Method for preparing quaternization modified tannin-based organic flocculant through irradiation grafting, product prepared by method and application of quaternization modified tannin-based organic flocculant

Abstract

The invention relates to the technical field of water treatment, in particular to a method for preparing a quaternized modified tannin-based organic flocculant through irradiation grafting, a product prepared through the method and application of the quaternized modified tannin-based organic flocculant. The method comprises the following steps: (1) under the irradiation of 30-60 mW / cm < 2 > of ultraviolet light, adding brominated vinyl triphenylphosphine into a mixture of tannic acid and a photoinitiator for reaction; (2) adjusting the ultraviolet intensity to 5-20 mW / cm < 2 > for reaction; (3) closing the ultraviolet reaction; and (4) precipitating the product with ethanol, filtering and washing to obtain the quaternary phosphonium modified tannin-based organic flocculant. Wherein the photoinitiator is selected from one of benzophenone and benzoin dimethyl ether. The quaternized modified tannin-based organic flocculant provided by the invention can efficiently remove algae in a water body in an environment-friendly manner, and avoids secondary pollution caused by algae cell rupture at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a method for preparing a quaternary phosphinated modified tannin-based organic flocculant by radiation grafting, and a product and application thereof. Background Art

[0002] my country's "2022 China Environmental Bulletin" pointed out that after monitoring 204 key lakes (reservoirs), it was found that the eutrophication rate was as high as 29.9%. The excessive reproduction of algae has caused a significant increase in the total organic carbon (TOC) and total organic nitrogen (TON) content in the water, resulting in a double pollution effect.

[0003] TOC is a key indicator for measuring the total amount of organic matter in water. The increase in its concentration has a direct impact on the dissolved oxygen level in the water, especially when algae blooms are severe, which will deplete the oxygen in the water or cause a sharp increase in pH, resulting in fish deaths. In addition, in conventional water treatment processes, TOC reacts with chlorine disinfectants to produce mutagenic and carcinogenic substances such as chloroform (THMs).

[0004] The increase in TON content will intensify algae reproduction, forming a vicious cycle of "nitrogen cycle imbalance-toxic substance generation-biocommunity destruction". Taking the Taihu Lake cyanobacteria bloom as an example, the TON concentration can reach several times the normal value, greatly promoting the dominant growth of pollution-resistant algae such as Microcystis, resulting in a significant decline in phytoplankton biodiversity.

[0005] Tannic acid is a natural polyphenol compound with abundant phenolic hydroxyl groups and good biodegradability, showing unique advantages in the treatment of algae-containing water. Tannic acid can bind to biomacromolecules such as proteins, enzymes, nucleic acids, etc. on the surface and inside of algae cells, interfere with cell material transport, metabolic regulation, gene expression and protein synthesis, inhibit algae growth and reproduction, and reduce the production of intracellular organic matter and algae toxins from the source; it can also cross-link with algae cell walls and cell membrane components, interfere with algae photosynthesis, reduce light energy absorption and conversion efficiency by affecting related pigments, proteins and electron transport chains, inhibit algae from obtaining energy and substances, and thus reduce algae toxin synthesis and release.

[0006] However, there are many problems with the practical application of natural tannic acid. On the one hand, the molecular weight distribution of tannic acid is uneven, the bridging ability of low molecular weight components is weak, and the solubility of high molecular weight components in water is insufficient. On the other hand, the surface of tannic acid is weakly negatively charged, and the electrostatic repulsion between tannic acid and algae cells, which usually have a strong negative charge on the surface, is significant. In order to achieve the ideal flocculation effect, the dosage of tannic acid needs to be increased by 3-5 times.

[0007] In order to solve the above problems of natural tannic acid, free radical graft copolymerization technology has become a research hotspot. The traditional grafting process generally uses ammonium persulfate (APS) as an initiator and needs to react in a hot water bath under nitrogen protection. However, the energy consumption of this process is relatively high, the grafting rate of the modified tannin-based flocculant obtained is low, the product structure is unstable, and the molecular weight distribution is also wide. Therefore, free radical graft copolymerization technology still faces some challenges in its actual promotion and application, and has not yet fully met the needs of efficient, stable and low-cost treatment of algae-containing water bodies. Summary of the invention

[0008] In order to solve the technical problem that tannic acid has a poor effect when used alone as a flocculant, the present invention provides a method for preparing a quaternary phosphine-modified tannin-based organic flocculant by radiation grafting, and its product and application. The quaternary phosphine-modified tannin-based organic flocculant can remove algae from water bodies efficiently and environmentally friendly, while avoiding secondary pollution caused by algae cell rupture.

