Method for preparing cationic tannin-based organic flocculants by enzymatic catalysis, and products and applications thereof

Abstract

The application relates to the technical field of water treatment, in particular to a method for preparing a cationic tannin-based organic flocculant by an enzyme catalysis method, a product and application thereof. The method comprises the following steps: tannin and allyl triphenylphosphonium chloride are reacted under the action of an enzyme catalyst for 2-10 hours, the reaction temperature is 30-60 DEG C, the enzyme is inactivated after the reaction is completed, then the product is purified through acetone, cleaned through ethanol, dried in a vacuum drying box, and the cationic tannin-based organic flocculant is obtained; wherein the enzyme catalyst is lipase B or horseradish peroxidase. The application adopts an enzyme as a catalyst, realizes the covalent grafting between the phenolic hydroxyl group in the tannin molecule and the allyl group of allyl triphenylphosphonium chloride through the specific catalysis of the enzyme. The cationic tannin-based organic flocculant provided by the application can efficiently remove colloidal particles, heavy metal ions and dye pollutants in wastewater, and is especially suitable for treating high-turbidity and high-colority industrial wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a method for preparing a cationic tannic acid-based organic flocculant using an enzyme catalysis method, and a product and application thereof. Background Art

[0002] The textile printing and dyeing industry plays a vital role in my country's national economy. To meet the needs of modern citizens, a large number of different dyes are used in the textile printing and dyeing process. According to statistics, approximately 10,000 synthetic and natural dyes are produced worldwide annually, with an annual output of up to 1.6 million tons. Significant dye waste occurs during production and application, with an estimated 10-15% of this total dye production discharged as wastewater. Dye production and textile printing and dyeing processes generate large amounts of industrial wastewater containing toxic dyes. These wastewaters are characterized by significant variability in water quality, high chroma, a high content of non-biodegradable organic matter, high biotoxicity, and persistent bioaccumulation, making them difficult to treat. Currently, the most commonly used methods for dye decolorization include adsorption, coagulation-sedimentation, membrane separation, chemical oxidation, photocatalytic oxidation, and biological treatment. Coagulation-sedimentation is the most widely used physicochemical treatment method due to its low operating costs, ease of operation, and high efficiency. In the coagulation-based treatment of dye wastewater, the performance of the coagulant or flocculant is a key factor in determining the quality of water purification and process operating costs. Currently, commonly used chemical flocculants are primarily classified into two categories: inorganic coagulants and synthetic organic polymer flocculants. However, inorganic coagulants also have numerous drawbacks in practical application, such as large dosages, large amounts of sludge generated, a narrow range of applications, the presence of residual metal elements, fragile flocs, and poor performance in treating low-temperature, low-turbidity water. Given these shortcomings of inorganic coagulants, the research and development and application of organic polymer flocculants have garnered significant attention.

[0003] The high-value comprehensive utilization of biomass has garnered widespread attention. Tannin, a plant polyphenol widely found in various parts of plants, is abundant, inexpensive, and readily available. Tannin is a green, natural polymer material with a polyphenolic hydroxyl structure and high chemical reactivity. Researchers have successfully introduced quaternary ammonium groups into tannin molecules through Mannich reactions and amination reactions. The resulting organic polymer flocculants exhibit enhanced positive charge, increased molecular weight, and significantly improved flocculation capacity. However, research on the introduction of quaternary phosphine groups into the molecular backbone of tannins is currently lacking. Summary of the Invention

[0004] In response to the current technical problem of lack of research on introducing quaternary phosphine groups into the molecular skeleton of tannins, the present invention provides a method for preparing a cationic tannic acid-based organic flocculant using an enzyme catalysis method, as well as its product and application.

[0005] In a first aspect, the present invention provides a method for preparing a cationic tannic acid-based organic flocculant by an enzyme catalysis method, comprising the following steps:

[0006] The tannic acid and allyl triphenylphosphine chloride are reacted under the action of an enzyme catalyst for 2-10 hours at a reaction temperature of 30-60° C. After the reaction, the enzyme is inactivated, and then purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

[0007] The enzyme catalyst is Candida antarctica lipase B (CAL-B) or horseradish peroxidase isoenzyme C (HRPC).

[0008] Furthermore, the molar ratio of tannic acid to allyltriphenylphosphine chloride is 1:1-3.

