Preparation method of high-purity ammonium polyvanadate and high-purity vanadium pentoxide

Abstract

The invention provides a preparation method of high-purity ammonium polyvanadate and high-purity vanadium pentoxide, and the preparation method comprises the following steps: mixing low-impurity ammonium metavanadate crystals with hot water to obtain a mixed solution system; and adding a sulfuric acid solution into the mixed solution system to carry out transformation vanadium precipitation, and carrying out solid-liquid separation to obtain high-purity ammonium polyvanadate. The method is simple in impurity removal condition, easy to operate, simple in process flow, low in energy consumption, high in vanadium recovery rate, good in impurity element removal effect, high in ammonium metavanadate utilization rate and wide in application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of vanadium chemical metallurgy, and in particular to a preparation method of high-purity ammonium polyvanadate and high-purity vanadium pentoxide. Background Art

[0002] High-purity ammonium polyvanadate (APV) is an important chemical raw material, mainly used in the production of vanadium pentoxide (V2O5), vanadium electrolyte, catalysts, etc. At present, the market demand for high-purity ammonium polyvanadate is growing steadily, so the process of extracting ammonium metavanadate from waste catalysts has also begun to develop.

[0003] In the process of preparing high-purity ammonium polyvanadate, solvent extraction and ion exchange technologies are usually used. These technologies can realize the recycling and reuse of waste catalysts, and the production process is green and pollution-free. The application fields of high-purity ammonium polyvanadate include chemical industry, catalysts, high-temperature materials, battery materials and pigments. Vanadium energy storage technology, especially all-vanadium liquid flow energy storage battery, is expected to become the preferred technology for safe, long-term and large-scale energy storage due to its high safety, ultra-long service life and recyclability of vanadium electrolyte. This will promote the rapid development of the high-purity ammonium polyvanadate market.

[0004] In terms of market development prospects, the high-purity ammonium polyvanadate market is expected to remain optimistic. With the increase in demand for vanadium products, the production and application of high-purity ammonium polyvanadate will be further developed, and the high-purity ammonium polyvanadate market has broad development prospects.

[0005] CN118387924A discloses an ammonium polyvanadate preparation system and a method for preparing ammonium polyvanadate using the ammonium polyvanadate preparation system, wherein the preparation system comprises a primary acid addition system, an ammonium addition system, a vanadium precipitation system, an acid supply system and a steam removal system. The preparation system of the method is precise, the equipment requirements are high, the operation process is complicated, the purification cost is high, and there is a lot of process wastewater, which does not meet the actual production conditions.

[0006] CN104876268B discloses a method for preparing high-density ammonium polyvanadate, wherein an alcohol amine, a soluble ammonium salt and a vanadium-containing solution are mixed to obtain a mixture, the pH value is adjusted to acidic and reacted, and then the reaction mixture obtained after the reaction is subjected to solid-liquid separation. This method requires the addition of alcohol amine and a soluble ammonium salt while obtaining ammonium polyvanadate, the wastewater solution has a complex composition, and a large amount of ammonia nitrogen wastewater is generated at the same time and needs to be treated, and the environmental protection treatment cost is high.

[0007] In recent years, the recycling and purification technology of vanadium resources and environmentally friendly purification processes have received more and more attention. The method of preparing high-purity ammonium metavanadate from ammonium polyvanadate needs further research to achieve the goal of simplifying, diversifying and cleaning the vanadium recycling and purification process. Summary of the invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing high-purity ammonium polyvanadate and high-purity vanadium pentoxide, the leaching conditions of the method are simple and easy to operate, the vanadium recovery rate is high, the purification effect is good, the energy consumption is low, the vanadium resource utilization rate is high, and the application prospect is broad.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing high-purity ammonium polyvanadate, the preparation method comprising the following steps:

[0011] The low-impurity ammonium metavanadate crystals are mixed with hot water to obtain a mixed solution system; a sulfuric acid solution is added to the mixed solution system to perform transformation precipitation of vanadium, and high-purity ammonium polyvanadate is obtained through solid-liquid separation.

[0012] The preparation method of high-purity ammonium polyvanadate provided by the invention comprises the following steps: firstly dissolving the ammonium metavanadate crystals containing impurities in hot water to achieve complete dissolution of the ammonium metavanadate containing impurities; and then adding a sulfuric acid solution to the mixed solution system to perform transformation and vanadium precipitation to achieve purification of the ammonium polyvanadate.

[0013] A core point of the present invention is that sulfuric acid solution must be added to the mixed solution system rather than randomly mixing the two. This is because the vanadium precipitation step is a very critical impurity separation process in the present invention. By adding sulfuric acid solution to the mixed solution system, the particle size of high-purity ammonium polyvanadate can be regulated. The regulation of the particle size can not only reduce the entrainment of impurities, but also is beneficial for the subsequent calcination to prepare vanadium pentoxide.

[0014] The purity of the high-purity ammonium polyvanadate in the present invention is above 99.5%, for example, it can be 99.5wt%, 99.6wt%, 99.7wt%, 99.8wt% or 99.9wt%.

[0015] Preferably, the temperature of the hot water is 90-100° C., for example, 90° C., 91° C., 92° C., 93° C., 94° C., 95° C., 96° C., 97° C., 98° C., 99° C. or 100° C., but is not limited to the listed values, and other values ​​not listed in the range are also applicable. This temperature is more conducive to the dissolution of ammonium metavanadate crystals.

[0016] Preferably, the liquid-to-solid ratio of the hot water to the ammonium metavanadate crystals is (15-20):1, for example, it can be 15.0:1, 15.5:1, 16.0:1, 16.5:1, 17.0:1, 17.5:1, 18.0:1, 18.5:1, 19.0:1, 19.5:1 or 20.0:1, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0017] Preferably, the impurities in the low-impurity ammonium metavanadate crystals include anionic elements.

[0018] Preferably, the anions in the low-impurity ammonium metavanadate crystals contain phosphorus, sulfur or silicon, or a combination of any one or at least two of them, wherein typical but non-limiting combinations are a combination of phosphorus and sulfur, a combination of silicon and sulfur, and a combination of phosphorus and silicon.

[0019] Preferably, in terms of mass percentage, the impurities in the low-impurity ammonium metavanadate crystals include Ca: 0.08-0.15%, P: 0.02-0.03%, S: 0.01-0.1%, Si: 0.15-0.2% and Fe: 0.1-0.25%.

[0020] Specifically, Ca: 0.08-0.15%, for example, it can be 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.12%, 0.13%, 0.14%, 0.15% or 0.15%, etc., but it is not limited to the listed values, and other values ​​not listed in the range are also applicable; P: 0.02-0.03%, for example, it can be 0.02%, 0.022%, 0.023%, 0.024%, 0.025%, 0.026%, 0.027%, 0.028%, 0.029% or 0.03%, etc., but it is not limited to the listed values, and other values ​​not listed in the range are also applicable; S: 0.01-0.1%, for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.21%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.25%, 0.26%, 0.27%, 0.2 0.06%, 0.07%, 0.08%, 0.09% or 0.1%, etc., but not limited to the listed values, and other values ​​not listed within the range are equally applicable; Si: 0.15-0.2%, for example, 0.15%, 0.156%, 0.162%, 0.167%, 0.173%, 0.178%, 0.184%, 0.189%, 0.195% or 0.2%, etc., but not limited to the listed values, and other values ​​not listed within the range are equally applicable; Fe: 0.1-0.25%, for example, 0.1%, 0.12%, 0.14%, 0.15%, 0.17%, 0.19%, 0.2%, 0.22%, 0.24% or 0.25%, etc., but not limited to the listed values, and other values ​​not listed within the range are equally applicable.

[0021] Preferably, the concentration of the sulfuric acid solution is 18-22wt%, for example, it can be 18wt%, 18.5wt%, 18.9wt%, 19.4wt%, 19.8wt%, 20.3wt%, 20.7wt%, 21.2wt%, 21.6wt% or 22wt%.

[0022] Preferably, the pH of the vanadium precipitation is 1.5 to 2.2, for example, it can be 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1 or 2.2.

[0023] Preferably, the temperature of vanadium precipitation is 90-100°C, for example, it can be 90°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C or 100°C.

[0024] Preferably, the vanadium precipitation time is 1 to 2 hours, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0025] Preferably, the stirring speed of the vanadium precipitation is 200-300 r / min, for example, it can be 200 r / min, 210 r / min, 220 r / min, 230 r / min, 240 r / min, 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min or 300 r / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0026] Preferably, the sulfuric acid solution is added at a rate of 10 to 20 mL / min.

