A method for removing molybdenum from tungstate based on a gradient vulcanization process and a tungstate

Abstract

The present application relates to the technical field of separation and purification, and particularly relates to a method for removing molybdenum from tungstate based on gradient sulfuration process and tungstate, the method for removing molybdenum comprises the following steps: based on soluble sulfide, a tungstate solution is sulfuration treated; based on soluble copper salt, the tungstate solution after sulfuration treatment is subjected to molybdenum impurity removal; the sulfuration treatment and molybdenum impurity removal are sequentially performed for multiple times, and a high-purity tungstate solution is obtained. The present application solves the problems of low molybdenum concentration in the preparation process of ultra-high-purity tungstate, low tungstate recovery rate, high energy consumption, harsh conditions and the like, adopts the gradient sulfuration molybdenum removal technology, realizes deep sulfuration of the low molybdenum concentration in the solution, improves the molybdenum removal rate and removal depth, and achieves good removal effect on the low molybdenum concentration.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of separation and purification, and particularly relates to a method for removing molybdenum from tungstate based on a gradient sulfidation process and tungstate. BACKGROUND

[0002] Metal tungsten has a wide application prospect in the field of special steel, semiconductor, etc. For example, high-purity tungsten has the advantages of high electron migration resistance, good high-temperature stability, and high electron emission coefficient, and is a key material for replacing copper to become a new generation of semiconductor chip diffusion barrier and bonding layer.

[0003] Molybdenum and tungsten are both elements of group VIB, and tungsten and molybdenum have more similar chemical properties compared with general adjacent period elements of the same group, which are called "similar elements". Molybdenum is the most difficult impurity to remove in the preparation process of high-purity tungsten. The existence of molybdenum will affect the conductivity of tungsten and have an adverse effect on the application of tungsten. The molybdenum content in ultra-high-purity tungsten used in the semiconductor field is required to be less than 0.1 ppm.

[0004] In the prior art, the traditional tungsten metallurgy process uses the property difference of "tungsten is oxygen-loving and molybdenum is sulfur-loving" to develop a selective precipitation method: preparing sulfides of the two elements that produce molybdenum and oxides of tungsten, and further separating molybdenum to realize the purification of tungsten. However, this method cannot meet the requirement of molybdenum content less than 0.1 ppm in ultra-high-purity tungsten, and generally uses a multiple crystallization method for further purification. The multiple crystallization method needs to "dissolve-crystallize" the soluble paratungstate (such as ammonium paratungstate APT) for more than several times to reach the required molybdenum concentration. However, the paratungstate (such as ammonium paratungstate APT) is difficult to dissolve in ammonia water, which requires high-pressure extreme environment and large energy consumption; at the same time, in order to ensure the product molybdenum removal rate, the single crystallization rate control is relatively low, resulting in a direct recovery rate of qualified ultra-high-purity ammonium paratungstate less than 60%. Therefore, there is a need in the market for a method for removing molybdenum from tungstate solution with high recovery rate and energy saving. SUMMARY

[0005] In view of the above analysis, the present application aims to provide a method for removing molybdenum from tungstate based on a gradient sulfidation process, which solves at least one of the problems of deep removal of extremely low concentration molybdenum in the preparation process of ultra-high-purity tungstate, low recovery rate of tungstate, high energy consumption, and harsh conditions.

[0006] The main purpose of the present application is achieved by the following technical solutions:

[0007] A method for removing molybdenum from tungstate based on a gradient sulfidation process, comprising:

[0008] sulfidation treatment of the tungstate solution based on soluble sulfide;

[0009] molybdenum impurity removal of the tungstate solution after sulfidation treatment based on soluble copper salt;

[0010] The sulfidation treatment and molybdenum removal are performed multiple times in sequence to obtain high-purity tungstate.

[0011] Preferably, the sulfidation treatment of the tungstate solution comprises adding an excess of a sulfidation reagent so that the molybdenum content in the sulfidation product is less than 0.1 ppm. 2- The molar ratio is more than 85%.

[0012] Preferably, the molybdenum removal of the tungstate solution after the sulfidation treatment comprises adding an excess of a soluble copper salt so that the molybdenum removal rate in the tungstate solution is more than 80%.

[0013] Preferably, the method for removing molybdenum from tungstate based on the gradient sulfidation process comprises:

[0014] Step 1: adding a sulfidation reagent to the tungstate solution for sulfidation treatment;

[0015] Step 2: adding a soluble copper salt to the solution after the sulfidation treatment for molybdenum removal to obtain a tungstate solution after molybdenum removal;

[0016] Step 3: using the tungstate solution after molybdenum removal in Step 2 as the raw material to be treated in Step 1, and performing multiple sequential treatments in the order of Step 1-Step 2.

[0017] Preferably, the sulfidation reagent is any one of sodium sulfide or ammonium sulfide.

[0018] Preferably, the amount of the sulfidation reagent satisfies that the molar concentration of the sulfidation reagent is 1×10 2 to 4×10 5 times the molar concentration of molybdenum in the tungstate solution.

[0019] Preferably, the soluble copper salt is one or more of copper sulfate, copper nitrate and copper chloride.

