CN114162870B - Ammonium paratungstate, preparation method thereof and bipolar membrane electrolysis device - Google Patents
Ammonium paratungstate, preparation method thereof and bipolar membrane electrolysis device Download PDFInfo
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Abstract
The invention provides ammonium paratungstate, a preparation method thereof and a bipolar membrane electrolysis device, wherein the preparation method comprises the following steps: and (3) performing bipolar membrane electrolysis by taking a sodium tungstate solution as an anolyte, and mixing the obtained anolyte with ammonia water to obtain the ammonium paratungstate. The invention adopts the bipolar membrane electrolysis-ammonia precipitation process, not only can realize the separation of tungsten and sodium in the sodium tungstate solution under the condition of not adding any chemical reagent, but also can directly prepare the ammonium paratungstate product with the purity higher than 99 percent by adding ammonia water. In addition, the bipolar membrane electrolysis-ammonia precipitation process can directly treat high-concentration sodium tungstate feed liquid, thereby greatly reducing the treatment capacity of raw materials, simultaneously realizing the recovery of sodium hydroxide, avoiding the generation of waste water from the source and realizing the low energy consumption and clean preparation of ammonium paratungstate.
Description
Technical Field
The invention belongs to the technical field of tungsten product preparation, and particularly relates to ammonium paratungstate, a preparation method thereof and a bipolar membrane electrolysis device.
Background
Ammonium paratungstate is a white crystalline powder with the molecular formula (NH) 4 ) 10 W 12 O 41 ·5H 2 O, an important raw material in the industrial production of tungsten, and is also used as an additive in the petrochemical industry. Because the morphology and impurities of the ammonium paratungstate have 'genetic characteristics' for subsequent products, the preparation of qualified ammonium paratungstate is of great importance.
At present, in industrial production, the separation of tungsten and sodium in a solution is mainly realized by traditional methods such as ion exchange, solvent extraction or chemical precipitation, and the like, and an ammonium tungstate solution is obtained. Wherein, ammoniation transformation is the must route of ammonium paratungstate production process, however because ammoniation transformation is gone to and need add sour adjustment solution pH toward, thereby the excess aqueous ammonia needs to be added to the transformation process, leads to generating a large amount of high salt waste water, and high salt waste water direct discharge can cause serious environmental pollution, and the while traditional approach generally uses the sodium tungstate solution of low concentration as the raw materials, and the suitability is lower.
CN111424170A discloses a method and a system for producing ammonium paratungstate by acidic extraction, wherein the method comprises the steps of leaching a tungsten mineral raw material to obtain mixed slurry, and then carrying out solid-liquid separation on the mixed slurry to obtain a sodium tungstate solution; then, carrying out advanced oxidation on the sodium tungstate solution to obtain a primary purified sodium tungstate solution, and then carrying out purification treatment to obtain a secondary purified sodium tungstate solution; then sequentially carrying out vulcanization and acid adjustment on the sodium tungstate solution subjected to secondary purification to remove molybdenum, so as to obtain a refined sodium tungstate solution and a molybdenum byproduct; and finally, sequentially extracting, back-extracting and crystallizing the refined sodium tungstate solution to obtain an ammonium paratungstate product. Although the method can obtain high-quality ammonium paratungstate products, the preparation process is complex, the energy consumption is large, and a large amount of high-salinity wastewater is generated.
CN108557890A discloses a method for preparing ammonium paratungstate, which comprises preparing ammonium paratungstate from high-concentration sodium tungstate solution as raw material, setting several ' in vivo microcirculation ' processes for treating waste water and waste liquid, separating and recovering ammonium chloride and sodium chloride by ' evaporative crystallization-heat filtration ', introducing ' Hou ' alkali preparation method ' to convert sodium chloride into ammonium chloride which can be recycled in the production process and sodium carbonate which can be used in high-pressure leaching process of tungsten mineral sodium carbonate, not only realizing directly preparing ammonium paratungstate from high-concentration sodium tungstate solution, but also eliminating pollution of waste water and waste salt to environment. However, the preparation process is complex, the energy consumption is high, and the popularization and the utilization are difficult.
CN104831305A discloses a method for preparing silver tungstate by using a cationic membrane electrolysis method, which takes a silver sheet as an anode, an inert electrode as a cathode, an aqueous solution containing a depolarizer and sodium tungstate as an anolyte, and an acid solution, an alkali solution or a salt solution as a cathodeLiquid; electrolyzing the aqueous solution containing the depolarizer and sodium tungstate by constant-current electrolysis or constant-voltage electrolysis in a double-chamber electrolytic cell with a cation membrane as a diaphragm until Na + The ions are all transferred to the cathode chamber; and washing, filtering and drying the product obtained in the anode chamber to obtain the high-purity impurity-free silver tungstate. The preparation method adopts cation membrane electrolysis, and the generation amount of the product is too low.
Therefore, the development of a preparation method of ammonium paratungstate realizes the clean transformation of the process of preparing ammonium tungstate from sodium tungstate on the basis of simplifying the preparation process, avoids the generation of wastewater, and is called a problem to be solved urgently in the tungsten industry.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide ammonium paratungstate, a preparation method thereof and a bipolar membrane electrolysis device, wherein the bipolar membrane electrolysis-ammonia precipitation process is adopted, so that the separation of tungsten and sodium in a sodium tungstate solution can be realized under the condition of not adding any chemical reagent, and an ammonium paratungstate product with the purity higher than 99 percent can be directly prepared by adding ammonia water. In addition, the bipolar membrane electrolysis-ammonia precipitation process can directly treat high-concentration sodium tungstate feed liquid, thereby greatly reducing the treatment capacity of raw materials, simultaneously realizing the recovery of sodium hydroxide, avoiding the generation of waste water from the source and realizing the clean preparation of ammonium paratungstate.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing ammonium paratungstate, comprising:
and (3) performing bipolar membrane electrolysis by taking a sodium tungstate solution as an anolyte, and mixing the obtained anolyte with ammonia water to obtain the ammonium paratungstate.
