A method for recovering valuable metals from waste denitration catalyst

Abstract

The invention provides a method for recovering valuable metals from a waste denitration catalyst, comprising the following steps: adding a hydrogen bond acceptor, a hydrogen bond donor and distilled water into a sealed flask to prepare a primary deep eutectic solvent; ball-milling and sieving the waste denitration catalyst to obtain a ball-milled material; adding the ball-milled material into the primary deep eutectic solvent, heating and leaching, centrifugation and separation to obtain a leachate and a leach residue; adding an ammonium salt precipitant into the leachate for reaction to obtain a precipitate and a precipitate; washing and drying the precipitate with 2% NH4Cl to obtain ammonium metavanadate; performing reduced pressure distillation on the precipitate, condensing and refluxing to obtain an ammonium salt mixture and a regenerated deep eutectic solvent, and recycling the mixture; adding ammonia water into the leached residue, adjusting the pH value with sodium hydroxide, performing high-energy ball milling to obtain a ball-milled liquid and a ball-milled residue; performing evaporation and crystallization on the ball-milled liquid to obtain ammonium metatungstate; washing and drying the ball-milled residue with ethanol and distilled water to obtain a titanium-rich residue with a titanium dioxide phase structure.

Description

Technical Field

[0001] The invention belongs to the technical field of waste catalyst recycling, and in particular relates to a method for recovering valuable metals from waste denitration catalysts. Background Art

[0002] SCR (selective catalytic reduction) denitration catalyst (with TiO2 as carrier and loaded with oxides such as V2O5-WO3) is widely used in coal-fired power generation units due to its advantages of low cost, high efficiency and reliable operation, which effectively controls the emission of NOx in flue gas. Its design life is generally 3 years. As more industries put forward requirements for NOx emission standards, the use of SCR denitration catalysts has increased year by year, and a large number of waste SCR denitration catalysts have been piled up. Among them, the waste SCR denitration catalyst contains valuable elements such as V, W, and Ti, which have high leaching toxicity. If not properly disposed of, it will cause great waste of resources and environmental pollution; the recovery rate of titanium dioxide (TiO2), which accounts for 80% to 85% of the mass ratio of SCR denitration catalyst, is only 30% to 50%, which limits the efficiency and economy of resource recycling to a certain extent.

[0003] CN115717201A discloses a method for recovering metal oxides from waste SCR denitration catalysts, comprising the following steps: mixing the pretreated catalyst with concentrated alkali, adding sodium carbonate, stirring the reaction thoroughly and filtering to obtain a crude titanate salt filter cake and a filtrate, washing the crude titanate salt filter cake to obtain purified titanate, and leaching the titanate with hydrochloric acid for titanium recovery; removing impurities from the filtrate containing vanadium and tungsten, recovering vanadium, precipitating tungsten, and recovering tungsten. However, this method first converts the titanium element in the carrier material into titanate, and then recovers titanium through hydrochloric acid leaching, which changes the carrier structure phase.

[0004] CN111020193A discloses a method for recovering vanadium, tungsten and titanium elements from waste SCR denitration catalysts, which comprises the steps of raw material pretreatment, vanadium separation and recovery, tungsten separation and recovery and titanium recovery, wherein the waste catalyst is leached with a weak acid and a small amount of fatty acid polyoxyethylene ester to extract vanadium element, the leached slag is mixed with sodium salt and roasted to extract tungsten element, and then the crude titanium slag is washed with dilute sulfuric acid and roasted and dried to obtain titanium-rich slag, and there is a transformation of the titanium phase in the carrier material during the roasting process.

[0005] CN116219157A discloses a method for recovering vanadium, tungsten and titanium from waste SCR catalyst by low-temperature sodium calcination, comprising the following steps: mixing sodium carbonate with crushed waste SCR catalyst, grinding to obtain ground material; pressing the ground material into blocks and calcining to obtain calcined material; crushing the calcined material, adding it to hot water for water leaching reaction, and performing solid-liquid separation after the reaction. The solid phase is a leaching residue containing titanium, and the liquid phase is a leaching solution containing vanadium and tungsten. The waste SCR catalyst is mixed with sodium carbonate and calcined at low temperature, and then leached in hot water. The vanadium and tungsten leaching rates can be greater than 95%, but the main component of the titanium-containing leaching residue obtained is sodium metatitanate, and a titanium dioxide product needs to be obtained through a longer process of acid hydrolysis-hydrolysis-calcination.

[0006] While the above method achieves efficient leaching and extraction of valuable metals such as vanadium and tungsten, it is generally accompanied by a phase transformation of titanium dioxide. Titanium dioxide is converted into titanate and then recycled by acid dissolution and hydrolysis. This process destroys the original phase of the carrier titanium dioxide and discharges a large amount of acid and alkali waste liquid, resulting in a low recovery rate of titanium dioxide.

[0007] Therefore, how to provide a method for recovering valuable metals from waste denitrification catalysts, which can efficiently and selectively separate and extract vanadium and tungsten valuable metals while stabilizing the physical structure of the carrier titanium dioxide, is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0008] The object of the present invention is to provide a method for recovering valuable metals from waste denitration catalysts to solve at least one of the above technical problems.

