater throughout the tank, minimizing damage to microplastics and flocs during flocculation, thus improving flocculation effect and stability. The integrated design of the reagent dosing device at the top of the reaction tank enables on-site preparation, drying, and precise dosing of the flocculant, improving the continuity and convenience of the treatment process.

[0025] Furthermore, the inclined plate is composed of multiple inverted frustum-shaped tubular components nested in sequence from small to large, each inverted frustum-shaped tubular component having the same height, and each inverted frustum-shaped tubular component having a superhydrophobic coating on its surface.

[0026] Explanation: The annular stepped inclined plate can efficiently trap flocs, preventing them from re-suspending, and facilitates the centralized collection and treatment of flocs, reducing the difficulty and cost of sludge treatment; the surface of the annular stepped inclined plate is coated with a superhydrophobic coating, which allows the flocs and microplastic mixtures deposited on the inclined plate to quickly slide to the bottom of the reaction tank under the flushing of water or slight vibration, preventing blockage of the inclined plate gaps. At the same time, the superhydrophobic coating can also reduce the adhesion of impurities on the inclined plate, reducing the frequency of equipment cleaning and maintenance.

[0027] Furthermore, the superhydrophobic coating is made of a modified resin coating; the preparation method of the modified resin coating is as follows:

[0028] First, take nano-titanium oxide, trimethylsilyl alcohol, and epoxy resin in a ratio of 10g: 5-6g: 100ml. Then, add trimethylsilyl alcohol to epoxy resin at a temperature of 30-40℃ and stir mechanically until uniform. Next, add nano-titanium oxide and ultrasonically disperse it uniformly to obtain component A. The ultrasonic frequency is 40-45kHz.

[0029] At a mass ratio of 3:1, the polyamide curing agent and the polyether-modified polysiloxane copolymer were mixed and stirred evenly at a temperature of 45-50°C to obtain component B.

[0030] Then, at a mass ratio of 20:1 to 2, component B is added to component A and ultrasonically dispersed evenly at an ultrasonic frequency of 30 to 35 kHz to obtain the modified resin coating.

[0031] The method for applying the modified resin coating to the surface of the inclined plate is as follows:

[0032] First, the modified resin coating is uniformly sprayed onto the surface of the inclined plate; the coating thickness is 50-100 μm, then dried at room temperature for 24-48 hours, and then heat-cured at a temperature of 60-80℃ for 2-4 hours.

[0033] Note: The modified resin coating obtained by the above method is suitable for the polyaluminum sulfate-titanium tetrachloride-polydimethyldiallylammonium chloride ternary composite flocculant of this invention. Because some hydroxyl groups (OH) in the silanol (Si-OH) in the modified resin coating can undergo condensation reactions with hydroxyl and carboxyl functional groups in the epoxy resin to form a Si-OC structure, this structure allows the coating to maintain good stability in humid environments, making it less susceptible to damage by water molecules and improving the coating's water resistance. Nano-titanium oxide can strengthen, toughen, and modify epoxy resin; under chemical bonding, nano-titanium oxide and epoxy resin can form a stronger bond, further improving the performance of the composite material. Simultaneously, some silanol and nano-titanium oxide may form a Si-O-Ti structure, which can form a silanol modification layer on the surface of nano-titanium oxide, thereby improving the dispersibility and compatibility of nano-titanium oxide in epoxy resin. The above-mentioned curing agent, LGH-7499, which acts as a flow leveling agent, makes the coating of component A easily adhere to the surface of the inclined plate, and the surface smoothness is high.

[0034] Furthermore, a check valve is provided at the top of the discharge vertical pipe, and a material distributor is installed inside it. Multiple openings are arranged vertically on the pipe wall of the discharge vertical pipe. The material distributor consists of a central shaft and multiple spiral blades evenly distributed on the central shaft.

[0035] Description: A rotary distributor is installed inside the discharge riser. The distributor consists of a central shaft and multiple spiral blades distributed along the shaft. The central shaft is driven by a motor to rotate slowly. When the flocculant falls from the top of the riser, it is evenly dispersed throughout the riser by the spiral blades, and then evenly discharged into the reaction tank through multiple openings. This prevents localized accumulation or concentrated discharge of flocculant within the riser, resulting in a more uniform distribution of flocculant in the reaction tank.

