A selective adsorption type photocatalytic reduction U(VI) material and its preparation method and application

Abstract

The invention discloses a selective adsorption type photocatalytic reduction U (VI) material and its preparation method and application. The selective adsorption type photocatalytic reduction material of the present invention is Cs2AgBiBr6@P‑PCN222;The halogen perovskite Cs2AgBiBr6 used has high stability and tolerance structure, can maintain photocatalytic activity under different pH and temperature conditions, light absorption, carrier mobility, chemical diversity are adjustable, and adjustable band structure utilizes visible light to carry out photocatalytic reduction of U (VI);The present invention loads halogen perovskite quantum dots onto MOFs material PCN‑222, effectively enhancing the stability of adsorption type photocatalytic material under different conditions, the metal elements in MOF material are in close contact with perovskite quantum dot photocatalytic material, and the photogenerated electrons in confinement can be rapidly transferred to the metal elements in MOF material, to promote charge separation, and realize efficient visible light photocatalytic reduction of U (VI). And the selective adsorption type photocatalytic reduction material of the present invention can be used not only for effectively treating uranium in radioactive wastewater, but also for uranium extraction.

Description

Technical Field

[0001] The present invention belongs to the technical field of radioactive wastewater pollution treatment and management, and specifically relates to a selective adsorption type photocatalytic reduction U(VI) material and a preparation method and application thereof. Background Art

[0002] The photocatalytic reduction method for treating uranium-containing wastewater is easily affected by environmental factors such as solution pH, ionic strength, and coexisting ions. Considering that there are many types of uranium-containing wastewater in actual application, their pH range is wide, and there are many coexisting ions, maintaining the catalytic activity of photocatalytic materials for U(VI) within a wide pH range and improving the catalytic selectivity of photocatalytic materials for U(VI) are important ways for engineering applications.

[0003] Existing technologies use semiconductor photocatalytic materials such as TiO2-based and titanate materials, g-C3N4-based materials, ZnO and other metal materials, MOF-based materials, and COF-based materials. These materials are affected by factors such as wastewater pH and ion species strength in uranium-containing wastewater, resulting in poor stability and ineffective catalytic performance. Summary of the Invention

[0004] In view of the above technical problems existing in the prior art, the object of the present invention is to provide a selective adsorption type photocatalytic reduction U(VI) material with good stability and improved charge separation, as well as a preparation method and application thereof.

[0005] To achieve the above-mentioned purpose of the invention, the technical solution adopted by the present invention is as follows: a selective adsorption-type photocatalytic reduction U(VI) material, which is an adsorption-type photocatalytic reduction material in which halogen perovskite quantum dots are loaded onto the MOFs material PCN-222.

[0006] Furthermore, the halogen perovskite is Cs2AgBiBr6, and the MOFs material PCN-222 is a phosphoryl-modified PCN-222 material (P-PCN222).

[0007] The present invention also provides a method for preparing a selective adsorption type photocatalytic reduction U(VI) material, comprising adding MOFs material PCN-222 to dichloromethane, adding halogen perovskite Cs2AgBiBr6, stirring and centrifuging, collecting the solid, washing the centrifuged solid with ethanol, and vacuum drying to obtain the selective adsorption type photocatalytic reduction material Cs2AgBiBr6@P-PCN222.

[0008] Furthermore, the preparation method of the halogen perovskite Cs2AgBiBr6 comprises the following steps:

[0009] (1) Add stoichiometric CsBr, AgBr, and BiBr to HBr acid (48%) and stir;

[0010] (2) The stirred mixture is heated in an oil bath and then cooled naturally;

[0011] (3) centrifuging the cooled mixture, collecting the precipitate and vacuum drying;

[0012] (4) dissolving the dried solid in dimethyl sulfoxide to obtain a clear solution;

[0013] (5) The transparent solution was added to dichloromethane, and the solid was collected by centrifugation and vacuum dried to obtain Cs2AgBiBr6.

[0014] Furthermore, the halogen perovskite Cs2AgBiBr6 is a nanocrystal.