[0009] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing a quaternary phosphine-modified tannin-based organic flocculant by radiation grafting, comprising the following steps: (1) 30-60 mW / cm 2 Under ultraviolet light, adding vinyl triphenylphosphine bromide to the mixture of tannic acid and photoinitiator to react; (2) Adjust the UV light intensity to 5-20 mW / cm 2 reaction; (3) Turn off the UV light reaction; (4) precipitating the product with ethanol, filtering and washing to obtain a quaternary phosphine-modified tannin-based organic flocculant; Wherein, the photoinitiator is selected from one of benzophenone and benzoin dimethyl ether.

[0010] Furthermore, in step (1), the mixture of tannic acid and photoinitiator is prepared according to the following method: Dissolve 2 g of tannic acid in water, place in a vacuum operating box, add photoinitiator, and stir evenly.

[0011] Furthermore, in step (1), the ratio of the amount of photoinitiator to tannic acid is 0.01-0.5 g: 1 g. The present invention balances the free radical generation efficiency and the product structure stability by controlling the amount of photoinitiator: too low an amount of photoinitiator will lead to insufficient grafting rate, while too high an amount of photoinitiator may cause excessive crosslinking or side reactions (such as monomer self-polymerization). At the same time, while ensuring sufficient reaction, this ratio can also reduce the negative impact of photoinitiator residues on the performance of quaternary phosphine-modified tannin-based organic flocculants, taking into account both economy and functionality.

[0012] Furthermore, in step (1), the ratio of vinyl triphenylphosphine bromide to tannic acid is 0.5-3 mol:1 mol. By controlling the ratio of vinyl triphenylphosphine bromide to tannic acid, the grafting density of the quaternary phosphine group can be controlled. At this ratio, the product obtained by the reaction will not have excessive monomer residues, the generation of monomer homopolymers is avoided, and the post-processing cost is reduced.

[0013] Furthermore, the reaction time in step (1), step (2) and step (3) is 10 minutes to 2 hours respectively.

[0014] In a second aspect, the present invention provides a preferred embodiment of a method for preparing a quaternary phosphine-modified tannin-based organic flocculant by irradiation grafting, comprising the following steps: Dissolve 2 g of tannic acid in water, place in a vacuum operating box, add 0.06 g of benzophenone, and stir for 10 minutes; irradiate with strong ultraviolet light at 50 mW / cm 2 , add vinyl triphenylphosphine bromide, the molar ratio of vinyl triphenylphosphine bromide to tannic acid is 2:1, the reaction time is 20 minutes; adjust the ultraviolet light intensity to 10 mW / cm 2 The reaction time is 1 hour, the ultraviolet light is turned off, and the reaction is continued for 1 hour; after the reaction is completed, the product is precipitated with ethanol, filtered and washed to obtain a quaternary phosphine-modified tannin-based organic flocculant.

[0015] In a third aspect, the present invention provides a quaternary phosphine-modified tannin-based organic flocculant prepared by the above method.

[0016] In a fourth aspect, the present invention also provides a use of the above-mentioned quaternary phosphine-modified tannin-based organic flocculant in treating algae liquid.

[0017] Furthermore, the application method is to add the quaternary phosphine-modified tannin-based organic flocculant to the algae liquid, stir at 200 rpm for 1.5 minutes, stir at 35 rpm for 15 minutes, and then settle for 30 minutes.

[0018] Furthermore, the addition amount of the quaternary phosphine modified tannin-based organic flocculant is 2-20 mg / L algae liquid.

[0019] The beneficial effects of the present invention are: The present invention uses natural tannic acid as a raw material and prepares an organic flocculant with high-efficiency flocculation performance, environmental friendliness and structural stability through a radiation grafting method. Traditional quaternary phosphonium salt modification methods mostly use a chemical initiation reaction system, which has problems such as low grafting rate, poor product stability, and inability to initiate at room temperature. The radiation grafting method proposed in the present invention combines the advantages of chemical grafting and free radical polymerization to achieve high-density grafting of quaternary phosphonium groups and controlled extension of molecular chains, and the product has both high charge density and high molecular weight characteristics.

[0020] The present invention adopts a gradient illumination strategy to more accurately control the reaction. High ultraviolet irradiance is used to increase the grafting rate of organic monomers, and low ultraviolet irradiation avoids the production of by-products and promotes chain growth reactions. Compared with some traditional chemical synthesis methods, the irradiation grafting method has potential advantages such as relatively mild reaction conditions and environmental friendliness.