[0036] The beneficial effects of this invention are:

[0037] (1) This invention is the first to propose using polyaluminum sulfate and titanium tetrachloride as a matrix, and combining them with polydimethyldiallyl ammonium chloride to improve the applicable pH range, enhance charge neutralization bridging and trapping capabilities, and strengthen adsorption bridging through polymer chains. This is a useful strategy to expand the working range of flocculants. This product has the advantages of strong flocculation ability, rapid demulsification, fast sedimentation speed, and small floc volume. It is a novel flocculant that is equally effective under alkaline and neutral conditions. It has a strong purification ability for fine suspended solids such as microplastics in water.

[0038] (2) This invention significantly improves the removal rate of microplastics through a special flocculant addition, stirring, and sedimentation structure design, which can greatly reduce the microplastic content in the treated water and reduce the risk of microplastic pollution to the environment. The uniform addition of the discharge vertical pipe and the stirring effect of the low-shear wide blades ensure that the flocculant and sewage are uniformly mixed throughout the tank, and reduce the damage to microplastics and flocs during the flocculation process, thereby improving the flocculation effect and stability. The annular stepped inclined plate can efficiently intercept flocs, prevent them from re-suspending, and facilitate the centralized collection and treatment of flocs, reducing the difficulty and cost of sludge treatment. The integrated design of the reagent addition device at the top of the reaction tank realizes the on-site preparation, drying, and precise addition of flocculant, improving the continuity and convenience of the treatment process. Attached Figure Description

[0039] Figure 1 This is a longitudinal sectional view of the device of the present invention;

[0040] 1-Agent dosing device, 2-Drive rod, 3-Low shear wide blade, 4-Discharge pipe, 5-Discharge vertical pipe, 6-Scraper, 7-Inclined plate, 71-Inverted frustum-shaped tubular component. Detailed Implementation

[0041] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0042] This invention provides a modified flocculant for rapidly removing microplastics from drinking water. The modified flocculant is a ternary composite flocculant consisting of polyaluminum sulfate, titanium tetrachloride, and polydimethyldiallylammonium chloride. This flocculant can efficiently remove microplastics from water through flocculation, exhibiting better and faster removal effects compared to existing technologies. This invention also provides a device for removing microplastics from water using this modified flocculant. This device can further accelerate the flocculation of microplastics by the flocculant, thereby further improving efficiency.

[0043] Existing flocculants suffer from structural deficiencies in removing microplastics from water (lacking stable, dense floc structures, network morphology, and the ability to neutralize, bridge, and trap microplastics). This results in their inability to rapidly flocculate and precipitate microplastics, and their inability to specifically capture microplastic particles in the water, leaving significant room for improvement in microplastic degradation. Furthermore, because microplastics float and aggregate on the water surface during flocculation, they are difficult to remove through effective sedimentation. Existing sedimentation structures do not fully consider the unique properties of microplastics, leading to low flocculation and sedimentation efficiency and excessive microplastic content in the effluent.

[0044] Example 1: A modified flocculant for rapidly removing microplastics from drinking water, comprising:

[0045] The modified flocculant is a ternary composite flocculant of polyaluminum sulfate-titanium tetrachloride-polydimethyldiallylammonium chloride; wherein, by weight, the modified flocculant contains polyaluminum sulfate, titanium tetrachloride and polydimethyldiallylammonium chloride in a ratio of 20 parts: 15 parts: 1 part.

[0046] The preparation method of the polyaluminum sulfate-titanium tetrachloride-polydimethyldiallylammonium chloride ternary composite flocculant includes:

[0047] S1. Dissolve 20 parts of solid polyaluminum sulfate in 100 parts of water to form a polyaluminum sulfate solution. Keep the temperature of the polyaluminum sulfate solution at 62°C, start stirring at a speed of 300 r / min, then add 5 parts of calcium chloride dihydrate and stir until dissolved. Then add 1 to 8 parts of manganese chloride and stir until dissolved. Keep warm for 30 min to form solution A.

[0048] S2. At a temperature of 63℃, add 5 parts of 20% polydimethyldiallylammonium chloride to 120 parts of solution A, and stir for 15 minutes at a stirring speed of 300 r / min to obtain solution C.

[0049] S3. At a temperature of 63℃, 15 parts of titanium tetrachloride were dissolved in 60 parts of ethanol and stirred for 15 minutes at a stirring speed of 100 r / min. At the same time, 1 part of polyethylene oxide was added and stirred until homogeneous to obtain solution B. The titanium tetrachloride was added at a dropping rate of 1 drop / s, with each drop being 0.5 ml, and was added to the ethanol. The mixture was shaken during the dropping process.

