Method for preparing low-chromium ammonium metavanadate

Abstract

The invention discloses a method for preparing low-chromium ammonium metavanadate, which comprises the following steps: adding an oxidizing agent into an impurity removal liquid for oxidation to obtain an oxidation liquid; carrying out deep desiliconization on the oxidized liquid to obtain a purified liquid; carrying out alkalescence ammonium salt vanadium precipitation on the purified liquid to obtain ammonium metavanadate; wherein the step of adding the oxidizing agent into the impurity removal liquid for oxidation comprises the substeps of selecting a first type of oxidizing agent or a second type of oxidizing agent based on the oxidation-reduction potential and the chromium concentration of the impurity removal liquid; the impurity removal liquid is obtained after the sodium modified vanadium liquid is subjected to selective reduction and chromium-silicon co-removal. According to the method, different oxidation measures are adopted for impurity removal liquids with different properties to improve the oxidation efficiency, reduce the oxidation cost and improve the quality of vanadium precipitates, and the method has the characteristics of high oxidation efficiency, low oxidation cost, good desilicication effect and good vanadium product quality.

Description

Technical Field

[0001] The invention relates to the technical field of vanadium oxide preparation, and in particular to a method for preparing low-chromium ammonium metavanadate. Background Art

[0002] Vanadium is a very rare metal element, mainly used in the steel industry to improve the strength, toughness and other properties of steel products. In recent years, the application of vanadium in non-steel fields has become more and more extensive, such as the hot energy storage field, vanadium-based positive electrode materials, and the research and application of all-vanadium liquid flow batteries have become more and more mature. There are also many applications in chemical catalysis, medicine, metal vanadium, vanadium alloys, titanium alloys and other fields. The application characteristics of vanadium in non-steel fields determine that the quality requirements of vanadium oxide are very high. For example, excessive concentrations of chromium and other pollutants in vanadium electrolytes will have an adverse effect on the function of the electrolyte and reduce the charging state due to electrolyte imbalance, which directly shortens the service life of vanadium batteries. The sodium roasting of vanadium slag-water leaching process is still the most widely used vanadium extraction process. Due to the similar properties of vanadium and chromium, part of the chromium is leached together with vanadium in the form of chromate during leaching. During the vanadium precipitation process, chromium will enter the precipitate of amino polyvanadate or amino metavanadate. This phenomenon leads to an increase in the chromium content in vanadium pentoxide, thereby reducing the purity of the product. Therefore, it is necessary to reduce the chromium content in the vanadium liquid, and then reduce the chromium entering the vanadium product, so as to improve the quality of vanadium products and meet the needs of multiple markets. In the industry, reduction chromium removal is often used to separate vanadium and chromium, and then the impurity removal liquid is used to precipitate vanadium to prepare vanadium products. However, such methods rarely involve the oxidation of the impurity removal liquid, because the trivalent chromium in the vanadium liquid is more easily absorbed into the vanadium product than the hexavalent chromium, resulting in serious excessive chromium content in the impurity removal liquid when producing vanadium products, large consumption of ammonium salt for vanadium precipitation, and low vanadium precipitation rate.

[0003] The prior art discloses a method for preparing low-silicon ammonium polyvanadate by reducing vanadium precipitation and desiliconization, comprising adding acid to a vanadium-containing solution, adjusting the pH value to 5-6, adding a reducing agent for reduction reaction, and obtaining a reduced vanadium solution; adjusting the pH value of the reduced vanadium solution to 2-3, adding an ammonium salt for reaction, filtering to obtain a vanadium precipitation filter cake after the reaction is completed, and washing the filter cake with deionized water by pulping, and then drying. According to the method for preparing low-silicon ammonium polyvanadate by reducing vanadium precipitation and desiliconization of the present invention, a deep desiliconization of a vanadium-containing solution can be achieved, and the silicon content in the prepared APV is reduced to below 20ppm, with excellent desiliconization effect. However, the method does not oxidize the impurity removal solution, and the excess reducing agent will reduce the vanadium under acidic conditions, which will affect the vanadium precipitation.

[0004] The prior art also discloses a method for directly precipitating vanadium from an acidic, impure vanadium-containing solution, which specifically discloses adding an oxidant to the vanadium-containing solution and oxidizing it at 40 to 70° C. for 0.2 to 1.0 h to obtain an oxidized vanadium solution; the amount of the oxidant added is 1.0 to 2.5 times the theoretical molar amount of the oxidant required to completely oxidize the low-valent vanadium in the vanadium-containing solution into pentavalent vanadium; the method clearly points out that the low-valent vanadium in the vanadium solution will affect the vanadium precipitation rate.

