A preparation method of a palladium@blue titanium dioxide composite electrode for electrocatalytic oxidation of wastewater treatment and application thereof

Abstract

The application relates to a preparation method of a palladium@blue titanium dioxide composite electrode for electrocatalytic oxidation wastewater treatment and application thereof. The application relates to the fields of environmental science and engineering electrocatalytic oxidation technology and 3D printing technology, and specifically relates to a preparation of an integrated three-dimensional porous palladium@blue titanium dioxide electrode and application of the electrode to efficient electrochemical degradation of florfenicol. Palladium powder, titanium dioxide superfine powder and palladium-carbon powder are mixed together, the three are uniformly mixed by using ball milling, and then a palladium-uniformly-distributed electrode is prepared by using 3D printing technology. Hydrogen and argon are used as protective gas during the printing process, the proportion of hydrogen is 1% to 3%, and the rest of the protective gas is argon. Since the printing bin cannot be guaranteed to be completely vacuum, a certain amount of oxygen exists, and under the action of laser high temperature, carbon elements in the palladium-carbon are oxidized to form carbon oxides.

Description

Technical Field

[0001] The present invention relates to the fields of environmental science and engineering electrocatalytic oxidation technology and 3D printing technology, specifically to the preparation of an integrated three-dimensional porous palladium@blue titanium dioxide electrode and its application in the efficient electrochemical degradation of florfenicol. Background Art

[0002] Antibiotics are widely used to treat and prevent human and animal diseases due to their low cost and broad-spectrum bactericidal properties. They are also widely used as growth promoters in aquaculture, animal husbandry, and agricultural production. Florfenicol (FLO) is a halogenated antibiotic specifically for food-producing animals. It is a structural homologue of chloramphenicol, with a similar mechanism of action and antimicrobial spectrum to chloramphenicol, effectively inhibiting the growth of both Gram-positive and Gram-negative bacteria. Since the European Union and numerous other countries banned the use of chloramphenicol in food-producing animals in 1994, global demand for florfenicol has rapidly increased, currently reaching 4,000 tons per year. Due to its small molecular weight, moderate hydrophilicity, and poor biodegradability, florfenicol cannot be degraded by conventional sewage treatment systems, resulting in its continuous accumulation in aquatic environments. Residual florfenicol in aquatic environments can disrupt the balance of aquatic ecosystems, induce the emergence of drug-resistant genes and resistant bacteria, and enter the human body through the food chain, causing multi-organ damage. Therefore, there is an urgent need to develop efficient technologies and methods to enhance the degradation of FLO and eliminate its toxicity before it is discharged into natural waters.

[0003] Halogen atoms play an important role in the antibacterial activity of halogen antibiotics. Microbial dehalogenation, Fenton reaction and zero-valent iron reduction have been widely used to eliminate the toxicity of halogenated pollutants. However, these technologies are limited by their high energy consumption, low efficiency and high energy consumption. In recent years, electrochemical reduction dehalogenation has attracted much attention due to its high efficiency, no need for additional reducing agents and few toxic byproducts. For the electrochemical reduction process, the cathode material is a key factor in improving the overall treatment efficiency. The key to achieving high dechlorination efficiency is to develop a suitable electrocatalyst. Among various materials, palladium-based electrocatalysts have been proven to be one of the most effective materials for cathode dechlorination, because palladium can not only catalyze the Volmer reaction (H + +e -→H*) to generate atomic hydrogen (H*) with high reduction activity, and also has a high atomic hydrogen (H*) adsorption and storage capacity. Due to the high efficiency of palladium atoms, palladium particles with ultrafine structure will show excellent dehalogenation performance. However, ultrafine palladium particles are prone to agglomeration and uneven distribution during actual operation, which subsequently leads to unstable pollutant treatment effects. Various substrate materials are used to disperse palladium so that its distribution is relatively uniform, such as materials such as reduced graphene oxide. However, palladium particles usually interact with these materials through oxygen-containing functional groups, and the interaction force is very weak, resulting in unstable electrode materials. In addition, the existing material preparation process usually involves cumbersome preparation processes such as high temperature and high pressure, which greatly limits its large-scale application. Summary of the Invention

