Disclosure of Invention
Aiming at the problems, the invention provides a preparation method of a composite photocatalyst and application of the composite photocatalyst in VOCs purification.
The purpose of the invention is realized by adopting the following technical scheme:
a preparation method of a composite photocatalyst comprises the following steps:
s1, respectively weighing polyvinylpyrrolidone, azodicyano valeric acid and styrene, mixing, adding an ethanol water solution, fully stirring uniformly, heating to boil within 30min, carrying out reflux reaction for 12-36h under the stirring condition, cooling, carrying out centrifugal separation on precipitate, washing the precipitate with methanol and/or deionized water, and then dispersing in methanol to obtain a suspension A, wherein the precipitation dispersion ratio is (3-4) mg/ml;
s2, weighing polyvinylpyrrolidone, completely dissolving the polyvinylpyrrolidone in methanol at a dissolving concentration of 1-5 wt.%, adding a nano photocatalyst, stirring and reacting for 1-60min, centrifugally separating precipitates, washing the precipitates with methanol and/or deionized water, drying, and dispersing in the suspension A to obtain a suspension B, wherein the precipitation dispersion ratio is (1-10) mg/ml;
wherein the nano photocatalyst comprises nano titanium dioxide, and the mass ratio of the polyvinylpyrrolidone to the nano photocatalyst is (1-100): 1;
s3, dissolving the alcohol-soluble salt of zinc and/or cobalt in methanol to obtain a solution A, wherein the dissolving concentration is 0.01-1 mol/L; dissolving an organic ligand in methanol to obtain a solution B, wherein the dissolving concentration is 0.01-1 mol/L; adding the suspension B into the solution A, fully stirring and mixing, adding the solution B, standing for 1-96h at 15-160 ℃, centrifugally separating and precipitating, washing the precipitate with methanol, N-dimethylformamide, tetrahydrofuran and deionized water in sequence, and drying to obtain the composite photocatalyst;
wherein the mixing volume ratio of the suspension B to the solution A to the solution B is 1: (1-100): (1-100).
Preferably, in step S1, the volume ratio of ethanol to water in the ethanol aqueous solution is (1-2): 1, the mass ratio of the polyvinylpyrrolidone to the azodicyano valeric acid, the styrene to the ethanol aqueous solution is (0.7-0.8): (0.1-0.2): 1: (20-25).
Preferably, the alcohol-soluble salt is one or more of zinc nitrate, zinc sulfate, cobalt nitrate, cobalt sulfate, cobalt chloride and hydrates thereof; the organic ligand is one or more of 2-methylimidazole, 1, 4-terephthalic acid and 2, 5-dihydroxy terephthalic acid.
Preferably, the nano titanium dioxide is reduction-treated titanium dioxide, and the preparation method of the reduction-treated titanium dioxide comprises the following steps:
respectively weighing sodium borohydride and nano titanium dioxide according to the weight ratio of (1-2): 4, after fully and uniformly mixing, heating to 200-300 ℃ in protective atmosphere or vacuum, carrying out heat preservation reaction for 20-60min, cooling, washing and drying the product, and grinding and crushing to obtain the catalyst.
Preferably, the nano-scale photocatalyst also comprises a sulfide solid solution of cadmium cobalt bimetal.
Preferably, the preparation method of the sulfide solid solution of the cadmium-cobalt bimetal comprises the following steps:
s1, respectively weighing 2-methylimidazole and surfactant, dissolving in deionized water, wherein the dissolving concentrations of the 2-methylimidazole and the surfactant in the deionized water are 0.1-1mol/L and 5-10mmol/L respectively to obtain a solution C, adding Co2+And Cd2+Fully stirring and dissolving the soluble salt to obtain a solution D, continuously stirring and reacting for 1-6h, centrifugally separating and precipitating, washing the precipitate with deionized water and methanol in sequence, and drying to obtain a product A;
s2, dispersing the product A in deionized water, wherein the dispersion ratio is (1-10) mg/ml, adding thioacetamide, fully stirring until the thioacetamide is dissolved to obtain a solution E, transferring the solution E into a reaction kettle with a polytetrafluoroethylene lining, heating to 86-92 ℃ at the temperature rise rate of not less than 10 ℃/min, carrying out heat preservation reaction for 12-16min, cooling, carrying out centrifugal separation on the precipitate, washing the precipitate with methanol and deionized water in sequence, drying, and grinding and crushing to obtain the cadmium-cobalt bimetallic sulfide solid solution;
wherein the mass ratio of the product A to the thioacetamide is (1.5-2): 1.
