CN113385192A

CN113385192A - Sulfur-doped TiO for water purification system of construction site2Method for producing thin film

Info

Publication number: CN113385192A
Application number: CN202110599046.XA
Authority: CN
Inventors: 虞文明; 王稷; 汪亚伟; 倪铭列
Original assignee: China MCC17 Group Co Ltd
Current assignee: China MCC17 Group Co Ltd
Priority date: 2021-05-31
Filing date: 2021-05-31
Publication date: 2021-09-14

Abstract

The invention discloses a preparation method of a sulfur-doped TiO2 film for a water purification system of a construction site, belonging to the technical field of water environment treatment. The invention comprises the following steps: s1, synthesis of sol: adopting a sol-gel process of self-assembly of a non-sulfurated hydrocarbon surfactant as a pore directing agent, and taking sulfuric acid as a precursor for preparing sulfur and water; s2, sulfur-doped TiO₂Preparing a film: preparation of sulfur-doped TiO by using borosilicate glass as substrate₂A film; s3, synthesizing sulfur-doped TiO₂Film characteristics: measuring with X-ray diffractometer to determine synthetic sulfur-doped TiO₂The crystal structure of the thin film; s4.MC-LR photocatalysis under visible light irradiationActivation, preparing solution in reactor, adding sulfur doped TiO₂A film. Has the advantages of strong thermal and chemical stability, relatively high photocatalytic activity, low toxicity, low cost and the like.

Description

Sulfur-doped TiO for water purification system of construction site2Method for producing thin film

Technical Field

The invention relates to the technical field of water environment treatment, in particular to sulfur-doped TiO for a water purification system of a construction site₂A method for preparing a film.

Background

Although different membranes (e.g., ultrafiltration and reverse osmosis) can remove viruses and bacteria from drinking water, this is not their primary goal. Microbial contamination in drinking water often occurs due to sewage discharge, septic tank leaks, and fecal matter that flows off of animal farms into the water. To protect drinking water from these microorganisms, water suppliers often add disinfectants, such as chlorine or ozone, to the drinking water. However, conventional disinfectants have certain limitations depending on the water chemistry and the type of microorganisms present. For example, the microorganism Cryptosporidium is highly resistant to traditional disinfection methods. When water has a high concentration of Total Organic Compounds (TOC) or other naturally occurring substances, the disinfectant itself reacts to form byproducts that may pose a health risk. It is generally believed that chlorination and ozonation will produce chlorinated and brominated Disinfection Byproducts (DBPs) that are potentially carcinogenic to humans. TiO2₂Photocatalyst is considered one of the best disinfection techniques because it does not produce dangerous DBPs. The conventional titanium dioxide particles and colloidal catalyst suspensions are difficult to separate and reuse and are not suitable for the treatment of drinking water, and therefore, how to separate the TiO₂The application of photocatalysts to water treatment and the removal and even inactivation of microorganisms without the by-products that may pose health risks is currently the biggest problem.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides a sulfur-doped TiO for a water purification system of a construction site₂The preparation method of the film has the advantages of strong thermal and chemical stability, relatively high photocatalytic activity, low toxicity, low cost and the like.

In order to achieve the purpose, the invention adopts the following technical scheme:

sulfur-doped TiO for water purification system of construction site₂A method for preparing a thin film comprising the steps ofThe method comprises the following steps:

s1, synthesis of sol: adopting a sol-gel process of self-assembly of a non-sulfurated hydrocarbon surfactant as a pore directing agent, and taking sulfuric acid as a precursor for preparing sulfur and water;

s2, sulfur-doped TiO₂Preparing a film: preparation of sulfur-doped TiO by using borosilicate glass as substrate₂A film;

s3, synthesizing sulfur-doped TiO₂Film characteristics: measuring with X-ray diffractometer to determine synthetic sulfur-doped TiO₂The crystal structure of the thin film;

s4. the photocatalytic activity of MC-LR under the irradiation of visible light, a solution is prepared in a reactor, and then sulfur-doped TiO is added₂A film.

