A method for recovering valuable metals Ti, V, and W from waste SCR denitration catalysts

Abstract

The present disclosure provides a method for recovering valuable metals Ti, V, and W from waste SCR denitration catalysts, comprising the following steps: 1) Crushing pretreatment; 2) Dissolving and extracting vanadium to obtain nano V2O5 sol; 3) Separating titanium and tungsten; 4) Peroxidation treatment to obtain nano TiO2 sol; 5) Separating to obtain nano WO3 sol. Compared with the dry or wet recovery processes in the prior art, the recovery method according to the present invention has mild process conditions and high recovery rates of valuable metals, and is suitable for large-scale production.

Description

Technical Field

[0001] The present invention belongs to the fields of chemical engineering and solid waste pollutant recycling and reuse. Specifically, it relates to a new process method for recovering valuable metals Ti, V, and W from waste SCR denitration catalysts through an acidification and peroxidation process and directly preparing corresponding nano-metal oxide sols. Background Art

[0002] China is a large energy-consuming country that has long relied mainly on thermal power generation. Therefore, thermal power plants are one of the main sources of NOx emissions. At present, the selective reduction method (SCR) is the most efficient, mature, and widely used denitration technology at home and abroad. The service life of denitration catalysts is about 16,000 - 20,000 hours. It is estimated that starting from 2018, 38,000 tons / year of SCR waste catalysts will be continuously and stably generated in China. At present, non-renewable waste denitration catalysts are basically landfilled. In the "Technical Specification for Flue Gas Denitration Engineering in Thermal Power Plants - Selective Catalytic Reduction Method" announced and implemented on April 1, 2010, the treatment method for SCR waste catalysts is to crush them and then landfill them. In fact, WO3, V2O5, and TiO2 contained in waste SCR catalysts themselves are all valuable resources. If they can be recovered and resourcefully utilized through separation and purification, each ton of waste catalysts can generate nearly 10,000 yuan in output value. Then each ton of waste SCR catalysts can generate at least 13,900 yuan in output value.

[0003] At present, the main methods for SCR recovery are dry method and wet method. The dry method mainly utilizes the components in the waste denitration catalyst to react with alkali under high-temperature roasting, and then realizes separation by the different solubilities of the reaction products during water leaching, which can separate TiO2, V2O5 and WO3 in the waste denitration catalyst. For example, the method described in CN105905945A. The wet method is to utilize the components in the waste denitration catalyst to react with chemical raw materials to dissolve tungsten trioxide and vanadium pentoxide. After filtration, different solutions are added to the liquid containing tungsten ions and vanadium ions for separation and precipitation. For example, the method described in CN105854957A. However, the existing recovery and treatment technologies for SCR waste catalysts are still based on traditional vanadium-titanium recovery. Although there are some domestic enterprises that can separately recover vanadium or tungsten in waste catalysts at present, due to the low content (0.5% - 1%), they cannot be classified into waste vanadium catalysts, and it is impossible to separate and purify vanadium and tungsten under the existing process conditions of enterprises specializing in waste vanadium catalyst recovery. For example, Chinese Patent CN104178636A discloses a method for recovering Ti, V, Mo and Si in SCR waste catalysts by activation calcination combined with acid leaching. First, the waste catalyst powder is mixed with NaCl powder and calcined at 600 - 800 °C for 4 - 6 hours, then the calcined solid is treated with a weak acid aqueous solution, and then substances such as H2MoO4 and NH4VO3 are precipitated through processes such as evaporation concentration and addition of ammonia water. Generally speaking, in the cost accounting of waste SCR catalyst recovery, the resource utilization of TiO2 is the most critical step, and the sales revenue of recovered titanium oxide accounts for 70% of the total sales revenue, which is the core factor determining the profit and loss of the project. Therefore, it is urgent to develop technologies with the recovery and utilization of denitration titanium white as the core. Summary of the Invention

[0004] Aiming at the problems existing in the above-mentioned prior art, according to one aspect of the present invention, an object of the present invention is to provide a method for recovering valuable metals Ti, V, and W from waste SCR denitration catalysts. The core of this method is to first utilize the solubility differences of metals V, W, and Ti in different acid solutions to achieve separation, and then directly prepare corresponding metal oxide nanocrystal products through a peroxide route to realize the high-value utilization of V, W, and Ti.

[0005] According to the method for recovering valuable metals Ti, V, and W from waste SCR denitration catalysts of the present invention, the method includes the following steps:

[0006] 1) Pretreatment

[0007] The waste SCR denitration catalyst is washed, dried, and then crushed into powder particles with an average particle size of 20 μm to 45 μm.

[0008] 2) Vanadium dissolution and extraction

[0009] At room temperature, the waste SCR denitration catalyst powder particles obtained in step 1) are dispersed in pure water, and the mass fraction of V2O5 in the suspension is controlled to be 0.01 wt% - 0.05 wt%. After stirring for 5 to 15 minutes, a H2O2 solution with a mass fraction of 20 wt% to 35 wt% is added, and the mass ratio of H2O2 to V2O5 is 2:1 to 20:1. After continuing to stir rapidly for 0.5 to 2 hours, filtration is carried out. The filtrate is a vanadium peroxide solution, and the filter residue is TiO2, WO3, Al2O3, SiO2, etc. The filter residue is washed and dried for standby. The filtrate is heated under reflux at 100 °C under normal pressure for 3 to 10 hours to obtain nano-V2O5 sol.