[0027] Preferably, when the temperature of the vanadium precipitate is 90-95° C., the rate of addition of the sulfuric acid solution to the vanadium precipitate is 10-15 mL / min, for example, 10.0 mL / min, 10.5 mL / min, 11.0 mL / min, 11.5 mL / min, 12.0 mL / min, 12.5 mL / min, 13.0 mL / min, 13.5 mL / min, 14.0 mL / min, 14.5 mL / min or 15.0 mL / min, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0028] Preferably, ammonium polyvanadate seeds are also added into the vanadium precipitation.

[0029] Preferably, the amount of the ammonium polyvanadate seeds added is 2 to 5 g / L, for example, 2 g / L, 2.2 g / L, 2.4 g / L, 3.1 g / L, 3.8 g / L, 4.5 g / L, 4.8 g / L or 5 g / L, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0030] Preferably, when the temperature of the vanadium precipitation is 95-100° C., the rate of addition of the sulfuric acid solution to the vanadium precipitation is 15-20 mL / min, for example, 15.0 mL / min, 15.5 mL / min, 16.0 mL / min, 16.5 mL / min, 17.0 mL / min, 17.5 mL / min, 18.0 mL / min, 18.5 mL / min, 19.0 mL / min, 19.5 mL / min or 20.0 mL / min, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0031] Preferably, the preparation of the low-impurity ammonium metavanadate crystals comprises:

[0032] After the crude ammonium metavanadate is dissolved, a dissolved liquid is obtained, and the dissolved liquid is mixed with an impurity remover to perform an impurity removal reaction, and the solid-liquid separation is performed to obtain an impurity-removed liquid; after the impurity-removed liquid is subjected to calcium removal and solid-liquid separation, a purified liquid is obtained. The purified liquid is subjected to recrystallization to obtain low-impurity ammonium metavanadate crystals.

[0033] One of the key points of the present invention is that: firstly, anionic impurities such as S, Si, and P in ammonium metavanadate are selectively removed by adding highly active calcium oxide, and the pH value needs to be controlled within a suitable pH range to achieve an effective impurity removal effect. The activity of lime has a great influence on the impurity removal effect. After impurity removal, there is an excess of Ca 2+ , it is necessary to add ammonium bicarbonate or ammonium carbonate to precipitate and remove it, so that the Ca impurities are reduced to a lower level.

[0034] Preferably, the crude ammonium metavanadate comprises a primary product prepared from vanadium slag and / or stone coal by roasting, leaching and crystallization.

[0035] Preferably, the content of NH4VO3 in the crude ammonium metavanadate is 95-98wt%, for example, it can be 95.0%, 95.5%, 96.0%, 96.5%, 97.0%, 97.5% or 98.0%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0036] Preferably, the crude ammonium metavanadate contains any one or a combination of at least two of Ca, P, S, Si or Fe, wherein typical but non-limiting combinations are a combination of Ca and P, a combination of S and P, and a combination of Ca and Si.

[0037] Preferably, the Ca content in the crude ammonium metavanadate is 0.15-0.3wt%, for example, it can be 0.15wt%, 0.17wt%, 0.19wt%, 0.2wt%, 0.22wt%, 0.24wt%, 0.25wt%, 0.27wt%, 0.29wt% or 0.3wt%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0038] Preferably, the P content in the crude ammonium metavanadate is 0.1-0.15wt%, for example, it can be 0.1wt%, 0.11wt%, 0.12wt%, 0.13wt%, 0.14wt% or 0.15wt%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0039] Preferably, the S content in the crude ammonium metavanadate is 0.1-0.18wt%, for example, it can be 0.1wt%, 0.11wt%, 0.12wt%, 0.13wt%, 0.14wt%, 0.15wt%, 0.16wt%, 0.17wt% or 0.18wt%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0040] Preferably, the Si content in the crude ammonium metavanadate is 0.2-0.3wt%, for example, it can be 0.2wt%, 0.22wt%, 0.23wt%, 0.24wt%, 0.25wt%, 0.26wt%, 0.27wt%, 0.28wt%, 0.29wt% or 0.3wt%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0041] Preferably, the Fe content in the crude ammonium metavanadate is 0.25-0.4wt%, for example, it can be 0.25wt%, 0.267wt%, 0.284wt%, 0.3wt%, 0.317wt%, 0.334wt%, 0.35wt%, 0.367wt%, 0.384wt% or 0.4wt%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0042] Preferably, the dissolving solvent comprises water.

[0043] Preferably, the liquid-to-solid ratio of the solvent to the crude ammonium metavanadate in the dissolution is (15-20):1, for example, it can be 15.0:1, 15.5:1, 16.0:1, 16.5:1, 17.0:1, 17.5:1, 18.0:1, 18.5:1, 19.0:1, 19.5:1 or 20.0:1, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0044] Preferably, the temperature of the dissolution process in the dissolution is 90-100°C, for example, it can be 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0045] Preferably, the impurity remover is activated calcium oxide.

[0046] Preferably, the active calcium oxide is calcium oxide obtained by calcining a calcium source at 900-1100° C. for 2-3 hours and storing the calcium oxide for no more than 24 hours.

[0047] Preferably, the calcium source comprises any one of calcium carbonate, calcium hydroxide or calcium oxide, or a combination of at least two thereof, wherein typical but non-limiting combinations are a combination of calcium carbonate and calcium hydroxide, a combination of calcium oxide and calcium hydroxide, and a combination of calcium carbonate and calcium oxide.

[0048] The calcination temperature can be 900°C, 940°C, 960°C, 1000°C, 1010°C, 1030°C, 1050°C, 1080°C or 1100°C, but is not limited to the values ​​listed, and other values ​​not listed in the range are also applicable. The calcination time is 2 to 3 hours, for example, it can be 2 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, etc.

[0049] Preferably, the service life of the activated calcium oxide does not exceed 24 hours. For example, it can be used 2 hours, 3 hours, 5 hours, 8 hours, 12 hours, 14 hours, 17 hours, 22 hours or 24 hours after the activated calcination, but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0050] Preferably, the dissolved liquid includes S element, P element and Si element.

[0051] Preferably, the molar ratio of the amount of the impurity remover added to the sum of the S element, the P element and the Si element in the solution after dissolution is (3-5):1, for example, it can be 3.0:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4.0:1, 4.2:1, 4.4:1, 4.6:1, 4.8:1 or 5.0:1, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0052] Preferably, the impurity remover is added in the form of a solution with a concentration of 10 to 15 wt%, for example, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5% or 15.0%, etc., but is not limited to the values ​​listed, and other values ​​not listed in the range are also applicable. The principle is that Ca 2+ It reacts with phosphate, sulfate and silicate ions in the solution to form calcium salts with small solubility products, thereby achieving the purpose of removing anionic impurities.

[0053] Preferably, the pH of the impurity removal reaction is 7.5 to 8, for example, it can be 7.50, 7.55, 7.60, 7.65, 7.70, 7.75, 7.80, 7.85, 7.90, 7.95 or 8.00, but it is not limited to the listed values, and other values ​​not listed in this range are also applicable. Too low pH will lead to excessive Ca impurity content in the solution, and too high pH will lead to unsatisfactory impurity removal effect of S, P, and Si.

[0054] The present invention preferably controls the pH of the ammonium metavanadate impurity removal reaction within the above range to avoid the situation where the ammonium metavanadate is wrapped up due to too low or too high pH, ​​which affects the reaction of the impurity elements with the impurity remover, and effectively ensures the effective removal of the impurity elements in the ammonium metavanadate.

[0055] Preferably, the temperature of the impurity removal reaction is 40-60°C, for example, it can be 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C or 60°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0056] Preferably, the time of the impurity removal reaction is 0.5 to 1 h, for example, it can be 0.50 h, 0.55 h, 0.60 h, 0.65 h, 0.70 h, 0.75 h, 0.80 h, 0.85 h, 0.90 h, 0.95 h or 1.00 h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0057] Preferably, the stirring rate of the impurity removal reaction is 500-700 r / min, for example, it can be 500 r / min, 520 r / min, 540 r / min, 560 r / min, 580 r / min, 600 r / min, 620 r / min, 640 r / min, 660 r / min, 680 r / min or 700 r / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0058] Preferably, a decalcifying agent is added during the decalcification process, and the decalcifying agent includes ammonium bicarbonate and / or ammonium carbonate.

[0059] Preferably, the amount of the decalcifier added is 3 to 5 times the theoretical amount of carbonate required for decalcification, for example, 3 times, 3.3 times, 3.5 times, 3.7 times, 3.9 times, 4.2 times, 4.4 times, 4.6 times, 4.8 times or 5 times, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0060] Preferably, the pH of the decalcification reaction is 8.0-8.5, for example, 8.0, 8.1, 8.2, 8.3, 8.4 or 8.5, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0061] Preferably, the reaction time for decalcification is 0.5 to 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, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0062] Preferably, the reaction temperature for decalcification is 60-70°C, for example, it can be 60°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0063] Preferably, the terminal temperature of the recrystallization is 30-50°C, for example, it can be 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C or 50°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0064] Preferably, the recrystallization time is 4 to 6 h, for example, 4.0 h, 4.2 h, 4.4 h, 4.6 h, 4.8 h, 5.0 h, 5.2 h, 5.4 h, 5.6 h, 5.8 h or 6.0 h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0065] Preferably, ammonium metavanadate seeds are added during the recrystallization process.

