Preparation method of high-purity ammonium paratungstate

Abstract

The application belongs to the technical field of non-ferrous metal smelting, and particularly relates to a preparation method of high-purity ammonium paratungstate, and the specific steps are as follows: low-purity ammonium paratungstate powder is heated to obtain a hydrous tungsten oxide compound; ammonia water and the hydrous tungsten oxide compound are mixed and heated to dissolve, so as to obtain an ammonium tungstate solution; the ammonium tungstate solution is subjected to evaporation crystallization to obtain ammonium paratungstate crystals; during the evaporation crystallization, the ammonium tungstate solution is in an ultrasonic and microwave heating environment, and the temperature and the rotating speed are both reduced with the crystallization; the ammonium paratungstate crystals are washed and dried to obtain high-purity ammonium paratungstate; and the application can improve the purity and the yield of ammonium paratungstate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-ferrous metal smelting, and particularly relates to a preparation method of high-purity ammonium paratungstate. BACKGROUND

[0002] Tungsten is a refractory non-ferrous metal and an important strategic resource, which has excellent properties such as high melting point, high hardness, wear resistance and corrosion resistance. In order to obtain more high-quality tungsten products, the chemical composition and purity of ammonium paratungstate are required to be higher and higher. At present, the production methods of high-purity ammonium paratungstate at home mainly include ion exchange method, extraction method and thermal dissociation-ammonia dissolution.

[0003] The ion exchange method can obtain ammonium paratungstate with high purity, and the product quality is easy to control. However, the inclusion of Na and other impurities in the resin pores is not conducive to cleaning, and the wastewater discharge is large. The extraction method is beneficial to washing Na impurities, does not introduce CI ions and copper salt, but the removal effect of P, As, Mo and other elements is poor. The thermal dissociation-ammonia dissolution method has a short process and simple operation, but the energy consumption is high, and the removal effect is poor only by crystallization. High-purity ammonium paratungstate needs to be obtained by multiple thermal dissociation-ammonia dissolution.

[0004] There are two problems in the ammonium paratungstate solution generated by direct ammonia water dissolution: first, the ammonia dissolution effect of ammonium paratungstate is poor, which leads to low conversion rate, and the obtained ammonium tungstate solution also has low concentration; second, the removal effect is affected. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method of high-purity ammonium paratungstate, which improves the purity and yield of ammonium paratungstate.

[0006] The content of the present application is a preparation method of high-purity ammonium paratungstate. Low-purity ammonium paratungstate powder is heated to obtain a hydrous tungsten oxide compound. Ammonia water and the hydrous tungsten oxide compound are mixed and dissolved by heating to obtain an ammonium tungstate solution. The ammonium tungstate solution is evaporated and crystallized to obtain ammonium paratungstate crystals. During the evaporation and crystallization, the ammonium tungstate solution is in an ultrasonic and microwave heating environment, and the temperature and rotation speed are reduced as the crystallization proceeds. The ammonium paratungstate crystals are washed and dried to obtain high-purity ammonium paratungstate.

[0007] Preferably, the heating temperature of the low-purity ammonium paratungstate powder is 220-300℃, and more preferably, the heating temperature of the low-purity ammonium paratungstate powder is 280℃.

[0008] Preferably, the concentration of the ammonia water is 25-28%.

[0009] Preferably, the temperature for mixing and dissolving the ammonia water and the hydrous tungsten oxide compound is 80-100℃, and preferably 95℃. The solid-liquid weight ratio is controlled between 1:3 and 1:4, and the reaction time is 5-7h.

[0010] Preferably, the frequency of the ultrasound is 25 kHz and the power is 1000 W.

[0011] Preferably, the power of the microwave heating is 500-700 W.

[0012] Preferably, during the evaporation crystallization, the temperature is gradually reduced from 90-110 DEG C to 60-80 DEG C and the rotation speed is reduced from 400-500 r / min to 250-350 r / min.

[0013] Preferably, during the initial concentration stage, the heating temperature is 90-110 DEG C and the stirring speed is 400-500 r / min.

[0014] During the crystal nucleus precipitation stage, the heating temperature is 80-100 DEG C and the stirring speed is 350-450 r / min.

[0015] During the crystal grain growth stage, the heating temperature is 70-90 DEG C and the stirring speed is 300-400 r / min.

