Large-size high-density ammonium metavanadate and preparation method thereof

Abstract

The invention belongs to the technical field of vanadium extraction, and particularly discloses large-size high-density ammonium metavanadate and a preparation method thereof. The method comprises the following steps: (1) roasting and crushing the vanadium slag to obtain refined vanadium slag; (2) carrying out alkaline leaching, acid adjustment and impurity removal on the refined vanadium slag to obtain a vanadium precipitation stock solution; (3) polyvinylpyrrolidone and soluble ammonium salt are added into the vanadium precipitation stock solution, the number-average molecular weight of the polyvinylpyrrolidone is 7000-10000, and the polyvinylpyrrolidone and the soluble ammonium salt react for 40-80 min at the temperature of 30-50 DEG C; and (4) after the reaction is finished, carrying out solid-liquid separation to obtain the large-size high-density ammonium metavanadate. In the vanadium precipitation process, polyvinylpyrrolidone is added as a surface dispersant and a nucleation modifier, so that the apparent density of an ammonium metavanadate product can be improved, the particle size of ammonium metavanadate is increased, and industrial application of ammonium metavanadate is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of vanadium extraction, and particularly relates to a large-size high-density ammonium metavanadate and a preparation method thereof. Background Art

[0002] Vanadium is a transition element with the element symbol V, atomic number 23, and atomic weight 50.94. Pure metallic vanadium is silver-gray and has relatively high melting and boiling points under standard atmospheric pressure. All the outermost electrons of vanadium can participate in bonding, combining with oxygen or other elements to form vanadium compounds with different valence states. According to the different valence states of vanadium, high-valence vanadium compounds have oxidizing properties, while low-valence ones have reducing properties.

[0003] Vanadium is a globally scarce resource and also a commonly used strategic metal, which is widely used in the fields of steel, chemical engineering, and aerospace. In addition, it also occupies an important position in the fields of electronic technology, military industry, etc. Among them, it is often used as an alloy additive in the steel industry, and the consumption accounts for more than 90% of the total consumption. Adding vanadium as an additive in steel can significantly change its properties. Data shows that adding 0.1% of vanadium in steel can increase the strength by 10% - 20%, reduce the structural weight by about 15% - 25%, and reduce the production cost by about 10%. The demand for vanadium resources in China is very large, and the production and consumption account for about 50% of the global vanadium product market. With the development of the economy and the prosperity of the steel market, there is a greater demand for high-quality vanadium steels such as high-quality steel, refined steel, and special steel. At present, the vanadium consumption intensity in the steel industry in China is relatively low, about 50 grams / ton of steel, far lower than the average level of developed countries such as Europe and the United States. In recent years, with the prosperity of the vanadium market, the demand and price of vanadium have increased year by year, and there is a large gap in vanadium demand in China. Therefore, the domestic vanadium industry has great development potential.

[0004] The main sources of vanadium in nature are vanadium-titanium magnetite, stone coal, and bauxite in the alumina industry. Vanadium is enriched in the form of waste residue during the extraction of alumina by the Bayer process or the sintering process. Since each alumina plant was put into production, the vanadium in the alumina solution system has been continuously enriched and increased. Vanadium precipitates during the processes of seed precipitation, transportation, storage, etc. when the temperature drops, which has a greater impact on the quality of alumina products and the production process. The reserves of vanadium-titanium magnetite and stone coal resources in China are very considerable, and both the proven reserves and the mining volume rank among the top in the world. However, whether it is the sodium roasting process or the calcification roasting process of vanadium slag from vanadium-titanium magnetite, or the sodium roasting process or the acid leaching process for extracting vanadium from stone coal, V 2 O 5 are all bulk mainstream products. And the acquisition of V 2 O 5 is basically obtained by adding ammonium salts to the vanadium-containing leaching solution, precipitating vanadium with ammonium salts to obtain vanadium-containing ammonium salts of various valence states, and then separating ammonium and vanadium by calcination. That is to say, in the current mainstream vanadium production process, ammonium metavanadate is V 2 O5 The intermediate product that must be obtained. The current mainstream vanadium extraction process is the roasting vanadium extraction process, which is the most widely used process and accounts for more than 90% of the vanadium slag vanadium extraction production capacity.