[0066] Preferably, the addition amount of the ammonium metavanadate seed crystals is 2 to 3 g / L, for example, it can be 2.0 g / L, 2.1 g / L, 2.2 g / L, 2.3 g / L, 2.4 g / L, 2.5 g / L, 2.6 g / L, 2.7 g / L, 2.8 g / L, 2.9 g / L or 3.0 g / L, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0067] The present invention has no particular 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 can be used, and can also be adjusted according to the actual process, for example, it can be filtration, centrifugation or sedimentation separation, etc., or a combination of different methods. In the present invention, the preferred filtration method includes a plate and frame filter press and / or a vacuum belt filter.

[0068] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0069] (1) dissolving crude ammonium metavanadate containing 95 to 98 wt % NH4VO3 at 90 to 100° C. in a liquid-to-solid ratio of (15 to 20):1 to obtain a dissolved liquid;

[0070] The dissolved liquid is mixed with active calcium oxide to carry out impurity removal reaction for 0.5 to 1 hour under the conditions of pH 7.5 to 8, temperature 40 to 60° C., and 500 to 700 r / min, wherein the molar ratio of the amount of active calcium oxide added to the sum of the S element, the P element, and the Si element in the dissolved solution is (3 to 5):1, and solid-liquid separation is performed to obtain an impurity-removed liquid; and according to the amount of Ca in the solution, 2+ 3 to 5 times the theoretical amount of carbonate ions required for complete precipitation, adding ammonium bicarbonate and / or ammonium carbonate to the impurity-removed liquid to adjust the pH to 8.0 to 8.5 for decalcification, the reaction temperature for decalcification is 60 to 70°C, the reaction time for decalcification is 0.5 to 1h, and then the purified liquid is obtained after liquid-solid separation;

[0071] (2) the purified liquid is recrystallized at 30-50° C., and 2-3 g / L of ammonium metavanadate seed crystals are added during the recrystallization process to obtain low-impurity ammonium metavanadate crystals;

[0072] (3) mixing low-impurity ammonium metavanadate crystals with 90-100° C. hot water at a liquid-to-solid ratio of (15-20):1 to obtain a mixed solution system;

[0073] (4) adding a sulfuric acid solution with a concentration of 18 to 22 wt % to the mixed solution system at a rate of 10 to 20 mL / min to perform transformation precipitation of vanadium, wherein the pH of the transformation precipitation is 1.5 to 2.2, the temperature is 90 to 100° C., the time is 1 to 2 h, the stirring speed is 200 to 300 r / min, and solid-liquid separation is performed to obtain high-purity ammonium polyvanadate.

[0074] In a second aspect, the present invention provides a method for preparing high-purity vanadium pentoxide, wherein the preparation method is carried out using the high-purity ammonium polyvanadate prepared by the preparation method of high-purity ammonium polyvanadate described in the first aspect.

[0075] The purity of the high-purity vanadium pentoxide in the present invention is above 99.5%, for example, it can be 99.5wt%, 99.6wt%, 99.7wt%, 99.8wt% or 99.9wt%.

[0076] Preferably, the method for preparing the high-purity vanadium pentoxide comprises: calcining the high-purity ammonium polyvanadate to obtain the high-purity vanadium pentoxide.

[0077] Preferably, the calcination temperature is 500-600°C, for example, it can be 500°C, 512°C, 523°C, 534°C, 545°C, 556°C, 567°C, 578°C, 589°C or 600°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0078] Preferably, the calcination atmosphere is an oxygen-containing atmosphere.

[0079] Preferably, the oxygen concentration in the oxygen-containing atmosphere is 20-30wt%, for example, it can be 20wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt% or 30wt%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0080] Preferably, the calcination time is 1 to 2.5 h, for example, 1 h, 1.2 h, 1.4 h, 1.5 h, 1.7 h, 1.9 h, 2 h, 2.2 h, 2.4 h or 2.5 h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0081] Compared with the prior art, the present invention has at least the following beneficial effects:

[0082] (1) The preparation method of high-purity ammonium polyvanadate provided by the present invention can effectively remove impurity elements such as sulfur, phosphorus, and silicon in ammonium polyvanadate only by dissolving, adjusting pH, and adding an impurity remover. The impurity removal process steps are simple and efficient, and there is no requirement for the content of impurity elements. Finally, high-purity ammonium metavanadate can be obtained, and the purity and particle size of the vanadium pentoxide after calcination are both large. Under preferred conditions, the purity of the vanadium pentoxide after calcination can reach more than 99.68wt%, the particle size of the vanadium pentoxide reaches -100 mesh, accounting for less than 85%, the particle size is large, and the impurity content in the vanadium pentoxide is low, wherein the S content is as low as less than 0.05wt%, the P content is as low as less than 0.02wt%, the Si content is as low as less than 0.02wt%, the Ca content is as low as less than 0.10wt%, and the Fe content is as low as less than 0.08wt%;

[0083] (2) In the preparation method of high-purity ammonium polyvanadate provided by the present invention, the ammonium metavanadate solution is subjected to a carbonate precipitation method to effectively remove the residual Ca in the solution, and the trace amounts of Ca, Mg, Al, Fe and other cations in the ammonium metavanadate can be further removed during the precipitation of vanadium with sulfuric acid. The cationic impurities in the ammonium metavanadate are deeply removed by two-step impurity removal, thereby obtaining a stable high-purity ammonium polyvanadate product.

[0084] (3) The preparation method of high-purity ammonium polyvanadate provided by the present invention has a short reaction process, low energy consumption loss, high vanadium recovery rate, and preferably a vanadium precipitation rate of more than 99%. It is clean and environmentally friendly, more beneficial to environmental protection, and can realize industrial production.

[0085] (4) The high-purity ammonium metavanadate prepared by the preparation method of high-purity ammonium polyvanadate provided by the present invention has high purity and low content of impurity elements, which can meet the purity requirements of vanadium products used in electrolytes and aviation manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 The present invention provides a flow chart of a method for preparing high-purity ammonium polyvanadate according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0087] 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.

[0088] As a specific embodiment of the present invention, a method for preparing high-purity ammonium polyvanadate is provided, and its flow diagram is as follows: Figure 1 As shown, the method comprises the following steps:

[0089] (1) After the crude ammonium metavanadate is dissolved, a dissolved liquid is obtained. The dissolved liquid is mixed with an impurity remover after adjusting the pH value to carry out an impurity removal reaction, and the solid-liquid separation is performed to obtain an impurity-removed liquid. After the impurity-removed liquid is subjected to calcium removal and solid-liquid separation, a purified liquid is obtained.

[0090] (2) The purified liquid is recrystallized to obtain low-impurity ammonium metavanadate crystals and a crystallization mother liquor; the crystallization mother liquor is recycled to step (1) and used as a dissolving solvent;

[0091] (3) mixing the low-impurity ammonium metavanadate crystals with hot water for secondary dissolution to obtain a mixed solution system;

[0092] (4) adding sulfuric acid solution to the mixed solution system to carry out transformation and vanadium precipitation, and obtaining high-purity ammonium polyvanadate and vanadium precipitation mother liquor through solid-liquid separation, and the vanadium precipitation mother liquor is circulated to the secondary dissolution process.

[0093] Example 1

[0094] This embodiment provides a method for preparing high-purity ammonium polyvanadate, and the method for preparing high-purity ammonium polyvanadate comprises the following steps:

[0095] (1) Crude ammonium metavanadate containing 98 wt% NH4VO3 was dissolved in hot water at 90°C according to a liquid-to-solid ratio of 15:1 to obtain a dissolved liquid. According to the mass percentage, the impurity content of the crude ammonium metavanadate is Ca: 0.15%, P: 0.1%, S: 0.1%, Si: 0.2% and Fe: 0.25%. The impurity concentrations in the dissolved liquid are Ca: 0.1 g / L, P: 0.067 g / L, S: 0.067 g / L, Si: 0.133 g / L and Fe: 0.167 g / L.

