CN116040752A - Preparation method and application of biochar electrode - Google Patents

Abstract

The invention relates to a preparation method of a metal-loaded biochar electrode by graphitized sycamore fruit balls, which comprises the steps of hydrothermally carbonizing the loaded metal and roasting graphitization in an inert atmosphere. Firstly, placing the sycamore fruit balls into an autoclave, and simultaneously adding a specified metal precursor solution into the autoclave; heating the autoclave in an oven to perform hydrothermal reaction, naturally cooling, cleaning and drying to obtain metal-loaded carbonized syringa amurensis fruit balls; immersing carbonized sycamore fruit balls loaded with metal into a potassium ferrate solution with a certain concentration for a certain time, transferring the immersed mixture into a tube furnace, and introducing non-oxidizing gas to calcine the mixture for a certain time to obtain graphitized sycamore fruit balls; and naturally cooling the graphitized fruit ball, washing and drying to obtain the biochar electrode. The beneficial effects of the invention are as follows: the method is characterized in that the biological carbon electrode is prepared by using the natural hollow tube structure of the syringa amurensis fruit ball existing in nature, and is used for removing nitrate nitrogen pollutants in water through electrocatalytic treatment, so that the nitrate nitrogen pollutants are converted into nitrogen with high selectivity.

Description

A kind of preparation method and application of biochar electrode

technical field

The invention relates to the technical field of electrode materials, in particular to a preparation method and application of a metal-loaded biochar electrode of graphitized sycamore fruit balls.

Background technique

The removal of nitrate nitrogen is an important part of improving the quality of water environment in the future. The pollution of nitrate nitrogen in groundwater is also very serious in the world. The nitrate nitrogen content in groundwater in many areas of the United States has an average annual increase of 0.8mg/L, and the concentration of nitrate nitrogen in German agricultural well water has a probability of exceeding 60mg/L. It can be seen that the effective removal of nitrate nitrogen is a long-term and arduous environmental restoration task in my country and even in the world.

Surface water itself has certain self-purification and self-repair functions. The cycle of self-repair is about 1400 years, and it is almost impossible to complete the purification and repair by itself. At present, many researchers at home and abroad have conducted in-depth research on nitrate nitrogen reduction and removal technology, which can be mainly divided into physical and chemical removal methods, biological denitrification methods and chemical reduction repair methods.

In the existing electrochemical reduction technology, powdered biochar materials are often used to make electrodes, which requires glue to coat the powdered materials on the electrode sheet. On the one hand, the cost is very high, and on the other hand, the electrode made in this way only works on the surface. , The mass transfer efficiency is low, and the carbonized powder coated on the electrode sheet will agglomerate, which will affect the stability of the electrode. The uniformity of the coating cannot be guaranteed, and the removal efficiency of nitrate nitrogen will be reduced.

The invention belongs to the technical field of electrode materials for electrochemical reduction of nitrate nitrogen. The graphitized syringa fruit ball biochar electrode is conducive to improving the selective adsorption of the electrode to nitrate nitrogen, and at the same time, the loaded metal can enhance the generation of active species to increase the nitrate nitrogen. Nitrogen selectivity, and finally achieve the purpose of efficient removal of nitrate nitrogen.

Contents of the invention

In order to overcome a small number of defects in the prior art, the present invention provides the preparation and application method of a metal-loaded biochar electrode from graphitized sycamore fruit balls, which not only has a wide range of raw materials and low cost, but also simplifies the process and reduces environmental pollution. risks of.

The preparation method of the metal-loaded biochar electrode of the graphitized syringa fruit balls involved in the present invention comprises the following steps:

S1. Put the cleaned and dried sycamore fruit balls into an autoclave with a polytetrafluoroethylene lining and a stainless steel jacket, and add a certain concentration of metal salt solution to the autoclave at the same time, so that the solution is immersed in the sycamore fruit balls;

S2. Put the autoclave in an oven and keep it at a certain temperature for a certain period of time to carbonize the syringa fruit balls. At the same time, load the metal on the surface of the syringa fruit balls for hydrothermal carbonization. By loading the metals, the electrocatalytic active sites on the electrode surface can be increased. The quantity of the electrode can enhance the high-capacity adsorption and high-selectivity removal capacity of nitrate nitrogen in water;

S3. Naturally cool the sycamore fruit balls after the hydrothermal reaction in an autoclave, then take out the fruit balls, and then wash them with deionized water. The cleaned fruit balls are dried in a vacuum environment at 80°C to obtain metal-loaded hydrothermal Carbonized sycamore fruit balls;

S4. After immersing the hydrothermally carbonized Platanus fruit balls with metal loading in a certain concentration of potassium ferrate solution for 8 hours, transfer them to a tube furnace, and feed a non-oxidizing gas into the tube furnace, and treat them at a certain temperature for a certain period of time. Time, potassium ferrate as an activator and catalyst is conducive to the simultaneous realization of further activation and graphitization of carbonized sycamore fruit balls;

S5, after finishing the treatment, the graphitized fruit balls are naturally cooled in a tube furnace. The graphitized plane tree fruit balls are hard and have better electrical conductivity, and then the graphitized fruit balls are cleaned to no impurities with deionized water. After drying in a drying oven, a metal-loaded biochar electrode of the graphitized Platanus fruit balls was obtained.

