CN114849734A - Preparation method for degrading microcystin aggregates in drinking water of construction site - Google Patents
Preparation method for degrading microcystin aggregates in drinking water of construction site Download PDFInfo
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- CN114849734A CN114849734A CN202210173324.XA CN202210173324A CN114849734A CN 114849734 A CN114849734 A CN 114849734A CN 202210173324 A CN202210173324 A CN 202210173324A CN 114849734 A CN114849734 A CN 114849734A
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- 230000000593 degrading effect Effects 0.000 title claims abstract description 15
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- SRUWWOSWHXIIIA-UKPGNTDSSA-N Cyanoginosin Chemical compound N1C(=O)[C@H](CCCN=C(N)N)NC(=O)[C@@H](C)[C@H](C(O)=O)NC(=O)[C@H](CC(C)C)NC(=O)[C@H](C)NC(=O)C(=C)N(C)C(=O)CC[C@H](C(O)=O)N(C)C(=O)[C@@H](C)[C@@H]1\C=C\C(\C)=C\[C@H](C)[C@@H](O)CC1=CC=CC=C1 SRUWWOSWHXIIIA-UKPGNTDSSA-N 0.000 title claims abstract description 11
- 108010067094 microcystin Proteins 0.000 title claims abstract description 11
- 238000010276 construction Methods 0.000 title claims abstract description 10
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- RNAMYOYQYRYFQY-UHFFFAOYSA-N 2-(4,4-difluoropiperidin-1-yl)-6-methoxy-n-(1-propan-2-ylpiperidin-4-yl)-7-(3-pyrrolidin-1-ylpropoxy)quinazolin-4-amine Chemical compound N1=C(N2CCC(F)(F)CC2)N=C2C=C(OCCCN3CCCC3)C(OC)=CC2=C1NC1CCN(C(C)C)CC1 RNAMYOYQYRYFQY-UHFFFAOYSA-N 0.000 description 1
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- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
- B01J27/04—Sulfides
-
- B01J35/39—
-
- B01J35/40—
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/0215—Coating
- B01J37/0228—Coating in several steps
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/024—Multiple impregnation or coating
- B01J37/0244—Coatings comprising several layers
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/30—Treatment of water, waste water, or sewage by irradiation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/30—Treatment of water, waste water, or sewage by irradiation
- C02F1/32—Treatment of water, waste water, or sewage by irradiation with ultraviolet light
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/34—Organic compounds containing oxygen
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/38—Organic compounds containing nitrogen
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/02—Non-contaminated water, e.g. for industrial water supply
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2305/00—Use of specific compounds during water treatment
- C02F2305/10—Photocatalysts
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/30—Wastewater or sewage treatment systems using renewable energies
- Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy
Abstract
The invention introduces a preparation method for degrading microcystin aggregates in drinking water of a construction site, in particular to S-modified monodisperse TiO 2 The preparation method of the aggregate is based on the nonionic surfactant controlled self-assembly technology and is based on an inorganic sulfur source (H) 2 SO 4 ) The visible light laser is synthesized by a novel sol methodActive S doped TiO 2 The nanocrystalline film carries out photocatalytic degradation on microcystin MC-LR under the irradiation of ultraviolet light and visible light. The method has simple and environment-friendly preparation process, and is compatible with pure TiO 2 In contrast, under UV-visible light irradiation, S-containing TiO 2 The photocatalytic activity of the sample was enhanced.
Description
Technical Field
The invention belongs to the field of water treatment, and particularly relates to a preparation method of microcystin aggregates in drinking water for degrading construction sites.
Background
Nano titanium dioxide (TiO) 2 ) Is a photocatalyst which is widely used for degrading environmental pollutants in water and air. TiO2 2 The physical and chemical properties of the photocatalyst have the characteristics of thermal stability, chemical stability, relatively high photocatalytic activity, low toxicity, low cost and the like, and the photocatalyst has the most potential for environmental remediation. However, only UV light (4-5% sunlight) can be used for TiO 2 Photocatalytic reaction, with a wider band gap (anatase with a band gap of about 3.2eV and rutile with a band gap of about 3.0 eV). Thus extending the TiO 2 It is important that the photoresponse of (a) is taken into the visible spectral range, which encompasses the large solar spectrum (-45% sunlight) in terms of energy availability. In recent years, efforts have been made to improve TiO 2 In order to make it function under visible light, various dopants of transition metal ions such as Fe, Co, Ag, Ni and non-metals C, N, F, S) are used, and different synthetic routes such as seed growth, Chemical Vapor Deposition (CVD), hydrothermal method, sol-gel method, etc. are used. Although transition metal doped TiO 2 Has good photocatalytic performance, but has the defects of low thermal stability, enhanced carrier recombination and the like.
Disclosure of Invention
In order to solve the technical problems, the inventor obtains the technical scheme of the invention through practice and summary, and the invention discloses a preparation method for degrading microcystin aggregates in construction site drinking water, wherein the aggregates are S-modified monodisperse TiO2 aggregates, and the preparation method comprises the following steps:
s1: adopting nonionic surfactant polyoxyethylene (80) sorbitol monooleate as a guiding pore agent;
s2: dissolving polyoxyethylene (80) sorbitol monooleate in isopropanol, adding titanium (IV) isopropanol as an alcohol oxygen precursor to the mixture of isopropanol and polyoxyethylene (80) sorbitol monooleate, and adding sulfuric acid as a reagent for a sulfur precursor and in-situ water;
s3: stirring the solution at room temperature for 24h to obtain a yellowish, transparent, uniform and stable solution; the pH value of the solution is 3.0 +/-0.2, and the viscosity is 6.48 +/-0.12 cP;
s4: preparing an S-doped TiO2 film by adopting a dip-coating method, wherein borosilicate glass is used as a substrate;
s41: before dip coating, the whole surface is washed by MilliQ grade water, then washed by ethanol, and dried under an infrared lamp, and the effective surface area is 10cm 2 Dip coating to control the extraction speed to be 12.3 +/-0.5 cm/min;
s42: after dip coating, the coating is put into a multi-section programmable high-temperature furnace for calcining, and the processes of dip coating and calcining are repeated for 5 times to obtain a 5-layer film.