[0009] Furthermore, the amount of enzyme catalyst added is 0.01-0.05 g / g tannic acid.

[0010] Furthermore, the enzyme activity of Candida antarctica lipase B or horseradish peroxidase isoenzyme C is 2000-2400 U / g. Furthermore, the reaction pH is 5-8. Within this pH range, tannic acid and allyltriphenylphosphonium chloride can be efficiently grafted under enzyme catalysis, producing a cationic tannic acid-based organic flocculant with ideal properties.

[0011] Furthermore, during the reaction process, oxygen is added to the reaction system every hour to effectively maintain the active center of the enzyme in an oxidized state, significantly improve the catalytic efficiency, and shorten the reaction time.

[0012] Furthermore, the reaction is carried out under stirring at a speed of 100-300 rpm.

[0013] In a second aspect, the present invention provides a preferred embodiment of a method for preparing a cationic tannic acid-based organic flocculant by an enzyme catalysis method, comprising the following steps:

[0014] 2 g of tannic acid was dissolved in an ethanol-water mixed solvent, and allyl triphenylphosphine chloride was added under stirring at 200 rpm (the molar ratio of tannic acid to allyl triphenylphosphine chloride was 1:1.5). 0.06 g of Candida antarctica lipase B was added and reacted for 6 hours. During this period, the reaction temperature was controlled at 40°C and the pH was 6.5. Oxygen was passed through for 10 minutes every hour. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme. The product was then purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

[0015] In a third aspect, the present invention provides a cationic tannic acid-based organic flocculant prepared by the above method.

[0016] In a fourth aspect, the present invention provides a use of the above-mentioned cationic tannic acid-based organic flocculant in treating colloidal particles, heavy metal ions and / or dye pollutants in wastewater.

[0017] Furthermore, the wastewater is printing and dyeing wastewater. Printing and dyeing wastewater is characterized by high turbidity and color, making it difficult to treat. Cationic tannic acid-based organic flocculants can fully demonstrate their advantages in treating this type of wastewater, effectively removing pollutants from printing and dyeing wastewater, reducing turbidity and color, achieving standard discharge of printing and dyeing wastewater, and reducing environmental pollution.

[0018] Furthermore, the application method is to add the cationic tannic acid-based organic flocculant into the wastewater, first stir it at a speed of 200 rpm for 30 seconds, then adjust the speed to 35 rpm and stir it for 15 minutes, and finally stop stirring and let it settle for 30 minutes.

[0019] The beneficial effects of the present invention are:

[0020] This invention uses enzymes as catalysts, achieving covalent grafting between the phenolic hydroxyl groups in tannic acid and the allyl groups in allyltriphenylphosphine chloride through the enzyme's specific catalytic action. Compared to traditional chemical methods (such as free radical initiation or metal catalysis), enzyme-catalyzed methods offer advantages such as high selectivity, the absence of byproducts, and mild reaction conditions.

[0021] Enzymatic methods do not require the use of toxic metal catalysts (such as Cu 2+ 、Fe 3+ ) or strong oxidants, reducing heavy metal pollution and organic waste discharge, in line with the concept of sustainable development. The reaction is carried out under normal pressure and moderate temperature conditions, with significantly lower energy consumption than traditional high-temperature and high-pressure synthesis processes.

[0022] The flocculant product provided by this invention combines the natural polyphenol structure of tannic acid (which provides antioxidant and antibacterial activity) with the cationic phosphine group of allyltriphenylphosphonium chloride (which imparts a strong positive charge), forming a highly effective cationic flocculant. The strong cationic properties of the phosphine group effectively neutralize negatively charged suspended particles in water. The polyphenol backbone of tannic acid enhances the rigidity and shear resistance of the molecular chain, improving flocculation and reusability. As a cationic flocculant, it can effectively remove colloidal particles, heavy metal ions, and dye contaminants from wastewater, making it particularly suitable for treating high-turbidity and high-color industrial wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 This is a TEM image of the cationic tannic acid-based organic flocculant prepared in Example 8 in a specific embodiment of the present invention.

[0025] Figure 2 It is the Zeta potential of the cationic tannic acid-based organic flocculant prepared in Example 8 in a specific embodiment of the present invention in the range of pH=2-12.

[0026] Figure 3 3 is a molecular weight distribution diagram of the cationic tannic acid-based organic flocculant prepared in Example 8 in a specific embodiment of the present invention.

