A method for preparing aluminum vanadate using spent SCR denitrification catalyst, aluminum vanadate and its applications

Abstract

This invention discloses a method for preparing aluminum vanadate using waste SCR denitrification catalyst, comprising the following steps: (1) leaching the waste SCR denitrification catalyst with sulfuric acid and ammonium sulfite, filtering to obtain acid leaching solution and acid leaching residue; (2) oxidizing the acid leaching solution obtained in step (1) by passing ozone through it to obtain a precursor suspension; (3) subjecting the precursor suspension obtained in step (2) to a hydrothermal reaction, collecting the precipitate, filtering, washing, and drying to obtain aluminum vanadate. This invention also provides aluminum vanadate and its applications. The method for preparing aluminum vanadate using waste SCR denitrification catalyst of this invention comprehensively and efficiently utilizes vanadium and aluminum elements in the waste SCR denitrification catalyst. Without element separation, aluminum vanadate products are directly synthesized in solution and can be used as an adsorbent to adsorb uranium. This invention comprehensively utilizes both elements, greatly reducing waste liquid generation and shortening the process flow.

Description

Technical Field

[0001] This invention belongs to the field of solid waste recycling, and particularly relates to a method for recycling waste SCR denitrification catalyst, as well as the recycled products and their applications. Background Technology

[0002] NO x NO is a common air pollutant that can cause various problems, including environmental pollution and human diseases. Selective catalytic reduction (SCR) is currently the most effective method for treating NO. x The most effective method is recycling, but when the catalyst is deactivated and cannot be regenerated, it needs to be recycled. Waste SCR denitrification catalysts contain various valuable metals such as vanadium and tungsten, and their output is huge, with the annual output of waste catalysts expected to remain at around 143,300 tons after 2025.

[0003] Currently, the main methods for recovering spent SCR denitrification catalysts are divided into two categories: wet methods and pyrometallurgical methods. Wet recovery mainly includes reducing acid leaching and pressurized alkaline leaching, while pyrometallurgical recovery mainly employs Na2CO3 roasting and composite roasting methods. Because V... 4+ The solubility is greater than V 5+ Therefore, in hydrometallurgical processes, reducing acid leaching is commonly used to improve the leaching rate of vanadium. Existing hydrometallurgical processes yield vanadium leachates that also contain aluminum and vanadium. Most current technologies remove aluminum as an impurity before efficiently recovering vanadium, resulting in complex processes and inefficient utilization of aluminum.

[0004] Aluminum vanadate is an adsorbent for uranium adsorption, and its direct preparation from the aforementioned vanadium leaching solution is of great significance. Furthermore, the vanadium in the vanadium leaching solution obtained in existing technologies is V... 4+ In its existing form, to ensure the formation of aluminum vanadate, it needs to be oxidized to V. 5+ The vanadate form is generated. Currently, commonly used oxidants mainly include liquid oxidants such as hydrogen peroxide and perchloric acid. For example, patent application CN104195342A discloses a method for recovering vanadium pentoxide from waste SCR denitrification catalysts. First, in an acidic solution, a reducing agent is used to reduce the pentavalent vanadium in the catalyst to the more soluble tetravalent vanadium. Then, perchloric acid is used as an oxidant to oxidize the tetravalent vanadium back to pentavalent vanadium. Patent application CN104384167A discloses a comprehensive recovery method for waste titanium-based vanadium-based SCR catalysts, using hydrogen peroxide as an oxidant to oxidize the low-valent vanadium solution, followed by extraction to separate vanadium and aluminum. While liquid oxidants such as hydrogen peroxide used in existing technologies are good oxidants for oxidizing low-valent vanadium, the addition of hydrogen peroxide leads to a significant dilution of the solution concentration, especially when the vanadium concentration in the leachate is already low, which is detrimental to subsequent recovery.

[0005] Therefore, a highly efficient and comprehensive method for recovering aluminum and vanadium from vanadium leaching solutions and preparing aluminum vanadate has broad market application prospects. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the shortcomings and defects mentioned in the background art above, and to provide a method for preparing aluminum vanadate using waste SCR denitrification catalyst that enables simultaneous and efficient recovery of aluminum and vanadium, as well as aluminum vanadate and its applications. To solve the above technical problem, the technical solution proposed by this invention is as follows:

[0007] A method for preparing aluminum vanadate using spent SCR denitration catalyst includes the following steps:

[0008] (1) Use sulfuric acid and ammonium sulfite to leach the waste SCR denitrification catalyst, and filter to obtain acid leaching solution and acid leaching residue;

[0009] (2) The acid leaching solution obtained in step (1) is oxidized by passing ozone through it to obtain a precursor suspension (yellow);

[0010] (3) The precursor suspension obtained in step (2) is placed in a Teflon reactor for hydrothermal reaction, the precipitate (green) is collected, filtered, washed (washed with deionized water and ethanol), and dried to obtain aluminum vanadate.

[0011] In the above-mentioned method for preparing aluminum vanadate using waste SCR denitrification catalyst, preferably, before oxidizing the acid leaching solution with ozone, ammonium hydroxide is added to adjust the pH of the solution to 2.8-3.2. This invention adjusts the pH before oxidation, which effectively reduces the rapid formation of ammonium vanadate precipitate during the subsequent pH adjustment process (if ozone is introduced first for oxidation, the pH value for pentavalent vanadium precipitation is 1.3-6.94, and ammonium vanadate precipitate will be generated during the subsequent pH adjustment, reducing the purity of the aluminum vanadate product). By adjusting the pH first and then controlling the subsequent oxidation process, the oxidation has a certain rate. The newly generated pentavalent vanadium, after stirring and the action of surfactants, is less likely to form ammonium vanadate precipitate, thus reducing the amount of ammonium vanadate precipitate and improving the purity of the final product, aluminum vanadate. Furthermore, our research shows that the quality of aluminum vanadate prepared at a pH of 2.8-3.2 is superior to that prepared at lower pH values. If the pH is too high, tetravalent vanadium will form VO(OH)2 precipitate, affecting the purity of the aluminum vanadate product.

