Method for preparing vanadium pentoxide through deep chromium removal

Abstract

The invention provides a method for preparing vanadium pentoxide through deep chromium removal, which comprises the following steps: (1) carrying out first vanadium precipitation on a vanadium-containing solution after carrying out first pH regulation by using a first acid solution, and carrying out first solid-liquid separation to obtain a first solid phase; the vanadium-containing solution contains chromium; (2) the first solid phase is dissolved again through alkali liquor, secondary vanadium precipitation is carried out after the pH of an obtained reconstitution liquid phase is secondarily adjusted through second acid liquor, secondary solid-liquid separation is carried out, and a second solid phase is obtained; and (3) washing and calcining the second solid phase to obtain vanadium pentoxide. According to the method, chromium in vanadium pentoxide can be effectively removed, the operation process is simple, and the application field is wide.

Description

Technical Field

[0001] The invention relates to the technical field of vanadium pentoxide, and in particular to a method for preparing vanadium pentoxide by deep removal of chromium. Background Art

[0002] Vanadium is an important strategic resource. Vanadium and its compounds have broad application prospects in energy storage, signal conversion and other fields, which have high requirements on the purity of vanadium products.

[0003] At present, the industry often uses the vanadium-containing solution obtained by sodium vanadium extraction as raw material, prepares intermediate products such as ammonium polyvanadate and ammonium metavanadate, and repeatedly dissolves and precipitates vanadium to achieve the purpose of removing impurities, and finally obtains high-purity vanadium pentoxide (purity 99.5% and above).

[0004] The vanadium-containing solution is alkaline and contains impurities such as silicon, phosphorus, and chromium, among which silicon and phosphorus are easy to remove. However, chromium has similar properties to vanadium and is easy to form chromate and enter the vanadate crystal, which has a great impact on the further purification of vanadium products.

[0005] Therefore, it is necessary to develop an effective method for removing chromium from vanadium pentoxide. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for preparing vanadium pentoxide by deep chromium removal. By adopting a two-step deep chromium removal method, efficient removal of vanadium in a vanadium-containing solution can be achieved, the operation process is simple, and the application prospect is broad.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing vanadium pentoxide by deep removal of chromium, the method comprising:

[0009] (1) a vanadium-containing solution is subjected to a first pH adjustment with a first acid solution, and then subjected to a first solid-liquid separation to obtain a first solid phase; the vanadium-containing solution contains chromium;

[0010] (2) the first solid phase is dissolved again with an alkali solution, the obtained complex solution phase is subjected to a second pH adjustment with a second acid solution, and then vanadium is precipitated for a second time, and then subjected to a second solid-liquid separation to obtain a second solid phase;

[0011] (3) The second solid phase is washed and calcined to obtain vanadium pentoxide.

[0012] The method for preparing vanadium pentoxide by deep chromium removal provided by the present invention comprises the following steps: firstly, after a first pH adjustment, a first vanadium precipitation is performed to obtain a sodium ammonium vanadate substance; the first solid phase containing the sodium ammonium vanadate substance is dissolved twice and then a second vanadium precipitation is performed; the values ​​of the first pH adjustment and the second pH adjustment are different, so an ammonium metavanadate solid phase is formed in the second vanadium precipitation, that is, the solid substances obtained from the first solid phase and the second solid phase in the present invention are different; and by separating the two in steps, efficient separation of vanadium and chromium can be achieved; the chromium content in the product is low, and the application prospect is broad.

[0013] It is worth noting that the first solid phase is an orange-yellow filter cake, and the second solid phase is a white filter cake.

[0014] Preferably, the vanadium concentration of the vanadium-containing solution in step (1) is 30-40 g / L, for example, 30 g / L, 32 g / L, 33 g / L, 34 g / L, 35 g / L, 36 g / L, 37 g / L, 38 g / L, 39 g / L or 40 g / L.

[0015] Preferably, the chromium concentration in the vanadium-containing solution is 3-5 g / L, for example, it can be 3 g / L, 3.3 g / L, 3.5 g / L, 3.7 g / L, 3.9 g / L, 4.2 g / L, 4.4 g / L, 4.6 g / L, 4.8 g / L or 5 g / L.

