Method for recovering molybdenum compound

Abstract

Provided is a method for recovering a molybdenum compound, with which it is possible to obtain a molybdenum oxide powder having a high purity and a large specific surface area from a solution containing a molybdenum component. A method for recovering a molybdenum compound, said method comprising: a precipitation step in which a solution containing a molybdenum component is subjected to a precipitation reaction in the presence of a catalyst A xMoyO3y + z (1) (in formula (1), A represents an element selected from the group consisting of Group 4, Group 8, Group 12, Group 13, and Group 14); 3y + z represents the number of oxygen contained in the molybdate, and z represents a number obtained by multiplying the valence of A by 1 / 2 of x. (2) precipitation of molybdate shown in the description; and a firing step for generating AOz (2) by pyrolyzing the molybdate (A in formula (2) is the same as A in formula (1). And z represents the number of oxygen that binds to A in formula (2) to form an oxide. ), and generates a vapor comprising molybdenum trioxide; a cooling process; and a recovery step.

Description

Technical Field

[0001] The present invention relates to a method for recovering molybdenum compounds. Background Art

[0002] Conventionally, molybdenum compounds such as molybdenum trioxide are suitable as fluxes when producing inorganic oxides such as alumina, zirconia, titanium dioxide, and silica by the flux method. In addition, molybdenum compounds are also widely used as catalysts.

[0003] However, molybdenum, which is a raw material for molybdenum compounds, is an element with high and volatile prices. Therefore, methods for reusing molybdenum compounds recovered from waste liquids containing molybdenum as raw materials are being studied.

[0004] As a method for recovering molybdenum for recovering molybdenum from used catalysts containing molybdenum, etc., for example, there is a method described in Patent Document 1.

[0005] Patent Document 1 describes a method for recovering molybdenum from a treatment solution that is an aqueous solution containing molybdenum. In the molybdenum recovery method described in Patent Document 1, the following steps are performed in sequence: an extraction step of extracting molybdenum by solvent extraction using the treatment solution; a back-extraction step of back-extracting the extraction solvent obtained in the extraction step; and a recovery step of adding an acid to the back-extraction solution obtained in the back-extraction step to recover molybdenum in the form of a molybdate precipitate.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2013-007107 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] In recent years, there has been an increasing demand for molybdenum oxide powders with high purity and large specific surface area in molybdenum compounds.

[0011] However, in conventional molybdenum compound recovery methods, it is difficult to obtain molybdenum oxide powders with high purity and large specific surface area from solutions containing molybdenum components such as waste liquids containing molybdenum. Therefore, the applications for which the recovered molybdenum oxide powders can be reused are few.

[0012] The present invention has been completed in view of the above circumstances, and an object thereof is to provide a method for recovering molybdenum compounds that can obtain molybdenum oxide powders with high purity and large specific surface area from a solution containing molybdenum components.

[0013] Means for Solving the Problems

[0014] [1] A method for recovering molybdenum compounds, comprising:

[0015] Precipitation step: In a solution containing a molybdenum component, A is caused to x Mo y O 3y+z (1) (In formula (1), A represents an element selected from Group 4, Group 8, Group 12, Group 13, and Group 14. 3y + z represents the number of oxygen atoms contained in the molybdate, and z represents the number obtained by multiplying the valence of A by 1 / 2 of x.) The molybdate shown is precipitated;

[0016] Firing step: The above molybdate is pyrolyzed to thereby generate AO z (2) (A in formula (2) is the same as A in formula (1). z represents the number of oxygen atoms that bond with A in formula (2) to form an oxide.) The oxide shown is generated, and a vapor composed of molybdenum trioxide is generated;

[0017] Cooling step: The vapor composed of molybdenum trioxide is cooled to generate a powder composed of molybdenum trioxide; and

[0018] Recovery step: The powder composed of molybdenum trioxide is recovered.

[0019] [2] The method for recovering a molybdenum compound according to [1], wherein, in the above precipitation step, a precipitation accelerator is added to the above solution containing a molybdenum component and stirred, whereby the above molybdate is precipitated, and the precipitation accelerator contains a compound containing one or more elements selected from the elements of Group 4, Group 8, Group 12, Group 13, and Group 14.

[0020] [3] The method for recovering a molybdenum compound according to [1], wherein, in the above precipitation step, a precipitation accelerator containing an aluminum compound is added to the above solution containing a molybdenum component and stirred, whereby the above molybdate is precipitated.