[0027] Figure 4 It is the efficiency of cationic tannic acid-based organic flocculants in treating actual printing and dyeing wastewater, among which Figure 4 (a) is the UV spectrum of the water sample before and after treatment with a cationic tannic acid-based organic flocculant at a dosage of 15 mg / L. Figure 4 (b) is the effect of cationic tannic acid-based organic flocculant on color, turbidity and COD cr Removal rate bar graph.

[0028] Figure 5 This is a picture of water samples before and after treatment with cationic tannic acid-based organic flocculants and the resulting flocs. Figure 5 (a) is a photo of the water sample before treatment with cationic tannic acid-based organic flocculant. Figure 5 (b) is a photo of a water sample treated with a cationic tannic acid-based organic flocculant. Figure 5 Middle (c) is a picture of flocs generated after treatment with a cationic tannic acid-based organic flocculant.

[0029] Figure 6 It is the three-dimensional fluorescence (3D-EEM) image of water samples before and after treatment with cationic tannic acid-based organic flocculant. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0031] A method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis comprises the following steps:

[0032] The tannic acid and allyl triphenylphosphine chloride are reacted under the action of an enzyme catalyst for 2-10 hours at a reaction temperature of 30-60° C. After the reaction, the enzyme is inactivated, and then purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

[0033] The enzyme catalyst is Candida antarctica lipase B (CAL-B) or horseradish peroxidase isoenzyme C (HRPC).

[0034] In a preferred embodiment of the present invention, the molar ratio of tannic acid to allyl triphenylphosphine chloride is 1:1-3. This molar ratio ensures a suitable reaction between tannic acid and allyl triphenylphosphine chloride, allowing sufficient allyl triphenylphosphine chloride to covalently graft the phenolic hydroxyl groups in the tannic acid molecules, thereby facilitating the production of a cationic tannic acid-based organic flocculant with ideal structure and properties. If the allyl triphenylphosphine chloride ratio is too low, the grafting effect will be poor, affecting the cationic properties and flocculation effect of the flocculant. If the ratio is too high, raw materials may be wasted, increasing costs, and potentially affecting the reaction selectivity and product purity.

[0035] As a preferred embodiment of the present invention, the enzyme catalyst is added in an amount of 0.01-0.05 g / g tannic acid. This addition range ensures that the enzyme catalyst exerts an effective catalytic effect in the reaction, while ensuring catalytic efficiency while avoiding problems such as slow reaction rate and incomplete reaction due to too little enzyme, or increased costs and potential impact on product purity due to too much enzyme. The appropriate enzyme amount can achieve an efficient catalytic reaction under relatively economical conditions, promote the grafting of tannic acid and allyltriphenylphosphine chloride, and thus obtain a high-performance cationic tannic acid-based organic flocculant.

[0036] As a preferred embodiment of the present invention, the enzyme activity of Candida antarctica lipase B or horseradish peroxidase isoenzyme C is 2000-2400 U / g. It has been demonstrated that both Candida antarctica lipase B and horseradish peroxidase isoenzyme C exhibit good catalytic activity and specificity at a dosage of 0.01-0.05 g / g tannic acid, effectively catalyzing the covalent grafting reaction between the phenolic hydroxyl group in the tannic acid molecule and the allyl group of allyltriphenylphosphine chloride.

[0037] As a preferred embodiment of the present invention, the reaction pH is 5-8. Too high or too low a pH value may lead to reduced enzyme activity or even inactivation, thereby affecting the reaction rate and product formation. This pH range provides a suitable reaction environment for the enzyme catalyst, ensuring that the enzyme activity is at a high level, which is conducive to the smooth progress of the catalytic reaction.

[0038] As a preferred embodiment of the present invention, oxygen is added to the reaction system every hour during the reaction. Supplementing oxygen ensures that the active center of the enzyme is maintained in a suitable oxidation state, thereby maintaining the efficient catalytic ability of the enzyme. By maintaining the activity of the enzyme, the reaction rate of tannic acid and allyltriphenylphosphine chloride can be accelerated, allowing the reaction to achieve a high conversion rate in a relatively short period of time, thereby improving production efficiency. It is also beneficial to control the reaction process, reduce the occurrence of side reactions, and improve the purity and quality of the product.

