A method for extracting vanadium from vanadium-containing steel slag

Abstract

The present application belongs to the technical field of metallurgical solid waste recycling, and particularly relates to a method for extracting vanadium from vanadium-containing steel slag, which comprises the following steps: 1) mixing vanadium-containing steel slag, organic alcohol, linear polyethyleneimine, tannic acid and water to obtain a mixture, adding grinding balls to the mixture for wet grinding, and passing CO2-containing industrial waste gas through the wet grinding process to obtain a slurry; 2) adding an ammonium group-containing carbonation reagent to the slurry, uniformly mixing, controlling the temperature for reaction, filtering for the first time, adjusting the pH of the filtrate to 1.5-2.5, cooling, filtering for the second time, and obtaining filter residue, and calcining the obtained filter residue to obtain V2O5. The linear polyethyleneimine is rich in primary amines and secondary amines, and can chemically adsorb and store CO2; and the linear polyethyleneimine can generate bicarbonate after combining with CO2. The tannic acid and the linear polyethyleneimine self-assemble to form a flexible network structure, the bicarbonate is enriched in the micro area of the network structure, a high-concentration bicarbonate microenvironment is formed, and wet grinding is strengthened, so that efficient decalcification and vanadium extraction can be realized without relying on high temperature and high pressure harsh conditions.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical solid waste recycling technology, specifically relating to a method for extracting vanadium from vanadium-containing steel slag. Background Technology

[0002] Vanadium is a high-melting-point rare metal with good plasticity, forgeability, and ductility. Its products possess many valuable physicochemical properties and special characteristics, resulting in a wide range of applications and huge market demand. Approximately 85%-90% of vanadium is used in the smelting of alloy steel. As the world's largest and continuously growing steel producer and consumer, my country has a significant demand for vanadium. Raw material sources for vanadium include vanadium-titanium magnetite, coal shale, and vanadium-containing steel slag. Vanadium-containing steel slag is produced during the steelmaking process using vanadium-containing molten iron. It is characterized by high basicity, low vanadium grade, and complex composition. Its main chemical components are CaO, FeO, SiO2, MgO, and V2O5, with CaO content as high as 30-50% and vanadium pentoxide content of 1-8%. Although the vanadium content is low, it is still higher than that in coal shale, making it an important raw material for vanadium extraction.

[0003] Vanadium extraction methods can be broadly classified into pyrometallurgical vanadium extraction and hydrometallurgical vanadium extraction. Pyrometallurgical vanadium extraction is mostly used for primary vanadium ore resources such as vanadium-titanium magnetite; hydrometallurgical vanadium extraction achieves the transfer of vanadium from the slag phase to the liquid phase through selective leaching, and has advantages such as strong versatility, high leaching efficiency, low energy consumption, excellent selectivity, and high product purity, and has become the mainstream process for vanadium extraction from vanadium-containing steel slag.

[0004] Existing wet vanadium extraction methods mostly employ a roasting-carbonation leaching route: first, vanadium is roasted to convert it into calcium vanadate, which is insoluble in water, and then leached by carbonation. However, the roasting process generally suffers from low vanadium recovery rates and high costs. To address these issues, researchers in this field have largely eliminated the roasting step, directly extracting vanadium through carbonation leaching. For example, patent CN111560523B discloses a process for purifying and recovering calcium components from vanadium-containing steel slag, which uses ammonium carbonate or ammonium bicarbonate as a carbonation agent to leach decalcify and extract vanadium from vanadium-containing steel slag. This process has the advantages of being simple and free from roasting pollution. Because vanadium-containing steel slag has a high calcium oxide content, the consumption of carbonation reagents is large, and the raw material cost remains high. Patent CN107236870B discloses a method for vanadium extraction by carbonization of vanadium-containing steel slag, which extracts vanadium through high-temperature and high-pressure carbon dioxide leaching. This method achieves the goal of vanadium extraction with no pollution, low cost, and high recovery rate, and can also achieve carbon fixation and emission reduction. However, the reaction conditions of high-temperature and high-pressure carbon dioxide (0.3-1.2MPa, 100-180℃) are harsh, and the equipment has high requirements for pressure resistance and corrosion resistance. The equipment investment and maintenance costs are high, making it difficult to promote large-scale industrialization.