[0050] S4. Add solution C to solution B at a volume ratio of 1:1, with the mixed solution of solutions C and B added at a dropping rate of 0.8 mL / min. The resulting mixture is then continuously stirred at 24°C for 90 min, followed by vacuum drying to obtain a solid powder of polyaluminum sulfate-titanium tetrachloride-polydimethyldiallylammonium chloride ternary composite flocculant. The vacuum drying temperature is 45°C, and the stirring speed during continuous stirring is 300 r / min.

[0051] Example 2

[0052] The difference between this embodiment and Example 1 is that the proportions of the raw materials are different. S1, 30 parts of solid polyaluminum sulfate are dissolved in 100 parts of water to form a polyaluminum sulfate solution. After stirring, 1 part of calcium chloride dihydrate is added and stirred until dissolved. Then, 8 parts of manganese chloride are added. S2, 8 parts of polydimethyldiallyl ammonium chloride with a mass fraction of 20% are added to 110 parts of solution A and stirred. S3, 10 parts of titanium tetrachloride are dissolved in 55 parts of ethanol and stirred.

[0053] Example 3

[0054] The difference between this embodiment and Example 1 is that the proportions of the raw materials are different. S1, 10 parts of solid polyaluminum sulfate are dissolved in 100 parts of water to form a polyaluminum sulfate solution. After stirring, 8 parts of calcium chloride dihydrate are added and stirred until dissolved. Then, 1 part of manganese chloride is added. S2, 1 to 8 parts of polydimethyldiallyl ammonium chloride with a mass fraction of 20% are added to 130 parts of solution A and stirred. S3, ~20 parts of titanium tetrachloride are dissolved in 65 parts of ethanol and stirred.

[0055] Example 4

[0056] The difference between this embodiment and Embodiment 1 is that the temperature parameters are different: S1, the temperature of the polyaluminum sulfate solution is maintained at 60°C; S2, the temperature is 65°C; S3, the temperature is 60°C; S4, the mixture is continuously stirred at 20°C, and then the mixture is vacuum dried at 35°C.

[0057] Example 5

[0058] The difference between this embodiment and Embodiment 1 is that the temperature parameters are different: S1, the temperature of the polyaluminum sulfate solution is maintained at 65°C; S2, the temperature is 60°C; S3, the temperature is 65°C; S4, the mixture is continuously stirred at 25°C, and then the mixture is vacuum dried at a temperature of 55°C.

[0059] Example 6

[0060] The difference between this embodiment and Embodiment 1 is that the stirring parameters are different: S1, stirring speed is 200 r / min; S2, stirring speed is 400 r / min, stirring time is 10 min; S3, stirring speed is 110 r / min, stirring time is 20 min; the dropping rate of titanium tetrachloride is 1 drop / s, and each drop is 0.5 ml; S4, the dropping rate of the mixed solution of solution C and solution B is 1 mL / min; the mixture is continuously stirred for 100 min at a stirring speed of 400 r / min.

[0061] Example 7

[0062] The difference between this embodiment and Embodiment 1 is that the stirring parameters are different: S1, stirring speed is 200 r / min; S2, stirring speed is 200 r / min, stirring time is 20 min; S3, stirring speed is 90 r / min, stirring time is 10 min; the dropping rate of titanium tetrachloride is 2 drops / s, each drop is 0.5 ml; S4, the dropping rate of the mixed solution of solution C and solution B is 0.5 mL / min; the mixture is continuously stirred for 80 min at a stirring speed of 200 r / min.

[0063] Comparative Example 1: Microplastic removal was performed using polyaluminum sulfate instead of the flocculant in the examples;

[0064] Comparative Example 2: Microplastic removal was performed using polydimethyldiallyl ammonium chloride instead of the flocculant in the examples;

[0065] Comparative Example 3: Microplastic removal was performed using polyaluminum chloride instead of the flocculant in the examples;

[0066] Comparative Example 4: Microplastic removal was performed using a titanium-based coagulant instead of the flocculant in the examples;

[0067] Comparative Example 5: A mixture obtained by directly mixing titanium-based coagulant and polydimethyldiallyl ammonium chloride at a mass ratio of 1:1 was used to replace the flocculant in the examples for the removal of microplastics;

[0068] Comparative Example 6: A mixture obtained by directly mixing polyaluminum sulfate, polydimethyldiallylammonium chloride, and titanium-based coagulant at a mass ratio of 1:1:1 was used to remove microplastics instead of the flocculant in the examples.

