A ternary photocatalyst for degrading pharmaceutical wastewater and a preparation method and application thereof

Abstract

The application discloses a ternary photocatalyst for degrading pharmaceutical wastewater and a preparation method and application thereof, and the preparation method comprises the following process: adding biochar powder into a potassium hydroxide solution, then adding melamine, and performing ultrasonic and stirring activation, and then drying, calcining, and naturally cooling, so as to obtain g-C3N4 / Biochar; the g-C3N4 / Biochar is added into a bismuth nitrate solution and uniformly mixed to obtain a solution A; potassium bromide is dissolved in a mixture of water and ammonia water to obtain a solution B, the solution B is slowly added into the solution A and stirred, and then centrifugation, washing and drying are performed, so as to obtain the ternary photocatalyst for degrading pharmaceutical wastewater. The application introduces another photocatalyst material on the basis of g-C3N4 material and biochar adsorption, and the photocatalytic capacity of the catalyst for the pharmaceutical wastewater is improved.

Description

Technical Field

[0001] This invention belongs to the field of industrial pharmaceutical wastewater treatment technology, specifically relating to a ternary photocatalyst for degrading pharmaceutical wastewater, its preparation method, and its application. Background Technology

[0002] Antibiotic pharmaceutical wastewater is a type of industrial pharmaceutical wastewater characterized by high concentration, poor biodegradability, and high toxicity. Among the many types of antibiotics produced, fluoroquinolones with piperazine rings are particularly difficult to treat due to their recalcitrant degradation and resistance to enzymes. Furthermore, because quinolone antibiotics are toxic and can cause drug resistance, and their production processes are complex, the wastewater contains a large amount of unextracted antibiotic components. If this pharmaceutical wastewater is discharged untreated or inadequately treated, it poses a significant potential hazard to the aquatic environment and human health. Biochar, a porous functional material with a large surface area, abundant and easily controllable surface functional groups, and strong adsorption capacity, prepared by pyrolysis of organic matter such as traditional Chinese medicine organic solid waste under limited oxygen conditions, is a commonly used material for purifying organic pollutants in pharmaceutical industrial wastewater. However, traditional biochar suffers from limited adsorption capacity, difficulty in recovery, and inability to be reused, hindering its large-scale application.

[0003] Combining biochar with semiconductor materials to form heterojunctions is an effective method for removing quinolone antibiotics from wastewater. On the one hand, biochar has adsorption properties, which can adsorb quinolone antibiotics in water; on the other hand, the construction of heterojunctions can promote carrier separation in semiconductor materials, thereby improving photocatalytic efficiency.

[0004] g-C3N4 is a non-metallic semiconductor that exhibits good photocatalytic activity under visible light irradiation. Its preparation method is simple, it has good chemical stability, and a suitable band gap energy (Eg; approximately 2.7 eV), making it widely used for the photocatalytic degradation of antibiotics in wastewater. However, the rapid charge recombination rate, narrow visible light absorption range, and small specific surface area of ​​g-C3N4 limit its use alone. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a ternary photocatalyst for degrading pharmaceutical wastewater, its preparation method, and its application. Based on g-C3N4 material, the present invention introduces another photocatalyst on the basis of biochar adsorption, thereby improving the photocatalytic ability of the catalyst for pharmaceutical wastewater.

[0006] The technical solution adopted in this invention is as follows:

[0007] A method for preparing a ternary photocatalyst for degrading pharmaceutical wastewater includes the following steps:

[0008] Biochar powder was added to potassium hydroxide solution, followed by melamine. The mixture was then activated by ultrasound and stirring, dried, ground into powder, calcined, and then cooled naturally to obtain g-C3N4 / Biochar.

[0009] The g-C3N4 / Biochar was added to a bismuth nitrate pentahydrate solution and mixed thoroughly to obtain solution A;

[0010] KBr was added to a mixture of ultrapure water and ammonia to dissolve the KBr, resulting in solution B.

[0011] Solution B was added to solution A to carry out the reaction, followed by centrifugation, washing, and drying to obtain the ternary photocatalyst for degrading pharmaceutical wastewater.