[0021] [4] The method for recovering a molybdenum compound according to [1], wherein, in the above precipitation step, a precipitation accelerator containing polyaluminum chloride is added to the above solution containing a molybdenum component and stirred, whereby the above molybdate is precipitated.

[0022] [5] The method for recovering a molybdenum compound according to [4], wherein the pH of the above solution containing a molybdenum component to which a precipitation accelerator containing polyaluminum chloride is added is adjusted to the range of 8 to 13.

[0023] [6] The method for recovering a molybdenum compound according to [1], wherein, in the recovery step, a powder of molybdenum trioxide having a purity of 99% or more and a specific surface area of 20 m 2 / g or more measured by the BET method is recovered.

[0024] Effects of the invention

[0025] According to the method for recovering molybdenum compounds of the present invention, a powder composed of molybdenum trioxide with high purity and a large specific surface area measured by the BET method is obtained from a solution containing a molybdenum component. Therefore, the recovered molybdenum trioxide can be preferably used as a flux, for example, in the case of manufacturing inorganic oxides such as alumina, zirconia, titanium dioxide, and silica by the flux method. In addition, it can be reused in various applications. Therefore, the method for recovering molybdenum compounds of the present invention can contribute to the reuse of molybdenum compounds and reduce the burden on the environment. Detailed Description of the Invention

[0026] In order to solve the above problems and obtain a molybdenum oxide powder with high purity and a large specific surface area from a solution containing a molybdenum component, the present inventors focused on the step in which the powder formed by cooling the vapor composed of molybdenum trioxide becomes a powder with high purity and a large specific surface area measured by the BET method, and conducted repeated in-depth research.

[0027] As a result, it was found that in a solution containing a molybdenum component, A x Mo y O 3y+z (1) (In formula (1), A represents an element selected from Group 4, Group 8, Group 12, Group 13, and Group 14. 3y + z represents the number of oxygen atoms contained in the molybdate, and z represents the number obtained by multiplying the valence of A by 1 / 2 of x.) The molybdate is precipitated and pyrolyzed to generate AO z (2) (A in formula (2) is the same as A in formula (1). z represents the number of oxygen atoms that bond with A in formula (2) to form an oxide.) The oxide is generated, and it is only necessary to generate a vapor composed of molybdenum trioxide.

[0028] Furthermore, the present inventors confirmed that in a solution containing a molybdenum component, the molybdate represented by formula (1) is precipitated and pyrolyzed to generate a vapor composed of molybdenum trioxide, which is cooled to generate a powder and recovered, thereby obtaining a powder composed of molybdenum trioxide with high purity and a large specific surface area measured by the BET method, and the present invention was conceived.

[0029] Hereinafter, the method for recovering molybdenum compounds of the present invention will be described in detail. The scope of the present invention is not limited to one embodiment described herein, and various modifications can be made without departing from the gist of the present invention. In addition, for specific parameters, when multiple upper limit values and lower limit values are described, any upper limit value and lower limit value among these upper limit values and lower limit values can be combined as an appropriate numerical range.

[0030] The method for recovering molybdenum compounds of the present embodiment has a precipitation step, a firing step, a cooling step, and a recovery step. The method for recovering molybdenum compounds of the present embodiment can be implemented in a batch mode or a continuous mode.

[0031] In the method for recovering a molybdenum compound according to this embodiment, a powder composed of molybdenum trioxide is recovered from a solution containing a molybdenum component. The solution containing a molybdenum component is a solution in which the component containing the molybdenum component is dispersed or dissolved in a medium.

[0032] The molybdenum component contained in the solution containing a molybdenum component only needs to be soluble in the solution containing a molybdenum component, and examples thereof include potassium molybdate, sodium molybdate, lithium molybdate, and the like.

[0033] The medium contained in the solution containing a molybdenum component may be an aqueous medium such as water or brine, an organic medium such as methanol, ethanol, or ethylene glycol, or a medium containing both an aqueous medium and an organic medium.

[0034] The solution containing a molybdenum component may also be a waste liquid containing molybdenum generated by washing a powder containing a molybdenum compound.

[0035] (Precipitation step)

[0036] In the precipitation step of the method for recovering a molybdenum compound according to this embodiment, A is caused to precipitate in a solution containing a molybdenum component. x Mo y O 3y+z (1) (In formula (1), A represents an element selected from Group 4, Group 8, Group 12, Group 13, and Group 14. 3y + z represents the number of oxygen atoms contained in the molybdate, and z represents the number obtained by multiplying the valence of A by 1 / 2 of x.) The molybdate shown by the formula (1) is precipitated. The molybdate shown by the formula (1) precipitated in the solution containing a molybdenum component may be only one kind or two or more kinds.