Further refinements in the present application are: in the step S42, the calcination temperature and time of each layer are controlled at 350 ℃ for 2 hours, 400 ℃ for 30min and 500 ℃ for 20min, all organic matters are removed, and then the layer is naturally cooled.
Further refinements in the present application are: in the step S42, the thickness of each film was 1.02. + -. 0.02. mu.m, and the total mass was 4.51. + -. 0.18 mg.
Further refinements in the present application are: in step S3, the molar ratio of the raw materials is polyoxyethylene (80) sorbitol monooleate: isopropyl alcohol: titanium (IV) isopropanol: sulfuric acid 1: 45: 1: 1.
compared with the prior art, the invention can obtain the following technical effects:
h2SO4 is used as a sulfur source, a novel sol method based on a self-assembly technology is adopted to successfully synthesize the visible light activated S-TiO2 film, and a nonionic surfactant is adopted to control the nano structure of the film. The morphological, structural, optical and porous properties of S-TiO2 were studied, and the results showed that the properties of the film were significantly dependent on the calcination temperature. According to XPS, FT-IR and EDX spectra, anionic (S2-) substituents are identified predominantly in the TiO2 lattice rather than cationic doping, with the cations S6+/S4+ being predominantly associated with surface sulfate groups, but the cations are more uniformly distributed in the film. A significant shift of the optical absorption edge to the visible region was found in S-TiO 2. A single EPR line was found at g 2.004, depending on the sulfur content and the change in photocatalytic activity of the material: the EPR intensity is significantly enhanced under visible light irradiation, indicating the presence of a band gap in TiO2 due to local energy state anion doping and/or oxygen vacancies. The S-TiO2 film prepared by calcining for 2 hours at 350 ℃ has the characteristics of highest sulfur content, highest specific surface area, small crystallite size, high porosity, large pore volume and very smooth and uniform surface, the mesoporous S-TiO2 film is the most effective photocatalyst for degrading MC-LR under visible light irradiation, and the same explanation shows that the calcination temperature is an important factor influencing the modification effect. Therefore, the S-TiO2 film with the nano structure prepared by the sulfuric acid-based sol-gel method is useful as an ambient visible light photocatalyst and has certain positive significance for degrading environmentally harmful organic matters.
The method has unique and superior performance, and the mesoporous S-TiO2 film is an effective photocatalyst for degrading MC-LR under the irradiation of visible light under the irradiation of ultraviolet light and visible light. The drinking safety is guaranteed.
Drawings
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1: TiO not doped with S 2 Film and sulfur doped TiO 2 Optical properties of (a): (a) calcination control group and S-TiO at different temperatures 2 Ultraviolet-visible absorption spectrum of (a); (b) diffuse reflectance spectra of S-doped samples and controls at S350.
FIG. 2: S-TiO 2 XRD patterns of the samples at different calcination temperatures.
FIG. 3: S-TiO 2 Pore size distribution and N 2 Adsorption-desorption isotherms.
FIG. 4: S-TiO at different calcination temperatures 2 HR-TEM image of the film: s350(a) and (d), S400(b) and (e), S500(c) and (f).
FIG. 5: (a) S-TiO at different calcination temperatures 2 Film and reference TiO 2 Micro-raman spectra of the film at excitation wavelengths 514.5 and 785 nm. The dotted line is the anatase raman mode. (b) Peak position and half-peak width changes at 514.5 and 785nm for the lowest frequency anatase mode. The inset shows the S-TiO at 514.5nm 2 E of (A) g Mode(s). (c) 200-750cm at 514.5nm -1 Multimodal fitting of raman spectra within a range.
FIG. 6: S-TiO 2 ESEM image of film: (a) s350, (b) S400, (c) S500, and (d) AFM analysis of the S350 film.
FIG. 7: S-TiO 2 XPS spectra and FT-IR analysis of films: (a) a wide scan measurement spectrum of S350; (b) film Ar under S350 + Etching for 40min to obtain binding energy; (c)3 samples in Ar + Etching for 40min to obtain binding energy; (d) three kinds of S-TiO 2 And reference TiO 2 FT-IR analysis of (1).
FIG. 8: S-TiO 2 EDX analysis of the films (white: elemental sulfur): (a) the EDX mapping mode of S350; (b) EDX mapping mode of S400; (c) the EDX mapping mode of S500; (d) and S350, element analysis of the film.
FIG. 9: (a) s350, EPR spectra and corresponding difference spectra under dark and visible light irradiation; (b) s400 and reference TiO at 10K temperature 2 EPR spectra under dark and visible/uv-visible illumination. Arrows and labels describe specific values of the magnetic force factor.
FIG. 10: sulfur doped TiO 2 Film visible light (lambda) at pH 5.8>420 nm). (a) Degradation of MC-LR by S350, S400, S500 and reference films; (b) s350 and control TiO 2 Degradation of MC-LR by the film; (c) s350, a factor control experiment proves that MC-LR can be degraded under the irradiation of visible light; (d) 3 cycles of MC-LR degradation for 10 h.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The application of the principles of the present invention will be further described with reference to the accompanying drawings and specific embodiments.
