A PDDA modified LaFeO3 / g-C3N5 magnetic composite photocatalyst, a preparation method thereof and application thereof in antibiotic degradation

Abstract

The application discloses a PDDA modified LaFeO3 / g-C3N5 magnetic composite photocatalyst, a preparation method thereof and application of the photocatalyst in antibiotic degradation, and comprises the following steps: (1) dispersing g-C3N5 in water and adjusting pH to obtain a g-C3N5 suspension; (2) dispersing LaFeO3 nanomaterial in water and adjusting pH, adding a PDDA solution and stirring, and then separating and drying to obtain PDDA modified LaFeO3 powder; (3) dispersing the PDDA modified LaFeO3 powder in water, and under stirring conditions, dropping the powder into the g-C3N5 suspension, continuing to stir and react, and then centrifuging and drying to obtain the magnetic composite photocatalyst. The PDDA modified LaFeO3 / g-C3N5 composite material obtained in the application has high catalytic activity, strong magnetic recovery performance and excellent stability, and realizes effective degradation of antibiotics in wastewater.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and in particular relates to a PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst, a preparation method thereof, and application in antibiotic degradation. Background Art

[0002] In recent years, antibiotics have been widely used as medicines and feed additives in a variety of fields, including healthcare, animal husbandry, and aquaculture. However, this surge in use has led to large amounts of untreated antibiotics entering the natural environment through hospital wastewater and livestock and poultry wastewater, triggering a global problem of antibiotic residue pollution. These residual antibiotics are not only toxic to aquatic organisms and soil microorganisms but can also accumulate through the food chain, posing a threat to human health.

[0003] Currently, treatment technologies for antibiotics in aquatic environments primarily rely on physical adsorption, biodegradation, and chemical oxidation. While physical adsorption is relatively simple to operate, it suffers from limited adsorption capacity and high adsorbent regeneration costs. Biodegradation, while environmentally friendly and cost-effective, is susceptible to interference from the antibacterial properties of antibiotics, resulting in unstable degradation efficiency and long treatment cycles. While chemical oxidation is highly effective, it is prone to secondary pollution and carries high treatment costs. Against this backdrop, photocatalytic technology, with its significant advantages of being both environmentally friendly and energy-efficient, has become a research hotspot in wastewater treatment.

[0004] However, existing photocatalysts have problems such as low magnetic recovery efficiency, narrow visible light response range, and easy agglomeration of nanoparticles. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide an efficient PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst, its preparation method and application in antibiotic degradation.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0007] A method for preparing a PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst comprises the following steps:

[0008] (1) Dispersing g-C3N5 in water and ultrasonically treating the suspension to obtain a suspension, adding ammonia water to the suspension to adjust the pH to 8-10 and stirring to obtain a g-C3N5 suspension;

[0009] (2) LaFeO3 nanomaterials were dispersed in water to obtain a suspension, ammonia water was added dropwise to the suspension to adjust the pH to 8-10, and then PDDA solution was added and stirred to allow PDDA to be adsorbed on the surface of LaFeO3 nanoparticles through electrostatic adsorption. PDDA-modified LaFeO3 powder was obtained after separation and drying;

[0010] (3) Dispersing the PDDA-modified LaFeO3 powder in water to obtain a dispersion, and dropping the dispersion into the g-C3N5 suspension prepared in step (1) under stirring conditions, continuing stirring and maintaining the pH at 8-11 by adding ammonia water, so that LaFeO3 and g-C3N5 are composited by electrostatic adsorption, and obtaining the PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst after centrifugation and drying.

[0011] As a further improvement, in step (1), the pH is adjusted to 8-10 and then stirred for at least 1 hour.

[0012] As a further improvement, in step (2), a PDDA solution with a concentration of 0.1 to 1 mg / mL was added and stirred for 1 to 3 hours.

[0013] As a further improvement, a PDDA solution with a concentration of 0.5-0.7 mg / mL was added in step (2).

[0014] As a further improvement, step (3) maintains the pH at 9-10.

[0015] As a further improvement, the mass ratio of PDDA-modified LaFeO3 and g-C3N5 in the PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst is 1:(0.1~1.5).

[0016] As a further improvement, the mass ratio of PDDA-modified LaFeO3 and g-C3N5 in the PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst is 1:(0.5~0.7).