[0010] 3) Titanium-tungsten separation

[0011] The filter residue containing TiO2 and WO3 obtained in step 2) is dissolved in a concentrated sulfuric acid solution with a mass fraction of 90 wt%. The mass ratio of the concentrated sulfuric acid solution to the filter residue is controlled to be 1.0:1 to 6:1. Heating and stirring are carried out at 60 to 90 °C for 2 to 6 hours to obtain a concentrated titanium solution. After cooling to room temperature, a dilute ammonia water solution with a mass fraction of 5% - 15% is slowly added dropwise thereto under stirring conditions until the pH value is 6 - 7. Filtration is carried out to obtain metatitanic acid precipitate and insoluble substances such as WO3, Al(OH)3, and SiO2. Centrifugal washing is carried out 5 - 8 times. The washed metatitanic acid precipitate is diluted with deionized water to a mass fraction of 1 wt% - 5%, and stirred for 5 - 10 minutes. Then, a H2O2 solution with a mass fraction of 20 wt% to 35 wt% is added, and the mass ratio of H2O2 to metatitanic acid is controlled to be 2:1 - 20:1. The temperature is raised to 60 °C and kept stirring for 10 - 30 minutes to obtain an orange-yellow titanium peroxide colloidal solution, and then filtration is carried out. The filter residue is insoluble impurities such as WO3, SiO2, and Al(OH)3. The filter residue is washed with deionized water many times, and the washing liquid is incorporated into the filtrate.

[0012] 4) Peroxidation

[0013] The titanium peroxide colloidal solution obtained in step 3) is heated under reflux at 100 °C under normal pressure for 3 to 10 hours to obtain nano-TiO2 sol.

[0014] 5) Tungsten separation

[0015] Under stirring conditions, slowly add dilute ammonia water with a mass fraction of 3% to 20% dropwise to the WO3-containing filter residue obtained in step 3), control the molar ratio of WO3 to NH3 to be 1:2 to 1:15, heat up to 20°C to 100°C, stir and react for 2 to 3 h to obtain an ammonium tungstate solution and insoluble substances such as Al(OH)3 and SiO2, filter, wash the filter residue repeatedly and dry it at 150°C, incorporate the washing solution into the filtrate, under stirring conditions, slowly add nitric acid to the filtrate to adjust the pH ≤ 1, centrifuge and wash the obtained tungstic acid precipitate 5 to 10 times, add deionized water until the mass fraction of tungstic acid is 1 wt% to 5 wt%, then add an H2O2 solution with a mass fraction of 20 wt% to 35 wt%, control the mass ratio of H2O2 to tungstic acid to be 2:1 to 10:1, stir rapidly, and heat under reflux at 100°C under normal pressure for 3 to 10 h to obtain a nano-WO3 sol.

[0016] Preferably, the average particle size of the powder particles in step 1) is 20 μm to 30 μm.

[0017] Preferably, the comminution in step 1) can adopt comminution methods such as crushing, grinding, and extrusion, and ball milling is preferably adopted.

[0018] Preferably, the mass fraction concentration of the H2O2 solution added in step 2) is 30 wt%.

[0019] Preferably, the mass ratio of H2O2 to V2O5 in step 2) is 2:1 to 15:1, and more preferably 2:1 to 10:1.

[0020] Preferably, the mass ratio of the concentrated sulfuric acid solution to the filter residue in step 3) is 1.0:1 to 6:1, and more preferably 1.5:1 to 3:1.

[0021] Preferably, the mass fraction concentration of the H2O2 solution added in step 3) is 30 wt%.

[0022] Preferably, the mass ratio of H2O2 to metatitanic acid in step 3) is 2:1 to 15:1, and more preferably 2:1 to 10:1.

[0023] Preferably, the mass fraction concentration of the dilute ammonia water in step 5) is 5% to 15%.

[0024] Preferably, the molar ratio of WO3 to NH3 in step 5) is 1:2 to 1:10, and more preferably 1:2 to 1:5.

[0025] Preferably, the main components of the filter residue in step 5) are Al(OH)3, SiO2, etc., and the powder obtained after drying can be used as an additive material for catalyst forming.

[0026] According to another aspect of the present invention, another object of the present invention is to provide a nano-V2O5 sol product, and the nano-V2O5 sol is obtained according to the above-mentioned recovery method of the present invention.

[0027] According to another aspect of the present invention, another object of the present invention is to provide a nano-TiO2 sol product, and the nano-TiO2 sol is obtained according to the above-mentioned recovery method of the present invention.

[0028] According to another aspect of the present invention, another object of the present invention is to provide a nano-WO3 sol product, and the nano-WO3 sol is obtained according to the above-mentioned recovery method of the present invention.

[0029] Beneficial effects

[0030] Compared with the dry or wet recovery processes in the prior art, the recovery method according to the present invention has mild process conditions, high recovery rate of valuable metals, and is suitable for large-scale production. Brief description of the drawings

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is a flow chart of the recovery method according to the present invention.

[0033] Figure 2 It is a transmission electron microscope image of the V2O5 product prepared in Example 1 of the present invention.

[0034] Figure 3 It is an XRD spectrum of the V2O5 product prepared in Example 1 of the present invention.

[0035] Figure 4 It is a transmission electron microscope image of the product of the TiO2 composite prepared in Example 1 of the present invention.

[0036] Figure 5 It is an XRD spectrum of the product of the TiO2 composite prepared in Example 1 of the present invention.

[0037] Figure 6 It is a transmission electron microscope image of the product of the WO3 composite prepared in Example 1 of the present invention.

[0038] Figure 7 It is an XRD spectrum of the product of the WO3 composite prepared in Example 1 of the present invention. Specific embodiments

[0039] In the following, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the appended claims should not be construed as being limited to the general and dictionary meanings, but should be interpreted based on the principle of appropriately defining the terms to allow the inventor to provide the best interpretation, and based on the meanings and concepts corresponding to the technical level of the present invention. Therefore, the description herein is only a preferred example for illustrative purposes and is not intended to limit the scope of the present invention. Thus, it should be understood that other equivalent implementations and modifications can be made without departing from the spirit and scope of the present invention.

[0040] The following will further describe in detail Figure 1 the recovery method of the present invention.

[0041] Currently, in the composition of domestic waste SCR denitration catalysts, the mass fractions of V2O5, WO3, and TiO2 are approximately 1 wt%, 3 - 9 wt%, and 76 - 85 wt% respectively. Among them, TiO2 has the largest proportion. And according to the reactivity of V, W, and Ti with hydrogen peroxide, in the recovery method of the present invention, metal V is extracted first because the content of metal V is the smallest. In this way, the dosage of various reaction materials in the recovery step of recovering metal V is the smallest, and the impact on the subsequent recovery and extraction steps is also the smallest. If W or Ti, especially Ti, is extracted first, due to the very high content of Ti, the dosage of reaction materials is large. When extracting metal V later, a larger equipment volume and higher energy consumption are required. At the same time, if the particle size of V2O5 particles is small enough, it can directly react with hydrogen peroxide to form vanadium peroxide, which is easier to extract than WO3 and TiO2.

