Molybdenum removal method in tungstate based on step-wise sulfurization step and tungstate

Abstract

To provide a method for removing molybdenum in tungstate based on step-wise sulfidation by overcoming issues such as the difficulty of removing extremely low concentrations of molybdenum in the producing process of ultra-high purity tungstate, the low recovery rate of tungstic acid, high energy consumption, and harsh conditions; by employing molybdenum removal technology based on staged sulfidation to enable deeply sulfurization of the extremely low concentrations of molybdenum in the solution, thereby enhancing the molybdenum removal rate and completeness, resulting in good removal efficiency for extremely low concentrations of molybdenum.SOLUTION: The method includes a process of sulfidation of a tungstate solution based on soluble sulfides, a process of molybdenum removal from the sulfated tungstate solution based on soluble copper salts, and performing the sulfidation process and molybdenum removal process sequentially multiple times to obtain high-purity tungstate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the field of separation and purification technology, and in particular to a method for removing molybdenum from tungstate based on a stepwise sulfurization process, and to a tungstate. [Background technology]

[0002] Tungsten metal is expected to be widely used in the fields of special steel, semiconductors, etc. For example, high purity tungsten has the advantages of high electromigration resistance, good high temperature stability, high electron emissivity, etc., and plays an important role as the diffusion barrier layer and bonding layer of the new generation semiconductor chip instead of copper.

[0003] Molybdenum and tungsten are group VIB elements, and have more similar chemical properties than their neighboring homologous elements in the periodic table, so they are called "similar elements". Molybdenum is the most difficult impurity to remove during the production of high-purity tungsten. The presence of molybdenum affects the electrical conductivity of tungsten, adversely affecting the application of tungsten, so the molybdenum content of ultra-high purity tungsten used in the semiconductor field must be less than 0.1 ppm.

[0004] In current technology, the traditional tungsten refining process utilizes the difference in the properties of "tungsten's oxygen affinity and molybdenum's sulfur affinity" to prepare molybdenum sulfide from elemental molybdenum, prepare tungsten oxide from elemental tungsten, and then separate the molybdenum to achieve purification of tungsten through selective precipitation. However, this method is far from reaching the requirement that the molybdenum content in ultra-high purity tungsten be less than 0.1 ppm, so further purification is usually performed through multiple crystallization. The multiple crystallization method requires multiple "dissolution and crystallization" of soluble paratungstate (such as ammonium paratungstate APT) to achieve the desired molybdenum concentration. However, paratungstates that are difficult to dissolve in ammonia (ammonium paratungstate APT) require an extreme high-pressure environment and large amounts of energy consumption, and the single crystallization rate must be kept relatively low to ensure the molybdenum removal rate of the product, resulting in a recovery rate of less than 60% of the qualified ultra-high purity ammonium paratungstate. Therefore, the industry is seeking a method to remove molybdenum from tungstate solutions with high recovery rate and energy saving. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above analysis, the present invention aims to propose a method for removing molybdenum from tungstate based on a stepwise sulfurization process, in order to solve at least one of the problems such as the difficulty of removing extremely low concentrations of molybdenum as completely as possible in the production process of ultra-high purity tungstate, the low recovery rate of tungstate, high energy consumption, and harsh conditions. [Means for solving the problem]

[0006] The object of the present invention is mainly achieved by means of the following technical solutions:

[0007] The method for removing molybdenum from tungstate based on a stepwise sulfurization process includes: sulfurizing the tungstate solution based on soluble sulfides; performing molybdenum removal on the sulfided tungstate solution based on a soluble copper salt; and a step of obtaining a high-purity tungstate by sequentially performing the sulfurization step and the molybdenum removal step multiple times.

[0008] Preferably, the step of sulfurizing the tungstate solution comprises adding an excess of sulfurizing agent to obtain MoS4 in the sulfurization product. 2- The molar ratio of

[0009] Preferably, the step of subjecting the sulfurized tungstate solution to molybdenum removal comprises adding an excess of a soluble copper salt to achieve a molybdenum removal rate of 80% or more in the tungstate solution.

[0010] Preferably, the method for removing molybdenum from tungstate based on a stepwise sulfurization process comprises: S1: adding a sulfurizing agent to a tungstate solution to perform a sulfurizing treatment; S2: Adding a soluble copper salt to the sulfurized tungstate solution to remove molybdenum, to obtain a molybdenum-removed tungstate solution; S3: Treating the molybdenum-removed tungstate solution of S2 as the pre-treatment raw material of S1 multiple times according to S1-S2.

[0011] Preferably, the sulfurizing agent is any one of sodium sulfide and ammonium sulfide.

[0012] Preferably, the amount of sulfurizing agent used is such that the molar concentration of the sulfurizing agent is 1×10 of the molar concentration of molybdenum in the tungstate solution. 2 Double ~4×10 5 The condition of doubling is met.

[0013] Preferably, the soluble copper salt is one or more of copper sulfate, copper nitrate and copper chloride.

[0014] Preferably, the amount of soluble copper salt used satisfies the condition that the molar concentration of the soluble copper salt is 4 to 14 times the molar concentration of molybdenum in the tungstate solution.

[0015] Preferably, in the sulfurization treatment, the sulfurization time is set to 24 h to 32 h and the sulfurization temperature is set to 30°C to 70°C, and / or, in the first molybdenum removal, the molybdenum removal time is set to 8 h to 12 h and the molybdenum removal temperature is set to 35°C to 65°C.

