Recovery method and application of lead halide in waste perovskite photocatalyst

Abstract

The invention discloses a recovery method and application of lead halide in a waste perovskite photocatalyst, and an efficient ion exchange-directional precipitation strategy is used for recovering and reusing PbX2 resources from the perovskite photocatalyst. The recycled PbX2 resource can be applied to synthesis of the perovskite photocatalyst again to form a closed-loop cycle; the APbXbased photocatalyst synthesized by using the recovered PbX2 shows good photocatalytic performance in an ethanol generation experiment, can still keep relatively high photocatalytic efficiency after being recycled for multiple times, and has good stability and reusability; through a closed-loop recovery and reutilization strategy, lead halide in the waste perovskite is converted into a reusable resource, lead is prevented from leaking into the environment, and the risk of environmental pollution is reduced. The environment problem of lead in the waste perovskite photocatalyst is effectively solved, the recycled and prepared material is excellent in photocatalytic performance, the experiment cost is reduced, and a new thought and method are provided for sustainable development and resource application of the perovskite material.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst technology, specifically to a method and application for recovering lead halide from waste perovskite photocatalysts. Background Technology

[0002] Lead halide perovskite materials have attracted widespread attention in the optoelectronic field due to their excellent optoelectronic properties (such as high photoluminescence quantum yield and tunable bandgap), among which all-inorganic CsPbBr3 perovskites have garnered significant interest due to their potential in photocatalysis. However, the heavy metal nature of lead limits the commercial application of perovskite materials. Improper disposal of waste perovskite materials can lead to lead leakage into the environment, polluting soil and water bodies and posing a serious threat to ecosystems and human health.

[0003] Currently, the main strategies for recovering lead from perovskite materials include organic solvent dissolution-precipitation and water-based dissolution-crystallization. Organic solvent dissolution-precipitation is a commonly used lead recovery method, utilizing highly polar organic solvents (such as dimethyl sulfoxide or γ-butyrolactone) to dissolve the perovskite, followed by precipitating lead salts by adding antisolvents (such as toluene or chlorobenzene) or iodide salts (such as KI, NaBr). However, various cations in perovskite (such as Pb)... 2+ Cs + MA + Lead halides typically dissolve together in organic solvents, may be adsorbed by resins and participate in subsequent reactions, resulting in low purity of lead in the precipitate or requiring complex purification procedures. Water-based dissolution-crystallization is another commonly used lead recovery method. It utilizes the significant temperature-dependent solubility of lead halides in water to immerse degraded perovskite in an aqueous solution to repair and recover high-quality perovskite crystals. This method is simple, environmentally friendly, and inexpensive. However, lead halides have extremely low solubility in pure water, especially for bromine-containing CsPbBr3 perovskites, leading to limited recovery efficiency. Furthermore, other ions may dissolve simultaneously in water, affecting the purity of the recovered lead halides.

[0004] Existing technologies such as organic solvent dissolution-precipitation and water-based dissolution-crystallization methods have many problems. Therefore, the recovery and reuse of lead remains the key to solving the environmental problems of perovskite materials. Thus, developing an efficient, environmentally friendly and low-cost method for recovering lead halides from perovskite photocatalysts has important research value. Summary of the Invention

[0005] In view of the problems existing in the above-mentioned background technology, the purpose of this invention is to provide a method and application for the recovery of lead halide from waste perovskite photocatalysts.

[0006] To achieve the above objectives, the present application adopts the following technical solution.

[0007] The first aspect of this application provides a method for recovering lead halide from waste perovskite photocatalysts, comprising the following steps: Step 1: Remove the waste perovskite photocatalyst Dissolving in dimethyl sulfoxide (DMSO) solvent yields a product containing A + Pb 2+ and X - The first solution; Step 2: Extract A from the first solution using a cation exchange resin. + and Pb 2+ The adsorption cycle is repeated multiple times, and A in the first solution + and Pb 2+ They are adsorbed onto the cation exchange resin; Step 3: Elute and release A from the cation exchange resin using a gradient HNO3 solution via ion exchange. + Pb 2 + , to obtain a substance containing A + and Pb 2+ The second solution; Step 4: Adjust the pH of the second solution with NaOH solution to make Pb 2+ The directional precipitation is Pb(OH)2, and the first precipitate is obtained after centrifugation; Step 5: Dissolve the first precipitate with dilute HNO3 solution. After the reaction, a product containing Pb is obtained. 2+ The third solution; Step 6: Add NaX solution to the third solution, centrifuge and wash after reaction, and dry to obtain PbX2.