[0069] Comparative Example 7: The difference from Example 1 is that in step S4, solution C and solution B are mixed in a volume ratio of 1:3.

[0070] Comparative Example 8: The difference from Example 1 is that in step S4, solution C and solution B are mixed at a volume ratio of 1:5.

[0071] Comparative Example 9: Unlike Example 1, calcium chloride dihydrate was not added.

[0072] Comparative Example 10: Unlike Example 1, no manganese chloride was added.

[0073] I. Assessing the effectiveness of flocculants;

[0074] Experimental Example 1: Based on the flocculants obtained in Examples 1 to 7 above, a flocculation test of microplastics was conducted to obtain the microplastic removal rate;

[0075] The flocculation test was conducted as follows: Microplastic microspheres with a particle size of 1 μm and a concentration of 10 ng / L (the number of microplastics in the initial 10 ng / L microplastic solution was 13600 MPs / L) were added to 1 L of wastewater and mixed. Then, 1 mg / L of flocculant was added and stirred at a speed of 50 r / min for 15 min. The removal rate of microplastics was then calculated, as shown in Table 1 below.

[0076] Table 1. Removal rates of microplastics treated by different methods.

[0077] Example Microplastic removal rate % Example 1 98.7 Comparative Example 1 88.7 Comparative Example 2 74.4 Comparative Example 3 85.2 Comparative Example 4 86.7 Comparative Example 5 84.2 Comparative Example 6 82.5 Comparative Example 7 89.7 Comparative Example 8 91.3 Comparative Example 9 90.8 Comparative Example 10 91.6

[0078] As shown in Table 1, comparing Example 1 and Comparative Example 1, Example 1 shows a better removal effect on microplastics. Comparative Example 1, which uses polyaluminum sulfate to directly flocculate and remove microplastics, suffers from a lower removal rate because the polyaluminum sulfate in Comparative Example 1 does not provide enough adsorption sites or a sufficiently large specific surface area compared to the method in Example 1. Furthermore, adding too much polyaluminum sulfate may cause micro-flocs to surround the microplastic particles, forming charged micro-flocs or microplastic complexes. The electrostatic repulsion between these complexes makes it difficult for them to approach each other and form large flocs, thus affecting the sedimentation removal effect. Most importantly, the flocculation effect of polyaluminum sulfate is greatly affected by pH value; under acidic or alkaline conditions, the hydrolysis products of aluminum sulfate are less stable, affecting the removal effect along with microplastics.

[0079] Comparing Example 1 and Comparative Example 2, it can be found that Example 1 has a better effect on removing microplastics. In Comparative Example 2, the flocculation effect of using only polydimethyldiallyl ammonium chloride is not good. This may be because polydimethyldiallyl ammonium chloride has poor selectivity in the process of treating microplastics. Due to the flocculation of other suspended solids and organic matter in the water, and because microplastics are small in size and may have a charged surface or be covered by organic matter, the interaction between polydimethyldiallyl ammonium chloride and microplastics is affected, reducing the flocculation efficiency. The ternary composite structure in Example 1 of this invention can enhance the interaction with microplastics and avoid the above-mentioned problems.

[0080] Comparing Example 1 and Comparative Example 3, it can be found that Example 1 has a better effect. This may be because Comparative Example 3 only uses polyaluminum chloride. The flocculation effect of aluminum chloride is highly dependent on the pH value of the water, resulting in poor stability and reliability of the flocculation effect. It may also lead to aluminum residue in the water. Long-term exposure may have adverse effects on human health and aquatic organisms and cause secondary pollution. In addition, polyaluminum chloride is not very efficient in treating some difficult pollutants such as microplastics. Example 1 of the present invention avoids the above problems by mixing polyaluminum chloride with the other two raw materials.

[0081] Comparing Example 1 and Comparative Example 4, it can be found that Example 1 has a better effect. This may be because, although titanium-based coagulants can effectively remove colloidal pollutants by exerting a mesh-sweeping effect under certain pH conditions (e.g., alkaline range), their removal efficiency for some soluble organic matter and anionic pollutants is significantly reduced. When titanium-based coagulants are mixed with other raw materials (e.g., the raw materials in Example 1 of this invention), their application range can be broadened and their charge neutralization ability under moderately alkaline conditions can be supplemented, thereby improving the removal rate of soluble pollutants.

