Bismuth-titanium composite oxide catalyst with light-driven self-healing function and application of bismuth-titanium composite oxide catalyst in catalytic precipitation and recovery of chloride ions in acid wastewater

Abstract

The invention discloses a bismuth-titanium composite oxide catalyst with a light-driven self-healing function and application of the bismuth-titanium composite oxide catalyst in catalytic precipitation and recovery of chloride ions in acid wastewater. The catalyst is cubic phase BiTiO, and the creativity of the catalyst is that triple function synergy is realized through Ti doping: adjacent Bi-O bonds are weakened to promote Biacidolysis and release; adsorbing and activating Cl as a Lewis acid site; and by utilizing the photocatalytic properties of the catalyst and the product BiOCl thereof, the in-situ regeneration of the catalyst is realized through an inactivated BiOCl covering layer caused by photo-generated hole oxygenolysis. On the basis, the invention constructs a'catalytic precipitation-light regeneration-chlorine recovery 'integrated closed-loop process: Cl in the wastewater is efficiently precipitated into BiOCl; the deactivated catalyst is regenerated by decomposing a BiOCl layer through illumination, and meanwhile released Cl is subjected to resource recovery; the regenerated catalyst is recycled. According to the method, the problem of passivation failure of a bismuth-based precipitation method is fundamentally solved, and the technical span from consumable treatment to sustainable catalysis and resource recovery is realized.

Description

Technical Field

[0001] This invention relates to the fields of environmental functional materials and advanced water treatment technology, specifically to a functional material with unique light-driven self-regeneration (self-healing) capabilities, and its innovative process and application in efficiently and sustainably removing chloride ions from high-salinity acidic industrial wastewater while simultaneously realizing the resource recovery of chlorine. Background Technology

[0002] Chloride ions (Cl⁻) are a common and serious pollutant in highly acidic industrial wastewater (such as wastewater from wet flue gas desulfurization, non-ferrous metal hydrometallurgical processes, and titanium dioxide production). Their high concentrations (often >2000 mg / L) and strong corrosiveness lead to severe equipment corrosion, difficulties in wastewater reuse, and interference with downstream resource recovery processes such as heavy metal precipitation. They are a key obstacle to achieving the goal of "zero discharge" (ZLD) for industrial wastewater.

[0003] Currently, deep dechlorination technologies for this type of wastewater all have significant limitations. Thermal evaporation / crystallization methods consume enormous amounts of energy (>50 kWh / m³); membrane methods such as reverse osmosis are prone to fouling and scaling, and have poor stability in strongly acidic environments; ion exchange methods require frequent resin regeneration, have high operating costs, and are severely affected by competition from coexisting anions. In contrast, chemical precipitation methods based on the formation of low-solubility precipitates have the advantages of simple principles and great potential. Among them, bismuth-based precipitants (such as Bi₂O₃, Bi(OH)₃) have attracted attention because they can form bismuth oxychloride (BiOCl) with Cl⁻, which has extremely low solubility (Ksp(BiOCl) ≈ 1.8×10⁻³¹) and is environmentally friendly. The basic reaction is: Bi³⁺ + Cl⁻ + H₂O → BiOCl↓ + 2H⁺.

[0004] However, the industrial application of this technology has always been constrained by an intrinsic scientific challenge: surface passivation. The dense BiOCl product layer generated in the early stages of the reaction rapidly coats the surface of the bismuth-based particles, forming physical and chemical barriers that severely hinder the continued release of the internal active components (Bi³⁺) and the inward transfer of external protons (H⁺), causing the reaction to quickly reach a "self-limiting" equilibrium. This results in a low actual utilization rate (typically <65%) of traditional bismuth-based materials (such as Bi₂O₃), essentially making them a "disposable" consumable that is not only costly but also generates large amounts of bismuth-containing sludge requiring disposal.

[0005] To overcome passivation, existing technologies have explored various approaches, but none have achieved a fundamental breakthrough. Regarding material modification: related studies have prepared bismuth oxides doped with metal ions such as iron and copper in order to improve the initial reaction rate, but have not solved the problem of complete deactivation caused by BiOCl coverage after long-term operation, and the material is not renewable.

