Preparation method and application of hematite material rich in oxygen vacancy type metal doping

Abstract

A preparation method and application of a hematite material rich in oxygen vacancy type metal doping, the present invention relates to a preparation method and application of a hematite material rich in oxygen vacancy type metal doping. In order to solve the problem of low removal rate of pollutants in water degraded by metal oxide activated PMS, the present invention synthesized α-Me x Fe 2‑x O3 materials are rich in OVs, which increases their active sites. The synergistic effect of the double metal ions further improves the catalytic efficiency. x Fe 2‑x O3 material has good catalytic performance and has a good performance at low α-Ni 0.2 Fe 1.8 Under the dosage of O3 and PMS, ACF can achieve a removal rate of 100% within 20 minutes. It still has high catalytic activity during multiple cycles, and the removal rate of aceclofenac is still as high as 82% after 5 cycles. The invention is applied to the field of water treatment technology.

Description

Technical Field

[0001] The present invention relates to a kind of hematite (α-Me x Fe 2-x O3) material preparation method and application. Background Art

[0002] Hematite (α-Fe2O3) is one of the most stable iron oxide materials and is widely used in advanced oxidation processes in water treatment (catalytic ozone oxidation, Fenton-like oxidation, photocatalytic oxidation, and catalytic persulfate oxidation, etc.). ·- ) as the leading advanced oxidation technology due to SO4 ·- The strong oxidizing properties of hematite (α-Fe2O3) have been widely studied. Generally, the efficiency of hematite (α-Fe2O3) as a catalyst to activate permonosulfate (PMS) is low, so it needs to be further improved. Oxygen vacancies (OVs) are a type of anion defect, which is formed by the separation of lattice oxygen under specific conditions to produce a lower binding energy on the oxide surface. OVs can change the structure of the material and the chemical properties of its surface, directly affecting its ionic / electronic properties, crystal structure, transport properties, and the absorption / desorption of reactants and reaction intermediates. OVs can effectively capture charge carriers and act as electron transfer stations to accelerate the charge transfer rate of electrons or holes, reduce the energy barrier of the reaction, and thus show excellent catalytic activity and stability. Based on this, the introduction of OVs can effectively improve the activation of metal oxides to decompose PMS to produce SO4 ·- effectiveness. Summary of the invention

[0003] The purpose of the present invention is to solve the problem of low removal rate of pollutants in water degraded by metal oxide activated PMS, and provide a hematite (α-Me x Fe 2-x O3) material preparation method and application.

[0004] The preparation method of a metal-doped hematite material rich in oxygen vacancy type according to the present invention is carried out according to the following steps: first, dissolving an inorganic divalent metal salt and an inorganic iron salt in deionized water, stirring to adjust the pH, and obtaining a solution A; wherein the molar ratio of the inorganic divalent metal salt to the inorganic iron salt is 0.005-0.5:1; second, activating, precipitating, filtering, and drying the solution A to obtain a precursor; and third, transferring the precursor to a muffle furnace, calcining at 300-1000° C., cooling, taking out, and grinding to obtain the metal-doped hematite material rich in oxygen vacancy type.

[0005] The present invention discloses a kind of hematite (α-Me x Fe 2-xApplication of O3) materials in activating persulfate to degrade pollutants in water.

[0006] The present invention synthesizes metal-doped hematite (α-Me) rich in oxygen vacancies by isomorphous substitution technology. x Fe 2-x O3) activates persulfate to produce reactive oxygen species (ROS) that can degrade pollutants. Isomorphous substitution refers to the phenomenon that an atom in the crystal structure of a clay mineral is replaced by another ion of similar size and typicality without destroying the crystal structure. It usually occurs between atoms of similar size and the same electrical properties. During the synthesis process, due to the intervention of divalent ions, oxygen vacancies are generated on the surface of the material and more Lewis acid sites are exposed. Oxygen vacancies and Lewis acid sites react with HSO5 - Forming surface complexes, ROS (SO4 ·- , OH, O2 ·- , 1 O2, SO5 ·- ), ROS attacks pollutants and eventually converts them into small molecules. During the reaction, the circulation between metal ions Me(Ⅱ) / Me(Ⅲ) and Fe(Ⅱ) / Fe(Ⅲ) makes α-Me x Fe 2-x O3 maintains its excellent catalytic performance after multiple cycles.

