Method for flash-jet joule heat preparation of solid waste-based bifunctional catalyst and application thereof

Abstract

The application discloses a kind of flash evaporation joule heat preparation solid waste-based bifunctional catalyst method and application, comprising the following steps: sewage sludge is mixed with green medium and carried out leaching reaction, and solid-liquid separation is carried out to obtain the sludge matrix after dealkalization;Rare earth tailings are pretreated with green medium and filtered, and composite acid liquid is added to selectively extract copper and manganese;The extract is subjected to solid-liquid separation, and an alkaline solution is added to the liquid phase to precipitate copper and manganese ions, and the obtained precipitate is mixed with the sludge matrix after dealkalization and green medium to obtain a composite precursor;The composite precursor is subjected to flash evaporation joule heat treatment to obtain a solid waste-based bifunctional catalyst;The application uses the sewage sludge after intensified dealkalization as the matrix, and the copper and manganese metals extracted from the rare earth tailings as the additive. The solid waste-based bifunctional catalyst synthesized quickly through flash evaporation joule heat technology can realize the rapid mass production of catalysts and effectively avoid the particle aggregation phenomenon caused by long-term cooling.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically to a method and application for preparing solid waste-based bifunctional catalysts by flash evaporation Joule heating. Background Technology

[0002] Economic development and accelerated industrialization have led to a continuous increase in wastewater generated from residential and industrial production worldwide. Given the diversity of wastewater types and the complexity of their components, the Fenton oxidation process, characterized by strong oxidizing power and non-selectivity, is increasingly being used in industrial wastewater treatment. The Fenton oxidation method utilizes highly oxidizing hydroxyl radicals under acidic conditions to oxidize and remove various recalcitrant organic pollutants from wastewater. However, the resulting wastewater sludge contains a large amount of harmful impurities and is a typical example of large-scale hazardous industrial waste. Currently, there is still a lack of large-scale, high-value utilization pathways for the effective use of this sludge. Wastewater sludge contains abundant resources such as Fe, Al, and Si, possessing the potential to prepare precursors for multifunctional materials.

[0003] Rare earth tailings are the residual solid waste generated during the mining and beneficiation of rare earth ore. After processing such as crushing, grinding, flotation, and magnetic separation, most of the rare earth elements are extracted from the rare earth ore. However, due to the extraction process and the occurrence state of the elements, a very small amount of unextracted rare earth elements and a certain amount of metal elements such as copper and manganese will remain. Copper, manganese, and other metal oxides have high catalytic activity and can be used to prepare catalyst additives after extraction and enrichment to enhance catalytic activity.

[0004] Flash Joule heating technology is based on the Joule heating effect, where heat is generated when an electric current passes through a resistive material. In catalyst preparation, the catalyst precursor is placed in a Joule heating sintering furnace. Electricity is applied, causing the conductive material inside the furnace to heat up rapidly, creating a high-temperature environment. Simultaneously, the solvent in the system evaporates instantaneously, allowing the catalyst precursor to rapidly concentrate, decompose, or undergo a chemical reaction within a short time. This enables rapid catalyst synthesis and significantly shortens the preparation cycle. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method and application for preparing solid waste-based bifunctional catalysts using flash Joule heating. The method uses wastewater sludge after enhanced alkali removal as the matrix and copper and manganese metals extracted from rare earth tailings as additives. The solid waste-based bifunctional catalyst is rapidly synthesized via flash Joule heating technology. This method not only enables rapid mass production of the catalyst, but the rapid heating and cooling process effectively avoids particle aggregation caused by prolonged cooling, promoting the formation of uniform and dense fine particles, increasing the specific surface area and active sites of the catalyst, and enhancing its catalytic activity.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect of the present invention, a method for preparing a solid waste-based bifunctional catalyst by flash Joule heating is provided, comprising the following steps:

[0008] (1) Sludge dealkalization: Sewage sludge is mixed with green media and leached under heating and stirring conditions. After solid-liquid separation, the dealkalized sludge matrix is ​​obtained.

[0009] (2) Metal extraction: The rare earth tailings are pretreated with green media and filtered. A composite acid solution is added to the pretreated rare earth tailings for selective extraction of copper and manganese.

