A method for recovering metals from vanadium, molybdenum and nickel-containing waste residues

Abstract

This invention provides a method for recovering metals from vanadium, molybdenum and nickel-containing waste slag: (1) Mixing vanadium, molybdenum and nickel-containing waste slag with sodium salt and decarbonizing / degreasing by roasting to obtain decarbonized / degreasing material; (2) Mixing the decarbonized / degreasing material, impurity removal agent, sodium hydroxide and pulping water, and subjecting the resulting mixed slurry to a first hydrothermal reaction, and after the reaction, separating the solid and liquid to obtain nickel slag and leachate, and using the washing water of the nickel slag after washing as the above-mentioned pulping water; (3) Mixing the leachate and vanadium precipitation agent and adjusting the pH value, and subjecting the mixture to a hydrothermal reaction to obtain a vanadium-containing intermediate and a vanadium precipitation mother liquor, and using the vanadium-containing intermediate to obtain a vanadium oxide product after washing and heat treatment, and using the washing water as pulping water; (4) Introducing CO2 into the vanadium precipitation mother liquor to carry out a carbonation reaction to obtain a sodium bicarbonate product and a sodium bicarbonate mother liquor; (5) Mixing the sodium bicarbonate mother liquor and water and adjusting the pH value, and carrying out crystallization aging to obtain molybdic acid and a molybdenum precipitation mother liquor; (6) Purifying the molybdenum precipitation mother liquor to obtain a sodium-containing product and a crystallization mother liquor. This invention has a short process, low technical difficulty, low cost, and is environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal solid waste resource utilization technology, and in particular to a method for recovering metals from vanadium, molybdenum and nickel-containing waste slag. Background Technology

[0002] Vanadium (V) and molybdenum (Mo), as important strategic non-ferrous metals, play an irreplaceable role in fields such as steel alloys, petrochemical catalysts, aerospace materials, new energy batteries, and national defense. my country's primary vanadium and molybdenum mineral resources are limited in reserves, and their lifespan is below the world average. With the rapid development of industries such as petroleum refining and thermal power plant denitrification, a large amount of vanadium and molybdenum-containing solid waste is generated annually. This mainly includes: spent catalysts from hydrodesulfurization (HDS) in petrochemicals, spent catalysts from selective catalytic reduction (SCR) denitrification, and petroleum slag generated during heavy oil combustion, gasification, or refining. These wastes typically contain 5%–16% vanadium pentoxide and 2%–10% Mo, along with associated valuable metals such as Ni and Co. The annual production reaches hundreds of thousands of tons and is listed in the National Hazardous Waste List. Improper handling not only wastes strategic resources but also causes soil, water, and secondary air pollution due to heavy metals, organic oils, and sulfides, leading to increasingly prominent environmental and resource pressures.

[0003] Currently, domestic and international methods for treating vanadium and molybdenum-containing waste residue can be broadly categorized into acid methods and alkaline methods. The acid method involves directly reacting the deoiled and decarbonized raw material with inorganic acids (sulfuric acid, hydrochloric acid, or nitric acid) under oxygen pressure to dissolve metals such as nickel, iron, and aluminum. Nickel is then extracted through purification and impurity removal. Vanadium and molybdenum enter the slag phase and are subsequently extracted using an alkaline method, involving processes such as extraction, impurity removal, ion exchange, vanadium precipitation with ammonium salts, and molybdic acid preparation. Patents related to this method include CN101713029A, CN113234930A, and CN102808082B. The alkaline method includes processes such as mixing the decarbonized and deoiled waste residue with sodium carbonate, roasting the mixture, water leaching the decarbonized / deoiled material, vanadium precipitation with ammonium salts from the leachate, molybdenum extraction, molybdic acid or molybdic acid preparation, and ion exchange. Patents related to this method include CN105274344A and CN100482814C.

[0004] While the above methods can achieve the resource utilization of valuable metals such as vanadium, molybdenum, and nickel, they generally suffer from problems such as long processes and poor operability. For example, the acid method causes nickel, iron, aluminum, and some vanadium and molybdenum to dissolve simultaneously, which increases the difficulty of purification and impurity removal, increases the length of the process, and reduces the yield of valuable metals. The alkaline leaching method involves purification, extraction, separation, and ammonium salt precipitation to prepare vanadium and molybdenum products. This method is energy-intensive and has a long process. In addition, if this method is extended to the field of putty, the high molybdenum and vanadium content in the putty will cause the amount of sodium vanadate and sodium molybdate melt formed during the sodium roasting process to exceed the maximum allowable melt amount of the roasting device, resulting in scale buildup in the furnace and making it difficult to operate smoothly.

[0005] In summary, while current methods can address the resource utilization of vanadium, molybdenum, and nickel-containing waste to some extent, they still suffer from problems such as long processes, complex operating conditions, and high energy consumption. Therefore, a new technology with a shorter process and lower energy consumption is urgently needed. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a method for recovering metals from vanadium, molybdenum and nickel-containing waste slag. Compared with traditional preparation methods, the process is simpler, the conditions are milder, the energy consumption is lower, and the economic benefits are more prominent.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for recovering metals from vanadium, molybdenum and nickel-containing waste slag, the method comprising the following steps:

[0009] (1) Mix vanadium, molybdenum and nickel-containing waste residue with sodium salt and roast it for decarbonization / deoiling to obtain decarbonized / deoiled material;

[0010] (2) The decarbonized / deoiled material, the impurity remover, sodium hydroxide and pulping water are mixed, and the resulting mixed slurry is subjected to a first hydrothermal reaction. After the reaction, solid and liquid separation is performed to obtain nickel slag and leachate. The washing water of the nickel slag after washing is used as the pulping water mentioned above.

