Visible light assisted Fenton reagent with wide pH value application range and preparation method and application thereof
1. A visible light assisted Fenton's reagent with a wide pH application range, wherein the molecular formula of the reagent is (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2O, wherein phen represents phenanthroline ligand, the crystal of the reagent belongs to an orthorhombic system, the space group is Pbcn, and the unit cell parameter is
2. A method for synthesizing fenton-like reagents with a wide pH application range according to claim 1, characterized by comprising the steps of:
1) under the condition of inert atmosphere, dissolving cobalt chloride hexahydrate in water, adding phenanthroline ligand, heating and stirring to react to obtain a mixed solution A;
2) will be (NH)4)2MoO4And KH2PO4Dissolving in water and stirring uniformly to prepare a mixed solution B;
3) quickly mixing the mixed solution A and the mixed solution B, and transferring the mixed solution A and the mixed solution B to a reaction kettle for reaction under a hydrothermal condition;
4) and cooling, filtering, washing and drying the hydrothermal reaction product to obtain the Fenton-like reagent.
3. The method for synthesizing fenton-like reagent having wide pH application range according to claim 2, wherein the molar ratio of cobalt chloride hexahydrate, phenanthroline and water in step 1) is 1.2:1: 350.
4. The method for synthesizing fenton-like reagent having wide pH application range according to claim 2, wherein the heating temperature in step 1) is 80 ℃ and the stirring reaction time is 2.5 hours.
5. The method for synthesizing Fenton's reagent having a wide pH value application range according to claim 2, wherein the step (NH) of step 2) is performed by4)2MoO4、KH2PO4And water in a molar ratio of 3:2: 400.
6. The method for synthesizing fenton-like reagent having wide pH application range according to claim 2, wherein the hydrothermal reaction temperature in step 3) is 180 ℃ and the hydrothermal reaction time is 7 days.
7. Use of the visible light assisted fenton's reagent with a wide pH application range according to claim 1, characterized by the following steps: under the condition of no light, reagent (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2Adding the O solution into the organic pollutant solution, mixing and stirring until adsorption balance is achieved, and then adding H with the mass percent concentration of 30% according to the volume ratio of 1:1002O2The aqueous solution is subjected to photocatalytic degradation reaction of organic pollutants by using a 300W xenon lamp as a visible light source at 25 ℃ under the condition of continuous stirring.
8. Use of the visible light assisted fenton's reagent with a wide pH application range according to claim 7, characterised in that the reagent (H) is3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2The concentration of the O solution was 40 mg/L.
9. The use of a visible light assisted fenton's reagent with a wide pH application range according to claim 7, wherein the organic contaminant solution is selected from one of methyl orange solution or rhodamine B solution.
10. The use of the visible light-assisted fenton reagent with a wide pH application range according to claim 7, wherein the concentration of the organic contaminant solution is 20mg/L and the pH is 3 to 9.