[0016] Preferably, in step (1), the first acid solution is a sulfuric acid solution.

[0017] Preferably, the first pH is adjusted to 4-6, for example, 4, 4.3, 4.5, 4.7, 4.9, 5.2, 5.4, 5.6, 5.8 or 6.

[0018] The first pH adjustment range in the present invention is very critical. When the pH value is high, the crystallized product contains ammonium metavanadate; when the pH value is low, the crystallized product contains ammonium polyvanadate. In addition, within the first pH adjustment range, chromium exists in the form of chromate, and the crystal structure of vanadium-chromium crystals is different, which reduces the embedding of chromium elements in vanadate crystals, and only a trace amount of chromium enters the first solid phase.

[0019] Preferably, ammonium sulfate is added to the first vanadium precipitate in step (1).

[0020] Preferably, the mass ratio of ammonium sulfate in the first vanadium precipitation to vanadium in the vanadium-containing solution is (0.8-1):1, for example, it can be 0.8:1, 0.83:1, 0.85:1, 0.87:1, 0.89:1, 0.92:1, 0.94:1, 0.96:1, 0.98:1 or 1:1, etc.

[0021] The mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution in the first vanadium precipitation in the present invention is very critical. When the mass ratio is too high, there is a problem of ammonium sulfate waste; when the mass ratio is too low, there is a problem of low vanadium precipitation rate.

[0022] Preferably, the temperature of the first vanadium precipitation is 20-30°C, for example, 20°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C.

[0023] Preferably, the stirring speed of the first vanadium precipitation is 400-500r / min, for example, it can be 400r / min, 410r / min, 420r / min, 430r / min, 445r / min, 450r / min, 460r / min, 470r / min, 480r / min or 500r / min.

[0024] Preferably, the stirring time of the first vanadium precipitation is 0.5-1 h, for example, it can be 0.5 h, 0.56 h, 0.62 h, 0.67 h, 0.73 h, 0.78 h, 0.84 h, 0.89 h, 0.95 h or 1 h.

[0025] Preferably, the vanadium concentration in the complex solution phase in step (2) is 30-40 g / L, for example, 30 g / L, 32 g / L, 33 g / L, 34 g / L, 35 g / L, 36 g / L, 37 g / L, 38 g / L, 39 g / L or 40 g / L.

[0026] Preferably, the chromium concentration in the complex solution phase is 0.05-0.2 g / L, for example, it can be 0.05 g / L, 0.07 g / L, 0.09 g / L, 0.1 g / L, 0.12 g / L, 0.14 g / L, 0.15 g / L, 0.17 g / L, 0.19 g / L or 0.2 g / L.

[0027] The chromium concentration in the complex solution phase of the present invention is very critical. When the concentration is too high, there is a problem of chromium impurities being entrained in the ammonium metavanadate.

[0028] Preferably, during the re-dissolution process, the mass ratio of alkali in the alkali solution to the first solid phase is (0.6-0.8):1, for example, it can be 0.6:1, 0.63:1, 0.65:1, 0.67:1, 0.69:1, 0.72:1, 0.74:1, 0.76:1, 0.78:1 or 0.8:1, etc.

[0029] Preferably, the alkali solution is sodium hydroxide solution.

[0030] Preferably, in step (2), the second acid solution is a sulfuric acid solution.

[0031] Preferably, the second pH is adjusted to 9-10, for example, 9, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9 or 10.

[0032] The second pH adjustment range in the present invention is very critical. When the pH value is high, there is a problem of too high ammonium addition coefficient; when the pH value is low, there is a problem that the product is sodium ammonium vanadate.

[0033] Preferably, ammonium sulfate is added to the second vanadium precipitate in step (2).

[0034] Preferably, the mass ratio of ammonium sulfate in the second vanadium precipitation to vanadium in the re-solution phase is (3-4):1, for example, it can be 3:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1 or 4:1.

[0035] Preferably, the temperature of the second vanadium precipitation is 50-70°C, for example, 50°C, 53°C, 55°C, 57°C, 59°C, 62°C, 64°C, 66°C, 68°C or 70°C.