[0020] Preferably, the amount of the soluble copper salt satisfies that the molar concentration of the soluble copper salt is 4 times to 14 times the molar concentration of molybdenum in the tungstate solution.

[0021] Preferably, the sulfidation time of the sulfidation treatment is 24h to 32h, the sulfidation temperature is 30℃ to 70℃, and / or the molybdenum removal time of the first molybdenum removal is 8h to 12h, and the molybdenum removal temperature is 35℃ to 65℃.

[0022] A tungstate prepared by the method for removing molybdenum from tungstate based on the gradient sulfidation process, wherein the content of molybdenum impurities in the tungstate is less than 0.1ppm.

[0023] Compared with the prior art, the present application can at least achieve one of the following beneficial effects:

[0024] (1) The present application adopts the stepwise vulcanization to remove molybdenum, so that the molybdenum vulcanization reaction and the coprecipitation reaction with copper salt slowly reach a reversible equilibrium, the molybdenum sulfide with deep vulcanization is obtained, and the molybdenum removal rate is improved, and good removal effect is obtained for extremely low concentration molybdenum;

[0025] (2) The present application adopts the soluble copper salt as the molybdenum removal reagent, and the molybdenum sulfide is coprecipitated and the impurities introduced by the vulcanizing reagent in the system are removed at the same time, the conditions are mild, and the molybdenum removal rate is high.

[0026] (3) The present application adopts the "vulcanization-soluble copper salt" stepwise vulcanization molybdenum removal process, and the selective removal of molybdenum can be realized, the soluble tungstate with molybdenum impurity content of 0.05ppm-15ppm can be prepared, and the total yield of tungstate after multiple sequential vulcanization and molybdenum removal is ≥80%, which not only achieves good separation effect, but also ensures high yield, which is much higher than the 60% of the existing process (recrystallization method).

[0027] (4) The present application adopts the "vulcanization-soluble copper salt" stepwise vulcanization molybdenum removal process, and the selective removal of molybdenum can be realized, the high-purity soluble tungstate with molybdenum impurity content <0.1ppm can be prepared, and the total yield of tungstate after multiple sequential vulcanization and molybdenum removal is ≥80%, which not only achieves good separation effect, but also ensures high yield.

[0028] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art upon examination of the following or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and attained by the instrumentalities expressed in the embodiment and particularly pointed out in the written description and claims. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The present application is a process flow diagram for stepwise vulcanization of tungstate solution to remove molybdenum. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present application will be specifically described below in conjunction with the drawings, wherein the drawings constitute a part of the present application and are used to explain the principles of the present application together with the embodiments of the present application, but are not used to limit the scope of the present application.

[0031] The applicant found that:

[0032] On the one hand, the molybdenum vulcanization reaction is a reversible reaction, and contains multiple reaction steps, and generates multiple molybdenum sulfide products, and when the molybdenum concentration is extremely low, the degree of forward progress of the reversible reaction is very low, the vulcanization effect is poor, the content of completely sulfided products in the molybdenum sulfide product is less, and the subsequent impurity removal and tungstate separation effect is poor, so the conventional selective precipitation method is difficult to further improve the separation effect of molybdenum and tungstate (for example, the molybdenum impurity content is less than 0.1ppm).

[0033] On the other hand, in the prior art, the low-temperature insoluble paratungstate (such as ammonium paratungstate) is "dissolved-crystallized" for multiple times by the recrystallization method, which requires high-pressure extreme environment and large energy consumption, and meanwhile, there is a contradiction that it is difficult to achieve high recovery rate and high impurity removal rate at the same time.

[0034] Based on the defects in the prior art, the application discloses a method for removing molybdenum from tungstate based on a gradient sulfidation process, which comprises the following steps:

[0035] Based on the soluble sulfide, the tungstate solution is sulfidized; based on the soluble copper salt, the tungstate solution after the sulfidization is treated to remove molybdenum; the sulfidization and the molybdenum removal are sequentially performed for multiple times to obtain a high-purity tungstate solution.

[0036] In the implementation, the soluble sulfide and the molybdenum impurities in the tungstate solution are subjected to molybdenum sulfidation reaction to generate a molybdenum sulfidation product; the soluble copper salt and sulfur generate copper sulfide precipitation, and the copper sulfide reacts with the molybdenum sulfidation product to generate a precipitate, thereby completing the separation of molybdenum from the tungstate solution system and the purification of the tungstate solution; the sulfidization and the molybdenum removal are performed for multiple times to further remove the molybdenum impurities in the tungstate solution.

[0037] Specifically, the molybdenum sulfidation reaction process using the soluble sulfide as a sulfidation reagent is as follows:

[0038]

[0039]

[0040]

[0041]

[0042]

[0043] wherein x is 1-3, and MoO x S 4-x 2- The molybdenum sulfidation product can be any one of (1)-(3).

[0044] The soluble copper salt and MoS4 2- The coprecipitation reaction satisfies:

[0045] MoS4 2- + CuS →Mo x Cu y S z ↓+S 2- (6)

[0046] The applicant finds that due to the reversible reaction in the sulfidation process, there are always un-sulfidized molybdate ions in the solution, and the sulfidation product is MoO3S 2-The amount of molybdenum ions not completely sulfidized will directly affect the subsequent impurity removal effect, so the one-time sulfidation cannot achieve deep removal of molybdenum.

