Preparation method of calcium vanadate and calcium vanadate

Abstract

The invention discloses a preparation method of calcium vanadate. The preparation method comprises the following steps: dissolving ammonium vanadate into a carbonate solution to obtain a vanadium-containing return solution; the vanadium-containing return solution is subjected to impurity removal, and purified vanadium liquid is obtained; adding a calcium salt precipitator into the purified vanadium liquid to obtain calcium vanadate; and washing and roasting the calcium vanadate to obtain the final calcium vanadate. The invention also discloses calcium vanadate. According to the scheme provided by the invention, after ammonium vanadate is dissolved in an ammonium bicarbonate solution to obtain a vanadium-containing return solution, deep impurity removal is carried out to obtain a purified vanadium solution, a calcium salt is added into the purified vanadium solution, a stirring reaction is carried out to prepare a calcium vanadate solid, the calcium vanadate solid is further roasted, and a high-purity calcium vanadate product is prepared. The high-purity calcium vanadate product can be prepared from common ammonium vanadate as a raw material through one-step dissolution, impurity removal and precipitation, the purity of the calcium vanadate can reach 99.8% or above, the technological process is short, the vanadium yield is high, and the production cost is low.

Description

Technical Field

[0001] The invention relates to the field of calcium vanadate, and in particular to a preparation method of calcium vanadate and the calcium vanadate. Background Art

[0002] Calcium vanadate, as a new type of ternary semiconductor material, is an important raw material for battery electrode materials, catalysts, laser materials, optical materials, high-purity metallic vanadium, and high-purity vanadium oxide. It has a wide range of applications and high quality requirements for calcium vanadate products. At present, the main processes for preparing calcium vanadate are hydrothermal method, sol-gel method, and solid-phase sintering method. The calcium vanadate products prepared by different processes have great differences in parameters such as product purity, crystal structure, specific surface area, and microstructure. However, all three processes require raw materials such as high-purity vanadium pentoxide, ammonium vanadate, sodium vanadate, and sodium metavanadate. There are problems of high production costs and complex processes, which seriously limit its application and production.

[0003] Since ordinary calcium vanadate has a high impurity content, it is difficult to meet the needs of fine chemicals. The existing high-purity calcium vanadate preparation technology has the problems of high production cost and complex process. For example, CN115259223B discloses a method for preparing ammonium metavanadate using calcium vanadate, in which calcium vanadate, ammonium acetate and CO2 are used as raw materials to produce ammonium metavanadate products. The purity of the calcium vanadate product directly affects the impurity content in the final ammonium metavanadate product. CN111268727B discloses a calcium vanadate composite material for positive active materials of aqueous zinc ion batteries, which is also made of high-purity vanadium pentoxide. Vanadium source raw materials are used to hydrothermally synthesize calcium vanadate, but the purity of vanadium pentoxide is required to reach 99.5% or above; there are also schemes that use calcium thermal reduction to directly reduce calcium vanadate to prepare metal vanadium powder. Due to the high impurity content in the calcium vanadate raw materials, the impurity content in the metal vanadium powder product is relatively high, resulting in a hard material and poor mechanical processing performance, which limits the application of the product; there are also schemes that use high-purity sodium metavanadate and calcium acetate as raw materials, and adopt ethylene glycol-water dual solvent thermal method to prepare flower-shaped calcium vanadate microspheres, but in order to ensure the quality of calcium vanadate, all high-purity vanadium and calcium sources must be used for production.

[0004] Therefore, it is urgent to develop a short-process, low-cost and efficient production technology to produce high-purity calcium vanadate products with a purity of more than 99.9%. Summary of the invention

[0005] In view of this, in order to overcome at least one aspect of the above problems, an embodiment of the present invention provides a method for preparing calcium vanadate comprising the following steps: Dissolving ammonium vanadate in a carbonate solution to obtain a vanadium-containing solution; removing impurities from the vanadium-containing return solution to obtain a purified vanadium solution; Adding a calcium salt precipitant to the purified vanadium solution to obtain calcium vanadate; The calcium vanadate is washed and calcined to obtain the final calcium vanadate.