[0017] As a further improvement, in step (3), stirring is continued for at least 2 hours after the dispersion liquid is added dropwise.

[0018] The present invention provides a PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst, which is prepared by adopting the preparation method.

[0019] The present invention also provides an application of the PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst in antibiotic degradation.

[0020] The present invention modifies the surface charge of LaFeO3 and g-C3N5 materials, constructing a positively charged layer on the LaFeO3 surface using the cationic polyelectrolyte PDDA and a negatively charged layer on the g-C3N5 surface through ammonia treatment. This allows for directed self-assembly of the two materials through electrostatic adsorption. By optimizing the LaFeO3 and g-C3N5 composite ratio, the cationic polyelectrolyte concentration, and the pH of the reaction system during composite reaction, a PDDA-modified LaFeO3 / g-C3N5 composite material with high catalytic activity, strong magnetic recovery properties, and excellent stability is prepared, effectively degrading antibiotics in wastewater.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention uses PDDA as a cationic polyelectrolyte to modify the surface of LaFeO3 and constructs a LaFeO3 / g-C3N5 magnetic composite photocatalyst through ionic electrostatic self-assembly technology. The antibiotic degradation rate can reach more than 95% under 12 W blue LED light irradiation for 60 minutes, and can be reused 5 times, which significantly exceeds the single LaFeO3, g-C3N5 and mechanical mixed materials, effectively solving the problem of poor photocatalytic activity.

[0023] (2) In the present invention, PDDA not only acts as a surface charge modifier, but also acts as a steric hindrance layer, effectively inhibiting the agglomeration of LaFeO3 nanoparticles and improving the structural stability of the composite material.

[0024] (3) In the present invention, PDDA itself can also be used as a high-efficiency flocculant or coagulant aid, which can neutralize the surface charge of negatively charged suspended particles and promote particle aggregation and sedimentation, thus effectively improving the treatment efficiency in actual wastewater treatment. DETAILED DESCRIPTION

[0025] To facilitate understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0026] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0027] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0028] In the present application, the perovskite structure LaFeO3 is modified by cationic polyelectrolyte diallyl dimethyl ammonium chloride (PDDA), combined with g-C3N5 material through ion-electrostatic self-assembly in alkaline solution, to obtain PDDA modified LaFeO3 / g-C3N5 magnetic composite material, realizing efficient photocatalytic degradation of antibiotic wastewater and convenient magnetic recovery of the catalyst.

[0029] In some specific embodiments, the PDDA modified LaFeO3 / g-C3N5 magnetic composite photocatalyst of the present application comprises the following steps:

[0030] (1) Disperse g-C3N5 in water and ultrasonically treat to obtain a suspension, add ammonia water to the suspension to adjust the pH to 8-10 and stir to obtain a g-C3N5 suspension.

[0031] In some embodiments, the preparation method of g-C3N5 is: 3-amino-1,2,4-triazole (3-AT) is used as a nitrogen source, heated to 580°C at a heating rate of 5°C / min under air atmosphere, and calcined for at least 3 hours to obtain the product g-C3N5; the nitrogen source can also be selected from urea, melamine, etc.

[0032] In some embodiments, after adjusting the pH to 8-10, stir at room temperature for at least 1 hour.

[0033] (2) Disperse LaFeO3 nanomaterial in water to obtain a suspension, add ammonia water dropwise to adjust the pH to 8-10, then add cationic polyelectrolyte polydiallyldimethylammonium chloride (PDDA) solution and stir, so that the cationic polyelectrolyte is uniformly adsorbed on the surface of LaFeO3 nanoparticles by electrostatic adsorption, and PDDA modified LaFeO3 powder is obtained after separation and drying.

[0034] In some embodiments, disperse LaFeO3 in water, stir at room temperature for 1 hour to obtain a suspension. Add ammonia water dropwise with a concentration of 0.1-1 mol / L.

[0035] In some embodiments, add polydiallyldimethylammonium chloride (PDDA) solution with a concentration of 0.1-1 mg / mL (preferably 0.3-1 mg / mL, more preferably 0.5-0.7 mg / mL), the amount added is 80-120 mL, and stir at a speed of 200-600 r / min at room temperature for 1-3 hours.