[0096] (2) Ammonia water is first added to the dissolved liquid to adjust the pH to 7.5, and then mixed with active calcium oxide to perform impurity removal reaction at a temperature of 40°C and 500r / min for 0.5h. The molar ratio of the amount of calcium hydroxide added to the sum of the S element, P element and Si element in the dissolved solution is 3:1. The active calcium oxide is activated by calcining calcium carbonate at 1100°C for 2.5h, and the service life of the active calcium oxide is 8h after calcination. After the active calcium oxide precipitation and impurity removal, the S, P and Si impurities in the solution are effectively removed, and the impurity-removed liquid is obtained after filtration. The impurity ion components in the impurity-removed liquid are Ca: 0.23g / L, P: 0.012g / L, S: 0.033g / L, Si: 0.088g / L and Fe: 0.155g / L.

[0097] (3) Add a small amount of ammonia water to the impurity-removed liquid to adjust the pH to 8.0, and then add ammonium bicarbonate to remove excess Ca 2+ The precipitate is removed to carry out the decalcification process. The amount of ammonium bicarbonate added is 3 times the theoretical amount of carbonate required for decalcification. The decalcification reaction time is 0.5h and the reaction temperature is 60°C. After filtration, a purified liquid is obtained. The impurity ion components in the purified liquid are Ca: 0.11g / L, P: 0.012g / L, S: 0.033g / L, Si: 0.088g / L and Fe: 0.125g / L.

[0098] (4) The purified liquid is cooled and recrystallized at 30°C, and 2 g / L of ammonium metavanadate seed crystals are added during the recrystallization process. The recrystallization time is 4 hours to obtain low-impurity ammonium metavanadate crystals and crystallization mother liquor, which is circulated to step (1) for hot water dissolution. The impurity components in the low-impurity ammonium metavanadate are Ca: 0.08%, P: 0.02%, S: 0.01%, Si: 0.08% and Fe: 0.1%.

[0099] (5) Mix low-impurity ammonium metavanadate crystals with 90°C hot water at a liquid-solid ratio of 15:1 to obtain a mixed solution system. (6) Add a 20wt% sulfuric acid solution to the mixed solution system at a rate of 10mL / min to perform transformation precipitation of vanadium. The pH of the transformation precipitation is 1.5, the temperature is 90°C, the time is 1h, and the stirring speed is 200r / min. At the same time, 2g / L of high-purity ammonium polyvanadate seeds are added to improve the crystallization efficiency and particle size. After filtration, high-purity large-particle ammonium polyvanadate is obtained, and the vanadium precipitation rate of ammonium polyvanadate reaches 99.77%. The particle size of high-purity polyvanadic acid is -100 mesh, accounting for 80%, and the impurity content is Ca: 0.03%, P: 0.02%, S: 0.01%, Si: 0.08% and Fe: 0.05%.

[0100] Example 2

[0101] This embodiment provides a method for preparing high-purity ammonium polyvanadate, and the method for preparing high-purity ammonium polyvanadate comprises the following steps:

[0102] (1) Crude ammonium metavanadate containing 95 wt% NH4VO3 was dissolved in hot water at 100°C according to a liquid-to-solid ratio of 20:1 to obtain a dissolved liquid. According to the mass percentage, the impurity content of the crude ammonium metavanadate is Ca: 0.3%, P: 0.15%, S: 0.18%, Si: 0.3% and Fe: 0.4%. The impurity concentrations in the dissolved liquid are Ca: 0.15 g / L, P: 0.075 g / L, S: 0.09 g / L, Si: 0.15 g / L and Fe: 0.2 g / L.

[0103] (2) Ammonia water is first added to the dissolved liquid to adjust the pH to 7.5, and then mixed with active calcium oxide to perform impurity removal reaction at a temperature of 40°C and 550r / min for 0.5h. The molar ratio of the amount of calcium hydroxide added to the sum of the S element, P element and Si element in the dissolved solution is 5:1. The active calcium oxide is activated by calcining calcium carbonate at 1100°C for 3h, and the service life of the active calcium oxide is 24h after calcination. After the active calcium oxide precipitation and impurity removal, the S, P and Si impurities in the solution are effectively removed, and the impurity-removed liquid is obtained after filtration. The impurity ion components in the impurity-removed liquid are Ca: 0.35g / L, P: 0.015g / L, S: 0.02g / L, Si: 0.08g / L and Fe: 0.2g / L.

[0104] (3) Add a small amount of ammonia water to the impurity-removed liquid to adjust the pH to 8.0, and then add ammonium bicarbonate to remove excess Ca 2+The precipitate is removed to carry out the decalcification process. The amount of ammonium bicarbonate added is 3 times the theoretical amount of carbonate required for decalcification. The decalcification reaction time is 0.5h and the reaction temperature is 60°C. After filtration, a purified liquid is obtained. The impurity ion components in the purified liquid are Ca: 0.09g / L, P: 0.015g / L, S: 0.02g / L, Si: 0.08g / L and Fe: 0.2g / L.

[0105] (4) The purified liquid is cooled and recrystallized at 30°C, and 2 g / L of ammonium metavanadate seed crystals are added during the recrystallization process. The recrystallization time is 4 hours to obtain low-impurity ammonium metavanadate crystals and crystallization mother liquor, which is circulated to step (1) for hot water dissolution. The impurity components in the low-impurity ammonium metavanadate are Ca: 0.07%, P: 0.012%, S: 0.018%, Si: 0.07% and Fe: 0.14%.

[0106] (5) Mixing low-doped ammonium metavanadate crystals with 90° C. hot water at a liquid-to-solid ratio of 20:1 to obtain a mixed solution system.

[0107] (6) A 20 wt% sulfuric acid solution is added to the mixed solution system at a speed of 10 mL / min to perform transformation precipitation of vanadium. The pH of the transformation precipitation is 1.8, the temperature is 90°C, the time is 2 hours, and the stirring speed is 200 r / min. At the same time, 2 g / L of high-purity ammonium polyvanadate seeds are added to improve the crystallization efficiency and particle size. After filtration, high-purity large-particle ammonium polyvanadate is obtained, and the vanadium precipitation rate of ammonium polyvanadate reaches 99.82%. The particle size of high-purity polyvanadic acid is -100 mesh, accounting for 76%, and the impurity content is Ca: 0.02%, P: 0.02%, S: 0.015%, Si: 0.07% and Fe: 0.04%.

[0108] Example 3

[0109] This embodiment provides a method for preparing high-purity ammonium polyvanadate, and the method for preparing high-purity ammonium polyvanadate comprises the following steps:

[0110] (1) Crude ammonium metavanadate containing 97 wt% NH4VO3 was dissolved in hot water at 95°C according to a liquid-to-solid ratio of 16:1 to obtain a dissolved liquid. According to the mass percentage, the impurity content of the crude ammonium metavanadate is Ca: 0.2%, P: 0.12%, S: 0.14%, Si: 0.23% and Fe: 0.35%. The impurity concentrations in the dissolved liquid are Ca: 0.125 g / L, P: 0.075 g / L, S: 0.088 g / L, Si: 0.144 g / L and Fe: 0.219 g / L.

[0111] (2) Ammonia water is first added to the dissolved liquid to adjust the pH to 7.7, and then mixed with active calcium oxide to perform impurity removal reaction at a temperature of 55°C and 500r / min for 0.5h. The molar ratio of the amount of calcium hydroxide added to the sum of the S element, P element and Si element in the dissolved solution is 3.5:1. The active calcium oxide is activated by calcining calcium carbonate at 1050°C for 2h, and the service life of the active calcium oxide is 5h after calcination. After the active calcium oxide precipitation and impurity removal, the S, P and Si impurities in the solution are effectively removed, and the impurity-removed liquid is obtained after filtration. The impurity ion components in the impurity-removed liquid are Ca: 0.43g / L, P: 0.022g / L, S: 0.013g / L, Si: 0.068g / L and Fe: 0.11g / L.

[0112] (3) Add a small amount of ammonia water to the impurity-removed liquid to adjust the pH to 8.3, and then add ammonium bicarbonate to remove excess Ca in the solution. 2+ The precipitation is removed to carry out the decalcification process. The amount of ammonium bicarbonate added is 5 times the theoretical amount of carbonate required for decalcification. The decalcification reaction time is 1 hour and the reaction temperature is 55°C. After filtration, a purified liquid is obtained. The impurity ion components in the purified liquid are Ca: 0.13g / L, P: 0.022g / L, S: 0.013g / L, Si: 0.068g / L and Fe: 0.11g / L.

[0113] (4) The purified liquid is cooled and recrystallized at 44°C, and 3 g / L of ammonium metavanadate seed crystals are added during the recrystallization process. The recrystallization time is 6 hours to obtain low-impurity ammonium metavanadate crystals and crystallization mother liquor, which is circulated to step (1) for hot water dissolution. The impurity components in the low-impurity ammonium metavanadate are Ca: 0.08%, P: 0.02%, S: 0.01%, Si: 0.07% and Fe: 0.09%.