Background
Well-known made of FeII+H2O2The formed Fenton reaction is a high-level oxidation reaction system, has extremely strong oxidation capacity and no selectivity, and can almost oxidize and degrade all organic pollutants; among them, solid-phase light (especially visible light) assisted (similar) fenton catalyst can utilize light energy to catalyze and degrade organic pollutants more effectively, and the catalyst can be recovered and recycled effectively, which is of great interest. However, the narrow pH range (usually 3-5) of conventional photo-Fenton reagent applications often produces some large negative effects, such as: the inability to treat basic contaminants, the tendency to generate other toxic materials under acidic conditions, and the increased cost of treatment, etc., limit its practical application in some fields. So far, studies reporting photo-Fenton catalytic agents with a wide pH range of application (especially alkaline) have been very rare. Therefore, the development of a new class of photo (especially visible light) Fenton catalytic agents with wider pH value application range has very important theoretical research significance and practical application value (dosage L., Soares P., Ayude M.et al. enhancement of a synthetic co-reactive by using catalytic agents for the treatment of the reaction of a synthetic co-reactive wastewater [ J].Chem.Eng.J.2015,277:86-96；An,X.,Tang,Q.,Lan,H.et al.Polyoxometalates/TiO2 Fenton-like photocatalysts with rearranged oxygen vacancies for enhanced synergetic degradtion[J].Applied Catalysis B:Environmental,2019,244,407-413.)。
In recent years, there has been much research on polyoxometalate-modified fenton systems, such as: PW (pseudo wire)12O40 3-System of/Fe (IV), AspPW12System of/Fe (III), AspSiW12System of/Fe (III), Ti2O/Fe-POM system, and the like. However, most of these fenton reagents are complex systems and have the common defects that: 1) the application range of the pH value is still narrow; 2) along with the reaction, the composite components are easy to separate from each other, so that the reaction efficiency is suddenly reduced; 3) it is necessary to use ultraviolet light as an excitation light source. (Chen L., Li X., Zhang J.et al.production of Hydroxyl Radical via the Activation of Peroxide by Hydroxylamine [ J].Environ.Sci.Technol.2015,49:10373-10379；Yu Q.,Feng L.,Chai X.et al.Enhanced surface Fenton degradation of BPAin soil with a high pH[J].Chemophere,2019,335-343.)
Disclosure of Invention
The invention aims to provide a visible light-assisted Fenton reagent with a brand-new structure and a wide pH value application range, and a preparation method and application thereof, and the solution of the invention is as follows:
a visible light assisted Fenton's reagent with a wide pH application range, wherein the molecular formula of the reagent is (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2O, wherein phen represents a phenanthroline ligand; the crystal of the reagent belongs to an orthorhombic system, the space group is Pbcn, and the unit cell parameter is
The synthetic method of the Fenton-like reagent with the wide pH value application range comprises the following steps:
1) under the condition of inert atmosphere, dissolving cobalt chloride hexahydrate in water, adding phenanthroline ligand, heating and stirring to react to obtain a mixed solution A;
2) will be (NH)4)2MoO4And KH2PO4Dissolving in water and stirring uniformly to prepare a mixed solution B;
3) quickly mixing the mixed solution A and the mixed solution B, and transferring the mixed solution A and the mixed solution B to a reaction kettle for reaction under a hydrothermal condition;
4) and cooling, filtering, washing and drying the hydrothermal reaction product to obtain the Fenton-like reagent.
Preferably, the molar ratio of the cobalt chloride hexahydrate, the phenanthroline and the water in the step 1) is 1.2:1: 350.
Preferably, the heating temperature in step 1) is 80 ℃ and the stirring reaction time is 2.5 hours.
Preferably, (NH) described in step 2)4)2MoO4、KH2PO4And water in a molar ratio of 3:2: 400.
Preferably, the hydrothermal reaction temperature in step 3) is 180 ℃, and the hydrothermal reaction time is 7 days.
The application of the visible light assisted Fenton reagent with the wide pH value application range comprises the following steps: under the condition of no light, reagent (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2Adding the O solution into the organic pollutant solution, mixing and stirring until adsorption balance is achieved, and then adding H with the mass percent concentration of 30% according to the volume ratio of 1:1002O2The aqueous solution is subjected to photocatalytic degradation reaction of organic pollutants by using a 300W xenon lamp as a visible light source at 25 ℃ under the condition of continuous stirring.
Preferably, the reagent (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2The concentration of the O solution was 40 mg/L.
Preferably, the organic contaminant solution is selected from one of a methyl orange solution or a rhodamine B solution.
Preferably, the concentration of the organic pollutant solution is 20mg/L, and the pH value is 3-9.
