A method for treating perovskite precursor synthesis waste liquid

Abstract

The present application relates to the field of wastewater treatment, in particular to a method for treating perovskite precursor synthesis waste liquid. ‑ (X=Br ‑ / Cl ‑ / I ‑ ) electrode potential, so that the oxidized state halogen element can be reduced and recovered in the subsequent step, and the recovery is complete. The present application does not need electrolysis, and is simple to operate and easy to industrialize; the selected precipitant soluble lead is low in cost, and at the same time, the recovered lead halide can be directly used for synthesis of perovskite precursor, reducing the waste of halogen elements and saving cost.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, specifically a method for treating waste liquid from the synthesis of perovskite precursors. Background Technology

[0002] Lead halide perovskite materials have excellent photoelectric properties, thermal stability, band gap and spectral response range. Perovskite solar cells based on lead formamidinium iodide (FAPbI3) can achieve photoelectric conversion efficiency of over 25% and have been widely used in fields such as solar cells.

[0003] The synthesis methods for lead halide perovskite materials include solution deposition and precursor redissolution coating. Among these, the precursor redissolution coating method has seen rapid development in recent years due to its advantages such as low requirements for raw material purity and ease of controlling stoichiometry.

[0004] The precursor re-dissolution coating method involves preparing a pure-phase perovskite compound, called a precursor, through a chemical reaction in an organic or aqueous solvent using lead raw materials (including lead halides), halogen raw materials, and monovalent cation raw materials. This precursor is then dissolved in a highly soluble organic solvent and further processed using other methods to form a thin film on the surface of electronic devices, thus enabling its application.

[0005] However, existing perovskite precursor preparation methods often involve the use of excessive amounts of halogen raw materials to ensure complete conversion of lead raw materials and product purity. These excessive halogens remain in the waste liquid at a high concentration after synthesis, resulting in wasted costs.

[0006] Common methods for recovering halogens typically utilize the physical properties of elemental halogens to recover them in their elemental form. However, halogens recovered in their elemental form do not have a clear application in the synthesis of perovskite precursors and must be further converted into compounds such as lead halides before they can be used.

[0007] In summary, perovskite precursor synthesis waste liquid has the advantages of clear composition and high concentration, and corresponding recovery potential. However, existing perovskite precursor synthesis technologies either fail to recover halogen elements from the subsequent waste liquid, resulting in waste and pollution; or they are applied to the more complex finished perovskite batteries, which involves cumbersome operations and energy-intensive steps such as calcination and evaporation, and the recovered halogens lack clear application scenarios. Therefore, proposing a low-cost, easy-to-operate halogen element recovery process that allows for direct reuse of the recovered products within the industry is an important issue for building a complete perovskite solar cell industry chain. Summary of the Invention

[0008] In view of this, the technical problem to be solved by the present invention is to provide a method for treating waste liquid from the synthesis of perovskite precursors. The method provided by the present invention can recover halogen elements in the form of lead halide from the waste liquid from the synthesis of perovskite precursors, thereby obtaining halogen raw materials with clear application scenarios. The recovery is thorough and the operation is simple.

[0009] This invention provides a method for treating waste liquid from perovskite precursor synthesis, comprising the following steps:

[0010] S1) Adjust the pH of the waste liquid from the synthesis of perovskite precursor to 3-7, filter it, and obtain the first precipitate and filtrate;

[0011] S2) After reducing the filtrate obtained in step S1), react it with soluble lead, filter it, and obtain the second precipitate and dehalogenated waste liquid.

[0012] The method for treating waste liquid from perovskite precursor synthesis provided by this invention is a process for recovering halogen raw materials and organic solvents from waste liquid from perovskite precursor synthesis. The waste liquid from perovskite precursor synthesis refers to the sum of aqueous and organic phase waste liquids obtained after reaction, washing and other steps in the preparation of perovskite precursor materials by aqueous synthesis method.

[0013] Specifically, the perovskite precursor synthesis waste liquid of the present invention is a mixture containing free halide anions, more specifically a mixture containing free halide anions, elemental iodine, monovalent cations, divalent lead ions, and acetic acid; wherein the molar concentration of the free halide anions is higher than 0.01 mol / L, preferably 0.5 mol / L to 1.5 mol / L; the amount of elemental iodine, monovalent cations, and acetic acid is not specified. The pH of the perovskite precursor synthesis waste liquid of the present invention is less than 3, preferably less than 1.2, and more preferably 0.9 to 1.1. Preferably, in the perovskite precursor synthesis waste liquid of the present invention, the concentration of the solutes other than divalent lead ions, free halide anions, and their derivatives should not be so high as to act as or form impurities in the recovered product during the treatment method of the present invention.