[0005] Vanadium slag contains heavy metals (such as vanadium, chromium, etc.). If it is improperly stockpiled or landfilled, it may pollute the soil and groundwater through leachate, threatening the ecological environment and human health. The technological breakthrough in the comprehensive utilization of vanadium slag not only solves the problem of hazardous waste disposal, but also transforms the "waste residue" into strategic resources, with triple economic, environmental and social benefits. It is the key path to promote the green transformation of industries such as alumina and participate in the global new energy competition. However, in the roasting process of vanadium slag, a large amount of high-salt ammonia-nitrogen wastewater is generated during the ammonium salt vanadium precipitation process. The salt content of the wastewater is relatively high, and the main pollutants are ammonia nitrogen, oxides, metal salts, etc. The direct discharge is extremely polluting. The original technologies such as ammonia distillation and concentration recovery can no longer meet the needs of industrial production of vanadium oxide due to problems such as high production costs and great technical difficulties in the operation and maintenance of equipment. Therefore, there is an urgent need to develop new technologies to solve the problems in the roasting vanadium extraction process of vanadium slag. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the present invention proposes a large-size high-density ammonium metavanadate and its preparation method to solve the technical problems of the existing ammonium metavanadate preparation process being relatively complex, the particle size of ammonium metavanadate being small, and the density being low.

[0007] To achieve the above object, the present invention provides the following technical solutions: A preparation method of large-size high-density ammonium metavanadate, comprising the following steps: (1) Roasting the vanadium slag blank and then crushing it to obtain refined vanadium slag; (2) Subjecting the refined vanadium slag to alkali leaching, acid adjustment, and purification to remove impurities to obtain a vanadium precipitation stock solution; (3) Placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinylpyrrolidone and soluble ammonium salt respectively, stirring evenly, adjusting the pH, and reacting at a temperature of 30-50 °C for 40-80 min; the number average molecular weight of the polyvinylpyrrolidone is 7000-10000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.006-0.03:1; (4) After the reaction is completed, solid-liquid separation is carried out, and the solid phase is washed and dried to obtain large-size high-density ammonium metavanadate.

[0008] When industrially producing ammonium metavanadate, in order to improve production efficiency, an excessive amount of ammonium salt is often added to the solution to completely precipitate vanadium within a short period of time. In this way, the supersaturation of the vanadium precipitation reaction is very high, and the bulk density of the obtained ammonium metavanadate is generally very small. As a result, a large amount of dust may be generated during the workshop operation process, which not only pollutes the environment and threatens the health of workers, but also causes inaccurate batching due to the volatilization of the powder, which is not conducive to production. To solve this problem, the present invention adds polyvinylpyrrolidone as a surface dispersant and nucleation modifier during the vanadium precipitation process. There is prior art content using hydroxyl-containing surfactants such as polyvinyl alcohol and polyethylene glycol as modifiers (CN104973626, CN113753952). However, polyvinyl alcohol has strong adhesiveness, which not only affects the purity of ammonium metavanadate but also is not conducive to the improvement of the particle size of ammonium metavanadate. Polyvinylpyrrolidone has both hydrophilic and lipophilic groups in its molecule, which can play a complexing role and better improve the particle size of ammonium metavanadate. Using polyvinylpyrrolidone with a number-average molecular weight of 7000 - 10000 as a modifier can not only improve the bulk density of the ammonium metavanadate product but also increase the particle size of ammonium metavanadate, which is beneficial to the industrial application of ammonium metavanadate. When the molecular weight of polyvinylpyrrolidone is too small, its mobility in the aqueous solution is strong, and it cannot be effectively adsorbed on the surface of ammonium metavanadate crystals, and thus cannot play a role in reducing the nucleation rate. When the molecular weight of polyvinylpyrrolidone is too large, the viscosity is too high, which is also not conducive to crystal growth and results in smaller crystal particles. Further, the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.01 - 0.03:1. An appropriate amount of polyvinylpyrrolidone can fully play a role in surface modification and improve the scale and density of ammonium metavanadate.

[0009] Further, the blank roasting temperature in step (1) is 700 - 900 °C. Through high-temperature blank roasting, not only can some impurities existing in the vanadium slag be removed, but also a small amount of low-valent vanadium in the vanadium slag can be oxidized to pentavalent vanadium, thereby increasing the vanadium yield. The blank roasting of this process is different from the ordinary sodium roasting process and calcification roasting process of vanadium slag. Using blank roasting can improve the vanadium recovery rate while having better environmental benefits.