In order to solve the technical problem, the method comprises the following steps:
a preparation method for degrading microcystin aggregates in drinking water at construction sites comprises the following steps:
s1: adopting nonionic surfactant polyoxyethylene (80) sorbitol monooleate as a guiding pore agent;
s2: dissolving polyoxyethylene (80) sorbitol monooleate in isopropanol, adding titanium (IV) isopropanol as an alcohol oxygen precursor to the mixture of isopropanol and polyoxyethylene (80) sorbitol monooleate, and adding sulfuric acid as a reagent for a sulfur precursor and in-situ water;
s3: stirring the solution at room temperature for 24h to obtain a yellowish, transparent, uniform and stable solution; the pH value of the solution is 3.0 +/-0.2, and the viscosity is 6.48 +/-0.12 cP;
s4: preparing an S-doped TiO2 film by adopting a dip-coating method, wherein borosilicate glass is used as a substrate;
s41: before dip coating, the whole surface is washed by MilliQ grade water, then washed by ethanol, and dried under an infrared lamp, and the effective surface area is 10cm 2 Dip coating to control the extraction speed to be 12.3 +/-0.5 cm/min;
s42: after dip coating, the coating is put into a multi-section programmable high-temperature furnace for calcining, and the processes of dip coating and calcining are repeated for 5 times to obtain a 5-layer film.
Further refinements in the present application are: in the step S42, the calcination temperature and time of each layer are controlled at 350 ℃ for 2 hours, 400 ℃ for 30min and 500 ℃ for 20min, all organic matters are removed, and then the layer is naturally cooled.
Further refinements in the present application are: in the step S42, the thickness of each film was 1.02. + -. 0.02. mu.m, and the total mass was 4.51. + -. 0.18 mg.
Further refinements in the present application are: in step S3, the molar ratio of the raw materials is polyoxyethylene (80) sorbitol monooleate: isopropyl alcohol: titanium (IV) isopropanol: sulfuric acid 1: 45: 1: 1.
the nonionic surfactant polyoxyethylene (80) sorbitol monooleate (Tween 80) is adopted as the pore-guiding agent. The surfactant was dissolved in isopropanol (iPrOH, 99.8%), then titanium (IV) isopropanol (TTIP, 97%) was added as an alcohol oxygen precursor to the mixture of iPrOH and Tween80, and finally sulfuric acid (H) was added 2 SO 4 95-98%) as reagents for the sulfur precursor and in situ water. The solution is stirred for 24 hours at room temperature, and the obtained solution is light yellow, transparent, uniform and stable. The pH value of the solution is about 3.0, and the viscosity is 6.48 +/-0.12 cP. The molar ratio of raw materials is Tween 80: iPrOH: TTIP: sulfuric acid 1: 45: 1: 1, while for the reference TiO2, the surfactant was excluded and the same molar ratio of acetic acid was used instead of sulfuric acid.
A dip coating process was used to prepare S-doped TiO2 thin films with borosilicate glass (micro-slide, gold seal) as the substrate. Before dip coating, the entire surface was rinsed with MilliQ grade water, then with ethanol, and then dried under an infrared lamp. Effective surface area of 10cm 2 Dip coating with extraction speed of 12.3 + -0.5 cm min -1 . After dip coating, the coating was calcined in a multi-stage programmable high temperature furnace (Paragon Model HT-22-D, Thermcraft Inc., Winston-Salem, NC). The baking temperature and time of each layer are controlled at 350 ℃ for 2 hours (S350); removing all organic substances at 400 deg.C for 30min (S400) and at 500 deg.C for 20min (S500), and naturally cooling. This treatment time gives TiO 2 The high crystallinity of (2) is based on the prior literature reports. The dipping and calcination processes were repeated 5 times to obtain a 5-layer film (thickness 1.02. + -. 0.02. mu.m; total mass 4.51. + -. 0.18 mg). In addition, the sulfur-doped TiO2 thin film was very difficult to collect samples from glass substrates due to the very low content of titanium dioxide, and therefore particles were prepared from thick films to characterize porosity and crystal structure. This approach is useful in order to quickly study the effect of sol conditions on the structural properties of the final material, although these particles are not exactly the same as those on the film. For S-doped TiO 2 Particle characterization, again using a multi-stage programmable high temperature furnace, the sol was oven dried on borosilicate glass petri dishes at 90 ℃ for 6 hours, and then heated at high temperatures at temperatures of 350, 400, and 500 for 24 hours, 12 hours, and 3 hours, respectively, to completely remove all organics and form thick films. TiO2 2 The particles were scraped from the thick film and ground.
