Method for preparing cationic tannic acid-based organic flocculant by enzyme catalysis method as well as product and application of cationic tannic acid-based organic flocculant

Abstract

The invention relates to the technical field of water treatment, in particular to a method for preparing a cationic tannin-based organic flocculant through an enzyme catalysis method, a product of the cationic tannin-based organic flocculant and application of the cationic tannin-based organic flocculant. The method comprises the following steps: enabling tannic acid and allyltriphenylphosphonium chloride to react for 2-10 hours under the action of an enzyme catalyst at the reaction temperature of 30-60 DEG C, deactivating enzyme after the reaction is finished, then purifying by acetone, cleaning by ethanol, and drying in a vacuum drying oven to obtain the cationic tannic acid-based organic flocculant. Wherein the enzyme catalyst is lipase B or horse radish peroxidase. According to the invention, enzyme is adopted as a catalyst, and covalent grafting between phenolic hydroxyl groups in tannic acid molecules and allyl groups of allyl triphenylphosphonium chloride is realized through specific catalysis of the enzyme. The cationic tannin-based organic flocculant provided by the invention can efficiently remove colloidal particles, heavy metal ions and dye pollutants in wastewater, and is especially suitable for treatment of high-turbidity and high-chroma industrial wastewater.

Description

Technical Field

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

[0002] The textile printing and dyeing industry occupies an important position in my country's national economy. In order to meet the needs of contemporary residents, a large number of different types of dyes are used in the textile printing and dyeing process. According to statistics, about 10,000 synthetic dyes and natural dyes are produced every year in the world, with an annual output of up to 1.6 million tons. There is a serious waste of dyes in the production and application process. It is estimated that 10-15% of the total amount of the above dyes is discharged as wastewater. A large amount of industrial wastewater containing toxic dyes is generated in the process of dye production and textile printing and dyeing. The characteristics of the wastewater are: large water quality changes, high chroma, high content of organic matter that is difficult to biodegrade, high biological toxicity and continuous bioaccumulation. It is a difficult-to-treat industrial wastewater. At present, the most commonly used methods for dye decolorization are adsorption, coagulation and sedimentation, membrane separation, chemical oxidation, photocatalytic oxidation and biological treatment. Among them, coagulation and sedimentation is the most widely used physical and chemical treatment method due to its low operating cost, simple operation and high application efficiency. In the process of coagulation treatment of dye wastewater, the performance of coagulant or flocculant is the key factor determining the water purification quality and process operation cost. At present, the commonly used chemical flocculants are mainly divided into two categories: inorganic coagulants and synthetic organic polymer flocculants. However, inorganic coagulants also have many shortcomings in practical application, such as: large dosage, large amount of sludge, narrow application range, residual metal elements, fragile flocs, and poor treatment effect of low-temperature and low-turbidity water. In view of the shortcomings of inorganic coagulants, the research and development and application of organic polymer flocculants have received widespread attention.

[0003] The high-value comprehensive utilization of biomass has received widespread attention. Tannin is a plant polyphenol that is widely found in various parts of plants. It is abundant in resources, cheap and easy to obtain. Tannin is a green and environmentally friendly natural polymer material with a polyphenolic hydroxyl structure and high chemical reactivity. At present, researchers have successfully introduced quaternary amine groups into tannin molecules through Mannich reaction, amination reaction, etc., and the prepared organic polymer flocculants have enhanced positive charge, increased molecular weight, and significantly improved flocculation ability. However, there is still a lack of research on introducing quaternary phosphine groups into the molecular skeleton of tannin. Summary of the invention

[0004] In view of the current technical problem of lack of research on introducing quaternary phosphine groups into the molecular skeleton of tannin, the present invention provides a method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis, and a product and application thereof.

[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: 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 by 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 (CAL-B) or horseradish peroxidase isozyme C (HRPC).

[0006] Furthermore, the molar ratio of tannic acid to allyl triphenylphosphine chloride is 1:1-3.

[0007] Furthermore, the amount of enzyme catalyst added is 0.01-0.05 g / g tannic acid.

[0008] Furthermore, the enzyme activity of Antarctic Candida lipase B or horseradish peroxidase isozyme C is 2000-2400 U / g. Furthermore, the reaction pH value is 5-8. Within this pH value range, tannic acid and allyl triphenylphosphine chloride can be efficiently grafted under the catalysis of the enzyme to generate a cationic tannic acid-based organic flocculant with ideal performance.

