Method for producing ammonium polyvanadate from high-sodium and high-oxalate vanadium slag

Abstract

Disclosed is a method for producing ammonium polyvanadate from high-sodium and high-oxalate vanadium slag, comprising: dissolving vanadium slag to be treated and carrying out primary pH adjustment on same to obtain a vanadium-containing solution; and carrying out sodium removal treatment and impurity removal treatment on the vanadium-containing solution to remove sodium ions, fluorine ions, phosphate radicals, and oxalate in the vanadium-containing solution to obtain a vanadium precipitation solution; and carrying out acidic vanadium precipitation on the vanadium precipitation solution to obtain ammonium polyvanadate.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority to Chinese patent application No. 202310080493.3, filed on January 13, 2023, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The disclosure relates to a field of light metal smelting, and in particular to a method for producing an ammonium polyvanadate from a high-sodium and high-oxalate vanadium slag. BACKGROUND

[0003] As a strategic metal, a vanadium has important application value. The vanadium is often recovered as a by-product of smelting processes for other metal. A bauxite is one of minerals containing the vanadium. During a production process of Bayer process, the vanadium enters a sodium aluminate solution and is continuously enriched, causing a decreased decomposition rate of an aluminum hydroxide to decrease and a refined granularity. At present, there are three main technical approaches aiming at a removement of the vanadium in an alumina production system: a mother liquor precipitation method, an adsorption extraction method, and a low-temperature crystallization method. The mother liquor precipitation method and adsorption extraction method are not widely used in industry because of their high cost and complicated process flow. The low-temperature crystallization method is currently widely used in industry.

[0004] The low-temperature crystallization method is a method of evaporating a mother liquor to increase concentrations of the vanadium and a caustic alkali, and then lowering a temperature of a solution to precipitate vanadates, phosphates, fluoride salts, and the like in the solution to obtain a vanadium-containing salt precipitation slag. The current way of treatment basically uses a vanadium slag to make an ammonium metavanadate, and then calcine the ammonium metavanadate into a vanadium pentoxide. In the related art, for example, Chinese patent application publication No. CN 103159259A, entitled “Method for extracting vanadium pentoxide from evaporation mother liquor in process of Bayer process production alumina”, discloses a way of cooling and crystallizing with the evaporation mother liquor to obtain vanadium salt crystallizations. CN 103159259A also describes in detail a process of preparing the vanadium pentoxide, in which the vanadium pentoxide is obtained through a process of dissolving a vanadium slag, removing impurities from calcium salts or magnesium salts, preparing and calcining an ammonium metavanadate. However, in a process of preparing the ammonium metavanadate, a vanadium content in a vanadium precipitation solution is high, a vanadium-precipitation rate is low, and a consumption of ammonium salts is large. SUMMARY

[0005] By utilizing one or more embodiments of the disclosure, a problem of low vanadium-precipitation rate in preparing an ammonium polyvanadate using a vanadium slag generated from a production of alumina is solved.

[0006] A method for producing an ammonium polyvanadate from a high-sodium and high-oxalate vanadium slag according to some embodiments of the disclosure includes: dissolving and performing a first pH adjustment on a vanadium slag to be treated to obtain a vanadium-containing solution; performing a sodium removal treatment and impurity removal treatment on the vanadium-containing solution to remove sodium ions, fluoride ions, phosphate radical and oxalate radical in the vanadium-containing solution to obtain a vanadium precipitation solution; and performing an acidic vanadium precipitation on the vanadium precipitation solution to obtain an ammonium polyvanadate. BRIEF DESCRIPTION OF DRAWINGS

[0007] The accompanying drawing, which is incorporated in and constitutes a portion of this specification, and illustrates embodiments consistent with the disclosure and serves to explain principles of the disclosure together with the description.

[0008] In order to more clearly illustrate the embodiments of the disclosure or the technical solutions in the related art, the accompanying drawings needed to be used in the description of the embodiments or the related art will be briefly introduced below. Obviously, for those skilled in the art, other accompanying drawings can also be obtained based on these accompanying drawings without creative efforts.