S1 includes the steps of:

s101, adopting a nonionic surfactant polyoxyethylene (80) sorbitol monooleate (Tween80) as a guiding pore agent. Dissolving a surfactant in isopropanol, adding titanium (IV) isopropanol serving as an alcohol oxygen precursor into a mixture of iPrOH and Tween80, finally adding sulfuric acid serving as a sulfur precursor and a reagent for in-situ formation of water, and stirring the solution at room temperature for 24 hours to obtain a light yellow, transparent, uniform and stable solution.

S2 includes the steps of:

s201. Prior to impregnation, the entire surface was rinsed with MilliQ grade water, then with ethanol and dried under an infrared lamp, sulfur-doped TiO₂The film is prepared by soaking method, and the extraction speed is controlled at 12.3 + -0.5 cm min^-1Effective surface area of 10cm²After the dip coating process, the coating is placed in a multi-stage programmable high temperature furnace for sintering. The sintering temperature and duration of each layer were controlled at 350 ℃ for 2 hours, 400 ℃ for 30 minutes, and 500 ℃ for 20 minutes to remove all organic matter, followed by natural cooling.

S3 includes the steps of:

s301, in order to measure the BET specific surface area, the pore volume, the porosity, the BJH pore diameter and the pore size distribution, after nitrogen purging is carried out for 2 hours at 150 ℃, an environmental scanning electron microscope is used for characterizing the film form under the acceleration voltage of 30 kilovolts, an energy dispersion X-ray spectrum installed in ESEM is used for observing the sulfur element distribution and determining the sulfur content in the film, the energy dispersion X-ray spectrum installed in ESEM is used for observing the sulfur element distribution and determining the sulfur content in the film, and the energy dispersion X-ray spectrum installed in ESEM is used for observing the sulfur element distribution and determining the sulfur content in the film.

S4 includes the steps of:

s401. all membranes were washed with MilliQ grade water, then dried under an infrared light lamp, and then subjected to photocatalytic evaluation, with initial concentration of MC-LR and pH being the experimental conditions chosen according to our predecessor's study, and two 15W fluorescent lamps (Cole-Parmer) were used as visible light sources. Under the irradiation of visible light, an ultraviolet filter is arranged under a light source, and the light intensity is 9.05 multiplied by 10^-5W cm^-2Determined by a broadband radiation power meter.

Compared with the prior art, the invention has the following beneficial effects:

the membrane has the advantages of strong thermal and chemical stability, relatively high photocatalytic activity, low toxicity, low cost and the like, can effectively degrade microcystins under the condition of visible light, is an effective degradation photocatalyst, and has wide prospect when being used as a visible light activation photocatalyst for environmental protection.

Drawings

Fig. 1 is a spectrum of a visible light illumination source.

FIG. 2 is a sulfur-doped TiO sample compared to a reference sample₂The optical properties of (A): a) reference UV-Vis absorption Spectrum and Sulfur doped TiO at different temperatures₂Calcification, (b) diffuse reflectance spectrum of S350 and reference. The insert shows a dowk figure.

FIG. 3 is a sulfur-doped TiO treated at different calcification temperatures₂XRD pattern of the sample.

FIG. 4 is a graph of pore size distribution of desulfurisation and N2 adsorption-desorption isothermal TiO₂And (4) sampling.

FIG. 5 is a sulfur-doped TiO₂HR-TEM images of fims: (a) and (d) represents S350, (b) and (e) represent S400, and (c) and (f) represent S500.

FIG. 6 is a graph of (a) sulfur-doped and reference TiO blends at excitation wavelengths of 514.5 and 785nm₂Micro-raman spectroscopy. The dotted line depicts the AnataThe sRaman mode. (b) Peak position and FWHM change of the 514.5 and 785nm lowest frequency Eg Anatase mode. The inset details the 514.5nm sulfur doped TiO₂Eg mode of (2). (c) The multimodal fitting range of the Raman spectrum is 200 and 750cm^-1514.5 nm.

FIG. 7 is a sulfur-doped TiO₂ESEM image of film: (a) AFM analysis of S350, (b) S400, (c) S500, and (d) S350 thin films.

FIG. 8 is TiO for sulfur doping₂XPS spectra and FT-IR analysis of films: (a) broad scan measurement spectrum of S350, (b) Ar of S350⁺Before and after etching, and (c) 40 min Ar of all samples⁺After etching, and (d) FT-IR analysis of the doped sulfur and reference TiO2 samples.