[0012] Preferably, the jujube shell powder is fine jujube shell powder, and the particle size of the fine jujube shell powder is 80 mesh or above.

[0013] Preferably, the mass ratio of potassium hydroxide to biochar powder is (1-4):1.

[0014] Preferably, the mass of the jujube shell powder is 0.1% to 1.0% of the mass of melamine.

[0015] Preferably, when preparing g-C3N4 / Biochar, the dried product is calcined at 400-600℃ for 1-4 hours, followed by natural cooling.

[0016] Preferably, the mass of g-C3N4 / Biochar is 1% to 9% of the mass of bismuth nitrate pentahydrate.

[0017] Preferably, the molar ratio of KBr to bismuth nitrate pentahydrate is (1.6-2.4):(1.6-2.4).

[0018] Preferably, when adding solution B to solution A for reaction, the reaction is continuously stirred for 4-6 hours. After adding solution B to solution A for reaction, the resulting suspension is centrifuged at 8000±100 r / min (where ±100 r / min is the equipment speed deviation) at room temperature. Then, the separated product is washed 2-4 times alternately with ultrapure water and anhydrous ethanol.

[0019] The present invention also provides a ternary photocatalyst for degrading pharmaceutical wastewater, which is prepared by the preparation method of the present invention as described above.

[0020] The present invention also provides the application of the ternary photocatalyst for degrading pharmaceutical wastewater, the catalyst being used for photocatalytic degradation of antibiotic pharmaceutical wastewater, the antibiotic including norfloxacin.

[0021] The present invention has the following technical effects:

[0022] This patent successfully prepared g-C3N4 / Biochar material using inexpensive, renewable biochar powder and melamine, activated with KOH via ultrasonication, followed by a one-step carbonization process. The use of biochar not only enables g-C3N4 / Biochar to adsorb antibiotics, but also, due to its conductivity, promotes carrier separation, enhancing the photocatalytic activity of g-C3N4. Based on g-C3N4 / Biochar, another semiconductor material, bismuth oxybromide, was introduced. Combining bismuth oxybromide with it overcomes the shortcomings of bismuth oxybromide, such as easy recombination of photogenerated carriers and a narrow absorption spectrum, while simultaneously increasing the redox potential of the photocatalyst, further enhancing the photocatalytic activity of the prepared ternary material. The g-C3N4 / Biochar / Bi4O5Br2 material prepared by this invention exhibits excellent photocatalytic activity, not only promoting photogenerated carrier separation and increasing light absorption capacity, but also adsorbing antibiotics from wastewater. Attached Figure Description

[0023] Figure 1 The graph shows the concentration-time variation of norfloxacin under visible light after treatment with the carbon nitride / biochar / bismuth oxybromide catalyst prepared in Example 1 of this invention.

[0024] Figure 2 This is a graph showing the change in catechin concentration over time under visible light after treatment with the carbon nitride / biochar / bismuth oxybromide catalyst prepared in Example 2 of this invention.

[0025] Figure 3 The XRD pattern of the carbon nitride / biochar / bismuth oxybromide catalyst prepared in Example 3 of this invention;

[0026] Figure 4 This is a SEM image of the carbon nitride / biochar / bismuth oxybromide catalyst prepared in Example 3 of the present invention;

[0027] Figure 5 EDS diagram of the carbon nitride / biochar / bismuth oxybromide catalyst prepared in Example 3 of this invention;

[0028] Figure 6 This is a TEM image of the carbon nitride / biochar / bismuth oxybromide catalyst prepared in Example 3 of the present invention;

[0029] Figure 7 The photocurrent diagram is shown for the carbon nitride / biochar / bismuth oxybromide catalyst prepared in Example 3 of this invention.

[0030] Figure 8 The graph shows the concentration-time variation of norfloxacin under visible light after treatment with the carbon nitride / biochar / bismuth oxybromide catalyst prepared in Example 3 of this invention.

[0031] Figure 9 The graph shows the concentration-time variation of norfloxacin under visible light after treatment with the carbon nitride / biochar / bismuth oxybromide catalyst prepared in Example 4 of this invention.