The electrolytic cell for bipolar membrane electrolysis in the invention has a plurality of compartments, and adopts a cation electrolytic membrane and a bipolar membrane simultaneously. Wherein, both sides of the bipolar membrane are respectively provided with the functions of an anode and a cathode, so that the anode, the cathode and the bipolar membrane can carry out electrolytic reaction in the electrolytic process of the bipolar membrane.
Wherein, the anode generates oxygen absorption reaction, and the equation is as follows:
4OH - ＝2H 2 O+O 2 +4e - ；
the hydrogen evolution reaction occurs at the cathode, and the equation is as follows:
4H 2 O+4e - ＝4OH - +2H 2 ；
by electrolysis of the anode and cathode to give O 2 And H 2 After proper collection, the obtained product can be respectively used as an oxidant for roasting scheelite/wolframite and a reducing agent for preparing low-valence tungsten oxide.
Bipolar membrane directly decomposes water molecules into H + And OH - The equation is as follows:
H 2 O＝OH - +H + ；
under the action of an electric field, the bipolar membrane can directly decompose water molecules into H + And OH - And hydrogen and oxygen are not generated, and compared with the traditional membrane electrolysis system, the power consumption can be greatly reduced.
According to the preparation method of ammonium paratungstate, provided by the invention, the bipolar membrane electrolysis-ammonia precipitation process is adopted, so that the separation of tungsten and sodium in a sodium tungstate solution can be realized under the condition of not adding any chemical reagent, and an ammonium paratungstate product with the purity higher than 99% can be directly prepared by adding ammonia water. In addition, the bipolar membrane electrolysis-ammonia precipitation process can directly treat high-concentration sodium tungstate feed liquid, thereby greatly reducing the treatment capacity of raw materials, simultaneously realizing the recovery of sodium hydroxide, avoiding the generation of waste water from the source and realizing the low energy consumption and clean preparation of ammonium paratungstate.
As a preferred technical solution of the present invention, the preparation process of the sodium tungstate solution includes:
roasting tungsten raw materials by sodium carbonate, and then leaching by water to obtain the sodium tungstate solution, or directly leaching by sodium hydroxide to obtain the sodium tungstate solution.
In the invention, the preparation method of the sodium tungstate solution comprises two methods: (1) roasting a tungsten raw material and sodium carbonate, and then performing water immersion treatment to obtain a sodium tungstate solution; (2) and (3) directly pressurizing and soaking the tungsten raw material by adopting a sodium hydroxide solution to obtain a sodium tungstate solution.
Preferably, the tungsten feedstock comprises any one of scheelite, wolframite or tungsten-containing catalyst.
Preferably, the concentration of tungsten element in the sodium tungstate solution is 10-400 g/L, for example, 10g/L, 50g/L, 100g/L, 150g/L, 200g/L, 250g/L, 300g/L, 350g/L or 400g/L, but not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the sodium tungstate solution has a sodium concentration of 2.5 to 100g/L, for example, 2.5g/L, 10g/L, 20g/L, 30g/L, 40g/L, 50g/L, 60g/L, 70g/L, 80g/L, 90g/L, or 100g/L, but not limited to the recited values, and other values not recited within the range of values are also applicable.
In the invention, the concentration ratio of tungsten element to sodium element in the sodium tungstate solution is about 4:1, and the sodium tungstate solution satisfying the concentration relation is all suitable for the invention.
Preferably, the catholyte of the bipolar membrane electrolysis comprises a sodium hydroxide solution;
preferably, a cathode solution is obtained after the bipolar membrane electrolysis is finished, and the cathode solution is returned to the preparation process of the sodium tungstate solution.
In the bipolar membrane electrolytic reaction process, the concentration of the cathode sodium hydroxide electrolyte is gradually increased, the cathode solution obtained after the bipolar membrane electrolytic reaction is finished is a concentrated sodium hydroxide solution, and the concentrated sodium hydroxide solution is returned to the preparation process of the sodium tungstate solution, so that the recycling is realized.
Preferably, the concentration of the catholyte is 2 to 100g/L, for example, 2g/L, 10g/L, 20g/L, 30g/L, 40g/L, 50g/L, 60g/L, 70g/L, 80g/L, 90g/L, or 100g/L, but is not limited to the recited values, and other non-recited values within this range are equally applicable.
In the invention, sodium ions in the anolyte pass through a cation exchange membrane and a bipolar membrane to be combined with hydroxide radicals generated by a cathode under the action of an electric field to generate sodium hydroxide, so that the pH of the anolyte is reduced, and WO in the solution 4 2- Gradually polymerising, in turn exhibiting HW 6 O 21 5- 、H 2 W 12 O 42 10- 、H 2 W 12 O 40 6- And the like in various polymerization states. And when the pH value of the anolyte is 1-2, transferring the anolyte with high tungsten/sodium ratio out and mixing the anolyte with ammonia water.
In a preferred embodiment of the present invention, the temperature of the bipolar membrane electrolysis is 20 to 80 ℃, and may be, for example, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range of values are also applicable.
Preferably, the current density of the bipolar membrane electrolysis is 200-2000A/m 2 For example, it may be 200A/m 2 、400A/m 2 、600A/m 2 、800A/m 2 、1000A/m 2 、1200A/m 2 、1400A/m 2 、1600A/m 2 、1800A/m 2 Or 2000A/m 2 However, the numerical values are not limited to the numerical values listed, and other numerical values not listed in the numerical range are also applicable.
The invention limits the current density of bipolar membrane electrolysis to 200-2000A/m 2 When the current density is lower than 200A/m 2 Too long reaction time and low current efficiency due to H produced by electrolysis + Will pass through the cation exchange membrane and contact with the cathode chamber OH - The ions are subjected to neutralization reaction, the current efficiency is reduced, and the waste of electric energy is caused; when the current density is lower than 2000A/m 2 When the current is too large, the electrode polarization voltage increases, which leads to an increase in the electrolytic voltage and a reduction in the electrode life.
Preferably, the membrane is electrolyzed for a time of 1 to 10 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, but not limited to the recited values, and other values not recited within the range of values are also applicable.
As a preferable technical scheme, the ammonium paratungstate solution is obtained by mixing the anode solution and the ammonia water, and the ammonium paratungstate solution is sequentially subjected to cooling, crystallization and filtration treatment to obtain the ammonium paratungstate.