[0012] In the above method for preparing aluminum vanadate using waste SCR denitrification catalyst, preferably, acid is added to the acid leaching solution obtained in step (1), and then waste SCR denitrification catalyst and ammonium sulfite are added to it for cyclic leaching. After multiple cyclic leachings, a high-concentration low-valence vanadium solution is obtained, and this high-concentration low-valence vanadium solution is used to replace the acid leaching solution in step (2). Addressing the problem that the vanadium content in the leaching solution of existing waste SCR denitrification catalyst treatment processes is low, thus affecting subsequent precipitation steps, this invention uses cyclic leaching to enrich vanadium, avoiding the problem of insufficient vanadium concentration in the solution leading to precipitation and the generation of large amounts of wastewater. Specifically, to increase the vanadium content in the acid leaching solution, an appropriate amount of concentrated sulfuric acid is added to the acid leaching solution, and then the same amount of waste SCR denitrification catalyst powder and ammonium sulfite as in step (1) are added for multiple cyclic leachings, such as 5 cyclic leachings, thereby enriching vanadium. After filtration, a high-concentration low-valence vanadium solution is obtained.

[0013] In the above method for preparing aluminum vanadate using spent SCR denitration catalyst, preferably, the concentration of sulfuric acid is 1.5-2 mol / L, the mass ratio of the spent SCR denitration catalyst to the volume of sulfuric acid is 1 g: 6-8 mL, and the mass ratio of the spent SCR denitration catalyst to ammonium sulfite is 1:(0.01-0.02). If the sulfuric acid concentration is too high or the amount used is too large, the vanadium leaching rate will not increase significantly, and the solution acidity will increase, requiring more reagent to adjust the solution pH. If the sulfuric acid concentration is too low or the amount used is too small, the vanadium leaching will be incomplete, and the leaching rate will decrease. Adding too much ammonium sulfite wastes reagent after the pentavalent vanadium has been completely reduced to tetravalent vanadium; adding too little will result in incomplete reduction of pentavalent vanadium.

[0014] In the above method for preparing aluminum vanadate from spent SCR denitration catalyst, preferably, the leaching of the spent SCR denitration catalyst using sulfuric acid and ammonium sulfite is carried out in a water bath at 80-90℃ for 1.5-2 hours. If the leaching temperature is too high, energy consumption is high, and the leaching rate is not significantly improved; if the temperature is too low, the mass transfer rate is slow, the leaching rate decreases, the reaction time is long, and energy is wasted. If the leaching time is too long, the leaching rate will not be significantly improved, wasting energy; if the time is too short, the leaching reaction is incomplete, and the leaching rate is low.

[0015] In the above method for preparing aluminum vanadate using spent SCR denitrification catalyst, preferably, the ozone gas flow rate is controlled at 10-20 mL / min, and the oxidation time is controlled at 20-30 min. If the ozone flow rate is too high, the gas-solid reaction contact area is limited, some ozone escapes, and the oxidation rate does not increase significantly. If the flow rate is too low, the oxidation rate is too slow, increasing the oxidation time and reaction energy consumption. If the ozone oxidation time is too long, the oxidation reaction ends, increasing reaction energy consumption; if the reaction time is too short, tetravalent vanadium is not completely oxidized, resulting in vanadium waste and low purity of the produced aluminum vanadate.

[0016] In the above method for preparing aluminum vanadate using waste SCR denitrification catalyst, preferably, polyvinylpyrrolidone (PVP) is added to the acid leaching solution at a liquid-to-solid ratio of 1 mL: 20-40 mg during ozone oxidation, while vigorous stirring is performed. The pentavalent metavanadate ions generated by ozone oxidation are prone to precipitate into ammonium vanadate precipitate under this pH environment, affecting product purity. This invention, by adding PVP and vigorous stirring during the oxidation process, avoids pentavalent vanadate precipitation and allows metavanadate and aluminum ions to initially combine.

[0017] In the above method for preparing aluminum vanadate using waste SCR denitration catalyst, preferably, the hydrothermal reaction is carried out at 160-180℃ for 6-8 hours. If the hydrothermal reaction temperature is too high or too low, or the holding time is too long or too short, the quality of the synthesized aluminum vanadate product will decrease.

[0018] In the above method for preparing aluminum vanadate using waste SCR denitration catalyst, preferably, the drying is carried out under vacuum conditions and kept at 80-90°C for 10-12 hours.