[0032] Figure 10 The graph shows the concentration-time variation of norfloxacin under visible light after treatment with the carbon nitride / biochar / bismuth oxybromide catalyst prepared in Example 5 of this invention. Detailed Implementation

[0033] The technical solution of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. These embodiments do not constitute a limitation on the present patent.

[0034] This invention employs a one-step carbonization method to prepare g-C3N4 / Biochar material. Based on biochar adsorption, a photocatalyst is introduced to treat antibiotics in wastewater from two aspects. During the degradation of norfloxacin using g-C3N4 / Biochar, it was found to be very ineffective. Therefore, a semiconductor material was added to the g-C3N4 / Biochar material to improve the catalyst's redox capacity.

[0035] The present invention relates to a method for preparing a ternary photocatalyst for degrading pharmaceutical wastewater, comprising the following steps:

[0036] Step 1: Preparation of g-C3N4 / Biochar at different ratios;

[0037] Step 2: System characterization of g-C3N4 / Biochar, and determination of the optimal ratio based on the photodegradation ability of Rhodamine B;

[0038] Step 3: Preparation of g-C3N4 / Biochar / Bi4O5Br2 in different proportions;

[0039] Step 4: System characterization of g-C3N4 / Biochar / Bi4O5Br2 and evaluation of its photocatalytic degradation ability of norfloxacin.

[0040] The detailed steps are as follows:

[0041] First, clean the jujube shells and dry them in an oven at 75-85℃. Then, grind them into powder using a grinder, pass the powder through an 80-mesh sieve, and collect the sieve residue to obtain fine jujube shell powder for later use.

[0042] The above-mentioned jujube shell powder was added to 40 mL of potassium hydroxide solution (the mass ratio of potassium hydroxide to jujube shell powder was (1-4):1), and a certain amount of melamine was added (the mass ratio of jujube shell powder to melamine was 0.1%, 0.25%, 0.5%, and 1%). The mixture was sonicated for 1 hour to obtain a suspension, then stirred and activated for 10-14 hours. After that, it was dried at 75-85℃, then ground into powder using an agate mortar and pestle. The powder was placed in a tube furnace and heated to 400-600℃ at a rate of 5℃ / min, and calcined for 1-4 hours. After that, it was cooled naturally to obtain g-C3N4 / Biochar in different proportions.

[0043] Photocatalytic degradation experiments showed that 0.25% g-C3N4 / Biochar exhibited the strongest degradation ability for Rhodamine B. Therefore, the following embodiments of this invention use 0.25% g-C3N4 / Biochar as a baseline. When preparing 0.25% g-C3N4 / Biochar, the stirring activation time was 12 hours, followed by drying at 80±5℃. The powder was then ground into powder using an agate mortar and placed in a tube furnace, heated to 550℃ at a rate of 5℃ / min, and calcined for 2 hours. The powder was then allowed to cool naturally to obtain the 0.25% g-C3N4 / Biochar.

[0044] Take 1.6-2.4 mmol of bismuth nitrate and place it in 20 ml of ethylene glycol. Sonicate for 8-12 min to dissolve the bismuth nitrate. Then add different masses of g-C3N4 / Biochar (g-C3N4 / Biochar to bismuth nitrate mass ratios of 1%, 3%, 5%, 7%, and 9%, respectively) and sonicate to dissolve to obtain solution A.

[0045] Weigh 1.6-2.4 mmol KBr into a beaker, add 8 ml of ultrapure water and 2 ml of ammonia solution with a solute mass percentage of 25% to dissolve KBr and obtain solution B;

[0046] Slowly add solution B to solution A and stir for 4-6 hours to obtain a suspension;

[0047] The obtained suspension was centrifuged at 8000±100 r / min and room temperature for 5 min. The precipitate was then washed alternately with ultrapure water and anhydrous ethanol, and then dried. The dried sample was ground into fine powder to obtain g-C3N4 / Biochar / Bi4O5Br2 in different proportions, which is the ternary photocatalyst of the present invention for degrading pharmaceutical wastewater. The catalyst is a g-C3N4 / Biochar / Bi4O5Br2 composite material, specifically an S-type photocatalyst.