[0007] The present invention has the following beneficial effects:

[0008] α-Me synthesized by the present invention x Fe 2-x O3 materials are rich in OVs, which increases their active sites, and the synergistic effect of the double metal ions further improves the catalytic efficiency. x Fe 2-x O3 material has good catalytic performance and has a low α-Ni 0.2 Fe 1.8 Under the conditions of O3 and PMS dosage, ACF can achieve 100% removal rate within 20 minutes. It still has high catalytic activity during multiple cycles, and the removal rate of aceclofenac is still as high as 82% after 5 cycles. It has the advantages of easy separation and recovery, convenient storage and transportation, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is α-Ni 0.2 Fe 1.8 XRD spectra of O3 and α-Fe2O3;

[0010] Figure 2 HRTEM image of α-Fe2O3;

[0011] Figure 3is α-Ni 0.2 Fe 1.8 HRTEM image of O3;

[0012] Figure 4 The degradation efficiency of aceclofenac (ACF) in different systems;

[0013] Figure 5 α-Fe2O3 and α-Ni 0.2 Fe 1.8 Cyclic experiment of O3 degradation of ACF;

[0014] Figure 6 It is a metal-doped hematite rich in oxygen vacancies (α-Me x Fe 2-x O3) ESR spectrum of the material;

[0015] Figure 7 It is a metal-doped hematite rich in oxygen vacancies (α-Me x Fe 2-x O3) material O1s XPS spectrum. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0017] Specific embodiment 1: In this embodiment, a metal-doped hematite rich in oxygen vacancy (α-Me x Fe 2-x The preparation method of the O3 material is carried out according to the following steps: 1. dissolving an inorganic divalent metal salt and an inorganic iron salt in deionized water, stirring to adjust the pH, and obtaining a solution A; wherein the molar ratio of the inorganic divalent metal salt to the inorganic iron salt is 0.005-0.5:1; 2. activating, precipitating, filtering, and drying the solution A to obtain a precursor; 3. transferring the precursor to a muffle furnace, calcining at 300°C-1000°C, cooling, taking out, and grinding to obtain a hematite material rich in oxygen vacancy type metal doping

[0018] In this embodiment, Me is a divalent metal ion.

[0019] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the divalent metal is Zn 2+ 、Co 2+ , Mn 2+ 、Ni 2+ Mg 2+ , Cu 2+ or Ca 2+ The rest is the same as the first specific implementation.

[0020] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: step 1 adjusts the pH to 8.0-12.0. The rest is the same as specific implementation method 1 or 2.

[0021] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that the activation temperature in step 2 is 40° C. to 85° C. and the activation time is 24 h to 120 h. The rest is the same as specific embodiments 1 to 3.

[0022] Specific implementation mode 5: This implementation mode is different from the specific implementation modes 1 to 4 in that the drying temperature in step 2 is 40° C. to 105° C. The rest is the same as the specific implementation modes 1 to 4.

[0023] Specific embodiment 6: This embodiment is a kind of oxygen vacancy-rich α-Me x Fe 2-x Application of O3 materials in activating persulfate to degrade pollutants in water.

[0024] Specific embodiment 7: This embodiment is different from specific embodiment 6 in that: oxygen vacancy-rich α-Me x Fe 2-x The application method of O3 material in activating persulfate to degrade pollutants in water is as follows: a. Add α-Me to the water containing pollutants. x Fe 2-x O3 material is mixed evenly by magnetic stirring to obtain a mixed liquid;

[0025] b. adding persulfate to the mixed solution to form a catalytic reaction system, adjusting the pH to 7, and starting the catalytic reaction; the concentration of persulfate in the catalytic system is 5.0 mg / L-1000 mg / L;

[0026] c. After the catalytic reaction is completed, the catalyst is recovered by using a magnet, washed with distilled water, and dried. The rest is the same as the sixth embodiment.

[0027] In this embodiment, the persulfate is peroxymonosulfate, wherein the peroxymonosulfate is a potassium peroxymonosulfate composite salt or a sodium peroxymonosulfate composite salt.

[0028] Specific implementation method 8: This implementation method is different from specific implementation methods 6 or 7 in that: α-Me x Fe 2-x The dosage of O3 is 5.0 mg / L to 2000 mg / L. The rest is the same as the sixth or seventh embodiment.

[0029] Specific embodiment 9: This embodiment differs from specific embodiments 6 to 8 in that the pH value of the catalytic reaction system is adjusted using 0.1-1.0 mol / L NaOH or 0.1-1.0 mol / L HNO3 solution. The rest is the same as specific embodiments 6 to 8.

[0030] Specific embodiment 10: This embodiment is different from specific embodiments 6 to 9 in that the drying temperature in step c is 40° C. to 85° C. The rest is the same as specific embodiments 6 to 9.