[0010] Further, the blank roasting time in step (1) is 1 - 3 h.

[0011] Further, the alkali used in the alkali leaching process in step (2) is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid. This process is relatively mature. Generally, a high-temperature alkali leaching process is adopted, the alkali liquor concentration is generally 20 - 40 wt%, the alkali leaching temperature is usually 140 - 200 °C, and the subsequent acid adjustment process can remove the excessive alkali liquor, which is convenient for impurity removal.

[0012] Further, the vanadium content in the vanadium precipitation stock solution in step (2) is 20 - 100 g / L.

[0013] Further, in step (2), vanadium in the vanadium precipitation stock solution exists in the form of pentavalent vanadium. Specifically, in the present invention, vanadium in the vanadium precipitation stock solution mainly exists in the form of sodium metavanadate.

[0014] Further, in step (3), the soluble ammonium salt is one or more of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium chloride, and ammonium nitrate.

[0015] Further, in step (3), any one of sulfuric acid, hydrochloric acid, and nitric acid is used to adjust the pH; the pH is adjusted to 7-10. After adding polyvinylpyrrolidone and the soluble ammonium salt to the vanadium precipitation stock solution, it is necessary to control the pH of the mixed solution between 7 and 10. If the pH is too high or too low, it will affect the nucleation and dispersion of polyvinylpyrrolidone, and it is impossible to prepare ammonium metavanadate with large size and high density.

[0016] Further, in step (3), the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 2-4:1; the reaction temperature is 35-45°C; the reaction time is 50-65 min. A suitable temperature can promote the increase of density and particle size. Generally speaking, the solubility of ammonium metavanadate increases slightly with the increase of temperature; when the temperature is too low, it is not conducive to the movement of polyvinylpyrrolidone molecules and the crystallization of ammonium metavanadate. Considering comprehensively, the reaction temperature of 35-45°C is more appropriate. As the time prolongs, the density of ammonium metavanadate gradually increases; however, if the time is too long, it will cause the ammonium metavanadate crystals to break, resulting in a decrease in density and particle size.

[0017] The present invention also provides a large-size and high-density ammonium metavanadate, which is prepared by the above method for preparing large-size and high-density ammonium metavanadate.

[0018] The technical solution of the present invention has the following advantages: In the vanadium precipitation process of the present invention, polyvinylpyrrolidone is added as a surface dispersant and nucleation modifier. Compared with the commonly used hydroxyl-containing surfactants such as polyvinyl alcohol and polyethylene glycol in the prior art, polyvinylpyrrolidone molecules have both hydrophilic groups and lipophilic groups, and can play a complexing role. Using polyvinylpyrrolidone with a number-average molecular weight of 7000-10000 as a modifier can not only improve the loose bulk density of the ammonium metavanadate product, but also increase the particle size of ammonium metavanadate, which is beneficial to the industrial application of ammonium metavanadate. When the molecular weight of polyvinylpyrrolidone is too small, its mobility in aqueous solution is strong, and it cannot be effectively adsorbed on the surface of ammonium metavanadate crystals, and cannot play the role of reducing the nucleation rate; when the molecular weight of polyvinylpyrrolidone is too large, the viscosity is too high, which is also not conducive to the growth of crystals, resulting in smaller crystal particles. Specific embodiments

[0019] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0020] Among them, in the vanadium precipitation stock solution used in the following examples and comparative examples, vanadium exists in the form of pentavalent vanadium, and the V (g / L) concentration is 34.10 g / L; in step (3), the soluble ammonium salt is ammonium sulfate, and sulfuric acid is used to adjust the pH.

[0021] Example 1 A method for preparing large-size high-density ammonium metavanadate, comprising the following steps: (1) Obtaining refined vanadium slag by subjecting vanadium slag to blank roasting and pulverization; the blank roasting temperature is 850 °C; the blank roasting time is 2 h; (2) Obtaining vanadium precipitation stock solution by subjecting the refined vanadium slag to alkali leaching, acid adjustment, purification and impurity removal; the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid; (2) Placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinylpyrrolidone and soluble ammonium salt respectively, stirring evenly, adjusting the pH to 7.5, and reacting at a temperature of 35 °C for 65 min; the number average molecular weight of the polyvinylpyrrolidone is 7000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.01:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 2:1; (3) After the reaction is completed, solid-liquid separation is carried out, and the solid phase is washed and dried to obtain large-size high-density ammonium metavanadate.