[0019] The acid leaching residue obtained by the method of preparing aluminum vanadate using waste SCR denitration catalyst of this invention can also be treated to recover tungsten to obtain ammonium paratungstate, specifically including the following steps:

[0020] (1) The acid leaching residue was leached with a mixed solution of sodium sulfide and sodium hydroxide, and WO4 was obtained after solid-liquid separation. 2- / WO x S 4-x 2- Solution and titanium-rich slag;

[0021] (2) Add the WO4 obtained in step (1) 2- / WO x S 4-x 2- A mixture of sulfide and alkali is added to the solution, followed by the addition of acid leaching residue for repeated leaching cycles (e.g., 5 times) to obtain high-concentration WO4. 2- / WO x S 4-x 2- Solution;

[0022] (3) Add the high concentration WO4 obtained in step (2) 2- / WO x S 4-x 2- Ozone is introduced into the solution for oxidation treatment to obtain WO4. 2- Solution;

[0023] (4) The WO4 obtained in step (3) 2-The solution was subjected to silica precipitation treatment, and an excess calcium source was added for precipitation treatment to obtain calcium tungstate solid;

[0024] (5) Add concentrated ammonia to the calcium tungstate solid obtained in step (4) and react. After filtration, obtain ammonium tungstate solution, then evaporate and concentrate, and cool and crystallize to obtain ammonium paratungstate. In order to improve the purity of the ammonium paratungstate product and remove impurities, the ammonium paratungstate can be recrystallized through multiple steps (5) to continuously improve the purity of the ammonium paratungstate product.

[0025] In the above-mentioned acid leaching residue treatment process, the mixed solution of sodium sulfide and sodium hydroxide is obtained by adding sodium hydroxide to a sodium sulfide solution. The concentration of the sodium sulfide solution is 1.5-2 mol / L, the mass ratio of the acid leaching residue to the volume of the sodium sulfide solution is 1 g: 6-7 mL, and the mass ratio of the acid leaching residue to the sodium hydroxide is (2-3): 1. Excessive concentration of sodium sulfide and its ratio with alkali do not significantly improve the leaching rate of tungsten; instead, they may increase the leaching rate of impurities. Conversely, excessively low concentrations of sodium sulfide and its ratio with alkali will decrease the leaching rate of tungsten. This invention demonstrates that controlling the sodium sulfide concentration and its ratio with alkali within the specified range can balance the leaching rates of tungsten and impurities.

[0026] In the above-mentioned acid leaching residue treatment process, when leaching the residue with a mixed solution of sodium sulfide and sodium hydroxide, the water bath temperature is controlled at 80-90℃, and the leaching time is 2.5-3 hours. If the leaching temperature is too low, the molecular thermal motion slows down, the mass transfer rate decreases, the reaction rate slows down, the reaction time is prolonged, and the reaction energy consumption increases. If the reaction temperature is too high, the reaction energy consumption increases, and there is no significant change in the improvement of tungsten leaching rate. The leaching process requires a certain reaction time. If the time is too short, the leaching rate is still in the rapid growth stage, and the leaching is incomplete. If the time is too long, the leaching rate will not increase significantly, increasing energy consumption.

[0027] In the above-mentioned treatment process for acid leaching residue, when ozone is introduced for oxidation, the ozone gas flow rate is 10-20 mL / min, and the ozone introduction time is 20-30 min. If the ozone flow rate is too low, the oxidant supply rate is too slow, reducing the reaction rate; if the ozone concentration is too high, the gas-solid reaction contact area is limited, the oxidation reaction rate is not significantly improved, and some ozone is wasted. If the ozone introduction time is too short, the reaction is incomplete, and the thiotungstate is not completely oxidized to tungstate, and the unoxidized thiotungstate precipitates along with the silicon. If the introduction time is too long, the thiotungstate is completely oxidized, and excess ozone is wasted.

[0028] In the above-mentioned acid leaching residue treatment process, during silicon precipitation, hydrochloric acid is used to adjust the solution pH to 8-9, and the reaction is carried out in a water bath at 80-90℃ for 1.5-2 hours. If the pH is too low or too high, silicon cannot precipitate in the form of silicic acid; if the precipitation temperature is too low, the precipitation reaction rate slows down, increasing the reaction time; if the temperature is too high, the reaction energy consumption increases, and the precipitation rate will not increase significantly. If the precipitation time is too short, the silicon in the leachate will not precipitate completely, affecting the purity of the subsequent ammonium paratungstate product; if the time is too long, the silicon precipitation rate will not increase significantly, increasing the reaction energy consumption.

[0029] In the above-mentioned acid leaching residue treatment process, when adding an excess calcium source for precipitation treatment, an excess calcium chloride is added to the silica-precipitated liquid at 80-90℃ and reacted for 3-4 hours.

[0030] In the above-mentioned treatment process for acid leaching residue, concentrated ammonia is added and reacted at 80-90℃ for 1.5-2 hours. The mass fraction of the concentrated ammonia is 25-30%, and the mass ratio of the calcium tungstate solid to the volume of the concentrated ammonia is 1g:1.3-1.5mL. Evaporation and concentration are carried out at 80-90℃, and the residue is then cooled and crystallized at room temperature for 1-2 days to obtain ammonium paratungstate. If the reaction temperature is too high, the reaction rate does not increase significantly and the energy consumption increases; if the temperature is too low, the reaction rate is too slow and the reaction time increases. Adding too much concentrated ammonia does not significantly increase the reaction rate; adding too little concentrated ammonia slows down the reaction rate, increases the reaction time, leads to incomplete reaction, and results in incomplete dissolution of calcium tungstate, causing tungsten loss.

[0031] In the above-mentioned acid leaching residue treatment process, in order to improve WO4 2- / WO x S 4-x 2- The content of tungsten in the solution, this invention introduces Na2WO4 / Na2WO4 x S 4-x A certain amount of sodium sulfide solution and sodium hydroxide solid are added to the solution, and then acid leaching residue powder is added for cyclic leaching to enrich tungsten. After filtration, a high concentration of Na₂WO₄ / Na₂WO₄ is obtained. x S 4-x Solution. The method for recovering tungsten from acid leaching residue of the present invention uses a circulating leaching method to increase the concentration of tungsten in the leachate. Addressing the problem of low tungsten content in the leachate of existing waste SCR denitrification catalyst treatment processes, which affects subsequent precipitation steps, the present invention uses a circulating leaching method to enrich tungsten, avoiding the problem of insufficient tungsten concentration in the solution leading to precipitation and the generation of large amounts of wastewater.