[0047] Preferably, the sulfidation treatment of the tungstate solution comprises: adding an excess of the sulfidation reagent, so that the sulfidation product in the tungstate solution is MoS4 2- The molar ratio is above 85%.

[0048] Specifically, the amount of the sulfidation reagent satisfies: the molar concentration of the sulfidation reagent is 1×10 2 ~ 4×10 5 ~ 4×10

[0049] Preferably, the amount of the sulfidation reagent changes dynamically with the molybdenum concentration, and the lower the molybdenum concentration, the higher the amount of the sulfidation reagent.

[0050] Specifically, the sulfidation time of the sulfidation process is 24h~32h.

[0051] Specifically, the sulfidation temperature is 30℃~70℃.

[0052] Correspondingly, corresponding to the gradient sulfidation process, after each sulfidation, a molybdenum impurity removal treatment is performed: the amount of the soluble copper salt changes dynamically with the molybdenum concentration, and the lower the molybdenum concentration, the higher the amount of the soluble copper salt.

[0053] Preferably, the molybdenum impurity removal process of the soluble copper salt on the tungstate solution comprises: adding an excess of the soluble copper salt, so that the molybdenum removal rate in the tungstate solution is above 80%.

[0054] Specifically, the amount of the soluble copper salt satisfies: the molar concentration of the soluble copper salt is 4 times~14 times the molar concentration of molybdenum in the tungstate solution.

[0055] Preferably, the amount of the soluble copper salt changes dynamically with the molybdenum concentration, and the lower the molybdenum concentration, the higher the amount of the soluble copper salt.

[0056] Specifically, the molybdenum removal time of the molybdenum impurity removal process is 8h~12h.

[0057] Specifically, the molybdenum removal temperature is 35℃~65℃.

[0058] It can be understood that the excess of the sulfidation reagent can ensure that most of the molybdenum ions exist in the form of MoS4 2- , the sulfidation degree is relatively complete, and it is beneficial to the formation of the sulfomolybdate precipitate.

[0059] It can be understood that the sulfidation process of molybdenum itself is a slow and reversible process, and when the molybdenum ion concentration is low, the reaction rate will slow down, and the sulfidation reaction will proceed to the right more slowly, so a longer reaction time is required. Sufficient sulfidation time can make molybdenum more fully sulfidized into MoS4 2-This ensures the effectiveness of subsequent molybdenum removal.

[0060] Understandably, an excess of soluble copper salts can ensure sufficient precipitation of molybdenum ions, while the excess Cu... 2+ Small amount, appropriate excess of Cu 2+ S can be added during the vulcanization process 2- It combines to form CuS precipitate, and CuS contributes to the precipitation of MoS4. 2- The precipitation process reduces the amount of copper ions remaining in the solution: Copper ions combine with sulfur ions or thiomolybdate ions in the solution to form precipitates, and the sulfur content in the solution is significantly higher than that of copper, which helps to reduce the amount of copper remaining in the solution.

[0061] It is understandable that the molybdenum removal process takes 8 to 12 hours to remove molybdenum, which allows for the precipitation of molybdenum as much as possible while saving time, thereby achieving the purpose of removing molybdenum.

[0062] In one feasible implementation, the molybdenum content in the raw material tungstate is 100ppm to 330.0ppm, the initial molybdenum concentration in the solution prepared by dissolving the tungstate is 10mg / L≤Mo≤100mg / L, and the amount of sulfiding agent used satisfies the following: the molar concentration of the sulfiding agent is 100 to 1000 times the molar concentration of molybdenum in the tungstate solution.

[0063] During implementation, an excessive amount of sulfiding reagent within this range results in MoS4 in the sulfidation products. 2- The molar ratio is above 90%.

[0064] Specifically, the amount of soluble copper salt used should meet the following requirement: the molar concentration of the soluble copper salt should be 3 to 4 times the molar concentration of molybdenum in the tungstate solution.

[0065] During implementation, the excess soluble copper salt in this range resulted in a molybdenum removal rate of over 90%, with the molybdenum impurity content in the tungstate solution ranging from 1 mg / L to 10 mg / L. After crystallization and concentration, the molybdenum impurity content in the tungstate was 10 ppm to 33.33 ppm.

[0066] In one feasible implementation, the molybdenum impurity content in the raw material tungstate is 10ppm to 33.33ppm, and the initial molybdenum concentration in the tungstate solution prepared after dissolution is 1mg / L≤Mo<10mg / L. The amount of sulfiding reagent used satisfies the following condition: the molar concentration of the sulfiding reagent is 1000 to 5000 times the molar concentration of molybdenum in the tungstate solution.

[0067] During implementation, an excessive amount of sulfiding reagent within this range results in MoS4 in the sulfidation products. 2- The molar ratio is above 90%.

[0068] Specifically, the amount of sulfiding reagent used should meet the following requirement: the molar concentration of the soluble copper salt should be 4 to 6 times the molar concentration of molybdenum in the tungstate solution.

[0069] In the implementation, the excess of soluble copper salt in the range makes the removal rate of molybdenum above 90%, the content of molybdenum in the tungstate solution is between 0.1 mg / L and 1 mg / L, and the content of molybdenum in the tungstate after crystallization and concentration is between 1.00 ppm and 3.33 ppm.