[0036] Preferably, the stirring speed of the second vanadium precipitation is 400-500 r / min, for example, it can be 400 r / min, 410 r / min, 420 r / min, 430 r / min, 445 r / min, 450 r / min, 460 r / min, 470 r / min, 480 r / min or 500 r / min.

[0037] Preferably, the stirring time of the second vanadium precipitation is 0.5-1 h, for example, it can be 0.5 h, 0.56 h, 0.62 h, 0.67 h, 0.73 h, 0.78 h, 0.84 h, 0.89 h, 0.95 h or 1 h.

[0038] Preferably, the washing liquid in step (3) is an ammonium sulfate solution.

[0039] The present invention preferably uses ammonium sulfate solution for washing, which has the advantage of reducing the dissolution loss of ammonium metavanadate compared to other solutions.

[0040] Preferably, the concentration of the ammonium sulfate solution in the washing is 30-50 g / L, for example, 30 g / L, 33 g / L, 35 g / L, 37 g / L, 39 g / L, 42 g / L, 44 g / L, 46 g / L, 48 g / L or 50 g / L.

[0041] Preferably, the calcination temperature in step (3) is 550-600°C, for example, it can be 550°C, 556°C, 562°C, 567°C, 573°C, 578°C, 584°C, 589°C, 595°C or 600°C.

[0042] Preferably, the calcination time is 1.5 to 2 h, for example, 1.5 h, 1.56 h, 1.62 h, 1.67 h, 1.73 h, 1.78 h, 1.84 h, 1.89 h, 1.95 h or 2 h.

[0043] As a preferred technical solution of the present invention, the method comprises the following steps:

[0044] (1) a vanadium-containing solution having a vanadium concentration of 30 to 40 g / L and a chromium concentration of 3 to 5 g / L is first adjusted to pH 4 to 6 by a first acid solution, and then subjected to a first vanadium precipitation at a temperature of 20 to 30° C. and 400 to 500 r / min for 0.5 to 1 h, wherein ammonium sulfate is added to the first vanadium precipitation, and the mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution is (0.8 to 1):1, and subjected to a first solid-liquid separation to obtain a first solid phase;

[0045] (2) the first solid phase is dissolved again by alkali solution, the mass ratio of alkali in the alkali solution to the first solid phase is (0.6-0.8):1, the obtained complex solution phase with a vanadium concentration of 30-40 g / L and a chromium concentration of 0.05-0.2 g / L is adjusted to pH 9-10 by a second acid solution, and then a second vanadium precipitation is carried out at a temperature of 50-70° C. and 400-500 r / min for 0.5-1 h, the second acid solution is a sulfuric acid solution, the mass ratio of ammonium sulfate in the second vanadium precipitation to vanadium in the complex solution phase is (3-4):1, and a second solid-liquid separation is carried out to obtain a second solid phase;

[0046] (3) The second solid phase is washed with an ammonium sulfate solution with a concentration of 30 to 50 g / L and calcined at 550 to 600° C. for 1.5 to 2 h to obtain vanadium pentoxide.

[0047] The present invention has no special limitation on the solid-liquid separation in the above process, and any device and method for solid-liquid separation known to those skilled in the art may be used, and may also be adjusted according to the actual process, such as filtration, centrifugation or sedimentation separation, or a combination of different methods.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] (1) The method for preparing vanadium pentoxide by deep chromium removal provided by the present invention has a simple process, is easy to operate, has low requirements on equipment, has low requirements on the chromium content in the initial vanadium-containing solution, and can process vanadium-containing solutions with different chromium concentrations;

[0050] (2) The method for preparing vanadium pentoxide by deep chromium removal provided by the present invention can obtain vanadium pentoxide with a purity of more than 99.8%, and the vanadium recovery rate of the overall process reaches more than 85%. The chromium content in the vanadium pentoxide is controlled within 0.1wt%, preferably within 0.02wt%, and has broad application prospects. DETAILED DESCRIPTION

[0051] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0052] It should be understood that, in the description of the present invention, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0053] Example 1

[0054] This embodiment provides a method for preparing vanadium pentoxide by deep removal of chromium, the method comprising the following steps:

