A method for recovering vanadium by deep leaching of vanadium extraction tailings

Abstract

The present invention discloses a method for recovering vanadium by deep leaching from vanadium extraction tailings. The vanadium extraction tailings are subjected to low-pH acid leaching and reduction to reduce the vanadium to a low-valent state. The vanadium concentration is then continuously increased through cyclic acid leaching. Finally, the vanadium is oxidized to a pentavalent state by adjusting the pH and adding an oxidant. Ultimately, a stable and high-concentration pentavalent vanadium is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of vanadium hydrometallurgy, and in particular to a method for recovering vanadium by deep leaching of vanadium-extracting tailings. Background Art

[0002] As an important microalloying element, vanadium is widely used in metallurgy, chemical industry, aerospace and other fields. It can significantly improve the strength, toughness and ductility of steel, providing important support for ensuring the quality of key projects.

[0003] Vanadium-titanium magnetite is treated at high temperatures in a blast furnace or electric furnace to produce vanadium-containing molten iron. This molten iron is then selectively oxidized to produce vanadium slag, which is then used as a raw material for vanadium extraction. In the vanadium oxide production process, calcification, roasting, and acid leaching of vanadium-containing materials is a typical vanadium extraction process. Since vanadium exists as pentavalent vanadium after roasting, the solution system is unstable when the leachate pH is low and the pentavalent vanadium concentration is high, and vanadium is easily hydrolyzed and precipitated, resulting in losses. Currently, to avoid the adverse effects of vanadium hydrolysis, the industry typically controls the acid leaching pH to 2.8-3.5. Within this pH range, high concentrations of pentavalent vanadium can be stably present, and the resulting vanadium extraction tailings have a TV content of 1.0%-1.7%.

[0004] For further extraction of vanadium from low-grade vanadium extraction tailings, efficient leaching of vanadium can be achieved by lowering the pH, but the resulting leachate has a low vanadium concentration and high impurity content. Vanadium recovery from low-concentration vanadium-containing solutions can be categorized into ion exchange, extraction, and evaporation concentration, depending on the method used to enrich vanadium. These methods all present high costs and certain environmental risks. Therefore, it is of great significance to provide a cost-effective, environmentally friendly method for effectively extracting vanadium from vanadium extraction tailings.

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

[0006] To solve the above technical problems, the embodiments of the present invention provide a method for recovering vanadium by deep leaching of vanadium-extracting tailings, so as to solve the technical problems existing in the prior art in further extracting vanadium from low-grade vanadium-extracting tailings.

[0007] To solve the above technical problems, some embodiments of the present invention disclose a method for deep leaching and recovering vanadium from vanadium extraction tailings, wherein the vanadium extraction tailings are subjected to low-pH acid leaching and reduction, and then the vanadium concentration is continuously increased through cyclic acid leaching. Finally, the vanadium is oxidized to pentavalent vanadium by adjusting the pH and adding an oxidant.

[0008] Further, including:

[0009] Step 1: taking vanadium extraction tailings, adding a leaching agent according to a predetermined liquid-solid ratio, adjusting the pH to 0.5-1.0, adding a reducing agent, and stirring the reaction at a first temperature for a first time to obtain a first solution;

[0010] Step 2: separating the first solution into solid and liquid to obtain a first leachate; and returning the first leachate to step 1 as a leaching agent;

[0011] Repeat steps 1 and 2 until the V concentration in the first leachate reaches 18 g / L or above, thereby obtaining a high-concentration vanadium-containing leachate;

[0012] Step 3: Adjusting the pH of the high-concentration vanadium-containing leachate to 2.8-3.5 with an acidity regulator, stirring and reacting for a second time, and then performing solid-liquid separation to obtain a second solution. (Since the vanadium extraction tailings contain a large amount of iron, during the low pH 0.5-1.0 acid leaching process, some iron (mainly +3 valent) enters the solution. The purpose of this process is to remove the trivalent iron ions in the solution. If this is not removed, in step 4, after the vanadium is oxidized to pentavalent iron, iron vanadate precipitation is likely to be generated, resulting in vanadium loss.)