[0011] (3) The leachate and vanadium precipitation agent are mixed and the pH value is adjusted to carry out a second hydrothermal reaction. After the reaction, solid-liquid separation is performed to obtain vanadium-containing intermediate and vanadium precipitation mother liquor. The vanadium-containing intermediate is washed and heat-treated in sequence to obtain vanadium oxide product. The washing water is returned to step (2) as pulping water.

[0012] (4) CO2 is introduced into the vanadium precipitation mother liquor to carry out a carbonation reaction. After the reaction is completed, sodium bicarbonate product and sodium bicarbonate mother liquor are obtained. The sodium bicarbonate product is returned to step (1) for use.

[0013] (5) Mix the sodium bicarbonate mother liquor and water and adjust the pH value to carry out crystallization aging to obtain molybdenum acid and molybdenum precipitation mother liquor;

[0014] (6) The molybdenum precipitation mother liquor is purified to obtain sodium-containing products and crystallization mother liquor. Part of the crystallization mother liquor is returned to step (2) as pulping water, and part of it is returned to step (5) to be mixed with the sodium bicarbonate mother liquor.

[0015] This invention enables efficient metal recycling, specifically including:

[0016] (1) In this invention, vanadium, molybdenum and nickel-containing waste residue is first mixed with sodium salt and then decarbonized / deoiled by roasting. This not only removes more than 90% of the carbon and oil from the waste residue, but also allows some of the vanadium and molybdenum in the waste residue to react with sodium to generate water-soluble sodium molybdate and sodium vanadate.

[0017] (2) Using decarbonized / deoiled materials as raw materials, vanadium and molybdenum are directly oxidized and leached by sodium hydroxide solution, and silicon is effectively removed by impurity removal agent to avoid silicon entering the leaching solution. This method can effectively extract vanadium and molybdenum from the waste residue, with an extraction rate of ≥95%. Nickel is separated from vanadium and molybdenum in the form of slag. This method utilizes the difference in redox properties of vanadium and molybdenum at different pH levels to achieve efficient separation of vanadium and molybdenum.

[0018] (3) Molybdenum acid is prepared by adjusting the pH value to precipitate molybdenum, thereby achieving the enrichment and recovery of molybdenum. This method eliminates the cumbersome process of recovering residual molybdenum by adsorption in the traditional process, which not only shortens the operation process, but also requires less investment and is simpler to operate.

[0019] The vanadium oxide product prepared by this method has a V2O5 content ≥99%, Na2O+K2O ≤0.2%, and Cr is below the detection limit, meeting the standard requirements of vanadium powder V2O599-P and above in standard YB / T 5304-2017; the prepared molybdic acid product has Mo ≥55%, and its quality meets the requirements for catalyst production.

[0020] As a preferred technical solution of the present invention, the vanadium, molybdenum and nickel-containing waste residue in step (1) includes waste catalyst and / or petrochemical ash solid waste residue.

[0021] Preferably, the sodium salt in step (1) includes sodium bicarbonate and / or sodium hydroxide.

[0022] Preferably, the mass ratio of sodium salt to vanadium, molybdenum and nickel-containing waste slag in step (1) is (0.01-0.05):1, for example, it can be 0.01:1, 0.02:1, 0.03:1, 0.04:1 or 0.05:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] The present invention controls the mass ratio of sodium salt to vanadium, molybdenum and nickel-containing waste slag within the above-mentioned range. The purpose is to stabilize the unreacted vanadium and molybdenum content in the decarburized clinker and reduce the amount of melt generated during the roasting process. If there is too much sodium salt, melt will easily be generated, causing ring formation in the reactor. If there is too little sodium salt, the composition of vanadium and molybdenum in the unreacted sodium will change, the downstream material ratio will fluctuate, and the volatility of production control will increase.

[0024] Preferably, the decarburization / deoiling roasting temperature is 400-900℃, for example, it can be 400℃, 500℃, 600℃, 700℃, 800℃ or 900℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 400-600℃.

[0025] Preferably, the decarbonization / deoiling roasting time is 3-5 h, for example, it can be 3 h, 3.5 h, 4 h, 4.5 h or 5 h, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] The decarbonization / deoiling roasting reaction system described in this invention requires control of the air intake to ensure that the carbon is not completely oxidized and that the metal is not completely oxidized to its highest valence state. The specific operation can be adjusted according to the implementation effect, and no specific limitation is made here.

[0027] As a preferred technical solution of the present invention, the impurity removal agent includes any one or a combination of at least two of magnesium oxide, magnesium sulfate, calcium oxide or calcium sulfate. Typical but non-limiting combinations include combinations of magnesium oxide and magnesium sulfate, combinations of magnesium sulfate and calcium oxide, combinations of calcium oxide and calcium sulfate, etc.