[0037] In the molybdate shown by the formula (1) precipitated in the precipitation step, A is an element selected from the elements of Group 4, Group 8, Group 12, Group 13, and Group 14, and is an element capable of reacting with molybdenum trioxide and / or molybdic acid to form a molybdenum compound.

[0038] Examples of the element of Group 4 include titanium, zirconium, hafnium, and the like. Examples of the element of Group 8 include iron, ruthenium, and the like. Examples of the element of Group 12 include zinc, and the like. Examples of the element of Group 13 include aluminum, gallium, indium, and the like. Examples of the element of Group 14 include silicon, germanium, tin, and the like.

[0039] Specifically, the molybdate shown by the formula (1) is preferably one or more molybdates selected from Ti(MoO4)2 in which A in the formula (1) is an element of Group 4, FeMoO4 and Fe2(MoO4)3 in which A in the formula (1) is an element of Group 8, ZnMoO4 in which A in the formula (1) is an element of Group 12, Al2(MoO4)3 in which A in the formula (1) is an element of Group 13, and Si(MoO4)2 in which A in the formula (1) is an element of Group 14.

[0040] These molybdates can be pyrolyzed at temperatures below 1300 °C. Therefore, in the firing process described later, the molybdates represented by formula (1) can be easily pyrolyzed, and vapors composed of molybdenum trioxide can be easily generated.

[0041] In the precipitation process, among the above molybdates, it is preferable to precipitate a compound of A in formula (1) as an aluminum compound, and it is particularly preferable to precipitate aluminum molybdate (Al2(MoO4)3). When A in formula (1) is aluminum, in the firing process described later, the molybdate is pyrolyzed to generate alumina containing aluminum oxide (Al2O3) and a molybdenum compound containing molybdenum trioxide (MoO3), and the molybdenum trioxide is vaporized. The molybdenum trioxide in the pyrolyzate containing solid-state aluminum oxide is not easily retained in the pyrolyzate and is easily separated from the pyrolyzate as a vapor. Therefore, when A in formula (1) is aluminum, it is possible to recover the powder composed of molybdenum trioxide with a high recovery rate, which is preferable.

[0042] In the molybdate represented by formula (1), 3y + z represents the number of oxygen contained in the molybdate, and z represents the number obtained by multiplying the valence of A by 1 / 2 of x. Therefore, x in formula (1) is determined according to the type of A in formula (1).

[0043] The precipitation process is preferably the following process: A precipitation promoter is added while stirring a solution containing a molybdenum component by a known method, and further stirred to precipitate the molybdate.

[0044] The precipitation promoter only needs to contain a compound that reacts with the molybdenum component contained in the solution containing the molybdenum component to form a molybdate, and can be appropriately determined according to the type of the solution containing the molybdenum component and the type of the molybdate precipitated in the precipitation process.

[0045] As the precipitation promoter, in order to precipitate a molybdate in which A in formula (1) is an element selected from Group 4, Group 8, Group 12, Group 13, and Group 14 in the molybdate represented by formula (1), a precipitation promoter containing a compound containing an element corresponding to A in formula (1) is used. As a compound containing an element selected from the elements in Group 4, Group 8, Group 12, Group 13, and Group 14, specifically, TiCl4, TiOSO4, Ti(C3H8)4, Zr(C4H9)4, ZrOCl2, ZrO(CH3COO)2, FeCl2, FeCl3, Zn(CH3COO)2, ZnCl2, AlCl3, Al(NO3)3, Al2(SO4)3, [Al2(OH) n Cl 6-n m , SiCl4, Si(OCH3)4, Si(OC2H5)4, etc.

[0046] ​Further, for example, when precipitating a molybdate in which A in formula (1) is aluminum among the molybdates represented by formula (1) in the precipitation step, it is preferable to use a precipitation accelerator containing an aluminum compound. As the precipitation accelerator containing an aluminum compound, specifically, a precipitation accelerator containing a compound such as polyaluminum chloride ([Al2(OH) n Cl 6-n m ), aluminum chloride (AlCl3), aluminum nitrate (Al(NO3)3), aluminum sulfate (Al2(SO4)3) can be cited. Particularly preferably, a precipitation accelerator containing polyaluminum chloride is used. The reason is that aluminum molybdate (Al2(MoO4)3) can be effectively precipitated as the molybdate represented by formula (1), and in the subsequent firing step, the molybdate represented by formula (1) undergoes pyrolysis, and it is easy to generate high-purity vapor composed of molybdenum trioxide. In addition, polyaluminum chloride is an inexpensive substance used as a flocculant for water treatment, has high stability and safety, and is easy to operate, so it is preferred.