[0013] Step 4: adding an oxidant to the second solution, adjusting the pH to 2.8-3.5 with an acidity regulator, performing an oxidation reaction at a second temperature for a second time, and then performing solid-liquid separation to obtain a third solution, and subjecting the third solution to ammonium salt precipitation to obtain a vanadium product.

[0014] Furthermore, in step 1, the first temperature is 20-70° C., and the first time is 10-60 minutes.

[0015] Furthermore, in step 1, the reducing agent is one or more of ferrous sulfate, sulfurous acid, iron particles, tartaric acid, and citric acid.

[0016] Furthermore, the molar amount of the reducing agent added is 0.3 to 1.0 times the molar amount of vanadium in the vanadium extraction tailings.

[0017] Furthermore, in step three, the second time is 5-60 minutes.

[0018] Furthermore, in step 4, the oxidant is one or more of hydrogen peroxide, air, and ammonium persulfate.

[0019] Furthermore, in step 4, the molar amount of the oxidant added is 0.5 to 2.0 times the molar amount of vanadium in the second solution.

[0020] Furthermore, in step 1, the predetermined liquid-to-solid ratio is 2 to 10 by mass.

[0021] Furthermore, in step three or step four, the acidity regulator is one or more of sulfuric acid, ammonia water, lime, and sodium hydroxide.

[0022] By adopting the above technical solution, the present invention has at least the following beneficial effects:

[0023] The present invention provides a method for recovering vanadium by deep leaching of vanadium extraction tailings. The method comprises the following steps: low-pH acid leaching and reduction are performed to reduce vanadium to a low-valent state. At this state, the vanadium can exist stably under low pH conditions; cyclic acid leaching is then performed to continuously increase the vanadium concentration; and finally, the pH is adjusted and an oxidant is added to oxidize the vanadium to a pentavalent state. At this state, a high concentration of pentavalent vanadium can exist stably. DETAILED DESCRIPTION

[0024] The embodiments of the present disclosure are further described in detail below with reference to the examples. The detailed description of the following examples is used to illustrate the principles of the present disclosure, but is not intended 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 within the scope of the claims.

[0025] The present disclosure provides these embodiments in order to make this disclosure thorough and complete, and to fully convey 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 parts and steps, the composition of materials, numerical expressions and numerical values ​​set forth in these embodiments should be interpreted as merely exemplary, and not as limiting.

[0026] It should be noted that, in the description of this disclosure, unless otherwise specified, "plurality" means greater than or equal to two; terms such as "upper," "lower," "left," "right," "inner," and "outer" indicating directions or positional relationships are intended solely to facilitate and simplify the description of this disclosure, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this disclosure. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0027] In addition, the terms "first," "second," and similar terms used in this disclosure do not denote any order, quantity, or importance, but are merely used to distinguish different parts. "Perpendicular" does not mean perpendicular in the strict sense, but rather means within the tolerance range. "Parallel" does not mean parallel in the strict sense, but rather means within the tolerance range. "Include" or "comprising" and similar terms mean that the elements preceding the term include the elements listed after the term, and do not exclude the possibility of also including other elements.

[0028] It should also be noted that, in the description of this disclosure, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in this disclosure depending on 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 intervening device between the specific device and the first or second device.

[0029] All terms used in this disclosure have the same meaning as understood by one of ordinary skill in the art to which this disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in, for example, common dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and should not be interpreted in an idealized or highly formal sense, unless explicitly defined as such herein.

[0030] 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.