[0036] In some embodiments, after the stirring is completed, the suspension is centrifuged and washed to remove the unabsorbed PDDA, and is placed in a vacuum oven at 60-80°C for drying for at least 12 hours, to finally obtain PDDA modified LaFeO3 powder.

[0037] In some embodiments, LaFeO3 nanomaterials are prepared using a sol-gel method, comprising the following steps:

[0038] (2.1) Add the citric acid solution dropwise to a mixed solution of lanthanum nitrate and ferric nitrate, and stir to obtain a mixed solution precursor.

[0039] In some embodiments, the molar ratio of lanthanum nitrate, ferric nitrate, and citric acid is 1:1:2.

[0040] In some embodiments, 0.015 mol of lanthanum nitrate and 0.015 mol of ferric nitrate are dissolved in at least 20 ml of deionized water and stirred at room temperature to fully mix and dissolve the lanthanum nitrate and ferric nitrate raw materials to obtain a mixed solution of lanthanum nitrate and ferric nitrate. 0.03 mol of citric acid is dissolved in at least 20 ml of deionized water to prepare a citric acid solution.

[0041] (2.2) The obtained mixed solution precursor is subjected to solvent evaporation and drying treatment to obtain a dry gel.

[0042] In some embodiments, the mixed solution precursor is transferred to a water bath at a temperature of not less than 90° C. to evaporate the solvent, and stirred for at least 4 hours to obtain a viscous gel. The gel is then transferred to an oven at a temperature of not less than 120° C. and dried for at least 12 hours to obtain a xerogel.

[0043] (2.3) The obtained dry gel is ground into powder (as a calcination precursor) and then calcined to obtain the product LaFeO3 magnetic nanomaterial.

[0044] In some embodiments, the calcination temperature is not less than 400° C., and the calcination time is at least 4 hours.

[0045] (3) Dispersing the PDDA-modified LaFeO3 powder in water to obtain a dispersion, and dropping the dispersion into the g-C3N5 suspension prepared in step (1) under stirring conditions, continuing stirring and maintaining the pH at 8-11 (preferably 9-10) by adding ammonia water, so that LaFeO3 and g-C3N5 are composited by electrostatic adsorption, and obtaining the PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst after centrifugation and drying.

[0046] In some embodiments, the mass ratio of PDDA-modified LaFeO3 to g-C3N5 is 1:(0.1-1.5), preferably 1:(0.3-1), and more preferably 1:(0.5-0.7).

[0047] In some embodiments, the PDDA modified LaFeO3 powder is dispersed in water, ultrasonic dispersion for 10 minutes, slowly drop g-C3N5 suspension liquid under stirring condition, preferably at a speed of 40 drops per minute, continue stirring for at least 2 hours after the drop is completed to ensure that the electrostatic adsorption is sufficient; during the compounding process, the pH of the system is continuously detected, and a small amount of ammonia water is continuously added to maintain the pH at about 8-11.

[0048] In some embodiments, after the compounding is completed, the mixed solution is centrifuged, the precipitate is washed with deionized water for three times, and is placed in a 60℃ vacuum oven for drying for at least 12 hours to obtain a PDDA modified LaFeO3 / g-C3N5 magnetic composite photocatalyst.

[0049] As a new type of carbon nitride material, g-C3N5 has a layered highly conjugated tri-s-triazine or triazine ring structure, which endows it with excellent chemical stability and mechanical strength, and a band gap of about 2.2-2.4eV, which is narrower than that of g-C3N4 (2.7eV), which can effectively widen the visible light absorption range and significantly improve the visible light utilization rate.

[0050] The perovskite type oxide LaFeO3 has a stable lattice structure, and its magnetic properties are convenient for magnetic separation and recovery. However, single LaFeO3 nanoparticles are easy to agglomerate, which reduces the specific surface area of the material and reduces the active sites, thereby limiting the photocatalytic efficiency.