[0048] The prepared ternary photocatalyst g-C3N4 / Biochar / Bi4O5Br2 was systematically characterized to study its morphology and elemental composition. At the same time, photocatalytic degradation experiments were carried out using the ternary photocatalyst under simulated sunlight conditions to evaluate its photocatalytic ability.

[0049] This invention employs simultaneous activation and carbonization to obtain g-C3N4 / Biochar, which exhibits a large surface area, strong light-harvesting performance, and high adsorption capacity. Subsequently, bismuth oxybromine is incorporated, overcoming the tendency of photocatalysts to aggregate. In this product, the introduction of biochar material improves the light absorption performance of carbon nitride material and addresses the issue of easy recombination of photogenerated carriers, thereby enhancing the photocatalytic activity of carbon nitride. Simultaneously, the introduction of bismuth oxybromine addresses the inherent problems of bismuth oxybromine's tendency to aggregate, weak adsorption, poor light-harvesting performance, and easy recombination of photogenerated carriers. This achieves simultaneous enhancement of light absorption, carrier separation, and catalytic mass transfer performance, solving the problems of easy aggregation, small specific surface area, weak light-harvesting performance, and low photogenerated carrier separation efficiency associated with bismuth oxybromine material. The invention also provides a ternary material of carbon nitride / jujube shell biochar / bismuth oxybromine that exhibits dual adsorption-photocatalytic removal of antibiotics from wastewater, prepared using the aforementioned method.

[0050] Example 1:

[0051] The preparation steps of the ternary photocatalyst for degrading pharmaceutical wastewater in this embodiment of the invention are as follows:

[0052] 1) Weigh 1.6 mmol of bismuth nitrate pentahydrate into 20 ml of ethylene glycol, sonicate for 10 min to dissolve the weighed bismuth nitrate pentahydrate, then add 6.47 mg of g-C3N4 / Biochar, sonicate for 40 min to disperse g-C3N4 / Biochar evenly, to obtain solution A;

[0053] 2) Take 1.6 mmol KBr and place it in a beaker. Add 8 ml of ultrapure water and 2 ml of 25% ammonia water to dissolve KBr and obtain solution B.

[0054] 3) Slowly add solution B to solution A;

[0055] 4) Stir the mixed solution for 4 hours to obtain a suspension;

[0056] 5) Place the suspension in a centrifuge and centrifuge for 6 min at 8000±100 r / min and 20±0.5℃. Then wash twice with ultrapure water and anhydrous ethanol, respectively.

[0057] 6) The product obtained in step 5) is dried and ground to obtain 1% g-C3N4 / Biochar / Bi4O5Br2.

[0058] like Figure 1As shown, 20 mg of the g-C3N4 / Biochar / Bi4O5Br2 photocatalytic composite material can degrade 76.69% of norfloxacin (10 mg / L) under visible light excitation.

[0059] Example 2:

[0060] The preparation steps of the ternary photocatalyst for degrading pharmaceutical wastewater in this embodiment of the invention are as follows:

[0061] 1) Weigh 1.6 mmol of bismuth nitrate pentahydrate into 20 ml of ethylene glycol, sonicate for 10 min to dissolve the weighed bismuth nitrate pentahydrate, then add 19.4 mg of g-C3N4 / Biochar, sonicate for 40 min to disperse g-C3N4 / Biochar evenly, to obtain solution A;

[0062] 2) Take 2.0 mmol KBr and place it in a beaker. Add 8 ml of ultrapure water and 2 ml of 25% ammonia water to dissolve KBr and obtain solution B.

[0063] 3) Slowly add solution B to solution A;

[0064] 4) Stir the mixed solution for 5 hours to obtain a suspension;

[0065] 5) Place the suspension in a centrifuge and centrifuge for 5 min at 8000±100 r / min and 20±0.5℃. Then wash twice with ultrapure water and anhydrous ethanol, respectively.