[0031] Some embodiments of the present invention disclose a method for recovering vanadium from vanadium extraction tailings through deep leaching. The vanadium extraction tailings are subjected to low-pH acid leaching and reduction, followed by a cyclic acid leaching process to continuously increase the vanadium concentration. Finally, the vanadium is oxidized to pentavalent vanadium by adjusting the pH and adding an oxidant. Specifically, the method includes:

[0032] Step 1: Take vanadium extraction tailings, add a leaching agent according to a predetermined liquid-to-solid ratio, adjust the pH to 0.5-1.0, then add a reducing agent, and stir the reaction at a first temperature for a first time to obtain a first solution; the first temperature is 20-70°C, and the first time is 10-60 minutes. The reducing agent is one or more of ferrous sulfate, sulfurous acid, iron particles, tartaric acid, and citric acid.

[0033] The molar amount of the reducing agent added is 0.3 to 1.0 times the molar amount of vanadium in the vanadium extraction tailings. The predetermined liquid-to-solid ratio is 2 to 10 by mass.

[0034] Step 2: separating the first solution into solid and liquid to obtain a first leachate; and returning the first leachate to step 1 as a leaching agent;

[0035] Repeat steps 1 and 2 until the V concentration in the first leachate reaches 18 g / L or above, thereby obtaining a high-concentration vanadium-containing leachate;

[0036] Step 3: Using an acidity regulator to adjust the pH of the high-concentration vanadium-containing leachate to 2.8-3.5, stirring and reacting for a second time, and then separating the solid and the liquid to obtain a second solution; the second time can be 5-60 minutes.

[0037] Step 4: Add an oxidant to the second solution, adjust the pH to 2.8-3.5 with an acidity regulator, conduct an oxidation reaction at a second temperature for a second time, and then separate the solid and liquid to obtain a third solution. The third solution is subjected to ammonium salt precipitation to obtain a vanadium product. The oxidant is one or more of hydrogen peroxide, air, and ammonium persulfate. The molar amount of the oxidant added is 0.5-2.0 times the molar amount of vanadium in the second solution.

[0038] The acidity regulator can be selected from one or more of sulfuric acid, ammonia water, lime, and sodium hydroxide.

[0039] The embodiments of the present invention address the problem that during the further low-pH vanadium extraction process of low-grade vanadium extraction tailings, the acid leaching solution obtained has a low pH, low vanadium concentration, high impurity content, and difficulty in effectively extracting vanadium. A method for enriching vanadium through cyclic acid leaching is proposed: first, the vanadium extraction tailings are subjected to low-pH acid leaching, and the vanadium is reduced to a low-valent state during the acid leaching process. At this time, the low-valent vanadium can exist stably under low pH conditions. Then, the vanadium concentration is continuously increased through cyclic acid leaching. Finally, the vanadium is oxidized to pentavalent vanadium by adjusting the pH and adding an oxidant. At this time, a high concentration of pentavalent vanadium can exist stably.

[0040] Some embodiments of the present invention disclose a method for recovering vanadium by deep leaching of vanadium extraction tailings, which comprises the following steps:

[0041] (1) Take vanadium extraction tailings, add a leaching agent according to a certain liquid-solid ratio, adjust the pH to 0.5-1.0 with sulfuric acid, add a reducing agent (at least one of ferrous sulfate, sulfurous acid, tartaric acid, and citric acid), and stir the reaction at 20-70°C for 10-60 minutes;

[0042] (2) solid-liquid separation to obtain leachate A; leachate A is returned to step (1) as a leaching agent, and step (1) is repeated until the V concentration in the leachate reaches 18 g / L or above, thereby obtaining a high-concentration vanadium-containing leachate B;

[0043] (3) controlling the pH of the leachate B in step (2) to 2.8 to 3.5 using an acidity regulator, stirring the reaction for 5 to 60 minutes, and performing solid-liquid separation to obtain solution C;

[0044] (4) Add an oxidant to solution C, use an acidity regulator to control the pH to 2.8-3.5, and carry out oxidation reaction at a temperature of 25-60°C for 5-60 minutes. After solid-liquid separation, solution D is obtained, which can be directly subjected to ammonium salt precipitation to prepare vanadium products.

[0045] Wherein: in step (1), the liquid-to-solid ratio of the leaching agent to the vanadium extraction tailings is 2-10; the leaching agent can be water or leachate A; and the added molar amount of the reducing agent is 0.3-1.0 times the molar amount of vanadium in the vanadium extraction tailings.