[0114] (5) Mixing low-doped ammonium metavanadate crystals with 94° C. hot water at a liquid-to-solid ratio of 16:1 to obtain a mixed solution system.

[0115] (6) A 20 wt% sulfuric acid solution is added to the mixed solution system at a speed of 20 mL / min to perform transformation precipitation of vanadium. The pH of the transformation precipitation is 2.1, the temperature is 94°C, the time is 1 hour, the stirring speed is 300 r / min, and 2 g / L of high-purity ammonium polyvanadate seeds are added to improve the crystallization efficiency and particle size. After filtration, high-purity large-particle ammonium polyvanadate is obtained, and the vanadium precipitation rate of ammonium polyvanadate reaches 99.79%. The particle size of high-purity polyvanadic acid is -100 mesh, accounting for 77%, and the impurity content is Ca: 0.03%, P: 0.02%, S: 0.01%, Si: 0.06% and Fe: 0.06%.

[0116] Example 4

[0117] This embodiment provides a method for preparing high-purity ammonium polyvanadate, and the method for preparing high-purity ammonium polyvanadate comprises the following steps:

[0118] (1) Crude ammonium metavanadate containing 96.5 wt% NH4VO3 was dissolved in hot water at 98°C according to a liquid-to-solid ratio of 17:1 to obtain a dissolved liquid. According to the mass percentage, the impurity content of the crude ammonium metavanadate is Ca: 0.25%, P: 0.11%, S: 0.13%, Si: 0.28% and Fe: 0.29%. The impurity concentrations in the dissolved liquid are Ca: 0.118 g / L, P: 0.071 g / L, S: 0.082 g / L, Si: 0.135 g / L and Fe: 0.21 g / L.

[0119] (2) Ammonia water is first added to the dissolved liquid to adjust the pH to 7.6, and then mixed with active calcium oxide to perform impurity removal reaction at a temperature of 40°C and 700r / min for 0.5h. The molar ratio of the amount of calcium hydroxide added to the sum of the S element, P element and Si element in the dissolved solution is 4:1. The active calcium oxide is activated by calcining calcium carbonate at 950°C for 2.5h, and the service life of the active calcium oxide is 2h after calcination. After the active calcium oxide precipitation and impurity removal, the S, P and Si impurities in the solution are effectively removed, and the impurity-removed liquid is obtained after filtration. The impurity ion components in the impurity-removed liquid are Ca: 0.45g / L, P: 0.018g / L, S: 0.035g / L, Si: 0.088g / L and Fe: 0.115g / L.

[0120] (3) Add a small amount of ammonia water to the impurity-removed liquid to adjust the pH to 8.0, and then add ammonium bicarbonate to remove excess Ca 2+ The precipitate is removed to carry out the decalcification process. The amount of ammonium bicarbonate added is 3.5 times the theoretical amount of carbonate required for decalcification. The decalcification reaction time is 0.9h and the reaction temperature is 40°C. After filtration, a purified liquid is obtained. The impurity ion components in the purified liquid are Ca: 0.05g / L, P: 0.018g / L, S: 0.035g / L, Si: 0.088g / L and Fe: 0.115g / L.

[0121] (4) The purified liquid is cooled and recrystallized at 45°C, and 2.5 g / L of ammonium metavanadate seed crystals are added during the recrystallization process. The recrystallization time is 5 hours to obtain low-impurity ammonium metavanadate crystals and crystallization mother liquor, which is circulated to step (1) for hot water dissolution. The impurity components in the low-impurity ammonium metavanadate are Ca: 0.08%, P: 0.02%, S: 0.02%, Si: 0.06% and Fe: 0.13%.

[0122] (5) Mixing low-doped ammonium metavanadate crystals with 95° C. hot water at a liquid-to-solid ratio of 17:1 to obtain a mixed solution system.

[0123] (6) A 20 wt% sulfuric acid solution was added to the mixed solution system at a speed of 10 mL / min to perform transformation precipitation of vanadium. The pH of the transformation precipitation was 1.5, the temperature was 95°C, the time was 1.2 h, the stirring speed was 300 r / min, and 3.2 g / L of high-purity ammonium polyvanadate seeds were added to improve the crystallization efficiency and particle size. After filtration, high-purity large-particle ammonium polyvanadate was obtained, and the vanadium precipitation rate of ammonium polyvanadate reached 99.83%. The particle size of high-purity polyvanadic acid was -100 mesh, accounting for 75%, and the impurity content was Ca: 0.03%, P: 0.02%, S: 0.01%, Si: 0.04% and Fe: 0.06%.

[0124] Example 5

[0125] This embodiment provides a method for preparing high-purity ammonium polyvanadate, and the method for preparing high-purity ammonium polyvanadate comprises the following steps:

[0126] (1) Crude ammonium metavanadate containing 96 wt% NH4VO3 was dissolved in hot water at 96°C according to a liquid-to-solid ratio of 19:1 to obtain a dissolved liquid. According to the mass percentage, the impurity content of the crude ammonium metavanadate is Ca: 0.27%, P: 0.13%, S: 0.14%, Si: 0.27% and Fe: 0.39%. The impurity concentrations in the dissolved liquid are Ca: 0.142 g / L, P: 0.068 g / L, S: 0.074 g / L, Si: 0.142 g / L and Fe: 0.205 g / L.

[0127] (2) Ammonia water is first added to the dissolved liquid to adjust the pH to 7.7, and then mixed with active calcium oxide to perform impurity removal reaction at a temperature of 60°C and 600r / min for 0.5h. The molar ratio of the amount of calcium hydroxide added to the sum of the S element, P element and Si element in the dissolved solution is 3:1. The active calcium oxide is activated by calcining calcium carbonate at 1080°C for 2h, and the service life of the active calcium oxide is 1h after calcination. After the active calcium oxide precipitation and impurity removal, the S, P and Si impurities in the solution are effectively removed, and the impurity-removed liquid is obtained after filtration. The impurity ion components in the impurity-removed liquid are Ca: 0.66g / L, P: 0.012g / L, S: 0.023g / L, Si: 0.081g / L, and Fe: 0.2g / L.

[0128] (3) Add a small amount of ammonia water to the impurity-removed liquid to adjust the pH to 8.2, and then add ammonium bicarbonate to remove excess Ca in the solution. 2+The precipitation is removed to carry out the decalcification process. The amount of ammonium bicarbonate added is 3.7 times the theoretical amount of carbonate required for decalcification. The decalcification reaction time is 0.8h and the reaction temperature is 45°C. After filtration, the purified liquid is obtained. The impurity ion components in the purified liquid are Ca: 0.06g / L, P: 0.012g / L, S: 0.023g / L, Si: 0.081g / L, Fe: 0.11g / L.

[0129] (4) The purified liquid is cooled and recrystallized at 38°C, and 2 g / L of ammonium metavanadate seed crystals are added during the recrystallization process. The recrystallization time is 4.5 hours to obtain low-impurity ammonium metavanadate crystals and crystallization mother liquor, which is circulated to step (1) for hot water dissolution. The impurity components in the low-impurity ammonium metavanadate are Ca: 0.07%, P: 0.03%, S: 0.02%, Si: 0.078% and Fe: 0.15%.

[0130] (5) Mixing low-doped ammonium metavanadate crystals with 99° C. hot water at a liquid-to-solid ratio of 19:1 to obtain a mixed solution system.

[0131] (6) A 20 wt% sulfuric acid solution is added to the mixed solution system at a speed of 15 mL / min to perform transformation precipitation of vanadium. The pH of the transformation precipitation is 2, the temperature is 99°C, the time is 1 hour, and the stirring speed is 250 r / min. At the same time, 4 g / L of high-purity ammonium polyvanadate seeds are added to improve the crystallization efficiency and particle size. After filtration, high-purity large-particle ammonium polyvanadate is obtained, and the vanadium precipitation rate of ammonium polyvanadate reaches 99.81%. The particle size of high-purity polyvanadic acid is -100 mesh, accounting for 80%, and the impurity content is Ca: 0.02%, P: 0.02%, S: 0.01%, Si: 0.055% and Fe: 0.065%.

[0132] Example 6

[0133] This embodiment provides a method for preparing high-purity ammonium polyvanadate, and the method for preparing high-purity ammonium polyvanadate comprises the following steps:

[0134] (1) Crude ammonium metavanadate containing 98 wt% NH4VO3 was dissolved in hot water at 91°C according to a liquid-to-solid ratio of 15:1 to obtain a dissolved liquid. According to the mass percentage, the impurity content of the crude ammonium metavanadate is Ca: 0.15%, P: 0.1%, S: 0.13%, Si: 0.25% and Fe: 0.25%. The impurity concentrations in the dissolved liquid are Ca: 0.1 g / L, P: 0.067 g / L, S: 0.087 g / L, Si: 0.167 g / L and Fe: 0.167 g / L respectively.

