CN117599830A - Preparation method of catalyst for photocatalytic extraction of uranium in seawater - Google Patents
Preparation method of catalyst for photocatalytic extraction of uranium in seawater Download PDFInfo
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- CN117599830A CN117599830A CN202311624456.0A CN202311624456A CN117599830A CN 117599830 A CN117599830 A CN 117599830A CN 202311624456 A CN202311624456 A CN 202311624456A CN 117599830 A CN117599830 A CN 117599830A
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- carbon nitride
- carboxylated carbon
- uranium
- seawater
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- 229910052770 Uranium Inorganic materials 0.000 title claims abstract description 55
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 title claims abstract description 54
- 230000001699 photocatalysis Effects 0.000 title claims abstract description 53
- 239000013535 sea water Substances 0.000 title claims abstract description 41
- 239000003054 catalyst Substances 0.000 title claims abstract description 31
- 238000000605 extraction Methods 0.000 title claims abstract description 28
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- JMANVNJQNLATNU-UHFFFAOYSA-N oxalonitrile Chemical compound N#CC#N JMANVNJQNLATNU-UHFFFAOYSA-N 0.000 claims abstract description 114
- WUPHOULIZUERAE-UHFFFAOYSA-N 3-(oxolan-2-yl)propanoic acid Chemical compound OC(=O)CCC1CCCO1 WUPHOULIZUERAE-UHFFFAOYSA-N 0.000 claims abstract description 53
- 229910052980 cadmium sulfide Inorganic materials 0.000 claims abstract description 51
- 239000002131 composite material Substances 0.000 claims abstract description 40
- 239000011941 photocatalyst Substances 0.000 claims abstract description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000008367 deionised water Substances 0.000 claims abstract description 18
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 18
- 239000007795 chemical reaction product Substances 0.000 claims abstract description 15
- 238000010992 reflux Methods 0.000 claims abstract description 14
- 238000006243 chemical reaction Methods 0.000 claims abstract description 13
- 238000003756 stirring Methods 0.000 claims abstract description 13
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 12
- 238000005406 washing Methods 0.000 claims abstract description 11
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 claims abstract description 10
- 239000008103 glucose Substances 0.000 claims abstract description 10
- CWERGRDVMFNCDR-UHFFFAOYSA-N thioglycolic acid Chemical compound OC(=O)CS CWERGRDVMFNCDR-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000007864 aqueous solution Substances 0.000 claims abstract description 9
- 229920000877 Melamine resin Polymers 0.000 claims abstract description 8
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims abstract description 8
- 230000003213 activating effect Effects 0.000 claims abstract description 7
- 239000012300 argon atmosphere Substances 0.000 claims abstract description 7
- XIEPJMXMMWZAAV-UHFFFAOYSA-N cadmium nitrate Inorganic materials [Cd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XIEPJMXMMWZAAV-UHFFFAOYSA-N 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims abstract description 7
- 238000000227 grinding Methods 0.000 claims abstract description 7
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 7
- 238000011068 loading method Methods 0.000 claims abstract description 7
- NMHMNPHRMNGLLB-UHFFFAOYSA-N phloretic acid Chemical compound OC(=O)CCC1=CC=C(O)C=C1 NMHMNPHRMNGLLB-UHFFFAOYSA-N 0.000 claims abstract description 7
- 238000007873 sieving Methods 0.000 claims abstract description 7
- 238000004108 freeze drying Methods 0.000 claims abstract description 6
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 claims abstract description 4
- 239000000047 product Substances 0.000 claims description 16
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- 238000000034 method Methods 0.000 claims description 13
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- 230000004913 activation Effects 0.000 claims description 4
- 238000004064 recycling Methods 0.000 abstract description 5
- 238000009777 vacuum freeze-drying Methods 0.000 abstract description 5
- 230000000694 effects Effects 0.000 abstract description 4
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- 238000006555 catalytic reaction Methods 0.000 abstract description 2
- 238000006722 reduction reaction Methods 0.000 description 24
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 21
- 229910052799 carbon Inorganic materials 0.000 description 20
- 230000009467 reduction Effects 0.000 description 20
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 15
- 239000000463 material Substances 0.000 description 13
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 11
- 238000000926 separation method Methods 0.000 description 9
- 238000004458 analytical method Methods 0.000 description 7
- 229910052793 cadmium Inorganic materials 0.000 description 7
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 7
- 238000011161 development Methods 0.000 description 7
- 238000007146 photocatalysis Methods 0.000 description 7
- 239000011148 porous material Substances 0.000 description 7
- 238000001179 sorption measurement Methods 0.000 description 6
- 230000009286 beneficial effect Effects 0.000 description 5
- -1 carboxyl modified carbon nitride Chemical class 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
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- 238000005516 engineering process Methods 0.000 description 4
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- 239000004065 semiconductor Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 238000002835 absorbance Methods 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 125000000524 functional group Chemical group 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 230000031700 light absorption Effects 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 230000001052 transient effect Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
