A biochar supported cobalt-iron alloy composite catalyst, a preparation method and application thereof

Abstract

The present application relates to a kind of biochar load cobalt iron alloy composite catalyst and its preparation method and application, with agricultural and forestry waste wheat straw and cobalt iron prussian blue derivative (CoFe-PBA) as precursor, by coprecipitation method and high-temperature calcination method, biochar load cobalt iron alloy (CoFe@BC) Composite catalyst is successfully prepared.Catalytic performance is explored by using tetracycline (TC) as target pollutant, with the catalyst activated persulfate (PMS) degradation TC.The catalyst can effectively and quickly activate PMS, and the degradation rate of TC is as high as 99.96%.After repeated use for 5 times, the degradation rate still remains above 70%.The present application provides a simple, low-cost strategy for preparing efficient PMS activator for antibiotic wastewater remediation.

Description

Technical Field

[0001] This invention relates to the field of organic wastewater treatment, and in particular to a biochar-supported cobalt-iron alloy composite catalyst, its preparation method, and its application. Background Technology

[0002] In recent years, tetracycline antibiotics have been widely and extensively used in pharmaceuticals, medical treatment, animal husbandry, and other industries, causing serious pollution to the water environment. Compared with traditional physical, chemical, and biological treatment methods, advanced oxidation processes (AOPs) have the advantages of strong oxidizing power, high reaction rate, and strong resistance to environmental interference. Persulfate (PMS)-based AOPs are considered a promising new technology for treating organic pollutants because PMS activation can generate sulfate radicals (SO42-), which have strong oxidizing power. ·- ). with hydroxyl radicals ( · Compared to OH, SO4 ·- It has advantages such as higher redox potential (2.5-3.1V), longer half-life (30-40μs), and wider acid and alkali resistance range (2.0-8.0), and has broad application prospects in practical applications.

[0003] PMS can be activated through various methods, including ultraviolet light, heat, ultrasound, transition metals (Co, Cu, Fe, and Mn), and carbon materials. Among these, transition metal ions, especially Co, are commonly used PMS activators. 2+ It has the best activation effect on PMS. However, Co is present during the reaction. 3+ Restored to Co 2+ It is a rate-limiting step that introduces another transition metal ion, such as Fe. 2+ It can achieve Co 2+ / Co 3+ The redox cycle. However, homogeneous catalysis of transition metal ions has many drawbacks: (1) the homogeneous catalytic system is only effective under acidic conditions and cannot be applied to a wide pH range; (2) due to their own reducing properties, transition metal ions will react with various oxidants in wastewater, resulting in metal ion precipitation, which greatly reduces their catalytic efficiency, and the accumulation of precipitation will produce chemical sludge that is harmful to the environment; (3) after the reaction, the catalyst is difficult to recover, resulting in resource waste, secondary pollution and other problems.

[0004] Therefore, a stable heterogeneous catalyst needs to be developed. Cobalt-iron bimetallic heterogeneous catalysts can avoid the leaching of transition metal ions and can be effectively separated from aqueous systems, enabling reuse. However, these catalysts are usually small in size and prone to aggregation, reducing the number of active sites exposed on the catalyst surface, thus limiting their application in antibiotic wastewater treatment. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art by providing a biochar-supported cobalt-iron alloy composite catalyst, its preparation method, and its application. The biochar-supported cobalt-iron alloy composite catalyst has a stable structure, a wide range of applications, and can be reused for a long period. It is also used for PMS-activated degradation of tetracycline.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing a biochar-supported cobalt-iron alloy composite catalyst, comprising the following specific steps:

[0008] (1) Pre-treatment of agricultural and forestry waste;

[0009] (2) The pretreated agricultural and forestry waste obtained in step (1) is calcined in an inert gas atmosphere to obtain biochar (BC);

[0010] (3) Add the biochar (BC), surfactant and sodium citrate dihydrate obtained in step (1) to the cobalt nitrate hexahydrate solution and stir magnetically to obtain mixed solution A;

[0011] (4) Potassium ferricyanide solution was slowly added dropwise to the mixed solution A obtained in step (3), stirred continuously, allowed to stand, centrifuged, and washed to obtain biochar-supported cobalt iron Prussian blue derivative (CoFe-PBA@BC);

[0012] (5) The biochar-supported cobalt-iron Prussian blue derivative (CoFe-PBA@BC) obtained in step (4) is calcined in air to obtain a biochar-supported cobalt-iron alloy (CoFe@BC) composite catalyst.

