Bimetal catalyst as well as preparation method and application thereof

Abstract

The invention discloses a bimetallic catalyst as well as a preparation method and application thereof. A mixture of biomass / derived carbon, ferric salt and other metal salts is used as a raw material, and under a vacuum-like state, a Joule heat technology is used for heating and cooling to obtain a product, namely the bimetallic catalyst. The bimetallic catalyst provided by the invention generates active substances such as free radicals, singlet oxygen and the like through excitation of an activating oxidant, and can degrade organic pollutants in a water body without difference; and the generation of iron mud is reduced by reducing the release of iron, so that the problem of secondary environmental pollution caused by the generation of the iron mud in the practical application of the Fenton-like technology is effectively relieved.

Description

Technical Field

[0001] The invention belongs to the field of organic solid waste resource recovery technology and environmental restoration technology, and particularly relates to a bimetallic catalyst and a preparation method and application thereof. Background Art

[0002] Water is the source of life, but the uncontrolled discharge of human domestic sewage and industrial wastewater has posed a huge threat to the sustainable use of water resources. Fenton-like technology is a powerful and effective water treatment technology because of its strong oxidative degradation ability, which can indiscriminately decompose and remove various organic pollutants in water. However, when iron-based catalysts containing divalent iron ions are applied to water, the release of iron ions often inevitably produces a large amount of solid waste, namely iron sludge; and improper waste treatment may also lead to serious secondary environmental pollution, which hinders the application of Fenton-like technology in actual wastewater. Therefore, how to prepare stable and safe iron-based catalysts, reduce the release of iron ions and achieve efficient organic wastewater treatment is an important technical problem at present. Summary of the invention

[0003] The primary purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and provide a method for preparing a bimetallic catalyst. The preparation method utilizes the principle of instantaneous high temperature and current reaction of Joule heat technology to stably and uniformly load the metal on a biomass-based carbon carrier, thereby obtaining a high-performance and safe bimetallic catalyst.

[0004] Another object of the present invention is to provide a bimetallic catalyst obtained by the above preparation method. The bimetallic catalyst can efficiently degrade organic pollutants in water, and the dissolution rate of metal elements is greatly reduced, which has a synergistic effect compared with a single metal catalyst.

[0005] Another object of the present invention is to provide applications of the bimetallic catalyst.

[0006] The object of the present invention is achieved by the following technical scheme: A method for preparing a bimetallic catalyst, comprising the following steps: using a mixture of biomass / derived carbon, iron salt and other metal salts as raw materials, heating them using Joule heat technology in an oxygen-free environment, and obtaining a product after cooling to obtain a bimetallic catalyst; preferably comprising the following steps:

[0007] (1) mixing the biomass / derived charcoal, iron salt and other metal salts uniformly to obtain a mixture;

[0008] (2) uniformly mixing the mixture and carbon black to obtain a precursor;

[0009] (3) Using Joule heat technology to treat the precursor obtained in step (2) to obtain a bimetallic catalyst.

[0010] The biomass / derived charcoal refers to at least one of biomass and derived charcoal.

[0011] The biomass is preferably waste biomass, including but not limited to: dead branches of trees, crop straw, edible fungus substrate, grain husks and fruit shells.

[0012] The derived charcoal is charcoal prepared by heating biomass.

[0013] The heating method includes but is not limited to pyrolysis and hydrothermal method.

[0014] The iron (Fe) salt is preferably a soluble iron salt, which is mixed with other metal salts and biomass / derived carbon in an environment with water as a dispersion medium, including ferric chloride, ferric sulfate, ferric nitrate, ferric acetate and their hydrated compounds.

[0015] The other metal (M) salt is preferably a soluble metal salt, which is mixed with iron salt and biomass / derived carbon in an environment with water as the dispersion medium, preferably a calcium salt, a magnesium salt, a zinc salt, a nickel salt, a manganese salt or a vanadium salt; more preferably calcium acetate, magnesium acetate, zinc acetate, nickel acetate, manganese acetate, manganese chloride, nickel chloride, vanadium chloride and their hydrated compounds.

[0016] The iron element in the iron salt and the metal (M) element in other metal salts are preferably in a molar ratio of 1:1 to 10; more preferably in a molar ratio of 1:1.