[0031] The following examples are used to verify the beneficial effects of the present invention:

[0032] Example 1

[0033] In this embodiment, a metal-doped hematite (α-Ni 0.2 Fe 1.8 The preparation method of O3) material is carried out according to the following steps:

[0034] 1. Dissolve Ni(NO3)2·6H2O and Fe(NO3)3·9H2O (Ni / Fe atomic molar ratio is 0.1:1) in a beaker filled with 100mL of deionized water and stir for 30min to evenly mix the manganese ions and iron ions. Slowly add ammonia water (wt. 25%) to the mixture until the solution pH is 11.0 and continue stirring for 30min;

[0035] Second, seal the beaker with plastic wrap, place it in a forced air drying oven, and activate it at 60°C for 72 hours. Then, separate the precipitate from the suspension by vacuum filtration, and wash the precipitate repeatedly with deionized water until the supernatant is neutral. Finally, dry the precipitate at 60°C for 8 hours;

[0036] 3. The precipitate was transferred to a reactor, calcined in a muffle furnace at 400°C for 2 h, cooled, taken out and ground in an agate mortar, and sealed for later use. As a reference, the synthesis process of α-Fe2O3 was the same without adding Ni(NO3)2·6H2O.

[0037] 4. Adding α-Ni to water bodies containing pollutants 0.2 Fe 1.8 O3 material, using magnetic stirring to mix evenly to obtain a mixed solution; in step 2, α-Ni 0.2 Fe 1.8 The O3 catalyst dosage was 100 mg / L, and the target pollutant was aceclofenac (ACF) with a concentration of 1.0 mg / L.

[0038] 5. The persulfate solution PMS solution in step 3 has a concentration of 20 mg / L, and the pH is adjusted with a 0.3 mol / L NaOH solution, and the initial pH of the solution is 7.0.

[0039] 6. After the catalytic reaction is completed, the catalyst is recovered using a magnet, washed with distilled water, and dried at 60°C.

[0040] This embodiment uses α-Fe2O3 as a control. Ni(NO3)2·6H2O is not added during the synthesis of α-Fe2O3. Other aspects are the same as those of this embodiment.

[0041] Figure 1 is α-Ni 0.2 Fe 1.8 XRD spectra of O3 and α-Fe2O3, Figure 1 It can be seen that after isomorphous substitution doping, the crystal form of α-Fe2O3 is still maintained. Figure 2 This is the HRTEM image of α-Fe2O3. Figure 3 is α-Ni 0.2 Fe 1.8 HRTEM image of O3. It can be seen from the figure that Ni 2+ The particle distribution of the doped catalyst is more uniform.

[0042] α-Ni 0.2 Fe 1.8 O3 can effectively activate PMS to degrade ACF. Figure 4 The degradation efficiency of aceclofenac (ACF) by different systems, where 1 is PMS, 2 is α-Fe2O3, and 3 is α-Ni 0.2 Fe 1.8 O3, 4 are α-Fe2O3 / PMS, 5 are α-Ni 0.2 Fe 1.8 O3 / PMS, reaction conditions: aceclofenac dosage 1.0 mg / L, peroxymonosulfate dosage 20 mg / L, α-Ni 0.2 Fe 1.8 O3 dosage 100mg / L, α-Fe2O3 dosage 100mg / L, pH value 7.0, α-Ni 0.2 Fe 1.8 O3 / PMS is α-Ni 0.2 Fe 1.8 O3 dosage 100mg / L, peroxymonosulfate dosage 20mg / L, from Figure 4 The results show that at lower α-Ni 0.2 Fe 1.8Under the conditions of O3 and PMS dosage, ACF can achieve 100% removal rate within 20 minutes. Compared with PMS and α-Fe2O3 / PMS oxidation, α-Ni 0.2 Fe 1.8 O3 / PMS catalytic oxidation can effectively improve the removal effect of ACF.

[0043] α-Fe2O3 and α-Ni 0.2 Fe 1.8 O3 degradation of ACF cycle experiment: continue to use aceclofenac as the target, verify the α-Ni 0.2 Fe 1.8 The catalytic efficiency of O3 during multiple cycles. Reaction conditions: aceclofenac dosage 1.0 mg / L, peroxymonosulfate dosage 20 mg / L, α-Ni 0.2 Fe 1.8 O3 dosage was 100 mg / L, pH value was 7.0, α-Fe2O3 was used as control, and the reaction conditions of the control group were the same as those of α-Ni 0.2 Fe 1.8 The results are the same as those of O3. Figure 5 As shown, where ● is α-Ni 0.2 Fe 1.8 O3 / PMS, ▲ is α-Fe2O3 / PMS, indicating that during repeated use, α-Ni 0.2 Fe 1.8 O3 can maintain a high catalytic effect. After 5 cycles of use, the removal rate of aceclofenac is still as high as 82%, while the removal rate of the control group is only 20% after 5 cycles of use.

