Method for removing iron from carbonated vanadium leach solution

Abstract

The present application relates to a method for removing iron from carbonated vanadium leaching solution, the pH value of the carbonated vanadium leaching solution is adjusted to a target pH value; then a soluble nickel salt is added, stirred and heated, filtered, and the filtrate is obtained to obtain a solution from which iron is removed. The target pH value is 10-12; the soluble nickel salt includes one or a mixture of any ratio of several of nickel sulfate, nickel chloride and nickel nitrate; the amount of the soluble nickel salt is added according to a molar ratio of nickel element to iron element in the carbonated vanadium leaching solution of 3.0-9.0; and the heating temperature is 90-100 DEG C. The present application realizes the purpose of deep iron removal by adding a soluble divalent nickel salt to the carbonated vanadium leaching solution at a target pH value, and realizes rapid and deep iron removal of the carbonated vanadium leaching solution, can reduce the content of iron and nickel in the vanadium solution to below 5 ppm, removes iron without introducing excessive nickel ions at the same time, has excellent impurity removal effect, and has no influence on the subsequent vanadium precipitation process.

Description

Technical Field

[0001] This invention belongs to the field of vanadium extraction and metallurgical technology, and specifically relates to a method for removing iron from vanadium carbonate leaching solutions. Background Technology

[0002] The main raw materials for vanadium extraction include vanadium-titanium magnetite, coal shale, and spent vanadium catalysts. The vast majority of these raw materials come from vanadium slag obtained after blast furnace smelting of vanadium-titanium magnetite. The sodium roasting-water leaching process is the mainstream industrial process for producing vanadium pentoxide from vanadium slag. However, with increasing emphasis on environmental protection, the serious pollution caused by ammonia nitrogen wastewater and mirabilite from the sodium roasting process, as well as its limitations in industrial production, have become increasingly prominent. In recent years, environmentally friendly calcination roasting technology for vanadium extraction has gained increasing attention. The vanadium slag calcination roasting-acid leaching process involves adding CaO, CaCO3, or other calcium-containing compounds in a certain proportion to high-calcium vanadium slag or ordinary vanadium slag, followed by oxidative calcination roasting. This oxidizes the low-valent vanadium in the vanadium slag to high-valent vanadium, which then reacts with calcium to form calcium vanadate. Calcium vanadate dissolves vanadium in sulfuric acid solution to produce vanadium products such as vanadium oxide. This process generates no ammonia-containing waste gas during roasting; the main gas produced is CO2, which is harmless, making it a clean vanadium extraction process. However, the acid leaching process requires highly corrosion-resistant leaching equipment. Furthermore, because acid leaching is non-selective, the leaching solution contains a large amount of metallic cation impurities such as iron and manganese, necessitating complex impurity removal processes such as extraction and ion exchange. This results in low purity vanadium pentoxide, limiting its industrial production.

[0003] To address the problems existing in the calcination-roasting-sulfuric acid leaching process, some scholars, based on the characteristic that calcium carbonate has a lower solubility than calcium vanadate, proposed a vanadium slag calcination-roasting-carbonation leaching process. The leaching agent is generally Na₂CO₃, NaHCO₃, (NH₄)₂CO₃, or NH₄HCO₃, etc. The leaching agent is added to the roasted clinker or CO₂ gas is introduced. 2- With VO 3- An exchange reaction occurs between ions, and calcium and phosphorus precipitate as calcium carbonate and calcium phosphate, respectively, while vanadium enters the leachate as vanadate. Compared with acid leaching, the carbonation leaching process has higher selectivity for vanadium dissolution and produces a leachate with fewer impurities. Iron impurities are the main problem that is difficult to remove. Therefore, if the problem of deep iron removal from vanadium carbonate leaching solution is solved, it is expected that a high-purity vanadium pentoxide preparation process with high purity, low process cost, and simple process steps can be developed using carbonation leaching solution as raw material.