preferably, in step s1, Co in the solution D2+And Cd2+The ratio of the amounts of the substances (1-3): 1, Co2+And Cd2+The sum of the concentrations of (A) and (B) is 0.1-1 mol/L.
Preferably, the preparation method further comprises step S4, specifically:
transferring the product prepared after drying in the step S3 into a vacuum furnace for activation heat treatment, heating to 225 ℃ at a heating rate of 5 ℃/min under a vacuum condition, preserving heat for 40min, naturally cooling, dispersing the product of the activation heat treatment in methanol at a dispersion ratio of (3-5) mg/ml to obtain a suspension C, weighing 1, 10-phenanthroline, dissolving in the methanol at a dissolution concentration of (0.5-1) mg/ml to obtain a solution F, dropwise adding the solution F into the suspension C under a stirring condition, stirring and reacting at 50-60 ℃ for 2-3h after dropwise adding, centrifugally separating and precipitating, washing the precipitate with methanol and deionized water in sequence, and drying to obtain the product;
wherein the mixing volume ratio of the solution F to the suspension C is 1: (2-3).
Another object of the present application is to provide a composite photocatalyst prepared by the aforementioned preparation method.
The application further aims to provide an application of the composite photocatalyst, and the composite photocatalyst is particularly used for catalyzing, degrading and purifying volatile organic compounds.
The invention has the beneficial effects that:
(1) according to the invention, a porous metal organic framework ZIF-8 is used as a carrier, nanometer titanium dioxide modified by PVP is highly and uniformly dispersed on the metal organic framework ZIF-8, so that the composite photocatalyst with large specific surface area and high dispersion degree is prepared, the adsorption performance of the photocatalyst on VOCs in a photocatalytic degradation process is enhanced, the photocatalytic oxidation performance on typical VOCs is obviously enhanced, and the problems of poor adsorption performance and low degradation efficiency of the traditional photocatalyst are solved;
(2) the ZIF-8 metal organic framework material has small pore diameter within a micropore range, and the small pore diameter provides larger specific surface area, but has the problems of large mass transfer resistance and low diffusion rate.
(3) According to the method, titanium dioxide is partially reduced through sodium borohydride, oxygen vacancies are generated on the surface of nano titanium dioxide, and are easily converted into surface hydroxyl groups, so that organic pollutants can be adsorbed more quickly, the conversion of a catalyst from chemisorption oxygen to active oxygen is promoted, and the catalytic oxidation effect is improved; according to the method, the cadmium-cobalt bimetallic sulfide solid solution is compounded with titanium dioxide, so that the visible light photocatalytic activity of the titanium dioxide is greatly improved, the strong electronic coupling between ZIF-8 and the cadmium-cobalt bimetallic sulfide is realized, and the high-activity atomic-level dispersed reduced titanium sites in the ZIF-8 are combined to generate high photocatalytic performance, and meanwhile, the ZIF-8 serving as a dispersion body is a high-performance carrier and an accelerant of a nanostructure photocatalyst, so that the photocatalytic activity of cadmium sulfide can be improved; the application also uses 1, 10-phenanthroline with strong electron donating capability as ligand molecules for coordination doping, and utilizes the proper molecular size of a phenanthrene condensed ring structure and the electron donating characteristic thereof to induce generation of a charge transfer effect, reduce the photogenerated electron-hole recombination rate and improve the photocatalytic performance.
Detailed Description
The invention is further described with reference to the following examples.