[0039] As a preferred embodiment of the present invention, the method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis can preferably be carried out according to the following steps:

[0040] 2 g of tannic acid was dissolved in an ethanol-water mixed solvent, and allyl triphenylphosphine chloride was added under stirring at 200 rpm. The molar ratio of tannic acid to allyl triphenylphosphine chloride was 1:1.5. 0.06 g of Candida antarctica lipase B was added and reacted for 6 hours. During this period, the reaction temperature was controlled at 40°C and the pH value was 6.5. Oxygen was passed through the mixture for 10 minutes every hour. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme. The mixture was then purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

[0041] These conditions work together to enable the reaction to proceed in an efficient and stable state, ensuring the stability and consistency of the quality and performance of the cationic tannic acid-based organic flocculant, which is conducive to the implementation of industrial production and the control of product quality.

[0042] A cationic tannic acid-based organic flocculant prepared by the method can be used to treat wastewater, especially high-turbidity and high-chroma wastewater, such as printing and dyeing wastewater.

[0043] When using the cationic tannic acid-based organic flocculant for wastewater treatment, the method first involves stirring at 200 rpm for 30 seconds to allow the flocculant to be quickly and evenly dispersed in the wastewater, fully contacting the pollutants, and improving the efficiency and effect of the reaction. The speed is then adjusted to 35 rpm and stirred for 15 minutes, which is conducive to the reaction between the flocculant and the pollutants and the formation of flocs, allowing the flocs to gradually grow. Finally, stirring is stopped and allowed to settle for 30 minutes to allow the formed flocs to fully settle and achieve solid-liquid separation, thereby achieving the purpose of efficiently removing pollutants and purifying wastewater. This operation method is simple and feasible, can fully utilize the performance of the cationic tannic acid-based organic flocculant, and improve the effect and efficiency of wastewater treatment.

[0044] Example 1

[0045] 2 g of tannic acid was dissolved in an ethanol-water mixture (volume ratio = 2:1). Allyl triphenylphosphine chloride was added at a stirring speed of 100 rpm to achieve a molar ratio of tannic acid to allyl triphenylphosphine chloride of 1:1.5. 0.06 g of Candida antarctica lipase B (2000-2400 U / g) was then added and allowed to react for 6 hours. The reaction temperature was maintained at 40°C and the pH was 6.5. The stirring speed was maintained at 100 rpm. Oxygen was introduced for 10 minutes every hour to enhance enzyme activity. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme. The mixture was then purified with acetone, washed with ethanol, and dried in a vacuum oven to obtain a cationic tannic acid-based organic flocculant. The zeta potential of the flocculant was measured using a zeta potential meter.

[0046] Following the same preparation method, the stirring speed was adjusted to 200 rpm, 250 rpm, or 300 rpm, and four groups of different cationic tannic acid-based organic flocculants were finally obtained. Their treatment effects on printing and dyeing wastewater were compared to determine the optimal stirring speed. The specific method is as follows:

[0047] Water samples from the wastewater treatment workshop of a textile printing and dyeing plant in Zibo were used as experimental water samples. One liter of the experimental water sample was accurately measured and placed in a 1-liter beaker. The sample was rapidly stirred at 200 rpm for 30 seconds on a coagulation mixer. Then, 15 mg of flocculant was added and the mixture was stirred at 200 rpm for another 30 seconds to thoroughly mix the flocculant with the experimental water sample. Next, the speed was adjusted to 35 rpm and the mixture was stirred slowly for 15 minutes. Finally, stirring was stopped and the mixture was allowed to settle for 30 minutes. After coagulation and sedimentation, approximately 5 mL of the supernatant was collected from 1-2 cm below the liquid surface using a syringe. The UV absorbance of the effluent was measured using a TU-1810 UV-Vis spectrophotometer to calculate the color removal rate.

[0048] The results are shown in Table 1 below. It can be seen that the Zeta potential of the organic flocculant prepared at a stirring speed of 200 rpm is the highest, which means that the flocculant has the strongest positive charge and the strongest adsorption and electrical neutralization effect, and can efficiently remove negatively charged dye molecules in the water. Therefore, the decolorization rate is also the highest, reaching 95.7%.

