CN109896545B - Hollow shell type titanium dioxide nano material, silver-loaded hollow shell type titanium dioxide nano material and preparation method thereof - Google Patents
Hollow shell type titanium dioxide nano material, silver-loaded hollow shell type titanium dioxide nano material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a hollow shell type titanium dioxide nano material, a silver-loaded hollow shell type titanium dioxide nano material and a preparation method thereof. The preparation method of the hollow shell type titanium dioxide nano material comprises the following steps: uniformly mixing the RF dispersion liquid and ammonia water by using absolute ethyl alcohol, then adding tetrabutyl titanate to react, and sequentially performing the steps of centrifugal separation, washing, drying and two-step roasting to prepare the hollow shell type titanium dioxide nano material, wherein the volume ratio of the absolute ethyl alcohol to the RF dispersion liquid to the ammonia water to the tetrabutyl titanate is (40-50): (4-6): (0.1-0.4): (0.75 to 1.5). Silver is deposited on the surface of the hollow shell type titanium dioxide nano material by an ultraviolet radiation deposition method, so that the silver-loaded hollow shell type titanium dioxide nano material is prepared. The hollow shell type titanium dioxide nano material and the silver-loaded hollow shell type titanium dioxide nano material prepared by the method are all in anatase crystal forms, and the degradation efficiency of phenol is high.
Description
Technical Field
The invention belongs to the field of inorganic nano photocatalyst materials and preparation thereof, and particularly relates to a hollow shell type titanium dioxide nano material, a silver-loaded hollow shell type titanium dioxide nano material and a preparation method thereof.
Background
The discharge of phenol-containing wastewater from petrochemical, pharmaceutical, pesticide, paper-making and other industries poses serious threats to the environment, and the high-concentration phenol-containing wastewater can corrode the skin and mucous membranes and destroy the biological central nervous system. The traditional treatment method of the phenol-containing wastewater mainly comprises the following steps: extraction method, adsorption method, chemical precipitation method, chemical oxidation method, etc., but these methods all can cause secondary pollution to a certain extent, and the energy consumption is large, and the degradation is not thorough. Under the environment advocating green chemistry, the appearance of the photocatalytic oxidation technology brings great convenience for solving the problem of phenolic wastewater.
Titanium dioxide (TiO)2) The photocatalyst has good adsorption and degradation capability on organic pollutants, has the advantages of no selectivity, no secondary pollution, low price, high efficiency and the like, and has attracted wide attention. But TiO 22Two major problems are mainly faced as photocatalysts: (1) TiO 22The forbidden bandwidth of the semiconductor determines that the semiconductor can only absorb light sources with the wavelength less than 387nm, the absorptivity to visible light is poor, and the utilization rate to solar energy is low; (2) the separation efficiency of photon-generated carriers is low, and the utilization rate of photon-generated electrons is low. New structure TiO2The design and development of the photocatalyst can further enhance the photocatalytic activity of the photocatalyst and expand TiO2The application range of the photocatalyst.
Chinese patent application CN201710683148.3 discloses a preparation method and application of a molybdenum disulfide-coated titanium dioxide hollow core-shell structure composite photocatalyst, although the composite photocatalyst prepared by the patent application can rapidly and efficiently reduce 4-nitrophenol into 4-aminophenol, the nitro group on the phenol is only converted into amino group, and the phenol main body is not degraded, as is known, the nitro group reduction is relatively easy, and the phenol degradation difficulty is very high, so that the composite photocatalyst prepared by the patent application is not suitable for treating phenol-containing wastewater; in addition, molybdenum disulfide is a flaky substance, and the supported flaky substance (such as molybdenum disulfide, graphene oxide, and the like) is likely to cause serious agglomeration of the supported substance and titanium dioxide, so that the specific surface area of the catalyst is seriously lost, and the degradation effect of the composite photocatalyst is influenced. Chinese patent application CN201310259237.7 discloses a silver-loaded nano titanium dioxide photocatalyst and a preparation method thereof, but the silver-loaded nano titanium dioxide photocatalyst prepared by the patent application has poor degradation efficiency on Methylene Blue (MB), and the degradation amount of MB can only reach about 70% within a 200min time period; it is well known that phenol is the most difficult to degrade and MB is the most degradable, among the common refractory contaminants phenol, Methylene Blue (MB), rhodamine b (rhb), and Methyl Orange (MO); therefore, the silver-loaded nano titanium dioxide photocatalyst prepared by the patent application is not suitable for treating phenol-containing wastewater as the photocatalyst.
In summary, it is therefore desirable to provide a novel titanium dioxide nanomaterial to improve the phenol degradation efficiency of titanium dioxide.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide a hollow shell type titanium dioxide nano material, a silver-loaded hollow shell type titanium dioxide nano material and a preparation method thereof. The prepared hollow shell type titanium dioxide nano material and the silver-loaded hollow shell type titanium dioxide nano material have the advantages of hollow structure, large specific surface area, reaction activity center positions inside and outside the hollow structure, high catalytic efficiency, high phenol degradation efficiency and capability of quickly and efficiently removing phenol; the preparation method has the advantages of simple process, high efficiency, low energy consumption, no pollution and the like.
In order to achieve the above object, the present invention provides, in a first aspect, a method for preparing a hollow shell-type titanium dioxide nanomaterial, the method comprising the steps of:
(1) uniformly mixing resorcinol-formaldehyde resin dispersion liquid and ammonia water by using absolute ethyl alcohol to obtain a mixed liquid, and then dropwise adding tetrabutyl titanate into the mixed liquid for reaction to obtain a reaction product solution; the volume ratio of the absolute ethyl alcohol to the resorcinol-formaldehyde resin dispersion liquid to the ammonia water to the tetrabutyl titanate is (40-50): (4-6): (0.1-0.4): (0.75 to 1.5);
(2) sequentially carrying out a centrifugal separation step, a washing step and a drying step on the reaction product solution obtained in the step (1) to obtain a titanium dioxide material with a core-shell structure; and
(3) and (3) roasting the titanium dioxide material with the core-shell structure obtained in the step (2) in a nitrogen atmosphere for 2-4 h, and then roasting in an air atmosphere for 2-4 h to obtain the hollow shell type titanium dioxide nano material.
Preferably, the method further comprises, before the step (1), a step of preparing the resorcinol-formalin resin dispersion, the step of preparing comprising the substeps of:
(a) uniformly mixing ammonia water with water and absolute ethyl alcohol to obtain a first mixed solution, adding resorcinol into the first mixed solution, and uniformly mixing to obtain a second mixed solution;
(b) adding a formaldehyde solution into the second mixed solution obtained in the step (a) to react to obtain a resorcinol formaldehyde resin solution, and then sequentially performing a centrifugal separation step and a washing step on the resorcinol formaldehyde resin solution to obtain resorcinol formaldehyde resin; and
(c) dispersing the resorcinol-formaldehyde resin obtained in the step (b) with absolute ethyl alcohol to obtain the resorcinol-formaldehyde resin dispersion liquid.
