A s-doped supported red mud-based prussian blue analogue derivative photocatalyst with a wide pH range, a preparation method and application thereof

Abstract

This invention discloses a sulfur-doped, supported red mud-based Prussian blue analogue photocatalyst with a wide pH range, its preparation method, and its applications. The method involves acid dissolving red mud raw material to obtain an iron-containing liquid. A sulfur-containing reducing agent and a potassium cobalt cyanide solution are then sequentially added to the iron-containing liquid for reduction and precipitation reactions. The resulting reaction product is separated into solid and liquid phases to obtain a solid product, which is then calcined under a protective atmosphere to obtain the final photocatalyst. This photocatalyst exhibits strong dispersibility, abundant active sites, stable structure, and recyclability, and can efficiently catalyze the degradation of antibiotics. Its preparation method is simple, low-cost, and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to an iron-based photocatalyst, specifically to an S-doped red mud-based Prussian blue analogue derivative photocatalyst, and also to its preparation method and application, belonging to the field of photocatalyst technology. Background Technology

[0002] Antibiotics are widely used in medicine, aquaculture, and animal husbandry. Between 30% and 90% of these antibiotics cannot be absorbed by organisms and enter surface water or groundwater systems as parent compounds or active metabolites. Even at low concentrations, antibiotics entering the environment can induce antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARBs), posing a serious threat to human health and ecological security. Traditional physical, chemical, and biological methods have been used to remove antibiotics from wastewater, achieving some success but also revealing drawbacks such as high operating costs, secondary pollution, and low efficiency. Therefore, developing economical, environmentally friendly, and efficient processes for treating antibiotic wastewater is of great significance for maintaining ecological stability, human health, and sustainable social development.

[0003] Photocatalysis is an advanced oxidation technology that utilizes renewable light energy to generate reactive oxygen species. One of its main challenges is the easy recombination of photogenerated carriers. Persulfate (PMS) is a precursor to highly oxidizing sulfate radicals (SO42-). ·- Photocatalysts are one of the main peroxides, and their excellent photogenerated electron-trapping ability has led to their use in photocatalysis. This strategy has been reported in numerous studies and provides important reference for developing green and efficient technologies for degrading antibiotics. To enhance the practical application value of this strategy, it is crucial to prepare photocatalysts that are low-cost, have excellent photoelectric properties, stable structures, and are reusable.

[0004] Red mud (RM) is a strongly alkaline waste rich in iron oxide and has been used to develop various iron-based photocatalysts. Prussian blue analogue derivatives (PBA-D) are a class of easily synthesized iron-based MOFs-derived materials. They not only overcome the inherent defects of PBA, such as poor water stability and difficult recovery, but also inherit the advantages of PBA, such as well-developed pores and exposed active sites. Furthermore, they acquire magnetic properties and a certain degree of photoresponsiveness. However, due to their tendency to aggregate during preparation, PBA-D, like PBA, exhibits significant agglomeration, which hinders its application given its relatively limited photocatalytic ability. In addition, most current studies suffer from a narrow pH application range, which severely affects the practical usability of the constructed systems. Therefore, developing a red mud-based photocatalyst with a wide pH range, high stability, and excellent photocatalytic performance is of great significance. Summary of the Invention

[0005] To address the problems existing in the prior art, the first objective of this invention is to provide an S-doped supported red mud-based Prussian blue analogue photocatalyst with a wide pH range. This catalyst possesses advantages such as abundant active sites, excellent photocatalytic performance, easy recovery, no risk of secondary pollution, and recyclability.

[0006] A second objective of this invention is to provide a method for preparing an S-doped supported red mud-based Prussian blue analogue photocatalyst with a wide pH range. This method is simple, low-cost, and suitable for industrial production.

[0007] A third objective of this invention is to provide an application of an S-doped supported red mud-based Prussian blue analogue photocatalyst with a wide pH range. This catalyst can photocatalytically activate PMS to degrade antibiotics in a wide pH system.