[0082] Comparing Example 1 with Comparative Examples 5 and 6, it can be found that Example 1 has a better removal effect. That is to say, even if the three raw materials, polyaluminum sulfate, polydimethyldiallylammonium chloride, and titanium-based coagulant, are mixed in pairs or directly without performing the steps of Example 1 of the present invention, the technical effect of the present invention cannot be achieved. The reason may be that the preparation steps in the present invention can form a specific structural morphology, thereby achieving a better effect. In contrast, Comparative Examples 5 and 6 directly mix the raw materials, which cannot form the specific structure of the present invention.

[0083] Comparing Example 1 with Comparative Examples 7 and 8, it can be found that the ratio of C solution to B solution in Example 1 is more optimized, therefore the parameters of Example 1 are more preferred. Comparing Example 1 with Comparative Example 9, it can be found that Comparative Example 9 did not add calcium chloride dihydrate. The addition of calcium chloride dihydrate, as a synergist, can effectively change the particle structure of the flocculants through the synergistic effect of calcium ions, making them more compact, improving the dispersibility of polyaluminum sulfate, and promoting the flocculation and sedimentation effect of polyaluminum sulfate. Comparing Example 1 with Comparative Example 9, it can be found that Comparative Example 9 did not add manganese chloride. The addition of manganese chloride, as a stabilizer, can promote the stability of polyaluminum sulfate through the coordination effect of manganese ions, inhibiting the hydrolysis reaction of aluminum ions, and enhancing its flocculation performance.

[0084] II. Determine the optimal parameters for flocculant treatment of microplastics;

[0085] Experimental Example 2: Taking Example 1 as an example, the difference from Experimental Example 1 is that the rotation speed was adjusted to 50 r / min, and the flocculation reaction time was controlled to 20 min. The dosage of the reagent was 2 mg / L, and the removal efficiency of microplastics reached 98%.

[0086] Experimental Example 3: Taking Example 1 as an example, the difference from Experimental Example 1 is that the rotation speed was adjusted to 40 r / min, and the flocculation reaction time was controlled to 20 min. The dosage of the reagent was 2 mg / L, and the removal efficiency of microplastics reached 98%.

[0087] Experimental Example 4: Taking Example 1 as an example, the difference from Experimental Example 1 is that the rotation speed was adjusted to 40 r / min and the flocculation reaction time was controlled to 10 min. The dosage of the reagent was 2 mg / L, and the removal efficiency of microplastics reached 91%.

[0088] As can be seen from the above comparison, the rotation speed and reaction time parameters in Experiment 1 have a significant impact on the removal of microplastics. Among them, the flocculation treatment parameters in Experiment 3 are more preferred.

[0089] Example 9:

[0090] This invention provides a device for rapidly removing microplastics from drinking water. The device includes a reaction tank and a reagent dosing device 1 located above the reaction tank. The reagent dosing device 1 contains the modified flocculant. A discharge vertical pipe 5 for uniformly dispensing the flocculant into the reaction tank is connected to the reagent dosing device 1 via a discharge pipe 4. The reaction tank contains a stirring component, which includes a low-shear wide blade 3 and a drive rod 2. The bottom of the reaction tank is a cone shape with an upward opening, and an inclined plate 7 is fixedly provided on the inner wall of the reaction tank. A scraper 6 is provided below the inclined plate 7 and is rotatably connected to the bottom of the reaction tank. The scraper 6 is rotatably contacted with the inclined plate 7.

[0091] The inclined plate 7 is composed of multiple inverted frustum-shaped tubular components 71 arranged sequentially from small to large. Each inverted frustum-shaped tubular component 71 has the same height, and the surface of each inverted frustum-shaped tubular component 71 is coated with a superhydrophobic coating.

[0092] The discharge vertical pipe 5 is equipped with a check valve at its top, and a distributor is installed inside the discharge vertical pipe 5. Multiple openings are vertically arranged on the pipe wall of the discharge vertical pipe 5. The distributor consists of a central shaft and multiple spiral blades evenly distributed along the central shaft. The central shaft is driven to rotate by a motor. When the flocculant falls from the top of the vertical pipe, it is evenly dispersed to various positions within the vertical pipe by the spiral blades, and then evenly discharged into the reaction tank through the multiple openings. This avoids localized accumulation or concentrated discharge of flocculant within the vertical pipe, resulting in a more uniform distribution of flocculant in the reaction tank.