[0004] Patent CN 105695738 B discloses a method for removing iron from vanadium-containing coal leaching solution. This patent uses vanadium-containing coal leaching solution as raw material, adding reduced iron powder and oxalic acid to the solution, adjusting the pH to 1.5-5, stirring and heating, washing and filtering to obtain a purified solution and a filter cake. The filter cake is then dried to obtain ferrous oxalate dihydrate as a byproduct. While this method can separate vanadium and iron from vanadium-containing coal leaching solution to some extent and recover iron, it is only suitable for acidic systems. Due to the large solubility product constant of ferrous oxalate, deep iron removal is not possible, and excessive reducing agent can reduce vanadium in the solution, resulting in vanadium loss during the iron removal process. Patent CN 101538649B discloses a method for removing iron from acid leaching solutions during vanadium extraction from coal shale. The method involves first adjusting the pH of the acid leaching solution to 2-4 with ammonia water, then extracting the solution with a mixed extractant. The mixed extractant is a mixture of kerosene and P204 extractant, where the P204 extractant is one or more of monobutyl phosphate, monooctyl phosphate, monohexyl phosphate, and citric acid. After extraction, the iron ions in the mixed extractant are back-extracted using dilute sulfuric acid, and the extractant is recycled. This method only reduces the iron ion concentration in the acid leaching solution by 65-82%, making it a simple and preliminary iron removal method. The iron ion concentration in the residual extract remains high, failing to achieve deep iron removal. Furthermore, extraction methods in industrial production suffer from common problems such as extractant emulsification, the production of a third phase, and the extractant's potential harm to health and volatility. Patent CN 109439898B discloses a method for removing iron from vanadium-containing shale using microbial treatment. This patent describes a process where ammonium sulfate, dipotassium hydrogen phosphate, potassium chloride, magnesium sulfate heptahydrate, and calcium nitrate are dissolved in distilled water to form a basic salt solution for a microbial culture medium. Then, 10–80 g of sterilized sulfur-containing purified material is added to this basic salt solution, and the mixture is used as a microbial culture medium. Next, 10–100 g of sterilized finely ground vanadium-containing shale powder is added, and the mixture is adjusted to obtain a mixed culture medium. Finally, *Thiobacillus ferrooxidans* culture is inoculated into the mixed culture medium, and the mixture is treated at 25–38°C and a shaking speed of 150–220 r / min for 15–35 days to obtain microbially treated vanadium-containing shale. However, this patented method is not only complex in its process flow and has a small processing capacity, making it unsuitable for industrial production, but also achieves an iron removal rate of only 60–65%, failing to deeply remove iron from vanadium-containing shale.

[0005] Fe 3+ In solution, it dissolves as the pH increases to form the corresponding ferrate, with the molecular formula [Fe(OH)4]. - Therefore, iron removal can be achieved by adjusting the pH value of the vanadium carbonate leaching solution and heating it to precipitate iron ions in the form of Fe(OH)3. However, this method cannot achieve deep iron removal.

[0006] In summary, existing methods for removing iron from vanadium-containing materials generally do not involve vanadium carbonate leaching solutions, and no research has been reported on iron removal from vanadium carbonate leaching solutions. When iron removal is involved from other materials, there are one or more problems such as low impurity removal rate, complex process flow, and high cost, which cannot fully meet the needs of industrial production of high-purity vanadium products.

[0007] Based on this, the present invention provides a method for removing iron from vanadium carbonate leaching solution. Summary of the Invention

[0008] This invention provides a method for removing iron from vanadium carbonate leaching solutions, thereby solving the problem of difficult deep iron removal from vanadium carbonate leaching solutions.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] Methods for removing iron from vanadium carbonate leaching solutions include:

[0011] Adjust the pH value of the vanadium carbonate leaching solution to the target pH value;

[0012] Add soluble nickel salt, stir and heat, filter, and collect the filtrate to obtain an iron-free solution.

[0013] Furthermore, the target pH value is 10–12.

[0014] As another aspect of the present invention, the target pH value is 11.

[0015] As another aspect of the present invention, the target pH value is 11.5.

[0016] Furthermore, the soluble nickel salt includes one or a mixture of nickel sulfate, nickel chloride, and nickel nitrate in any proportion.

[0017] Furthermore, the amount of soluble nickel salt added is based on a molar ratio of nickel to iron in the vanadium carbonate leaching solution of 3.0 to 9.0.

[0018] Furthermore, the heating temperature is 90–100°C.

[0019] As another aspect of the present invention, the heating temperature is 95°C.

[0020] Furthermore, the stirring time is 1 to 6 hours.

[0021] As another aspect of the present invention, the stirring time is 4 hours.

