Deep defluorination method and system for flue gas purification acidic wastewater

Abstract

The invention relates to the field of smelting chemistry, in particular to a deep defluorination method and system for flue gas purification contaminated acid wastewater. The method comprises the following steps: acquiring a preliminary fluorine separation wastewater information set, performing electrochemical-photocatalytic synergistic complex breaking treatment, converting stable fluorine complexes in wastewater into free fluorine ions, and synchronously pre-depositing part of heavy metals to generate a to-be-treated wastewater information set taking the free fluorine ions as a dominant form; based on the to-be-treated wastewater information set, under the condition of maintaining strong acidity, acid-resistant molecularly imprinted polymer specific adsorption of fluorine ions is carried out, and a deep defluorination purification wastewater information set is generated; based on the deep defluorination purification wastewater information set, adsorbent regeneration and eluent treatment are carried out, a high-purity calcium fluoride product is converted and recovered, and a whole-process fluorine resource recovery report is generated. In the deep fluorine removal process of the waste acid wastewater, the wastewater with the fluorine content reaching the standard is discharged, and resource circulation is achieved.

Description

Technical Field

[0001] This application relates to the field of metallurgical chemistry, and in particular to a method and system for deep defluorination of flue gas purification wastewater. Background Technology

[0002] In the field of fluoride-containing wastewater treatment in high-end manufacturing, the acidic fluoride-containing wastewater generated by industries such as semiconductors, photovoltaics, and electrolytic aluminum has complex composition and poses a great environmental hazard. Its deep purification and fluoride resource recovery are directly related to the development of major industries, ecological environment safety, and resource recycling. It is one of the key links in promoting new industrialization and building "zero-waste cities".

[0003] However, existing methods for treating fluoride-containing wastewater lack a mechanism for efficiently and selectively destroying fluoride complexes that exist stably in strongly acidic environments and simultaneously regulating fluoride speciation under low pH conditions. This not only makes it difficult to achieve efficient deep removal and targeted recovery of fluoride, but also generates a large amount of hazardous sludge due to the reliance on large-scale neutralization and precipitation, resulting in secondary pollution and resource waste. Summary of the Invention

[0004] This application provides a method and system for deep defluorination of acidic wastewater through flue gas purification to solve the above-mentioned technical problems.

[0005] In a first aspect, this application provides a method for deep defluorination of acidic wastewater from flue gas purification. The method includes: acquiring a preliminary fluoride separation wastewater information set; performing electrochemical-photocatalytic synergistic complex-breaking treatment to convert stable fluoride complexes in the wastewater into free fluoride ions, and simultaneously pre-depositing some heavy metals to generate a wastewater information set to be treated with free fluoride ions as the dominant form; based on the wastewater information set to be treated, performing acid-resistant molecularly imprinted polymer-specific adsorption of fluoride ions under strongly acidic conditions to generate a deep defluorination and purification wastewater information set; and based on the deep defluorination and purification wastewater information set, performing adsorbent regeneration and eluent treatment to convert and recover high-purity calcium fluoride products, and generating a full-process fluoride resource recovery report.

[0006] Through the above technical solutions, the fluoride content of wastewater can be discharged in compliance with standards by efficiently dissociating complexed fluoride, while simultaneously removing heavy metals; fluoride resources are recovered and converted into industrial-grade calcium fluoride, achieving resource recycling; the adsorbent can be reused, reducing treatment costs; and the entire process is free of secondary pollution, providing a reliable solution for the harmless treatment and resource utilization of acidic wastewater.

[0007] Optionally, obtaining the preliminary fluoride separation wastewater information set includes: performing multi-stage gradient sedimentation treatment on the flue gas purification acid wastewater, removing suspended solids by using an acid-resistant ceramic membrane microfiltration system while maintaining the original pH of the wastewater; performing selective ion pre-enrichment treatment on the wastewater after the multi-stage gradient sedimentation treatment, passing the wastewater through a specific type of acid-resistant anion exchange resin column under pH < 1 conditions to selectively adsorb and separate fluorosilicate ions in the wastewater; and using the wastewater state and separation data after the selective ion pre-enrichment treatment as the preliminary fluoride separation wastewater information set.

[0008] Optionally, the generation of the wastewater information set dominated by free fluoride ions includes: adding the pre-fluoride separation wastewater to a three-dimensional electrode electrochemical reactor, wherein the anode is a boron-doped diamond-coated electrode, the cathode is a titanium-based mesh electrode, and activated carbon fibers loaded with titanium dioxide are added as particle electrodes and catalysts; under the synergistic effect of electric field and photocatalysis, the stable fluoride complexes in the wastewater are destroyed and converted into free fluoride ions, and at the same time, some heavy metal ions are pre-deposited; the state data of the wastewater dominated by free fluoride ions after the synergistic effect of electric field and photocatalysis is used as the wastewater information set to be treated.

[0009] Optionally, the step of destroying stable fluoride complexes in wastewater and converting them into free fluoride ions under the synergistic effect of an electric field and photocatalysis includes: applying an electric field to the boron-doped diamond-coated electrode to generate hydroxyl radicals on its surface, using the strong oxidizing properties of the hydroxyl radicals to attack and destroy the metal-fluorine coordination bonds of the stable fluoride complexes, so that the fluorine element in the destroyed complexes is released into the strongly acidic wastewater in the form of free fluoride ions.

[0010] Optionally, the simultaneous pre-deposition of some heavy metal ions includes: photo-exciting the activated carbon fiber loaded with titanium dioxide in the reactor while applying an electric field to induce a catalytic effect and enhance the complex-breaking process; applying an electric field to the titanium-based mesh electrode to induce a hydrogen evolution reaction on its surface; and utilizing the local pH increase in the cathode area caused by the hydrogen evolution reaction to convert some heavy metal ions into precipitates in this local alkaline environment, thus completing the pre-deposition.

[0011] Optionally, the generation of the deep defluoridation and purification wastewater information set includes: based on the wastewater information set to be treated, using an acid-resistant fluoride ion imprinted polymer prepolymerized under acidic conditions with fluoride ions as a template as a specific adsorbent; passing the complex-broken wastewater corresponding to the wastewater information set to be treated, with a pH value of 0.5-1.5, into an adsorption device filled with the acid-resistant fluoride ion imprinted polymer for dynamic adsorption; controlling the adsorption conditions so that the free fluoride ions in the wastewater are selectively captured, and the effluent fluoride ion concentration drops below a preset concentration threshold; and using the wastewater state data after the specific adsorption treatment as the deep defluoridation and purification wastewater information set.

[0012] Optionally, the use of an acid-resistant fluoride ion imprinted polymer, prepolymerized under acidic conditions using fluoride ions as a template, as a specific adsorbent material includes: in an acidic polymerization system, using free fluoride ions as template molecules, reacting them with functional monomers, crosslinking agents, and initiators to synthesize a polymer precursor containing template molecules; removing the template molecules from the polymer precursor through an elution step, thereby forming imprinted cavities in the polymer matrix that are specifically complementary to the free fluoride ions in terms of size, shape, and chemical action sites, to obtain the acid-resistant fluoride ion imprinted polymer; the imprinted cavities in the acid-resistant fluoride ion imprinted polymer are configured to maintain structural stability in the strongly acidic wastewater with pH < 2 and exhibit high adsorption selectivity for fluoride ions.

[0013] Optionally, the controlled adsorption conditions include: configuring the adsorption device as a fixed-bed adsorption tower comprising at least two stages connected in series; controlling the flow rate of wastewater through the fixed-bed adsorption tower to ensure sufficient contact reaction time between the wastewater and the acid-resistant fluoride-imprinted polymer; and by controlling the number of stages of the fixed-bed adsorption tower in series and the contact reaction time, under a highly acidic environment and in the presence of high concentrations of chloride and sulfate ions, ensuring that the fluoride concentration in the effluent is stably reduced to below 1.0 mg / L.

[0014] Optionally, generating the full-process fluoride resource recovery report includes: based on the deep defluorination and purification wastewater information set, using a low-concentration ammonia solution to elute and regenerate the adsorbed saturated acid-resistant fluoride ion imprinted polymer, desorbing the adsorbed fluoride ions into the eluent in the form of ammonium fluoride; rinsing the acid-resistant fluoride ion imprinted polymer after ammonia elution with a dilute sulfuric acid solution to restore it to an active form suitable for adsorption by the strongly acidic wastewater; introducing a calcium chloride solution into the eluent rich in ammonium fluoride, reacting to generate calcium fluoride precipitate, and performing solid-liquid separation, washing, and drying of the calcium fluoride precipitate to obtain a high-purity calcium fluoride product; and generating the full-process fluoride resource recovery report based on the process data and results of adsorbent regeneration, fluoride ion recovery, and product generation.