[0008] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing a S-doped supported red mud-based Prussian blue analogue photocatalyst with a wide pH range. The method involves acid dissolving red mud raw material to obtain an iron-containing liquid, then sequentially adding a sulfur-containing reducing agent and a potassium cobalt cyanide solution to the iron-containing liquid for reduction and precipitation reactions. The resulting reaction product is separated into solid and liquid phases to obtain a solid product, which is then calcined in a protective atmosphere to obtain the final product.

[0009] The acid solution serves to remove alkali and dissolve iron from the red mud. The main reaction formulas involved in the above preparation process are as follows:

[0010] S 2- +8Fe 3+ +4H₂O→8Fe 2+ +SO4 2- +8H + ;

[0011] 3Fe 2+ +2[Co(CN)6] 3- →Fe3[Co(CN)6]2↓.

[0012] As a preferred embodiment, the conditions for the acid dissolution process are as follows: at least one of hydrochloric acid, sulfuric acid, and nitric acid is used as the acid dissolution solution, the liquid-to-solid ratio is 60-140 mL: 3-7 g, the temperature is 85-95 °C, and the time is 2-4 h.

[0013] As a preferred embodiment, the acid solution is hydrochloric acid. Because hydrochloric acid is volatile, it does not affect the composition or properties of the material, making it more suitable for the acid dissolution process of red mud raw materials.

[0014] As a preferred embodiment, the concentration of the acid solution is 5–7 mol / L.

[0015] As a preferred embodiment, the sulfur-containing reducing agent includes at least one of ammonium sulfide, sodium sulfide, and potassium sulfide.

[0016] As a preferred embodiment, the molar amount of the sulfur-containing reducing agent is 1 to 3 times the amount of iron in the red mud raw material.

[0017] As a preferred embodiment, the conditions for the reduction reaction are: room temperature and time of 15–40 min.

[0018] As a preferred embodiment, the molar ratio of potassium cobalt cyanide to iron in the red mud in the potassium cobalt cyanide solution is 1 to 4:4.

[0019] As a preferred embodiment, the concentration of the potassium cobalt cyanide solution is 0.02–0.08 mol / L.

[0020] As a preferred embodiment, the dropping rate of the potassium cobalt cyanide solution is 2–6 mL / min. If the dropping rate of the potassium cobalt cyanide solution is too fast, the reaction may be too rapid, causing the formed PBA to aggregate rapidly, resulting in a reduction in specific surface area, porosity, and exposed active sites.

[0021] As a preferred embodiment, the precipitation reaction is performed under the following conditions: room temperature and time of 10–14 hours.

[0022] As a preferred embodiment, the protective atmosphere is nitrogen, the calcination temperature is 300–600°C, and the calcination time is 1–3 hours. More preferably, the calcination temperature is 500°C.

[0023] The present invention also provides an S-doped supported red mud-based Prussian blue analogue photocatalyst with a wide pH range, which is prepared by the above method.

[0024] This invention also provides an application of an S-doped supported red mud-based Prussian blue analogue photocatalyst with a wide pH range for the photocatalytic degradation of antibiotics in persulfate (PMS) solution. This catalyst can efficiently catalyze the degradation of antibiotics by persulfate over a wide pH range and can be magnetically recovered and reused without generating secondary pollution.

[0025] As a preferred option, the light is visible light.

[0026] As a preferred option, the antibiotic is oxytetracycline.

[0027] As a preferred embodiment, the concentration of the photocatalyst in the solution is not less than 0.1 g / L.

[0028] As a preferred embodiment, the concentration of the persulfate in the solution is not less than 1 mM.

[0029] As a preferred embodiment, the concentration of the antibiotic in the solution is 5–30 ppm.

[0030] As a preferred embodiment, the initial pH of the solution is 3–11, and the temperature is 20–50°C.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) For the first time, a photocatalyst with low cost, abundant active sites, excellent photocatalytic performance, wide pH application range, easy recycling and no risk of secondary pollution was prepared using red mud, which improved the availability of red mud resources;

[0033] (2) The S-doped supported red mud-based Prussian blue analogue derivative photocatalyst can activate PMS under visible light irradiation to efficiently degrade antibiotic pollutants in solutions with pH 3 to 11, achieving the effect of "treating waste with waste".