Preferably, in the step (a), the volume ratio of the water, the absolute ethyl alcohol and the ammonia water is (30-60): (10-20): (0.2 to 0.4); the molar ratio of the resorcinol to the formaldehyde contained in the formaldehyde solution is 1: (1-2); and/or in the step (b), the reaction temperature is 30-35 ℃, and the reaction time is 18-30 h.
Preferably, in the step (1), the reaction temperature is 70-100 ℃, and the reaction time is 2-4 h.
Preferably, the temperature of the firing in a nitrogen atmosphere and/or the temperature of the firing in an air atmosphere is 400 to 500 ℃.
The invention provides in a second aspect the hollow shell titanium dioxide nanomaterial prepared by the preparation method of the first aspect.
The invention provides a preparation method of silver-loaded hollow shell type titanium dioxide nano material in a third aspect, which comprises the following steps:
s1, uniformly dispersing the hollow shell type titanium dioxide nano material prepared by the preparation method in the first aspect by using a silver nitrate aqueous solution to obtain a hollow shell type titanium dioxide dispersion liquid; and
s2, treating the hollow shell type titanium dioxide dispersion liquid with ultraviolet light to load silver on the surface of the hollow shell type titanium dioxide nano material, and obtaining the silver-loaded hollow shell type titanium dioxide nano material.
Preferably, the mass ratio of the hollow shell type titanium dioxide nano material to the silver nitrate contained in the silver nitrate aqueous solution is 0.1 (0.001-0.015), and preferably 0.1 (0.0015-0.009).
Preferably, the concentration of the silver nitrate aqueous solution is 0.03-0.19 g/L.
In a fourth aspect, the invention provides a silver-loaded hollow shell titanium dioxide nanomaterial prepared by the preparation method in the third aspect.
Compared with the prior art, the invention at least has the following beneficial effects:
1. the invention adopts resorcinol formaldehyde Resin (RF) as a template to prepare the titanium dioxide material (RF @ TiO) with the core-shell structure2) Then obtaining the hollow shell type titanium dioxide nano material (hollow structure TiO) with a novel structure by two-step roasting2) TiO having such a hollow structure2The nano structure has large specific surface area, active centers inside and outside, and high catalytic efficiency; in addition, the invention deposits silver (Ag) on the hollow structure TiO by an ultraviolet radiation deposition method2The surface adopts Ag load to further improve the space of photon-generated carriersThe separation efficiency of the hollow shell type titanium dioxide nano material is improved greatly, and the photocatalytic reaction activity of the hollow shell type titanium dioxide nano material and the degradation efficiency of phenol are improved greatly.
2. According to the invention, through the reasonable proportion of the absolute ethyl alcohol, the resorcinol-formaldehyde resin dispersion liquid, the ammonia water and the tetrabutyl titanate, especially the reasonable amount of the ammonia water, the titanium dioxide particles are effectively ensured to be in a state of little agglomeration or monodispersion, the thickness of a shell layer can be regulated and controlled between 20nm and 90nm, and the problems that the existing titanium dioxide particles and silver combined as a photocatalyst are too small and easy to agglomerate, and the active center is not fully exposed, so that the catalytic efficiency is low are effectively avoided.
3. The preparation method has the advantages of simple flow, high efficiency, low energy consumption, no pollution and the like; the prepared hollow shell type titanium dioxide nano material and the silver-loaded hollow shell type titanium dioxide nano material are all in anatase crystal forms, the phenol degradation efficiency is high, phenol can be quickly and efficiently removed, the phenol degradation rate of the hollow shell type titanium dioxide nano material can reach about 90% in a period of 150-210 min, and the phenol degradation rate of the silver-loaded hollow shell type titanium dioxide nano material can reach about 90% in a period of 90-120 min.
Drawings
FIG. 1 is a hollow TiO prepared in example 12Scanning electron micrograph (SEM picture) of (a). In the figure (a), (b), (c) and (d) correspond to SEM pictures of HT-0.10, HT-0.20, HT-0.30 and HT-0.35, respectively, for the samples.
FIG. 2 is a hollow TiO prepared in example 12Transmission electron microscopy (TEM images). In the figure, (a), (b), (c) and (d) correspond to TEM images of samples HT-0.10, HT-0.20, HT-0.30 and HT-0.35, respectively.
FIG. 3 is a hollow TiO prepared in example 12X-ray diffraction pattern (XRD pattern) of the sample. In the figure, the XRD patterns of (a), (b), (c) and (d) correspond to those of HT-0.35, HT-0.30, HT-0.20 and HT-0.10, respectively.
FIG. 4 shows HT @ Ag and hollow TiO prepared in example 12X-ray diffraction pattern (XRD pattern) of the sample. In the figure, (a), (b), (c) and (d) are divided intoCorresponding to samples HT-9, HT-6, HT-3 and HT-0.30 (hollow TiO)2) XRD spectrum of (1).
FIG. 5 is a hollow TiO prepared in example 12And high resolution transmission electron microscopy images (high power TEM images) of HT @ Ag samples. In the figure, (a) corresponds to hollow TiO2(HT-0.30), in which (b) corresponds to the high-power TEM image of HT @ Ag (HT-6).
FIG. 6 shows four kinds of hollow TiO in example 22Ultraviolet-visible absorption spectrum of (a). In the figure, (a), (b), (c) and (d) respectively correspond to ultraviolet-visible absorption spectrograms of samples HT-0.10, HT-0.20, HT-0.30 and HT-0.35 after different times of illumination (0min, 15min, 30min, 60min, 120min, 150min, 210min and 240 min).
FIG. 7 shows the results of example 2 using four kinds of hollow TiO2The change curve of the phenol concentration along with the degradation time when the catalyst is degraded is shown.
FIG. 8 is a chart of UV-VIS absorption spectra of the four HT @ Ag types in example 3. In the figure, (a), (b), (c) and (d) respectively correspond to ultraviolet-visible absorption spectrograms of samples HT-1.5, HT-3, HT-6 and HT-9 after different times of illumination (0min, 10min, 20min, 30min, 45min, 60min, 75min, 90min, 105min and 120 min); wherein, the ultraviolet-visible absorption spectrogram after HT-3 is not detected and irradiated for 120min, and the ultraviolet-visible absorption spectrogram after HT-6 is not detected and irradiated for 105min and 120 min.