[0009] To achieve the above-mentioned object, the first aspect of the present invention provides a method for recovering valuable metals from waste denitration catalysts, the method comprising the following steps: S1, adding a hydrogen bond acceptor, a hydrogen bond donor and distilled water into a sealed flask, stirring and reacting at 80-100°C, cooling to room temperature, and obtaining a primary deep eutectic solvent; S2, ball-milling and sieving the waste denitration catalyst to obtain a ball-milled material; S3, adding the ball-milled material to the primary deep eutectic solvent, sealing, heating and stirring to react, centrifuging, and obtaining a leachate and a leachate residue; S4, adding an ammonium salt precipitant to the leachate, stirring and reacting at room temperature, filtering, and obtaining a precipitate and a precipitate; S5, using 2% NH4C l. Wash the precipitate and dry it to obtain ammonium metavanadate; S6. Perform vacuum distillation on the precipitate, condense and reflux it to obtain an ammonium salt mixture and a regenerated deep eutectic solvent; the ammonium salt mixture is reused as the ammonium salt precipitant; distilled water is added to the regenerated deep eutectic solvent and reused as the original deep eutectic solvent; S7. Ammonia water is added to the leached residue, the pH value is adjusted to 8-14 with sodium hydroxide, and high-energy ball milling is performed to obtain a ball milling liquid and a ball milling residue; S8. The ball milling liquid is evaporated and crystallized to obtain ammonium metatungstate; S9. The ball milling residue is washed with ethanol to obtain a washing; the washing is washed with distilled water, and dried to obtain titanium-rich slag.

[0010] In the first aspect, in S1, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:2 to 4:1, the amount of distilled water added is 10% to 50% of the total mass of the hydrogen bond acceptor and the hydrogen bond donor; and the stirring reaction time is 60 to 120 minutes.

[0011] In the first aspect, the hydrogen bond acceptor includes at least one of polyethylene glycol 400 and choline chloride; the hydrogen bond donor includes at least one of p-toluenesulfonic acid, malonic acid, glycolic acid, malic acid, lactic acid, tartaric acid, glycolic acid, and citric acid.

[0012] In the first aspect, in S2, the mesh size of the sieve used for the sieving is 200 meshes.

[0013] In the first aspect, in S3, the conditions of the heating and stirring reaction include: a heating temperature of 60 to 80° C., a stirring time of 9 to 15 hours; and a liquid-to-solid ratio of the native deep eutectic solvent to the ball mill material of 5:1 to 50:1.

[0014] In the first aspect, in S4, the conditions for the room temperature stirring reaction include: the reaction time is 10 to 90 min, the stirring speed is 400 to 800 rpm; the ammonium salt precipitant is composed of ammonium chloride, ammonium sulfate and ammonium nitrate, and the molar ratio of the ammonium chloride, the ammonium sulfate and the ammonium nitrate is 2:1:1.

[0015] In the first aspect, in S5, the washing is performed three times; and the drying conditions include: a drying temperature of 100° C. and a drying time of 6 hours.

[0016] In the first aspect, in S6, the conditions of the reduced pressure distillation include: the reduced pressure distillation temperature is 60-100°C, the reduced pressure distillation time is 0.5-3h, the stirring speed is 400-600rpm, and the pressure is 0.03-0.08MPa; the supplementary content of the distilled water is 10%-50% of the mass of the regenerated deep eutectic solvent.

[0017] In the first aspect, in S7, the mass concentration of the ammonia water is 10% to 30%; the conditions of the high-energy ball milling include: a liquid-solid ratio of 1:4 to 1:1, a ball-to-material ratio of 10:1 to 30:1, and a ball milling time of 30 to 180 min.

[0018] In the first aspect, in S8, the evaporation crystallization conditions include: the evaporation crystallization temperature is 105° C., and the evaporation crystallization time is 3.5 h.

[0019] Beneficial effects:

[0020] The present invention provides a method for recovering valuable metals from waste denitration catalysts. First, a hydrogen bond acceptor, a hydrogen bond donor and distilled water are placed at 80-100° C. for sealed reaction to obtain a low melting point and highly selective primary deep eutectic solvent; the waste denitration catalyst is ball-milled and sieved to obtain a ball mill material with uniform particle size; secondly, the ball mill material is added to the primary deep eutectic solvent, heated and leached to dissolve the V-containing components in the ball mill material, and centrifuged to obtain a V-containing leaching solution and a W- and Ti-containing leaching residue; then, an ammonium salt precipitant is added to the V-containing leaching solution for reaction, and after filtering, the leaching residue is filtered and filtered. A precipitate and a precipitate liquid are obtained, and the precipitate is washed with 2% NH4Cl and dried to obtain high-purity ammonium metavanadate; the precipitate liquid is subjected to reduced pressure distillation, condensation and reflux to obtain an ammonium salt mixture and a regenerated deep eutectic solvent, and the mixture is recycled; finally, ammonia water is added to the leached residue containing W and Ti, and the pH value is adjusted to 8-14 with sodium hydroxide, and W and Ti in the leached residue are separated by high-energy ball milling to obtain a ball milling liquid and a ball milling residue, and the ball milling liquid is subjected to evaporation and crystallization to obtain high-purity ammonium metatungstate, and the ball milling residue is washed with ethanol and distilled water and dried to obtain a rich residue with a phase structure maintained. The present invention creatively prepares a mild native deep eutectic solvent with efficient selective separation of vanadium in waste denitrification catalysts, and then separates the V-containing component by heating leaching; separates the W-containing component and titanium dioxide by adjusting the pH value and high-energy ball milling. That is, the present application can not only efficiently and selectively separate and extract V and W through native deep eutectic solvent and high-energy ball milling, but also stabilize the physical phase structure of the titanium dioxide carrier, thus providing a basis for the subsequent high-value application of titanium dioxide.