[0004] The present invention combines palladium powder, ultrafine titanium dioxide powder, and palladium-on-carbon powder, ball milling the mixture, and then using 3D printing technology to produce an electrode with uniform palladium distribution. The inventors discovered for the first time that during the printing process, hydrogen and argon are used as shielding gases, with hydrogen accounting for 1% to 3% and the remaining shielding gas being argon. Furthermore, since the printing chamber cannot guarantee a complete vacuum, a certain amount of oxygen will be present. Under the action of the high temperature of the laser, the carbon element in the palladium-on-carbon is oxidized to form carbon oxides. Due to the introduction of hydrogen and the oxygen content, trace amounts of carbon are oxidized to form carbon monoxide, leaving the palladium element uniformly distributed in the electrode. The simultaneous action of carbon monoxide and hydrogen causes the titanium dioxide to be reduced to blue titanium dioxide in real time during the printing process. Blue titanium dioxide has a stronger electron transport ability than ordinary titanium dioxide and the palladium adheres more firmly. The integrated three-dimensional porous palladium@blue titanium dioxide electrode prepared by selective metal melting 3D printing can effectively degrade FLO.

[0005] The present invention provides a method for preparing a palladium@blue titanium dioxide composite electrode for electrocatalytic oxidation wastewater treatment, comprising the following steps:

[0006] (1) Place equal amounts of steel balls in four ball mill jars, so that the weight of the steel balls is about 4 times the weight of the powder added in step (2).

[0007] (2) Weigh (0%-1.5%) palladium powder, titanium dioxide powder and palladium carbon powder with a mass ratio of 1%-3% and place them in a ball mill, and add 3-5 ml of ethanol.

[0008] (3) Place the ball mill in step (2) on a planetary ball mill, set the parameters, and rotate forward and reverse for 1 hour each.

[0009] (4) Dry the powder (particle size of 2-10 μm) ground in step (3) in an oven at a temperature of 70-200° C. for 2-5 hours to obtain a certain amount of dry powder.

[0010] (5) The dry powder obtained in step (4) was passed through a 200-mesh sieve and shaken on an oscillator until all the dry powder was sieved into the iron plate containing the powder at the bottom.

[0011] (6) Select a selective laser melting 3D printing device, install the metal printing plate of the printing device and level it so that the four planes of the metal printing plate are parallel, install a scraper so that it is parallel to the metal printing plate and lower it to a position that just fits the metal printing plate.

[0012] (7) Pour the dry powder obtained in step (5) into the powder tank of the 3D printer and adjust the powder tank to a suitable position for powder spreading operation.

[0013] (8) Turn on the cooling water and protective gas pump to reduce the oxygen content in the printer to 250ppm, open and download the pre-modeled porous 3D structure, and use the scanning strategy of rotating 90° alternately in the X and Y directions at equal intervals. The scanning speed range is 900-1200mm / s, the laser power range is 190-220W, the scanning spacing is 0.07-0.11mm, the powder layer thickness is 0.05mm, and the peak value is set to 100. Printing can be carried out after turning on the laser.

[0014] (9) Cut the printed palladium@blue titanium dioxide composite electrode from the metal printing plate using a water jet. Soak it in industrial alcohol (greater than 99.7%) and ultrasonicate it for 10-15 minutes, repeating 2-3 times.

[0015] The palladium@blue titanium dioxide composite electrode was used as the working electrode to degrade FLO wastewater in the following manner:

[0016] An H-type electrolytic cell was used as the reaction vessel, with a palladium-blue titanium dioxide composite electrode as the working electrode and a saturated calomel electrode as the reference electrode, separated by a distance of 0.5 to 1 cm. A platinum sheet served as the counter electrode. Simulated pollutants were added, and 50 to 100 mM sodium sulfate was used as the electrolyte. The working electrode potential was -1 to -1.2 V vs. SHE. Samples were collected using a 1 ml sterile syringe at time points of 0, 15, 30, 45, 60, 90, and 120 min, filtered through a filter tip, and transferred to a 1.5 ml liquid chromatography vial. All samples were then placed in a high-performance liquid chromatograph to determine the residual pollutant concentration.

[0017] The present invention has the following beneficial effects:

[0018] (1) The present invention adopts an integrated three-dimensional porous palladium@blue titanium dioxide composite electrode prepared by selective laser melting 3D printing technology as the working electrode, which overcomes the previous phenomenon of uneven loading or aggregation of palladium elements on the electrode. The electrode manufacturing steps of the present invention are simple and controllable, which is convenient for large-scale production and application.