Further, the temperature of the oven in S2 is set at 100°C-350°C, and the water heating time is 8h-18h.

Further, the metal salt solution is a copper salt solution or a nickel salt solution.

Further, the metal salt solution is one of sulfate, nitrate, and chloride salt, and the concentration of the metal salt solution is 0.5˜50 mmol/L.

Further, the concentration of the potassium ferrate solution is 0.02～0.5mol/L

Further, the non-oxidizing gas is one of hydrogen, argon, helium, nitrogen, carbon dioxide, and carbon monoxide.

Further, in the step S5, the temperature of the tube furnace is set at 600° C. to 1500° C., and the constant temperature treatment time of the composite biochar material is 1.5 h to 5 h.

A metal-loaded biochar electrode of graphitized syringa fruit balls is prepared by combining the above-mentioned hydrothermal method with a calcination method. Wherein the hydrothermal method refers to steps S1-S3, and the calcination method refers to steps S4 and S5.

Application of a metal-loaded biochar electrode of graphitized syringa fruit balls in the process of removing nitrate nitrogen. A ruthenium-iridium-titanium-coated electrode is used as a counter electrode with a size of 30mm×30mm×1mm, and the prepared biochar electrode is used as a working electrode , using sodium nitrate as electrolyte solution to degrade nitrate, and the voltage is controlled at -0.8V～-1.5V during the degradation process.

The benefit of the present invention lies in that: the biochar electrode is prepared by using the natural hollow tube structure of the plane tree fruit ball existing in nature, and after two-step heating, it is hydrothermally carbonized and graphitized to support the metal, and it is used for electrocatalytic removal Nitrate nitrogen pollutants in water, so that it is converted into nitrogen gas with high selectivity.

At the same time, this method puts the sycamore fruit balls into use, which can also solve the problem that the mature fruit balls of this plant interfere with people's daily life seasonally.

Provided is a method for preparing a biomass electrode by using sycamore fruit balls, and simultaneously loading metal compounds on the surface of the formed graphitized biochar, and using it for an electrocatalytic process of converting nitrate nitrogen into nitrogen in water.

With respect to the mode that plane tree is crushed into electrodes in the prior art, the present invention utilizes the structure of plane tree itself (plane tree fruit hairs are hard and nodal, each joint is a hollow tubular structure, and there are brown ring-shaped protrusions at the end of the joint. , has adsorption performance), not only can simplify the preparation process of the electrode, but also the plane tree as an overall structure is convenient to arrange, and overcomes the cumbersome defect of the electrode processing process in the prior art.

In order to make the above and other objects, features and advantages of the present invention more comprehensible, preferred embodiments will be described in detail below together with the accompanying drawings.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Figure 1 is a schematic diagram of an electrolytic cell.

FIG. 2 is a graph showing the experimental results of the electrocatalytic degradation of nitrate in water by the nickel-loaded biochar electrode in Example 1. FIG.

FIG. 3 is a graph showing the experimental results of the electrocatalytic degradation of nitrate in water by the copper-loaded biochar electrode in Example 2. FIG.

Fig. 4 is a schematic diagram of the preparation method of the metal-loaded biochar electrode of graphitized Platanus fruit balls.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1, the preparation method of nickel-loaded biochar electrode and the removal effect of nitrate in water by electrocatalytic degradation

In a preferred embodiment of the present invention, a method for preparing a biochar electrode of graphitized sycamore fruit balls loaded with nickel metal comprises the following steps:

S1, put the cleaned and dried syringa fruit balls into an autoclave with a polytetrafluoroethylene lining and a stainless steel jacket, and add 5mmol/L nickel sulfate solution to the autoclave at the same time, so that the solution is immersed in the syringa fruit balls;

S2. Put the autoclave in an oven and keep it at 120°C for 8 hours to carbonize the syringa fruit balls. At the same time, metal nickel is loaded on the surface of the syringa fruit balls for hydrothermal carbonization. By loading metal nickel, the electrocatalytic activity on the electrode surface can be effectively increased. The number of sites enhances the electrode's high-capacity adsorption and high-selectivity removal capacity for nitrate nitrogen in water;

