Manganese sulfate solution manufacturing method

Abstract

To provide at least one of an industrially applicable manufacturing method of a manganese sulfate solution, that does not generate jarosite and comprises a step of selectively removing potassium from a sulfuric acid acidic manganese solution; and a manufacturing method of manganese oxide using the manganese sulfate solution.SOLUTION: A manufacturing method of a manganese sulfate solution comprises a step of adsorbing a potassium ion on a zeolite by making a molar ratio of silica to alumina be 6 or more, and bringing the manganese sulfate solution containing the potassium ion into contact with the zeolite containing an oxygen 8-membered ring in a skeletal structure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to the selective removal of potassium from acidic manganese sulfate solutions. [Background technology]

[0002] Acidic manganese solution is widely used as a raw material for manganese dioxide and other products. Industrially, acidic manganese solution is produced by reducing and roasting naturally occurring manganese ore to produce reduced ore, which is then treated with an acid solution. Because the raw ore contains potassium, it is necessary to remove the potassium in the production of acidic manganese solution.

[0003] An example of a commonly produced acidic manganese solution is manganese sulfate (MnSO4). A widely used method for removing potassium in the industrial production of manganese sulfate is to dissolve reduced ore in a sulfuric acid solution, add an iron-based agent to precipitate the potassium as jarosite (KFe3(SO4)2(OH)6), and then remove it by solid-liquid separation (hereinafter also referred to as the "jarosite method") (for example, Patent Documents 1 and 2).

[0004] Furthermore, as a method for removing potassium using an adsorbent, a method has been disclosed in which potassium is removed from a manganese sulfate solution by bringing the manganese sulfate solution into contact with a manganese dioxide adsorbent (Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-178749 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-219316 [Patent Document 3] Japanese Patent Application Publication No. 4-31323 [Non-patent literature]

[0006] [Non-Patent Document 1] Chemistry of Materials, 1995, 7, 148-153 Summary of the Invention [Problem to be solved by the invention]

[0007] The jarosite process requires a large amount of iron-based chemicals to produce jarosite, and the equipment and costs involved tend to be large. Furthermore, jarosite is discharged mixed with slag containing various impurities, making it difficult to reuse. Therefore, the slag containing jarosite is disposed of as is in landfills, placing a heavy burden on the environment.

[0008] In contrast, the potassium removal method using a manganese dioxide-based adsorbent disclosed in Patent Document 3 does not involve the formation of jarosite. However, manganese dioxide-based adsorbents are unstable in acidic environments (e.g., Non-Patent Document 1). This necessitates frequent replacement of the adsorbent, making the method of Patent Document 3 difficult to use in industrial production.

[0009] The present disclosure aims to provide at least one of an industrially applicable method for producing a manganese sulfate solution by selectively removing potassium from an acidic manganese sulfate solution without producing jarosite, and a method for producing manganese oxide using the manganese sulfate solution. [Means for solving the problem]

[0010] This disclosure has investigated an industrially applicable method for producing a manganese sulfate solution by selectively removing potassium from an acidic manganese sulfate solution. As a result, it has been found that by applying potassium adsorption to a zeolite with a specific structure, it is possible to selectively remove potassium from an acidic manganese sulfate solution without forming jarosite. It has also been found that selective removal of potassium from a manganese sulfate solution can be stably performed in an acidic environment.

[0011] That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows. [1] A method for producing a manganese sulfate solution, comprising the steps of contacting a manganese sulfate solution containing potassium ions with a zeolite having a silica to alumina molar ratio of 6 or more and containing an 8-membered oxygen ring in its framework, and allowing the potassium ions to be adsorbed onto the zeolite. [2] The method for producing a manganese sulfate solution according to [1], wherein the zeolite containing an 8-membered oxygen ring in its framework is a zeolite having one or more framework structures selected from the group consisting of CHA type, FER type, HEU type, MOR type, SZR type, and YFI type. [3] The method for producing a manganese sulfate solution according to [1] or [2] above, wherein the pH of the manganese sulfate solution containing potassium is 6 or less. [4] The method for producing a manganese sulfate solution according to any one of [1] to [3], wherein the molar ratio of manganese ions to potassium ions in the potassium-containing manganese sulfate solution is 10 or more and 2000 or less. [5] A method for producing manganese oxide, using a manganese sulfate solution obtained by the method for producing a manganese sulfate solution according to any one of [1] to [4] above. [6] A method for treating a manganese sulfate solution, comprising the step of contacting a manganese sulfate solution containing potassium ions with a zeolite having a silica to alumina molar ratio of 6 or more and containing an 8-membered oxygen ring in its framework structure, and allowing the potassium ions to be adsorbed onto the zeolite. [Effects of the Invention]

[0012] The present disclosure provides at least one of an industrially applicable method for producing a manganese sulfate solution by selectively removing potassium from an acidic manganese sulfate solution without producing jarosite, and a method for producing manganese oxide using the manganese sulfate solution. DETAILED DESCRIPTION OF THE INVENTION

[0013] The method for producing a manganese sulfate solution according to the present disclosure will be described below with reference to an example embodiment. The present disclosure includes any combination of the configurations and parameters disclosed herein, and also includes any combination of the upper and lower limits of the values ​​disclosed herein.