Properties and Properties
Characterization of Sulfur-doped Titania films
Using an X' pert PRO (Philips) X-ray diffractometer using Cu K
The X-ray diffraction pattern of sulfur-doped Ti02 was determined for the radiation source. The sample was purged with nitrogen at 150 ℃ for 2 hours, and then the specific surface area, pore volume, porosity, pore diameter and pore diameter distribution were measured using a pore analyzer. The film morphology was characterized using an environmental scanning electron microscope (ESEM, Philips XL 30ESEM-FEG) at an accelerating voltage of 30 kV. In addition, the distribution of sulfur element was observed by using self-carried energy dispersive X-ray energy spectrum (EDX) in ESEM, and the sulfur content in the film was measured. The optoelectronic properties were obtained from the diffuse reflectance spectra obtained on a UV-Vis instrument equipped with an integrated sphere attachment (ISR 1200) (Shimadzu 2501 PC). With Ba 2 SO 4 The surface roughness of the sulfur-doped titanium dioxide film was observed for reference to a standard material. The elemental composition and electronic structure were determined using a multimode Atomic Force Microscope (AFM). Adopting a fly angle of 45 degrees and a vacuum degree of 10 degrees -8 And 10 -9 Mg K.alpha.X-rays of Torr were subjected to X-ray photoelectron spectroscopy (XPS) analysis. The binding energy was corrected based on Fourier transform infrared spectroscopy (FT-IR) analysis at 284.6eV peak of the C1s level. The presence of sulfur groups was detected using a high resolution transmission electron microscope (HR-TEM) spectrometer. Crystal size and crystal structure information were obtained with 200kV field emission for TEM image analysis. Samples were prepared in methanol (HPLC grade), treated with a sonicator for 30min, and then fixed on a carbon coated copper grid (LC325-Cu, EMS) to measure micro-raman spectra in back-scattering. Use of Ar on Renishaw inVia reflectance microscope + The ion laser (lambda is 514.5nm) and a high-power near-infrared (NIR) diode laser (lambda is 785nm) are used as excitation sources, and laser beams are focused on a sample through a 50 x objective lens, wherein the laser power density is 1.5W/m 2 . Is kept at a low level (<0.1mW/μm 2 ) This is done to avoid local overheating of the sample. Electron Paramagnetic Resonance (EPR) measurements were performed using the X-band (v ≈ 9.42GHz), a 200D spectrometer equipped with an ESR 900 cryostat for measurements at low temperatures, and in EPR the sample was directly illuminated with continuous visible light. The cavity uses a Luxeon dimmable Light Emitting Diode (LED) with a controlled wavelength in the blue region, i.e. in the spectral region between 440 and 460nm, while a 360 watt halogen lamp is equipped with an infrared filter for white light illumination.
Photocatalytic activity of sulfur-doped titanium dioxide thin film under visible light irradiation:
a borosilicate glass dish (. phi.10 cm) was used as a photoreactor for photocatalytic evaluation of the films. Two 15W fluorescent lamps were used as the visible light source, and the initial concentration was 500. mu. g L according to the experimental conditions such as the initial concentration and pH of MC-LR of predecessors -1 MC-LR in reactor with MilliQ water solution, adjusting pH to 5.8, membrane with MilliQ water, drying under infrared lamp, and mixing with sulfur-doped TiO 2 The film was placed in solution for photocatalytic evaluation. 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 -5 W cm 2 (determined by a broadband radiation power meter). Samples of 0.2mL were taken at 0, 1, 3, 5 and 10 hours. The concentration of MC-LR in the samples was quantified using high performance liquid chromatography and the method reported by Antoniou et al. HPLC method used a Discovery HS C18 column (150 mm. times.2.1 mm, 3 μm particle size, Supelco). The flow rate was 0.2mL/min and the amount of sample was 20. mu.L. In the meantime, to solve the health and safety issues, all operations were conducted in a sterilized class III biosafety cabinet for MC-LR photocatalytic activity testing.
Results and discussion
Analysis of S-doped TiO 2 Physical properties of (a):
sulfur doped TiO 2 Ultraviolet-visible absorption spectra of samples calcined at different temperatures and compared with TiO 2 The controls were compared. As shown in FIG. 1, in order to obtain TiO 2 The indirect band gap value is obtained from the ultraviolet-visible light diffuse reflectance and the ultraviolet-visible light diffuse reflectance by adopting a Kubelka-Munk mitigation function Tauc diagram.
S350 and control TiO extrapolated from the Linear part of the Curve 2 The fading function (see fig. 1 (b)). In S-doped TiO 2 In the thin film group, S350 showed the strongest absorption in the visible range, compared with the same area control TiO 2 The absorption of (a) is very low. From the Tauc diagram, it was confirmed that the indirect band gap value of S350 was 2.94 eV, while that of the control TiO 2 3.18eV (FIG. 1(b)), which is comparable to TiO in anatase form 2 Very close (3.2 eV). Although significantly smaller than the S350 film (fig. 1(a)), we also observed a red shift in absorption when the S-doped films (S400 and S500) were calcined at higher temperatures. Observation of S-TiO from the above 2 Absorption spectrum shift, and the characteristics of the film show that S is doped by a sol-gel method of a self-assembled surfactant, and the film is an extended TiO 2 Is effective for photochemical activity in the visible light range.
FIG. 2 is S-SiO 2 X-ray diffraction (XRD) patterns under different calcination conditions. Anatase TiO 2 (A) Has clear and broad diffraction peak for S-TiO 2 The calcination was carried out, and it was found that increasing the calcination temperature resulted in S-TiO 2 The diffraction peaks of the samples gradually narrowed, indicating that TiO 2 The size and crystallinity of the crystal are increased. From the value of the (101) diffraction peak most intense in anatase under the condition of S350, the average grain size of the anatase smallest was determined to be 3nm using the Scherrer' S formula. Thus, a film annealed at a lower temperature can achieve a higher specific surface area, and the increase in surface area increases the number of photocatalytically active sites per unit mass of catalyst, thereby improving photocatalytic activity. Despite the TiO content 2 The small diameter of the nanoparticles may reduce the average distance of the initial electron-hole pairs and the average number of hops before the free holes, where the surface recombines with the trapped electrons, and this adverse size effect is not the dominant factor in this experiment.