FIG. 9 is a sulfur-doped TiO₂EDX analysis of the film (white: elemental sulfur): A) EDX mapping pattern of S350, EDX mapping pattern of S400, EDX mapping pattern of S500, and D elemental analysis of the S350 film.

FIG. 10 is (a) S350 and corresponding differential spectra under dim and visible light illumination, and (b) S400 and reference TiO₂Specific values of the g-factor are described under T ═ 10k. arrows and labels under dim light and visible or uv-visible illumination.

FIG. 11 shows the results of the measurement of visible light (pH5.8, sulfur-containing TiO)₂The photocatalytic activity of the film is irradiated by visible light (+)>420 nm): (a) degradation of MC-LR containing S350, S400, S500 and reference, (b) use of S350 and reference TiO₂(ii) degradation of MC-LR, (c) a control experiment using S350 to confirm degradation of MC-LR under visible light irradiation, and (d) a multi-cycle test of MC-LR degradation for 10 hours.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

Example 1

Sulfur-doped TiO for water purification system of construction site₂The preparation method of the film comprises the following steps:

S1 includes the steps of:

S2 includes the steps of:

s201. Prior to impregnation, the entire surface was rinsed with MilliQ grade water, then with ethanol and dried under an infrared lamp, sulfur-doped TiO₂The film is prepared by soaking method, and the extraction speed is controlled at 12.3 + -0.5 cm min^-1Effective surface area of 10cm²After the dip coating process, the coating is placed onAnd sintering in a multi-section programmable high-temperature furnace. The sintering temperature and duration of each layer were controlled at 350 ℃ for 2 hours, 400 ℃ for 30 minutes, and 500 ℃ for 20 minutes to remove all organic matter, followed by natural cooling.

S3 includes the steps of:

S4 includes the steps of:

Sulfur doped TiO₂The sample of UV-visible absorption spectrum is calcined at different temperatures and compared with the reference TiO₂Comparative examples were performed. To obtain TiO₂The Kubelka-Munk mitigation function Tauc graph is adopted as an indirect band gap value sample. The plot is obtained from the UV-Vis diffuse reflectance, the value of which is given by S350 and the reference TiO₂The linear part of each curve in the Kubelka-Munk mitigation function was extrapolated (FIG. 2 (b)). In sulfur-doped TiO₂In the film, S350 showed the strongest absorption in the visible range, in contrast to TiO in the same region₂The absorption of (a) is very low. The indirect bandgap value of S350, determined from the Tauc plot, is 2.94eV, compared to the reference TiO₂3.18eV (FIG. 2(b)), which is comparable to TiO in anatase₂Very close to phase (3.2 eV). In the case of calcification at higher temperatures of the doped films (S400 and S500), a red shift in absorption was also observed, although to a significant extentMuch smaller than the S350 film (fig. 2 (a)). S-TiO₂The observed change in film absorption indicates that sulfur doping by self-assembled surfactant-based sol-gel process is indeed effective in extending TiO₂An optical response in the visible range.

FIG. 3 illustrates sulfur-doped TiO compounds at different calcification temperatures₂XRD pattern of (a). XRD analysis confirmed the presence of Anatase TiO for each sample₂The corresponding definition is clear, broad and diffraction peak. S-TiO₂The increase in the sintering temperature of the sample resulted in a gradual reduction in the diffraction peak, indicating that TiO₂The crystal size and crystallinity increase. Thus, the minimum average crystal size of S350 is S350, determined as the anastataplug of the most intense (101) diffraction peak using the Scherrer equation. Thus, thin films annealed at low temperatures are expected to have high BET surface areas, thereby enhancing photocatalytic activity, since an increase in surface area results in an increase in the number of photocatalytically active sites per unit mass of catalyst. Albeit TiO₂The small diameter of the nanoparticles can reduce the initial mean electron pore pair distance and the mean number of hops before the surface free pores, but in this case this detrimental size effect is not dominant.