[0047] When using a precipitation accelerator containing polyaluminum chloride as the precipitation accelerator, it is preferable to adjust the pH of the molybdenum-containing component solution added with the precipitation accelerator containing polyaluminum chloride to the range of 8 to 13. The reason is that the aluminum ions supplied from polyaluminum chloride to the molybdenum-containing component solution are easily combined with the molybdenum component contained in the molybdenum-containing component solution. As a result, the precipitation of aluminum molybdate as the molybdate represented by formula (1) is promoted, and the molybdenum component in the molybdenum-containing component solution can be recovered with a higher recovery rate.

[0048] As a method for adjusting the pH of the molybdenum-containing component solution added with the precipitation accelerator containing polyaluminum chloride to the range of 8 to 13, a method such as adding a known pH adjuster to the molybdenum-containing component solution and stirring can be used. As the pH adjuster, for example, potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonia water, tetraethylammonium hydroxide, etc. can be used. The type and amount of the pH adjuster can be appropriately determined according to the composition and pH of the molybdenum-containing component solution.

[0049] The molybdate represented by formula (1) precipitated in the molybdenum-containing component solution in the precipitation step is preferably recovered from the molybdenum-containing component solution by a known method. As a method for recovering the molybdate represented by formula (1), for example, a method of filtering the molybdenum-containing component solution to separate it from the medium can be used. The molybdate represented by formula (1) recovered from the molybdenum-containing component solution is preferably dried by a known method to form a powder, and then used in the firing step.

[0050] (Firing step)

[0051] ​In the firing step of the method for recovering a molybdenum compound according to this embodiment, the molybdate represented by formula (1) precipitated in the precipitation step is pyrolyzed. As a heating method for pyrolyzing the molybdate represented by formula (1), a known method can be used.

[0052] In this embodiment, the following method is used: recovering from a solution containing a molybdenum component, putting the molybdate represented by formula (1) made into powder into a heat treatment furnace for heating to pyrolyze it.

[0053] In the firing step, the molybdate represented by formula (1) is pyrolyzed, thereby generating AO z (2) (A in formula (2) is the same as A in formula (1). z represents the number of oxygen atoms bonded to A in formula (2) to form an oxide.) The oxide shown, and a vapor composed of molybdenum trioxide is generated.

[0054] In the oxide represented by formula (2), z represents the number of oxygen atoms bonded to A in formula (2) to form an oxide, and is determined according to the type of A in formula (2), etc.

[0055] In the firing step, the firing conditions for pyrolyzing the molybdate represented by formula (1) may be any temperature range above the temperature at which molybdenum trioxide can be vaporized and less than the temperature at which the oxide represented by formula (2) melts, and can be appropriately determined according to the type (composition) and amount of the molybdate represented by formula (1), etc.

[0056] For example, when the molybdate represented by formula (1) is aluminum molybdate (Al2(MoO4)3), the firing conditions can be set to 1 hour to 48 hours at a temperature of 900 °C to 1300 °C in an air atmosphere and at normal pressure.

[0057] In the firing step, when pyrolyzing the molybdate represented by formula (1), it can be carried out through an arbitrary heating curve, and can be appropriately determined according to the type (composition) and amount of the molybdate represented by formula (1), etc.

[0058] That is, when pyrolyzing the molybdate represented by formula (1), the temperature can be raised or lowered continuously or stepwise within a specified temperature range to change the heating temperature, or it can be maintained at a certain temperature within the specified temperature range for a certain time. For example, it can be heated from room temperature at a certain heating rate, maintained at a specified temperature for a certain time, and then cooled to room temperature at a certain cooling rate.

[0059] (Cooling step)

[0060] The vapor composed of molybdenum trioxide generated in the firing step is cooled by a known method in the cooling step to generate a powder composed of molybdenum trioxide.

[0061] In the present embodiment, in the calcining step, the vapor composed of molybdenum trioxide generated in the heat treatment furnace is preferably discharged from the heat treatment furnace by a known method and supplied to a cooling pipe, and cooled in the cooling pipe to form a powder.