[0005] Based on this, the existing technology still needs to be improved. Summary of the invention

[0006] In order to solve the above technical problems, the embodiment of the present invention provides a method for preparing low-chromium ammonium metavanadate to solve the adverse effects of untreated impurity removal liquid on vanadium precipitation in the prior art.

[0007] In order to solve the above technical problems, some embodiments of the present invention disclose a method for preparing low-chromium ammonium metavanadate, comprising: Adding an oxidant to the impurity removal liquid for oxidation to obtain an oxidized liquid; Deeply desiliconizing the oxidizing liquid to obtain a purified liquid; The purified liquid is subjected to weak alkaline ammonium salt precipitation of vanadium to obtain ammonium metavanadate; Wherein, adding an oxidant to the impurity removal liquid for oxidation comprises: selecting a first type of oxidant or a second type of oxidant based on the redox potential and chromium concentration of the impurity removal liquid; The impurity removal liquid is obtained by selectively reducing chromium and silicon with sodium vanadium solution.

[0008] In some embodiments, if the redox potential of the impurity removal liquid is -450mV~0mV, hydrogen peroxide is selected as the first type of oxidant; If the redox potential of the impurity removal solution is higher than 0 mV, one or a mixture of ammonium persulfate and sodium persulfate is selected as the second type of oxidant.

[0009] In some embodiments, if the chromium concentration in the impurity removal solution is less than 0.3 g / L, hydrogen peroxide is selected as the first type of oxidant; If the chromium concentration in the impurity removal solution is in the range of 0.3 g / L to 0.8 g / L, one of ammonium persulfate and sodium persulfate or a mixture of the two is selected as the second type of oxidant.

[0010] In some embodiments, when hydrogen peroxide is selected as the first type of oxidant, the amount of hydrogen peroxide added is calculated by molar ratio: O （双氧水中的氧） / Cr （钒液中的Cr） =2~7.

[0011] In some embodiments, when hydrogen peroxide is selected as the first type of oxidant, the oxidation temperature is 20° C. to 90° C., the oxidation time is 10 min to 60 min, and the ORP value after oxidation is controlled to be ≥100 mV.

[0012] In some embodiments, the concentration of hydrogen peroxide is 27.5% to 35% by mass, and the pH is 2 to 3.

[0013] In some embodiments, when one or a mixture of ammonium persulfate and sodium persulfate is selected as the second type of oxidant, the amount of the second type of oxide added is calculated by the molar ratio: S （氧化剂中的硫） / Cr （钒液中的Cr） =2~7.

[0014] In some embodiments, when one or a mixture of ammonium persulfate and sodium persulfate is selected as the second type of oxidant, the oxidation temperature is 20° C. to 90° C., the oxidation time is 10 min to 60 min, and the ORP value after oxidation is controlled to be ≥300 mV.

[0015] In some embodiments, deep desiliconization of the oxidizing solution comprises: Use sulfuric acid to adjust the solution pH to 8.5-9.5, let it stand for 4h to 48h, and let it stand at 20℃ to 60℃; the concentration of sulfuric acid is 50% to 98%; In addition, the desiliconized slag obtained by deep desiliconization is washed once with clean water, the amount of washing water is 1% to 5% of the impurity removal liquid, and the obtained washing liquid is incorporated into the purification liquid.

[0016] In some embodiments, subjecting the purified liquid to weakly alkaline ammonium salt precipitation of vanadium comprises: In terms of mass ratio, the amount of ammonium salt added is: TV / ammonium sulfate = 2.0-4.0, precipitation temperature 10°C-40°C, precipitation time 2h-5h; Preferably, in terms of mass ratio, the amount of ammonium salt added is: In terms of mass ratio, the amount of ammonium salt added is: TV / ammonium sulfate = 3.0-4.0, the precipitation temperature is 20°C-30°C, and the precipitation time is 2h-3h.