[0049] Table 1 Electrical properties and decolorization efficiency of organic flocculants prepared at different stirring speeds

[0050]

[0051] Example 2

[0052] Based on Example 1, the reaction stirring speed was set to 200 rpm, and the molar ratio of tannic acid to allyl triphenylphosphine chloride was adjusted to prepare a cationic tannic acid-based organic flocculant. The specific scheme is as follows:

[0053] 2 g of tannic acid was dissolved in an ethanol-water mixture (volume ratio = 2:1). Allyl triphenylphosphine chloride was added with stirring at 200 rpm. The molar ratio of tannic acid to allyl triphenylphosphine chloride was 1:1, 1:1.5, 1:2, 1:2.5, or 1:3. Then, 0.06 g of Candida antarctica lipase B (2000-2400 U / g) was added and allowed to react for 6 hours. The reaction temperature was maintained at 40°C and the pH was 6.5. The stirring speed was maintained at 200 rpm. Oxygen was introduced for 10 minutes every hour to enhance enzyme activity. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme. The mixture was then purified with acetone, washed with ethanol, and dried in a vacuum oven to obtain a cationic tannic acid-based organic flocculant. The zeta potential of the flocculant was measured using a zeta potential meter.

[0054] The treatment effects of five different groups of cationic tannic acid-based organic flocculants on printing and dyeing wastewater were compared to determine the optimal molar ratio of tannic acid to allyltriphenylphosphine chloride. The test method was the same as that in Example 1.

[0055] The results are shown in Table 2 below. It can be seen that the organic flocculants prepared with a molar ratio of tannic acid to allyl triphenylphosphonium chloride of 1:1.5 and 1:2 exhibited higher zeta potentials, indicating a strong positive charge and strong adsorption and charge neutralization effect, enabling efficient removal of negatively charged dye molecules from water. Consequently, the decolorization rates were high, reaching 95.7% and 95.2%, respectively. Although the molar ratio of tannic acid to allyl triphenylphosphonium chloride of 1:2 was slightly more positive than that of 1:1.5, the decolorization rate indicated that the molar ratio of 1:1.5 was more effective. This is because the molar ratio of 1:2 is too large, resulting in partial entanglement and aggregation of the cationic side chains, which creates a steric hindrance and hinders contact and flocculation with the pollutants.

[0056] Table 2 Electrical properties and decolorization efficiency of organic flocculants at different molar ratios of tannic acid to allyl triphenylphosphine chloride

[0057]

[0058] Example 3

[0059] Based on Examples 1 and 2, the reaction stirring speed was set to 200 rpm, the molar ratio of tannic acid to allyltriphenylphosphine chloride was set to 1:1.5, and the type of enzyme catalyst was adjusted to prepare a cationic tannic acid-based organic flocculant. The specific scheme is as follows:

[0060] 2 g of tannic acid was dissolved in an ethanol-water mixture (volume ratio = 2:1). Allyl triphenylphosphine chloride was added at a stirring speed of 200 rpm (the molar ratio of tannic acid to allyl triphenylphosphine chloride was 1:1.5). 0.06 g of an enzyme catalyst (one of Candida antarctica lipase B and horseradish peroxidase isoenzyme C) was then added and allowed to react for 6 hours. The reaction temperature was maintained at 40°C and the pH was 6.5. The stirring speed was maintained at 200 rpm. Oxygen was introduced for 10 minutes every hour to enhance enzyme activity. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme. The mixture was then purified with acetone, washed with ethanol, and dried in a vacuum oven to obtain a cationic tannic acid-based organic flocculant. The zeta potential of the flocculant was measured using a zeta potential meter.

[0061] The treatment effects of two different groups of cationic tannic acid-based organic flocculants on printing and dyeing wastewater were compared to determine the optimal enzyme catalyst type. The test method was the same as that in Example 1.

[0062] The results are shown in Table 3 below. It can be seen that the organic flocculant prepared when Candida antarctica lipase B is used as the enzyme catalyst has the highest Zeta potential, which indicates that the flocculant has the strongest positive charge and the strongest adsorption and charge neutralization effect, and can efficiently remove negatively charged dye molecules in the water. Therefore, the decolorization rate is also high, reaching 95.7%.