[0062] As a method of cooling the vapor composed of molybdenum trioxide in the cooling pipe, for example, cooling can be performed by a known method such as a method of conveying cooled gas into the cooling pipe, a method of cooling the outside of the cooling pipe by a cooling device, or the like.

[0063] The cooling rate of the vapor composed of molybdenum trioxide is preferably in the range of 500°C / second to 10,000°C / second, and more preferably in the range of 1,000°C / second to 10,000°C / second, for example, in the temperature range of 800°C from the highest temperature when the molybdate represented by formula (1) is pyrolyzed, to solidify the molybdenum trioxide. If the cooling rate of the vapor composed of molybdenum trioxide in the temperature range of the above-mentioned highest temperature to 800°C is 500°C / second or more, it is easy to obtain a powder of molybdenum trioxide with a small particle size, and a powder of molybdenum trioxide with a larger specific surface area measured by the BET method is obtained. In addition, if the cooling rate of the vapor composed of molybdenum trioxide in the temperature range of the above-mentioned highest temperature to 800°C is 1,000°C / second or more, the cooling process can be carried out efficiently, which is more preferred.

[0064] (Recycling process)

[0065] The powder composed of molybdenum trioxide generated in the cooling step is recovered in the recovery step. The powder composed of molybdenum trioxide can be recovered by using a known recovery unit.

[0066] The powder composed of molybdenum trioxide recovered from the solution containing molybdenum components by the method for recovering molybdenum compounds of the present embodiment is a powder obtained by precipitating the molybdate represented by formula (1) in the solution containing molybdenum components (precipitation step), pyrolyzing it to generate an oxide represented by formula (2), and generating vapor composed of molybdenum trioxide (calcination step), cooling the vapor composed of molybdenum trioxide to generate powder (cooling step), and recovering it (recovery step). Therefore, it is a powder of molybdenum trioxide with high purity and large specific surface area measured by BET method.

[0067] Specifically, by using the method for recovering a molybdenum compound of the present embodiment, it is possible to recover a molybdenum compound having a purity of 99% or more and a specific surface area of ​​20 m2 as measured by the BET method. 2 / g or more of molybdenum trioxide powder. In addition, according to the method for recovering a molybdenum compound of the present embodiment, it is possible to recover molybdenum trioxide powder having an average primary particle size of 70 nm or less.

[0068] In this specification, the average particle size of the primary particles of the molybdenum oxide powder refers to the value measured and calculated by the method <1> or <2> shown below.

[0069] <1> Using a scanning electron microscope (SEM) and / or a transmission electron microscope (TEM), observe the particles of the molybdenum trioxide powder at a magnification of 100,000 times. Then, for any 50 particles, measure the major axis and the minor axis, calculate the primary particle size as the average value thereof, and calculate its average value.

[0070] <2> Using a specific surface area measuring device for gas adsorption methods such as the BET method, measure the specific surface area of the molybdenum oxide powder. In addition, using a true density measuring device for the gas displacement method, measure the density of the molybdenum oxide powder. Then, use the following (Equation 1) to calculate the primary particle size of the molybdenum oxide powder.

[0071] Specific surface area (m 2 / g) = 6000 / ρd (Equation 1)

[0072] (In (Equation 1), ρ represents the density (g / cm 3 ). d represents the primary particle size (nm).)

[0073] The molybdenum trioxide powder obtained by the molybdenum compound recovery method of this embodiment has a high purity and a large specific surface area measured by the BET method, and thus can be reused in various applications. For example, in the case of manufacturing inorganic oxides such as alumina, zirconia, titanium dioxide, and silica using the flux method, it can be suitably used as a flux. In addition, due to the large specific surface area of the molybdenum trioxide powder, it can also be suitably used for applications such as antibacterial agents and antiviral agents. Furthermore, it can also be used as a raw material for molybdenum compounds with high purity and a large specific surface area measured by the BET method. Therefore, the molybdenum compound recovery method of this embodiment can contribute to the reuse of molybdenum compounds and can reduce the burden on the environment.

[0074] Examples

[0075] Hereinafter, the present invention will be described more specifically by way of examples. It should be noted that the present invention is not limited to the following examples.

[0076] [Example 1]

[0077] As a molybdenum-containing component solution, prepare a waste liquid generated by washing the fired alumina with water, which contains potassium molybdate used as a flux during the firing of alumina. Therefore, the molybdenum-containing component solution used in Example 1 dissolves potassium molybdate in an aqueous medium containing water.