The principle of the invention is as follows:
the visible light-assisted Fenton reagent (H) with wide pH value application range provided by the invention3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2O is a bonding type compound having a completely new structure, and it can be seen from its crystal structure (as shown in FIG. 1) that the compound is a molybdenum-phosphorus-oxygen atom cluster ([ Mo ] with a Stranberg configurationVI 5O15(PO4)2]6-) A one-dimensional divalent cobalt-containing compound co-modified with an organic ligand (phen). The compound is applied to degradation research of organic pollutants as a Fenton-like reagent, and results show that the compound is even at pH 9, visible light and H2O2Under the condition, the degradation rate of the compound to common organic pollutants (methyl orange and rhodamine B) within 50 minutes exceeds 93 percent. The main reason why the compound has good performance of catalyzing and degrading organic matters is that the compound can be regarded as 'single-component' Fenton-like reagent (Co)2+Is a catalytic center), so that the problem that the components in the composite catalytic system are easy to mutually separate is avoided, and the polyoxometallate and the organic ligand phenanthroline (phen) in the compound structure can change the catalytic center of the Fenton reagent and H through the combination of a delocalized electron-rich conjugation effect and a ligand effect2O2The redox potential of the reaction is increased to broaden the application range of the pH value (Zhang Y., Zhou M.A critical review of the application of chemical reagents to enable Fenton-like reagents at high pH values [ J]Journal of Hazardous materials.2019,362: 432-. In addition, the polyoxometallate to which the compound belongs is a nontoxic, stable and structurally adjustable multifunctional compound which is rich in electrons and has the characteristic of large delocalized electron conjugation; with a cageThe characteristics of the structure and strong acid, strong oxidation, high negative charge and pseudoliquid phase are the reasons for their particular suitability as cocatalysts, and have been widely used in various homogeneous and heterogeneous catalytic systems (Long D. -L., Cronin L. purification of the front in polyoxometalates and metal oxide reactor systems [ J. ]]Dalton Transactions,2012,41:202-207.)。
Compared with the existing other polyoxometallate modified cluster compound Fenton reagent, the method has the following advantages:
(1) the visible light-assisted Fenton reagent with wide pH value application range provided by the invention is a brand-new molybdenum-phosphorus-oxygen atom cluster ([ Mo ]VI 5O15(PO4)2]6-) A one-dimensional divalent cobalt-containing compound co-modified with an organic ligand (phen); the method provides a new idea for reference for the preparation of the bonded single-component catalytic reagent and the subsequent synthesis of related materials. The study of the structure and property relationships of polyoxometalate-based catalytic materials would also be a significant effort.
(2) The preparation method of the visible light-assisted Fenton reagent with the wide pH value application range is simple, and the yield can reach 67 percent (calculated based on the content of cobalt).
(3) The visible light-assisted Fenton reagent with wide pH value application range provided by the invention can be used as a high-efficiency solid-phase light-assisted Fenton reagent, and has the advantages of visible light response, wide pH value application range, stable property, reusability and the like.
(4) The visible light-assisted Fenton reagent with wide pH value application range provided by the invention can provide a new thought for preparing a new polyoxometallate-based functional material with structure guidance.
Drawings
FIG. 1 Compound (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2Crystal structure of O.
FIG. 2 Compound (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2An X-ray energy spectrum (EDS) elemental qualitative analysis test result chart of O.
FIG. 3 Compound (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2X-ray photoelectron spectroscopy (XPS) test results of O.
Compound of FIG. 4 (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2And an experimental determination X-ray powder diffraction (XRD) of O, a theoretical simulation XRD and an XRD contrast analysis result chart of the experimental determination after the compound is used as a photocatalyst to catalyze and degrade methyl orange and rhodamine B.
FIG. 5 Compound (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2And O is used as a test result graph of the photocatalyst for catalyzing and degrading the methyl orange and the rhodamine B under different initial pH values.
Compound of FIG. 6 (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2And O is used as a stability and repeatability test result chart of the photocatalyst for catalyzing and degrading methyl orange and rhodamine B when the initial pH value is 9.
FIG. 7 Compound (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2And when the initial pH value of O is 9, the obtained product is used as a Fourier transform infrared spectroscopy (FT-IR) test comparison analysis result graph before and after a photocatalyst catalytic degradation methyl orange and rhodamine B test.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and examples. It is also to be understood that the following examples are intended to illustrate the present invention and are not to be construed as limiting the scope of the invention, and that the particular materials, reaction times and temperatures, process parameters, etc. listed in the examples are exemplary only and are intended to be exemplary of suitable ranges, and that insubstantial modifications and adaptations of the invention by those skilled in the art in light of the foregoing description are intended to be within the scope of the invention.