[0005] Therefore, it is necessary to develop a direct carbonation leaching method for vanadium extraction from vanadium-containing steel slag that features mild reaction conditions, low equipment requirements, low consumption of carbonation reagents, high vanadium leaching recovery rate, and simple and easily industrialized process, in order to solve the technical problems existing in the current technology. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for extracting vanadium from vanadium-containing steel slag. The method involves first wet milling a mixture of vanadium-containing steel slag, organic alcohol, linear polyethyleneimine (LPEI), tannic acid, and water. Subsequently, calcium is further fixed, vanadium is precipitated, and the mixture is calcined using a carbonation reagent to obtain high-purity V₂O₅. The LPEI molecular chain is rich in primary and secondary amine groups (-NH₂, -NH⁻). These amine groups can undergo a reversible protonation reaction with introduced CO₂. On one hand, this chemically adsorbs and buffers CO₂, effectively increasing its solubility in aqueous solution; on the other hand, the amine groups can generate bicarbonate ions after combining with CO₂. Tannic acid forms intermolecular hydrogen bonds with the amino groups of LPEI through its own phenolic hydroxyl groups, allowing the LPEI chain segments to fully extend and expose more CO2 adsorption and reaction sites. At the same time, the two self-assemble through hydrogen bonds to form a flexible network structure. Bicarbonate is enriched in the micro-regions of this network structure, forming a high-concentration bicarbonate microenvironment. With the help of wet grinding, the efficiency of carbonation and calcium fixation reaction under low pressure and low temperature conditions is greatly improved. It can directionally consume calcium oxide in steel slag and achieve efficient decalcification without relying on high temperature and high pressure conditions, thus reducing the requirements of the process on the pressure resistance and high temperature resistance of the equipment.

[0007] To achieve the above objectives, the following technical solution is adopted:

[0008] A method for extracting vanadium from vanadium-containing steel slag includes the following steps:

[0009] 1) Vanadium-containing steel slag, organic alcohol, linear polyethyleneimine, tannic acid and water are mixed to obtain a mixture. Grinding balls are added to the mixture for wet grinding. During the wet grinding process, industrial waste gas containing CO2 is passed through to obtain a slurry.

[0010] 2) Add an ammonium-containing carbonation reagent to the slurry and mix well. Control the temperature and react. Filter for the first time, adjust the pH of the filtrate to 1.5-2.5, cool down, filter for the second time, and obtain filter residue. Calcine the obtained filter residue to obtain V2O5.

[0011] The purpose of step 1) passing CO2 gas and wet grinding is to consume calcium oxide to generate calcium carbonate and dissolve vanadium, thereby reducing the consumption of the carbonation reagent in step 2) by calcium oxide; the purpose of step 2) is to further remove residual calcium with the carbonation reagent, provide ammonium ions to precipitate vanadium, filter to remove calcium carbonate and slag phase, adjust the pH of the filtrate to 1.5-2.5, cool and precipitate vanadium to obtain ammonium polyvanadate, and calcinate ammonium polyvanadate to obtain high-purity V2O5.