[0017] The amount of the biomass / derived carbon is preferably calculated based on the ratio of total metal elements (Fe+M) to biomass / derived carbon of 0.1 to 20 mmol (Fe+M) / g biomass / derived carbon; more preferably, it is calculated based on the ratio of total metal elements (Fe+M) to biomass / derived carbon of 2.8 mmol (Fe+M) / g biomass / derived carbon.

[0018] When the iron salt and the other metal salts described in step (1) are soluble salts, the mixing method is preferably to add the iron salt, other metal salts and biomass / derived carbon into deionized water and stir so that the metal ions can be evenly distributed on the surface of or in the biomass / derived carbon.

[0019] The stirring conditions are preferably as follows: temperature is 25-45° C., rotation speed is 60-200 rpm, and time is set to 20-120 minutes.

[0020] When the mixture in step (2) is an aqueous solution, it is first dried and then mixed with carbon black.

[0021] The carbon black described in step (2) is used as a conductive agent to trigger the circuit.

[0022] The amount of carbon black described in step (2) is not limited, and the amount that can trigger the circuit is within the protection scope of the present invention; its amount is preferably 0 to 20% of the dry weight of the mixture; when the reaction raw materials contain substances with conductive properties, such as derived carbon, the amount of carbon black added can be 0.

[0023] The mixing method in step (2) is preferably grinding.

[0024] The treatment environment described in step (3) is preferably an oxygen-free environment.

[0025] The oxygen-free environment is a vacuum-like environment or an environment filled with inert gas.

[0026] The inert gas includes but is not limited to nitrogen, argon and helium.

[0027] The parameters of the Joule heating technology described in step (3) are preferably: direct current, the voltage is set to 100-380V, the number of direct current triggers is 1-10 times, and the reaction time for each time is 10-1000ms; more preferably: the voltage is 250V, the reaction time for each time is 30ms, and the number of triggers is 3 times.

[0028] A bimetallic catalyst is obtained by the above preparation method.

[0029] The use of the above bimetallic catalyst in degrading organic pollutants preferably comprises the following steps: adding the bimetallic catalyst and an oxidant to the organic pollutants for reaction.

[0030] The organic pollutants include antibiotics, dyes, pesticides, veterinary drugs, etc.; preferably, chloramphenicol.

[0031] The organic pollutants are preferably organic pollutants in wastewater.

[0032] The concentration of the organic pollutants is 0-200 mg / L, excluding the endpoint value 0; preferably 60 mg / L.

[0033] The oxidant is preferably at least one of hydrogen peroxide and persulfate.

[0034] The persulfate is preferably at least one of potassium peroxymonosulfate, potassium peroxydisulfate, sodium peroxymonosulfate and sodium peroxydisulfate.

[0035] The dosage of the bimetallic catalyst is determined according to the concentration of the organic pollutants, preferably 0.01-2 g / L; more preferably 1 g / L.

[0036] The dosage of the oxidant is determined according to the concentration of the organic pollutants, preferably 1-10 mmol / L, more preferably 7 mmol / L.

[0037] The reaction conditions are preferably as follows: temperature of 5 to 55° C., reaction time of 5 to 100 minutes, and pH of 3 to 12.

[0038] Compared with the prior art, the present invention has the following advantages and effects:

[0039] (1) The present invention utilizes Joule heat technology to prepare bimetallic catalysts. Joule heat technology can instantly generate ultra-high temperature and electrical stripping effects, and can directly carbonize biomass and its derived carbon into a carbon carrier with a graphene layer structure; and promote the fusion of iron and vanadium elements. The fused metal nanoparticles can be evenly and stably dispersed on the biomass-based carbon carrier formed simultaneously, so that the material has better electron transfer ability.

[0040] (2) The bimetallic catalyst provided by the present invention can generate free radicals, singlet oxygen and other active substances by activating oxidants, and can indiscriminately degrade organic pollutants in water bodies; and can reduce the generation of iron sludge by reducing the release of iron, thereby effectively alleviating the problem of secondary environmental pollution caused by the generation of iron sludge in practical applications of Fenton-like technology.