[0009] FIG. 1 shows a flow chart of a method for producing an ammonium polyvanadate from a high-sodium and high-oxalate vanadium slag according to some embodiments of the disclosure;

[0010] FIG. 2 shows a process flow chart of a method for producing an ammonium polyvanadate from a high-sodium and high-oxalate vanadium slag according to some embodiments of the disclosure;

[0011] FIG. 3 shows a process flow chart of a first sodium removal treatment according to some embodiments of the disclosure; and

[0012] FIG. 4 shows a process flow diagram of a second sodium removal treatment according to some embodiments of the disclosure. DETAILED DESCRIPTION

[0013] In order to make purposes, technical solutions and advantages of the embodiments of the disclosure clearer, the technical solutions in the embodiments of the disclosure will be clearly and completely described below in conjunction with the accompanying drawing according to the embodiments of the disclosure. Obviously, the described embodiments are some embodiments of the disclosure, but not all embodiments. Based on the embodiments in the disclosure, all other embodiments obtained by those skilled in the art without any creative efforts fall within the scope of protection sought by the disclosure.

[0014] Unless otherwise specified, various raw materials, reagents, instruments, and equipment used in the disclosure are commercially available or obtained through existing methods.

[0015] The applicant discovered during research that a vanadium slag, obtained by cooling and crystallization with the Bayer process for a production of alumina as a wet process for alkaline treatment of bauxite, has a high sodium content, where a content of Na2O can reach 40%-50%. Also, because the vanadium in a solution is precipitated as a complex salt formed by a fluorine, phosphorus, and vanadium, in which a content of the phosphorus is as high as 6%-8%, far beyond a conventional production process of vanadium. At the same time, an organic matter in an alumina production system will also be precipitated as an alkalinity increases and a temperature decreases, causing that the vanadium slag contains a certain amount of sodium oxalate, a content of which can reach 40%. Therefore, the vanadium slag obtained in a production process for an alumina is a vanadium salt crystallization with high sodium, high sodium oxalate and high impurities, which is difficult to treat. In particular, when a mole ratio of [Na2O] / [V2O5] in a vanadium precipitation solution is greater than 2.55, a quality of ammonium polyvanadate product and a vanadium-precipitation rate will decrease. On the other hand, a presence of the organic matter will also lead to a decrease in the vanadium-precipitation rate.

[0016] A method for producing an ammonium polyvanadate from a high-sodium and high-oxalate vanadium slag according to some embodiments of the disclosure includes: dissolving and performing a first pH adjustment on a vanadium slag to be treated, to obtain a vanadium-containing solution; performing a sodium removal treatment and impurity removal treatment on the vanadium-containing solution to remove sodium ions, fluoride ions, phosphate radical and oxalate radical in the vanadium-containing solution to obtain a vanadium precipitation solution; and performing an acidic vanadium precipitation on the vanadium precipitation solution to obtain an ammonium polyvanadate.

[0017] The method for producing an ammonium polyvanadate from a high-sodium and high-oxalate vanadium slag according to some embodiments of the disclosure can ameliorate a problem of low vanadium-precipitation rate in preparing an ammonium polyvanadate using a vanadium slag generated from a production of alumina.

[0018] As shown in FIGS. 1 and 2, the method for producing the ammonium polyvanadate from the high-sodium and high-oxalate vanadium slag according to some embodiments of the disclosure comprises:

[0019] Step S0, washing a vanadium slag to be treated until a color of the vanadium slag to be treated is white;

[0020] Step S1, dissolving and performing a first pH adjustment on the vanadium slag to be treated, to obtain a vanadium-containing solution;

[0021] Step S2, performing a sodium removal treatment and impurity removal treatment on the vanadium-containing solution to remove sodium ions, fluoride ions, phosphate radical and oxalate radical in the vanadium-containing solution to obtain a vanadium precipitation solution; and

[0022] Step S3, performing an acidic vanadium precipitation on the vanadium precipitation solution to obtain an ammonium polyvanadate.

[0023] In one or more embodiments, in step S0, a washing liquid for the washing is a cold water, and a temperature of the cold water ranges from 20°C-45°C.

[0024] In one or more embodiments, in step S1, a dissolving temperature ranges from 60°C-90°C; a target pH value of the first pH adjustment ranges from 9-11; a way for the first pH adjustment is to introduce carbon dioxide; and a liquid-solid ratio of the vanadium-containing solution ranges from 1.4-2.5.

[0025] In one or more embodiments, a dissolving temperature being controlled to range from 60° C-90° C, is to enable the vanadium slag to be dissolved as much as possible and maintain a relatively high vanadium concentration. A too high dissolving temperature has an adverse effect that a solubility of the vanadium slag is not greatly improved, and thus an energy consumption is high. A too low dissolving temperature has an adverse effect that the solubility of the vanadium slag is low, a vanadium concentration is low, to be disadvantageous to improving a production efficiency.