[0013] Furthermore, in step (1), the agricultural and forestry waste is wheat straw.

[0014] Further, in step (1), the specific steps for pretreating agricultural and forestry waste are as follows: wash the agricultural and forestry waste with deionized water and anhydrous ethanol respectively, dry it, grind it and then sieve it for later use.

[0015] Furthermore, in step (2), the inert gas is nitrogen.

[0016] Furthermore, in step (2), the calcination temperature is 500-700°C, preferably 600°C, and the calcination time is 1.5-2.5 hours, preferably 2 hours.

[0017] Furthermore, in step (2), the biochar (BC) is wheat straw biochar.

[0018] Furthermore, in step (3), the surfactant is PVP K30.

[0019] Further, in step (3), the mass ratio of biochar (BC), surfactant and sodium citrate dihydrate is (0.1-0.3):(1.0-2.0):(1.0-2.0), preferably 0.2:1.5:1.5.

[0020] Further, in step (3), the ratio of biochar (BC) to cobalt nitrate hexahydrate solution is (0.1g-0.3g): (80ml-120ml).

[0021] Furthermore, in step (3), the magnetic stirring time is 20 to 40 minutes, preferably 30 minutes.

[0022] Further, in step (4), the concentration ratio of the cobalt nitrate hexahydrate solution and the potassium ferricyanide solution is (0.01-0.03):0.01, preferably 0.02:0.01.

[0023] Further, in step (4), the volume ratio of the cobalt nitrate hexahydrate solution to the potassium ferricyanide solution is (4-6):5, preferably 1:1.

[0024] Furthermore, in step (4), the stirring time is 20 to 40 minutes, preferably 30 minutes.

[0025] Furthermore, in step (4), the settling time is 20 to 30 hours, preferably 24 hours.

[0026] Furthermore, in step (5), the calcination temperature is 400-600℃, preferably 500℃, and the calcination time is 1.5-2.5h, preferably 2h.

[0027] The present invention also provides a biochar-supported cobalt-iron alloy composite catalyst. The biochar-supported cobalt-iron alloy composite catalyst obtained by the above preparation method is composed of cobalt-iron alloy nanoparticles and biochar, with the cobalt-iron alloy nanoparticles uniformly distributed on the outer surface of the biochar.

[0028] Furthermore, the cobalt-iron alloy nanoparticles have a particle size of 50-70 nm.

[0029] Furthermore, the biochar-supported cobalt-iron alloy composite catalyst has abundant open-pipeline structures.

[0030] In addition, the present invention also provides an application of a biochar-supported cobalt-iron alloy composite catalyst, specifically the application of the biochar-supported cobalt-iron alloy composite catalyst obtained by the above preparation method in the degradation of tetracycline.

[0031] Furthermore, the specific steps for applying the biochar-supported cobalt-iron alloy composite catalyst in tetracycline degradation are as follows:

[0032] (1) The biochar-supported cobalt-iron alloy composite catalyst was dispersed in a tetracycline hydrochloride solution and shaken to obtain a mixed solution B;

[0033] (2) Add persulfate (PMS) to the mixed solution B obtained in step (1) to begin the degradation of tetracycline;

[0034] (3) After degradation, take the suspension, filter it, add methanol to terminate the reaction.

[0035] Furthermore, in step (1), the oscillation time is 10 to 30 minutes, preferably 20 minutes, and the oscillation temperature is 20 to 30°C, preferably 25°C.

[0036] Furthermore, in step (1), the concentration of the biochar-supported cobalt-iron alloy composite catalyst is 30-110 mg / L.

[0037] Furthermore, in step (1), the initial concentration of the tetracycline hydrochloride solution is 10-40 mg / L and the pH is 5-10.

[0038] Furthermore, in step (2), the concentration of persulfate is 0.5-2.5 mmol / L.

[0039] As a preferred technical solution, the concentration of the biochar-supported cobalt-iron alloy composite catalyst is 50 mg / L;

[0040] The initial concentration of the tetracycline hydrochloride solution was 20 mg / L, and the pH was 7.