S-TiO is shown by FIG. 3 2 The mesoporous materialTo N 2 Adsorption-desorption isotherms of (D), Table 1 summarizes the S-TiO 2 Specific surface area, total pore volume, porosity, crystal size and value of D (101) calcined at different temperatures. The Barrett, Joyner and Halenda (BJH) pore size distributions of S350 are narrower, indicating better uniformity of the pores, but the specific surface areas and pore volumes are significantly higher, 179.3. + -. 0.5m 2 g -1 And 0.13 cm 3 g -1 . During the calcination temperature rise, the overall structural performance of the material except the crystallinity is degraded due to sintering and crystal growth, but the material still maintains the highly porous characteristic at 400 ℃, but the S500 initial pore structure is seriously collapsed, so that the specific surface area is remarkably reduced, the pore size distribution is widened, and the obvious shift to the larger pore size distribution is realized. These results are in parallel with some recent observations regarding calcination temperature vs. TiO 2 The structural impact was studied consistently.
TABLE 1S-TiO calcination temperatures 2 Characteristic of the material
a: the amount of gas adsorbed was converted to liquid volume as determined by mercury intrusion under nitrogen at a relative pressure of 0.99.
b: based on pore volume and 3.9g/cm 3 Anatase density. Porosity (%) ═ pore volume (cm) 3 (ii)/g)/(pore volume (cm) 3 Volume of non-porous solid catalyst (cm) (/ g) 3 /g)) 100%; volume (cm) of non-porous solid catalyst 3 (g) ═ 1/nonporous solid catalyst density.
c: by X-ray diffraction (XRD), using Scherrer's formula, D ═ 0.9 λ/(B × cos θ), where λ ═ 0.154nm and B ═ maximum peak half width (FWHM) were obtained.
d: according to Bragg's law: d ═ λ/(2 × sin θ), where
FIG. 4 shows S-TiO 2 HR-TEM image and fast Fourier of thin filmThe results of the transform (FFT) analysis. S-TiO 2 As the calcination temperature was increased from 350 ℃ to 500 ℃, the average crystal size of the sample increased from 6.1nm to 9.9 nm, which is consistent with the corresponding change in crystallite size estimated from the XRD peaks. While in HR-TEM analysis with respect to S350 partially amorphous TiO was found 2 While S400 and S500 did not precipitate amorphous TiO 2 . Phase is to obtain TiO with good crystallization 2 The calcination temperature needs to be maintained at least 400 ℃. A clear loop was always observed in the FFT modes of fig. 4(a), (b) and (c), indicating that all samples had a dominant crystalline phase. In addition, the lattice stripe layer spacing of all samples is 0.350-0.352 nm, which is similar to that of TiO in FIG. 4.4(d), (e) and (f) 2 The 0.352nm lattice spacing of the anatase (101) face is similar. These results confirmed that all S-TiO 2 The samples all crystallized in the anatase phase, consistent with XRD analysis results.
Further research on S-TiO by Raman spectroscopy 2 The structural characteristics of (a). FIG. 5(a) shows S-TiO 2 And reference TiO 2 Raman spectra at 514.5 and 785 nm. All samples showed anatase TiO at both excitation wavelengths 2 The typical Raman-active mode of (a) corresponds to the XRD determined material phase composition. The raman spectrum is significantly narrowed and shifted after increasing the calcination temperature, especially at 500 ℃. Multi-peak fit spectra of Raman spectra indicated that the most intense anatase peak mode occurs at the Full Width Half Maximum (FWHM) (bracketed) 147(26) cm of the S350 sample -1 (E g )、403(37)cm -1 (B 1g )、522(44)cm -1 (A 1g ，B 1g ) And 635(55) cm -1 (E g ) In frequency, and in the case of S500, these parameters are transformed and scaled down to 143 (12) cm -1 (E g )、395(26)cm -1 (B 1g )、517(27)cm -1 (A 1g ，B 1g ) And 638(30) cm -1 (E g ). The latter parameter is related to the reference TiO 2 Is very close to, approaching the level of bulk anatase. This change can be explained by the partial release of the optical phonon confinement effect, resulting in broadening and blue-shifting of the raman mode in the nanomaterial. Anatase Raman lightThe spectral width is significantly reduced, the frequency shifts to higher wavenumbers, and the S500 sample is most pronounced, reflecting the calcination at higher temperatures of anatase crystals in S-TiO 2 And the results of XRD and HR-TEM are confirmed.
FIG. 5(b) shows the lowest frequency E in detail g The peak position and half-peak width changes in the mode are most commonly used to detect phonon confinement effects in anatase. These two parameters change dramatically as the calcination temperature is increased from 400 ℃ to 500 ℃, showing a significant increase in crystallinity from XRD results. However, the lowest frequency E relative to S500, S350 g Broadening of the mode (14 cm) -1 ) Much higher than its frequency shift (4 cm) -1 ) Clearly deviating from the linear proportionality of raman shift to FWHM derived from phonon confinement effect. E of S350 g Width of pattern (FWHM 26 cm) -1 ) Then close to the peak observed by phonon confinement model of nanocrystals with a size of 4nm (147 cm) -1 ) Specific prediction (-152 cm) -1 ) Much smaller. This difference means that except for the S-TiO calcined at lower temperatures 2 In addition to the reduced nanoparticle size, other factors such as strain and structural defects in the S350 and S400 films also affect the change in the anatase raman mode.