When the ammonium paratungstate solution is crystallized, seed crystals can be added into the ammonium paratungstate solution, and the ammonium paratungstate can be obtained after standing.
Preferably, the ammonia water and the anode solution are mixed in a molar ratio of nitrogen to tungsten of (0.5 to 3):1, for example, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.3:1, 2.5:1, 2.8:1 or 3:1, but not limited to the recited values, and other values not recited in the range of values are also applicable.
The method limits the ammonia water and the anode solution to be mixed according to the molar ratio of nitrogen to tungsten being (0.5-3): 1, and when the molar ratio of nitrogen to tungsten is lower than 0.5:1, the purity of an ammonium paratungstate product is reduced due to the excessively low ammonia amount; when the molar ratio of nitrogen to tungsten is higher than 3:1, the purity of the ammonium paratungstate product is not improved any more, and the continuous increase of the ammonia amount is not helpful for improving the product purity, but rather increases the consumption of ammonia water.
Preferably, the temperature at which the anode solution and the ammonia water are mixed is 30 to 60 ℃, and may be, for example, 30 ℃, 32 ℃, 35 ℃, 38 ℃, 40 ℃, 43 ℃, 45 ℃, 48 ℃, 50 ℃, 52 ℃, 55 ℃, 57 ℃ or 60 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
The method limits the mixing temperature of the anode solution and the ammonia water to be 30-60 ℃, and when the temperature is lower than 30 ℃, the purity of the obtained ammonium paratungstate is reduced, because when the reaction temperature is too low, the reaction rate of the ammonia water and the polymeric tungstate is too slow, and the amount of the generated ammonium paratungstate is very small; when the temperature is higher than 60 ℃, the purity of the obtained ammonium paratungstate is also reduced, because sodium ammonium paratungstate begins to be generated when the temperature is higher than 60 ℃, so that the purity of the ammonium paratungstate product is reduced. Therefore, it is shown that when the anode solution is mixed with aqueous ammonia to perform ammonia precipitation, the temperature needs to be controlled within a specific range to obtain high-purity ammonium paratungstate.
Preferably, the mixing of the anodic solution with the aqueous ammonia is carried out under stirring.
Preferably, the stirring rate is 100-500rpm/min, such as 100rpm/min, 150rpm/min, 200rpm/min, 250rpm/min, 300rpm/min, 350rpm/min, 400rpm/min, 450rpm/min or 500rpm/min, but is not limited to the recited values, and other non-recited values within the range are equally applicable.
Preferably, the stirring time is 1 to 5 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, mother liquor and the ammonium paratungstate are respectively obtained after the filtration treatment, dilute sodium tungstate solution and ammonia gas are respectively obtained after the mother liquor is subjected to deamination treatment, the dilute sodium tungstate solution is recycled into the sodium tungstate solution, and the ammonia gas is dissolved in water and then returns to the process of mixing the anode solution and the ammonia water.
In the invention, no wastewater or other solid wastes are generated in the bipolar membrane electrolysis-ammonia precipitation process, and the crystallized mother liquor can be recycled, thereby realizing 100 percent recycle of tungsten.
As a preferable technical solution of the present invention, the preparation method comprises:
(1) taking a sodium tungstate solution with tungsten concentration of 10-400 g/L and sodium concentration of 2.5-100 g/L as an anolyte, taking sodium hydroxide with concentration of 2-100 g/L as a catholyte, and at the temperature of 20-80 ℃, taking 200-2000A/m 2 Performing bipolar membrane electrolysis for 1-10 h at the current density;
(2) after the bipolar membrane electrolysis is finished, returning the obtained cathode solution to the preparation process of the sodium tungstate solution, transferring the obtained anode solution, and stirring and mixing ammonia water and the anode solution for 1-5 hours at a nitrogen-tungsten molar ratio of (0.5-3) to 1 at a rotation speed of 100-500rpm/min and a temperature of 30-60 ℃ to obtain an ammonium paratungstate solution;
(3) and (3) sequentially cooling, crystallizing and filtering the ammonium paratungstate solution obtained in the step (2) to obtain mother liquor and ammonium paratungstate respectively, deaminating the mother liquor to obtain dilute sodium tungstate solution and ammonia gas respectively, recycling the dilute sodium tungstate solution to the sodium tungstate solution, and dissolving the ammonia gas in water and then returning to the process of mixing the anode solution with ammonia water.
In a second aspect, the present invention provides an ammonium paratungstate, which is prepared by the preparation method of the first aspect.
In a third aspect, the present invention provides a bipolar membrane electrolysis apparatus for carrying out the preparation method of the first aspect, comprising an electrolysis cell, wherein an anode chamber, at least one single electrolysis chamber and a cathode chamber are connected in series in sequence through a bipolar membrane in the electrolysis cell, and an anode electrode and a cathode electrode are respectively inserted into the anode chamber and the cathode chamber.
The single electrolysis chamber comprises an acid chamber, an alkali chamber and a cation exchange membrane positioned between the acid chamber and the alkali chamber, wherein anolyte is injected into the anode chamber and the acid chamber, and catholyte is injected into the cathode chamber and the alkali chamber.
In the invention, bipolar membranes are arranged between the anode chamber and the acid chamber of the adjacent single electrolysis chamber, between the alkali chamber of the single electrolysis chamber and the acid chamber of the adjacent single electrolysis chamber, and between the cathode chamber and the alkali chamber of the adjacent single electrolysis chamber; when the anode electrode and the cathode electrode are communicated with a power supply, the anode electrode and the cathode electrode are subjected to an electrolysis reaction together with the bipolar membrane.