[0042] In step 1) of the recovery method according to the present invention, the waste SCR denitration catalyst is subjected to a pulverization pretreatment. Since the waste SCR denitration catalyst often has serious caking phenomena, in order to facilitate the extraction of valuable metals, the waste SCR denitration catalyst needs to be pulverized. Especially when the waste SCR denitration catalyst is pulverized to an average particle size of 20 μm to 45 μm, preferably 20 μm to 30 μm, the subsequent recovery effect is the best. It is well known to those skilled in the art to pulverize the waste SCR denitration catalyst as much as possible for extraction. However, the inventor of the present invention found that for the recovery and extraction method of the present invention, the pulverization particle size of the waste SCR denitration catalyst is not the smaller the better. For example, when it is lower than 20 μm, a large amount of TiO2 will be doped in the final product in the step of extracting V. This may be because the content of TiO2 is very high and the particle size is too small, resulting in an increase in the reactivity of the particles, so that Ti also coordinates with hydrogen peroxide and then remains in the solution. Therefore, in the recovery method of the present invention, the average particle size of the pulverized waste SCR denitration catalyst is controlled to be 20 μm to 45 μm, preferably 20 μm to 30 μm, with the best effect.

[0043] In step 2) of the recovery method according to the present invention, preferably, the waste SCR denitration catalyst powder particles in step 1) are dispersed in pure water, and the mass fraction of V2O5 in the suspension needs to be controlled at 0.01 wt% to 0.05 wt%. Controlling the concentration of V2O5 within a lower range can ensure that after adding the H2O2 solution subsequently, H2O2 mainly undergoes a coordination reaction with V2O5, effectively avoiding other impurities remaining in the solution.

[0044] Preferably, the mass fraction concentration of the H2O2 solution added in step 2) is 20 wt% to 35 wt%, more preferably 30 wt%. If the concentration of the H2O2 solution is too low, the reactivity will be reduced; if the concentration is too high, due to the safety issues of H2O2 itself, higher requirements are imposed on the equipment. Considering the reaction progress and economy, it is beneficial to control the concentration of the H2O2 solution within the above range.

[0045] Preferably, the mass ratio of H2O2 to V2O5 in step 2) is 2:1 to 15:1, more preferably 2:1 to 10:1. When the mass ratio of H2O2 to V2O5 is lower than 2:1, that is, H2O2 is insufficient, V2O5 may not be fully coordinated with H2O2; when the mass ratio of H2O2 to V2O5 is higher than 15:1, that is, H2O2 is in excess, although V2O5 undergoes a sufficient coordination reaction, other metals may also undergo coordination and remain in the solution, and it is not economical enough.

[0046] Preferably, the mass ratio of the concentrated sulfuric acid solution to the filter residue in step 3) is 1.0:1 to 6:1, more preferably 1.5:1 to 3:1. If the concentrated sulfuric acid is too little, it may not be sufficient to dissolve Ti in the filter residue, resulting in insufficient Ti recovery; if the concentrated sulfuric acid is too much, on the one hand, it is not economical enough, and on the other hand, it causes greater pressure on subsequent neutralization reactions, separation, and waste liquid treatment, etc.

[0047] Preferably, the mass fraction concentration of the H2O2 solution added in step 3) is 20 wt% to 35 wt%, more preferably 30 wt%. If the concentration of the H2O2 solution is too low, the reactivity will be reduced; if the concentration is too high, due to the safety issues of H2O2 itself, higher requirements are imposed on the equipment. Considering the reaction progress and economy, it is beneficial to control the concentration of the H2O2 solution within the above range.

[0048] Preferably, the mass ratio of H2O2 to metatitanic acid in step 3) is 2:1 to 15:1, more preferably 2:1 to 10:1. When the mass ratio of H2O2 to V2O5 is lower than 2:1, that is, H2O2 is insufficient, metatitanic acid may not be fully coordinated with H2O2; when the mass ratio of H2O2 to metatitanic acid is higher than 15:1, that is, H2O2 is in excess, and it is not economical enough.

[0049] Preferably, the molar ratio of NH3 to WO3 in step 5) is 2:1 to 10:1, more preferably 1:2 to 1:5. When the molar ratio of NH3 to WO3 is 2:1, i.e., NH3 is insufficient, WO3 may not be fully coordinated; when the molar ratio of NH3 to WO3 is higher than 10:1, i.e., NH3 is in excess, it is not economical at the same time.

[0050] The following examples are only listed as examples of the embodiments of the present invention and do not constitute any limitation to the present invention. Those skilled in the art can understand that modifications within the scope not deviating from the essence and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following examples are commercially available products.

[0051] In addition, unless otherwise specified, the reagents and solvents disclosed below are purchased from Beijing Innochem (innochem). TEM is performed using a JEOL JEM-2100 transmission electron microscope from Japan, and XRD is performed using a D8 Focus powder X-ray diffractometer from Bruker, Germany.

[0052] Example 1

[0053] 1) Pretreatment

[0054] The waste SCR denitration catalyst with mass fractions of V2O5, WO3, and TiO2 being 1 wt%, 5 wt%, and 80 wt% respectively is washed, dried, crushed, and ball-milled into powder particles with a particle size of 325 mesh (45 μm), and then sieved.

[0055] 2) Dissolution and vanadium extraction

[0056] Weigh 36.4 g of the sieved waste SCR denitration catalyst powder, disperse it in 320 mL of deionized water, add 3.2 mL of 30 wt% H2O2 after stirring for 10 min, continue to stir rapidly for 2 h and then filter. The filter residue is repeatedly rinsed with a small amount of deionized water, dried, and cooled, and the washing solution is collected into the filtrate. The filtrate is heated under reflux at 100 °C for 3 h to obtain a nano-V2O5 sol, and the nano-V2O5 sol is dried at 150 °C for 10 h to obtain 0.33 g of solid, and the recovery rate of V is 90.6%. Figure 2 The TEM photo results of... confirm that the obtained V2O5 presents a nanobelt structure, Figure 3 The XRD pattern of... confirms that the obtained nanobelt is vanadium pentoxide crystal.