[0015] Secondly, this application provides a deep defluorination system for flue gas purification of acidic wastewater. The system includes: a preliminary treatment module for acquiring a preliminary fluoride separation wastewater information set, performing electrochemical-photocatalytic synergistic complex-breaking treatment to convert stable fluoride complexes in the wastewater into free fluoride ions, and simultaneously pre-depositing some heavy metals to generate a wastewater information set to be treated with free fluoride ions as the dominant form; a deep defluorination module for performing specific adsorption of fluoride ions by acid-resistant molecularly imprinted polymers under strongly acidic conditions based on the wastewater information set to be treated, to generate a deep defluorination purified wastewater information set; and a resource recovery module for performing adsorbent regeneration and eluent treatment based on the deep defluorination purified wastewater information set, converting and recovering high-purity calcium fluoride products, and generating a full-process fluoride resource recovery report. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram illustrating an application scenario provided in one embodiment of this application; Figure 2 A flowchart of a method for deep defluorination of acidic wastewater through flue gas purification, provided in an embodiment of this application; Figure 3 This is a schematic diagram of a flue gas purification system for deep defluorination of acidic wastewater, provided as an embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0019] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0020] The embodiments of this application will now be described in further detail with reference to the accompanying drawings.

[0021] Existing methods for treating fluoride-containing wastewater lack a mechanism for efficiently and selectively destroying fluoride complexes that exist stably in strongly acidic environments, while simultaneously regulating the fluoride speciation under low pH conditions. This not only makes it difficult to achieve efficient and targeted removal and recovery of fluoride, but also generates a large amount of hazardous sludge due to the reliance on large-scale neutralization and precipitation, resulting in secondary pollution and resource waste.

[0022] Based on this, this application provides a method and system for deep defluorination of flue gas purification acidic wastewater. First, an information set of the flue gas purification acidic wastewater after preliminary fluoride separation is obtained. Then, through electrochemical-photocatalytic synergistic complex breaking, stable fluoride complexes are dissociated into free fluoride ions, while simultaneously pre-depositing some heavy metals, forming an information set of the wastewater to be treated. Under strongly acidic conditions, acid-resistant molecularly imprinted polymers are used to specifically adsorb fluoride ions, generating a deep defluorination and purification wastewater information set. Finally, the saturated polymer is regenerated, and the eluent is treated to convert fluoride ions into high-purity calcium fluoride. The entire process data is integrated to generate a full-process fluoride resource recovery report, which is then output to factory staff. Through efficient dissociation of complexed fluoride, the fluoride content of the wastewater meets discharge standards, while simultaneously removing heavy metals; fluoride resources are recovered and converted into industrial-grade calcium fluoride, achieving resource recycling; the adsorbent can be reused, reducing treatment costs; the entire process is free of secondary pollution, providing a reliable solution for the harmless treatment and resource recovery of acidic wastewater.

[0023] Figure 1 This is a schematic diagram illustrating an application scenario provided by this application. In the process of deep defluorination of acidic wastewater, the method provided in this application achieves compliant discharge of wastewater with fluoride content, simultaneously removes heavy metals, and recovers fluoride resources by converting them into industrial-grade calcium fluoride, thus achieving resource recycling.

[0024] Specifically, the method of this application is applied to any server that communicates with the wastewater treatment control system. The server obtains a preliminary fluoride separation wastewater information set provided by the wastewater treatment control system. First, it acquires the information set of flue gas purification acidic wastewater after preliminary fluoride separation. Then, through electrochemical-photocatalytic synergistic complex breaking, stable fluoride complexes are dissociated into free fluoride ions, and some heavy metals are pre-deposited simultaneously, forming a wastewater information set to be treated. Under strongly acidic conditions, acid-resistant molecularly imprinted polymers are used to specifically adsorb fluoride ions, generating a deep fluoride removal and purification wastewater information set. Finally, the saturated polymer is regenerated, and the eluent is treated to convert fluoride ions into high-purity calcium fluoride. The entire process data is integrated to generate a full-process fluoride resource recovery report, which is then output to factory staff.

[0025] For specific implementation details, please refer to the following examples.

[0026] Figure 2The flowchart of a method for deep fluoride removal from flue gas purification waste acid wastewater provided by an embodiment of the present application. The method of this embodiment can be applied to the server in the above scenarios. As Figure 2 shown, the method includes: S201. Obtain the preliminary fluoride separation wastewater information set, perform electrochemical-photocatalytic synergistic complex-breaking treatment, convert the stable fluoride complexes in the wastewater into free fluoride ions, and synchronously pre-deposit part of the heavy metals to generate a wastewater information set to be treated dominated by free fluoride ions.

[0027] The preliminary fluoride separation wastewater information set can be the waste acid wastewater generated during the flue gas purification process after conventional preliminary fluoride separation treatment (such as simple chemical precipitation, gravity sedimentation, etc.), forming a set of key parameters including wastewater pH value, total fluoride content, fluoride complex form and content, heavy metal ion (such as lead, cadmium, arsenic, etc.) concentration, suspended solid content, etc. The data comes from the primary wastewater treatment unit supporting the flue gas purification system, and is collected and uploaded to the wastewater treatment control system in real time by the water quality monitoring equipment of this unit. The electrochemical-photocatalytic synergistic complex-breaking treatment can be the combination of electrochemical redox technology and photocatalytic degradation technology. Through the synergistic effect of the electric field and photogenerated carriers, the coordination bond structure of the stable fluoride complex is destroyed to achieve the treatment process of complex dissociation. The stable fluoride complex can be a compound with a stable structure formed by the coordination bond between fluoride ions and metal ions (such as iron, aluminum, calcium, etc.) in the waste acid wastewater and is difficult to dissociate by conventional methods (such as [FeF6]³ - 、[AlF6]³ - etc.), which is one of the core pollutants causing the fluoride content in waste acid wastewater to exceed the standard. The free fluoride ion can be the fluoride ion (F - ) released after the dissociation of the stable fluoride complex and not forming a coordination bond with other ions, which is the target pollutant for subsequent adsorption treatment. The wastewater information set to be treated can be a set of parameters including free fluoride ion concentration, remaining heavy metal concentration, wastewater pH value, redox potential, etc. after the electrochemical-photocatalytic synergistic complex-breaking treatment.

[0028] Specifically, acidic wastewater from flue gas purification is highly polluting wastewater generated during flue gas desulfurization and denitrification processes in industries such as metallurgy, chemical engineering, and waste incineration. Its composition is complex and highly corrosive, containing not only fluoride levels far exceeding emission standards but also large amounts of heavy metal ions and stable fluoride complexes. Existing conventional defluorination technologies have significant limitations: Firstly, most of the fluoride in acidic wastewater exists in the form of stable fluoride complexes. These complexes have stable structures, and conventional chemical precipitation methods (such as adding calcium salts) can only remove a small amount of free fluoride ions, resulting in extremely low removal efficiency for complexed fluoride, leading to the wastewater's fluoride content still failing to meet standards after treatment. Secondly, heavy metal ions in the wastewater compete with fluoride ions for adsorption sites and may also contaminate the adsorbents used in subsequent treatment, reducing their lifespan and defluorination efficiency. Furthermore, heavy metals themselves are significant pollutants; if not removed in advance, they will increase the difficulty of subsequent treatment and cause secondary pollution. In addition, if complexed fluoride cannot be converted into free fluoride ions, subsequent fluoride resource recovery will be impossible, resulting in a waste of valuable fluoride resources. In this step, the pre-treated fluoride-containing wastewater is pumped into an electrochemical-photocatalytic synergistic reactor. An anodic oxidation reaction is activated by applying an electric current, while a UV light source is simultaneously activated to excite the catalyst. Under the synergistic oxidation effect of electrochemistry and photocatalysis, the stable organic and inorganic fluoride complexes in the wastewater are efficiently destroyed, releasing free fluoride ions. Simultaneously, some heavy metal ions dissociated from the complexes are reduced and deposited in the cathode region or form hydroxide flocs, achieving pre-removal. This innovative electrochemical-photocatalytic synergistic technology achieves highly efficient destruction of stubborn fluoride complexes, successfully converting difficult-to-treat complexed fluoride into easily removable free fluoride, solving a key challenge in deep defluorination processes.

[0029] S202. Based on the information set of the wastewater to be treated, under the condition of maintaining strong acidity, acid-resistant molecularly imprinted polymers are used for specific adsorption of fluoride ions to generate a deep defluorination and purification wastewater information set.

[0030] Acid-resistant molecularly imprinted polymers (MIMs) are high-molecular materials with specific spatial structures and binding sites, prepared by cross-linking polymerization using fluoride ions as template molecules and acid-resistant monomers (such as methacrylic acid and vinylbenzenesulfonic acid). They possess the characteristics of stability in strongly acidic environments and high specificity in recognizing and adsorbing fluoride ions. Specific adsorption refers to the selective adsorption process in which acid-resistant MIMs preferentially recognize and adsorb fluoride ions in wastewater through specific binding sites on their surface that match the size and structure of fluoride ions, while exhibiting extremely weak adsorption capacity for other anions (such as sulfate and chloride ions). The information set for deep defluorination and purification wastewater can be a set of wastewater parameters that, after specific adsorption treatment, meet national emission standards and resource recovery requirements for fluoride content, and whose water quality parameters (such as pH value, heavy metal residue, and concentration of other anions) comply with subsequent discharge or reuse standards.