Example 1:
(H3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2the synthesis steps of the O complex are as follows:
1) the required equipment and reagents are first moved into a glove box. After argon (Ar) is filled, sequentially adding distilled water (30.0mL) and cobalt chloride hexahydrate (1.150g) into a conical flask with a small diameter under the condition of continuous stirring for complete dissolution, then adding phenanthroline (0.75g), adjusting the temperature of a constant-temperature magnetic stirrer to 80 ℃, and stirring for reacting for 2.5 hours to obtain a mixed solution A;
2) will be (NH)4)2MoO4·4H2O(1.800g)、KH2PO4(0.560g) and distilled water (15mL) to obtain a mixed solution B;
3) stirring the mixed solution A and the mixed solution B by a glass rod according to the volume ratio of 2:1, quickly mixing, quickly transferring to a 30mL polytetrafluoroethylene stainless steel reaction kettle, wherein the loading of the reaction kettle is about 75%, and carrying out hydrothermal reaction at 180 ℃ for one week;
4) and closing the electric heating constant-temperature drying box, naturally cooling the reaction kettle along with the temperature of the drying box, filtering the final target product, and washing the final target product with distilled water to obtain reddish brown blocky crystals, wherein the yield is 67 percent (calculated based on the content of cobalt). The chemical formula is determined to be (H) through X-ray single crystal diffraction measurement, structure analysis and structure characterization3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2And O. Elemental analysis calculation: (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2O: theoretical calculation value: mo, 30.57; co, 7.52; p, 3.95; c, 18.34; n, 3.57; h, 2.42; the experimental measurement value is that Mo, 29.75; co, 7.93; p, 4.18; c, 17.55; n, 3.19; h, 2.63. The theoretical calculation result of the valence of the variable valence element is as follows: mo1(6.12), Mo2(6.13), Mo3 (6.14); co1 (2.32); p1 (4.81).
Characterization of the reddish brown bulk crystals obtained above:
TABLE 1
(1) Structural characterization:
selecting the single crystal with regular shape and proper size obtained in the above example 1, placing the single crystal in a condition of 293(2) K and using graphite to monochromate Mo-K alpha rays for a Rigaku RAXIS-IV single crystal diffractometerAs an incident light source, in a certain theta rangeAnd collecting diffraction points in a scanning mode for structural analysis and correction. The non-hydrogen atoms are solved by a direct method, and the coordinates and the anisotropic thermal parameters of the non-hydrogen atoms are corrected by a full matrix least square method. Mixed hydrogenation, wherein hydrogen atoms adopt isotropic thermal parameters; non-hydrogen atoms adopt anisotropic thermal parameters. The resolution of the crystal structure and the structural modification are done by the SHELXT (Sheldrick,2015) and SHELXL-2015(Sheldrick,2015) packages, respectively. Detailed crystallographic and structural modification data are shown in table 1, and the structure is shown in figure 1.
From the above analysis of the single crystal structure, (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2The crystal of O belongs to an orthorhombic system, a space group Pbcn and unit cell parameters of
(2) Qualitative analysis of X-ray energy spectrum (EDS) elements and quantitative analysis of inductively coupled plasma emission spectroscopy (ICP) elements:
the elemental analysis results were: the experimental value is 29.75; co, 7.93; p, 4.18; c, 17.55; n, 3.19; h,2.63, theoretical: mo, 30.57; co, 7.52; p, 3.95; c, 18.34; n, 3.57; h, 2.42; the results of elemental qualitative analysis by X-ray spectroscopy (EDS) are shown in fig. 2: further, the synthesized compound contains C, N, O, P, Co and Mo. From these two analyses combined with X-ray single crystal diffraction, the brown bulk crystal obtained can be determined to have the chemical formula (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2O。
(3) X-ray photoelectron spectroscopy (XPS):
to (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2The crystal of O is subjected to XPS characterization, and an XPS energy spectrum is shown in FIG. 3, and the valence of variable valence elements in the compound is calculated by combining theory, so that the valence results are as follows: mo1(6.12), Mo2(6.13), Mo3 (6.14); co1 (2.32); p1 (4.81); from the results, it was found that the synthesized compound contained cobalt in a lower valence state +2 and molybdenum in a higher valence state +6, respectively.
