Treatment method of perovskite precursor synthesis waste liquid

Abstract

The invention relates to the field of wastewater treatment, in particular to a treatment method of perovskite precursor synthesis waste liquid. According to the method, the pH value of the strongly acidic perovskite precursor synthesis waste liquid is adjusted to be more than 3, so that the electrode potential of X2 / X-(X = Br <-> / Cl <-> / I <->) is reduced, the elemental halogen in the oxidation state can be reduced and recovered in the subsequent steps, and the recovery is thorough. The method is free of electrolysis, simple to operate and easy to industrialize; the used precipitant soluble lead is low in cost, and meanwhile, the recycled lead halide can be directly used for synthesizing the perovskite precursor, so that the waste of halogen elements is reduced, and the cost is saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wastewater treatment, and particularly relates to a treatment method for perovskite precursor synthesis waste liquid. BACKGROUND

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

[0003] The synthesis methods of lead halide perovskite materials include solution deposition method and precursor redissolution coating method. The precursor redissolution coating method has been rapidly developed in recent years due to its low purity requirement for raw materials and easy control of stoichiometric ratio.

[0004] The specific operation of the precursor redissolution coating method is to prepare a pure-phase perovskite compound, called a precursor, by using lead raw materials, halogen raw materials and monovalent cation raw materials including lead halide in an organic solvent or aqueous solvent in advance through chemical reaction. The precursor is dissolved in an organic solvent with high solubility, and then a thin film is formed on the surface of an electronic device through other methods, thereby obtaining an application.

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

[0006] Common halogen element recovery methods usually utilize the physical properties of halogen elements to recover halogen elements in the form of simple substances. However, halogen elements recovered in the form of simple substances do not have a clear application scenario in perovskite precursor synthesis, and still need to be further converted into compounds such as lead halide before they can be applied.

[0007] In summary, perovskite precursor synthesis waste liquid has the advantages of clear composition and high concentration, and has corresponding recycling potential. However, the existing perovskite precursor synthesis technology either does not recycle halogen elements in the subsequent waste liquid, causing waste and pollution, or is applied to finished perovskite cells with complex composition, which is complicated to operate and has high energy consumption steps such as calcination and evaporation. Moreover, the recovered halogens do not have a clear application scenario. Therefore, it is an important task to develop a low-cost, easy-to-operate halogen element recycling process whose recovered products can be directly reused in the industry, so as to build a perfect perovskite solar cell industry chain. SUMMARY

[0008] Therefore, the technical problem to be solved by the present application is to provide a method for treating perovskite precursor synthesis waste liquid, which can recover halogen elements in the form of lead halide from the perovskite precursor synthesis waste liquid, obtain halogen raw materials with a clear application scenario, and is complete in recovery and simple in operation.

[0009] The present application provides a method for treating perovskite precursor synthesis waste liquid, comprising the following steps:

[0010] S1) adjusting the pH of the perovskite precursor synthesis waste liquid to 3-7, filtering to obtain a first precipitate and a filtrate;

[0011] S2) reacting the filtrate obtained in step S1) after reduction with soluble lead, filtering to obtain a second precipitate and a dehalogenation waste liquid.

[0012] The method for treating perovskite precursor synthesis waste liquid provided by the present application is a process for recovering halogen raw materials and organic solvents from perovskite precursor synthesis waste liquid, and the perovskite precursor synthesis waste liquid referred to herein is the sum of aqueous phase waste liquid and organic phase waste liquid obtained after preparing perovskite precursor materials by aqueous phase synthesis method, through reaction, washing and other steps.

[0013] Specifically, the perovskite precursor synthesis waste liquid according to the present application is a mixture containing free halide ions, more specifically a mixture containing free halide ions, elemental iodine, monovalent cations, divalent lead ions and acetic acid; wherein the molar concentration of the free halide ions is higher than 0.01 mol / L, preferably 0.5 mol / L-1.5 mol / L; the elemental iodine, monovalent cations and acetic acid are all indefinite amounts. The pH of the perovskite precursor synthesis waste liquid according to the present application is less than 3, preferably less than 1.2, more preferably 0.9-1.1. Preferably, in the perovskite precursor synthesis waste liquid according to the present application, the concentration of the remaining substances other than divalent lead ions, free halide ions and derivatives of both should not be so high as to be mixed in the recovered product as or form impurities.