[0019] (2) The integrated three-dimensional porous palladium@blue titanium dioxide electrode prepared by the selective laser melting 3D printing technology of the present invention can realize the conversion of titanium dioxide to blue titanium dioxide in real time during the printing process. Compared with titanium dioxide, blue titanium dioxide has higher electron transmission efficiency, thereby improving the utilization rate of atomic hydrogen and thus enhancing the electrocatalytic reduction efficiency, reducing energy consumption and improving current efficiency.

[0020] (3) The electrode prepared by selective laser melting 3D printing in the present invention has a three-dimensional structure, which greatly enhances water mass transfer, improves the contact between polluted water and the electrode surface, and avoids the effects of short life and diffusion restriction of active species on the electrode surface.

[0021] (4) The present invention can effectively treat antibiotic wastewater with strong biological toxicity. No other toxic and harmful substances are produced during the treatment process. It has stable operation, small footprint and simple operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope image of the 3D printed three-dimensional porous palladium@blue titanium dioxide composite electrode;

[0023] Figure 2 Degradation curves of florfenicol for different materials for 3D printing;

[0024] Figure 3 This is the degradation curve of florfenicol under different palladium doping amounts. DETAILED DESCRIPTION

[0025] The present invention provides a method and application for preparing a three-dimensional porous palladium@blue titanium dioxide composite electrode by selective laser melting 3D printing. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to examples below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In the present invention, Figure 1 This is a scanning electron microscope image of the 3D printed three-dimensional porous palladium@blue titanium dioxide composite electrode; Figure 2 Degradation curves of florfenicol for different materials for 3D printing; Figure 3 This is the degradation curve of florfenicol under different palladium doping amounts.

[0026] Example 1:

[0027] Comparison of the degradation of florfenicol using the selective laser melting 3D printed three-dimensional porous palladium@blue titanium dioxide composite electrode provided by the present invention and different 3D printed materials. The material preparation method and the process of florfenicol degradation include the following steps:

[0028] (1) Place equal amounts of steel balls in four ball mill jars, so that the weight of the steel balls is about 4 times the weight of the powder added in step (2).

[0029] (2) A certain amount (1%) of palladium powder, titanium dioxide powder (1%) and palladium carbon powder were weighed in a certain proportion and placed in a ball mill, and a certain amount of 4 ml of ethanol was added.

[0030] (3) Place the ball mill in step (2) on a planetary ball mill.

[0031] Bidirectional mode, given frequency 45.83HZ, interval length 5.00min, running length 30.00min, running number 1 time.

[0032] (4) Dry the powder (particle size of 15-53 μm) obtained in step (3) in an oven at a temperature of 70-200° C. for 2-5 hours to obtain a certain amount of dry powder.

[0033] (5) The dry powder obtained in step (4) was passed through a 200-mesh sieve and shaken on an oscillator until all the dry powder was sieved into the iron plate containing the powder at the bottom.

[0034] (6) Select Hanbang SLM-280 laser 3D printing equipment, install the metal printing plate of the metal 3D printing equipment and level it so that the four planes of the printing plate are parallel, install the scraper so that it is parallel to the metal printing plate and lower it to a position that just fits the metal printing plate.

[0035] (7) Pour the dry powder obtained in step (5) into the powder tank of the 3D printer, and adjust the powder tank to a position where the dry powder is slightly higher than the metal printing plate for powder spreading operation.

[0036] (8) Turn on the cooling water and protective gas pump to reduce the dissolved oxygen content in the printer to 250 mg / L, open and download the pre-modeled porous 3D structure (the scanning strategy uses 90° rotation and alternating scanning in the X and Y directions with equal spacing, the scanning speed range is 900-1200 mm / s, the laser power range is 190-220 W, the scanning spacing is 0.07-0.11 mm, and the powder layer thickness is 0.05 mm), set the peak value to 100, and turn on the laser before printing.

[0037] (9) Cut the printed 3D iron material from the metal printing plate with a water jet. Soak it in industrial alcohol (greater than 99.7%) and ultrasonicate it for 10-15 minutes, repeating 2-3 times.

[0038] (10) An H-type electrolytic cell was used as the reaction vessel, a palladium-blue titanium dioxide composite electrode was used as the working electrode, a saturated calomel electrode was used as the reference electrode, and the distance between the two was 0.5-1 cm. A platinum sheet was used as the counter electrode. Simulated pollutants were added, and 50-100 mM sodium sulfate was used as the electrolyte. The working potential of the working electrode was -1 to -1.2 V vs. SHE. Samples were taken with a 1 ml sterile syringe at time points of 0, 15, 30, 45, 60, 90, and 120 min, filtered through a filter head, and transferred to a 1.5 ml liquid phase vial. All samples were then placed in a high performance liquid chromatograph to determine the residual concentration of the pollutant.