[0016] During the crystal grain aging stage, the heating temperature is 60-80 DEG C and the stirring speed is 250-350 r / min.

[0017] Preferably, after the evaporation crystallization, suction filtration is performed to separate the ammonium paratungstate crystals and the mother liquor, thereby obtaining the ammonium paratungstate crystals.

[0018] Preferably, the ammonium paratungstate crystals are washed with water, suction filtered, and dried, thereby obtaining high-purity ammonium paratungstate.

[0019] The present application has the following advantages: the present application uses low-purity ammonium paratungstate as raw material, places it in a furnace at a certain temperature, and then dissolves it in ammonia water for a certain time to obtain an ammonium tungstate solution; the ammonium tungstate solution is subjected to ultrasonic-microwave-assisted stepwise evaporation crystallization to generate a mixture of crystallization mother liquor and ammonium paratungstate; the mixture is subjected to suction filtration, washing, and drying to obtain high-purity ammonium paratungstate.

[0020] The present application controls the temperature and rotation speed during different crystallization stages, reduces the temperature and rotation speed as the crystallization proceeds, and uses the different solubilities of Mo, K, Na, S, P, and other impurities at certain temperatures to make the impurities distribute in the liquid phase.

[0021] The present application simultaneously uses microwave heating and ultrasound to increase the solution supersaturation ratio, thereby increasing the crystallization driving force.

[0022] The present application performs thermal dissociation-ammonia dissolution treatment before evaporation crystallization, because under high-temperature conditions, ammonium paratungstate can be decomposed to obtain highly active amorphous tungsten oxide compounds that are easily soluble in ammonia water, during which a small amount of impurities can be volatilized, which is beneficial to the dissolution of the raw material in ammonia water.

[0023] The segmented evaporation crystallization in the application, the crystallization process can be divided into the formation of crystal nucleus and the growth of crystal in general, and can be further divided into four parts of initial concentration, crystal nucleus precipitation, crystal grain growth and crystal grain aging by controlling the process parameters such as temperature, stirring time and speed, ultrasonic and microwave in different stages of evaporation crystallization, analyzing the distribution rule of impurity elements in solid-liquid phase, and further enriching the impurity elements in the liquid phase as much as possible.

[0024] In the application, temperature is an important factor affecting the size of the crystal, when the supersaturation of the solution is certain, fine crystals are generally obtained when the crystallization temperature is low, and coarse crystals are generally obtained when the crystallization temperature is high, which is caused by the different effects of temperature on the formation and growth rate of crystal nucleus.

[0025] In the application, stirring has a special effect on the generation of ammonium paratungstate by evaporation crystallization, because the generation of ammonium paratungstate from ammonium tungstate is an ammonia loss process, stirring is beneficial to the escape of ammonia, so as to accelerate the reaction of generating ammonium paratungstate; at the same time, stirring and reducing atmosphere ammonia have the effect of inducing nucleation, which is beneficial to reducing the required supersaturation. The stirring intensity affects the size and uniformity of the crystal.

[0026] In the application, the ultrasonic-microwave synergistic device is introduced in the segmented evaporation crystallization, which can make the ammonium paratungstate crystal particles smaller than the ammonium paratungstate crystal particles without ultrasonic-microwave synergistic effect, more uniform and narrower in particle size range. Ultrasonic can accelerate the crystallization speed of ammonium tungstate solution, especially significantly improve the crystal nucleus formation rate and accelerate the time of crystal nucleus appearance. The greater the microwave power, the faster the ammonium tungstate solution is heated, and with the rapid evaporation of water, the supersaturation of the solution increases rapidly, which is beneficial to the generation of crystal, and with the increase of microwave power, the particle size of ammonium paratungstate gradually decreases.