[0032] In the above-mentioned acid leaching residue treatment process, sodium sulfide + sodium hydroxide is used to leach the acid leaching residue, yielding sodium thiotungstate, which is a series of substances including sodium monothiotungstate, sodium dithiotungstate, sodium trithiotungstate, tungsten sulfide, and sodium tungstate. Therefore, the tungsten leaching rate is significantly higher than that of sodium tungstate, which is only produced when leaching with sodium hydroxide. Furthermore, sodium sulfide, as a leaching agent, has weak alkalinity and poor binding ability with silicon. Compared to traditional leaching agents such as sodium hydroxide, the impurity leaching rate is lower (using traditional leaching agents such as sodium hydroxide, which are more alkaline, the silicon leaching rate can reach 34.2%, while the tungsten leaching rate is relatively low. Under the same conditions, using sodium sulfide + sodium hydroxide as the leaching agent, the silicon leaching rate is 16.2%, and the tungsten leaching rate is increased by about 20%). Considering the WO4 in the leaching solution... 2- / WO x S 4-x 2- The solution contains some thiotungstate ions, which are not conducive to the subsequent tungsten extraction steps. This invention further uses ozone as an oxidant to convert it into sodium tungstate, which is beneficial for the subsequent precipitation and recovery of tungsten.

[0033] In the aforementioned acid leaching residue treatment process, a fully wet process is employed to efficiently recover tungsten. Since tungsten exhibits both sulfide and oxy-affinity, this invention uses sodium sulfide coupled with sodium hydroxide as the leaching agent. Using sodium sulfide not only reduces the alkali consumption of alkaline leaching but also achieves higher leaching efficiency, realizing the efficient utilization of tungsten in the acid leaching residue. Compared to the traditional method using sodium hydroxide, which suffers from high alkali consumption and high impurity leaching rate, the method of this invention achieves a higher leaching rate, lower alkali consumption, and lower impurity leaching rate, thus realizing highly efficient leaching of the acid leaching residue.

[0034] In the above-mentioned acid leaching residue treatment process, ozone oxidation is used to maintain the solution concentration. Since the presence of thiotungstate ions in the solution is detrimental to subsequent tungsten extraction steps, this invention utilizes ozone to convert thiotungstate ions to tungstate ions. This conversion is achieved without reducing the tungsten element concentration, which is beneficial for subsequent precipitation and recovery, and avoids the use of hydrogen peroxide or potassium chlorate oxidants to reduce the solution concentration or introduce new impurities. Furthermore, given that this invention uses sodium sulfide as the leaching agent, the high binding energy between tungsten and sulfur allows for ozone oxidation to convert it to sodium tungstate before subsequent impurity removal processes, thus improving the tungsten recovery rate.

[0035] As a general technical concept, the present invention also provides an aluminum vanadate prepared by the above-mentioned method for preparing aluminum vanadate using waste SCR denitrification catalyst, wherein the aluminum vanadate has a sea urchin-like microstructure.

[0036] As a general technical concept, the present invention also provides an application of the above-mentioned aluminum vanadate as a uranium adsorbent.

[0037] This invention targets spent SCR denitrification catalysts, employing a fully wet treatment process to simultaneously recover aluminum and vanadium. Through exploratory research and repeated experimental verification, this invention first uses ammonium sulfite as a reducing agent, utilizing sulfuric acid to leach tetravalent vanadium, achieving highly efficient vanadium leaching. A cyclic leaching method is used to increase the concentration of vanadium ions in the solution. Then, ammonium hydroxide is used to adjust the solution pH to 2.8-3.2. Next, ozone is used as an oxidant, achieving the oxidation of low-valent vanadium while maintaining the vanadium ion concentration in the solution. Finally, through the action of surfactant PVP, a hydrothermal reaction is used to comprehensively utilize pentavalent metavanadate and aluminum ions to prepare aluminum vanadate, achieving multi-component comprehensive utilization of spent SCR denitrification catalysts.

[0038] Compared with the prior art, the advantages of the present invention are as follows:

[0039] 1. The present invention uses ammonium sulfite as a reducing agent to prepare aluminum vanadate from waste SCR denitrification catalyst. It utilizes sulfuric acid to reduce and leach tetravalent vanadium, achieving efficient leaching of vanadium without introducing other impurity ions, and the ammonium ions are easily removed.

[0040] 2. This invention utilizes waste SCR denitrification catalyst to prepare aluminum vanadate, employing ozone instead of liquid oxidants such as hydrogen peroxide. Ozone oxidation avoids a decrease in solution concentration. For the preparation of aluminum vanadate, low-valent vanadium needs to be oxidized to pentavalent metavanadate ions, followed by a hydrothermal reaction to prepare aluminum vanadate. Compared to existing methods using hydrogen peroxide oxidation, using ozone as the oxidant avoids vanadium dilution during oxidation and does not introduce new impurities, achieving a highly efficient precipitation reaction of vanadium and aluminum.