[0041] The concentration of persulfate was 1.5 mmol / L.

[0042] Furthermore, in step (3), the volume ratio of the suspension to methanol is 1:1.5-2.5, preferably 1:2.

[0043] The principle of this invention is as follows:

[0044] This invention utilizes advanced oxidation technology for PMS activation by transition metals. Using agricultural and forestry waste wheat straw and cobalt-iron Prussian blue derivatives as precursors, a biochar-supported cobalt-iron alloy (CoFe@BC) composite catalyst was successfully prepared via co-precipitation and a two-step calcination method. Biochar possesses characteristics such as large specific surface area, abundant pore structure, numerous surface active sites, and high stability, which can effectively improve the dispersibility of the cobalt-iron bimetallic composite, increase the number of exposed active sites on the catalyst surface, and thus enhance the activation effect on PMS. This invention provides a simple and low-cost strategy for preparing highly efficient PMS activators for antibiotic wastewater remediation.

[0045] In this invention, sodium citrate dihydrate can effectively reduce the crystallization rate. Sodium citrate, through coordination with cobalt ions, slows down the rate at which cobalt ions combine with ferricyanide ions to form precipitates, thereby controlling the product morphology and yielding a cobalt-iron Prussian blue derivative with a regular cubic structure. The surfactant PVP K30 can regulate the growth of cubic crystals. When new crystal nuclei appear and begin to grow in the reaction system, PVP K30 immediately acts on their surface, effectively controlling the direction of crystal growth and preventing aggregation during growth, thus ensuring the product morphology and improving particle dispersibility. Furthermore, the biochar-supported cobalt-iron Prussian blue derivative, after calcination in air, yields a biochar-supported cobalt-iron alloy composite, indicating that biochar plays a strong reducing role during calcination, reducing the cobalt-iron bimetallic compound to a cobalt-iron alloy, thereby improving the catalytic efficiency of the catalyst.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] (1) This invention uses cobalt iron Prussian blue derivatives with regular cubic morphology as precursors to synthesize dual transition metal nano-heterogeneous catalysts, which can effectively improve the activation effect of PMS.

[0048] (2) In order to further improve the dispersibility and catalytic effect of nanoparticles, the present invention uses wheat straw, an agricultural and forestry waste, as biomass and obtains a biochar-supported bimetallic composite catalyst by calcination. The biochar not only improves the dispersibility of nanoparticles and increases the number of active sites exposed on the surface, but also plays a strong reducing role, successfully reducing the cobalt-iron Prussian blue derivative to cobalt-iron alloy.

[0049] (3) The raw materials selected in this invention are widely available, green and low-cost, and the preparation method is simple. No additional reducing agent is required. The biochar-supported cobalt-iron alloy composite catalyst with strong PMS activation effect can be successfully obtained by co-precipitation and two-step calcination.

[0050] (4) The biochar-supported cobalt-iron alloy composite catalyst provided by the present invention has shown excellent performance in activating PMS to degrade tetracycline. The degradation rate of tetracycline is as high as 99.96%, and the degradation rate is still more than 70% after being reused 5 times.

[0051] (5) The biochar-supported cobalt-iron alloy composite catalyst provided by the present invention has a wide pH range and is expected to be used in the treatment of actual antibiotic-contaminated wastewater. Attached Figure Description

[0052] Figure 1 SEM images of BC (a, b), CoFe-PBA@BC (c, d), and CoFe@BC (e, f) obtained in Example 1;

[0053] Figure 2 The XRD patterns of BC, CoFe-PBA@BC and CoFe@BC obtained in Example 1 are shown below.

[0054] Figure 3 This is a schematic diagram illustrating the degradation effects of BC, CoFe-PBA@BC, and CoFe@BC on tetracycline in Example 6.

[0055] Figure 4 This is a schematic diagram showing the effect of PMS concentration on tetracycline degradation and the first-order reaction rate constant k in Example 2.

[0056] Figure 5 This is a schematic diagram showing the effect of catalyst dosage on tetracycline degradation and the first-order reaction rate constant k in Example 3.

[0057] Figure 6 This is a schematic diagram showing the effect of the initial concentration of tetracycline on the degradation effect of tetracycline and the first-order reaction rate constant k in Example 4.