[0006] Regarding process enhancement: Some studies have attempted to introduce ultraviolet (UV) irradiation into the Bi₂O₃ system, observing a slight increase in Cl⁻ removal rate, which was attributed to the indirect oxidation of Cl⁻ by photocatalytically generated hydroxyl radicals (·OH). However, this "photo-assisted oxidation" strategy has two major drawbacks: First, the selective oxidation efficiency of Cl⁻ by ·OH is low and not the dominant pathway; second, and more importantly, it completely ignores the core issue of the "passivation layer itself (BiOCl)," failing to utilize light energy to actively attack and remove the BiOCl layer that leads to deactivation. Therefore, its enhancement effect is limited (<10%) and cannot change the material's consumption properties.

[0007] In terms of mechanism understanding: existing research has a vague understanding of the mechanism of action of dopants, mostly staying at the level of macroscopic performance correlation, and lacking the ability to reveal the synergistic mechanism of how dopants simultaneously regulate "reactant release (Bi³⁺)", "reactant activation (Cl⁻)" and "product conversion (BiOCl)" at the atomic / electronic scale.

[0008] Therefore, a long-standing paradox exists in the existing technology: the byproduct (BiOCl) generated by the precipitation method is precisely the cause of its failure. Developing a smart material and process that can actively identify and utilize energy (such as light energy) to convert or remove this byproduct in situ, thereby achieving catalyst self-regeneration, is the key to breaking through the current technological bottleneck and promoting the sustainable application of bismuth-based precipitation methods, and is also the starting point of this invention. Summary of the Invention

[0009] (a) Purpose of the invention The primary objective of this invention is to overcome the core defect of existing bismuth-based precipitants, which suffer irreversible deactivation due to surface BiOCl passivation, and to provide a novel titanium-doped bismuth oxide (BiO2) with "self-diagnostic" and "self-repair" capabilities. 12 TiO 20 This invention relates to intelligent catalytic materials. The core idea is to integrate the "efficient precipitation of Cl⁻" and the "regeneration function of in-situ decomposition of deactivated products using light energy" into a single material system through precise crystal engineering and electronic structure design. Another objective of this invention is to provide a controllable and scalable preparation method for this material, and to construct an integrated process and system based on this material, encompassing "catalytic precipitation-photoregeneration-chlorine recovery," ultimately achieving a fundamental shift from a linear "catalyst-waste" treatment model to a closed-loop resource recovery model of "catalyst addition-regeneration-recycling."

[0010] (II) Technical Solution To achieve the above-mentioned objectives, the present invention proposes the following three levels of technical solutions: Level 1: Materials Design and Functional Innovation The catalytic material provided by this invention is a cubic phase titanium-doped bismuth oxide (Bi) with a defined stoichiometric ratio and crystal structure. 12 TiO 20 (Space Group I23). The inventive essence of this invention is embodied in Ti 4 Doping with ⁺ enables the intrinsic synergy and coupling of three key functions at the atomic / electronic scale, and its mechanism of action is as follows: 1) “Bi³⁺ release switch” function (lattice activation): Density functional theory (DFT) calculations show (see appendix) Figure 5 ), Ti 4 After the introduction of ⁺, it forms a strong covalent Ti-O bond with the surrounding oxygen atoms. This localized strong bonding effect, through long-range electronic interactions, significantly weakens the Bi-O bond between specific Bi sites and oxygen (manifested as a decrease in the electronic localization function (ELF) value). These "pre-weakened" Bi-O bonds become "active sites" preferentially attacked by protons (H⁺) in acidic environments, thereby greatly promoting the controllable and efficient release of Bi³⁺ from the crystal interior to the solution interface, solving the "source" problem of precipitation reaction. 2) "Cl⁻ trapping and activator" function (interface activation): Ti exposed on the material surface 4 The ⁺ ion, due to its high charge density, is a strong Lewis acid center. Cl⁻ (Lewis base) in wastewater will be chemisorbed onto Ti through coordination. 4 ⁺ site. This process not only achieves spatial enrichment of Cl⁻ near the active site, but more importantly, the lone pair electrons of Cl⁻ move towards Ti. 4 The empty orbital transfer of ⁺ leads to a decrease in the electron cloud density of Cl⁻ and an increase in the exposure of the Cl nucleus, i.e., "electron activation" occurs, which significantly enhances its electrophilic reactivity with Bi³⁺. 3) "Built-in regeneration engine" function (photo-driven self-healing): The material of this invention (Bi) 12 TiO 20 Both photogenerated electron-hole pairs (Eg ≈ 3.1 eV) and their deactivation products (BiOCl, Eg ≈ 3.4 eV) belong to wide bandgap semiconductors. Under light excitation (especially ultraviolet and some visible light), electron-hole pairs can be generated. This invention creatively utilizes the extremely strong oxidation ability of photogenerated holes (h⁺) to directly guide them to the BiOCl passivation layer. h⁺ can oxidize Cl⁻ ions in the BiOCl lattice, triggering a solid-state decomposition reaction: BiOCl + 2h⁺ → Bi³⁺ + ½O₂ + Cl₂↑. This reaction is like a "molecular-level scalpel", which can etch away the BiOCl capping layer that causes deactivation from the outside to the inside, exposing the fresh BiOCl layer with the above-mentioned functions (1) and (2) in situ. 12 TiO 20 The surface is thus used to achieve the "self-healing" and activity regeneration of the catalyst.