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- 238000004770 highest occupied molecular orbital Methods 0.000 description 2
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000012086 standard solution Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- MARUHZGHZWCEQU-UHFFFAOYSA-N 5-phenyl-2h-tetrazole Chemical compound C1=CC=CC=C1C1=NNN=N1 MARUHZGHZWCEQU-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 1
- 238000003775 Density Functional Theory Methods 0.000 description 1
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 238000001157 Fourier transform infrared spectrum Methods 0.000 description 1
- 241000282412 Homo Species 0.000 description 1
- 230000010757 Reduction Activity Effects 0.000 description 1
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- 230000002411 adverse Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- UHYPYGJEEGLRJD-UHFFFAOYSA-N cadmium(2+);selenium(2-) Chemical compound [Se-2].[Cd+2] UHYPYGJEEGLRJD-UHFFFAOYSA-N 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 230000021523 carboxylation Effects 0.000 description 1
- 238000006473 carboxylation reaction Methods 0.000 description 1
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- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
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- 238000002189 fluorescence spectrum Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 239000002638 heterogeneous catalyst Substances 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
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- 229920002239 polyacrylonitrile Polymers 0.000 description 1
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- 238000000870 ultraviolet spectroscopy Methods 0.000 description 1
- 150000003671 uranium compounds Chemical class 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/30—Treatment of water, waste water, or sewage by irradiation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
- B01J37/341—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation
- B01J37/343—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation of ultrasonic wave energy
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G43/00—Compounds of uranium
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
- C22B60/02—Obtaining thorium, uranium, or other actinides
- C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
- C22B60/0217—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes
- C22B60/0252—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries
- C22B60/0278—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries by chemical methods
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/006—Radioactive compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/08—Seawater, e.g. for desalination
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Abstract
The invention relates to a preparation method of a catalyst for photocatalytic extraction of uranium in seawater, which comprises the following steps: preparing carboxylated carbon nitride: activating melamine at high temperature under argon atmosphere, cooling, grinding, sieving, ultrasonically dispersing in nitric acid aqueous solution, carrying out reflux reaction, centrifuging, washing, and vacuum freeze-drying for 24h to obtain carboxylated carbon nitride; constructing a carboxylated carbon nitride/cadmium sulfide composite photocatalyst: sequentially dispersing carboxylated carbon nitride, glucose and cadmium nitrate in deionized water by ultrasonic, stirring for reaction, adding thioglycollic acid, continuously stirring, performing hydrothermal reaction, washing and freeze-drying the obtained reaction product, and obtaining the carboxylated carbon nitride/cadmium sulfide composite photocatalyst with the cadmium sulfide loading amount of 10-30%. The composite photocatalyst obtained by the invention can realize high-efficiency and rapid extraction of U (VI) in seawater, and the composite catalyst still maintains high stability, high catalytic reaction activity and good recycling performance after elution and recovery.
Description
Technical Field
The invention relates to the technical field of photocatalysis seawater uranium extraction, in particular to a preparation method of a catalyst for photocatalysis uranium extraction in seawater.
Background
Currently, almost 16% of the world's electrical energy is produced by 441 nuclear reactors, while more than 40% of 9 countries' energy production comes from nuclear energy. The nuclear energy has the advantages of cleanness, no pollution, high energy density, low comprehensive cost and the like, and the nuclear energy power generation can not generate carbon dioxide which aggravates the global warming effect. Therefore, nuclear energy is considered as the most promising future sustainable energy source for humans, and is receiving wide attention both at home and abroad. The energy structure adjustment force is also being increased in China, and clean excellent energy sources such as nuclear power, wind power, hydropower and the like are actively developed. As the primary high energy fuel for the reactor, 1 kg of uranium is available with energy equivalent to 2050 tons of premium coal burned. Therefore, the development and safe supply of uranium is critical for the long-term sustainable development of nuclear energy. However, the uranium reserves on land are not abundant and are extremely uneven in distribution, only few countries have limited uranium ores, only 100 ten thousand tons of the uranium ores have industrial exploitation value, the total amount of the low-grade uranium ores and uranium compounds which are byproducts of the low-grade uranium ores is not more than 500 ten thousand tons, and according to the current consumption speed, only 80-120 years of human use can be maintained, so that the future nuclear energy development requirement is difficult to meet.