[0022] The beneficial effects of this invention are:

[0023] This invention achieves deep iron removal by adding soluble divalent nickel salts to a vanadium carbonate leaching solution with a target pH value. The underlying principles are as follows:

[0024] The precipitation-promoting effect of hydrolysis: Both divalent nickel ions and trivalent iron ions can hydrolyze to form nickel hydroxide precipitate under alkaline conditions. Since the solubility product constant of nickel hydroxide is much greater than that of iron hydroxide, trivalent iron ions preferentially precipitate divalent nickel ions. Therefore, the hydrolysis and precipitation of a large number of divalent nickel ions also promotes the hydrolysis and precipitation of iron ions. The chemical formula is expressed as follows:

[0025] Ni 2+ +OH - →Ni(OH)2↓

[0026] Fe 3+ +OH - →Cr(OH)3↓

[0027] Coprecipitation: Divalent nickel ions and trivalent iron ions also undergo a coprecipitation reaction during hydrolysis, forming coprecipitates of ferric hydroxide and nickel hydroxide. The precipitates of the two ions interact and promote each other, resulting in a synergistic precipitation effect. The chemical formulas are as follows:

[0028] Ni(OH)2+Fe(OH)3→Ni(OH)2·Fe(OH)3↓

[0029] Based on the above two effects, the addition of soluble divalent nickel salts can achieve the purpose of deep iron removal in vanadium carbonate leaching solution.

[0030] This invention achieves rapid and deep iron removal from vanadium carbonate leaching solutions, reducing the iron and nickel content in the vanadium solution to below 5 ppm. While removing iron, it does not introduce excessive nickel ions, resulting in excellent impurity removal and no impact on the subsequent vanadium precipitation process.

[0031] The rapid and deep iron removal method proposed in this invention is a chemical precipitation method. It has the advantages of simple and easy-to-use process, low equipment requirements, convenient operation, short process, easy to scale up operation, and cheap nickel salt market price, making it very suitable for industrial production.

[0032] Using the iron-removed solution obtained by the present invention as the raw material for vanadium extraction, the purity of vanadium pentoxide obtained by the downstream vanadium precipitation process is ≥99.9%, which solves the problem of high cost in the preparation process of high-purity vanadium pentoxide.

[0033] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 A flowchart of a method for removing iron from vanadium carbonate leaching solution according to an embodiment of the present invention is shown. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] like Figure 1 As shown, the method for removing iron from vanadium carbonate leaching solution includes:

[0038] Adjust the pH value of the vanadium carbonate leaching solution to the target pH value;

[0039] Add soluble nickel salt, stir and heat, filter, and collect the filtrate to obtain an iron-free solution.

[0040] The target pH value is 10-12. If the pH is too low, Fe 3+ and Ni 2+ Incomplete hydrolysis results in a low iron removal rate; when the pH is too high, some hydroxides will dissolve again in the alkaline solution, which will actually increase the amount of impurities.

[0041] The soluble nickel salt is added in an amount such that the molar ratio of nickel to iron in the vanadium carbonate leaching solution is 3.0–9.0. 2+ Insufficient iron removal due to low Ni content 2+ Excessive concentrations will introduce too much nickel, increasing material consumption and causing Ni concentrations in the solution to rise. 2+ Exceeding the standard;

[0042] The soluble nickel salt is one or a mixture of several of nickel sulfate (NiSO4·6H2O), nickel chloride (NiCl2·6H2O), and nickel nitrate (Ni(NO3)2·6H2O) in any proportion;

[0043] The heating temperature is 90–100°C. Higher temperatures accelerate the Fe… 3+The water leaching rate, nickel-iron co-precipitation rate, and iron removal rate were improved.

[0044] The stirring time is 1–6 hours. If the time is too short, Fe… 3+ and Ni 2+ Incomplete reaction affects the final iron removal rate, and excessive time increases energy consumption and cost.

[0045] Example 1

[0046] 500 ml of vanadium carbonate leaching solution containing 0.057 g / L of iron was measured. The pH of the vanadium carbonate leaching solution was adjusted to 10 with sodium hydroxide. 0.40 g of NiSO4·6H2O was added, and the mixture was stirred at 90 °C for 1 h. After the reaction was completed, the filter cake and filtrate were obtained by filtration. The Fe content in the filtrate was measured to be 5.1 ppm and the Ni content was 4.6 ppm.

[0047] Comparative Example 1

[0048] 500 ml of vanadium carbonate leaching solution containing 0.057 g / L of iron was measured. The pH of the vanadium carbonate leaching solution was adjusted to 10 with sodium hydroxide. The solution was stirred and reacted at 90 °C for 1 h. After the reaction was completed, the filter cake and filtrate were obtained by filtration. The Fe content in the filtrate was measured to be 0.034 g / L.