[0135] (2) Ammonia water is first added to the dissolved liquid to adjust the pH to 7.8, and then mixed with active calcium oxide to perform impurity removal reaction at a temperature of 50°C and 550r / min for 0.5h. The molar ratio of the amount of calcium hydroxide added to the sum of the S element, P element and Si element in the dissolved solution is 4.5:1. The active calcium oxide is activated by calcining calcium carbonate at 1000°C for 2h, and the service life of the active calcium oxide is 0.5h after calcination. After the active calcium oxide precipitation and impurity removal, the S, P and Si impurities in the solution are effectively removed, and the impurity-removed liquid is obtained after filtration. The impurity ion components in the impurity-removed liquid are Ca: 0.42g / L, P: 0.012g / L, S: 0.023g / L, Si: 0.068g / L, and Fe: 0.155g / L.

[0136] (3) Add a small amount of ammonia water to the impurity-removed liquid to adjust the pH to 8.1, and then add ammonium bicarbonate to remove excess Ca in the solution. 2+ The precipitation is removed to carry out the decalcification process. The amount of ammonium bicarbonate added is 4.5 times the theoretical amount of carbonate required for decalcification. The decalcification reaction time is 1 hour and the reaction temperature is 60°C. After filtration, the purified liquid is obtained. The impurity ion components in the purified liquid are Ca: 0.12g / L, P: 0.012g / L, S: 0.023g / L, Si: 0.068g / L, Fe: 0.09g / L.

[0137] (4) The purified liquid is cooled and recrystallized at 50°C, and 2.8 g / L of ammonium metavanadate seed crystals are added during the recrystallization process. The recrystallization time is 5.5 hours to obtain low-impurity ammonium metavanadate crystals and crystallization mother liquor, which is circulated to step (1) for hot water dissolution. The impurity components in the low-impurity ammonium metavanadate are Ca: 0.07%, P: 0.03%, S: 0.03%, Si: 0.08% and Fe: 0.1%.

[0138] (5) Mixing low-doped ammonium metavanadate crystals with 100° C. hot water at a liquid-to-solid ratio of 15:1 to obtain a mixed solution system.

[0139] (6) A 20 wt% sulfuric acid solution is added to the mixed solution system at a speed of 10 mL / min to perform transformation precipitation of vanadium. The pH of the transformation precipitation is 2.2, the temperature is 100°C, the time is 1.8 hours, the stirring speed is 200 r / min, and 3 g / L of high-purity ammonium polyvanadate seeds are added to improve the crystallization efficiency and particle size. After filtration, high-purity large-particle ammonium polyvanadate is obtained, and the vanadium precipitation rate of ammonium polyvanadate reaches 99.73%. The particle size of high-purity polyvanadic acid is -100 mesh, accounting for 80%, and the impurity content is Ca: 0.04%, P: 0.02%, S: 0.02%, Si: 0.077% and Fe: 0.051%.

[0140] Example 7

[0141] This embodiment provides a method for preparing high-purity ammonium polyvanadate, and the method for preparing high-purity ammonium polyvanadate comprises the following steps:

[0142] (1) Crude ammonium metavanadate containing 96 wt% NH4VO3 was dissolved in hot water at 90°C according to a liquid-to-solid ratio of 18:1 to obtain a dissolved liquid. According to the mass percentage, the impurity content of the crude ammonium metavanadate is Ca: 0.2%, P: 0.1%, S: 0.16%, Si: 0.2% and Fe: 0.25%. The impurity concentrations in the dissolved liquid are Ca: 0.111 g / L, P: 0.056 g / L, S: 0.072 g / L, Si: 0.111 g / L and Fe: 0.137 g / L.

[0143] (2) Ammonia water is first added to the dissolved liquid to adjust the pH to 8, and then mixed with active calcium oxide to perform impurity removal reaction at a temperature of 60°C and 700r / min for 0.5h. The molar ratio of the amount of calcium hydroxide added to the sum of the S element, P element and Si element in the dissolved solution is 3:1. The active calcium oxide is activated by calcining calcium carbonate at 900°C for 3h, and the service life of the active calcium oxide is 12h after calcination. After the active calcium oxide precipitation and impurity removal, the S, P and Si impurities in the solution are effectively removed, and the impurity-removed liquid is obtained after filtration. The impurity ion components in the impurity-removed liquid are Ca: 0.44g / L, P: 0.011g / L, S: 0.033g / L, Si: 0.055g / L, and Fe: 0.125g / L.

[0144] (3) Add a small amount of ammonia water to the impurity-removed solution to adjust the pH to 8.5, and then add ammonium bicarbonate to remove excess Ca 2+ The precipitate is removed to carry out the decalcification process. The amount of ammonium bicarbonate added is 3 times the theoretical amount of carbonate required for decalcification. The decalcification reaction time is 0.5h and the reaction temperature is 60°C. After filtration, a purified liquid is obtained. The impurity ion components in the purified liquid are Ca: 0.11g / L, P: 0.011g / L, S: 0.033g / L, Si: 0.055g / L and Fe: 0.115g / L.

[0145] (4) The purified liquid is cooled and recrystallized at 40°C, and 2 g / L of ammonium metavanadate seed crystals are added during the recrystallization process. The recrystallization time is 4 hours to obtain low-impurity ammonium metavanadate crystals and crystallization mother liquor, which is circulated to step (1) for hot water dissolution. The impurity components in the low-impurity ammonium metavanadate are Ca: 0.06%, P: 0.02%, S: 0.02%, Si: 0.08% and Fe: 0.14%.

[0146] (5) Mixing low-doped ammonium metavanadate crystals with 95° C. hot water at a liquid-to-solid ratio of 18:1 to obtain a mixed solution system.

[0147] (6) A 20wt% sulfuric acid solution was added to the mixed solution system at a speed of 18mL / min to perform transformation precipitation of vanadium. The pH of the transformation precipitation was 1.5, the temperature was 95°C, the time was 1h, the stirring speed was 200r / min, and 5g / L of high-purity ammonium polyvanadate seeds were added to improve the crystallization efficiency and particle size. After filtration, high-purity large-particle ammonium polyvanadate was obtained, and the vanadium precipitation rate of ammonium polyvanadate reached 99.81%. The particle size of high-purity polyvanadic acid was -100 mesh, accounting for 80%, and the impurity content was: Ca: 0.03%, P: 0.02%, S: 0.01%, Si: 0.06% and Fe: 0.05%.

[0148] Example 8

[0149] This embodiment provides a method for preparing high-purity ammonium polyvanadate. The method for preparing high-purity ammonium polyvanadate is the same as that of Example 1 except that no active calcium oxide is added after adjusting the solution pH to 7.5 in step (1), and no further description is given here. At this time, the concentration of impurity ions in the solution remains unchanged, and after adding ammonium bicarbonate, only the Ca concentration drops from 0.1g / L to 0.08g / L, and the concentrations of other impurity ions remain unchanged. The purity of the finally obtained ammonium polyvanadate is 98.77%, the particle size is -100 mesh 82%, and the impurity content is: Ca: 0.13%, P: 0.08%, S: 0.08%, Si: 0.18% and Fe: 0.22%.

[0150] Example 9

[0151] The present embodiment provides a method for preparing high-purity ammonium polyvanadate. The method for preparing high-purity ammonium polyvanadate is the same as that of Example 1 except that the pH of the solution is not adjusted in step (1) and active calcium oxide is directly added. The above method will not be described in detail. The addition of calcium to remove impurities without adjusting the pH has a certain effect of removing impurities, but the effect is very poor. The impurity ion components in the solution after impurity removal are Ca: 0.25g / L, P: 0.055g / L, S: 0.043g / L, Si: 0.081g / L, and Fe: 0.145g / L. The purity of the ammonium polyvanadate finally obtained is 98.86%, the particle size is -100 mesh 83%, and the impurity content is: Ca: 0.09%, P: 0.06%, S: 0.07%, Si: 0.15% and Fe: 0.2%.

[0152] In this embodiment, the active calcium oxide must be precipitated at an appropriate pH. If the pH is too low, Ca 2+The solubility of calcium oxide is large, resulting in excessive Ca content in the product; if the pH is too high, the active calcium oxide will easily form calcium hydroxide, resulting in the inability to completely release the activity of calcium oxide, thereby causing the removal effect of P, S and Si to deteriorate.

[0153] Example 10

[0154] This embodiment provides a method for preparing high-purity ammonium polyvanadate, which is the same as that of Example 1 except that the recrystallization in step (2) is not performed, and is not described in detail here. The purity of the finally prepared ammonium polyvanadate is 98.88%, the particle size is -100 mesh 80%, and the impurity content is: Ca: 0.12%, P: 0.06%, S: 0.08%, Si: 0.12% and Fe: 0.18%.