[0017] By adopting the above technical solution, the present invention has at least the following beneficial effects: The invention provides a method for preparing low-chromium ammonium metavanadate, which adopts different oxidation measures for impurity removal liquids of different properties to improve oxidation efficiency, reduce oxidation costs, and improve the quality of vanadium precipitates. The invention has the characteristics of high oxidation efficiency, low oxidation cost, good desiliconization effect, and good vanadium product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 The present invention is a flow chart of a method for preparing low-chromium ammonium metavanadate disclosed in some embodiments of the present invention. DETAILED DESCRIPTION

[0020] The following is a further detailed description of the embodiments of the present disclosure in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to exemplarily illustrate the principles of the present disclosure, but cannot be used to limit the scope of the present disclosure. The present disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

[0021] The present disclosure provides these embodiments to make the present disclosure thorough and complete, and to fully express the scope of the present disclosure to those skilled in the art. It should be noted that unless otherwise specifically stated, the relative arrangement of the parts and steps, the composition of the materials, the numerical expressions and the numerical values ​​set forth in these embodiments should be interpreted as being merely exemplary, and not as limiting.

[0022] It should be noted that, in the description of the present disclosure, unless otherwise specified, the meaning of "multiple" is greater than or equal to two; the terms "upper", "lower", "left", "right", "inner", "outer", etc., indicating the orientation or positional relationship, are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present disclosure. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0023] In addition, the words "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different parts. "Vertical" does not mean vertical in the strict sense, but is within the tolerance range. "Parallel" does not mean parallel in the strict sense, but is within the tolerance range. "Include" or "comprising" and similar words mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of including other elements.

[0024] It should also be noted that in the description of the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to the specific circumstances. When a specific device is described as being located between a first device and a second device, there may or may not be an intermediate device between the specific device and the first device or the second device.

[0025] All terms used in the present disclosure have the same meanings as those understood by those of ordinary skill in the art to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries, for example, should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an idealized or extremely formal sense, unless explicitly defined as such herein.

[0026] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0027] like Figure 1 As shown, some embodiments of the present invention disclose a method for preparing low-chromium ammonium metavanadate, comprising: adding an oxidant to an impurity removal liquid for oxidation to obtain an oxidized liquid; performing deep desiliconization on the oxidized liquid to obtain a purified liquid; performing weak alkaline ammonium salt vanadium precipitation on the purified liquid to obtain ammonium metavanadate; Among them, adding an oxidant to the impurity-removing liquid for oxidation includes: selecting a first type of oxidant or a second type of oxidant based on the redox potential and chromium concentration of the impurity-removing liquid; if the redox potential of the impurity-removing liquid is -450mV~0mV, selecting hydrogen peroxide as the first type of oxidant; if the redox potential of the impurity-removing liquid is higher than 0mV, selecting one or a mixture of ammonium persulfate and sodium persulfate as the second type of oxidant.

[0028] The raw material used in the above embodiment is the impurity removal liquid after the sodium vanadium liquid is selectively reduced to remove chromium and silicon. The redox potential of the impurity removal liquid is generally -450mV to 180mV, the chromium concentration in the impurity removal liquid is 0.001g / L to 0.8g / L, and the vanadium concentration is 30g / L to 60g / L. If the impurity removal liquid is not oxidized to precipitate vanadium, most of the trivalent chromium in the impurity removal liquid will enter the vanadium product. When the chromium content in the impurity removal liquid exceeds the upper limit, the chromium content of the vanadium product will exceed the standard. At the same time, more than 90% of Si in the vanadium liquid will enter the ammonium metavanadate product along with the precipitation reaction. Therefore, the impurity removal liquid after the sodium vanadium liquid is selectively reduced to remove chromium and silicon requires oxidation treatment and deep desiliconization treatment.

[0029] Some embodiments of the present invention disclose a method for preparing low-chromium ammonium metavanadate, comprising: adding an oxidant to an impurity removal liquid for oxidation to obtain an oxidized liquid, wherein the impurity removal liquid is an impurity removal liquid obtained by selectively reducing chromium and silicon with a sodium vanadium liquid; performing deep desiliconization on the oxidized liquid to obtain a purified liquid; performing weak alkaline ammonium salt vanadium precipitation on the purified liquid to obtain ammonium metavanadate; The step of adding an oxidant to the impurity removal liquid for oxidation comprises: selecting a first type of oxidant or a second type of oxidant based on the redox potential and chromium concentration of the impurity removal liquid; if the chromium concentration in the impurity removal liquid is less than 0.3 g / L, selecting hydrogen peroxide as the first type of oxidant; if the chromium concentration in the impurity removal liquid is in the range of 0.3 g / L to 0.8 g / L, selecting one of ammonium persulfate and sodium persulfate or a mixture of the two as the second type of oxidant.