Ocean is the biggest uranium resource treasury in the world, and total reserve is up to 45 hundred million tons, is nearly 1000 times of the established land uranium reserve, and provides huge potential fuel sources for nuclear energy development. If the uranium in the seawater can be completely extracted, the contained fission energy can ensure the energy requirement of a human for tens of thousands of years. Although various techniques for extracting uranium from seawater have been attempted, such as ion exchange, extraction, membrane separation, chemical reduction, adsorption, coprecipitation, bubble separation, and algal concentration, the concentration of uranium in seawater is low (1000 tons of seawater contains only 3 g of uranium), and weakly alkaline (HCO) 3 − The concentration of the water can reach up to 2.75 mM), the salinity is high, the components are complex, and the like, so that the traditional seawater uranium extraction technology still faces a plurality of challenges and difficulties in practical application. Therefore, the development of a novel and efficient technique for extracting uranium from seawater is particularly important and imperative.
The photocatalysis technology can directly utilize endless sunlight, has lower cost, higher energy efficiency and wider applicability, is expected to efficiently extract uranium in seawater, and is used for desalting seawater, extracting uranium and co-producing a photothermal photocatalysis membrane, a preparation method thereof (CN 114931862B) and high-dispersivity C 3 N 4 Composite material for extracting uranium from sea water and preparation method thereof (CN 115228500A), preparation method of sea water extracted uranium amidoxime group cyclized polyacrylonitrile material (CN 202210754446.8), sea water desalination-extracted uranium co-production semiconductor photoreduction membrane and preparation method thereof (CN 202210598986.1), preparation of ethylenediamine coated cadmium telluride nano-belt photocatalyst, separation method of uranium in radioactive wastewater (CN 202110245812), photocatalytic uranium capturing two-dimensional flaky semiconductor and preparation method thereof (CN 202210754425), preparation and application of Ag doped CdSe nano-sheet photocatalytic material for uranium reduction separationThe preparation and application of mesoporous titania photocatalyst for photocatalytic reduction of uranium (CN 202110775914) and the like are related to the content.
The photocatalyst is a core and key for separating enriched uranium from seawater by utilizing a photocatalysis technology. Compared with a plurality of photocatalysts, the graphite phase carbon nitride is a nonmetallic catalytic material, has the advantages of high stability, simple and convenient synthesis, low cost and the like, and becomes an excellent choice of uranium catalytic extraction catalysts. However, the carbonate (hydrogen) in seawater is prone to complex with U (VI) to form a negatively charged monodentate or bidentate complex, resulting in lower affinity with the catalyst and lower reduction potential of the resulting complex, making it difficult to be directly catalytically reduced. Thus, the efficient photocatalytic reduction of U (VI) is severely hampered by the presence of bicarbonate in the seawater. Furthermore, the photocatalytic reduction system of U (VI) needs to introduce methanol as a sacrificial agent or to be carried out in an inert atmosphere (to eliminate the adverse effect of excessive dissolved oxygen on reduction), which not only increases the uranium extraction cost and technical difficulty, but also can cause secondary chemical pollution. Therefore, how to effectively reduce U (VI) to U (IV) in an open environment, containing a carbon (hydrogen) radical system, without the aid of a sacrificial agent remains a great challenge, and development of a novel efficient photocatalyst or photocatalytic reduction technology is urgently needed to promote application of the photocatalytic method in uranium extraction from seawater.
Disclosure of Invention
The invention aims to provide a preparation method of a catalyst for photocatalytic extraction of uranium in seawater, which is efficient and economical.
In order to solve the problems, the preparation method of the catalyst for photocatalytic extraction of uranium in seawater comprises the following steps:
preparing carboxylated carbon nitride:
activating melamine at 550 ℃ for 4 hours under argon atmosphere, cooling, grinding and sieving to obtain an activated product; ultrasonically dispersing the activated product into 4-6M nitric acid aqueous solution, carrying out reflux reaction for 6-24 h at 120-130 ℃, centrifuging, washing, and freeze-drying in vacuum for 24h to obtain carboxylated carbon nitride;
constructing a carboxylated carbon nitride/cadmium sulfide composite photocatalyst:
the carboxylated carbon nitride, glucose and cadmium nitrate (Cd (NO 3 ) 2 ·4H 2 Sequentially dispersing in deionized water by ultrasonic, stirring and reacting for 4 hours, adding thioglycollic acid, and continuously stirring for 1 hour to obtain a uniform mixture; the uniform mixture is subjected to hydrothermal reaction for 2 hours at 170-190 ℃, and the obtained reaction product is washed by deionized water and freeze-dried to obtain the carboxylated carbon nitride/cadmium sulfide composite photocatalyst with the cadmium sulfide loading amount of 10-30%; the carboxylated carbon nitride: glucose: the mass ratio of thioglycollic acid is 1:2:6.
the medium-high temperature activation heating rate is controlled to be 4-5 ℃/min.
The mesh diameter of the screen mesh screened in the step (A) is more than 200 meshes.
In the step (A), the solid-liquid mass volume ratio of an activation product to a nitric acid aqueous solution is 1: 40-1: 50.
in the step (A), the condition of washing the reflux reaction product is that the pH value of the suspension is stabilized at 6-7.