[0034] (3) The preparation method is simple and the cost is low, making it suitable for industrial production. Attached Figure Description

[0035] Figure 1 The X-ray diffraction (XRD) patterns of the SRPD and RM raw materials prepared in Example 1, the ARM prepared in Comparative Example 1, the R-ARM prepared in Comparative Example 2, the RPD prepared in Comparative Example 3, and the PD prepared in Comparative Example 4 are shown.

[0036] Figure 2 The images show scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) images of SRPD (e and h) prepared in Example 1, RM raw material (a), ARM prepared in Comparative Example 1 (b), R-ARM prepared in Comparative Example 2 (c), RPD (d and g) prepared in Comparative Example 3, and PD (f) prepared in Comparative Example 4.

[0037] Figure 3 This is a high-resolution transmission electron microscope (HRTEM) image of the SRPD prepared in Example 1.

[0038] Figure 4 The Co 2p and Fe 2p X-ray photoelectron spectroscopy (XPS) spectra of the SRPD (a and d) prepared in Example 1, the RPD (b and e) prepared in Comparative Example 3, and the PD (c and f) prepared in Comparative Example 4 are shown.

[0039] Figure 5The UV diffuse reflectance (a) and corresponding Tauc diagram (b), XPS valence band spectrum (ch) and transient photocurrent response diagram (i) of the SRPD and RM raw materials prepared in Example 1, the ARM prepared in Comparative Example 1, the R-ARM prepared in Comparative Example 2, the RPD prepared in Comparative Example 3, and the PD prepared in Comparative Example 4 are shown.

[0040] Figure 6 The SRPD and RM raw materials prepared in Example 1, the ARM prepared in Comparative Example 1, the R-ARM prepared in Comparative Example 2, the RPD prepared in Comparative Example 3, and the PD prepared in Comparative Example 4 were activated by PMS to degrade oxytetracycline under visible light (a) and related kinetic calculations were performed (b).

[0041] Figure 7 To investigate the degradation of oxytetracycline by the SRPD / PMS / Vis system constructed using the SRPD prepared in Example 1 at different SRPD doses (a) and different PMS concentrations (b).

[0042] Figure 8 The degradation of oxytetracycline by the SRPD / PMS / Vis system constructed using the SRPD prepared in Example 1 under different pH conditions (a) and related kinetic calculations (b).

[0043] Figure 9 This refers to the case where the SRPD prepared in Example 1 is reused to degrade oxytetracycline.

[0044] Figure 10 This is a comparison chart showing the degradation effects of SRPD-300, SRPD-400, SRPD-500 and SRPD-600 catalysts prepared at different calcination temperatures in Example 7 on oxytetracycline. Detailed Implementation

[0045] The following specific embodiments or implementation methods are intended to further illustrate the present invention, and are not intended to limit the present invention.

[0046] The red mud used in this invention was purchased from the Guangxi Branch of Aluminum Corporation of China Limited. It belongs to Bayer red mud and mainly contains phases such as hematite, gibbsite, boehmite, nepheline, hydrogarnet, and calcite. The contents of Fe, Ca, Al, Na, Si, and Ti are 18.06%, 11.61%, 9.72%, 7.37%, 7.13%, and 3.97%, respectively.

[0047] Example 1

[0048] The following is a photocatalyst based on an S-doped supported red mud-based Prussian blue analogue, comprising the following steps:

[0049] (1) Take 5g of red mud into a conical flask containing 100mL of hydrochloric acid solution with a concentration of 2.4mol / L, and disperse it ultrasonically for 15min;

[0050] (2) Place it in a water bath and stir magnetically at 90°C for 2 hours;

[0051] (3) After cooling to room temperature, add 16 mmol of ammonium sulfide and stir for 30 min.

[0052] (4) While stirring, add 50 mL of a 0.04 mol / L potassium cobalt cyanide solution dropwise at a rate of 4 mL / min.