[0031] Specifically, after the first step of electrochemical-photocatalytic synergistic complex-breaking treatment, the wastewater remains in a strongly acidic environment and contains a large amount of free fluoride ions and a small amount of incompletely deposited heavy metal ions. At this point, deep removal of free fluoride ions is necessary to achieve wastewater discharge compliance. However, existing conventional adsorbents (such as activated alumina, zeolite, and ordinary ion exchange resins) have significant drawbacks under strongly acidic conditions: firstly, the adsorption performance of these adsorbents is sensitive to pH; in a strongly acidic environment, their surface active sites are easily occupied by hydrogen ions, leading to a significant decrease in adsorption capacity and making deep removal of fluoride ions impossible; secondly, conventional adsorbents lack specificity and simultaneously adsorb other anions in the wastewater, such as sulfate and chloride ions, which not only reduces the adsorption efficiency of fluoride ions but also shortens the regeneration cycle of the adsorbent, increasing treatment costs. Furthermore, if specific adsorption of fluoride ions cannot be achieved, the purity of the fluoride recovered through subsequent elution will be extremely low, making it difficult to recover and utilize high-value fluorine resources. This step involves passing the highly acidic wastewater to be treated through a fixed-bed adsorption column containing an acid-resistant molecularly imprinted polymer adsorbent at a constant flow rate. Under acidic conditions, the adsorbent selectively captures free fluoride ions in the wastewater by utilizing pre-synthesized, highly specific recognition holes that perfectly match the spatial and chemical structure of fluoride ions. Meanwhile, a large number of competing ions, such as chloride and sulfate ions, are largely unadsorbed. When the effluent fluoride concentration approaches a set threshold, the system switches to a backup adsorption column, while the saturated column enters an offline regeneration process, thus producing deeply purified wastewater. By utilizing the high selectivity of the acid-resistant molecularly imprinted polymer, precise and efficient adsorption of fluoride ions is achieved under highly acidic raw water conditions, successfully reducing the fluoride concentration to extremely low levels and solving the selective challenge of deep fluoride removal from complex, acidic, and high-salinity wastewater.

[0032] S203. Based on the information set of deep defluorination and purification wastewater, adsorbent regeneration and eluent treatment are carried out to convert and recover high-purity calcium fluoride products and generate a full-process fluorine resource recovery report.

[0033] Adsorbent regeneration involves treating saturated, acid-resistant molecularly imprinted polymers with a specific eluent to desorb adsorbed fluoride ions from the polymer binding sites, restoring the polymer's adsorption performance for recycling. Eluent treatment involves chemically treating the eluent after fluoride ion desorption to convert the fluoride ions into the target product (calcium fluoride) and then separating it. High-purity calcium fluoride products are solid calcium fluoride products with a purity ≥98% generated by the reaction of fluoride and calcium ions. These products meet industrial-grade calcium fluoride product standards (such as GB / T 4291-2017 "Fluorite") and can be used in metallurgy, chemical industry, and other sectors. A comprehensive fluorine resource recovery report includes key data such as process data and results related to adsorbent regeneration, fluoride ion recovery, and product generation.

[0034] Specifically, in the previous adsorption process, after the acid-resistant molecularly imprinted polymer reaches saturation with adsorbed fluoride ions, its adsorption performance is lost. Direct disposal would result in a serious waste of adsorbent resources and significantly increase the operating costs of wastewater treatment. Furthermore, if the adsorbed fluoride ions cannot be effectively recovered, not only is valuable fluoride resource wasted, but secondary pollution may also occur after the adsorbent is discarded. In addition, most existing defluorination technologies only focus on achieving wastewater discharge standards, neglecting the recovery and utilization of fluoride resources. This step uses a low-concentration alkaline eluent to perform reverse elution on the saturated adsorption column, desorbing the highly selectively adsorbed fluoride ions and regenerating the adsorbent for reuse. The collected high-concentration fluoride ion eluent is reacted with a calcium salt solution under strictly controlled conditions to generate calcium fluoride precipitate. After filtration, washing, and drying, high-purity calcium fluoride product is obtained. This efficient adsorbent regeneration technology significantly reduces operating costs, and by converting the fluoride-containing eluent into marketable calcium fluoride product, a closed-loop recovery and value-added utilization of fluoride resources is achieved, completely eliminating the risk of secondary pollution from hazardous waste.

[0035] The method provided in this embodiment first obtains the information set of flue gas purification acidic wastewater after preliminary fluoride separation. Through electrochemical-photocatalytic synergistic complex breaking, stable fluoride complexes are dissociated into free fluoride ions, while simultaneously pre-depositing some heavy metals, forming the wastewater information set to be treated. Under strongly acidic conditions, acid-resistant molecularly imprinted polymers are used to specifically adsorb fluoride ions, generating a deep fluoride removal and purification wastewater information set. Finally, the saturated polymer is regenerated, and the eluent is treated to convert fluoride ions into high-purity calcium fluoride. The entire process data is integrated to generate a full-process fluoride resource recovery report, which is then output to factory staff. Through efficient dissociation of complexed fluoride, wastewater fluoride content meets discharge standards, while simultaneously removing heavy metals; fluoride resources are recovered and converted into industrial-grade calcium fluoride, achieving resource recycling; the adsorbent can be reused, reducing treatment costs; the entire process is free of secondary pollution, providing a reliable solution for the harmless and resource-based treatment of acidic wastewater.

[0036] In some embodiments, the acidic wastewater from flue gas purification undergoes multi-stage gradient sedimentation treatment. Suspended solids are removed by an acid-resistant ceramic membrane microfiltration system while maintaining the original pH of the wastewater. The wastewater after multi-stage gradient sedimentation is then subjected to selective ion pre-enrichment treatment. Under pH < 1 conditions, the wastewater is passed through a specific type of acid-resistant anion exchange resin column to selectively adsorb and separate fluorosilicate ions from the wastewater. The state and separation data of the wastewater after selective ion pre-enrichment treatment are used as a preliminary fluoride separation wastewater information set.

[0037] Multi-stage gradient sedimentation treatment involves sequentially passing acidic wastewater through multi-stage sedimentation tanks with gradually adjusted parameters (retention time, stirring intensity, etc.) to progressively separate suspended solids of different particle sizes. The aim is to improve suspended solids removal efficiency through staged treatment and avoid incomplete separation issues caused by single-stage sedimentation. Acid-resistant ceramic membrane microfiltration systems utilize strongly acid-resistant ceramic membranes (materials such as α-Al₂O₃ and ZrO₂) as the filter medium, with pore sizes of 0.1-1 μm, specifically designed to retain fine suspended solids in acidic wastewater. Suspended solids can be solid particles suspended in acidic wastewater, including dust introduced during flue gas purification, fine precipitates generated by chemical reactions (such as calcium sulfate microcrystals), and organic impurities, with particle sizes ranging from 0.1 μm to 1 mm. Selective ion pre-enrichment treatment utilizes the specific adsorption capacity of functional materials for target ions in wastewater under specific process conditions to separate and enrich target ions from other ions. The aim is to remove some difficult-to-treat complexed fluoride in advance. Specific acid-resistant anion exchange resin columns can be reaction columns filled with customized strong-base quaternary ammonium anion exchange resin (resin type D201-F acid-resistant modified resin). The resin has undergone acid-resistant treatment and can operate stably in strongly acidic environments with pH < 1, exhibiting high specific adsorption capacity for fluorosilicate ions. Fluorosilicate ions can be stable complexed anions (SiF6²) formed by the combination of fluoride ions and silicon ions in acidic wastewater. - ), is one of the main forms in which complexed fluorine exists, and it is difficult to remove effectively using conventional chemical precipitation and complex-breaking techniques.

[0038] Specifically, traditional flue gas purification technologies for the preliminary treatment of acidic wastewater have several key drawbacks: single-stage sedimentation can only remove large suspended solids (particle size ≥100μm), while fine particles (≤50μm) are prone to residue, which can subsequently contaminate the complex-breaking electrodes and clog the adsorption packing; ordinary filter materials are not resistant to strong acid corrosion and cannot selectively separate stable complexed fluoride such as fluorosilicate, causing these difficult-to-treat fluorides to enter subsequent processes, significantly increasing the complex-breaking and adsorption load; some processes blindly adjust the pH value, causing fluoride form transformation or premature precipitation of heavy metals, which in turn exacerbates the treatment difficulty, while lacking systematic data collection, it cannot provide accurate support for subsequent processes. To address the above issues, this step first introduces the acidic wastewater (pH approximately 1.5) generated from flue gas purification into a three-stage series gradient settling tank. The first stage involves natural settling for 90 minutes to remove dust particles ≥100μm. The second stage involves weak stirring at 30 rpm for 60 minutes to coagulate particles of 50-100μm. The third stage involves settling for 40 minutes to separate fine precipitates of 20-50μm. After settling, the sludge is discharged through the bottom sludge outlet and disposed of as hazardous waste. Subsequently, the supernatant is sent to an acid-resistant ceramic membrane microfiltration system (membrane pore size 0.5μm, material α-Al₂O₃). The transmembrane pressure is controlled at 0.3MPa, the wastewater flow rate at 9m / h, and the temperature at 30℃. The original pH of the wastewater is maintained without additional adjustment, and monitoring is performed using an online turbidity meter to ensure... The suspended solids removal rate is ≥98%. If the turbidity exceeds the standard, the membrane module is backwashed with 5% sulfuric acid solution. Then, concentrated sulfuric acid is added through an automatic dosing device to adjust the pH of the wastewater to 0.6 (meeting the pH < 1 requirement). The wastewater is then passed through a reaction column (1.5m high and 0.3m in diameter) filled with D201-F type acid-resistant anion exchange resin at a flow rate of 2 BV / h. Fluorosilicate ions are selectively adsorbed at 28℃. Finally, data such as the suspended solids content (e.g., reduced to 50mg / L after sedimentation and 5mg / L after microfiltration), fluorosilicate concentration (e.g., 80mg / L before adsorption and 12mg / L after adsorption), and pH value after each stage of treatment are collected and integrated to form a preliminary fluoride separation wastewater information set and transmitted to the control system.