[0010] (3) Component composite: The extract is subjected to solid-liquid separation, and an alkaline solution is added to the liquid phase to precipitate copper and manganese ions. The precipitate is mixed with the dealkalized sludge matrix and green media, and after heating, stirring, filtering and drying, a composite precursor is obtained.

[0011] (4) Heat treatment: The composite precursor is subjected to flash joule heat treatment to obtain a solid waste-based bifunctional catalyst.

[0012] In some embodiments of the present invention, during the sludge dealkalization treatment, the sewage sludge and green medium are mixed at a solid-liquid ratio of 1:1 to 1:3, the stirring rate is 200 to 400 r / min, the leaching temperature during the leaching reaction is 30 to 50°C, and the leaching time is 30 to 50 min.

[0013] In some embodiments of the present invention, the sludge dealkalization process is carried out in a leaching chamber, and an ultrasonic energy field is applied outside the leaching chamber while stirring. The ultrasonic power is 800-2000W, preferably 1300-1700W.

[0014] In some embodiments of the present invention, the green medium used in the sludge dealkalization and metal extraction process is reclaimed water from a wastewater treatment plant or desalinated seawater.

[0015] In some embodiments of the present invention, during metal extraction, a green medium is used to wash the rare earth tailings. The filtered rare earth tailings and the composite acid solution are mixed at a solid-liquid ratio of 1:3 to 1:6. The composite acid solution is prepared by mixing citric acid solution and acetic acid solution at a ratio of 1:1 to 1:2. The concentration of the citric acid solution is 0.5 to 0.7 mol / L, and the concentration of the acetic acid solution is 0.2 to 0.4 mol / L.

[0016] In some embodiments of the present invention, the selective extraction process of copper and manganese is carried out in an elemental extraction chamber. During extraction, a microwave energy field is applied outside the extraction chamber, with a microwave power of 20-35 kW, an extraction time of 20-35 min, and an extraction temperature of 65-85 °C.

[0017] In some embodiments of the present invention, the alkaline solution added during the component compounding process is industrial ammonia water with a concentration of 15% to 23%, and the addition ratio is 10% to 28% of the solution to be reacted.

[0018] Furthermore, the frequency of the heating and stirring process is 300–500 r / min, the time is 30–50 min, and the temperature is 60–90 °C.

[0019] In some embodiments of the present invention, the temperature at which the composite precursor undergoes flash Joule heat treatment during the heat treatment process is 400–550°C.

[0020] In a second aspect of the invention, a solid waste-based bifunctional catalyst is provided, which is prepared using the method described in the first aspect.

[0021] In a second aspect of the invention, an application of a solid waste-based bifunctional catalyst is provided, wherein the solid waste-based bifunctional catalyst described in the second aspect is applied to the fields of VOCs gas adsorption and SCR flue gas denitrification.

[0022] One or more technical solutions of the present invention have the following beneficial effects:

[0023] (1) This invention provides a method for preparing a solid waste-based bifunctional catalyst using flash Joule heating. The alkaline substances in sewage sludge mainly exist in the form of CaSO4. Based on the types and occurrence states of these alkaline substances, a method is proposed to enhance the leaching of alkali metals and alkaline earth metals in the sludge through ultrasonic cavitation in conjunction with a green medium. The impact force and microjets generated by ultrasonic cavitation cause strong impact and vibration on the particles in the solid-liquid two-phase system, intensifying the molecular motion and accelerating the reaction process, thus greatly improving the dealkali removal rate of the sewage sludge. Using reclaimed water or desalinated seawater as a green liquid medium not only reduces environmental pollution and effectively alleviates water shortages but also significantly reduces operating costs.

[0024] (2) This invention employs a microwave oscillation coupled composite acid system for the selective and directional extraction of copper and manganese metals from rare earth tailings. By developing a novel composite acid system, the leaching of copper and manganese metals is achieved while reducing the leaching of impurity metals, thus realizing the selective and directional extraction of copper and manganese metal elements. Internal heating and stirring, along with an external microwave field, accelerate the molecular motion in the reaction system, reduce surface tension, and increase the frequency and intensity of collisions between molecules, significantly improving the leaching rate.