[0051] The application creatively proposes a method combining surface modification of cationic polyelectrolyte and ion electrostatic self-assembly technology to realize efficient compounding of LaFeO3 and g-C3N5. The surface charge state of LaFeO3 is modified by cationic polyelectrolyte diallyldimethylammonium chloride PDDA, and g-C3N5 is surface treated by ammonia water. The two are synthesized into PDDA-LaFeO3 / g-C3N5 composite material through ion electrostatic self-assembly technology in an alkaline environment system. This method not only effectively solves the problem of nanoparticle agglomeration, but also retains the magnetic recovery characteristics of the material, providing a high-performance catalyst for antibiotic wastewater treatment.

[0052] In the application, the selection of ammonia water is based on its multiple roles in material surface charge regulation, polyelectrolyte adsorption and composite interface construction:

[0053] 1) By adjusting, the solution pH can be maintained at 8-10, which promotes the deprotonation of the hydroxyl group on the surface of LaFeO3 to form negative charge sites (OH-), which provides sites for electrostatic adsorption of cationic polyelectrolyte (PDDA), and ammonia water can promote the exposure of amino groups (-NH2) on the surface of g-C3N5, which provides a driving force for the subsequent ion electrostatic self-assembly.

[0054] 2) As a weak base, ammonia slowly releases OH - ions, avoiding local pH unevenness, ensuring that PDDA is evenly coated on the LaFeO3 surface, forming a stable positive charge modification layer, and inhibiting the agglomeration of nanoparticles.

[0055] 3) Ammonia is volatile and can be completely removed during the washing process without introducing metal ion impurities. It is also low-cost and safe to operate.

[0056] The present invention discloses a PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst for treating antibiotic-containing wastewater. The antibiotics include one or more of tetracycline, oxytetracycline, and chlortetracycline. The initial concentration of the antibiotic wastewater is 20-50 mg / L. The PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst is used at a dosage of 0.2 g per liter of the antibiotic wastewater. The catalyst degrades the antibiotics under visible light (visible light response range 400-650 nm), for example, under irradiation with a blue LED (wavelength 450-480 nm).

[0057] The mechanism of the LaFeO3 / g-C3N5 magnetic composite photocatalyst modified by PDDA in treating antibiotic wastewater is as follows: LaFeO3 is a perovskite-type magnetic oxide with a lattice structure. The redox couple has excellent electron transfer ability, while the conjugated triazine ring structure of g-C3N5 can efficiently capture visible light. The two form a heterojunction interface through cationic polyelectrolyte modification and ionic electrostatic self-assembly, constructing a unique "light absorption-carrier separation-oxidative degradation" synergistic system under visible light irradiation. The electrons in the conduction band of LaFeO3 react with dissolved oxygen to generate superoxide radicals ( ), as the main oxidizing species to attack antibiotic molecules; the holes on the valence band of g-C3N5 ( ) will synergistically oxidize organic matter to form " leading, A dual-pathway degradation mechanism.

[0058] Example 1:

[0059] The invention discloses a LaFeO3 / g-C3N5 magnetic composite catalyst modified with PDDA, and its preparation and application in the treatment of antibiotic-containing wastewater, which specifically comprises the following steps:

[0060] a. Add 5 g of 3-amino-1,2,4-triazole (3-AT) to a quartz crucible and heat to 580 °C at 5 °C / min in air. Calcinate for at least 3 hours to obtain a brown solid, the product g-C3N5.

[0061] b. LaFeO3 perovskite material was prepared by sol-gel method. 0.015 mol of lanthanum nitrate hexahydrate and 0.015 mol of ferric nitrate nonahydrate were weighed and dissolved in 20 ml of distilled water. 0.03 mol of citric acid was weighed and dissolved in 20 ml of distilled water. The mixtures were stirred for about half an hour. After being evenly mixed, the citric acid solution was slowly added dropwise to the mixed solution of nitrates and stirred at room temperature to obtain a mixed solution precursor. The mixed solution precursor was transferred to a 90°C water bath to evaporate the solvent. After stirring for at least 4 hours, a viscous gel was obtained. The gel was then transferred to a 120°C oven and dried for 12 hours to obtain a dry gel. The powder was transferred to a quartz boat and placed in a tube furnace at 450°C. The dry gel powder was calcined for at least 4 hours. The calcined product was then cooled to room temperature to obtain the product LaFeO3 magnetic nanomaterial.