[0030] The embodiment of the present invention discloses a method for preparing low-chromium ammonium metavanadate, wherein the raw material used is the impurity removal liquid after the sodium vanadium solution selectively reduces the chromium and silicon co-removal, and the sodium vanadium solution selectively reduces the chromium and silicon co-removal in the following three situations: ① When the pH of the vanadium solution is high, the main reactions for selective reduction and chromium removal are as follows:

[0031] In this process, the hexavalent chromium in the solution mainly consumes the reducing agent. There are more low-valent sulfates in the impurity removal solution, some vanadates, low trivalent chromium content, and no hexavalent chromium. When the impurity removal solution does not oxidize vanadium precipitation, the low-valent sulfates and some vanadates in the impurity removal solution will cause more tetravalent vanadium in the vanadium solution to be unable to be effectively precipitated under the conditions of acidic ammonium salt vanadium precipitation, thereby reducing the vanadium precipitation rate.

[0032] ②When the pH of vanadium solution is moderate, the main reactions are as follows:

[0033] In this process, the reducing agent is mainly consumed by hexavalent chromium and pentavalent vanadium in the solution. Vanadium and chromium compete to consume the reducing agent, resulting in incomplete removal of chromium in the impurity removal liquid. The impurity removal liquid contains more low-valent sulfates and a certain amount of hexavalent chromium, trivalent chromium and vanadate.

[0034] ③When the pH of vanadium solution is low, the main reactions are as follows:

[0035] Most of the reducing agent during chromium removal is consumed by hexavalent chromium and pentavalent vanadium, the content of low-valent sulfate and trivalent chromium is low, and the chromium content in the impurity removal liquid is high, mainly hexavalent chromium.

[0036] If the impurity removal solution is not oxidized to precipitate ammonium metavanadate, the pH of the vanadium precipitation solution decreases during the addition of ammonium sulfate or acid adjustment process, and the low-valent sulfur salts in the solution will undergo self-oxidation-reduction reactions or be oxidized by high-valent vanadium to generate insoluble sulfur-containing substances, causing the color of the ammonium metavanadate to turn black and the sulfur element to exceed the standard; when the pH of the vanadium precipitation solution decreases, the oxidizability of hexavalent chromium and pentavalent vanadium in the solution will increase, and hexavalent chromium and pentavalent vanadium will continue to react with low-valent sulfur salts, especially hexavalent chromium, resulting in Cr(OH)3 precipitation in the vanadium precipitation solution and entering the ammonium metavanadate, causing the chromium content in the ammonium metavanadate to exceed the standard; furthermore, when the pH of the vanadium precipitation solution decreases, Si in the solution will precipitate to produce flocculent precipitation and enter the ammonium metavanadate, causing the Si content in the ammonium metavanadate to exceed the standard. Therefore, the impurity removal solution after the selective reduction of chromium and silicon by sodium vanadium solution needs to be oxidized before high-purity ammonium metavanadate can be precipitated. Different oxidation measures are needed for impurity removal solutions with different properties to improve oxidation efficiency, reduce oxidation costs, and improve the quality of ammonium metavanadate.

[0037] When the redox potential of the impurity removal liquid is -450mV~0mV, and the chromium concentration is ≤0.3g / L, the chromium content in the impurity removal liquid is relatively low and the pH of the impurity removal liquid is relatively high. At this time, hydrogen peroxide oxidation can effectively oxidize the low-valent S, Cr, and V in the impurity removal liquid into high-valent ones. After oxidation, the pH of the oxidation liquid is adjusted. After standing for a period of time, the precipitated precipitate is filtered out to obtain the vanadium precipitation stock solution. Ammonium salt is added to the vanadium precipitation stock solution to precipitate ammonium metavanadate.

[0038] When the pH of the impurity removal liquid is low, the redox potential of the impurity removal liquid is greater than 0mV, the chromium concentration is greater than 0.3g / L, and there are fewer reducing substances in the solution. If the impurity removal liquid is oxidized with hydrogen peroxide, hydrogen peroxide is not enough to oxidize trivalent chromium, and there is no substance in the solution that can completely consume hydrogen peroxide. Most of the added hydrogen peroxide will remain in the impurity removal liquid and form peroxide with vanadium, affecting the subsequent vanadium precipitation rate. This impurity removal liquid can be oxidized with sodium persulfate or ammonium persulfate. After oxidation, adjust the pH of the oxidation liquid, let it stand for a period of time, filter out the precipitated precipitate, and obtain the vanadium precipitation stock solution. Add ammonium salt to the vanadium precipitation stock solution to precipitate ammonium metavanadate.