[0058] Figure 7 This is a schematic diagram showing the effect of pH on tetracycline degradation and the first-order reaction rate constant k in Example 5.

[0059] Figure 8 This is a schematic diagram showing the degradation rate of tetracycline by CoFe@BC in 5 cycles of testing in Example 7.

[0060] Figure 9 This is a schematic diagram of the standard curve of tetracycline concentration versus absorbance obtained in Example 1;

[0061] Figure 10 The image shows a SEM image of CoFe@BC obtained in Example 8.

[0062] Figure 11 The image shown is a SEM image of CoFe@BC obtained in Example 9. Detailed Implementation

[0063] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0064] A method for preparing a biochar-supported cobalt-iron alloy composite catalyst, the method comprising the following steps:

[0065] (1) The wheat straw was washed with deionized water and anhydrous ethanol, dried, ground and sieved. Then the treated wheat straw was calcined at 600℃ for 2h under a nitrogen atmosphere to obtain wheat straw biochar (BC).

[0066] (2) Add BC, PVP K30 and sodium citrate dihydrate to 100 mL of cobalt nitrate hexahydrate solution and stir magnetically for 30 min to mix evenly to obtain a mixed solution; the mass ratio of BC, PVP K30 and sodium citrate dihydrate is (0.1-0.3):(1.0-2.0):(1.0-2.0), and the ratio of biochar (BC) to cobalt nitrate hexahydrate solution is (0.1 g-0.3 g):(80 ml-120 ml).

[0067] (3) Then, 100 mL of potassium ferricyanide solution was slowly added dropwise to the above mixed solution. After stirring continuously for 30 min, the mixture was allowed to stand for 24 h. Finally, the product was collected by centrifugation and washed to obtain biochar-supported cobalt iron Prussian blue derivative (CoFe-PBA@BC). The concentration ratio of cobalt nitrate hexahydrate solution to potassium ferricyanide solution was (0.01-0.03):0.01, and the volume ratio of cobalt nitrate hexahydrate solution to potassium ferricyanide solution was (4-6):5.

[0068] (4) CoFe-PBA@BC was calcined in air at a certain temperature for 2 hours to obtain biochar-supported cobalt-iron alloy (CoFe@BC) composite catalyst; the calcination temperature was 400-600℃.

[0069] This invention also provides a biochar-supported cobalt-iron alloy composite catalyst, which is composed of cobalt-iron alloy nanoparticles and biochar. The cobalt-iron alloy nanoparticles are uniformly distributed on the outer surface of the biochar, and the particle size of the cobalt-iron alloy nanoparticles is 50-70 nm.

[0070] The biochar-supported cobalt-iron alloy composite catalyst has abundant open-pipeline structures.

[0071] Furthermore, this invention also provides an application of a biochar-supported cobalt-iron alloy composite catalyst in tetracycline degradation, the specific steps of which are as follows:

[0072] (1) Disperse the CoFe@BC catalyst in a tetracycline hydrochloride solution and place it in a constant temperature shaker (25℃) for 20 min to reach adsorption equilibrium to obtain a mixed solution; the amount of CoFe@BC catalyst is 30-110 mg / L, the initial concentration of the tetracycline hydrochloride solution is 10-40 mg / L, and the pH is 5-10.

[0073] (2) Then, a certain concentration of persulfate (PMS) was added to the above solution to start the degradation of tetracycline; the concentration of PMS was 0.5-2.5 mmol / L.

[0074] (3) Use a syringe to collect 1 mL of suspension from the reaction system and filter it through a 0.22 μm filter. Add 2 mL of methanol to the filtered solution to terminate the reaction.

[0075] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0076] Example 1

[0077] This embodiment provides a method for preparing a biochar-supported cobalt-iron alloy composite catalyst, the specific steps of which are as follows:

[0078] (1) The wheat straw was washed with deionized water and anhydrous ethanol, dried, ground and passed through an 80-mesh sieve. Then the treated wheat straw was calcined at 600℃ for 2 hours under a nitrogen atmosphere to obtain wheat straw biochar (BC).

[0079] (2) Add 0.2g BC, 1.5g PVP K30 and 1.5g sodium citrate dihydrate to 100mL of 0.02mol / L cobalt nitrate hexahydrate solution and stir magnetically for 30min to mix evenly.