[0022] Example 2 A method for preparing large-size high-density ammonium metavanadate, comprising the following steps: (1) Obtaining refined vanadium slag by subjecting vanadium slag to blank roasting and pulverization; the blank roasting temperature is 850 °C; the blank roasting time is 2 h; (2) Obtaining vanadium precipitation stock solution by subjecting the refined vanadium slag to alkali leaching, acid adjustment, purification and impurity removal; the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid; (2) Placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinylpyrrolidone and soluble ammonium salt respectively, stirring evenly, adjusting the pH to 10, and reacting at a temperature of 45 °C for 50 min; the number average molecular weight of the polyvinylpyrrolidone is 10000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.02:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 4:1; After the reaction is completed, solid-liquid separation is carried out, and the solid phase is washed and dried to obtain large-sized high-density ammonium metavanadate.

[0023] Example 3 A method for preparing large-sized high-density ammonium metavanadate, comprising the following steps: (1) Vanadium slag is subjected to blank roasting and pulverization to obtain refined vanadium slag; the blank roasting temperature is 850 °C; the blank roasting time is 2 h; (2) The refined vanadium slag is subjected to alkali leaching, acid adjustment, purification and impurity removal to obtain a vanadium precipitation stock solution; the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid; (2) Place the vanadium precipitation stock solution in a reaction kettle, add polyvinylpyrrolidone and soluble ammonium salt respectively, stir evenly, adjust the pH to 10, and react for 58 min at a temperature of 35 °C; the number average molecular weight of the polyvinylpyrrolidone is 10,000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.012:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 4:1; (3) After the reaction is completed, solid-liquid separation is carried out, and the solid phase is washed and dried to obtain large-sized high-density ammonium metavanadate.

[0024] Example 4 A method for preparing large-sized high-density ammonium metavanadate, comprising the following steps: (1) Vanadium slag is subjected to blank roasting and pulverization to obtain refined vanadium slag; the blank roasting temperature is 850 °C; the blank roasting time is 2 h; (2) The refined vanadium slag is subjected to alkali leaching, acid adjustment, purification and impurity removal to obtain a vanadium precipitation stock solution; the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid; (2) Place the vanadium precipitation stock solution in a reaction kettle, add polyvinylpyrrolidone and soluble ammonium salt respectively, stir evenly, adjust the pH to 7.5, and react for 65 min at a temperature of 45 °C; the number average molecular weight of the polyvinylpyrrolidone is 7,000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.028:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 2.5:1; (3) After the reaction is completed, solid-liquid separation is carried out, and the solid phase is washed and dried to obtain large-sized high-density ammonium metavanadate.

[0025] Example 5 A method for preparing large-sized high-density ammonium metavanadate, comprising the following steps: (1) Vanadium slag is subjected to blank roasting and pulverization to obtain refined vanadium slag; the blank roasting temperature is 850 °C; the blank roasting time is 2 h; (2)The refined vanadium slag is subjected to alkali leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation stock solution; the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid; (2)Place the vanadium precipitation stock solution in a reaction kettle, add polyvinylpyrrolidone and soluble ammonium salt respectively, stir evenly, adjust the pH to 8, and react for 62 min at a temperature of 38 °C; the number-average molecular weight of the polyvinylpyrrolidone is 8000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.015:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3.5:1; (3)After the reaction is completed, perform solid-liquid separation, wash and dry the solid phase to obtain large-size high-density ammonium metavanadate.

[0026] Example 6 A preparation method of large-size high-density ammonium metavanadate, comprising the following steps: (1)The vanadium slag is subjected to blank roasting and pulverization to obtain refined vanadium slag; the blank roasting temperature is 850 °C; the blank roasting time is 2 h; (2)The refined vanadium slag is subjected to alkali leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation stock solution; the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid; (2)Place the vanadium precipitation stock solution in a reaction kettle, add polyvinylpyrrolidone and soluble ammonium salt respectively, stir evenly, adjust the pH to 9, and react for 55 min at a temperature of 43 °C; the number-average molecular weight of the polyvinylpyrrolidone is 9000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.025:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3.6:1; (3)After the reaction is completed, perform solid-liquid separation, wash and dry the solid phase to obtain large-size high-density ammonium metavanadate.