[0039] The method provided in this embodiment uses multi-stage gradient sedimentation to separate suspended solids of different particle sizes. Combined with acid-resistant ceramic membrane microfiltration, it achieves deep purification. Under strongly acidic conditions with pH < 1, a special resin is used to selectively adsorb fluorosilicate ions. This avoids interference from impurities and abnormal transformation of fluorine forms, and can remove difficult-to-treat complexed fluorine in advance. This provides a reliable basis for the parameter optimization of subsequent deep treatment and is a core pre-process to ensure the efficient and stable operation of the overall process.

[0040] In some embodiments, preliminary fluoride separation wastewater is added to a three-dimensional electrode electrochemical reactor, wherein the anode is a boron-doped diamond-coated electrode, the cathode is a titanium-based mesh electrode, and activated carbon fibers loaded with titanium dioxide are added as particle electrodes and catalysts; under the synergistic effect of electric field and photocatalysis, stable fluoride complexes in the wastewater are destroyed and converted into free fluoride ions, and some heavy metal ions are pre-deposited simultaneously; the state data of the wastewater after the synergistic effect of electric field and photocatalysis, with free fluoride ions as the dominant form, is used as the wastewater information set to be treated.

[0041] A three-dimensional electrode electrochemical reactor can be an integrated reaction device that adds particle electrodes to a traditional two-dimensional flat electrode (anode and cathode) to form a three-dimensional electrode system, and integrates an ultraviolet irradiation module. A boron-doped diamond-coated electrode can be an electrode with a titanium plate as a substrate, coated with a boron-doped diamond film (doping concentration of 500-1000 ppm) using chemical vapor deposition (CVD) technology. A titanium-based mesh electrode can be a cathode made of pure titanium wire (0.5 mm in diameter) woven into a mesh structure (pore size 5-10 mm), featuring a large specific surface area, excellent conductivity, resistance to strong acid corrosion, and resistance to fouling, which can promote cathode reduction reactions and heavy metal ion deposition. Titanium dioxide-loaded activated carbon fiber can be a composite functional material formed by loading nano-titanium dioxide (particle size 20-50 nm) onto activated carbon fiber (specific surface area 1000-1500 m² / g) as a carrier using a sol-gel method.

[0042] Specifically, traditional single-mode complex breaking technology has significant drawbacks: single electrochemical complex breaking has high energy consumption (requiring a high voltage of 20-30V), and the electrode is easily passivated (the passivation rate of graphite electrode exceeds 30% after 100 hours), and the dissociation rate of stable fluorine complexes is only 40%-60%; single photocatalytic complex breaking has easy recombination of photogenerated carriers, the reaction takes more than 120 minutes, and the catalyst is prone to agglomeration and deactivation in a strongly acidic environment. Neither of these methods can remove heavy metals simultaneously, resulting in heavy metals competing for adsorption sites and contaminating the adsorbent. To address the above issues, this step involves feeding preliminary fluoride separation wastewater (pH approximately 0.7) at a flow rate of 10 m³ / h into a three-dimensional electrode electrochemical reactor (effective volume 5 m³) made of polytetrafluoroethylene. The anode in the reactor uses a boron-doped diamond-coated electrode (1 m × 0.5 m × 0.01 m, boron doping concentration 800 ppm), and the cathode uses a titanium-based mesh electrode (5 mm pore size, 0.5 mm wire diameter), with a 10 cm distance between the electrodes. Simultaneously, 5 g / L of supported titanium dioxide activated carbon fiber (specific surface area 1200 m² / g) is added as a particle electrode and catalyst, and stirred at 50 r / min to ensure uniform dispersion. Subsequently, a 15V DC power supply (current density 10 mA / cm²) and an ultraviolet irradiation module (254 nm low-pressure mercury lamp, light intensity 20 mW / cm²) are activated, maintaining the reaction temperature at 35℃ for 75 minutes. Under the synergistic effect of the electric field and photocatalysis, stable fluoride complexes (such as [FeF6]³) are destroyed. - It is converted into free fluoride ions, simultaneously causing Pb² to... + Heavy metals are allowed to precipitate (such as Pb(OH)2) and settle to the bottom sludge outlet. Finally, data such as free fluoride concentration (e.g., 80 mg / L after complex breaking), heavy metal residue (e.g., reduced to 0.5 mg / L), and pH value are collected by online monitoring equipment, integrated to form a wastewater information set to be treated, and transmitted to the control system.

[0043] The method provided in this embodiment employs a three-dimensional electrode electrochemical reactor, combined with acid-resistant electrodes and composite particle electrodes. Through the synergistic effect of electric field and photocatalysis, it not only solves the problems of incomplete complex breaking and poor adaptability to operating conditions in traditional technologies, but also enables simultaneous pre-deposition of heavy metals to avoid subsequent adsorption interference. At the same time, it generates accurate datasets to support subsequent regulation, which is the core link to ensure efficient and stable deep defluorination.

[0044] In some embodiments, an electric field is applied to a boron-doped diamond-coated electrode to generate hydroxyl radicals on its surface. The strong oxidizing properties of the hydroxyl radicals are used to attack and break the metal-fluorine coordination bonds of the stable fluorine complex, causing the fluorine element in the broken complex to be released into the strongly acidic wastewater in the form of free fluoride ions.

[0045] Hydroxyl radicals can be highly oxidizing reactive substances (redox potential approximately 2.8V) generated by the oxidation and decomposition of water molecules (H2O) during the oxygen evolution reaction on the surface of a boron-doped diamond-coated electrode under an electric field. Their strong oxidizing power can directly break the metal-fluorine coordination bonds with high chemical bond energy. Metal-fluorine coordination bonds are chemical bonds formed between metal ions and fluoride ions in stable fluorine complexes through coordination interactions. The metal ion provides empty orbitals, and the fluoride ion provides lone pairs of electrons, forming a stable coordination structure. This is the core chemical bond that maintains the stable existence of the fluorine complex.

[0046] Specifically, traditional complex breaking technologies have significant shortcomings: the oxidant used in chemical oxidation methods (such as hydrogen peroxide) has an oxidation potential of only about 1.77V, which is far from sufficient to break the metal-fluorine coordination bond, and the complex breaking rate is less than 30%; ordinary graphite and platinum electrodes are easily passivated in strongly acidic environments (the passivation rate of graphite electrodes exceeds 40% after 50 hours), resulting in weak oxidizing properties of the active substances and easy generation of by-products that cause secondary pollution. High-voltage operation also leads to a surge in energy consumption. To address the above issues, this step first confirms that a boron-doped diamond-coated electrode (1m × 0.6m × 0.01m, boron doping concentration 800ppm) has been installed at the anode in the three-dimensional electrode electrochemical reactor, with a 12cm gap between it and the titanium-based mesh cathode. After stable connection, preliminary fluoride separation wastewater with a pH of approximately 0.7 is injected into the reactor, maintaining a wastewater volume of 5m³ and submerging the electrode by 10cm. Subsequently, a DC regulated power supply is started, applying an 18V voltage and controlling the current density at 12mA / cm². Voltage and current fluctuations are monitored in real time to ensure they do not exceed ±0.5V and ±0.3mA / cm², respectively, while maintaining the wastewater temperature in the reactor at 32℃. Under the influence of the electric field, water molecules on the electrode surface are oxidized to generate hydroxyl radicals, which continuously attack [FeF6]³. - The metal-fluorine coordination bonds of the complex were established, and the entire reaction lasted for 80 minutes. During this period, the concentration of free fluoride ions was monitored by ion chromatography (e.g., from 20 mg / L to 85 mg / L) until the concentration no longer increased significantly, at which point the electric field was stopped.

[0047] The boron-doped diamond-coated electrode provided in this embodiment can efficiently generate hydroxyl radicals under an electric field, which can precisely break metal-fluorine coordination bonds. Moreover, the electrode is acid-resistant and passivation-resistant, and can operate stably for a long time. It completely solves the problems of incomplete complex breaking, high energy consumption and poor stability of traditional technologies, and is the core guarantee for converting stable fluorine complexes into free fluoride ions.

[0048] In some embodiments, while applying an electric field, the activated carbon fibers loaded with titanium dioxide in the reactor are photo-excited to produce a catalytic effect, thereby enhancing the complex breaking process; by applying an electric field to the titanium-based mesh electrode, a hydrogen evolution reaction occurs on its surface; by utilizing the local pH increase in the cathode area caused by the hydrogen evolution reaction, some heavy metal ions are converted into precipitates in this local alkaline environment, thus completing the pre-deposition.

