Fluorescent permeation wastewater treatment agent and preparation method thereof

Abstract

The invention relates to the technical field of industrial wastewater treatment, and discloses a fluorescent permeation wastewater treatment agent and a preparation method thereof.The agent is composed of a capture assembly agent and a delayed cross-linking agent which are independently subpackaged, and the use volume ratio is 1: 0.3-1: 0.7. Wherein the capture assembly agent is an acetic acid aqueous solution containing chitosan and tannic acid; the retardation cross-linking agent is an aqueous solution containing zirconium salt and citric acid, and the molar ratio of zirconium ions to citric acid is 1: 0.3-1: 0.6. The preparation method comprises the following steps: step-by-step dissolution and assembly of chitosan and tannic acid, and pre-complexation reaction of zircon salt and citric acid. Through the coordination competitive hysteresis effect of citric acid, the surface precipitation rate is delayed, premature closing of the floc surface is avoided, zirconium ions are promoted to diffuse into aggregates, a deep compact network is constructed, the water content of sludge is remarkably reduced, and the problem of standing color reversion caused by untight wrapping after fluorescent permeation wastewater treatment is effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial wastewater treatment, in particular to a fluorescent permeation wastewater treatment agent and a preparation method thereof. BACKGROUND

[0002] The fluorescent permeation detection process is widely used in the fields of aerospace and precision manufacturing. The wastewater generated by the process contains high concentrations of fluorescent dyes, surfactants and emulsified oils, and has the characteristics of high chemical stability, severe emulsification and high colority. Currently, chemical coagulation is commonly used in industry to treat such wastewater. Inorganic salt coagulants or organic polymer flocculants are added to separate pollutants from water bodies through electro-neutralization and adsorption bridging.

[0003] However, the floc structure formed by the existing conventional coagulants is usually loose and hydrophilic. Since its removal of small molecule fluorescent dyes mainly depends on physical adsorption or physical wrapping, the binding force is weak, and the wrapped dyes are easily desorbed and diffuse into the water phase during standing and settling or subsequent filtration, resulting in color return in the supernatant after treatment, and the effluent quality is difficult to stabilize and meet the standards. At the same time, the loose floc structure binds a large amount of free water, resulting in high water content in the final sludge, increasing the load of subsequent solid-liquid separation and hazardous waste disposal.

[0004] In recent years, the technology of constructing metal-organic coordination networks using biomass materials (such as chitosan, tannic acid) and metal ions has been tried in the field of water treatment. However, the coordination affinity between polyphenol hydroxyl groups and high-valence metal ions (such as zirconium ions) is strong, and the reaction rate is fast. In actual mixing process, the two can easily form a dense precipitate on the surface of the aggregate instantaneously, hindering the diffusion of metal ions into the interior of the aggregate. This rapid surface sealing effect leads to uneven density inside and outside the cross-linked network formed, making it difficult to form a compact overall structure, and unable to effectively reduce the water content of the sludge. In addition, the complex reagent containing high-activity coordination groups is prone to oxidation and deterioration or spontaneous gelation during storage, limiting its practical engineering application. SUMMARY

[0005] The technical problem solved by the present application is that when treating fluorescent permeation wastewater, the existing technology causes loose floc structure, loose pollutant wrapping and standing color return due to fast reaction kinetics.

[0006] To solve the above problems, the present application provides the following technical solutions: In a first aspect, the present application provides a fluorescent permeation wastewater treatment agent, which adopts the following technical solutions: A fluorescent permeation wastewater treatment agent includes separately packaged trapping and assembling agents and a delayed crosslinking agent, wherein the volume ratio of the trapping and assembling agent to the delayed crosslinking agent is 1:0.3 to 1:0.7 during use. The trapping and assembling agent is an aqueous solution of acetic acid containing chitosan and tannic acid, wherein, based on the total volume of the trapping and assembling agent, the volume concentration of acetic acid is 1.0% to 3.0%, the content of chitosan is 10 g / L to 20 g / L, and the content of tannic acid is 50 g / L to 100 g / L. The delayed crosslinking agent is an aqueous solution containing zirconium salt and citric acid, wherein the molar concentration of zirconium ions in the delayed crosslinking agent is 0.1 mol / L to 0.5 mol / L, and the molar ratio of zirconium ions to citric acid is 1:0.3 to 1:0.6.