[0014] The terms used in this embodiment are as follows:

[0015] An "aluminosilicate" is a composite oxide having a structure consisting of a repeating network of aluminum (Al) and silicon (Si) via oxygen (O). Among aluminosilicates, those that have a crystalline XRD peak in their powder X-ray diffraction (hereinafter also referred to as "XRD") pattern are called "crystalline aluminosilicates," and those that do not have a crystalline XRD peak are called "amorphous aluminosilicates."

[0016] In this embodiment, the XRD pattern can be obtained by XRD measurement under the following conditions.

[0017] Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Scan condition: 10° / min Measurement range: 2θ=5° to 40° Divergence vertical limit slit: 10mm Divergence / entrance slit: 1° Scattering slit: open Receiving slit: open Detector: Semiconductor detector (D / teX Ultra2) Filter: Not used The XRD pattern can be measured using a general powder X-ray diffractometer (for example, Ultima IV, manufactured by Rigaku Corporation). A crystalline XRD peak is a peak whose peak top 2θ is identified and detected in an XRD pattern analysis using general analysis software, and whose half-width is 2θ = 0.10° or less.

[0018] "Zeolite" refers to a compound having a regular structure in which skeleton atoms (hereinafter also referred to as "T atoms") are connected via oxygen (O), and the T atoms are at least one of metal atoms and metalloid atoms. Examples of metal atoms include one or more atoms selected from the group consisting of aluminum (Al), titanium (Ti), iron (Fe), zinc (Zn), gallium (Ga), and tin (Sn), with aluminum being preferred. Examples of metalloid atoms include one or more atoms selected from the group consisting of boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te), with silicon being preferred.

[0019] A "zeolite-like substance" is a compound having a regular structure in which T atoms are oxygen-mediated, and the T atoms contain at least one atom other than a metal or metalloid. Examples of zeolite-like substances include complex phosphorus compounds containing phosphorus (P) as the T atom, such as aluminophosphate (AlPO) and silicoaluminophosphate (SAPO).

[0020] The "skeletal structure" (hereinafter also referred to as "zeolite structure") of a zeolite or zeolite-like substance is a skeletal structure identified by the skeletal structure code (hereinafter also referred to as "skeleton code") established by the Structure Commission of the International Zeolite Association. For example, the FER structure is a skeletal structure identified by the structure code "FER." The FER structure can be identified by comparing it with the XRD pattern (hereinafter also referred to as "reference pattern") listed in the FER Zeolite Framework Types on the IZA Structure Commission's website http: / / www.iza-structure.org / databases / . With regard to the zeolite structure, the terms skeletal structure, crystalline structure, and crystalline phase are used interchangeably.

[0021] In the present embodiment, "-type zeolite" such as "FER-type zeolite" means a zeolite having a zeolite structure of the corresponding structure code, and particularly means a crystalline aluminosilicate having a zeolite structure of the corresponding structure code. In addition, an intergrowth structure of two or more skeletal structures is distinguished from a zeolite consisting of one skeletal structure. For example, a zeolite having an intergrowth structure of CHA-type and AEI-type (CHA / AEI-type) is distinguished from a zeolite having a CHA-type skeletal structure and a zeolite having an AEI-type skeletal structure, respectively.

[0022] An "8-membered oxygen ring" is a ring structure consisting of eight oxygen atoms and a T atom between them. Hereinafter, it will be referred to as an "n-membered oxygen ring" depending on the number of oxygen atoms, n, that make up the ring.

[0023] "Selectivity" is a ratio defined by the following formula (1), which is the ion exchange rate of a specific ion species (for example, potassium) relative to the molar amount of ion-exchangeable ions in the zeolite.

[0024] Selectivity [%] = ([M] × n) / [Al] × 100 (1) In equation (1), [M] is the molar concentration [mol / g] of a particular ion species in the zeolite, n is its valence, and [Al] is the molar concentration [mol / g] of aluminum ions in the zeolite.

[0025] [M] and [Al] can be determined by ICP atomic emission spectrometry using a general ICP-AES device (for example, product name: OPTIMA3000DV, manufactured by PERKIN-ELMER).

[0026] The present embodiment will be described below.

[0027] The method for producing a manganese sulfate solution of the present embodiment is a production method (hereinafter also referred to as the "production method of the present embodiment") that includes a step of contacting a manganese sulfate solution containing potassium ions (hereinafter also referred to as the "pre-treatment solution") with a zeolite having a silica to alumina molar ratio of 6 or more and containing an 8-membered oxygen ring in its framework structure (hereinafter also referred to as the "8-membered ring zeolite"), and adsorbing potassium ions onto the zeolite (hereinafter also referred to as the "potassium removal step"). <8-membered ring zeolite> The zeolite used in the production method of this embodiment is a zeolite containing an eight-membered oxygen ring in its framework (hereinafter referred to as an "eight-membered ring zeolite"). Zeolites A and X have traditionally been known as ion exchangers with high heat resistance and high selectivity. However, these zeolites cannot be used as ion exchangers in acidic solutions such as manganese sulfate solutions because their structure collapses in acidic environments. In contrast, this embodiment focuses on eight-membered ring zeolites, and by using an eight-membered ring zeolite with the above-mentioned alumina-to-silica molar ratio, it is possible to treat the pre-treatment solution without structural collapse even in an acidic environment. One of the reasons why eight-membered ring zeolites can be used is thought to be that, in addition to the effect of the eight-membered oxygen rings in suppressing the desorption of aluminum ions, potassium easily enters the pores inside the zeolite of this embodiment, making it difficult for potassium adsorbed to desorb from the zeolite.