[0049] Activated carbon fiber can be a composite functional material formed by uniformly loading nano-titanium dioxide (particle size 20-50nm) onto the surface of high specific surface area activated carbon fiber as a carrier via a sol-gel method. The catalytic effect can be achieved by the photogenerated electron-hole pairs generated after photoexcitation of the titanium dioxide-loaded activated carbon fiber, which synergistically interact with active substances (such as hydroxyl radicals) in the reactor to accelerate the chemical action of breaking the metal-fluorine coordination bonds of stable fluorine complexes. The core is to reduce the reaction activation energy and improve the complex-breaking efficiency. The enhanced complex-breaking process can be achieved by synergistically combining the catalytic effect generated by photoexcitation with the complex-breaking effect of hydroxyl radicals generated by the electric field of the boron-doped diamond-coated electrode, significantly improving the dissociation efficiency of stable fluorine complexes. Compared to a single complex-breaking method, this process significantly optimizes the complex-breaking rate and thoroughness. The hydrogen evolution reaction can be the water molecule reduction reaction (2H₂O + 2e⁻) occurring on the surface of the titanium-based mesh electrode under an electric field. - →H₂↑+2OH - The reaction products are hydrogen gas and hydroxide ions, which is the direct cause of the local pH increase in the cathode area. This local pH increase can be attributed to the accumulation of hydroxide ions produced by the hydrogen evolution reaction near the surface of the titanium-based mesh electrode. These ions cannot quickly diffuse into the overall strongly acidic wastewater (pH < 1), causing the pH value in the local area around the electrode to rise from < 1 to an alkaline microenvironment of 3-5. This local pH change is limited to a few millimeters on the cathode surface and does not affect the overall strongly acidic nature of the wastewater. Some heavy metal ions may be lead (Pb²⁺) present in the acidic wastewater. + ), cadmium (Cd² + ), arsenic (As³) + Heavy metal ions, such as those with high toxicity and a tendency to form hydroxide precipitates, are major pollutants in wastewater and interfere with subsequent adsorption processes. Pre-deposition can be a pretreatment process that, while stabilizing and breaking down fluoride complexes, induces the formation of precipitates from heavy metal ions through a localized alkaline environment, thus separating them from the wastewater. The aim is to remove heavy metal pollution and adsorption interference factors in advance.

[0050] Specifically, traditional technologies separate complex breaking and heavy metal removal into independent steps, requiring the addition of a neutralization precipitation tank and the addition of alkaline agents to adjust the overall pH to 8-10. This not only results in a lengthy process, a surge in equipment investment and floor space, but also disrupts the strongly acidic complex breaking environment, causing incompletely dissociated fluorine complexes to re-stabilize, necessitating secondary complex breaking and resulting in fluorine resource loss. Furthermore, single complex breaking technology is inefficient, as photogenerated electron-hole pairs easily recombine, the active material for electric field complex breaking is limited, and the retention of heavy metal ions throughout the process competes for adsorption sites and contaminates the adsorbent, shortening its regeneration cycle. To address the above issues, this step confirmed that the titanium-based mesh cathode (5mm pore size, 0.5mm wire diameter) and the boron-doped diamond-coated anode in the three-dimensional electrode electrochemical reactor were spaced 12cm apart. 5g / L of activated carbon fiber loaded with titanium dioxide (specific surface area 1200m² / g) was uniformly added. The ultraviolet light module (wavelength 254nm) at the top of the reactor was 30cm away from the fiber. A 15V DC power supply (current density 10mA / cm²) was activated, and photoexcitation (light intensity 20mW / cm²) was simultaneously turned on. The fiber generated photogenerated electron-hole pairs, enhancing complex disruption. A hydrogen evolution reaction occurred at the cathode, causing the local pH to rise to approximately 4. The wastewater contained Pb²... + Cd² + Heavy metal ions in this locally alkaline environment generate Pb(OH)2 and Cd(OH)2 precipitates, which settle to the bottom cone-shaped precipitation zone and are periodically discharged for disposal. The reaction continues for 80 minutes, and the heavy metal residue is monitored by atomic absorption spectrophotometer (e.g., reduced to 0.3 mg / L), while the concentration of free fluoride ions is tracked by ion chromatography. The data are integrated into the wastewater information set to be treated.

[0051] The method provided in this embodiment, which combines photo-excitation-enhanced complex breaking with the hydrogen evolution reaction of the titanium-based mesh electrode, utilizes catalysis to improve complex breaking efficiency and induces heavy metal precipitation through local pH increase at the cathode. This eliminates the need for neutralization of the overall wastewater, avoids fluoride complex rebound, shortens the process, reduces sludge production, and removes adsorption interference factors in advance. This is the core link to ensure the high efficiency and stability of the process.

[0052] In some embodiments, based on the wastewater information set to be treated, an acid-resistant fluoride ion imprinted polymer, prepolymerized under acidic conditions using fluoride ions as a template, is used as a specific adsorbent material. The complex-broken wastewater corresponding to the wastewater information set to be treated, with a pH value of 0.5-1.5, is passed into an adsorption device filled with the acid-resistant fluoride ion imprinted polymer for dynamic adsorption. The adsorption conditions are controlled so that free fluoride ions in the wastewater are selectively captured, and the fluoride ion concentration in the effluent is reduced to below a preset concentration threshold. The state data of the wastewater after specific adsorption treatment is used as the deep defluorination and purification wastewater information set.

[0053] Acid-resistant fluoride ion-imprinted polymers can be polymeric materials formed by polymerization and elution of template molecules in an acidic system using fluoride ions as templates. Specific adsorbent materials can be functional materials that exhibit high selective adsorption capacity only for the target substance (free fluoride ions in this example), while having extremely weak adsorption capacity for other coexisting ions (such as chloride ions and sulfate ions). Their core characteristics are "targeted recognition" and "efficient capture." Adsorption conditions can be achieved by controlling parameters such as wastewater flow rate, adsorption temperature, and the number of adsorption stages in series. The core objective is to ensure sufficient contact time between the wastewater and the adsorbent material to achieve efficient capture of free fluoride ions and ensure that the effluent meets standards. Selective capture can be a process in which the acid-resistant fluoride ion-imprinted polymer, through specific imprinted cavities in its matrix, preferentially adsorbs fluoride ions only through coordination and hydrogen bonding, while almost completely ignoring high concentrations of coexisting anions such as chloride ions and sulfate ions in the wastewater. The preset concentration threshold can be the upper limit of effluent fluoride concentration set according to national environmental emission standards and subsequent fluoride resource recovery requirements. In this embodiment, it is preset to 1.0 mg / L (to meet the dual requirements of sensitive area discharge and resource recovery).

[0054] Specifically, traditional adsorption technologies have many fatal flaws: conventional adsorbents (such as activated alumina and ordinary resins) are easily hydrolyzed or protonated in strongly acidic environments with a pH of 0.5-1.5, and their adsorption capacity is only 20%-30% of that under neutral conditions. Moreover, their selectivity is extremely poor. Under competition from high concentrations of chloride ions (such as 3000 mg / L) and sulfate ions (such as 6000 mg / L), their effective adsorption capacity for fluoride ions drops significantly. Single-stage static adsorption or low-stage dynamic adsorption cannot meet the needs of continuous industrial treatment. It is difficult to stably reduce the fluoride ion concentration in the effluent to below 1.0 mg / L, and there is a lack of systematic data support, leading to blind regeneration and recovery processes. To address the above issues, this step first retrieves the wastewater information set and verifies that the wastewater pH is 0.8 (within the 0.5-1.5 range), free fluoride ion concentration is 85 mg / L, chloride ion concentration is 3000 mg / L, and sulfate ion concentration is 6000 mg / L, confirming that the adsorption requirements are met. Subsequently, a two-stage series-connected acid-resistant fiberglass fixed-bed adsorption tower (each stage is 2.0 m high and 0.5 m in diameter) is started. The tower is filled with acid-resistant fluoride ion imprinted polymer with a particle size of 0.5-1.0 mm (80 mg / L per stage). Wastewater (0L) is introduced at a flow rate of 3 BV / h via a metering pump, maintaining an adsorption temperature of 28℃. As the wastewater flows through the polymer bed, fluoride ions are captured by specific imprinted holes. Coexisting ions are then carried by the water through the second-stage tower for further purification. The concentration of fluoride ions in the effluent is monitored in real time by an online ion chromatograph at the outlet to ensure that the concentration is stably reduced to below 1.0 mg / L. Finally, parameters such as effluent quality, treated water volume, and adsorption time are collected and integrated to form a deep defluorination and purification wastewater information set, which is then transmitted to the subsequent process control system.

[0055] The method provided in this embodiment employs an acid-resistant imprinted polymer with fluoride ions as a template. Its specific imprinted holes can accurately capture fluoride ions in a strongly acidic and highly competitive ion environment. Dynamic adsorption and multi-level series design ensure sufficient contact time, while generating a dataset to constrain subsequent processes. This is the core link to achieve deep defluorination, operating condition adaptation and resource recycling linkage.

[0056] In some embodiments, in an acidic polymerization system, free fluoride ions are used as template molecules to undergo polymerization reactions with functional monomers, crosslinking agents, and initiators to synthesize a polymer precursor containing template molecules. The template molecules are removed from the polymer precursor through an elution step, thereby forming imprinted cavities in the polymer matrix that are specifically complementary to free fluoride ions in terms of size, shape, and chemical action sites, to obtain an acid-resistant fluoride ion imprinted polymer. The imprinted cavities in the acid-resistant fluoride ion imprinted polymer are configured to maintain structural stability in strongly acidic wastewater with pH < 2 and exhibit high adsorption selectivity for fluoride ions.