[0044] Example 2: Preparation of oxygen vacancy-rich metal-doped hematite α-Ni 0.6 Fe 1.4 O3, using α-Ni 0.6 Fe 1.4 O activated PMS to degrade ACF, aceclofenac dosage 1.0 mg / L, peroxymonosulfate dosage 20 mg / L, α-Ni 0.6 Fe 1.4 With an O3 dosage of 100 mg / L and a pH value of 7.0, ACF can achieve a removal rate of 72.9% within 20 minutes.

[0045] Example 3: Preparation of oxygen vacancy-rich metal-doped hematite α-Ni 0.4 Fe 1.6 O3, using α-Ni 0.4 Fe 1.6 O3 activated PMS to degrade ACF, aceclofenac dosage 1.0 mg / L, peroxymonosulfate dosage 20 mg / L, α-Ni 0.4 Fe1.6 With an O3 dosage of 100 mg / L and a pH value of 7.0, ACF can achieve a removal rate of 89.4% within 20 minutes.

[0046] Example 4: Preparation of oxygen vacancy-rich metal-doped hematite α-Ni 0.1 Fe 1.9 O3, using α-Ni 0.1 Fe 1.9 O3 activated PMS to degrade ACF, aceclofenac dosage 1.0 mg / L, peroxymonosulfate dosage 20 mg / L, α-Ni 0.1 Fe 1.9 With an O3 dosage of 100 mg / L and a pH value of 7.0, ACF can achieve a removal rate of 83.3% within 20 minutes.

[0047] The PMS used in the above embodiment is potassium peroxymonosulfate complex salt.

[0048] Figure 6 is α-Ni 0.6 Fe 1.4 O3、α-Ni 0.4 Fe 1.6 O3、α-Ni 0.1 Fe 1.9 O3、α-Ni 0.2 Fe 1.8 ESR spectra of O3 and α-Fe2O3; 1 is α-Fe2O3, 2 is α-Ni 0.1 Fe 1.9 O3, 3 is α-Ni 0.2 Fe 1.8 O3, 4 are α-Ni 0.4 Fe 1.6 O3, 5 are α-Ni 0.6 Fe 1.4 O3; ESR spectrum reveals the formation of oxygen vacancies. As can be seen from the figure, no ESR signal is observed in α-Fe2O3. However, doped with Ni 2+ ESR signals belonging to oxygen vacancies appeared in the catalysts of Ni and Ni, and the signal intensity gradually increased, indicating that more oxygen vacancies were formed. 2+ The doping leads to the absence of oxygen in the structure of the synthesized catalyst and changes the properties of the catalyst.

[0049] In order to further quantitatively analyze the content of oxygen vacancies, O1s XPS spectroscopy was performed on the catalyst. Figure 7 is α-Ni 0.6 Fe 1.4 O3、α-Ni 0.4 Fe 1.6O3、α-Ni 0.1 Fe 1.9 O3、α-Ni 0.2 Fe 1.8 O3 and α-Fe2O3O1s XPS spectra. Figure 7 The binding energies at 529.4, 530.2, and 531.5 eV are respectively attributed to the lattice oxygen (O L ), surface chemically adsorbed oxygen (O ads ) and oxygen vacancies (OV). The relative content of OV varies with Ni 2+ doping gradually increases, indicating that Ni 2+ Doping can effectively construct OV in the α-Fe2O3 structure.

Claims

1. A metal-doped hematite α-Ni rich in oxygen vacancies 0.2 Fe 1.8 The application of O3 material in activating persulfate to degrade aceclofenac in water is characterized by: The material preparation method is carried out according to the following steps: Dissolve Ni(NO3)2·6H2O and Fe(NO3)3·9H2O in a beaker containing 100 mL of deionized water, stir for 30 min to evenly mix nickel ions and iron ions, slowly drop ammonia water into the mixture until the pH value of the solution is 11.0, and continue stirring for 30 min; wherein the molar ratio of Ni to Fe atoms is 0.1:1, and the concentration of ammonia water is wt. 25%; The beaker was sealed with plastic wrap, placed in a forced air drying oven, and activated at 60°C for 72 h. Then, the precipitate was separated from the suspension by vacuum filtration. The precipitate was repeatedly washed with deionized water until the supernatant was neutral. Finally, the precipitate was dried at 60°C for 8 h. The precipitate was transferred to a reactor, calcined in a muffle furnace at 400 °C for 2 h, cooled, taken out, ground with an agate mortar, and sealed for later use.

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