[0009] Furthermore, during the reaction, 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.

[0010] Furthermore, the reaction is carried out under stirring at a speed of 100-300 rpm.

[0011] 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: 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, and 0.06 g of Antarctic Candida lipase B was added to react for 6 hours, during which the reaction temperature was controlled at 40°C and the pH value was 6.5, and oxygen was passed for 10 minutes every 1 hour; after the reaction, the pH was adjusted to 3.0 to inactivate the enzyme, and then it was purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

[0012] In a third aspect, the present invention provides a cationic tannic acid-based organic flocculant prepared by the above method.

[0013] 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.

[0014] Furthermore, the wastewater is printing and dyeing wastewater. Printing and dyeing wastewater has the characteristics of high turbidity and high chroma, and is difficult to treat. When treating such wastewater, cationic tannic acid-based organic flocculants can give full play to their advantages, effectively remove pollutants in printing and dyeing wastewater, reduce the turbidity and chroma of wastewater, achieve standard discharge of printing and dyeing wastewater, and reduce pollution to the environment.

[0015] Furthermore, the application method is to put 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.

[0016] The beneficial effects of the present invention are: The present invention uses enzyme as a catalyst to achieve covalent grafting between the phenolic hydroxyl group in the tannic acid molecule and the allyl group of allyltriphenylphosphine chloride through the specific catalytic action of the enzyme. Compared with traditional chemical methods (such as free radical initiation or metal catalysis), the enzyme catalysis method has the advantages of high selectivity, no by-products, mild reaction conditions, etc.

[0017] 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 liquid discharge, in line with the concept of sustainable development. The reaction is carried out under normal pressure and medium temperature conditions, and the energy consumption is significantly lower than the traditional high temperature and high pressure synthesis process.

[0018] The flocculant product provided by the present invention combines the natural polyphenol structure of tannic acid (providing antioxidant and antibacterial activity) with the cationic phosphine group of allyl triphenylphosphine chloride (imparting strong positive charge characteristics), forming an efficient cationic flocculant. The strong cationic characteristics of the phosphine group can effectively neutralize negatively charged suspended particles in the water body, and the polyphenol skeleton of tannic acid enhances the rigidity and shear resistance of the molecular chain, thereby improving the flocculation effect and reusability. As a cationic flocculant, it can efficiently remove colloidal particles, heavy metal ions and dye pollutants in wastewater, and is particularly suitable for the treatment of high turbidity and high chromaticity industrial wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1It is a TEM image of the cationic tannic acid-based organic flocculant prepared in Example 8 in a specific embodiment of the present invention.

[0021] Figure 2 It is the Zeta potential of the cationic tannic acid-based organic flocculant prepared in Example 8 in the specific implementation manner of the present invention in the range of pH=2-12.

[0022] Figure 3 It 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.

[0023] Figure 4 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 the 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.

[0024] 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 a water sample before treatment with a 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 (c) is a picture of flocs generated after treatment with a cationic tannic acid-based organic flocculant.

[0025] 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

[0026] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in 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 creative work should fall within the scope of protection of the present invention.

[0027] A method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis comprises the following steps: 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 by 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 (CAL-B) or horseradish peroxidase isozyme C (HRPC).

[0028] As a preferred embodiment of the present invention, the molar ratio of tannic acid to allyl triphenylphosphine chloride is 1:1-3. This molar ratio range ensures that tannic acid and allyl triphenylphosphine chloride can react appropriately, so that the phenolic hydroxyl groups in the tannic acid molecules have enough allyl triphenylphosphine chloride to undergo covalent grafting reaction, which is conducive to the generation of a cationic tannic acid-based organic flocculant with an ideal structure and performance. If the proportion of allyl triphenylphosphine chloride is too low, the grafting effect is poor, affecting the cationic characteristics and flocculation effect of the flocculant; if the proportion is too high, it may cause a waste of raw materials, increase costs, and may also affect the selectivity of the reaction and the purity of the product.

[0029] As a preferred embodiment of the present invention, the amount of enzyme catalyst added is 0.01-0.05 g / g tannic acid. This amount range can ensure that the enzyme catalyst plays an effective catalytic role in the reaction, and while ensuring the catalytic efficiency, avoid the problems of too slow reaction rate and incomplete reaction due to too little enzyme, or increased cost due to too much enzyme and possible impact on product purity. The appropriate amount of enzyme can achieve efficient catalytic reaction under relatively economical conditions, promote the grafting of tannic acid and allyl triphenylphosphine chloride, and thus obtain a cationic tannic acid-based organic flocculant with good performance.