[0027] In summary, the application solves the problem of poor effect of direct ammonia dissolution process of ammonium paratungstate by heat dissociation-ammonia dissolution combined with segmented evaporation crystallization treated by ultrasonic-microwave synergy, which can significantly improve the purity of ammonium paratungstate and increase the direct yield. The heat dissociation-ammonia dissolution combined with segmented evaporation crystallization treatment has higher product purity, fewer evaporation crystallization cycles, more energy saving, lower cost, simple operation process and simple process flow. DETAILED DESCRIPTION

[0028] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below. In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application, and therefore the present application is not limited to the specific embodiments disclosed below.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0030] Embodiment 1

[0031] The embodiment 1 of the present application provides a method for preparing high-purity ammonium paratungstate, which comprises heat dissociation-ammonia solution combined with step-by-step evaporation crystallization treatment of ammonium paratungstate, and the treatment comprises:

[0032] The raw material is 3N ammonium paratungstate powder, 30g of which is weighed and placed in a tube furnace, heated at 280℃ for 50min to obtain a water-containing tungsten oxide compound;

[0033] 200ml of 25% ammonia water is taken, and the heated ammonium paratungstate powder is poured into the ammonia water, which is placed in a high-pressure reaction kettle, and the rotor is rotated to accelerate dissolution. The heating temperature is 95℃, and the solution is obtained after 6h of incubation;

[0034] The ammonium tungstate solution is poured into a beaker in an ultrasonic-microwave environment, the ultrasonic frequency is controlled at 25kHz, the power is 1000W, and the microwave power is 700W. In the initial concentration stage of evaporation crystallization, it is heated to 100℃, and the rotation speed is set to 500r / min; in the crystal nucleus precipitation stage, the heating temperature is adjusted to 90℃, and the rotation speed is 400r / min; in the crystal grain growth stage, the temperature is adjusted to 80℃, and the rotation speed is 350r / min; in the crystal grain aging stage, the heating temperature is adjusted to 70℃, and the rotation speed is 300r / min, until the solution in the reaction is only about one-third, the experiment is stopped, and the crystallization rate is ensured;

[0035] The mixture of ammonium paratungstate crystals and the crystallization mother liquor is filtered with a vacuum pump to separate the mother liquor from the ammonium paratungstate crystals, and the ammonium paratungstate crystals are washed with distilled water and filtered with a vacuum pump, repeated twice, and then the washed ammonium paratungstate crystals are placed in an oven for drying. The final ammonium paratungstate has a purity of >4.5N (99.995%), and the weight of the dried ammonium paratungstate is weighed, compared with the mass of the initially introduced ammonium paratungstate, and the direct yield reaches 52.6%.

[0036] Example 2

[0037] Example 2 of the present application provides a method for preparing high-purity ammonium paratungstate, which comprises heat dissociation-ammonia solution combined with stepwise evaporation crystallization treatment of ammonium paratungstate, and the treatment comprises:

[0038] The raw material is 3N ammonium paratungstate powder, 30g of which is weighed and placed in a tube furnace, heated at 270℃ for 60min to obtain a water-containing tungsten oxide compound;

[0039] 200ml of ammonia water with a concentration of 28% is taken, and the heated ammonium paratungstate powder is poured into the ammonia water, which is placed in a high-pressure reaction kettle, and the rotor is rotated to accelerate dissolution, the heating temperature is 90℃, and after 6h of incubation, an ammonium tungstate solution is obtained;

[0040] The ammonium tungstate solution is poured into a beaker in an ultrasonic environment, the ultrasonic frequency is controlled at 25kHz, the power is 1000W, and the microwave power is 700W. In the initial concentration stage of evaporation crystallization, it is heated to 95℃, and the rotation speed is set to 450r / min; in the crystal nucleus precipitation stage, the heating temperature is adjusted to 90℃, and the rotation speed is 400r / min; in the crystal grain growth stage, the temperature is adjusted to 80℃, and the rotation speed is 300r / min; in the crystal grain aging stage, the heating temperature is adjusted to 70℃, and the rotation speed is 300r / min, until the solution in the reaction is only about one-third, the experiment is stopped, and the crystallization rate is ensured;

[0041] The mixture of ammonium paratungstate crystals and the crystallization mother liquor is filtered with a vacuum pump to separate the mother liquor from the ammonium paratungstate crystals, and the ammonium paratungstate crystals are washed with distilled water and filtered with a vacuum pump, and after repeating twice, the washed ammonium paratungstate crystals are placed in an oven for drying.

[0042] The final ammonium paratungstate has a purity of 4.5N, and the weight of the dried ammonium paratungstate is weighed, which is compared with the mass of the initially introduced ammonium paratungstate, and the direct yield reaches 52.1%.