S3. Naturally cool the metal nickel-loaded sycamore fruit balls after the hydrothermal reaction in an autoclave, then take out the fruit balls, and then wash them with deionized water. The cleaned fruit balls are dried in a vacuum environment at 80°C to obtain metal nickel Loaded hydrothermal carbonization of plane tree fruit balls;

S4. After immersing the hydrothermally carbonized Platanus fruit balls loaded with metallic nickel in 0.1mol/L potassium ferrate solution for 8 hours, transfer them to a tube furnace, and feed non-oxidizing gas into the tube furnace, at a certain temperature Under treatment for a certain period of time, potassium ferrate as an activator and catalyst is conducive to the simultaneous realization of further activation and graphitization of carbonized sycamore fruit balls;

S5. After the treatment, the graphitized fruit balls are cooled naturally in a tube furnace, and then the graphitized fruit balls are cleaned with deionized water until there are no impurities. After drying in a drying oven, the graphitized Platanus fruit balls are loaded with nickel biochar electrode.

In the above embodiment, the non-oxidizing gas is one of hydrogen, argon, helium, nitrogen, carbon dioxide, and carbon monoxide. In the actual implementation process, the gas fed into the tube furnace is argon, and the stability of carbon in argon is better. In other embodiments, other non-oxidizing gases may also be selected according to cost and difficulty of obtaining.

The invention discloses a metal-loaded biochar electrode of graphitized sycamore fruit balls, which is prepared by combining the above-mentioned hydrothermal method and calcination method. Wherein the hydrothermal method refers to steps S1-S3, and the calcination method refers to steps S4 and S5.

The application of a metal-loaded biochar electrode of graphitized Platanus fruit balls in the process of nitrate degradation, using a ruthenium iridium titanium coating electrode as the counter electrode, the size is 30mm × 30mm × 1mm, the prepared biochar electrode is used as the working electrode, Sodium nitrate was used as the electrolyte solution to degrade nitrate nitrogen, and the voltage was controlled at -1.2V during the degradation process.

In order to verify the application effect of the biochar electrode prepared in the process of nitrate degradation by the preparation method of the biochar electrode of graphitized sycamore fruit balls loaded with metals in the present invention, the following experiments were carried out:

Referring to Figure 1, the experimental equipment includes a regulated power supply, the prepared biochar electrode is the working electrode, the ruthenium iridium titanium coating electrode is the counter electrode, and the calomel electrode is the reference electrode. The electrolysis experiment is carried out in a 150mL beaker. Stir with a magnetic stirrer to keep the electrolyte solution homogeneous.

Before the experiment on the prepared nickel-loaded biochar electrode, soak the prepared biochar electrode in 100mg/L sodium nitrate for 5h to eliminate the influence of adsorption. Add 100mL of 100mg/L sodium nitrate solution in a 150mL beaker, the prepared nickel-loaded biochar graphitized electrode is used as a working electrode, the ruthenium-iridium-titanium coated electrode is used as a counter electrode, and the calomel electrode is used as a reference electrode. remain at -1.2V. Take out 1mL solution at intervals to detect the nitrate nitrogen, nitrite nitrogen and ammonium nitrogen. The detection results are shown in Figure 2. The removal can reach more than 85%, and the nitrogen selectivity can reach 78.6%, realizing the removal of nitrate and converting it into N ₂ .

Example 2: Preparation method of copper-loaded biochar electrode and effect of removing nitrate in water by electrocatalysis

The main steps of Example 2 are the same as those of Example 1, except that the step S1 includes adding 5 mmol/L copper sulfate to the autoclave.

Before the experiment, soak the prepared biochar electrode in 100mg/L sodium nitrate for 5h to eliminate the influence of adsorption, add 100mL of 100mg/L sodium nitrate solution into a 150mL beaker, and prepare the prepared copper-loaded biochar graphitized electrode Used as a working electrode, a ruthenium-iridium-titanium-coated electrode was used as a counter electrode, and a calomel electrode was used as a reference electrode, and the voltage was maintained at -1.2V. Take out 1mL solution at intervals to detect nitrate nitrogen, nitrite nitrogen and ammonium nitrogen. The experimental results are shown in Figure 3. It can be clearly seen from the figure that the copper-loaded biochar graphitized electrode can remove nitrate. Reach more than 90%, and nitrogen selectivity can reach 81.2%.