[0049] Example 2

[0050] 500 ml of vanadium carbonate leaching solution containing 0.102 g / L of iron was measured. The pH of the vanadium carbonate leaching solution was adjusted to 11.5 with sodium hydroxide. 1.52 g of NiCl2·6H2O was added, and the mixture was stirred at 95 °C for 4 h. After the reaction was completed, the filter cake and filtrate were obtained by filtration. The Fe content in the filtrate was measured to be 1.2 ppm and the Ni content was 0.9 ppm.

[0051] Comparative Example 2

[0052] 500 ml of vanadium carbonate leaching solution containing 0.102 g / L of iron was measured. The pH of the vanadium carbonate leaching solution was adjusted to 10 with sodium hydroxide. The solution was stirred and reacted at 90 °C for 4 h. After the reaction was completed, the filter cake and filtrate were obtained by filtration. The Fe content in the filtrate was measured to be 0.042 g / L.

[0053] Example 3

[0054] 500 ml of vanadium carbonate leaching solution containing 0.088 g / L of iron was measured. The pH of the vanadium carbonate leaching solution was adjusted to 11 with sodium hydroxide. 1.14 g of Ni(NO3)2·6H2O was added, and the mixture was stirred at 98 °C for 2 h. After the reaction was completed, the filter cake and filtrate were obtained by filtration. The Fe content in the filtrate was measured to be 4.4 ppm and the Ni content was 1.8 ppm.

[0055] Example 4

[0056] 500 ml of vanadium carbonate leaching solution containing 0.057 g / L of iron was measured. The pH of the vanadium carbonate leaching solution was adjusted to 12 with sodium hydroxide. 1.09 g of NiCl2·6H2O was added, and the mixture was stirred at 100 °C for 6 h. After the reaction was completed, the filter cake and filtrate were obtained by filtration. The Fe content in the filtrate was measured to be 0.8 ppm and the Ni content was 2.5 ppm.

[0057] A comparison of the Fe and Ni content data in the filtrates obtained from Examples 1-4 and Comparative Examples 1-2 shows that:

[0058] The iron and nickel content in the filtrate obtained by the iron removal methods used in Examples 1-4 was reduced to below 5 ppm. No excessive nickel ions were introduced during the iron removal process, resulting in excellent impurity removal and no impact on the downstream vanadium precipitation process.

[0059] Furthermore, the iron content in the filtrate obtained in Examples 1-2 is much lower than the iron content in the filtrate obtained in Comparative Examples 1-2.

[0060] Vanadium pentoxide was prepared by back-end vanadium precipitation according to Table 1, and the purity of the obtained vanadium pentoxide was tested. The purity results are shown in Table 1.

[0061] Table 1

[0062]

[0063]

[0064] As can be seen from the data in Table 1, the purity of vanadium pentoxide obtained by using the iron removal solution obtained in Examples 1-4 as the raw material for vanadium extraction and through the downstream vanadium precipitation process is ≥99.9%.

[0065] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for removing iron from vanadium carbonate leaching solution, characterized in that, include: Adjust the pH value of the vanadium carbonate leaching solution to the target pH value; Add soluble nickel salt, stir and heat, filter, and take the filtrate to obtain an iron-free solution; The soluble nickel salt is added in an amount that is 3.0 to 9.0 molar ratio of nickel to iron in the vanadium carbonate leaching solution. The stirring time is 1 to 6 hours.

2. The method for removing iron from vanadium carbonate leaching solution according to claim 1, characterized in that, The target pH value is 10~12.

3. The method for removing iron from vanadium carbonate leaching solution according to claim 1 or 2, characterized in that, The target pH value is 11.

4. The method for removing iron from vanadium carbonate leaching solution according to claim 1 or 2, characterized in that, The target pH value is 11.

5.

5. The method for removing iron from vanadium carbonate leaching solution according to claim 1, characterized in that, The soluble nickel salt includes one or a mixture of nickel sulfate, nickel chloride, and nickel nitrate in any proportion.

6. The method for removing iron from vanadium carbonate leaching solution according to any one of claims 1, 2, and 5, characterized in that, The heating temperature is 90~100℃.

7. The method for removing iron from vanadium carbonate leaching solution according to any one of claims 1, 2, and 5, characterized in that, The heating temperature is 95°C.

8. The method for removing iron from vanadium carbonate leaching solution according to any one of claims 1, 2, and 5, characterized in that, The stirring time is 4 hours.

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