[0026] In one or more embodiments, a target pH value of the first pH adjustment is controlled to range from 9-11 because under this condition, a cryolite structure can be produced and it is advantageous to a subsequent removal of impurities. A too large or too small target pH value of the first pH adjustment will be disadvantageous to a production of cryolite or lead to a decrease in a removal rate of impurities.

[0027] In one or more embodiments, a liquid-solid ratio of the vanadium-containing solution is controlled to range from 1.4-2.5 because it can ensure the vanadium concentration in a solution and improve the production efficiency. A too high liquid-solid ratio of the vanadium-containing solution has an adverse effect that the vanadium concentration in the solution is low and the production efficiency is low. A too small liquid-solid ratio of the vanadium-containing solution has an adverse effect that the vanadium slag is not completely dissolved and a leaching rate of vanadium is low.

[0028] In one or more embodiments, the step S2 includes:

[0029] Step S2.1, performing a first sodium removal treatment on the vanadium-containing solution to remove the sodium ions, to obtain a first sodium removal solution and a cryolite;

[0030] Step S2.2, performing the impurity removal treatment on the first sodium removal solution to remove the fluoride ions, the phosphate radical and the oxalate radical, to obtain a primary vanadium precipitation solution; and,

[0031] Step S2.3, performing a second sodium removal treatment on the primary vanadium precipitation solution to remove the sodium ions, to obtain a vanadium precipitation solution and a sodium bicarbonate.

[0032] In one or more embodiments, in step S2.1, a sodium removal agent for the first sodium removal treatment contains aluminum ions. A relationship between a molar content a of the aluminum ions and a molar content b of fluorine elements in the vanadium-containing solution satisfies: a:b = (1.2-1.4):6. A reaction time of the first sodium removal treatment ranges from 40 min-60 min. In some embodiments, the sodium removal agent for the first sodium removal treatment may be selected from an aluminum chloride and / or an aluminum sulfate.

[0033] In one or more embodiments, a molar ratio of the aluminum ions and the fluorine elements in the vanadium-containing solution is controlled to be (1.2-1.4):6, because it is conducive to a formation of the cryolite structure. This molar ratio, taken too large, has an adverse effect that aluminum elements are introduced as an impurity. This molar ratio, taken too small, has an adverse effect of a low removal rate of the fluorine.

[0034] In one or more embodiments, in step S2.2, an impurity removal agent for the impurity removal treatment contains calcium ions. A relationship between a molar content c of the calcium ions and a sum d of molar contents of the fluoride ions, the phosphate radical and the oxalate radical in the first sodium removal solution satisfies: c:d=(1.1-1.2):1. In some embodiments, the impurity removal agent for the impurity removal treatment may be selected from a calcium hydroxide and / or a calcium bicarbonate.

[0035] In one or more embodiments, the molar ratio of the molar content of the impurity removal agent added and a sum of molar contents of the impurities (phosphorus, fluorine, and oxalate radical) is controlled to range from 1.1-1.2 times to achieve a removal of impurities and obtain qualified products. This molar ratio, taken too large, has an adverse effect of a high loss rate of the vanadium. This molar ratio, taken too small, has an adverse effect of a low removal rate of impurities and a too high content of impurities in the product.

[0036] In some embodiments, the step S2.3 includes:

[0037] introducing a carbon dioxide into the primary vanadium precipitation solution to perform a second sodium removal treatment to remove the sodium ions, to obtain a vanadium precipitation solution and a sodium bicarbonate; a temperature of the primary vanadium precipitation solution ranges from 45°C-60°C.

[0038] In one or more embodiments, the temperature of the primary vanadium precipitation solution is controlled to range from 45°C-60°C to utilize a precipitation of the sodium bicarbonate. This temperature being taken too large has an adverse effect of a decomposition of the sodium bicarbonate. This temperature being taken too small has an adverse effect of a high energy consumption and a high cost.