[0028] The eight-membered ring zeolite used in the production method of this embodiment includes zeolites having one or more framework structures selected from the group consisting of AEI type, AFT type, AFX type, CHA type, EAB type, ERI type, ESV type, FER type, GME type, HEU type, KFI type, LEV type, LTA type, LTL type, MAZ type, MEL type, MER type, MFS type, MOR type, MOZ type, MRT type, MWF type, OFF type, PAU type, PTT type, PTY type, PWN type, PWW type, RHO type, RTH type, SFW type, STI type, SZR type, TUN type, UFI type, and YFI type, and preferably the AEI type, AFX type, Zeolites having one or more skeletal structures selected from the group consisting of CHA, ERI, FER, HEU, KFI, LEV, MEL, MER, MFS, MOR, MRT, MWF, PAU, PTT, PTY, PWN, RHO, SFW, STI, SZR, TUN, UFI, and YFI types, more preferably zeolites having one or more skeletal structures selected from the group consisting of CHA, FER, HEU, MOR, SZR, and YFI types, and even more preferably zeolites having at least one skeletal structure of CHA and FER. The eight-membered ring zeolite used in the production method of this embodiment may have an intergrowth structure containing at least one of the above skeletal structures, such as CHA / AEI, CHA / AFX, or CHA / GME.

[0029] In the production method of this embodiment, the 8-membered ring zeolite is preferably at least one of a zeolite containing a 5-membered oxygen ring in addition to an 8-membered oxygen ring in the framework structure, and a zeolite in which the largest pore contains an 8-membered oxygen ring, which makes the structure less likely to collapse in an acidic environment.

[0030] Examples of 8-membered ring zeolites containing 5-membered oxygen rings include zeolites having one or more skeletal structures selected from the group consisting of ESV type, FER type, HEU type, MAZ type, MEL type, MFS type, MOR type, PTY type, PWW type, STI type, SZR type, TUN type, and YFI type, and zeolites having one or more skeletal structures selected from the group consisting of FER type, HEU type, MOR type, SZR type, and YFI type are preferred.

[0031] Examples of 8-membered ring zeolites in which the largest pore is an 8-membered oxygen ring include zeolites having one or more skeletal structures selected from the group consisting of AEI type, AFT type, AFX type, CHA type, EAB type, ERI type, ESV type, KFI type, LEV type, LTA type, MER type, MRT type, MWF type, PAU type, PTT type, PWN type, RHO type, RTH type, SFW type, and UFI type, and zeolites having a CHA type skeletal structure are preferred.

[0032] In the production method of this embodiment, the eight-membered ring zeolite preferably contains pores with two or more dimensions, which improves the diffusibility of ions and makes them more easily adsorbed.

[0033] Examples of eight-membered ring zeolites containing two-dimensional or higher pores include zeolites having one or more skeletal structures selected from the group consisting of AEI type, AFT type, AFX type, CHA type, EAB type, ERI type, FER type, GME type, HEU type, KFI type, LEV type, LTA type, MAZ type, MEL type, MER type, MFS type, MOZ type, MRT type, MWF type, OFF type, PAU type, PTT type, PTY type, PWN type, PWW type, RHO type, RTH type, SFW type, STI type, SZR type, TUN type, UFI type, and YFI type. Zeolites having one or more skeletal structures selected from the group consisting of CHA type, FER type, HEU type, SZR type, and YFI type are preferred. Zeolites having at least one of a CHA type and a FER type skeletal structure are more preferred, and zeolites having a FER type skeletal structure are even more preferred.

[0034] In this embodiment, the molar ratio of silica to alumina in the 8-membered ring zeolite (hereinafter also referred to as the "SiO2 / Al2O3 ratio") is 6 or more. If the SiO2 / Al2O3 ratio of the 8-membered ring zeolite is less than 6, the structure is likely to collapse, and the 8-membered ring zeolite does not exhibit stable potassium adsorption ability in an acidic environment. Therefore, the SiO2 / Al2O3 ratio of the 8-membered ring zeolite is preferably 6 or more, 8 or more, 10 or more, 13 or more, or 15 or more, and is preferably 100 or less, 80 or less, 50 or less, or 35 or less. Furthermore, in order to achieve the effect of more easily improving potassium adsorption performance from the pre-treatment solution, the SiO2 / Al2O3 ratio of the 8-membered ring zeolite is preferably 6 or more and 100 or less, 8 or more and 80 or less, or 15 or more and 35 or less.

[0035] In this embodiment, the 8-membered ring zeolite is an aluminosilicate having the above SiO2 / Al2O3 ratio. This allows for high durability and potassium adsorption performance in an acidic environment. The 8-membered ring zeolite is preferably a crystalline aluminosilicate.