It can be clearly seen from Figures 2 and 3 that the nickel-loaded biochar electrode and the copper-loaded biochar electrode prepared by the present invention can achieve continuous and effective removal of nitrate, and the duration is long. The invention utilizes the structure of the sycamore fruit ball itself (the sycamore fruit hair is hard and nodular, each section is a hollow tubular structure, and there are brown ring-shaped protrusions at the end of the internode, which has adsorption properties), not only can simplify the preparation process of the electrode, In addition, the planar tree fruit ball is easy to arrange as an overall structure, overcomes the cumbersome defect of the electrode processing process in the prior art, and can effectively reduce the removal cost while ensuring the removal effect on nitrate.

In the present invention, specific examples have been applied to explain the principles and implementation methods of the present invention, and the descriptions of the above examples are only used to help understand the method of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to this The idea of the invention will have changes in the specific implementation and scope of application. To sum up, the contents of this specification should not be construed as limiting the present invention.

Claims (10)

1. a preparation method of a graphitized syringa fruit ball loaded metal biochar electrode, characterized in that, comprising the following steps: S1. Put the cleaned and dried sycamore fruit balls into an autoclave with a polytetrafluoroethylene lining and a stainless steel jacket, and add a certain concentration of metal salt solution to the autoclave at the same time, so that the solution is immersed in the sycamore fruit balls; S2. Put the autoclave in an oven and keep it at a certain temperature for a certain period of time to carbonize the syringa fruit balls. At the same time, load the metal on the surface of the syringa fruit balls for hydrothermal carbonization. By loading the metals, the electrocatalytic active sites on the electrode surface can be increased. The quantity of the electrode can enhance the high-capacity adsorption and high-selectivity removal capacity of nitrate nitrogen in water; S3. Naturally cool the sycamore fruit balls after the hydrothermal reaction in an autoclave, then take out the fruit balls, and then wash them with deionized water. The cleaned fruit balls are dried in a vacuum environment at 80°C to obtain metal-loaded hydrothermal Carbonized sycamore fruit balls; S4. After immersing the hydrothermal carbonized Platanus fruit balls loaded with metal in a certain concentration of potassium ferrate solution for 8 hours, transfer them to a tube furnace, and pass non-oxidizing gas into the tube furnace, and process at a certain temperature For a certain period of time, potassium ferrate as an activator and catalyst is conducive to the further activation and graphitization of carbonized Platanus fruit balls simultaneously; S5, after finishing the treatment, the graphitized fruit balls are naturally cooled in a tube furnace. The graphitized plane tree fruit balls are hard and have better electrical conductivity, and then the graphitized fruit balls are cleaned to no impurities with deionized water. After drying in a drying oven, metal-loaded graphitized syringa fruit balls are obtained. 2. the preparation method of the biochar electrode of graphitized Platanus fruit ball load metal according to claim 1, is characterized in that, described non-oxidizing gas is hydrogen, argon, helium, nitrogen, carbon dioxide, carbon monoxide A sort of. 3. the preparation method of the biochar electrode of the graphitized fruit ball Platanus persicae according to claim 1, is characterized in that, also comprises the Platanus persica fruit ball that collects is cleaned up, cleans to water clarification with deionized water, after drying Tumble dry in box. 4. The preparation method of the metal-loaded biochar electrode of graphitized syringa fruit balls according to claim 1, characterized in that, in the step S2, the temperature of the oven is set to 120°C to 200°C, and the hydrothermal time is It is 8h ~ 18h. 5. The preparation method of the biochar electrode of graphitized Platanus fruit balls loaded with metal according to claim 1, characterized in that, the metal salt solution is a copper salt solution or a nickel salt solution. 6. the preparation method of the biochar electrode of graphitized Platanus fruit ball load metal according to claim 1, is characterized in that, described metal salt solution is a kind of in sulfate, nitrate, chloride salt and described The concentration of the metal salt solution is 0.5-50 mmol/L. 7 . The method for preparing a metal-loaded biochar electrode of graphitized Platanus persica fruit balls according to claim 1 , wherein the concentration of the potassium ferrate solution is 0.02 to 0.5 mol/L. 8 . The method for preparing a metal-loaded biochar electrode of graphitized Platanus persica fruit balls according to claim 1 , wherein the temperature of the tube furnace is set at 600-1500° C., and the constant temperature treatment time is 2 hours. 9. A metal-loaded biochar electrode of graphitized syringa fruit balls, characterized in that: prepared by the preparation method of the metal-loaded biochar electrode of graphitized syringa fruit balls according to any one of claims 1-8 . 10. The application of a metal-loaded biochar electrode of graphitized Platanus fruit balls in the process of removing nitrate nitrogen, characterized in that: a ruthenium-iridium-titanium coated electrode is used as the anode plate, and the size is 30mm×30mm×1mm, and the prepared The biochar electrode is used as the cathode, and sodium nitrate is used as the electrolyte solution to remove nitrate nitrogen, and the voltage is controlled at -0.8V to -1.5V during the removal process.

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