[0021] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A process for recovering valuable metals from waste denitration catalysts in this application Figure 1 ;

[0024] Figure 2 A process for recovering valuable metals from waste denitration catalysts in this application Figure 2 . DETAILED DESCRIPTION

[0025] The present invention will be described in detail below in conjunction with specific implementations and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific implementations and examples are used to illustrate the present invention, rather than to limit the present invention.

[0026] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. In the event of a conflict, the present specification takes precedence.

[0027] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or obtained by existing methods.

[0028] See also Figure 1-2 The present application provides a method for recovering valuable metals from a waste denitration catalyst, the method comprising the following steps:

[0029] S1. Add a hydrogen bond acceptor, a hydrogen bond donor and distilled water into a sealed flask, stir and react at 80-100°C, and cool to room temperature to obtain a native deep eutectic solvent;

[0030] S2, ball-milling and sieving the waste denitration catalyst to obtain a ball-milled material;

[0031] S3, adding the ball mill to the native deep eutectic solvent, sealing, heating and stirring for reaction, and centrifuging to obtain a leachate and a leach residue;

[0032] S4, adding an ammonium salt precipitant to the leachate, stirring the reaction at room temperature, and filtering to obtain a precipitate and a precipitate;

[0033] S5, washing the precipitate with 2% NH4Cl, and drying to obtain ammonium metavanadate;

[0034] S6, performing vacuum distillation on the precipitate, condensing and refluxing to obtain an ammonium salt mixture and a regenerated deep eutectic solvent; the ammonium salt mixture is reused as the ammonium salt precipitant; distilled water is added to the regenerated deep eutectic solvent and reused as the primary deep eutectic solvent;

[0035] S7, adding ammonia water to the leached residue, adjusting the pH value to 8-14 with sodium hydroxide, and performing high-energy ball milling to obtain a ball milling liquid and ball milling residue;

[0036] S8, evaporating and crystallizing the ball milling liquid to obtain ammonium metatungstate;

[0037] S9, washing the ball mill residue with ethanol to obtain a washing product; washing the washing product with distilled water, and drying to obtain titanium-rich slag.

[0038] Specifically, the present invention provides a method for recovering valuable metals from waste denitration catalysts. First, a hydrogen bond acceptor, a hydrogen bond donor and distilled water are placed in a sealed reaction at 80-100° C. to obtain a low melting point and highly selective primary deep eutectic solvent; the waste denitration catalyst is ball-milled and sieved to obtain a ball mill material with uniform particle size; secondly, the ball mill material is added to the primary deep eutectic solvent, heated and leached to dissolve the V-containing components in the ball mill material, and centrifuged to obtain a V-containing leaching solution and a leaching residue containing W and Ti; then, an ammonium salt precipitant is added to the V-containing leaching solution for reaction. After filtering, a precipitate and a precipitate liquid are obtained. The precipitate is washed with 2% NH4Cl and dried to obtain high-purity ammonium metavanadate. The precipitate liquid is subjected to reduced pressure distillation, condensation and reflux to obtain an ammonium salt mixture and a regenerated deep eutectic solvent, which are recycled. Finally, ammonia water is added to the leached residue containing W and Ti, and the pH value is adjusted to 8-14 with sodium hydroxide. The W and Ti in the leached residue are separated by high-energy ball milling to obtain a ball milling liquid and a ball milling residue. The ball milling liquid is subjected to evaporation and crystallization to obtain high-purity ammonium metatungstate. The ball milling residue is washed with ethanol and distilled water and dried to obtain a rich residue with a phase structure maintained. The present invention creatively prepares a primary deep eutectic solvent that is highly selective and mild for waste denitration catalysts, and then separates the V-containing component by heating and leaching; and separates the W-containing component and titanium dioxide by adjusting the pH value and high-energy ball milling. That is, the present application can not only efficiently and selectively separate and extract V and W through the primary deep eutectic solvent, but also stabilize the physical phase structure of the titanium dioxide carrier, thus providing a basis for the subsequent high-value application of titanium dioxide.

[0039] In some possible embodiments, in S1, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:2 to 4:1, the amount of distilled water added is 10% to 50% of the total mass of the hydrogen bond acceptor and the hydrogen bond donor; and the stirring reaction time is 60 to 120 min.

[0040] In some possible embodiments, the hydrogen bond acceptor includes at least one of polyethylene glycol 400 and choline chloride; the hydrogen bond donor includes at least one of p-toluenesulfonic acid, malonic acid, glycolic acid, malic acid, lactic acid, tartaric acid, glycolic acid, and citric acid.