[0078] Using a fluorescent X-ray analysis (XRF) apparatus (trade name: Primus IV; manufactured by Rigaku Corporation), the residue obtained by drying a solution containing a molybdenum component was analyzed. Using the results, the molybdenum content (converted to molybdenum trioxide) contained in the solution containing the molybdenum component was calculated. As a result, the molybdenum content (converted to molybdenum trioxide) in the solution containing the molybdenum component used in Example 1 was 6.85% by mass.

[0079] (Precipitation step)

[0080] To 5000 g of a solution containing a molybdenum component, 750 g of an aqueous solution of basic polyaluminum chloride (manufactured by Daimyo Chemical Industry Co., Ltd.; Taipac) as a precipitation accelerator was added while stirring using a mechanical stirrer, and further stirring was carried out. Then, potassium hydroxide as a pH adjuster was added and stirred, whereby the pH of the solution containing the molybdenum component was adjusted to 9, and a white precipitate was precipitated.

[0081] Next, to the solution containing the molybdenum component in which the white precipitate had precipitated, ion-exchanged water was added while performing suction filtration, whereby the white precipitate was washed, and at the same time, it was separated from the medium and recovered. Then, the recovered white precipitate was dried to form a powder.

[0082] The precipitate of Example 1 as a powder obtained after drying was identified by the following method. First, elemental analysis of the precipitate of Example 1 was performed using fluorescent X-ray analysis (XRF) (trade name: Primus IV; manufactured by Rigaku Corporation). In addition, the substance obtained by heat-treating the precipitate of Example 1 at 600 °C for 1 hour was analyzed using X-ray diffraction analysis (XRD) (trade name: Ultima IV; manufactured by Rigaku Corporation). Then, based on the elemental ratio obtained from the results of elemental analysis using XRF and the spectral intensity obtained from the results of XRD, the composition of the precipitate of Example 1 was confirmed. As a result, it was confirmed that the precipitate of Example 1 was a mixture of aluminum oxide (Al2O3) and aluminum molybdate (Al2(MoO4)3).

[0083] (Firing step)

[0084] Next, the white precipitate as a powder was recovered from the solution containing the molybdenum component and placed in a heat treatment furnace and heated under the following firing conditions. That is, in an air atmosphere, the temperature was raised from room temperature to 1100 °C at a rate of 5 °C / minute, the pressure was not controlled and kept at atmospheric pressure, and after maintaining at a temperature of 1100 °C for 10 hours, it was naturally cooled to room temperature.

[0085] The fired product is recovered from the heat treatment furnace after the firing process and identified by the same method as the precipitate in Example 1. As a result, it was confirmed that the fired product in Example 1 was a mixture of alumina (Al2O3) and molybdenum trioxide (MoO3).

[0086] (Cooling process) (Recovery process)

[0087] On the other hand, in the firing process, the vapor generated in the heat treatment furnace is discharged from the heat treatment furnace and supplied to the cooling pipe. The vapor is cooled in the cooling pipe to form a powder at a cooling rate of 2000 °C / second in the temperature range of 1100 °C to 800 °C, which is the highest temperature when the molybdate in Example 1 pyrolyzes, and 270 g of the powder is recovered.

[0088] The powder recovered by the recovery method of Example 1 was identified by X-ray diffraction (XRD) measurement, and the purity was calculated by X-ray fluorescence analysis (XRF). As a result, it was confirmed that the powder (vapor generated in the firing process) recovered by the recovery method of Example 1 was molybdenum trioxide (MoO3) with a purity of 99.7%.

[0089] In addition, the recovery rate of the powder recovered by the recovery method of Example 1 was calculated by the following (Equation 2). As a result, the recovery rate was 78.8%.

[0090] Recovery rate (%) = {(Mo content II / Mo content I) × 100} (Equation 2)

[0091] (In (Equation 2), Mo content I is the molybdenum content (converted to molybdenum trioxide) (g) contained in the molybdenum-containing component solution. Mo content II is the molybdenum content (converted to molybdenum trioxide) (g) in the recovered powder.)

[0092] In addition, for the powder recovered by the recovery method of Example 1, the specific surface area and the average primary particle diameter measured by the BET method were measured by the following method. As a result, the specific surface area measured by the BET method was 50 m 2 / g, and the average primary particle diameter was 30 nm.