[0036] In this embodiment, the particle diameter D50 of the 8-membered ring zeolite is preferably 1 μm or more, 3 μm or more, 5 μm or more, or 7 μm or more, and 20 μm or less, 15 μm or less, or 12 μm or less, in that the adsorption performance of potassium ions is likely to be high, and examples thereof include 1 μm or more and 20 μm or less, 3 μm or more and 15 μm or more, 5 μm or more and 12 μm or less, or 7 μm or more and 12 μm or less.

[0037] The particle size D50 of 8-membered ring zeolite is the particle size corresponding to the D50 (median diameter) of the volume particle size distribution obtained by laser diffraction / scattering using a general particle size distribution measuring device (e.g., MT-3100II, manufactured by Microtrac-Bell). Specific measurement conditions include the following:

[0038] Measurement range: 0.02 to 2000 μm Particle refractive index: 1.66 Particle permeability: permeation Particle shape: non-spherical Solvent refractive index: 1.333 Ultrasonic pretreatment: None In this embodiment, the potassium (K) ion selectivity of the 8-membered ring zeolite can be 10% or more, 15% or more, or 20% or more. This allows the potassium ions to be adsorbed by efficiently utilizing the ion exchange capacity of the zeolite. A high potassium ion selectivity is preferred, and examples include 95% or less, 50% or less, or 30% or less, such as 10% to 95%, 15% to 50%, or 20% to 30%.

[0039] The selectivity of the 8-membered ring zeolite for potassium ions can be calculated from the above formula (1) as follows:

[0040] Potassium ion selectivity [%] = ([K] x 1) / [Al] x 100 In this embodiment, the manganese (Mn) ion selectivity of the eight-membered ring zeolite is preferably 50% or less, 40% or less, or 30% or less. This allows the ion exchange capacity of the zeolite to be efficiently utilized to adsorb potassium ions. A low manganese ion selectivity is preferred, and is preferably, for example, 0% or more and 50% or less, more than 0% and 50% or less, or even 5% or more and 40% or less.

[0041] The selectivity of the eight-membered ring zeolite for manganese ions can be calculated from the above formula (1) as follows:

[0042] Manganese ion selectivity [%] = ([Mn] × 2) / [Al] × 100 (However, all manganese ions adsorbed on the 8-membered ring zeolite are divalent (Mn 2+ ) In this embodiment, the calcium (Ca) ion selectivity of the 8-membered ring zeolite is preferably less than 10%, 7% or less, or 5% or less. This allows the ion exchange capacity of the zeolite to be efficiently utilized to adsorb potassium ions. A low calcium ion selectivity is preferred, and is preferably, for example, 0% or more but less than 10%, more than 0% but less than 10%, or even 1% or more but 5%.

[0043] The selectivity of the 8-membered ring zeolite for calcium ions can be calculated from the above formula (1) as follows:

[0044] Calcium ion selectivity [%] = ([Ca] x 2) / [Al] x 100 In this embodiment, the magnesium (Mg) ion selectivity of the 8-membered ring zeolite is preferably less than 10%, 7% or less, or 5% or less. This allows the ion exchange capacity of the zeolite to be efficiently utilized to adsorb potassium ions. A low magnesium ion selectivity is preferred, and is preferably, for example, 0% or more but less than 10%, more than 0% but less than 10%, or even 1% or more but 5%.

[0045] The selectivity of the eight-membered ring zeolite for magnesium ions can be calculated from the above formula (1) as follows:

[0046] Ion selectivity for magnesium ions [%] = ([Mg] × 2) / [Al] × 100 In this embodiment, the 8-membered ring zeolite subjected to the potassium removal step may be one exchanged with any cation, but is preferably one exchanged with protons or sodium ions (i.e., the cation type is proton type or sodium type). If potassium ions are partially contained, the ion exchange capacity of the zeolite will substantially decrease, so it is preferable that the amount of potassium ions in the zeolite be as small as possible. The exchange rate of potassium ions relative to the molar amount of ion-exchangeable ions in the 8-membered ring zeolite is preferably 0% or more and 5% or less, and more preferably 0% or more and 2% or less.

[0047] The potassium ion exchange rate of the 8-membered ring zeolite can be calculated from the above formula (1) as follows:

[0048] Potassium ion exchange rate [%] = ([K] x 1) / [Al] x 100 The pre-treatment solution used in the manufacturing method of this embodiment is a manganese sulfate solution containing potassium, and in particular, a manganese sulfate solution obtained by dissolving manganese ore in sulfuric acid.