[0039] In addition, if the appearance color requirements of ammonium metavanadate are relatively high, sodium persulfate or ammonium persulfate is used for oxidation. The peroxide formed by hydrogen peroxide and vanadium causes the ammonium metavanadate to appear pink. Hydrogen peroxide oxidation cannot be used. The pH of the oxidation solution needs to be adjusted after the oxidation operation, and ammonium salt is added to the vanadium precipitation stock solution to precipitate the ammonium metavanadate.

[0040] After the sodium vanadium liquid selectively reduces the impurity removal liquid after the chromium and silicon are co-removed, the impurity removal liquid can be oxidized by the above oxidation measures, thereby improving the quality of the purified liquid after the impurity removal liquid is oxidized, improving the vanadium precipitation rate of the purified liquid, reducing the trivalent chromium in the purified liquid, and then reducing the Cr content in the vanadium precipitate AMV, thereby improving the quality of the vanadium product. The present invention has the characteristics of high oxidation efficiency, low oxidation cost, good vanadium product quality and high vanadium precipitation rate of the purified liquid.

[0041] Therefore, when the redox potential of the impurity removal liquid is -450mV~0mV, and the chromium concentration is ≤0.3g / L, hydrogen peroxide is used for oxidation; when the redox potential of the impurity removal liquid is greater than 0mV, and the chromium concentration is greater than 0.3g / L, the impurity removal liquid can be oxidized with sodium persulfate or ammonium persulfate; in addition, if the appearance color of ammonium metavanadate is required to be relatively high, sodium persulfate or ammonium persulfate is used for oxidation, and the peroxide formed by hydrogen peroxide and vanadium causes the ammonium metavanadate to appear pink, so hydrogen peroxide cannot be used for oxidation. After the impurity removal liquid is oxidized, the pH is adjusted, and after standing and settling for a period of time, the purified liquid is filtered, and ammonium salt is added to the purified liquid, and then the temperature is lowered to precipitate ammonium metavanadate. The composition of the vanadium liquid is shown in Table 1.

[0042] Table 1

[0043] Specifically, the steps include: Step 1: adding an oxidant to the impurity removal liquid for oxidation; If the redox potential of the impurity removal solution is -450mV~0mV and the chromium concentration is <0.3g / L, the impurity removal solution can be oxidized by hydrogen peroxide. The amount of hydrogen peroxide added is O (oxygen in hydrogen peroxide) / Cr (Cr in vanadium solution) = 2~7 (molar ratio), the oxidation temperature is 20℃~90℃, the oxidation time is 10min~60min, and the ORP value after oxidation is controlled to be ≥100mV; the hydrogen peroxide concentration is 27.5%~35% (mass fraction), and the pH is 2~3; If the redox potential of the impurity removal solution is > 0mV and the chromium concentration is 0.3g / L~0.8g / L, ammonium persulfate or sodium persulfate, or a mixture of the two, is required for oxidation. The amount of oxidant added is S (sulfur in the oxidant) / Cr (Cr in the vanadium solution) = 2~7 (molar ratio), the oxidation temperature is 20℃~90℃, the oxidation time is 10min~60min, and the ORP value after oxidation is controlled to be ≥300mV; If the detected redox potential or chromium concentration is in the middle, any one of the methods can be selected for oxidation.

[0044] The composition of the impurity removal liquid is shown in Table 2.

[0045] Table 2

[0046] b. Deep desiliconization of the oxidation liquid to obtain a purified liquid; The method includes: adjusting the solution pH to 8.5-9.5 with sulfuric acid, standing for 4h to 48h, and standing at a temperature of 20℃ to 60℃. The concentration of sulfuric acid is 50% to 98%; the desiliconized slag obtained by deep desiliconization can be washed once with clean water, and the amount of washing water is 1% to 5% of the impurity removal liquid, and the washing liquid is incorporated into the purification liquid.