Specifically, the two ends of the electrolytic cell are respectively provided with an anode chamber and a cathode chamber, a plurality of single electrolytic chambers are arranged between the anode chamber and the cathode chamber, the acid chamber of each single electrolytic chamber is equivalent to the anode chamber, the alkali chamber is equivalent to the cathode chamber, and a cation exchange membrane is arranged between the acid chamber and the alkali chamber, so that each single electrolytic chamber can complete the electrolytic reaction on sodium tungstate. Meanwhile, bipolar membranes are arranged among the anode chamber, the single electrolysis chambers and the cathode chamber, and two sides of each bipolar membrane are respectively used as an anode electrode and a cathode electrode, so that the anode chamber, the single electrolysis chambers and the cathode chamber can be electrically connected in series only by respectively inserting the anode electrode and the cathode electrode into the anode chamber and the cathode chamber, and the energy consumption is greatly reduced while the yield of high-purity ammonium paratungstate prepared by membrane electrolysis is increased.
In a preferred embodiment of the present invention, the number of the single electrolytic cells is 1 to 25, for example, 1, 5, 10, 15, 20 or 25, but the number is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.
The number of the single electrolysis chambers is limited to 1-25, because when the number of the single electrolysis chambers is more than 25, the voltage value applied to the anode electrode and the cathode electrode is too large, and the anode electrode, the cathode electrode, the bipolar membrane or the cation exchange membrane can be damaged.
As a preferred embodiment of the present invention, the cation exchange membrane comprises a dupont N series cation exchange membrane or an asahi nitroxide F series cation exchange membrane.
Preferably, the bipolar membrane comprises a tyrant TRJBM type bipolar membrane.
As a preferable technical solution of the present invention, the anode electrode includes a ruthenium-plated mesh titanium electrode or a platinum-plated mesh titanium electrode.
Preferably, the cathode electrode comprises any one of a mesh carbon steel electrode, a nickel electrode or a nickel-plated carbon steel electrode.
Compared with the prior art, the invention has the following beneficial effects:
according to the ammonium paratungstate, the preparation method thereof and the bipolar membrane electrolysis device, the bipolar membrane electrolysis-ammonia precipitation process is adopted, so that the separation of tungsten and sodium in a sodium tungstate solution can be realized under the condition of not adding any chemical reagent, and an ammonium paratungstate product with the purity higher than 99% can be directly prepared by adding ammonia water. In addition, the bipolar membrane electrolysis-ammonia precipitation process can directly treat high-concentration sodium tungstate feed liquid, thereby greatly reducing the treatment capacity of raw materials, simultaneously realizing the recovery of sodium hydroxide, avoiding the generation of waste water from the source and realizing the low energy consumption and clean preparation of ammonium paratungstate.
Drawings
FIG. 1 is a schematic structural diagram of a bipolar membrane electrolysis device for preparing ammonium paratungstate according to an embodiment of the present invention.
Fig. 2 is a process flow diagram of a method for preparing ammonium paratungstate according to embodiments 1 to 8 of the present invention.
FIG. 3 is an XRD pattern of ammonium paratungstate prepared in example 1 of the present invention.
Wherein, 1-anode chamber; 2-an acid chamber; 3-an alkali chamber; 4-a cathode chamber; 5-an anode electrode; 6-bipolar membrane; 7-a cation exchange membrane; 8-cathode electrode.
Detailed Description
It is to be understood that in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be taken as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate a number of the indicated technical features. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
It should be noted that, in the description of the present invention, unless otherwise explicitly specified or limited, the terms "disposed," "connected" and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
In one embodiment, the invention provides a bipolar membrane electrolysis device for preparing ammonium paratungstate, as shown in figure 1, the bipolar membrane electrolysis device comprises an electrolysis bath, wherein an anode chamber 1, at least one single electrolysis chamber and a cathode chamber 4 are connected in series in sequence through a bipolar membrane 6, and an anode electrode 5 and a cathode electrode 8 are respectively inserted into the anode chamber 1 and the cathode chamber 4.
The single electrolysis chamber comprises an acid chamber 2, an alkali chamber 3 and a cation exchange membrane 7 positioned between the acid chamber 2 and the alkali chamber 3, anolyte is injected into the anode chamber 1 and the acid chamber 2, and catholyte is injected into the cathode chamber 4 and the alkali chamber 3.
In the invention, bipolar membranes 6 are arranged between the anode chamber 1 and the acid chamber 2 of the adjacent single electrolysis chamber, between the alkali chamber 3 of the single electrolysis chamber and the acid chamber 2 of the adjacent single electrolysis chamber, and between the cathode chamber 4 and the alkali chamber 3 of the adjacent single electrolysis chamber; when the anode electrode 5 and the cathode electrode 8 are communicated with a power supply, the electrolysis reaction is carried out together with the bipolar membrane 6.
Specifically, the two ends of the electrolytic cell are respectively provided with an anode chamber 1 and a cathode chamber 4, a plurality of single electrolytic chambers are arranged between the anode chamber 1 and the cathode chamber 4, an acid chamber 2 of each single electrolytic chamber is equivalent to the anode chamber 1, an alkali chamber 3 is equivalent to the cathode chamber 4, and a cation exchange membrane 7 is arranged between the acid chamber 2 and the alkali chamber 3, so that each single electrolytic chamber can complete the electrolytic reaction on sodium tungstate. Meanwhile, bipolar membranes 6 are arranged among the anode chamber 1, the single electrolysis chambers and the cathode chamber 4, and two sides of each bipolar membrane 6 are respectively used as an anode electrode 5 and a cathode electrode 8, so that the anode chamber 1, the single electrolysis chambers and the cathode chamber 4 can be electrically connected in series only by respectively inserting the anode electrode 5 and the cathode electrode 8 into the anode chamber 1 and the cathode chamber 4, and the energy consumption is greatly reduced while the yield of high-purity ammonium paratungstate prepared by membrane electrolysis is increased.
Furthermore, the number of the single electrolysis chambers is 1-25. The number of the single electrolysis chambers is limited to 1-25, because when the number of the single electrolysis chambers is more than 25, the voltage value applied to the anode electrode 5 and the cathode electrode 8 is too large, which can cause damage to the anode electrode 5, the cathode electrode 8, the bipolar membrane 6 or the cation exchange membrane 7.
Further, the cation exchange membrane 7 includes a dupont N series cation exchange membrane 7 or an asahi nitroxide F series cation exchange membrane 7; the bipolar membrane 6 comprises a tyrant TRJBM type bipolar membrane 6; the anode electrode 5 comprises a ruthenium-plated mesh titanium electrode or a platinum-plated mesh titanium electrode; the cathode electrode 8 comprises any one of a mesh carbon steel electrode, a nickel electrode or a nickel-plated carbon steel electrode.