[0039] In one or more embodiments, the step S3 includes:

[0040] Step S3.1, performing a second pH adjustment on the vanadium precipitation solution until a pH value ranges from 6-7, and then adding a vanadium-precipitation agent, and raising a temperature to range from 90°C-99°C; wherein the vanadium-precipitation agent includes an ammonium salt, and a relationship between a molar content e of the ammonium salt and a molar content f of vanadium in the vanadium precipitation solution satisfies: e:f=(1.3-1.8):1. In some embodiments, the ammonium salt may be selected from an ammonium sulfate; and

[0041] Step S3.2, adding a sulfuric acid to the vanadium precipitation solution with a temperature ranging from 90°C-99°C until a pH value ranges from 2-3 for a vanadium precipitation to obtain an ammonium polyvanadate; wherein a time of the vanadium precipitation ranges from 40 min-60 min.

[0042] With the above designs, to optimize a extraction process for the vanadium in a production process of alumina, by removing the sodium and oxalate in an alumina production system, an impact of the sodium and oxalate on a process of the vanadium precipitation is reduced, and the cryolite and the sodium bicarbonate are recovered. Thus, a resource utilization rate is improved, processes are optimized. A vanadium-precipitation rate can be increased. An amount of used vanadium-precipitation agent can be reduced.

[0043] The disclosure is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the disclosure and are not intended to limit a scope sought for by the disclosure. Experimental methods without specifying specific conditions in the following examples are typically performed in accordance with national standards in China. If there is no corresponding national standards in China, general international standards, conventional conditions, or conditions recommended by the manufacturer shall be followed.

[0044] Example 1

[0045] A precipitated vanadium slag at a certain alumina plant is taken as an example. A moisture content of a salt precipitation slag is 45%, and a vanadium content of the salt precipitation slag is 9% (calculated on a dry basis). 70 g vanadium slag is dissolved with a liquid-to-solid ratio of 1.7 and a temperature of 80°C. If the vanadium slag is not washed before being dissolved, in a solution with unwashed vanadium slag, a vanadium concentration is 30 g / L, and a sodium-ion concentration is 99 g / L. In this example, before the vanadium slag is dissolved, a same amount of the vanadium slag is washed with 20°C cold water. Then, in a solution with washed vanadium slag, a vanadium concentration is 26 g / L, a sodium-ion concentration is 70 g / L, a fluorine concentration is 7.5 g / L, and an oxalate concentration is 5.4 g / L. A carbon dioxide is introduced to adjust a pH of the solution to be 9. A first sodium removal treatment is performed on the solution, that is, an aluminum chloride is added in with an added amount of a molar ratio of [Al:F] of 1.6:6, and a reaction time is 40 min. Then the solution is filtrated to obtain 1.41 g of solid cryolite and a first sodium removal solution. In the first sodium removal solution, a fluorine concentration is reduced to be 2.21 g / L, and a sodium concentration is 66.2 g / L. A calcium hydroxide is added into the first sodium removal solution to perform an impurity removal, to remove impurities such as phosphorus, fluorine, and oxalate radical in the solution. A mole ratio of an added amount of the calcium hydroxide and an amount of the impurities (the phosphorus, fluorine, and oxalate radical) is 1.2. After the impurity removal, concentrations of the phosphorus, fluorine, and oxalate radical in the solution are relatively low and can not be detected. A second sodium removal treatment is performed on the solution after the impurity removal, that is, the solution after the impurity removal is cooled to be 45°C, and a carbon dioxide gas is introduced. When no precipitations are precipitated, 13.5 g of solid sodium bicarbonate and a vanadium precipitation solution are obtained through a filtration. A sodium in the vanadium precipitation solution is 39.2 g / L. After a sodium removal is completed, an acidic vanadium precipitation is carried out, that is, a sulfuric acid is used to adjust a pH of the vanadium precipitation solution to be 6, an ammonium sulfate is added as a vanadium-precipitation agent, and a molar ratio of an amount of the vanadium-precipitation agent used and an amount of vanadium is 1.3. A temperature of the solution is raised to be 90°C, and a pH value of the solution is adjusted to be about 3 for reacting for 60 minutes, and then a product of ammonium polyvanadate is obtained by a filtration and washing. The vanadium concentration in the solution after the vanadium precipitation is 0.01 g / L.