[0028] Preferably, the mass ratio of the impurity removal agent to the decarbonization / deoiling material in step (2) is (0.01-0.05):1, for example, it can be 0.01:1, 0.02:1, 0.03:1, 0.04:1 or 0.05:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the amount of sodium hydroxide added in step (2) is such that the ratio of the total amount of sodium in the system to the total amount of vanadium and molybdenum in the decarbonized / deoiled material is (1-1.2):1, for example, it can be 1:1, 1.1:1 or 1.2:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the liquid-solid ratio of the pulping water to the decarbonized / deoiled material in step (2) is (2-4):1 mL / g, for example, it can be 2:1 mL / g, 2.5:1 mL / g, 3:1 mL / g, 3.5:1 mL / g or 4:1 mL / g, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the liquid-to-solid ratio of the washing water to the nickel slag in step (2) is (4-6):1 mL / g, for example, it can be 4:1 mL / g, 4.5:1 mL / g, 5:1 mL / g, 5.5:1 mL / g or 6:1 mL / g, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] As a preferred technical solution of the present invention, the temperature of the first hydrothermal reaction is 90-150℃, for example, it can be 90℃, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 110-130℃.

[0033] Preferably, the time for the first hydrothermal reaction is 2-5 h, for example, it can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 3-4 h.

[0034] Preferably, the reaction gas of the first hydrothermal reaction includes oxygen and / or air.

[0035] Preferably, if the reaction pressure of the first hydrothermal reaction is 0.1-3 MPa, for example, it can be 0.1 MPa, 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa or 3 MPa, but is not limited to the listed values, other unlisted values ​​within the range are also applicable.

[0036] Preferably, if the reaction gas of the first hydrothermal reaction is oxygen, the reaction pressure is 0.1-2 MPa, for example, it can be 0.1 MPa, 0.5 MPa, 1 MPa, 1.5 MPa or 2 MPa, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.5-1 MPa.

[0037] Preferably, if the reaction gas of the first hydrothermal reaction is air, the reaction pressure is 0.5-3 MPa, for example, it can be 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa or 3 MPa, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 1-2 MPa.

[0038] As a preferred technical solution of the present invention, the vanadium precipitation agent includes any one or a combination of at least two of formic acid, oxalic acid, sodium formate, sodium oxalate, glucose, sucrose, fructose, glycerol, citric acid, formaldehyde, hydrazine hydrate, sodium sulfite, sodium metabisulfite, or sodium hydrosulfite. Typical but non-limiting combinations include combinations of formic acid and oxalic acid, combinations of oxalic acid and sodium formate, combinations of citric acid and formaldehyde, and combinations of hydrazine hydrate and sodium sulfite.

[0039] Preferably, the amount of vanadium precipitating agent added satisfies the following condition: the total amount of electron transfer it provides is 1.2-2 times the total amount of electron transfer required for the conversion of pentavalent vanadium to tetravalent vanadium in the leachate. For example, it can be 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, or 2 times, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, with 1.2 times being the preferred value.

[0040] Preferably, step (3) of adjusting the pH value includes: adding an acidifying agent to the mixture of the leachate and the vanadium precipitant to adjust the pH value to 7-9, for example, it can be 7, 7.5, 8, 8.5 or 9, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the acidifying agent includes any one or a combination of at least two of CO2, formic acid, oxalic acid, or acetic acid.

[0042] As a preferred technical solution of the present invention, the temperature of the second hydrothermal reaction is 130-190℃, for example, it can be 130℃, 140℃, 150℃, 160℃, 170℃, 180℃ or 190℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0043] Preferably, the time for the second hydrothermal reaction is 3-6 h, for example, it can be 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] As a preferred technical solution of the present invention, the temperature of the heat treatment is 200-500℃, for example, it can be 200℃, 250℃, 300℃, 350℃, 400℃, 450℃ or 500℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0045] Preferably, the heat treatment time is 2-4 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] Preferably, the reaction atmosphere for the heat treatment includes air and / or oxygen.

[0047] As a preferred technical solution of the present invention, the CO2 flow rate in step (4) is: CO2 is continuously introduced to keep the pressure of the reaction system at 0.2-0.4 MPa, for example, it can be 0.2 MPa, 0.3 MPa or 0.4 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] Preferably, the temperature of the carbonation reaction is 30-60°C, for example, it can be 30°C, 40°C, 50°C or 60°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 30-40°C.

[0049] Preferably, the carbonation reaction time is 2-3 h, for example, 2 h, 2.5 h or 3 h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] As a preferred technical solution of the present invention, the volume ratio of sodium bicarbonate mother liquor to water in step (5) is (3-5):1, for example, it can be 3:1, 4:1 or 5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] Preferably, the pH value is adjusted to 0.5-2 in step (5), for example, it can be 0.5, 1 or 2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.5-1.

[0052] Preferably, the method for adjusting the pH value in step (5) includes: introducing the sodium bicarbonate mother liquor, water and inorganic acid into the reaction system in a parallel flow.

[0053] Preferably, the inorganic acid includes sulfuric acid.

[0054] Preferably, the crystallization aging temperature is 70-100℃, for example, it can be 70℃, 80℃, 90℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 70-90℃.