[0055] (1) a vanadium-containing solution having a vanadium concentration of 30 g / L and a chromium concentration of 3 g / L is first adjusted to pH 5.0 by a first acid solution (sulfuric acid solution), and then ammonium sulfate is added, wherein the mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution is 1:1, and a first vanadium precipitation is performed at a temperature of 25° C. and 450 r / min for 0.5 h, and then filtered to obtain a first solid phase;

[0056] (2) the first solid phase is added back into water, sodium hydroxide is added to dissolve it again, the mass ratio of alkali to the first solid phase is 0.7:1, the obtained complex solution phase with a vanadium concentration of 35 g / L and a chromium concentration of 0.1 g / L is adjusted to pH 10 by a second acid solution (sulfuric acid), and ammonium sulfate is added, the mass ratio of ammonium sulfate to vanadium in the complex solution phase is 3.5:1, the temperature is 60°C, 500 r / min, and the second vanadium precipitation is carried out for 0.5 h, and the solution is separated by filtration to obtain a second solid phase;

[0057] (3) The second solid phase was washed with an ammonium sulfate solution with a concentration of 30 g / L and calcined at 550° C. for 2 h to obtain vanadium pentoxide.

[0058] Example 2

[0059] This embodiment provides a method for preparing vanadium pentoxide by deep removal of chromium, the method comprising the following steps:

[0060] (1) a vanadium-containing solution having a vanadium concentration of 35 g / L and a chromium concentration of 3.5 g / L (vanadium exists in the form of sodium vanadate, and chromium exists in the form of sodium chromate) is first adjusted to pH 5.5 by a first acid solution (sulfuric acid solution), and then ammonium sulfate is added, with a mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution of 0.8:1, and a first vanadium precipitation is performed at a temperature of 20° C. and 500 r / min for 1 hour, and then filtered to obtain a first solid phase;

[0061] (2) the first solid phase is added back into water, sodium hydroxide is added to dissolve it again, the mass ratio of alkali to the first solid phase is 0.6:1, the obtained complex solution phase with a vanadium concentration of 30 g / L and a chromium concentration of 0.08 g / L is adjusted to pH 9 by a second acid solution (sulfuric acid), and ammonium sulfate is added, the mass ratio of ammonium sulfate to vanadium in the complex solution phase is 4:1, the temperature is 50° C., 500 r / min, and the second vanadium precipitation is carried out for 0.8 h, and the solution is separated by filtration to obtain a second solid phase;

[0062] (3) The second solid phase was washed with an ammonium sulfate solution with a concentration of 50 g / L and calcined at 580° C. for 1.8 h to obtain vanadium pentoxide.

[0063] Example 3

[0064] This embodiment provides a method for preparing vanadium pentoxide by deep removal of chromium, the method comprising the following steps:

[0065] (1) a vanadium-containing solution having a vanadium concentration of 40 g / L and a chromium concentration of 5 g / L (vanadium exists in the form of sodium vanadate, and chromium exists in the form of sodium chromate) is first adjusted to pH 6 by a first acid solution (sulfuric acid solution), and then ammonium sulfate is added, with a mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution of 1:1, and a first vanadium precipitation is performed at a temperature of 25° C. and 450 r / min for 0.8 h, and then filtered to obtain a first solid phase;

[0066] (2) the first solid phase is added back into water, sodium hydroxide is added to dissolve it again, the mass ratio of alkali to the first solid phase is 0.8:1, the obtained complex solution phase with a vanadium concentration of 35 g / L and a chromium concentration of 0.15 g / L is adjusted to pH 9.5 by a second acid solution (sulfuric acid), ammonium sulfate is added, the mass ratio of ammonium sulfate to vanadium in the complex solution phase is 3.5:1, the temperature is 55° C., 450 r / min, and the second vanadium precipitation is carried out for 0.5 h, and the solution is separated by filtration to obtain a second solid phase;

[0067] (3) The second solid phase was washed with an ammonium sulfate solution with a concentration of 45 g / L and calcined at 600° C. for 1.5 h to obtain vanadium pentoxide.