[0046] Example 2

[0047] A precipitated vanadium slag at a certain alumina plant is taken as an example. A moisture content of a salt precipitation slag is 45%, and a vanadium content of the salt precipitation slag is 9% (calculated on a dry basis). 70 g vanadium slag is dissolved with a liquid-to-solid ratio of 1.4 and a temperature of 80°C. If the vanadium slag is not washed before being dissolved, in a solution with unwashed vanadium slag, a vanadium concentration is 34.5 g / L, and a sodium-ion concentration is 114 g / L. In this example, before the vanadium slag is dissolved, the same amount of the vanadium slag is washed with 45°C cold water. Then, in a solution with washed vanadium slag, a vanadium concentration is 29.7 g / L, a sodium-ion concentration is 67 g / L, a fluorine concentration is 9.05 g / L, and an oxalate concentration is 6.8 g / L. A carbon dioxide is introduced to adjust a pH of the solution to be 11. A first sodium removal treatment is performed on the solution, that is an aluminum sulfate is added in with an added amount of a molar ratio of [Al:F] of 1.2:6, and a reaction time is 60 min. Then the solution is filtrated to obtain 1.40 g of solid cryolite and a first sodium removal solution. In the first sodium removal solution, a fluorine concentration is reduced to be 3.24 g / L, and a sodium concentration is 62.7 g / L. A calcium bicarbonate is added into the first sodium removal solution to perform an impurity removal, to remove impurities such as phosphorus, fluorine, and oxalate radical in the solution. A mole ratio of an added amount of the calcium bicarbonate and an amount of the impurities (the phosphorus, fluorine, and oxalate radical) is 1.1. After the impurity removal, concentrations of the phosphorus, fluorine, and oxalate radical in the solution are relatively low and could not be detected. A second sodium removal treatment is performed on the solution after the impurity removal, that is, the solution after the impurity removal is cooled to be 60°C, and a carbon dioxide gas is introduced. When no precipitation is precipitated, 8.43 g of solid sodium bicarbonate and a vanadium precipitation solution are obtained through a filtration. A sodium in the vanadium precipitation solution is 42.5 g / L. After a sodium removal is completed, an acidic vanadium precipitation is carried out, that is, a sulfuric acid is used to adjust a pH of the vanadium precipitation solution to be 7, an ammonium sulfate is added as a vanadium-precipitation agent, and a molar ratio of an amount of the vanadium-precipitation agent used and an amount of vanadium is 1.6. A temperature of the solution is raised to be 95°C, and a pH value of the solution is adjusted to be about 2.5 for reacting for 60 minutes, and then a product of ammonium polyvanadate is obtained by filtration and washing. The vanadium concentration in the solution after the vanadium precipitation is 0.01 g / L.

[0048] Example 3

[0049] A precipitated vanadium slag at a certain alumina plant is taken as an example. A moisture content of a salt precipitation slag is 45%, and a vanadium content of the salt precipitation slag is 9% (calculated on a dry basis). 70 g vanadium slag is dissolved with a liquid-to-solid ratio of 2.5 and a temperature of 60°C. If the vanadium slag is not washed before being dissolved, in a solution with unwashed vanadium slag, a vanadium concentration is 22.5 g / L, and a sodium-ion concentration is 74.25 g / L. In this example, before the vanadium slag is dissolved, the same amount of the vanadium slag is washed with 45°C cold water. Then, in a solution with washed vanadium slag, a vanadium concentration is 19.4 g / L, a sodium-ion concentration is 61 g / L, a fluorine concentration is 5.6 g / L, and an oxalate concentration is 4.3 g / L. A carbon dioxide is introduced to adjust a pH of the solution to be 9. The solution is subjected to a first sodium removal treatment, that is an aluminum chloride is added in with an added amount of a molar ratio of [Al:F] of 1.2:6, and a reaction time is 60 min. Then the solution is filtrated to obtain 1.60 g of solid cryolite and a first sodium removal solution. In the first sodium removal solution, a fluorine concentration is reduced to be 1.14 g / L, and a sodium concentration is 57.4 g / L. A calcium hydroxide is added into the first sodium removal solution to perform an impurity removal, to remove impurities such as phosphorus, fluorine, and oxalate radical in the solution. A mole ratio of a mole ratio of an added amount of the calcium hydroxide and an amount of the impurities (the phosphorus, fluorine, and oxalate radical) is 1.2. After the impurity removal, concentrations of the phosphorus, fluorine, and oxalate radical in the solution are relatively low and could not be detected. A second sodium removal treatment is performed on the solution after the impurity removal, that is, the solution after the impurity removal is cooled to be 60°C, and a carbon dioxide gas is introduced. When no precipitation is precipitated, 10.1 g of solid sodium bicarbonate and a vanadium precipitation solution are obtained through filtration. A sodium in the vanadium precipitation solution is 43.4 g / L. After a sodium removal is completed, an acidic vanadium precipitation is carried out, that is, a sulfuric acid is used to adjust a pH of the vanadium precipitation solution to be 7, an ammonium sulfate is added as a vanadium-precipitation agent, and a molar ratio of an amount of the vanadium-precipitation agent used and an amount of vanadium is 1.8. A temperature of the solution is raised to be 99°C, and a pH value of the solution is adjusted to be about 2 for reacting for 40 minutes, and then a product of ammonium polyvanadate is obtained by filtration and washing. The vanadium concentration in the solution after the vanadium precipitation is 0.01 g / L.