FIG. 4 shows sulfur-doped TiO₂The N2 adsorption-desorption isotherms of (a) are typical of mesoporous materials, the pore size distribution of barrett, geoina and harrada (BJH) being very narrow, meaning that the uniformity of the pores is good, while the BET surface area and pore size volume thereof are significantly high, values of 179.3 ± 0.5m² g^-1And 0.13cm³ g^-1. In addition to crystallinity, the overall structural properties deteriorate during sintering due to sintering and growth of crystals, although the material retains highly porous properties at 400 ℃. However, the initial porous structure of S500 severely collapsed, resulting in a significant reduction in BET surface area, an expansion in pore size distribution, and a significant shift to higher pore sizes. These results are in turn relevant to the recent sintering temperature vs. TiO₂The effects of structural properties work consistently.

FIG. 5 shows the effect on sulfur-doped TiO₂HR-TEM and Fast Fourier Transform (FFT) analysis of the samples. S-TiO₂The average crystal size of the sample increased from 6.1nm to 9.9nm when the calcification temperature was raised from 350 to 500 ℃, which is consistent with XRD peak estimationCorresponding change in crystal size of (a). However, some amorphous TiO₂HR-TEM analysis by S350 was identified, whereas the amorphous phase traces of S400 and S500 could not be resolved. To obtain well-crystallized TiO₂The calcification temperature needs to be maintained at least 400 ℃. In the FFT modes in fig. 5(a), (b) and (c), a clear loop was always observed, indicating one dominant crystal phase for all samples. Furthermore, for all samples, lattice edges with interlayer distance in the range of 0.350-0.352nm have been resolved, similar to FIGS. 5(d), (e) and (f) [41 ]]Medium TiO2₂0.352nm lattice spacing of Anatase (101) plane. These results demonstrate that all sulfur-doped TiO₂The sample crystallized at the ananasase stage, consistent with XRD analysis.

Raman spectroscopy further investigated S-TiO₂The structural characteristics of (a). FIG. 6(a) shows the Raman spectra of sulfur-doped and reference TiO at 514.5 and 785nm, respectively₂. All samples showed two excitation wavelengths]Of Alatata plug TiO₂The characteristic raman-active mode of the phase is consistent with the XRD-determined phase composition of the material. An increase in calcification temperature, especially at 500 ℃, results in significant narrowing and shifting of the raman band. Multimodal fitting of Raman spectra shows that the most intense Abeta Cork mode occurs at a full width at half maximum (FWHM) (in brackets) of 147(26) cm^-1(Eg)，403(37)cm^-1(B1g)，522(44)cm^-1(A1g, B1g) and 635(55) cm^-1(Eg) for S350, while they are shifted and narrowed to 143(12) cm^-1(eg)，395(26)cm^-1(B1g)，517(27)cm^-1(A1g, B1g) and 638(30) cm^-1(Eg) was used for S500. The latter parameter is very close to TiO₂And they approach the parameters of bulk ananas plug. This change can be qualitatively explained by the effect of partial release of optical phonon confinement, resulting in an expansion of the raman mode and a blue shift in the nanomaterial. Specifically, the most prominent in the S500 sample, the width and frequency of the Arnattas Raman band decreased significantly, reflecting the S-TiO₂The growth of the crystals of Nautase, Calcification, at higher temperatures confirms the results of XRD and HR-TEM.

FIG. 6(b) shows the lowest frequency in detailThe peak location of the Eg mode and the evolution process of the FWHM (inset of fig. 6 (b)), are most commonly used to detect the pseudonoise limiting effect of anata plug. Both of these parameters vary greatly as the temperature is increased from 400 ℃ to 500 ℃, with the crystallinity strongly enhanced according to XRD results (figure 3). However, the width of the lowest frequency Eg mode (14 cm)^-1) Much higher than the frequency shift of S350 relative to S500 (4 cm)^-1) There is a clear departure from the linear scaling of the raman shift and FWHM, whereas FWHM is the phonon confinement effect. In fact, although S350(FWHM ═ 26 cm)^-1) The Eg mode width of (A) was approximately calculated from the phonon-constrained model of the size of + -4 nm Natta plug nanocrystals, but the peak positions were observed (147 cm)^-1) Is less than the predicted peak position (152 cm)^-1) Is rather small. This difference means that, in addition to S-TiO calcified at lower temperatures₂In addition to the reduction in nanoparticle size, factors such as strain and structural defects in the S350 and S400 films also contribute to changes in the anata raman mode.