[0008] Furthermore, in step 1, the waste perovskite photocatalyst In this context, A represents Cs and Rb; the waste perovskite photocatalyst In the NaX solution, X represents Br, Cl, or I; preferably, A represents Cs and X represents Br.

[0009] Furthermore, in step 1, the waste perovskite photocatalyst The solid-liquid ratio of the dimethyl sulfoxide (DMSO) solvent is 60-100 g / L; the waste perovskite photocatalyst The weight ratio of the cation exchange resin in step 2 to that in a single application is 1:0.5-1.5.

[0010] Furthermore, in step 2, the cation exchange resin reacts with the first solution for 0.5-2 hours, and the adsorption cycle is repeated more than 5 times.

[0011] Furthermore, in step 3, the concentrations (v / v) of the gradient HNO3 solution are 10%, 5%, 2.5%, and 1%, and the elution conditions are a stirring reaction for 0.5-2 h.

[0012] Furthermore, in step 4, the concentration of the NaOH solution is 0.1-2 M, and the pH value is adjusted to 8-10.

[0013] Furthermore, in step 6, the concentration of the NaX solution is 0.1-2 M, and the drying conditions are drying at 70-90 °C for 8-16 h.

[0014] Furthermore, the volume ratio of the dimethyl sulfoxide (DMSO) solvent in step 1, the gradient HNO3 solution in step 3, and the dilute HNO3 solution in step 5 is 1:1-2:1-2.

[0015] A second aspect of this application provides lead halide obtained by the above-described recycling method.

[0016] A third aspect of this application provides the use of the aforementioned lead halide in the preparation of perovskite photocatalysts.

[0017] Compared with the shortcomings and deficiencies of existing technologies, the present invention has the following beneficial effects: 1. This invention proposes a highly efficient ion exchange-directed precipitation strategy for the recovery and reuse of lead (Pb) resources from perovskite photocatalysts, offering significant technical advantages and application value. Through multiple adsorption cycles and gradient HNO3 solution elution, a significantly higher lead recovery efficiency than existing technologies is achieved. The high-purity lead halide recovered through directed precipitation and purification steps can be directly used as a lead source for resynthesis. Basic photocatalyst.

[0018] 2. This invention, through... The PbX2 resources recovered from perovskite-based photocatalysts can be reused in the synthesis of perovskite-based photocatalysts, forming a closed-loop cycle. This material reuse reduces lead waste and lowers costs, resulting in significant economic and environmental benefits and broad market prospects for practical applications.

[0019] 3. This invention uses recycled PbX2 to synthesize The photocatalyst exhibited excellent photocatalytic performance in ethanol production experiments, maintaining high photocatalytic efficiency even after multiple cycles, demonstrating good stability and reusability. In contrast, existing technologies typically show a significant decline in photocatalytic performance after repeated cycles, making it difficult to maintain high activity.