[0006] In some embodiments, dissolving ammonium vanadate into a carbonate solution to obtain a vanadium-containing solution further comprises: The ammonium vanadate is added to the carbonate solution at a liquid-to-solid ratio of 20-30:1 mL / g; The reaction was stirred at a temperature of 75-95° C. until the sodium vanadate was completely dissolved.

[0007] In some embodiments, the carbonate solution is ammonium carbonate and / or ammonium bicarbonate, with a concentration of 20-50 g / L.

[0008] In some embodiments, removing impurities from the vanadium-containing return solution to obtain a purified vanadium solution further comprises: adding a calcium salt impurity remover to the vanadium-containing return solution; The reaction is stirred at a temperature of 75-95°C for 15-60 minutes, followed by solid-liquid separation to obtain purified vanadium liquid.

[0009] In some embodiments, adding a calcium salt impurity remover to the vanadium-containing return solution further comprises: Calcium oxide and / or calcium hydroxide is used as the calcium salt impurity remover, and the addition amount of the calcium salt impurity remover is 2-10 g / L.

[0010] In some embodiments, adding a calcium salt precipitant to the purified vanadium solution to obtain calcium vanadate further comprises: The reaction is stirred at a temperature of 75-95°C for 30-90 minutes, and then the solid and liquid are separated to obtain calcium vanadate.

[0011] In some embodiments, it also includes: Calcium oxide and / or calcium hydroxide is used as the calcium salt precipitant, and the calcium salt precipitant is added according to a molar ratio of Ca:V in the purified vanadium solution of 1.0-1.5:1.

[0012] In some embodiments, washing and calcining the calcium vanadate to obtain the final calcium vanadate further comprises: The calcium vanadate is added into pure water at a liquid-solid ratio of 5-15:1 mL / g, stirred and washed for 15-60 min, and solid-liquid separation is performed to obtain washed calcium vanadate.

[0013] In some embodiments, it also includes: The washed calcium vanadate is calcined at a temperature of 300-500° C. in an oxidizing atmosphere, and the final calcium vanadate is obtained after being kept at the temperature for 30-90 minutes.

[0014] Based on the same inventive concept, according to another aspect of the present invention, an embodiment of the present invention further provides a calcium vanadate, which is prepared by the method described in any one of the above embodiments.

[0015] The present invention has one of the following beneficial technical effects: the scheme proposed by the present invention is to dissolve ammonium vanadate in an ammonium bicarbonate solution to obtain a vanadium-containing return solution, perform deep impurity removal to obtain a purified vanadium liquid, add calcium salt to the purified vanadium liquid, stir the reaction to prepare a calcium vanadate solid, and further calcine the calcium vanadate solid to prepare a high-purity calcium vanadate product. Thus, a high-purity calcium vanadate product can be prepared by using ordinary ammonium vanadate as a raw material through a one-step dissolution, impurity removal and precipitation, and the purity of the calcium vanadate can reach more than 99.8%, the process flow is short, the vanadium yield is high, and the production cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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 in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic flow chart of a method for preparing calcium vanadate provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0019] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. The subsequent embodiments will not explain this one by one.

[0020] According to one aspect of the present invention, an embodiment of the present invention provides a method for preparing calcium vanadate, such as Figure 1 As shown, it may include the steps of: Dissolving ammonium vanadate in a carbonate solution to obtain a vanadium-containing solution; removing impurities from the vanadium-containing return solution to obtain a purified vanadium solution; Adding a calcium salt precipitant to the purified vanadium solution to obtain calcium vanadate; The calcium vanadate is washed and calcined to obtain the final calcium vanadate.

[0021] The scheme proposed by the present invention is to dissolve ammonium vanadate in an ammonium bicarbonate solution to obtain a vanadium-containing return solution, perform deep impurity removal to obtain a purified vanadium liquid, add calcium salt to the purified vanadium liquid, stir the reaction to prepare a calcium vanadate solid, and further calcine the calcium vanadate solid to prepare a high-purity calcium vanadate product. Thus, a high-purity calcium vanadate product can be prepared by using ordinary ammonium vanadate as a raw material through a one-step dissolution, impurity removal and precipitation, and the purity of the calcium vanadate can reach more than 99.8%, with a short process flow, a high vanadium yield and low production cost.