[0030] As a preferred embodiment of the present invention, the enzyme activity of Antarctic Candida lipase B or horseradish peroxidase isozyme C is 2000-2400 U / g. It has been verified that the two enzymes, Antarctic Candida lipase B or horseradish peroxidase isozyme C, have good catalytic activity and specificity at a dosage of 0.01-0.05 g / g tannic acid, and can effectively catalyze the covalent grafting reaction between the phenolic hydroxyl group in the tannic acid molecule and the allyl group of allyltriphenylphosphine chloride.

[0031] 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 or even inactivated enzyme activity, thereby affecting the reaction rate and product generation. This pH range provides a suitable reaction environment for the enzyme catalyst, ensures that the activity of the enzyme is at a high level, and is conducive to the smooth progress of the catalytic reaction.

[0032] As a preferred embodiment of the present invention, during the reaction process, oxygen is added to the reaction system every 1 hour. Supplementing oxygen can ensure 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, so that the reaction can reach a higher conversion rate in a shorter time, improve production efficiency, and also help control the reaction process, reduce the occurrence of side reactions, and improve the purity and quality of the product.

[0033] As a preferred embodiment of the present invention, the method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis can be preferably carried out according to 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, and 0.06 g of Antarctic Candida lipase B was added to react for 6 hours, during which the reaction temperature was controlled at 40°C and the pH value was 6.5, and oxygen was passed for 10 minutes every 1 hour; after the reaction, the pH was adjusted to 3.0 to inactivate the enzyme, and then it was purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

[0034] These conditions cooperate with each other 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.

[0035] A cationic tannic acid-based organic flocculant prepared by the method can be used to treat wastewater, especially high turbidity and high chromaticity wastewater, such as printing and dyeing wastewater.

[0036] When the cationic tannic acid-based organic flocculant is used to treat wastewater, it is first stirred at a speed of 200 rpm for 30 seconds, so that the flocculant can be quickly and evenly dispersed in the wastewater, fully contacted with the pollutants, and improve the efficiency and effect of the reaction, and then the speed is 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 floccules, so that the floccules gradually grow, and finally the stirring is stopped and precipitated for 30 minutes, so that the formed floccules can be fully settled, and solid-liquid separation is achieved, thereby achieving the purpose of efficiently removing pollutants and purifying wastewater. This operation method is simple and feasible, and can give full play to the performance of the cationic tannic acid-based organic flocculant and improve the effect and efficiency of wastewater treatment.

[0037] Example 1 2 g of tannic acid was dissolved in an ethanol-water mixed solvent (volume ratio = 2:1), and allyl triphenylphosphine chloride was added at a stirring speed of 100 rpm, and the molar ratio of tannic acid to allyl triphenylphosphine chloride was 1:1.5. Then 0.06 g of Antarctic Candida lipase B (2000-2400 U / g) was added to react for 6 hours, during which the reaction temperature was controlled at 40℃, the pH value was 6.5, the stirring speed was maintained at 100 rpm, and oxygen was passed for 10 minutes every 1 hour to improve the activity of the enzyme; after the reaction, the pH was adjusted to 3.0 to inactivate the enzyme, and then purified by acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant. The Zeta potential of the flocculant was detected by a Zeta potential meter.

[0038] According to the same preparation method, the stirring speed was adjusted to 200 rpm, 250 rpm or 300 rpm, and finally four groups of different cationic tannic acid-based organic flocculants were obtained, and their treatment effects on printing and dyeing wastewater were compared to determine the optimal stirring speed. The specific method is as follows: Take the water sample from the sewage treatment workshop of a textile printing and dyeing factory in Zibo as the experimental water sample. Accurately measure 1 L of the experimental water sample and place it in a 1 L beaker. Stir it rapidly at 200 rpm for 30 seconds on a coagulation agitator. Then, add 15 mg of flocculant and continue to stir rapidly at 200 rpm for 30 seconds to fully mix the agent with the experimental water sample. Next, adjust the speed to 35 rpm and stir slowly for 15 minutes. Finally, stop stirring and let it settle for 30 minutes. After the coagulation and sedimentation, use a syringe to take about 5 mL of the supernatant 1-2 cm below the liquid surface, and use a TU-1810 UV-visible spectrophotometer to measure the UV absorbance of the effluent and calculate its chromaticity removal rate.