[0014] The solvent for the perovskite precursor synthesis waste liquid described in this invention is water or an aqueous solution. Specifically, water should be used as a single solvent or the main solvent. When the solvent for the perovskite precursor synthesis waste liquid is water as the main solvent, that is, when the solvent component is not only water, the secondary solvent is one or more of ethanol, acetic acid, ethyl acetate, dichloromethane, chloroform, tetrachloromethane, petroleum ether, and N,N-dimethylformamide.

[0015] This invention first adjusts the pH of the perovskite precursor synthesis waste liquid to 3-7, then filters it to obtain a first precipitate and filtrate. This invention reduces the X² / X² ratio by adjusting the strongly acidic perovskite precursor synthesis waste liquid to a pH above 3. -(X=Br) - / Cl - / I - The electrode potential allows the oxidized halogen element to be reduced and recovered in subsequent steps.

[0016] Preferably, this invention uses soluble lead to adjust the pH. The amount of soluble lead added should be such that the pH after addition is 3-7. Using soluble lead to adjust the pH avoids introducing additional impurities, incidentally recovers a small amount of lead halide precipitate, and simultaneously adjusts the pH to 3-7 to ensure the successful subsequent reduction reaction. Specifically, an appropriate amount of soluble lead is added to the perovskite precursor synthesis waste liquid under stirring to adjust the pH to 3-7 to produce lead halide (PbX2, X=Br). - / Cl - / I - The mixture is precipitated to obtain a solid-liquid mixture, which is then filtered to obtain a first precipitate and a filtrate. The first precipitate is lead halide precipitate, which is a portion of the halogen elements recovered in the form of lead halide from the perovskite precursor synthesis waste liquid. The soluble lead in this invention is Pb, which is soluble in acidic aqueous solutions. 2+ The active ingredient is a lead-containing compound. Preferably, the soluble lead includes one or more of lead acetate, lead carbonate, lead oxide, and lead hydroxide.

[0017] After obtaining the first precipitate and filtrate, this invention reduces the filtrate and reacts it with soluble lead, followed by filtration to obtain the second precipitate and dehalogenation waste liquid. This invention reduces the filtrate to reduce elemental halogens, rather than oxidizing halide anions, thus directly recovering lead halides that can be used for perovskite precursor synthesis.

[0018] Specifically, in this invention, the filtrate from step S1) is reduced with a reducing agent and then reacted with soluble lead, followed by filtration to obtain a second precipitate and dehalogenation waste liquid. More specifically, a reducing agent is added to the filtrate from step S1), stirred evenly, and allowed to stand for a period of time. Subsequently, excess soluble lead is added to produce a solid-liquid mixture. The resulting solid-liquid mixture is filtered to obtain a second precipitate and dehalogenation waste liquid, wherein the second precipitate is a lead halide precipitate, which is a portion of the halogen elements recovered in the form of lead halide from the perovskite precursor synthesis waste liquid.

[0019] The reducing agent described in this invention includes one or more of formic acid, formate, and formaldehyde, preferably formic acid. This invention selects formic acid-like compounds that can ultimately be oxidized to carbonic acid / carbon dioxide, are relatively resistant to acidic systems, do not require excessive neutralization, and avoid introducing additional impurities into the waste liquid, thus ensuring the purity of the recovered lead halide. The reducing agent selected in this invention is inexpensive and easily degrades naturally.

[0020] The reduction time described in this invention is 24 h to 72 h, specifically, after adding the reducing agent and stirring until homogeneous, it is allowed to stand for 24 h to 72 h. The molar amount of the reducing agent in this invention is 0 to 0.5 times excess relative to the oxidizing substances in the perovskite precursor synthesis waste liquid. The longer standing time ensures complete reduction, eliminating the need for additional energy-consuming steps such as stirring; the excess reducing agent also contributes to complete reduction. This invention can determine whether the reduction is complete by observing the filtrate change from dark brown to transparent and colorless.

[0021] In steps S1) and S2) of this invention, the total molar amount of lead in the sum of the amounts of soluble lead used is 1 to 3 times excess relative to the halogen in the perovskite precursor synthesis waste liquid. Since soluble lead compounds such as lead acetate are themselves weak electrolytes or can form weak electrolytes, the added soluble lead compounds must be in excess, while also ensuring that all remaining halide ions in the filtrate after reduction in step S1) precipitate as lead halides.