[0068] Example 4

[0069] This embodiment provides a method for preparing vanadium pentoxide by deep removal of chromium. The method is the same as that of Embodiment 1 except for first adjusting the pH to 3.0, and will not be described in detail here.

[0070] Example 5

[0071] This embodiment provides a method for preparing vanadium pentoxide by deep removal of chromium. The method is the same as that of Embodiment 1 except for first adjusting the pH to 7.0, and will not be described in detail here.

[0072] Example 6

[0073] This embodiment provides a method for preparing vanadium pentoxide by deep removal of chromium. The method is the same as that of Embodiment 1 except that the mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution is 0.7:1, and thus will not be described in detail.

[0074] Example 7

[0075] This embodiment provides a method for preparing vanadium pentoxide by deep removal of chromium. The method is the same as that of Embodiment 1 except that the mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution is 1.2:1, and thus will not be described in detail.

[0076] Example 8

[0077] This embodiment provides a method for preparing vanadium pentoxide by deep removal of chromium. The method is the same as that of Embodiment 1 except for the second step of adjusting the pH to 8.0, and will not be described in detail here.

[0078] Example 9

[0079] This embodiment provides a method for preparing vanadium pentoxide by deep removal of chromium. The method is the same as that of Embodiment 1 except for the second step of adjusting the pH to 11, and will not be described in detail here.

[0080] Example 10

[0081] This embodiment provides a method for preparing vanadium pentoxide by deep removal of chromium. The method is the same as that of Embodiment 1 except that the mass ratio of ammonium sulfate to vanadium in the complex solution phase is 4.5:1, and thus will not be described in detail.

[0082] Embodiment 11

[0083] This embodiment provides a method for preparing vanadium pentoxide by deep removal of chromium. The method is the same as that of Embodiment 1 except that the mass ratio of ammonium sulfate to vanadium in the complex solution phase is 2.5:1, and thus will not be described in detail.

[0084] Comparative Example 1

[0085] This comparative example provides a method for preparing vanadium pentoxide by removing chromium. The method is the same as Example 1 except that the redissolution in step (1) and step (2) is not performed and the vanadium-containing solution is directly subjected to a second pH adjustment and vanadium precipitation. The details are not described here.

[0086] Comparative Example 2

[0087] This comparative example provides a method for preparing vanadium pentoxide by removing chromium. The method is the same as Example 1 except that step (2) is not performed and step (3) is performed directly in the first solid phase, and the rest is not described here.

[0088] Test method: The purity of vanadium pentoxide is tested by ammonium ferrous sulfate titration, and the chromium content in vanadium pentoxide is tested by inductively coupled plasma atomic emission spectrometry. The mass of vanadium in vanadium pentoxide is divided by the total mass of vanadium in the original vanadium-containing solution, which is recorded as the recovery rate of vanadium.

[0089] The test results of the above embodiments and comparative examples are shown in Table 1.

[0090] Table 1

[0091]

[0092]

[0093] From Table 1 we can see that:

[0094] (1) It can be seen from Examples 1 to 3 that the method for preparing vanadium pentoxide by deep chromium removal provided by the present invention can separate a vanadium-containing solution with a high chromium content, and the operation method is simple and easy. Specifically, after two stages of vanadium precipitation and calcination, the purity of vanadium pentoxide reaches more than 99.8%, wherein the chromium content is reduced to less than 0.02%, and the yield is more than 85%, and the application prospect is broad;

[0095] (2) It can be seen from the combination of Example 1 and Examples 4 to 5 that the first adjustment of pH to 5.0 in Example 1 is compared with the first adjustment of pH to 3.0 and the first adjustment of pH to 7.0 in Examples 4 to 5, respectively. The purity of vanadium pentoxide in Example 1 is above 99.93%, and the yield is above 86.37%, while the purity of vanadium pentoxide in Examples 4 to 5 is only 99.79% and 99.77%, respectively, and the yield is only 38.61% and 66.99%, respectively. This shows that the present invention can further improve the purity and yield of vanadium pentoxide by preferably controlling the range of the first adjustment of pH within a reasonable range;