[0007] By adopting the above technical solution, this invention utilizes a coordination competition retardation mechanism to achieve deep removal and solidification of pollutants. The specific mechanism and effects are as follows: Assembly and Capture: The tannic acid in the capture assembling agent is rich in phenolic hydroxyl groups and aromatic ring structures, while chitosan segments provide a positively charged backbone. Together, they work synergistically to adsorb fluorescent dyes and surfactant molecules from wastewater through hydrogen bonding, electrostatic attraction, and π-π stacking effects, forming micellar aggregates containing pollutants in the aqueous phase.

[0008] Kinetic hysteresis regulation: Citric acid, pre-selected in the hysteresis crosslinking agent, acts as a competing ligand, forming a metastable complex with zirconium ions. This complex occupies some coordination sites of the zirconium ions, reducing the rate of direct hydrolysis or instantaneous precipitation reaction with tannic acid. This hysteresis effect prevents the formation of a dense barrier layer on the micelle surface upon instantaneous mixing of the two agents, providing time for the internal diffusion of metal ions.

[0009] Deep cross-linking and solidification: During the mixing reaction, zirconium ions undergo slow ligand exchange driven by the stronger coordination ability of tannic acid. Zirconium ions are gradually released from the citric acid complex and enter the micelles, forming high-strength coordination bonds with the tannic acid backbone. This process drives micelle contraction, constructing a dense metal-organic coordination polymer network that immobilizes pollutants within this network structure, reducing sludge moisture content and improving precipitate stability.

[0010] Preferably, the volume ratio of the capturing assembly agent to the delayed crosslinking agent is 1:0.5; based on the total volume of the capturing assembly agent, the volume concentration of acetic acid is 2.0%, the content of chitosan is 15 g / L, and the content of tannic acid is 75 g / L; in the delayed crosslinking agent, the molar concentration of zirconium ions is 0.3 mol / L, and the molar ratio of zirconium ions to citric acid is 1:0.45.

[0011] By employing the above technical solution, controlling the molar ratio of zirconium ions to citric acid at 1:0.45, and combining it with a reagent volume ratio of 1:0.5, a better reaction kinetic equilibrium can be achieved. If the proportion of citric acid is too low, the retardation effect is insufficient, easily leading to rapid surface sealing; if the proportion of citric acid is too high, the zirconium-citric acid complex is too stable, hindering the ligand replacement reaction and preventing the formation of the network structure. This optimized ratio is beneficial for improving fluorescence removal rate and reducing sludge moisture content.

[0012] Preferably, the degree of deacetylation of the chitosan is ≥85%, the tannic acid is gallnut tannin, and the zirconium salt is zirconium oxychloride octahydrate.

[0013] By adopting the above technical solutions, chitosan with a high degree of deacetylation provides more amino sites, which enhances its solubility and positive charge density in acetic acid solution and is conducive to micelle formation; gallnut tannin has a specific polyphenol hydroxyl structure and a high degree of coordination configuration matching with zirconium ions, which is conducive to the formation of a dense cross-linked network.

[0014] Secondly, this invention provides a method for preparing a fluorescent permeation wastewater treatment agent, employing the following technical solution: A method for preparing a fluorescent permeation wastewater treatment agent includes the following steps: S1. Mix glacial acetic acid with water to prepare an acetic acid aqueous solution. Add chitosan to the acetic acid aqueous solution and stir until dissolved to obtain a chitosan precursor solution. S2. Add tannic acid to the chitosan precursor solution obtained in step S1 and stir until dissolved to obtain the capturing assembly agent. S3. Dissolve zirconium salt in water to prepare zirconium salt mother liquor, add citric acid to zirconium salt mother liquor, stir to carry out pre-complexation reaction, and obtain delayed crosslinking agent; S4. The capturing assembly agent obtained in step S2 and the delayed crosslinking agent obtained in step S3 are stored separately to obtain the fluorescent permeation wastewater treatment agent.

[0015] By adopting the above technical solution, this invention establishes a stepwise controlled preparation process, ensuring the functional activity and reaction sequence of each component. The specific mechanism and effects are as follows: Component dissolution and molecular chain extension: Steps S1 and S2 employ a stepwise dissolution method to prepare the capturing assembly. First, protonation is used in an acidic environment to promote the extension of chitosan molecular chains, exposing amino sites. Subsequently, tannic acid is introduced, allowing both to form a precursor solution in a homogeneous system through hydrogen bonding. This preparation sequence avoids local aggregation caused by competitive dissolution of components, ensuring the uniformity of the capturing assembly.