[0049] The pre-treatment solution contains potassium, and the potassium ion concentration, for example, can be 40 mass ppm or more, 60 mass ppm or more, 80 mass ppm or more, 100 mass ppm or more, or 120 mass ppm or more, as the mass ratio of potassium ions to the pre-treatment solution, and can also be 10,000 mass ppm or less, 5,000 mass ppm or less, or 1,000 mass ppm or less. Specific examples of the potassium ion concentration range of the manganese sulfate solution obtained by dissolving manganese ore in sulfuric acid include 40 mass ppm or more and 10,000 mass ppm or less, 60 mass ppm or more and 5,000 mass ppm or less, and even 80 mass ppm or more and 500 mass ppm or less. <Pre-treatment solution> In the pre-treatment solution, manganese sulfate was Mn 2+ ions and SO4 2- Included as ions However, the pre-treatment solution is Mn 2+ The manganese ions may contain manganese ions having a different valence from the manganese ions. 3+ ion, Mn 4+ ions and MnO4 2- The ions may be one or more selected from the group consisting of:

[0050] The manganese ion concentration of the pre-treatment solution may be any concentration that allows use as a raw material for manganese oxide, and may be 1% by mass or more, 2% by mass or more, 3% by mass or more, or 3.5% by mass or more, and 12% by mass or less, 10% by mass or less, or 8% by mass or less, with 1% by mass or more and 12% by mass or less, 2% by mass or more and 10% by mass or less, or 3% by mass or more and 8% by mass or less being preferred.

[0051] The "manganese ion concentration" refers to the concentration of the total amount of manganese ions in a solution. The manganese ion concentration can be determined by ICP atomic emission spectroscopy using a general ICP-AES device (for example, product name: OPTIMA3000DV, manufactured by PERKIN-ELMER).

[0052] The molar ratio of manganese ions to potassium ions contained in the solution before treatment (hereinafter also referred to as the "liquid phase Mn / K molar ratio") may be 10 or more, 50 or more, 100 or more, 150 or more, or 180 or more, or 3000 or less, 2500 or less, 1500 or less, 1000 or less, or 800 or less, with preferred ranges being 10 or more and 3000 or less, 50 or more and 2500 or less, 100 or more and 1500 or less, 150 or more and 1000 or less, or 180 or more and 800 or less. Within these ranges, high potassium selectivity can be exhibited, and the potassium concentration of the manganese sulfate solution can be reduced without using excessive zeolite.

[0053] The pre-treatment solution may contain ions other than potassium ions and manganese ions. Examples of such ions include sodium ions, cobalt ions, magnesium ions, and / or calcium ions, and / or magnesium ions and / or calcium ions. To facilitate selective adsorption of potassium, the selectivity of impurities other than potassium is preferably less than 20%, 10% or less, or 5% or less. The lower the selectivity of impurities other than potassium, the better, but it is preferably 0.1% or more, 0.2% or more, or 0.5% or more. Specific ranges for the selectivity of impurities other than potassium include 0.1% or more but less than 20%, 0.2% or more to 10% or less, or 0.5% or more to 5% or less.

[0054] The manufacturing method of this embodiment may include a step of removing ions other than the potassium ions and manganese ions from the pre-treatment solution (hereinafter referred to as an "impurity removing step") before the potassium removing step.

[0055] The method for removing ions other than potassium ions and manganese ions from the pre-treatment solution is not particularly limited, and any known method can be used.

[0056] The solvent of the pre-treatment solution may be at least one of water and alcohol, but it is preferable that it is water, that is, the pre-treatment solution is an aqueous manganese sulfate solution.

[0057] The pH of the pre-treatment solution is preferably 6 or less. This makes it difficult for manganese oxide to precipitate. Furthermore, in the method for producing a manganese sulfate solution of this embodiment, since it is not necessary to produce jarosite, the pH does not need to be excessively low. Furthermore, since dealumination from zeolite is difficult to occur, the pH of the pre-treatment solution is preferably 3 or more and 6 or less, more preferably 4 or more and 6 or less.

[0058] The pre-treatment solution can be produced by a known method, for example, a method for producing a manganese sulfate solution, which includes a step of dissolving naturally occurring manganese ore in sulfuric acid or an aqueous sulfuric acid solution. <Potassium removal process> In the potassium removal step, the method of contacting the 8-membered ring zeolite with the pre-treatment solution includes a method in which the two are uniformly contacted, such as a batch method, a continuous method, or a combination of a batch method and a continuous method. An example of a batch contact method is a method in which zeolite powder and the pre-treatment solution are mixed by stirring and then subjected to solid-liquid separation. An example of a continuous contact method is a method in which zeolite molded into a desired shape is packed in a column or the like and the pre-treatment solution is passed through the column. A continuous method is preferred in terms of high production efficiency of the manganese sulfate solution.

[0059] The contact conditions between the 8-membered ring zeolite and the pre-treatment solution can be set arbitrarily so as to obtain a manganese sulfate solution with an impurity concentration suited to the purpose.

[0060] The temperature at which the 8-membered ring zeolite is brought into contact with the pre-treatment solution is not particularly limited, but examples thereof include room temperature (20±10°C), 40°C or higher, 60°C or higher, or 70°C or higher. It is sufficient if the temperature is 100°C or lower, 95°C or lower, or 90°C or lower, and preferably 40°C or higher and 100°C or lower, 60°C or higher and 95°C or lower, or 70°C or higher and 90°C or lower.