[0016] The tungstate produced by the method for removing molybdenum from tungstate based on the stepwise sulfurization process has a molybdenum impurity content of less than 0.1 ppm in the tungstate. Effect of the Invention

[0017] The present invention may achieve at least one of the following beneficial effects over the current art:

[0018] (1) The present invention adopts a molybdenum removal technology based on stepwise sulfurization, which allows the sulfurization reaction of molybdenum and the coprecipitation reaction with copper salt to slowly reach a reversible equilibrium, thereby obtaining deeply sulfurized molybdenum sulfides, thereby improving the molybdenum removal rate and achieving good removal effect for extremely low concentrations of molybdenum.

[0019] (2) The present invention uses a soluble copper salt as a molybdenum removal agent, which undergoes a coprecipitation reaction with molybdenum sulfide and removes impurities such as sulfurizing agents introduced into the system, thereby making the reaction conditions milder and increasing the molybdenum removal rate.

[0020] (3) The present invention adopts a molybdenum removal technology based on stepwise sulfurization of "sulfurization-adding soluble copper salt", thereby selectively removing molybdenum and purifying soluble tungstate with a molybdenum impurity content of 0.05 ppm to 15 ppm. In addition, the total yield of tungstate from which molybdenum has been removed reaches ≥ 80% through multiple successive sulfurization processes, which not only achieves a good separation effect, but also guarantees a much higher yield than the 60% of the current technology (recrystallization method).

[0021] (4) The present invention adopts a molybdenum removal technology based on stepwise sulfurization of "sulfurization-adding soluble copper salt" to selectively remove molybdenum and purify high-purity soluble tungstate with a molybdenum impurity content of <0.1 ppm. In addition, the total yield of tungstate from which molybdenum has been removed reaches ≥80% through multiple successive sulfurization processes, thereby not only achieving a good separation effect but also ensuring a high yield.

[0022] Other features and advantages of the present invention are set forth in the following specification, and some of the advantages will be apparent from the specification or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and attained by the contents particularly pointed out in the examples and drawings of the specification. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a process flow diagram of a method for removing molybdenum from tungstate based on a stepwise sulfurization process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] We will now describe preferred embodiments of the present invention in combination with the drawings, which constitute a part of the present invention and, together with the embodiments of the present invention, explain the principles of the present invention and are not used to limit the scope of the present invention.

[0025] The findings we obtained through our research are as follows:

[0026] On the one hand, the sulfurization reaction of molybdenum, as a reversible reaction, has multiple reaction steps to produce various molybdenum sulfides. When the molybdenum concentration is extremely low, it will proceed in the reverse direction, but the tendency to proceed in the forward direction is very weak, so the sulfurization effect is poor, the content of the complete sulfurization product in the molybdenum sulfide product is low, and the subsequent impurity removal and tungstate separation effects are poor. Therefore, it is difficult for the traditional selective precipitation method to further improve the separation effect of molybdenum and tungstate (for example, the molybdenum impurity content is less than 0.1 ppm).

[0027] On the other hand, the current technology (recrystallization method) requires multiple "dissolution and crystallization" of paratungstates (e.g., ammonium paratungstate), which are difficult to dissolve at low temperatures, and requires an extreme high-pressure environment and large amounts of energy consumption. In addition, it is contradictory in that it does not simultaneously have a high recovery rate and a high impurity removal rate.

[0028] In view of the deficiencies in the current technology, the present invention proposes a method for removing molybdenum from tungstate based on a stepwise sulfurization process.

[0029] The method includes the steps of sulfurizing a tungstate solution based on a soluble sulfide, performing molybdenum removal on the sulfurized tungstate solution based on a soluble copper salt, and sequentially performing the sulfurization step and the molybdenum removal step multiple times to obtain a high-purity tungstate.

[0030] In carrying out the method, the soluble sulfide and the molybdenum impurities in the tungstate solution undergo a molybdenum sulfurization reaction to produce a molybdenum sulfide product; the soluble copper salt reacts with sulfur to produce a copper sulfide precipitate, and the copper sulfide reacts with the molybdenum sulfide product to form a precipitate, thereby completing the steps of separating molybdenum from the tungstate solution system to purify the tungstate solution; and the sulfurization process and the molybdenum removal process are carried out multiple times to further remove the molybdenum impurities in the tungstate solution.

[0031] Specifically, the sulfurization reaction of molybdenum using a soluble sulfide as a sulfurization agent is as follows. [ka]

[0032] Here, set X to 1 to 3 and MoO x S 4-x 2- can be a molybdenum sulfide product represented by any one of reaction formulas (1) to (3).

[0033] Soluble copper salts and MoS4 2- The coprecipitation reaction is carried out according to the following reaction formula: MoS4 2- + CuS →Mo x Cu y S z ↓+S 2- (6)

[0034] Our research shows that due to the existence of reversible reactions in the sulfurization process, there are always unsulfurized molybdate ions in the solution, and the sulfurization product is MoO3S. 2- The number of incompletely sulfurized molybdenum ions directly affects the subsequent impurity removal effect, so it is not possible to achieve complete molybdenum removal in a single sulfurization.

[0035] Preferably, the step of sulfurizing the tungstate solution comprises adding an excess of sulfurizing agent to obtain MoS4 in the sulfurization product. 2- The molar ratio of

[0036] Specifically, the amount of sulfurizing agent used is set so that the molar concentration of the sulfurizing agent is 1×10 of the molar concentration of molybdenum in the tungstate solution. 2 Double ~4×10 5 The condition of doubling is met.

[0037] Preferably, with the dynamic change of the molybdenum concentration, the lower the molybdenum concentration, the more sulfurizing agent is used.