[0057] The acidic polymerization system can be a reaction system with a pH < 2 adjusted by strong acids such as sulfuric acid or hydrochloric acid, providing an acidic environment for the coordination and polymerization of template molecules and functional monomers, ensuring that the synthesized polymer is suitable for subsequent strong acidic wastewater treatment conditions. Functional monomers can be small molecule compounds that can interact with template molecules through coordination bonds, hydrogen bonds, etc., and possess polymerization activity. Crosslinking agents can be compounds that enable crosslinking polymerization of the functional monomer and template molecule combination, forming a three-dimensional network structure. Initiators can be substances that can initiate free radical polymerization reactions between functional monomers and crosslinking agents under certain conditions (such as heating or light). The polymer precursor can be an untreated polymer compound containing template molecules (free fluoride ions) formed after the polymerization reaction, with a preliminary spatial configuration adapted to the template molecules, serving as an intermediate product in the preparation of imprinted polymers. The elution step can be a process of soaking the polymer precursor with a specific eluent (such as dilute hydrochloric acid or sodium fluoride solution) to disrupt the interaction between template molecules and functional monomers, removing the template molecules from the polymer network. Imprinted cavities are three-dimensional cavity structures left in the polymer matrix after template molecules are eluted. These cavities are completely complementary to the template molecules (free fluoride ions) in size, shape, and chemical interaction sites, and are the core structure for achieving specific adsorption of fluoride ions. High adsorption selectivity refers to the polymer's ability to preferentially recognize and adsorb fluoride ions in strongly acidic wastewater containing high concentrations of chloride ions, sulfate ions, and other coexisting anions, while exhibiting extremely low adsorption capacity for other anions.

[0058] Specifically, traditional adsorption materials (such as activated alumina and ordinary ion exchange resins) are prone to hydrolysis, protonation, or structural collapse in strongly acidic environments with pH < 2. Their adsorption capacity is only 10%-20% of that under neutral conditions. Furthermore, they lack adsorption sites that are precisely matched with fluoride ions. Under competition from high concentrations of chloride ions (e.g., 3000 mg / L) and sulfate ions (e.g., 6000 mg / L), the amount of fluoride ions adsorbed is only 20%-30% of that under uncompetitive conditions, making it difficult to stably reduce the effluent concentration to below 1.0 mg / L. At the same time, the adsorption is unstable, the purity of desorbed fluoride ions is low, and it is impossible to prepare high-purity calcium fluoride. To address the above issues, this step involves adding 200 mL of deionized water to a 500 mL three-necked flask, adjusting the pH to 1.0 with 98% concentrated sulfuric acid, adding 0.05 mol / L sodium fluoride (to provide a free fluoride ion template), and stirring for 30 minutes to ensure uniform dispersion. Then, 0.2 mol / L of the functional monomer methacrylic acid is added, and the mixture is stirred for 60 minutes to form a monomer-template complex. Subsequently, 0.5 mol / L of the crosslinking agent ethylene glycol dimethacrylate and 0.01 mol / L of the initiator azobisisobutyronitrile are added. Stir for 20 minutes to mix thoroughly; place the flask in a 68℃ constant temperature water bath and polymerize for 8 hours under nitrogen protection to obtain the polymer precursor. After washing three times with deionized water and drying under vacuum at 60℃ for 12 hours, elute with 0.1mol / L dilute hydrochloric acid at 40℃ and 150r / min for 6 hours (changing the eluent every 2 hours). Finally, wash with deionized water until the washing solution is neutral and dry under vacuum at 50℃ for 8 hours to obtain an acid-resistant fluoride ion imprinted polymer, whose imprinted holes can exist stably in an environment with pH < 2.

[0059] The method provided in this embodiment adapts the acidic polymerization system to strongly acidic conditions in advance, and uses fluoride ions as templates to guide the formation of specific imprinted holes. After elution, highly efficient adsorption sites are retained. This not only solves the core defects of traditional materials such as poor acid resistance and weak selectivity, but also provides key material support for the high-purity recovery of fluorine resources. It is the core link to achieve the linkage between deep defluorination and resource utilization.

[0060] In some embodiments, the adsorption device is configured to include at least two stages of fixed-bed adsorption towers connected in series; the flow rate of wastewater through the fixed-bed adsorption tower is controlled to ensure that the wastewater has sufficient contact reaction time with the acid-resistant fluoride-imprinted polymer; by controlling the number of stages of the fixed-bed adsorption towers connected in series and the contact reaction time, the fluoride concentration in the effluent is stably reduced to below 1.0 mg / L under a highly acidic environment and in the presence of high concentrations of chloride and sulfate ions.

[0061] The adsorption device can be a core reaction unit used to carry acid-resistant fluoride ion-imprinted polymers, enabling efficient contact between wastewater and the adsorbent material. Its structural design directly affects the adsorption efficiency and treatment effect. A fixed-bed adsorption tower can be a combination of two or more independent fixed-bed adsorption towers connected sequentially by pipelines to form a continuous adsorption process. A "two-stage" configuration is the basic configuration, and the number of stages can be increased according to the fluoride ion concentration and treatment volume of the wastewater. Each tower is filled with acid-resistant fluoride ion-imprinted polymers, ensuring deep purification through multi-stage relay adsorption. Competing background factors can include a significantly higher concentration of chloride ions (1000-5000 mg / L) and sulfate ions (5000-10000 mg / L) in the wastewater compared to the fluoride ion concentration (50-100 mg / L). These ions compete with fluoride ions for adsorption sites, constituting the main interference background in the adsorption process.

[0062] Specifically, traditional adsorption condition control has key defects: it often uses a single-stage fixed-bed adsorption tower with excessively high flow rates (5-8 BV / h), resulting in a contact time of only 10-20 minutes between wastewater and adsorption material. Fluoride ions are not fully adsorbed before flowing out, and the effluent concentration often reaches 3-5 mg / L. It lacks coordinated control of the number of stages and flow rate. Under the competition of high concentrations of chloride ions (e.g., 4000 mg / L) and sulfate ions (e.g., 7000 mg / L), adsorption sites are easily occupied, and the effective adsorption capacity of fluoride ions drops sharply. The single-stage tower has weak shock resistance, and fluctuations in influent concentration directly lead to effluent exceeding standards. To address the above issues, this step involves constructing a two-stage series of acid-resistant fiberglass fixed-bed adsorption towers (each stage is 2.5m high and 0.6m in inner diameter). Each stage is filled with 1000L of acid-resistant fluoride ion-imprinted polymer with a particle size of 0.5-1.0mm. Online monitoring equipment is installed at the inlet and outlet of the towers. Based on the wastewater information set (pH 1.0, fluoride ion 90mg / L, chloride ion 4000mg / L, sulfate ion 7000mg / L), a contact time of 60 minutes is calculated, and the wastewater flow rate is set at 2 BV / h. The wastewater is pumped into the first-stage tower via a metering pump. After preliminary adsorption, it flows into the second-stage tower for further purification. The fluoride ion concentration is monitored in real time at the outlet using an online ion chromatograph. If the concentration approaches 0.8mg / L, the flow rate is reduced to 1.5 BV / h to extend the contact time to 80 minutes, or the third-stage standby tower is activated. The tower operates continuously for 72 hours, recording inlet and outlet concentrations, flow rates, and other data to ensure that the fluoride ion concentration in the effluent remains stably below 1.0mg / L.

[0063] The method provided in this embodiment, based on at least two stages of series fixed beds forming a relay adsorption, precisely controls the flow rate to ensure sufficient contact time, and coordinates the number of stages and contact time to resist interference from competing ions and cope with water quality fluctuations, ensuring that the effluent fluoride ion concentration is stably reduced to below 1.0 mg / L. This is the core link to realize the industrialization of deep defluoridation while taking into account both efficiency and stability.

[0064] In some embodiments, based on the information set of deep defluorination and purification wastewater, a low-concentration ammonia solution is used to elute and regenerate the saturated acid-resistant fluoride-imprinted polymer, desorbing the adsorbed fluoride ions into the eluent in the form of ammonium fluoride. The acid-resistant fluoride-imprinted polymer after ammonia elution is rinsed with dilute sulfuric acid solution to restore it to an active form suitable for adsorption in strongly acidic wastewater. A calcium chloride solution is introduced into the ammonium fluoride-rich eluent, reacting to generate calcium fluoride precipitate. The calcium fluoride precipitate is then subjected to solid-liquid separation, washing, and drying to obtain a high-purity calcium fluoride product. Based on the process data and results of adsorbent regeneration, fluoride ion recovery, and product generation, a full-process fluoride resource recovery report is generated.