FIG. 9 is a graph of phenol concentration versus degradation time for the degradation of example 3 using four HT @ Ag catalysts.
FIG. 10 is a Scanning Electron Microscope (SEM) picture of resorcinol-formalin Resin (RF) prepared by using different amounts of ammonia water according to the present invention. In the figure, the amounts of aqueous ammonia used for preparing RF are 0.2mL, 0.25mL, 0.30mL, 0.35mL and 0.4mL, respectively, for (a), (b), (c), (d) and (e).
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention provides a preparation method of a hollow shell type titanium dioxide nano material in a first aspect, which comprises the following steps:
(1) uniformly mixing resorcinol-formaldehyde resin dispersion liquid and ammonia water by using absolute ethyl alcohol to obtain a mixed liquid, and then dropwise adding tetrabutyl titanate (butyl titanate) into the mixed liquid for reaction to obtain a reaction product solution; the volume ratio of the absolute ethyl alcohol to the resorcinol-formaldehyde resin dispersion (RF dispersion), to the ammonia water to the tetrabutyl titanate is (40-50): (4-6): (0.1-0.4): (0.75-1.5) (e.g., 40:4:0.1:0.75, 40:4:0.2:0.75, 40:4:0.3:0.75, 40:4:0.4:0.75, 45:5:0.1:1, 45:5:0.2:1, 45:5:0.3:1, 45:5:0.4:1, 50:6:0.1:1.5, 50:6:0.2:1.5, 50:6:0.3:1.5, or 50:6:0.4: 1.5); in the invention, the ammonia water is an ammonia water solution, for example, the ammonia water solution can contain 25-28 wt% of ammonia; in the present invention, the temperature for dropping tetrabutyl titanate into the mixed solution to carry out the reaction may be, for example, 70 to 100 ℃, and the reaction time may be, for example, 2 to 4 hours.
(2) Sequentially carrying out a centrifugal separation step, a washing step and a drying step on the reaction product solution obtained in the step (1) to obtain a titanium dioxide material with a core-shell structure; in the present invention, for example, a sample obtained by the centrifugal separation step may be washed with anhydrous ethanol a plurality of times, and then the washed sample may be dried at 60 ℃ overnight to obtain a titanium dioxide material having a core-shell structure; in the present invention, the titanium dioxide material having a core-shell structure is also referred to as RF @ TiO2。
(3) Firstly, the titanium dioxide material with the core-shell structure obtained in the step (2) is put in a nitrogen atmosphere (N)2Atmosphere), roasting for 2-4 h (for example, 2, 2.5, 3, 3.5 or 4h), and then roasting for 2-4 h (for example, 2, 2.5, 3, 3.5 or 4h) in an air atmosphere (air atmosphere) to prepare a hollow shell type titanium dioxide nano material; in the present invention, the temperature of calcination in a nitrogen atmosphere and/or the temperature of calcination in an air atmosphere may be, for exampleIs 400 to 500 ℃; in the present invention, the hollow shell type titanium dioxide nanomaterial is also referred to as hollow structure TiO2Or hollow TiO2Or HT. In the present invention, the firing in a nitrogen atmosphere is performed to carbonize RF, and the subsequent firing in air is performed to remove the carbonized RF to obtain hollow TiO2(spherical TiO)2) Avoiding the direct roasting in the air, and the violent volume expansion of the hollow TiO caused by the direct contact of the RF and the air2Broken into semi-spherical TiO2(crushing of TiO)2) (ii) a The crushed titanium dioxide has no surface isotropy of spherical titanium dioxide, and when the next step of loading small spherical particles is carried out, the load distribution is uneven, so that a large amount of load is distributed in the inner layer of the concave surface of the crushed titanium dioxide, the load on the inner side of the concave surface is possibly too high, and the load on the outer side of the concave surface is too low, so that the physicochemical properties of the inner side and the outer side of the fragment are not uniform, and the photocatalytic activity is seriously influenced.
The invention adopts resorcinol formaldehyde Resin (RF) as a template to prepare the titanium dioxide material (RF @ TiO) with the core-shell structure2) Then obtaining the hollow shell type titanium dioxide nano material (hollow structure TiO) with a novel structure by two-step roasting2) TiO having such a hollow structure2The nano structure has large specific surface area, active centers inside and outside, and high catalytic efficiency; according to the invention, through the reasonable proportion of the absolute ethyl alcohol, the resorcinol-formaldehyde resin dispersion liquid, the ammonia water and the tetrabutyl titanate, particularly the reasonable amount of the ammonia water in the step (1), the titanium dioxide particles are effectively ensured to be in a state of less agglomeration or monodispersion, the thickness of a shell layer can be regulated and controlled between 20nm and 90nm, and the problems that the existing titanium dioxide particles and silver combined as a photocatalyst are too small and easy to agglomerate, and the active center is not fully exposed, so that the catalytic efficiency is low are effectively avoided. In step (1) of the present invention, the amount of ammonia should not be too large, otherwise there will be a large amount of TiO2Not coated on the RF surface but adhered to each other, RF @ TiO2Serious agglomeration occurs to form a large blocky structure, so that the prepared hollow shell type titanium dioxide nano material is finally degraded to phenolThe effect is poor; in the step (1) of the present invention, the amount of the resorcinol-formalin resin dispersion used determines the amount of TiO2The thickness of the shell layer; RF inside, TiO2On the outside, a ball-in-ball structure is formed when TiO2When the amount of the precursor (tetrabutyl titanate) is constant, different thicknesses are determined by different RF (radio frequency) amounts, and the shell thickness of the hollow shell type titanium dioxide nano material prepared by the method can be regulated and controlled between 20nm and 90 nm.
According to some embodiments, RF @ TiO2The preparation process comprises the following steps: putting 5mL of the RF dispersion liquid into 45mL of absolute ethyl alcohol and 0.10-0.30 mL of ammonia water solution, carrying out ultrasonic treatment for 0.5h, putting the mixture into a three-neck flask, putting the three-neck flask into a heat collection type constant-temperature magnetic stirrer, and stirring for 1h at room temperature, so that the resorcinol-formaldehyde resin dispersion liquid and the ammonia water are uniformly mixed by the absolute ethyl alcohol; dropwise adding 0.75-1.5 mL of tetrabutyl titanate to react at 85 ℃ for 2.5h, centrifuging (centrifugal separation), washing a sample obtained by centrifugal separation for three times by using absolute ethyl alcohol, and finally drying at 60 ℃ overnight to obtain the RF @ TiO2。
According to some embodiments, the hollow TiO2The preparation process comprises the following steps: drying the obtained RF @ TiO2Sample is in N2Roasting at 500 ℃ for 3h in an atmosphere, and then roasting at 500 ℃ for 3h in an air atmosphere to obtain the hollow TiO2(HT). In the present invention, the temperature increase rate for increasing to the baking temperature in a nitrogen atmosphere and/or increasing to the baking temperature in an air atmosphere may be, for example, 1.5 to 3 ℃/min (e.g., 1.5, 2, 2.5, or 3 ℃/min). In the present invention, TiO before firing2Is amorphous titanium dioxide and has no catalytic activity; too fast a temperature rise rate may affect TiO2Anatase formation and easy formation of TiO2Agglomeration during crystallization; anatase has better adsorption capacity to organic matters and lower recombination capacity of photo-generated electron-hole pairs, so that the photocatalytic activity is higher.