[0015] Furthermore, the preparation method of PCN-222 comprises the following steps:

[0016] (1) Add appropriate amounts of ZrCl4, benzoic acid, and water to dimethylformamide (DMF) and stir to obtain a mixed solution;

[0017] (2) Add an appropriate amount of TCCP to the above mixed solution and further dissolve it, and stir;

[0018] (3) The stirred solution is sealed and heated, and the product PCN-222 is separated by centrifugation;

[0019] (4) suspending the isolated product PCN-222 in a DMF solution containing hydrochloric acid, heating and stirring to obtain a mixture;

[0020] (5) The above mixture was purified by adding methanol and acetone solutions at the same time, and the purified product was vacuum dried to obtain nano PCN-222.

[0021] Furthermore, in the step (5), the mixture is added to a methanol and acetone solution and purified for a certain period of time to extract the PCN-222 therein; then the extracted PCN-222 is added to a methanol and acetone solution and purified again, and purified three times in total.

[0022] Furthermore, the preparation method of the phosphoryl-modified P-PCN222 material comprises the following steps:

[0023] (1) Add the above-mentioned nano PCN-222 to the phosphonic acid solution, seal and heat, and rotate at intervals;

[0024] (2) centrifuging the reactants to collect solids;

[0025] (3) soaking the collected solid in a fresh solvent, and centrifuging the soaked solution to collect the solid;

[0026] (4) Washing the solid with methanol and acetone in turn; and vacuum drying to obtain phosphoryl-modified PCN222 material (P-PCN222).

[0027] The present invention also provides an application of a selective adsorption type photocatalytic reduction U(VI) material, wherein the material is applied to the treatment of uranium wastewater in radioactive wastewater.

[0028] The present invention also provides an application of a selective adsorption type photocatalytic reduction U(VI) material, wherein the material is applied to uranium extraction.

[0029] The beneficial effects brought about by the technical solution of the present invention are a selective adsorption-type photocatalytic reduction U(VI) material and its preparation method and application. The selective adsorption-type photocatalytic reduction U(VI) material of the present invention is Cs2AgBiBr6@P-PCN222; the halogen perovskite Cs2AgBiBr6 used in the present invention has a high stability and tolerance structure, can maintain photocatalytic activity under different pH and temperature conditions, and the light absorption, carrier mobility, and chemical diversity are adjustable. The band structure can be adjusted to use visible light for photocatalytic reduction of U(VI); the present invention loads halogen perovskite quantum dots onto the MOFs material PCN-222, effectively enhancing the stability of the adsorption-type photocatalytic material under different conditions. The metal elements in the MOF material are in close contact with the perovskite quantum dot photocatalytic material, and the confined photogenerated electrons can be rapidly transferred to the metal elements in the MOF material to promote charge separation and realize efficient visible light photocatalytic reduction of U(VI). The selective adsorption-type photocatalytic reduction material Cs2AgBiBr6@P-PCN222 of the present invention can not only be used to effectively treat uranium in radioactive wastewater, but also can be used for uranium extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the process of preparing a selective adsorption type photocatalytic reduction U(VI) material according to Example 1 of the present invention;

[0031] Figure 2 This is a SEM image of the halogen perovskite Cs2AgBiBr6 prepared in Example 1 of the present invention;

[0032] Figure 3 This is a SEM image of PCN-222 prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0034] Example 1

[0035] An embodiment of the present invention provides a selective adsorption-type photocatalytic reduction U(VI) material, wherein the material is an adsorption-type photocatalytic reduction U(VI) material in which halogen perovskite quantum dots are loaded onto a MOFs material PCN-222.

[0036] Preferably, the halogen perovskite is Cs2AgBiBr6, and the MOFs material PCN-222 is a phosphoryl-modified PCN-222 material (P-PCN222).