[0041] 3. The method of preparing aluminum vanadate from waste SCR denitrification catalyst of the present invention comprehensively and efficiently utilizes vanadium and aluminum elements in waste SCR denitrification catalyst. Without element separation, aluminum vanadate product is synthesized directly in solution. It can be used as an adsorbent to adsorb uranium. Compared with the traditional method of extracting vanadium to prepare ammonium vanadate and removing aluminum as an impurity, the present invention comprehensively utilizes the two elements, greatly reduces the generation of waste liquid, and has a short process flow. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a process flow diagram of the method for preparing aluminum vanadate using waste SCR denitrification catalyst according to the present invention.

[0044] Figure 2 This is a process flow diagram of the method for preparing aluminum vanadate and ammonium paratungstate using waste SCR denitrification catalyst in Example 3. Detailed Implementation

[0045] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0046] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0047] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0048] The main components of the waste SCR denitrification catalyst to be treated in the following examples and comparative examples are V: 0.63%, Al: 9.65%, Ti: 17.3%, W: 1.55%, Mg: 4.31%, Fe: 0.26%, and Si: 28.15%.

[0049] Example 1:

[0050] like Figure 1 As shown, a method for preparing aluminum vanadate using spent SCR denitrification catalyst includes the following steps:

[0051] (1) After drying and crushing the waste SCR denitrification catalyst, it is screened with an 80-mesh standard sieve to ensure that the particle size is controlled below 178μm.

[0052] (2) Take 4g of the sieved material and place it in a beaker. According to the ratio of the mass of the waste SCR denitrification catalyst to the volume of sulfuric acid of 1g:8mL, add sulfuric acid solution with a concentration of 1.5mol / L. After mixing, place it in a water bath at 90℃ and add 0.05g of (NH4)2SO3. After reacting for 2h, separate the solid and liquid to obtain low-concentration low-valence vanadium solution (the leaching residue is washed with water and the washing liquid is returned to the low-concentration low-valence vanadium solution) and acid leaching residue. Under the reaction conditions, the vanadium leaching rate is 89.58% and the vanadium concentration in the solution is 538mg / L.

[0053] (3) Add an appropriate amount of concentrated sulfuric acid to the low-concentration, low-valence vanadium solution, and then add the same waste SCR denitrification catalyst and ammonium sulfite as in step (2) and leach under the same conditions. After five cycles of leaching, a high-concentration, low-valence vanadium leachate is obtained, the vanadium leaching rate is reduced to 84.5%, and the concentration of vanadium in the solution increases to 2301 mg / L.

[0054] (4) After adding NH4OH to the above high-concentration low-valence vanadium solution to adjust the pH value of the solution to 3, take 100 mL of high-concentration low-valence vanadium leaching solution, introduce ozone at a flow rate of 10 mL / min into it to oxidize the vanadium element, and at the same time add 3 g of PVP as a surfactant into the leaching solution, stir vigorously (stirring rate of 1000 rpm), and after reacting for 30 min, a yellow precursor suspension is obtained.

[0055] (5) The yellow precursor suspension was placed in a Teflon reactor for hydrothermal reaction. After being kept at 160°C for 6 hours, the green precipitate was obtained by filtration. The precipitation rate of vanadium reached 95%. After washing with deionized water and ethanol, the precipitate was placed in a vacuum drying oven and kept at 80°C for 12 hours to obtain the final product, aluminum vanadate HAVO. The purity of the prepared aluminum vanadate product reached 98%.

[0056] The aluminum vanadate product prepared in this embodiment has a porous, urchin-like microstructure, which can be used as a uranium adsorbent. The relatively complete three-dimensional microstructure can provide more space to store uranium ions and has more adsorption site regions, thus exhibiting superior adsorption performance.

[0057] Example 2:

[0058] A method for preparing aluminum vanadate using spent SCR denitration catalyst includes the following steps:

[0059] (1) After drying and crushing the waste SCR denitrification catalyst, it is screened with an 80-mesh standard sieve to ensure that the particle size is controlled below 178μm.

[0060] (2) Take 4g of the sieved material and place it in a beaker. According to the ratio of the mass of the waste SCR denitrification catalyst to the volume of sulfuric acid of 1g:6mL, add sulfuric acid solution with a concentration of 2mol / L. After mixing, place it in a water bath at 90℃ and add 0.06g of (NH4)2SO3. After reacting for 1.5h, separate the solid and liquid to obtain a low-concentration low-valence vanadium solution. Under the reaction conditions, the vanadium leaching rate is 90.32% and the vanadium concentration in the solution is 546mg / L.

[0061] (3) Add an appropriate amount of concentrated sulfuric acid to the low-concentration, low-valence vanadium solution, and then add the same waste SCR denitrification catalyst and ammonium sulfite as in step (2) and leach under the same conditions. After five cycles of leaching, a high-concentration, high-valence vanadium leachate is obtained, the vanadium leaching rate is reduced to 85.6%, and the concentration of vanadium in the solution increases to 2339 mg / L.

[0062] (4) After adding NH4OH to the above high-concentration low-valence vanadium solution to adjust the pH value of the solution to 2.8, take 100 mL of high-concentration low-valence vanadium leaching solution, introduce ozone at a flow rate of 10 mL / min into it to oxidize the vanadium element, and at the same time take 3 g of PVP as a surfactant and add it to the leaching solution. After stirring vigorously for 30 min, a yellow precursor suspension is obtained.

[0063] (5) The yellow precursor suspension was placed in a Teflon reactor for hydrothermal reaction. After being kept at 160°C for 6 hours, the green precipitate was obtained by filtration. The precipitation rate of vanadium reached 95%. After washing with deionized water and ethanol, the precipitate was placed in a vacuum drying oven and kept at 80°C for 12 hours to obtain the final product, aluminum vanadate HAVO. The purity of the prepared aluminum vanadate product reached 98%.