According to some preferred embodiments, the method further comprises, before step (1), a step of preparing the resorcinol-formalin resin dispersion, the step of preparing comprising the substeps of:
(a) uniformly mixing ammonia water with water (such as distilled water or deionized water) and absolute ethyl alcohol to obtain a first mixed solution, and then adding resorcinol into the first mixed solution and uniformly mixing to obtain a second mixed solution;
(b) adding a formaldehyde solution into the second mixed solution obtained in the step (a) to react to obtain a resorcinol formaldehyde resin solution, and then sequentially performing a centrifugal separation step and a washing step on the resorcinol formaldehyde resin solution to obtain resorcinol formaldehyde resin; and
(c) dispersing the resorcinol-formaldehyde resin obtained in the step (b) with absolute ethyl alcohol to obtain the resorcinol-formaldehyde resin dispersion liquid.
According to some preferred embodiments, in the step (a), the volume ratio of the water, the absolute ethanol and the ammonia water is (30-60): (10-20): (0.2-0.4) (e.g., 30:10:0.2, 30:10:0.25, 30:10:0.3, 30:10:0.35, 30:10:0.4, 40:16:0.2, 40:16:0.25, 40:16:0.3, 40:16:0.35, 40:16:0.4, 50:20:0.2, 50:20:0.25, 50:20:0.3, 50:20:0.35, 50:20:0.4, 60:20:0.2, 60:20:0.25, 60:20:0.3, 60:20:0.35, or 60:20: 0.4); in the step (a) of the present invention, the difference of the amount of ammonia has a significant influence on the morphology of the resorcinol-formalin resin, and when the amounts of other raw materials such as water and absolute ethanol are the same, the Scanning Electron Microscope (SEM) of the resorcinol-formalin Resin (RF) prepared by using different amounts of ammonia is shown in fig. 10, in which fig. 10, the scales of (a), (b), (c), (d), and (e) are 500 nm: from (a) and (b) in fig. 10, it can be seen that when the amount of ammonia is 0.2mL or 0.25mL, the RF particles have significant agglomeration, nonuniform particle dispersion, and some irregular shapes, because the small amount of ammonia does not provide enough hydrogen bonds and hydroxymethyl groups in the emulsion, which is not favorable for the rapid progress of the condensation reaction and for forming RF nano-beads with bead sizes; as can be seen from the graphs (c), (d) and (e), the prepared RF nanospheres are in a monodisperse state; as can be seen from the graph (c), when the amount of ammonia was 0.30mL, the obtained monodisperse nanospheres had a non-uniform particle size distribution, which may be due to surface tension of the RF nanospheres(ii) an effect; as can be seen from the graph (e), when the amount of ammonia water is 0.4mL, the prepared RF nanospheres with uniform particle size have slight agglomeration phenomenon, because the polymerization reaction speed of resorcinol and formaldehyde is too fast due to the excessive addition of ammonia water, and ammonium ions (NH) on the surface of emulsion droplets4 +) The rate of providing positive charge is insufficient to effectively prevent RF agglomeration; as can be seen from the graph (d), when the amount of ammonia was 0.35mL, monodisperse RF nanospheres having uniform particle size were obtained; in the present invention, the polymerization rate, surface tension, hydrogen bonding, etc. of RF play an important role in the preparation of monodisperse RF nanospheres having uniform particle size.
According to some preferred embodiments, the molar ratio of resorcinol to formaldehyde contained in the formaldehyde solution is 1: (1-2) (e.g., 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2) is preferably 1: 1.5; and/or in the step (b), the reaction temperature is 30-35 ℃, and the reaction time is 18-30 h (such as 18, 20, 22, 24, 26, 28 or 30 h).
According to some embodiments, the RF dispersion is prepared by: adding 0.35mL of ammonia water into a solution of 40mL of distilled water and 16mL of absolute ethyl alcohol, placing the solution into a three-neck flask, placing the three-neck flask into a heat-collecting constant-temperature magnetic stirrer, stirring at room temperature for 1h to fully mix the ammonia water and the aqueous solution of the absolute ethyl alcohol to obtain a first mixed solution which is beneficial to the next reaction, then adding 0.4g of resorcinol into the first mixed solution, and continuously stirring for 0.5h to uniformly mix to obtain a second mixed solution; heating the second mixed solution to 30 ℃, adding 0.56mL of formaldehyde solution for reaction for 24h to obtain resorcinol formaldehyde resin solution, centrifuging the resorcinol formaldehyde resin solution, washing a sample obtained by centrifuging for three times by using a mixed solution of absolute ethyl alcohol and distilled water to obtain resorcinol formaldehyde resin; dispersing the obtained resorcinol-formaldehyde resin into 40mL of absolute ethyl alcohol to obtain the resorcinol-formaldehyde resin dispersion liquid for later use.
According to some preferred embodiments, in step (1), the reaction temperature is 70 to 100 ℃ (e.g., 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃), and the reaction time is 2 to 4 hours (e.g., 2, 2.5, 3, 3.5 or 4 hours).
According to some preferred embodiments, the temperature of the firing in the nitrogen atmosphere and/or the temperature of the firing in the air atmosphere is 400 to 500 ℃ (e.g., 400 ℃, 450 ℃ or 500 ℃).
The invention provides in a second aspect the hollow shell titanium dioxide nanomaterial prepared by the preparation method of the first aspect. The hollow shell type titanium dioxide nano material prepared by the method has high phenol degradation efficiency, can quickly and efficiently remove phenol, and has a phenol degradation rate of about 90% in a period of 150-210 min.