[0053] (5) Stir continuously for 2 hours, then let stand for 12 hours;

[0054] (6) After repeating the "high-speed centrifugation-deionized water washing" three times, the resulting solid was placed in an 80℃ oven to dry;

[0055] (7) The dried sample was calcined at 500℃ in a nitrogen atmosphere for 2h to obtain the S-doped supported red mud-based Prussian blue analogue photocatalyst, denoted as SRPD.

[0056] Comparative Example 1

[0057] The preparation steps of acid-soluble RM materials are as follows:

[0058] (1) Take 5g of red mud into a conical flask containing 100mL of hydrochloric acid solution with a concentration of 2.4mol / L, and disperse it ultrasonically for 15min;

[0059] (2) Place it in a water bath and stir magnetically at 90°C for 2 hours;

[0060] (3) After cooling to room temperature, repeat the "high-speed centrifugation-deionized water washing" three times, and put the obtained solid into an 80℃ oven to dry, thus obtaining acid-soluble RM, denoted as ARM;

[0061] Comparative Example 2

[0062] The preparation steps for calcined acid-soluble RM materials are as follows:

[0063] (1) Take 5g of red mud into a conical flask containing 100mL of hydrochloric acid solution with a concentration of 2.4mol / L, and disperse it ultrasonically for 15min;

[0064] (2) Place it in a water bath and stir magnetically at 90°C for 2 hours;

[0065] (3) After cooling to room temperature, repeat the "high-speed centrifugation-deionized water washing" three times, and put the obtained solid into an 80℃ oven to dry;

[0066] (4) The dried sample was calcined at 500℃ under a nitrogen atmosphere for 2 hours to obtain the calcined acid-soluble RM, denoted as R-ARM.

[0067] Comparative Example 3

[0068] The preparation steps of the undoped supported red mud-based Prussian blue analogue photocatalyst are as follows:

[0069] (1) Take 5g of red mud into a conical flask containing 100mL of hydrochloric acid solution with a concentration of 2.4mol / L, and disperse it ultrasonically for 15min;

[0070] (2) Place it in a water bath and stir magnetically at 90°C for 2 hours;

[0071] (3) After cooling to room temperature, add 8 mmol of ascorbic acid and stir for 30 min.

[0072] (4) While stirring, add 50 mL of a 0.04 mol / L potassium cobalt cyanide solution dropwise at a rate of 4 mL / min.

[0073] (5) Stir continuously for 2 hours, then let stand for 12 hours;

[0074] (6) After repeating the "high-speed centrifugation-deionized water washing" three times, the resulting solid was placed in an 80℃ oven to dry;

[0075] (7) The dried sample was calcined at 500℃ in a nitrogen atmosphere for 2 hours to obtain a supported red mud-based Prussian blue analogue photocatalyst without S doping, denoted as RPD.

[0076] Comparative Example 4

[0077] The preparation steps of the Prussian blue analogue derivative photocatalyst are as follows:

[0078] (1) Prepare 100 mL of 0.06 mol / L FeSO4·7H2O solution in an Erlenmeyer flask, and denote it as solution A;

[0079] (2) Prepare 50 mL of 0.04 mol / L potassium cobalt cyanide solution in an Erlenmeyer flask, and denote it as solution B;

[0080] (3) While stirring, add solution B dropwise to solution A at a rate of 4 mL / min;

[0081] (4) Stir continuously for 2 hours, then let stand for 12 hours;

[0082] (5) After repeating the "high-speed centrifugation-deionized water washing" three times, the resulting solid was placed in an 80℃ oven to dry.

[0083] (7) The dried sample was calcined at 500℃ under a nitrogen atmosphere for 2 hours to obtain the Prussian blue analog derivative photocatalyst, denoted as PD.