[0062] c. Weigh 1 g of the LaFeO3 material obtained in step (b) and disperse it in 100 ml of deionized water. Stir at room temperature for 1 hour to obtain a suspension. Add 1 mol / L ammonia water dropwise to the suspension and stir the suspension continuously to maintain the pH range at about 8.5. Add 100 ml of 0.5 mg / mL PDDA and stir at room temperature for 2 hours at a speed of 200 to 600 r / min. After stirring, centrifuge the suspension in step (c), wash to remove unadsorbed cationic polyelectrolyte, and dry in a vacuum oven at 60 to 80°C for at least 12 hours to obtain PDDA-modified LaFeO3 powder.

[0063] d. Weigh 0.5 g of the material g-C3N5 obtained in step (a) and disperse it in 100 ml of deionized water. Ultrasonicate for half an hour to form a uniform suspension. Slowly add 1 mol / L ammonia to adjust the pH to around 10 and stir at room temperature for at least 1 hour.

[0064] e. Weigh 1 g of the PDDA-modified LaFeO3 powder obtained in step (c) and disperse it in 100 ml of deionized water. Ultrasonic dispersion was performed for 10 minutes. The mixture was slowly dripped into the suspension prepared in step (d) at a rate of 40 drops per minute under stirring. Stirring was continued for at least 2 hours after the addition was completed to ensure sufficient electrostatic adsorption. The pH of the system was continuously monitored during the compounding process, and ammonia was continuously added to ensure that the pH was maintained at around 10 (±0.2).

[0065] f. The mixed solution in step (e) was centrifuged, the precipitate was washed three times with deionized water, and dried in a vacuum oven at 60 ° C for at least 12 hours to obtain a PDDA-modified LaFeO3 / g-C3N5-50% magnetic composite material, referred to as PDDA-LaFeO3 / g-C3N5-50%;

[0066] g. Application of PDDA-modified LaFeO3 / g-C3N5 catalyst in photocatalytic treatment of antibiotic-containing wastewater, the specific steps are as follows:

[0067] g.1 Weigh 10 mg of PDDA-LaFeO3 / g-C3N5-50% catalyst and mix it with 50 mL of 25 mg / L tetracycline solution in a reaction vessel. Ultrasonicate for 5 minutes to ensure uniform mixing.

[0068] g.2 Place the reaction system in the dark for 30 minutes to allow the tetracycline to fully adsorb onto the catalyst surface. Then, illuminate the reaction at room temperature for 60 minutes using a 12 W LED blue light source (wavelength 450-480 nm).

[0069] g.3 After the reaction is completed, separate the product from the catalyst and use ultraviolet absorption spectroscopy to detect the degradation rate of the antibiotic.

[0070] Example 2:

[0071] The PDDA-modified LaFeO3 / g-C3N5 magnetic composite catalyst, its preparation, and application in the treatment of antibiotic-containing wastewater are as follows: the specific steps are as shown in Example 1, except that in steps (d) to (f), the catalyst prepared by combining the PDDA-modified LaFeO3 material and the g-C3N5 material in a mass ratio of 1:0.3 (0.3 g of g-C3N5 is weighed) is denoted as PDDA-LaFeO3 / g-C3N5-30%.

[0072] Example 3:

[0073] The PDDA-modified LaFeO3 / g-C3N5 magnetic composite catalyst, its preparation, and application in the treatment of antibiotic-containing wastewater are as follows: the specific steps are as shown in Example 1, except that in steps (d) to (f), the catalyst prepared by combining the PDDA-modified LaFeO3 material and the g-C3N5 material in a mass ratio of 1:0.7 (0.7 g of g-C3N5 is weighed) is denoted as PDDA-LaFeO3 / g-C3N5-70%.

[0074] Example 4:

[0075] The PDDA-modified LaFeO3 / g-C3N5 magnetic composite catalyst, its preparation, and application in the treatment of antibiotic-containing wastewater are as follows: the specific steps are as shown in Example 1, except that in steps (d) to (f), the catalyst prepared by combining the PDDA-modified LaFeO3 material and the g-C3N5 material in a mass ratio of 1:1 (1 g of g-C3N5 is weighed) is recorded as PDDA-LaFeO3 / g-C3N5-100%.