Further, careful analysis of the micro-raman spectrum revealed that a series of weak but distinct peaks appeared in S350 and S400 in addition to the phonon mode of the anatase main phase (fig. 5 (c)). Low frequency Raman bands at 246, 298, 323 and 362cm -1 A small portion of the brookite phase was observed, with surfactant-assisted sol-gel for TiO preparation 2 The situation is similar for nanomaterials. In the reference samples of the two excitation wavelengths, the Raman modes of the brookite are not resolved, whereas in S500 the Raman mode is 246cm -1 This relatively intense peak can still be traced back to the fact that the relatively large enhanced raman scattering of the anatase crystals masks all other features. Furthermore, at 450cm -1 And-580 cm -1 Two broad bands of significant relative intensity were also found, in particular S350 and S400, as shown in fig. 3. These bands are close to rutile TiO 2 Primary raman mode nanoparticles. At S350 andin the raman spectrum of S400, these two bands have higher spectral weights relative to anatase, and the rutile phase should also be detectable by XRD. However, S-TiO at different calcination temperatures 2 There was no trace of rutile in the XRD pattern. These bands are formed mainly by the lower calcination temperature resulting in the formation of less crystalline TiO 2 (amorphous TiO) 2 At 450cm -1 And-610 cm -1 Where a wider raman band appears), consistent with HR-TEM results for S350.
Fig. 6 shows ESEM images and AFM analyses of S350, S400 and S500 thin films. ESEM images show that there is no crack calcination process after S350 and S400 films. AFM analysis confirmed that the surface of the S350 film was very uniform and smooth, with a surface roughness of only 0.72 nm. This result shows that very fine nanoparticles are uniformly deposited on the glass substrate, filling the spaces between the particles, improving the rough film surface during dip coating. In the case of S500, cracks on the thin film were observed by ESEM analysis, and as shown in the figure, the generation of these cracks was caused by sintering and growth of crystals upon high-temperature firing.
Sulfur doped TiO 2 Electronic properties of the film:
XPS was used to identify TiO 2 The presence of sulfur in the film. As shown in fig. 7(a) - (c). Ar (Ar) + In the presence of S-TiO 2 The film was further etched for 40min to achieve the following: cleaning the film surface by removing the uppermost atomic layer and studying S in TiO 2 Incorporation into the crystal lattice. In this case, impurity peaks of Na 1s, Na 2s and C1s generated by adsorption of Na (leached from the glass substrate) and foreign C from the atmosphere in the original thin film are effectively suppressed during etching. FIG. 7(a) shows the reaction with Ar + Broad spectral measurement spectrum of S350 thin film after 40min of etching, where the predominant O, Ti and S elements can be determined by the corresponding O1S, Ti 2p and S2 p peaks. FIG. 7(b) shows a detailed comparison of Ar + In the S2 p nuclear level spectrum of S350 after etching, two broad peaks were observed at 161 and 168.5 eV. The XPS peak with a binding energy of 160-163eV in the S2 p nuclear energy level region is due to O 2- Quilt S 2- Resulting in the formation of a Ti-S bond at 167-The peak in the eV range is due to S 6+ And S 4+ The presence of these two higher valency S. In S-TiO 2 The formation of the latter peak is controversial, since it may be associated with Ti 4+ Is replaced by S 6+ /S 4+ Either in the presence of sulfate/sulfite groups (SO) 4 2- /SO 3 2- ) To which TiO is coordinated 2 By Ti with the surface 4+ Similar to the formation of titanium sulfide.
Ar + The etching obviously reduces the S2 p peak of the S350 film under higher binding energy, and reduces the sulfur content from 7.3 percent to about 4.1 percent. This indicates that the sulfur at the 168.5eV XPS peak is primarily derived from S-doped TiO 2 Surface with TiO 2 The presence of surface anchored sulfate groups. Notably, when sulfuric acid or a sulfate reagent is used as the sulfur source, S-TiO 2 In a systematic way present S 6+ /S 4+ XPS peak, but only when thiourea is used in the precursor solution, S 2 The XPS peak of (a) will appear. On the other hand, Ar at S350 + After 40min of etching, the S2 p peak was still present at 161eV, but did not change much, as shown in FIG. 7(b), demonstrating the substitution of S 2- Ions being introduced into the TiO 2 In the crystal lattice. Calcination at higher temperatures resulted in a gradual decrease in the intensity of the two S2 p peaks, with a decrease in sulfur content from 4.1% of S350 to 0.7% of S500, indicating that the annihilation of sulfur was concentrated on the thermal anneal.
FIG. 7(d) shows sulfur-doped TiO 2 Comparison of the FT-IR spectrum of (a) with a reference film. The presence of Ti-S and Ti-O-S bonds can be considered from the following points: at 1127 and 1046cm -1 There are distinct bands corresponding to S-O (1130 cm) -1 ) And Ti-S (1045 cm) -1 ) And (5) vibrating. On the other hand due to SO 4 2- With radicals bound to TiO 2 And at-1400 cm -1 Expected to appear characteristic S ═ O stretching modes, and the existence of the S ═ O stretching modes is expected to be in a frequency range (1000- -1 ) The same is true. However, in the latter case, S-TiO 2 No banding was observed on the film, indicating that a small amount of sulfate groups were present on the surface of the hydrous titanium dioxideOr, most likely, surface sulfates in the form of high ions, where the S-O vibration band moves below 1300 cm.
For independent determination of the sulfur content and its use in S-TiO 2 EDX analysis was performed on different samples. In EDX analysis as shown in fig. 8, elements of Na, Al, Ca, K, Si, and V leached from the glass substrate during the heat treatment were detected, and the obtained data showed that the S distribution was uniform but the content thereof decreased with an increase in the firing temperature (5.8% for S350 and 3.7% for S400) as shown in fig. 8 (d). In EDX analysis, the content of sulfur was higher than that measured by XPS after etching, but sulfur was not detected in S500. This result is likely due to the different resolution of each instrument. In addition, no carbon element was detected by EDX, indicating that annealing at 350 ℃ for 2 hours was sufficient to remove residual C in the film.