[0093] The superhydrophobic coating is made of modified resin coating; the preparation method of the modified resin coating is as follows:

[0094] First, nano titanium dioxide, trimethylsilane, and epoxy resin were taken in a ratio of 10g:5.5g:100ml. Then, trimethylsilane was added to epoxy resin at 35℃ and mechanically stirred until uniform. Then, nano titanium dioxide was added and ultrasonically dispersed until uniform to obtain component A. The ultrasonic frequency was 42kHz.

[0095] At a mass ratio of 3:1, polyamide curing agent and LGH-7499 (polyether modified polysiloxane copolymer) were mixed and stirred evenly at 43°C to obtain component B.

[0096] Then, at a mass ratio of 20:1.5, component B was added to component A and ultrasonically dispersed evenly at an ultrasonic frequency of 33kHz to obtain the modified resin coating.

[0097] It is understood that the device provided by the present invention can solve the problems of difficult microplastic removal and cumbersome operation of existing flocculation devices when treating microplastic wastewater, thereby further improving the microplastic removal efficiency based on Example 1.

[0098] The specific principle is as follows: The reaction tank is cylindrical in shape, with a reagent dosing device 1 installed on one side of the top. The reagent dosing device 1 includes two mixing chambers and a vacuum drying device, allowing for the preparation and drying pretreatment of the flocculant at the top of the reaction tank, ensuring the quality and activity of the flocculant. The discharge port 4 of the reagent dosing device 1 is connected to a discharge vertical pipe 5, which contains a distributor. The distributor consists of a central shaft and multiple spiral blades distributed along the shaft, with the central shaft driven to rotate by a motor. When the flocculant falls from the top of the discharge vertical pipe 5, it is evenly dispersed to various positions within the vertical pipe by the spiral blades, and then evenly discharged into the reaction tank through multiple openings. This prevents localized accumulation or concentrated discharge of the flocculant within the vertical pipe, resulting in a more uniform distribution of the flocculant in the reaction tank. A drive rod 2 is installed at the center of the reaction tank, with three sets of low-shear wide blades 3 on the drive rod 2, each set consisting of four blades with a large surface area. This paddle design allows for radial and axial pumping of water, ensuring thorough mixing of flocculant and wastewater while avoiding excessive shearing damage to microplastics and existing flocs. This promotes stable flocculation and further floc growth. A circular stepped inclined plate, sloping at the bottom of the reaction tank with a lower center and higher edges, is coated with a superhydrophobic coating. This allows the flocs and microplastic mixture settled on the plate to quickly slide to the bottom of the tank under water flow or slight vibration, preventing clogging of the plate gaps. The superhydrophobic coating also reduces impurities adhering to the plate, decreasing the frequency of equipment cleaning and maintenance. This structure effectively traps flocs, preventing them from resuspending due to water flow disturbance, and guides the settled flocs towards the center of the tank bottom for easier subsequent cleaning. The reaction tank adopts a central inlet and central outlet method, which changes the traditional peripheral inlet or outlet mode. The central inlet allows the wastewater to quickly come into contact with the flocculant and stirring device in the central area when it enters the reaction tank, promoting the rapid start of the reaction. The central outlet allows the treated water to flow out from the central area, reducing the possibility of microplastics floating to the water surface and flowing out with the effluent, thus effectively solving the problem of fine microplastics floating and reducing sedimentation efficiency.

[0099] Example 10: The difference from Example 9 lies in the preparation parameters. The preparation method of the modified resin coating is as follows: First, nano-titanium oxide, trimethylsilane, and epoxy resin are taken in a ratio of 10g:5g:100ml. Then, trimethylsilane is added to epoxy resin at 30℃ and mechanically stirred until uniform. Then, nano-titanium oxide is added and ultrasonically dispersed until uniform to obtain component A at an ultrasonic frequency of 40kHz. Polyamide curing agent and LGH-7499 are mixed at a mass ratio of 3:1 at 45℃ and stirred until uniform to obtain component B. Then, component B is added to component A at a mass ratio of 20:2 and ultrasonically dispersed until uniform at an ultrasonic frequency of 35kHz to obtain the modified resin coating.