[0064] Comparative Example 1:

[0065] A method for preparing aluminum vanadate using spent SCR denitration catalyst includes the following steps:

[0066] (1) After drying and crushing the waste SCR denitrification catalyst, it is screened with an 80-mesh standard sieve to ensure that the particle size is controlled below 178μm.

[0067] (2) Take 4g of the sieved material and place it in a beaker. According to the ratio of the mass of the waste SCR denitrification catalyst to the volume of sulfuric acid of 1g:4mL, add sulfuric acid solution with a concentration of 1mol / L. After mixing, place it in a water bath at 50℃ and add 0.02g of (NH4)2SO3. After reacting for 1h, separate the solid and liquid to obtain a low-concentration low-valence vanadium solution. Under the reaction conditions, the vanadium leaching rate is 41.53% and the vanadium concentration in the solution is 204mg / L.

[0068] (3) Add an appropriate amount of concentrated sulfuric acid to the low-concentration, low-valence vanadium solution, and then add the same waste SCR denitrification catalyst and ammonium sulfite as in step (2) and leach under the same conditions. After five cycles of leaching, a high-concentration, high-valence vanadium leachate is obtained, the vanadium leaching rate is reduced to 37.2%, and the concentration of vanadium in the solution increases to 996 mg / L.

[0069] (4) After adding NH4OH to the above high-concentration low-valence vanadium solution to adjust the pH value of the solution to 3, take 100 mL of high-concentration low-valence vanadium leaching solution, introduce ozone at a flow rate of 10 mL / min into it to oxidize the vanadium element, and at the same time add 3 g of PVP as a surfactant into the leaching solution, stir vigorously, and after reacting for 30 min, a yellow precursor suspension is obtained.

[0070] (5) The yellow precursor suspension was placed in a Teflon reactor for hydrothermal reaction. After being kept at 160°C for 6 hours, the green precipitate was obtained by filtration. The precipitation rate of vanadium reached 95%. After washing with deionized water and ethanol, the precipitate was placed in a vacuum drying oven and kept at 80°C for 12 hours. The final product, aluminum vanadate (HAVO), was less.

[0071] Comparative Example 2:

[0072] A method for preparing aluminum vanadate using spent SCR denitration catalyst includes the following steps:

[0073] (1) After drying and crushing the waste SCR denitrification catalyst, it is screened with an 80-mesh standard sieve to ensure that the particle size is controlled below 178μm.

[0074] (2) Take 4g of the sieved material and place it in a beaker. According to the ratio of the mass of the waste SCR denitrification catalyst to the volume of sulfuric acid of 1g:8mL, add sulfuric acid solution with a concentration of 1.5mol / L. After mixing, place it in a water bath at 90℃ and add 0.05g of Na2SO3. After reacting for 2h, separate the solid and liquid to obtain a low-concentration low-valence vanadium solution. Under the reaction conditions, the vanadium leaching rate is 89.58% and the vanadium concentration in the solution is 538mg / L.

[0075] (3) Add an appropriate amount of concentrated sulfuric acid to the low-concentration, low-valence vanadium solution, and then add the same waste SCR denitrification catalyst and ammonium sulfite as in step (2) and leach under the same conditions. After five cycles of leaching, a high-concentration, high-valence vanadium leachate is obtained, the vanadium leaching rate is reduced to 84.5%, and the concentration of vanadium in the solution increases to 2301 mg / L.

[0076] (4) After adding NH4OH to the above high-concentration low-valence vanadium solution to adjust the pH value of the solution to 3, take 100 mL of high-concentration low-valence vanadium leaching solution, introduce ozone at a flow rate of 5 mL / min into it to oxidize the vanadium element, and at the same time add 3 g PVP as a surfactant into the leaching solution, stir vigorously, and after reacting for 10 min, a yellow precursor suspension is obtained.

[0077] (5) The yellow precursor suspension was placed in a Teflon reactor for hydrothermal reaction. After being kept at 160°C for 6 hours, the green precipitate was obtained by filtration. The precipitation rate of vanadium was about 64%. After washing with deionized water and ethanol, the precipitate was placed in a vacuum drying oven and kept at 80°C for 12 hours. The final product, aluminum vanadate (HAVO), was less.

[0078] Comparative Example 3:

[0079] A method for preparing aluminum vanadate using spent SCR denitration catalyst includes the following steps:

[0080] (1) After drying and crushing the waste SCR denitrification catalyst, it is screened with an 80-mesh standard sieve to ensure that the particle size is controlled below 178μm.

[0081] (2) Take 4g of the sieved material and place it in a beaker. According to the ratio of the mass of the waste SCR denitrification catalyst to the volume of sulfuric acid of 1g:8mL, add sulfuric acid solution with a concentration of 1.5mol / L. After mixing, place it in a water bath at 90℃ and add 0.05g of (NH4)2SO3. After reacting for 2h, separate the solid and liquid to obtain a low-concentration low-valence vanadium solution. Under the reaction conditions, the vanadium leaching rate is 89.58% and the vanadium concentration in the solution is 538mg / L.

[0082] (3) Add an appropriate amount of concentrated sulfuric acid to the low-concentration, low-valence vanadium solution, and then add the same waste SCR denitrification catalyst and ammonium sulfite as in step (2) and leach under the same conditions. After five cycles of leaching, a high-concentration, low-valence vanadium leachate is obtained, the vanadium leaching rate is reduced to 84.5%, and the concentration of vanadium in the solution increases to 2301 mg / L.