Furthermore, detailed spectral analysis of the micro-raman spectra showed a series of weak but distinct peaks for S350 and S400 in addition to the phonon pattern of the main atanatta plug phase (fig. 6 (c)). 246. 298, 323 and 362cm^-1The lower frequency Raman frequency band can be distributed to Brukt TiO₂A fraction of the contribution of the phase, similar to TiO written by surfactant assisted sol-gel methods₂In the case of nanomaterials. The Brookt Raman mode cannot be resolved into two excitation wavelengths in the reference sample, and is 246cm^-1The relatively strong peak can still be tracked in S500, where the enhanced raman scattering from the relatively large atashinite masks all other contributions. Furthermore, at +450 and +580cm^-1And in particular S350 and S400, as shown in fig. 6(c), two other broad bands of significant relative intensity are identified. These bands are close to the gold, iron and TiO₂Raman mode of the nanoparticle. Given the relatively high spectral weights of these two bands and the star bands in the S350 and S400 Raman spectra, XRD should also be able to detect the aureological gas phase. However, regardless of the calcification temperature (FIG. 3), in sulfur-doped TiO₂In the XRD pattern (2), no gold was resolved. The origin of these bands may beMainly due to TiO₂Due to the low sintering temperature, the crystallinity is low (wide Raman band occurs at +450 and +610 cm)^-1Amorphous TiO₂This is consistent with the HR-TEM result of S350.

Fig. 7 shows ESEM images of S350, S400 and S500 films and AFM analysis of S350 films. ESEM images show that there are no cracks in the S350 and S400 films after the sintering process. AFM analysis (fig. 7(d))) confirmed that the surface of the S350 film was very uniform and smooth, with a surface roughness of only 0.72 nm. In this case, very fine nanoparticles are uniformly deposited on the glass substrate, filling the space between the particles, and improving the rough film surface during the dipping process. However, in the case of S500, the ESEM analysis observed cracks on the film as shown in fig. 7 (c). Cracks are caused by sintering and crystal growth at high sintering temperatures.

XPS was used to identify TiO₂The presence of sulfur species in the film is shown in FIGS. 8(a) - (c). Ar (Ar)⁺Etching on sulfur-doped TiO ₂40 minutes on the film by removing the topmost atomic layer and exploring for sulfur into the TiO₂The crystal lattice is introduced, so that the surface of the film is cleaned. In this case, impurity peaks of

Na

1s and 2 and C1 generated from Na (leaching from the glass substrate) and C adsorbed in the original thin film (adsorption from the atmosphere) are effectively suppressed at the time of etching. FIG. 8(a) shows the use of Ar⁺A broad scan of the etched S350 film measured a spectrum that was 40 minutes, where the predominant O, Ti and S elements could be identified by the corresponding O1, Ti 2p, and S2 p peaks. FIG. 8(b) shows a detailed comparison of Ar⁺The S2 p core level spectra of S350 before and after etching, two broad peaks were observed at 161 and 168.5 eV. The XPS peak of the S2 p core level region, with a binding energy of 160-163eV, is attributed to the formation of Ti-S bonds due to O^2-Quilt S^2-Instead, the peak in the range of 167-170eV is due to S⁶⁺And S⁴⁺The presence of a species. The origin of the latter peak is in sulfur-doped TiO₂In some disputes because it may be with S⁶⁺/S⁴⁺cions substituted for Ti⁴⁺Ions or sulphate/sulphate groups (SO)_42-/SO_32-) By the presence of surface Ti⁴⁺The ionic, bitronate bonds are coordinated, similar to sulfate.