[0012] In step 1), the mass ratio of the vanadium-containing steel slag, organic alcohol, linear polyethyleneimine, tannic acid, and water is 1:0.0003-0.0005:0.05-0.15:0.01-0.03:3-4, preferably 1:0.0003-0.0005:0.10-0.15:0.02-0.03:3-4. The vanadium-containing steel slag contains 1-8 wt% vanadium pentoxide (V₂O₅) by mass; 15-30 wt% total iron (TFe) by mass, of which 5-10 wt% is metallic iron; 35-50 wt% calcium (CaO) and 8-20 wt% silicon (SiO₂) by mass. The vanadium-containing steel slag has a D50 particle size of 1-10 mm. The organic alcohol is selected from at least one of ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, glycerol, dipropylene glycol, tripropylene glycol, pentaerythritol, xylitol, and sorbitol. The linear polyethyleneimine has a number-average molecular weight of 2100-5000. The grinding balls are made of alumina or zirconium oxide. The grinding balls are a mixture of grinding balls with a diameter of 0.5-1 mm and 1-1.5 mm in a ratio of 2-3:1. The ball-to-material ratio is 4-6:1. The wet grinding conditions are: 40-80℃, rotation speed 300-600 r / min, and time 8-12 h. The CO2 volume content in the CO2-containing industrial waste gas is 60-85%. The volume-to-mass ratio of the total CO2-containing industrial waste gas during the wet grinding process to the vanadium-containing steel slag is 450-1200:1 (L / kg). The flow rate of the CO2-containing industrial waste gas is 1-1.5 L / min.

[0013] In step 2), the ammonium-containing carbonation reagent is selected from at least one of ammonium carbonate and ammonium bicarbonate. The ammonium group in the ammonium-containing carbonation reagent satisfies n(NH4)2 + NH4+ with the vanadium in the vanadium-containing steel slag. + The ratio of n(V) to n(V) is 2-3:1. The temperature-controlled reaction is carried out at 30-70℃ for 0.5-2.5 hours. The pH of the filtrate is adjusted to 1.5-2.5 using 5-20wt% sulfuric acid. After the first filtration, washing is performed 1-3 times with water, and the washings are combined with the filtrate. After the second filtration, washing and drying are performed. The washing is performed 1-3 times with water. The drying is performed at 40-80℃ to constant weight. The cooling is performed at 0-25℃. The calcination is performed in air at 500-550℃ for 1-3 hours.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] I. This invention first wet-mills a mixture of vanadium-containing steel slag, organic alcohol, linear polyethyleneimine, tannic acid, and water. Subsequently, it further solidifies calcium, precipitates vanadium, and calcines to obtain high-purity V2O5 through a carbonation reagent. The LPEI (linear polyethyleneimine) molecular chain is rich in a large number of primary and secondary amine groups (-NH2, -NH-). The amine groups can undergo a reversible protonation reaction with the introduced CO2. On the one hand, CO2 is buffered by chemical adsorption, which effectively improves the solubility of CO2 in aqueous solution. On the other hand, the amine groups can generate bicarbonate after combining with CO2. Tannic acid forms intermolecular hydrogen bonds with the amino groups of LPEI through its own phenolic hydroxyl groups, allowing the LPEI chain segments to fully extend and expose more CO2 adsorption and reaction sites. At the same time, the two self-assemble through hydrogen bonds to form a flexible network structure. Bicarbonate is enriched in the micro-regions of this network structure, forming a high-concentration bicarbonate microenvironment. With the help of wet grinding, the efficiency of carbonation and calcium fixation reaction under low pressure and low temperature conditions is greatly improved. It can directionally consume calcium oxide in steel slag and achieve efficient decalcification without relying on high temperature and high pressure conditions, thus reducing the requirements of the process on the pressure resistance and high temperature resistance of the equipment.

[0016] Second, this invention does not require harsh conditions of high temperature and high pressure. It can directly utilize industrial waste gas with a CO2 volume fraction of 60-85% to complete carbonation leaching under normal pressure. The gas flow rate is controlled at 1-1.5L / min. Wet grinding enhances the dissociation of vanadium mineral phase, achieving both efficient vanadium leaching and carbon fixation utilization of industrial waste gas. Subsequently, high-purity V2O5 is obtained through vanadium precipitation by carbonation and calcination. The overall reaction conditions are mild, with low requirements for equipment pressure resistance and corrosion resistance, significantly reducing equipment investment and operating costs, and facilitating large-scale industrial promotion and application. Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, all "parts" mentioned in the embodiments of the present invention are parts by weight. All reagents used are commercially available in the art.