[0014] The solvent of the perovskite precursor synthesis waste liquid according to the present application is water or an aqueous solution, specifically water as the single solvent or the main solvent. When the solvent of the perovskite precursor synthesis waste liquid is mainly water, i.e. the composition of the solvent 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] The perovskite precursor synthesis waste liquid is first adjusted to a pH of 3-7, and filtered to obtain a first precipitate and a filtrate. By adjusting the strongly acidic perovskite precursor synthesis waste liquid to a pH of 3 or higher, the X2 / X -(X=Br - / Cl - / I - ) electrode potential, so that the oxidized halogen element can be reduced and recovered in the subsequent step.

[0016] Preferably, the present application uses soluble lead to adjust the pH, and the amount of added soluble lead should meet the pH of 3-7 after addition. Using soluble lead to adjust the pH can avoid introducing additional impurities, and at the same time, a small amount of lead halide precipitate is recovered, and the pH is adjusted to 3-7 to successfully realize the subsequent reduction reaction. Specifically, under stirring, a proper amount of soluble lead is added to the perovskite precursor synthesis waste liquid, and the pH is adjusted to 3-7 to produce lead halide (PbX2, X=Br - / Cl - / I - ) precipitate, obtaining a solid-liquid mixture, and then filtering the solid-liquid mixture to obtain a first precipitate and a filtrate; at this time, the first precipitate is the lead halide precipitate, which is part of the halogen elements in the perovskite precursor synthesis waste liquid recovered in the form of lead halide. The soluble lead in the present application is a lead-containing compound with Pb 2+ as the effective ingredient that can be dissolved in an acidic aqueous solution. 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 the filtrate in the present application, the filtrate is reduced and reacted with soluble lead, filtered to obtain a second precipitate and a dehalogenation waste liquid. Reducing the filtrate in the present application can reduce the halogen element in the form of oxidized halogen anion, and directly recover the lead halide that can be used for perovskite precursor synthesis.

[0018] Specifically, the filtrate in step S1) is reduced by a reducing agent and reacted with soluble lead, filtered to obtain a second precipitate and a dehalogenation waste liquid. More specifically, a reducing agent is added to the filtrate in step S1), stirred uniformly, and then placed for a period of time, and then an excess of soluble lead is added to produce a solid-liquid mixture; the obtained solid-liquid mixture is filtered to obtain a second precipitate and a dehalogenation waste liquid, wherein the second precipitate is a lead halide precipitate, which is part of the halogen elements in the perovskite precursor synthesis waste liquid recovered in the form of lead halide.

[0019] The reducing agent in the present application includes one or more of formic acid, formate, and formaldehyde, and is preferably formic acid. The present application selects formic acid and the like compounds that can be oxidized to carbonic acid / carbon dioxide in the end, which is more resistant to acidic systems, does not need to be excessively neutralized, and at the same time avoids introducing additional impurities into the waste liquid, ensuring the purity of the recovered lead halide. The reducing agent selected by the present application is inexpensive and easy to degrade naturally.

[0020] The reducing time in the application is 24 h-72 h, specifically, after adding the reducing agent and stirring uniformly, the solution is left to stand for 24 h-72 h. The molar amount of the reducing agent is 0-0.5 times more than the oxidizing substance in the perovskite precursor synthesis waste liquid. The longer standing time is to ensure sufficient reduction, and no additional energy consumption steps such as stirring are required. The excess reducing agent also helps to ensure sufficient reduction. The application can be judged whether it is fully reduced by observing that the filtrate changes from dark brown to transparent and colorless.

[0021] The molar amount of lead element in the total amount of the soluble lead used in the step S1) and the step S2) is 1-3 times more than the halogen in the perovskite precursor synthesis waste liquid. Since the soluble lead compound such as lead acetate is a weak electrolyte or will form a weak electrolyte, the amount of the added soluble lead compound needs to be excessive, which also ensures that all the residual halide ions in the filtrate after the reduction in the step S1) are precipitated in the form of lead halide.