[0046] In steps (3) and (4), the acidity regulator is one or more of sulfuric acid, ammonia water, lime, and sodium hydroxide.

[0047] In step (4), the oxidant is one or more of hydrogen peroxide, air, and ammonium persulfate, and the added molar amount is 0.5 to 2.0 times the molar amount of vanadium in the solution.

[0048] Example 1:

[0049] (1) Take 100 g of vanadium extraction tailings (TV = 1.63%), add 300 mL of water (leaching agent), adjust the pH to 1.0 with sulfuric acid, add 10 mL of sulfurous acid (containing 6% SO2), and stir the reaction at 30°C for 60 minutes;

[0050] (2) solid-liquid separation to obtain leachate A (V = 1.80 g / L, Fe = 0.41 g / L); leachate A is returned to step (1) as a leaching agent for 12 cycles of leaching to obtain vanadium-containing leachate B (V = 19.85 g / L, Fe = 3.12 g / L) and a leaching residue (the residues after 12 cycles are mixed and measured to have a TV of 1.05%);

[0051] (3) The pH of the leachate B was adjusted to 3.0 with concentrated ammonia water, stirred for 20 min, and solid-liquid separation was performed to obtain solution C (V = 18.82 g / L, Fe = 0.23 g / L);

[0052] (4) 30 mL of 30% hydrogen peroxide was added to solution C, the pH was controlled to ~2.8, and the oxidation reaction was carried out at 30°C for 20 min. After solid-liquid separation, solution D (V = 17.05 g / L, Fe = 0.02 g / L) was obtained, and vanadium product was directly prepared by ammonium salt precipitation.

[0053] Comparative Example 1:

[0054] (1) Take 100 g of vanadium extraction tailings (TV = 1.63%), add 300 mL of water (leaching agent), adjust the pH to 1.0 with sulfuric acid, and stir the reaction at 30°C for 60 min;

[0055] (2) solid-liquid separation to obtain leachate A (V = 1.86 g / L, Fe = 0.43 g / L); leachate A is returned to step (1) as a leaching agent for 12 cycles of leaching to obtain vanadium-containing leachate B (V = 8.30 g / L, Fe = 1.95 g / L) and a leaching residue (the average TV of the residue after 12 cycles is 1.35%).

[0056] (3) The pH of the leachate B was adjusted to 3.0 with concentrated ammonia water, and the mixture was stirred for 20 min. The solid-liquid separation was performed to obtain solution C (V = 4.87 g / L, Fe = 0.08 g / L).

[0057] In the above Example 1 and Comparative Example 1, during the vanadium extraction tailings cyclic acid leaching process, the corresponding vanadium concentrations in the leachate are shown in Table 1 below:

[0058] Table 1 Vanadium concentration in leachate corresponding to different cycle times during acid leaching (gL) -1

[0059] frequency 1 2 3 4 5 6 7 8 9 10 11 12 Implementation 1 1.80 3.49 5.18 6.87 8.56 10.24 11.84 13.44 15.04 16.65 18.25 19.85 Comparison 1 1.86 3.55 4.99 6.07 6.96 7.67 8.21 8.56 8.74 8.92 9.19 8.30

[0060] As shown in Table 1, direct acid leaching of the vanadium extraction tailings results in a gradual increase in the vanadium concentration of the leachate with increasing cycle number. In Comparative Example 1, where no tartaric acid was added and the solution pH was 1.0, when the vanadium concentration rose above 5 g / L, the dissolved pentavalent vanadium readily hydrolyzed and precipitated back into the slag. Consequently, the increase in vanadium concentration in the leachate of Comparative Example 1 was smaller than that in Example 1, and the TV content of the leached residue of Comparative Example 1 was higher than that of Example 1.

