Non-stoichiometric bismuth oxybromide for degrading organic pollutants by photocatalytic activation of peracetic acid and solid-phase preparation method of non-stoichiometric bismuth oxybromide

Abstract

The invention discloses non-stoichiometric bismuth oxybromide for degrading organic pollutants by photocatalytic activation of peracetic acid and a solid-phase preparation method of the non-stoichiometric bismuth oxybromide. Bismuth nitrate pentahydrate and potassium bromide are used as synthetic raw materials, and the bismuth nitrate pentahydrate and the potassium bromide are put into a muffle furnace to be fired at the temperature of 500 DEG C according to the molar ratio of 1: 1 to obtain the non-stoichiometric bismuth oxybromide Bi12O17Br2 (Ns-BiOBr). The non-stoichiometric bismuth oxybromide (Ns-BiOBr) catalyst prepared by the preparation method disclosed by the invention is synthesized in one step by precisely regulating the molar ratio and temperature of a bismuth source and a bromine source; compared with a common hydrothermal method, the method is more concise and easy to regulate and control, and compared with a traditional stoichiometric ratio BiOBr material, the BiOBr material has more efficient PAA photocatalytic activation degradation capacity. The preparation process is simple, parameters are easy to control, complex post-treatment steps are not needed, and the high-efficiency pollutant degradation performance and the long-term stability are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalysis, and in particular to a non-stoichiometric bismuth oxybromide for photocatalytically activating peracetic acid to degrade organic pollutants and a solid phase preparation method thereof. Background Art

[0002] With the acceleration of industrialization and urbanization, the situation of refractory organic pollutants (such as antibiotics and pesticides) in water bodies is serious. Traditional advanced oxidation processes (AOPs) rely on hydroxyl radicals (HO • ) or sulfate radical (SO4 •− ), but there are problems such as low oxidant utilization and secondary pollution of metal catalysts. Peracetic acid (PAA) is a green oxidant. Compared with other oxidants (hydrogen peroxide, persulfate, etc.), it has both high oxidation potential (1.96 V) and stability, but its targeted degradation efficiency when used alone is limited by the free radical generation rate and mass transfer efficiency.

[0003] The photocatalytic activation of PAA technology is based on solar-driven reaction, avoiding the risk of metal catalyst pollution, and generating HO by synchronously activating PAA. • 、CH3COO • and 1 O2 and other multi-active species can double the pollutant degradation rate, and the reaction system can adapt to a wide pH range (3-9). The degradation pathway is dominated by non-toxic mineralization, and the toxicity of by-products is reduced by more than 60% compared with traditional processes, providing an efficient, green and engineering-promotable innovative solution for the treatment of highly toxic organic pollutants.

[0004] Bi 12 O 17 Br2 (Ns-BiOBr) is an excellent photocatalytic material, but the current common preparation method of this catalyst is still the traditional hydrothermal synthesis method with multiple steps, high temperature and high pressure. The preparation method is cumbersome, and the low precision of the bromine-bismuth molar ratio control leads to poor crystal phase stability of the material, which restricts the improvement of photocatalytic performance, and there is no precedent for photocatalytic activation of PAA. In response to the above problems, this patent uses a solid-phase method to synthesize Ns-BiOBr in one step by precisely controlling the molar ratio and temperature of the bismuth source and the bromine source, and realizes the photocatalytic activation of PAA to efficiently remove organic pollutants in water, aiming to establish a simple, stable and efficient deep treatment technology for pollutants. Summary of the invention

[0005] In view of this, the problem to be solved by the present invention is to provide a non-stoichiometric bismuth oxybromide for photocatalytic activation of peracetic acid to degrade organic pollutants and a solid phase preparation method thereof. The material synthesis process is simple and has a more efficient photocatalytic activation of PAA to degrade organic pollutants.

[0006] The present invention provides a solid phase preparation method for non-stoichiometric bismuth oxybromide for photocatalytic activation of peracetic acid to degrade organic pollutants, comprising the following steps: (A) Adding bismuth source and bromine source into the crucible in sequence; (B) Use a glass rod to disperse and mix the two. (C) The solid is dispersed in a crucible and heated at a fixed temperature. After natural cooling, it is ground using a mortar to obtain non-stoichiometric bismuth oxybromide Bi. 12 O 17 Br2 and labeled as Ns-BiOBr.