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

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

[0024] The application provides a method for treating a perovskite precursor synthesis waste liquid. The application adjusts the perovskite precursor synthesis waste liquid with strong acidity to a pH of 3 or more, so as to reduce the electrode potential of X2 / X - (X=Br - / Cl - / I - ), so that the halogen element in the oxidized state can be reduced and recovered in the subsequent steps. The application does not need electrolysis, is simple to operate, and is 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 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. To the synthesis waste solution, 70 g of lead acetate solid was added and stirred vigorously until it dissolved and immediately produced a large amount of yellowish lead iodide precipitate. After 3 h of continuous stirring, the stirring was stopped to allow the lead iodide to settle, and most of the solid-liquid mixture was separated by decantation.

[0035] F. The lead iodide recovered from step C and step E was combined and washed with water and ethyl acetate each for three times alternately, and dried in an oven at 60 °C for 12 h to obtain the recovered lead iodide, as shown in Figure 1 Figure 1 XRD pattern of the lead iodide recovered from Example 1 of the present application. The washing solution was combined with the bulk of the waste solution from step E to form the dehalogenation waste solution. The I - concentration was 8.00 g / L, and the I - concentration was 0.061 g / L, with a recovery rate of 99.2%.

[0036] Example 2

[0037] 1000 mL of halogen recovery from the synthesis waste solution for preparing CsPbBr3perovskite precursor:

[0038] A. According to the synthesis flow, it was known that the synthesis waste solution mainly contained bromide ions with a concentration of about 1 mol / L, cesium ions with a concentration of about 0.02 mol / L, and acetic acid with a concentration of about 1 mol / L. The pH of the synthesis waste solution was measured to be 1 using pH paper. The waste solution was light reddish brown.

[0039] B. Two 10 mL samples of the synthesis waste solution were taken, one without treatment and one with excess sodium sulfite to reduce the bromine element in it. The complete reduction of bromine element was marked by the complete fading of the solution. The bromide ion concentration was measured to be 1.20 mol / L and 1.30 mol / L, respectively, which indicated that the bromine element concentration in the waste solution was about 0.100 mol / L.

[0040] C. To the remaining synthesis waste solution, 10 g of lead acetate solid was added and stirred until it dissolved and immediately produced white lead bromide precipitate. After standing, most of the solid-liquid mixture was separated by decantation. The pH of the synthesis waste solution was measured to be 3 using pH paper.

[0041] D. To the synthesis waste solution, 5.0 g of sodium formate was added and stirred until it dissolved. After standing for 24 h, it was observed that the waste solution gradually faded. After 24 h, it was found that the solution was completely colorless, indicating that the bromine element had been completely reduced.

[0042] E. To the synthesis waste solution, 70 g of lead acetate solid was added and stirred vigorously until it dissolved and immediately produced a large amount of white lead bromide precipitate. After 3 h of continuous stirring, the stirring was stopped to allow the lead bromide to settle, and most of the solid-liquid mixture was separated by decantation. ​

[0043] F, the recovered lead bromide from step C, step E, was found to contain a small amount of orange material, which was due to the formation of a small amount of CsPbBr3 from the produced lead bromide and cesium ions in the waste solution. The recovered lead bromide was washed with water and ethyl acetate three times in succession until it was white, and dried in an oven at 60 °C for 12 h. The washings were combined with the bulk of the waste solution from step E to form the dehalogenation waste solution.

[0044] The above description is merely preferred embodiments of the application, but the protection scope of the application is not limited thereto. Any person skilled in the art, according to the technical range disclosed in the application and the inventive concept, makes equivalent replacements or changes within the technical range disclosed in the application, and the application should be covered within the protection scope of the application.

Claims

1. A method for treating waste liquid from perovskite precursor synthesis, characterized in that, Includes the following steps: 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; 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.

2. The processing method according to claim 1, characterized in that, In step S1), the pH of the waste liquid from the synthesis of the perovskite precursor is less than 3.

3. 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.

4. The processing method according to claim 1, characterized in that, In step S1), the pH of the perovskite precursor synthesis waste liquid is adjusted using soluble lead.

5. The processing method according to claim 4, characterized in that, In steps S1) and S2), the soluble lead is Pb, which is soluble in acidic aqueous solutions. 2+ Lead-containing compounds that are the active ingredient.

6. The processing method according to claim 3, characterized in that, 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.

7. 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.

8. The processing method according to claim 7, characterized in that, The reduction time is 24 h to 72 h.

9. 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.

10. 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; In step S2), the reduction is carried out using a reducing agent, which includes one or more of formic acid, formate, and formaldehyde.

Images