[0061] The molar ratio of manganese ions to potassium ions contained in the 8-membered ring zeolite after the potassium removal step (hereinafter also referred to as the "solid-phase Mn / K molar ratio") is preferably lower than the liquid-phase Mn / K molar ratio of the pre-treatment solution. This confirms that the 8-membered ring zeolite selectively adsorbs potassium ions from the pre-treatment solution. The value obtained by dividing the liquid-phase Mn / K molar ratio of the pre-treatment solution by the solid-phase Mn / K molar ratio after contacting the 8-membered ring zeolite with the pre-treatment solution (hereinafter also referred to as the "K concentration ratio") may be greater than 1, and is preferably 20 or more, 50 or more, 100 or more, or 150 or more, and is 1000 or less, 500 or less, or 200 or less, with the ranges of 20 to 1000, 50 to 500, and 100 to 200 being preferred. By achieving this range, the potassium concentration of the manganese sulfate solution can be reduced using a small amount of zeolite. By contacting the pre-treatment solution with a sufficient amount of zeolite to adsorb the potassium contained in the pre-treatment solution to a target concentration, potassium can be selectively removed from the manganese sulfate acid solution without the formation of jarosite. The ratio of the 8-membered ring zeolite to the pre-treatment solution when contacting them is not particularly limited. For example, the ratio of the sum (mol) of the ion exchange capacity of the 8-membered ring zeolite used to the potassium ion content of the pre-treatment solution (hereinafter also referred to as the "contact ratio") can be set as an index. The contact ratio is preferably 1 or more, 1.5 or more, 2 or more, 3 or more, 4 or more, or 5 or more, and 20 or less, 15 or less, or 10 or less, with the ranges of 1 or more to 20 or less, 1.5 or more to 15 or less, and 2 or more to 10 or less being preferred. By setting the contact ratio within these ranges, the 8-membered ring zeolite can be efficiently utilized to adequately adsorb potassium ions.

[0062] The potassium ion concentration in the manganese sulfate solution obtained by the potassium removal step (hereinafter also referred to as the "treated solution") is determined depending on the purpose of producing the manganese sulfate solution, and it is sufficient if the potassium ion concentration is lower than that of the pre-treatment solution. The potassium ion concentration of the treated solution is, for example, 80 mass ppm or less, 60 mass ppm or less, 40 mass ppm or less, 20 mass ppm or less, or 10 mass ppm or less, or 0.1 mass ppm or more, 0.3 mass ppm or more, 1 mass ppm or more, 3 mass ppm or more, or 5 mass ppm or more. Examples of the range include 0.1 mass ppm to 80 mass ppm or less, 0.3 mass ppm to 60 mass ppm or less, 1 mass ppm to 40 mass ppm or less, 3 mass ppm to 20 mass ppm or less, or 5 mass ppm to 10 mass ppm or less. However, because potassium ions are adsorbed by zeolite, the concentration of the treated solution is necessarily lower than that of the pre-treatment solution.

[0063] The 8-membered ring zeolite subjected to the potassium removal step can be reused by removing the adsorbed potassium ions.

[0064] As a method for removing potassium from the potassium-containing 8-membered ring zeolite after being subjected to the potassium removal step, it is preferable to include a step of contacting the 8-membered ring zeolite that has been subjected to the potassium removal step with a treating agent (hereinafter also referred to as a "regeneration step").

[0065] The treating agent for the regeneration step may be any agent capable of ion-exchanging and removing cations, including potassium, contained in the zeolite, and may be a mineral acid, an organic acid, a metal salt, or an ion-exchange resin, preferably a mineral acid. As the mineral acid, one or more selected from the group consisting of hydrochloric acid, nitric acid, and sulfuric acid are preferred, and hydrochloric acid is more preferred. [Example]

[0066] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples. <Crystalline phase identification> An XRD pattern was obtained using a powder X-ray diffractometer (device name: Ultima IV, manufactured by Rigaku Corporation) under the following conditions.

[0067] Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Scan condition: 10° / min Measurement range: 2θ=5° to 40° Divergence vertical limit slit: 10mm Divergence / entrance slit: 1° Scattering slit: open Receiving slit: open Detector: Semiconductor detector (D / teX Ultra2) Filter: Not used The crystalline phase of the sample was identified by comparing the obtained XRD pattern with the XRD pattern listed in the Zeolite Framework Types on the IZA Structure Committee homepage http: / / www.iza-structure.org / databases / . <Particle size D50> The particle diameter D50 was determined by measuring the cumulative volume particle size distribution using a laser diffraction / scattering particle size distribution analyzer (device name: Microtrac MT3300EXII, manufactured by Microtrac Bell Co., Ltd.). The measurement conditions are as follows:

[0068] Measurement range: 0.02 to 2000 μm Particle refractive index: 1.66 Particle permeability: permeation Particle shape: non-spherical Solvent refractive index: 1.333 Ultrasonic pretreatment: None The particle diameter D50 [μm] was obtained from the obtained cumulative volume particle size distribution.