[0041] This is because, in the present application, by selecting different hydrogen bond acceptors and different hydrogen bond donors, adjusting the molar ratio of hydrogen bond acceptors to hydrogen bond donors, and adding an appropriate amount of distilled water, a closed reaction is carried out to form a homogeneous phase to obtain a native deep eutectic solvent, and through continuous experiments, the leaching effect of the native deep eutectic solvent on the waste deNOx catalyst is explored, and finally the types of hydrogen bond acceptors and hydrogen bond donors, and the molar ratio of hydrogen bond acceptors to hydrogen bond donors are determined to be 1:2 to 4:1, the amount of distilled water added is 10% to 50% of the total mass of the hydrogen bond acceptors and hydrogen bond donors, the closed reaction temperature is 80 to 100°C, and the reaction time is 60 to 120 min. The native deep eutectic solvent formed under such conditions has a low melting point and high selectivity for the valuable metal vanadium in the waste deNOx catalyst.

[0042] In some possible embodiments, in S2, the mesh size of the sieve used for screening is 200 meshes.

[0043] Those skilled in the art will appreciate that screening the waste denitration catalyst after ball milling through a 200-mesh sieve can control the particle size of the waste denitration catalyst ball mill material, so that it can fully contact the native deep eutectic solvent and improve the leaching efficiency.

[0044] In some possible embodiments, in S3, the conditions of the heating and stirring reaction include: a heating temperature of 60 to 80° C., a stirring time of 9 to 15 hours; and a liquid-to-solid ratio of the native deep eutectic solvent to the ball mill material of 5:1 to 50:1.

[0045] This is because the native deep eutectic solvent in the present application has good solubility for V-containing components. By controlling the heating temperature to 60-80°C, the stirring time to 9-15h, and the liquid-solid ratio of the native deep eutectic solvent to the ball mill to be 5:1-50:1, the native deep eutectic solvent can extract the V-containing components from the waste deNOx catalyst ball mill (forming a leachate), and will not or very little dissolve the W-containing components and TiO2 (forming a leachate residue), thereby achieving the efficient selectivity of the native deep eutectic solvent for the valuable metals in the waste deNOx catalyst ball mill.

[0046] In some possible embodiments, in S4, the conditions for the room temperature stirring reaction include: a reaction time of 10 to 90 min, a stirring speed of 400 to 800 rpm; the ammonium salt precipitant is composed of ammonium chloride, ammonium sulfate and ammonium nitrate, and the molar ratio of the ammonium chloride, the ammonium sulfate and the ammonium nitrate is 2:1:1.

[0047] Those skilled in the art can understand that the leachate contains component V and native deep eutectic solvent. In order to purify the component containing V, an ammonium salt precipitant is added to precipitate the component containing V from the leachate, thereby obtaining a precipitate and a precipitate.

[0048] In some possible embodiments, in S5, the washing is performed three times; and the drying conditions include: a drying temperature of 100° C. and a drying time of 6 hours.

[0049] In some possible embodiments, in S6, the conditions of the reduced pressure distillation include: the reduced pressure distillation temperature is 60-100°C, the reduced pressure distillation time is 0.5-3h, the stirring speed is 400-600rpm, and the pressure is 0.03-0.08MPa; the supplementary content of the distilled water is 10%-50% of the mass of the regenerated deep eutectic solvent.

[0050] This is because, after the precipitate is distilled under reduced pressure and condensed and refluxed, the deep eutectic solvent and water are separated, thereby obtaining a regenerated deep eutectic solvent with changed melting point and boiling point. By adding distilled water to the regenerated deep eutectic solvent, it reaches the ratio of the original deep eutectic solvent, restoring its lower melting point and high selectivity; the ammonium salt mixture is precipitated from the precipitate, collected, and can be used as an ammonium salt precipitant to treat the leachate.

[0051] In some possible embodiments, in S7, the mass concentration of the ammonia water is 10% to 30%; the conditions of the high-energy ball milling include: a liquid-to-solid ratio of 1:4 to 1:1, a ball-to-material ratio of 10:1 to 30:1, and a ball milling time of 30 to 180 min.

[0052] Those skilled in the art can understand that adding ammonia water with a mass concentration of 10% to 30% to the leached residue and controlling the pH value to 8 to 14 by sodium hydroxide can ensure that the W-containing component is completely dissolved to form an ammonium metatungstate solution without destroying the physical structure of titanium dioxide; then high-energy ball milling can be used to increase the dissolution rate of the W-containing component, thereby improving work efficiency.

[0053] In some possible embodiments, in S8, the evaporation crystallization conditions include: an evaporation crystallization temperature of 105° C. and an evaporation crystallization time of 3.5 h.

[0054] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0055] Example 1

[0056] A method for recovering valuable metals from a waste denitration catalyst comprises the following steps:

[0057] (1) Constant temperature stirring: choline chloride and p-toluenesulfonic acid are mixed in a molar ratio of 1:1, and the added mass of distilled water is 30% of the total mass of choline chloride and p-toluenesulfonic acid. The mixture is added into a sealed flask and placed in a heat collecting stirring device for stirring reaction to form a uniform phase. The reaction temperature is 80° C. and the stirring time is 110 min. After the reaction is completed, the mixture is cooled to room temperature to obtain a native deep eutectic solvent.