[0016] Metal center pre-complexation regulation: Step S3 is the key step in constructing the hysteresis effect. By pre-mixing zirconium salt and citric acid in a pure water system and controlling the stirring conditions, the highly coordinating citrate ion preferentially occupies some of the coordination orbitals of the zirconium ion, forming a stable "zirconium-citric acid" pre-complexation precursor. This step changes the state of the zirconium ion, transforming it from a highly reactive free ion into a metastable complex ion, providing a chemical basis for the kinetic hysteresis in the subsequent wastewater treatment process.

[0017] Two-component independent system: Step S4 establishes an independent storage strategy. Because the tannic acid in the capturing assembly agent and the zirconium ions in the delayed crosslinking agent are highly reactive, a crosslinking reaction occurs upon contact. Independent storage blocks the chemical reaction of the reagent in its non-working state, ensuring the storage stability of the reagent and ensuring that the crosslinking reaction only occurs after addition to the wastewater system.

[0018] Preferably, in step S1, stirring continues until the chitosan precursor liquid is completely dissolved and free of particles, appearing clear and transparent; the stirring speed is 300 rpm to 500 rpm, and the stirring time is 40 minutes to 60 minutes. In step S2, stirring continues until the capturing assembly agent becomes reddish-brown and transparent, and the stirring time is 20 minutes to 30 minutes.

[0019] By employing the above technical solution and controlling the dissolution state and stirring parameters, it is ensured that the chitosan molecular chains are completely dispersed in the acetic acid solution, preventing microparticles caused by uneven dissolution from affecting the subsequent loading of tannic acid. The reddish-brown transparent endpoint indicator ensures that tannic acid has not undergone oxidative self-polymerization or precipitation.

[0020] Preferably, in step S3, the zirconium salt is zirconium oxychloride octahydrate, and the citric acid is citric acid monohydrate; the stirring speed of the pre-complexation reaction is 250 rpm to 300 rpm, and the stirring time of the pre-complexation reaction is 15 minutes to 20 minutes.

[0021] By adopting the above technical solution, the solubility and hydrolysis behavior of zirconium oxychloride octahydrate in water can be controlled. A pre-complexation time of 15 to 20 minutes is sufficient for citric acid and zirconium ions to reach coordination equilibrium and form a homogeneous pre-complexed system; the rotation speed is controlled at 250 rpm to 300 rpm to ensure the uniformity of mixing and avoid the introduction of air bubbles due to excessive shear force.

[0022] Preferably, the water used in steps S1 and S3 is deionized water, and steps S1 to S3 are all carried out at room temperature.

[0023] By adopting the above technical solution, the use of deionized water eliminates the interference of impurity ions in the water on the coordination reaction. Room temperature preparation conditions avoid the thermal oxidation of tannic acid and the degradation of chitosan that may occur at high temperatures, thus reducing production energy consumption.

[0024] This invention provides a fluorescent permeation wastewater treatment agent and its preparation method. It has the following beneficial effects: 1. This invention effectively regulates the reaction kinetics between zirconium ions and tannic acid by introducing a specific molar ratio of citric acid as a competing ligand into the delayed crosslinking agent. The pre-complexation effect of citric acid on zirconium ions delays the precipitation rate at the moment of reagent mixing, preventing premature closure of the floc surface and allowing zirconium ions to diffuse into the interior of the micelle aggregates for deep crosslinking. This uniform and dense crosslinking structure significantly reduces the volume index of the flocs, resulting in a compact precipitate structure and thus reducing the final sludge moisture content, which is beneficial for subsequent solid-liquid separation treatment.

[0025] 2. This invention utilizes the synergistic assembly effect of chitosan and tannic acid to adsorb and capture fluorescent dyes and surfactants in wastewater, forming stable primary aggregates. Combined with the coordination and cross-linking effect of zirconium ions, a highly stable metal-organic network is constructed inside the aggregates. This network structure restricts the desorption and diffusion of small molecule pollutants, effectively solving the problem of color reversion after standing due to the weak physical encapsulation of pollutants after traditional flocculant treatment, and ensuring the long-term stability of the effluent quality.

[0026] 3. This invention employs a two-component independent packaging system, combined with a stepwise dissolution and pre-complexation preparation process, which solves the problem of storage stability after mixing highly active components. It captures the polyphenolic component in the assembly agent and the metal component in the retardant crosslinking agent to be physically isolated during storage, avoiding spontaneous gelation or oxidative failure in non-working states. At the same time, the pre-complexation process ensures the reproducibility of the retardation effect and guarantees the uniformity of the treatment effect of the agent in practical applications. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments and comparative examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Experimental materials: The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0029] Tannic acid, CAS No.: 1401-55-4, is extracted from gallnut (gall tannin), with a weight-average molecular weight of 1500 to 1700 Da and a tannin content of ≥95%.