[0061] At the same time, since vanadium was not reduced, during the pH adjustment process in step (3), pentavalent vanadium in the solution reacted with iron to form a precipitate, that is, the vanadium concentration of comparative solution B (V = 8.30 g / L) was reduced to 4.87 g / L after pH adjustment.

[0062] Example 2:

[0063] (1) Take 100 g of vanadium extraction tailings (TV = 1.34%), add 400 mL of water (leaching agent), adjust the pH to 0.8 with sulfuric acid, add 1.6 g of citric acid, and stir the reaction at 50°C for 40 min;

[0064] (2) solid-liquid separation to obtain leachate A (V = 1.45 g / L, Fe = 0.65 g / L); leachate A is returned to step (1) as a leaching agent for 16 cycles of leaching to obtain vanadium-containing leachate B (V = 20.34 g / L, Fe = 6.90 g / L) and a leaching residue (average TV of the residue after 16 cycles = 0.95%);

[0065] (3) The pH of the leachate B was adjusted to 3.2 with concentrated ammonia water, stirred for 20 min, and solid-liquid separation was performed to obtain solution C (V = 18.15 g / L, Fe = 0.28 g / L);

[0066] (4) Add 24 g of ammonium persulfate to solution C, control the pH to ~3.5, and carry out oxidation reaction at 45°C for 5 to 30 min. After solid-liquid separation, solution D (V = 17.01 g / L, Fe = 0.03 g / L) is obtained, and ammonium salt precipitation is directly performed to prepare vanadium product.

[0067] Comparative Example 2:

[0068] To the vanadium-containing leachate B (V = 20.34 g / L, Fe = 6.90 g / L) obtained in step (2) of Example 2, 24 g of ammonium persulfate was added, the pH was controlled to ~ 3.5, and an oxidation reaction was carried out at a temperature of 45 ° C for 5 to 30 minutes. Solution D (V = 10.51 g / L, Fe = 0.05 g / L) was obtained by solid-liquid separation.

[0069] In Comparative Example 2, solution B (containing a large amount of vanadium and iron) was directly oxidized and the pH was adjusted. After the low-valent vanadium was oxidized to a high-valent vanadium, it reacted with the iron in the solution to form a precipitate, resulting in the loss of vanadium.

[0070] Example 3:

[0071] (1) Take 100 g of vanadium extraction tailings (TV = 1.24%), add 500 mL of water (leaching agent), adjust the pH to 0.5 with sulfuric acid, add 2.4 g of ferrous sulfate, and stir the reaction at 60°C for 20 min;

[0072] (2) solid-liquid separation to obtain leachate A (V = 1.13 g / L, Fe = 0.94 g / L); leachate A is returned to step (1) as a leaching agent for 20 cycles of leaching to obtain vanadium-containing leachate B (V = 19.77 g / L, Fe = 11.02 g / L) and a leaching residue (average TV of the residue after 20 cycles = 0.72%);

[0073] (3) The pH of the leachate B was adjusted to 2.8 with concentrated ammonia water, stirred for 20 min, and solid-liquid separation was performed to obtain solution C (V = 17.91 g / L, Fe = 0.31 g / L);

[0074] (4) Air was introduced into solution C for 2 h, and 15 mL of hydrogen peroxide was added at the same time. The pH was controlled to be ~3.0, and the oxidation reaction was carried out at 60°C for 60 min. After solid-liquid separation, solution D (V = 17.04 g / L, Fe = 0.03 g / L) was obtained, and vanadium product was directly prepared by ammonium salt precipitation.

[0075] Comparative Example 3:

[0076] The pH of the leachate B (V = 19.77 g / L, Fe = 8.02 g / L) of Example 3 was adjusted to 1.8 with concentrated ammonia water, and the mixture was stirred for 20 minutes, and the solid-liquid separation was performed to obtain a solution C (V = 18.21 g / L, Fe = 1.52 g / L);

[0077] Air was introduced into solution C for 2 h, and 15 mL of hydrogen peroxide was added at the same time. The pH was controlled at ~3.0, and the oxidation reaction was carried out at 60°C for 60 min. After solid-liquid separation, solution D (V = 13.52 g / L, Fe = 0.04 g / L) was obtained, which was directly subjected to ammonium salt precipitation to prepare vanadium products.