[0038] Specifically, in the sulfurization treatment, the sulfurization time is set to 24 hours to 32 hours, and the sulfurization temperature is set to 30°C to 70°C.

[0039] Therefore, the stepwise sulfurization process corresponds to removing molybdenum after each sulfurization. With the dynamic change of molybdenum concentration, the lower the molybdenum concentration, the more soluble copper salt is used.

[0040] Preferably, the step of subjecting the tungstate solution to molybdenum removal using a soluble copper salt comprises adding an excess of the soluble copper salt to achieve a molybdenum removal rate of 80% or more in the tungstate solution.

[0041] Specifically, the amount of the soluble copper salt used satisfies the condition that the molar concentration of the soluble copper salt is 4 to 14 times the molar concentration of molybdenum in the tungstate solution.

[0042] Preferably, with the dynamics of the molybdenum concentration, the lower the molybdenum concentration, the more soluble copper salt is used.

[0043] Specifically, in the molybdenum removal step, the molybdenum removal time is set to 8 hours to 12 hours, and the molybdenum removal temperature is set to 35°C to 65°C.

[0044] Excessive sulfurization reagent converts most of the molybdenum ions into MoS4 2- It is understood that the relatively complete degree of sulfidation promotes the formation of molybdate sulfide precipitates.

[0045] The sulfurization process of molybdenum itself is a slowly reversible process, and it is understandable that a longer reaction time is required because the reaction rate is slower when the concentration of molybdenum ions is low, which allows the sulfurization reaction to proceed slowly to the right. A sufficient sulfurization time is required to convert molybdenum more completely into MoS4 2- to ensure the subsequent molybdenum removal effect.

[0046] The excess of soluble copper salts ensures complete precipitation of molybdenum ions, and Cu 2+ The excess of Cu becomes smaller, but the appropriate excess 2+ S added during the sulfurization process 2- and form CuS precipitates, and in addition, CuS forms MoS4 2- It is understandable that the copper ions will promote the precipitation of sulfur ions or sulfomolybdic acid groups in the solution to form precipitates, and the sulfur element in the solution is in great excess compared to the copper element, which helps to reduce the copper residue in the solution.

[0047] It is understandable that in the molybdenum removal process, the molybdenum removal time is set to 8h-12h, so as to allow molybdenum to precipitate as much as possible to achieve the purpose of molybdenum removal, based on time saving.

[0048] In one possible embodiment, the molybdenum content in the raw tungstate is set to 100 ppm to 330.0 ppm, and the initial molybdenum concentration in the tungstate solution after preparation for dissolution is set to 10 mg / L≦Mo≦100 mg / L. The amount of sulfurizing agent used satisfies the condition that the molar concentration of the sulfurizing agent is 100 to 1000 times the molar concentration of molybdenum in the tungstate solution.

[0049] In practice, excess sulfurization reagent within this range reduces the amount of MoS4 in the sulfurization product. 2- The molar ratio of exceeds 90%.

[0050] Specifically, the amount of the soluble copper salt used satisfies the condition that the molar concentration of the soluble copper salt is three to four times the molar concentration of molybdenum in the tungstate solution.

[0051] In practice, the excess soluble copper salt within this range ensures that the molybdenum removal rate exceeds 90%, the molybdenum impurity content in the tungstate solution reaches 1 mg / L-10 mg / L, and the molybdenum impurity content in the tungstate after crystallization and concentration reaches 10 ppm-33.33 ppm.

[0052] In one possible embodiment, the molybdenum content in the raw tungstate is set to 10 ppm to 33.33 ppm, and the initial molybdenum concentration in the tungstate solution after preparation for dissolution is set to 1 mg / L≦Mo≦10 mg / L. The amount of sulfurizing agent used satisfies the condition that the molar concentration of the sulfurizing agent is 1000 to 5000 times the molar concentration of molybdenum in the tungstate solution.

[0053] In practice, excess sulfurization reagent within this range reduces the amount of MoS4 in the sulfurization product. 2- The molar ratio of exceeds 90%.

[0054] Specifically, the amount of the soluble copper salt used satisfies the condition that the molar concentration of the soluble copper salt is 4 to 6 times the molar concentration of molybdenum in the tungstate solution.

[0055] In practice, the excess soluble copper salt within this range ensures that the molybdenum removal rate exceeds 90%, the molybdenum impurity content in the tungstate solution reaches 0.1 mg / L-1 mg / L, and the molybdenum impurity content in the tungstate after crystallization and concentration reaches 1.00 ppm-3.33 ppm.

[0056] In one possible embodiment, the molybdenum content in the raw tungstate is set to 1.00 ppm to 3.33 ppm, and the initial molybdenum concentration in the tungstate solution after preparation for dissolution is set to 0.1 mg / L≦Mo≦1 mg / L. The amount of sulfurizing agent used is set such that the molar concentration of the sulfurizing agent is 5×10 of the molar concentration of molybdenum in the tungstate solution. 3 Double ~6×10 4 The condition of doubling is met.

[0057] In practice, excess sulfurization reagent within this range reduces the amount of MoS4 in the sulfurization product. 2- The molar ratio of exceeds 90%.

[0058] Specifically, the amount of the soluble copper salt used satisfies the condition that the molar concentration of the soluble copper salt is 6 to 8 times the molar concentration of molybdenum in the tungstate solution.

[0059] In practice, the excess soluble copper salt within this range ensures that the molybdenum removal rate exceeds 85%, the molybdenum impurity content in the tungstate solution reaches 0.01 mg / L-0.1 mg / L, and the molybdenum impurity content in the tungstate after crystallization and concentration reaches 0.1 ppm-0.5 ppm.