[0041] In summary, the bimetallic catalyst obtained by Joule heating technology not only has a stronger effect on degrading organic pollutants than single metal catalysts, but also greatly reduces the dissolution of iron and vanadium elements, optimizes secondary pollution, and is more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a graph showing the changes in temperature, current and voltage values ​​monitored during the preparation of the bimetallic catalyst FeV in Example 1.

[0043] Figure 2 This is a diagram showing the degradation effects of single metal and bimetallic catalysts on chloramphenicol in Example 1.

[0044] Figure 3 This is a comparison chart of metal dissolution of single and double metal catalysts during the degradation of chloramphenicol in Example 1.

[0045] Figure 4 This is a diagram showing the degradation effect of the bimetallic catalyst on chloramphenicol under different pH conditions in Example 2. DETAILED DESCRIPTION

[0046] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0047] Example 1

[0048] The Joule heating device consists of three parts: a power control system, a reaction box, and an oscilloscope monitoring system. The power control system and the oscilloscope monitoring system are connected to the reaction box respectively. The power control system can set the current trigger type and adjust the reaction parameters. The reaction box is used to place samples, which are connected to the sample tube through electrodes at both ends. The sample is squeezed before the reaction to reduce the internal resistance of the sample. The oscilloscope monitoring system can monitor the voltage and current changes during the reaction. Specific operation process: (1) Place the quartz tube containing the sample in the reaction box and connect it to the metal electrodes at both ends; (2) Vacuum pump until the box is oxygen-free; (3) Set the reaction conditions and start it, and observe whether the circuit reaction is triggered; (4) Take out the sample after the reaction is completed.

[0049] The single and bimetallic catalysts were prepared using Joule heat equipment and the differences in the degradation effects on chloramphenicol were compared to verify the high efficiency of bimetallic catalysts in the degradation of organic pollutants and their safety to the environment. The specific operation steps are as follows:

[0050] (1) Material preparation:

[0051] A. Sawdust and water were mixed in a hydrothermal reactor at a mass ratio of 1:15, the temperature was set at 270°C, the reaction was carried out for 60 minutes, and after the reaction was completed, the mixture was filtered and dried to obtain sawdust-derived hydrothermal charcoal.

[0052] B. Mix ferric acetate and sawdust-derived hydrothermal carbon in deionized water, and the amount of ferric acetate is calculated according to the ratio of iron element to hydrothermal carbon of 2.8mmol / g C; place in a constant temperature oscillating box, mix thoroughly at 25°C and 150rpm for 60 minutes to obtain mixture A. After drying, add carbon black in an amount of 10% by mass of mixture A, and grind and mix in a mortar to obtain a material precursor. Then put the sample into a quartz tube, put graphite carbon rods at both ends, and place it in a reaction box and connect it to the metal electrode. The reaction conditions are set as follows: voltage of 250V, reaction time of 30ms, and triggering times of 3 times to obtain a single metal catalyst Fe.

[0053] C. Mix vanadium trichloride and sawdust-derived hydrothermal carbon in deionized water, and the amount of vanadium trichloride is calculated based on the ratio of vanadium element to hydrothermal carbon of 2.8mmol / g C; place in a constant temperature oscillating box, mix thoroughly at 25°C and 150rpm for 60 minutes to obtain mixture B. After drying, add carbon black in an amount of 10% by mass of mixture B, and grind and mix in a mortar to obtain a material precursor. The sample is then placed in a quartz tube, and graphite carbon rods are placed at both ends and placed in a reaction box connected to the metal electrode. The reaction conditions are set as follows: voltage of 250V, reaction time of 30ms, and triggering times of 3 times to obtain a single metal catalyst V.

[0054] D. Mix ferrous acetate, vanadium trichloride and sawdust-derived hydrothermal charcoal in deionized water with a molar ratio of iron to vanadium of 1:1. The amount of ferrous acetate and vanadium trichloride is calculated based on the ratio of iron vanadium to hydrothermal charcoal of 2.8 mmol / g C. Place in a constant temperature oscillating box and mix thoroughly at 25°C and 150rpm for 60 minutes to obtain a mixture C. After drying, add carbon black in an amount of 10% of the mass ratio of mixture C, and grind and mix in a mortar to obtain a material precursor. The sample is then placed in a quartz tube, graphite carbon rods are placed at both ends, and then placed in a reaction box and connected to the metal electrodes. The reaction conditions are set as follows: voltage of 250V, reaction time of 30ms, and triggering times of 3 times to obtain a bimetallic catalyst FeV. The temperature peak, current and voltage change values ​​of the bimetallic catalyst prepared by Joule heat technology are shown in the following table. Figure 1 shown.