[0080] (3) Then, 100 mL of 0.01 mol / L potassium ferricyanide solution was slowly added dropwise to the above mixed solution. After stirring continuously for 30 min, the mixture was allowed to stand for 24 h. Finally, the product was collected by centrifugation and washed to obtain the biochar-supported cobalt iron Prussian blue derivative (CoFe-PBA@BC).

[0081] (4) CoFe-PBA@BC was calcined at 500℃ for 2 hours in air to obtain biochar-supported cobalt-iron alloy (CoFe@BC) composite catalyst.

[0082] Depend on Figure 1 It is evident that BC possesses abundant tubular structures; CoFe-PBA exhibits a regular cubic structure and is uniformly distributed on the surface of biochar; CoFe@BC possesses abundant open tubular structures, with cobalt-iron alloy nanoparticles uniformly distributed on the surface of biochar, with a size of approximately 50-70 nm.

[0083] Depend on Figure 2As can be seen, the broad diffraction peaks at 22° and 44° in the XRD pattern of BC correspond to the (002) and (100) crystal planes of graphite carbon, respectively. The CoFe-PBA@BC spectrum shows obvious diffraction peaks at 2θ = 15.3°, 17.7°, 25.1°, 35.8°, 40.2°, 44.2°, and 51.5°, which can be attributed to the (111), (200), (220), (400), (420), (422), and (440) crystal planes of Co2Fe(CN)6. The diffraction peaks at 45.0° and 65.5° in the XRD pattern of CoFe@BC correspond to the cobalt-iron alloy (Co... 0.7 Fe 0.3 (110) and (200) crystal planes.

[0084] Furthermore, this embodiment also provides an application of a biochar-supported cobalt-iron alloy composite catalyst in tetracycline degradation, the specific steps of which are as follows:

[0085] (1) Disperse the CoFe@BC catalyst in a tetracycline hydrochloride solution and place it in a constant temperature shaker (25℃) for 20 min to reach adsorption equilibrium to obtain a mixed solution; the amount of CoFe@BC catalyst is 30-110 mg / L, the initial concentration of the tetracycline hydrochloride solution is 10-40 mg / L, and the pH is 5-10.

[0086] (2) Then, a certain concentration of persulfate (PMS) was added to the above solution to start the degradation of tetracycline; the concentration of PMS was 0.5-2.5 mmol / L.

[0087] (3) Use a syringe to collect 1 mL of suspension from the reaction system and filter it through a 0.22 μm filter. Add 2 mL of methanol to the filtered solution to terminate the reaction.

[0088] (4) The absorbance of the mixed solution at a wavelength of 369 nm was measured by a UV-Vis spectrophotometer. The measurement was performed continuously for 60 min, and the absorbance change was recorded. The concentration of tetracycline in the tetracycline hydrochloride solution was calculated using the absorbance, and the degradation rate of tetracycline was thus calculated.

[0089] like Figure 9 As shown, the standard curve of tetracycline concentration versus absorbance is: y = 0.0367x + 0.0018, where x is the concentration of tetracycline (unit: mg / L) and y is the absorbance.

[0090] The formula for calculating the degradation rate of tetracycline is as follows:

[0091]

[0092] Where C0 is the initial concentration of tetracycline.

[0093] C t The concentration of tetracycline at time t during the reaction;

[0094] The degradation of tetracycline by the CoFe@BC catalyst follows a first-order reaction kinetic equation, and the corresponding first-order reaction rate constant k is calculated as follows:

[0095]

[0096] Where t is the reaction time.

[0097] C0 is the initial concentration of tetracycline.

[0098] C t The concentration of tetracycline is given at time t during the reaction.

[0099] Example 2

[0100] This embodiment provides an application of a biochar-supported cobalt-iron alloy composite catalyst, and the specific steps are as follows:

[0101] The CoFe@BC obtained in Example 1 was dispersed in a 20 mg / L tetracycline hydrochloride solution at pH 7 to achieve a final catalyst concentration of 50 mg / L. The solution was then shaken in a constant-temperature shaker for 20 min to reach adsorption equilibrium. PMS at concentrations of 0.5, 1.0, 1.5, 2.0, and 2.5 mmol / L was added to the solution to initiate tetracycline degradation. One mL of suspension was collected from the reaction system using a syringe and filtered through a 0.22 μm filter. Two mL of methanol was added to the filtered solution to terminate the reaction. The absorbance of the mixed solution at 369 nm was measured using a UV-Vis spectrophotometer for 60 min, and the absorbance changes were recorded.