[0037] Uranium-containing wastewater contains a large number of coexisting ions. The presence of cations such as Sr, Cs, Am, Th, Pb and Pu in the solution will inhibit the adsorption of U(VI) by photocatalytic materials, while some multivalent nuclides such as Am, Pu, Tc, etc. will compete with U(VI) for photoelectrons, thereby affecting the photocatalytic efficiency. pH is also an important factor affecting the photocatalytic efficiency. Usually, the pH of uranium-containing wastewater varies widely. For uranium-containing wastewater produced by uranium mining and smelting wastewater and post-treatment processes, the pH is generally strongly acidic. On the one hand, H + It will compete with U(VI) for photogenerated electrons. The embodiment of the present invention uses a halogen perovskite Cs2AgBiBr6 with a highly stable and tolerant structure. It can maintain photocatalytic activity under different pH and temperature conditions. The light absorption, carrier mobility, and chemical diversity are adjustable, and the band structure can be adjusted to use visible light for photocatalytic reduction of U(VI). The embodiment of the present invention loads the halogen perovskite Cs2AgBiBr6 quantum dots onto the MOFs material PCN-222. Due to the confinement effect of the porous MOF, ultra-small and uniformly distributed perovskite photocatalytic material quantum dots (QDs) and functional groups with U selective adsorption can be generated in the pores of the MOF, which can enhance the selective adsorption of U. At the same time, the close contact between the photocatalytic material quantum dots (QDs) and the catalytic active centers of the MOF can shorten the charge transfer distance, improve the photoinduced charge separation efficiency and catalytic activity of the QDs, and achieve efficient visible light photocatalytic reduction of U(VI).

[0038] Refer to the attached Figure 1 The embodiment of the present invention also provides a method for preparing a selective adsorption type photocatalytic reduction U(VI) material, wherein the MOFs material PCN-222 is added to dichloromethane, and a transparent solution of the halogen perovskite Cs2AgBiBr6 is added. After stirring and centrifugation, the solid is collected, the centrifuged solid is washed with ethanol, and vacuum dried to obtain the selective adsorption type photocatalytic reduction material Cs2AgBiBr6@P-PCN222.

[0039] Preferably, the MOFs material PCN-222 is a phosphoryl-modified PCN-222 material.

[0040] Preferably, the preparation method of the halogen perovskite Cs2AgBiBr6 comprises the following steps:

[0041] (1) Add stoichiometric CsBr, AgBr, and BiBr to HBr acid (48%) and stir;

[0042] (2) The stirred mixture is heated in an oil bath and then cooled naturally;

[0043] (3) centrifuging the cooled mixture, collecting the precipitate and vacuum drying;

[0044] (4) dissolving the dried solid in dimethyl sulfoxide to obtain a Cs2AgBiBr6 transparent solution;

[0045] (5) The transparent solution was added to dichloromethane, and the solid was collected by centrifugation and vacuum dried to obtain Cs2AgBiBr6.

[0046] Preferably, the halogen perovskite Cs2AgBiBr6 is a nanocrystal.

[0047] Refer to the attached Figure 2 The particle size distribution of Cs2AgBiBr6 prepared by the method of the embodiment of the present invention is relatively uniform, and some particles have slight clustering phenomenon.

[0048] Preferably, the preparation method of PCN-222 comprises the following steps:

[0049] (1) Add appropriate amounts of ZrCl4, benzoic acid, and water to dimethylformamide (DMF) and stir to obtain a mixed solution;

[0050] (2) Add an appropriate amount of TCCP to the above mixed solution and further dissolve it, and stir;

[0051] (3) The stirred solution is sealed and heated, and the product PCN-222 is separated by centrifugation;

[0052] (4) suspending the isolated product PCN-222 in a DMF solution containing hydrochloric acid, heating and stirring to obtain a mixture;

[0053] (5) The above mixture was purified by adding methanol and acetone solutions at the same time, and the purified product was vacuum dried to obtain nano PCN-222.

[0054] Preferably, in step (5), the mixture is added to a methanol and acetone solution and purified for a certain period of time to extract the PCN-222 therein; then the extracted PCN-222 is added to a methanol and acetone solution for further purification, and the purification is performed three times in total.

[0055] Refer to the attached Figure 3The PCN-222 prepared in the present invention exhibits a rod-like structure with evenly distributed pores on its surface. Its structure can accommodate Cs2AgBiBr6 quantum dots and functional groups with strong U(VI) binding ability.

[0056] Preferably, the method for preparing the phosphoryl-modified PCN-222 material comprises the following steps:

[0057] (1) Add the PCN-222 prepared above to the phosphonic acid solution, seal and heat, and rotate at intervals;

[0058] (2) centrifuging the reactants to collect solids;

[0059] (3) soaking the collected solid in a fresh phosphonic acid solution, and centrifuging the soaked solution to collect the solid;

[0060] (4) Washing the solid with methanol and acetone in turn; and vacuum drying to obtain phosphoryl-modified PCN222 material (P-PCN222).