[0020] 4. This invention utilizes a closed-loop recycling and reuse strategy to convert lead halides from waste perovskite into reusable resources, preventing lead leakage into the environment and reducing the risk of environmental pollution. This strategy not only solves the environmental problem of lead in waste perovskite photocatalysts but also achieves efficient resource recycling, meeting the requirements of sustainable development. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the process for recovering PbBr2 from waste perovskite photocatalysts and re-preparing CsPbBr3 perovskite photocatalysts provided in Examples 1 and 2 of the present invention. Figure 2 This is a graph showing the lead content of each step in the PbBr2 recovery method in Embodiment 2 of the present invention; Figure 3 This is the X-ray diffraction pattern (XRD pattern) of PbBr2 recovered in Example 2 of the present invention. Figure 4 This is the X-ray diffraction pattern (XRD pattern) of the CsPbBr3 / BiOBr heterojunction constructed in Example 6 of the present invention. Figure 5 This is a comparison chart of the photocatalytic CO2 reduction reaction performance of the monomers CsPbBr3 and BiOBr provided in Example 4 and the CsPbBr3 / BiOBr heterojunction provided in Example 6. Figure 6 This is a comparison chart of the photocatalytic CO2 reduction performance of CsPbBr3 provided in Example 3 of the present invention (CsPbBr3 prepared from recycled PbBr2) and CsPbBr3 provided in Comparative Example 1 (CsPbBr3 prepared from commercial PbBr2). Figure 7 This is a comparison chart of the photocatalytic CO2 reduction performance of the CsPbBr3 / BiOBr heterojunction provided in Example 5 of the present invention (CsPbBr3 / BiOBr heterojunction prepared with recycled PbBr2) and the CsPbBr3 / BiOBr heterojunction provided in Comparative Example 2 (CsPbBr3 / BiOBr heterojunction prepared with commercial PbBr2). Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] The method for recovering lead halides from waste perovskite photocatalysts is as follows: Example 1

[0024] Step 1: Add 1 g of perovskite CsPbBr3 to 12.5 mL of dimethyl sulfoxide (DMSO) and stir for 30 min. At this point, the perovskite is completely dissolved, yielding a solution containing CsPbBr3. + Pb 2+ and Br - The first solution of ions; Step 2: Add 1 g of fresh cation exchange resin to the first solution above and stir for 0.5-2 h, specifically 1 h, to fully adsorb Cs. + and Pb 2+ Subsequently, the adsorbed resin was collected, and 1g of fresh resin was added back to the remaining first solution. This adsorption cycle was repeated at least 5 times, specifically 5 times, to ensure sufficient capture of Cs. + and Pb 2+ , so that Cs in the first solution + and Pb 2+ They are adsorbed onto the cation exchange resin; Step 3: Transfer the collected resin to a beaker, and sequentially add 17.5 mL of HNO3 at different concentration gradients (10%, 5%, 2.5%, 1% HNO3 / H2O, v / v). Stir the reaction for 0.5-2 h, specifically 1 h, to release the ions adsorbed in the resin. After each addition, separate the resin and mix with acidic eluent. The final product contains Cs. + and Pb 2+ The second solution; Step 4: Use a 0.1-2 M NaOH solution, specifically a 1 M NaOH solution, to adjust the pH of the second solution to 8-10, specifically to 9.1, to allow Pb to... 2+ The directional precipitation of Pb(OH)₂ involves the presence of Cs in the solution during this process. + It does not participate in the reaction. The precipitate is collected by centrifugation to obtain the first precipitate; Step 5: Dissolve the first precipitate in 17.5 mL of dilute HNO3 solution. After the reaction, a product containing Pb is obtained. 2+ The third solution; Step 6: Finally, add 0.1-2 M NaBr solution (specifically 1 M NaBr solution) to the third solution above to form PbBr2 precipitate. After centrifugation, wash several times with deionized water to remove Na+. + and residual Br - PbBr2 was recovered from perovskite after drying at 70-90 °C for 8-16 h, specifically at 80 °C for 12 h. Example 2