The solid-liquid mass ratio of carboxylated carbon nitride to deionized water in the step (II) is 1-2: 100.
the freeze drying condition in the step is that the temperature is-50 ℃ and the time is 12-24 hours.
Compared with the prior art, the invention has the following advantages:
1. according to the invention, the carboxyl functional group capable of withdrawing electrons is introduced into the surface of the carbon nitride, so that the affinity of the catalyst to U (VI) is effectively improved, the conduction band potential of the material is reduced, the chemical form of U (VI) at the catalyst-water interface is regulated, the catalyst is easier to reduce, the charge separation capability and the service life of carriers are improved, and the photocatalytic performance of the catalyst is greatly improved; further, the catalyst is coupled with a narrow-bandgap cadmium sulfide semiconductor to construct a composite catalyst, and the ideal photocatalytic reduction efficiency for U (VI) is maintained under the conditions of no addition of a sacrificial agent, in an air atmosphere, natural light and in seawater.
2. The invention vulcanizes narrow band gapThe cadmium semiconductor and carboxylated carbon nitride are coupled to construct a type II heterogeneous catalyst, the energy band structure is utilized to regulate and control active free radicals effectively, and the material is promoted to adsorb more dissolved oxygen and reduce the dissolved oxygen to form O 2− Meanwhile, the generation of OH is inhibited to a certain extent, and the photocatalytic reduction rate of U (VI) is greatly improved.
3. The composite photocatalyst obtained by the invention can realize high-efficiency and rapid extraction of U (VI) in seawater, and the composite catalyst still maintains high stability, high catalytic reaction activity and good recycling performance after elution and recovery.
4. According to the invention, graphite-phase carbon nitride and cadmium sulfide are selected as basic raw materials, and through systematic research and preparation process optimization, a heterogeneous photocatalyst capable of directly utilizing sunlight to efficiently and selectively drive U (VI) to reduce and fix is successfully developed, separation and extraction of uranium in seawater are realized, and Cd is hardly released to the environment 2+ Solves the problem of practical application in the photocatalysis of the seawater for uranium extraction, provides a green and efficient new way for the development of the seawater uranium extraction technology, and has good industrial application prospect and social benefit.
Drawings
The following describes the embodiments of the present invention in further detail with reference to the drawings.
FIG. 1 is an XRD pattern for carbon nitride, carboxylated carbon nitride (left) and carboxylated carbon nitride/cadmium sulfide (right).
Fig. 2 is a FTIR diagram of carbon nitride, carboxylated carbon nitride.
FIG. 3 is an SEM image of carboxylated carbon nitride-6 (left) and carboxylated carbon nitride-24 (right).
Fig. 4 is an SEM image of carbon nitride (left) and carboxylated carbon nitride/cadmium sulfide (right).
FIG. 5 is an ultraviolet-visible diffuse reflectance spectrum (left) and a transient photocurrent response curve (right) of carbon nitride, carboxylated carbon nitride and carboxylated carbon nitride/cadmium sulfide composites.
FIG. 6 shows the photocatalytic reduction kinetics (left) and photocatalytic reduction reaction rate constants (right) for U (VI) for carbon nitride and carboxylated carbon nitride/cadmium sulfide composites.
FIG. 7 is an evaluation of recycling performance of carboxylated carbon nitride/cadmium sulfide composite materials prepared according to the present invention.
Detailed Description
The preparation method of the catalyst for the photocatalytic extraction of uranium in seawater comprises the following steps:
preparing carboxylated carbon nitride:
and (3) activating the melamine at a high temperature of 550 ℃ for 4 hours under argon atmosphere, and controlling the heating rate to be 4-5 ℃/min. Then cooling, grinding and sieving with a sieve of more than 200 meshes to obtain an activated product; the activated product is ultrasonically dispersed in 4-6M nitric acid aqueous solution, and the solid-liquid mass volume ratio (g/ml) of the activated product to the nitric acid aqueous solution is 1: 40-1: 50. reflux reaction is carried out for 6-24 hours at 120-130 ℃, and the obtained reflux reaction product is subjected to centrifugation, deionized water washing until the pH value of suspension is stabilized at 6-7, and then vacuum freeze drying is carried out for 24 hours, thus obtaining carboxylated carbon nitride; finally, samples obtained by reflux reactions in nitric acid solution for 6h and 24h were labeled carboxylated carbon nitride-6 and carboxylated carbon nitride-24, respectively.