[0050] Example 4

[0051] A precipitated vanadium slag at a certain alumina plant is taken as an example. A moisture content of a salt precipitation slag is 45%, and a vanadium content of the salt precipitation slag is 9% (calculated on a dry basis). 70 g vanadium slag is dissolved with a liquid-to-solid ratio of 1.7 and a temperature of 85°C. If the vanadium slag is not washed before being dissolved, in a solution with unwashed vanadium slag, a vanadium concentration is 30 g / L, and a sodium-ion concentration is 99 g / L. In this example, before the vanadium slag is dissolved, the same amount of the vanadium slag is washed with 25°C cold water. Then, in a solution with washed vanadium slag, a vanadium concentration is 25 g / L, a sodium-ion concentration is 67 g / L, a fluorine concentration is 6.5 g / L, and an oxalate concentration is 5.2 g / L. A carbon dioxide is introduced to adjust a pH of the solution to be 9. A first sodium removal treatment is performed on the solution, that is an aluminum chloride is added in with an added amount of a molar ratio of [Al:F] of 1.2:6, and a reaction time is 50 min. Then the solution is filtrated to obtain 1.32 g of solid cryolite and a first sodium removal solution. In the first sodium removal solution, a fluorine concentration is reduced to be 1.32 g / L, and a sodium concentration is 62.5 g / L. A calcium bicarbonate is added into the first sodium removal solution to perform an impurity removal, to remove impurities such as phosphorus, fluorine, and oxalate radical in the solution. A mole ratio of an added amount of the calcium bicarbonate and an amount of the impurities (the phosphorus, fluorine, and oxalate radical) is 1.1. After the impurity removal, concentrations of the phosphorus, fluorine, and oxalate radical in the solution are relatively low and could not be detected. A second sodium removal treatment is performed on the solution after the impurity removal, that is, the solution after the impurity removal is cooled to be 45°C, and a carbon dioxide gas is introduced. When no precipitations are precipitated, 11.8 g of solid sodium bicarbonate and a vanadium precipitation solution are obtained through a filtration. A sodium in the vanadium precipitation solution is 40.6 g / L. After a sodium removal is completed, an acidic vanadium precipitation is carried out, that is, a sulfuric acid is used to adjust a pH of the vanadium precipitation solution to be 6, an ammonium sulfate is added as a vanadium-precipitation agent, and a molar ratio of an amount of the vanadium-precipitation agent used and an amount of vanadium is 1.4. A temperature of the solution is raised to be 90°C, and a pH value of the solution is adjusted to be about 3 for reacting for 60 minutes, and then a product of ammonium polyvanadate is obtained by a filtration and washing. The vanadium concentration in the solution after the vanadium precipitation is 0.01 g / L.

[0052] Comparative Example 1

[0053] A precipitated vanadium slag at a certain alumina plant is taken as an example. A moisture content of a salt precipitation slag is 45%, and a vanadium content of the salt precipitation slag is 9% (calculated on a dry basis). 70 g vanadium slag is dissolved with a liquid-to-solid ratio of 1.7 and at a temperature of 85°C. The vanadium slag is not washed before being dissolved. In a solution with unwashed vanadium slag, a vanadium concentration is 30 g / L and a sodium-ion concentration is 99 g / L. A sulfuric acid was added to adjust a pH of the solution to be 9. A magnesium sulfate is then added to perform an impurity removal, to remove impurities such as phosphorus, fluorine, and oxalate radical in the solution. A mole ratio of an added amount of the magnesium sulfate and an amount of the impurities (the phosphorus, fluorine, and oxalate radical) is 1.2. After the impurity removal, concentrations of the phosphorus, fluorine, and oxalate radical in the solution are relatively low and could not be detected. A sulfuric acid is used to adjust a pH of the solution after the impurity removal to be 7, an ammonium sulfate is added as a vanadium-precipitation agent, and a molar ratio of an amount of the vanadium-precipitation agent used and an amount of vanadium is 1.8. A temperature of the solution is raised to be 99°C, and a pH value of the solution is adjusted to be about 2 for reacting for 40 minutes, and then a product of ammonium polyvanadate is obtained by filtration and washing. A content of sodium as impurity in the product is 8.5%. A vanadium concentration in the solution after a vanadium precipitation is 3.2 g / L.