[0057] 3) Titanium-tungsten separation

[0058] Take 33 mL of concentrated sulfuric acid with a mass fraction of 90 wt%, add the filter residue, heat and stir for 2 h to obtain a concentrated titanium solution. Under stirring conditions, slowly add a dilute ammonia water solution with a mass fraction of 5 wt% to it until the pH value reaches 7. Continue to stir for 10 min and then filter to obtain metatitanic acid precipitate and insoluble substances such as WO3, Al(OH)3, and SiO2, and centrifuge and wash 7 times. The washed metatitanic acid precipitate is diluted with 430 mL of deionized water and stirred for 10 min, and then 290 mL of a H2O2 solution with a mass fraction of 30% is added. Heat up to 60 °C and stir at a constant temperature for 20 min to obtain an orange-yellow titanium peroxide colloidal solution, and then filter. The filter residue is insoluble impurities such as WO3, SiO2, and Al(OH)3, and the filter residue is washed with deionized water multiple times, and the washing liquid is incorporated into the filtrate.

[0059] 4) Peroxidation

[0060] Obtain an orange-yellow titanium peroxide colloidal solution, heat and reflux at 100 °C for 3 h to obtain a nano-TiO2 sol. Dry the nano-TiO2 sol at 150 °C for 10 h to obtain 26.77 g of solid, and the recovery rate of TiO2 is 91.9%; Figure 4 The TEM results confirm that the obtained TiO2 is nanoparticles, Figure 5 The XRD pattern confirms that the obtained nanoparticles are titanium oxide crystals.

[0061] 5) Separation of tungsten

[0062] For the filter residue containing WO3, under stirring conditions, add 50 mL of deionized water, then add 13 g of dilute ammonia water with a mass fraction of 10%, heat up to 100 °C, continue to stir for 3 h and then filter to obtain an ammonium tungstate solution and insoluble substances such as Al(OH)3 and SiO2. Filter, and wash the filter residue repeatedly, and incorporate the washing liquid into the filtrate. Dry the filter residue at 150 °C for 5 h, and the obtained powder can be used as an additive material for catalyst shaping. Under stirring conditions, slowly add nitric acid to the filtrate to adjust the pH ≤ 1 to obtain a tungsten acid precipitate, centrifuge and wash 7 times, add 27 mL of deionized water, then add 16 mL of a H2O2 solution with a mass fraction of 30 wt%, stir rapidly, heat and reflux at 100 °C for 3 h to obtain a nano-WO3 sol. Dry the nano-WO3 sol at 150 °C for 10 h to obtain 1.75 g of solid, and the recovery rate of WO3 is 96.1%. Figure 6 The TEM photo results confirm that the obtained WO3 is nanowire particles, Figure 7 The XRD pattern confirms that the obtained nanowires are tungsten oxide crystals.

[0063] Example 2

[0064] 1) Pretreatment

[0065] The waste SCR denitration catalyst with mass fractions of V2O5, WO3, and TiO2 being 1 wt%, 5 wt%, and 80 wt% respectively is washed, dried, crushed, and ball-milled into powder particles with a particle size of 325 mesh (45 μm), and then sieved.

[0066] 2) Vanadium extraction by dissolution

[0067] Weigh 36.4 g of the sieved waste SCR denitration catalyst powder, disperse it in 320 mL of deionized water, stir for 10 min, then add 1.6 mL of H2O2 with a mass fraction of 30 wt%, continue to stir rapidly for 2 h, and then filter. The filter residue is repeatedly washed with a small amount of deionized water, dried, and cooled, and the washing solution is collected into the filtrate. The filtrate is heated under reflux at 100 °C for 3 h to obtain nano-V2O5 sol. The nano-V2O5 sol is dried at 250 °C for 3 h to obtain 0.31 g of solid, and the recovery rate of V is 85.1%.

[0068] 3) Separation of titanium and tungsten

[0069] Take 33 mL of concentrated sulfuric acid with a mass fraction of 90 wt%, add the filter residue, heat and stir for 2 h to obtain a concentrated titanium solution. Under stirring conditions, slowly dropwise add a dilute ammonia water solution with a mass fraction of 5 wt% to a pH value of 7, continue to stir for 10 min, and then filter to obtain metatitanic acid precipitate and insoluble substances such as WO3, Al(OH)3, and SiO2, and centrifuge and wash 7 times. The washed metatitanic acid precipitate is diluted with 430 mL of deionized water and stirred for 10 min, and then 150 mL of H2O2 solution with a mass fraction of 30% is added. The temperature is raised to 60 °C and stirred at a constant temperature for 20 min to obtain an orange-yellow titanium peroxide colloidal solution, and then filtered. The filter residue is WO3, SiO2, Al(OH)3 and other insoluble impurities, and the filter residue is washed with deionized water multiple times, and the washing solution is incorporated into the filtrate.

[0070] 4) Peroxidation

[0071] The obtained orange-yellow titanium peroxide colloidal solution is heated under reflux at 100 °C for 3 h to obtain nano-TiO2 sol. The nano-TiO2 sol is dried at 150 °C for 10 h to obtain 26.21 g of solid, and the recovery rate of TiO2 is 90%;

[0072] 5) Separation of tungsten

[0073] The filter residue containing WO3 was added with 50 mL of deionized water under stirring conditions, and then 13 g of 10% dilute ammonia water was added. The temperature was raised to 80 °C, and stirring was continued for 3 h before filtration to obtain ammonium tungstate solution and insoluble substances such as Al(OH)3 and SiO2. After filtration, the filter residue was washed repeatedly, and the washing liquid was incorporated into the filtrate. The filter residue was dried at 150 °C for 2 h, and the obtained powder could be used as an additive material for catalyst forming. Under stirring conditions, nitric acid was slowly added to the filtrate to adjust the pH ≤ 1, and the obtained tungstic acid precipitate was centrifugally washed 7 times. 27 mL of deionized water was added, and then 8 mL of 30 wt% H2O2 solution was added. After rapid stirring, it was heated under reflux at 100 °C for 3 h to obtain nano-WO3 sol. The nano-WO3 sol was dried at 150 °C for 10 h to obtain 1.75 g of solid, and the recovery rate of WO3 was 86.4%.