[0102] like Figure 4 As shown, the catalyst exhibited the highest degradation rate of tetracycline (97.60%) at a PMS concentration of 1.5 mmol / L, with a corresponding first-order reaction rate constant k of 0.05651 min⁻¹. -1 .

[0103] Example 3

[0104] This embodiment provides an application of a biochar-supported cobalt-iron alloy composite catalyst, and the specific steps are as follows:

[0105] The CoFe@BC obtained in Example 1 was dispersed in a 20 mg / L tetracycline hydrochloride solution at pH 7, resulting in final catalyst concentrations of 30, 50, 70, 90, and 110 mg / L. The solution was then shaken in a constant-temperature shaker for 20 min to reach adsorption equilibrium. Next, 1.5 mmol / L PMS was added to the solution to initiate tetracycline degradation. One mL of the suspension was collected from the reaction system using a syringe and filtered through a 0.22 μm filter. Two mL of methanol was added to the filtered solution to terminate the reaction. The absorbance of the mixed solution at 369 nm was measured using a UV-Vis spectrophotometer for 60 min, and the absorbance changes were recorded.

[0106] like Figure 5 As shown, the catalyst exhibits the highest degradation rate of tetracycline (99.96%) when the catalyst dosage is 50 mg / L, with a corresponding first-order reaction rate constant k of 0.07986 min⁻¹. -1 .

[0107] Example 4

[0108] This embodiment provides an application of a biochar-supported cobalt-iron alloy composite catalyst, and the specific steps are as follows:

[0109] The CoFe@BC obtained in Example 1 was dispersed in tetracycline hydrochloride solutions of 10, 20, 30, and 40 mg / L, pH=7, to achieve a final catalyst concentration of 50 mg / L. The solutions were then shaken in a constant-temperature shaker for 20 min to reach adsorption equilibrium. Then, 1.5 mmol / L PMS was added to the solutions to initiate tetracycline degradation. One mL of the suspension was collected from the reaction system using a syringe and filtered through a 0.22 μm filter. Two mL of methanol was added to the filtered solution to terminate the reaction. The absorbance of the mixed solution at 369 nm was measured using a UV-Vis spectrophotometer for 60 min, and the absorbance changes were recorded.

[0110] like Figure 6 As shown, the catalyst achieved the highest degradation rate of tetracycline (99.96%) when the initial concentration of tetracycline was 20 mg / L, with a corresponding first-order reaction rate constant k of 0.07986 min⁻¹. -1 .

[0111] Example 5

[0112] This embodiment provides an application of a biochar-supported cobalt-iron alloy composite catalyst, and the specific steps are as follows:

[0113] The CoFe@BC obtained in Example 1 was dispersed in tetracycline hydrochloride solutions of 20 mg / L with pH values ​​of 5, 6, 7, 8, 9, and 10 to achieve a final catalyst concentration of 50 mg / L. The solution was shaken in a constant-temperature shaker for 20 min to reach adsorption equilibrium. Then, 1.5 mmol / L PMS was added to the solution to initiate tetracycline degradation. 1 mL of the suspension was collected from the reaction system using a syringe and filtered through a 0.22 μm filter. 2 mL of methanol was added to the filtered solution to terminate the reaction. The absorbance of the mixed solution at 369 nm was measured using a UV-Vis spectrophotometer for 60 min, and the absorbance changes were recorded.

[0114] like Figure 7 As shown, the catalyst exhibited the highest degradation rate of tetracycline (97.00%) at pH 7, with a corresponding first-order reaction rate constant k of 0.03196 min⁻¹. -1 .