[0054] Comparative Example 2

[0055] A precipitated vanadium slag at a certain alumina plant is taken as an example. A moisture content of a salt precipitation slag is 45%, and a vanadium content of a salt precipitation slag is 9% (calculated on a dry basis). 70 g vanadium slag is dissolved with a liquid-to-solid ratio of 1.7 and at a temperature of 85°C. The vanadium slag is not washed before being dissolved. In a solution with unwashed vanadium slag, a vanadium concentration is 30 g / L and a sodium-ion concentration is 99 g / L. A hydrochloric acid was added to adjust a pH of the solution to be 9. A magnesium chloride is then added to perform an impurity removal, to remove impurities such as phosphorus, fluorine, and oxalate radical in the solution. A mole ratio of an added amount of the magnesium chloride and an amount of the impurities (the phosphorus, fluorine, and oxalate radical) is 1.2. After the impurity removal, concentrations of the phosphorus, fluorine, and oxalate radical in the solution are relatively low and could not be detected. A temperature of the solution was decreased to be 45°C, and an ammonium chloride is added as a vanadium-precipitation agent, and a molar ratio of an amount of the vanadium-precipitation agent used and an amount of vanadium is 3.5. After reacting for 40 min, a product of ammonium metavanadate is obtained by filtration and washing. A vanadium concentration in the solution after a vanadium precipitation is 0.18 g / L.

[0056] By comparing the comparative examples with the examples, it can be concluded that the method for producing the ammonium polyvanadate from the high-sodium and high-oxalate vanadium slag according to the embodiments of the disclosure can effectively improve the vanadium-precipitation rate and reduce the amount of vanadium-precipitation agent used.

[0057] The method for producing the ammonium polyvanadate from the high-sodium and high-oxalate vanadium slag according to some embodiments of the disclosure has the following advantages compared with the related art.

[0058] In the method for producing the ammonium polyvanadate from the high-sodium and high-oxalate vanadium slag according to some embodiments of the disclosure, the sodium removal treatment and impurity removal treatment are performed before the vanadium precipitation, and thus at least a portion of impurity ions such as sodium ions, fluoride ions, phosphate radical and oxalate radical are removed, thereby reducing impacts of the impurity ions on a process of the vanadium precipitation, thereby effectively improving the vanadium-precipitation rate, and reducing the amount of vanadium-precipitation agent used.

[0059] Various embodiments of the present disclosure may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and simplicity and should not be understood as a hard limit to the scope of the present disclosure; therefore, the described range should be considered to have specifically disclosed all possible subranges as well as the single values within such a range. For example, a description of a range from 1 to 6 should be considered to have disclosed subranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, and from 3 to 6, and a single number within the stated range, such as 1, 2, 3, 4, 5, and 6, which applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it is intended to include any cited number (fractional or whole) within the indicated range.

[0060] In the disclosure, unless otherwise specified, the directional words used such as “upper” and “lower” refer specifically to the direction of the figure in the drawing. In addition, in the description of the present disclosure, the terms “including”, “comprising” and the like refer to “including but not limited to”. In the disclosure, relational terms such as “first” and “second” are merely used to distinguish one entity or operation from another and do not necessarily require or imply any such actual relationship or sequence between these entities or operations. In the disclosure, “and / or” describes the relationship between associated objects, indicating that there may be three relationships. For example, A and / or B may refer to: A alone, both A and B, and B alone. In which, A and B can be singular or plural. In the disclosure, “at least one” refers to one or more, and “plurality” refers to two or more. “At least one”, “at least one of the following” or similar expressions thereof refers to any combination of these items, including single items or any combination of plural items. For example, “at least one of a, b, or c”, or “at least one of a, b, and c” may represent: a, b, c, a~b (that is, a and b) , a~c, b~c, or a~b~c in which a, b, and c can each be single or multiple.