[0083] (4) After adding NH4OH to the above high-concentration low-valence vanadium solution to adjust the pH value of the solution to 3, take 100 mL of high-concentration low-valence vanadium leaching solution, add excess hydrogen peroxide to it, and at the same time add 3 g of PVP as a surfactant to the leaching solution, stir vigorously, and after reacting for 30 min, a yellow precursor suspension is obtained.

[0084] (5) The yellow precursor suspension was placed in a Teflon reactor for hydrothermal reaction. After being kept at 160°C for 6 hours, the green precipitate was obtained by filtration. The precipitation rate of vanadium was about 83%. After washing with deionized water and ethanol, the precipitate was placed in a vacuum drying oven and kept at 80°C for 12 hours to obtain the final product, aluminum vanadate (HAVO), which was relatively less.

[0085] Comparative Example 4:

[0086] A method for preparing aluminum vanadate using spent SCR denitration catalyst includes the following steps:

[0087] (1) After drying and crushing the waste SCR denitrification catalyst, it is screened with an 80-mesh standard sieve to ensure that the particle size is controlled below 178μm.

[0088] (2) Take 4g of the sieved material and place it in a beaker. According to the ratio of the mass of the waste SCR denitrification catalyst to the volume of sulfuric acid of 1g:8mL, add sulfuric acid solution with a concentration of 1.5mol / L. After mixing, place it in a water bath at 90℃ and add 0.05g of Na2SO3. After reacting for 2h, separate the solid and liquid to obtain a low-concentration low-valence vanadium solution. Under the reaction conditions, the vanadium leaching rate is 89.58% and the vanadium concentration in the solution is 538mg / L.

[0089] (3) Add an appropriate amount of concentrated sulfuric acid to the low-concentration, low-valence vanadium solution, and then add the same waste SCR denitrification catalyst and ammonium sulfite as in step (2) and leach under the same conditions. After five cycles of leaching, a high-concentration, high-valence vanadium leachate is obtained, the vanadium leaching rate is reduced to 84.5%, and the concentration of vanadium in the solution increases to 2301 mg / L.

[0090] (4) Take 100 mL of high-concentration low-valence vanadium solution and pass ozone at a flow rate of 10 mL / min to oxidize the vanadium element. Then add NH4OH to adjust the pH of the solution to 3. At the same time, take 3 g of PVP as a surfactant and add it to the leaching solution. Stir vigorously and react for 30 min to obtain a yellow precursor suspension.

[0091] (5) The yellow precursor suspension was placed in a Teflon reactor for hydrothermal reaction. After being kept at 160°C for 6 hours, the green precipitate was obtained by filtration. The precipitation rate of vanadium reached 94%. After washing with deionized water and ethanol, it was placed in a vacuum drying oven and kept at 80°C for 12 hours to obtain the final aluminum vanadate HAVO with low purity, not higher than 85%.

[0092] Comparative Example 5:

[0093] A method for preparing aluminum vanadate using spent SCR denitration catalyst includes the following steps:

[0094] (1) After drying and crushing the waste SCR denitrification catalyst, it is screened with an 80-mesh standard sieve to ensure that the particle size is controlled below 178μm.

[0095] (2) Take 4g of the sieved material and place it in a beaker. According to the ratio of the mass of the waste SCR denitrification catalyst to the volume of sulfuric acid of 1g:8mL, add sulfuric acid solution with a concentration of 1.5mol / L. After mixing, place it in a water bath at 90℃ and add 0.05g of (NH4)2SO3. After reacting for 2h, separate the solid and liquid to obtain a low-concentration low-valence vanadium solution. Under the reaction conditions, the vanadium leaching rate is 89.58% and the vanadium concentration in the solution is 538mg / L.

[0096] (3) Add an appropriate amount of concentrated sulfuric acid to the low-concentration, low-valence vanadium solution, and then add the same waste SCR denitrification catalyst and ammonium sulfite as in step (2) and leach under the same conditions. After five cycles of leaching, a high-concentration, low-valence vanadium leachate is obtained, the vanadium leaching rate is reduced to 84.5%, and the concentration of vanadium in the solution increases to 2301 mg / L.

[0097] (4) After adding NH4OH to the above high-concentration low-valence vanadium solution to adjust the pH value of the solution to 2, take 100 mL of high-concentration low-valence vanadium leaching solution, introduce ozone at a flow rate of 10 mL / min into it to oxidize the vanadium element, and at the same time add 3 g PVP as a surfactant into the leaching solution, stir vigorously, and after reacting for 30 min, a yellow precursor suspension is obtained.

[0098] (5) The yellow precursor suspension was placed in a Teflon reactor for hydrothermal reaction. After being kept at 160°C for 6 hours, the green precipitate was obtained by filtration. The precipitation rate of vanadium reached 95%. After washing with deionized water and ethanol, the precipitate was placed in a vacuum drying oven and kept at 80°C for 12 hours to obtain the final product, aluminum vanadate HAVO-2.

[0099] The aluminum vanadate product prepared in this comparative example has a three-dimensional porous seaweed-shaped microstructure. Compared with the aluminum vanadate prepared in Example 1 at pH 3, which has a sea urchin-like microstructure with distributed pores, the relatively complete three-dimensional microstructure in Example 1 can provide more space to store uranium ions and has more adsorption site regions, thus exhibiting superior adsorption performance.