Example 1
The embodiment provides a bipolar membrane electrolysis device, in which a cation exchange membrane 7 and a bipolar membrane 6 are respectively a dupont N117 cation exchange membrane and a tyrting TRJBM type bipolar membrane, and an anode electrode 5 and a cathode electrode 8 are respectively a titanium-plated platinum electrode and a carbon steel electrode; the number of single electrolysis chambers in the bipolar membrane electrolysis device is 15.
Based on the above bipolar membrane electrolysis apparatus, this embodiment also provides a preparation method of ammonium paratungstate, as shown in fig. 2, the preparation method includes:
(1) roasting scheelite by sodium carbonate, then carrying out water leaching and impurity removal to obtain a sodium tungstate solution with a tungsten concentration of 188g/L and a sodium concentration of 49g/L as an anolyte, respectively adding the sodium tungstate solution into an anode chamber 1 and an acid chamber 2 of a bipolar membrane electrolysis device, respectively adding sodium hydroxide with a concentration of 40g/L as a catholyte into a cathode chamber 4 and an alkali chamber 3 of the bipolar membrane electrolysis device, and carrying out water leaching and impurity removal at a temperature of 40 ℃ and 1000A/m 2 The current density of (2) is subjected to bipolar membrane electrolysis for 4 hours;
(2) after the bipolar membrane electrolysis is finished, returning the obtained cathode solution (concentrated sodium hydroxide solution) to the preparation process of the sodium tungstate solution, transferring the obtained anode solution (solution with high tungsten/sodium ratio), and stirring and mixing the anode solution and ammonia water for 1 hour at the rotation speed of 300rpm/min and the temperature of 39 ℃ according to the molar ratio of nitrogen to tungsten of 3:1 to obtain an ammonium paratungstate solution;
(3) and (3) sequentially cooling, crystallizing and filtering the ammonium paratungstate solution obtained in the step (2) to obtain mother liquor and ammonium paratungstate respectively, deaminating the mother liquor to obtain dilute sodium tungstate solution and ammonia gas respectively, recycling the dilute sodium tungstate solution to the sodium tungstate solution, and dissolving the ammonia gas in water and then returning to the process of mixing the anode solution with ammonia water.
In this example, XRD characterization of the crystal obtained after cooling crystallization is performed, as shown in FIG. 3, to obtain a compound of formula (NH) 4 ) 10 (H 2 W 12 O 42 )·4H 2 Ammonium paratungstate crystal product of O.
Example 2
The embodiment provides a bipolar membrane electrolysis device, wherein a cation exchange membrane 7 and a bipolar membrane 6 in the bipolar membrane electrolysis device are an Asahi nitre F8080 cation exchange membrane and a Tirun TRJBM type bipolar membrane respectively, and an anode electrode 5 and a cathode electrode 8 are a titanium platinized electrode and a nickel electrode respectively; the number of single electrolysis chambers in the bipolar membrane electrolysis device is 20.
Based on the bipolar membrane electrolysis apparatus, this embodiment further provides a preparation method of ammonium paratungstate, as shown in fig. 2, the preparation method includes:
(1) taking wolframite as a raw material, adopting sodium hydroxide solution to directly carry out pressure leaching and then carrying out impurity removal to obtain a sodium tungstate solution with the tungsten concentration of 309g/L and the sodium concentration of 81g/L as anolyte, respectively adding the sodium tungstate solution into an anode chamber 1 and an acid chamber 2 of a bipolar membrane electrolysis device, respectively adding sodium hydroxide with the sodium concentration of 90g/L as catholyte into a cathode chamber 4 and an alkali chamber 3 of the bipolar membrane electrolysis device, and at the temperature of 50 ℃, at 950A/m 2 4h of bipolar membrane electrolysis;
(2) after the bipolar membrane electrolysis is finished, returning the obtained cathode solution (concentrated sodium hydroxide solution) to the preparation process of the sodium tungstate solution, transferring the obtained anode solution (solution with high tungsten/sodium ratio), and stirring and mixing the anode solution and ammonia water for 3 hours at the rotation speed of 200rpm/min and the temperature of 47 ℃ according to the molar ratio of nitrogen to tungsten of 2:1 to obtain an ammonium paratungstate solution;
(3) and (3) sequentially cooling, crystallizing and filtering the ammonium paratungstate solution obtained in the step (2) to obtain mother liquor and ammonium paratungstate respectively, deaminizing the mother liquor to obtain dilute sodium tungstate solution and ammonia gas respectively, recycling the dilute sodium tungstate solution into the sodium tungstate solution, and dissolving the ammonia gas in water and then returning to the process of mixing the anode solution and ammonia water.
Example 3
The embodiment provides a bipolar membrane electrolysis device, wherein a cation exchange membrane 7 and a bipolar membrane 6 in the bipolar membrane electrolysis device are an Asahi nitre F8080 cation exchange membrane and a Tingrun TRJBM type bipolar membrane respectively, and an anode electrode 5 and a cathode electrode 8 are a titanium platinized electrode and a nickel-plated electrode respectively; the number of single electrolysis chambers in the bipolar membrane electrolysis device is 10.