[0021] With natural tannic acid as the skeleton, the degradation products are non-toxic and harmless, overcoming the secondary pollution risk of traditional synthetic flocculants (such as polyacrylamide); the products have cationic flocculation, heavy metal chelation (through phenolic hydroxyl groups and quaternary phosphine groups) and antibacterial properties (the antibacterial properties of quaternary phosphonium salts), and the raw materials are cheap and easy to obtain (tannic acid and quaternary phosphonium salts are both commercially available products); the reaction conditions are mild (normal pressure, medium and low temperature), and the equipment requirements are low; the process flow is simple, no complicated post-processing is required, and it is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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.

[0023] Figure 1 In a specific embodiment, OD 680 Standard curve for measuring the density of Microcystis aeruginosa.

[0024] Figure 2 It is the molecular weight distribution diagram of quaternary phosphine modified tannin based organic flocculant.

[0025] Figure 3 This is a transmission electron micrograph of a quaternary phosphine-modified tannin-based organic flocculant.

[0026] Figure 4 This is the removal rate curve of algae cells at different dosages of quaternary phosphine-modified tannin-based organic flocculants.

[0027] Figure 5 This is a scanning electron microscope image of the algae solution before and after the addition of the quaternary phosphine-modified tannin-based organic flocculant.

[0028] Figure 6 This is the removal rate curve of soluble organic matter at different dosages of quaternary phosphine-modified tannin-based organic flocculants.

[0029] Figure 7 This is a comparison chart of the removal effects of total organic carbon and total organic nitrogen in algae liquid before and after the addition of quaternary phosphine-modified tannin-based organic flocculant. DETAILED DESCRIPTION

[0030] 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.

[0031] A method for preparing a quaternary phosphine-modified tannin-based organic flocculant by radiation grafting comprises the following steps: (1) 30-60 mW / cm 2 Adding vinyl triphenylphosphine bromide to the mixture of tannic acid and photoinitiator under ultraviolet light, reacting for a first time; (2) Adjust the UV light intensity to 5-20 mW / cm 2 , react the second time; (3) Turn off the UV light and react for the third time; (4) precipitating the product with ethanol, filtering and washing to obtain a quaternary phosphine-modified tannin-based organic flocculant; Wherein, the photoinitiator is selected from one of benzophenone and benzoin dimethyl ether; The first time, the second time and the third time are respectively 10 minutes to 2 hours.

[0032] Through high irradiance (30-60 mW / cm 2 ) quickly initiates the free radical grafting reaction and increases the grafting rate of quaternary phosphine groups; switching to low irradiance (5-20 mW / cm 2 ) after the self-polymerization side reaction of the monomer is inhibited, while allowing the molecular chain to extend to form a high molecular weight product; after turning off the ultraviolet light, the residual free radicals are used to complete the chain growth, and finally a flocculant with high charge density and strong bridging ability is formed.

[0033] As a preferred embodiment of the present invention, in step (1), the mixture of tannic acid and photoinitiator is prepared as follows: 2 g of tannic acid is dissolved in water, placed in a vacuum operation box, photoinitiator is added, and stirred evenly. Dissolving tannic acid in water and placing it in a vacuum operation box can remove impurities such as air in the system to prevent them from interfering with the reaction, ensure a pure reaction environment, facilitate the subsequent uniform mixing of photoinitiator and tannic acid, and lay a foundation for the smooth progress of the subsequent reaction.

[0034] As a preferred embodiment of the present invention, in step (1), the ratio of tannic acid to photoinitiator is 1 g: 0.01-0.5 g. Within this ratio, the photoinitiator can effectively initiate the reaction. Too little photoinitiator may not fully initiate the reaction, resulting in a low grafting rate; too much photoinitiator may induce unnecessary side reactions and affect product performance. The appropriate ratio can ensure efficient reaction and good product performance.

[0035] As a preferred embodiment of the present invention, in step (1), the ratio of vinyl triphenylphosphine bromide to tannic acid is 0.5-3 mol:1 mol. At this ratio, it can be ensured that there is a sufficient amount of vinyl triphenylphosphine bromide to undergo grafting reaction with tannic acid to form a product with a suitable quaternary phosphine group density. If the ratio is too low, the quaternary phosphine groups grafted onto tannic acid are small, affecting the flocculation and other properties of the product; if the ratio is too high, it may cause a waste of raw materials, excessive monomer residues, or cause the product structure to be too complex, affecting its performance stability.