[0022] In some embodiments, dissolving ammonium vanadate into a carbonate solution to obtain a vanadium-containing solution further comprises: The ammonium vanadate is added to the carbonate solution at a liquid-to-solid ratio of 20-30:1 mL / g; The reaction was stirred at a temperature of 75-95° C. until the sodium vanadate was completely dissolved.

[0023] In some embodiments, the carbonate solution is ammonium carbonate and / or ammonium bicarbonate, with a concentration of 20-50 g / L.

[0024] In some embodiments, removing impurities from the vanadium-containing return solution to obtain a purified vanadium solution further comprises: adding a calcium salt impurity remover to the vanadium-containing return solution; The reaction is stirred at a temperature of 75-95°C for 15-60 minutes, followed by solid-liquid separation to obtain purified vanadium liquid.

[0025] In some embodiments, adding a calcium salt impurity remover to the vanadium-containing return solution further comprises: Calcium oxide and / or calcium hydroxide is used as the calcium salt impurity remover, and the addition amount of the calcium salt impurity remover is 2-10 g / L.

[0026] In some embodiments, adding a calcium salt precipitant to the purified vanadium solution to obtain calcium vanadate further comprises: The reaction is stirred at a temperature of 75-95°C for 30-90 minutes, and then the solid and liquid are separated to obtain calcium vanadate.

[0027] In some embodiments, it also includes: Calcium oxide and / or calcium hydroxide is used as the calcium salt precipitant, and the calcium salt precipitant is added according to a molar ratio of Ca:V in the purified vanadium solution of 1.0-1.5:1.

[0028] In some embodiments, washing and calcining the calcium vanadate to obtain the final calcium vanadate further comprises: The calcium vanadate is added into pure water at a liquid-solid ratio of 5-15:1 mL / g, stirred and washed for 15-60 min, and solid-liquid separation is performed to obtain washed calcium vanadate.

[0029] In some embodiments, it also includes: The washed calcium vanadate is calcined at a temperature of 300-500° C. in an oxidizing atmosphere, and the final calcium vanadate is obtained after being kept at the temperature for 30-90 minutes.

[0030] Specifically, first, ammonium vanadate is added to the carbonate solution at a liquid-solid ratio of 20-30:1 mL / g, stirred evenly, and then heated to 75-95°C, stirred and reacted until the sodium vanadate solid is basically dissolved completely to obtain a vanadium-containing return solution. Then, a calcium salt impurity remover is added to the vanadium-containing return solution, kept at 75-95°C, stirred and reacted for 15-60 minutes, and then solid-liquid separation is performed to obtain purified vanadium liquid and impurity-removed slag. Then, a calcium salt precipitant is added to the purified vanadium liquid, kept at 75-95°C, stirred and reacted for 30-90 minutes, and then solid-liquid separation is performed to obtain calcium vanadate and an upper layer liquid. Then, calcium vanadate is added to pure water at a liquid-solid ratio of 5-15:1 mL / g, stirred and washed for 15-60 minutes, and solid-liquid separation is performed to obtain washed calcium vanadate and washing water. Finally, the washed calcium vanadate is heated to 300-500°C in an oxidizing atmosphere for roasting, and taken out after being kept warm for 30-90 minutes to obtain a high-purity calcium vanadate product.

[0031] Among them, the ammonium vanadate is produced by the vanadium slag calcification vanadium extraction process, and the main impurities are Al, K, Ca, Fe, Mn, Si, and P, and the content is no more than 1wt%, and the other contents are no more than 0.05wt%; the carbonate is one or more of ammonium carbonate and ammonium bicarbonate, and the concentration is 20-50g / L; the calcium salt impurity remover and calcium salt precipitant are one or more of calcium oxide and calcium hydroxide, and the amount of calcium salt impurity remover is 2-10g / L, and the amount of calcium salt precipitant is added according to the molar ratio of Ca:V=1.0-1.5:1 in the purified vanadium liquid. The purity of calcium vanadate product can reach more than 99.8%, and the vanadium yield can reach more than 95%.