[0074] Example 3

[0075] 1) Pretreatment

[0076] The waste SCR denitration catalyst with mass fractions of V2O5, WO3, and TiO2 being 1 wt%, 5 wt%, and 80 wt% respectively was cleaned, dried, crushed, and ball-milled into powder particles with a particle size of 325 mesh (45 μm), and then sieved.

[0077] 2) Dissolution and vanadium extraction

[0078] 36.4 g of the sieved waste SCR denitration catalyst powder was weighed and dispersed in 320 mL of deionized water. After stirring for 10 min, 0.8 mL of 30 wt% H2O2 was added, and rapid stirring was continued for 2 h before filtration. The filter residue was repeatedly rinsed with a small amount of deionized water, dried, and cooled, and the washing liquid was collected into the filtrate. The filtrate was heated under reflux at 100 °C for 3 h to obtain nano-V2O5 sol. The nano-V2O5 sol was dried at 250 °C for 3 h to obtain 0.286 g of solid, and the recovery rate of V was 78.6%.

[0079] 3) Titanium-tungsten separation

[0080] 33 mL of 90 wt% concentrated sulfuric acid was taken and added to the filter residue, and it was heated and stirred for 2 h to obtain concentrated titanium solution. Under stirring conditions, 5 wt% dilute ammonia water solution was slowly added dropwise to it until the pH value reached 7, and stirring was continued for 10 min before filtration to obtain metatitanic acid precipitate and insoluble substances such as WO3, Al(OH)3, and SiO2, which were centrifugally washed 7 times. The washed metatitanic acid precipitate was diluted with 430 mL of deionized water and stirred for 10 min, and then 60 mL of 30% H2O2 solution was added. The temperature was raised to 60 °C and stirred at a constant temperature for 20 min to obtain an orange-yellow titanium peroxide colloidal solution, and then filtered. The filter residue was insoluble impurities such as WO3, SiO2, and Al(OH)3, and the filter residue was washed with deionized water many times, and the washing liquid was incorporated into the filtrate.

[0081] 4) Peroxidation

[0082] An orange-yellow titanium peroxide colloidal solution is obtained, heated under reflux at 100 °C for 3 h to obtain a nano-TiO2 sol, and the nano-TiO2 sol is dried at 150 °C for 10 h to obtain 25.17 g of solid, with a TiO2 recovery rate of 86.4%;

[0083] 5) Separation of tungsten

[0084] For the filter residue containing WO3, under stirring conditions, 50 mL of deionized water is added, then 13 g of 10% by mass of dilute ammonia water is added, the temperature is raised to 60 °C, and stirring is continued for 3 h followed by filtration to obtain an ammonium tungstate solution and insoluble substances such as Al(OH)3 and SiO2. The filter residue is washed repeatedly, and the washing liquid is incorporated into the filtrate. The filter residue is dried at 150 °C for 2 h, and the obtained powder can be used as an additive material for catalyst forming. Under stirring conditions, nitric acid is slowly added to the filtrate to adjust the pH ≤ 1, and the obtained tungstic acid precipitate is centrifugally washed 7 times, 27 mL of deionized water is added, then 3.5 mL of 30 wt% H2O2 solution is added, and rapid stirring is carried out. It is heated under reflux at 100 °C for 3 h to obtain a nano-WO3 sol, and the nano-WO3 sol is dried at 150 °C for 10 h to obtain 1.47 g of solid, with a WO3 recovery rate of 80.7%.

[0085] Example 4

[0086] 1) Pretreatment

[0087] The waste SCR denitration catalyst with mass fractions of V2O5, WO3, and TiO2 being 1 wt%, 5 wt%, and 80 wt% respectively is cleaned, dried, crushed, and ball-milled to powder particles with a particle size of 325 mesh (45 μm), and then sieved.

[0088] 2) Dissolution and vanadium extraction

[0089] Weigh 36.4 g of the sieved waste SCR denitration catalyst powder, disperse it in 320 mL of deionized water, stir for 10 min, then add 2 mL of 30 wt% H2O2, continue rapid stirring for 3 h, and then filter. The filter residue is repeatedly rinsed with a small amount of deionized water, dried, and cooled, and the washing liquid is collected into the filtrate. The filtrate is heated under reflux at 100 °C for 5 h to obtain a nano-V2O5 sol, and the nano-V2O5 sol is dried at 250 °C for 3 h to obtain 0.32 g of solid, with a V recovery rate of 87.9%.

[0090] 3) Separation of titanium and tungsten

[0091] Take 33 mL of concentrated sulfuric acid with a mass fraction of 90 wt%, add the filter residue, heat and stir for 2 h to obtain a concentrated titanium solution. Under stirring conditions, slowly dropwise add a dilute ammonia water solution with a mass fraction of 5 wt% to it until the pH value reaches 7. Continue to stir for 10 min and then filter to obtain metatitanic acid precipitate and insoluble substances such as WO3, Al(OH)3, and SiO2, and centrifuge and wash 7 times. The washed metatitanic acid precipitate is diluted with 580 mL of deionized water and stirred for 10 min, and then 80 mL of H2O2 solution with a mass fraction of 30% is added. Heat up to 60 °C and stir at a constant temperature for 30 min to obtain an orange-yellow titanium peroxide colloidal solution, and then filter. The filter residue is insoluble impurities such as WO3, SiO2, and Al(OH)3, and the filter residue is washed with deionized water multiple times, and the washing liquid is incorporated into the filtrate.