[0043] Comparative Example 1

[0044] Comparative Example 1 is compared with Example 1, and the comparative experiment without heat dissociation is as follows:

[0045] The raw material is 3N ammonium paratungstate powder, 30g of which is weighed, 200ml of ammonia water with a concentration of 25% is taken, and the ammonium paratungstate powder is poured into the ammonia water, which is placed in a high-pressure reaction kettle, and the rotor is rotated to accelerate dissolution, the heating temperature is 95℃, and after 6h of incubation, an ammonium tungstate solution is obtained;

[0046] The ammonium tungstate solution is poured into a beaker in an ultrasonic environment, the ultrasonic frequency is controlled to be 25 kHz, the power is 1000 W, the microwave power is 700 W, in the initial concentration stage of evaporation crystallization, it is heated to 100°C, the rotation speed is set to 500 r / min; in the crystal nucleus precipitation stage, the heating temperature is adjusted to 90°C, the rotation speed is 400 r / min; in the crystal grain growth stage, the temperature is adjusted to 80°C, the rotation speed is 350 r / min; in the crystal grain aging stage, the heating temperature is adjusted to 70°C, the rotation speed is 300 r / min, until the solution in the reaction is only about one-third left, the experiment is stopped, and the crystallization rate is ensured;

[0047] The mixture of ammonium paratungstate crystals and the crystallization mother liquor is filtered by a vacuum pump to separate the mother liquor from the ammonium paratungstate crystals, and the ammonium paratungstate crystals are washed with distilled water and filtered by a vacuum pump, and after repeating twice, the washed ammonium paratungstate crystals are placed in an oven for drying.

[0048] The purity of the finally obtained ammonium paratungstate reaches 4N, the weight of the dried ammonium paratungstate is weighed, and compared with the weight of the initially introduced ammonium paratungstate, the direct yield is less than 50%.

[0049] Comparative Example 2

[0050] Comparative Example 2 and Example 2 are compared, and a comparative experiment of using a conventional evaporation crystallization instead of a segmented evaporation crystallization is carried out. The specific steps are as follows:

[0051] The raw material is 3N ammonium paratungstate powder, 30g of ammonium paratungstate powder is weighed and placed in a tube furnace, and heated at 270°C for 60min;

[0052] 200ml of ammonia water with a concentration of 28% is taken, the heated ammonium paratungstate powder is poured into the ammonia water, and the mixture is placed in a high-pressure reaction kettle, and the rotor is rotated to accelerate dissolution, the heating temperature is adjusted to 90°C, and after 6h of heat preservation, an ammonium tungstate solution is obtained;

[0053] The ammonium tungstate solution is poured into a beaker in an ultrasonic-microwave environment, the ultrasonic frequency is controlled to be 25 kHz, the power is 1000 W, the microwave power is 700 W, and the evaporation crystallization is heated to 100°C, and the rotation speed is set to 500 r / min, until the solution in the reaction is only about one-third left, the experiment is stopped;

[0054] The mixture of ammonium paratungstate crystals and the crystallization mother liquor is filtered by a vacuum pump to separate the mother liquor from the ammonium paratungstate crystals, and the ammonium paratungstate crystals are washed with distilled water and filtered by a vacuum pump, and after repeating twice, the washed ammonium paratungstate crystals are placed in an oven for drying.

[0055] The purity of the finally obtained ammonium paratungstate is less than 4N, the weight of the dried ammonium paratungstate is weighed, and compared with the weight of the initially introduced ammonium paratungstate, the direct yield reaches 51.1%.

[0056] Example 3

[0057] Example 3 of the present application provides a method for preparing high-purity ammonium paratungstate, which comprises heat dissociation-ammonia solution combined with stepwise evaporation crystallization treatment of ammonium paratungstate, the treatment comprising:

[0058] The raw material is 3N ammonium paratungstate powder, 30g of which is weighed and placed in a tube furnace, heated at 280℃ for 50min to obtain a hydrous tungsten oxide compound;

[0059] Take 200ml of 25% ammonia water, pour the heated ammonium paratungstate powder into the ammonia water, and place it in a high-pressure reaction kettle, use the rotor to accelerate dissolution, heat to 95℃, and keep the temperature for 6h to obtain an ammonium tungstate solution;