[0060] In one possible embodiment, the molybdenum content in the raw tungstate is set to 0.1 ppm to 0.5 ppm, and the initial molybdenum concentration in the tungstate solution after preparation for dissolution is set to 0.01 mg / L≦Mo≦0.1 mg / L. The amount of sulfurizing agent used is set such that the molar concentration of the sulfurizing agent is 6×10 of the molar concentration of molybdenum in the tungstate solution. 4 Double ~4×10 5 The condition of doubling is met.

[0061] In practice, excess sulfurization reagent within this range reduces the amount of MoS4 in the sulfurization product. 2- The molar ratio of exceeds 85%.

[0062] Specifically, the amount of the soluble copper salt used satisfies the condition that the molar concentration of the soluble copper salt is 8 to 14 times the molar concentration of molybdenum in the tungstate solution.

[0063] In practice, the excess soluble copper salt within this range ensures that the molybdenum removal rate exceeds 80%, the molybdenum impurity content in the tungstate solution reaches 0.002mg / L-0.02mg / L, and the molybdenum impurity content in the tungstate after crystallization and concentration reaches 0.02ppm-0.1ppm.

[0064] Compared with the current technology, the present invention adopts a molybdenum removal technology based on stepwise sulfurization, which allows the molybdenum sulfurization reaction and the coprecipitation reaction with copper salt to slowly reach a reversible equilibrium, thereby obtaining deeply sulfurized molybdenum sulfides, thereby increasing the molybdenum removal rate and achieving good removal effect for extremely low concentrations of molybdenum.

[0065] Compared with the current technology, the present invention uses a soluble copper salt as a molybdenum removal agent and adjusts the amount of copper salt used to deeply remove very low concentrations of molybdenum and excess copper simultaneously, making the reaction conditions milder and increasing the molybdenum removal rate.

[0066] Specifically, as shown in FIG. 1, the present invention proposes a method for removing molybdenum from tungstate based on a stepwise sulfurization process.

[0067] The method comprises: S1: adding a sulfurizing agent to a tungstate solution to perform a sulfurizing treatment; S2: Adding a soluble copper salt to the sulfurized tungstate solution to remove molybdenum, to obtain a molybdenum-removed tungstate solution; S3: Treating the molybdenum-removed tungstate solution of S2 as the pre-treatment raw material of S1 multiple times according to S1-S2.

[0068] Specifically, the tungstate solution described in S1 is an ammonium tungstate solution or a sodium tungstate solution, the concentration of the solution calculated based on WO3 is 100 g / L-250 g / L, and the molybdenum concentration is less than 100 mg / L.

[0069] Specifically, the sulfurizing agent is either sodium sulfide or ammonium sulfide.

[0070] Specifically, the soluble copper salt is one or more of copper sulfate, copper nitrate, and copper chloride.

[0071] Specifically, there is an excess of sulfurizing agent in the sulfurization process, and there is S in the solution. 2- Since there is an excess of soluble copper salts, after the copper reacts with the sulfurized molybdenum ions to form a precipitate, S 2- The presence of copper causes the 2- to form a CuS precipitate; this allows for the possibility of controlling the copper content in solution by controlling the amount of soluble copper salt used.

[0072] Preferably, in S3, the sequential process according to S1-S2 may be repeated 3 to 5 times.

[0073] It should be noted that the tungstate needs to be sampled to detect the molybdenum content before sulfurization. After one round of sulfurization and impurity removal is completed, sampling is carried out again to dynamically adjust the conditions for the next stage according to the impurity removal effect, or to determine whether sulfide-molybdenum removal is required in the next stage.

[0074] Specifically, the method for removing molybdenum from tungstate further includes a step of crystallizing and concentrating the purified tungstate solution to prepare a high-purity tungstate.

[0075] Specifically, in the method for removing molybdenum from tungstate, the molybdenum removal rate reaches ≧80%, and the yield of tungstate reaches ≧80%.

[0076] Preferably, in the method for removing molybdenum from tungstate, the molybdenum removal rate reaches ≧90%.

[0077] Compared with the current technology of purifying tungstate by multiple crystallization, the present invention adopts a stepwise sulfurization process, and enters the next stage when the molybdenum removal process does not reach the required concentration. It can be understood that no matter how many times the molybdenum removal process is performed, the tungstate is in solution, and the loss of tungsten element is very small, which can guarantee a high yield of ammonium paratungstate.

[0078] Another aspect of the present invention provides a high-purity tungstate produced by the method for removing molybdenum from a tungstate, and the content of molybdenum impurities in the tungstate is suppressed to 0.05 ppm to 15 ppm.

[0079] Preferably, the molybdenum impurity content in the tungstate is kept to <0.1 ppm.

[0080] We provide the following examples and comparative examples to further illustrate the technical solutions of the present invention. EXAMPLES

[0081] In this embodiment, ammonium tungstate solution (WO3 concentration 150g / L, molybdenum concentration 18mg / L) is prepared using commercially available ammonium paratungstate (content of molybdenum impurity 120ppm), and the molybdenum impurity is removed to produce high-purity ammonium paratungstate. The steps are as follows:

[0082] S1: Select 200ml of ammonium tungstate solution, select ammonium sulfide as the sulfurizing agent, add the sulfurizing agent in an amount equivalent to 1000 times the molar concentration of molybdenum in the tungstate solution, set the sulfurizing time to 24h, and set the sulfurizing temperature to 60°C.