The invention provides a preparation method of silver-loaded hollow shell type titanium dioxide nano material in a third aspect, which comprises the following steps:
s1, uniformly dispersing the hollow shell type titanium dioxide nano material prepared by the preparation method in the first aspect by using a silver nitrate aqueous solution to obtain a hollow shell type titanium dioxide dispersion liquid; and
s2, processing the hollow shell type titanium dioxide dispersion liquid by ultraviolet light to load silver on the surface of the hollow shell type titanium dioxide nano material to prepare the silver-loaded hollow shell type titanium dioxide nano material; in the present invention, for example, a high-pressure mercury lamp or a black light lamp can be used as a light source of ultraviolet light; in the present invention, the silver (Ag) -supported hollow shell titanium dioxide nanomaterial is also referred to as HT @ Ag.
The invention deposits silver on the hollow structure TiO by ultraviolet radiation deposition method2The surface adopts Ag load to further improve the separation efficiency of photon-generated carriers on the space, thereby greatly improving the photocatalytic reaction activity of the hollow shell type titanium dioxide nano material and the degradation efficiency of phenol. The hollow shell type titanium dioxide nano material and the silver-loaded hollow shell type titanium dioxide nano material prepared by the invention are all in anatase crystal form, after silver is loaded, anatase is not damaged and is converted into rutile phase or brookite phase, anatase has better adsorption capacity on organic matters and photo-generated electrons thereofLower recombination capacity of the hole pairs and therefore higher photocatalytic activity; the silver-loaded hollow shell type titanium dioxide nano material prepared by the invention has high phenol degradation efficiency, can quickly and efficiently remove phenol, and has a phenol degradation rate of about 90% in a period of 90-120 min.
According to some preferred embodiments, the method further comprises subjecting the prepared silver-supported hollow shell-type titanium dioxide nanomaterial to a centrifugal separation step, a washing step, and a drying step in this order.
According to some preferred embodiments, the mass ratio of the hollow shell titanium dioxide nanomaterial to the silver nitrate contained in the aqueous silver nitrate solution is 0.1 (0.001 to 0.015) (e.g., 0.1:0.001, 0.1:0.0015, 0.1:0.002, 0.1:0.0025, 0.1:0.003, 0.1:0.004, 0.1:0.005, 0.1:0.006, 0.1:0.007, 0.1:0.008, 0.1:0.009, 0.1:0.01, 0.1:0.012, or 1:0.015), preferably 0.1 (0.0015 to 0.009) (e.g., 0.1:0.0015, 0.1:0.002, 0.1:0.0025, 0.1:0.003, 0.1:0.004, 0.1:0.005, 0.008, 0.1:0.006, 0.009, 0.1:0.009, or 0.1: 0.009). In the invention, the mass ratio of the hollow shell type titanium dioxide nano material to the silver nitrate contained in the silver nitrate aqueous solution is preferably 0.1 (0.0015-0.009), and more preferably 0.1:0.006, so that the prepared HT @ Ag has the best photocatalytic degradation effect on a phenol solution, and phenol can be removed more quickly.
According to some preferred embodiments, the concentration of the aqueous silver nitrate solution is 0.03 to 0.19g/L (e.g., 0.03, 0.04, 0.05, 0.06, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, or 0.19 g/L). In the present invention, the silver nitrate aqueous solution means an aqueous solution containing silver nitrate, and the concentration of the silver nitrate aqueous solution means the mass of silver nitrate contained in a unit volume of the silver nitrate aqueous solution.
According to some embodiments, the process for preparing HT @ Ag comprises: taking hollow TiO2Particles (HT particles) 0.1g were dispersed in 80mL of distilled water containing different amounts of silver nitrate (e.g., 0.0015g, 0.003g, 0.006g, and 0.009g), and sonicated for 5min to obtain a hollow shell titanium dioxide dispersion; transferring the hollow shell titanium dioxide dispersion to a reactor200mL quartz tube, and under the condition of magnetic stirring, irradiating for 1h under 350W high-pressure mercury lamp, wherein the quartz tube is 15cm away from the high-pressure mercury lamp, centrifuging and washing three times with a mixed solution of absolute ethyl alcohol and distilled water to obtain a series of HT @ Ag samples, and drying at 60 ℃ overnight.
In a fourth aspect, the invention provides a silver-loaded hollow shell titanium dioxide nanomaterial prepared by the preparation method in the third aspect.
The invention will be further illustrated by way of example, but the scope of protection is not limited to these examples.
Example 1: hollow TiO 22And HT @ Ag.
Preparation of RF dispersion: adding 0.35mL of ammonia water into a solution of 40mL of distilled water and 16mL of absolute ethyl alcohol, placing the solution into a three-neck flask, placing the three-neck flask into a heat-collecting constant-temperature magnetic stirrer, stirring at room temperature for 1h, adding 0.4g of resorcinol, continuously stirring for 0.5h, heating to 30 ℃, adding 0.56mL of formaldehyde solution, reacting for 24h, centrifuging, washing with a mixed solution of absolute ethyl alcohol and distilled water for three times to obtain a sample, and dispersing in 40mL of absolute ethyl alcohol to obtain an RF dispersion solution for later use.
②RF@TiO2The preparation of (1): taking four parts of 5mLRF dispersion liquid, respectively placing the dispersion liquid in 45mL of absolute ethyl alcohol and ammonia water solutions of 0.10mL, 0.20mL, 0.30mL and 0.35mL, carrying out ultrasonic treatment for 0.5h, placing the dispersion liquid in a three-neck flask, placing the three-neck flask in a heat collection type constant-temperature magnetic stirrer, stirring for 1h at room temperature to obtain four parts of mixed liquid, dropwise adding 1mL of tetrabutyl titanate into each part of mixed liquid, reacting for 2.5h at 85 ℃ to obtain four parts of reaction product solution, centrifuging each part of reaction product solution, and washing for three times by absolute ethyl alcohol to obtain four parts of samples (RF @ TiO)2Sample), four samples were dried overnight at 60 ℃.
③ hollow TiO2Preparation of (HT): four samples obtained after drying are firstly subjected to N2Roasting at 500 deg.C for 3h in air atmosphere, and roasting at 500 deg.C for 3h in air atmosphere to obtain hollow TiO2(HT); in N2The rate of temperature rise to the firing temperature in an atmosphere and to the firing temperature in an air atmosphereThe rate is 2 ℃/min; subjecting the obtained hollow TiO to2(HT) samples were designated as HT-0.10, HT-0.20, HT-0.30 and HT-0.35, respectively, depending on the amount of ammonia used in the sample group (C).