[0100] Example 11: The difference from Example 9 lies in the preparation parameters. The preparation method of the modified resin coating is as follows: First, nano-titanium oxide, trimethylsilane, and epoxy resin are taken in a ratio of 10g:6g:100ml. Then, trimethylsilane is added to epoxy resin at 40℃ and mechanically stirred until uniform. Then, nano-titanium oxide is added and ultrasonically dispersed until uniform to obtain component A at an ultrasonic frequency of 45kHz. Polyamide curing agent and LGH-7499 are mixed at a mass ratio of 3:1 at 50℃ and stirred until uniform to obtain component B. Then, component B is added to component A at a mass ratio of 20:1 and ultrasonically dispersed until uniform at an ultrasonic frequency of 30kHz to obtain the modified resin coating.

[0101] 3. Using equipment to treat microplastics in water;

[0102] Experimental Example 4: In reactor 1, perform the operations of steps S1 and S2 in Example 1;

[0103] In mixing vessel 2, the operation of step S3 in Example 1 is completed;

[0104] Solution C in reactor 1 is added to solution B in reactor 2, and then transferred to a vacuum drying device for drying to obtain polyaluminum sulfate-titanium tetrachloride-polydimethyldiallylammonium chloride ternary composite flocculant; the discharge valve is opened, and the flocculant is evenly added to the reaction tank through multiple openings of the discharge vertical pipe 5;

[0105] The motor of drive rod 2 is started, which drives three sets of low-shear wide blades 3 to rotate at a speed of 50 r / min. Wastewater enters the central area of ​​the reaction tank through the middle inlet and mixes rapidly with the added flocculant; the flocculation reaction time is controlled at 15 min. The dosage of the agent is 1 mg / L.

[0106] The bottom of the reaction tank is conical with a cone angle of 30°; the bottom has a circular stepped inclined plate with an inclination angle of 60°; the gap between the scraper 6 and the bottom of the sedimentation tank is 50mm; a wire brush is installed at the bottom of the scraper to contact the bottom of the sedimentation tank; the scraper 6 rotates at 0.8r / min.

[0107] Comparative Example 12: The same equipment as in Experimental Example 4 was used, except that the stirring blades were conventional commercially available turbine blades.

[0108] Comparative Example 13: The same equipment as in Experimental Example 4 was used, except that the water inlet was located above the reaction tank and the water outlet was located in the middle of the side wall of the reaction tank.

[0109] Experimental Example 5: Using the equipment of Experimental Example 4, Comparative Example 12 and Comparative Example 13, wastewater with the same pollution index and microplastic content was subjected to flocculation treatment. After 15 minutes, the microplastic removal efficiency of Example 4 reached 98.7%, while that of Comparative Example 12 and Comparative Example 13 reached 93.4% and 94.7% respectively. In comparison, the setup in Experimental Example 4 was more conducive to the removal of microplastics from wastewater.

[0110] Comparative Example 14: No superhydrophobic coating was applied to the inclined plate;

[0111] Comparative Example 15: The superhydrophobic coating on the inclined plate is epoxy resin;

[0112] The inclined plates (fiberglass material) of Experimental Example 4 and Comparative Example 14 were tested. The experimental procedure was as follows: the inclined plates were placed in an aqueous solution of nitric acid with a pH of 5, and then 60% of the solution volume of flocculant and microplastic-bound flocculants were added. After soaking for 5 days, the plates were removed. It can be observed that flocculants adhered to the surfaces of Comparative Example 14 and Comparative Example 15, while no flocculants adhered to the surface of the inclined plate in Experimental Example 4. It can be seen that the coating of the present invention used in Experimental Example 4 has a good effect.