Example 1
A preparation method of the composite photocatalyst comprises the following steps:
s1, weighing 2.0g of polyvinylpyrrolidone, 0.6g of azodicyano valeric acid and 3.0g of styrene respectively, mixing, adding 25ml of ethanol water solution with the volume ratio of 2:1, fully and uniformly stirring, heating to boil within 30min, refluxing and reacting for 24h under the stirring condition, cooling, centrifugally separating and precipitating, washing the precipitate with methanol and/or deionized water, and then dispersing in methanol to obtain a suspension A, wherein the precipitation dispersion ratio is 3 mg/ml;
s2, weighing 2.0g of polyvinylpyrrolidone, completely dissolving the polyvinylpyrrolidone in 40ml of methanol, adding 0.5g of nano titanium dioxide (P25), stirring for reacting for 20min, centrifugally separating precipitates, washing the precipitates with methanol and/or deionized water, drying, and dispersing in the suspension A to obtain a suspension B, wherein the dispersion ratio of the precipitates is 4 mg/ml;
s3, dissolving zinc nitrate and/or cobalt nitrate in methanol to obtain a solution A, wherein the dissolving concentration is 0.1 mol/L; dissolving 2-methylimidazole in methanol to obtain a solution B, wherein the dissolving concentration is 0.1 mol/L; adding the suspension B into the solution A, fully stirring and mixing, and then adding the solution B, wherein the mixing volume ratio of the suspension B to the solution A to the solution B is 1: 50: and 50, standing at normal temperature for 24 hours, centrifugally separating and precipitating, washing the precipitate with methanol, N-dimethylformamide, tetrahydrofuran and deionized water in sequence, and drying to obtain the composite photocatalyst.
FIG. 1 is a TEM image of the composite photocatalyst prepared in this example. It can be seen from the TEM images that the P25 nanoparticles have no significant agglomeration, which indicates that the P25 nanoparticles are successfully dispersed on the porous organic framework.
Acetone is used as an adsorbate, and a nitrogen adsorption apparatus (BELSORP-max) is adopted to test the adsorption capacity of the composite photocatalyst to the acetone, wherein the adsorption temperature is (30 ℃). Fig. 2 is an adsorption isotherm of the composite photocatalyst prepared in this embodiment and P25 on acetone, and it can be seen from this that, under the same relative pressure condition, the adsorption performance of the composite photocatalyst prepared in this embodiment on acetone is always higher than that of P25, and when the relative pressure is 1, the adsorption value of P25 on acetone is 100mg/g, and the adsorption value of the composite photocatalyst on acetone is 253.9mg/g, which is significantly improved compared with that of P25 on acetone (100.3mg/g), so that compounding ZIF-8 and P25 not only can effectively increase the adsorption performance on acetone, but also can increase the photocatalytic oxidation performance of the composite photocatalyst on acetone.
Example 2
A preparation method of the composite photocatalyst comprises the following steps:
s1, weighing 2.0g of polyvinylpyrrolidone, 0.6g of azodicyano valeric acid and 3.0g of styrene respectively, mixing, adding 25ml of ethanol water solution with the volume ratio of 2:1, fully and uniformly stirring, heating to boil within 30min, refluxing and reacting for 24h under the stirring condition, cooling, centrifugally separating and precipitating, washing the precipitate with methanol and/or deionized water, and then dispersing in methanol to obtain a suspension A, wherein the precipitation dispersion ratio is 3 mg/ml;
s2, weighing 2.0g of polyvinylpyrrolidone, completely dissolving the polyvinylpyrrolidone in 40ml of methanol, adding 0.5g of reduced titanium dioxide, stirring for reacting for 20min, centrifugally separating precipitates, washing the precipitates with methanol and/or deionized water, drying, and dispersing in the suspension A to obtain a suspension B, wherein the dispersion ratio of the precipitates is 4 mg/ml;
s3, dissolving zinc nitrate and/or cobalt nitrate in methanol to obtain a solution A, wherein the dissolving concentration is 0.1 mol/L; dissolving 2-methylimidazole in methanol to obtain a solution B, wherein the dissolving concentration is 0.1 mol/L; adding the suspension B into the solution A, fully stirring and mixing, and then adding the solution B, wherein the mixing volume ratio of the suspension B to the solution A to the solution B is 1: 50: 50, standing at normal temperature for 24 hours, centrifugally separating and precipitating, washing the precipitate with methanol, N-dimethylformamide, tetrahydrofuran and deionized water in sequence, and drying to obtain the composite photocatalyst;
the preparation method of the titanium dioxide subjected to reduction treatment comprises the following steps:
respectively weighing sodium borohydride and nano titanium dioxide (P25) according to the weight ratio of 1: 2, after fully and uniformly mixing, heating to 250 ℃ in protective atmosphere or vacuum, preserving heat for reaction for 40min, cooling, washing and drying the product, and grinding and crushing to obtain the catalyst.