[0055] Preferably, the crystallization aging time is 0.5-2 h, for example, it can be 0.5 h, 1 h, 1.5 h or 2 h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] As a preferred technical solution of the present invention, the purification in step (6) includes cooling crystallization.

[0057] Preferably, the cooling crystallization temperature is 5-10℃, for example, it can be 5℃, 6℃, 7℃, 8℃, 9℃ or 10℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0059] (1) The method for recovering metals from vanadium, molybdenum and nickel-containing waste slag provided by the present invention has a short process, low energy consumption and strong operability;

[0060] (2) The vanadium oxide product prepared by this method has a V2O5 content ≥99%, Na2O+K2O ≤0.2%, and Cr is below the detection limit, which meets the standard requirements of vanadium powder V2O599-P and above in standard YB / T 5304-2017; the prepared molybdic acid product has Mo ≥55%, and the quality meets the requirements for catalyst production. Detailed Implementation

[0061] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0062] It should be clarified that any use of the process provided in the embodiments of the present invention or any substitution or change of conventional data falls within the protection and disclosure scope of the present invention.

[0063] Example 1

[0064] This embodiment provides a method for recovering metals from vanadium, molybdenum, and nickel-containing waste slag, the method comprising the following steps:

[0065] (1) The vanadium, molybdenum and nickel catalyst waste residue was mixed with sodium bicarbonate and then deoiled and roasted. The mass ratio of sodium bicarbonate to vanadium, molybdenum and nickel catalyst waste residue was 0.03:1. The roasting temperature was 550℃ and the time was 3 h to obtain decarbonized / deoiled material.

[0066] (2) The degreasing material, the impurity removal agent magnesium oxide, sodium hydroxide and pulping water are mixed. The mass ratio of the impurity removal agent magnesium oxide to the decarbonization / degreasing material is 0.01:1. The amount of sodium hydroxide added is such that the ratio of the total amount of sodium in the system to the total amount of vanadium and molybdenum in the decarbonization / degreasing material is 1.1:1. The liquid-solid ratio of pulping water to degreasing material is 3:1 mL / g. Under an oxygen atmosphere, the resulting mixed slurry undergoes a first hydrothermal reaction at a temperature of 110℃ for 3 h and a pressure of 0.3 MPa. After the reaction, solid and liquid separation is performed to obtain nickel slag and leachate. The washing water of the nickel slag after washing is used as the pulping water. The liquid-solid ratio of the washing water of the nickel slag to the nickel slag is 5:1 mL / g.

[0067] (3) Mix the leachate and sodium formate, a vanadium precipitant, and add formic acid to adjust the pH to 8. The amount of sodium formate added satisfies the following: the total amount of electron transfer it provides is 1.5 times the total amount of electron transfer required for the conversion of pentavalent vanadium in the leachate to tetravalent vanadium. A second hydrothermal reaction is carried out at a temperature of 190°C for 3 hours. After the reaction, solid and liquid are separated to obtain a vanadium-containing intermediate and a vanadium precipitate mother liquor. The vanadium-containing intermediate is washed and heat-treated in sequence to obtain vanadium oxide products. The heat treatment temperature is 300°C for 3 hours and the atmosphere is air. The washing water is returned to step (2) as pulping water.

[0068] (4) CO2 is introduced into the vanadium precipitation mother liquor to carry out a carbonation reaction. The reaction temperature is 50°C and the time is 2.5h. The pressure of the reaction system is kept at 0.3 MPa. After the reaction is completed, sodium bicarbonate product and sodium bicarbonate mother liquor are obtained. The sodium bicarbonate product is returned to step (1) for use.

[0069] (5) Mix the sodium bicarbonate mother liquor and water, and introduce sulfuric acid to adjust the pH value to 1. The volume ratio of sodium bicarbonate mother liquor to water is 4:1. Crystallize and age at 80°C for 2 hours to obtain molybdic acid and molybdenum precipitate mother liquor.

[0070] (6) Cool the molybdenum precipitation mother liquor at a temperature of 5°C to obtain Glauber's salt product and crystallization mother liquor. Part of the crystallization mother liquor is returned to step (2) as pulping water, and part of it is returned to step (5) to be mixed with the sodium bicarbonate mother liquor.

[0071] Example 2

[0072] This embodiment provides a method for recovering metals from vanadium, molybdenum, and nickel-containing waste slag, the method comprising the following steps:

[0073] (1) The vanadium, molybdenum and nickel catalyst waste residue was mixed with sodium bicarbonate and deoiled and roasted. The mass ratio of sodium bicarbonate to vanadium, molybdenum and nickel catalyst waste residue was 0.01:1. The roasting temperature was 550℃ and the time was 3 h to obtain decarbonized / deoiled material.

[0074] (2) The degreasing material, the impurity removal agent magnesium oxide, sodium hydroxide and pulping water are mixed. The mass ratio of the impurity removal agent magnesium oxide to the decarbonization / degreasing material is 0.01:1. The amount of sodium hydroxide added is such that the ratio of the total amount of sodium in the system to the total amount of vanadium and molybdenum in the decarbonization / degreasing material is 1.2:1. The liquid-solid ratio of pulping water to degreasing material is 3.5:1 mL / g. Under an oxygen atmosphere, the resulting mixed slurry undergoes a first hydrothermal reaction at a temperature of 130℃ for 3 h and a pressure of 0.1 MPa. After the reaction, solid and liquid separation is performed to obtain nickel slag and leachate. The washing water of the nickel slag after washing is used as the pulping water. The liquid-solid ratio of the washing water of the nickel slag to the nickel slag is 4:1 mL / g.