[0036] As a preferred embodiment of the present invention, a preferred embodiment of the method for preparing a quaternary phosphine-modified tannin-based organic flocculant by radiation grafting comprises the following steps: Dissolve 2 g of tannic acid in water, place in a vacuum operating box, add 0.06 g of benzophenone, and stir for 10 minutes; irradiate with strong ultraviolet light at 50 mW / cm 2 , add vinyl triphenylphosphine bromide, the molar ratio of vinyl triphenylphosphine bromide to tannic acid is 2:1, the reaction time is 20 minutes; adjust the ultraviolet light intensity to 10 mW / cm 2 The reaction time is 1 hour, the ultraviolet light is turned off, and the reaction is continued for 1 hour; after the reaction is completed, the product is precipitated with ethanol, filtered and washed to obtain a quaternary phosphine-modified tannin-based organic flocculant.

[0037] A quaternary phosphine-modified tannin-based organic flocculant prepared by the above method can be used to treat algae liquid, specifically to efficiently and environmentally friendly remove algae in water bodies, reduce the total organic carbon (OCD) and total organic nitrogen (OND) contents in water bodies, and the algae cells are not easily damaged during the coagulation process, and no intracellular algal toxins will be produced.

[0038] As a preferred embodiment of the present invention, the addition amount of the quaternary phosphine modified tannin-based organic flocculant is 2-20 mg / L algae liquid. Within this addition amount range, the quaternary phosphine modified tannin-based organic flocculant can effectively flocculate the algae liquid. If the addition amount is too small, the flocculation effect is not obvious, and the impurities in the algae liquid cannot be effectively removed; if the addition amount is too large, not only will the flocculant be wasted, but it may also have an adverse effect on subsequent treatment, such as increasing the treatment cost and the difficulty of subsequent treatment.

[0039] Within this addition amount range, the quaternary phosphine modified tannin-based organic flocculant can achieve efficient flocculation of algae liquid. When the addition amount is less than 2 mg / L, the problem of limited floc formation due to insufficient active sites may occur, making it difficult to effectively remove algae and suspended solids; when the addition amount of the quaternary phosphine modified tannin-based organic flocculant exceeds 20 mg / L, there is a problem of excessive addition, which not only causes a waste of resources, but also may cause redispersion due to excessive density of flocs, and increase the energy consumption of solid-liquid separation and the subsequent sludge treatment load.

[0040] As a preferred embodiment of the present invention, after the quaternary phosphine modified tannin-based organic flocculant is added to the algae liquid, it is stirred at a high speed of 200 rpm for 1.5 minutes to allow the flocculant to be quickly and evenly dispersed in the algae liquid, fully contact the algae cells and impurities, and promote the rapid flocculation reaction; it is then stirred at a lower speed of 35 rpm for 15 minutes, which helps the further growth and stability of the flocs and avoids the damage of the formed flocs caused by high-speed stirring; finally, it is precipitated for 30 minutes to fully separate the flocculated impurities from the water, thereby achieving the purpose of efficiently treating the algae liquid.

[0041] Example 1 A method for preparing a quaternary phosphine-modified tannin-based organic flocculant by radiation grafting comprises the following steps: (1) Dissolve 2 g of tannic acid in water, place in a vacuum operating box, add 0.06 g of benzophenone, and stir for 10 minutes; A gradient illumination strategy was used, first at 50 mW / cm 2 Under strong ultraviolet light, slowly add vinyl triphenylphosphine bromide to the prepared mixture of tannic acid and photoinitiator, control the amount ratio of vinyl triphenylphosphine bromide to tannic acid to be 0.5 mol:1 mol, and react for 20 minutes; (2) Adjust the UV light intensity to 10 mW / cm 2 , react for 1 hour; (3) Turn off the UV light and continue the reaction for 1 hour; (4) After the reaction is completed, the product is precipitated with ethanol, filtered and washed to obtain a quaternary phosphine-modified tannin-based organic flocculant.

[0042] According to the same preparation method, the dosage ratio of vinyl triphenylphosphine bromide to tannic acid in step (1) was adjusted to 1 mol: 1 mol, 2 mol: 1 mol or 3 mol: 1 mol, and finally four groups of different quaternary phosphine modified tannin-based organic flocculants were obtained, and their treatment effects on algae liquid were compared to determine the optimal dosage ratio of vinyl triphenylphosphine bromide to tannic acid in step (1). The specific method is as follows: The preparation concentration is 10 8After stirring at 200 rpm for 1.5 minutes, 20 mg / L of quaternary phosphine modified tannin-based organic flocculant was added to the solution of Microcystis aeruginosa, and the mixture was stirred at 200 rpm for 1.5 minutes, then at 35 rpm for 15 minutes, and then precipitated for 30 minutes. The supernatant was taken after precipitation and the OD was measured by UV spectrophotometer. 680 , through the standard curve (such as Figure 1 The algae cell concentration after treatment was calculated (as shown in Table 1), and then the removal rate was calculated; the removal efficiency of soluble organic matter in water was tested with a TOC meter. The results are shown in Table 1.