[0039] 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%.

[0040] Table 1 Electrical properties and decolorization efficiency of organic flocculants prepared at different stirring speeds

[0041] Example 2 On the basis of Example 1, the reaction stirring speed was selected to be 200 rpm, and then 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: 2 g of tannic acid was dissolved in an ethanol-water mixed solvent (volume ratio = 2:1), and 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, 1:1.5, 1:2, 1:2.5 or 1:3. Then 0.06 g of Antarctic Candida lipase B (2000-2400 U / g) was added to react for 6 hours. During this period, the reaction temperature was controlled at 40℃ and the pH value was 6.5. The stirring speed was maintained at 200 rpm. Oxygen was passed for 10 minutes every 1 hour to improve the activity of the enzyme. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme, and then purified by acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant. The Zeta potential of the flocculant was detected by a Zeta potential meter.

[0042] 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 allyl triphenylphosphine chloride. The test method was the same as that in Example 1.

[0043] The results are shown in Table 2 below. It can be seen that the Zeta potential of the organic flocculant prepared when the molar ratio of tannic acid to allyl triphenyl phosphine chloride is 1:1.5 and 1:2 is higher, which indicates that the flocculant has a strong positive charge and a strong adsorption and electrical neutralization effect, and can efficiently remove negatively charged dye molecules in the water body. Therefore, the decolorization rate is also high, reaching 95.7% and 95.2% respectively. Although the positive charge of the molar ratio of tannic acid to allyl triphenyl phosphine chloride is 1:2, it is slightly higher than that of 1:1.5, but the decolorization rate shows that the effect is better at 1:1.5. This is because the monomer amount is too large at 1:2, and the cationic side chain will have a partial entanglement and aggregation phenomenon, resulting in a steric hindrance effect, which is not conducive to contact flocculation with pollutants.

[0044] Table 2 Electrical properties and decolorization efficiency of organic flocculants at different molar ratios of tannic acid to allyl triphenylphosphine chloride

[0045] Example 3 On the basis of Example 1 and Example 2, the reaction stirring speed was selected to be 200 rpm, the molar ratio of tannic acid to allyl triphenylphosphine chloride was 1:1.5, and then the type of enzyme catalyst was adjusted to prepare a cationic tannic acid-based organic flocculant. The specific scheme is as follows: 2 g of tannic acid was dissolved in an ethanol-water mixed solvent (volume ratio = 2:1), and 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, and then 0.06 g of enzyme catalyst was added for 6 hours. The enzyme catalyst was one of Antarctic Candida lipase B and horseradish peroxidase isozyme C, and the activity of the enzyme catalyst was 2000-2400 U / g. During this period, the reaction temperature was controlled at 40℃, the pH value was 6.5, the stirring speed was maintained at 200 rpm, and oxygen was passed for 10 minutes every 1 hour to improve the activity of the enzyme; after the reaction, the pH was adjusted to 3.0 to inactivate the enzyme, and then purified by acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant. The Zeta potential of the flocculant was detected by a Zeta potential meter.

[0046] The treatment effects of two groups of different cationic tannic acid-based organic flocculants on printing and dyeing wastewater were compared to determine the best enzyme catalyst type. The test method was the same as that in Example 1.

[0047] The results are shown in Table 3 below. It can be seen that the Zeta potential of the organic flocculant prepared when Antarctic Candida lipase B is used as the enzyme catalyst 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%.

[0048] Table 3 Electrical properties and decolorization efficiency of organic flocculants under different enzyme catalysts

[0049] Example 4 On the basis of Examples 1 to 3, the reaction stirring speed was selected to be 200 rpm, the molar ratio of tannic acid to allyl triphenylphosphine chloride was 1:1.5, the enzyme catalyst was selected to be Antarctic Candida lipase B, and then the catalyst dosage was adjusted to prepare a cationic tannic acid-based organic flocculant. The specific scheme is as follows: 2 g of tannic acid was dissolved in an ethanol-water mixed solvent (volume ratio = 2:1), and 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. Then, different masses (0.02 g, 0.04 g, 0.06 g, 0.08 g or 0.1 g) of Candida antarctica lipase B (2000-2400 U / g) were added to react for 6 hours. During this period, the reaction temperature was controlled at 40℃ and the pH value was 6.5. The stirring speed was maintained at 200 rpm. Oxygen was passed for 10 minutes every 1 hour to improve the activity of the enzyme. After the reaction, the pH was adjusted to 3.0 to inactivate the enzyme, and then purified by acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant. The Zeta potential of the flocculant was detected by a Zeta potential meter.