[0055] E. Mix ferric acetate, copper acetate and sawdust-derived hydrothermal carbon in deionized water, the molar ratio of iron to copper is 1:1, and the amount of ferric acetate and copper acetate is calculated according to the ratio of iron and copper elements to hydrothermal carbon of 2.8mmol / gC; place in a constant temperature oscillating box, mix thoroughly at 25°C and 150rpm for 60 minutes to obtain a mixture D. After drying, add carbon black in an amount of 10% of the mass ratio of mixture D, and grind and mix in a mortar to obtain a material precursor. The sample is then placed in a quartz tube, and graphite carbon rods are placed at both ends and placed in a reaction box connected to the metal electrode. The reaction conditions are set as follows: voltage of 250V, reaction time of 30ms, and triggering times of 3 times to obtain a bimetallic catalyst FeCu.

[0056] (2) Degradation of organic pollutants: The target pollutant of the degradation reaction is chloramphenicol. In a 50mL glass tube, a bimetallic catalyst and sodium persulfate were added to a chloramphenicol solution with a concentration of 60mg / L, and the initial pH was set to 3 to obtain a reaction system; wherein, the concentration of the bimetallic catalyst in the reaction system was 1g / L, and the concentration of sodium persulfate in the reaction system was 7mmol / L. The glass tube was placed in a constant temperature oscillating box for degradation reaction at a temperature of 25°C and a rotation speed of 150rpm. Part of the solution was taken out at 5, 15, 35, 55 and 75 minutes in the reaction, filtered and mixed with an equal volume of methanol (chromatographic grade), and the chloramphenicol concentration in the solution was determined in a high performance liquid phase and the degradation efficiency was calculated. The degradation effect of the single and bimetallic catalysts prepared by Joule heat technology on chloramphenicol is shown in Figure 2. Figure 2 .

[0057] Figure 1 The results show that Joule heating technology can provide ultra-high temperature instantly, drive the high graphitization of organic matter to obtain excellent carbon carriers, and promote the fusion and dispersion of bimetallic materials; rapid annealing ensures the uniformity of the bimetallic fusion structure and avoids its recombination into a single metal compound during long annealing.

[0058] Figure 2 The results show that the bimetallic catalyst synthesized by Joule heating technology can more effectively degrade chloramphenicol in the solution than the monometallic catalyst. 60.3% of chloramphenicol was degraded within 5 minutes, and almost complete degradation of chloramphenicol (99.2%) was achieved after 55 minutes. Compared with the monometallic catalyst and the composite of iron and other elements, the bimetallic catalyst prepared by iron vanadium has a faster degradation rate and more significant degradation effect.

[0059] Figure 3 The results show that after 75 minutes of reaction, the total iron and total vanadium released in the reaction system of the bimetallic catalyst are 37.7% and 6.7% of the single metal iron catalyst and vanadium catalyst. In addition, the total iron release remains at a stable level after 15 minutes. Therefore, the bimetallic catalyst not only enhances the degradation effect but also reduces the dissolution of metals, reducing the risk of secondary pollution to the environment.

[0060] Example 2

[0061] (1) Material preparation: Mix ferric acetate and vanadium trichloride with sawdust-derived hydrothermal carbon in deionized water and mix thoroughly at 25°C and 150rpm for 60 minutes, wherein the molar ratio of iron to vanadium elements is 1:1, and the ratio to hydrothermal carbon is 2.8mmol / gC. After drying, add carbon black in an amount of 10% by mass of the mixture and grind and mix in a mortar. Then put the sample into a quartz tube, put graphite carbon rods at both ends and place it in a reaction box connected to the electrodes. The reaction conditions are set as follows: voltage of 250V, reaction time of 30ms, and number of reactions of 3 times.