[0030] Chitosan, CAS No.: 9012-76-4, degree of deacetylation ≥85%, viscosity of 1% acetic acid aqueous solution at 20℃ is 20 to 100 mPa·s.

[0031] Zirconium oxychloride octahydrate, CAS No.: 13520-92-8 Citric acid monohydrate, CAS No.: 5949-29-1.

[0032] All other experimental water, common acid-base adjusters, and reagents used to prepare simulated pollutants were commercially available analytical grade products.

[0033] In the application of this invention, the recommended volume ratio of the capturing assembly agent to the delayed crosslinking agent is 1:0.3 to 1:0.7, with the optimal volume ratio being 1:0.5. In practical applications, this ratio can be finely adjusted within this range according to the degree of wastewater pollution.

[0034] Example 1: This example provides a method for preparing a fluorescent permeation wastewater treatment agent, including the following steps: Measure out glacial acetic acid and add it to deionized water, mix well to prepare an acetic acid aqueous solution with a volume concentration of 1.0%; Chitosan was added to an aqueous acetic acid solution at a dosage of 10 g / L and magnetically stirred at 300 rpm for 40 minutes at room temperature until it was completely dissolved and free of particles, resulting in a clear and transparent chitosan precursor solution. Add tannic acid at a dosage of 50 g / L to the chitosan precursor solution and continue stirring for 20 minutes until completely dissolved to obtain a reddish-brown transparent capturing assembly agent. Take another deionized water and dissolve zirconium oxychloride octahydrate in it to prepare a zirconium salt mother liquor with a zirconium ion molar concentration of 0.1 mol / L; Citric acid monohydrate was added to the zirconium salt mother liquor at a molar ratio of zirconium ions to citric acid of 1:0.3. The mixture was stirred at 250 rpm for 15 minutes at room temperature to allow the ligand to fully pre-complex with the metal center, resulting in a colorless and transparent delayed crosslinking agent. The capturing assembly agent and the delayed crosslinking agent are packaged and stored separately to obtain the fluorescent permeation wastewater treatment agent.

[0035] Example 2: This example provides a method for preparing a fluorescent permeation wastewater treatment agent, including the following steps: Measure out glacial acetic acid and add it to deionized water, mix well to prepare an acetic acid aqueous solution with a volume concentration of 2.0%; Chitosan was added to an aqueous acetic acid solution at a dosage of 15 g / L and magnetically stirred at 400 rpm for 50 minutes at room temperature until it was completely dissolved and free of particles, resulting in a clear and transparent chitosan precursor solution. Add tannic acid at a dosage of 75 g / L to the chitosan precursor solution and continue stirring for 25 minutes until completely dissolved to obtain a reddish-brown transparent capturing assembly agent. Take another deionized water and dissolve zirconium oxychloride octahydrate in it to prepare a zirconium salt mother liquor with a zirconium ion molar concentration of 0.3 mol / L; Citric acid monohydrate was added to the zirconium salt mother liquor at a molar ratio of zirconium ions to citric acid of 1:0.45. The mixture was stirred at 250 rpm for 18 minutes at room temperature to allow the ligand to fully pre-complex with the metal center, resulting in a colorless and transparent delayed crosslinking agent. The capturing assembly agent and the delayed crosslinking agent are packaged and stored separately to obtain the fluorescent permeation wastewater treatment agent.

[0036] Example 3: This example provides a method for preparing a fluorescent permeation wastewater treatment agent, including the following steps: Measure out glacial acetic acid and add it to deionized water, mix well to prepare an acetic acid aqueous solution with a volume concentration of 3.0%; Chitosan was added to an aqueous acetic acid solution at a dosage of 20 g / L and magnetically stirred at 500 rpm for 60 minutes at room temperature until it was completely dissolved and free of particles, resulting in a clear and transparent chitosan precursor solution. Add tannic acid at a dosage of 100 g / L to the chitosan precursor solution and continue stirring for 30 minutes until completely dissolved to obtain a reddish-brown transparent capturing assembly agent. Take another deionized water and dissolve zirconium oxychloride octahydrate in it to prepare a zirconium salt mother liquor with a zirconium ion molar concentration of 0.5 mol / L; Citric acid monohydrate was added to the zirconium salt mother liquor at a molar ratio of zirconium ions to citric acid of 1:0.6. The mixture was stirred at 300 rpm for 20 minutes at room temperature to allow the ligand to fully pre-complex with the metal center, resulting in a slightly yellow and transparent delayed crosslinking agent. The capturing assembly agent and the delayed crosslinking agent are packaged and stored separately to obtain the fluorescent permeation wastewater treatment agent.