[0076] Embodiment 5:

[0077] The PDDA-modified LaFeO3 / g-C3N5 magnetic composite catalyst, its preparation, and application in the treatment of antibiotic-containing wastewater are described in Example 1. The difference is that in step (c), PDDA with a concentration of 0.3 mg / mL is used for modification. The prepared material is designated as PDDA-LaFeO3 / g-C3N5-50%-A.

[0078] Example 6:

[0079] The PDDA-modified LaFeO3 / g-C3N5 magnetic composite catalyst, its preparation, and application in the treatment of antibiotic-containing wastewater are as follows: the specific steps are as shown in Example 1, except that in step (c), PDDA with a concentration of 0.7 mg / mL is used for modification. The prepared material is recorded as PDDA-LaFeO3 / g-C3N5-50%-B.

[0080] Embodiment seven:

[0081] The PDDA-modified LaFeO3 / g-C3N5 magnetic composite catalyst, its preparation, and its application in the treatment of antibiotic-containing wastewater are as follows: the specific steps are shown in Example 1, except that in step (c), PDDA with a concentration of 1.0 mg / mL is used for modification, and the prepared material is recorded as PDDA-LaFeO3 / g-C3N5-50%-C.

[0082] Embodiment 8:

[0083] A PDDA-modified LaFeO3 / g-C3N5 magnetic composite catalyst, its preparation, and its application in the treatment of antibiotic-containing wastewater are described in Example 1. The specific steps are as follows, except that in step (e), the pH of the system is maintained at approximately 8 (±0.2) during ionic electrostatic self-assembly. The prepared material is designated as PDDA-LaFeO3 / g-C3N5-50%-D.

[0084] Embodiment 9:

[0085] PDDA modified LaFeO3 / g-C3N5 magnetic composite catalyst, its preparation and application in antibiotic-containing wastewater treatment, the specific steps are seen in example one, the difference is that in step (e), the pH of the system is maintained at about 9 (± 0.2) during the ionic electrostatic self-assembly, the prepared material is recorded as PDDA-LaFeO3 / g-C3N5-50%-E.

[0086] Example ten:

[0087] PDDA modified LaFeO3 / g-C3N5 magnetic composite catalyst, its preparation and application in antibiotic-containing wastewater treatment, the specific steps are seen in example one, the difference is that in step (e), the pH of the system is maintained at about 11 (± 0.2) during the ionic electrostatic self-assembly, the prepared material is recorded as PDDA-LaFeO3 / g-C3N5-50%-F.

[0088] Comparative example one:

[0089] PDDA modified LaFeO3 / g-C3N5 magnetic composite catalyst, its preparation and application in antibiotic-containing wastewater treatment, the specific steps are seen in example one, the difference is that the materials synthesized in steps (a), (c) are mixed by mechanical grinding, and the grinding and dispersion are carried out for 2 hours with a mortar, and the prepared catalyst is recorded as PDDA-LaFeO3 / g-C3N5-50%-G.

[0090] Comparative example two:

[0091] As a control, LaFeO3 catalyst, its preparation and application in antibiotic-containing wastewater treatment, the specific steps are seen in example one, the difference is that the material LaFeO3 prepared in step (b) is used as a catalyst.

[0092] Comparative example three:

[0093] As a control, PDDA modified LaFeO3 catalyst, its preparation and application in antibiotic-containing wastewater treatment, the specific steps are seen in example one, the difference is that the PDDA modified LaFeO3 prepared in steps (b)-(c) is used as a catalyst, and is recorded as PDDA-LaFeO3.

[0094] Comparative example four:

[0095] As a control, g-C3N5 catalyst, its preparation and application in antibiotic-containing wastewater treatment, the specific steps are seen in example one, the difference is that the g-C3N5 prepared in step (a) is used as a catalyst.

[0096] Comparative example five:

[0097] The same as Example 1, except that LaFeO 3 as the catalyst was not modified with PDDA (step (c) was omitted), denoted as LaFeO 3 / g-C 3 N 5-50%.

[0098] Comparative Example 6:

[0099] The same as Example 1, except that no ammonia treatment was used (no ammonia was added during steps (c), (d) and (e)), denoted as PDDA-LaFeO3 / g-C3N5-50%-H.