[0065] Low-concentration ammonia solution can be ammonia water (NH3) with a concentration of 3%-8%. The H2O solution, possessing mild alkalinity and desorption capabilities, can disrupt the coordination between fluoride ions and imprinted holes without corroding the polymer structure. Elution and regeneration can involve soaking the saturated polymer in a low-concentration ammonia solution. The alkaline environment disrupts the chemical interaction between fluoride ions and imprinted holes, causing fluoride ions to desorb into the eluent and simultaneously restoring the polymer's adsorption activity. A 5%-10% sulfuric acid (H2SO4) solution is used to neutralize residual ammonia on the polymer surface after ammonia elution, restoring the polymer's acidic adsorption environment. A 1-2 mol / L calcium chloride (CaCl2) aqueous solution is the core reagent for reacting with ammonium fluoride to form calcium fluoride precipitate. Calcium fluoride precipitate is a sparingly soluble solid compound formed by the metathesis reaction of ammonium fluoride and calcium chloride. Its extremely low solubility makes it easily purified through solid-liquid separation, making it a target product for fluorine resource recovery. Solid-liquid separation can be a process of separating calcium fluoride precipitate from the post-reaction solution through methods such as filtration. The core equipment is an acid-resistant plate and frame filter press made of polytetrafluoroethylene (PTFE), suitable for strongly acidic reaction environments. Washing can involve rinsing the surface of the calcium fluoride precipitate with deionized water to remove attached chloride ions (Cl). - ), ammonium ions (NH4+) + The process of removing impurities such as calcium fluoride ensures product purity. Drying involves removing moisture from the washed calcium fluoride precipitate at low temperatures, avoiding the decomposition of impurities or product clumping caused by high temperatures. High-purity calcium fluoride products can be solid calcium fluoride with a purity of ≥98%, conforming to industrial-grade fluorite standards (GB / T 4291-2017), and can be directly used in metallurgical fluxing, chemical fluorochemical raw materials, and other fields.

[0066] Specifically, traditional technologies have several key drawbacks: saturated defluorination adsorbents are often directly disposed of as hazardous waste, which not only wastes adsorbent resources (the cost of new materials accounts for 40%-60% of operating costs) but also generates a large amount of fluorine-containing hazardous waste, posing a risk of secondary pollution. Furthermore, regeneration technologies often use high-concentration acid-base elution, which easily damages the adsorbent structure, resulting in a regeneration rate of only 50%-60%. Most processes neglect fluorine resource recovery, leading to the loss or neutralization of valuable fluoride ions with hazardous waste. Even when attempts are made to recover fluoride, the low purity of the eluent prevents the production of high-purity products. Additionally, there is a lack of integrated data across the entire process, making process operation reliant on experience and hindering precise parameter optimization. To address the above issues, this step retrieves information from the deep defluorination wastewater purification database to confirm that the fluoride ion concentration at the adsorption unit outlet is stable at 0.8 mg / L, indicating that the adsorbent is saturated. A 5% low-concentration ammonia solution is prepared (200 L of 25% concentrated ammonia diluted with 800 L of deionized water), and this solution is reverse-flowed into a two-stage series fixed-bed adsorption tower at a flow rate of 1 BV / h. The tower temperature is controlled at 30°C, and the eluent is eluted for 120 minutes. The eluent containing 15% ammonium fluoride is collected. Next, an 8% dilute sulfuric acid solution is prepared (80 L of 98% concentrated sulfuric acid diluted with 920 L of deionized water), and this solution is used to flush the adsorption tower at a flow rate of 1.5 BV / h for 30 minutes to neutralize the residual ammonia, restoring the adsorbent to its acidic active form. The flushing wastewater is then neutralized and discharged in compliance with standards. 000L of ammonium fluoride eluent was pumped into an acid-resistant reactor. Under stirring at 40℃ and 200r / min, 800L of 1.5mol / L calcium chloride solution was slowly added at a molar ratio of 1:1.2. The reaction was carried out for 60 minutes to form calcium fluoride precipitate. Solid-liquid separation was performed using an acid-resistant plate and frame filter press. The filter cake was washed three times with deionized water (500L each time) to remove impurities. After drying in a vacuum drying oven at 60℃ for 4 hours, a calcium fluoride product with a purity of 98.5% was obtained. Finally, the regeneration parameters (ammonia concentration 5%, elution time 120 minutes, regeneration rate 95%), recovery data (desorption rate 98%, product yield 120kg), energy consumption, reagent consumption, and other information were integrated to generate a full-process fluorine resource recovery report.

[0067] The method provided in this embodiment utilizes a low-concentration ammonia solution for gentle elution, which efficiently removes fluoride ions without damaging the adsorbent. Rinsing with dilute sulfuric acid restores the adsorbent to its acidic active form, enabling its recycling. A directed reaction of ammonium fluoride and calcium chloride prepares high-purity calcium fluoride, realizing the resource utilization of fluorine. The integrated data from the entire process forms a recovery report, providing a basis for process optimization and cost accounting. This approach solves the problems of waste, pollution, and inefficiency associated with traditional technologies, and achieves a closed loop of "deep fluoride removal - resource recovery - recycling," representing a core link that balances environmental protection and economic efficiency.

[0068] Figure 3 This is a schematic diagram of a flue gas purification and deep defluorination system for acidic wastewater, provided in one embodiment of this application. Figure 3As shown, the flue gas purification and deep defluorination system 300 for acidic wastewater in this embodiment includes: a preliminary treatment module 301, a deep defluorination module 302, and a resource recovery module 303.

[0069] The preliminary treatment module 301 is used to acquire the preliminary fluoride separation wastewater information set, perform electrochemical-photocatalytic synergistic complex breaking treatment, convert the stable fluoride complexes in the wastewater into free fluoride ions, and simultaneously pre-deposit some heavy metals to generate a wastewater information set to be treated with free fluoride ions as the dominant form. The deep defluorination module 302 is used to perform acid-resistant molecularly imprinted polymer-specific adsorption of fluoride ions under strong acidic conditions based on the wastewater information set to be treated, thereby generating a deep defluorination and purified wastewater information set. The resource recovery module 303 is used to regenerate the adsorbent and treat the eluent based on the information set of the deep defluorination and purification wastewater, convert and recover high-purity calcium fluoride products, and generate a full-process fluorine resource recovery report.

[0070] Optionally, the preliminary processing module 301, when acquiring the preliminary fluoride separation wastewater information set, is specifically used for: The flue gas purification acid wastewater is subjected to multi-stage gradient sedimentation treatment, and suspended solids are removed by an acid-resistant ceramic membrane microfiltration system while maintaining the original pH of the wastewater. The wastewater that has undergone the multi-stage gradient sedimentation treatment is subjected to selective ion pre-enrichment treatment. Under the condition of pH < 1, the wastewater is passed through a specific type of acid-resistant anion exchange resin column to selectively adsorb and separate fluorosilicate ions in the wastewater. The wastewater state and separation data after selective ion pre-enrichment treatment will be used as the preliminary fluoride separation wastewater information set.

[0071] Optionally, when generating the wastewater information set dominated by free fluoride ions, the preliminary processing module 301 is specifically used for: The preliminary fluoride separation wastewater is added to a three-dimensional electrode electrochemical reactor, wherein the anode is a boron-doped diamond-coated electrode, the cathode is a titanium-based mesh electrode, and activated carbon fiber loaded with titanium dioxide is added as a particle electrode and catalyst. Under the synergistic effect of electric field and photocatalysis, stable fluoride complexes in wastewater are destroyed and converted into free fluoride ions, while simultaneously promoting the pre-deposition of some heavy metal ions. The wastewater state data, which is dominated by free fluoride ions after the synergistic effect of the electric field and photocatalysis, is used as the wastewater information set to be treated.

[0072] Optionally, the preliminary treatment module 301, when breaking down stable fluoride complexes in wastewater and converting them into free fluoride ions under the synergistic effect of an electric field and photocatalysis, is specifically used for: By applying an electric field to the boron-doped diamond-coated electrode, hydroxyl radicals are generated on its surface. The strong oxidizing properties of the hydroxyl radicals attack and break the metal-fluorine coordination bonds of the stable fluorine complex, causing the fluorine element in the broken complex to be released into the strongly acidic wastewater in the form of free fluoride ions.

[0073] Optionally, the preliminary processing module 301, when simultaneously inducing the pre-deposition of some heavy metal ions, is specifically used for: While applying an electric field, the activated carbon fibers loaded with titanium dioxide in the reactor are photo-excited to produce a catalytic effect, thereby enhancing the complex-breaking process. By applying an electric field to the titanium-based mesh electrode, a hydrogen evolution reaction occurs on its surface; By utilizing the localized pH increase in the cathode region caused by the hydrogen evolution reaction, some heavy metal ions are converted into precipitates in this localized alkaline environment, thus completing the pre-deposition.

[0074] Optionally, the deep defluorination module 302, when generating the deep defluorination purified wastewater information set, is specifically used for: Based on the information set of the wastewater to be treated, an acid-resistant fluoride ion imprinted polymer, which is prepolymerized under acidic conditions using fluoride ions as a template, is used as a specific adsorbent material. The wastewater after complex-breaking treatment, with a pH value of 0.5-1.5 corresponding to the wastewater information set to be treated, is passed into an adsorption device filled with the acid-resistant fluoride ion imprinted polymer for dynamic adsorption. By controlling the adsorption conditions, the free fluoride ions in the wastewater are selectively captured, and the fluoride ion concentration in the effluent is reduced to below a preset concentration threshold. The wastewater state data after the specific adsorption treatment is used as the information set of the deep defluorination and purification wastewater.

[0075] Optionally, when the deep defluorination module 302 is based on the use of an acid-resistant fluoride ion-imprinted polymer prepolymerized under acidic conditions with fluoride ions as a template as a specific adsorbent material, it is specifically used for: In an acidic polymerization system, free fluoride ions are used as template molecules to undergo polymerization reactions with functional monomers, crosslinking agents, and initiators to synthesize polymer precursors containing template molecules. The template molecule is removed from the polymer precursor by an elution step, thereby forming an imprinted cavity in the polymer matrix that is specifically complementary to the free fluoride ion in terms of size, shape and chemical action site, to obtain the acid-resistant fluoride ion imprinted polymer. The imprinted cavities in the acid-resistant fluoride ion imprinted polymer are configured to maintain structural stability in the strongly acidic wastewater with pH < 2 and exhibit high adsorption selectivity for fluoride ions.