[0025] (3) This invention uses wastewater sludge after enhanced alkali removal as the matrix and copper and manganese metals extracted from rare earth tailings as additives. The resulting solid waste-based bifunctional catalyst is rapidly synthesized via flash Joule heating technology. This not only enables rapid mass production of the catalyst, but the rapid heating and cooling process effectively avoids particle aggregation caused by prolonged cooling, promoting the formation of uniform and dense fine particles, increasing the specific surface area and active sites of the catalyst, and enhancing its catalytic activity. By using wastewater sludge and rare earth tailings—two major solid waste sources—as catalyst raw materials, a bifunctional catalyst suitable for VOCs gas adsorption and SCR flue gas denitrification is prepared, realizing the high-value utilization of solid waste and expanding new avenues for the resource utilization of major solid wastes. Attached Figure Description

[0026] Figure 1 A flowchart of the method for preparing solid waste-based bifunctional catalysts by flash Joule heating according to the present invention;

[0027] Figure 2 The denitrification activity diagram of the solid waste-based bifunctional catalyst prepared in the embodiments of the present invention is shown.

[0028] Figure 3 The image shows the VOCs adsorption capacity of the solid waste-based bifunctional catalyst prepared in the embodiments of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] In a typical embodiment of the present invention, a method for preparing a solid waste-based bifunctional catalyst by flash Joule heating is proposed, such as... Figure 1 As shown, it includes the following steps:

[0031] Step 1: Add high-moisture-content sewage sludge to the leaching chamber, then inject green media into the leaching chamber according to a certain solid-liquid ratio, raise the temperature inside the leaching chamber and continuously stir. After the reaction is complete, perform solid-liquid separation and introduce the dealkalized sludge matrix into the mixing chamber. These steps enhance the leaching and dealkalization of the sludge.

[0032] Specifically, green media uses environmentally friendly liquid media such as reclaimed water from sewage treatment plants or desalinated seawater, which can not only reduce environmental pollution and effectively alleviate water shortage problems, but also greatly reduce operating costs.

[0033] After adding the green medium, the solid-liquid ratio is 1:1 to 1:3, the stirring rate is 200 to 400 r / min, the leaching temperature is 30 to 50℃, and the leaching time is 30 to 50 min. When the solid-liquid ratio is within the range of 1:1 to 1:3, the green medium can be fully mixed with the sludge, and there is sufficient liquid medium to leach alkali metals and alkaline earth metals. A solid-liquid ratio lower than this range will result in insufficient liquid medium during the dealkali leaching process, affecting the dealkali removal efficiency of the sludge. A higher dealkali removal rate ensures that the precursor has excellent pore structure and catalytic activity. A solid-liquid ratio exceeding this range does not significantly improve the dealkali removal efficiency of the sludge and wastes a large amount of water resources. When the stirring rate is 200 to 400 r / min, the solid and liquid phases are uniformly mixed, and the liquid medium can fully react with the sludge. A stirring rate lower than this range will result in uneven mixing of the suspension and a slower reaction rate, affecting the dealkali removal efficiency of the sludge. A stirring rate higher than this range has no significant impact on the dealkali removal efficiency of the sludge and will result in energy waste. The leaching effect of the suspension is optimal when the leaching temperature and leaching time are within the specified range. Below this reaction range, the leaching process cannot be fully reacted due to the low reaction temperature and short time. A large number of alkali metals and alkaline earth metals remain in the sludge, affecting the denitrification activity of the catalyst. When the leaching temperature and leaching time exceed this range, some free iron and manganese ions will enter the liquid phase system due to the long-term high temperature of the suspension, resulting in a decrease in the active components in the catalyst precursor and affecting the denitrification effect of the catalyst.

[0034] Furthermore, in step one, an ultrasonic energy field is applied outside the leaching chamber during stirring. The ultrasonic power is 800–2000 W, preferably 1300–1700 W. Applying an ultrasonic energy field enhances the sludge leaching effect. The impact force and microjets generated by ultrasonic cavitation cause strong impact and vibration on the particles in the solid-liquid two-phase system, intensifying the molecular motion and accelerating the reaction process, thus greatly improving the dealkali removal rate of the wastewater sludge. Experiments have shown that controlling the ultrasonic power within 1300–1700 W yields the best dealkali removal effect. Below this range, the suspension becomes unevenly mixed, the reaction rate is slow, and the dealkali removal effect of the sludge is affected. Above this power range, there is no significant impact on the dealkali removal effect of the sludge, and energy is wasted.