[0007] Preferably, the bismuth source is bismuth nitrate pentahydrate, and the bromine source is potassium bromide, and the molar ratio of the two is 1:1.

[0008] Preferably, the reaction in step (C) is carried out in a muffle furnace, the reaction temperature is 500° C., and the reaction time is 3 h.

[0009] The technical solution of the present invention has the following advantages: The present invention provides a solid phase preparation method of a non-stoichiometric bismuth oxybromide material (Ns-BiOBr) based on precise proportional temperature control and having high-efficiency photocatalytic activation PAA degradation performance.

[0010] Ns-BiOBr is synthesized by controlling a certain temperature and reagent ratio by using a solid phase method, and the precise controllability of the chemical composition of the material is achieved under the conditions of a bismuth source to bromine source molar ratio of 1:1 and a firing temperature of 500 °C. It matches the standard card JCPDS No. 37-0701, and the material has a flaky structure, which is conducive to the improvement of specific surface energy, thereby facilitating the degradation of organic pollutants in water.

[0011] The activation of PAA depends on the ultraviolet irradiation-induced homolysis of the OO bonds to generate HO • and organic free radicals (RO • ) to degrade organic pollutants. Visible light with a longer wavelength does not have enough energy to break peroxide bonds. Ns-BiOBr enhances the absorption of visible light and improves the catalytic activity of PAA activation and pollutant oxidation under visible light (Vis), causing PAA to decompose and produce a variety of active species, such as hydroxyl radicals (HO • ), acetoxy radical (CH3COO • ) and hydrogen peroxide (H2O2), etc., which are beneficial to decompose and oxidize organic pollutants in water.

[0012] In addition, 12 O 17 The conduction band potential of Br2 (E CB, -0.36 eV) than O2 / O2 •− (-0.33 V / SHE) is more negative, and the photogenerated electrons in the conduction band reduce the dissolved oxygen in water to generate O2 •− .Bi 12 O 17 O2 produced from Br2 •− It can be further reduced by electrons to generate H2O2, or oxidized by photogenerated holes to generate 1 O2.Bi 12 O 17 The conduction band potential of Br2 (Ev B , 2.29 eV) than HO • / OH − (1.99 V / SHE) and HO • / H2O (2.27 V / SHE) correction, therefore, the holes accumulated in the valence band will convert OH − / H2O is oxidized to HO • . ROS (including O2 •− , 1 O2, and HO • ) are both highly oxidizing and can sustainably degrade the target pollutant sulfadimethoxine (SMZ). In addition, compared with the stoichiometric BiOBr, its smaller band gap energy reduces the electron transition energy, improves the generation and separation efficiency of photogenerated carriers, reduces electron-hole recombination, and is beneficial to the generation of active species and the degradation of SMZ.

[0013] The preparation method of the present invention has simple operation, high synthesis efficiency, high photocatalytic activation PAA degradation performance and good catalyst stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1a The photocatalyst prepared in Example 1 was used to perform photocatalytic activation of PAA to degrade SMZ.

[0015] Figure 1b The photocatalyst prepared in Example 2 was used to perform photocatalytic activation of PAA to degrade SMZ.

[0016] Figure 1c The curves of PAA degradation of SMZ by Ns-BiOBr and BiOBr prepared in Examples 1 and 3, respectively, with and without light.

[0017] Figure 1d Pseudo-first-order kinetic fitting of the PAA-activated SMZ degradation curves of Ns-BiOBr and BiOBr prepared in Examples 1 and 3, respectively, with and without light.

[0018] Figure 2aThis is the curve of photocatalytic activation of PAA to degrade SMZ by Ns-BiOBr prepared in Example 1 under the influence of different catalyst dosages.

[0019] Figure 2b This is the curve of photocatalytic activation of PAA to degrade SMZ by Ns-BiOBr prepared in Example 1 under the influence of different PAA dosages.

[0020] Figure 3a -b are the XRD spectra of Ns-BiOBr samples synthesized under different preparation conditions in Examples 1-2.

[0021] Figure 4 This is the XPS spectrum of Ns-BiOBr prepared in Example 1.

[0022] Figure 5 SEM and TEM images of Ns-BiOBr prepared in Example 1.

[0023] Figure 6 UV-Vis images, Mott-Schottky images and band gap structure diagrams of Ns-BiOBr and BiOBr prepared in Examples 1 and 3, respectively.

[0024] Figure 7 This is a diagram of the recycling of Ns-BiOBr prepared in Example 1 to photocatalytically activate PAA to degrade SMZ.