[0032] Example 1 Step 1: Add ammonium vanadate to the carbonate solution at a liquid-solid ratio of 20:1 mL / g, stir evenly, heat to 95°C, and stir until the sodium vanadate solid is basically dissolved completely to obtain a vanadium-containing solution; Step 2: Add calcium salt impurity remover to the vanadium-containing return solution, keep the temperature at 95°C, stir and react for 40 minutes, and then separate the solid and liquid to obtain purified vanadium liquid and impurity-removing slag; Step 3: Add calcium salt precipitant to the purified vanadium solution, keep the temperature at 95°C, stir and react for 40 minutes, separate the solid and liquid, and obtain calcium vanadate and the upper liquid; Step 4: adding calcium vanadate to pure water at a liquid-solid ratio of 5:1 mL / g, stirring and washing for 60 min, and performing solid-liquid separation to obtain washed calcium vanadate and washing water; Step 5: The washed calcium vanadate is heated to 500° C. in an oxidizing atmosphere for calcination, and taken out after being kept at the temperature for 30 minutes to obtain a high-purity calcium vanadate product.

[0033] The ammonium vanadate is produced by the vanadium slag calcification vanadium extraction process, and the main impurities are Al content 0.05wt%, K content 0.19wt%, Ca content 0.13wt%, Fe content 0.16wt%, Mn content 0.34wt%, Si content 0.28wt%, P content 0.02wt%, and other contents do not exceed 0.05wt%; The carbonate is ammonium carbonate with a concentration of 50 g / L; The calcium salt impurity remover and calcium salt precipitant are calcium hydroxide, the calcium salt impurity remover is added in an amount of 5 g / L, and the calcium salt precipitant is added in an amount according to the molar ratio of Ca:V=1.0:1 in the purified vanadium solution.

[0034] The purity of calcium vanadate product reaches over 99.82%, and the vanadium yield reaches 95.5%.

[0035] Example 2 Step 1: Add ammonium vanadate to the carbonate solution at a liquid-solid ratio of 30:1 mL / g, stir evenly, heat to 75°C, and stir until the sodium vanadate solid is basically dissolved completely to obtain a vanadium-containing solution; Step 2: Add calcium salt impurity remover to the vanadium-containing return solution, keep the temperature at 75°C, stir and react for 60 minutes, and then separate the solid and liquid to obtain purified vanadium liquid and impurity-removing slag; Step 3: Add calcium salt precipitant to the purified vanadium solution, keep the temperature at 75°C, stir and react for 90 minutes, separate the solid and liquid, and obtain calcium vanadate and the upper liquid; Step 4: Add calcium vanadate to pure water at a liquid-solid ratio of 15:1 mL / g, stir and wash for 15 minutes, separate the solid and the liquid, and obtain washed calcium vanadate and washing water; Step 5: The washed calcium vanadate is heated to 450° C. in an oxidizing atmosphere for calcination, and then taken out after being kept warm for 60 minutes to obtain a high-purity calcium vanadate product.

[0036] The ammonium vanadate is produced by a calcification vanadium extraction process, and the main impurities are Al content of 0.09wt%, K content of 0.11wt%, Ca content of 0.19wt%, Fe content of 0.14wt%, Mn content of 0.18wt%, Si content of 0.32wt%, P content of 0.07wt%, and other contents are no more than 0.05wt%; The carbonate is ammonium bicarbonate with a concentration of 20 g / L; The calcium salt impurity remover and calcium salt precipitant are calcium oxide, the calcium salt impurity remover is added in an amount of 10 g / L, and the calcium salt precipitant is added in an amount according to the molar ratio of Ca:V=1.25:1 in the purified vanadium solution.

[0037] The purity of calcium vanadate product reaches 99.95%, and the vanadium yield reaches 96.2.