[0043] Table 1 Coagulation efficiency of flocculants at different dosage ratios of vinyl triphenylphosphine bromide and tannic acid

[0044] The results show that when the ratio of vinyl triphenylphosphine bromide to tannic acid in step (1) is 2 mol:1 mol, the coagulation effect of the quaternary phosphine modified tannin-based organic flocculant finally prepared is the best.

[0045] Example 2 On the basis of Example 1, the ratio of vinyl triphenylphosphine bromide to tannic acid in step (1) was selected to be 2 mol:1 mol, and then the type of photoinitiator used in step (1) was adjusted to prepare a quaternary phosphine-modified tannin-based organic flocculant. The specific scheme is as follows: (1) Dissolve 2 g of tannic acid in water, place in a vacuum operating box, add 0.06 g of a photoinitiator, which is selected from benzophenone or benzoin dimethyl ether, and stir for 10 minutes; A gradient illumination strategy was used, first at 50 mW / cm 2 Under strong ultraviolet light, slowly add vinyl triphenylphosphine bromide to the prepared mixture of tannic acid and photoinitiator, control the amount ratio of vinyl triphenylphosphine bromide to tannic acid to be 2 mol:1 mol, and react for 20 minutes; (2) Adjust the UV light intensity to 10 mW / cm 2 , react for 1 hour; (3) Turn off the UV light and continue the reaction for 1 hour; (4) After the reaction is completed, the product is precipitated with ethanol, filtered and washed to obtain a quaternary phosphine-modified tannin-based organic flocculant.

[0046] The treatment effects of two groups of different quaternary phosphine-modified tannin-based organic flocculants on Microcystis aeruginosa liquid were compared to determine the best photoinitiator type in step (1), and the test method was the same as in Example 1. The results are shown in Table 2 below.

[0047] Table 2 Coagulation efficiency of flocculants prepared with different photoinitiators

[0048] The results show that when benzophenone is selected as the photoinitiator in step (1), the coagulation effect of the quaternary phosphine-modified tannin-based organic flocculant finally prepared is the best.

[0049] Example 3 On the basis of Example 1 and Example 2, the ratio of brominated vinyl triphenylphosphine to tannic acid in step (1) is selected to be 2 mol:1 mol, the type of photoinitiator is benzophenone, and then the dosage of the photoinitiator in step (1) is adjusted to prepare a quaternary phosphine-modified tannin-based organic flocculant. The specific scheme is as follows: (1) Dissolve 2 g of tannic acid in water, place in a vacuum operating box, add different masses (0.02 g, 0.04 g, 0.06 g, 0.08 g, 1 g) of benzophenone, and stir for 10 minutes; A gradient illumination strategy was used, first at 50 mW / cm 2 Under strong ultraviolet light, slowly add vinyl triphenylphosphine bromide to the prepared mixture of tannic acid and photoinitiator, control the amount ratio of vinyl triphenylphosphine bromide to tannic acid to be 2 mol:1 mol, and react for 20 minutes; (2) Adjust the UV light intensity to 10 mW / cm 2 , react for 1 hour; (3) Turn off the UV light and continue the reaction for 1 hour; (4) After the reaction is completed, the product is precipitated with ethanol, filtered and washed to obtain a quaternary phosphine-modified tannin-based organic flocculant.

[0050] The treatment effects of five groups of different quaternary phosphine-modified tannin-based organic flocculants on the Microcystis aeruginosa liquid were compared to determine the optimal dosage ratio of the photoinitiator to tannic acid in step (1). The test method was the same as that in Example 1. The results are shown in Table 3 below.

[0051] Table 3 Coagulation efficiency of flocculants at different photoinitiator dosages

[0052] The results show that when the photoinitiator in step (1) is added at a ratio of 0.03 g / 1 g tannic acid, the coagulation effect of the quaternary phosphine-modified tannin-based organic flocculant prepared is the best.