Preparing the HT @ Ag by ultraviolet diffraction catalysis: taking a sample of HT-0.30 particles, 0.1g dispersing in four 80mL distilled water containing 0.0015g, 0.003g, 0.006g and 0.009g silver nitrate respectively, and performing ultrasonic treatment for 5min to obtain four hollow shell type titanium dioxide dispersions; transferring four parts of the hollow shell type titanium dioxide dispersion liquid into a 200mL quartz tube, irradiating for 1h under a 350W high-pressure mercury lamp under the condition of magnetic stirring, centrifuging and washing for three times by using a mixed solution of absolute ethyl alcohol and distilled water to obtain a series of HT @ Ag samples, and drying at 60 ℃ overnight; the HT @ Ag samples were noted as HT-1.5, HT-3, HT-6 and HT-9, respectively, depending on the amount of silver nitrate, which in turn corresponded to 0.0015g, 0.003g, 0.006g and 0.009g, and also indicated theoretical silver contents (in weight percent) of HT @ Ag as 1.5%, 3%, 6% and 9%, respectively.
Four parts of hollow TiO prepared in this example2A Scanning Electron Microscope (SEM) image of the sample is shown in fig. 1. As can be seen from fig. 1, when the amount of aqueous ammonia was 0.1mL and 0.2mL, it is apparent that the particles were in a monodisperse state and the particle size was uniform, and tetrabutyl titanate (TBOT) was perfectly hydrolyzed on the RF surface by heterogeneous nucleation-homogeneous nucleation; when the amount of aqueous ammonia was 0.3mL, the particles were slightly stuck to each other, probably due to the increase in the amount of aqueous ammonia, which caused the hydroxyl ions OH in the solution-The content is higher, the hydrolysis condensation rate of TBOT is too fast, most of titanium oligomer is coated on the surface of RF, but adjacent to RF @ TiO2Homogeneous nucleation occurs between shell titanium oligomer obtained by hydrolysis, so that RF @ TiO2Partial adhesion; when the amount of ammonia water is 0.35mL, a large amount of TiO is added2Not coated on the RF surface but adhered to each other, RF @ TiO2Severe agglomeration occurs to form large blocky structures, probably due to the hydroxide ions OH-The content is increased continuously, so that the hydrolytic condensation rate of TBOT is larger than that of titanium oligomer at RF @ TiO2Homogeneous nucleation rate of the surface, with a small fraction of titanium oligomers coated on the RF surface, butIs that the majority of the titanium oligomer is not at RF @ TiO2Is a homogeneous nucleation between titanium oligomers, coated with RF @ TiO2The surface, forming a large coating.
Four parts of hollow TiO prepared in this example2A Transmission Electron Microscopy (TEM) image of the sample is shown in fig. 2. As can be seen from FIG. 2, the hollow structure TiO is obtained by the present invention through two-step calcination2Nanoparticles with different thicknesses, hollow TiO structure with the increase of the dosage of ammonia water2The thickness of the shell layer is gradually increased, and when the dosage of ammonia water is increased from 0.1mL to 0.2mL, the hollow structure TiO2There is a very large increase in shell thickness, from about 20nm to about 73 nm; when the amount of ammonia water was increased to 0.3mL and 0.35mL, the hollow TiO particles2The shell thicknesses were about 85nm and 90nm, respectively. The inventor finds that the dosage of ammonia water is continuously increased, and TiO with a hollow structure2The shell thickness does not increase too much.
Four parts of hollow TiO prepared in this example2The X-ray diffraction spectrum (XRD spectrum) of the sample is shown in fig. 3, wherein the abscissa 2 θ represents twice the diffraction angle (2 θ diffraction angle) in degrees (degree), and the ordinate Intensities represents intensity; in fig. 3, characteristic peaks appear at 2 θ diffraction angles of 25.34 °, 37.78 °, 48.02 °, 53.92 °, and 55.08 °, corresponding to TiO, respectively2The (101), (004), (200), (105) and (211) crystal planes of anatase (JCPDS 21-1272); in FIG. 3, no characteristic peak appears at other positions, and the hollow TiO obtained by the two-step calcination of this example is illustrated2All samples were in the anatase form.
The results of X-ray spectroscopy (EDS elemental analysis) on four samples of HT @ Ag obtained in this example are shown in Table 1, and from the results in Table 1, it is understood that Ag has been successfully supported on hollow TiO2On the surface, although the actual loading was deviated from the theoretical loading, it is likely that a part of the silver nitrate crystals were not reduced and lost after centrifugation.
The hollow TiO samples obtained in this example, when three HT 3, HT 6 and HT 9 @ Ag samples were used in an amount of 0.3mL with ammonia2X-ray diffraction pattern (XRD pattern) of sample (HT-0.30) such asFIG. 4 is a graph in which the abscissa 2 θ represents twice the diffraction angle (2 θ diffraction angle) in degrees (degree), and the ordinate Intensiies represents the intensity; in FIG. 4, as is apparent from comparison of XRD patterns of (a) to (c) and (d), anatase titanium dioxide has characteristic peaks, indicating that after Ag is supported, anatase is not destroyed and is converted into rutile phase or brookite phase, and a new characteristic peak, which is a characteristic peak of silver, appears at a 2 theta diffraction angle of 44 degrees, indicating that Ag is supported on hollow TiO in the present invention2Of (2) is provided.
Hollow TiO produced in this example2And HT @ Ag sample high resolution transmission electron microscopy (high power TEM) As shown in FIG. 5, it is apparent from FIG. 5 that the sample obtained in this example possesses excellent cleanliness, wherein the lattice spacing is 0.35nm for the 101 plane of titanium dioxide and 0.24nm for the 111 plane of silver.
Example 2: hollow TiO 22(HT) experiments on phenol degradation.
Weighing 20mg of the four HT nanoparticles in example 1, respectively, dispersing in four 40mL phenol suspension solutions with a concentration of 400 [ mu ] mol/L, stirring the four phenol suspension solutions containing the HT nanoparticles in a dark environment for 30 minutes to achieve adsorption-desorption equilibrium of phenol on the surfaces of the composite nanoparticles, turning on a high-pressure mercury lamp, taking out 2mL suspension after different times of illumination (sampling every 15min or 30 min), centrifuging to separate out the catalyst, analyzing the supernatant (UV 1900/UV1901PCS), wherein the UV-visible absorption spectrum of phenol and its intermediate product is shown in FIG. 6, wherein the UV absorption peak corresponding to phenol is 270nm, the horizontal coordinate Waength in the figure represents the Wavelength, the unit is nm, and the vertical coordinate Absorbance in the figure represents the Absorbance.