[0058] (2) ball milling and screening: the waste denitration catalyst is ball milled and sieved through a 200-mesh sieve to obtain a ball mill material;

[0059] (3) Heating leaching: Add ball milled material to the original deep eutectic solvent with a liquid-to-solid ratio of 10:1, seal it, and place it in a heat collecting stirring device for heating and stirring reaction. The heating temperature is 70°C and the stirring time is 15 hours. After the reaction is completed, centrifuge to obtain a leachate containing V and a leach residue containing W and Ti;

[0060] (4) ammonium salt precipitation: adding an ammonium salt precipitant (ammonium chloride, ammonium sulfate and ammonium nitrate in a molar ratio of 2:1:1) to the V-containing leachate, reacting at room temperature for 60 min, stirring at a speed of 500 rpm, and filtering to obtain a precipitate and a precipitate;

[0061] (5) Washing and drying: The precipitate was washed three times with 2% NH4Cl and dried in an oven at 100°C for 6 h to obtain ammonium metavanadate;

[0062] (6) Vacuum distillation: The precipitate is subjected to vacuum distillation and condensation reflux to obtain an ammonium salt mixture and a regenerated deep eutectic solvent, the vacuum distillation temperature is 60° C., the vacuum distillation time is 0.5 h, the stirring speed is 600 rpm, and the pressure is 0.05 MPa; the ammonium salt mixture is reused in the ammonium salt precipitation step as an ammonium salt precipitant; distilled water is added to the regenerated deep eutectic solvent and reused as the original deep eutectic solvent in the heating leaching step, and the added content of distilled water is 30% of the mass of the regenerated deep eutectic solvent;

[0063] (7) High-energy ball milling: adding 25% ammonia water to the leached residue containing W and Ti, adjusting the pH value to 13 with sodium hydroxide, and performing high-energy ball milling to obtain a ball milling liquid and ball milling residue; wherein the process conditions of the high-energy ball milling are: liquid-to-solid ratio 1:1, ball-to-material ratio 25:1, and ball milling time 180 min;

[0064] (8) Evaporation and crystallization: The ball milling liquid is evaporated and crystallized to obtain ammonium metatungstate; wherein the conditions of evaporation and crystallization are: evaporation and crystallization temperature is 105° C., and evaporation and crystallization time is 3.5 h;

[0065] (9) Washing and drying: The ball mill residue is washed with ethanol to obtain a washing product; the washing product is washed with distilled water and dried to obtain titanium-rich slag.

[0066] The test results show that the leaching rate of vanadium is 96.8%, while the leaching rates of titanium and tungsten are 0.12% and 0.096% respectively; the recovery rates of vanadium and tungsten are 99.5% and 98.6% respectively.

[0067] Example 2

[0068] A method for recovering valuable metals from a waste denitration catalyst comprises the following steps:

[0069] (1) Constant temperature stirring: polyethylene glycol 400 and p-toluenesulfonic acid are mixed in a molar ratio of 1:2, and the added mass of distilled water is 20% of the total mass of polyethylene glycol 400 and p-toluenesulfonic acid. The mixture is added into a sealed flask and placed in a heat collecting stirring device for stirring reaction to form a uniform phase. The reaction temperature is 90° C. and the stirring time is 120 min. After the reaction is completed, the mixture is cooled to room temperature to obtain a native deep eutectic solvent.

[0070] (2) ball milling and screening: the waste denitration catalyst is ball milled and sieved through a 200-mesh sieve to obtain a ball mill material;

[0071] (3) Heating leaching: Add ball milled material to the original deep eutectic solvent with a liquid-to-solid ratio of 20:1, seal it, and place it in a heat collecting stirring device for heating and stirring reaction. The heating temperature is 80°C and the stirring time is 12 hours. After the reaction is completed, centrifuge to obtain a leachate containing V and a leach residue containing W and Ti;

[0072] (4) ammonium salt precipitation: adding an ammonium salt precipitant (ammonium chloride, ammonium sulfate and ammonium nitrate in a molar ratio of 2:1:1) to the V-containing leachate, reacting at room temperature for 90 min, stirring at a speed of 800 rpm, and filtering to obtain a precipitate and a precipitate;

[0073] (5) Washing and drying: The precipitate was washed three times with 2% NH4Cl and dried in an oven at 100°C for 6 h to obtain ammonium metavanadate;

[0074] (6) Vacuum distillation: The precipitate is subjected to vacuum distillation and condensation reflux to obtain an ammonium salt mixture and a regenerated deep eutectic solvent, the vacuum distillation temperature is 70° C., the vacuum distillation time is 1.5 h, the stirring speed is 450 rpm, and the pressure is 0.04 MPa; the ammonium salt mixture is reused in the ammonium salt precipitation step as an ammonium salt precipitant; distilled water is added to the regenerated deep eutectic solvent and reused as the original deep eutectic solvent in the heating leaching step, and the added content of distilled water is 20% of the mass of the regenerated deep eutectic solvent;