[0061] The above descriptions are only embodiments of the disclosure, enabling those skilled in the art to understand or implement the disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principle defined in the disclosure may be practiced in other embodiments without departing from the spirit or scope of the disclosure. Therefore, the disclosure is not to be limited to the embodiments shown in the disclosure but is to be accorded the widest scope consistent with the principles and novel features claimed in the disclosure.

Claims

1. A method for producing an ammonium polyvanadate from a high-sodium and high-oxalate vanadium slag, comprising:dissolving and performing a first pH adjustment on a vanadium slag to be treated to obtain a vanadium-containing solution;performing a sodium removal treatment and impurity removal treatment on the vanadium-containing solution to remove sodium ions, fluoride ions, phosphate radical and oxalate radical in the vanadium-containing solution to obtain a vanadium precipitation solution; andperforming an acidic vanadium precipitation on the vanadium precipitation solution to obtain an ammonium polyvanadate.

2. The method according to claim 1, wherein the performing the sodium removal treatment and the impurity removal treatment on the vanadium-containing solution to remove the sodium ions, fluoride ions, phosphate radical and oxalate radical in the vanadium-containing solution to obtain the vanadium precipitation solution, comprisesperforming a first sodium removal treatment on the vanadium-containing solution to remove the sodium ions, to obtain a first sodium removal solution and a cryolite;performing the impurity removal treatment on the first sodium removal solution to remove the fluoride ions, the phosphate radical and the oxalate radical, to obtain a primary vanadium precipitation solution; andperforming a second sodium removal treatment on the primary vanadium precipitation solution to remove the sodium ions, to obtain the vanadium precipitation solution and a sodium bicarbonate.

3. The method according to claim 2, wherein a sodium removal agent for the first sodium removal treatment contains aluminum ions; anda relationship between a molar content a of the aluminum ions and a molar content b of fluorine elements in the vanadium-containing solution satisfies: a:b = (1.2-1.4):6, and / or a reaction time of the first sodium removal treatment ranges from 40 min-60 min.

4. The method according to claim 3, wherein the sodium removal agent for the first sodiumremoval treatment comprises an aluminum chloride and / or an aluminum sulfate.

5. The method according to claim 2, wherein an impurity removal agent for the impurity removal treatment contains calcium ions, and wherein a relationship between a molar content c of the calcium ions and a sum d of molar contents of the fluoride ions, the phosphate radical and the oxalate radical in the first sodium removal solution satisfies: c:d=(1.1-1.2):1.

6. The method according to claim 5, wherein the impurity removal agent for the impurity removal treatment comprises a calcium hydroxide and / or a calcium bicarbonate.

7. The method according to claim 2, wherein the performing the second sodium removal treatment on the primary vanadium precipitation solution to remove the sodium ions, to obtain the vanadium precipitation solution and the sodium bicarbonate, comprises:introducing a carbon dioxide into the primary vanadium precipitation solution to perform a second sodium removal treatment so as to remove the sodium ions, to obtain a vanadium precipitation solution and a sodium bicarbonate; and / ora temperature of the primary vanadium precipitation solution is 45°C-60°C.

8. The method according to claim 1, wherein a dissolving temperature ranges from 60°C-90°C; and / or,a target pH value of the first pH adjustment ranges from 9-11; and / or,a way for the first pH adjustment is to introduce carbon dioxide;a liquid-solid ratio of the vanadium-containing solution ranges from 1.4-2.5.

9. The method according to claim 1, wherein the performing the acidic vanadium precipitation on the vanadium precipitation solution to obtain the ammonium polyvanadate, comprises:performing a second pH adjustment on the vanadium precipitation solution until a pH value ranges from 6-7, and then adding a vanadium-precipitation agent, and raising a temperature to range from 90°C-99°C;adding a sulfuric acid to the vanadium precipitation solution with a temperature ranging from 90°C-99°C until a pH value ranges from 2-3 for a vanadium precipitation to obtain an ammonium polyvanadate;wherein the vanadium-precipitation agent comprises an ammonium salt, and a relationship between a molar content e of the ammonium salt and a molar content f of vanadium in the vanadium precipitation solution satisfies: e:f=(1.3-1.8):1;a time of the vanadium precipitation ranges from 40 min-60 min.

10. The method according to claim 1, wherein before the dissolving, the method further comprises:washing a vanadium slag to be treated until a color of the vanadium slag to be treated is white, and a temperature of a washing liquid for the washing ranges from 20°C-45°C.

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