[0075] (3) Mix the leachate and vanadium precipitant glucose and add acetic acid to adjust the pH to 8. The amount of vanadium precipitant glucose added is such that the total amount of electron transfer it provides is 1.5 times the total amount of electron transfer required for the conversion of pentavalent vanadium in the leachate to tetravalent vanadium. A second hydrothermal reaction is carried out at a temperature of 150°C for 3 hours. After the reaction, solid and liquid are separated to obtain vanadium-containing intermediate and vanadium precipitate mother liquor. The vanadium-containing intermediate is washed and heat-treated in sequence to obtain vanadium oxide product. The heat treatment temperature is 400°C for 2 hours and the atmosphere is air. The washing water is returned to step (2) as pulping water.

[0076] (4) CO2 is introduced into the vanadium precipitation mother liquor to carry out a carbonation reaction. The reaction temperature is 30°C and the time is 3 h. The pressure of the reaction system is kept at 0.4 MPa. After the reaction is completed, sodium bicarbonate product and sodium bicarbonate mother liquor are obtained. The sodium bicarbonate product is returned to step (1) for use.

[0077] (5) Mix the sodium bicarbonate mother liquor and water, and introduce sulfuric acid to adjust the pH value to 0.7. The volume ratio of sodium bicarbonate mother liquor to water is 3:1. Crystallize and age at 85°C for 2 hours to obtain molybdic acid and molybdenum precipitate mother liquor.

[0078] (6) Cool the molybdenum precipitation mother liquor at a temperature of 7°C to obtain Glauber's salt product and crystallization mother liquor. Part of the crystallization mother liquor is returned to step (2) as pulping water, and part of it is returned to step (5) to be mixed with the sodium bicarbonate mother liquor.

[0079] Example 3

[0080] This embodiment provides a method for recovering metals from vanadium, molybdenum, and nickel-containing waste slag, the method comprising the following steps:

[0081] (1) Mix vanadium, molybdenum and nickel-containing oil ash solid waste with sodium bicarbonate and decarbonize and roast. The mass ratio of sodium bicarbonate to vanadium, molybdenum and nickel-containing oil ash solid waste is 0.05:1. The roasting temperature is 550℃ and the time is 3 h to obtain decarbonized / deoiled material.

[0082] (2) The decarbonized material, the impurity remover calcium oxide, sodium hydroxide and pulping water are mixed. The mass ratio of the impurity remover calcium oxide to the decarbonized / deoiled material is 0.02:1. The amount of sodium hydroxide added is such that the ratio of the total amount of sodium in the system to the total amount of vanadium and molybdenum in the decarbonized / deoiled material is 1:1. The liquid-solid ratio of the pulping water to the deoiled material is 4:1 mL / g. Under an oxygen atmosphere, the resulting mixed slurry undergoes a first hydrothermal reaction at a temperature of 110°C for 2.5 h and a pressure of 0.5 MPa. After the reaction, the solid and liquid are separated to obtain nickel slag and leachate. The washing water of the nickel slag after washing is used as the pulping water. The liquid-solid ratio of the washing water of the nickel slag to the nickel slag is 6:1 mL / g.

[0083] (3) The leachate and vanadium precipitating agent hydrazine hydrate are mixed and formic acid is added to adjust the pH value to 8. The amount of vanadium precipitating agent hydrazine hydrate added satisfies that the total amount of electron transfer provided by it is 1.4 times the total amount of electron transfer required for the conversion of pentavalent vanadium in the leachate to tetravalent vanadium. A second hydrothermal reaction is carried out at a temperature of 150°C for 4 hours. After the reaction, solid and liquid separation is performed to obtain vanadium-containing intermediate and vanadium precipitating mother liquor. The vanadium-containing intermediate is washed and heat-treated in sequence to obtain vanadium oxide product. The heat treatment temperature is 500°C for 2 hours and the atmosphere is air. The washing water is returned to step (2) as pulping water.

[0084] (4) CO2 is introduced into the vanadium precipitation mother liquor to carry out a carbonation reaction. The reaction temperature is 60°C and the time is 2 h. The pressure of the reaction system is kept at 0.2 MPa. After the reaction is completed, sodium bicarbonate product and sodium bicarbonate mother liquor are obtained. The sodium bicarbonate product is returned to step (1) for use.

[0085] (5) Mix the sodium bicarbonate mother liquor and water, and introduce sulfuric acid to adjust the pH value to 0.5. The volume ratio of sodium bicarbonate mother liquor to water is 4:1. Crystallize and age at 90°C for 2 hours to obtain molybdic acid and molybdenum precipitate mother liquor.

[0086] (6) Cool the molybdenum precipitation mother liquor at a temperature of 10°C to obtain Glauber's salt product and crystallization mother liquor. Part of the crystallization mother liquor is returned to step (2) as pulping water, and part of it is returned to step (5) to be mixed with the sodium bicarbonate mother liquor.