[0066] 6) The product obtained in step 5) is dried and ground to obtain 3% g-C3N4 / Biochar / Bi4O5Br2.

[0067] like Figure 2 As shown, 20 mg of the g-C3N4 / Biochar / Bi4O5Br2 photocatalytic composite material can degrade 73.38% of norfloxacin (10 mg / L) under visible light excitation.

[0068] Example 3:

[0069] The preparation steps of the ternary photocatalyst for degrading pharmaceutical wastewater in this embodiment of the invention are as follows:

[0070] 1) Weigh 2.0 mmol of bismuth nitrate pentahydrate into 20 ml of ethylene glycol, sonicate for 10 min to dissolve the weighed bismuth nitrate pentahydrate, then add 48.5 mg of g-C3N4 / Biochar, sonicate for 40 min to disperse g-C3N4 / Biochar evenly, to obtain solution A;

[0071] 2) Take 2.0 mmol KBr and place it in a beaker. Add 8 ml of ultrapure water and 2 ml of 25% ammonia water to dissolve KBr and obtain solution B.

[0072] 3) Slowly add solution B to solution A;

[0073] 4) Stir the mixed solution for 5 hours to obtain a suspension;

[0074] 5) Place the suspension in a centrifuge and centrifuge at 8000 r / min and 20℃ for 5 min, then wash twice with ultrapure water and anhydrous ethanol respectively.

[0075] 6) The product obtained in step 5) is dried and ground to obtain 5% g-C3N4 / Biochar / Bi4O5Br2.

[0076] like Figure 3 As shown, in the XRD diffraction peaks of the g-C3N4 / Biochar / Bi4O5Br2 composite material, the characteristic peak of Bi4O5Br2 can be clearly seen, while the XRD characteristic peaks of Biochar and g-C3N4 are masked by the Bi4O5Br2 peak due to their weaker peak intensities.

[0077] like Figure 4 As shown, the g-C3N4 / Biochar / Bi4O5Br2 composite material has an irregular stacked nanosheet structure, in which Bi4O5Br2 and g-C3N4 are distributed on the porous Biochar material.

[0078] like Figure 5 As shown, Bi, Br, O, N and C elements can be clearly seen in the EDS spectrum of the g-C3N4 / Biochar / Bi4O5Br2 composite material.

[0079] like Figure 6 As shown in the TEM image of the g-C3N4 / Biochar / Bi4O5Br2 composite material, g-C3N4, Biochar, and Bi4O5Br2 can be observed distributed throughout the g-C3N4 / Biochar / Bi4O5Br2 composite material.

[0080] like Figure 7 As shown, the g-C3N4 / Biochar / Bi4O5Br2 composite material has a higher photocurrent density than g-C3N4 / Biochar,Bi4O5Br2 and g-C3N4, indicating that it has a higher separation and migration efficiency of photogenerated carriers.

[0081] like Figure 8As shown, 20 mg of the g-C3N4 / Biochar / Bi4O5Br2 photocatalytic composite material can degrade 91.37% of norfloxacin (10 mg / L) under visible light excitation.

[0082] Example 4:

[0083] The preparation steps of the ternary photocatalyst for degrading pharmaceutical wastewater in this embodiment of the invention are as follows:

[0084] 1) Weigh 2.0 mmol of bismuth nitrate pentahydrate into 20 ml of ethylene glycol, sonicate for 10 min to dissolve the weighed bismuth nitrate pentahydrate, then add 67.9 mg of g-C3N4 / Biochar, sonicate for 40 min to disperse g-C3N4 / Biochar evenly, to obtain solution A;

[0085] 2) Take 2.4 mmol KBr and place it in a beaker. Add 8 ml of ultrapure water and 2 ml of 25% ammonia water to dissolve KBr and obtain solution B.

[0086] 3) Slowly add solution B to solution A;

[0087] 4) Stir the mixed solution for 4 hours to obtain a suspension;

[0088] 5) Place the suspension in a centrifuge and centrifuge for 5 min at 8000±100 r / min and 20±0.5℃. Then wash twice with ultrapure water and anhydrous ethanol, respectively.