[0011] The three functions mentioned above do not exist independently, but rather are based on Ti. 4 -French doping is the central focus in Bi 12 TiO 20 This organic whole is formed within a specific phase. No doping or modification in the prior art has reported such a clear, complete, and mutually supportive "trinity" synergistic mechanism. This makes the material of the present invention no longer a simple reactant, but an intelligent catalytic system with a "work-rest (deactivation)-repair (regeneration)" life cycle.

[0012] Second level: Controllable material preparation methods To achieve the aforementioned functional materials, this invention provides a stable and repeatable sol-gel-high-temperature crystallization preparation method. The core of this method lies in ensuring atomically uniform doping of titanium and high-purity transformation of the precursor into the target cubic phase. Key steps include: separate preparation and homogenization of bismuth / titanium precursor solutions; co-precipitation with strictly controlled pH to obtain a homogeneous hydroxide precursor; sufficient aging to optimize the precursor structure; and the crucial high-temperature crystallization step (calcination temperature ≥ 625°C), which drives the complete transformation of the amorphous precursor into the active cubic phase Bi. 12 TiO 20 The decisive factors are precise control of the Bi / Ti feed ratio (12:1) and calcination regime (650°C, 2h) to obtain products with well-crystallized structure and optimal performance.

[0013] Third level: Integrated processes and systems Based on the aforementioned intelligent catalytic material, this invention constructs an innovative integrated process for water treatment and resource recovery (see appendix). Figure 6 Its core process is as follows: 1) Catalytic precipitation dechlorination: Under acidic conditions (e.g., pH 0.1-1.5), the catalyst is mixed with chlorine-containing wastewater. The catalyst rapidly releases Bi³⁺ and activates the adsorbed Cl⁻, efficiently generating BiOCl precipitate, achieving deep removal of Cl⁻ (effluent Cl⁻ can be reduced to <200 mg / L). After solid-liquid separation, purified water is obtained. 2) Photo-driven regeneration and chlorine recovery: The separated "deactivated" catalyst (loaded with BiOCl) is fed into a photo-regeneration reactor. Under light irradiation, the catalyst initiates a self-regeneration process, decomposing the BiOCl layer, restoring its activity, and simultaneously releasing chlorine gas (Cl₂). Cl₂ can be recovered as a chemical raw material (e.g., by passing it through NaOH solution to produce NaClO), realizing the resource-based transformation of pollutants. 3) Catalyst recycling: The regenerated catalyst returns to the first step to begin a new treatment cycle. This closed loop of "treatment-regeneration-recovery-retreatment" fundamentally eliminates the continuous generation of passivation waste and converts chloride ions into valuable products.

[0014] The system can be designed as an intermittent integrated reactor, or as a continuous / semi-continuous system consisting of a sedimentation tank, a photoreactor, and separation and reflux devices.

[0015] (III) Beneficial Effects Compared with the prior art, the present invention has the following outstanding substantive features and significant progress: The revolutionary principle: For the first time, the photochemical properties of the final precipitate product (BiOCl) of the target pollutant (Cl⁻) itself were proposed and realized to drive the regeneration cycle of the catalyst. This ingenious concept of turning "waste" (passivation layer) into "treasure" (regeneration driving force and chlorine source) is not obvious to those skilled in the art.