Based on the above bipolar membrane electrolysis apparatus, this embodiment also provides a preparation method of ammonium paratungstate, as shown in fig. 2, the preparation method includes:
(1) taking scheelite as a raw material, adopting sodium hydroxide solution to directly carry out pressure leaching and then carrying out impurity removal to obtain sodium tungstate solution with the tungsten concentration of 262g/L and the sodium concentration of 70g/L as anolyte, respectively adding the sodium tungstate solution into an anode chamber 1 and an acid chamber 2 of a bipolar membrane electrolysis device, respectively adding sodium hydroxide with the sodium concentration of 90g/L as catholyte into a cathode chamber 4 and an alkali chamber 3 of the bipolar membrane electrolysis device, and carrying out pressure leaching at the temperature of 63 ℃ and 1350A/m 2 The current density of (2) is adopted to carry out bipolar membrane electrolysis for 6 hours;
(2) after the bipolar membrane electrolysis is finished, returning the obtained cathode solution (concentrated sodium hydroxide solution) to the preparation process of the sodium tungstate solution, transferring the obtained anode solution (solution with high tungsten/sodium ratio), and stirring and mixing the anode solution and ammonia water for 2 hours at the rotation speed of 400rpm/min and the temperature of 47 ℃ according to the molar ratio of nitrogen to tungsten of 1:1 to obtain an ammonium paratungstate solution;
(3) and (3) sequentially cooling, crystallizing and filtering the ammonium paratungstate solution obtained in the step (2) to obtain mother liquor and ammonium paratungstate respectively, deaminizing the mother liquor to obtain dilute sodium tungstate solution and ammonia gas respectively, recycling the dilute sodium tungstate solution into the sodium tungstate solution, and dissolving the ammonia gas in water and then returning to the process of mixing the anode solution and ammonia water.
Example 4
The embodiment provides a bipolar membrane electrolysis device, wherein a cation exchange membrane 7 and a bipolar membrane 6 in the bipolar membrane electrolysis device are an Asahi nitre F8080 cation exchange membrane and a Tirun TRJBM type bipolar membrane respectively, and an anode electrode 5 and a cathode electrode 8 are a titanium platinized electrode and a nickel electrode respectively; the number of single electrolysis chambers in the bipolar membrane electrolysis device is 12.
Based on the above bipolar membrane electrolysis apparatus, this embodiment also provides a preparation method of ammonium paratungstate, as shown in fig. 2, the preparation method includes:
(1) roasting wolframite by sodium carbonate, then carrying out water leaching and impurity removal to obtain a sodium tungstate solution with the tungsten concentration of 115g/L and the sodium concentration of 29g/L, which is taken as an anolyte, respectively adding the sodium tungstate solution into an anode chamber 1 and an acid chamber 2 of a bipolar membrane electrolysis device, taking sodium hydroxide with the concentration of 36g/L as a catholyte, respectively adding the sodium tungstate solution into a cathode chamber 4 and an alkali chamber 3 of the bipolar membrane electrolysis device, and carrying out water leaching and impurity removal at the temperature of 73 ℃ and at the temperature of 800A/m 2 The current density of (2) is subjected to bipolar membrane electrolysis for 4 hours;
(2) after the bipolar membrane electrolysis is finished, returning the obtained cathode solution (concentrated sodium hydroxide solution) to the preparation process of the sodium tungstate solution, transferring the obtained anode solution (solution with high tungsten/sodium ratio), and stirring and mixing the anode solution and ammonia water for 2 hours at the rotation speed of 400rpm/min and the temperature of 42 ℃ according to the molar ratio of nitrogen to tungsten of 1:1 to obtain an ammonium paratungstate solution;
(3) and (3) sequentially cooling, crystallizing and filtering the ammonium paratungstate solution obtained in the step (2) to obtain mother liquor and ammonium paratungstate respectively, deaminizing the mother liquor to obtain dilute sodium tungstate solution and ammonia gas respectively, recycling the dilute sodium tungstate solution into the sodium tungstate solution, and dissolving the ammonia gas in water and then returning to the process of mixing the anode solution and ammonia water.
Example 5
The embodiment provides a bipolar membrane electrolysis device, wherein a cation exchange membrane 7 and a bipolar membrane 6 in the bipolar membrane electrolysis device are respectively a DuPont N117 cation exchange membrane and a Tingrun TRJBM type bipolar membrane, and an anode electrode 5 and a cathode electrode 8 are respectively a titanium platinum-plated electrode and a carbon steel electrode; the number of single electrolysis chambers in the bipolar membrane electrolysis device is 5.
Based on the above bipolar membrane electrolysis apparatus, this embodiment also provides a preparation method of ammonium paratungstate, as shown in fig. 2, the preparation method includes:
(1) taking scheelite as a raw material, adopting sodium hydroxide solution to directly carry out pressure leaching and then remove impurities to obtain a sodium tungstate solution with the tungsten concentration of 219g/L and the sodium concentration of 56g/L as anolyte, respectively adding the sodium tungstate solution into an anode chamber 1 and an acid chamber 2 of a bipolar membrane electrolysis device, respectively adding sodium hydroxide with the sodium concentration of 53g/L as catholyte into a cathode chamber 4 and an alkali chamber 3 of the bipolar membrane electrolysis device, and carrying out pressure leaching at 73 ℃ and 800A/m 2 The current density of (2) is subjected to bipolar membrane electrolysis for 4 hours;
(2) after the bipolar membrane electrolysis is finished, returning the obtained cathode solution (concentrated sodium hydroxide solution) to the preparation process of the sodium tungstate solution, transferring the obtained anode solution (solution with high tungsten/sodium ratio), and stirring and mixing the anode solution and ammonia water for 1 hour at the rotation speed of 500rpm/min and the temperature of 40 ℃ according to the molar ratio of nitrogen to tungsten of 2:1 to obtain an ammonium paratungstate solution;
(3) and (3) sequentially cooling, crystallizing and filtering the ammonium paratungstate solution obtained in the step (2) to obtain mother liquor and ammonium paratungstate respectively, deaminating the mother liquor to obtain dilute sodium tungstate solution and ammonia gas respectively, recycling the dilute sodium tungstate solution to the sodium tungstate solution, and dissolving the ammonia gas in water and then returning to the process of mixing the anode solution with ammonia water.
Example 6
The embodiment provides a bipolar membrane electrolysis device, wherein a cation exchange membrane 7 and a bipolar membrane 6 in the bipolar membrane electrolysis device are an Asahi nitre F8090 cation exchange membrane and a Tirun TRJBM type bipolar membrane respectively, and an anode electrode 5 and a cathode electrode 8 are a titanium platinum-plated electrode and a nickel electrode respectively; the number of single electrolysis chambers in the bipolar membrane electrolysis device is 25.