[0075] (7) High-energy ball milling: adding 20% ​​ammonia water to the leached residue containing W and Ti, adjusting the pH value to 8 with sodium hydroxide, and performing high-energy ball milling to obtain a ball milling liquid and ball milling residue; wherein the process conditions of the high-energy ball milling are: liquid-to-solid ratio 1:2, ball-to-material ratio 25:1, and ball milling time 48 min;

[0076] (8) Evaporation and crystallization: The ball milling liquid is evaporated and crystallized to obtain ammonium metatungstate; wherein the conditions of evaporation and crystallization are: evaporation and crystallization temperature is 105° C., and evaporation and crystallization time is 3.5 h;

[0077] (9) Washing and drying: The ball mill residue is washed with ethanol to obtain a washing product; the washing product is washed with distilled water and dried to obtain titanium-rich slag.

[0078] The test results show that the vanadium leaching rate is 94.3%, while the titanium and tungsten leaching rates are 0.07% and 0.032% respectively; the recovery rates of vanadium and tungsten are 98.3% and 99.3% respectively.

[0079] Example 3

[0080] A method for recovering valuable metals from a waste denitration catalyst comprises the following steps:

[0081] (1) Constant temperature stirring: choline chloride and oxalic acid are mixed in a molar ratio of 3:1, and the added mass of distilled water is 28% of the total mass of choline chloride and oxalic acid. The mixture is added into a sealed flask and placed in a heat collecting stirring device for stirring reaction to form a uniform phase. The reaction temperature is 85° C. and the stirring time is 86 min. After the reaction is completed, the mixture is cooled to room temperature to obtain a native deep eutectic solvent.

[0082] (2) ball milling and screening: the waste denitration catalyst is ball milled and sieved through a 200-mesh sieve to obtain a ball mill material;

[0083] (3) Heating leaching: Add ball milled material to the original deep eutectic solvent with a liquid-to-solid ratio of 5:1, seal it, and place it in a heat collecting stirring device for heating and stirring reaction. The heating temperature is 75°C and the stirring time is 9.5 hours. After the reaction is completed, centrifuge to obtain a leachate containing V and a leach residue containing W and Ti;

[0084] (4) ammonium salt precipitation: adding an ammonium salt precipitant (ammonium chloride, ammonium sulfate and ammonium nitrate in a molar ratio of 2:1:1) to the V-containing leachate, reacting at room temperature for 75 min, stirring at a speed of 650 rpm, and filtering to obtain a precipitate and a precipitate;

[0085] (5) Washing and drying: The precipitate was washed three times with 2% NH4Cl and dried in an oven at 100°C for 6 h to obtain ammonium metavanadate;

[0086] (6) Vacuum distillation: The precipitate is subjected to vacuum distillation and condensation reflux to obtain an ammonium salt mixture and a regenerated deep eutectic solvent, the vacuum distillation temperature is 85° C., the vacuum distillation time is 2.5 h, the stirring speed is 400 rpm, and the pressure is 0.03 MPa; the ammonium salt mixture is reused in the ammonium salt precipitation step as an ammonium salt precipitant; distilled water is added to the regenerated deep eutectic solvent and reused as the original deep eutectic solvent in the heating leaching step, and the added content of distilled water is 28% of the mass of the regenerated deep eutectic solvent;

[0087] (7) High-energy ball milling: adding 10% ammonia water to the leached residue containing W and Ti, adjusting the pH value to 11 with sodium hydroxide, and performing high-energy ball milling to obtain a ball milling liquid and ball milling residue; wherein the process conditions of the high-energy ball milling are: liquid-to-solid ratio 1:2.4, ball-to-material ratio 30:1, and ball milling time 156 min;

[0088] (8) Evaporation and crystallization: The ball milling liquid is evaporated and crystallized to obtain ammonium metatungstate; wherein the conditions of evaporation and crystallization are: evaporation and crystallization temperature is 105° C., and evaporation and crystallization time is 3.5 h;

[0089] (9) Washing and drying: The ball mill residue is washed with ethanol to obtain a washing product; the washing product is washed with distilled water and dried to obtain titanium-rich slag.

[0090] The test results show that the vanadium leaching rate is 95.8%, while the titanium and tungsten leaching rates are 0.07% and 0.051% respectively; the recovery rates of vanadium and tungsten are 99.2% and 98.7% respectively.

[0091] Example 4

[0092] A method for recovering valuable metals from a waste denitration catalyst comprises the following steps:

[0093] (1) Constant temperature stirring: choline chloride and malonic acid are mixed in a molar ratio of 3:2, and the added mass of distilled water is 15% of the total mass of choline chloride and malonic acid. The mixture is added into a sealed flask and placed in a heat collecting stirring device for stirring reaction to form a uniform phase. The reaction temperature is 94° C. and the stirring time is 78 min. After the reaction is completed, the mixture is cooled to room temperature to obtain a native deep eutectic solvent.