[0016] Multifunctional Intelligent Integration of Materials: The material of this invention is the first reported single compound integrating the functions of a "promoter (Bi³⁺ source)," an "activator (Cl⁻ adsorption / activation center)," and a "regenerator (photocatalyst)." This is achieved through a single doping element (Ti). 4 ⁺) The multifunctional synergistic design achieved in a specific crystal phase represents a leap forward in materials design concepts and demonstrates a high degree of creativity. 1) Economic efficiency and sustainability of the process: The recyclability of the catalyst brings the consumption of bismuth to near zero, significantly reducing operating costs (estimated to be more than 80% lower than the traditional Bi₂O₃ method). Simultaneously, the resource value of the byproduct Cl₂ can offset some of the energy consumption, making the entire process more economically competitive and in line with the principles of green chemistry and circular economy. 2) Practicality and robustness of the technology: The photo-regeneration mechanism effectively compensates for the decrease in precipitation efficiency caused by fluctuations in influent pH (e.g., pH rising to 1.0-1.5), broadening the process operating window and enhancing the ability to cope with actual wastewater quality changes. 3) Complete and implementable solution: From the atomic-level design mechanism of the materials, detailed synthesis steps and parameters, to the complete process flow diagram and system composition, this invention provides fully disclosed information sufficient for those skilled in the art to reproduce and implement this solution. Attached Figure Description

[0017] Figure 1 The X-ray diffraction (XRD) patterns of the materials obtained by calcination at different temperatures in Example 1 demonstrate that a pure cubic phase Bi is formed at 650°C. 12 TiO 20 .

[0018] Figure 2 In Example 2, the present invention Bi 12 TiO 20 The chloride ion removal kinetics of the catalyst and pure Bi2O3 under the same conditions (pH 0.1, [Cl⁻]0=5000 mg / L) were compared, demonstrating its ultra-high activity.

[0019] Figure 3 In Example 3, Bi 12 TiO 20 The comparison of final dechlorination efficiency under dark and light conditions at different initial pH levels demonstrates the crucial role of photoregeneration in widening the pH window.

[0020] Figure 4 In Example 4, (ac) fresh Bi 12 TiO 20 The scanning electron microscope (SEM) morphology and energy dispersive spectroscopy (EDS) elemental distribution of the sample after (df) reaction (covered with BiOCl) are compared to visually demonstrate the formation of the BiOCl layer and the fixation of Cl element.

[0021] Figure 5 In Example 4, Bi was calculated based on first-principles calculations. 12 TiO 20 The electronic localization function (ELF) diagram on the (011) crystal plane shows arrows indicating the adjacent Bi-O bond regions that are significantly weakened due to Ti doping (central bright area), providing theoretical evidence for the "lattice activation" function.

[0022] Figure 6 : Schematic diagram of the integrated closed-loop process system of "catalytic precipitation-photoregeneration-chlorine recovery" proposed in this invention.

[0023] Figure 7 In Example 5, Bi 12 TiO 20 Results of the catalyst's dechlorination performance stability test after three "use-photoregeneration" cycles. Specific implementation methods

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, the scope of protection of this invention is not limited to the following embodiments.

[0025] Example 1: Catalyst Bi 12 TiO 20 Preparation and structural confirmation This embodiment aims to detail the synthesis process of the catalyst and verify its crystal structure.

[0026] Precursor preparation: Weigh 48.50 g Bi(NO3)3·5H2O (0.10 mol) and dissolve it in 200 mL of 1.0 mol / L HNO3. Stir at 50°C to obtain a clear solution A. Measure 2.80 mL of tetrabutyl titanate (0.00830 mol) and add it to 400 mL of anhydrous ethanol. Sonicate for 30 min to obtain a homogeneous sol B. Under mechanical stirring at 500 rpm, add solution B dropwise to solution A at approximately 3 mL / min. After the addition is complete, adjust the pH of the system to 10.0±0.1 with 2.0 mol / L NaOH solution, forming a pale yellow precipitate. Transfer the suspension to a 50°C water bath and age it with stirring for 6 h. Centrifuge (8000 rpm, 10 min) to collect the precipitate, and wash it three times each with deionized water and anhydrous ethanol, alternating between the two. Dry at 80°C for 12 h to obtain a pale yellow precursor powder.