Based on the bipolar membrane electrolysis apparatus in the above embodiment, this example provides a preparation method of ammonium paratungstate, as shown in fig. 2, the preparation method includes:
(1) roasting scheelite by sodium carbonate, then carrying out water leaching and impurity removal to obtain sodium tungstate solution with the tungsten concentration of 373g/L and the sodium concentration of 98g/L, which is taken as anolyte, respectively adding the sodium tungstate solution into an anode chamber 1 and an acid chamber 2 of a bipolar membrane electrolysis device, and taking sodium hydroxide with the concentration of 83g/L as catholyteAdding into cathode chamber 4 and alkali chamber 3 of bipolar membrane electrolysis device, respectively, at 43 deg.C at 1500A/m 2 The current density of the anode is 8 hours;
(2) after the bipolar membrane electrolysis is finished, returning the obtained cathode solution (concentrated sodium hydroxide solution) to the preparation process of the sodium tungstate solution, transferring the obtained anode solution (solution with high tungsten/sodium ratio), and stirring and mixing the anode solution and ammonia water for 3 hours at the rotation speed of 200rpm/min and the temperature of 51 ℃ according to the molar ratio of nitrogen to tungsten of 3:1 to obtain an ammonium paratungstate solution;
(3) and (3) sequentially cooling, crystallizing and filtering the ammonium paratungstate solution obtained in the step (2) to obtain mother liquor and ammonium paratungstate respectively, deaminizing the mother liquor to obtain dilute sodium tungstate solution and ammonia gas respectively, recycling the dilute sodium tungstate solution into the sodium tungstate solution, and dissolving the ammonia gas in water and then returning to the process of mixing the anode solution and ammonia water.
Example 7
The embodiment provides a bipolar membrane electrolysis device, wherein a cation exchange membrane 7 and a bipolar membrane 6 in the bipolar membrane electrolysis device are an Asahi nitre F8090 cation exchange membrane and a Tirun TRJBM type bipolar membrane respectively, and an anode electrode 5 and a cathode electrode 8 are a titanium platinum-plated electrode and a nickel electrode respectively; the number of single electrolysis chambers in the bipolar membrane electrolysis device is 18.
Based on the above bipolar membrane electrolysis apparatus, this embodiment also provides a preparation method of ammonium paratungstate, as shown in fig. 2, the preparation method includes:
(1) roasting scheelite by sodium carbonate, then carrying out water leaching and impurity removal to obtain a sodium tungstate solution with a tungsten concentration of 400g/L and a sodium concentration of 100g/L as an anolyte, respectively adding the sodium tungstate solution into an anode chamber 1 and an acid chamber 2 of a bipolar membrane electrolysis device, respectively adding sodium hydroxide with a sodium concentration of 100g/L as a catholyte into a cathode chamber 4 and an alkali chamber 3 of the bipolar membrane electrolysis device, and carrying out treatment at a temperature of 20 ℃ and 200A/m 2 The current density of (2) is subjected to bipolar membrane electrolysis for 1 h;
(2) after the bipolar membrane electrolysis is finished, returning the obtained cathode solution (concentrated sodium hydroxide solution) to the preparation process of the sodium tungstate solution, transferring the obtained anode solution (solution with high tungsten/sodium ratio), and stirring and mixing the anode solution and ammonia water for 2 hours at the rotation speed of 400rpm/min and the temperature of 60 ℃ according to the molar ratio of nitrogen to tungsten of 0.5:1 to obtain an ammonium paratungstate solution;
(3) and (3) sequentially cooling, crystallizing and filtering the ammonium paratungstate solution obtained in the step (2) to obtain mother liquor and ammonium paratungstate respectively, deaminizing the mother liquor to obtain dilute sodium tungstate solution and ammonia gas respectively, recycling the dilute sodium tungstate solution into the sodium tungstate solution, and dissolving the ammonia gas in water and then returning to the process of mixing the anode solution and ammonia water.
Example 8
The embodiment provides a bipolar membrane electrolysis device, wherein a cation exchange membrane 7 and a bipolar membrane 6 in the bipolar membrane electrolysis device are an Asahi nitre F8090 cation exchange membrane and a Tirun TRJBM type bipolar membrane respectively, and an anode electrode 5 and a cathode electrode 8 are a titanium platinum-plated electrode and a nickel electrode respectively; the number of single electrolysis chambers in the bipolar membrane electrolysis device is 1.
Based on the above bipolar membrane electrolysis apparatus, this embodiment also provides a preparation method of ammonium paratungstate, as shown in fig. 2, the preparation method includes:
(1) roasting wolframite by sodium carbonate, then carrying out water leaching for impurity removal to obtain a sodium tungstate solution with the tungsten concentration of 10g/L and the sodium concentration of 2.5g/L as an anolyte, respectively adding the sodium tungstate solution into an anode chamber 1 and an acid chamber 2 of a bipolar membrane electrolysis device, respectively adding sodium hydroxide with the sodium hydroxide concentration of 2g/L as a catholyte into a cathode chamber 4 and an alkali chamber 3 of the bipolar membrane electrolysis device, and at the temperature of 80 ℃, at the temperature of 2000A/m 2 The current density of (2) is 10 h;
(2) after the bipolar membrane electrolysis is finished, returning the obtained cathode solution (concentrated sodium hydroxide solution) to the preparation process of the sodium tungstate solution, transferring the obtained anode solution (solution with high tungsten/sodium ratio), and stirring and mixing the anode solution and ammonia water for 5 hours at the rotation speed of 100rpm/min and the temperature of 30 ℃ according to the molar ratio of nitrogen to tungsten of 3:1 to obtain an ammonium paratungstate solution;
(3) and (3) sequentially cooling, crystallizing and filtering the ammonium paratungstate solution obtained in the step (2) to obtain mother liquor and ammonium paratungstate respectively, deaminizing the mother liquor to obtain dilute sodium tungstate solution and ammonia gas respectively, recycling the dilute sodium tungstate solution into the sodium tungstate solution, and dissolving the ammonia gas in water and then returning to the process of mixing the anode solution and ammonia water.
Example 9
This example differs from example 1 in that the anodic solution and aqueous ammonia were mixed with stirring in step (2) at a nitrogen to tungsten molar ratio of 4:1, and the remaining process parameters and operating steps were the same as in example 1.