[0025] Step 1: Add 2 g of perovskite CsPbBr3 to 25 mL of dimethyl sulfoxide (DMSO) and stir for 30 min. At this point, the perovskite is completely dissolved, yielding a solution containing CsPbBr3. + Pb 2+ and Br - The first solution of ions; Step 2: Add 2 g of fresh cation exchange resin to the first solution above, and stir the reaction for 0.5-2 h, specifically 1 h, to fully adsorb Cs. + and Pb 2+ Subsequently, the adsorbed resin was collected, and 1g of fresh resin was added back to the remaining first solution. This adsorption cycle was repeated at least 5 times, specifically 5 times, to ensure sufficient capture of Cs. + and Pb 2+ , so that Cs in the first solution + and Pb 2+ They are adsorbed onto the cation exchange resin; Step 3: Transfer the collected resin to a beaker, and sequentially add 35 mL of HNO3 at different concentration gradients (10%, 5%, 2.5%, 1% HNO3 / H2O, v / v). Stir the reaction for 0.5-2 h, specifically 1 h, to release the ions adsorbed in the resin. After each addition, separate the resin and mix with acidic eluent. The final product contains Cs. + and Pb 2+ The second solution; Step 4: Use a 0.1-2 M NaOH solution, specifically a 1 M NaOH solution, to adjust the pH of the second solution to 8-10, specifically to 9.1, to allow Pb to... 2+ The directional precipitation of Pb(OH)₂ involves the presence of Cs in the solution during this process. + It does not participate in the reaction. The precipitate is collected by centrifugation to obtain the first precipitate; Step 5: Dissolve the first precipitate in 35 mL of dilute HNO3 solution. After the reaction, a product containing Pb is obtained. 2+ The third solution; Step 6: Finally, add 0.1-2 M NaBr solution (specifically 1 M NaBr solution) to the third solution above to form PbBr2 precipitate. After centrifugation, wash several times with deionized water to remove Na+. + and residual Br - PbBr2 was recovered from perovskite after drying at 70-90 °C for 8-16 h, specifically at 80 °C for 12 h.

[0026] Initial Pb after perovskite dissolved in DMSO in Example 22+ The content was 780 mg. After resin adsorption, ion exchange, directional precipitation, precipitate dissolution, and bromine source conversion, the Pb in PbBr2 was reduced. 2+ The final recovery amount was 718.1 mg, and the overall recovery efficiency of the perovskite catalyst was 92.06%. The corresponding Pb was calculated. 2+ The conversion efficiencies were 99.91%, 92.89%, 99.67%, 100%, and 99.52%, respectively. Figure 2 Pb in each step of Example 2 was quantified. 2+ The conversion efficiency demonstrates the significant advantages of ion exchange and directional precipitation strategies in lead recovery.

[0027] The PbBr2 recovered in Example 2 was subjected to XRD analysis, and its X-ray diffraction pattern (XRD pattern) is shown below. Figure 3 As shown, the recovered PbBr2 exhibited diffraction peaks consistent with the PDF card, with no impurity peaks, and completely overlapped with the standard PDF card, confirming the effective recovery of PbBr2 resources from the CsPbBr3-based catalyst.

[0028] Applications of lead halides in waste perovskite photocatalysts: Preparation of CsPbBr3 (CPB) photocatalyst Example 3

[0029] Step 1: Under magnetic stirring, 91 mg of PbBr2 and 53 mg of CsBr recovered in Examples 1-2 above were dissolved in 4 mL of DMSO to obtain a perovskite precursor solution. Step 2: Add 10 mL of isopropanol dropwise to the above solution and stir for 20 min, producing an orange precipitate. Collect the precipitate by centrifugation and wash it three times with isopropanol. Step 3: Vacuum dry overnight at 60 °C; Step 4: After heating at 140 °C for 20 min, the original CsPbBr3 was prepared. Example 4

[0030] Step 1: Under magnetic stirring, 455 mg of PbBr2 and 265 mg of CsBr recovered in Examples 1-2 above were dissolved in 20 mL of DMSO to obtain a perovskite precursor solution. Step 2: Add 50 mL of isopropanol dropwise to the above solution and stir for 20 min, producing an orange precipitate. Collect the precipitate by centrifugation and wash it three times with isopropanol. Step 3: Vacuum dry overnight at 60 °C; Step 4: After heating at 140 °C for 20 min, the original CsPbBr3 was prepared.