Constructing a carboxylated carbon nitride/cadmium sulfide composite photocatalyst:
carboxylated carbon nitride, glucose and cadmium nitrate (Cd (NO 3 ) 2 ·4H 2 Sequentially dispersing in deionized water by ultrasonic, stirring and reacting for 4 hours, adding thioglycollic acid, and continuously stirring for 1 hour to obtain a uniform mixture; wherein: the solid-liquid mass ratio (g/g) of the carboxylated carbon nitride to the deionized water is 1-2: 100; carboxylated carbon nitride: glucose: the mass ratio (g/g) of thioglycollic acid is 1:2:6.
and carrying out hydrothermal reaction on the uniform mixture for 2 hours at 170-190 ℃, washing the obtained reaction product by deionized water, and freeze-drying at-50 ℃ for 12-24 hours to obtain the carboxylated carbon nitride/cadmium sulfide composite photocatalyst with the cadmium sulfide loading of 10-30%.
According to the invention, the catalyst with the cadmium sulfide loading of 10-30% can be prepared by changing the cadmium sulfide ratio (cadmium sulfide: carboxylated carbon nitride mass ratio (g/g) of 0.62-1.86).
Example 1 a method for preparing a catalyst for photocatalytic extraction of uranium in seawater, comprising the following steps:
preparing carboxylated carbon nitride:
and (3) activating the melamine at a high temperature of 550 ℃ for 4 hours under argon atmosphere, and controlling the heating rate to be 4-5 ℃/min. Then cooling, grinding and sieving with a 200-mesh sieve to obtain an activated product; and (3) ultrasonically dispersing the 5g activated product into 4M aqueous nitric acid solution, carrying out reflux reaction at 130 ℃ for 6 hours, centrifuging and washing the obtained reflux reaction product until the pH value of a suspension is stabilized at 6-7, and then carrying out vacuum freeze drying for 24 hours to obtain 4.5g of carboxylated carbon nitride, and marking the carboxylated carbon nitride-6.
Constructing a carboxylated carbon nitride/cadmium sulfide composite photocatalyst:
2g of carboxylated carbon nitride-6, 4g of glucose and 0.62g of cadmium nitrate (Cd (NO) 3 ) 2 ·4H 2 And O) sequentially dispersing in 200g of deionized water by ultrasonic, stirring and reacting for 4 hours, adding 12g of thioglycollic acid, and continuously stirring for 1 hour to obtain a uniform mixture. The uniform mixture is subjected to hydrothermal reaction for 2 hours at 190 ℃, and the obtained reaction product is washed by deionized water and freeze-dried for 24 hours at-50 ℃ to obtain 2.2g of carboxylated carbon nitride/cadmium sulfide composite photocatalyst with 10% cadmium sulfide loading capacity, which is denoted as carboxylated carbon nitride-6/cadmium sulfide-10.
Example 2 a method for preparing a catalyst for photocatalytic extraction of uranium in seawater, comprising the steps of:
preparing carboxylated carbon nitride:
and (3) activating the melamine at a high temperature of 550 ℃ for 4 hours under argon atmosphere, and controlling the heating rate to be 4-5 ℃/min. Then cooling, grinding and sieving with a 200-mesh sieve to obtain an activated product; and (3) ultrasonically dispersing the 5g activated product into a 5M nitric acid aqueous solution, carrying out reflux reaction at 120 ℃ for 24 hours, centrifuging and washing the obtained reflux reaction product until the pH value of a suspension is stabilized at 6-7, and then carrying out vacuum freeze drying for 24 hours to obtain 4.5g of carboxylated carbon nitride, and marking the carboxylated carbon nitride-24.
Constructing a carboxylated carbon nitride/cadmium sulfide composite photocatalyst:
2g of carboxylated carbon nitride-24, 4g of glucose and 0.62g of cadmium nitrate (Cd (NO) 3 ) 2 ·4H 2 O) is dispersed in 200g deionized water by ultrasonic in turn and stirred for reaction for 4h,then 12g of thioglycollic acid is added and stirring is continued for 1h, thus obtaining a uniform mixture. The uniform mixture is subjected to hydrothermal reaction at 170 ℃ for 2 hours, and the obtained reaction product is washed by deionized water and freeze-dried at-50 ℃ for 12 hours, so that 2.2g of carboxylated carbon nitride/cadmium sulfide composite photocatalyst with 10% cadmium sulfide load is obtained, and the carboxylated carbon nitride-24/cadmium sulfide-10 is marked.
Example 3 a method for preparing a catalyst for photocatalytic extraction of uranium in seawater, comprising the steps of:
preparing carboxylated carbon nitride:
and (3) activating the melamine at a high temperature of 550 ℃ for 4 hours under argon atmosphere, and controlling the heating rate to be 4-5 ℃/min. Then cooling, grinding and sieving with a 200-mesh sieve to obtain an activated product; and (3) ultrasonically dispersing the 5g activated product into a 6M aqueous solution of nitric acid, carrying out reflux reaction for 24 hours at 120 ℃, centrifuging and washing the obtained reflux reaction product until the pH value of a suspension is stabilized at 6-7, and then carrying out vacuum freeze drying for 24 hours to obtain 4.5g of carboxylated carbon nitride, namely the carboxylated carbon nitride-24.