[0035] Step 2: The rare earth tailings in the leaching chamber are repeatedly washed with a green medium to remove impurities and some water-soluble metal elements. After filtration, the rare earth tailings are injected into the element extraction chamber. Subsequently, a composite acid solution is added at a certain solid-liquid ratio to selectively and directionally extract copper and manganese metals. Through the above steps, selective and directional extraction of metals from the tailings is achieved.

[0036] Specifically, the green medium uses environmentally friendly liquid media such as reclaimed water from sewage treatment plants or desalinated seawater. By using reclaimed water or desalinated seawater as the green liquid medium, not only can environmental pollution be reduced and water shortages be effectively alleviated, but operating costs can also be greatly reduced. Through filtration, alkaline components removed during the leaching process can be filtered out, and solid-liquid separation can be achieved.

[0037] Furthermore, by adding a composite acid solution to react with copper and manganese metals, selective and directional extraction of copper and manganese metals is achieved. The solid-liquid ratio after adding the composite acid solution is 1:3 to 1:6. The composite acid solution is prepared by mixing citric acid solution and acetic acid solution in a ratio of 1:1 to 1:2. The concentration of citric acid solution is 0.5 to 1 mol / L, and the concentration of acetic acid solution is 0.2 to 0.4 mol / L.

[0038] Furthermore, during directional extraction, a microwave energy field was applied outside the extraction chamber, with a microwave power of 20–35 kW, an extraction time of 20–35 min, and an extraction temperature of 65–85 °C. Applying a microwave energy field outside the elemental extraction chamber enhanced the extraction effect. Since the extracted metal elements and their occurrence states differed, the experiment showed that microwave leaching was more effective in this location.

[0039] Step 3: Perform solid-liquid separation on the solution after the reaction in Step 2. Add an alkaline solution to the liquid to precipitate free copper and manganese ions. Enrich the precipitate and add it to the mixing chamber to fully mix with the dealkali-treated sludge matrix and green media. Heat the mixture and stir continuously. After the reaction is complete, perform solid-liquid separation, and then dry the precursor. Through the above steps, high-efficiency loading of solid waste additives is achieved.

[0040] Specifically, the added alkaline solution is industrial ammonia water with a concentration of 15% to 23%, and the addition ratio is 10% to 28% of the solution to be reacted. The alkaline solution is used to reduce the free active metal, so that it is uniformly precipitated on the surface of the precursor, thereby improving the catalyst activity and lowering the reaction temperature window.

[0041] Furthermore, the frequency of the heating and stirring process is 300–500 r / min, the time is 30–50 min, and the temperature is 60–90 °C.

[0042] Step 4: The dried precursor is placed in a Joule thermal sintering furnace for rapid heating to obtain a solid waste-based bifunctional catalyst. Rapid heating to 400–550℃ generates active metal oxides such as ferric oxide and copper oxide within this calcination temperature range, exhibiting high catalytic activity. The solid waste-based bifunctional catalyst rapidly synthesized via flash Joule thermal technology not only enables rapid mass production of the catalyst, but the rapid heating and cooling process effectively avoids particle aggregation caused by prolonged cooling, promoting the formation of uniform, dense, fine particles, increasing the specific surface area and active sites of the catalyst, and enhancing its catalytic activity.

[0043] In a typical embodiment of the present invention, a solid waste-based bifunctional catalyst is proposed, which is prepared by the above-described method.

[0044] In a typical embodiment of the present invention, an application of a solid waste-based bifunctional catalyst is proposed, such as the application of the above-mentioned solid waste-based bifunctional catalyst in the fields of VOCs gas adsorption and SCR flue gas denitrification.