[0027] Example 7 A preparation method of large-size high-density ammonium metavanadate, comprising the following steps: (1)The vanadium slag is subjected to blank roasting and pulverization to obtain refined vanadium slag; the blank roasting temperature is 850 °C; the blank roasting time is 2 h; (2)The refined vanadium slag is subjected to alkali leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation stock solution; the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid; (2)Place the vanadium precipitation stock solution in a reaction kettle, add polyvinylpyrrolidone and soluble ammonium salt respectively, stir evenly, adjust the pH to 9, and react for 56 min at a temperature of 30 °C; the number-average molecular weight of the polyvinylpyrrolidone is 8000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.02:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3:1; After the reaction is completed, solid-liquid separation is carried out, and the solid phase is washed and dried to obtain large-size high-density ammonium metavanadate.

[0028] Example 8 A method for preparing large-size high-density ammonium metavanadate, comprising the following steps: (1) Vanadium slag is subjected to blank roasting and pulverization to obtain refined vanadium slag; the blank roasting temperature is 850 °C; the blank roasting time is 2 h; (2) The refined vanadium slag is subjected to alkali leaching, acid adjustment, and purification to remove impurities to obtain a vanadium precipitation stock solution; the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid; (2) The vanadium precipitation stock solution is placed in a reaction kettle, polyvinylpyrrolidone and a soluble ammonium salt are respectively added, stirred evenly, the pH is adjusted to 9, and the reaction is carried out at a temperature of 50 °C for 56 min; the number average molecular weight of the polyvinylpyrrolidone is 8000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.02:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3:1; After the reaction is completed, solid-liquid separation is carried out, and the solid phase is washed and dried to obtain large-size high-density ammonium metavanadate.

[0029] Example 9 A method for preparing large-size high-density ammonium metavanadate, comprising the following steps: (1) Vanadium slag is subjected to blank roasting and pulverization to obtain refined vanadium slag; the blank roasting temperature is 850 °C; the blank roasting time is 2 h; (2) The refined vanadium slag is subjected to alkali leaching, acid adjustment, and purification to remove impurities to obtain a vanadium precipitation stock solution; the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid; (2) The vanadium precipitation stock solution is placed in a reaction kettle, polyvinylpyrrolidone and a soluble ammonium salt are respectively added, stirred evenly, the pH is adjusted to 9, and the reaction is carried out at a temperature of 40 °C for 56 min; the number average molecular weight of the polyvinylpyrrolidone is 8000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.006:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3:1; After the reaction is completed, solid-liquid separation is carried out, and the solid phase is washed and dried to obtain large-size high-density ammonium metavanadate.

[0030] Example 10 A method for preparing large-size high-density ammonium metavanadate, comprising the following steps: (1) Vanadium slag is subjected to blank roasting and pulverization to obtain refined vanadium slag; the blank roasting temperature is 850 °C; the blank roasting time is 2 h; (2)The refined vanadium slag is subjected to alkali leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation stock solution; the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid; (2)The vanadium precipitation stock solution is placed in a reaction kettle, polyvinylpyrrolidone and a soluble ammonium salt are added respectively, stirred evenly, the pH is adjusted to 9, and the reaction is carried out for 80 min at a temperature of 40 °C; the number-average molecular weight of the polyvinylpyrrolidone is 8000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.02:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3:1; (3)After the reaction is completed, solid-liquid separation is carried out, and the solid phase is washed and dried to obtain large-size high-density ammonium metavanadate.

[0031] Example 11 A preparation method of large-size high-density ammonium metavanadate, comprising the following steps: (1)The vanadium slag is subjected to blank roasting and crushing to obtain refined vanadium slag; the blank roasting temperature is 850 °C; the blank roasting time is 2 h; (2)The refined vanadium slag is subjected to alkali leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation stock solution; the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid; (2)The vanadium precipitation stock solution is placed in a reaction kettle, polyvinylpyrrolidone and a soluble ammonium salt are added respectively, stirred evenly, the pH is adjusted to 9, and the reaction is carried out for 56 min at a temperature of 40 °C; the number-average molecular weight of the polyvinylpyrrolidone is 8000, and the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.02:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3:1; (3)After the reaction is completed, solid-liquid separation is carried out, and the solid phase is washed and dried to obtain large-size high-density ammonium metavanadate.