[0096] (3) It can be seen from Example 1 and Examples 6 to 7 that the mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution in Example 1 is 1:1. Compared with the mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution of 0.7:1 and the mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution of 1.2:1 in Examples 6 to 7, the purity of vanadium pentoxide in Example 1 is above 99.93%, and the yield is 86.37%, while the purity of vanadium pentoxide in Examples 6 to 7 is 99.78% and 99.93%, respectively, and the yield is 10.1%. The results show that the mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution in Example 6 is 0.7:1, and the vanadium precipitation rate is only 93.34%. The vanadium precipitation rate is lower than that when the mass ratio is (0.8-1.0):1, which affects the recovery rate of vanadium. In Example 7, there is a waste of ammonium sulfate, which shows that the present invention can further improve the purity of vanadium pentoxide and effectively ensure the yield of vanadium pentoxide by preferably controlling the mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution within a reasonable range.

[0097] (4) It can be seen from the combination of Example 1 and Examples 8 to 9 that the second adjustment of pH to 10.0 in Example 1 is compared with the second adjustment of pH to 8.0 and the second adjustment of pH to 11 in Examples 8 to 9. The purity of vanadium pentoxide in Example 1 is 99.93%, and the yield is 86.37%, while the purity of vanadium pentoxide in Examples 8 to 9 is 96.55% and 99.86%, respectively, and the yield is only 58.02% and 81.72%, respectively. This is because when the second adjustment of pH to 8.0 in Example 8, sodium ammonium vanadate exists in the product, resulting in the presence of sodium impurities in the roasting product, which affects the purity of vanadium pentoxide. When the second adjustment of pH to 11 in Example 9, the ammonium addition coefficient required for the re-dissolved phase is increased, and the vanadium precipitation rate with the same ammonium addition coefficient is reduced. This shows that the present invention can further improve the purity of vanadium pentoxide and effectively ensure the yield of vanadium pentoxide by preferably controlling the numerical range of the second adjustment of pH within a reasonable range;

[0098] (5) It can be seen from Example 1 and Examples 10 to 11 that the mass ratio of ammonium sulfate to vanadium in the complex solution phase in Example 1 is 3.5:1. Compared with the mass ratio of ammonium sulfate to vanadium in the complex solution phase of 4.5:1 and the mass ratio of ammonium sulfate to vanadium in the complex solution phase of 2.5:1 in Examples 10 to 11, the purity of vanadium pentoxide in Example 1 is 99.93% and the yield is 86.37%, while the purity of vanadium pentoxide in Examples 10 to 11 is 99.75% and 99.84%, respectively, and the yields are 90.94% and 72.71%, respectively. In addition, there is a waste of ammonium sulfate in Example 10. This shows that the present invention can further improve the purity of vanadium pentoxide and effectively ensure the yield of vanadium pentoxide by preferably controlling the mass ratio of ammonium sulfate to vanadium in the complex solution phase within a reasonable range;

[0099] (6) It can be seen from the combination of Example 1 and Comparative Examples 1 to 2 that in Comparative Example 1, the redissolution in step (1) and step (2) is not performed, and the vanadium-containing solution is directly subjected to the second pH adjustment and vanadium precipitation, resulting in a very low degree of vanadium-chromium separation, resulting in a high chromium content in the crystals, affecting the purity of vanadium pentoxide, and the final purity of vanadium pentoxide is only 99.68%; in Comparative Example 2, step (2) is not performed, and step (3) is directly performed using the first solid phase, resulting in the presence of sodium in the roasted product, and the final purity of vanadium pentoxide is only 93.26%. This shows that the method for preparing vanadium pentoxide by deep chromium removal provided by the present invention has a better effect of separating vanadium-containing solutions with high chromium concentrations by adopting a two-step vanadium precipitation process.

[0100] The present invention illustrates the detailed features of the present invention through the above embodiments, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvement to the present invention, equivalent replacement of the technical features selected by the present invention, addition of auxiliary technical features, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing vanadium pentoxide by deep chromium removal, characterized in that: The method comprises: (1) a vanadium-containing solution is subjected to a first pH adjustment with a first acid solution, and then subjected to a first solid-liquid separation to obtain a first solid phase; the vanadium-containing solution contains chromium; (2) the first solid phase is dissolved again with an alkali solution, the obtained complex solution phase is subjected to a second pH adjustment with a second acid solution, and then vanadium is precipitated for a second time, and then subjected to a second solid-liquid separation to obtain a second solid phase; (3) The second solid phase is washed and calcined to obtain vanadium pentoxide.