[0039] (11) Repeat step (10) for all electrodes, the purpose of which is to significantly improve the degradation of florfenicol by the electrode of the present invention compared with other electrodes, specifically as follows: Figure 2 .

[0040] Example 2:

[0041] The selective laser melting 3D printing method provided by the present invention is used to print a three-dimensional porous palladium@blue titanium dioxide composite electrode, and the degradation of florfenicol by different palladium doping amounts is compared. The material preparation method and the process of degrading florfenicol include the following steps:

[0042] (1) Place equal amounts of steel balls in four ball mill jars, so that the weight of the steel balls is about 4 times the weight of the powder added in step (2).

[0043] (2) Palladium powder, titanium dioxide powder and palladium carbon powder with a mass ratio of 0%, 0.1%, 0.5%, 0.7%, 1.0% and 1.5% are weighed and placed in a ball mill, and a certain amount of ethanol is added.

[0044] (3) Place the ball mill in step (2) on a planetary ball mill.

[0045] Bidirectional mode, given frequency 45.83 Hz, interval length 5.00 min, operation length 30.00 min, operation number 1. (4) Dry the powder obtained in step (3) (particle size 15-53 μm) in an oven at a temperature of 70-200 ° C for 2 to 5 hours to obtain a certain amount of dry powder.

[0046] (5) The dry powder obtained in step (4) was passed through a 200-mesh sieve and shaken on an oscillator until all the dry powder was sieved into the iron plate containing the powder at the bottom.

[0047] (6) Select Hanbang SLM-280 laser 3D printing equipment, install the metal printing plate of the metal 3D printing equipment and level it so that the four planes of the printing plate are parallel, install the scraper so that it is parallel to the metal printing plate and lower it to a position that just fits the metal printing plate.

[0048] (7) Pour the dry powder obtained in step (5) into the powder tank of the 3D printer, and adjust the powder tank to a position where the dry powder is slightly higher than the metal printing plate for powder spreading operation.

[0049] (8) Turn on the cooling water and protective air pump to reduce the dissolved oxygen content in the printer to 250 mg / L, open and download the pre-modeled porous 3D structure (the scanning strategy uses 90° rotation and alternating scanning in the X and Y directions with equal spacing, the scanning speed range is 900-1200 mm / s, the laser power range is 190-220 W, the scanning spacing is 0.07-0.11 mm, and the powder layer thickness is 0.05 mm), set the peak value to 100, and turn on the laser before printing.

[0050] (9) Cut the printed 3D iron material from the printing plate with a water jet. Soak it in industrial alcohol (greater than 99.7%) and ultrasonicate it for 10-15 minutes, repeating 2-3 times.

[0051] (10) An H-type electrolytic cell was used as the reaction vessel, a palladium-blue titanium dioxide composite electrode was used as the working electrode, a saturated calomel electrode was used as the reference electrode, and the distance between the two was 0.5-1 cm. A platinum sheet was used as the counter electrode. Simulated pollutants were added, and 50-100 mM sodium sulfate was used as the electrolyte. The working potential of the working electrode was -1 to -1.2 V vs. SHE. Samples were taken with a 1 ml sterile syringe at time points of 0, 15, 30, 45, 60, 90, and 120 min, filtered through a filter head, and transferred to a 1.5 ml liquid phase vial. All samples were then placed in a high performance liquid chromatograph to determine the residual concentration of the pollutant.

[0052] (11) Repeat step (10) for all electrodes with different palladium doping amounts.

[0053] like Figure 2 As shown, the removal rate of florfenicol by the three-dimensional porous palladium@blue titanium dioxide composite electrode was 92.93%, the removal rate of florfenicol by the palladium@titanium dioxide electrode was 78.44%, the removal rate of florfenicol by the palladium@titanium electrode was 59.87%, and the removal rate of florfenicol by the blue titanium dioxide electrode was 23.26%.