[0047] c. Using the purified liquid to precipitate vanadium with weakly alkaline ammonium salt; Among them, the amount of ammonium salt added is TV / ammonium sulfate = 2.0-4.0 (mass ratio), preferably TV / ammonium sulfate = 3.0-4.0 (mass ratio), the precipitation temperature is 10°C-40°C, preferably 20°C-30°C, the precipitation time is 2h-5h, preferably 2h-3h, and high-quality AMV and vanadium precipitation supernatant are obtained after solid-liquid separation; the obtained AMV can be washed once, the washing water is clean water, the washing water temperature is controlled to be 10°C-35°C, and the washing water volume is 5%-10% of the vanadium precipitation purification liquid volume.

[0048] The composition of the purification solution is shown in Table 3.

[0049] Table 3

[0050] Example 1 The Cr concentration in the original vanadium solution is 2.7 g / L, and the composition of the impurity-removing solution is shown in Table 4.

[0051] Table 4

[0052] 200mL of impurity-removing vanadium liquid was measured with a measuring cylinder, and the pH and redox potential of the impurity-removing liquid were measured. The redox potential was -350mV, and the chromium concentration was 0.002g / L. The impurity-removing liquid could be oxidized with hydrogen peroxide. The amount of hydrogen peroxide added was O (oxygen in hydrogen peroxide) / Cr (Cr in vanadium liquid) = 2 (molar ratio). 1.176mL of 30% hydrogen peroxide was taken, the pH was 2, the oxidation temperature was 30℃, the oxidation time was 10min, and the ORP value after oxidation was controlled to be 120mV; 98% sulfuric acid was used to adjust the solution pH to 9.5, the standing time was 4h, the standing temperature was 60℃, and the solid-liquid separation was performed to obtain the purified liquid and the deep desiliconized slag. The deep desiliconized slag was washed once with clean water, and the washing water volume was about 10mL, which was 5% of the impurity-removing liquid. The washing liquid was added to the purified liquid to obtain 200mL of purified liquid. The amount of ammonium salt added to the purification liquid is TV / ammonium sulfate = 4.0 (mass ratio), about 40g. The precipitation is carried out at a precipitation temperature of 40°C for 5h. After solid-liquid separation, high-quality AMV (about 33.2g) and vanadium precipitation supernatant are obtained. The obtained AMV is washed once with clean water. The washing water temperature is controlled at 35°C. The washing water volume is 10% of the vanadium precipitation purification liquid volume, about 20mL.

[0053] The obtained high-quality AMV components are shown in Table 5 in terms of mass percentage.

[0054] Table 5

[0055] Example 2 The Cr concentration in the original vanadium solution is 2.7 g / L, and the composition of the impurity-removing solution is shown in Table 6.

[0056] Table 6

[0057] 200mL of impurity-removing vanadium liquid was measured with a measuring cylinder, and the pH and redox potential of the impurity-removing liquid were measured. The pH of the impurity-removing liquid was 9.8 (measured at 60℃), the redox potential was 140mV, and when the chromium concentration was 0.8g / L, the impurity-removing liquid could be oxidized by ammonium persulfate, and the amount of ammonium persulfate added was S (sulfur in the oxidant) / Cr (Cr in the vanadium liquid) = 5 (molar ratio) 5.92g, the oxidation temperature was 90℃, the oxidation time was 60min, and the ORP value after oxidation was 450mV. The solution pH was adjusted to 8.5 with 50% sulfuric acid, the standing time was 48h, the standing temperature was 20℃, and the solid-liquid separation was performed to obtain the purified liquid and deep desiliconized slag. The deep desiliconized slag was washed once with clean water, and the washing water volume was about 2mL, which was 1% of the impurity-removing liquid. The washing liquid was added to the purified liquid to obtain 200mL of purified liquid. The amount of ammonium salt added to the purification liquid is TV / ammonium sulfate = 2.0 (mass ratio), about 19.2g. The precipitation is carried out at a precipitation temperature of 10°C for 2h. After solid-liquid separation, high-quality AMV (about 31.8g) and vanadium precipitation supernatant are obtained. The obtained AMV is washed once with clean water. The washing water temperature is controlled at 10°C. The washing water volume is 5% of the vanadium precipitation purification liquid volume, about 10mL.

[0058] The composition of high-quality AMV in terms of mass percentage is shown in Table 7.

[0059] Table 7

[0060] So far, various embodiments of the present disclosure have been described in detail. In order to avoid obscuring the concept of the present disclosure, some details known in the art are not described. Based on the above description, those skilled in the art can fully understand how to implement the technical solution disclosed here.