[0060] Pour the ammonium tungstate solution into a beaker in an ultrasonic-microwave environment, control the ultrasonic frequency to be 25kHz, the power to be 1000W, and the microwave power to be 700W, in the initial concentration stage of evaporation crystallization, heat to 100℃, and set the rotation speed to 500r / min; in the crystal nucleus precipitation stage, adjust the heating temperature to 100℃, and the rotation speed to 400r / min; in the crystal grain growth stage, adjust the temperature to 80℃, and the rotation speed to 350r / min; in the crystal grain aging stage, adjust the heating temperature to 70℃, and the rotation speed to 250r / min, until the solution in the reaction is only about one-third left, stop the experiment, and ensure the crystallization rate;

[0061] The mixture of ammonium paratungstate crystals and the crystallization mother liquor is filtered with a vacuum pump to separate the mother liquor from the ammonium paratungstate crystals, and the ammonium paratungstate crystals are washed with distilled water and filtered with a vacuum pump, repeated twice, and then the washed ammonium paratungstate crystals are placed in an oven for drying. The final ammonium paratungstate has a purity of 4.5N, and the weight of the dried ammonium paratungstate is weighed, compared with the weight of the initially introduced ammonium paratungstate, and the direct yield is 53.7%.

[0062] Comparative Example 3

[0063] Comparative Example 3 is compared with Example 3, and there is no microwave heating in the stepwise evaporation crystallization. The specific steps are as follows:

[0064] The raw material is 3N ammonium paratungstate powder, 30g of which is weighed and placed in a tube furnace, heated at 280℃ for 50min to obtain a hydrous tungsten oxide compound;

[0065] Take 200ml of 25% ammonia water, pour the heated ammonium paratungstate powder into the ammonia water, and place it in a high-pressure reaction kettle, use the rotor to accelerate dissolution, heat to 95℃, and keep the temperature for 6h to obtain an ammonium tungstate solution;

[0066] The ammonium tungstate solution is poured into a beaker in an ultrasonic environment, water bath heating is adopted, the ultrasonic frequency is controlled to be 25 kHz, the power is 1000 W, in the initial stage of evaporation crystallization concentration, it is heated to 100 DEG C, the rotation speed is set to 500 r / min; in the crystal nucleus precipitation stage, the heating temperature is adjusted to 100 DEG C, the rotation speed is 400 r / min; in the crystal grain growth stage, the temperature is adjusted to 80 DEG C, the rotation speed is 350 r / min; in the crystal grain aging stage, the heating temperature is adjusted to 70 DEG C, the rotation speed is 250 r / min, until the solution in the reaction is only about one-third, the experiment is stopped, and the crystallization rate is ensured;

[0067] The mixture of ammonium paratungstate crystals and the crystallization mother liquor is filtered by a vacuum pump to separate the mother liquor from the ammonium paratungstate crystals, and then the ammonium paratungstate crystals are washed with distilled water and filtered by a vacuum pump, and after repeated twice, the washed ammonium paratungstate crystals are placed in an oven for drying. Finally, the purity of the obtained ammonium paratungstate reaches 4N, and the weight of the dried ammonium paratungstate is weighed, compared with the weight of the initially introduced ammonium paratungstate, and the direct yield reaches 50.3%.

[0068] Example 4

[0069] The embodiment 4 of the present application provides a preparation method of high-purity ammonium paratungstate, which is subjected to heat dissociation-ammonia solution combined segmented evaporation crystallization treatment, and the treatment comprises the following steps:

[0070] The raw material is 3N ammonium paratungstate powder, 30g of the ammonium paratungstate powder is weighed and placed in a tube furnace, and heated at 280 DEG C for 50 min to obtain a water-containing tungsten oxide compound;

[0071] 200ml of ammonia water with a concentration of 25% is taken, the heated ammonium paratungstate powder is poured into the ammonia water, and the mixture is placed in a high-pressure reaction kettle, and the rotation of the rotor is used to accelerate the dissolution, the heating temperature is 95 DEG C, and after 6h of heat preservation, an ammonium tungstate solution is obtained;

[0072] The ammonium tungstate solution is poured into a beaker in an ultrasonic-microwave environment, the ultrasonic frequency is controlled to be 25 kHz, the power is 1000 W, the microwave power is 700 W, in the initial stage of evaporation crystallization concentration, it is heated to 110 DEG C, the rotation speed is set to 500 r / min; in the crystal nucleus precipitation stage, the heating temperature is adjusted to 100 DEG C, the rotation speed is 450 r / min; in the crystal grain growth stage, the temperature is adjusted to 90 DEG C, the rotation speed is 350 r / min; in the crystal grain aging stage, the heating temperature is adjusted to 70 DEG C, the rotation speed is 350 r / min, until the solution in the reaction is only about one-third, the experiment is stopped, and the crystallization rate is ensured;