[0038] Example 3 Step 1: Add ammonium vanadate to the carbonate solution at a liquid-solid ratio of 25:1 mL / g, stir evenly, heat to 85°C, and stir until the sodium vanadate solid is basically dissolved completely to obtain a vanadium-containing solution; Step 2: Add calcium salt impurity remover to the vanadium-containing return solution, keep the temperature at 85°C, stir and react for 45 minutes, and then separate the solid and liquid to obtain purified vanadium liquid and impurity-removing slag; Step 3: Add calcium salt precipitant to the purified vanadium solution, keep the temperature at 85°C, stir and react for 30 minutes, separate the solid and liquid, and obtain calcium vanadate and the upper liquid; Step 4: adding calcium vanadate to pure water at a liquid-solid ratio of 10:1 mL / g, stirring and washing for 45 minutes, and performing solid-liquid separation to obtain washed calcium vanadate and washing water; Step 5: The washed calcium vanadate is heated to 300° C. in an oxidizing atmosphere for calcination, and taken out after being kept at the temperature for 90 minutes to obtain a high-purity calcium vanadate product.

[0039] The ammonium vanadate is produced by a vanadium slag calcification vanadium extraction process, and the main impurities are Al content of 0.09wt%, K content of 0.18wt%, Ca content of 0.09wt%, Fe content of 0.09wt%, Mn content of 0.09wt%, Si content of 0.09wt%, P content of 0.09wt%, and other contents are no more than 0.05wt%; The carbonate is one or more of ammonium bicarbonate, with a concentration of 30 g / L; The calcium salt impurity remover is calcium oxide, the calcium salt precipitant is calcium hydroxide, the calcium salt impurity remover is added in an amount of 2 g / L, and the calcium salt precipitant is added in an amount according to a molar ratio of Ca:V=1.5:1 in the purified vanadium solution.

[0040] The purity of calcium vanadate product can reach 99.91%, and the vanadium yield can reach 97.3%.

[0041] The scheme proposed by the present invention is to dissolve ammonium vanadate in an ammonium bicarbonate solution to obtain a vanadium-containing return solution, perform deep impurity removal to obtain a purified vanadium liquid, add calcium salt to the purified vanadium liquid, stir the reaction to prepare a calcium vanadate solid, and further calcine the calcium vanadate solid to prepare a high-purity calcium vanadate product. Thus, a high-purity calcium vanadate product can be prepared by using ordinary ammonium vanadate as a raw material through a one-step dissolution, impurity removal and precipitation, and the purity of the calcium vanadate can reach more than 99.8%, with a short process flow, a high vanadium yield and low production cost.

[0042] Based on the same inventive concept, according to another aspect of the present invention, an embodiment of the present invention further provides a calcium vanadate, wherein the calcium vanadate is prepared by the following steps: Dissolving ammonium vanadate in a carbonate solution to obtain a vanadium-containing solution; removing impurities from the vanadium-containing return solution to obtain a purified vanadium solution; Adding a calcium salt precipitant to the purified vanadium solution to obtain calcium vanadate; The calcium vanadate is washed and calcined to obtain the final calcium vanadate.

[0043] In some embodiments, dissolving ammonium vanadate into a carbonate solution to obtain a vanadium-containing solution further comprises: The ammonium vanadate is added to the carbonate solution at a liquid-to-solid ratio of 20-30:1 mL / g; The reaction was stirred at a temperature of 75-95° C. until the sodium vanadate was completely dissolved.

[0044] In some embodiments, the carbonate solution is ammonium carbonate and / or ammonium bicarbonate, with a concentration of 20-50 g / L.

[0045] In some embodiments, removing impurities from the vanadium-containing return solution to obtain a purified vanadium solution further comprises: adding a calcium salt impurity remover to the vanadium-containing return solution; The reaction is stirred at a temperature of 75-95°C for 15-60 minutes, followed by solid-liquid separation to obtain purified vanadium liquid.

[0046] In some embodiments, adding a calcium salt impurity remover to the vanadium-containing return solution further comprises: Calcium oxide and / or calcium hydroxide is used as the calcium salt impurity remover, and the addition amount of the calcium salt impurity remover is 2-10 g / L.