[0037] Comparative Example 1: Compared with Example 2, the difference is that when preparing the delayed crosslinking agent, citric acid monohydrate was not added, and zirconium salt mother liquor with a zirconium ion molar concentration of 0.3 mol / L was directly used as the delayed crosslinking agent. All other aspects are the same.

[0038] Comparative Example 2: Compared with Example 2, the difference is that when preparing the delayed crosslinking agent, the amount of citric acid monohydrate added was adjusted so that the molar ratio of zirconium ions to citric acid was 1:1.0, and all other aspects were the same.

[0039] Comparative Example 3: Compared with Example 2, the difference is that when preparing the delayed crosslinking agent, the amount of citric acid monohydrate added was adjusted so that the molar ratio of zirconium ions to citric acid was 1:0.1, and all other aspects were the same.

[0040] Comparative Example 4: Compared with Example 2, the difference is that tannic acid was not added when preparing the capturing assembly agent. Only the chitosan precursor liquid obtained by dissolving chitosan at 15 g / L in 2.0% acetic acid aqueous solution was used as the capturing assembly agent. All other aspects were the same.

[0041] Comparative Example 5: Compared with Example 2, the difference is that when preparing the delayed crosslinking agent, an equimolar amount of aluminum trichloride hexahydrate was used instead of zirconium oxychloride octahydrate, and citric acid monohydrate was not added; all other aspects were the same.

[0042] In order to objectively evaluate the treatment performance of the reagents prepared in the various embodiments and comparative examples of the present invention, the following unified performance testing method and general application process are established: The simulated fluorescent permeation wastewater was prepared by adding 10g of kerosene, 5g of octylphenol polyoxyethylene ether (OP-10), and 0.5g of rhodamine B sequentially to 10L of tap water. The mixture was emulsified using a high-speed shear emulsifier at 3000rpm for 10 minutes to produce a simulated wastewater with strong fluorescence and a milky white, turbid appearance. The initial COD value of this wastewater was approximately 2600mg / L, and it exhibited strong bright yellow fluorescence under ultraviolet light.

[0043] The standard treatment process involves taking the simulated wastewater mentioned above and performing the following standardized treatment operations: Measure 500 mL of simulated wastewater into a beaker of a six-piece stirrer, and use 1.0 mol / L sulfuric acid solution or sodium hydroxide solution to adjust the pH value of the wastewater to 4.5. Turn on the stirrer and set the speed to 300 rpm. Use a pipette to add 1.5 mL of the capture assembly agent prepared by each example or comparative example (equivalent to a dosage of 3.0 mL / L; for comparative examples 4 and 5, add the corresponding reagents in the same volume) to the wastewater and keep stirring for 2 minutes. While maintaining a constant rotation speed of 300 rpm, add 0.75 mL of the delayed crosslinking agent prepared in each example or comparative example (equivalent to a dosage of 1.5 mL / L; for comparative examples 1-5, add the corresponding reagents in equal volumes) to the wastewater and stir rapidly for 45 seconds; Reduce the stirring speed to 50 rpm and stir slowly for 10 minutes, then observe the floc growth. Stop stirring and let it stand and settle for 20 minutes; Use a syringe to extract the supernatant from 2 cm below the liquid surface for water quality index testing; filter and collect the flocculent sediment at the bottom for sludge performance testing; Performance index measurement methods: COD removal rate (%): The chemical oxygen demand (COD) of raw water and treated supernatant was determined by potassium dichromate method (GB / T11914-1989) and the removal rate was calculated.

[0044] Fluorescence removal rate (%): Using a fluorescence spectrophotometer, with the excitation wavelength set to 554 nm, the fluorescence intensity of the raw water and the treated supernatant at the emission wavelength of 580 nm was measured, and the reduction rate of fluorescence intensity was calculated.

[0045] Sludge moisture content (%): Collect the filtered wet sludge, weigh it and record it as m1, dry it in an oven at 105℃ until constant weight, weigh it and record it as m2. The formula for calculating the moisture content is (m1−m2) / m1×100%.

[0046] Transmittance (%): The transmittance of the supernatant was measured at a wavelength of 600 nm using a UV-Vis spectrophotometer with deionized water as a reference.