TiO 2 Inducing the existence of paramagnetic center under the irradiation of visible light, and using electron paramagnetic resonance spectrum to S-TiO 2 A study was conducted. FIG. 9 compares the EPR spectra of S350 and S400 at 10K temperature in the dark and in the visible (440-460nm) for different samples. The S350 sample showed abundant spectra under dark and uv illumination at 10K, with the EPR powder spectrum having an extended fine structure in the dark (fig. 8 a)).
The origin of this spectrum and TiO 2 The spectrum of the anisotropic EPR powder with a single paramagnetic center with the expected spin S-1/2 cannot be determined (or with sulfur-containing radicals), where 33 The natural abundance of the S isotope is very low (0.76%), and the detection of hyperfine structures is excluded (I ═ 3/2). Visible light irradiation has no influence on the EPR spectrum expanded by S350, and the EPR spectrum disappears after high-temperature calcination, which indicates that the bottom layer has the characteristic of poor paramagnetic thermal stability. On the high-sulfur surface of S350 nanoparticles, high spin (S) due to coupling of sulfur radicals with anisotropic g tensor>1/2) paramagnetic center (e.g. SO) 4- ) From XPS and EDX results, the EPR spectral origin of S350 can be explained, where the apparent presence of zero-field splitting can explain the extended fine structure.
On the other hand, the EPR spectrum obtained under visible light and dark light was subtracted. A single stenosis at g-2.0040 (5) is disclosedThe peak width of the EPR line of (a) is 9G, this line is masked by the extended EPR spectrum of S350 in the dark (. under visible illumination, the individual EPR line of S400 is significantly enhanced at G2.004, the extended EPR spectrum is completely suppressed in this case, the original S400 sample in the dark easily recognizes the individual EPR signal, while its intensity increases sharply under visible illumination (by 7 times within 10 min), but no shift or broadening is observed 2 None at all. In connection with this, a series of weak EPR lines were observed in the dark, which are Ti of anatase 3+ The site has the characteristics of an oxygen-related center and a captured electron.
Under the illumination of UV-Vis, the EPR spectral intensity is obviously enhanced, and the most obvious is an anisotropic EPR powder spectrum with diamond g tensor and a principal value g x ＝2.023,g y 2.009 and g z 2.003, due to the formation of superoxide radical (O) after capture of anatase surface pores 2 - ) And the result is that. The unique evolution of the individual EPR signals under visible light, derived from XPS and EDX, and their photocatalytic activity towards MC-LR degradation, has a good correlation, indicating that the origin of the EPR line is related to the doping of sulfur and TiO 2 The modification of the lattice structure of (A) is closely related and can be considered to be due to S 2- Replacing the doped oxygen to form localized interstitial internal state ions. The sub-gaps of these impurity states are illuminated by visible light (mainly concentrated on the two magnets), making the TiO less dense due to the lower EPR intensity of the starting material 2 The electrons in (1) are excited, and a local non-paired electron is left while excitation is carried out, so that the situation that the electrons in TiO are excited can be explained 2 Is visible light activated EPR signal in the conduction band. Another explanation is based on single electron trapping in oxygen vacancies, formally positively charged F + Color center, which produces a clear EPR line at g-2.004, with significant enhancement under visible light illumination. TiO2 2 The TiO with negative ion doping and reduction needs to form oxygen vacancy in crystal lattice while doping sulfur, and has visible light activity 2 The materials all have this distinct feature and are in sulfated TiO 2 Especially obvious in the middle. In this case, visible light is excitedTiO 2 The increase in the intensity of the EPR signal (g ═ 2.004) under visible illumination can also be explained by the empty (donor) state of the valence band electrons, or by the more complex electron transition pathway involving electron extraction from the F color center (electron pairs trapped in the oxygen vacancy).
Sulfur doped TiO 2 Photocatalytic activity of the film:
research into S-TiO under visible light conditions 2 Photocatalytic activity of (1). FIG. 10(a) shows S-TiO calcined at different temperatures at pH 5.8 2 Degradation of MC-LR by several films. All of the S-TiO under the above conditions 2 The film shows obvious photocatalytic activity on the degradation of MC-LR, wherein the degradation performance of S350 is the best. On the other hand, TiO is used in dark or visible light conditions 2 The control film has no obvious sign of degradation to MC-LR, and the residual quantity of MC-LR is similar. In addition, according to previous work, MC-LR was not degraded under visible light as observed using Degussa P25 film. It is therefore believed that the photocatalytic activity of these films in the visible light region is due to the effective doping of sulfur and the increase in the specific surface area and porosity of the films after doping (fig. 10 (b)). To verify the S-TiO 2 The photocatalytic activity of the film under visible light irradiation was measured under the condition of pH 5.8 in a control experiment (FIG. 10 (c)). The adsorption of MC-LR in the dark and the photocatalytic degradation under visible light irradiation were carried out in a control experiment over a period of 5 hours by adjusting the pH of the solution to 5.8. After 5 hours, MC-LR remained around 65% of the initial concentration for dark adsorption and 33% for photocatalytic degradation. Then in successive experiments (FIG. 10(c)), both reactors were placed in dark conditions, since TiO is responsible for the 2 And MC-LR were both negatively charged, so their pH was increased to the basic range (pH 9.3) to observe the desorption of MC-LR. Under the condition of pH 9.3, after the first 30min, the recovery rate of MC-LR under dark adsorption is 90%. The recovery rate of the MC-LR degraded by photocatalysis is only 38 percent. After 7h (total time 12h), the recovery of MC-LR was 92% and 40% of the initial concentration, respectively. These results show that S-TiO 2 Photo-induced electron transfer may occur on the surface of the film and MC-LRThe MC-LR is effectively degraded under the irradiation of visible light. Furthermore, the study showed the use of S-TiO 2 The membrane has higher adsorption capacity to MC-LR under experimental conditions. The results of the experiment concerning the recycling of the thin film are shown in FIG. 10(d), and the photocatalytic activity of S350 was slightly decreased when the same film was repeatedly tested under visible light irradiation for 10 hours. The film still maintains higher activity of degrading MC-LR by photocatalysis in 3 times of cycle experiments. All test results show S-TiO 2 The film has strong mechanical stability and reusability under experimental conditions.