[0053] Example 4 On the basis of Examples 1 to 3, the ratio of brominated vinyl triphenylphosphine to tannic acid in step (1) is selected to be 2 mol:1 mol, the type of photoinitiator is benzophenone, and the ratio of photoinitiator to tannic acid is 0.03 g:1 g. Then, the irradiation intensity of the strong ultraviolet light in step (1) is adjusted (i.e., the first irradiation intensity gradient in the gradient irradiation strategy) to prepare a quaternary phosphine modified tannin-based organic flocculant. The specific scheme is as follows: (1) Dissolve 2 g of tannic acid in water, place in a vacuum operating box, add 0.06 g of benzophenone, and stir for 10 minutes; A gradient illumination strategy was used, first at 30 mW / cm 2 , 40 mW / cm 2 , 50 mW / cm 2 or 60 mW / cm 2 Under strong ultraviolet light, slowly add vinyl triphenylphosphine bromide to the prepared mixture of tannic acid and photoinitiator, control the amount ratio of vinyl triphenylphosphine bromide to tannic acid to be 2 mol:1 mol, and react for 20 minutes; (2) Adjust the UV light intensity to 10 mW / cm 2 , react for 1 hour; (3) Turn off the UV light and continue the reaction for 1 hour; (4) After the reaction is completed, the product is precipitated with ethanol, filtered and washed to obtain a quaternary phosphine-modified tannin-based organic flocculant.

[0054] The treatment effects of four groups of different quaternary phosphine modified tannin-based organic flocculants on the Microcystis aeruginosa liquid were compared to determine the optimal irradiation intensity of step (1), and the test method was the same as that of Example 1. The results are shown in Table 4 below.

[0055] Table 4 Coagulation efficiency of flocculants under different first irradiation intensity gradients

[0056] The results show that the irradiation intensity of the strong ultraviolet light in step (1) is 50 mW / cm 2 When , the coagulation effect of the quaternary phosphine modified tannin based organic flocculant finally prepared is the best.

[0057] Example 5 On the basis of Examples 1 to 4, the ratio of vinyl triphenylphosphine bromide to tannic acid in step (1) is selected to be 2 mol:1 mol, the type of photoinitiator is benzophenone, the ratio of photoinitiator to tannic acid is 0.03 g:1 g, and the irradiation intensity of strong ultraviolet light is 50 mW / cm 2Then, the irradiation intensity of the weak ultraviolet light in step (2) is adjusted (i.e., the second irradiation intensity gradient in the gradient illumination strategy) to prepare a quaternary phosphine-modified tannin-based organic flocculant. The specific scheme is as follows: (1) Dissolve 2 g of tannic acid in water, place in a vacuum operating box, add 0.06 g of benzophenone, and stir for 10 minutes; A gradient illumination strategy was used, first at 50 mW / cm 2 Under strong ultraviolet light, slowly add vinyl triphenylphosphine bromide to the prepared mixture of tannic acid and photoinitiator, control the amount ratio of vinyl triphenylphosphine bromide to tannic acid to be 2 mol:1 mol, and react for 20 minutes; (2) Adjust the UV light intensity to 5 mW / cm 2 , 10 mW / cm 2 , 15 mW / cm 2 or 20 mW / cm 2 , react for 1 hour; (3) Turn off the UV light and continue the reaction for 1 hour; (4) After the reaction is completed, the product is precipitated with ethanol, filtered and washed to obtain a quaternary phosphine-modified tannin-based organic flocculant.

[0058] The treatment effects of four groups of different quaternary phosphine modified tannin-based organic flocculants on the Microcystis aeruginosa liquid were compared to determine the optimal irradiation intensity of step (1), and the test method was the same as that of Example 1. The results are shown in Table 5 below.

[0059] Table 5 Coagulation efficiency of flocculants under different second irradiation intensity gradients

[0060] The results show that the irradiation intensity of weak ultraviolet light in step (2) is 10 mW / cm 2 When , the coagulation effect of the quaternary phosphine modified tannin based organic flocculant finally prepared is the best.

[0061] Example 6 Based on Examples 1 to 5, the best method for preparing quaternary phosphine-modified tannin-based organic flocculant by radiation grafting is as follows: Dissolve 2 g of tannic acid in water, place in a vacuum operating box, add 0.06 g of benzophenone, and stir for 10 minutes; irradiate with strong ultraviolet light at 50 mW / cm 2 , add vinyl triphenylphosphine bromide, the molar ratio of vinyl triphenylphosphine bromide to tannic acid is 2:1, the reaction time is 20 minutes; adjust the ultraviolet light intensity to 10 mW / cm 2The reaction time is 1 hour, the ultraviolet light is turned off, and the reaction is continued for 1 hour; after the reaction is completed, the product is precipitated with ethanol, filtered and washed to obtain a quaternary phosphine-modified tannin-based organic flocculant.