[0092] 4) Peroxidation

[0093] Obtain an orange-yellow titanium peroxide colloidal solution, heat and reflux at 100 °C for 3 h to obtain a nano-TiO2 sol. Dry the nano-TiO2 sol at 150 °C for 10 h to obtain 25.71 g of solid, and the recovery rate of TiO2 is 88.2%;

[0094] 5) Separation of tungsten

[0095] For the filter residue containing WO3, under stirring conditions, add 50 mL of deionized water, then add 13 g of dilute ammonia water with a mass fraction of 10%, heat up to 40 °C, continue to stir for 3 h and then filter to obtain an ammonium tungstate solution and insoluble substances such as Al(OH)3 and SiO2. Filter, and wash the filter residue repeatedly, and incorporate the washing liquid into the filtrate. Dry the filter residue at 150 °C for 2 h, and the obtained powder can be used as an additive material for catalyst forming. Under stirring conditions, slowly add nitric acid to the filtrate to adjust the pH ≤ 1 to obtain a tungstic acid precipitate, centrifuge and wash 7 times, add 27 mL of deionized water, then add 5 mL of H2O2 solution with a mass fraction of 30 wt%, stir rapidly, heat and reflux at 100 °C for 3 h to obtain a nano-WO3 sol. Dry the nano-WO3 sol at 150 °C for 10 h to obtain 1.47 g of solid, and the recovery rate of WO3 is 74.7%.

[0096] Example 5

[0097] 1) Pretreatment

[0098] The waste SCR denitration catalyst with mass fractions of V2O5, WO3, and TiO2 being 1 wt%, 5 wt%, and 80 wt% respectively is cleaned, dried, crushed, and ball-milled into powder particles with a particle size of 325 mesh (45 μm), and then sieved.

[0099] 2) Dissolution and vanadium extraction

[0100] Weigh 36.4 g of the sieved waste SCR denitration catalyst powder, disperse it in 320 mL of deionized water, add 2 mL of 30 wt% H2O2 after stirring for 10 min, continue to stir rapidly for 3 h and then filter. The filter residue is repeatedly rinsed with a small amount of deionized water, dried, cooled, and the washing liquid is collected into the filtrate. The filtrate is heated under reflux at 100 °C for 5 h to obtain a nano-V2O5 sol. The nano-V2O5 sol is dried at 250 °C for 3 h to obtain 0.32 g of solid, and the recovery rate of V is 87.9%.

[0101] 3) Titanium-tungsten separation

[0102] Take 33 mL of concentrated sulfuric acid with a mass fraction of 90 wt%, add the filter residue, heat and stir for 2 h to obtain a concentrated titanium solution. Under stirring conditions, slowly add a 5 wt% dilute ammonia water solution to it until the pH value is 7, continue to stir for 10 min and then filter to obtain metatitanic acid precipitate and insoluble substances such as WO3, Al(OH)3, and SiO2, and centrifuge and wash 7 times. The washed metatitanic acid precipitate is diluted with 580 mL of deionized water and stirred for 10 min, and then 80 mL of 30% H2O2 solution is added. The temperature is raised to 60 °C and stirred at a constant temperature for 30 min to obtain an orange-yellow titanium peroxide colloidal solution and then filter. The filter residue is insoluble impurities such as WO3, SiO2, and Al(OH)3, and the filter residue is washed with deionized water multiple times, and the washing liquid is incorporated into the filtrate.

[0103] 4) Peroxidation

[0104] The orange-yellow titanium peroxide colloidal solution is heated under reflux at 100 °C for 3 h to obtain a nano-TiO2 sol. The nano-TiO2 sol is dried at 150 °C for 10 h to obtain 25.71 g of solid, and the recovery rate of TiO2 is 88.2%;

[0105] 5) Tungsten separation

[0106] For the filter residue containing WO3, under stirring conditions, add 50 mL of deionized water, then add 13 g of 10% dilute ammonia water, raise the temperature to 20 °C, continue to stir for 3 h and then filter to obtain an ammonium tungstate solution and insoluble substances such as Al(OH)3 and SiO2. Filter, and the filter residue is repeatedly washed, and the washing liquid is incorporated into the filtrate. The filter residue is dried at 150 °C for 2 h, and the obtained powder can be used as an additive material for catalyst shaping. Under stirring conditions, slowly add nitric acid to the filtrate to adjust the pH ≤ 1 to obtain a tungstic acid precipitate, centrifuge and wash 7 times, add 27 mL of deionized water, then add 5 mL of 30 wt% H2O2 solution, stir rapidly, heat under reflux at 100 °C for 3 h to obtain a nano-WO3 sol. The nano-WO3 sol is dried at 150 °C for 10 h to obtain 1.21 g of solid, and the recovery rate of WO3 is 66.4%.

[0107] Example 6

[0108] 1) Pretreatment

[0109] The waste SCR denitration catalyst with mass fractions of V2O5, WO3, and TiO2 being 1 wt%, 5 wt%, and 80 wt% respectively is washed, dried, crushed, and ball-milled into powder particles with a particle size of 325 mesh (45 μm), and then sieved.

[0110] 2) Vanadium dissolution and extraction

[0111] Weigh 36.4 g of the sieved waste SCR denitration catalyst powder, disperse it in 320 mL of deionized water, stir for 10 min, then add 2 mL of H2O2 with a mass fraction of 30 wt%, continue to stir rapidly for 3 h and then filter. The filter residue is repeatedly rinsed with a small amount of deionized water, dried, and cooled, and the washing solution is collected into the filtrate. The filtrate is heated under reflux at 100 °C for 5 h to obtain nano-V2O5 sol, and the nano-V2O5 sol is dried at 250 °C for 3 h to obtain 0.32 g of solid, and the recovery rate of V is 87.9%.