[0061] Although some specific embodiments of the present disclosure have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. It should be understood by those skilled in the art that the above embodiments may be modified or some technical features may be replaced by equivalents without departing from the scope and spirit of the present disclosure. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there is no structural conflict.

Claims

1. A method for preparing low-chromium ammonium metavanadate, characterized in that: include: Adding an oxidant to the impurity removal liquid for oxidation to obtain an oxidized liquid; Deeply desiliconizing the oxidizing liquid to obtain a purified liquid; The purified liquid is subjected to weak alkaline ammonium salt precipitation of vanadium to obtain ammonium metavanadate; Wherein, adding an oxidant to the impurity removal liquid for oxidation comprises: selecting a first type of oxidant or a second type of oxidant based on the redox potential and / or chromium concentration of the impurity removal liquid; The impurity removal liquid is obtained by selectively reducing chromium and silicon with sodium vanadium solution.

2. The method for preparing low-chromium ammonium metavanadate according to claim 1, characterized in that: If the redox potential of the impurity removal liquid is -450mV~0mV, hydrogen peroxide is selected as the first type of oxidant; If the redox potential of the impurity removal solution is higher than 0 mV, one or a mixture of ammonium persulfate and sodium persulfate is selected as the second oxidant.

3. The method for preparing low-chromium ammonium metavanadate according to claim 2, characterized in that: If the chromium concentration in the impurity removal solution is less than 0.3 g / L, hydrogen peroxide is selected as the first type of oxidant; If the chromium concentration in the impurity removal solution is in the range of 0.3 g / L to 0.8 g / L, one or a mixture of ammonium persulfate and sodium persulfate is selected as the second type of oxidant.

4. The method for preparing low-chromium ammonium metavanadate according to claim 2, characterized in that: When hydrogen peroxide is selected as the first type of oxidant, the amount of hydrogen peroxide added is calculated based on the molar ratio: O （双氧水中的氧） / Cr （钒液中的Cr） =2~7。 5. The method for preparing low-chromium ammonium metavanadate according to claim 2, characterized in that: When hydrogen peroxide is selected as the first type of oxidant, the oxidation temperature is 20°C to 90°C, the oxidation time is 10min to 60min, and the ORP value after oxidation is controlled to be ≥100mV.

6. The method for preparing low-chromium ammonium metavanadate according to claim 4, characterized in that: Calculated by mass percentage, the concentration of hydrogen peroxide is 27.5% to 35%, and the pH is 2 to 3.

7. The method for preparing low-chromium ammonium metavanadate according to claim 2, characterized in that: When one or a mixture of ammonium persulfate and sodium persulfate is selected as the second type of oxidant, the amount of the second type of oxide added is calculated by the molar ratio: S （氧化剂中的硫） / Cr （钒液中的Cr） =2~7。 8. The method for preparing low-chromium ammonium metavanadate according to claim 2, characterized in that: When one of ammonium persulfate and sodium persulfate or a mixture of the two is selected as the second type of oxidant, the oxidation temperature is 20°C to 90°C, the oxidation time is 10min to 60min, and the ORP value after oxidation is controlled to be ≥300mV.

9. The method for preparing low-chromium ammonium metavanadate according to claim 1, characterized in that: The deep desiliconization of the oxidation solution comprises: Use sulfuric acid to adjust the solution pH to 8.5-9.5, let it stand for 4h to 48h, and let it stand at 20℃ to 60℃; the concentration of sulfuric acid is 50% to 98%; In addition, the desiliconized slag obtained by deep desiliconization is washed once with clean water, the amount of washing water is 1% to 5% of the impurity removal liquid, and the obtained washing liquid is incorporated into the purification liquid.

10. The method for preparing low-chromium ammonium metavanadate according to claim 1, characterized in that: The purified liquid is subjected to weakly alkaline ammonium salt precipitation of vanadium, comprising: In terms of mass ratio, the amount of ammonium salt added is: TV / ammonium sulfate = 2.0-4.0, precipitation temperature 10°C-40°C, precipitation time 2h-5h; Preferably, the amount of ammonium salt added is: In terms of mass ratio, the amount of ammonium salt added is: TV / ammonium sulfate = 3.0-4.0, the precipitation temperature is 20°C-30°C, and the precipitation time is 2h-3h.

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