[0093] [Measurement method of specific surface area: BET method]

[0094] Using a specific surface area meter (manufactured by MicrotracBEL, BELSORP-mini), the nitrogen adsorption amount based on the BET method was measured for the powder recovered by the recovery method of Example 1, and the surface area per 1 g of the sample was calculated based on the result as the specific surface area (m 2 / g) of the powder recovered by the recovery method of Example 1.

[0095] [Method for Measuring Average Particle Size of Primary Particles]

[0096] The powder recovered by the recovery method of Example 1 was photographed using a transmission electron microscope (TEM; manufactured by JEOL Ltd.; JEM1400). For the particles (i.e., primary particles) that are the smallest units constituting the aggregates on the obtained two-dimensional image, the major axis (Feret diameter of the longest part observed) and the minor axis (Feret diameter that is short in the vertical direction with respect to the Feret diameter of the longest part) were measured, and their average value was taken as the primary particle size. The same operation was performed on 50 randomly selected primary particles, and the average value of the primary particle sizes of the 50 primary particles was calculated as the average particle size of the primary particles of the powder recovered by the recovery method of Example 1.

[0097] [Example 2]

[0098] As the molybdenum-containing component solution, a 10 wt% sodium molybdate aqueous solution (molybdenum content (converted to molybdenum trioxide) is 7 wt%) prepared by adding 4412.5 g of ion-exchanged water to 587.5 g of sodium molybdate dihydrate (reagent manufactured by Kanto Chemical Co., Inc.) was used, and the precipitation step, firing step, cooling step, and recovery step were carried out in the same manner as in Example 1. In addition, the precipitate and fired product generated in the precipitation step were identified by the same method as in Example 1.

[0099] As a result, the precipitate of Example 2 was a mixture of aluminum oxide (Al2O3) and aluminum molybdate (Al2(MoO4)3). In addition, the fired product obtained in Example 2 was a mixture of aluminum oxide (Al2O3) and molybdenum trioxide (MoO3).

[0100] In addition, in Example 2, the mass of MoO3 recovered by cooling in the cooling pipe was 260 g, and the recovery rate was 74.3%.

[0101] [Example 3]

[0102] As the precipitation accelerator, 940 g of an aqueous aluminum sulfate solution (manufactured by Daimyo Chemical Industry Co., Ltd.) was used instead of the aqueous basic polyaluminum chloride solution, and the precipitation step, firing step, cooling step, and recovery step were carried out in the same manner as in Example 1. In addition, the precipitate and fired product generated in the precipitation step were identified by the same method as in Example 1.

[0103] As a result, the precipitate generated in the precipitation step of Example 3 was a mixture of aluminum oxide (Al2O3) and aluminum molybdate (Al2(MoO4)3). In addition, the fired product obtained in Example 3 was a mixture of aluminum oxide (Al2O3) and molybdenum trioxide (MoO3).

[0104] In addition, in Example 3, the mass of the recovered MoO3 cooled in the cooling pipe was 210 g, and the recovery rate was 61.3%.

[0105] [Comparative Example 1]

[0106] Prepare a solution containing a molybdenum component identical to the solution containing a molybdenum component used in the recovery method of Example 1.

[0107] (Precipitation step)

[0108] Add potassium hydroxide as a pH regulator to 1000 g of the solution containing a molybdenum component and stir to adjust the pH of the solution containing a molybdenum component to 9. In the solution containing a molybdenum component after pH adjustment, while stirring with a mechanical stirrer, add 300 g of an aqueous solution prepared by making calcium chloride (a reagent manufactured by Kanto Chemical Co., Inc.) into 10% by mass with ion-exchanged water as a precipitation accelerator, and further stir to precipitate a white precipitate.

[0109] Next, in the same manner as in the recovery method of Example 1, the solution containing a molybdenum component with a white precipitate deposited thereon was suction-filtered and recovered, and dried to form a powder.

[0110] The precipitate of Comparative Example 1, which was a powder formed after drying, was identified by the same method as the precipitate of Example 1. As a result, it was confirmed that the precipitate of Comparative Example 1 was a mixture of calcium oxide (CaO) and calcium molybdate (CaMoO4).

[0111] (Firing step) (Cooling step) (Recovery step)

[0112] Then, instead of the white precipitate formed after drying obtained in the precipitation step of Example 1, the white precipitate formed after drying obtained in the precipitation step of Comparative Example 1 was used, and the firing step, cooling step, and recovery step were carried out in the same manner as in the recovery method of Example 1 except for this.