[0062] The molecular weight of the prepared quaternary phosphine modified tannin based organic flocculant was determined by gel chromatography, such as Figure 2 As shown in the figure, the molecular weight of the quaternary phosphine modified tannin-based organic flocculant is significantly increased. By area calculation, the average molecular weight of the quaternary phosphine modified tannin-based organic flocculant is 2.98×10 6 g / mol, as a high molecular polymer, it can provide a stronger adsorption bridging effect through its high molecular structure to adsorb and capture pollution.

[0063] Since the flocculant has good water solubility, it can rely on its polymer structure to interact with pollutants to destabilize and precipitate them. Therefore, the morphology of the quaternary phosphinated modified tannin-based organic flocculant prepared in this example in water was observed under a transmission electron microscope. Figure 3 As shown, the quaternary phosphine-modified tannin-based organic flocculant is in a highly branched state, and its polymer side chains are extended in water without entanglement and aggregation. Therefore, it can provide more active sites to adsorb pollutants and avoid the adverse effects of steric hindrance effects.

[0064] The effect of the dosage of quaternary phosphine modified tannin-based organic flocculant on the treatment of Microcystis aeruginosa algae liquid was studied. The specific method is as follows: Preparation 10 8 cell / mL of Microcystis aeruginosa liquid was stirred at 200 rpm for 1.5 minutes, then 2-20 mg / L of quaternary phosphine-modified tannin-based organic flocculant was added, stirred at 200 rpm for 1.5 minutes, then stirred at 35 rpm for 15 minutes, and then precipitated for 30 minutes. After precipitation, the supernatant was taken and the OD was measured by UV spectrophotometer. 680 The algae cell concentration after treatment was calculated by the standard curve, and then the removal rate was calculated; the TOC meter was used to detect the removal efficiency of soluble organic matter in water; and the size exclusion chromatography-mass spectrometry technology was used to determine the removal efficiency of quaternary phosphine-modified tannin organic flocculant for different types of organic matter.

[0065] The experimental results show that quaternary phosphine modified tannin organic flocculant can effectively remove algal cells and maintain the integrity of algal cells during the coagulation process. Figure 4 Figure 3 is the removal rate curve of algae cells with the change of dosage. When the dosage of quaternary phosphine modified tannin organic flocculant is 20 mg / L, the removal rate of algae cells is the highest.

[0066] Figure 5(a) is a scanning electron microscope image of the Microcystis aeruginosa liquid before coagulation, and (b) is a scanning electron microscope image of the flocs formed after coagulation with the addition of quaternary phosphine-modified tannin organic flocculant. Comparing the two images, it can be seen that the coagulant is wrapped around the outside of the algae cells, which can completely capture and flocculate the algae cells. After coagulation, the algae cells are basically intact, thus avoiding the release of a large amount of intracellular organic matter, especially algal toxins.

[0067] Figure 6 This is the removal rate curve of soluble organic matter (DOC) with the change of dosage. When the dosage of seasonal phosphine modified tannin organic flocculant exceeds 14 mg / L, the removal rate of soluble organic matter can reach more than 50%.

[0068] Figure 7 The figure shows the removal effect of quaternary phosphine modified tannin organic flocculant on total organic carbon (OCD) and total organic nitrogen (OND). The green line shows the test result of Microcystis aeruginosa solution before coagulation, and the yellow line shows the test result after coagulation with quaternary phosphine modified tannin organic flocculant. The results show that quaternary phosphine modified tannin organic flocculant can effectively remove OCD and OND in water. Calculated by peak area integration method, the removal rate of OCD and OND by quaternary phosphine modified tannin organic flocculant can reach 81% and 74% respectively.

[0069] Comparative Example 1 Comparative Example 1 provides a method for treating a Microcystis aeruginosa liquid using tannic acid alone, specifically, adding tannic acid directly to 10 8 cell / mL of Microcystis aeruginosa liquid was stirred at 200 rpm for 1.5 minutes, then at 35 rpm for 15 minutes, and then precipitated for 30 minutes. After precipitation, the supernatant was taken, and the algal cell removal rate was calculated to be 27.3%, and the soluble organic matter removal rate was 7.6%.