[0155] In this embodiment, recrystallization is a purification process for both cationic and anionic impurities. If recrystallization is not performed, the impurity content in the final product will be high, especially the impurities of cationic Ca and Fe will be more obvious.

[0156] Embodiment 11

[0157] This embodiment provides a method for preparing high-purity ammonium polyvanadate, which is the same as that of Example 1 except that the introduction rate of sulfuric acid solution in step (4) is 16 mL / min, and is not described in detail here. The purity of high-purity polyvanadic acid is 99.43%, the particle size is -200 mesh, accounting for 80%, and the impurity content is Ca: 0.03%, P: 0.08%, S: 0.02%, Si: 0.12% and Fe: 0.11%.

[0158] In this embodiment, the high addition speed will lead to the formation of a large number of ammonium polyvanadate agglomerates. These agglomerates are composed of extremely fine ammonium polyvanadate crystals, which have small particles and strong impurity adsorption performance, especially anionic impurities, resulting in reduced product purity.

[0159] Example 12

[0160] This embodiment provides a method for preparing high-purity ammonium polyvanadate. The method for preparing high-purity ammonium polyvanadate is the same as that of Example 1 except that the introduction rate of sulfuric acid solution in step (4) is 8 mL / min, and the details are not repeated here. The vanadium precipitation rate of the prepared ammonium polyvanadate is 95.3%. The purity of polyvanadic acid is 99.78%, the particle size is -100 mesh, accounting for 83%, and the impurity content is Ca: 0.03%, P: 0.02%, S: 0.01%, Si: 0.075% and Fe: 0.052%.

[0161] In this embodiment, the addition rate of sulfuric acid is too low, which will cause the reverse reaction of vanadium precipitation to occur gradually, resulting in a decrease in the vanadium precipitation rate.

[0162] Embodiment 13

[0163] This embodiment provides a method for preparing high-purity ammonium polyvanadate. The method for preparing high-purity ammonium polyvanadate is the same as that of Example 1 except that the pH of vanadium precipitation in step (4) is 1.0, and no further description is given here. The vanadium precipitation rate of the prepared ammonium polyvanadate is 80.2%. The purity of polyvanadic acid is 99.79%, the particle size is -100 mesh, accounting for 82%, and the impurity content is Ca: 0.025%, P: 0.02%, S: 0.013%, Si: 0.07% and Fe: 0.052%.

[0164] In this embodiment, the low pH of vanadium precipitation will lead to a decrease in the vanadium precipitation rate. At this time, part of the vanadium in the solution is not precipitated in the form of ammonium polyvanadate, but appears as +5 valence VO2 + ions appear, resulting in a decrease in the vanadium precipitation rate.

[0165] Embodiment 14

[0166] This embodiment provides a method for preparing high-purity ammonium polyvanadate. The method for preparing high-purity ammonium polyvanadate is the same as that of Example 1 except that the pH of vanadium precipitation in step (4) is 3.0, and no further description is given here. The vanadium precipitation rate of the prepared ammonium polyvanadate is 75.2%. The purity of polyvanadic acid is 99.80%, the particle size is -100 mesh, accounting for 84%, and the impurity content is Ca: 0.025%, P: 0.02%, S: 0.013%, Si: 0.068% and Fe: 0.048%.

[0167] In this embodiment, the pH of vanadium precipitation is too high, so the transformation of ammonium metavanadate to ammonium polyvanadate is not complete, and the vanadium precipitation rate is reduced.

[0168] Embodiment 15

[0169] This embodiment provides a method for preparing high-purity ammonium polyvanadate. The method for preparing high-purity ammonium polyvanadate is the same as that of Example 1 except that the temperature for precipitating vanadium in step (4) is 98°C, and the details are not described here. The vanadium precipitation rate of the prepared ammonium polyvanadate is 99.5%. The purity of polyvanadic acid is 99.80%, the particle size is -100 mesh, accounting for 82%, and the impurity content is Ca: 0.023%, P: 0.02%, S: 0.012%, Si: 0.072% and Fe: 0.048%.

[0170] In this embodiment, the high temperature is used, which leads to increased energy consumption while having little improvement on the vanadium deposition effect.

[0171] Example 16

[0172] This embodiment provides a method for preparing high-purity ammonium polyvanadate. The method for preparing high-purity ammonium polyvanadate is the same as that of Example 1 except that the temperature for precipitating vanadium in step (4) is 85°C, and the rest is not repeated here. The vanadium precipitation rate of the prepared ammonium polyvanadate is 90.2%, and the particle size of the ammonium polyvanadate is -150 mesh 80%. The purity of polyvanadic acid is 99.41%, and the impurity content is Ca: 0.04%, P: 0.08%, S: 0.022%, Si: 0.12% and Fe: 0.11%.

[0173] In this embodiment, the vanadium precipitation temperature is too low, which will lead to fine ammonium polyvanadate particles, incomplete vanadium precipitation and low vanadium precipitation rate.

[0174] Comparative Example 1

[0175] This comparative example provides a method for preparing high-purity ammonium polyvanadate. The method for preparing high-purity ammonium polyvanadate is the same as Example 1 except that the mixed solution system is added to the sulfuric acid solution at the same speed, and the rest is not repeated here. The vanadium precipitation rate of the prepared ammonium polyvanadate is 88.2%, and the particle size of the ammonium polyvanadate is -200 mesh 70%. The particle size of the ammonium polyvanadate is -200 mesh 80%. The purity of polyvanadic acid is 99.40%, and the impurity content is Ca: 0.04%, P: 0.08%, S: 0.025%, Si: 0.12% and Fe: 0.11%.

[0176] In this comparative example, adding sulfuric acid at the same speed will result in failure to precipitate large particles of ammonium polyvanadate, and the vanadium precipitation rate is low.

[0177] Comparative Example 2

[0178] This comparative example provides a method for preparing high-purity ammonium polyvanadate, which is the same as Example 1 except that step (3) and step (4) are not performed, and the rest are not repeated here. The purity of the ammonium polyvanadate finally obtained is 98.55%, the particle size is -100 mesh 80%, and the impurity content is: Ca: 0.18%, P: 0.08%, S: 0.08%, Si: 0.21% and Fe: 0.25%.

[0179] Test method: The purity of ammonium polyvanadate in ammonium polyvanadate is tested by chemical titration. A small amount of ammonium polyvanadate is accurately weighed and then dissolved into the solution. The S and P contents in ammonium polyvanadate are tested by ion chromatography. The impurity contents of Si, Ca and Fe in ammonium polyvanadate are tested by ICP method. The particle size of ammonium polyvanadate is tested by physical screening method. The recovery rate of vanadium is calculated by the change of V content in the solution before and after crystallization or precipitation.

[0180] Application Example 1

[0181] This application example provides a method for preparing high-purity vanadium pentoxide, which comprises: calcining the high-purity ammonium polyvanadate prepared in Example 1 at a temperature of 500° C. and an atmosphere with an oxygen concentration of 20% for 1 hour to obtain the high-purity vanadium pentoxide.

[0182] Application Example 2

[0183] This application example provides a method for preparing high-purity vanadium pentoxide, which comprises: calcining the high-purity ammonium polyvanadate prepared in Example 2 at a temperature of 550° C. and an atmosphere with an oxygen concentration of 28% for 2 hours to obtain the high-purity vanadium pentoxide.

[0184] Application Example 3

[0185] This application example provides a method for preparing high-purity vanadium pentoxide, which comprises: calcining the high-purity ammonium polyvanadate prepared in Example 3 at a temperature of 560° C. and an atmosphere with an oxygen concentration of 24% for 2.5 hours to obtain the high-purity vanadium pentoxide.

[0186] Application Example 4

[0187] This application example provides a method for preparing high-purity vanadium pentoxide, which comprises: calcining the high-purity ammonium polyvanadate prepared in Example 4 at a temperature of 600° C. and an atmosphere with an oxygen concentration of 25% for 1.9 hours to obtain the high-purity vanadium pentoxide.

[0188] Application Example 5

[0189] This application example provides a method for preparing high-purity vanadium pentoxide, which comprises: calcining the high-purity ammonium polyvanadate prepared in Example 5 at a temperature of 500° C. and an atmosphere with an oxygen concentration of 30% for 2.2 hours to obtain the high-purity vanadium pentoxide.

[0190] Application Example 6

[0191] This application example provides a method for preparing high-purity vanadium pentoxide, which comprises: calcining the high-purity ammonium polyvanadate prepared in Example 5 at a temperature of 500° C. and an atmosphere with an oxygen concentration of 20% for 2.4 hours to obtain the high-purity vanadium pentoxide.