[0045] Example 1

[0046] Wastewater sludge with a moisture content of over 95% was added to the leaching chamber, followed by the injection of reclaimed water at a solid-liquid ratio of 1:2. The temperature inside the leaching chamber was raised to 35°C, the stirring speed was set to 200 r / min, and the power of the ultrasonic energy field outside the leaching chamber was set to 1000 W. After leaching for 30 minutes, the suspension was subjected to solid-liquid separation, and the dealkalized sludge matrix was introduced into the mixing chamber for later use. Rare earth tailings in the leaching chamber were repeatedly washed with reclaimed water to remove impurities and some water-soluble metal elements. After filtration, the rare earth tailings were injected into the element extraction chamber, and a composite acid solution was added at a solid-liquid ratio of 1:3, with a citric acid solution and acetic acid solution ratio of 1:1. The power of the external microwave energy field was set to 25 kW, the extraction temperature to 80°C, and solid-liquid separation was performed after a reaction of 30 minutes. 20% industrial ammonia solution was added to the separated liquid to precipitate free copper and manganese ions. The precipitate was enriched and added to a mixing chamber, where it was thoroughly mixed with the dealkali-treated sludge matrix and recycled water. The mixture was heated to 60°C and stirred at 400 rpm for 45 minutes. After filtration, the precursor was dried. The dried precursor was then placed in a Joule heating furnace and rapidly heated to 450°C to obtain solid waste-based bifunctional catalyst 1. The catalyst's performance in SCR flue gas denitrification and VOCs adsorption was tested using a fixed-bed flue gas testing system.

[0047] Example 2

[0048] Wastewater sludge with a moisture content of over 95% was added to the leaching chamber, followed by the injection of reclaimed water at a solid-liquid ratio of 1:1. The temperature inside the leaching chamber was raised to 35°C, the stirring rate was set to 300 r / min, and the power of the ultrasonic energy field outside the leaching chamber was set to 1500 W. After leaching for 40 minutes, the suspension was subjected to solid-liquid separation, and the dealkalized sludge matrix was introduced into the mixing chamber for later use. Rare earth tailings in the leaching chamber were repeatedly washed with reclaimed water to remove impurities and some water-soluble metal elements. After filtration, the rare earth tailings were injected into the element extraction chamber, and a composite acid solution was added at a solid-liquid ratio of 1:5, with the ratio of citric acid solution to acetic acid solution being 1:1. The power of the external microwave energy field was set to 30 kW, the extraction temperature to 80°C, and solid-liquid separation was performed after a reaction of 35 minutes. 20% industrial ammonia solution was added to the separated liquid to precipitate free copper and manganese ions. The precipitate was enriched and added to a mixing chamber, where it was thoroughly mixed with the dealkali-treated sludge matrix and reclaimed water. The mixture was heated to 80°C and stirred at 400 rpm for 30 minutes. After filtration, the precursor was dried. The dried precursor was then placed in a Joule heating furnace and rapidly heated to 500°C to obtain solid waste-based bifunctional catalyst 2. The catalyst's performance in SCR flue gas denitrification and VOCs adsorption was tested using a fixed-bed flue gas testing system.

[0049] Example 3

[0050] Wastewater sludge with a moisture content of over 95% was added to the leaching chamber, followed by the injection of reclaimed water at a solid-liquid ratio of 1:1. The temperature inside the leaching chamber was raised to 50℃, the stirring rate was set to 200 r / min, and the power of the ultrasonic energy field outside the leaching chamber was set to 1700W. After leaching for 40 minutes, the suspension was subjected to solid-liquid separation, and the dealkalized sludge matrix was introduced into the mixing chamber for later use. Rare earth tailings in the leaching chamber were repeatedly washed with reclaimed water to remove impurities and some water-soluble metal elements. After filtration, the rare earth tailings were injected into the element extraction chamber, and a composite acid solution was added at a solid-liquid ratio of 1:3, with the ratio of citric acid solution to acetic acid solution being 1:2. The power of the external microwave energy field was set to 30kW, the extraction temperature to 70℃, and solid-liquid separation was performed after a reaction of 30 minutes. 15% industrial ammonia solution was added to the separated liquid to precipitate free copper and manganese ions. The precipitate was enriched and added to a mixing chamber, where it was thoroughly mixed with the dealkali-treated sludge matrix and recycled water. The mixture was heated to 60°C and stirred at 400 rpm for 45 minutes. After filtration, the precursor was dried. The dried precursor was then placed in a Joule heating furnace and rapidly heated to 550°C to obtain solid waste-based bifunctional catalyst 3. The catalyst's performance in SCR flue gas denitrification and VOCs adsorption was tested using a fixed-bed flue gas testing system.