[0063] Table 3 Electrical properties and decolorization efficiency of organic flocculants under different enzyme catalysts

[0064]

[0065] Example 4

[0066] Based on Examples 1 to 3, the reaction stirring speed was set at 200 rpm, the molar ratio of tannic acid to allyltriphenylphosphine chloride was 1:1.5, and the enzyme catalyst was Candida antarctica lipase B. The catalyst dosage was then adjusted to prepare a cationic tannic acid-based organic flocculant. The specific scheme is as follows:

[0067] 2 g of tannic acid was dissolved in an ethanol-water mixture (volume ratio = 2:1). Allyl triphenylphosphine chloride was added at a molar ratio of 1:1.5 under stirring at 200 rpm. Then, different amounts of Candida antarctica lipase B (2000-2400 U / g) (0.02 g, 0.04 g, 0.06 g, 0.08 g, or 0.1 g) were added and reacted for 6 hours. The reaction temperature was maintained at 40°C and the pH was 6.5. The stirring speed was maintained at 200 rpm. Oxygen was introduced for 10 minutes every hour to enhance enzyme activity. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme. The mixture was then purified with acetone, washed with ethanol, and dried in a vacuum oven to obtain a cationic tannic acid-based organic flocculant. The zeta potential of the flocculant was measured using a zeta potential meter.

[0068] The treatment effects of five different groups of cationic tannic acid-based organic flocculants on printing and dyeing wastewater were compared to determine the optimal dosage of the enzyme catalyst. The test method was the same as that in Example 1.

[0069] The results are shown in Table 4 below. It can be seen that when the dosage of Antarctic Candida lipase B is 0.06 g, the Zeta potential of the prepared organic flocculant is the highest, which means that the flocculant has the strongest positive charge and the strongest adsorption and electrical neutralization effect, and can efficiently remove negatively charged dye molecules in the water. Therefore, the decolorization rate is also high, reaching 95.7%.

[0070] Table 4 Electrical properties and decolorization efficiency of organic flocculants at different enzyme catalyst dosages

[0071]

[0072] Example 5

[0073] Based on Examples 1 to 4, the reaction stirring speed was selected to be 200 rpm, the molar ratio of tannic acid to allyltriphenylphosphine chloride was 1:1.5, the enzyme catalyst was selected to be Candida antarctica lipase B, and the amount of enzyme catalyst added was 0.03 g / g tannic acid. The reaction temperature was then adjusted to prepare a cationic tannic acid-based organic flocculant. The specific scheme is as follows:

[0074] 2 g of tannic acid was dissolved in an ethanol-water mixture (volume ratio = 2:1). Allyl triphenylphosphine chloride was added at a molar ratio of 1:1.5 under stirring at 200 rpm. Then, 0.06 g of Candida antarctica lipase B (2000-2400 U / g) was added and allowed to react for 6 hours. The reaction temperature was controlled at 30°C, 40°C, 50°C, or 60°C, and the pH was 6.5. The stirring speed was maintained at 200 rpm. Oxygen was introduced for 10 minutes every hour to enhance enzyme activity. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme. The mixture was then purified with acetone, washed with ethanol, and dried in a vacuum oven to obtain a cationic tannic acid-based organic flocculant. The zeta potential of the flocculant was measured using a zeta potential meter.

[0075] The treatment effects of four different groups of cationic tannic acid-based organic flocculants on printing and dyeing wastewater were compared to determine the optimal reaction temperature. The test method was the same as that in Example 1.

[0076] The results are shown in Table 5 below. It can be seen that the Zeta potential of the organic flocculant prepared at a reaction temperature of 40°C is the highest, which means that the flocculant has the strongest positive charge and the strongest adsorption and electrical neutralization effect, and can efficiently remove negatively charged dye molecules in the water. Therefore, the decolorization rate is also high, reaching 95.7%.

[0077] Table 5 Electrical properties and decolorization efficiency of organic flocculants at different reaction temperatures

[0078]

[0079] Example 6

[0080] Based on Examples 1 to 5, the reaction stirring speed was selected to be 200 rpm, the molar ratio of tannic acid to allyltriphenylphosphine chloride was 1:1.5, the enzyme catalyst was selected to be Candida antarctica lipase B, the amount of enzyme catalyst added was 0.03 g / g tannic acid, the reaction temperature was 40°C, and the reaction pH was adjusted to prepare a cationic tannic acid-based organic flocculant. The specific scheme is as follows:

[0081] 2 g of tannic acid was dissolved in an ethanol-water mixture (volume ratio = 2:1). Allyl triphenylphosphine chloride was added at a molar ratio of 1:1.5. 0.06 g of Candida antarctica lipase B (2000-2400 U / g) was then added and allowed to react for 6 hours. The reaction temperature was maintained at 40°C and the pH was 5, 6, 6.5, 7, or 8. The stirring speed was maintained at 200 rpm. Oxygen was introduced for 10 minutes every hour to enhance enzyme activity. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme. The mixture was then purified with acetone, washed with ethanol, and dried in a vacuum oven to obtain a cationic tannic acid-based organic flocculant. The zeta potential of the flocculant was measured using a zeta potential meter.