[0073] The mixture of ammonium paratungstate crystals and crystallization mother liquor is filtered by vacuum pump to separate the mother liquor from the ammonium paratungstate crystals, and the ammonium paratungstate crystals are washed with distilled water and filtered by vacuum pump, and the washed ammonium paratungstate crystals are dried in an oven after being repeated twice. The purity of the obtained ammonium paratungstate is 4.5N, and the weight of the dried ammonium paratungstate is compared with the weight of the initially introduced ammonium paratungstate, and the direct yield is 54.8%.

[0074] Comparative Example 4

[0075] Comparative Example 4 is compared with Example 4, and a comparison test is performed without ultrasound in the segmented evaporation crystallization. The specific steps are as follows:

[0076] The raw material is 3N ammonium paratungstate powder, 30g of which is weighed and placed in a tube furnace, and heated at 280℃ for 50min to obtain a hydrous tungsten oxide compound;

[0077] 200ml of 25% ammonia water is taken, and the heated ammonium paratungstate powder is poured into the ammonia water, which is placed in a high-pressure reaction kettle, and the rotor is rotated to accelerate dissolution. The heating temperature is 95℃, and the ammonium tungstate solution is obtained after being kept for 6h;

[0078] The ammonium tungstate solution is poured into a beaker in a microwave environment, and the microwave power is 700W. In the initial concentration stage of evaporation crystallization, it is heated to 110℃, and the rotation speed is set to 500r / min; in the crystal nucleus precipitation stage, the heating temperature is adjusted to 100℃, and the rotation speed is 450r / min; in the crystal grain growth stage, the temperature is adjusted to 90℃, and the rotation speed is 350r / min; in the crystal grain aging stage, the heating temperature is adjusted to 70℃, and the rotation speed is 350r / min, until the solution in the reaction is only about one-third, the experiment is stopped, and the crystallization rate is ensured;

[0079] The mixture of ammonium paratungstate crystals and crystallization mother liquor is filtered by vacuum pump to separate the mother liquor from the ammonium paratungstate crystals, and the ammonium paratungstate crystals are washed with distilled water and filtered by vacuum pump, and the washed ammonium paratungstate crystals are dried in an oven after being repeated twice. The purity of the obtained ammonium paratungstate is >4.5N, and the weight of the dried ammonium paratungstate is compared with the weight of the initially introduced ammonium paratungstate, and the direct yield is >50.4%.

[0080] Example 5

[0081] Example 5 of the present application provides a method for preparing high-purity ammonium paratungstate, which comprises heat dissociation-ammonia dissolution combined with segmented evaporation crystallization of ammonium paratungstate, and the treatment comprises:

[0082] The raw material is 3N ammonium paratungstate powder, 30g of which is weighed and placed in a tube furnace, and heated at 280℃ for 50min to obtain a hydrous tungsten oxide compound;

[0083] Take 200 ml of 25% ammonia water, pour the heated ammonium paratungstate powder into the ammonia water, and place it in a high-pressure reaction kettle. Use the rotor to accelerate dissolution. Heat to 95°C and keep for 6 hours to obtain an ammonium tungstate solution;

[0084] Pour the ammonium tungstate solution into a beaker in an ultrasonic-microwave environment. Control the ultrasonic frequency at 25 kHz and the power at 1000 W. The microwave power is 700 W. In the initial concentration stage of evaporation crystallization, heat to 95°C and set the rotation speed to 500 r / min. In the crystal nucleus precipitation stage, adjust the heating temperature to 95°C and the rotation speed to 450 r / min. In the crystal grain growth stage, adjust the temperature to 90°C and the rotation speed to 350 r / min. In the crystal grain aging stage, adjust the heating temperature to 60°C and the rotation speed to 350 r / min. Stop the experiment when the solution in the reaction is only about one-third left to ensure the crystallization rate;

[0085] The mixture of ammonium paratungstate crystals and the crystallization mother liquor is filtered with a vacuum pump to separate the mother liquor from the ammonium paratungstate crystals. The ammonium paratungstate crystals are then washed with distilled water and filtered with a vacuum pump. Repeat the washing process twice. Finally, the washed ammonium paratungstate crystals are placed in an oven to dry.