[0078] In Comparative Example 3, the pH of the leachate B was adjusted to 1.8, and the Fe concentration in the obtained solution C was higher than that in Example 3. Subsequently, the vanadium was oxidized to a high valence and reacted with the iron in the solution to form a precipitate, resulting in the loss of vanadium.

[0079] Thus far, various embodiments of the present disclosure have been described in detail. To avoid obscuring the concept of the present disclosure, some details known in the art have not been described. Based on the above description, those skilled in the art can fully understand how to implement the technical solutions disclosed herein.

[0080] Although some specific embodiments of the present disclosure have been described in detail through examples, those skilled in the art will understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Those skilled in the art will understand that the above embodiments may be modified or some technical features may be replaced with equivalents without departing from the scope and spirit of the present disclosure. In particular, as long as there are no structural conflicts, the various technical features mentioned in the various embodiments may be combined in any manner.

Claims

1. A method for recovering vanadium by deep leaching of vanadium extraction tailings, characterized in that: The vanadium extraction tailings are subjected to low pH acid leaching and reduction, and then the vanadium concentration is continuously increased through cyclic acid leaching. Finally, the vanadium is oxidized to pentavalent by adjusting the pH and adding an oxidant; including: Step 1: taking vanadium extraction tailings, adding a leaching agent according to a predetermined liquid-solid ratio, adjusting the pH to 0.5-1.0, adding a reducing agent, and stirring the reaction at a first temperature for a first time to obtain a first solution; Step 2: separating the first solution into solid and liquid to obtain a first leachate; and returning the first leachate to step 1 as a leaching agent; Repeat steps 1 and 2 until the V concentration in the first leachate reaches 18 g / L or above, thereby obtaining a high-concentration vanadium-containing leachate; Step 3: adjusting the pH of the high-concentration vanadium-containing leachate to 2.8-3.5 with an acidity regulator, stirring and reacting for a second time, and then separating the solid and the liquid to obtain a second solution; Step 4: Add an oxidant to the second solution, adjust the pH to 2.8-3.5 with an acidity regulator, perform an oxidation reaction at a second temperature for a second time, and then perform solid-liquid separation to obtain a third solution, and perform ammonium salt precipitation of vanadium on the third solution to obtain a vanadium product; In step 1, the reducing agent is one or more of ferrous sulfate, sulfurous acid, iron particles, tartaric acid, and citric acid.

2. The method for recovering vanadium by deep leaching of vanadium-extracting tailings according to claim 1, wherein: In step 1, the first temperature is 20-70° C., and the first time is 10-60 minutes.

3. The method for recovering vanadium by deep leaching of vanadium-extracting tailings according to claim 1, wherein: The molar amount of the reducing agent added is 0.3 to 1.0 times the molar amount of vanadium in the vanadium extraction tailings.

4. The method for recovering vanadium by deep leaching of vanadium extraction tailings according to claim 1, wherein: In step 3, the second time is 5-60 minutes.

5. The method for recovering vanadium by deep leaching of vanadium extraction tailings according to claim 1, characterized in that: In step 4, the oxidant is one or more of hydrogen peroxide, air, and ammonium persulfate.

6. The method for recovering vanadium by deep leaching of vanadium-extracting tailings according to claim 4, characterized in that: In step 4, the molar amount of the oxidant added is 0.5 to 2.0 times the molar amount of vanadium in the second solution.

7. The method for recovering vanadium by deep leaching of vanadium extraction tailings according to claim 1, characterized in that: In step 1, the predetermined liquid-to-solid ratio is 2 to 10 by mass.

8. The method for recovering vanadium by deep leaching of vanadium extraction tailings according to claim 1, characterized in that: In step 3 or step 4, the acidity regulator is one or more of sulfuric acid, ammonia water, lime, and sodium hydroxide.