[0100] Comparative Example 7:

[0101] The same as Example 1, except that 1 mol / L NaOH aqueous solution was used instead of ammonia water in steps (c), (d) and (e), and was recorded as PDDA-LaFeO3 / g-C3N5-50%-I.

[0102] Comparative Example 8:

[0103] The same as Example 1, except that in step (a), g-C3N4 is synthesized and then compounded (g-C3N5 is replaced by g-C3N4), which is recorded as PDDA-LaFeO3 / g-C3N4.

[0104] Example 11:

[0105] The same as Example 1, but with different materials, was used to examine the treatment capacity of antibiotic wastewater discharged from an actual pharmaceutical company. Testing showed that the wastewater contained tetracycline, with an initial concentration of 53 mg / L.

[0106] The effects of the above examples and comparative examples on photocatalytic degradation of antibiotic wastewater are shown in Table 1. Degradation rate = (initial tetracycline concentration - final tetracycline concentration) / initial tetracycline concentration × 100%:

[0107]

[0108] The reaction conditions for Examples 1 to 10 and the comparative example were as follows: 10 mg of catalyst, 50 ml of a 25 mg / L tetracycline aqueous solution, 1000 rpm, 12 W LED blue light, and 60 min. The reaction conditions for Example 12 were as follows: 10 mg of catalyst, 50 ml of a 53 mg / L tetracycline-containing wastewater, 1000 rpm, 12 W LED blue light, and 60 min.

[0109] Example 12:

[0110] Similar to Example 1, except that the PDDA-LaFeO3 / g-C3N5-50% catalyst was tested for its reusability in photocatalytic degradation of antibiotic wastewater. After each cycle, the composite material was separated and recovered using an external magnetic field, washed with distilled water until neutral, and dried overnight in an 80°C oven. The recovery rate exceeded 90%. The experimental results, shown in Table 2, show that the catalyst could be reused five times without significant degradation in catalytic performance, demonstrating its good cyclic stability.

[0111]

[0112] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any form. Therefore, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical solution of the present invention and are based on the technical essence of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst, characterized in that: The following steps are included: (1) Dispersing g-C3N5 in water and ultrasonically treating the suspension to obtain a suspension, adding ammonia water to the suspension to adjust the pH to 8-10 and stirring to obtain a g-C3N5 suspension; (2) LaFeO3 nanomaterials were dispersed in water to obtain a suspension, ammonia water was added dropwise to the suspension to adjust the pH to 8-10, and then PDDA solution was added and stirred to allow PDDA to be adsorbed on the surface of LaFeO3 nanoparticles through electrostatic adsorption. PDDA-modified LaFeO3 powder was obtained after separation and drying; (3) Dispersing the PDDA-modified LaFeO3 powder in water to obtain a dispersion, and dropping the dispersion into the g-C3N5 suspension prepared in step (1) under stirring conditions, continuing stirring and maintaining the pH at 8-11 by adding ammonia water, so that LaFeO3 and g-C3N5 are composited by electrostatic adsorption, and obtaining the PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst after centrifugation and drying.

2. The preparation method according to claim 1, characterized in that Step (1) Adjust the pH to 8-10 and stir for at least 1 hour.

3. The preparation method according to claim 1, characterized in that In step (2), a PDDA solution with a concentration of 0.1 to 1 mg / mL was added and stirred for 1 to 3 hours.

4. The preparation method according to claim 3, characterized in that In step (2), a PDDA solution with a concentration of 0.5-0.7 mg / mL was added.

5. The preparation method according to any one of claims 1 to 4, characterized in that Step (3) maintains the pH at 9-10.

6. The preparation method according to any one of claims 1 to 4, characterized in that The mass ratio of PDDA-modified LaFeO3 and g-C3N5 in the PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst is 1:(0.1~1.5).

7. The preparation method according to claim 6, characterized in that The mass ratio of PDDA-modified LaFeO3 and g-C3N5 in the PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst is 1:(0.5~0.7).

8. The preparation method according to any one of claims 1 to 4, characterized in that After the dispersion is added dropwise in step (3), stirring is continued for at least 2 hours.

9. A PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the PDDA-modified LaFeO3 / g-C3N5 magnetic composite photocatalyst according to claim 9 in antibiotic degradation, characterized in that: The antibiotics include one or more of tetracycline, oxytetracycline and chlortetracycline.

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