[0047] Experimental procedure: The capturing assembly agent and the delayed crosslinking agent prepared in Example 2 were selected as test objects. Based on the standard treatment process, two sets of comparative experiments were set up to examine the effects of pH value and agent dosage on the treatment effect.

[0048] In the first group of experiments, the dosage of the capture assembly agent was fixed at 3.0 mL / L, and the dosage of the delayed crosslinking agent was 1.5 mL / L. The initial pH of 500 mL of simulated wastewater was adjusted to 3.0, 4.0, 4.5, 5.0, 6.0, and 7.0, respectively, using sulfuric acid or sodium hydroxide solution. In the second group of experiments, the initial pH of the simulated wastewater was fixed at 4.5, the dosage of the capture assembly agent was 3.0 mL / L, and the dosage of the delayed crosslinking agent was set to 0.5 mL / L, 1.0 mL / L, 1.5 mL / L, 2.0 mL / L, and 2.5 mL / L, respectively. All samples were mixed, reacted, and allowed to settle according to the aforementioned standard process. The supernatant was then used to determine the transmittance, COD removal rate, and fluorescence removal rate, and the sludge moisture content was determined by filtration and weighing. Experimental data: Table 1. Data Record of the Influence of Different pH Values ​​and Agent B Dosage on Wastewater Treatment Indicators

[0049] (Note: The parameter settings for group B-3 are the same as those for group A-3, and the data contain normal experimental error perturbations.) Results and Conclusions: Based on the data in Table 1 and the reaction mechanism analysis, pH value has a significant regulatory effect on the coordination assembly process of the system. Data shows that COD removal rate and fluorescence removal rate peak in the pH range of 4.0 to 5.0, while sludge moisture content decreases to its lowest level. Within this pH range, the phenolic hydroxyl groups in tannic acid molecules maintain a suitable degree of deprotonation, preserving both hydrogen bond adsorption capacity and the activity of coordination exchange with zirconium ions. Zirconium ions in the delayed crosslinking agent gradually cleave into the tannic acid backbone through ligand exchange, forming a dense coordination polymer network. When the pH is below 4.0, the higher proton concentration in the solution inhibits the coordination activity of the phenolic hydroxyl groups, leading to a decrease in crosslinking density and a looser floc structure.

[0050] When the pH is above 6.0, the hydrolysis rate of zirconium ions accelerates significantly, exceeding the coordination rate. A large number of zirconium ions escape the control of citric acid and preferentially undergo hydroxyl bridging to form amorphous zirconium hydroxide precipitate clusters. These amorphous precipitates cannot form long-range ordered cross-linked networks like tannic acid-zirconium coordination bonds, resulting in a loose floc structure and increased water binding force. Simultaneously, the adsorption of organic pollutants on the hydroxide surface is weak and irreversible, leading to decreased treatment efficiency and increased sludge moisture content.

[0051] The dosage of the delayed crosslinking agent showed a stoichiometric correlation with the removal effect. At lower dosages, the system lacked sufficient metal nodes to connect tannic acid-pollutant micelles, resulting in insufficient closure of the network structure and preventing some pollutants from being precipitated and captured. As the dosage increased to 1.5 mL / L, the various indicators tended to stabilize. Further increasing the dosage did not significantly improve the removal rate; excessive zirconium salt introduced excess charge, and the resulting electrostatic repulsion effect may have hindered further densification of the flocs. Experimental results confirmed that the agent prepared in Example 2, at around pH 4.5 and a specific dosage ratio, could achieve pollutant removal and solidification through a coordination competition retardation mechanism.

[0052] Test Example 2: Experimental Steps: The reagents prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were selected as test subjects. Eight 500 mL portions of simulated fluorescent permeation wastewater, adjusted to pH 4.5, were placed in a six-unit stirrer. Examples 1 to 3 and Comparative Examples 1 to 3 all added the corresponding capture assembly agent (1.5 mL) and delayed crosslinking agent (0.75 mL) according to the standard process. Comparative Example 4 added an equal volume of chitosan acetic acid solution (excluding tannic acid) and the delayed crosslinking agent prepared in Example 2; Comparative Example 5 added the capture assembly agent prepared in Example 2 and an equimolar aluminum salt-citric acid solution. All groups underwent rapid stirring, slow stirring, and static sedimentation. After the reaction, the COD removal rate, fluorescence removal rate, and bottom sludge moisture content of the supernatant were measured. The supernatant was extracted, sealed, and allowed to stand in the dark for 24 hours. The fluorescence intensity was measured again, and the color return rate was calculated to evaluate the stability of pollutant solidification. Experimental data: Table 2. Performance comparison of the fluorescent permeation wastewater treatment in the examples and comparative examples