Ar of S350 film⁺The etching resulted in a significant reduction of the S2 p peak at high binding energies, reducing the sulfur content from 7.3 to about 4.1%. This indicates that the sulfide at the 168.5eV XPS peak originates mainly from the surface of the sulfur-doped TiO2 and is therefore likely to anchor to the TiO₂The presence of the above sulfate group. Notably, S⁶⁺/S⁴⁺XPS peak at S-TiO₂Is systematically observed when sulfuric acid or a sulfate reagent is used as the sulfur source, and S^2-The XPS peak is only present when sulfuric acid is used in the precursor solution. On the other hand, the S2 p peak was at 161eV for 40 minutes Ar⁺Etching S350 with slight variations, as shown in FIG. 8(b), verifying the substitute S^2-Ions being incorporated into TiO₂A crystal lattice. High temperature sintering results in a gradual decrease in the junction resistance of the two S2 p peaks, resulting in a decrease in the sulfur content of S350 from 4.1% to 0.7% of S500, indicating that the sulfur centers are annihilated upon thermal annealing.

FIG. 8(d) shows sulfur-doped TiO₂FT-IR spectra of the films compared to the reference film. The presence of Ti-S and Ti-O-S bonds may be suggested to be based on 1127 and 1046cm^-1Respectively corresponding to S-O (1130 cm)^-1) And Ti-S (1045 cm)^-1) And (5) vibrating. On the other hand, due to the presence of binding to TiO₂SO of_42-The composite infrared band is expected to be in the same frequency range (1000-^-1) While a typical S + O stretch mode is expected to be (1400 cm)^-1). However, in all sulfur doped TiO₂The absence of the latter band on the film indicates an insufficient number of sulfate groups or a high probability of surface sulfate in the form of high ions on the surface of the titanium hydrate, where the S-O vibration band shifts to 1300cm^-1The following is a description.

To independently determine the doped TiO₂The sulfur content in the film and its distribution were analyzed by EDX (see fig. 9). During EDX analysis, Na, Al, Ca, K, Si, and V elements leached from the glass substrate during heat treatment were detected, as shown in fig. 9 (d). The data obtained show that sulfur is on the flyThe distribution on the film is uniform, and the content of the coating decreases with the increase of the sintering temperature (5.8 percent to 3.7 percent of S350 is S400). In EDX analysis, the sulfur content was higher than the content determined by XPS after etching, although no sulfur content was detected for S500. This result is likely due to the different resolution of each instrument. Furthermore, EDX did not detect carbon, indicating that annealing at 350 ℃ for 2 hours was sufficient to remove TiO during calcification₂Residual carbon in the film.

Subsequently, the EPR spectrum was used under visible light illumination for TiO₂The presence of induced paramagnetic centers was investigated. FIG. 10 compares the EPR spectra of S350 and S400 under dark and visible light (440-460nm) with that of a reference sample under dark and ultraviolet illumination at 10K. The S350 sample had an abundant EPR powder spectrum with extended fine structure in the dark (fig. 10 (a)).

The origin of this spectrum was not discernible from the spectrum of the single paramagnetic centered anisotropic EPR powder, which is expected in TiO₂Medium predicted spin S ═ 1 ═ 2 or sulfur-containing groups, with very low natural abundance (0.76%)³³The S isotope (I ═ 3+2) excludes detection of ultrafine structures. Visible light illumination had no effect on the extended EPR spectrum of S350 (fig. 10(a)) which disappeared upon sintering at high temperature (fig. 10(b)), indicating poor thermal stability of the underlying paramagnetic defects. High autorotation (S)>1/2) paramagnetic center results from the coupling of sulfur radicals to anisotropic g-tension (e.g., SO on the highly sulfided surface of S350 nanoparticles as a result of XPS and EDX_4-) The origin of the S350EPR spectrum can be explained, where the presence of a significant zero-field split can explain the extended fine structure.

On the other hand, subtraction of EPR spectra obtained under visible and dark conditions revealed a narrow EPR line at G2.0040 (5) with a peak-to-peak width of 9G, masked in the dark by the extended EPR spectrum of S350 (fig. 10(a) — a single EPR line with a significant intensity enhancement at G2.004 under visible light illumination is clearly demonstrated in S400 with the extended EPR spectrum completely suppressed (fig. 10 (b)). in this case, the unique EPR signal is easily identified in the original S400 sample, and its intensity increases sharply under visible light illumination (7 times Vis illumination, in Vis illumination)A 7-fold increase within 10 minutes of illumination) without any change or magnification being observed. The EPR line can hardly track S500, but in the reference TiO₂Is completely absent from the sample. In this case, Ti at the center in relation to oxygen and at the stopper of the Anata³⁺The site observes a series of weak EPR lines. The intensity of the EPR spectrum was greatly enhanced upon uv illumination (fig. 10(b)), the most obvious including an anisotropic EPR powder spectrum with a rhombohedral g-tensor and principal values gx 2.023, gy 2.009 and gz 2.003 resulting from the formation of superoxide radical O upon pore trapping on the surface of the asian sals_2-。