[0047] In some embodiments, adding a calcium salt precipitant to the purified vanadium solution to obtain calcium vanadate further comprises: The reaction is stirred at a temperature of 75-95°C for 30-90 minutes, and then the solid and liquid are separated to obtain calcium vanadate.

[0048] In some embodiments, it also includes: Calcium oxide and / or calcium hydroxide is used as the calcium salt precipitant, and the calcium salt precipitant is added according to a molar ratio of Ca:V in the purified vanadium solution of 1.0-1.5:1.

[0049] In some embodiments, washing and calcining the calcium vanadate to obtain the final calcium vanadate further comprises: The calcium vanadate is added into pure water at a liquid-solid ratio of 5-15:1 mL / g, stirred and washed for 15-60 min, and solid-liquid separation is performed to obtain washed calcium vanadate.

[0050] In some embodiments, it also includes: The washed calcium vanadate is calcined at a temperature of 300-500° C. in an oxidizing atmosphere, and the final calcium vanadate is obtained after being kept at the temperature for 30-90 minutes.

[0051] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope disclosed in the embodiments of the present invention as defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0052] It should be understood that, as used herein, the singular forms "a", "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" refers to any and all possible combinations including one or more of the associated listed items.

[0053] The serial numbers of the embodiments disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0054] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the above embodiments of the present invention, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for preparing calcium vanadate, characterized in that: The following steps are involved: Dissolving ammonium vanadate in a carbonate solution to obtain a vanadium-containing solution; removing impurities from the vanadium-containing return solution to obtain a purified vanadium solution; Adding a calcium salt precipitant to the purified vanadium solution to obtain calcium vanadate; The calcium vanadate is washed and calcined to obtain the final calcium vanadate.

2. The method according to claim 1, characterized in that Dissolving ammonium vanadate in a carbonate solution to obtain a vanadium-containing solution further comprises: The ammonium vanadate is added to the carbonate solution at a liquid-to-solid ratio of 20-30:1 mL / g; The reaction was stirred at a temperature of 75-95° C. until the sodium vanadate was completely dissolved.

3. The method according to claim 2, characterized in that The carbonate solution is ammonium carbonate and / or ammonium bicarbonate, and the concentration is 20-50 g / L.

4. The method according to claim 1, characterized in that The vanadium-containing return solution is subjected to impurity removal to obtain purified vanadium solution, further comprising: adding a calcium salt impurity remover to the vanadium-containing return solution; The reaction is stirred at a temperature of 75-95°C for 15-60 minutes, followed by solid-liquid separation to obtain purified vanadium liquid.

5. The method according to claim 4, characterized in that Adding a calcium salt impurity remover to the vanadium-containing return solution further comprises: Calcium oxide and / or calcium hydroxide is used as the calcium salt impurity remover, and the addition amount of the calcium salt impurity remover is 2-10 g / L.

6. The method according to claim 1, characterized in that Adding a calcium salt precipitant to the purified vanadium solution to obtain calcium vanadate further comprises: The reaction is stirred at a temperature of 75-95°C for 30-90 minutes, and then the solid and liquid are separated to obtain calcium vanadate.

7. The method according to claim 6, characterized in that Also includes: Calcium oxide and / or calcium hydroxide is used as the calcium salt precipitant, and the calcium salt precipitant is added according to a molar ratio of Ca:V in the purified vanadium solution of 1.0-1.5:

1.

8. The method according to claim 1, characterized in that The calcium vanadate is washed and calcined to obtain the final calcium vanadate, further comprising: The calcium vanadate is added into pure water at a liquid-solid ratio of 5-15:1 mL / g, stirred and washed for 15-60 min, and solid-liquid separation is performed to obtain washed calcium vanadate.

9. The method according to claim 8, characterized in that Also includes: The washed calcium vanadate is calcined at a temperature of 300-500° C. in an oxidizing atmosphere, and the final calcium vanadate is obtained after being kept at the temperature for 30-90 minutes.

10. A calcium vanadate, characterized in that The calcium vanadate is prepared based on the method described in any one of claims 1-9.

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