[0053] (Note: - indicates that it has not formed. In Comparative Example 2, the system only became turbid and did not form obvious sedimentary flocs, so the sludge moisture content and color return rate could not be effectively measured.) Results and Conclusions: Table 2 shows that the coordination competition lag system has a decisive influence on the treatment performance. All indicators of Examples 1 to 3 are superior to the comparative examples. Example 2 showed the highest fluorescence removal rate and the lowest color return rate, with a sludge moisture content of approximately 72%, indicating that the system formed a dense sedimentation structure and the pollutants were effectively fixed within the coordination polymer network.

[0054] Data from Comparative Examples 1 and 3 indicate that a lack of sufficient citric acid ligands leads to runaway reaction kinetics. Under conditions of no or insufficient ligands, the reaction rate between zirconium ions and tannic acid is too rapid, easily forming a dense layer on the micelle surface, hindering the diffusion of metal ions into the interior, resulting in incomplete cross-linking of internal pollutants. High sludge moisture content and 24-hour color return rate indicate a loose internal structure of the flocs, with some unfixed fluorescent dyes leaching out over time.

[0055] Comparative Example 2 showed that when citric acid was in excess, the zirconium-citric acid complex was too stable, hindering the displacement reaction of tannic acid and preventing the formation of a network precipitate, resulting in an extremely low removal rate. This confirms the necessity of controlling the ratio of zirconium to ligand within a specific range to balance the retardation effect and thermodynamic feasibility of the reaction.

[0056] Comparative Example 4 data shows that the absence of tannic acid significantly reduces the system's adsorption capacity for aromatic fluorescent dyes, and chitosan cannot effectively remove soluble dyes on its own. Comparative Example 5 uses aluminum salt instead of zirconium salt. Due to the lower binding strength and coordination number of the aluminum-tannic acid complex compared to the zirconium system, the resulting floc structure is loose and has weak shear resistance, leading to a decrease in removal rate and an increase in sludge moisture content.

[0057] Test column 3: The experimental procedure used reagents prepared in Example 2, Comparative Example 1, and Comparative Example 5 as test objects. Three 500 mL portions of simulated fluorescent permeation wastewater, adjusted to pH 4.5, were placed in beakers using a six-unit stirrer. The reagents were added and stirred according to the standard treatment procedure. After slow stirring, the reaction mixture was immediately transferred to a 1000 mL graduated cylinder, allowed to stand, and timed. The height of the solid-liquid separation interface was recorded at different time points (0 min, 1 min, 3 min, 5 min, 10 min, 20 min, and 30 min) during the settling process, with the initial liquid level uniformly set at 25.0 cm. After 30 minutes of settling, the supernatant was drawn from 2 cm below the liquid surface to measure the initial turbidity (NTU1). The bottom precipitate was then mixed with the supernatant, and stirred at 800 rpm for 3 minutes using a high-shear emulsifier to simulate high-intensity hydraulic shear. After shearing was stopped, the mixture was allowed to settle for another 20 minutes. A sample of the supernatant was taken from 2 cm below the surface to measure the turbidity after shearing (NTU²), and the turbidity increase (ΔNTU) was calculated. Experimental data: Table 3. Dynamic and shear stability test data of the settlement interface height

[0058] Results Analysis and Conclusions: Table 3 shows the changes in the sedimentation interface height, reflecting the floc growth kinetics of different systems. In Comparative Example 1, the interface height decreased rapidly in the first 3 minutes of the reaction, indicating that in the absence of citric acid's retardation effect, zirconium ions reacted rapidly with tannic acid upon contact, resulting in a relatively loose floc structure and a larger final sedimentation volume (interface height 6.7 cm). Example 2 exhibited a slower initial sedimentation rate, characteristic of the reaction induction period, indicating that the formation of the zirconium citrate complex reduced the reactivity of free metal ions and slowed the nucleation rate. This retardation effect allowed sufficient time for zirconium ions to diffuse into the micelles, and the subsequent sedimentation process showed orderly floc contraction, resulting in a smaller final precipitate volume (interface height 2.9 cm) and a higher packing density.