[0031] Constructing CsPbBr3 / BiOBr heterojunction (CPB / BOB) catalysts Example 5

[0032] Step 1: Under magnetic stirring, dissolve 91 mg of PbBr2 and 53 mg of CsBr recovered in Examples 1-2 above in 4 mL of DMSO to form solution A; Step 2: Disperse 50 mg of BiOBr cocatalyst (BOB) in 10 mL of isopropanol and sonicate for 20 min to prepare dispersion B; Step 3: Under continuous stirring, add dispersion B dropwise to solution A and continue stirring for 20 min, producing an orange precipitate. Collect the precipitate by centrifugation and wash it three times with isopropanol. Step 4: Vacuum dry overnight at 60 °C; Step 5: After heating at 140 °C for 20 min, a CsPbBr3 / BiOBr heterojunction was constructed. Example 6

[0033] Step 1: Under magnetic stirring, dissolve 455 mg of PbBr2 and 265 mg of CsBr recovered in Examples 1-2 above in 20 mL of DMSO to form solution A; Step 2: Disperse 250 mg of BiOBr cocatalyst in 50 mL of isopropanol and sonicate for 20 min to prepare dispersion B; Step 3: Under continuous stirring, add dispersion B dropwise to solution A and continue stirring for 20 min, producing an orange precipitate. Collect the precipitate by centrifugation and wash it three times with isopropanol. Step 4: Vacuum dry overnight at 60 °C; Step 5: After heating at 140 °C for 20 min, a CsPbBr3 / BiOBr heterojunction was constructed.

[0034] XRD analysis was performed on the CsPbBr3 / BiOBr heterojunction constructed in Example 6, and its X-ray diffraction pattern (XRD pattern) is shown below. Figure 4As shown, the peaks at 21.5°, 30.6°, and 37.6° of the CsPbBr3 / BiOBr heterojunction sample correspond to the (110), (-200), and (-202) planes of CsPbBr3 (JCPDS: 18-0364), while the peaks at 25.2° and 31.7° are attributed to the (101) and (102) planes of BiOBr (JCPDS: 78-0348), respectively. This indicates the successful synthesis of the CsPbBr3 / BiOBr heterojunction and also demonstrates the high crystallinity and high phase purity of the catalyst.

[0035] The photocatalytic activity of the samples was evaluated by reducing CO2 under simulated sunlight. 30 mg of the CsPbBr3 / BiOBr heterojunction constructed in Example 6 was sonicated and uniformly dispersed in a quartz tube containing 10 mL acetonitrile and 0.1 mL deionized water. Subsequently, the solution was bubbled with ultra-high purity CO2 gas (99.999%) for 10 minutes to displace air, followed by a 1-hour dark treatment to establish adsorption-desorption equilibrium between CO2 and the catalyst. A 300 W xenon lamp equipped with an AM 1.5 filter was used as the light source, and the photocatalytic reaction was carried out under illumination for 4 hours. After the reaction, 1 mL of gas was extracted from the gas phase of the reactor for gas chromatography analysis. Simultaneously, the reaction mixture was centrifuged, and the liquid products in the supernatant were quantitatively analyzed to comprehensively evaluate the efficiency and selectivity of the photocatalytic CO2 reduction.

[0036] Figure 5 The results showed that after 4 hours of sunlight exposure, the yield of CH3CH2OH from the CPB / BOB prepared in Example 6 was 54.62 μmol·g. -1 ·h -1 The selectivity was 98.4%, significantly higher than the original CPB (32.82 μmol·g) provided in Example 4. -1 ·h -1 (selectivity of 98.8%) and BOB (40.5 μmol·g) -1 ·h -1 The selectivity was 98.0%. This indicates that the CPB / BOB composite material exhibits excellent performance in the photocatalytic CO2 reduction reaction, with high ethanol yield and selectivity. Comparative Example 1

[0037] Step 1: Under magnetic stirring, 91 mg of commercial PbBr2 and 53 mg of CsBr were dissolved in 4 mL of DMSO to obtain a perovskite precursor solution. Step 2: Add 10 mL of isopropanol dropwise to the above solution and stir for 20 min, producing an orange precipitate. Collect the precipitate by centrifugation and wash it three times with isopropanol. Step 3: Vacuum dry overnight at 60 °C; Step 4: After heating at 140 °C for 20 min, the original CsPbBr3 was prepared. Comparative Example 2