[0018] Linear polyethyleneimine 764604, Mn 2100, from Aldrich.

[0019] Linear polyethyleneimine 764582, Mn 5000, from Aldrich.

[0020] Branched polyethyleneimine SP-018, Mn 1800, from Wuhan Zhuochuang Yuanhang Chemical Co., Ltd.

[0021] A cement plant emits flue gas containing CO2, with a CO2 volume content of 60%.

[0022] The vanadium-containing steel slag came from a steel plant. The vanadium content (vanadium pentoxide, V2O5) was 2.5 wt%, the iron content (TFe) was 25.1 wt%, the metallic iron content was 8.2 wt%, the calcium content (calcium oxide, CaO) was 41.2 wt%, the silicon content (silicon dioxide, SiO2) was 13.8 wt%, and the D50 particle size was 4.2 mm.

[0023] Example 1

[0024] 1) Take 1 kg of vanadium-containing steel slag, weigh and mix it with diethylene glycol, linear polyethyleneimine 764582, tannic acid and water in a mass ratio of 1:0.0003:0.10:0.03:4 to obtain a mixture. Add grinding balls to the mixture with a ball-to-material ratio of 6:1. The grinding balls are a mixture of zirconia balls with a diameter of 1 mm and 1.5 mm in a 2:1 ratio. Wet grinding is carried out at 40℃, 600 r / min, and for 8 hours. During the wet grinding process, CO2-containing flue gas is introduced at a flow rate of 1.5 L / min to obtain a slurry.

[0025] 2) Add ammonium carbonate to the slurry and mix well. The ammonium group in the ammonium carbonate and the vanadium in the vanadium-containing steel slag satisfy n(NH4)2. + ): n(V) = 3:1, react at 70℃ for 0.5h, filter, wash with water 3 times, combine the washing liquids into the filtrate, adjust the pH of the filtrate to 1.5 with 10wt% sulfuric acid, cool to 5℃, filter, wash the filter residue 3 times with water, dry the filter residue at 80℃ to constant weight, and finally calcine the obtained filter residue at 550℃ for 1h in air atmosphere to obtain V2O5.

[0026] Example 2

[0027] The rest is the same as in Example 1, except that in step 1), linear polyethyleneimine 764582 is replaced with an equal mass of linear polyethyleneimine 764604.

[0028] Example 3

[0029] The rest is the same as in Example 1, except that in step 1), vanadium-containing steel slag, diethylene glycol, linear polyethyleneimine 764582, tannic acid, and water are mixed in a mass ratio of 1:0.0003:0.15:0.02:4.

[0030] Example 4

[0031] The rest is the same as in Example 1, except that in step 1), vanadium-containing steel slag, diethylene glycol, linear polyethyleneimine 764582, tannic acid, and water are mixed in a mass ratio of 1:0.0003:0.10:0.01:4.

[0032] Example 5

[0033] The rest is the same as in Example 1, except that in step 1), vanadium-containing steel slag, diethylene glycol, linear polyethyleneimine 764582, tannic acid, and water are mixed in a mass ratio of 1:0.0003:0.05:0.03:4.

[0034] Example 6

[0035] The rest is the same as in Example 1, except that in step 1), the temperature is 80°C, the rotation speed is 300 r / min, the wet grinding time is 12 h, and the CO2-containing flue gas is introduced during the wet grinding process at a flow rate of 1.0 L / min.

[0036] Example 7

[0037] The rest is the same as in Example 1, except that in step 2), ammonium bicarbonate is added to the slurry and mixed thoroughly. The ammonium group in the ammonium bicarbonate satisfies the n(NH4) group with the vanadium group in the vanadium-containing steel slag. + ): n(V) = 3: 1.