[0059] The turbidity increment data reflects the shear stability of the internal structure of the flocs. Comparative Example 1 showed a significant increase in turbidity after shearing, with an increment of 25.2 NTU, indicating that its flocs mainly relied on shallow connections or physical aggregation formed by rapid surface reactions, resulting in low structural strength and easy breakage under turbulent conditions. Example 2 showed a turbidity increment of only 2.5 NTU, indicating that through a delayed crosslinking mechanism, zirconium ions and the tannic acid framework constructed a dense coordination network deep within the micelles. This structure has high rigidity, resisting hydraulic shear damage and preventing the re-release of captured pollutants. The data for Comparative Example 5 fell between these two, suggesting that the coordination strength of aluminum salts and the lack of kinetically controlled reaction modes make it difficult to form a high-density crosslinked structure. The experimental results confirm that the kinetic delay effect produced by a specific zirconium-citric acid ratio is key to constructing a high-density, high-stability precipitation structure.

Claims

1. A fluorescent permeation wastewater treatment agent, characterized in that, It includes separately packaged trapping assemblies and delayed crosslinking agents, and the volume ratio of the trapping assemblies to the delayed crosslinking agents is 1:0.3 to 1:0.7 when in use; The capturing assembly agent is an aqueous solution of acetic acid containing chitosan and tannic acid. Based on the total volume of the capturing assembly agent, the volume concentration of acetic acid is 1.0% to 3.0%, the content of chitosan is 10 g / L to 20 g / L, and the content of tannic acid is 50 g / L to 100 g / L. The delayed crosslinking agent is an aqueous solution containing zirconium salt and citric acid. In the delayed crosslinking agent, the molar concentration of zirconium ions is 0.1 mol / L to 0.5 mol / L, and the molar ratio of zirconium ions to citric acid is 1:0.3 to 1:0.

6.

2. The fluorescent permeation wastewater treatment agent according to claim 1, characterized in that, The volume ratio of the capturing assembly agent to the delayed crosslinking agent is 1:0.5; Based on the total volume of the capturing assembly agent, the volume concentration of acetic acid is 2.0%, the content of chitosan is 15 g / L, and the content of tannic acid is 75 g / L; In the delayed crosslinking agent, the molar concentration of zirconium ions is 0.3 mol / L, and the molar ratio of zirconium ions to citric acid is 1:0.

45.

3. The fluorescent permeation wastewater treatment agent according to claim 1, characterized in that, The degree of deacetylation of the chitosan is ≥85%, the tannic acid is gallnut tannin, and the zirconium salt is zirconium oxychloride octahydrate.

4. A method for preparing a fluorescent permeation wastewater treatment agent, characterized in that, The preparation of a fluorescent permeation wastewater treatment agent according to any one of claims 1-3 includes the following steps: S1. Prepare an aqueous acetic acid solution by mixing glacial acetic acid and water, add chitosan to the aqueous acetic acid solution and stir until dissolved to obtain a chitosan precursor solution; S2. Add tannic acid to the chitosan precursor liquid obtained in step S1 and stir until dissolved to obtain the capturing assembly agent. S3. Dissolve zirconium salt in water to prepare zirconium salt mother liquor, add citric acid to the zirconium salt mother liquor, stir to carry out pre-complexation reaction, and obtain a delayed crosslinking agent; S4. The capturing assembly agent obtained in step S2 and the delayed crosslinking agent obtained in step S3 are stored separately to obtain the fluorescent permeation wastewater treatment agent.

5. The method for preparing a fluorescent permeation wastewater treatment agent according to claim 4, characterized in that, In step S1, the stirring continues until the chitosan precursor liquid is completely dissolved and free of particles, and is clear and transparent.

6. The method for preparing a fluorescent permeation wastewater treatment agent according to claim 4, characterized in that, In step S1, the stirring speed is 300 rpm to 500 rpm, and the stirring time is 40 minutes to 60 minutes.

7. The method for preparing a fluorescent permeation wastewater treatment agent according to claim 4, characterized in that, In step S2, the stirring continues until the capturing assembly agent becomes reddish-brown and transparent, and the stirring time is 20 to 30 minutes.

8. The method for preparing a fluorescent permeation wastewater treatment agent according to claim 4, characterized in that, In step S3, the zirconium salt is zirconium oxychloride octahydrate, and the citric acid is citric acid monohydrate.

9. The method for preparing a fluorescent permeation wastewater treatment agent according to claim 4, characterized in that, In step S3, the stirring speed of the pre-complexation reaction is 250 rpm to 300 rpm, and the stirring time of the pre-complexation reaction is 15 minutes to 20 minutes.

10. The method for preparing a fluorescent permeation wastewater treatment agent according to claim 4, characterized in that, The water used in steps S1 and S3 is deionized water, and steps S1 to S3 are all carried out at room temperature.

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