As can be seen from FIG. 6, when the phenol degradation efficiency (degradation rate) reached about 90%, HT-0.10 took 210min, HT-0.20 took 180min, HT-0.30 took 150min, and HT-0.35 took 240 min; when HT-0.10, HT-0.20, HT-0.30 and HT-0.35 are used as photocatalyst to degrade phenol, the degradation curve of phenol with time is shown in FIG. 7, and the specific phenol concentration and corresponding phenol degradation efficiency are shown in Table 2. In FIG. 7, the abscissa Irradiation time represents the degradation time in min, and the ordinate C represents the concentration in μ M (μmol/L); as can be seen from FIG. 7, when the amount of ammonia water is 0.30mL, phenol is completely degraded in 180min of ultraviolet light diffraction, wherein the photocatalytic performance is most obvious when the ultraviolet light is irradiated for 30-60 min. From the results in Table 2, it can be seen that HT-0.30 has significant advantages over the other three samples, especially over HT-0.10 and HT-0.35, wherein the HT-0.30 degradation efficiency reaches 95.74% at 150min of UV diffraction, which is much higher than the amount of nano titanium dioxide hollow sphere catalyst reported in the literature, which is 1.0g/L, and the degradation efficiency to phenol at 180min of UV diffraction is 81% (see: Dian-Ping W, Qian Z, Shuu-Xin L. Synthesis of nanosize TiO 2hollow sphere acid catalytic hydrolysis-hydrolysis method [ J ]. Journal of Functional Materials,2012,43(23):3222 + 3227+ 3231.).
Example 3: HT @ Ag degradation of phenol.
Weighing 20mg of the four HT @ Ag nanoparticles in example 1, respectively dispersing the four HT @ Ag nanoparticles in four 40mL phenol suspension solutions with a concentration of 400 mu mol/L, stirring the four phenol suspension solutions containing the HT @ Ag nanoparticles in a dark environment for 30 minutes to achieve adsorption-desorption balance of phenol on the surfaces of the composite nanoparticles, turning on a high-pressure mercury lamp, taking out 2mL of suspension after different times of illumination (sampling every 10min or 15 min), centrifuging to separate out a catalyst, analyzing a supernatant (an ultraviolet-visible spectrophotometer UV1900/UV1901PCS), wherein ultraviolet-visible absorption spectrograms of phenol and an intermediate product are shown in figure 8, wherein an ultraviolet absorption peak corresponding to phenol is 270nm, an abscissa Wavelength in the figure represents Wavelength, a unit is nm, and an ordinate Absorb in the figure represents Absorbance.
As can be seen from FIG. 8, in comparison with samples HT-1.5, HT-3 and HT-9, the absorbance of phenol and its intermediates is almost 0 at 90min of UV light diffraction of sample HT-6, and it can be seen that phenol and its intermediates are almost completely degraded; although the HT-1.5, HT-3.0 and HT-9 have poor photocatalytic performance, the photocatalytic performance has obvious advantages compared with that of the pure HT-0.30; when HT-1.5, HT-3, HT-6 and HT-9 are used as photocatalyst to degrade phenol, the degradation curve of phenol along with time is shown in FIG. 9, and the specific obtained phenol concentration and the corresponding phenol degradation efficiency are shown in Table 3. In FIG. 9, the abscissa Irradiation time represents the degradation time in min, and the ordinate C represents the concentration in μ M (μmol/L); as can be seen from FIG. 9, when the light is turned on to carry out the photocatalytic reaction on the phenol solution, the phenol concentration of the phenol solution tends to increase first and then degrade, wherein the HT-6 degradation rate is fastest, the phenol is completely degraded within 90min, and the degradation curve is linear, which indicates that the degradation rate is quite stable. From the results in Table 3, it can be seen that HT-3 and HT-6 have excellent photocatalytic performance, and the degradation rates within 90min are 88.753% and 98.978%, respectively, and the photocatalytic efficiency of the silver-loaded hollow shell titanium dioxide nanomaterial is significantly improved compared with the silver-unloaded hollow titanium dioxide nanomaterial.
Comparative example 1: RF @ TiO2And HT @ Ag.
Comparative example 1 RF @ TiO was prepared in substantially the same manner as in example 1 (Steps (r), phi, and phi were the same)2And HT @ Ag, except that: (iii) in N, four samples obtained after drying2Calcining at 500 deg.C for 6h in N2The heating rate of the atmosphere to the roasting temperature is 2 ℃/min.
The same test method as in example 2 was used to test the four RF @ TiO films produced in this comparative example2The degradation efficiency of the nano particles to phenol is tested, and after the nano particles are irradiated for 240min, the dosage of ammonia water is respectively 0.1mL, 0.20mL, 0.30mL and 0.35mL to prepare RF @ TiO2The degradation efficiency of the nanoparticles to phenol was 58%, 65%, 76% and 49%, respectively.
The four HT @ Ag nanoparticles prepared in this comparative example were tested for their phenol degradation efficiency by the same test method as in example 3, and after 120min of light irradiation, the phenol degradation efficiency of the HT @ Ag nanoparticles prepared in 0.0015g, 0.003g, 0.006g and 0.009g were 59%, 67%, 78% and 50%, respectively.
Comparative example 2: breaking of TiO2And crushing the TiO2Preparation experiment of @ Ag.
Comparative example 2 the crushed TiO was prepared by substantially the same method as in example 1 (same Steps (r), 2 and (r))2And crushing the TiO2@ Ag, except that: and thirdly, roasting the four dried samples for 6 hours at 500 ℃ in an air atmosphere, and raising the temperature to the roasting temperature in the air atmosphere at a temperature rise rate of 2 ℃/min.
The same test method as in example 2 was used for the four crushed TiO powders obtained in this comparative example2The degradation efficiency of the nano particles to phenol is tested, and the result is as follows: when the phenol degradation efficiency (degradation rate) reaches about 90 percent, 0.10mL of ammonia water is used to prepare the broken TiO2Takes 190min, uses 0.20mL of ammonia water to prepare the broken TiO2170min is consumed, and the dosage of ammonia water is 0.30mL in the ② process2The time is 135min, and the dosage of ammonia water is 0.35mL to prepare the broken TiO2It took 210 min.
The same test method as in example 3 was used for the four crushed TiO powders obtained in this comparative example2Testing the degradation efficiency of the @ Ag nano-particles on phenol, and after 90min of illumination, respectively using 0.0015g, 0.003g, 0.006g and 0.009g of prepared broken TiO with the silver nitrate2The degradation efficiency of the @ Ag nanoparticles to phenol was 41%, 62%, 71%, and 46%, respectively.