[0070] In a feasible implementation, the content of molybdenum in the raw tungstate is between 1.00 ppm and 3.33 ppm, the initial molybdenum concentration in the tungstate solution after dissolution is 0.1 mg / L≤Mo<1 mg / L, and the amount of sulfuration reagent satisfies that the molar concentration of the sulfuration reagent is 5×10 3 4 times the molar concentration of molybdenum in the tungstate solution.

[0071] In the implementation, the excess of sulfuration reagent in the range makes the molar ratio of MoS4 2- in the sulfuration product above 90%.

[0072] Specifically, the amount of sulfuration reagent satisfies that the molar concentration of soluble copper salt is 6 times to 8 times the molar concentration of molybdenum in the tungstate solution.

[0073] In the implementation, the excess of soluble copper salt in the range makes the removal rate of molybdenum above 85%, the content of molybdenum in the tungstate solution is between 0.01 mg / L and 0.1 mg / L, and the content of molybdenum in the tungstate after crystallization and concentration is between 0.1 ppm and 0.5 ppm.

[0074] In a feasible implementation, the content of molybdenum in the raw tungstate is between 0.1 ppm and 0.5 ppm, the initial molybdenum concentration in the tungstate solution after dissolution is 0.01 mg / L≤Mo<0.1 mg / L, and the amount of sulfuration reagent satisfies that the molar concentration of the sulfuration reagent is 6×10 4 5 times the molar concentration of molybdenum in the tungstate solution.

[0075] In the implementation, the excess of sulfuration reagent in the range makes the molar ratio of MoS4 2- in the sulfuration product above 85%.

[0076] Specifically, the amount of sulfuration reagent satisfies that the molar concentration of soluble copper salt is 8 times to 14 times the molar concentration of molybdenum in the tungstate solution.

[0077] In the implementation, the excess of soluble copper salt in the range makes the removal rate of molybdenum above 80%, the content of molybdenum in the tungstate solution is between 0.002 mg / L and 0.02 mg / L, and the content of molybdenum in the tungstate after crystallization and concentration is between 0.02 ppm and 0.1 ppm.

[0078] ​​Compared with the prior art, the present application adopts the gradient vulcanization molybdenum removal technology, so that the molybdenum vulcanization reaction and the copper salt precipitation reaction slowly reach a reversible equilibrium, the molybdenum sulfide of deep vulcanization is obtained, and the molybdenum removal rate is improved, and good removal effect is achieved on extremely low concentration molybdenum.

[0079] Compared with the prior art, the present application adopts the gradient vulcanization molybdenum removal technology, so that the molybdenum vulcanization reaction and the copper salt precipitation reaction slowly reach a reversible equilibrium, the molybdenum sulfide of deep vulcanization is obtained, and the molybdenum removal rate is improved, and good removal effect is achieved on extremely low concentration molybdenum.

[0080] Specifically, the present application discloses a tungstate molybdenum removal method based on a gradient vulcanization process, as shown in the formula (I): Figure 1 As shown in the formula (I), the method comprises the following steps:

[0081] Step 1: adding a vulcanization reagent to a tungstate solution for vulcanization treatment;

[0082] Step 2: adding a soluble copper salt to the solution after the vulcanization treatment for molybdenum removal, to obtain a tungstate solution after molybdenum removal;

[0083] Step 3: taking the tungstate solution after molybdenum removal in step 2 as the raw material to be treated in step 1, and sequentially treating multiple times according to the sequence of step 1-step 2.

[0084] Specifically, the tungstate solution in step 1 is an ammonium tungstate solution or a sodium tungstate solution, wherein the concentration calculated based on WO3 is 100 g / L-250 g / L, and the molybdenum concentration is less than 100 mg / L.

[0085] Specifically, the vulcanization reagent is any one of sodium sulfide or ammonium sulfide.

[0086] Specifically, the soluble copper salt is one or more of copper sulfate, copper chloride and copper nitrate.

[0087] Specifically, due to the excess of the vulcanization reagent in the vulcanization process, S 2- exists in the solution, and the soluble copper salt is also excessive, and copper and the molybdenum ion after vulcanization form a precipitate, and due to the existence of S 2- , copper combines with it to form a CuS precipitate; by controlling the amount of the soluble copper salt, the copper content in the solution can be controlled.

[0088] Preferably, the repetition of step 1 to step 2 in step 3 can be repeated 3-5 times.

[0089] It should be noted that before vulcanization, the tungstate needs to be sampled to detect the molybdenum content; after completing the vulcanization and impurity removal once, sampling is performed again, and the conditions of the next gradient are dynamically adjusted according to the impurity removal effect or it is judged whether the next vulcanization-molybdenum removal needs to be performed.

[0090] Specifically, the above tungstate solution molybdenum removal method further comprises: preparing high-purity tungstate by crystallization and concentration of the purified tungstate solution.

[0091] Specifically, the molybdenum removal rate of the tungstate molybdenum removal method is ≥80%, and the tungstate yield is ≥80%.

[0092] Preferably, the molybdenum removal rate of the tungstate molybdenum removal method is ≥90%.