[0038] Example 8

[0039] 1) Take 1 kg of vanadium-containing steel slag, weigh and mix the vanadium-containing steel slag, glycerol, linear polyethyleneimine 764582, tannic acid and water in a mass ratio of 1:0.0005:0.1:0.03:3 to obtain a mixture. Add grinding balls to the mixture with a ball-to-material ratio of 4:1. The grinding balls are a mixture of zirconia balls with a diameter of 0.5 mm and 1.0 mm in a 3:1 ratio. Wet grind at 40℃, 600 r / min, for 8 hours. During the wet grinding process, CO2-containing flue gas is introduced at a flow rate of 1.0 L / min to obtain a slurry.

[0040] 2) Add ammonium carbonate to the slurry and mix well. The ammonium group in the ammonium carbonate and the vanadium in the vanadium-containing steel slag satisfy n(NH4)2. + ): n(V) = 2:1, react at 30℃ for 2.5h, filter, wash with water 3 times, combine the washing liquid with the filtrate, adjust the pH of the filtrate to 1.5 with 10wt% sulfuric acid, cool to 5℃, filter, wash the filter residue with water 3 times, dry the filter residue at 80℃ to constant weight, and finally calcine the obtained filter residue at 550℃ for 1h in air atmosphere to obtain V2O5.

[0041] Comparative Example 1

[0042] The rest is the same as in Example 1, except that in step 1), branched polyethyleneimine SP-018 of equal mass is used instead of linear polyethyleneimine 764582.

[0043] Comparative Example 2

[0044] The rest is the same as in Example 1, except that tannic acid is not added in step 1).

[0045] The above embodiments and comparative examples were subjected to the following performance tests:

[0046] 1. Vanadium recovery rate: The mass of vanadium in vanadium pentoxide, m1(V), was determined by ICP-OES; the mass of total vanadium in vanadium-containing steel slag, m0(V), was determined by ICP-OES.

[0047] Vanadium recovery rate = m1(V) / m0(V) × 100%

[0048] 2. Purity of V2O5: The purity was tested according to standard YB / T 5328-2009 Vanadium pentoxide, determination of vanadium pentoxide content by potassium permanganate oxidation-ferrous ammonium sulfate titration method.

[0049] Table 1 Performance Test Results

[0050]

[0051] As can be seen from Table 1, the method for extracting vanadium from vanadium-containing steel slag of the present invention has a high recovery rate, which is as high as 88.4-93.2%, and the purity of the obtained V2O5 is high, which is as high as 98.9-99.5%.

[0052] As can be seen from Table 1, Examples 1 and 2, and Comparative Example 1, only linear polyethyleneimine can synergistically improve the recovery rate with tannic acid in this invention. The likely reason is that branched polyethyleneimine molecules are dendritic and contain a large number of primary, tertiary, and secondary amines. After protonation, they have a high positive charge density and strong molecular rigidity. When carbon dioxide is introduced, branched polyethyleneimine undergoes protonation and electrostatic attraction with negatively charged vanadate ions, rapidly forming a network cross-linked structure, which easily leads to co-precipitation. Linear polyethyleneimine, after protonation, has a low and dispersed positive charge density, a loose charge distribution, and its molecular chains can extend. The weak electrostatic interaction with vanadate ions is insufficient to form a cross-linked structure, preventing co-precipitation and ensuring that vanadate ions remain in the filtrate, thus improving the vanadium recovery rate.

[0053] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A method for extracting vanadium from vanadium-containing steel slag, characterized in that, Includes the following steps: 1) Vanadium-containing steel slag, organic alcohol, linear polyethyleneimine, tannic acid and water are mixed to obtain a mixture. Grinding balls are added to the mixture for wet grinding. During the wet grinding process, industrial waste gas containing CO2 is passed through to obtain a slurry. 2) Add an ammonium-containing carbonation reagent to the slurry and mix well. Control the temperature and react. Filter for the first time, adjust the pH of the filtrate to 1.5-2.5, cool down, filter for the second time, and obtain filter residue. Calcine the obtained filter residue to obtain V2O5.