[0083] S2: Add copper chloride to the ammonium tungstate solution after sulfurization to remove molybdenum, and add copper salt in an amount that is four times the molar concentration of molybdenum in the tungstate solution, set the molybdenum removal time to 8h, and set the impurity removal temperature to 60°C. After removing the impurities, obtain a high-purity ammonium paratungstate solution, and prepare ammonium paratungstate through evaporation and crystallization. According to calculations, under these conditions, for a single sulfide-molybdenum removal process, the molybdenum removal rate reaches 89%, and the yield of tungstate reaches 83%. After a single step of sulfurization-molybdenum impurity removal, the molybdenum content in the ammonium paratungstate solution reaches 1.98mg / L, and the molybdenum content in the ammonium paratungstate reaches 13.2ppm. EXAMPLES

[0084] In this embodiment, commercially available sodium tungstate (content of molybdenum impurity is 200 ppm) is used to prepare sodium tungstate solution (WO3 concentration is 200 g / L, molybdenum concentration is 40 mg / L), and the molybdenum impurity is removed to produce high-purity sodium tungstate. The steps are as follows:

[0085] S1: Select 100ml of sodium tungstate solution, select sodium sulfide as the sulfurizing agent, add the sulfurizing agent in an amount that is 800 times the molar concentration of molybdenum in the tungstate solution, set the sulfurizing time to 20h, and set the sulfurizing temperature to 60°C.

[0086] S2: copper sulfate is added to the sodium tungstate solution after sulfurization to remove molybdenum, and the amount of copper salt added is equivalent to four times the molar concentration of molybdenum in the tungstate solution, and the molybdenum removal time is set to 8h and the impurity removal temperature is set to 50°C. After removing the impurities, high-purity sodium tungstate is obtained, and sodium tungstate is produced through evaporation and crystallization. According to calculations, under these conditions, for a single sulfide-molybdenum removal process, the molybdenum removal rate reaches 94%, and the yield of tungstate reaches 82%. After a single step of sulfurization-molybdenum impurity removal, the molybdenum content in the sodium tungstate solution reaches 2.4mg / L, and the molybdenum content in sodium tungstate reaches 12ppm. EXAMPLES

[0087] In this embodiment, commercially available ammonium paratungstate (content of molybdenum impurity is 20 ppm) is used to prepare ammonium tungstate solution (WO3 concentration is 250 g / L, molybdenum concentration is 5 mg / L), and the molybdenum impurities are removed to purify high-purity ammonium paratungstate. The steps are as follows:

[0088] S1: Select 100ml of ammonium tungstate solution, select ammonium sulfide as the sulfurizing agent, add the sulfurizing agent in an amount equivalent to making its molar concentration 4000 times that of the molybdenum in the tungstate solution, set the sulfurizing time to 26h, and set the sulfurizing temperature to 60°C.

[0089] S2: Add copper sulfate to the ammonium tungstate solution after sulfurization to remove molybdenum, and add copper salt in an amount that is equivalent to 8 times the molar concentration of molybdenum in the tungstate solution, set the molybdenum removal time to 10h, and set the impurity removal temperature to 60°C. After removing the impurities, obtain high-purity ammonium paratungstate solution, and prepare ammonium paratungstate through evaporation and crystallization. According to calculations, under these conditions, for a single sulfide-molybdenum removal process, the molybdenum removal rate reaches 89%, and the yield of tungstate reaches 82.5%. After a single step of sulfurization-molybdenum impurity removal, detection shows that the molybdenum content in the ammonium paratungstate solution reaches 0.55mg / L, and the molybdenum content in ammonium paratungstate reaches 2.42ppm. EXAMPLES

[0090] In this example, the ammonium tungstate solution (with molybdenum content of 1.98 mg / L) obtained after purification in Example 1 is selected as the pre-treatment raw material to remove molybdenum impurities so as to purify high-purity ammonium paratungstate. The steps are as follows:

[0091] S1: Select 100ml of ammonium tungstate solution, select ammonium sulfide as the sulfurizing agent, add the sulfurizing agent in an amount equivalent to 6000 times the molar concentration of molybdenum in the tungstate solution, set the sulfurizing time to 24h, and set the sulfurizing temperature to 60°C.

[0092] S2: Add copper nitrate to the ammonium tungstate solution after sulfurization to remove molybdenum, the amount of copper salt added is equivalent to 6 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time is set to 8h, and the impurity removal temperature is set to 60°C. After removing the impurities, a high-purity ammonium paratungstate solution is obtained, and ammonium paratungstate is produced through evaporation and crystallization. According to calculations, the molybdenum removal rate reaches 88% for a single sulfide-molybdenum removal process under these conditions. After two rounds of stepwise sulfurization-molybdenum impurity removal, the yield of tungstate reaches 83.5%. In this embodiment, the tungstate solution after one round of stepwise sulfurization-molybdenum impurity removal in Example 1 is used as the pre-treatment raw material, so it actually undergoes two rounds of stepwise sulfurization-molybdenum impurity removal. Through detection, the molybdenum content in the ammonium paratungstate solution reaches 0.238 mg / L, and the molybdenum content in ammonium paratungstate reaches 1.584 ppm. EXAMPLES

[0093] In this example, the sodium tungstate solution (with molybdenum content of 2.4 mg / L) obtained after purification in Example 2 is selected as the pre-treatment raw material to remove molybdenum impurities so as to purify high-purity sodium paratungstate. The steps are as follows:

[0094] S1: Select 100ml of sodium tungstate solution, select sodium sulfide as the sulfurizing agent, add the sulfurizing agent in an amount equivalent to making its molar concentration 5500 times that of molybdenum in the tungstate solution, set the sulfurizing time to 24h, and set the sulfurizing temperature to 60°C.