[0192] Application Examples 7 to 16 and Comparative Application Examples 1 to 2

[0193] Application Examples 7 to 16 and Application Comparative Examples 1 to 2 provide a method for preparing high-purity vanadium pentoxide. The preparation method of high-purity vanadium pentoxide is the same as Application Example 1 except that the high-purity ammonium polyvanadate in Examples 7 to 16 and Comparative Examples 1 to 2 is used respectively, and will not be repeated here.

[0194] Test method: The purity of vanadium pentoxide is tested by chemical titration. A small amount of vanadium pentoxide is accurately weighed and dissolved into the solution. The S and P contents in vanadium pentoxide are tested by ion chromatography. The impurity contents of Si, Ca, Fe, etc. in vanadium pentoxide are tested by ICP method, and the contents are shown in Table 1.

[0195] Table 1

[0196]

[0197]

[0198] From Table 1, we can see the following points:

[0199] (1) It can be seen from the comprehensive application examples 1 to 7 that the preparation method of high-purity ammonium polyvanadate provided by the present invention has the advantage of high vanadium recovery rate, and the purity of vanadium pentoxide after calcination can reach more than 99.68wt%, the particle size of vanadium pentoxide reaches -100 mesh, accounting for less than 85%, the particle size is large, and the impurity content in vanadium pentoxide is low, wherein the S content is as low as within 0.05wt%, the P content is as low as within 0.02wt%, the Si content is as low as within 0.02wt%, the Ca content is as low as within 0.10wt%, and the Fe content is as low as within 0.08wt%.

[0200] (2) It can be seen from Application Example 1 and Application Examples 8 to 10 that in Application Example 8, after adjusting the solution pH to 7.5, no activated calcium oxide was added, in Application Example 9, the solution pH was not adjusted and activated calcium oxide was directly added, and in Application Example 10, the recrystallization of step (2) was not performed. Finally, the purity of vanadium pentoxide in Application Examples 8 to 10 was lower than that in Application Example 1. This shows that the present invention preferably increases the purity of vanadium pentoxide by more than 99% through the mutual coordination of various steps.

[0201] (3) It can be seen from Application Example 1 and Application Examples 11 to 12 that the present invention preferably controls the introduction rate of the sulfuric acid solution within a reasonable range, which can simultaneously ensure the vanadium precipitation rate and the purity of the final vanadium pentoxide.

[0202] (4) It can be seen from Application Example 1 and Application Examples 13 to 16 that the preparation method of high-purity ammonium polyvanadate provided by the present invention preferably controls the temperature and pH conditions for vanadium precipitation, which can better ensure the vanadium precipitation rate while improving the product purity of vanadium pentoxide.

[0203] (5) In Comparative Example 1, the mixed solution system is added to the sulfuric acid solution at the same speed, resulting in a small particle size of the final vanadium pentoxide and a low vanadium precipitation rate; while in Comparative Example 2, steps (3) and (4) are not performed, and the final vanadium pentoxide product has the lowest purity.

[0204] 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 high-purity ammonium polyvanadate, characterized in that: The preparation method comprises the following steps: The low-impurity ammonium metavanadate crystals are mixed with hot water to obtain a mixed solution system; a sulfuric acid solution is added to the mixed solution system to perform transformation precipitation of vanadium, and high-purity ammonium polyvanadate is obtained through solid-liquid separation.

2. The preparation method according to claim 1, characterized in that: The temperature of the hot water is 90-100°C; Preferably, the liquid-to-solid ratio of the hot water to the ammonium metavanadate crystals is (15-20):1; Preferably, the impurities in the low-impurity ammonium metavanadate crystals include anionic elements; Preferably, the anion elements in the low-impurity ammonium metavanadate crystals include any one or a combination of at least two of phosphorus, sulfur or silicon; Preferably, in terms of mass percentage, the impurities in the low-impurity ammonium metavanadate crystals include Ca: 0.08-0.15%, P: 0.02-0.03%, S: 0.01-0.1%, Si: 0.15-0.2% and Fe: 0.1-0.25%.

3. The preparation method according to claim 1 or 2, characterized in that: The concentration of the sulfuric acid solution is 18-22 wt %; Preferably, the pH of the vanadium precipitation is 1.5 to 2.2; Preferably, the temperature of the vanadium precipitation is 90-100°C; Preferably, ammonium polyvanadate seeds are also added to the vanadium precipitation; Preferably, the amount of the ammonium polyvanadate seed added is 2 to 5 g / L; Preferably, the vanadium precipitation time is 1 to 2 hours; Preferably, the stirring speed of the vanadium precipitation is 200-300 r / min; Preferably, the sulfuric acid solution is added at a rate of 10 to 20 mL / min.

4. The preparation method according to any one of claims 1 to 3, characterized in that: When the temperature of the vanadium precipitation is 90-95°C, the rate of adding the sulfuric acid solution to the vanadium precipitation is 10-15 mL / min; Preferably, when the temperature of the vanadium precipitation is 95-100° C., the rate of adding the sulfuric acid solution to the vanadium precipitation is 15-20 mL / min.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The preparation of the low-impurity ammonium metavanadate crystals comprises: After the crude ammonium metavanadate is dissolved, a dissolved liquid is obtained, the dissolved liquid is mixed with an impurity remover to perform an impurity removal reaction, and the solid-liquid separation is performed to obtain an impurity-removed liquid; the impurity-removed liquid is subjected to decalcification and solid-liquid separation to obtain a purified liquid; The purified liquid is recrystallized to obtain low-impurity ammonium metavanadate crystals.

6. The preparation method according to claim 5, characterized in that: The content of NH4VO3 in the crude ammonium metavanadate is 95-98wt%; Preferably, the crude ammonium metavanadate contains any one or a combination of at least two of Ca, P, S, Si or Fe; Preferably, the Ca content in the crude ammonium metavanadate is 0.15-0.3wt%; Preferably, the P content in the crude ammonium metavanadate is 0.1 to 0.15 wt %; Preferably, the S content in the crude ammonium metavanadate is 0.1 to 0.18 wt %; Preferably, the Si content in the crude ammonium metavanadate is 0.2-0.3 wt%; Preferably, the Fe content in the crude ammonium metavanadate is 0.25-0.4 wt%.

7. The preparation method according to claim 5 or 6, characterized in that: The dissolving solvent includes water; Preferably, the liquid-to-solid ratio of the solvent to the crude ammonium metavanadate in the dissolution is (15-20):1; Preferably, the temperature of the dissolution process is 90-100°C.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The impurity remover is active calcium oxide; Preferably, the active calcium oxide is calcium oxide obtained by calcining the calcium source at 900-1100° C. for 2-3 hours and storing it for no more than 24 hours; Preferably, the calcium source includes any one of calcium carbonate, calcium hydroxide or calcium oxide, or a combination of at least two thereof; Preferably, the dissolved liquid includes S element, P element and Si element; Preferably, the molar ratio of the amount of the impurity remover added to the sum of the S element, the P element and the Si element in the solution after dissolution is (3-5):1; Preferably, the pH of the impurity removal reaction is 7.5 to 8; Preferably, the temperature of the impurity removal reaction is 40-60°C; Preferably, the impurity removal reaction time is 0.5 to 1 h; Preferably, the stirring rate of the impurity removal reaction is 500-700 r / min; Preferably, a decalcifying agent is added during the decalcification, and the decalcifying agent includes ammonium bicarbonate and / or ammonium carbonate; Preferably, the amount of the decalcifier added is 3 to 5 times the theoretical amount of carbonate required for decalcification; Preferably, the reaction pH of the calcium removal is 8.0 to 8.5; Preferably, the reaction time of the calcium removal is 0.5 to 1 h; Preferably, the reaction temperature of the decalcification is 60-70°C; Preferably, the terminal temperature of the recrystallization is 30 to 50°C; Preferably, the recrystallization time is 4-6h; Preferably, ammonium metavanadate seeds are added during the recrystallization process; Preferably, the addition amount of the ammonium metavanadate seed crystals is 2-3 g / L.

9. A method for preparing high-purity vanadium pentoxide, characterized in that: The preparation method is carried out by using the high-purity ammonium polyvanadate prepared by the preparation method of high-purity ammonium polyvanadate described in any one of claims 1 to 8.

10. The preparation method according to claim 9, characterized in that: The preparation method of the high-purity vanadium pentoxide comprises: calcining the high-purity ammonium polyvanadate to obtain the high-purity vanadium pentoxide; Preferably, the calcination temperature is 500-600°C; Preferably, the calcination atmosphere is an oxygen-containing atmosphere; Preferably, the oxygen concentration in the oxygen-containing atmosphere is 20 to 30 wt %; Preferably, the calcination time is 1 to 2.5 hours.

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