[0051] Example 4

[0052] Wastewater sludge with a moisture content of over 95% was added to the leaching chamber, followed by the injection of reclaimed water at a solid-liquid ratio of 1:1. The temperature inside the leaching chamber was raised to 40℃, the stirring rate was set to 400 r / min, and the power of the ultrasonic energy field outside the leaching chamber was set to 1700W. After leaching for 40 minutes, the suspension was subjected to solid-liquid separation, and the dealkalized sludge matrix was introduced into the mixing chamber for later use. Rare earth tailings in the leaching chamber were repeatedly washed with reclaimed water to remove impurities and some water-soluble metal elements. After filtration, the rare earth tailings were injected into the element extraction chamber, and a composite acid solution was added at a solid-liquid ratio of 1:6, with the ratio of citric acid solution to acetic acid solution being 1:2. The power of the external microwave energy field was set to 35kW, the extraction temperature to 80℃, and solid-liquid separation was performed after a reaction of 35 minutes. 23% industrial ammonia solution was added to the separated liquid to precipitate free copper and manganese ions. The precipitate was enriched and added to a mixing chamber, where it was thoroughly mixed with the dealkali-treated sludge matrix and recycled water. The mixture was heated to 90°C and stirred at 500 rpm for 50 minutes. After filtration, the precursor was dried. The dried precursor was then placed in a Joule heating furnace and rapidly heated to 550°C to obtain solid waste-based bifunctional catalyst 4. The catalyst's performance in SCR flue gas denitrification and VOCs adsorption was tested using a fixed-bed flue gas testing system.

[0053] Comparative Example 1

[0054] The difference from Example 1 is that Example 1 involved ultrasonic treatment during the sludge dealkali removal process, while Comparative Example 1 did not involve ultrasonic treatment during the sludge dealkali removal process, resulting in a solid waste-based bifunctional catalyst 5. The catalyst's performance in SCR flue gas denitrification and VOCs adsorption was tested using a fixed-bed flue gas testing system.

[0055] Comparative Example 2

[0056] The difference between Example 2 and Comparative Example 2 is that, in the metal extraction process, Example 2 uses a composite acid for metal extraction, while Comparative Example 2 only uses citric acid solution for extraction, resulting in solid waste-based bifunctional catalyst 6. The catalyst's performance in SCR flue gas denitrification and VOCs adsorption was tested using a fixed-bed flue gas testing system.

[0057] Comparative Example 3

[0058] The difference between Example 3 and Comparative Example 3 is that, in the metal extraction process, Example 3 used an external microwave energy field to heat to the extraction temperature, while Comparative Example 3 used a water bath to heat to the extraction temperature of 70°C, resulting in a solid waste-based bifunctional catalyst 7. The catalyst's performance in SCR flue gas denitrification and VOCs adsorption was tested using a fixed-bed flue gas testing system.

[0059] Comparative Example 4

[0060] The difference between Example 4 and Comparative Example 4 is that the composite acid used in Example 4 is a mixture of citric acid solution and acetic acid solution, while Comparative Example 4 uses a mixture of aminosulfonic acid solution and acetic acid solution, with the same mixing ratio. Comparative Example 4 yielded a solid waste-based bifunctional catalyst 8. The catalyst's performance in SCR flue gas denitrification and VOCs adsorption was tested using a fixed-bed flue gas testing system.

[0061] The SCR flue gas denitrification and VOCs adsorption performance of the solid waste-based bifunctional catalysts prepared in Examples 1-4 and Comparative Examples 1-4 were tested, and the results are as follows: Figure 2 and Figure 3 As shown, the denitrification activity of catalyst 1 obtained in Example 1 reaches 100% at 319℃, and the VOCs gas adsorption performance is 284.97%; the denitrification activity of catalyst 2 obtained in Example 2 reaches 100% at 302℃, and the VOCs gas adsorption performance is 328.57%; the denitrification activity of catalyst 3 obtained in Example 3 reaches 100% at 309℃, and the VOCs gas adsorption performance is 296.27%; the denitrification activity of catalyst 4 obtained in Example 4 reaches 100% at 291℃, and the VOCs gas adsorption performance is 334.85%; comparatively... The denitrification activity of catalyst 5 obtained in Example 1 was the highest at 338℃, reaching only 85.63%, with a VOCs gas adsorption capacity of 174.34%. The denitrification activity of catalyst 6 obtained in Comparative Example 2 reached 100% at 307℃, with a VOCs gas adsorption capacity of 248.87%. The denitrification activity of catalyst 7 obtained in Comparative Example 3 reached 100% at 341℃, with a VOCs gas adsorption capacity of 213.55%. The denitrification activity of catalyst 8 obtained in Comparative Example 4 reached 100% at 328℃, with a VOCs gas adsorption capacity of 244.57%.