[0070] Comparative Example 2 Comparative Example 2 provides a method for treating a Microcystis aeruginosa algae liquid with a quaternary phosphated modified tannin organic polymer flocculant prepared by a traditional free radical-initiated graft copolymerization method, specifically, dissolving 2 g of tannic acid in pure water, adjusting the solution pH to 7.5, placing the solution in a water bath at 70°C for heating, passing high-purity nitrogen for 30 minutes, maintaining continuous stirring at 250 rpm, then adding 0.05 g of potassium persulfate initiator, reacting for 15 minutes, then adding tetrabutyl phosphonium bromide solution dropwise, the molar ratio of tetrabutyl phosphonium bromide to tannic acid is 3 mol / 1 mol, reacting for 4 hours, after the reaction is completed, cooling to room temperature, precipitating in acetone, washing with ethanol, and finally washing with deionized water, and freeze-drying the precipitate to obtain the quaternary phosphated modified tannin organic polymer flocculant of Comparative Example 2. According to the addition amount of 20 mg / L, the quaternary phosphated modified tannin organic polymer flocculant is directly added to 108 cell / mL of Microcystis aeruginosa liquid was stirred at 200 rpm for 1.5 minutes, then at 35 rpm for 15 minutes, and then precipitated for 30 minutes. After precipitation, the supernatant was taken, and the algal cell removal rate was calculated to be 78.6%, and the soluble organic matter removal rate was 21.8%.

[0071] 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 quaternary phosphine-modified tannin-based organic flocculant by irradiation grafting, characterized in that: The steps include: (1) 30-60 mW / cm 2 Under ultraviolet light, adding vinyl triphenylphosphine bromide to the mixture of tannic acid and photoinitiator to react; (2) Adjust the UV light intensity to 5-20 mW / cm 2 reaction; (3) Turn off the UV light reaction; (4) precipitating the product with ethanol, filtering and washing to obtain a quaternary phosphine-modified tannin-based organic flocculant; Wherein, the photoinitiator is selected from one of benzophenone and benzoin dimethyl ether.

2. The method for preparing a quaternary phosphine-modified tannin-based organic flocculant by irradiation grafting according to claim 1, characterized in that: In step (1), a mixture of tannic acid and a photoinitiator is prepared as follows: Dissolve 2 g of tannic acid in water, place in a vacuum operating box, add photoinitiator, and stir evenly.

3. The method for preparing a quaternary phosphine-modified tannin-based organic flocculant by radiation grafting according to claim 1, characterized in that: In step (1), the ratio of photoinitiator to tannic acid is 0.01-0.5 g:1 g.

4. The method for preparing a quaternary phosphine-modified tannin-based organic flocculant by radiation grafting according to claim 1, characterized in that: In step (1), the ratio of vinyl triphenylphosphine bromide to tannic acid is 0.5-3 mol:1 mol.

5. The method for preparing a quaternary phosphine-modified tannin-based organic flocculant by radiation grafting according to claim 1, characterized in that: The reaction time in step (1), step (2) and step (3) is 10 minutes to 2 hours respectively.

6. A method for preparing a quaternary phosphine-modified tannin-based organic flocculant by irradiation grafting, characterized in that: The steps include: Dissolve 2 g of tannic acid in water, place in a vacuum operating box, add 0.06 g of benzophenone, and stir for 10 minutes; irradiate with strong ultraviolet light at 50 mW / cm 2 , add vinyl triphenylphosphine bromide, the molar ratio of vinyl triphenylphosphine bromide to tannic acid is 2:1, the reaction time is 20 minutes; adjust the ultraviolet light intensity to 10 mW / cm 2 The reaction time is 1 hour, the ultraviolet light is turned off, and the reaction is continued for 1 hour; after the reaction is completed, the product is precipitated with ethanol, filtered and washed to obtain a quaternary phosphine-modified tannin-based organic flocculant.

7. A quaternary phosphine modified tannin-based organic flocculant, characterized in that: The flocculant is prepared by the method for preparing a quaternary phosphinated modified tannin-based organic flocculant by irradiation grafting as described in any one of claims 1 to 6.

8. Use of the quaternary phosphine-modified tannin-based organic flocculant as claimed in claim 7 in treating algae liquid.

9. The use according to claim 8, characterized in that The application method is to add the quaternary phosphine modified tannin-based organic flocculant into the algae liquid, stir at 200 rpm for 1.5 minutes, stir at 35 rpm for 15 minutes, and then settle for 30 minutes.

10. The use according to claim 9, characterized in that The addition amount of the quaternary phosphine modified tannin-based organic flocculant is 2-20 mg / L algae liquid.

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