[0069] Example 1 FER-type zeolite (product name: HSZ (registered trademark)-720KOA: ​​manufactured by Tosoh Corporation, SiO2 / Al2O3 molar ratio: 18.0, cation type: potassium type, K2O content: 5.3 mass%, Na2O content: 1.4 mass%) was subjected to an acid treatment as follows. First, the zeolite was dispersed in 10 times its mass of pure water to obtain a slurry. The obtained slurry was filtered, and 2 mol / L hydrochloric acid (manufactured by Kishida Chemical Co., Ltd.) in an amount 20 times its mass relative to the zeolite was poured into the obtained cake. Next, pure water in an amount 10 times its mass relative to the zeolite was poured into the cake to wash it. After washing, the cake was dried in the air at 110°C for 15 hours to obtain the zeolite of this example.

[0070] The zeolite used in this example was a FER-type zeolite (SiO / AlO molar ratio: 18.6, cation type: proton type, KO content: less than 0.1% by mass, NaO content: less than 0.1% by mass, potassium ion exchange rate: 0%, particle size D50: 10.9 μm).

[0071] Example 2 A cyclohexyldimethylethylammonium (hereinafter also referred to as "CDMEA") hydroxide aqueous solution, a CDMEA bromide aqueous solution, a sodium hydroxide aqueous solution, pure water, and amorphous aluminosilicate (SAR: 18.3) were mixed to obtain a raw material composition having the following molar composition.

[0072] SiO2 / Al2O3= 18.3 CDMEA / Si = 0.08 Na / Si = 0.04 K / Si = 0.11 H2O / Si = 15 OH / Si = 0.160 The resulting raw material composition was sealed in an 80 mL stainless steel autoclave and heated at 150°C for 48 hours while rotating at 55 rpm. The heated product was subjected to solid-liquid separation, and the resulting solid was washed with 20 times the mass of pure water. The washed solid was dried in the air at 110°C for 20 hours to obtain a crystallized product.

[0073] The obtained crystallized material was calcined in air at 600°C for 2 hours to obtain a calcined material.

[0074] The acid treatment was carried out in the same manner as in Example 1, except that the fired product was used as the zeolite, to obtain the zeolite of this example.

[0075] The zeolite in this example was a CHA-type zeolite (SiO2 / Al2O3 molar ratio: 19.7, cation type: proton type, potassium ion exchange rate: 0%, Na2O: less than 0.1 mass%, K2O: less than 0.1 mass%).

[0076] Example 3 A sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, pure water, and amorphous aluminosilicate (SAR: 24.3) were mixed to obtain a raw material composition having the following molar composition.

[0077] SiO2 / Al2O3= 24.3 Na / Si = 0.13 K / Si = 0.08 H2O / Si = 16 OH / Si = 0.21 The obtained raw material composition was subjected to hydrothermal treatment in the same manner as in Example 2, except that it was heated at 180° C. for 24 hours, to obtain a crystallized product.

[0078] The acid treatment was carried out in the same manner as in Example 1, except that the crystallized product was used, to obtain the zeolite of this example.

[0079] The zeolite used in this example was a FER-type zeolite (SiO2 / Al2O3 molar ratio: 23.3, cation type: proton type, K2O content: less than 0.1 mass%, Na2O content: less than 0.1 mass%, potassium ion exchange rate: 0%, particle size D50: 9.9 μm).

[0080] Example 4 An aqueous solution of (1-adamantyl)trimethylammonium (hereinafter also referred to as "ATMA") hydroxide, an aqueous solution of sodium hydroxide, pure water, and amorphous aluminosilicate (SAR: 25.3) were mixed to obtain a raw material composition having the following molar composition.

[0081] SiO2 / Al2O3= 25.3 ATMA / Si = 0.08 Na / Si = 0.08 K / Si = 0.08 H2O / Si = 18 OH / Si = 0.24 The hydrothermal treatment, calcination treatment, and acid treatment were carried out in the same manner as in Example 2, except that the obtained raw material composition was used, to obtain the zeolite of this example.

[0082] The zeolite used in this example was a CHA-type zeolite (SiO2 / Al2O3 ratio: 24.7, cation type: proton type, potassium ion exchange rate: 0%, Na2O: less than 0.1 mass%, K2O: less than 0.1 mass%, particle size D50: 5.2 μm).

[0083] Example 5 MOR type zeolite (product name: HSZ (registered trademark)-640HOA: manufactured by Tosoh Corporation, SiO2 / Al2O3 molar ratio 18.6, cation type: proton type, K2O content: less than 0.1 mass%, Na2O content: less than 0.1 mass%) was used as the zeolite in this example.

[0084] Comparative Example 1 A sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, pure water, and amorphous aluminosilicate (SAR: 12.4) were mixed to obtain a raw material composition having the following molar composition.

[0085] SiO2 / Al2O3= 12.4 Na / Si = 0.14 K / Si = 0.09 H2O / Si = 16 OH / Si = 0.23 The obtained raw material composition was subjected to hydrothermal treatment and acid treatment in the same manner as in Example 3, except that it was heated at 180° C. for 36 hours, to obtain the zeolite of this comparative example.

[0086] The zeolite in this comparative example was FER-type zeolite (SiO2 / Al2O3 molar ratio: 14.1, cation type: proton type, K2O content: 0.3 mass%, Na2O content: less than 0.1 mass%, potassium ion exchange rate: 0%, particle size D50: 53.8 μm).