[0112] 3) Titanium and tungsten separation

[0113] Take 33 mL of concentrated sulfuric acid with a mass fraction of 90 wt%, add the filter residue, heat and stir for 2 h to obtain a concentrated titanium solution. Under stirring conditions, slowly add a dilute ammonia water solution with a mass fraction of 5 wt% to it until the pH value reaches 7, continue to stir for 10 min and then filter to obtain metatitanic acid precipitate and insoluble substances such as WO3, Al(OH)3, and SiO2, and centrifuge and wash 7 times. The washed metatitanic acid precipitate is diluted with 580 mL of deionized water and stirred for 10 min, and then 80 mL of H2O2 solution with a mass fraction of 30% is added. The temperature is raised to 60 °C and stirred at a constant temperature for 30 min to obtain an orange-yellow titanium peroxide colloidal solution and then filter. The filter residue is insoluble impurities such as WO3, SiO2, and Al(OH)3, and the filter residue is washed with deionized water multiple times, and the washing solution is incorporated into the filtrate.

[0114] 4) Peroxidation

[0115] The obtained orange-yellow titanium peroxide colloidal solution is heated under reflux at 100 °C for 3 h to obtain nano-TiO2 sol, and the nano-TiO2 sol is dried at 150 °C for 10 h to obtain 25.71 g of solid, and the recovery rate of TiO2 is 88.2%;

[0116] 5) Tungsten separation

[0117] The filter residue containing WO3, under stirring conditions, 50 mL of deionized water was added, then 5.2 g of 10% by mass of dilute ammonia water was added, the temperature was raised to 20 °C, and stirring was continued for 3 h followed by filtration to obtain ammonium tungstate solution and insoluble substances such as Al(OH)3 and SiO2. After filtration, the filter residue was washed repeatedly, and the washing liquid was incorporated into the filtrate. The filter residue was dried at 150 °C for 2 h, and the obtained powder could be used as an additive material for catalyst forming. Under stirring conditions, nitric acid was slowly added to the filtrate to adjust the pH ≤ 1, and the obtained tungstic acid precipitate was centrifugally washed 7 times, 27 mL of deionized water was added, then 5 mL of 30 wt% H2O2 solution was added, and rapid stirring was carried out, followed by heating under reflux at 100 °C for 3 h to obtain nano-WO3 sol. The nano-WO3 sol was dried at 150 °C for 10 h to obtain 1.06 g of solid, and the recovery rate of WO3 was 58.3%.

[0118] Example 7

[0119] 1) Pretreatment

[0120] The waste SCR denitration catalyst with mass fractions of V2O5, WO3, and TiO2 being 1 wt%, 5 wt%, and 80 wt% respectively was cleaned, dried, crushed, and ball-milled to powder particles with a particle size of 325 mesh (45 μm), and then sieved.

[0121] 2) Dissolution and vanadium extraction

[0122] 36.4 g of the sieved waste SCR denitration catalyst powder was weighed and dispersed in 320 mL of deionized water. After stirring for 10 min, 2 mL of 30 wt% H2O2 was added, and rapid stirring was continued for 3 h followed by filtration. The filter residue was repeatedly rinsed with a small amount of deionized water, dried, and cooled, and the washing liquid was collected into the filtrate. The filtrate was heated under reflux at 100 °C for 5 h to obtain nano-V2O5 sol. The nano-V2O5 sol was dried at 250 °C for 3 h to obtain 0.32 g of solid, and the recovery rate of V was 87.9%.

[0123] 3) Titanium-tungsten separation

[0124] 33 mL of 90 wt% concentrated sulfuric acid was taken and added to the filter residue, and heating and stirring were carried out for 2 h to obtain concentrated titanium liquid. Under stirring conditions, 5 wt% dilute ammonia water solution was slowly added dropwise to it until the pH value reached 7, and stirring was continued for 10 min followed by filtration to obtain metatitanic acid precipitate and insoluble substances such as WO3, Al(OH)3, and SiO2, which were centrifugally washed 7 times. The washed metatitanic acid precipitate was diluted with 580 mL of deionized water and stirred for 10 min, then 80 mL of 30% H2O2 solution was added. The temperature was raised to 60 °C and stirred at a constant temperature for 30 min to obtain an orange-yellow titanium peroxide colloidal solution followed by filtration. The filter residue was WO3, SiO2, Al(OH)3 and other insoluble impurities, and the filter residue was washed with deionized water many times, and the washing liquid was incorporated into the filtrate.

[0125] 4) Peroxidation

[0126] An orange-yellow titanium peroxide colloidal solution is obtained, heated under reflux at 100 °C for 3 h to obtain a nano-TiO2 sol, and the nano-TiO2 sol is dried at 150 °C for 10 h to obtain 25.71 g of solid, and the recovery rate of TiO2 is 88.2%;

[0127] 5) Separation of tungsten

[0128] For the filter residue containing WO3, under stirring conditions, 50 mL of deionized water is added, then 10.6 g of 10% by mass of dilute ammonia water is added, the temperature is raised to 40 °C, and stirring is continued for 3 h followed by filtration to obtain an ammonium tungstate solution and insoluble substances such as Al(OH)3 and SiO2. After filtration, the filter residue is washed repeatedly, and the washing liquid is incorporated into the filtrate. The filter residue is dried at 150 °C for 2 h, and the obtained powder can be used as an additive material for catalyst forming. Under stirring conditions, nitric acid is slowly added to the filtrate to adjust the pH ≤ 1, and the obtained tungstic acid precipitate is centrifugally washed 7 times, 27 mL of deionized water is added, then 5 mL of 30 wt% H2O2 solution is added, and rapid stirring is carried out. It is heated under reflux at 100 °C for 3 h to obtain a nano-WO3 sol, and the nano-WO3 sol is dried at 150 °C for 10 h to obtain 1.23 g of solid, and the recovery rate of WO3 is 67.5%.

[0129] Comparative Example 1

[0130] Except that in the pretreatment step 1), the waste SCR denitration catalyst is ball-milled to a particle size of 15 μm, V, Ti, and W are extracted in the same manner as in Example 1. The results show that a large amount of metatitanic acid is contained in the nano-V2O5 sol obtained in the step 2) of extracting V, the extraction rate of V is 91.4%, and the content of metatitanic acid in the product is about 15 wt%.