[0093] It can be understood that, compared with the existing multiple crystallization purification tungstate process, the present application uses gradient sulfuration, and when the molybdenum concentration is not removed to the required concentration, it will enter the next gradient. Regardless of the number of molybdenum removal gradients, the tungstate is in a solution state, and the loss of tungsten is extremely small, so the high yield of ammonium paratungstate can be ensured.

[0094] On the other hand, the present application discloses a high-purity tungstate prepared by the above tungstate molybdenum removal method, and the molybdenum impurity content of the tungstate is 0.05ppm-15ppm.

[0095] Preferably, the molybdenum impurity content of the tungstate is <0.1ppm.

[0096] In order to further illustrate the technical solutions of the present application, the following examples and comparative examples are further provided:

[0097] Example 1

[0098] In this example, commercially available ammonium paratungstate (molybdenum impurity content 120ppm) is used to prepare ammonium tungstate solution (WO3 concentration 150g / L, molybdenum concentration 18mg / L) to remove molybdenum impurities, purify and prepare high-purity ammonium paratungstate, including the following steps:

[0099] Step 1: select 200ml ammonium tungstate solution, select ammonium sulfide as the sulfuration reagent, the addition amount is 1000 times the molar concentration of molybdenum in the tungstate solution, the sulfuration time is 24h, and the sulfuration temperature is 60℃;

[0100] Step 2: after sulfuration, copper chloride is added to the ammonium tungstate solution to remove molybdenum, the addition amount of copper salt is 4 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time is 8h, and the impurity removal temperature is 60℃. After impurity removal, a high-purity ammonium paratungstate solution is obtained, and ammonium paratungstate is prepared by evaporation and crystallization. According to the calculation, the molybdenum removal rate of single sulfuration-molybdenum removal operation under this condition is 89%, and the tungstate yield is 83%. After one-time sequential sulfuration and molybdenum removal, the molybdenum content of the ammonium paratungstate solution is 1.98mg / L, and the ammonium paratungstate is 13.2ppm.

[0101] Example 2

[0102] The present embodiment selects commercially available sodium tungstate (molybdenum impurity content 200 ppm) to prepare a sodium tungstate solution (WO3 concentration 200 g / L, molybdenum concentration 40 mg / L) to remove molybdenum impurities and purify to prepare high-purity sodium tungstate, including the following steps:

[0103] Step 1: Select 100 ml of sodium tungstate solution, select sodium sulfide as the sulfidation reagent, and add an amount of 800 times the molar concentration of molybdenum in the tungstate solution, the sulfidation time is 20 h, and the sulfidation temperature is 60°C;

[0104] Step 2: After sulfidation, copper sulfate is added to the sodium tungstate solution to remove molybdenum, the amount of copper salt added is 4 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time is 8 h, and the impurity removal temperature is 50°C. After impurity removal, a high-purity sodium tungstate solution is obtained, and sodium tungstate is prepared by evaporation and crystallization. Under the above conditions, the single sulfidation-molybdenum removal operation has a molybdenum removal rate of 94%, and the tungstate yield is 82%. After one-time sequential sulfidation and molybdenum removal, the molybdenum content of the sodium tungstate solution after molybdenum removal is detected to be 2.4 mg / L, and the molybdenum content of the sodium tungstate is 12 ppm.

[0105] Example 3

[0106] The present embodiment selects commercially available sodium tungstate (molybdenum impurity content 200 ppm) to prepare a sodium tungstate solution (WO3 concentration 200 g / L, molybdenum concentration 40 mg / L) to remove molybdenum impurities and purify to prepare high-purity sodium tungstate, including the following steps:

[0107] Step 1: Select 100 ml of sodium tungstate solution, select sodium sulfide as the sulfidation reagent, and add an amount of 800 times the molar concentration of molybdenum in the tungstate solution, the sulfidation time is 20 h, and the sulfidation temperature is 60°C;

[0108] Step 2: After sulfidation, copper sulfate is added to the sodium tungstate solution to remove molybdenum, the amount of copper salt added is 4 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time is 8 h, and the impurity removal temperature is 50°C. After impurity removal, a high-purity sodium tungstate solution is obtained, and sodium tungstate is prepared by evaporation and crystallization. Under the above conditions, the single sulfidation-molybdenum removal operation has a molybdenum removal rate of 94%, and the tungstate yield is 82%. After one-time sequential sulfidation and molybdenum removal, the molybdenum content of the sodium tungstate solution after molybdenum removal is detected to be 2.4 mg / L, and the molybdenum content of the sodium tungstate is 12 ppm.