[0094] (2) ball milling and screening: the waste denitration catalyst is ball milled and sieved through a 200-mesh sieve to obtain a ball mill material;

[0095] (3) Heating leaching: Add ball milled material to the original deep eutectic solvent with a liquid-to-solid ratio of 40:1, seal it, and place it in a heat collecting stirring device for heating and stirring reaction. The heating temperature is 73°C and the stirring time is 10.6 hours. After the reaction is completed, centrifuge to obtain a leachate containing V and a leach residue containing W and Ti;

[0096] (4) ammonium salt precipitation: adding an ammonium salt precipitant (ammonium chloride, ammonium sulfate and ammonium nitrate in a molar ratio of 2:1:1) to the V-containing leachate, reacting at room temperature for 45 min at a stirring speed of 550 rpm, and filtering to obtain a precipitate and a precipitate;

[0097] (5) Washing and drying: The precipitate was washed three times with 2% NH4Cl and dried in an oven at 100°C for 6 h to obtain ammonium metavanadate;

[0098] (6) Vacuum distillation: The precipitate is subjected to vacuum distillation and condensation reflux to obtain an ammonium salt mixture and a regenerated deep eutectic solvent, the vacuum distillation temperature is 94° C., the vacuum distillation time is 1.8 h, the stirring speed is 560 rpm, and the pressure is 0.07 MPa; the ammonium salt mixture is reused in the ammonium salt precipitation step as an ammonium salt precipitant; distilled water is added to the regenerated deep eutectic solvent and reused as the original deep eutectic solvent in the heating leaching step, and the added content of distilled water is 15% of the mass of the regenerated deep eutectic solvent;

[0099] (7) High-energy ball milling: adding 15% ammonia water to the leached residue containing W and Ti, adjusting the pH value to 9 with sodium hydroxide, and performing high-energy ball milling to obtain a ball milling liquid and ball milling residue; wherein the process conditions of the high-energy ball milling are: liquid-to-solid ratio 1:3.2, ball-to-material ratio 18:1, and ball milling time 65 min;

[0100] (8) Evaporation and crystallization: The ball milling liquid is evaporated and crystallized to obtain ammonium metatungstate; wherein the conditions of the evaporation and crystallization are: the evaporation and crystallization temperature is 105° C., and the evaporation and crystallization time is 3.5 h;

[0101] (9) Washing and drying: The ball mill residue is washed with ethanol to obtain a washing product; the washing product is washed with distilled water and dried to obtain titanium-rich slag.

[0102] The test results show that the vanadium leaching rate is 97.2%, while the titanium and tungsten leaching rates are 0.14% and 0.048% respectively; the recovery rates of vanadium and tungsten are 98.5% and 99.3% respectively.

[0103] Example 5

[0104] A method for recovering valuable metals from a waste denitration catalyst comprises the following steps:

[0105] (1) Constant temperature stirring: choline chloride and citric acid are mixed at a molar ratio of 4:1, and the added mass of distilled water is 23% of the total mass of choline chloride and citric acid. The mixture is added into a sealed flask and placed in a heat collecting stirring device for stirring reaction to form a uniform phase. The reaction temperature is 87° C. and the stirring time is 90 min. After the reaction is completed, the mixture is cooled to room temperature to obtain a native deep eutectic solvent.

[0106] (2) ball milling and screening: the waste denitration catalyst is ball milled and sieved through a 200-mesh sieve to obtain a ball mill material;

[0107] (3) Heating leaching: Add ball milled material to the original deep eutectic solvent with a liquid-to-solid ratio of 35:1, seal it, and place it in a heat collecting stirring device for heating and stirring reaction. The heating temperature is 65°C and the stirring time is 14.5 hours. After the reaction is completed, centrifuge to obtain a leachate containing V and a leach residue containing W and Ti;

[0108] (4) ammonium salt precipitation: adding an ammonium salt precipitant (ammonium chloride, ammonium sulfate and ammonium nitrate in a molar ratio of 2:1:1) to the V-containing leachate, reacting at room temperature for 20 min at a stirring speed of 480 rpm, and filtering to obtain a precipitate and a precipitate;

[0109] (5) Washing and drying: The precipitate was washed three times with 2% NH4Cl and dried in an oven at 100°C for 6 h to obtain ammonium metavanadate;

[0110] (6) Vacuum distillation: The precipitate is subjected to vacuum distillation and condensation reflux to obtain an ammonium salt mixture and a regenerated deep eutectic solvent, the vacuum distillation temperature is 83° C., the vacuum distillation time is 1.25 h, the stirring speed is 490 rpm, and the pressure is 0.06 MPa; the ammonium salt mixture is reused in the ammonium salt precipitation step as an ammonium salt precipitant; distilled water is added to the regenerated deep eutectic solvent and reused as the original deep eutectic solvent in the heating leaching step, and the added content of distilled water is 23% of the mass of the regenerated deep eutectic solvent;

[0111] (7) High-energy ball milling: adding 28% ammonia water to the leached residue containing W and Ti, adjusting the pH value to 8 with sodium hydroxide, and performing high-energy ball milling to obtain a ball milling liquid and ball milling residue; wherein the process conditions of the high-energy ball milling are: liquid-to-solid ratio 1:1.25, ball-to-material ratio 14:1, and ball milling time 150 min;

[0112] (8) Evaporation and crystallization: The ball milling liquid is evaporated and crystallized to obtain ammonium metatungstate; wherein the conditions of the evaporation and crystallization are: the evaporation and crystallization temperature is 105° C., and the evaporation and crystallization time is 3.5 h;

[0113] (9) Washing and drying: The ball mill residue is washed with ethanol to obtain a washing product; the washing product is washed with distilled water and dried to obtain titanium-rich slag.