[0100] Example 3:

[0101] like Figure 2 As shown, a method for preparing aluminum vanadate and ammonium paratungstate using spent SCR denitrification catalyst includes the following steps:

[0102] Steps (1)-(5) are the same as in Example 1:

[0103] (6) Take 4g of acid leaching residue and place it in a beaker. Add 2mol / L Na2S solution at a ratio of 1g:6mL (mass of acid leaching residue to volume of Na2S solution). After mixing, place the beaker in an 80℃ water bath and add sodium hydroxide solid at a ratio of 1:3 (mass of alkali residue to alkali residue). After reacting for 2.5h, separate the solid and liquid. The leaching rate of W is 85.24%, and the concentration of tungsten in the solution is 701mg / L (wash the filter residue with water, collect the washing liquid and add it to the filtrate). A low concentration Na2WO4 / Na2WO4 is obtained. x S 4-x The leaching rate of silicon impurities in the solution and titanium-rich slag was 16.2%.

[0104] (7) To increase the tungsten content in the solution, the above-mentioned low-concentration Na2WO4 / Na2WO4 was added. x S 4-x A certain amount of sodium sulfide and sodium hydroxide solids were added to the solution, followed by the addition of acid leaching residue powder for leaching. After five cycles of leaching, a high concentration of Na₂WO₄ / Na₂WO₄ was obtained. x S 4-x The concentration of tungsten in the solution increased to 3926 mg / L.

[0105] (8) In high concentrations of Na2WO4 / Na2WO x S 4-x Ozone gas was bubbled into the solution at a flow rate of 10 mL / min for 30 minutes to induce oxidation and transformation, resulting in a high-concentration Na2WO4 solution.

[0106] (9) The pH of a high-concentration Na2WO4 solution was adjusted to 9 using hydrochloric acid, and the solution was reacted at 80°C in a water bath for 2 hours to precipitate H2SiO3 and remove silicon. Under these conditions, the silicon precipitation rate reached 95%. Excess calcium chloride was then added to the solution for precipitation, converting sodium tungstate into solid calcium tungstate. The reaction was carried out at 80°C in a water bath for 4 hours. After solid-liquid separation, solid calcium tungstate was obtained, and the tungsten precipitation rate reached 98.4%.

[0107] (10) Calcium tungstate solid and concentrated ammonia water with a mass fraction of 25-30% are reacted in a water bath at 90℃ for 2 hours to obtain ammonium tungstate solution. Impurities such as Ca and Fe react with ammonia water to form insoluble calcium hydroxide and iron hydroxide precipitates, which are removed by filtration.

[0108] (11) Ammonium tungstate, which has high solubility, is converted into ammonium paratungstate, which has low solubility, by evaporation, concentration, and cooling crystallization, and then crystallized from the solution. The ammonium tungstate solution is heated at 90°C and then placed at room temperature for cooling crystallization for 1 day. After filtration, ammonium paratungstate crystals are obtained. When the evaporation rate of the solution reaches 90%, the crystallization rate of ammonium paratungstate exceeds 89%, and the purity of the ammonium paratungstate product obtained at this time exceeds 95%. After repeating the purification operations of steps (5) and (6) several times, the purity of the obtained ammonium paratungstate crystals exceeds 99.9%.

Claims

1. A method for preparing aluminum vanadate using spent SCR denitrification catalyst, characterized in that, Includes the following steps: (1) Use sulfuric acid and ammonium sulfite to leach the waste SCR denitrification catalyst, and filter to obtain acid leaching solution and acid leaching residue; (2) The acid leaching solution obtained in step (1) is oxidized by passing ozone through it to obtain a precursor suspension; (3) The precursor suspension obtained in step (2) is subjected to hydrothermal reaction, the precipitate is collected, filtered, washed and dried to obtain aluminum vanadate; Before oxidizing the acid leaching solution with ozone, ammonium hydroxide is added to the acid leaching solution to adjust the pH value to 2.8-3.

2. The concentration of sulfuric acid is 1.5-2 mol / L, the mass ratio of the spent SCR denitrification catalyst to the volume of sulfuric acid is 1 g: 6-8 mL, and the mass ratio of the spent SCR denitrification catalyst to ammonium sulfite is 1: (0.01-0.02). When leaching spent SCR denitrification catalyst with sulfuric acid and ammonium sulfite, the reaction is carried out in a water bath at 80-90℃ for 1.5-2 hours. When introducing ozone for oxidation, the ozone gas flow rate should be controlled at 10-20 mL / min, and the oxidation time should be controlled at 20-30 min. While introducing ozone for oxidation, polyvinylpyrrolidone is added to the acid leaching solution at a liquid-to-solid ratio of 1 mL: 20-40 mg, and the mixture is stirred vigorously.

2. The method for preparing aluminum vanadate using spent SCR denitrification catalyst according to claim 1, characterized in that, Add acid to the acid leaching solution obtained in step (1), and then add waste SCR denitrification catalyst and ammonium sulfite to it for cyclic leaching. Repeat the cyclic leaching multiple times to obtain a high-concentration low-valence vanadium solution, and use the high-concentration low-valence vanadium solution to replace the acid leaching solution in step (2).

3. The method for preparing aluminum vanadate using spent SCR denitrification catalyst according to claim 1 or 2, characterized in that, The hydrothermal reaction was kept at 160-180℃ for 6-8 hours.

4. Aluminum vanadate prepared by the method for preparing aluminum vanadate using spent SCR denitration catalyst as described in any one of claims 1-3, characterized in that, The aluminum vanadate has a sea urchin-like microstructure.

5. The use of aluminum vanadate prepared by the method for preparing aluminum vanadate using waste SCR denitrification catalyst as described in any one of claims 1-3, or the aluminum vanadate as described in claim 4, as a uranium adsorbent.

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