[0113] The fired product was recovered from the heat treatment furnace after the firing step and identified by the same method as the precipitate of Example 1. As a result, it was confirmed that the fired product of Comparative Example 1 was a mixture of calcium oxide (CaO) and calcium molybdate (CaMoO4).

[0114] In addition, in Comparative Example 1, no vapor was generated in the heat treatment furnace during the firing step, and no formation of powder in the cooling pipe could be confirmed during the cooling step.

[0115] For the precipitates in the precipitation step of the recovery methods of Examples 1 to 3 and Comparative Example 1 and the fired products recovered from the heat treatment furnace after the firing step, the molybdenum content (converted to molybdenum trioxide) was measured based on the elemental analysis results using fluorescence X-ray analysis (XRF). The results are shown in Tables 1 and 2.

[0116] In addition, the "precipitation promoter", "pH of the molybdenum-containing component solution", "A in the molybdate represented by formula (1)", "composition of the precipitate precipitated in the precipitation step", and "molybdenum content in the precipitate (converted to MoO3)" used in the recovery methods of Examples 1 to 3 and Comparative Example 1 are shown in Table 1.

[0117] [Table 1]

[0118]

[0119] The "composition of the fired product", "molybdenum content in the fired product (converted to MoO3)", "purity", "specific surface area", "average particle size of primary particles", and "recovery rate" of MoO3 cooled and recovered in the cooling pipe in the firing step of the recovery method of Example 1 are shown in Table 2.

[0120] [Table 2]

[0121]

[0122] As shown in Table 2, in the recovery methods of Examples 1 to 3, molybdenum oxide powder with high purity, large specific surface area, and small average particle size of primary particles can be recovered from the molybdenum-containing component solution. In addition, it can be confirmed that the recovery rates in the recovery methods of Examples 1 to 3 are 60% or more, and molybdenum trioxide can be recovered from the molybdenum-containing component solution with a high recovery rate. This is because, in Examples 1 to 3, Al2(MoO4)3 precipitated in the precipitation step pyrolyzes in the firing step to generate vapor composed of molybdenum trioxide.

[0123] In contrast, in the recovery method of Comparative Example 1, CaMoO4 precipitated in the precipitation step did not pyrolyze in the firing step, so vapor composed of molybdenum trioxide was not generated and molybdenum trioxide could not be recovered.

Claims

1. A method for recovering a molybdenum compound, comprising: In the precipitation step, A is added to the solution containing molybdenum. x Mo y O 3y+z The molybdate shown in (1) is precipitated, wherein A in the formula (1) represents an element selected from Group 4, Group 8, Group 12, Group 13, and Group 14, 3y+z represents the number of oxygen contained in the molybdate, and z represents the number of the valence of A multiplied by 1 / 2 of x; In the calcining step, the molybdate is thermally decomposed to generate AO z (2) and generates a vapor consisting of molybdenum trioxide, wherein A in formula (2) is the same as A in formula (1), and z represents the number of oxygen atoms bonded to A in formula (2) to generate an oxide; A cooling step of cooling the vapor composed of molybdenum trioxide to generate a powder composed of molybdenum trioxide; and The recovery step recovers the powder composed of molybdenum trioxide.

2. The method for recovering a molybdenum compound according to claim 1, wherein: In the precipitation step, a precipitation accelerator is added to the solution containing the molybdenum component and stirred to precipitate the molybdate, wherein the precipitation accelerator contains a compound containing one or more elements selected from Group 4, Group 8, Group 12, Group 13, and Group 14 elements.

3. The method for recovering a molybdenum compound according to claim 1, wherein: In the precipitation step, a precipitation accelerator including an aluminum compound is added to the solution containing the molybdenum component and stirred to precipitate the molybdate.

4. The method for recovering a molybdenum compound according to claim 1, wherein: In the precipitation step, a precipitation accelerator including polyaluminum chloride is added to the solution containing the molybdenum component and stirred to precipitate the molybdate.

5. The method for recovering a molybdenum compound according to claim 4, wherein: The pH of the solution containing the molybdenum component to which the precipitation accelerator including polyaluminum chloride is added is adjusted to a range of 8 to 13.

6. The method for recovering a molybdenum compound according to claim 1, wherein: In the recovery process, the recovery purity is more than 99%, and the specific surface area measured by the BET method is 20m 2 / g or more of molybdenum trioxide powder.

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