[0084] like Figure 1 As shown, RM is mainly composed of hematite, gibbsite, diaspore, nepheline, hydrogarnet, and calcite. ARM mainly consists of hematite, gibbsite, and diaspore. R-ARM mainly contains hematite and corundum phases. PD mainly detects (Co) 0.62 Fe 1.38 FeO4 and Fe3N. The phases in RPD are a combination of those in R-ARM and PD. Compared to RPD, the S-containing phase Fe3S4 was also detected in SRPD.

[0085] like Figure 2 As shown, RM consists of irregularly shaped particles with uneven particle size. ARM and R-ARM show corrosion relative to RM, exposing large amounts of matrix at the bottom. PD particles are smaller and exhibit severe agglomeration. In RPD, the RM matrix more uniformly loads PD particles, significantly improving PD dispersibility, and the PD particle size is significantly increased, exhibiting a polyhedral shape. Compared to RPD, the PD particles on the SRPD surface are surrounded by plate-like or rod-shaped sulfur-containing species, which are Fe3S4.

[0086] like Figure 3 As shown, element S is not only distributed around the SRPD particles, but also incorporated in small amounts into the PD particles. Lattice fringes of the Fe3S4(944) crystal plane were detected both within and around the SRPD particles, indicating that S is incorporated into the material through interactions with Fe in the RM matrix and Fe in the PD particles.

[0087] like Figure 4 As shown, Co in SRPD 2+ and Fe 2+ The content of these elements is higher than that of RPD, and they are all active sites for activating PMS, indicating that the incorporation of S helps to increase the number of active sites. Fe in PD 2+ It has the highest content, but severe aggregation affects its activation efficiency for PMS.

[0088] like Figure 5As shown, SRPD exhibits stronger absorption in the visible light band than RPD, indicating that S incorporation contributes to visible light absorption. The band gaps of RM, ARM, R-ARM, RPD, SRPD, and PD are 1.89 eV, 1.57 eV, 1.57 eV, 1.45 eV, 1.34 eV, and 0.90 eV, respectively, and their valence band gaps are 1.21 eV, 1.26 eV, 1.26 eV, 0.54 eV, 0.19 eV, and 0.11 eV, respectively. Correspondingly, their conduction bands are located at -0.68 eV, -0.31 eV, -0.31 eV, -0.91 eV, -1.15 eV, and -0.79 eV, respectively, indicating that SRPD has stronger surface reactivity. The instantaneous photocurrent response shows that SRPD has the highest photogenerated carrier separation efficiency. In summary, S incorporation significantly improves the photocatalytic performance of the materials.

[0089] Example 2

[0090] The following describes the process of activating PMS with different materials to degrade oxytetracycline under visible light, including the following steps:

[0091] (1) Use 0.1 mol / L sulfuric acid and sodium hydroxide to adjust the pH of 10 ppm oxytetracycline solution to 5.0, and then measure 50 mL of the solution and pour it into the tubular reactor;

[0092] (2) Take 0.005g of red mud raw material, SRPD prepared in Example 1, ARM prepared in Comparative Example 1, R-ARM prepared in Comparative Example 2, RPD prepared in Comparative Example 3 and PD prepared in Comparative Example 4 respectively into the reaction solution, turn on magnetic stirring in the photochemical reaction chamber and carry out the adsorption test under dark conditions.

[0093] (3) After 30 min, turn on the visible light source and add 0.5 mL of 100 mM PMS solution to make the concentration of PMS in the solution system 1 mM for photocatalytic degradation reaction. The reaction time is 10 min; 0.5 mL of 200 mM PMS solution is added.

[0094] (4) Take 0.5 mL of the reaction solution every 2 min, and immediately add 0.2 mL of methanol for quenching. Then, use a UV-Vis spectrophotometer to measure the concentration of the remaining oxytetracycline at a wavelength of 353 nm, and calculate the degradation rate (%) by the formula: [(C0-C...]]. t The degradation efficiency was calculated using Ln(C0 / C0)×100 and the degradation efficiency was calculated using Ln(C0 / C0)×100. t ) = kt to calculate the corresponding reaction rate constant.