[0054] The present invention mixes palladium powder, ultrafine titanium dioxide powder and palladium carbon powder together, uses ball milling to mix the three evenly, and then uses 3D printing technology to prepare an electrode with uniform palladium distribution. During the printing process, hydrogen and argon are used as protective gases, with hydrogen accounting for 1% to 3% and the remaining protective gas being argon. Since the printing chamber cannot guarantee complete vacuum, a certain amount of oxygen will exist. Under the action of high temperature laser, the carbon element in the palladium carbon is oxidized to form carbon oxides. Due to the introduction of hydrogen and the action of trace oxygen, carbon monoxide is formed, leaving the palladium element evenly distributed in the electrode; the simultaneous action of carbon monoxide and hydrogen causes titanium dioxide to be reduced to blue titanium dioxide in real time during the printing process. Blue titanium dioxide has stronger electron transmission ability than ordinary titanium dioxide and palladium adheres more firmly; the integrated three-dimensional porous palladium@blue titanium dioxide electrode prepared by selective metal melting 3D printing is used to efficiently degrade FLO. Figure 3 As shown, the removal rate of florfenicol by the three-dimensional porous palladium@blue titanium dioxide composite electrode with a palladium doping amount of 0.0% is 23.26%, the removal rate of florfenicol by the composite electrode with a palladium doping amount of 0.1% is 47.97%, the removal rate of florfenicol by the composite electrode with a palladium doping amount of 0.5% is 54.46%, the removal rate of florfenicol by the composite electrode with a palladium doping amount of 0.7% is 73.80%, the removal rate of florfenicol by the composite electrode with a palladium doping amount of 1.0% is 92.93%, and the removal rate of florfenicol by the composite electrode with a palladium doping amount of 1.5% is 84.97%.

Claims

1. A method for preparing a palladium@blue titanium dioxide composite electrode for electrocatalytic oxidation wastewater treatment comprises the following steps: (1) Place equal amounts of steel balls in four ball mill jars, so that the weight of the steel balls is about 4 times the weight of the powder added in step (2); (2) Weigh palladium powder (0%-1.5%), titanium dioxide powder, and palladium-carbon powder (1%-3%) in a mass ratio and place them in a ball mill, then add 3-5 ml of ethanol; (3) Place the ball mill in step (2) on a planetary ball mill in bidirectional mode, with a given frequency of 45.83 Hz, an interval of 5.00 min, a running time of 30.00 min, and a running number of 1; (4) drying the powder (particle size 2-10 μm) ground in step (3) in an oven at a temperature of 70-200° C. for 2-5 hours to obtain a certain amount of dry powder; (5) The dry powder obtained in step (4) was passed through a 200-mesh sieve and shaken on an oscillator until all the dry powder was sieved into the iron plate containing the powder at the bottom; (6) Selecting a selective laser melting 3D printing device, installing the metal printing plate of the printing device and leveling it so that the four planes of the metal printing plate are parallel, installing a scraper so that it is parallel to the metal printing plate and lowering it to a position that just fits the metal printing plate; (7) Pour the dry powder obtained in step (5) into the powder tank of the 3D printer and adjust the powder tank to a suitable position for powder spreading operation; (8) Open the cooling water valve and the protective gas pump, wherein the protective gas contains 1%-3% hydrogen, so that the oxygen content in the printer drops to 250ppm. Under the action of the high temperature of the laser and the action of trace oxygen, the carbon element in the palladium carbon is oxidized to form carbon monoxide, and the remaining palladium element is evenly distributed in the electrode; under the action of carbon monoxide and hydrogen, the titanium dioxide is reduced to blue titanium dioxide in real time during the printing process; then open and download the pre-modeled porous 3D structure, and the scanning strategy adopts the X and Y directions to rotate 90° alternately for scanning at equal intervals, the scanning speed range is 900-1200mm / s, the laser power range is 190-220W, the scanning interval is 0.07-0.11mm, the powder layer thickness is 0.05mm, the peak value is set to 100, and printing can be carried out after the laser is turned on; (9) The printed palladium@blue titanium dioxide composite electrode was cut from the metal printing plate using a water jet, and then immersed in industrial alcohol (greater than 99.7%) and ultrasonicated for 10 to 15 minutes, and repeated 2 to 3 times.

2. A method for treating wastewater containing florfenicol, characterized in that: The palladium@blue titanium dioxide composite electrode according to claim 1 is used as the working electrode, the saturated calomel electrode is used as the reference electrode, the distance between the two is 0.5 to 1 cm, a platinum sheet is used as the counter electrode, simulated pollutants are added, and 50 to 100 mM sodium sulfate is used as the electrolyte; wherein the working potential of the working electrode is -1 to -1.2 V vs SHE.

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