Constructing a carboxylated carbon nitride/cadmium sulfide composite photocatalyst:
2g of carboxylated carbon nitride-24, 4g of glucose and 1.86g of cadmium nitrate (Cd (NO) 3 ) 2 ·4H 2 And O) sequentially dispersing in 200g of deionized water by ultrasonic, stirring and reacting for 4 hours, adding 12g of thioglycollic acid, and continuously stirring for 1 hour to obtain a uniform mixture. The uniform mixture is subjected to hydrothermal reaction for 2 hours at 190 ℃, and the obtained reaction product is washed by deionized water and freeze-dried for 24 hours at-50 ℃ to obtain 2.6g of carboxylated carbon nitride/cadmium sulfide composite photocatalyst with 30% cadmium sulfide loading capacity, which is denoted as carboxylated carbon nitride-24/cadmium sulfide-30.
Comparative example 1:
preparing carbon nitride: under the protection of argon, 25g of melamine is placed in a muffle furnace, heated to 550 ℃ at a rate of 4 ℃ per min and activated for 4 hours at high temperature. The activated product is ground after being cooled to room temperature and is sieved by a 200-mesh sieve, so as to obtain 15g of carbon nitride yellow powder; its phase composition and specific surface area were tested.
The materials obtained in examples 1 to 3 and comparative example 1 were subjected to photocatalytic performance test, and the test procedure was as follows: 9mg of catalyst powder, 0.375: 0.375 m, were added to a 25: 25 mL quartz tubeL U (VI) standard solution, deionized water and a certain amount of NaHCO 3 The solution was brought to a total volume of 15 mL and the pH was adjusted to 8.2; before the photocatalytic reaction, the dark adsorption reaction is carried out for 120min under the dark condition so as to reach the adsorption-desorption balance. Then under the irradiation of natural light, taking out 1mL of suspension at fixed time intervals, and filtering with a fiber water system filter membrane with the thickness of 0.22 mu m; the concentration of U (VI) in the filtrate was measured using ICP-OES or UV-Vis spectrophotometry, and each data run in parallel 3-5 times to average.
2.5. 2.5 mL methanol was added as a hole scavenger to a quartz tube to which the catalyst powder and U (VI) standard solution were added, and photocatalytic performance testing was performed in an SGY-II type photochemical reaction apparatus.
Characterization of carboxylated carbon nitride/cadmium sulfide and evaluation of photocatalytic reduction U (VI) performance
Composition and functional group analysis:
FIG. 1 is an XRD pattern for carbon nitride, carboxylated carbon nitride and carboxylated carbon nitride/cadmium sulfide. From the XRD pattern of the carboxylated carbon nitride/cadmium sulfide composite material, it is evident that the characteristic diffraction peaks (2θ=24.4 °, 26.1 °, 27.8 °, 43.5 °, 47.4 ° and 51.6 °) of carbon nitride (2θ=13.1° and 27.5 °) and cadmium sulfide, confirm that the cadmium sulfide particles were successfully loaded on the carboxylated carbon nitride surface to form the composite material. Wherein the strong diffraction peak at 13.1 ° corresponds to the (100) crystal plane of carbon nitride; the carboxylated carbon nitride had a reduced peak intensity of the (100) crystal plane, indicating that the in-plane stacking structure of the 3-s-triazine units was destroyed. As can be seen from the FT-IR spectrum of the above sample (FIG. 2), carboxylated carbon nitride and carbon nitride are respectively 809, 1634, 1572, 1463 and 1411cm −1 And the like, a distinct characteristic absorption peak appears. Compared with carbon nitride, 3000-3500 cm of carboxylated carbon nitride −1 The absorption at this point is attributable to the higher intensity of the broad absorption peak of the hydroxyl (-OH and-COOH) functional groups, indicating that the surface of the carbon nitride forms carboxyl groups upon strong oxidation by nitric acid. From the O1s spectrum, it was found that the carboxylated carbon nitride showed a new peak of o—c=o at a binding energy of 532.0eV, which also confirmed the formation of carboxyl groups. The carboxyl content in the sample is determined by titration, and the result shows that the carbon nitride and the carboxylated nitrogenThe amount of carboxyl groups measured on the carbon black was 0.205mmol/g and 1.243 to 1.735mmol/g, respectively. Together, the above results confirm that the carboxyl groups were successfully modified on the surface of carbon nitride.