[0038] Step 1: Under magnetic stirring, 455 mg of commercial PbBr2 and 265 mg of CsBr were dissolved in 20 mL of DMSO to obtain a perovskite precursor solution. Step 2: Add 50 mL of isopropanol dropwise to the above solution and stir for 20 min, producing an orange precipitate. Collect the precipitate by centrifugation and wash it three times with isopropanol. Step 3: Vacuum dry overnight at 60 °C; Step 4: After heating at 140 °C for 20 min, the original CsPbBr3 was prepared. Comparative Example 3

[0039] Step 1: Under magnetic stirring, dissolve 91 mg of commercial PbBr2 and 53 mg of CsBr in 4 mL of DMSO to form solution A; Step 2: Disperse 50 mg of BiOBr cocatalyst in 10 mL of isopropanol and sonicate for 20 min to prepare dispersion B; Step 3: Under continuous stirring, add dispersion B dropwise to solution A and continue stirring for 20 min, producing an orange precipitate. Collect the precipitate by centrifugation and wash it three times with isopropanol. Step 4: Vacuum dry overnight at 60 °C; Step 5: After heating at 140 °C for 20 min, a CsPbBr3 / BiOBr heterojunction is constructed. Comparative Example 4

[0040] Step 1: Under magnetic stirring, dissolve 455 mg of commercial PbBr2 and 265 mg of CsBr in 20 mL of DMSO to form solution A; Step 2: Disperse 250 mg of BiOBr cocatalyst in 50 mL of isopropanol and sonicate for 20 min to prepare dispersion B; Step 3: Under continuous stirring, add dispersion B dropwise to solution A and continue stirring for 20 min, producing an orange precipitate. Collect the precipitate by centrifugation and wash it three times with isopropanol. Step 4: Vacuum dry overnight at 60 °C; Step 5: After heating at 140 °C for 20 min, a CsPbBr3 / BiOBr heterojunction is constructed.

[0041] After the original CsPbBr3 provided in Comparative Example 1 was tested for photocatalysis, it was recovered into PbBr2 using the recovery method provided in this invention. Then, the recovered PbBr2 was reused as a precursor for the synthesis of CPB and CPB / BOB catalysts using the method of preparing CsPbBr3 (CPB) photocatalyst (refer to Example 3) and the method of constructing CsPbBr3 / BiOBr heterojunction catalyst (refer to Example 5).

[0042] Figure 6 The results showed that in the first cycle, the ethanol production rate of R-CPB-1 (CsPbBr3 prepared from PbBr2 recovered in the first cycle) was 32.77 μmol·g. -1 ·h -1 It retained 99.85% of the C-CPB (CsPbBr3 prepared from commercially available PbBr2) activity. Furthermore, no significant yield decrease occurred after 5 cycles, with R-CPB-5 (31.80 μmol·g⁻¹) showing the desired yield. -1 ·h -1 The recovered PbBr2 retained 94.56% of the activity of the C-CPB synthesized from commercially available PbBr2. This indicates that the recovered PbBr2 can maintain high photocatalytic performance after multiple cycles, demonstrating good stability and reusability.

[0043] Figure 7 The results showed that in the first cycle, the ethanol production rate of R-CPB / BOB-1 (a CsPbBr3 / BiOBr heterojunction prepared from the first-cycle-recovered PbBr2) was 51.65 μmol·g. -1 ·h -1 It retained 94.56% of the C-CPB / BOB (CsPbBr3 / BiOBr heterojunction prepared using commercially available PbBr2) activity. Furthermore, no significant yield decrease occurred after 5 cycles, with R-CPB / BOB-5 (45.40 μmol·g⁻¹) showing the desired yield. -1 ·h -1 The C-CPB / BOB synthesized from commercially available PbBr2 retained 83.12% of its activity. This further demonstrates that the recovered PbBr2 can maintain high photocatalytic performance after multiple cycles, exhibiting good stability and reusability.