From the results of the present comparative example, it is understood that although the crushed titanium dioxide produced by the present comparative example has a better degradation effect than the spherical titanium dioxide, since more specific surface area and more active sites are exposed after crushing; however, the crushed titanium dioxide prepared in the comparative example has much lower phenol degradation efficiency after being loaded with silver than the hollow TiO2The degradation efficiency of the (spherical titanium dioxide) silver-loaded phenol is probably because the crushed titanium dioxide has no surface isotropy of the spherical titanium dioxide, and when the next step of loading small spherical particles is carried out, the load distribution is uneven, so that a large amount of load is distributed in the inner layer of the concave surface of the crushed titanium dioxide, the load on the inner side of the concave surface is possibly too high, and the load on the outer side of the concave surface is too low, so that the physicochemical properties of the inner side and the outer side of the fragment are not uniform, and the photocatalytic activity is seriously influenced.
Comparative example 3
A preparation method of a molybdenum disulfide-coated titanium dioxide hollow core-shell structure composite photocatalyst comprises the following steps:
firstly, SiO2Dispersing the powder in the mixed solution to obtain a reaction system, ultrasonically dispersing for 15min, adding tetrabutyl titanate into the reaction system to obtain a suspension, stirring the suspension for 12h under the water bath condition of the temperature of 45 ℃, centrifugally separating, washing and drying to obtain a white solid, calcining the white solid for 1h under the condition of the temperature of 550 ℃ to obtain SiO2@TiO2(ii) a The mixed solution is absolute ethyl alcohol and NH3·H2Mixed solution of O, NH3·H2The weight percentage of O is 25 to 28 percent; the SiO2The ratio of the mass of the powder to the volume of the mixed solution is 0.15g:200 mL; the SiO2The ratio of the mass of the powder to the volume of tetrabutyl titanate was 1g:1 mL.
Secondly, 0.15g (NH)4)6Mo7O24·4H2O and 0.32g of urea were dissolved in 30mL of deionized water, and 0.1g of SiO obtained in step one was added thereto2@TiO2Transferring the mixture into a reaction kettle after ultrasonic dispersion for 20min, reacting for 10h at the temperature of 180 ℃ to obtain black precipitate, washing the black precipitate for 3-5 times by using ethanol, and then washing for 3-5 times by using deionized water to obtain a clean sample; drying a clean sample at 50 ℃ for 10-14 h to obtain black powder, and adding the black powder into NH with the concentration of 0.1mol/L4HF2Stirring the solution for 30min, washing and drying to obtain the hollow core-shell structure TiO2@MoS2A composite photocatalyst is provided.
The same test method as in example 3 was used for the TiO with hollow core-shell structure prepared in this comparative example2@MoS2The composite photocatalyst is used for testing the degradation efficiency of phenol, and after the composite photocatalyst is illuminated for 120min, TiO is used2@MoS2The degradation efficiency of the composite photocatalyst to phenol only reaches 36%.
Table 1: and comparing the element contents of the HT @ Ag samples after Ag loading.
Table 2: different hollow TiO2The phenol residual concentration and the degradation rate of the nano-particles in different illumination time.
Table 3: phenol residual concentration and degradation rate of different HT @ Ag nanoparticles in different illumination time.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A preparation method of a hollow shell type titanium dioxide nano material is characterized by comprising the following steps:
(1) uniformly mixing resorcinol-formaldehyde resin dispersion liquid and ammonia water by using absolute ethyl alcohol to obtain a mixed liquid, and then dropwise adding tetrabutyl titanate into the mixed liquid for reaction to obtain a reaction product solution; the volume ratio of the absolute ethyl alcohol to the resorcinol formaldehyde resin dispersion liquid to the ammonia water to the tetrabutyl titanate is 45:5 (0.1-0.3) to 1;
(2) sequentially carrying out a centrifugal separation step, a washing step and a drying step on the reaction product solution obtained in the step (1) to obtain a titanium dioxide material with a core-shell structure; and
(3) roasting the titanium dioxide material with the core-shell structure obtained in the step (2) in a nitrogen atmosphere for 2-4 h, and then roasting in an air atmosphere for 2-4 h to prepare a hollow shell type titanium dioxide nano material;
the method further comprises a step of preparing the resorcinol-formalin resin dispersion before the step (1), the preparation step comprising the substeps of:
(a) uniformly mixing ammonia water with water and absolute ethyl alcohol to obtain a first mixed solution, adding resorcinol into the first mixed solution, and uniformly mixing to obtain a second mixed solution; in the step (a), the volume ratio of the water, the absolute ethyl alcohol and the ammonia water is 40:16: 0.35;
(b) adding a formaldehyde solution into the second mixed solution obtained in the step (a) to react to obtain a resorcinol formaldehyde resin solution, and then sequentially performing a centrifugal separation step and a washing step on the resorcinol formaldehyde resin solution to obtain resorcinol formaldehyde resin; and
(c) dispersing the resorcinol-formaldehyde resin obtained in the step (b) with absolute ethyl alcohol to obtain the resorcinol-formaldehyde resin dispersion liquid.
2. The method of claim 1, wherein:
the molar ratio of the resorcinol to the formaldehyde contained in the formaldehyde solution is 1: (1-2); and/or
In the step (b), the reaction temperature is 30-35 ℃, and the reaction time is 18-30 h.
3. The production method according to claim 1 or 2, characterized in that:
in the step (1), the reaction temperature is 70-100 ℃, and the reaction time is 2-4 h.
4. The production method according to claim 1 or 2, characterized in that:
the temperature of roasting in the nitrogen atmosphere and/or the temperature of roasting in the air atmosphere is 400-500 ℃.
5. The hollow shell type titanium dioxide nanomaterial produced by the production method according to any one of claims 1 to 4.
6. A preparation method of a silver-loaded hollow shell type titanium dioxide nano material is characterized by comprising the following steps:
s1, uniformly dispersing the hollow shell type titanium dioxide nano material prepared by the preparation method of any one of claims 1 to 4 by using a silver nitrate aqueous solution to obtain a hollow shell type titanium dioxide dispersion liquid; and
s2, treating the hollow shell type titanium dioxide dispersion liquid with ultraviolet light to load silver on the surface of the hollow shell type titanium dioxide nano material, and obtaining the silver-loaded hollow shell type titanium dioxide nano material.
7. The method of claim 6, wherein:
the mass ratio of the hollow shell type titanium dioxide nano material to silver nitrate contained in the silver nitrate water solution is 0.1 (0.001-0.015).
8. The method of claim 7, wherein:
the mass ratio of the hollow shell type titanium dioxide nano material to the silver nitrate contained in the silver nitrate water solution is 0.1 (0.0015-0.009).
9. The production method according to any one of claims 6 to 8, characterized in that:
the concentration of the silver nitrate water solution is 0.03-0.19 g/L.
10. The silver-supported hollow shell-type titanium dioxide nanomaterial produced by the production method according to any one of claims 6 to 9.
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