[0115] Example 6

[0116] This embodiment provides an application of a biochar-supported cobalt-iron alloy composite catalyst, and the specific steps are as follows:

[0117] The BC, CoFe-PBA@BC, and CoFe@BC obtained in Example 1 were dispersed in a 20 mg / L tetracycline hydrochloride solution at pH 7, respectively, to achieve a final catalyst concentration of 50 mg / L. The solutions were then shaken in a constant-temperature shaker for 20 min to reach adsorption equilibrium. Then, 1.5 mmol / L PMS was added to the solution to initiate tetracycline degradation. One mL of suspension was collected from the reaction system using a syringe and filtered through a 0.22 μm filter. Two mL of methanol was added to the filtered solution to terminate the reaction. The absorbance of the mixed solution at 369 nm was measured using a UV-Vis spectrophotometer for 60 min, and the absorbance changes were recorded. The degradation effects of different catalysts on tetracycline were compared.

[0118] like Figure 3 As shown, compared with BC and CoFe-PBA@BC, CoFe@BC has the best degradation effect on tetracycline, with a tetracycline removal rate of up to 95.50%.

[0119] Example 7

[0120] This embodiment provides an application of a biochar-supported cobalt-iron alloy composite catalyst, and the specific steps are as follows:

[0121] The CoFe@BC obtained in Example 1 was dispersed in a 20 mg / L tetracycline hydrochloride solution at pH 7 to achieve a final catalyst concentration of 50 mg / L. The solution was then shaken in a constant-temperature shaker for 20 min to reach adsorption equilibrium. Next, 1.5 mmol / L PMS was added to the solution to initiate tetracycline degradation. After degradation, the CoFe@BC was centrifuged, washed, and dried, and the tetracycline was further degraded under the same conditions.

[0122] like Figure 8 As shown, after five repeated uses, CoFe@BC still achieved a 71.23% degradation rate of tetracycline, indicating that the synthesized catalyst is relatively stable and can be reused for a long time in practical applications.

[0123] Example 8

[0124] This embodiment provides a method for preparing a biochar-supported cobalt-iron alloy composite catalyst, the specific steps of which are as follows:

[0125] (1) The wheat straw was washed with deionized water and anhydrous ethanol, dried, ground and passed through an 80-mesh sieve. Then the treated wheat straw was calcined at 600℃ for 2 hours under a nitrogen atmosphere to obtain wheat straw biochar (BC).

[0126] (2) Add 0.1g BC, 1.0g PVP K30 and 1.0g sodium citrate dihydrate to 100mL of 0.01mol / L cobalt nitrate hexahydrate solution and stir magnetically for 30min to mix evenly.

[0127] (3) Then, 100 mL of 0.01 mol / L potassium ferricyanide solution was slowly added dropwise to the above mixed solution. After stirring continuously for 30 min, the mixture was allowed to stand for 24 h. Finally, the product was collected by centrifugation and washed to obtain the biochar-supported cobalt iron Prussian blue derivative (CoFe-PBA@BC).

[0128] (4) CoFe-PBA@BC was calcined at 400℃ for 2 hours in air to obtain biochar-supported cobalt-iron alloy (CoFe@BC) composite catalyst.

[0129] Example 9

[0130] This embodiment provides a method for preparing a biochar-supported cobalt-iron alloy composite catalyst, the specific steps of which are as follows:

[0131] (1) The wheat straw was washed with deionized water and anhydrous ethanol, dried, ground and passed through an 80-mesh sieve. Then the treated wheat straw was calcined at 600℃ for 2 hours under a nitrogen atmosphere to obtain wheat straw biochar (BC).

[0132] (2) Add 0.3g BC, 2.0g PVP K30 and 2.0g sodium citrate dihydrate to 100mL of 0.03mol / L cobalt nitrate hexahydrate solution and stir magnetically for 30min to mix evenly.

[0133] (3) Then, 100 mL of 0.01 mol / L potassium ferricyanide solution was slowly added dropwise to the above mixed solution. After stirring continuously for 30 min, the mixture was allowed to stand for 24 h. Finally, the product was collected by centrifugation and washed to obtain the biochar-supported cobalt iron Prussian blue derivative (CoFe-PBA@BC).

[0134] (4) CoFe-PBA@BC was calcined at 600℃ for 2 hours in air to obtain biochar-supported cobalt-iron alloy (CoFe@BC) composite catalyst.