[0027] High-temperature crystallization: After grinding the precursor, approximately 10 g was placed in an alumina crucible and then placed in a muffle furnace. The program was set to heat to 650 °C at a rate of 5 °C / min, hold for 2 h, and then allow to cool naturally. The resulting product, after grinding, was designated Cat-BTO.

[0028] Preparation of control sample: Following the same steps but without adding a titanium source, pure Bi2O3 was obtained by calcination at 500°C, denoted as Cat-Bi2O3.

[0029] Structural characterization (XRD): Results are as follows Figure 1 As shown. The Cat-Bi₂O₃ spectrum is consistent with the monoclinic α-Bi₂O₃ standard card (PDF#71-2274). After calcination at 650°C, the diffraction peaks of Cat-BTO are consistent with those of the cubic Bi₂O₃ phase. 12 TiO 20 The standard card (PDF# 34-0097, space group I23) showed a perfect match, with no other impurity peaks, confirming the successful synthesis of the high-purity target phase.

[0030] Example 2: Intrinsic Dechlorination Performance Test This embodiment verifies the limiting performance of the catalyst of the present invention under optimal acidic conditions.

[0031] Experimental Method: A simulated wastewater with a Cl⁻ concentration of 5000 mg / L was prepared, and the pH was adjusted to 0.10 with concentrated H₂SO₄. Cat-BTO and Cat-Bi₂O₃ (calculated at a Bi:Cl molar ratio of 1:1, amounting to 0.732 g and 0.718 g respectively) were weighed and added to 100 mL of the above wastewater (250 mL Erlenmeyer flask). After sealing, the flask was placed in a constant-temperature shaker (150 rpm) at 25°C in the dark. Samples were taken at 10, 20, 40, 60, 90, and 120 min, filtered through a 0.22 μm filter membrane, and the Cl⁻ concentration of the filtrate was determined by automatic potentiometric titration (AgNO₃ titration).

[0032] Results and Discussion: Figure 2 As shown, Cat-BTO exhibits remarkable reaction rate and capacity, with a removal rate exceeding 80% after 40 minutes and reaching an extremely high removal rate of 96.4% (residual Cl⁻ ~180 mg / L) after 120 minutes. In contrast, the Cat-Bi₂O₃ reaction is slow, reaching a plateau of only 64.4% after 120 minutes. This directly demonstrates the decisive enhancement of reaction kinetics by the dual functions of "lattice activation" and "interface activation" brought about by Ti doping.

[0033] Example 3: Verification of photoregeneration effect and investigation of pH adaptability This embodiment examines the importance of photoregeneration under more practical conditions (slightly lower acidity).

[0034] Experimental setup: Wastewater with [Cl⁻]₀ = 5000 mg / L and initial pH values ​​of 0.5 and 1.0 was prepared. A 300W xenon lamp (with an AM1.5G filter) was used to simulate sunlight, with a light intensity of ~100 mW / cm². The reaction was carried out in a quartz reactor with a cooling jacket, and the temperature was controlled at 25±2°C.

[0035] Experimental procedure: 100 mL of wastewater was taken from each group and Cat-BTO (Bi:Cl=1:1) was added. Adsorption equilibrium was established by first reacting in the dark for 30 min, then the light source was turned on, for a total reaction time of 150 min (dark + light). Samples were taken and analyzed throughout the process.

[0036] Results and Discussion: Figure 3 The results showed that at pH=0.5, light irradiation increased the final removal rate from 78.2% in the dark to 86.4%. The effect was even more significant at pH=1.0: the removal rate in the dark, which plummeted to 54.0% due to insufficient H⁺, jumped to 67.2% under light, a relative increase of 24.4%. This strongly demonstrates that photoregeneration can effectively overcome the kinetic limitations caused by increased pH, broaden the practical pH window of the technology, and reduce the consumption of reagents for strong acid adjustment.

[0037] Example 4: Microscopic and electronic structural evidence of the reaction mechanism This embodiment provides direct evidence for the innovative mechanism of the invention through advanced characterization techniques.