Specific surface area and microtopography analysis:
as is clear from Table 1, the specific surface areas of the carbon nitride and carboxylated carbon nitride were 13.26 and 39.76 to 40.35m, respectively 2 Per gram, the total pore volume is 0.07 and 0.14-0.15 cm respectively 3 And/g, the average pore diameters are respectively 20.81 and 13.35-13.57 nm. Compared with the original carbon nitride material, the carboxylated carbon nitride material has obviously improved specific surface area and pore volume, and is beneficial to improving the light utilization efficiency and light absorption capacity. From the microscopic morphology analysis, it can be seen (fig. 3) that, unlike the stacking of the large lamellar structure of carbon nitride, the small lamellar layers in the carboxylated carbon nitride material obtained by acid etching are stacked or aggregated with each other, resulting in smaller pore diameter and larger pore volume, which is also beneficial for the distribution of cadmium sulfide nano-spherical particles on the surface of the carboxylated carbon nitride lamellar layers. As shown in fig. 4, the sharp lattice fringes in TEM and the specific lattice spacing (0.338 and 0.354 nm) substantially coincide with the cadmium sulfide crystal planes, further confirming successful coupling of carboxylated carbon nitride to cadmium sulfide and formation of heterostructures.
TABLE 1 specific surface area, pore volume, average pore size and photo-current values of carbon nitride and carboxylated carbon nitride
Band structure and absorbance analysis:
as can be seen from the ultraviolet-visible diffuse reflectance spectrum chart (left of FIG. 5), compared with carbon nitride, carboxylated carbon nitride has higher absorbance in the wavelength range of 200-420 nm, which indicates that the carboxylated carbon nitride has better absorbance in the ultraviolet region. As is apparent from the transient photocurrent response curve (right side of fig. 5) of the carboxylated carbon nitride and carboxylated carbon nitride/cadmium sulfide composite material, the coupling of cadmium sulfide significantly improves the photocurrent intensity thereof; and the intrinsic fluorescence lifetime of the composite material is longer (about 38.34 ns), and the composite material has higher transmission rate of photogenerated carriers. From the transient fluorescence spectrum analysis of the material, the PL intensity of carbon nitride is highest, while the PL intensity of carboxylated carbon nitride-24 is lowest, and it is confirmed that carboxyl-modified carbon nitride can contribute to the separation of photogenerated electrons and holes.
The electrochemical impedance spectrum further reflects that the carboxyl modified carbon nitride is beneficial to the effective separation of charges, and the interfacial charge transfer is further accelerated. From the flat band potential (E of the material in Table 2 fb ) The data show that the flat band potential of the carbon nitride is higher than that of the carboxyl carbon nitride material, and the negative shift of the flat band potential shows that the carboxyl carbon nitride has higher conductivity and higher electron donor density, has stronger reducing capability after illumination, and is beneficial to improving the photocatalytic reduction performance of the carboxyl carbon nitride on U (VI).
TABLE 2 flatband potential, level differences and band gap values for carbon nitride, carboxylated carbon nitride and carboxylated carbon nitride/cadmium sulfide
The energy level difference of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) of the carboxyl modification to the carbon nitride structure is calculated by adopting the density functional theory, and as-C (identical to N) and-COOH in carboxylated carbon nitride are electron withdrawing groups, the band gap can be reduced along with the introduction of carboxyl, and the narrower band gap is reduced, so that the carboxylated carbon nitride is easier to capture more photons to reduce U (VI).
Based on the analysis of the results, the carboxylated carbon nitride/cadmium sulfide composite material is of a typical II-type energy band arrangement structure, and compared with carbon nitride, the carboxylated carbon nitride/cadmium sulfide composite material heterostructure enlarges the light absorption range and obviously reduces the band gap energy band, so that the carboxylated carbon nitride/cadmium sulfide composite material is beneficial to capturing more photons for the photocatalytic reduction reaction of U (VI).
In summary, compared with carbon nitride, the carboxylated carbon nitride/cadmium sulfide composite material has the characteristics of stronger U (VI) adsorption affinity, higher light absorption capacity, narrower band gap, higher carrier separation capacity, longer carrier service life and the like, which are all helpful for enhancing the photocatalytic reduction activity of U (VI).