[0050] 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.

[0051] 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%.

[0052] Table 4 Electrical properties and decolorization efficiency of organic flocculants at different enzyme catalyst dosages

[0053] Example 5 On the basis of Examples 1 to 4, the reaction stirring speed was selected to be 200 rpm, the molar ratio of tannic acid to allyl triphenylphosphine chloride was 1:1.5, the enzyme catalyst was selected to be Antarctic Candida lipase B, the amount of enzyme catalyst added was 0.03 g / g tannic acid, and then the reaction temperature was adjusted to prepare a cationic tannic acid-based organic flocculant. The specific scheme is as follows: 2 g of tannic acid was dissolved in an ethanol-water mixed solvent (volume ratio = 2:1), and 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, and then 0.06 g of Antarctic Candida lipase B (2000-2400 U / g) was added to react for 6 hours, during which the reaction temperature was controlled at 30℃, 40℃, 50℃ or 60℃, the pH value was 6.5, the stirring speed was maintained at 200 rpm, and oxygen was passed for 10 minutes every 1 hour to improve the activity of the enzyme; after the reaction, the pH was adjusted to 3.0 to inactivate the enzyme, and then purified by acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant. The Zeta potential of the flocculant was detected by a Zeta potential meter.

[0054] The treatment effects of four groups of different 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.

[0055] 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%.

[0056] Table 5 Electrical properties and decolorization efficiency of organic flocculants at different reaction temperatures

[0057] Example 6 On the basis of Examples 1 to 5, the reaction stirring speed is selected to be 200 rpm, the molar ratio of tannic acid to allyl triphenylphosphine chloride is 1:1.5, the enzyme catalyst is selected to be Antarctic Candida lipase B, the amount of enzyme catalyst added is 0.03 g / g tannic acid, the reaction temperature is 40°C, and then the reaction pH is adjusted to prepare a cationic tannic acid-based organic flocculant. The specific scheme is as follows: 2 g of tannic acid was dissolved in an ethanol-water mixed solvent (volume ratio = 2:1), and 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, and then 0.06 g of Antarctic Candida lipase B (2000-2400 U / g) was added to react for 6 hours, during which the reaction temperature was controlled at 40℃, the pH value was 5, 6, 6.5, 7 or 8, the stirring speed was maintained at 200 rpm, and oxygen was passed for 10 minutes every 1 hour to improve the activity of the enzyme; after the reaction, the pH was adjusted to 3.0 to inactivate the enzyme, and then purified by acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant. The Zeta potential of the flocculant was detected by a Zeta potential meter.

[0058] 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.

[0059] 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%.

[0060] Table 6 Electrical properties and decolorization efficiency of organic flocculants at different reaction pH values

[0061] Example 7 On the basis of Examples 1 to 6, the reaction stirring speed is selected to be 200 rpm, the molar ratio of tannic acid to allyl triphenylphosphine chloride is 1:1.5, the enzyme catalyst is Antarctic Candida lipase B, the amount of enzyme catalyst added is 0.03 g / g tannic acid, the reaction temperature is 40°C, the reaction pH is 6.5, and then the reaction time is adjusted to prepare a cationic tannic acid-based organic flocculant. The specific scheme is as follows: 2 g of tannic acid was dissolved in an ethanol-water mixed solvent (volume ratio = 2:1), and 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, and then 0.06 g of Antarctic Candida lipase B (2000-2400 U / g) was added to react for different times (2 hours, 4 hours, 6 hours, 8 hours or 10 hours), during which the reaction temperature was controlled at 40°C and the pH value was 6.5. The stirring speed was maintained at 200 rpm, and oxygen was passed for 10 minutes every 1 hour to improve the activity of the enzyme; after the reaction was completed, the pH was adjusted to 3.0 to inactivate the enzyme, and then it was purified by acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

[0062] 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.

[0063] The results are shown in Table 7 below. It can be seen that the Zeta potential of the organic flocculant prepared when the reaction time is 8 hours 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 body. Therefore, the decolorization rate is also high, reaching 95.9%. However, when the reaction time is 6 hours, the decolorization rate has reached 95.7%. Considering the coagulation efficiency and economic benefits, 6 hours is the best reaction time.