Example 3
A preparation method of the composite photocatalyst comprises the following steps:
s1, weighing 2.0g of polyvinylpyrrolidone, 0.6g of azodicyano valeric acid and 3.0g of styrene respectively, mixing, adding 25ml of ethanol water solution with the volume ratio of 2:1, fully and uniformly stirring, heating to boil within 30min, refluxing and reacting for 24h under the stirring condition, cooling, centrifugally separating and precipitating, washing the precipitate with methanol and/or deionized water, and then dispersing in methanol to obtain a suspension A, wherein the precipitation dispersion ratio is 3 mg/ml;
s2, weighing 2.0g of polyvinylpyrrolidone, completely dissolving the polyvinylpyrrolidone in 40ml of methanol, adding 0.5g of reduced titanium dioxide and 0.14g of cadmium-cobalt bimetallic sulfide solid solution, stirring and reacting for 20min, centrifugally separating and precipitating, washing and drying the precipitate with methanol and/or deionized water, and re-dispersing in the suspension A to obtain a suspension B, wherein the precipitation dispersion ratio is 4 mg/ml;
s3, dissolving zinc nitrate and/or cobalt nitrate in methanol to obtain a solution A, wherein the dissolving concentration is 0.1 mol/L; dissolving 2-methylimidazole in methanol to obtain a solution B, wherein the dissolving concentration is 0.1 mol/L; adding the suspension B into the solution A, fully stirring and mixing, and then adding the solution B, wherein the mixing volume ratio of the suspension B to the solution A to the solution B is 1: 50: 50, standing at normal temperature for 24 hours, centrifugally separating and precipitating, washing the precipitate with methanol, N-dimethylformamide, tetrahydrofuran and deionized water in sequence, and drying to obtain the composite photocatalyst;
the preparation method of the titanium dioxide subjected to reduction treatment comprises the following steps:
respectively weighing sodium borohydride and nano titanium dioxide (P25) according to the weight ratio of 1: 2, after fully and uniformly mixing, heating to 250 ℃ under protective atmosphere or vacuum, preserving heat for reaction for 40min, cooling, washing and drying a product, and grinding and crushing to obtain the catalyst;
the preparation method of the cadmium-cobalt bimetallic sulfide solid solution comprises the following steps:
s1, minuteRespectively weighing 2-methylimidazole and polyvinylpyrrolidone, dissolving in deionized water to obtain solutions with the concentration of 0.1mol/L and 8mmol/L, adding Co2+And Cd2+Is prepared into Co2+And Cd2+The concentration of the solution is 0.3mol/L and 0.1mol/L respectively, the solution D is obtained after fully stirring and dissolving, the stirring reaction is continued for 4 hours, the centrifugal separation and precipitation are carried out, the precipitation is washed by deionized water and methanol in sequence, and the product A is obtained after drying;
s2, dispersing the product A in deionized water at a dispersion ratio of 5mg/ml, and adding thioacetamide, wherein the mass ratio of the product A to the thioacetamide is 1.6: 1, fully stirring until the solution is dissolved to obtain a solution E, transferring the solution E into a reaction kettle with a polytetrafluoroethylene lining, heating to 90 ℃ at the heating rate of 20 ℃/min, carrying out heat preservation reaction for 15min, cooling, carrying out centrifugal separation and precipitation, washing the precipitate with methanol and deionized water in sequence, drying, and grinding and crushing to obtain the cadmium-cobalt bimetallic sulfide solid solution.