[0082] The treatment effects of five different groups of cationic tannic acid-based organic flocculants on printing and dyeing wastewater were compared to determine the optimal reaction pH value. The test method was the same as that in Example 1.

[0083] The results are shown in Table 6 below. It can be seen that the Zeta potential of the organic flocculant prepared when the reaction pH value is 6.5 is the highest, which means that the flocculant has the strongest positive charge and the strongest adsorption and electrical neutralization effect, and can efficiently remove negatively charged dye molecules in the water. Therefore, the decolorization rate is also high, reaching 95.7%.

[0084] Table 6 Electrical properties and decolorization efficiency of organic flocculants at different reaction pH values

[0085]

[0086] Example 7

[0087] Based on Examples 1 to 6, the reaction stirring speed was selected to be 200 rpm, the molar ratio of tannic acid to allyltriphenylphosphine chloride was 1:1.5, the enzyme catalyst was selected to be Candida antarctica lipase B, the amount of enzyme catalyst added was 0.03 g / g tannic acid, the reaction temperature was 40°C, the reaction pH was 6.5, and the reaction time was adjusted to prepare a cationic tannic acid-based organic flocculant. The specific scheme is as follows:

[0088] 2 g of tannic acid was dissolved in an ethanol-water mixed solvent (volume ratio = 2:1). Allyl triphenylphosphine chloride was added with stirring at 200 rpm (the molar ratio of tannic acid to allyl triphenylphosphine chloride was 1:1.5). Then, 0.06 g of Candida antarctica lipase B (2000-2400 U / g) was added and reacted for different times (2 hours, 4 hours, 6 hours, 8 hours, or 10 hours). During this period, the reaction temperature was controlled at 40°C and the pH value was 6.5. The stirring speed was maintained at 200 rpm. Oxygen was introduced for 10 minutes every hour to enhance enzyme activity. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme. The mixture was then purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

[0089] The treatment effects of five different groups of cationic tannic acid-based organic flocculants on printing and dyeing wastewater were compared to determine the optimal reaction time. The test method was the same as that in Example 1.

[0090] The results are shown in Table 7 below. It can be seen that the organic flocculant prepared with an 8-hour reaction time had the highest zeta potential. This indicates that the flocculant is most positively charged and has the strongest adsorption and charge neutralization effect, effectively removing negatively charged dye molecules from the water. Consequently, the decolorization rate was high, reaching 95.9%. However, after 6 hours of reaction, the decolorization rate reached 95.7%. Considering both coagulation efficiency and economic benefits, 6 hours is the optimal reaction time.

[0091] Table 7 Electrical properties and decolorization efficiency of organic flocculants at different reaction times

[0092]

[0093] Example 8

[0094] Based on Examples 1 to 7, the best solution for the enzymatic method of preparing cationic tannic acid-based organic flocculants is as follows:

[0095] 2 g of tannic acid was dissolved in an ethanol-water mixed solvent, and allyl triphenylphosphine chloride was added under stirring at 200 rpm. The molar ratio of tannic acid to allyl triphenylphosphine chloride was 1:1.5. 0.06 g of Candida antarctica lipase B (2000-2400 U / g) was added and reacted for 6 hours. During this period, the reaction temperature was controlled at 40°C and the pH value was 6.5. Oxygen was passed through for 10 minutes every hour. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme. The mixture was then purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

[0096] The TEM image of the cationic tannic acid-based organic flocculant prepared in this example is as follows: Figure 1As shown in the figure, the organic flocculant is in an extended state in water, has a polymer chain structure, and its side chains are highly branched, so it can provide a large number of active sites for contact and flocculation with pollutants; in addition, its polymer chain structure can be adsorbed on the surface of multiple pollutants at the same time, so the generated flocs are larger in size and easier to settle naturally.