[0087] Example 4

[0088] This embodiment provides a method for recovering metals from vanadium, molybdenum, and nickel-containing waste slag, the method comprising the following steps:

[0089] (1) The vanadium, molybdenum and nickel catalyst waste residue is mixed with sodium hydroxide and deoiled and roasted. The mass ratio of the sodium salt to the vanadium, molybdenum and nickel catalyst waste residue is 0.03:1. The roasting temperature is 400℃ and the time is 5 h to obtain decarbonized / deoiled material.

[0090] (2) The degreasing material, the impurity removal agent calcium oxide, sodium hydroxide and pulping water are mixed. The mass ratio of the impurity removal agent calcium oxide to the decarbonization / degreasing material is 0.03:1. The amount of sodium hydroxide added is such that the ratio of the total amount of sodium in the system to the total amount of vanadium and molybdenum in the decarbonization / degreasing material is 1.2:1. The liquid-solid ratio of pulping water to degreasing material is 4:1 mL / g. Under the atmosphere of air, the resulting mixed slurry undergoes a first hydrothermal reaction at a temperature of 90°C for 5 h and a pressure of 0.5 MPa. After the reaction, solid-liquid separation is performed to obtain nickel slag and leachate. The washing water of the nickel slag after washing is used as the above-mentioned pulping water. The liquid-solid ratio of the washing water of the nickel slag to the nickel slag is 6:1 mL / g.

[0091] (3) The leachate and vanadium precipitating agent citric acid are mixed and acetic acid is introduced to adjust the pH value to 7. The amount of vanadium precipitating agent citric acid added is satisfied that the total amount of electron transfer provided by it is 1.2 times the total amount of electron transfer required for the conversion of pentavalent vanadium in the leachate to tetravalent vanadium. A second hydrothermal reaction is carried out at a temperature of 130°C for 6 hours. After the reaction, solid and liquid separation is performed to obtain vanadium-containing intermediate and vanadium precipitating mother liquor. The vanadium-containing intermediate is washed and heat-treated in sequence to obtain vanadium oxide product. The heat treatment temperature is 200°C for 4 hours and the atmosphere is air. The washing water is returned to step (2) as pulping water.

[0092] (4) CO2 is introduced into the vanadium precipitation mother liquor to carry out a carbonation reaction. The reaction temperature is 40°C and the time is 2.5h. The pressure of the reaction system is kept at 0.3 MPa. After the reaction is completed, sodium bicarbonate product and sodium bicarbonate mother liquor are obtained. The sodium bicarbonate product is returned to step (1) for use.

[0093] (5) Mix the sodium bicarbonate mother liquor and water, and introduce sulfuric acid to adjust the pH value to 2. The volume ratio of sodium bicarbonate mother liquor to water is 5:1. Crystallize and age at 70°C for 2 hours to obtain molybdic acid and molybdenum precipitate mother liquor.

[0094] (6) The molybdenum precipitation mother liquor is cooled and crystallized at a temperature of 5°C to obtain a sodium-containing product and a crystallization mother liquor. Part of the crystallization mother liquor is returned to step (2) as pulping water, and part of it is returned to step (5) to be mixed with the sodium bicarbonate mother liquor.

[0095] Example 5

[0096] This embodiment provides a method for recovering metals from vanadium, molybdenum, and nickel-containing waste slag, the method comprising the following steps:

[0097] (1) The vanadium, molybdenum and nickel catalyst waste residue is mixed with sodium bicarbonate and deoiled and roasted. The mass ratio of the sodium salt to the vanadium, molybdenum and nickel catalyst waste residue is 0.03:1. The roasting temperature is 900℃ and the time is 3 h to obtain decarbonized / deoiled material.

[0098] (2) The degreasing material, the impurity removal agent calcium sulfate, sodium hydroxide and pulping water are mixed. The mass ratio of the impurity removal agent calcium sulfate to the decarbonization / degreasing material is 0.04:1. The amount of sodium hydroxide added is such that the ratio of the total amount of sodium in the system to the total amount of vanadium and molybdenum in the decarbonization / degreasing material is 1.2:1. The liquid-solid ratio of pulping water to degreasing material is 4:1 mL / g. Under the atmosphere of air, the resulting mixed slurry undergoes a first hydrothermal reaction at a temperature of 150℃ for 2 h and a pressure of 3 MPa. After the reaction, solid-liquid separation is performed to obtain nickel slag and leachate. The washing water of the nickel slag after washing is used as the above-mentioned pulping water. The liquid-solid ratio of the washing water of the nickel slag to the nickel slag is 5:1 mL / g.

[0099] (3) The leachate and vanadium precipitant sodium metabisulfite are mixed and CO2 is introduced to adjust the pH value to 9. The amount of sodium metabisulfite added satisfies the following: the total amount of electron transfer it provides is twice the amount of electron transfer required for the conversion of pentavalent vanadium in the leachate to tetravalent vanadium. A second hydrothermal reaction is carried out at a temperature of 190°C for 3 hours. After the reaction, solid and liquid are separated to obtain vanadium-containing intermediate and vanadium precipitate mother liquor. The vanadium-containing intermediate is washed and heat-treated in sequence to obtain vanadium oxide product. The heat treatment temperature is 300°C for 3 hours and the atmosphere is oxygen. The washing water is returned to step (2) as pulping water.