Example 4
A preparation method of the composite photocatalyst comprises the following steps:
s1, weighing 2.0g of polyvinylpyrrolidone, 0.6g of azodicyano valeric acid and 3.0g of styrene respectively, mixing, adding 25ml of ethanol water solution with the volume ratio of 2:1, fully and uniformly stirring, heating to boil within 30min, refluxing and reacting for 24h under the stirring condition, cooling, centrifugally separating and precipitating, washing the precipitate with methanol and/or deionized water, and then dispersing in methanol to obtain a suspension A, wherein the precipitation dispersion ratio is 3 mg/ml;
s2, weighing 2.0g of polyvinylpyrrolidone, completely dissolving the polyvinylpyrrolidone in 40ml of methanol, adding 0.5g of nano titanium dioxide (P25), stirring for reacting for 20min, centrifugally separating precipitates, washing the precipitates with methanol and/or deionized water, drying, and dispersing in the suspension A to obtain a suspension B, wherein the dispersion ratio of the precipitates is 4 mg/ml;
s3, dissolving zinc nitrate and/or cobalt nitrate in methanol to obtain a solution A, wherein the dissolving concentration is 0.1 mol/L; dissolving 2-methylimidazole in methanol to obtain a solution B, wherein the dissolving concentration is 0.1 mol/L; adding the suspension B into the solution A, fully stirring and mixing, and then adding the solution B, wherein the mixing volume ratio of the suspension B to the solution A to the solution B is 1: 50: 50, standing for 24 hours at normal temperature, centrifugally separating and precipitating, washing the precipitate with methanol, N-dimethylformamide, tetrahydrofuran and deionized water in sequence, and drying;
s4, transferring the product obtained after drying in the step S3 into a vacuum furnace for activation heat treatment, heating to 225 ℃ at a heating rate of 5 ℃/min under a vacuum condition, preserving heat for 40min, naturally cooling, dispersing the product of the activation heat treatment in methanol at a dispersion ratio of 3mg/ml to obtain a suspension C, weighing 1, 10-phenanthroline, dissolving in methanol at a dissolution concentration of 0.7mg/ml to obtain a solution F, dropwise adding the solution F into the suspension C under a stirring condition, wherein the mixing volume ratio of the solution F to the suspension C is 1: and 2, stirring and reacting for 2 hours at the temperature of 50-60 ℃ after the dropwise addition is finished, centrifugally separating and precipitating, washing the precipitate with methanol and deionized water in sequence, and drying to obtain the composite photocatalyst.
Photocatalytic Performance test
The test is carried out in a closed glass reactor with the internal volume of 100ml, quartz glass is arranged at the top of the reactor, a gas inlet, a gas outlet, a gas sampling port and a temperature sensor are arranged, cooling water is circulated by a circulating water pump to enable the photocatalytic reaction to be carried out under the normal temperature condition, so that the influence of the thermal effect on the experimental result is eliminated, and a 300W xenon lamp is used for simulating a sunlight source.
Firstly, 2ml of deionized water is dropped into the bottom of the reactor, then a quartz reactor (30mm multiplied by 20mm) filled with 50mg of composite photocatalyst is placed at the bottom of the reactor, and pure O is introduced2(2atm) to remove the air in the device, injecting 3 μ L of toluene/formaldehyde solution into the reactor with a micro-injector, placing the reactor in the dark for 30min to establish adsorption-desorption equilibrium between the sample and toluene/formaldehyde, then turning on the xenon lamp to perform photocatalytic degradation reaction, taking 500 μ L of reacted gas sample out of the sampling port with a glass syringe at regular time intervals to perform quantitative analysis, and performing a blank experiment without composite photocatalyst under the same conditions to eliminate the photolysis from degrading toluene/formaldehydeThe initial concentration of toluene and formaldehyde is 0.8mg/L and 0.16mg/L, and the test results are shown in the following table.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.