[0061] An embodiment of the present invention further provides an application of a selective adsorption-type photocatalytic reduction U(VI) material, wherein the material is applied to the treatment of uranium wastewater in radioactive wastewater.

[0062] An embodiment of the present invention further provides an application of a selective adsorption-type photocatalytic reduction U(VI) material, wherein the material is applied to uranium extraction.

[0063] Example 2

[0064] The selective adsorption type photocatalytic reduction U(VI) material was prepared by the method of Example 1 of the present invention. The MOFs material PCN-222 was added to 50 mL of dichloromethane, and 5 mL of a transparent solution of halogen perovskite Cs2AgBiBr6 was added. The solid was collected after stirring and centrifugation, and the centrifuged solid was washed with ethanol and vacuum dried at 60°C to obtain the selective adsorption type photocatalytic reduction material Cs2AgBiBr6@P-PCN222.

[0065] Preferably, the preparation method of the halogen perovskite Cs2AgBiBr6 comprises the following steps:

[0066] (1) Add 0.426 g or 2.0 mmol of CsBr, 0.188 g or 1.0 mmol of AgBr, and 0.449 g or 1.0 mmol of BiBr to 48% HBr acid and stir for 30 min.

[0067] (2) The stirred mixture was heated in an oil bath at 110°C for 2 h and then naturally cooled to room temperature;

[0068] (3) centrifuging the cooled mixture, collecting the precipitate and drying it in a vacuum at 60°C for 24 h;

[0069] (4) The dried solid was dissolved in 50 mmol of dimethyl sulfoxide to obtain a transparent Cs2AgBiBr6 solution;

[0070] (5) The transparent solution was added to dichloromethane, and the solid was collected by centrifugation and vacuum dried to obtain Cs2AgBiBr6.

[0071] Preferably, the halogen perovskite Cs2AgBiBr6 is a nanocrystal.

[0072] Preferably, the preparation method of PCN-222 comprises the following steps:

[0073] (1) 40 mg ZrCl4, 1000 mg benzoic acid, and 800 μL water were added to 8 mL dimethylformamide (DMF) and stirred to obtain a mixed solution;

[0074] (2) Dissolve 40 mg of TCCP in the above mixed solution and stir for 10 min;

[0075] (3) The stirred solution was transferred to a 20 mL headspace vial, sealed, heated at 120 °C for 24 h, and centrifuged at 5000 rpm for 20 min to produce PCN-222;

[0076] (4) The isolated product PCN-222 was suspended in 100 ml of DMF solution containing 1.5 mL of 4 mol / L hydrochloric acid, and heated and stirred at 120° C. for 12 h to obtain a mixture;

[0077] (5) The above mixture was added to methanol and acetone for purification for 8 hours to extract PCN-222. The extracted PCN-222 was added to new methanol and acetone solvents for further purification. After purification for 48 hours, the mixture was vacuum-dried at 100°C for 12 hours to obtain nano PCN-222.

[0078] Preferably, the preparation method of the phosphoryl-modified P-PCN222 material comprises the following steps:

[0079] (1) Add 125 mg or 0.01 mmol of PCN-222 prepared above to 10 mL or 0.02 mol of phosphonic acid solution, seal the container, and heat at 60°C for 24 h while rotating.

[0080] (2) centrifuging the reactants to collect solids;

[0081] (3) soaking the collected solid in a phosphonic acid solution, and centrifuging the soaked solution to collect the solid;

[0082] (4) The solid was washed with methanol and acetone in sequence; and dried under vacuum at 60° C. to obtain phosphoryl-modified PCN222 material (P-PCN222).