[0044] Additionally, as shown in Table 1 below, the total cost of commercial PbBr2 is ¥14.45 (¥11.36 / g × 1.272 g). Recovering 1.272 g of PbBr2 from waste perovskite photocatalyst requires 25 ml DMSO for perovskite dissolution, 10 g resin for ion adsorption, and 8 ml HNO3 for Pb.2+ Release and dissolution of Pb(OH)₂, 2.8 g NaOH for pH adjustment, 4 g NaBr for Pb. 2+ The cost of materials is ¥8.26 per 1.272 g PbBr2 when all materials are used once. By reusing DMSO and resin for five cycles, the cost is reduced to ¥3.90 per 1.272 g PbBr2, a 73.01% reduction compared to commercial PbBr2. This cost analysis demonstrates that a closed-loop recycling and reuse strategy can significantly reduce experimental costs and improve economic efficiency.

[0045] Table 1. Price comparison between recycled PbBr2 and commercially available PbBr2

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering lead halide from waste perovskite photocatalysts, characterized in that, Includes the following steps: Step 1: Remove the waste perovskite photocatalyst Dissolving in dimethyl sulfoxide (DMSO) solvent yields a product containing A + Pb 2+ and X - The first solution; Step 2: Extract A from the first solution using a cation exchange resin. + and Pb 2+ The adsorption cycle is repeated multiple times, and A in the first solution + and Pb 2+ They are adsorbed onto the cation exchange resin; Step 3: Elute and release A from the cation exchange resin using a gradient HNO3 solution via ion exchange. + Pb 2+ , to obtain a substance containing A + and Pb 2+ The second solution; Step 4: Adjust the pH of the second solution with NaOH solution to make Pb 2+ The directional precipitation is Pb(OH)2, and the first precipitate is obtained after centrifugation; Step 5: Dissolve the first precipitate with dilute HNO3 solution. After the reaction, a product containing Pb is obtained. 2+ The third solution; Step 6: Add NaX solution to the third solution, centrifuge and wash after reaction, and dry to obtain PbX2.

2. The method for recovering lead halide from waste perovskite photocatalysts as described in claim 1, characterized in that, In step 1, the waste perovskite photocatalyst In this context, A represents Cs and Rb; the waste perovskite photocatalyst In the NaX solution, X represents Br, Cl, or I; preferably, A represents Cs and X represents Br.

3. The method for recovering lead halide from waste perovskite photocatalysts as described in claim 1, characterized in that, In step 1, the waste perovskite photocatalyst The solid-liquid ratio of the dimethyl sulfoxide (DMSO) solvent is 60-100 g / L; the waste perovskite photocatalyst The weight ratio of the amount of cation exchange resin used in step 2 to that used in a single application is 1:0.5-1.

5.

4. The method for recovering lead halide from waste perovskite photocatalysts as described in claim 1, characterized in that, In step 2, the cation exchange resin reacts with the first solution by stirring for 0.5-2 hours, and the adsorption cycle is repeated more than 5 times.

5. The method for recovering lead halide from waste perovskite photocatalysts as described in claim 1, characterized in that, In step 3, the concentrations (v / v) of the gradient HNO3 solution are 10%, 5%, 2.5%, and 1%, and the elution conditions are stirring reaction for 0.5-2 h.

6. The method for recovering lead halide from waste perovskite photocatalysts as described in claim 1, characterized in that, In step 4, the concentration of the NaOH solution is 0.1-2 M, and the pH value is adjusted to 8-10.

7. The method for recovering lead halide from waste perovskite photocatalysts as described in claim 1, characterized in that, In step 6, the concentration of the NaX solution is 0.1-2 M, and the drying conditions are drying at 70-90 °C for 8-16 h.

8. The method for recovering lead halide from waste perovskite photocatalysts as described in claim 1, characterized in that, The volume ratio of the dimethyl sulfoxide (DMSO) solvent in step 1, the gradient HNO3 solution in step 3, and the dilute HNO3 solution in step 5 is 1:1-2:1-2.

9. Lead halide obtained by the recycling method according to any one of claims 1-8.

10. The use of lead halide as described in claim 9 in the preparation of perovskite photocatalysts.

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