[0064] Table 7 Electrical properties and decolorization efficiency of organic flocculants at different reaction times

[0065] Example 8 Based on Examples 1 to 7, the best solution for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis is as follows: 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, and 0.06 g of Antarctic Candida lipase B (2000-2400 U / g) was added to react for 6 hours, during which the reaction temperature was controlled at 40°C and the pH value was 6.5, and oxygen was passed for 10 minutes every 1 hour; after the reaction, the pH was adjusted to 3.0 to inactivate the enzyme, and then it was purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

[0066] The TEM image of the cationic tannic acid-based organic flocculant prepared in this example is as follows: Figure 1As shown, 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 surfaces of multiple pollutants at the same time, so the generated flocs are larger in size and easier to settle naturally.

[0067] The Zeta potential of the cationic tannic acid-based organic flocculant prepared in this example in the pH range of 2-12 is as follows: Figure 2 As shown, the results show that the cationic tannic acid-based organic flocculant has a strong positive charge in the pH range of 2-12, up to 69.8 mV, and therefore has a strong adsorption charge neutralization effect.

[0068] The molecular weight distribution of the cationic tannic acid-based organic flocculant prepared in this example 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.

[0069] Use the cationic tannic acid-based organic flocculant prepared in this embodiment to treat printing and dyeing wastewater, accurately measure 1L of experimental water sample (taken from the wastewater treatment workshop of a textile printing and dyeing factory in Zibo) and place it in a 1L beaker, and quickly stir it at 200 rpm on a coagulation agitator for 30 seconds; then, add 15 mg of flocculant, first stir at 200 rpm for 30 seconds, then adjust the speed to 35 rpm and stir for 15 minutes, finally stop stirring and let it settle for 30 minutes. After the coagulation and sedimentation is completed, use a syringe to take about 5 mL of the supernatant 1-2 cm below the liquid surface, use a TU-1810 UV-visible spectrophotometer and a 2100Q portable turbidity meter to measure the ultraviolet absorbance and residual turbidity of the effluent, and calculate the chromaticity removal rate and turbidity removal rate. The national standard method is used to measure the COD in the water before and after coagulation. Cr The fluorescence intensity of the water samples before and after treatment was detected by three-dimensional fluorescence.

[0070] 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).

[0071] Figure 5 The changes in water samples before and after treatment and the pictures of 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.

[0072] Figure 6 The three-dimensional fluorescence images of the 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.

[0073] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis, characterized in that: The steps include: 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 by acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant; Wherein, the enzyme catalyst is Antarctic Candida lipase B or horseradish peroxidase isozyme C.

2. The method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis as claimed in claim 1, characterized in that: The molar ratio of tannic acid to allyl triphenylphosphine chloride is 1:1-3.

3. The method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis according to claim 1, characterized in that: The amount of enzyme catalyst added is 0.01-0.05 g / g tannic acid.

4. The method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis according to claim 1, characterized in that: The enzyme activity of Candida antarctica lipase B or horseradish peroxidase isozyme C is 2000-2400 U / g.

5. The method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis as claimed in claim 1, characterized in that: The reaction pH is 5-8.

6. The method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis as claimed in claim 1, characterized in that: During the reaction, oxygen was added to the reaction system every hour.

7. The method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis as claimed in claim 1, characterized in that: The reaction is carried out under stirring at a speed of 100-300 rpm.

8. The method for preparing a cationic tannic acid-based organic flocculant by enzyme catalysis as claimed in claim 1, characterized in that: The steps include: 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, and 0.06 g of Antarctic Candida lipase B was added to react for 6 hours, during which the reaction temperature was controlled at 40°C and the pH value was 6.5, and oxygen was passed for 10 minutes every 1 hour; after the reaction, the pH was adjusted to 3.0 to inactivate the enzyme, and then it was purified with acetone, washed with ethanol, and dried in a vacuum drying oven to obtain a cationic tannic acid-based organic flocculant.

9. A cationic tannic acid-based organic flocculant, characterized in that: The method is prepared by the method according to any one of claims 1 to 8.

10. Use of the cationic tannic acid-based organic flocculant as claimed in claim 9 in treating colloidal particles, heavy metal ions and / or dye pollutants in wastewater.

Images