[0131] Comparative Example 2

[0132] Except that in step 2), the mass ratio of H2O2 to V2O5 is 20:1, V, Ti, and W are extracted in the same manner as in Example 1. The results show that a large amount of metatitanic acid is contained in the nano-V2O5 sol obtained in the step of extracting V, the extraction rate of V is 89.7%, and the content of metatitanic acid in the product is about 12 wt%.

[0133] As mentioned above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for recovering valuable metals Ti, V, and W from waste SCR denitration catalysts, comprising the following steps: 1) Pretreatment The waste SCR denitration catalyst is washed, dried, and then crushed into powder particles with an average particle size of 20 μm to 45 μm; 2) Dissolution and vanadium extraction At room temperature, the powder particles of the waste SCR denitration catalyst obtained in step 1) are dispersed in pure water, the mass fraction of V2O5 in the suspension is controlled to be 0.01 wt% - 0.05 wt%, stirred for 5 to 15 min, and then a H2O2 solution with a mass fraction of 20 wt% to 35 wt% is added. The mass ratio of H2O2 to V2O5 is 2:1 to 20:

1. After continuing to stir rapidly for 0.5 - 2 h, filtration is carried out. The filtrate is a vanadium peroxide solution, and the filter residue is TiO2, WO3, Al2O3, and SiO2. The filter residue is washed and dried for standby. The filtrate is heated under reflux at 100 °C under normal pressure for 3 - 10 h to obtain a nano-V2O5 sol; 3) Titanium-tungsten separation The filter residue containing TiO2 and WO3 obtained in step 2) is dissolved in a concentrated sulfuric acid solution with a mass fraction of 90 wt%. The mass ratio of the concentrated sulfuric acid solution to the filter residue is controlled to be 1.0:1 to 6:

1. It is heated and stirred at 60 to 90 °C for 2 to 6 hours to obtain a concentrated titanium solution. After cooling to room temperature, a dilute ammonia water solution with a mass fraction of 5% - 15% is slowly added dropwise thereto under stirring until the pH value is 6 - 7. Filtration is carried out to obtain a metatitanic acid precipitate and insoluble substances such as WO3, Al(OH)3, and SiO2. It is centrifuged and washed 5 - 8 times. The washed metatitanic acid precipitate is diluted with deionized water to a mass fraction of 1 wt% - 5%, and stirred for 5 - 10 min. Then a H2O2 solution with a mass fraction of 20 wt% to 35 wt% is added. The mass ratio of H2O2 to metatitanic acid is controlled to be 2:1 - 20:

1. It is heated to 60 °C and stirred at a constant temperature for 10 - 30 min to obtain an orange-yellow titanium peroxide colloidal solution, and then filtered. The filter residue is insoluble impurities such as WO3, SiO2, and Al(OH)3. The filter residue is washed with deionized water multiple times, and the washing solution is incorporated into the filtrate; 4) Peroxidation The titanium peroxide colloidal solution obtained in step 3) is heated under reflux at 100 °C under normal pressure for 3 - 10 h to obtain a nano-TiO2 sol; 5) Tungsten separation Under stirring conditions, slowly drop dilute ammonia water with a mass fraction of 3% to 20% into the WO3-containing filter residue obtained in step 3), control the molar ratio of WO3 to NH3 to be 1:2 to 1:15, heat up to 20°C to 100°C, and stir and react for 2 to 3 h to obtain an ammonium tungstate solution and insoluble substances of Al(OH)3 and SiO2. Filter, wash the filter residue repeatedly and dry it at 150°C, and incorporate the washing liquid into the filtrate. Under stirring conditions, slowly add nitric acid to the filtrate to adjust the pH ≤ 1. The obtained tungstic acid precipitate is centrifugally washed 5 to 10 times, add deionized water until the mass fraction of tungstic acid is 1 wt% to 5 wt%, then add an H2O2 solution with a mass fraction of 20 wt% to 35 wt%, control the mass ratio of H2O2 to tungstic acid to be 2:1 to 10:1, stir rapidly, and heat and reflux at 100°C under normal pressure for 3 to 10 h to obtain a nano-WO3 sol.

2. The method according to claim 1, wherein In step 1), the average particle size of the powder particles is 20 μm to 30 μm.

3. The method according to claim 1, wherein In step 1), the comminution adopts a comminution method of crushing, grinding, and extrusion.

4. The method according to claim 3, characterized in that In step 1), the comminution adopts ball milling.

5. The method according to claim 1, characterized in that, In step 2), the mass fraction concentration of the added H2O2 solution is 30 wt%; the mass ratio of H2O2 to V2O5 is 2:1 to 15:

1.

6. The method according to claim 5, wherein In step 2), the mass ratio of H2O2 to V2O5 is 2:1 to 10:

1.

7. The method according to claim 1, wherein In step 3), the mass ratio of the concentrated sulfuric acid solution to the filter residue is 1.0:1 to 6:1; In step 3), the mass fraction concentration of the added H2O2 solution is 30 wt%; In step 3), the mass ratio of H2O2 to metatitanic acid is 2:1 to 15:

1.

8. The method according to claim 7, wherein In step 3), the mass ratio of the concentrated sulfuric acid solution to the filter residue is 1.5:1 to 3:1; In step 3), the mass ratio of H2O2 to metatitanic acid is 2:1 to 10:

1.

9. The method according to claim 1, characterized in that In step 5), the mass fraction concentration of the dilute ammonia water is 5% to 15%; In step 5), the molar ratio of WO3 to NH3 is 1:2 to 1:10; In step 5), the main components of the filter residue are Al(OH)3 and SiO2, and the powder obtained after drying is used as an additive material for catalyst forming.

10. The method according to claim 9, wherein In step 5), the molar ratio of WO3 to NH3 is 1:2 to 1:

5.

11. A nano-V2O5 sol product, wherein the nano-V2O5 sol is obtained according to the method described in any one of claims 1 to 10 of this right.

12. A nano-TiO2 sol product, wherein the nano-TiO2 sol is obtained according to the method described in any one of claims 1 to 10 of this right.

13. A nano-WO3 sol product, wherein the nano-WO3 sol is obtained according to the method described in any one of claims 1 to 10 of this right.

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