[0109] Example 4

[0110] The present embodiment selects commercially available sodium tungstate (molybdenum impurity content 200 ppm) to prepare a sodium tungstate solution (WO3 concentration 200 g / L, molybdenum concentration 40 mg / L) to remove molybdenum impurities and purify to prepare high-purity sodium tungstate, including the following steps:

[0111] Step 1: Select 100 ml of sodium tungstate solution, select sodium sulfide as the sulfidation reagent, and add an amount of 800 times the molar concentration of molybdenum in the tungstate solution, the sulfidation time is 20 h, and the sulfidation temperature is 60°C;

[0112] Step 2: After sulfidation, copper nitrate is added to the ammonium tungstate solution to remove molybdenum. The amount of copper salt added is 6 times the molar concentration of molybdenum in the tungstate solution. The molybdenum removal time is 8 hours, and the impurity removal temperature is 60°C. After impurity removal, a high-purity ammonium tungstate solution is obtained, and ammonium paratungstate is prepared by evaporation and crystallization. Under the above conditions, the molybdenum removal rate of single sulfidation-molybdenum removal operation is 88%, and the tungstate recovery rate of two sequential sulfidation-molybdenum removal is 83.5%. In this example, the tungstate solution after one sequential sulfidation-molybdenum removal in Example 1 is used as the raw material to be processed. In this example, two sequential sulfidation-molybdenum removal operations are actually performed. The molybdenum content of the ammonium paratungstate solution after molybdenum removal is 0.238 mg / L, and the molybdenum content of ammonium paratungstate is 1.584 ppm.

[0113] Example 5

[0114] In this example, the sodium tungstate solution (molybdenum content of 2.4 mg / L) obtained after purification in Example 2 is used as the raw material to be processed to remove molybdenum impurities and prepare high-purity sodium tungstate. The process includes the following steps:

[0115] Step 1: Select 100 ml of sodium tungstate solution. Sodium sulfide is used as the sulfidation reagent, and the amount added is 5500 times the molar concentration of molybdenum in the tungstate solution. The sulfidation time is 24 hours, and the sulfidation temperature is 60°C.

[0116] Step 2: After sulfidation, copper nitrate is added to the sodium tungstate solution to remove molybdenum. The amount of copper salt added is 6 times the molar concentration of molybdenum in the tungstate solution. The molybdenum removal time is 8 hours, and the impurity removal temperature is 60°C. After impurity removal, a high-purity sodium tungstate solution is obtained, and ammonium paratungstate is prepared by evaporation and crystallization. Under the above conditions, the molybdenum removal rate of single sulfidation-molybdenum removal operation is 88%, and the tungstate recovery rate of two sequential sulfidation-molybdenum removal is 83.5%. In this example, the tungstate solution after one sequential sulfidation-molybdenum removal in Example 1 is used as the raw material to be processed. In this example, two sequential sulfidation-molybdenum removal operations are actually performed. The molybdenum content of the ammonium paratungstate solution after molybdenum removal is 0.238 mg / L, and the molybdenum content of ammonium paratungstate is 1.584 ppm.

[0117] Example 6

[0118] In this example, the ammonium tungstate solution (molybdenum content of 0.238 mg / L) obtained after purification in Example 4 is used as the raw material to be processed to remove molybdenum impurities and prepare high-purity ammonium paratungstate. The process includes the following steps:

[0119] Step 1: Select 100 ml of ammonium tungstate solution. Ammonium sulfide is used as the sulfidation reagent, and the amount added is 40000 times the molar concentration of molybdenum in the tungstate solution. The sulfidation time is 28 hours, and the sulfidation temperature is 60°C.

[0120] Step 2: 100 ml of the ammonium tungstate solution after sulfidation was added with copper sulfate to remove molybdenum, the amount of copper salt added was 8 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time was 10 h, and the impurity removal temperature was 60°C, and high-purity ammonium tungstate solution was obtained after molybdenum removal, and ammonium paratungstate was prepared by evaporation and crystallization. The yield of tungstate after three sequential sulfidation and molybdenum removal was 81%, the molybdenum removal rate of single sulfidation-molybdenum removal operation under this condition was 86.1%, and the molybdenum content of ammonium paratungstate was 0.300 ppm.

[0121] Example 7

[0122] In this example, the sodium tungstate solution (molybdenum content of 0.253 mg / L) obtained after purification in Example 5 was used as the raw material to be treated, and molybdenum impurities were removed to prepare high-purity sodium tungstate, including the following steps:

[0123] Step 1: 100 ml of the ammonium tungstate solution after sulfidation was added with copper sulfate to remove molybdenum, the amount of copper salt added was 8 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time was 10 h, and the impurity removal temperature was 60°C, and high-purity ammonium tungstate solution was obtained after molybdenum removal, and ammonium paratungstate was prepared by evaporation and crystallization. The yield of tungstate after three sequential sulfidation and molybdenum removal was 81%, the molybdenum removal rate of single sulfidation-molybdenum removal operation under this condition was 86.1%, and the molybdenum content of ammonium paratungstate was 0.300 ppm.

[0124] Step 2: 100 ml of the ammonium tungstate solution after sulfidation was added with copper sulfate to remove molybdenum, the amount of copper salt added was 8 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time was 10 h, and the impurity removal temperature was 60°C, and high-purity ammonium tungstate solution was obtained after molybdenum removal, and ammonium paratungstate was prepared by evaporation and crystallization. The yield of tungstate after three sequential sulfidation and molybdenum removal was 81%, the molybdenum removal rate of single sulfidation-molybdenum removal operation under this condition was 86.1%, and the molybdenum content of ammonium paratungstate was 0.300 ppm.