[0095] S2: copper nitrate is added to the sodium tungstate solution after sulfurization to remove molybdenum, the amount of copper salt added is equivalent to 6 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time is set to 8h, and the impurity removal temperature is set to 60°C. After removing the impurities, a high-purity sodium paratungstate solution is obtained, and sodium paratungstate is produced through evaporation and crystallization. According to calculations, the molybdenum removal rate reaches 87.2% for a single sulfide-molybdenum removal process under these conditions. After two stages of sulfurization-molybdenum impurity removal, the yield of tungstate reaches 82%. In this embodiment, the tungstate solution after one stage of sulfurization-molybdenum impurity removal in Example 2 is used as the pre-treatment raw material, so it actually undergoes two stages of sulfurization-molybdenum impurity removal. Through detection, the molybdenum content in the sodium paratungstate solution reaches 0.253 mg / L, and the molybdenum content in sodium paratungstate reaches 2.16 ppm. EXAMPLES

[0096] In this example, the ammonium tungstate solution (with molybdenum content of 0.238 mg / L) obtained after purification in Example 4 is selected as the pre-treatment raw material to remove molybdenum impurities so as to purify high-purity ammonium paratungstate. The steps are as follows:

[0097] S1: Select 100ml of ammonium tungstate solution, select ammonium sulfide as the sulfurizing agent, add the sulfurizing agent in an amount that is 40,000 times the molar concentration of molybdenum in the tungstate solution, set the sulfurizing time to 28h, and set the sulfurizing temperature to 60°C.

[0098] S2: Add copper nitrate to the ammonium tungstate solution after sulfurization to remove molybdenum, the amount of copper salt added is equivalent to 8 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time is set to 10h, and the impurity removal temperature is set to 60°C. After removing the impurities, a high-purity ammonium paratungstate solution is obtained, and ammonium paratungstate is produced through evaporation and crystallization. According to calculations, the molybdenum removal rate reaches 86.1% for a single sulfide-molybdenum removal process under these conditions. After three rounds of stepwise sulfurization-molybdenum impurity removal, the yield of tungstate reaches 81%. In this embodiment, the tungstate solution after two rounds of stepwise sulfurization-molybdenum impurity removal in Example 4 is used as the pre-treatment raw material, so the stepwise sulfurization-molybdenum impurity removal is actually carried out three times. Through detection, the molybdenum content in the ammonium paratungstate solution reaches 0.033 mg / L, and the molybdenum content in ammonium paratungstate reaches 0.300 ppm. EXAMPLES

[0099] In this example, the sodium tungstate solution (with molybdenum content of 0.253 mg / L) obtained after purification in Example 5 is selected as the pre-treatment raw material to remove molybdenum impurities so as to purify high-purity sodium paratungstate. The steps are as follows:

[0100] S1: Select 100ml of sodium tungstate solution, select sodium sulfide as the sulfurizing agent, add the sulfurizing agent in an amount that is 37000 times the molar concentration of molybdenum in the tungstate solution, set the sulfurizing time to 28h, and set the sulfurizing temperature to 60°C.

[0101] S2: copper sulfate is added to the sodium tungstate solution after sulfurization to remove molybdenum, the amount of copper salt added is equivalent to 8 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time is set to 10h, and the impurity removal temperature is set to 60°C. After removing the impurities, a high-purity sodium paratungstate solution is obtained, and sodium paratungstate is produced through evaporation and crystallization. According to calculations, the molybdenum removal rate reaches 85.2% for a single sulfide-molybdenum removal process under these conditions. After three stages of sulfurization-molybdenum impurity removal, the yield of tungstate reaches 80.6%. In this embodiment, the tungstate solution after two stages of sulfurization-molybdenum impurity removal in Example 5 is used as the pre-treatment raw material, so it actually undergoes three stages of sulfurization-molybdenum impurity removal. Through detection, the molybdenum content in the sodium paratungstate solution reaches 0.038 mg / L, and the molybdenum content in sodium paratungstate reaches 0.419 ppm. EXAMPLES

[0102] In this example, the ammonium tungstate solution (with molybdenum content of 0.033 mg / L) obtained after purification in Example 6 is selected as the pre-treatment raw material to remove molybdenum impurities so as to purify high-purity ammonium paratungstate. The steps are as follows:

[0103] S1: Select 100ml of ammonium tungstate solution, select ammonium sulfide as the sulfurizing agent, add the sulfurizing agent in an amount that is 380000 times the molar concentration of molybdenum in the tungstate solution, set the sulfurizing time to 32h, and set the sulfurizing temperature to 60°C.

[0104] S2: Add copper nitrate to the ammonium tungstate solution after sulfurization to remove molybdenum, the amount of copper salt added is equivalent to 12 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time is set to 12h, and the impurity removal temperature is set to 60°C. After removing the impurities, a high-purity ammonium paratungstate solution is obtained, and ammonium paratungstate is produced through evaporation and crystallization. According to calculations, the molybdenum removal rate reaches 79.8% for a single sulfide-molybdenum removal process under these conditions. After four rounds of stepwise sulfurization-molybdenum impurity removal, the yield of tungstate reaches 80.4%. In this embodiment, the tungstate solution after three rounds of stepwise sulfurization-molybdenum impurity removal in Example 6 is used as the pre-treatment raw material, so the stepwise sulfurization-molybdenum impurity removal is actually carried out four times. Through detection, the molybdenum content in the ammonium paratungstate solution reaches 0.0067 mg / L, and the molybdenum content in ammonium paratungstate reaches 0.061 ppm. EXAMPLES

[0105] In this example, the sodium tungstate solution (with molybdenum content of 0.038mg / L) obtained after purification in Example 7 is selected as the pre-treatment raw material to remove molybdenum impurities so as to purify high-purity sodium paratungstate. The steps are as follows:

[0106] S1: Select 100ml of sodium tungstate solution, select sodium sulfide as the sulfurizing agent, add the sulfurizing agent in an amount that is 400,000 times the molar concentration of molybdenum in the tungstate solution, set the sulfurizing time to 32h, and set the sulfurizing temperature to 60°C.