[0095] like Figure 6 As shown, SRPD can activate PMS under visible light irradiation and efficiently degrade oxytetracycline, degrading almost 90% of oxytetracycline within 10 minutes, with a degradation rate constant of 0.197 min.-1 The efficiency of SRPD was 3.34, 3.79, 3.28, 1.63, and 1.89 times that of RM, ARM, R-ARM, RPD, and PD, respectively. The excellent photocatalytic activation and degradation performance of the SRPD system is related to the abundant active sites, strong visible light absorption capacity, high photogenerated carrier separation efficiency, and strong surface reactivity of SRPD.

[0096] Example 3

[0097] This example demonstrates the effect of different doses of SRPD material on the degradation of oxytetracycline by activated PMS under visible light:

[0098] (1) Use 0.1 mol / L sulfuric acid and sodium hydroxide to adjust the pH of 10 ppm oxytetracycline solution to 5.0, and then measure 50 mL of the solution and pour it into the tubular reactor.

[0099] (2) Take 0, 0.0025, 0.005, 0.01 and 0.015 g of the SRPD material prepared in Example 1 respectively into 5 tubular reactors containing reaction solutions, turn on magnetic stirring in the photochemical reaction chamber and conduct adsorption tests under dark conditions;

[0100] (3) After 30 min, turn on the visible light source and add 0.5 mL of 100 mM PMS solution to make the concentration of PMS in the solution system 1 mM for photocatalytic degradation reaction. The reaction time is 10 min.

[0101] (4) Take 0.5 mL of the reaction solution every 2 min, and immediately add 0.2 mL of methanol for quenching. Then, use a UV-Vis spectrophotometer to measure the concentration of the remaining oxytetracycline at a wavelength of 353 nm, and calculate the degradation rate (%) by the formula: [(C0-C...]]. t Calculate the degradation efficiency using [) / C0]×100.

[0102] like Figure 7 As shown in a, the degradation rate initially increased with the increase of SRPD addition, reaching its highest level (92.81%) at 0.2 g / L. However, when the concentration exceeded 0.3 g / L, the degradation rate decreased. This was due to the excessive aggregation of SRPD, which led to a reduction in the number of active sites and a decrease in visible light transmittance.

[0103] Example 4

[0104] This example demonstrates the photocatalytic activation and degradation effect of oxytetracycline at different concentrations of PMS:

[0105] (1) Use 0.1 mol / L sulfuric acid and sodium hydroxide to adjust the pH of 10 ppm oxytetracycline solution to 5.0, and then measure 50 mL of the solution and pour it into the tubular reactor.

[0106] (2) Take 5 portions of 0.01g of SRPD material prepared in Example 1 into 5 tubular reactors containing reaction solutions, turn on magnetic stirring in the photochemical reaction chamber and conduct adsorption tests under dark conditions.

[0107] (3) After 30 min, turn on the visible light source and add 0 mL, 0.25 mL, 0.5 mL, 0.75 mL and 1.0 mL of 100 mM PMS solution to the five reactors respectively, so that the concentration of PMS in the solution system is 0 mM, 0.5 mM, 1 mM, 1.5 mM and 2 mM respectively for photocatalytic degradation reaction, and the reaction time is 10 min;

[0108] (4) Take 0.5 mL of the reaction solution every 2 min, and immediately add 0.2 mL of methanol for quenching. Then, use a UV-Vis spectrophotometer to measure the concentration of the remaining oxytetracycline at a wavelength of 353 nm, and calculate the degradation rate (%) by the formula: [(C0-C...]]. t Calculate the degradation efficiency using [) / C0]×100.

[0109] like Figure 7 As shown in Figure b, it can be seen from the figure that the degradation rate gradually increases with the increase of PMS concentration in the system, but the increase in degradation rate is not obvious when it exceeds 1 mM. This is caused by the self-quenching or transformation of too many reactive oxygen species.

[0110] Example 5

[0111] This example demonstrates the effect of solution pH on the photocatalytic activation and degradation of oxytetracycline.