[0125] Example 8

[0126] In this example, the sodium tungstate solution (molybdenum content of 0.253 mg / L) obtained after purification in Example 5 was used as the raw material to be treated, and molybdenum impurities were removed to prepare high-purity sodium tungstate, including the following steps:

[0127] Step 1: 100 ml of the ammonium tungstate solution after sulfidation was added with copper sulfate to remove molybdenum, the amount of copper salt added was 8 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time was 10 h, and the impurity removal temperature was 60°C, and high-purity ammonium tungstate solution was obtained after molybdenum removal, and ammonium paratungstate was prepared by evaporation and crystallization. The yield of tungstate after three sequential sulfidation and molybdenum removal was 81%, the molybdenum removal rate of single sulfidation-molybdenum removal operation under this condition was 86.1%, and the molybdenum content of ammonium paratungstate was 0.300 ppm.

[0128] Step 2: After sulfidation, copper sulfate is added to the ammonium tungstate solution to remove molybdenum. The amount of copper salt added is 12 times the molar concentration of molybdenum in the tungstate solution. The molybdenum removal time is 12 hours, and the impurity removal temperature is 60°C. After impurity removal, a high-purity ammonium tungstate solution is obtained, and ammonium paratungstate is prepared by evaporation and crystallization. Under the above conditions, the molybdenum removal rate of single sulfidation-molybdenum removal operation is 79.8%, and the tungstate yield of four consecutive sulfidation-molybdenum removal is 80.4%. In this example, the tungstate solution after three consecutive sulfidation-molybdenum removal in Example 6 is used as the raw material to be treated. Therefore, the actual process involves four consecutive sulfidation-molybdenum removal. The molybdenum content in the ammonium paratungstate solution after molybdenum removal is 0.0067 mg / L, and the molybdenum content in ammonium paratungstate is 0.061 ppm.

[0129] Example 9

[0130] In this example, the purified sodium tungstate solution obtained in Example 7 (with a molybdenum content of 0.038 mg / L) is used as the raw material to be treated to remove molybdenum impurities and prepare high-purity sodium tungstate. The process includes the following steps:

[0131] Step 1: Select 100 ml of sodium tungstate solution. Sodium sulfide is selected as the sulfidation reagent, and the amount added is 400,000 times the molar concentration of molybdenum in the tungstate solution. The sulfidation time is 32 hours, and the sulfidation temperature is 60°C.

[0132] Step 2: After sulfidation, copper sulfate is added to the sodium tungstate solution to remove molybdenum. The amount of copper salt added is 12 times the molar concentration of molybdenum in the tungstate solution. The molybdenum removal time is 12 hours, and the impurity removal temperature is 60°C. After impurity removal, a high-purity sodium tungstate solution is obtained, and sodium tungstate is prepared by evaporation and crystallization. Under the above conditions, the molybdenum removal rate of single sulfidation-molybdenum removal operation is 80.4%, and the tungstate yield of four consecutive sulfidation-molybdenum removal is 80%. In this example, the tungstate solution after three consecutive sulfidation-molybdenum removal in Example 7 is used as the raw material to be treated. Therefore, the actual process involves four consecutive sulfidation-molybdenum removal. The molybdenum content in the sodium tungstate solution after molybdenum removal is 0.0074 mg / L, and the molybdenum content in sodium tungstate is 0.082 ppm.

[0133] Comparative Example 1

[0134] Compared with Example 1, the difference lies in that the amount of sulfidation reagent added is 80 times the molar concentration of molybdenum in the tungstate solution, and the rest of the conditions are the same. According to the calculation, the molybdenum removal rate of single sulfidation-molybdenum removal operation under the above conditions is 5%, and the tungstate yield is 85%. The molybdenum content in ammonium paratungstate after molybdenum removal is 114 ppm.

[0135] Comparative Example 2

[0136] Compared with Example 1, the difference lies in that the sulfidation time is 12 hours, and the rest of the conditions are the same. According to the calculation, the molybdenum removal rate of single sulfidation-molybdenum removal operation under the above conditions is 58%, and the tungstate yield is 84.6%. The molybdenum content in ammonium paratungstate after molybdenum removal is 50.4 ppm.

[0137] Comparative Example 3

[0138] Comparative Example 3

[0139] Comparative Example 4

[0140] Comparative Example 4

[0141] Comparative Example 5

[0142] Comparative Example 5

[0143] Comparative Example 6

[0144] Comparative Example 6

[0145] Comparative Example 7

[0146] Comparative Example 7

[0147] Comparative Example 8

[0148] Comparative Example 8

[0149] Comparative Example 9

[0150] The difference between the example 6 and the example 7 is that the sulfuration time is 12h, and the rest of the conditions are the same. The calculated single sulfuration-molybdenum removal operation molybdenum removal rate is 45%, the three times sequential sulfuration-molybdenum removal operation tungstate yield is 82.4%, and the detected ammonium paratungstate molybdenum content after molybdenum removal is 1.187ppm.

[0151] Comparative example 10

[0152] The difference between the example 6 and the example 7 is that the sulfuration time is 12h, and the rest of the conditions are the same. The calculated single sulfuration-molybdenum removal operation molybdenum removal rate is 45%, the three times sequential sulfuration-molybdenum removal operation tungstate yield is 82.4%, and the detected ammonium paratungstate molybdenum content after molybdenum removal is 1.187ppm.