[0062] (2) Degradation of organic pollutants: The target pollutant is chloramphenicol. In a 50 mL glass tube, a bimetallic catalyst with a final concentration of 1 g / L and sodium persulfate with a final concentration of 7 mmol / L were added to a chloramphenicol solution with a concentration of 60 mg / L, and different pH values ​​were set to 3, 5, 7, 9, and 11. The glass tube was placed in a constant temperature oscillating box for degradation reaction at a temperature of 25°C and a rotation speed of 150 rpm. Part of the solution was taken out at 5, 15, 35, 55, and 75 minutes in the reaction, filtered, and mixed with an equal volume of methanol (chromatographic grade). The chloramphenicol concentration in the solution was determined in a high performance liquid phase and the degradation efficiency was calculated. The degradation effect of the bimetallic catalyst on chloramphenicol under different pH conditions is shown in the figure. Figure 4 .

[0063] Figure 4The results show that the bimetallic catalyst has obvious differences in the degradation effect of chloramphenicol under different pH conditions. At pH 3, 5, 7, 9 and 11, after 75 minutes of reaction, the degradation efficiency of chloramphenicol was 99.2%, 62.5%, 58.2%, 54.4% and 20.9%, respectively, indicating that under acidic conditions (pH < 5), the bimetallic catalyst shows a higher degradation efficiency. Alkaline conditions reduce the activation and degradation effects because metal ions react with hydroxide to easily generate precipitation. Therefore, in actual wastewater treatment, the pH of the wastewater can be adjusted to ensure the safety and effectiveness of the bimetallic catalyst during use.

[0064] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a bimetallic catalyst, characterized in that The following steps are involved: (1) mixing the biomass / derived charcoal, iron salt and other metal salts uniformly to obtain a mixture; (2) uniformly mixing the mixture and carbon black to obtain a precursor; (3) treating the precursor obtained in step (2) using Joule heat technology to obtain a bimetallic catalyst; The biomass / derived charcoal refers to at least one of biomass and derived charcoal; The other metal salts are calcium salts, magnesium salts, zinc salts, nickel salts, manganese salts or vanadium salts.

2. The method for preparing a bimetallic catalyst according to claim 1, characterized in that: The biomass is waste biomass; The derived charcoal is charcoal prepared by heating biomass; The iron salt is a soluble iron salt; The other metal salts are soluble metal salts.

3. The method for preparing a bimetallic catalyst according to claim 1, characterized in that: The elements in the iron salt and the metal elements in other metal salts are mixed in a molar ratio of 1:1 to 10; The amount of the biomass / derived carbon is calculated based on the ratio of total metal elements to biomass / derived carbon being 0.1 to 20 mmol / g biomass / derived carbon.

4. The method for preparing a bimetallic catalyst according to claim 1, characterized in that: When the iron salt and the other metal salt in step (1) are soluble salts, the mixing method is to add the iron salt, the other metal salt and the biomass / derived carbon into deionized water and stir; When the mixture in step (2) is an aqueous solution, it is first dried and then mixed with carbon black.

5. The method for preparing a bimetallic catalyst according to claim 1, characterized in that: The amount of carbon black in step (2) is 0 to 20% of the dry weight of the mixture; The mixing method described in step (2) is grinding.

6. The method for preparing a bimetallic catalyst according to claim 1, characterized in that: The treatment environment described in step (3) is an oxygen-free environment; The parameters of the Joule heat technology described in step (3) are: direct current, the voltage is set to 100-380V, the number of direct current triggering is 1-10 times, each reaction time is 10-1000ms, and the current is 5-30A.

7. A bimetallic catalyst, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the bimetallic catalyst according to claim 7 in degrading organic pollutants.

9. The use according to claim 8, characterized in that The method comprises the following steps: adding the bimetallic catalyst and oxidant as claimed in claim 7 into organic pollutants for reaction.

10. The use according to claim 9, characterized in that: The organic pollutants include antibiotics, dyes, pesticides, and veterinary drugs; The oxidant is at least one of hydrogen peroxide and persulfate; The dosage of the bimetallic catalyst is 0.01-2 g / L; The dosage of the oxidant is 1-10 mmol / L.

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