[0025] Figure 8 Isotherms of Ns-BiOBr and BiOBr prepared in Examples 1 and 3, respectively. DETAILED DESCRIPTION

[0026] In order to further describe the invention, a non-stoichiometric bismuth oxybromide for photocatalytic activation of peracetic acid to degrade organic pollutants and a solid phase preparation method thereof provided by the present invention are described in detail with reference to examples. Example 1

[0027] 1 mmol Bi(NO3)3•5H2O solid powder and 1 mmol KBr solid powder were added into a 50 mL corundum crucible in sequence.

[0028] Use a glass rod to disperse and mix the Bi(NO3)3•5H2O solid powder and KBr solid powder.

[0029] The dispersed and mixed reagents were placed in a muffle furnace, heated at a rate of 5 °C / min to 500 °C and maintained for 3 h.

[0030] After naturally cooling to room temperature, the sample in the crucible was transferred into a mortar and ground. The obtained fine particle product was named Ns-BiOBr-1:1.

[0031] Keeping the heating rate and synthesis temperature of the sample in the muffle furnace unchanged, the molar ratio of Bi(NO3)3•5H2O and KBr was adjusted to 3:1, 2:1, 1:2, and 1:3. The other steps were the same and they were named Ns-BiOBr-3:1, Ns-BiOBr-2:1, Ns-BiOBr-1:2, and Ns-BiOBr-1:3, respectively. Example 2

[0032] 1 mmol Bi(NO3)3•5H2O solid powder and 1 mmol KBr solid powder were added into a 50 mL corundum crucible in sequence.

[0033] Use a glass rod to disperse and mix the Bi(NO3)3•5H2O solid powder and KBr solid powder.

[0034] The dispersed and mixed reagents were placed in a muffle furnace, heated at a rate of 5 °C / min, and heated to 500 °C and maintained for 3 h.

[0035] After naturally cooling to room temperature, the sample in the crucible was transferred into a mortar and ground. The obtained fine particle product was named Ns-BiOBr-500.

[0036] The molar ratio of Bi(NO3)3•5H2O and KBr of the synthesized samples was kept at 1:1, the heating rate in the muffle furnace was kept constant at 5℃ / min, and the temperature of the muffle furnace was adjusted to 300℃, 400℃, and 600℃. The other steps were the same and they were named Ns-BiOBr-300, Ns-BiOBr-400, and Ns-BiOBr-600, respectively.

[0037] Figure 1a -b shows that the Ns-BiOBr photocatalyst prepared under the conditions of Bi(NO3)3•5H2O and KBr molar ratio of 1:1, heating rate of 5 ℃ / min, and heating to 500 ℃ for 3 h has the highest degradation efficiency for SMZ photocatalytic activation of PAA degradation. Example 3

[0038] Add 3.2 mmol Bi(NO3)3•5H2O into 21 mL ethanol solution and stir magnetically for 1 h to obtain solution A.

[0039] Add 3.2 mmol KBr into 21 mL ultrapure water and stir magnetically for 1 h to obtain solution B.

[0040] Solution B was added dropwise into solution A and magnetically stirred for 90 min to mix well.

[0041] The above mixture was transferred into a 100 mL polytetrafluoroethylene reactor and maintained at 160 °C for 12 h.

[0042] After naturally cooling to room temperature, the solid was separated by centrifugation, washed three times with ethanol and water respectively, and dried at 60 °C to obtain the final product named BiOBr.

[0043] according to Figure 1a The degradation effect of Ns-BiOBr on SMZ showed that the photocatalytic activation of PAA to degrade SMZ was most significant when the molar ratio of bromine source to bismuth source was 1:1 and the temperature was 500 °C.

[0044] according to Figure 1c The degradation effect of Ns-BiOBr on SMZ showed that the photocatalytic activation of PAA by the prepared Ns-BiOBr was more effective in degrading SMZ than that by BiOBr.

[0045] according to Figure 2a -b The curve of Ns-BiOBr photocatalytic activation of PAA for SMZ degradation under different catalyst dosages and different PAA concentrations. Considering the reaction cost and efficiency, compared with other reaction conditions, when the catalyst dosage is 0.3 g / L and the PAA addition concentration is 0.5 mM, the photocatalytic activation of PAA for SMZ degradation is more green and efficient.