[0153] Comparative example 11

[0154] The difference between the example 6 and the example 7 is that the sulfuration time is 12h, and the rest of the conditions are the same. The calculated single sulfuration-molybdenum removal operation molybdenum removal rate is 45%, the three times sequential sulfuration-molybdenum removal operation tungstate yield is 82.4%, and the detected ammonium paratungstate molybdenum content after molybdenum removal is 1.187ppm.

[0155] Comparative example 12

[0156] The difference between the example 6 and the example 7 is that the sulfuration time is 12h, and the rest of the conditions are the same. The calculated single sulfuration-molybdenum removal operation molybdenum removal rate is 45%, the three times sequential sulfuration-molybdenum removal operation tungstate yield is 82.4%, and the detected ammonium paratungstate molybdenum content after molybdenum removal is 1.187ppm.

[0157] Comparative example 13

[0158] The difference between the example 6 and the example 7 is that the sulfuration time is 12h, and the rest of the conditions are the same. The calculated single sulfuration-molybdenum removal operation molybdenum removal rate is 45%, the three times sequential sulfuration-molybdenum removal operation tungstate yield is 82.4%, and the detected ammonium paratungstate molybdenum content after molybdenum removal is 1.187ppm.

[0159] Comparative example 14

[0160] The difference between the example 6 and the example 7 is that the sulfuration time is 12h, and the rest of the conditions are the same. The calculated single sulfuration-molybdenum removal operation molybdenum removal rate is 45%, the three times sequential sulfuration-molybdenum removal operation tungstate yield is 82.4%, and the detected ammonium paratungstate molybdenum content after molybdenum removal is 1.187ppm.

[0161] Comparative example 15

[0162] Compared with Example 8, the difference is that the molybdenum removal time is 6h, and the rest conditions are the same, the calculated molybdenum removal rate is 47.8%, the tungstate yield after four times of sequential vulcanization and molybdenum removal is 80.4%, and the detection shows that the molybdenum content of ammonium paratungstate after molybdenum removal is 0.158ppm.

[0163] From Examples 1-9, it can be seen that the soluble tungstate with the molybdenum impurity content of 0.05ppm-15ppm can be purified and prepared, and the tungstate yield is ≥80%, which ensures a high yield under the excellent separation effect; preferably, the molybdenum content of the purified tungstate is <0.1ppm.

[0164] From the comparison of Examples and Comparative Examples, it can be seen that the reaction conditions other than the relative limited ranges of the raw material ratio and the reaction time in the molybdenum removal process of the sulfuration and the soluble copper salt help to improve the molybdenum impurity removal rate.

[0165] The above is only the preferred specific implementation of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A process for removal of molybdenum as tungstate based on a stepwise sulfidation process, characterized in that, The application relates to a tungstate removal method based on a gradient sulfidation process. The tungstate solution is sulfidized based on a soluble sulfide; The sulfidization and molybdenum removal are sequentially performed for multiple times to obtain high-purity tungstate; the gradient sulfidation and molybdenum removal technology is adopted to make the molybdenum sulfidation reaction and the copper salt precipitation reaction slow to reach a reversible balance, and the molybdenum sulfide is deeply sulfidized; the soluble copper salt is adopted as the molybdenum removal reagent, and the deep removal of the extremely low-concentration molybdenum and the excess copper is realized by adjusting the copper salt amount. The tungstate molybdenum removal method comprises the following steps: Step 1: a sulfidation reagent is added into the tungstate solution to perform sulfidation treatment; Step 2: the soluble copper salt is added into the solution after the sulfidation treatment to perform molybdenum removal, and the tungstate solution after the molybdenum removal is obtained; the molar concentration of the soluble copper salt is 12-14 times that of the molar concentration of the molybdenum in the tungstate solution; the molybdenum removal is performed at 60-65 DEG C for 8-12 hours; The excess amount of sulfuration reagent is added to make the MoS4 2- The sulfuration treatment is carried out at 60-70°C for 24-32 hours with the molar ratio of 85% or more, and the molar concentration of the sulfuration reagent is 3.8x10 5 -4x10 5 -4x10 Step 3: the tungstate solution after the molybdenum removal in step 2 is taken as the raw material to be treated in step 1, and the sequence of step 1-step 2 is sequentially performed for more than 3 times; The prepared ultra-high-purity tungstate contains not more than 0.1 ppm of molybdenum impurities. The molybdenum removal of the tungstate solution after the sulfidation treatment comprises the following steps: the excess soluble copper salt is added into the tungstate solution, and the molybdenum removal rate is not less than 80%.

2. The method for removing molybdenum as tungstate based on a step-sulfidation process according to claim 1, characterized in that, The sulfidation reagent is any one of sodium sulfide or ammonium sulfide.

3. The method for removing molybdenum as tungstate based on a fractional vulcanization process according to claim 2, characterized in that, The soluble copper salt is one or more of copper sulfate, copper nitrate and copper chloride.

4. The method for removing molybdenum as tungstate based on the fractional vulcanization process according to claim 3, characterized in that, The tungstate prepared by the tungstate molybdenum removal method based on the gradient sulfidation process in any one of claims 1-4 contains not more than 0.1 ppm of molybdenum impurities.

5. A tungstate salt, characterized in that, ​

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