[0135] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. The application of a biochar-supported cobalt-iron alloy composite catalyst in tetracycline degradation, characterized in that, The biochar-supported cobalt-iron alloy composite catalyst is composed of cobalt-iron alloy nanoparticles and biochar. The cobalt-iron alloy nanoparticles are uniformly distributed on the outer surface of the biochar, and the particle size of the cobalt-iron alloy nanoparticles is 50-70 nm. The composite catalyst was prepared by the following method: (1) Pre-treatment of agricultural and forestry waste; the agricultural and forestry waste is wheat straw; (2) The pretreated agricultural and forestry waste obtained in step (1) is calcined in an inert gas atmosphere to obtain biochar; (3) Add the biochar, surfactant and sodium citrate dihydrate obtained in step (2) to the cobalt nitrate hexahydrate solution and stir magnetically to obtain mixed solution A; the surfactant is PVP K30; (4) Potassium ferricyanide solution was slowly added dropwise to the mixed solution A obtained in step (3), and after continuous stirring, it was allowed to stand, centrifuged, and washed to obtain biochar-supported cobalt iron Prussian blue derivative. (5) The biochar-supported cobalt-iron Prussian blue derivative obtained in step (4) is calcined at 400~600℃ for 1.5~2.5h in air atmosphere to obtain a biochar-supported cobalt-iron alloy composite catalyst. The specific steps for applying the composite catalyst in tetracycline degradation are as follows: S1: The biochar-supported cobalt-iron alloy composite catalyst was dispersed in a tetracycline hydrochloride solution with a pH of 5-10 and shaken to obtain mixed solution B; S2: Add persulfate to solution B obtained in step S1 to begin the degradation of tetracycline; S3: After degradation is complete, take the suspension, filter it, add methanol to terminate the reaction.

2. The application of the biochar-supported cobalt-iron alloy composite catalyst according to claim 1 in the degradation of tetracycline, characterized in that, The biochar-supported cobalt-iron alloy composite catalyst has an open, tubular structure.

3. The application of the biochar-supported cobalt-iron alloy composite catalyst according to claim 1 in the degradation of tetracycline, characterized in that, In step (1), the specific steps for pre-treating agricultural and forestry waste are as follows: wash the agricultural and forestry waste with deionized water and anhydrous ethanol respectively, dry it, grind it and then sieve it for later use.

4. The application of the biochar-supported cobalt-iron alloy composite catalyst according to claim 1 in the degradation of tetracycline, characterized in that, In step (2), the calcination temperature is 500~700℃ and the calcination time is 1.5~2.5h; The biochar is wheat straw biochar.

5. The application of the biochar-supported cobalt-iron alloy composite catalyst according to claim 1 in the degradation of tetracycline, characterized in that, In step (3), the mass ratio of biochar, surfactant and sodium citrate dihydrate is (0.1-0.3):(1.0-2.0):(1.0-2.0). Biochar: Cobalt nitrate hexahydrate solution = (0.1g-0.3g): (80ml-120ml); The magnetic stirring time is 20~40 min.

6. The application of the biochar-supported cobalt-iron alloy composite catalyst according to claim 1 in the degradation of tetracycline, characterized in that, In step (4), the concentration ratio of the cobalt nitrate hexahydrate solution to the potassium ferricyanide solution is (0.01-0.03):0.01; The volume ratio of the cobalt nitrate hexahydrate solution to the potassium ferricyanide solution is (4-6):5; The stirring time is 20-40 min; The settling time is 20-30 hours.

7. The application of the biochar-supported cobalt-iron alloy composite catalyst according to claim 1 in the degradation of tetracycline, characterized in that, In step (5), the calcination temperature is 500°C.

8. The application of the biochar-supported cobalt-iron alloy composite catalyst according to claim 1 in the degradation of tetracycline, characterized in that, In step S1, the oscillation time is 10~30 min and the oscillation temperature is 20~30℃; The concentration of the biochar-supported cobalt-iron alloy composite catalyst is 30-110 mg / L; The initial concentration of the tetracycline hydrochloride solution is 10-40 mg / L.

9. The application of the biochar-supported cobalt-iron alloy composite catalyst according to claim 1 in the degradation of tetracycline, characterized in that, In step S2, the concentration of persulfate is 0.5-2.5 mmol / L; In step S3, the volume ratio of the suspension to methanol is 1:1.5-2.5.

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