[0107] S2: copper sulfate is added to the sodium tungstate solution after sulfurization to remove molybdenum, the amount of copper salt added is equivalent to 12 times the molar concentration of molybdenum in the tungstate solution, the molybdenum removal time is set to 12h, and the impurity removal temperature is set to 60°C. After removing the impurities, a high-purity sodium paratungstate solution is obtained, and sodium paratungstate is produced through evaporation and crystallization. According to calculations, the molybdenum removal rate reaches 80.4% for a single sulfide-molybdenum removal process under these conditions. After four stages of sulfurization-molybdenum impurity removal, the yield of tungstate reaches 80%. In this embodiment, the tungstate solution after three stages of sulfurization-molybdenum impurity removal in Example 7 is used as the pre-treatment raw material, so it actually undergoes four stages of sulfurization-molybdenum impurity removal. Through detection, the molybdenum content in the sodium paratungstate solution reaches 0.0074 mg / L, and the molybdenum content in the sodium paratungstate reaches 0.082 ppm. Comparative Example 1

[0108] The difference from Example 1 lies in that the amount of sulfurizing agent added is equivalent to 80 times the molar concentration of molybdenum in the tungstate solution. The remaining conditions are the same. According to calculations, under these conditions, for a single sulfide-molybdenum removal process, the molybdenum removal rate reaches 5%, and the tungstate yield reaches 85%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 114 ppm. Comparative Example 2

[0109] The difference from Example 1 is that the sulfurization time is set to 12h. The remaining conditions are the same. According to calculation, for a single sulfide-molybdenum removal process under these conditions, the molybdenum removal rate reaches 58%, and the yield of tungstate reaches 84.6%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 50.4ppm. Comparative Example 3

[0110] The difference from Example 1 lies in that the molybdenum removal time is set to 6 h. The remaining conditions are the same. According to calculation, under these conditions, for a single sulfide-molybdenum removal process, the molybdenum removal rate reaches 72%, and the yield of tungstate reaches 84.5%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 33.6 ppm. Comparative Example 4

[0111] The difference from Example 4 is that the amount of sulfurizing agent added is equivalent to 800 times the molar concentration of molybdenum in the tungstate solution. The remaining conditions are the same. According to calculations, under these conditions, the molybdenum removal rate for a single sulfide-molybdenum removal process reaches 39%, and the yield of tungstate after two stages of sulfurization-molybdenum impurity removal reaches 83.2%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 8.052 ppm. Comparative Example 5

[0112] The difference from Example 4 is that the sulfurization time is set to 12h. The remaining conditions are the same. According to calculation, under these conditions, the molybdenum removal rate for a single sulfide-molybdenum removal process reaches 48%, and the yield of tungstate after two stages of sulfurization-molybdenum impurity removal reaches 82.9%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 6.864ppm. Comparative Example 6

[0113] The difference from Example 4 is that the amount of copper salt added is equivalent to three times the molar concentration of molybdenum in the tungstate solution. The remaining conditions are the same. According to calculations, under these conditions, the molybdenum removal rate for a single sulfide-molybdenum removal process reaches 71.2%, and the yield of tungstate after two stages of sulfide-molybdenum impurity removal reaches 81.7%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 3.802 ppm. Comparative Example 7

[0114] The difference from Example 4 is that the molybdenum removal time is set to 6h. The remaining conditions are the same. According to calculation, under these conditions, the molybdenum removal rate reaches 70% for a single sulfide-molybdenum removal process, and the yield of tungstate after two stages of sulfide-molybdenum impurity removal reaches 82.4%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 3.96ppm. Comparative Example 8

[0115] The difference from Example 6 is that the amount of sulfurizing agent added is equivalent to a molar concentration of 4000 times the molar concentration of molybdenum in the tungstate solution. The remaining conditions are the same. According to calculations, under these conditions, the molybdenum removal rate for a single sulfide-molybdenum removal process reaches 16%, and the yield of tungstate after three stages of sulfurization-molybdenum impurity removal reaches 81.6%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 1.813 ppm. Comparative Example 9

[0116] The difference from Example 6 is that the sulfurization time is set to 12h. The remaining conditions are the same. According to calculation, under these conditions, the molybdenum removal rate for a single sulfide-molybdenum removal process reaches 45%, and the yield of tungstate after three stages of sulfurization-molybdenum impurity removal reaches 82.4%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 1.187ppm. Comparative Example 10

[0117] The difference from Example 6 is that the amount of copper salt added is equivalent to a molar concentration of 5 times that of molybdenum in the tungstate solution. The remaining conditions are the same. According to calculations, under these conditions, the molybdenum removal rate for a single sulfide-molybdenum removal process reaches 65%, and the yield of tungstate after three stages of sulfide-molybdenum impurity removal reaches 80.4%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 0.755 ppm. Comparative Example 11

[0118] The difference from Example 6 is that the molybdenum removal time is set to 6h. The remaining conditions are the same. According to calculations, under these conditions, the molybdenum removal rate for a single sulfide-molybdenum removal process reaches 57%, and the yield of tungstate after three stages of sulfide-molybdenum impurity removal reaches 80.8%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 0.928ppm. Comparative Example 12