Conclusion
With H 2 SO 4 As a sulfur source, the visible light activated S-TiO is successfully synthesized by adopting a novel sol method based on self-assembly technology 2 And the film adopts nonionic surfactant to control the nano structure of the film. Research into S-TiO 2 The morphology, structure, optical and porous properties of the film, the results show that the properties of the film are significantly dependent on the calcination temperature. According to XPS, FT-IR and EDX spectra, at TiO 2 The crystal lattice is mainly identified as anion (S) 2- ) Substituents other than cations, in which the cation S is present 6+ /S 4+ The cations are primarily associated with surface sulfate groups, but the distribution of the cations in the membrane is relatively uniform. In S-TiO 2 A significant shift of the optical absorption edge towards the visible region is found. At 2.004 g, a single EPR line is found, and the strength of the EPR line depends on the content of sulfur and the change of the photocatalytic activity of the material: the EPR intensity is obviously enhanced under the irradiation of visible light, which indicates that TiO 2 There is a band gap caused by local energy state anion doping and/or oxygen vacancy. Calcining S-TiO prepared for 2 hours at 350 DEG C 2 The film has the characteristics of highest sulfur content, highest specific surface area, small crystallite size, high porosity, large pore volume and very smooth and uniform surface, and the mesoporous S-TiO 2 The film is the photocatalyst which is most effective in degrading MC-LR under the irradiation of visible light, and the explanation also shows that the roasting temperature is an important factor influencing the modification effect. Thus, the sulfuric acid-based sol-gel process produces nanostructured S-TiO 2 The film is used as ambient visible lightThe catalyst is useful and has a certain positive significance for degrading harmful organic matters in the environment.
By means of the scheme and test result analysis, the invention at least has the following advantages: the mesoporous S-TiO has unique and excellent performance, and is irradiated by ultraviolet light and visible light 2 The film is a photocatalyst effective in degrading MC-LR under irradiation of visible light. The drinking safety is guaranteed.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (4)
1. A preparation method for degrading microcystin aggregates in drinking water at construction sites is characterized by comprising the following steps: the aggregate is S-modified monodisperse TiO2 aggregate, and the preparation steps are as follows:
s1: adopting nonionic surfactant polyoxyethylene (80) sorbitol monooleate as a guiding pore agent;
s2: dissolving polyoxyethylene (80) sorbitol monooleate in isopropanol, adding titanium (IV) isopropanol as an alcohol oxygen precursor to the mixture of isopropanol and polyoxyethylene (80) sorbitol monooleate, and finally adding sulfuric acid as a reagent for a sulfur precursor and in-situ water;
s3: stirring the solution at room temperature for 24h to obtain a yellowish, transparent, uniform and stable solution; the pH value of the solution is 3.0 +/-0.2, and the viscosity is 6.48 +/-0.12 cP;
s4: preparing an S-doped TiO2 film by adopting a dip-coating method, and taking borosilicate glass as a substrate;
s41: before dip coating, the whole surface is washed with MilliQ grade water, then washed with ethanol, and then dried under an infrared lamp, and the effective surface area is 10cm 2 Dip coating to control the extraction speed to be 12.3 +/-0.5 cm/min;
s42: after dip coating, the coating is put into a multi-section programmable high-temperature furnace for calcining, and the processes of dip coating and calcining are repeated for 5 times to obtain a 5-layer film.
2. The method for preparing microcystin aggregates in degradable construction site drinking water as claimed in claim 1, wherein: in the step S42, the roasting temperature and time of each layer are controlled at 350 ℃ for 2 hours, 400 ℃ for 30min and 500 ℃ for 20min respectively, all organic matters are removed, and then the layer is naturally cooled.
3. The method for preparing microcystin aggregates in degradable construction site drinking water as claimed in claim 1, wherein: in the step S42, the thickness of each film was 1.02. + -. 0.02. mu.m, and the total mass was 4.51. + -. 0.18 mg.
4. The method for preparing microcystin aggregates in degradable construction site drinking water as claimed in claim 1, wherein: in step S3, the molar ratio of the starting materials was polyoxyethylene (80) sorbitol monooleate, isopropanol, titanium (IV) isopropanol, sulfuric acid 1: 45: 1.
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| CN113385192A (en) * | 2021-05-31 | 2021-09-14 | 中国十七冶集团有限公司 | Sulfur-doped TiO for water purification system of construction site2Method for producing thin film |
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| WO2016146944A1 (en) * | 2015-03-19 | 2016-09-22 | Institut National Polytechnique De Toulouse | Method for preparing materials made from sulfur-doped titanium dioxide, materials obtained and applications in photocatalysis |
| CN113385192A (en) * | 2021-05-31 | 2021-09-14 | 中国十七冶集团有限公司 | Sulfur-doped TiO for water purification system of construction site2Method for producing thin film |
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