[0038] Morphology and elemental distribution (SEM-EDS): Fresh Cat-BTO and the solid after the reaction in Example 2 (washed and dried, denoted as Spent-Cat) were characterized. Figure 4 The AC assay shows that the fresh catalyst consists of dense particles of 0.5-2 μm with uniform distribution of Bi, Ti, and O elements. Figure 4 Data from digital imaging showed that after the reaction, typical BiOCl nanosheet flower-like structures "grew" on the particle surface, and EDS surface scanning clearly showed that Cl elements were uniformly and strongly covered on the particle surface (co-located with Bi and O), while Ti signals were relatively independent, which directly confirmed the formation of the BiOCl passivation layer and the effective fixation of Cl.

[0039] Electronic Structure Theory Calculation (ELF): Optimization of Bi using DFT calculations 12 TiO 20 Crystal structure and plot its (011) plane ELF diagram ( Figure 5 In the figure, the area around the Ti atoms (the central warm-colored region) shows a high ELF value, indicating a strong covalent Ti-O bond. Key finding: Several Bi-O bond regions near the Ti atoms (indicated by the arrows in the figure) exhibit significantly low ELF values ​​(cool tones), directly visualizing the existence of "weakened Bi-O bonds" at the electronic scale, providing a solid quantum chemical theoretical basis for the "lattice activation" function.

[0040] Example 5: Validation of catalyst cycle stability and process sustainability This embodiment verifies the recyclability of the catalyst and the closed-loop feasibility of the entire process.

[0041] Cyclic experiment: Round 1: Take 100 mL of wastewater with pH=1.0 and [Cl⁻]₀=5000 mg / L, add Cat-BTO (Bi:Cl=1:1), and react in the dark for 120 min. Measure the removal rate (R1), and recover the solids by centrifugation.

[0042] Regeneration: Disperse the recovered solids in 50 mL of water with pH=2 and irradiate under simulated sunlight for 60 min.

[0043] Round 2: The regenerated solids were recovered and added to fresh wastewater of the same amount. The reaction was carried out in the dark for 120 min, and the removal rate (R2) was measured.

[0044] Round 3: Repeat the regeneration and reaction steps to obtain R3.

[0045] Result: As Figure 7 As shown, R1 was 54.0%. After photoregeneration, R2 recovered to 48.5%, significantly higher than the control group without any regeneration treatment (<10%). R3 remained at 45.2%. The results indicate that the photoregeneration process can effectively restore most of the catalyst activity, supporting its multiple cycles and preliminarily verifying the sustainability of the "catalysis-regeneration" closed-loop process.

[0046] Process Summary Based on all embodiments, the complete process of the present invention is as follows: Figure 6 As shown: Chlorinated acidic wastewater enters the system and comes into contact with the recycled catalyst. In the "catalytic precipitation unit," Cl⁻ is efficiently precipitated and removed. The catalyst loaded with BiOCl enters the "photoregeneration unit," where it decomposes BiOCl under light-driven conditions, regenerating the catalyst and releasing Cl₂. The Cl₂ is collected and utilized by the "resource recovery unit." The regenerated catalyst is returned to the precipitation unit, forming a material and energy cycle. This system successfully combines environmental remediation with resource recovery.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A smart regenerable catalyst for chloride ion removal and resource recovery in acidic wastewater, characterized in that, The catalyst is a titanium-doped bismuth oxide with a cubic crystal structure and the general chemical formula Bi. 12 TiO 20 The space group is I23; The catalyst achieves a closed-loop cycle of "precipitation-passivation-regeneration" through the synergistic integration of the following functionalities: (1) Lattice activation function: Ti 4 ⁺ Doping into [Bi 12 O 22 The cage-like framework induces a decrease in the localization of electrons in adjacent Bi-O bonds, forming easily broken sites that are sensitive to protons (H⁺), thereby enabling the targeted and controllable release of Bi³⁺ ions under acidic conditions; (2) Interfacial adsorption-activation function: Ti exposed on the catalyst surface 4 The ⁺ ion, as a strong Lewis acid center, specifically chemisorbs Cl⁻ ions in the solution and reduces the activation energy of Cl⁻ through electron transfer. (3) In-situ photo-regeneration function: The catalyst and the surface passivation layer bismuth oxychloride (BiOCl) generated by the reaction both have photocatalytic activity. Under light irradiation, photogenerated holes (h⁺) can directly oxidize Cl⁻ in the BiOCl lattice, driving the solid phase change reaction: BiOCl(s) + 2h⁺ → Bi³⁺(aq) + ½O2(g) + Cl2(g), thereby exfoliating the passivation layer in situ and regenerating the catalyst interface with initial activity.