[0119] The difference from Example 8 is that the amount of sulfurizing agent added is equivalent to a molar concentration of 55,000 times the molar concentration of molybdenum in the tungstate solution. The remaining conditions are the same. According to calculations, under these conditions, the molybdenum removal rate for a single sulfide-molybdenum removal process reaches 18%, and the yield of tungstate after four stages of sulfurization-molybdenum impurity removal reaches 80.5%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 0.248 ppm. Comparative Example 13

[0120] The difference from Example 8 is that the sulfurization time is set to 12h. The remaining conditions are the same. According to calculation, under these conditions, the molybdenum removal rate for a single sulfide-molybdenum removal process reaches 39.6%, and the yield of tungstate after four stages of sulfurization-molybdenum impurity removal reaches 81.1%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 0.182ppm. Comparative Example 14

[0121] The difference from Example 8 is that the amount of copper salt added is equivalent to 7 times the molar concentration of molybdenum in the tungstate solution. The remaining conditions are the same. According to calculations, under these conditions, the molybdenum removal rate for a single sulfide-molybdenum removal process reaches 52.5%, and the yield of tungstate after four stages of sulfide-molybdenum impurity removal reaches 80.7%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 0.143 ppm. Comparative Example 15

[0122] The difference from Example 8 is that the molybdenum removal time is set to 6h. The remaining conditions are the same. According to calculations, under these conditions, the molybdenum removal rate for a single sulfide-molybdenum removal process reaches 47.8%, and the yield of tungstate after four stages of sulfide-molybdenum impurity removal reaches 80.4%. According to detection, the molybdenum content in the ammonium paratungstate from which molybdenum has been removed reaches 0.158ppm.

[0123] According to the results of Examples 1 to 9, the present invention can purify soluble tungstic acid with molybdenum impurity content of 0.05 ppm to 15 ppm, and the yield of tungstate can reach ≧80%, which combines excellent separation effect and higher yield.Preferably, the molybdenum content in the purified tungstate can reach <0.1 ppm.

[0124] Comparing the Examples with the Comparative Examples, it can be seen that the removal rate of molybdenum impurities can be effectively improved by the reaction conditions outside the limited ranges of the raw material ratio and reaction time in the sulfurization process and the molybdenum removal process from soluble copper salts.

[0125] The above content is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any modifications or replacements that a person skilled in the art can easily think of within the technical scope disclosed by the present invention should be included in the scope of protection of the present invention.

Claims

1. sulfurizing the tungstate solution based on soluble sulfides; performing molybdenum removal on the sulfided tungstate solution based on a soluble copper salt; and a step of sequentially performing the sulfurization step and the molybdenum removal step multiple times to obtain a high-purity tungstate.

1. A method for removing molybdenum from tungstate based on a stepwise sulfurization process, comprising:

2. The above process of sulfurizing the tungstate solution involves adding an excess of sulfurizing agent to the solution, thereby reducing the amount of MoS in the sulfurization product. 4 2- reaches a molar ratio of 85% or more; 2. The method for removing molybdenum from tungstate based on the stepwise sulfurization process according to claim 1.

3. The step of subjecting the sulfurized tungstate solution to molybdenum removal includes adding an excess of a soluble copper salt to the tungstate solution to achieve a molybdenum removal rate of 80% or more.

3. The method for removing molybdenum from tungstate based on the stepwise sulfurization process according to claim 2.

4. The method for removing molybdenum from tungstate based on a stepwise sulfurization process comprises: S1: adding a sulfurizing agent to a tungstate solution to perform a sulfurizing treatment; S2: Adding a soluble copper salt to the sulfurized tungstate solution to remove molybdenum, to obtain a molybdenum-removed tungstate solution; S3: The molybdenum-removed tungstate solution of S2 is treated as a pre-treatment raw material of S1 according to S1-S2 in sequence for multiple times; 4. The method for removing molybdenum from tungstate based on the stepwise sulfurization process according to claim 3.

5. 5. The method for removing molybdenum from tungstate based on a stepwise sulfurization process according to claim 4, wherein the sulfurization agent is either one of sodium sulfide and ammonium sulfide.

6. The amount of the sulfurizing agent used is such that the molar concentration of the sulfurizing agent is 1×10 of the molar concentration of molybdenum in the tungstate solution. 2 Times to 4 x 10 5 Meet the condition of doubling, 5. The method for removing molybdenum from tungstate based on a stepwise sulfurization process according to claim 4.

7. 5. The method for removing molybdenum from tungstate based on stepwise sulfurization process according to claim 4, wherein the soluble copper salt is one or more of copper sulfate, copper nitrate and copper chloride.

8. The amount of the soluble copper salt used satisfies the condition that the molar concentration of the soluble copper salt is 4 to 14 times the molar concentration of molybdenum in the tungstate solution; 5. The method for removing molybdenum from tungstate based on a stepwise sulfurization process according to claim 4.

9. In the sulfurization treatment, the sulfurization time is set to 24h-32h and the sulfurization temperature is set to 30°C-70°C; and / or in the first molybdenum removal, the molybdenum removal time is set to 8h-12h and the molybdenum removal temperature is set to 35°C-65°C; 5. The method for removing molybdenum from tungstate based on a stepwise sulfurization process according to claim 4.

10. The molybdenum removal method for the tungstate based on the stepwise sulfurization process according to any one of claims 1 to 9 is used to produce the tungstate, and the molybdenum impurity content is less than 0.1 ppm.

4. A tungstate comprising:

Images