[0100] (4) CO2 is introduced into the vanadium precipitation mother liquor to carry out a carbonation reaction. The reaction temperature is 50°C and the time is 2.5h. The pressure of the reaction system is kept at 0.3 MPa. After the reaction is completed, sodium bicarbonate product and sodium bicarbonate mother liquor are obtained. The sodium bicarbonate product is returned to step (1) for use.

[0101] (5) Mix the sodium bicarbonate mother liquor and water, and introduce sulfuric acid to adjust the pH value to 1. The volume ratio of sodium bicarbonate mother liquor to water is 4:1. Perform crystallization aging at 100°C for 0.5 h to obtain molybdic acid and molybdenum precipitate mother liquor.

[0102] (6) The molybdenum precipitation mother liquor is cooled and crystallized at a temperature of 8°C to obtain a sodium-containing product and a crystallization mother liquor. Part of the crystallization mother liquor is returned to step (2) as pulping water, and part of it is returned to step (5) to be mixed with the sodium bicarbonate mother liquor.

[0103] Example 6

[0104] This embodiment provides a method for recovering metals from vanadium, molybdenum and nickel-containing waste slag. The only difference between this method and Embodiment 1 is that the pH value in step (3) is changed to 6, and the rest is the same as Embodiment 1.

[0105] Example 7

[0106] This embodiment provides a method for recovering metals from vanadium, molybdenum and nickel-containing waste slag. The only difference between this method and Embodiment 1 is that the pH value in step (3) is changed to 10, and the rest is the same as Embodiment 1.

[0107] Example 8

[0108] This embodiment provides a method for recovering metals from vanadium, molybdenum and nickel-containing waste slag. The only difference between this method and Embodiment 1 is that the pH value in step (5) is changed to 0.2, and the rest is the same as Embodiment 1.

[0109] Example 9

[0110] This embodiment provides a method for recovering metals from vanadium, molybdenum and nickel-containing waste slag. The only difference between this method and Embodiment 1 is that the pH value in step (5) is changed to 2.5, and the rest is the same as Embodiment 1.

[0111] Comparative Example 1

[0112] This comparative example provides a method for recovering metals from vanadium, molybdenum and nickel-containing waste slag. The only difference between this method and Example 1 is that step (1) is omitted, and the raw materials, impurity remover, sodium hydroxide and pulping water are directly mixed to carry out the first hydrothermal reaction. All other aspects are the same as in Example 1.

[0113] Performance testing

[0114] The products obtained from the methods for recovering metals from vanadium, molybdenum and nickel-containing waste provided in the examples and comparative examples were subjected to performance tests. The purity test method was as follows: V2O5 was tested according to the test method for vanadium in standard YB / T5328-2009, and molybdic acid was tested according to the test method in standard YS / T555.1-2009. The results are shown in Table 1.

[0115]

[0116] Note: "-" in the table indicates no data, and the first hydrothermal reaction is carried out directly. Due to the high oil content, vanadium and molybdenum cannot be leached out.

[0117] A comprehensive comparison of Examples 1 and 6-9 shows that if the pH is lowered, the water content of vanadium will increase, resulting in a large amount of impurities and thus lower product quality. Furthermore, vanadium cannot be deeply removed, and residual vanadium will enter the molybdic acid product, ultimately reducing its quality. If the pH is increased, vanadium cannot precipitate effectively and will enter the molybdic acid product, failing to meet quality requirements. Lowering the pH during molybdic acid preparation will cause the molybdic acid particles to become finer, increasing the water content and increasing impurities, thus lowering product quality. Increasing the pH for molybdic acid precipitation will reduce the precipitation rate, lowering the yield per batch.

[0118] A comprehensive comparison of Example 1 and Comparative Example 1 shows that if the raw materials are not decarbonized or deoiled during roasting, and hydrothermal leaching is carried out directly, vanadium and molybdenum cannot be effectively leached, and the reaction is not feasible. Therefore, decarbonization or deoiling is indispensable.

[0119] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recovering metals from vanadium, molybdenum and nickel-containing waste slag, characterized in that, The method includes the following steps: (1) Mix vanadium, molybdenum and nickel-containing waste residue with sodium salt and roast it for decarbonization / deoiling to obtain decarbonized / deoiled material; (2) The decarbonized / deoiled material, the impurity remover, sodium hydroxide and pulping water are mixed, and the resulting mixed slurry is subjected to a first hydrothermal reaction. After the reaction, solid and liquid separation is performed to obtain nickel slag and leachate. The washing water of the nickel slag after washing is used as the pulping water mentioned above. (3) The leachate and vanadium precipitation agent are mixed and the pH value is adjusted to carry out a second hydrothermal reaction. After the reaction, solid-liquid separation is performed to obtain vanadium-containing intermediate and vanadium precipitation mother liquor. The vanadium-containing intermediate is washed and heat-treated in sequence to obtain vanadium oxide product. The washing water is returned to step (2) as pulping water. (4) CO2 is introduced into the vanadium precipitation mother liquor to carry out a carbonation reaction. After the reaction is completed, sodium bicarbonate product and sodium bicarbonate mother liquor are obtained. The sodium bicarbonate product is returned to step (1) for use. (5) Mix the sodium bicarbonate mother liquor and water and adjust the pH value to carry out crystallization aging to obtain molybdenum acid and molybdenum precipitation mother liquor; (6) The molybdenum precipitation mother liquor is purified to obtain sodium-containing products and crystallization mother liquor. Part of the crystallization mother liquor is returned to step (2) as pulping water, and part of it is returned to step (5) to be mixed with the sodium bicarbonate mother liquor.