[0112] (1) Use 0.1 mol / L sulfuric acid and sodium hydroxide to adjust the pH of 10 ppm oxytetracycline solution to 3.0, 5.0, 7.0, 9.0 and 11.0 respectively, and then measure 50 mL of the solution and pour it into 5 tubular reactors.

[0113] (2) Take 0.01g of the SRPD prepared in Example 1 into the reaction solution, turn on magnetic stirring in the photochemical reaction chamber, and conduct an adsorption test under dark conditions;

[0114] (3) After 30 min, turn on the visible light source and add 0.5 mL of 100 mM PMS solution to make the concentration of PMS in the solution system 1 mM for photocatalytic degradation reaction. The reaction time is 10 min.

[0115] (4) Take 0.5 mL of the reaction solution every 2 min, and immediately add 0.2 mL of methanol for quenching. Then, use a UV-Vis spectrophotometer to measure the concentration of the remaining oxytetracycline at a wavelength of 353 nm, and calculate the degradation rate (%) by the formula: [(C0-C...]]. tThe degradation efficiency was calculated using Ln(C0 / C0)×100 and the degradation efficiency was calculated using Ln(C0 / C0)×100. t ) = kt to calculate the corresponding reaction rate constant.

[0116] like Figure 8 As shown, within the pH range of 3–11, the SRPD photocatalytic activation system achieved high degradation rates (92.81–96.08%), with corresponding degradation rate constants ranging from 0.223 to 0.275 min. -1 The system's ability to maintain excellent degradation efficiency over a wide pH range is likely related to the role of S species in SRPD as electron donors in the regeneration of active sites.

[0117] Example 6

[0118] This embodiment is a test of the recycling effect of the SRPD material prepared by the present invention:

[0119] (1) Use 0.1 mol / L sulfuric acid and sodium hydroxide to adjust the pH of 10 ppm oxytetracycline solution to 5.0, and then measure 50 mL of the solution and pour it into the tubular reactor;

[0120] (2) Take 0.01g of the SRPD prepared in Example 1 into the reaction solution, turn on magnetic stirring in the photochemical reaction chamber, and conduct an adsorption test under dark conditions;

[0121] (3) After 30 min, turn on the visible light source and add 0.5 mL of 100 mM PMS solution to make the concentration of PMS in the solution system 1 mM for photocatalytic degradation reaction. The reaction time is 10 min.

[0122] (4) Take 0.5 mL of the reaction solution every 2 min, and immediately add 0.2 mL of methanol for quenching. Then, use a UV-Vis spectrophotometer to measure the concentration of the remaining oxytetracycline at a wavelength of 353 nm, and calculate the degradation rate (%) by the formula: [(C0-C...]]. t Calculate the degradation efficiency using [) / C0]×100.

[0123] (5) After the reaction is completed, SRPD is attracted and gathered at the bottom of the tubular reactor by an external magnet. Then, the supernatant reaction residue is poured off, and then fresh oxytetracycline solution is poured in to carry out photocatalytic activation degradation test under the same conditions as before. This process is repeated 5 times.

[0124] like Figure 9 As shown, after five repeated uses, the photocatalytic degradation rate of oxytetracycline remained at around 85%, indicating that SRPD has a relatively stable structure and strong reusability; this is due to the active site (Co) of SRPD during the degradation process. 2+ / Fe 2+This is caused by the continuous generation of regenerative and reactive oxygen species.

[0125] Example 7

[0126] The preparation steps of SRPD materials at different calcination temperatures are as follows:

[0127] (1) Take 5g of red mud into a conical flask containing 100mL of hydrochloric acid solution with a concentration of 2.4mol / L, and disperse it ultrasonically for 15min;

[0128] (2) Place it in a water bath and stir magnetically at 90°C for 2 hours;

[0129] (3) After cooling to room temperature, add 16 mmol of ammonium sulfide and stir for 30 min.

[0130] (4) While stirring, add 50 mL of a 0.04 mol / L potassium cobalt cyanide solution dropwise at a rate of 4 mL / min.