[0083] The selective adsorption type photocatalytic reduction U(VI) material Cs2AgBiBr6@P-PCN222 prepared in the embodiment of the present invention was used to photocatalytically reduce U(VI). A 100 mL heat-resistant side irradiation photoreactor was used to photocatalytically reduce U(VI) in gas. A 300-W Xe lamp (Solar edge 700, set to 100 mW cm -2 ) was used as a light source. 20 mg of Cs2AgBiBr6@P-PCN222 adsorption-type photocatalytic material was dispersed in 50 mL of uranyl solution with a concentration of 50 mg / L. The photocatalytic reactor was connected to a constant temperature cooling water device, and the air valve was opened to introduce nitrogen to eliminate dissolved oxygen in the solution. First, the magnetic stirrer speed was set to 500 r / min. After mixing for 1 hour under light-proof conditions, 1 mL of the mixed solution was taken using a microporous filter membrane, and the U concentration in the mixed solution was measured to eliminate the influence of adsorption on the system. Then, the Xe lamp was turned on for a photocatalytic reduction experiment. 1 mL of the mixed solution was taken at regular intervals, and the U concentration in the mixed solution at different time periods was measured. U(VI) was photocatalytically reduced for 3 hours, and the U concentration in the final mixed solution was measured after 3 hours. Different ionic strengths and pH values ​​were set, and the removal of U(VI) by the adsorption-type photocatalytic material Cs2AgBiBr6@P-PCN222 under different conditions was tested. The results showed that the overall removal rate of U(VI) by the material was greater than 90% under different conditions. This shows that the material of the embodiment of the present invention has high efficiency, low cost, and does not produce secondary pollution. It can not only promote the application of photocatalytic materials and technologies in the treatment and purification of radioactive uranium-containing wastewater, but can also be used for uranium extraction.

[0084] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A selective adsorption type photocatalytic reduction U(VI) material, characterized in that: The material is an adsorption-type photocatalytic reduction material in which halogen perovskite quantum dots are loaded onto the MOFs material PCN-222; The halogen perovskite is Cs2AgBiBr6, and the MOFs material PCN-222 is a phosphoryl-modified PCN-222 material; The preparation method of the phosphoryl-modified PCN222 material, The following steps are included: (1) Add the prepared PCN-222 to the phosphonic acid solution, seal and heat, and rotate at intervals; (2) centrifuging the reactants to collect the solids; (3) Soaking the collected solids in fresh phosphonic acid, and centrifuging the soaked solution to collect the solids; (4) The solid was washed with methanol and acetone in sequence; and the phosphoryl-modified PCN222 material was obtained after vacuum drying.

2. The method for preparing a selective adsorption type photocatalytic reduction U(VI) material according to claim 1, characterized in that: The phosphoryl-modified PCN-222 was added to dichloromethane, and the halide perovskite Cs2AgBiBr6 was added. The solid was collected after stirring and centrifugation. The centrifuged solid was washed with ethanol and vacuum dried to obtain the selective adsorption photocatalytic reduction material Cs2AgBiBr6@P-PCN222.

3. The method for preparing a selective adsorption type photocatalytic reduction U(VI) material according to claim 1, wherein: Preparation method of halogen perovskite Cs2AgBiBr6, The following steps are included: (1) Add stoichiometric ratios of CsBr, AgBr, and BiBr to HBr acid and stir. (2) The stirred mixture is heated in an oil bath and then cooled naturally; (3) centrifuging the cooled mixture, collecting the precipitate and vacuum drying; (4) Dissolving the dried solid in dimethyl sulfoxide to obtain a transparent Cs2AgBiBr6 solution; (5) The transparent solution was added to dichloromethane, and the solid was collected by centrifugation and vacuum dried to obtain Cs2AgBiBr6.

4. The method for preparing a selective adsorption type photocatalytic reduction U(VI) material according to claim 3, wherein: The halogen perovskite Cs2AgBiBr6 is a nanocrystal.

5. The method for preparing a selective adsorption type photocatalytic reduction U(VI) material according to claim 1, wherein: The preparation method of PCN-222 comprises the following steps: (1) Add appropriate amounts of ZrCl4, benzoic acid, and water to dimethylformamide (DMF) and stir to obtain a mixed solution; (2) Take an appropriate amount of TCCP and further dissolve it in the above mixed solution, and stir; (3) The stirred solution is sealed and heated, and the product PCN-222 is separated by centrifugation; (4) suspending the isolated product PCN-222 in a DMF solution containing hydrochloric acid, heating and stirring to obtain a mixture; (5) The above mixture was purified by adding methanol and acetone solutions at the same time, and the purified product was vacuum dried to obtain nano PCN-222.

6. The use of the selective adsorption type photocatalytic reduction U(VI) material according to claim 1, characterized in that: The material is used for treating uranium wastewater in radioactive wastewater.

7. The use of the selective adsorption type photocatalytic reduction U(VI) material according to claim 1, characterized in that: The material is used for uranium extraction.

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