Claims

1. A modified flocculant for rapidly removing microplastics from drinking water, characterized in that, The modified flocculant is a ternary composite flocculant of polyaluminum sulfate-titanium tetrachloride-polydimethyldiallyl ammonium chloride; wherein, by weight, the modified flocculant contains polyaluminum sulfate, titanium tetrachloride and polydimethyldiallyl ammonium chloride in a ratio of 10-30 parts: 10-20 parts: 0.2-1.6 parts. The preparation method of the polyaluminum sulfate-titanium tetrachloride-polydimethyldiallylammonium chloride ternary composite flocculant includes: S1. Dissolve 10-30 parts of solid polyaluminum sulfate in 100 parts of water to form a polyaluminum sulfate solution. Keep the temperature of the polyaluminum sulfate solution at 60-65°C, start stirring at a speed of 200-400 r / min, then add 1-8 parts of calcium chloride dihydrate and stir until dissolved. Then add 1-8 parts of manganese chloride and stir until dissolved. Keep warm for 30 minutes to form solution A. S2. At a temperature of 60-65℃, add 1-8 parts of 20% polydimethyldiallylammonium chloride to 110-130 parts of solution A, and then stir for 10-20 minutes at a stirring speed of 200-400 r / min to obtain solution C. S3. At a temperature of 60~65℃, add 10~20 parts of titanium tetrachloride to 55~65 parts of ethanol to dissolve, and then stir for 10~20 min at a stirring speed of 90~110 r / min. While stirring, add 1 part of polyethylene oxide to obtain solution B. S4. According to the volume ratio of solution C to solution B of 1:1, add solution C to solution B to obtain a mixture. Then, stir the mixture continuously at 20~25℃ for 80~100min. Subsequently, vacuum dry the mixture to obtain a solid powder of polyaluminum sulfate-titanium tetrachloride-polydimethyldiallylammonium chloride ternary composite flocculant.

2. The modified flocculant for rapidly removing microplastics from drinking water as described in claim 1, characterized in that, The vacuum drying temperature described in S4 is 35~55℃.

3. The modified flocculant for rapidly removing microplastics from drinking water as described in claim 2, characterized in that, The stirring speed during continuous stirring in S4 is 200~400 r / min.

4. The modified flocculant for rapidly removing microplastics from drinking water as described in claim 2, characterized in that, In S3, titanium tetrachloride is added at a rate of 1-2 drops / s, with each drop being 0.5 ml, and is added to ethanol while shaking during the addition process.

5. The modified flocculant for rapidly removing microplastics from drinking water as described in claim 2, characterized in that, In step S4, the dropping rate of the mixed solution of solution C and solution B is 0.5~1 mL / min.

6. A device for rapidly removing microplastics from drinking water, based on a modified flocculant for rapidly removing microplastics from drinking water as described in any one of claims 1 to 5, characterized in that, The reaction tank includes a reaction tank and a reagent dosing device (1) located above the reaction tank. The reagent dosing device (1) contains the modified flocculant. A discharge vertical pipe (5) for uniformly discharging flocculant into the reaction tank is connected to the reagent dosing device (1) via a discharge pipe (4). The reaction tank contains a stirring component, which includes a low-shear wide blade (3) and a drive rod (2). The bottom of the reaction tank is shaped like an upward-opening cone. An inclined plate (7) is fixedly provided on the inner wall of the reaction tank. A scraper (6) is provided below the inclined plate (7). The scraper (6) is rotatably connected to the bottom of the reaction tank. The scraper (6) and the inclined plate (7) are rotatably contacted. The inclined plate (7) is composed of multiple inverted frustum-shaped tubular components (71) arranged sequentially from small to large. Each inverted frustum-shaped tubular component (71) has the same height, and the surface of each inverted frustum-shaped tubular component (71) is coated with a superhydrophobic coating. The superhydrophobic coating is made of modified resin coating; the preparation method of the modified resin coating is as follows: First, take nano-titanium oxide, trimethylsilyl alcohol, and epoxy resin in a ratio of 10g: 5~6g: 100ml. Then, add trimethylsilyl alcohol to epoxy resin at a temperature of 30~40℃ and stir mechanically until uniform. Then, add nano-titanium oxide and ultrasonically disperse it uniformly to obtain component A. The ultrasonic frequency is 40~45kHz. At a mass ratio of 3:1, the polyamide curing agent and the polyether-modified polysiloxane copolymer were mixed and stirred evenly at a temperature of 45~50℃ to obtain component B. Then, at a mass ratio of 20:1~2, component B is added to component A and ultrasonically dispersed evenly at an ultrasonic frequency of 30~35kHz to obtain the modified resin coating.

7. The device for rapidly removing microplastics from drinking water as described in claim 6, characterized in that, The top of the discharge vertical pipe (5) is equipped with a check valve, and a material distributor is installed inside the discharge vertical pipe (5). Multiple openings are arranged vertically on the pipe wall of the discharge vertical pipe (5). The material distributor consists of a central shaft and multiple spiral blades evenly distributed along the central shaft.

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