2. The intelligent regeneration catalyst according to claim 1, characterized in that, It is prepared by the following sol-gel-high temperature crystallization method: a. Dissolve Bi(NO3)3·5H2O in 0.8-1.2 mol / L nitric acid aqueous solution to form a clear bismuth precursor solution; b. Tetrabutyl titanate is uniformly dispersed in anhydrous ethanol to form a titanium precursor sol; c. While stirring continuously, add the sol obtained in step b to the solution obtained in step a, and then adjust the pH of the mixture to 9.5-10.5 with an alkaline precipitant to generate a coprecipitate; d. The coprecipitate is aged at 45-65°C for 4-8 hours, and then centrifuged, washed, and dried to obtain an amorphous precursor; e. Calcine the precursor in air at 625-675°C for 1.5-3 hours to obtain crystalline cubic Bi. 12 TiO 20 catalyst.

3. The preparation method according to claim 2, characterized in that, In steps a and b, the molar ratio of Bi to Ti is 12.0±0.1:1; in step e, the heating rate of the calcination is 3-8°C / min, preferably constant temperature calcination at 650±5°C for 2 hours.

4. A method for the sustainable removal of chloride ions and recovery of chlorine resources from acidic wastewater based on catalytic precipitation and photo-driven regeneration, characterized in that, Using the catalyst according to any one of claims 1-3, the following two coupled unit operations are performed cyclically: (A) Catalytic precipitation unit: The catalyst is added to chloride-containing wastewater with pH ≤ 2.0 and a solid-liquid reaction is carried out under dark conditions to precipitate chloride ions in the form of BiOCl and fix them on the catalyst surface, thereby achieving deep dechlorination of the wastewater; (B) Photo-driven regeneration and resource recovery unit: The catalyst loaded with BiOCl in step (A) is separated and placed under light conditions to decompose the BiOCl layer by utilizing its photocatalytic activity, thereby regenerating the catalyst activity. At the same time, the byproduct chlorine gas (Cl2) is collected for resource utilization. The catalyst regenerated in step (B) is returned to step (A) for reuse, thus forming a sustainable processing and resource recovery system for material cycling and energy input.

5. The method according to claim 4, characterized in that, In step (A), the pH of the wastewater is 0.1-1.5, and the chloride ion concentration is 1000-20000 mg / L; the amount of catalyst added is 0.8:1 to 1.2:1 based on the molar ratio of Bi to Cl.

6. The method according to claim 4, characterized in that, In step (B), the illumination is a light source with a wavelength range including ultraviolet light and part of visible light in the range of 250-420 nm, a light intensity of 50-150 mW / cm², and an illumination time of 30-120 minutes.

7. The method according to claim 4, characterized in that, Steps (A) and (B) are carried out intermittently in an integrated reactor by alternating control of the switching on and off of the light source; or, they are carried out continuously or semi-continuously in separate precipitation reactors and photoregeneration reactors.

8. A system for implementing the method according to any one of claims 4-7, characterized in that, include: A catalytic precipitation reaction apparatus for carrying out the catalytic precipitation reaction of chloride ions; A solid-liquid separation device, connected to the precipitation reaction device, is used to separate the catalyst loaded with BiOCl from the purified wastewater; A photo-regeneration reaction device, connected to the solid-liquid separation device, is used to receive the catalyst loaded with BiOCl and carry out a photo-driven regeneration reaction. The device is equipped with a light source and a chlorine gas collection and processing unit. A catalyst reflux device is used to transport the regenerated catalyst back to the catalytic precipitation reaction device.

9. The use of the catalyst according to any one of claims 1-3 in the preparation of reagents or catalytic packing materials for treating wet flue gas desulfurization wastewater, non-ferrous metal smelting acidic wastewater or chemical chlorine-containing acidic wastewater.

10. A method for chlorine resource recovery, characterized in that, The method described in any one of claims 4-7 or the system described in claim 8 converts chloride ions in wastewater into chlorine gas (Cl2) and collects, absorbs or purifies it.

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