[0086] The final ammonium paratungstate has a purity of 4.5N. Weigh the dried ammonium paratungstate and compare it with the initial weight of the ammonium paratungstate introduced. The direct yield reaches 52.1%.

[0087] Comparative Example 5

[0088] Comparative Example 5 is compared with Example 5. The comparative experiment uses a segmented evaporation crystallization process without ultrasonic-microwave cooperation. The specific steps are as follows:

[0089] The raw material is 3N ammonium paratungstate powder. Weigh 30g of ammonium paratungstate powder and place it in a tube furnace. Heat at 280°C for 50 minutes to obtain a water-containing tungsten oxide compound;

[0090] Take 200 ml of 25% ammonia water, pour the heated ammonium paratungstate powder into the ammonia water, and place it in a high-pressure reaction kettle. Use the rotor to accelerate dissolution. Heat to 95°C and keep for 6 hours to obtain an ammonium tungstate solution;

[0091] The ammonium tungstate solution is poured into a beaker, and in the initial concentration stage of evaporation crystallization, it is heated to 95℃, and the rotation speed is set to 500 r / min; in the crystal nucleus precipitation stage, the heating temperature is adjusted to 95℃, and the rotation speed is 450 r / min; in the crystal grain growth stage, the temperature is adjusted to 90℃, and the rotation speed is 350 r / min; in the crystal grain aging stage, the heating temperature is adjusted to 60℃, and the rotation speed is 350 r / min; until the solution in the reaction is only about one-third left, the experiment is stopped, and the crystallization rate is ensured;

[0092] The mixture of ammonium paratungstate crystals and the crystallization mother liquor is filtered by a vacuum pump to separate the mother liquor from the ammonium paratungstate crystals, and then the ammonium paratungstate crystals are washed with distilled water and filtered by a vacuum pump, and the washing is repeated twice. The washed ammonium paratungstate crystals are placed in an oven for drying. The purity of the finally obtained ammonium paratungstate reaches 4N, and the weight of the dried ammonium paratungstate is weighed. Compared with the weight of the initially introduced ammonium paratungstate, the direct yield reaches 50.1%.

[0093] Example 6

[0094] The embodiment 6 of the present application provides a method for preparing high-purity ammonium paratungstate, which comprises heat dissociation-ammonia solution combined with segmented evaporation crystallization of ammonium paratungstate, and the treatment comprises:

[0095] The raw material is 3N ammonium paratungstate powder, 30g of which is weighed and placed in a tube furnace, and heated at 290℃ for 50min to obtain a water-containing tungsten oxide compound;

[0096] 200ml of ammonia water with a concentration of 26% is taken, and the heated ammonium paratungstate powder is poured into the ammonia water, which is placed in a high-pressure reaction kettle, and dissolved by using a rotor to accelerate the dissolution. The heating temperature is 95℃, and the solution is kept for 5.5h to obtain an ammonium tungstate solution;

[0097] The ammonium tungstate solution is poured into a beaker in an ultrasonic environment, the ultrasonic frequency is controlled to be 25kHz, the power is 1000W, and the microwave power is 700W. In the initial concentration stage of evaporation crystallization, it is heated to 110℃, and the rotation speed is set to 500 r / min; in the crystal nucleus precipitation stage, the heating temperature is adjusted to 95℃, and the rotation speed is 400 r / min; in the crystal grain growth stage, the temperature is adjusted to 90℃, and the rotation speed is 400 r / min; in the crystal grain aging stage, the heating temperature is adjusted to 80℃, and the rotation speed is 350 r / min; until the solution in the reaction is only about one-third left, the experiment is stopped, and the crystallization rate is ensured;

[0098] The mixture of ammonium paratungstate crystals and the crystallization mother liquor is filtered by a vacuum pump to separate the mother liquor from the ammonium paratungstate crystals, and then the ammonium paratungstate crystals are washed with distilled water and filtered by a vacuum pump, and the washing is repeated twice. The washed ammonium paratungstate crystals are placed in an oven for drying.