(4) X-ray powder diffraction (XRD):
para compound (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2The X-ray powder diffraction (XRD) characterization of O is carried out, and the experimental result and the theoretical simulation result are shown in figure 4: the results show that the simulated value of the powder diffraction of the synthesized compound can be well matched with the experimental value, the structural analysis of the synthesized compound is proved to be correct, and the obtained product has high phase purity; at the same time, as a Fenton-like photocatalyst compound (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2The comparison result of the actually measured XRD after the catalytic degradation reaction of methyl orange and rhodamine B and the XRD pattern before the reaction is also highly consistent, and the compound (H) is proved3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2And in related photocatalysis experiments, the crystal form is kept complete and the structure is stable.
(5) As fenton-like reagents, catalytic efficiency tests for degradation of organic pollutants (methyl orange and rhodamine B):
in the absence of light, the concentration of (H) is 40mg/L3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2The O solution and methyl orange solution or rhodamine B solution (the concentration is 20 mg.L) which is adjusted to different pH values (3-9) by using 0.1M HCl solution or 0.1M NaOH solution in advance-1) Mixing and stirring for 30 minutes to reach adsorption balance; then 30% H is added in the ratio V/V1: 1002O2The aqueous solution is subjected to photocatalytic degradation reaction at a constant temperature of 25 ℃ under the condition of continuous stirring by taking a 300W xenon lamp as a visible light source; detecting the degraded pollutants by using an ultraviolet-visible (200 nm-1500 nm) absorption spectrometer and a spectrophotometer (the characteristic absorption wavelength is 464nm for methyl orange and 554nm for rhodamine B) every 10 minutes; and drying the photocatalyst after reaction after high-speed centrifugal separation for repeated use or subsequent stability test. Compound (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2The experimental results of the degradation test of organic pollutants (methyl orange and rhodamine B) performed under different pH values and visible light assisted conditions with O as a fenton-like reagent are shown in fig. 5: the results of the absorbance (fig. 5a and 5B) and uv-vis (fig. 5c and 5d) measurements on the degradation products of methyl orange and rhodamine B show that: the synthesized compound is used as a Fenton reagent, has high catalytic degradation efficiency on both methyl orange and rhodamine B under the conditions of visible light excitation and pH (3-9), and has a degradation rate of 93% in 50 minutes.
(6) As fenton-like reagents, stability and reproducibility tests during degradation of organic contaminants (methyl orange and rhodamine B):
compound (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2And O is used as a Fenton-like reagent, and the stability and repeatability of degradation of organic pollutants (methyl orange and rhodamine B) are tested under the conditions of pH 9 and visible light assistance. (H)3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2O as a Fenton-like reagent is recovered and reused for 4 times in photocatalytic degradation experiments of methyl orange and rhodamine B. The experimental results are shown in fig. 6, and the results show that: the synthesized compound has good chemical stability, and the repeated utilization rate exceeds 87%. Further, compound (H) at pH 9 and assisted by visible light3O)2[CoII(phen)(H2O)2]2[MoVI 5O15(PO4)2]·4H2The experimental result of the Fourier transform infrared spectroscopy (FT-IR) comparison of the organic pollutants (methyl orange and rhodamine B) before and after the degradation by using O as the Fenton-like reagent is shown in FIG. 7, and the result shows that: the infrared spectrograms before and after the reaction are almost maintainedIn line, the chemical stability of the synthesized compound in the above-mentioned photocatalytic degradation of organic pollutants was also further confirmed.