[0131] (5) Stir continuously for 2 hours, then let stand for 12 hours;

[0132] (6) After repeating the "high-speed centrifugation-deionized water washing" three times, the resulting solid was placed in an 80℃ oven to dry;

[0133] (7) The dried samples were calcined at 300, 400, 500 and 600 °C in a nitrogen atmosphere for 2 h to obtain S-doped supported red mud-based Prussian blue analogue photocatalysts at different calcination temperatures, which were denoted as SRPD-300, SRPD-400, SRPD-500 and SRPD-600, respectively.

[0134] (8) The obtained material was subjected to photocatalytic activation degradation test of oxytetracycline according to the conditions in Example 2.

[0135] like Figure 10 As shown, the SRPD-300, SRPD-400, SRPD-500 and SRPD-600 photocatalytic activation systems can all achieve a degradation efficiency of over 80% within 10 minutes.

Claims

1. A method for preparing a S-doped supported red mud-based Prussian blue analogue derivative photocatalyst with a wide pH range, characterized by: Red mud raw material is acid-dissolved to obtain iron-containing liquid. Then, sulfur-containing reducing agent and potassium cobalt cyanide solution are added to the iron-containing liquid in sequence to carry out reduction and precipitation reaction. The reaction product is separated into solid and liquid to obtain solid product. The solid product is calcined in a protective atmosphere to obtain the final product. The sulfur-containing reducing agent includes at least one of ammonium sulfide, sodium sulfide, and potassium sulfide; The molar amount of the sulfur-containing reducing agent is 1 to 3 times that of the iron element in the red mud raw material.

2. A process for the preparation of a S-doped supported red mud-based Prussian blue analogue derivative photocatalyst with a wide pH range according to claim 1, characterized by: The conditions for the acid dissolution process are as follows: at least one of hydrochloric acid, sulfuric acid, and nitric acid is used as the acid dissolution solution, the liquid-to-solid ratio is 60-140 mL: 3-7 g, the temperature is 85-95℃, and the time is 2-4 h.

3. A process for the preparation of a S-doped supported red mud-based Prussian blue analogue derivative photocatalyst with a wide pH range according to claim 1, characterized by: The conditions for the reduction reaction are: room temperature and time of 15-40 min.

4. The method for preparing a S-doped supported red mud-based Prussian blue analogue photocatalyst with a wide pH range according to claim 1, characterized in that: The molar ratio of potassium cobalt cyanide to iron in the red mud in the potassium cobalt cyanide solution is 1~4:

4.

5. The method for preparing a S-doped supported red mud-based Prussian blue analogue photocatalyst with a wide pH range according to claim 1 or 4, characterized in that: The concentration of the potassium cobalt cyanide solution is 0.02~0.08 mol / L; The potassium cobalt cyanide solution was added at a rate of 2-6 mL / min.

6. A process for the preparation of a S-doped supported red mud-based Prussian blue analogue derivative photocatalyst having a wide pH range according to claim 1, characterized by: The precipitation reaction conditions are: room temperature and 10-14 hours.

7. A process for the preparation of a S-doped supported red mud-based Prussian blue analogue derivative photocatalyst having a wide pH range according to claim 1, characterized by: The protective atmosphere is nitrogen, the calcination temperature is 300~600℃, and the calcination time is 1~3h.

8. A S-doped supported red mud-based Prussian blue analogue photocatalyst with a wide pH range, characterized in that: Prepared by the method described in any one of claims 1 to 7.

9. Use of a wide pH range S-doped supported red mud-based Prussian blue analogues derivative photocatalyst according to claim 8, characterized in that: Antibiotics used in the photocatalytic degradation of persulfate solutions.

10. Use of a wide pH range S-doped supported red mud-based Prussian blue analogues derivative photocatalyst according to claim 9, characterized by the fact that it is used in the treatment of water and wastewater. The antibiotic is oxytetracycline; the concentration of the photocatalyst in the solution is not less than 0.1 g / L; the concentration of the persulfate in the solution is not less than 1 mM; the concentration of the antibiotic in the solution is 5-30 ppm; the initial pH of the solution is 3-11, and the temperature is 20-50℃.

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