[0099] The purity of the final obtained ammonium paratungstate reaches 4.5N. The weight of the dried ammonium paratungstate is weighed, and the direct yield reaches 53.2% compared with the mass of the initially introduced ammonium paratungstate.

[0100] Example 7

[0101] Comparative Example 6 is compared with Example 6, which is a comparison experiment of adjusting the temperature and rotation speed in the initial concentration and crystal nucleus precipitation stages. The specific steps are as follows:

[0102] The raw material is 3N ammonium paratungstate powder, 30g of which is weighed and placed in a tube furnace, heated at 290℃ for 50min, to obtain a water-containing tungsten oxide compound;

[0103] 200ml of 26% ammonia water is taken, and the heated ammonium paratungstate powder is poured into the ammonia water, which is placed in a high-pressure reaction kettle, and the rotor is used to accelerate the dissolution. The heating temperature is 95℃, and the solution of ammonium paratungstate is obtained after 5.5h of incubation;

[0104] The ammonium paratungstate solution is poured into a beaker in an ultrasonic environment, the ultrasonic frequency is controlled at 25kHz, the power is 1000W, and the microwave power is 700W. In the initial concentration, crystal nucleus precipitation and crystal grain growth stages of evaporation crystallization, it is heated to 90℃, and the rotation speed is set to 400r / min; in the crystal grain aging stage, the heating temperature is adjusted to 70℃, and the rotation speed is 300r / min, until the solution in the reaction is only about one-third, the experiment is stopped, and the crystallization rate is ensured.

[0105] The mixture of ammonium paratungstate crystals and the crystallization mother liquor is filtered by a vacuum pump to separate the mother liquor from the ammonium paratungstate crystals. The ammonium paratungstate crystals are washed with distilled water and filtered by a vacuum pump. After repeating twice, the washed ammonium paratungstate crystals are placed in an oven for drying.

[0106] The purity of the final obtained ammonium paratungstate reaches 4.5N. The weight of the dried ammonium paratungstate is weighed, and the direct yield reaches 53.2% compared with the mass of the initially introduced ammonium paratungstate.

[0107] The technical features of the above-mentioned examples can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above-mentioned examples are not described, but as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0108] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing high-purity ammonium paratungstate, characterized in that, Low-purity ammonium paratungstate powder was heated to obtain a hydrated tungsten oxide compound; ammonia water and the hydrated tungsten oxide compound were mixed and heated to dissolve, yielding an ammonium tungstate solution; the ammonium tungstate solution was evaporated and crystallized to obtain ammonium paratungstate crystals. During evaporation and crystallization, the ammonium tungstate solution was subjected to ultrasonic and microwave heating, and the temperature and rotation speed decreased as crystallization progressed; the ammonium paratungstate crystals were washed and dried to obtain high-purity ammonium paratungstate; during the evaporation and crystallization process... In the initial concentration stage, the heating temperature is 90~110℃ and the stirring speed is 400~500r / min; During the crystal nucleation stage, the heating temperature is 80~100℃ and the stirring speed is 350~450r / min; During the grain growth stage, the heating temperature is 70~90℃ and the stirring speed is 300~400r / min; During the grain aging stage, the heating temperature is 60~80℃ and the stirring speed is 250~350r / min.

2. The method for preparing high-purity ammonium paratungstate as described in claim 1, characterized in that, The heating temperature for low-purity ammonium paratungstate powder is 220~300℃.

3. The method for preparing high-purity ammonium paratungstate as described in claim 1, characterized in that, The heating temperature for low-purity ammonium paratungstate powder is 280℃.

4. The method for preparing high-purity ammonium paratungstate as described in claim 1, characterized in that, The concentration of ammonia water is 25-28%.

5. The method for preparing high-purity ammonium paratungstate as described in claim 1, characterized in that, Ammonia water and hydrated tungsten oxide compound are mixed and heated to dissolve at a temperature of 80~100℃.

6. The method for preparing high-purity ammonium paratungstate as described in claim 1, characterized in that, The ultrasound frequency is 25kHz and the power is 1000W.

7. The method for preparing high-purity ammonium paratungstate as described in claim 1, characterized in that, The power of microwave heating is 500~700W.

8. The method for preparing high-purity ammonium paratungstate as described in claim 1, characterized in that, After evaporation and crystallization, the ammonium paratungstate crystals and mother liquor are separated by filtration to obtain ammonium paratungstate crystals.