2. The method for extracting vanadium from vanadium-containing steel slag according to claim 1, characterized in that, In step 1), the mass ratio of the vanadium-containing steel slag, organic alcohol, linear polyethyleneimine, tannic acid, and water is 1:0.0003-0.0005:0.05-0.15:0.01-0.03:3-4, preferably 1:0.0003-0.0005:0.10-0.15:0.02-0.03:3-4.

3. The method for extracting vanadium from vanadium-containing steel slag according to claim 1, characterized in that, In step 1), the vanadium-containing steel slag has a vanadium pentoxide (V2O5) mass fraction of 1-8 wt%; the total iron (TFe) mass fraction of the vanadium-containing steel slag has a total iron (TFe) mass fraction of 15-30 wt%, of which the metallic iron mass fraction is 5-10 wt%; the calcium mass fraction of the vanadium-containing steel slag has a calcium oxide (CaO) mass fraction of 35-50 wt%, and the silicon mass fraction of the vanadium dioxide (SiO2) mass fraction of 8-20 wt%; the vanadium-containing steel slag has a D50 particle size of 1-10 mm.

4. The method for extracting vanadium from vanadium-containing steel slag according to claim 1, characterized in that, In step 1), the linear polyethyleneimine has a number-average molecular weight of 2100-5000; the organic alcohol is selected from at least one of ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, glycerol, dimeric glycerol, trimeric glycerol, pentaerythritol, xylitol, and sorbitol.

5. The method for extracting vanadium from vanadium-containing steel slag according to claim 1, characterized in that, In step 1), the grinding balls are made of alumina or zirconium oxide; the grinding balls are a mixture of grinding balls with a diameter of 0.5-1 mm and grinding balls with a diameter of 1-1.5 mm in a ratio of 2-3:

1. The ball-to-material ratio is 4-6:

1.

6. The method for extracting vanadium from vanadium-containing steel slag according to claim 1, characterized in that, In step 1), the wet grinding conditions are: 40-80℃, rotation speed 300-600r / min, time 8-12h; the CO2 volume content in the CO2-containing industrial waste gas is 60-85%; the volume-to-mass ratio of the total CO2-containing industrial waste gas to the vanadium-containing steel slag during the wet grinding process is 450-1200:1 (L / kg); and the air flow rate of the CO2-containing industrial waste gas is 1-1.5L / min.

7. The method for extracting vanadium from vanadium-containing steel slag according to claim 1, characterized in that, In step 2), the ammonium-containing carbonation reagent is selected from at least one of ammonium carbonate and ammonium bicarbonate; the ammonium group in the ammonium-containing carbonation reagent satisfies n(NH4)2 with the vanadium in the vanadium-containing steel slag. + ): n(V) = 2-3:

1.

8. The method for extracting vanadium from vanadium-containing steel slag according to claim 1, characterized in that, In step 2), the temperature-controlled reaction is controlled at 30-70℃ for 0.5-2.5h.

9. The method for extracting vanadium from vanadium-containing steel slag according to claim 1, characterized in that, In step 2), adjusting the pH of the filtrate to 1.5-2.5 is done by using 5-20 wt% sulfuric acid; the cooling is done by cooling to 0-25°C.

10. The method for extracting vanadium from vanadium-containing steel slag according to claim 1, characterized in that, In step 2), the first filtration also includes washing, washing with water 1-3 times, and combining the washing liquid into the filtrate; the second filtration also includes washing and drying operations. The washing process involves washing with water 1-3 times; the drying process involves drying at 40-80℃ to constant weight; and the calcination process involves calcining in air at 500-550℃ for 1-3 hours.

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