2. The method according to claim 1, characterized in that, The vanadium, molybdenum and nickel-containing waste residue in step (1) includes waste catalyst and / or petrochemical ash solid waste residue; Preferably, the sodium salt in step (1) comprises sodium bicarbonate and / or sodium hydroxide; Preferably, the mass ratio of the sodium salt to the vanadium, molybdenum and nickel-containing waste slag in step (1) is (0.01-0.05):1; Preferably, the decarburization / deoiling roasting temperature is 400-900℃, more preferably 400-600℃; Preferably, the decarbonization / deoiling roasting time is 3-5 h.

3. The method according to claim 1 or 2, characterized in that, The impurity removal agent includes any one or a combination of at least two of magnesium oxide, magnesium sulfate, calcium oxide, or calcium sulfate. Preferably, the mass ratio of the impurity removal agent to the decarbonized / deoiled material in step (2) is (0.01-0.05):1; Preferably, the amount of sodium hydroxide added in step (2) is such that the ratio of the total amount of sodium in the system to the total amount of vanadium and molybdenum in the decarbonized / deoiled material is (1-1.2):

1. Preferably, the liquid-to-solid ratio of the pulping water to the decarbonized / deoiled material in step (2) is (2-4):1 mL / g; Preferably, the liquid-to-solid ratio of the washing water to the nickel slag in step (2) is (4-6):1 mL / g.

4. The method according to any one of claims 1 to 3, characterized in that, The temperature of the first hydrothermal reaction is 90-150℃, preferably 110-130℃; Preferably, the first hydrothermal reaction takes 2-5 hours, more preferably 3-4 hours; Preferably, the reaction gas of the first hydrothermal reaction includes oxygen and / or air; Preferably, the reaction pressure of the first hydrothermal reaction is 0.1-3 MPa; Preferably, if the reaction gas of the first hydrothermal reaction is oxygen, the reaction pressure is 0.1-2 MPa, preferably 0.5-1 MPa; Preferably, if the reaction gas of the first hydrothermal reaction is air, the reaction pressure is 0.5-3 MPa, preferably 1-2 MPa.

5. The method according to any one of claims 1 to 4, characterized in that, The vanadium precipitation agent includes any one or a combination of at least two of the following: formic acid, oxalic acid, sodium formate, sodium oxalate, glucose, sucrose, fructose, glycerol, citric acid, formaldehyde, hydrazine hydrate, sodium sulfite, sodium metabisulfite, or sodium hydrosulfite. Preferably, the amount of vanadium precipitation agent added satisfies the following condition: the total amount of electron transfer it provides is 1.2-2 times the total amount of electron transfer required for the conversion of pentavalent vanadium to tetravalent vanadium in the leachate, preferably 1.2 times; Preferably, step (3) of adjusting the pH value includes: adding an acidifying agent to the mixture of the leachate and the vanadium precipitant to adjust the pH value to 7-9; Preferably, the acidifying agent includes any one or a combination of at least two of CO2, formic acid, oxalic acid, or acetic acid.

6. The method according to any one of claims 1 to 5, characterized in that, The temperature of the second hydrothermal reaction is 130-190℃; Preferably, the second hydrothermal reaction takes 3-6 hours.

7. The method according to any one of claims 1 to 6, characterized in that, The heat treatment temperature is 200-500℃; Preferably, the heat treatment time is 2-4 hours; Preferably, the reaction atmosphere for the heat treatment includes air and / or oxygen.

8. The method according to any one of claims 1 to 7, characterized in that, The CO2 flow rate in step (4) is: CO2 is continuously introduced to maintain the pressure of the reaction system at 0.2-0.4 MPa; Preferably, the carbonation reaction temperature is 30-60℃, more preferably 30-40℃; Preferably, the carbonation reaction takes 2-3 hours.

9. The method according to any one of claims 1 to 8, characterized in that, The volume ratio of sodium bicarbonate mother liquor to water in step (5) is (3-5):1; Preferably, step (5) involves adjusting the pH value to 0.5-2, more preferably 0.5-1; Preferably, the method for adjusting the pH value in step (5) includes: introducing the sodium bicarbonate mother liquor, water and inorganic acid into the reaction system in a parallel flow; Preferably, the inorganic acid includes sulfuric acid; Preferably, the crystallization aging temperature is 70-100℃, more preferably 70-90℃; Preferably, the crystallization aging time is 0.5-2 h.

10. The method according to any one of claims 1 to 9, characterized in that, The purification process in step (6) includes cooling crystallization; Preferably, the cooling crystallization temperature is 5-10°C.

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