[0062] Comparative analysis of Example 1 with Comparative Example 1, Example 2 with Comparative Example 2, Example 3 with Comparative Example 3, and Example 4 with Comparative Example 4 shows that the ultrasonic treatment during sludge dealkalization, the use of a composite solution of citric acid and acetic acid for metal selection during metal extraction, and the use of microwave energy field heating to the extraction temperature during metal extraction all effectively improve the catalytic performance and gas adsorption performance of the catalyst. Furthermore, comparative analysis of the solid waste-based bifunctional catalysts prepared in Examples 1-4 and Comparative Examples 1-4 with the original catalyst (referring to wastewater sludge that has only undergone drying treatment) shows that the method provided by this invention can significantly improve catalyst activity, reduce catalyst reaction temperature, and increase catalyst adsorption capacity by more than 10 times.

[0063] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a solid waste-based bifunctional catalyst by flash evaporation Joule heating, characterized in that, Includes the following steps: (1) Sludge dealkalization: Sewage sludge is mixed with green media and leached under heating and stirring conditions. The sludge matrix after dealkalization is obtained by solid-liquid separation. The sludge dealkalization process is carried out in the leaching chamber. An ultrasonic energy field is applied outside the leaching chamber while stirring. The ultrasonic power is 800~2000 W. (2) Metal extraction: The rare earth tailings were pretreated with green media and filtered. A composite acid solution was added to the pretreated rare earth tailings for selective extraction of copper and manganese. The selective extraction of copper and manganese was carried out in the element extraction chamber. At the same time as extraction, a microwave energy field was applied outside the extraction chamber. The microwave power was 20~35 kW, the extraction time was 20~35 min, and the extraction temperature was 65~85 ℃. The rare earth tailings were washed with green media. The filtered rare earth tailings and the composite acid solution were mixed at a solid-liquid ratio of 1:3~1:

6. The composite acid solution was prepared by mixing citric acid solution and acetic acid solution at a ratio of 1:1~1:

2. The concentration of citric acid solution was 0.5~0.7 mol / L, and the concentration of acetic acid solution was 0.2~0.4 mol / L. (3) Component composite: The extract is subjected to solid-liquid separation, and an alkaline solution is added to the liquid phase to precipitate copper and manganese ions. The precipitate is mixed with the dealkalized sludge matrix and green medium, and after heating, stirring, filtering and drying, a composite precursor is obtained. (4) Heat treatment: The composite precursor is subjected to flash joule heat treatment to obtain a solid waste-based bifunctional catalyst; The temperature for flash Joule heat treatment of the composite precursor is 400~550℃; The green media used in sludge dealkalization and metal extraction processes are reclaimed water from wastewater treatment plants or desalinated seawater.

2. The method for preparing solid waste-based bifunctional catalysts by flash evaporation Joule heating as described in claim 1, characterized in that, During the sludge dealkali treatment, the sewage sludge and green media are mixed at a solid-liquid ratio of 1:1 to 1:3, the stirring speed is 200 to 400 r / min, the leaching temperature is 30 to 50 ℃, and the leaching time is 30 to 50 min.

3. The method for preparing solid waste-based bifunctional catalysts by flash evaporation Joule heating as described in claim 1, characterized in that, The ultrasonic power is 1300~1700 W.

4. The method for preparing solid waste-based bifunctional catalysts by flash evaporation Joule heating as described in claim 1, characterized in that, The alkaline solution added during the component compounding process is industrial ammonia water with a concentration of 15% to 23%, and the addition ratio is 10% to 28% of the liquid phase. The frequency of the heating and stirring process is 300~500 r / min, the time is 30~50 min, and the temperature is 60~90℃.

5. A solid waste-based bifunctional catalyst, characterized in that, It is prepared by the method described in any one of claims 1-4.

6. An application of a solid waste-based bifunctional catalyst, characterized in that, The solid waste-based bifunctional catalyst as described in claim 5 is applied to the fields of VOCs gas adsorption and SCR flue gas denitrification.

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