[0114] The test results show that the vanadium leaching rate is 96.5%, while the titanium and tungsten leaching rates are 0.1% and 0.063% respectively; the recovery rates of vanadium and tungsten are 99.6% and 99.1% respectively.

[0115] In summary, compared with the prior art, the present invention has at least the following advantages:

[0116] (1) The present invention not only simplifies the recycling process of waste denitration catalysts and realizes the separation and purification of vanadium and tungsten, but also maintains the stability of the phase structure of titanium dioxide, meeting the dual requirements of extracting valuable metals and retaining the carrier phase at the same time;

[0117] (2) The present invention uses a low melting point, high selectivity native deep eutectic solvent as the leaching solvent for the waste denitration catalyst, which enhances the leaching effect and improves the recovery rate of vanadium and tungsten;

[0118] (3) The present invention realizes the reuse of ammonium salt precipitant and native deep eutectic solvent, thereby reducing production costs.

[0119] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article, or apparatus.

[0120] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0121] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for recovering valuable metals from waste denitration catalysts, characterized in that: The method comprises the following steps: S1. Add a hydrogen bond acceptor, a hydrogen bond donor and distilled water into a sealed flask, stir and react at 80-100°C, and cool to room temperature to obtain a native deep eutectic solvent; S2, ball-milling and sieving the waste denitration catalyst to obtain a ball-milled material; S3, adding the ball mill to the native deep eutectic solvent, sealing, heating and stirring for reaction, and centrifuging to obtain a leachate and a leach residue; S4, adding an ammonium salt precipitant to the leachate, stirring the reaction at room temperature, and filtering to obtain a precipitate and a precipitate; S5, washing the precipitate with 2% NH4Cl, and drying to obtain ammonium metavanadate; S6, performing vacuum distillation on the precipitate, condensing and refluxing to obtain an ammonium salt mixture and a regenerated deep eutectic solvent; the ammonium salt mixture is reused as the ammonium salt precipitant; distilled water is added to the regenerated deep eutectic solvent and reused as the primary deep eutectic solvent; S7, adding ammonia water to the leached residue, adjusting the pH value to 8-14 with sodium hydroxide, and performing high-energy ball milling to obtain a ball milling liquid and ball milling residue; S8, evaporating and crystallizing the ball milling liquid to obtain ammonium metatungstate; S9, washing the ball mill residue with ethanol to obtain a washing; washing the washing with distilled water, and drying to obtain titanium-rich slag; In S1, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:2 to 4:1, the amount of distilled water added is 10% to 50% of the total mass of the hydrogen bond acceptor and the hydrogen bond donor; the stirring reaction time is 60 to 120 minutes; The hydrogen bond acceptor includes at least one of polyethylene glycol 400 and choline chloride; the hydrogen bond donor includes at least one of p-toluenesulfonic acid, malonic acid, glycolic acid, malic acid, lactic acid, tartaric acid, glycolic acid, and citric acid; In S3, the conditions of the heating and stirring reaction include: a heating temperature of 60 to 80° C., a stirring time of 9 to 15 hours; a liquid-to-solid ratio of the native deep eutectic solvent to the ball mill material of 5:1 to 50:1; In S4, the conditions for the room temperature stirring reaction include: a reaction time of 10 to 90 minutes, a stirring speed of 400 to 800 rpm; the ammonium salt precipitant is composed of ammonium chloride, ammonium sulfate and ammonium nitrate, and the molar ratio of the ammonium chloride, the ammonium sulfate and the ammonium nitrate is 2:1:1; In S6, the conditions of the vacuum distillation include: the vacuum distillation temperature is 60-100° C., the vacuum distillation time is 0.5-3 h, the stirring speed is 400-600 rpm, and the pressure is 0.03-0.08 MPa; the supplementary content of the distilled water is 10%-50% of the mass of the regenerated deep eutectic solvent; In S7, the mass concentration of the ammonia water is 10% to 30%; the conditions of the high-energy ball milling include: a liquid-to-solid ratio of 1:4 to 1:1, a ball-to-material ratio of 10:1 to 30:1, and a ball milling time of 30 to 180 minutes.

2. The method for recovering valuable metals from waste denitration catalysts according to claim 1, characterized in that: In S2, the mesh size of the sieve used for screening is 200 meshes.

3. The method for recovering valuable metals from waste denitration catalysts according to claim 1, characterized in that: In S5, the washing is performed three times; the drying conditions include: a drying temperature of 100° C. and a drying time of 6 hours.

4. The method for recovering valuable metals from waste denitration catalysts according to claim 1, characterized in that: In S8, the evaporation crystallization conditions include: the evaporation crystallization temperature is 105°C, and the evaporation crystallization time is 3.5h.

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