[0097] The Zeta potential of the cationic tannic acid-based organic flocculant prepared in this embodiment in the pH range of 2-12 is as follows: Figure 2 As shown in the figure, the results show that the cationic tannic acid-based organic flocculant has a strong positive charge in the pH range of 2-12, with the highest value reaching 69.8 mV, and therefore has a strong adsorption charge neutralization effect.

[0098] The molecular weight distribution of the cationic tannic acid-based organic flocculant prepared in this embodiment is as follows: Figure 3 As shown, the average molecular weight is 3.95×10 5 g / mol, so the flocculant can provide adsorption bridging effect.

[0099] The cationic tannic acid-based organic flocculant prepared in this embodiment was used to treat printing and dyeing wastewater. 1 L of experimental water sample (taken from the wastewater treatment workshop of a textile printing and dyeing factory in Zibo) was accurately measured and placed in a 1 L beaker. It was rapidly stirred at a speed of 200 rpm for 30 seconds on a coagulation agitator; then, 15 mg of flocculant was added, and the mixture was first stirred at a speed of 200 rpm for 30 seconds, and then the speed was adjusted to 35 rpm and stirred for 15 minutes. Finally, the stirring was stopped and allowed to settle for 30 minutes. After the coagulation and sedimentation were completed, about 5 mL of the supernatant 1-2 cm below the liquid surface was taken with a syringe, and the ultraviolet absorbance and residual turbidity of the effluent were measured with a TU-1810 UV-visible spectrophotometer and a 2100Q portable turbidity meter to calculate the chromaticity removal rate and turbidity removal rate. The national standard method was used to measure the COD in the water before and after coagulation. Cr The fluorescence intensity of water samples before and after treatment was detected using three-dimensional fluorescence.

[0100] Figure 4 The results show that the decolorization rate of the flocculant is 95%, the turbidity removal rate is 90%, and the COD cr The removal rate reaches 42%, which is better than traditional inorganic coagulants and organic polymer flocculants (such as polyacrylamide and polydimethyldiallyl ammonium chloride).

[0101] Figure 5 The changes in water samples before and after treatment and the pictures of the generated flocs are shown. It can be seen that the flocculant of the present invention can selectively remove dye molecules, so the generated flocs are blue, and the chromaticity of the effluent is the coexisting pollutants such as oil-containing emulsions and surfactants introduced in the printing and dyeing process.

[0102] Figure 6 The three-dimensional fluorescence images of water samples before and after coagulation show that the product of the present invention can effectively reduce the fluorescence intensity of printing and dyeing wastewater.

[0103] Although the present invention has been described in detail with reference to the accompanying drawings and in conjunction with preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any changes or substitutions that can be easily conceived by persons skilled in the art within the technical scope disclosed in the present invention shall be within the scope of protection of the present invention.

Claims

1. A cationic tannic acid-based organic flocculant, characterized in that: The preparation method is enzyme catalysis, and the preparation method comprises the following steps: Tannic acid and allyl triphenylphosphine chloride are reacted under the action of an enzyme catalyst for 6 hours at a reaction temperature of 40°C. After the reaction, the enzyme is inactivated, and then purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant. The enzyme catalyst is Candida antarctica lipase B; The molar ratio of tannic acid and allyltriphenylphosphine chloride is 1:1.5; The amount of enzyme catalyst added was 0.03 g / g tannic acid; The activity of Candida antarctica lipase B is 2000-2400 U / g; The reaction pH was 6.5; During the reaction, oxygen was added to the reaction system every hour; The reaction was carried out under stirring at a speed of 200 rpm; The cationic tannic acid-based organic flocculant can be used to treat printing and dyeing wastewater.

2. A cationic tannic acid-based organic flocculant according to claim 1, characterized in that: The preparation method comprises the following steps: 2 g of tannic acid was dissolved in an ethanol-water mixed solvent, and allyl triphenylphosphine chloride was added under stirring at 200 rpm. The molar ratio of tannic acid to allyl triphenylphosphine chloride was 1:1.

5. 0.06 g of Candida antarctica lipase B was added and reacted for 6 hours. During this period, the reaction temperature was controlled at 40°C and the pH value was 6.

5. Oxygen was passed through the mixture for 10 minutes every hour. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme. The mixture was then purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

3. Use of the cationic tannic acid-based organic flocculant according to claim 1 or 2 in treating colloidal particles, heavy metal ions and / or dye pollutants in wastewater.

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