[0076] Optionally, the deep defluorination module 302, based on the controlled adsorption conditions, is specifically used for: The adsorption device is configured as a fixed-bed adsorption tower comprising at least two stages connected in series; The flow rate of wastewater through the fixed-bed adsorption tower is controlled to ensure that the wastewater has sufficient contact reaction time with the acid-resistant fluoride ion-imprinted polymer. By controlling the number of series stages of the fixed-bed adsorption tower and the contact reaction time, the fluoride concentration in the effluent is stably reduced to below 1.0 mg / L under strongly acidic conditions and in the presence of high concentrations of chloride and sulfate ions.

[0077] Optionally, the resource recycling module 303 is specifically used for: Based on the aforementioned deep defluorination and wastewater purification information set, a low-concentration ammonia solution is used to elute and regenerate the adsorbed saturated acid-resistant fluoride-imprinted polymer, and the adsorbed fluoride ions are desorbed into the eluent in the form of ammonium fluoride. The acid-resistant fluoride ion imprinted polymer, after being eluted with ammonia water, was rinsed with dilute sulfuric acid solution to restore it to an active form suitable for adsorption of the strongly acidic wastewater. A calcium chloride solution is introduced into the eluent rich in ammonium fluoride, and a calcium fluoride precipitate is formed by the reaction. The calcium fluoride precipitate is then subjected to solid-liquid separation, washing and drying to obtain a high-purity calcium fluoride product. Based on the process data and results of adsorbent regeneration, fluoride ion recovery, and product generation, a full-process fluorine resource recovery report is generated.

[0078] The system in this embodiment can be used to execute the methods of any of the above embodiments, and its implementation principle and technical effect are similar, so they will not be described again here.

Claims

1. A method for deep defluorination of acidic wastewater from flue gas purification, characterized in that, include: A preliminary fluoride separation wastewater information set was obtained, and electrochemical-photocatalytic synergistic complex-breaking treatment was carried out to convert stable fluoride complexes in the wastewater into free fluoride ions, and simultaneously pre-deposited some heavy metals to generate a wastewater information set to be treated with free fluoride ions as the dominant form. Based on the wastewater information set to be treated, under the condition of maintaining strong acidity, acid-resistant molecularly imprinted polymers are used for the specific adsorption of fluoride ions to generate a deep defluorination and purification wastewater information set. Based on the aforementioned information set of deep defluorination and purification wastewater, adsorbent regeneration and eluent treatment are carried out to convert and recover high-purity calcium fluoride products, generating a full-process fluorine resource recovery report.

2. The method according to claim 1, characterized in that, The acquisition of the preliminary fluoride separation wastewater information set includes: The flue gas purification acid wastewater is subjected to multi-stage gradient sedimentation treatment, and suspended solids are removed by an acid-resistant ceramic membrane microfiltration system while maintaining the original pH of the wastewater. The wastewater that has undergone the multi-stage gradient sedimentation treatment is subjected to selective ion pre-enrichment treatment. Under the condition of pH < 1, the wastewater is passed through a specific type of acid-resistant anion exchange resin column to selectively adsorb and separate fluorosilicate ions in the wastewater. The wastewater state and separation data after selective ion pre-enrichment treatment will be used as the preliminary fluoride separation wastewater information set.

3. The method according to claim 1, characterized in that, The generation of the wastewater information set to be treated, dominated by free fluoride ions, includes: The preliminary fluoride separation wastewater is added to a three-dimensional electrode electrochemical reactor, wherein the anode is a boron-doped diamond-coated electrode, the cathode is a titanium-based mesh electrode, and activated carbon fibers loaded with titanium dioxide are added as particle electrodes and catalysts. Under the synergistic effect of electric field and photocatalysis, stable fluoride complexes in wastewater are destroyed and converted into free fluoride ions, while simultaneously promoting the pre-deposition of some heavy metal ions. The wastewater state data, which is dominated by free fluoride ions after the synergistic effect of the electric field and photocatalysis, is used as the wastewater information set to be treated.

4. The method according to claim 3, characterized in that, The process of destroying stable fluoride complexes in wastewater and converting them into free fluoride ions under the synergistic effect of an electric field and photocatalysis includes: By applying an electric field to the boron-doped diamond-coated electrode, hydroxyl radicals are generated on its surface. The strong oxidizing properties of the hydroxyl radicals attack and break the metal-fluorine coordination bonds of the stable fluorine complex, causing the fluorine element in the broken complex to be released into the strongly acidic wastewater in the form of free fluoride ions.

5. The method according to claim 4, characterized in that, The synchronization process induces pre-deposition of some heavy metal ions, including: While applying an electric field, the activated carbon fibers loaded with titanium dioxide in the reactor are photo-excited to produce a catalytic effect, thereby enhancing the complex-breaking process. By applying an electric field to the titanium-based mesh electrode, a hydrogen evolution reaction occurs on its surface; By utilizing the localized pH increase in the cathode region caused by the hydrogen evolution reaction, some heavy metal ions are converted into precipitates in this localized alkaline environment, thus completing the pre-deposition.

6. The method according to claim 5, characterized in that, The generated information set of deep defluoridation and purification wastewater includes: Based on the information set of the wastewater to be treated, an acid-resistant fluoride ion imprinted polymer, which is prepolymerized under acidic conditions using fluoride ions as a template, is used as a specific adsorbent material. The wastewater after complex-breaking treatment, with a pH value of 0.5-1.5 corresponding to the wastewater information set to be treated, is passed into an adsorption device filled with the acid-resistant fluoride ion imprinted polymer for dynamic adsorption. By controlling the adsorption conditions, the free fluoride ions in the wastewater are selectively captured, and the fluoride ion concentration in the effluent is reduced to below a preset concentration threshold. The wastewater state data after the specific adsorption treatment is used as the information set of the deep defluorination and purification wastewater.

7. The method according to claim 6, characterized in that, The method employs an acid-resistant fluoride ion-imprinted polymer, prepolymerized under acidic conditions using fluoride ions as a template, as a specific adsorbent material, comprising: In an acidic polymerization system, free fluoride ions are used as template molecules to undergo polymerization reactions with functional monomers, crosslinking agents, and initiators to synthesize polymer precursors containing template molecules. The template molecule is removed from the polymer precursor by an elution step, thereby forming an imprinted cavity in the polymer matrix that is specifically complementary to the free fluoride ion in terms of size, shape and chemical action site, to obtain the acid-resistant fluoride ion imprinted polymer. The imprinted cavities in the acid-resistant fluoride ion imprinted polymer are configured to maintain structural stability in the strongly acidic wastewater with pH < 2 and exhibit high adsorption selectivity for fluoride ions.

8. The method according to claim 7, characterized in that, The controlled adsorption conditions include: The adsorption device is configured as a fixed-bed adsorption tower comprising at least two stages connected in series; The flow rate of wastewater through the fixed-bed adsorption tower is controlled to ensure that the wastewater has sufficient contact reaction time with the acid-resistant fluoride ion-imprinted polymer. By controlling the number of series stages of the fixed-bed adsorption tower and the contact reaction time, the fluoride concentration in the effluent is stably reduced to below 1.0 mg / L under strongly acidic conditions and in the presence of high concentrations of chloride and sulfate ions.

9. The method according to claim 8, characterized in that, The generation of the full-process fluorine resource recovery report includes: Based on the aforementioned deep defluorination and wastewater purification information set, a low-concentration ammonia solution is used to elute and regenerate the adsorbed saturated acid-resistant fluoride-imprinted polymer, and the adsorbed fluoride ions are desorbed into the eluent in the form of ammonium fluoride. The acid-resistant fluoride ion imprinted polymer, after being eluted with ammonia water, was rinsed with dilute sulfuric acid solution to restore it to an active form suitable for adsorption of the strongly acidic wastewater. A calcium chloride solution is introduced into the eluent rich in ammonium fluoride, and a calcium fluoride precipitate is formed by the reaction. The calcium fluoride precipitate is then subjected to solid-liquid separation, washing and drying to obtain a high-purity calcium fluoride product. Based on the process data and results of adsorbent regeneration, fluoride ion recovery, and product generation, a full-process fluorine resource recovery report is generated.

10. A deep defluorination system for flue gas purification of acidic wastewater, characterized in that, The method applied to any one of claims 1-9 includes: The preliminary treatment module is used to acquire a preliminary fluoride separation wastewater information set, perform electrochemical-photocatalytic synergistic complex-breaking treatment, convert stable fluoride complexes in the wastewater into free fluoride ions, and simultaneously pre-deposit some heavy metals to generate a wastewater information set to be treated with free fluoride ions as the dominant form. The deep defluoridation module is used to perform acid-resistant molecularly imprinted polymer-specific adsorption of fluoride ions under strong acidic conditions based on the wastewater information set to be treated, thereby generating a deep defluoridation and purification wastewater information set. The resource recovery module is used to regenerate the adsorbent and treat the eluent based on the information set of the deep defluorination and purification wastewater, convert and recover high-purity calcium fluoride products, and generate a full-process fluoride resource recovery report.

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