[0032] Comparative Example 1 A preparation method of large-size high-density ammonium metavanadate, the preparation process of which is basically the same as that of Example 11, the difference is that the number-average molecular weight of the polyvinylpyrrolidone is 5000.

[0033] Comparative Example 2 A preparation method of large-size high-density ammonium metavanadate, the preparation process of which is basically the same as that of Example 11, the difference is that the number-average molecular weight of the polyvinylpyrrolidone is 13000.

[0034] Comparative Example 3 A preparation method of large-size high-density ammonium metavanadate, the preparation process of which is basically the same as that of Example 11, the difference is that the mass ratio of polyvinylpyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.05:1.

[0035] Comparative Example 4 A preparation method of large-size high-density ammonium metavanadate, the preparation process of which is basically the same as that of Example 11, except that polyvinyl alcohol with a number-average molecular weight of 8,000 is used to replace polyvinylpyrrolidone. Performance tests were carried out on the large-size high-density ammonium metavanadate prepared in Examples 1-11 and Comparative Examples 1-4: the purity (%) of ammonium metavanadate was tested using a spectrometer; the bulk density (g / cm 3 3) of ammonium metavanadate was tested using a densitometer; and the particle size D50 (μm) of ammonium metavanadate was tested using a laser particle size analyzer.

[0036] Table 1 Performance of large-size high-density ammonium metavanadate prepared in Examples 1-11 and Comparative Examples 1-4 Continued Table 1 As can be seen from Examples 1-11, polyvinylpyrrolidone was added as a surface dispersant and nucleation modifier during the vanadium precipitation process of the present invention. It can not only improve the bulk density and purity of the ammonium metavanadate product, but also increase the particle size of ammonium metavanadate, which is beneficial to the industrial application of ammonium metavanadate.

[0037] Comparative Examples 1-3 show that the molecular weight of polyvinylpyrrolidone affects the product performance. When the molecular weight of polyvinylpyrrolidone is too small, its mobility in the aqueous solution is strong, and it cannot be effectively adsorbed on the surface of ammonium metavanadate crystals, and it cannot play the role of reducing the nucleation rate; when the molecular weight of polyvinylpyrrolidone is too large, the viscosity is too large, which is also not conducive to crystal growth, resulting in smaller crystal particles. At the same time, when the amount of polyvinylpyrrolidone used is too large, the viscosity of the solution is likely to be too large, which is not conducive to the growth of crystal grains. Comparative Example 4 shows that although polyvinyl alcohol improves the size of ammonium metavanadate to a certain extent, its adhesiveness is large, resulting in a decrease in the purity of ammonium metavanadate.

[0038] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing large-size and high-density ammonium metavanadate, characterized in that: The following steps are involved: (1) roasting and crushing the vanadium slag to obtain refined vanadium slag; (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation stock solution; (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH, and reacting at a temperature of 30-50° C. for 40-80 minutes; the number average molecular weight of the polyvinyl pyrrolidone is 7000-10000, and the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.006-0.03:1; (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

2. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, characterized in that: The blank calcination temperature of step (1) is 700-900°C.

3. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, characterized in that: The blank roasting time in step (1) is 1-3h.

4. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, characterized in that: In step (2), the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid.

5. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, characterized in that: The vanadium content in the vanadium precipitation solution in step (2) is 20-100 g / L.

6. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, characterized in that: In step (2), the vanadium in the vanadium precipitation solution exists in the form of pentavalent vanadium.

7. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, characterized in that: In step (3), the soluble ammonium salt is one or more of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium chloride and ammonium nitrate.

8. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, characterized in that: In step (3), any one of sulfuric acid, hydrochloric acid and nitric acid is used to adjust the pH; preferably, the pH is adjusted to 7-10.

9. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, characterized in that: In step (3), the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation solution is 2-4:1; the reaction temperature is 35-45° C.; preferably, the reaction time is 50-65 min.

10. A large-size, high-density ammonium metavanadate, characterized in that: The invention is prepared by the preparation method of large-size and high-density ammonium metavanadate described in any one of claims 1 to 9.

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