[0022] The method for treating waste liquid from perovskite precursor synthesis provided by this invention further includes washing the first precipitate in step S1) and the second precipitate in step S2) with water and an organic solvent, respectively. Specifically, the first precipitate in step S1) and the second precipitate in step S2) are combined, washed several times with water and an organic solvent, and dried to obtain a high-purity lead halide raw material that can be directly used for perovskite synthesis. The washing liquid is then combined with the dehalogenation waste liquid from step S2) to form a dehalogenation waste liquid.

[0023] The organic solvent described in this invention includes one or more of ethyl acetate, ethanol, and methanol. In step S1), the first precipitate includes one or more of lead bromide, lead chloride, and lead iodide; in step S2), the second precipitate includes one or more of lead bromide, lead chloride, and lead iodide. Washing the first precipitate in step S1) and the second precipitate in step S2) improves the purity of the recovered precipitate, that is, improves the purity of the recovered lead halide. The degree of dehalogenation of the dehalogenation wastewater is related to the amount of soluble lead compound added in step S2), and the recovery rate of lead halide can reach over 99%.

[0024] This invention provides a method for treating waste liquid from perovskite precursor synthesis. The method involves adjusting the strongly acidic waste liquid to a pH above 3 to reduce the X² / X² ratio. - (X=Br) - / Cl - / I - The electrode potential allows the oxidized halogen element to be reduced and recovered in subsequent steps, ensuring complete recovery. This invention eliminates the need for electrolysis, is simple to operate, and is easily industrialized. The selected precipitant, lead soluble in lead, is inexpensive, and the recovered lead halide can be directly used in the synthesis of perovskite precursors, reducing the waste of halogen elements and saving costs. Attached Figure Description

[0025] Figure 1 The image shows the XRD pattern of lead iodide recovered in Example 1 of this invention. Detailed Implementation

[0026] This invention discloses a method for treating waste liquid from the synthesis of perovskite precursors. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0027] The present invention will be further described below with reference to the embodiments:

[0028] Example 1

[0029] Halogen recovery from 1000 mL of waste liquid used in the synthesis of FAPbI3 perovskite precursor:

[0030] A. According to the synthesis process, the synthesis waste liquid mainly contains approximately 1 mol / L of iodide ions, approximately 0.02 mol / L of formamidin cations, and approximately 1 mol / L of acetic acid. The pH of the synthesis waste liquid was measured to be 1 using pH paper. The waste liquid is purplish-black, and starch paper detected the presence of elemental iodine.

[0031] B. Take two 10 mL portions of the synthetic waste liquid. Leave one portion untreated and add excess sodium sulfite to the other to reduce the iodine. Use starch paper to test if the iodine reduction is complete. The iodide ion concentrations were measured to be 1.00 mol / L and 1.21 mol / L respectively using an iodide ion electrode. Based on this, the concentration of iodine in the waste liquid is estimated to be approximately 0.105 mol / L.

[0032] C. Add 10 g of solid lead acetate to the remaining synthetic waste liquid, stir to dissolve it, and immediately form a golden-yellow lead iodide precipitate. Because the resulting lead iodide is fine and difficult to filter, most of the solid-liquid mixture is separated by decantation after settling. The pH of the synthetic waste liquid was measured to be 3 using pH paper.

[0033] D. Add 7.0 g of sodium formate to the synthetic waste liquid, stir to dissolve, and let stand for 24 h. During this period, the waste liquid was observed to gradually fade. After 24 h, the solution was found to be completely colorless, and starch paper was used to test that there was no residual iodine in the synthetic waste liquid.

[0034] E. Add 70 g of solid lead acetate to the synthetic waste liquid and stir vigorously to dissolve it, immediately producing a large amount of golden-yellow lead iodide precipitate. After stirring continuously for 3 hours, stop stirring to allow the lead iodide to settle, and then separate most of the solid-liquid mixture by decantation.

[0035] F. Summarize the lead iodide recovered in steps C and E, wash three times each with alternating water and ethyl acetate, and dry in an oven at 60°C for 12 hours to obtain the recovered lead iodide. Figure 1 As shown, Figure 1 The XRD pattern of lead iodide recovered in Example 1 of this invention is shown. The washing liquid and the main body of the waste liquid obtained in step E were combined to form the dehalogenation waste liquid. Iodide was detected using an iodide ion electrode in the synthesis waste liquid before the reaction in step E. - The concentration was 8.00 g / L, and the I in the dehalogenation waste liquid from step F was measured. - The concentration was 0.061 g / L, and the recovery rate was 99.2%.