Photocatalytic reduction performance analysis and practical application performance evaluation:
as proved by the batch adsorption test result of U (VI), the adsorption rate of carbon nitride to U (VI) is 12% in the presence of 2.0 mM carbonate (hydrogen), and the adsorption rates of carboxylated carbon nitride-6 and carboxylated carbon nitride-24 to U (VI) are 1.5 and 3.2 times, which show that the introduction of carboxyl greatly improves the affinity of U (VI) on the surface of the catalyst. Further comparing the photocatalytic reduction removal efficiency of the carbon nitride and carboxylated carbon nitride/cadmium sulfide composite material on U (VI) (left in fig. 6), it is known that since the e-and h+ photo-generated carbon nitride are easy to rapidly recombine, the photocatalytic activity is lower, methanol is required to be added as an electron donor to improve the photocatalytic efficiency, but even if methanol is added, only about 70% of U (VI) can be removed by photocatalysis within 40min, and after the carboxylated carbon nitride and cadmium sulfide are compounded, the photocatalytic reduction efficiency of U (VI) is greatly improved, U (VI) can be completely removed within 6min, and the photocatalytic reduction efficiency is higher. As can be seen from comparison of the photocatalytic reduction reaction rate constants (right of FIG. 6 and Table 3) of the carboxylated carbon nitride/cadmium sulfide composite material, the photocatalytic reduction rates of U (VI) by carboxylated carbon nitride-6/cadmium sulfide-10, carboxylated carbon nitride-24/cadmium sulfide-10 and carboxylated carbon nitride-24/cadmium sulfide-30 are 0.1285, 0.2788 and 0.6435 min, respectively −1 The reaction rate is far higher than that of the carbon nitride material (0.0107 min −1 And methanol as an electron donor), this demonstrates that carboxylation and the introduction of cadmium sulfide greatly improve the photoactivity of the composite and the photocatalytic reduction rate to U (VI), again without any electron donor involved in the reaction.
TABLE 3 comparison of photocatalytic reduction rates for U (VI) for carboxylated carbon nitride/cadmium sulfide composites
After the photocatalytic reaction is finished, the reaction product powder is collected and dispersed in pure water, and after the reaction product powder is continuously stirred in the air for 24 hours, about 60 percent of uranium precipitate can be released again. Then, 0 is added to the mixture.1M Na 2 CO 3 The solution is vibrated for 60min, and uranium can be completely eluted and recovered. Therefore, the whole elution process is simple, efficient and pollution-free. In particular, the carboxylated carbon nitride/cadmium sulfide composite material after uranium elution can be recycled for a plurality of times, and after the composite material is subjected to recycling for 3 times, the photocatalytic reduction efficiency of U (VI) of the composite material is still maintained to be more than 99.5% (see figure 7), and the composite material has excellent recycling performance and economy. The carboxyl carbon nitride/cadmium sulfide composite photocatalyst does not release Cd in the photocatalytic reduction process of U (VI) 2+ Therefore, the composite catalyst is used for extracting uranium from seawater, is an efficient, green and economic uranium separation and recovery technology, and has important practical significance for extracting uranium from seawater.
Claims (7)
1. The preparation method of the catalyst for the photocatalytic extraction of uranium in seawater comprises the following steps:
preparing carboxylated carbon nitride:
activating melamine at 550 ℃ for 4 hours under argon atmosphere, cooling, grinding and sieving to obtain an activated product; ultrasonically dispersing the activated product into 4-6M nitric acid aqueous solution, carrying out reflux reaction for 6-24 h at 120-130 ℃, centrifuging, washing, and freeze-drying in vacuum for 24h to obtain carboxylated carbon nitride;
constructing a carboxylated carbon nitride/cadmium sulfide composite photocatalyst:
sequentially ultrasonically dispersing the carboxylated carbon nitride, glucose and cadmium nitrate in deionized water, stirring and reacting for 4 hours, adding thioglycollic acid, and continuously stirring for 1 hour to obtain a uniform mixture; the uniform mixture is subjected to hydrothermal reaction for 2 hours at 170-190 ℃, and the obtained reaction product is washed by deionized water and freeze-dried to obtain the carboxylated carbon nitride/cadmium sulfide composite photocatalyst with the cadmium sulfide loading amount of 10-30%; the carboxylated carbon nitride: glucose: the mass ratio of thioglycollic acid is 1:2:6.
2. the method for preparing the catalyst for photocatalytic extraction of uranium in seawater as claimed in claim 1, wherein: the medium-high temperature activation heating rate is controlled to be 4-5 ℃/min.
3. The method for preparing the catalyst for photocatalytic extraction of uranium in seawater as claimed in claim 1, wherein: the mesh diameter of the screen mesh screened in the step (A) is more than 200 meshes.
4. The method for preparing the catalyst for photocatalytic extraction of uranium in seawater as claimed in claim 1, wherein: in the step (A), the solid-liquid mass volume ratio of an activation product to a nitric acid aqueous solution is 1: 40-1: 50.
5. the method for preparing the catalyst for photocatalytic extraction of uranium in seawater as claimed in claim 1, wherein: in the step (A), the condition of washing the reflux reaction product is that the pH value of the suspension is stabilized at 6-7.
6. The method for preparing the catalyst for photocatalytic extraction of uranium in seawater as claimed in claim 1, wherein: the solid-liquid mass ratio of carboxylated carbon nitride to deionized water in the step (II) is 1-2: 100.
7. the method for preparing the catalyst for photocatalytic extraction of uranium in seawater as claimed in claim 1, wherein: the freeze drying condition in the step is that the temperature is-50 ℃ and the time is 12-24 hours.
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