The changes in sulfur content in sulfur-doped samples inferred from XPS and EDX, as well as their photocatalytic activity towards MC-LR degradation, have a clear evolution under visible light. This means that the origin of the EPR line is doped with sulfur and TiO₂The accompanying structural modification of the crystal lattice is closely related. In this case, S is due to^2-It is reasonable to form a local gap state by ion substitution doping with oxygen. The sub-band gap illumination of visible light in these impurity states should be mainly in two magnetic states due to the low EPR intensity in the dark starting material, promoting TiO₂Excitation of electrons in the conduction band leaves a local unpaired electron that can account for the visible light-activated EPR signal. Formally using positively charged F according to single electron capture in oxygen vacancies⁺Color center, another explanation can be proposed that at g 2.004 a sharp EPR line is produced, enhancing significantly under visible light illumination. Therefore, it is necessary to mix TiO₂Oxygen vacancies in the lattice form simultaneously with the sulfur doping, a distinguishing feature that appears to be formed by Anion doping with visible photoactivity and reduced TiO₂Materials are shared and can be especially popularized among tetans. In this case, from TiO₂Visible light excitation of electrons that are valence-carrying to the vacant (donor) state, or through more complex electron transition pathways, involves interpretation from the F color center (electron to electron trapped in the oxygen vacancy), and can also account for the increase in g-2.004 EPR signal intensity upon visible light illumination.

Desulfurated TiO in water under visible light irradiation with MC-LR₂The photocatalytic activity of the film was investigated. FIG. 11(a) shows the degradation of MC-LR at pH5.8, with different films sintered at different temperatures. All sulfur-doped TiO₂The films all showed significant photocatalytic activity for degradation of MC-LR under visible light irradiation, with S350 having the highest performance. On the other hand, reference TiO₂The film had no significant degradation of MC-LR, and the residual concentration of MC-LR was similar in both dark and visible light conditions. Notably, according to previous work, no degradation of MC-LR was observed in visible light using Degussa P25 film as a reference photocatalyst. Therefore, the photocatalytic activity of these films in the visible light region is due to effective doping with sulfur, plus the surface area and doping level of the doped sulfur-doped film increase (fig. 11 (b)). To confirm sulfur-doped TiO₂The photocatalytic activity of the film under irradiation with visible light was controlled at pH5.8 (FIG. 11 (c)). Thus, in a 5 hour control experiment, MC-LR was adsorbed under dark conditions and its photocatalytic degradation under visible light irradiation by adjusting the solution pH to 5.8. After 5 hours, the MC-LR remained around 65% of the initial concentration adsorbed in the dark, and the concentration of photocatalytic degradation remained at 33%. Then, in a continuous experiment (fig. 11(c)), both reactors were placed in the dark and the pH was increased to the alkaline range (pH 9.3) to observe the desorption of MC-LR due to TiO₂And the charge of MC-LR is negative. After 30 minutes at pH9.3, 90% of the MC-LR was recovered in the case of dark adsorption. However, in the case of photocatalytic degradation, only 38% of the MC-LR was recovered. After 7 hours (12 hours total), MC-LR was restored up to 92% and 40% of the original concentration for two experiments. These results, of course, indicate that photoinduced electron transfer may occur in sulfur-doped TiO₂The MC-LR is effectively degraded on the surface of the film under the irradiation of visible light. In addition, studies have shown that, under the conditions of the applied experiments, sulfur-doped TiO₂The film has high adsorption capacity to MC-LR. As shown in fig. 11(d), the photocatalytic activity of S350 was slightly decreased in 10 hours when the same film was repeatedly tested under irradiation of visible light. However, the results show that the degradation of MC-LR by this film still maintains a high photocatalytic activity in 3 cycles of experiments. This indicates sulfur-dopedTiO₂The films were mechanically stable and reusable under these experimental conditions.