[0036] Example 2

[0037] Halogen recovery from 1000 mL of waste liquid used in the synthesis of CsPbBr3 perovskite precursor:

[0038] A. According to the synthesis process, the synthesis waste liquid mainly contains bromide ions at a concentration of approximately 1 mol / L, cesium ions at a concentration of approximately 0.02 mol / L, and acetic acid at a concentration of approximately 1 mol / L. The pH of the synthesis waste liquid, measured using pH paper, is 1. The waste liquid is light reddish-brown.

[0039] B. Take two 10 mL portions of the synthetic waste liquid. Leave one portion untreated and add excess sodium sulfite to the other to reduce the bromine. Complete reduction of bromine is indicated by complete decolorization of the solution. The bromide ion concentrations were measured using a bromide ion electrode and found to be 1.20 mol / L and 1.30 mol / L, respectively. Based on this, the concentration of bromine in the waste liquid is estimated to be approximately 0.100 mol / L.

[0040] C. Add 10 g of solid lead acetate to the remaining synthetic waste liquid, stir to dissolve it, and a white lead bromide precipitate will immediately form. After standing, most of the solid-liquid mixture is separated by decantation. The pH of the synthetic waste liquid is measured to be 3 using pH paper.

[0041] D. Add 5.0 g of sodium formate to the synthesis waste liquid, stir to dissolve, and let stand for 24 h. During this period, the waste liquid was observed to gradually fade. After 24 h, the solution was found to be completely colorless, indicating that the bromine had been completely reduced.

[0042] E. Add 70 g of solid lead acetate to the synthesis waste liquid, stir vigorously to dissolve it, and immediately a large amount of white lead bromide precipitate will form. After stirring continuously for 3 h, stop stirring to allow the lead bromide to settle, and then separate most of the solid-liquid mixture by decantation.

[0043] F. Summarizing the lead bromide recovered in steps C and E, a small amount of orange substance was found. This is because the generated lead bromide reacted with cesium ions in the waste liquid to form a small amount of CsPbBr3. The solution was washed three times with water and ethyl acetate until it turned white, and then dried in an oven at 60°C for 12 hours to obtain the recovered lead bromide. The washing solution and the main body of the waste liquid obtained in step E were combined to form the dehalogenation waste liquid.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for treating waste liquid from perovskite precursor synthesis, characterized in that, Includes the following steps: S1) The pH of the waste liquid from the synthesis of perovskite precursor was adjusted to 3-7 using soluble lead, and then filtered to obtain the first precipitate and filtrate. The pH of the waste liquid from the synthesis of the perovskite precursor is less than 3; the soluble lead is Pb, which is soluble in acidic aqueous solutions. 2+ Lead-containing compounds that are the active ingredient; S2) The filtrate obtained in step S1) is reduced and then reacted with soluble lead, followed by filtration to obtain a second precipitate and dehalogenation waste liquid; the soluble lead is Pb soluble in acidic aqueous solution. 2+ Lead-containing compounds that are the active ingredient; In steps S1) and S2), the molar amount of lead in the total amount of soluble lead used is 1 to 3 times more excessive than the halogen in the perovskite precursor synthesis waste liquid. In step S2), the reduction is carried out using a reducing agent, which includes one or more of formic acid, formate, and formaldehyde.

2. The processing method according to claim 1, characterized in that, In step S1), the waste liquid from the synthesis of the perovskite precursor contains free halide anions with a molar concentration higher than 0.01 mol / L.

3. The processing method according to claim 1, characterized in that, In step S2), the filtrate from step S1) is reduced using a reducing agent, wherein the molar amount of the reducing agent is 0 to 0.5 times in excess of the oxidizing substances in the perovskite precursor synthesis waste liquid.

4. The processing method according to claim 1, characterized in that, The reduction time is 24 h to 72 h.

5. The processing method according to claim 1, characterized in that, It also includes washing the first precipitate in step S1) and the second precipitate in step S2) with water and organic solvent respectively; The organic solvent includes one or more of ethyl acetate, ethanol, and methanol.

6. The processing method according to claim 1, characterized in that, In step S1), the solvent of the perovskite precursor synthesis waste liquid is water or an aqueous solution, wherein the aqueous solution is one or more of the following: ethanol, acetic acid, ethyl acetate, dichloromethane, chloroform, tetrachloromethane, petroleum ether, and N,N-dimethylformamide. In step S1), the first precipitate includes one or more of lead bromide, lead chloride, and lead iodide; In step S2), the second precipitate includes one or more of lead bromide, lead chloride, and lead iodide.

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