[0046] according to Figure 3a -b's XRD spectrum results show that Ns-BiOBr prepared under different conditions has different diffraction peaks, and the formation of non-stoichiometric bismuth oxybromide can be precisely controlled by controlling the proportional temperature. According to Example 1, when the condition temperature is 500 °C: when the molar ratio of bismuth to bromine is adjusted to 3:1 and 2:1, the non-stoichiometric bismuth oxybromide prepared is Bi2O3, which is consistent with the standard card JCPDSNO. 04-2034; when the molar ratio of bismuth to bromine is adjusted to 1:1, the non-stoichiometric bismuth oxybromide prepared is Bi 12 O7Br2, which is consistent with the standard card JCPDS NO. 37-0701; when the molar ratio of bismuth to bromine is adjusted to 1:2 and 1:3, the non-stoichiometric bismuth oxybromide prepared is Bi4O5Br2, which is consistent with the standard card JCPDS NO. 97-4498. According to Example 2, when the condition ratio is 1:1: when the temperature is adjusted to 300 °C and 400 °C, the non-stoichiometric bismuth oxybromide prepared is Bi2O 2.7 , which is consistent with the standard card JCPDSNO. 97-0359; when the temperature is adjusted to 500 ℃ and 600 ℃, the prepared non-stoichiometric bismuth oxybromide is Bi 12O7Br2, in accordance with standard card JCPDS NO. 37-0701.

[0047] according to Figure 4 The SEM results show that Ns-BiOBr is an irregular nanosheet structure stacked in layers.

[0048] according to Figure 5 XPS spectrum analysis shows that the binding energy in the Bi 4f spectrum of Ns-BiOBr exists at 159.4 eV and 164.7 eV; the binding energy in the Br 3d spectrum exists at 68.2 eV and 69.3 eV; the binding energy in the O 1s spectrum exists at 529.4 eV, 531.6 eV and 532.6 eV, corresponding to the existence of lattice oxygen, oxygen defects and adsorbed oxygen, respectively. The abundant oxygen defects in Ns-BiOBr are beneficial to its light absorption and the effective separation of photogenerated electrons and holes.

[0049] according to Figure 6 The analysis results show that the flat band potential of Ns-BiOBr is -0.36 V and the band gap width is 2.65 e. Therefore, its conduction band potential is -0.36 V and the valence band potential is 2.26 eV. Compared with the integral BiOBr, Ns-BiOBr has a narrower band gap width, which is conducive to photon absorption and excitation to generate more photogenerated carriers.

[0050] according to Figure 7 The recycling results show that after five recycling times, the degradation rate of SMZ by Ns-BiOBr can still reach 92%, which shows good material stability.

[0051] according to Figure 8 The BET results show that Ns-BiOBr has a large specific surface area, which is conducive to exposing more active sites on the material surface, and is beneficial to the adsorption of PAA and target pollutants on the material surface and the subsequent catalytic oxidation degradation process.

[0052] The above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it. It should be pointed out that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A non-stoichiometric bismuth oxybromide for photocatalytic activation of peracetic acid to degrade organic pollutants and a solid phase preparation method thereof, characterized in that: The steps include: (A) Adding bismuth source and bromine source into the crucible in sequence; (B) Use a glass rod to disperse and mix the two. (C) The solid is dispersed in a crucible and heated at a fixed temperature. After natural cooling, it is ground using a mortar to obtain non-stoichiometric bismuth oxybromide Bi. 12 O 17 Br2 and labeled as Ns-BiOBr; Wherein, the bismuth source in step (A) is bismuth nitrate pentahydrate, and the bromine source is potassium bromide.

2. The preparation method according to claim 1, characterized in that: The molar ratio of the bismuth source to the bromine source is 1:

1.

3. The preparation method according to claim 1, characterized in that: The bismuth source and the bromine source are dispersed and mixed using a glass rod.

4. The preparation method according to claim 1, characterized in that: In step (C), the fixed temperature is 500 °C and the heating time is 3 h.

5. The method according to any one of claims 1 to 4 is used to prepare non-stoichiometric bismuth oxybromide Ns-BiOBr having a photocatalytic activation effect on PAA.

6. Use of the non-stoichiometric bismuth oxybromide Ns-BiOBr according to claim 5 in photocatalytic activation of PAA to degrade organic pollutants.

7. The use according to claim 6, characterized in that: It can be used for photocatalytic activation of PAA to degrade organic pollutants.

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