Visible light active sulfur doped TiO₂The film adopts self-assembly technology and adopts non-sunlight surfactant to control the nanostructure and H₂SO₄As a sulfur source, a sol-gel method was successfully synthesized. Sulfur doped TiO discovery₂The morphology, structure, optical and porous properties of the film are clearly dependent on the sintering temperature. According to the mapping of XPS, FT-IR and EDX, sulfur is mainly recognized as TiO₂Cation (S) in the lattice^2-) Surrogate, and S primarily associated with surface sulfate groups rather than cation doping⁶⁺/S⁴⁺And its distribution is uniform throughout the film. Detection of sulfur-doped TiO₂Significant shift of the light absorbing edge of the film to the visible region. An EPR line was identified at g-2.004, depending on the sulfur content and the change in photocatalytic activity of the material. Under visible illumination, the EPR intensity is significantly enhanced, indicating that TiO is due to the presence of a photoacid S agonist and/or oxygen vacancies₂There are local energy states in the band gap. Sintering at 350 c for 2 hours provided the highest sulfur content and BET surface area, small spar size, high porosity, large pore volume, and a very smooth and uniform surface for sulfur-doped TiO2 films. Corresponding mesoporous sulfur-doped TiO₂The film is the photocatalyst with the most effective degradation of MC-LR under the irradiation of visible light, and shows that the sintering temperature is an important factor for effective modification of sulfur and high material reactivity. Furthermore, this is based on H₂SO₄In the preparation of nano-structure sulfur-doped TiO by sol-gel method₂The films are also useful as visible light activated photocatalysts for environmental applications.

By the scheme, the invention at least has the following advantages:

the sulfur-doped titanium dioxide film has the advantages of strong thermal and chemical stability, relatively high photocatalytic activity, low toxicity, low cost and the like, can effectively degrade microcystins under the condition of visible light, is an effective degradation photocatalyst, and has wide prospect when being used as a visible light activation photocatalyst for environmental protection.

The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto. The substitution may be of partial structures, devices, method steps, or may be a complete solution. The technical solution and the inventive concept thereof according to the present invention should be equally replaced or changed within the protection scope of the present invention.

Claims

1. Sulfur-doped TiO for water purification system of construction site₂The preparation method of the film is characterized by comprising the following steps: the method comprises the following steps:

2. The sulfur-doped TiO for the water purification system of construction sites according to claim 1₂The preparation method of the film is characterized by comprising the following steps: s1 includes the steps of:

3. According to claim2 the sulfur-doped TiO for the water purification system of the construction site₂The preparation method of the film is characterized by comprising the following steps: s2 includes the steps of:

s201. Prior to impregnation, the entire surface was rinsed with MilliQ grade water, then with ethanol and dried under an infrared lamp, sulfur-doped TiO₂The film is prepared by soaking method, and the extraction speed is controlled at 12.3 + -0.5 cmin^-1Effective surface area of 10cm²After the dip coating process, the coating is placed in a multi-stage programmable high temperature furnace for sintering. The sintering temperature and duration of each layer were controlled at 350 ℃ for 2 hours, 400 ℃ for 30 minutes, and 500 ℃ for 20 minutes to remove all organic matter, followed by natural cooling.

4. Sulfur-doped TiO for water purification systems of construction sites according to claim 3₂The preparation method of the film is characterized by comprising the following steps: s3 includes the steps of:

5. The sulfur-doped TiO for the water purification system of construction sites according to claim 4₂The preparation method of the film is characterized by comprising the following steps: s4 includes the steps of:

s401. all membranes were washed with MilliQ grade water, then dried under an infrared light lamp, and then subjected to photocatalytic evaluation, with initial concentration of MC-LR and pH being the experimental conditions chosen according to our predecessor's study, and two 15W fluorescent lamps (Cole-Parmer) were used as visible light sources. Under the irradiation of visible light, an ultraviolet filter is arranged under a light source, and the light intensity is 9.05 multiplied by 10^-5Wcm^-2Determined by a broadband radiation power meter.