2. The method according to claim 1, characterized in that The vanadium concentration of the vanadium-containing solution in step (1) is 30 to 40 g / L; Preferably, the chromium concentration in the vanadium-containing solution is 3-5 g / L.

3. The method according to claim 1 or 2, characterized in that: In step (1), the first acid solution is a sulfuric acid solution; Preferably, the first step is to adjust the pH to 4-6.

4. The method according to any one of claims 1 to 3, characterized in that: In step (1), ammonium sulfate is added to the first vanadium precipitate; Preferably, the mass ratio of ammonium sulfate in the first vanadium precipitation to vanadium in the vanadium-containing solution is (0.8-1):1; Preferably, the temperature of the first vanadium precipitation is 20-30°C; Preferably, the stirring speed of the first vanadium precipitation is 400-500 r / min; Preferably, the stirring time of the first vanadium precipitation is 0.5 to 1 h.

5. The method according to any one of claims 1 to 4, characterized in that: The vanadium concentration in the reconstituted solution phase in step (2) is 30-40 g / L; Preferably, the chromium concentration in the reconstituted solution phase is 0.05 to 0.2 g / L; Preferably, during the re-dissolving process, the mass ratio of the alkali in the alkali solution to the first solid phase is (0.6-0.8):1; Preferably, the alkali solution is sodium hydroxide solution.

6. The method according to any one of claims 1 to 5, characterized in that: In step (2), the second acid solution is a sulfuric acid solution; Preferably, the second step is to adjust the pH to 9-10.

7. The method according to any one of claims 1 to 6, characterized in that: In step (2), ammonium sulfate is added to the second vanadium precipitate; Preferably, the mass ratio of ammonium sulfate in the second vanadium precipitation to vanadium in the re-solution phase is (3-4):1; Preferably, the temperature of the second vanadium precipitation is 50-70°C; Preferably, the stirring speed of the second vanadium precipitation is 400-500 r / min; Preferably, the stirring time of the second vanadium precipitation is 0.5 to 1 h.

8. The method according to any one of claims 1 to 7, characterized in that: The washing liquid in step (3) is an ammonium sulfate solution; Preferably, the concentration of the ammonium sulfate solution in the washing is 30-50 g / L.

9. The method according to any one of claims 1 to 8, characterized in that: The calcination temperature in step (3) is 550-600°C; Preferably, the calcination time is 1.5 to 2 hours.

10. The method according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: (1) a vanadium-containing solution having a vanadium concentration of 30 to 40 g / L and a chromium concentration of 3 to 5 g / L is first adjusted to pH 4 to 6 by a first acid solution, and then subjected to a first vanadium precipitation at a temperature of 20 to 30° C. and 400 to 500 r / min for 0.5 to 1 h, wherein ammonium sulfate is added to the first vanadium precipitation, and the mass ratio of ammonium sulfate to vanadium in the vanadium-containing solution is (0.8 to 1):1, and subjected to a first solid-liquid separation to obtain a first solid phase; (2) the first solid phase is dissolved again by alkali solution, the mass ratio of alkali in the alkali solution to the first solid phase is (0.6-0.8):1, the obtained complex solution phase with a vanadium concentration of 30-40 g / L and a chromium concentration of 0.05-0.2 g / L is adjusted to pH 9-10 by a second acid solution, and then a second vanadium precipitation is carried out at a temperature of 50-70° C. and 400-500 r / min for 0.5-1 h, the second acid solution is a sulfuric acid solution, the mass ratio of ammonium sulfate in the second vanadium precipitation to vanadium in the complex solution phase is (3-4):1, and a second solid-liquid separation is carried out to obtain a second solid phase; (3) The second solid phase is washed with an ammonium sulfate solution with a concentration of 30 to 50 g / L and calcined at 550 to 600° C. for 1.5 to 2 h to obtain vanadium pentoxide.

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