Example 10
This example is different from example 1 in that the anodic solution and ammonia water were stirred and mixed in step (2) at a nitrogen to tungsten molar ratio of 0.25:1, and the remaining process parameters and operation steps were the same as in example 1.
Comparative example 1
This comparative example is different from example 1 in that the temperature at which the anode solution and aqueous ammonia are mixed in step (2) is 70 c, and the remaining process parameters and operation steps are the same as those of example 1.
Comparative example 2
This comparative example is different from example 1 in that the temperature of mixing the anode solution with aqueous ammonia in step (2) is 24 deg.c, and the remaining process parameters and operation steps are the same as those of example 1.
The purity of the ammonium paratungstate products prepared in examples 1 to 10 and comparative examples 1 to 2 is shown in Table 1.
TABLE 1
From the data of table 1, one can see:
(1) the purity of the ammonium paratungstate obtained in examples 1 to 8 is higher than 99%, which shows that the bipolar membrane electrolysis-ammonia precipitation process can realize high-efficiency separation of tungsten and sodium in a sodium tungstate solution without adding any chemical reagent, and the ammonium paratungstate product with high purity can be directly prepared by adding ammonia water.
(2) The purity of the ammonium paratungstate obtained in examples 9 and 10 is lower than that of example 1, because the addition amount of the ammonia water in example 9 is too large, when the molar ratio of nitrogen to tungsten is higher than 3:1, the purity of the ammonium paratungstate product is not improved any more, and the continuous increase of the ammonia amount is not helpful for improving the product purity, but rather increases the consumption of the ammonia water. In example 10, the amount of ammonia added was too low, and the purity of the ammonium paratungstate product was lowered due to the insufficient amount of ammonia. Thus, it is shown that controlling the amount of ammonia added within a suitable range is critical to the preparation of a high purity ammonium paratungstate product.
(3) The ammonium paratungstate obtained in comparative examples 1 and 2 had a lower purity than that of example 1, because the temperature at which the anode solution was mixed with the aqueous ammonia was too high in comparative example 1 and too low in comparative example 2. It is shown that the ammonium paratungstate product purity is reduced when the temperature at which the anode solution is mixed with the aqueous ammonia (i.e., the temperature at which ammonia is precipitated) is too high or too low. Therefore, the preparation of a high-purity ammonium tungstate product requires that the temperature at which the anode solution is mixed with the aqueous ammonia be controlled within a specific range.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (9)
1. A preparation method of ammonium paratungstate is characterized by comprising the following steps:
performing bipolar membrane electrolysis by taking a sodium tungstate solution as an anolyte, and mixing the obtained anolyte with ammonia water to obtain the ammonium paratungstate;
the preparation process of the sodium tungstate solution comprises the following steps:
roasting a tungsten raw material by sodium carbonate, and then leaching the roasted tungsten raw material by water to obtain the sodium tungstate solution, or directly leaching the tungsten raw material by sodium hydroxide to obtain the sodium tungstate solution;
the tungsten raw material comprises any one of scheelite, wolframite or tungsten-containing catalyst;
the concentration of tungsten element in the sodium tungstate solution is 10-400 g/L;
the sodium element concentration of the sodium tungstate solution is 2.5-100 g/L;
the cathode electrolyte for bipolar membrane electrolysis comprises a sodium hydroxide solution;
obtaining a cathode solution after the bipolar membrane electrolysis is finished, and returning the cathode solution to the preparation process of the sodium tungstate solution;
the concentration of the catholyte is 2-100 g/L;
the temperature of the bipolar membrane electrolysis is 20-80 ℃;
the current density of the bipolar membrane electrolysis is 200-2000A/m 2 ；
The time of the bipolar membrane electrolysis is 1-10 h.
2. The preparation method according to claim 1, wherein the anode solution is mixed with the ammonia water to obtain an ammonium paratungstate solution, and the ammonium paratungstate solution is sequentially subjected to cooling, crystallization and filtration to obtain the ammonium paratungstate.
3. The method according to claim 1, wherein the aqueous ammonia is mixed with the anode solution in a molar ratio of nitrogen to tungsten of (0.5-3): 1.
4. The method according to claim 1, wherein the temperature of the mixture of the anode solution and the aqueous ammonia is 30 to 60 ℃.
5. The method of claim 1, wherein the mixing of the anode solution and the aqueous ammonia is performed under stirring.
6. The method as claimed in claim 5, wherein the stirring rate is 100-500 rpm/min.
7. The preparation method according to claim 5, wherein the stirring time is 1-5 hours.
8. The preparation method according to claim 2, wherein a mother liquor and the ammonium paratungstate are obtained after the filtration treatment, a dilute sodium tungstate solution and ammonia gas are obtained after the deamination treatment of the mother liquor, the dilute sodium tungstate solution is recycled into the sodium tungstate solution, and the ammonia gas is dissolved in water and then returned to the process of mixing the anode solution with the ammonia water.
9. The method of manufacturing according to claim 1, comprising:
(1) taking a sodium tungstate solution with tungsten concentration of 10-400 g/L and sodium concentration of 2.5-100 g/L as an anolyte, taking sodium hydroxide with concentration of 2-100 g/L as a catholyte, and at the temperature of 20-80 ℃, taking 200-2000A/m 2 Carrying out bipolar membrane electrolysis for 1-10 h at the current density;
(2) after the bipolar membrane electrolysis is finished, returning the obtained cathode solution to the preparation process of the sodium tungstate solution, transferring the obtained anode solution, and stirring and mixing ammonia water and the anode solution for 1-5 hours at the rotation speed of 100 plus materials at 500rpm/min and the temperature of 30-60 ℃ according to the molar ratio of nitrogen to tungsten (0.5-3) to 1 to obtain an ammonium paratungstate solution;
(3) and (3) sequentially cooling, crystallizing and filtering the ammonium paratungstate solution obtained in the step (2) to obtain mother liquor and ammonium paratungstate respectively, deaminizing the mother liquor to obtain dilute sodium tungstate solution and ammonia gas respectively, recycling the dilute sodium tungstate solution into the sodium tungstate solution, and dissolving the ammonia gas in water and then returning to the process of mixing the anode solution and ammonia water.
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