[0089] 6) The product obtained in step 5) is dried and ground to obtain 7% g-C3N4 / Biochar / Bi4O5Br2.

[0090] like Figure 9 As shown, 20 mg of the g-C3N4 / Biochar / Bi4O5Br2 photocatalytic composite material can degrade 62.84% of norfloxacin (10 mg / L) under visible light excitation.

[0091] Example 5:

[0092] The preparation steps of the ternary photocatalyst for degrading pharmaceutical wastewater in this embodiment of the invention are as follows:

[0093] 1) Weigh 2.0 mmol of bismuth nitrate pentahydrate into 20 ml of ethylene glycol, sonicate for 8-12 min to dissolve the weighed bismuth nitrate pentahydrate, then add 87.3 mg of g-C3N4 / Biochar, sonicate for 40 min to disperse g-C3N4 / Biochar evenly, to obtain solution A;

[0094] 2) Take 1.6 mmol KBr and place it in a beaker. Add 8 ml of ultrapure water and 2 ml of 25% ammonia water to dissolve KBr and obtain solution B.

[0095] 3) Slowly add solution B to solution A;

[0096] 4) Stir the mixed solution for 6 hours to obtain a suspension;

[0097] 5) Place the suspension in a centrifuge and centrifuge for 5 min at 8000±100 r / min and 20±0.5℃. Then wash twice with ultrapure water and anhydrous ethanol, respectively.

[0098] 6) The product obtained in step 5) is dried and ground to obtain 9% g-C3N4 / Biochar / Bi4O5Br2.

[0099] like Figure 10 As shown, 20 mg of the g-C3N4 / Biochar / Bi4O5Br2 photocatalytic composite material can degrade 72.06% of norfloxacin (10 mg / L) under visible light excitation.

Claims

1. A method for preparing a ternary photocatalyst for degrading pharmaceutical wastewater, characterized in that, The process includes the following: Biochar powder was added to a potassium hydroxide solution, followed by melamine. The mixture was then activated by ultrasound and stirring, dried, and the dried product was ground into powder and calcined. After natural cooling, g-C3N4 / Biochar was obtained. The biochar powder was made from fine jujube shell powder with a particle size of 80 mesh or larger. The mass ratio of potassium hydroxide to jujube shell powder was (1-4):

1. The mass of the fine jujube shell powder was 0.1% to 1.0% of the mass of melamine. The g-C3N4 / Biochar was added to a bismuth nitrate pentahydrate solution and mixed thoroughly to obtain solution A; wherein the mass of g-C3N4 / Biochar was 1% to 9% of the mass of bismuth nitrate pentahydrate. KBr was dissolved in a mixture of ammonia and ultrapure water to obtain solution B; wherein the molar ratio of KBr to bismuth nitrate pentahydrate was (1.6-2.4):(1.6-2.4). Solution B was added to solution A to carry out the reaction, followed by centrifugation, washing, and drying to obtain the ternary photocatalyst used for degrading pharmaceutical wastewater.

2. The method for preparing a ternary photocatalyst for degrading pharmaceutical wastewater according to claim 1, characterized in that, When preparing g-C3N4 / Biochar, the dried product is calcined at 400-600℃ for 1-4 hours, followed by natural cooling.

3. The method for preparing a ternary photocatalyst for degrading pharmaceutical wastewater according to claim 1, characterized in that, When adding solution B to solution A to carry out the reaction, the reaction should be stirred continuously for 4-6 hours. After adding solution B to solution A to react, the resulting suspension is centrifuged at 7900-8100 r / min at room temperature. The separated product is then washed 2-4 times alternately with ultrapure water and anhydrous ethanol.

4. A ternary photocatalyst for degrading pharmaceutical wastewater, characterized in that, The catalyst was prepared by the method described in any one of claims 1-3.

5. The application of the ternary photocatalyst for degrading pharmaceutical wastewater as described in claim 4, characterized in that, The catalyst is used for the photocatalytic degradation of antibiotic pharmaceutical wastewater, including norfloxacin.

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