[0087] Comparative Example 2 FER-type zeolite (product name: HSZ (registered trademark)-770HOA: manufactured by Tosoh Corporation, SiO / AlO molar ratio: 97.3, cation type: proton type, KO content: less than 0.1% by mass, NaO content: less than 0.1% by mass, potassium ion exchange rate: 0%) was used as the zeolite of this comparative example.

[0088] Comparative Example 3 FAU-type zeolite (product name: HSZ (registered trademark)-350HUA: manufactured by Tosoh Corporation, SiO / AlO molar ratio: 11.1, cation type: proton type, KO content: less than 0.1% by mass, NaO content: less than 0.1% by mass, potassium ion exchange rate: 0%) was used as the zeolite of this comparative example.

[0089] Comparative Example 4 FAU-type zeolite (product name: HSZ (registered trademark)-373HUA: manufactured by Tosoh Corporation, SiO / AlO molar ratio: 30.0, cation type: proton type, KO content: less than 0.1% by mass, NaO content: less than 0.1% by mass, potassium ion exchange rate: 0%) was used as the zeolite of this comparative example.

[0090] Comparative Example 5 MFI type zeolite (product name: HSZ (registered trademark)-822HOA: manufactured by Tosoh Corporation, SiO / AlO molar ratio: 24.0, cation type: proton type, KO content: less than 0.1% by mass, NaO content: less than 0.1% by mass, potassium ion exchange rate: 0%) was used as the zeolite of this comparative example.

[0091] Comparative Example 6 Beta zeolite (product name: HSZ (registered trademark)-920NHA: manufactured by Tosoh Corporation, SiO / AlO molar ratio: 17.7, cation type: ammonium type, KO content: less than 0.1% by mass, NaO content: less than 0.1% by mass) was calcined in air at 600°C for 2 hours to obtain the zeolite of this comparative example.

[0092] The zeolite in this comparative example was beta zeolite (SiO2 / Al2O3 molar ratio: 17.7, cation type: proton type, K2O content: less than 0.1 mass%, Na2O content: less than 0.1 mass%, potassium ion exchange rate: 0%).

[0093] Comparative Example 7 An ATMA hydroxide aqueous solution, a sodium hydroxide aqueous solution, pure water, and amorphous aluminosilicate (SAR: 13.1) were mixed to obtain a raw material composition having the following molar composition.

[0094] SiO2 / Al2O3= 13.1 ATMA / Si = 0.08 Na / Si = 0.08 K / Si = 0.08 H2O / Si = 18 OH / Si = 0.24 The hydrothermal treatment, calcination treatment, and acid treatment were carried out in the same manner as in Example 2, except that the obtained raw material composition was used, to obtain the zeolite of this example.

[0095] The zeolite in this example was a CHA-type zeolite (SiO2 / Al2O3 ratio: 13.6, cation type: proton type, potassium ion exchange rate: 0%, Na2O: less than 0.1 mass%, K2O: less than 0.1 mass%). [Adsorption evaluation 1] The potassium ion adsorption performance of Examples 1 and 2 was evaluated.

[0096] That is, as a manganese sulfate solution containing potassium, an aqueous solution containing K2SO4, MnSO4, MgSO4, and CaSO4 and having the following composition was prepared and designated as pre-treatment solution 1.

[0097] K: 0.0041mol / L (147 mass ppm) Mn: 0.79mol / L (40038 mass ppm) Mg: 0.043mol / L (970 mass ppm) Ca: 0.016mol / L (589 mass ppm) Liquid phase Mn / K molar ratio: 194 pH: 4.5 752 mg of zeolite powder (corresponding to a contact magnification of approximately 3 times) was weighed and added to 100 mL of the pre-treatment solution in a resin container to form a slurry. The slurry was kept at approximately 80°C and shaken at 200 rpm for 20 minutes, after which solid-liquid separation was performed and the filtrate was collected. The solid content was washed by passing 10 times the mass of pure water through it, and then dried in air at 110°C for 4 hours to prepare a measurement sample.

[0098] The concentrations of aluminum, potassium, manganese, magnesium, and calcium in the filtrate and the measurement sample were measured by ICP atomic emission spectroscopy using an ICP-AES device (product name: OPTIMA3000DV, manufactured by PERKIN-ELMER), and the potassium concentration in the filtrate after adsorption evaluation (hereinafter also referred to as the "filtrate potassium concentration") and the selectivity for each element were determined. Furthermore, the solid-phase Mn / K molar ratio was determined from the concentration ratio of manganese to potassium, and the K enrichment rate was calculated.

[0099] The selectivity, solid phase Mn / K molar ratio, K enrichment rate, and filtrate potassium concentration of each measurement sample are shown in the table below.

[0100] [Table 1]

[0101] Table 1 shows that the zeolite of this example can remove potassium from the manganese sulfate solution at a high K concentration rate. The potassium concentration in the filtrate was 30 ppm by mass in Example 1 and 58 ppm by mass in Example 2. These results show that the production method of this embodiment produced a manganese sulfate solution in which potassium was selectively removed from the untreated solution. [Durability rating 1] For the measurement sample after the adsorption evaluation 1, a durability evaluation (regeneration step) was carried out by the following method.

[0102] That is, after the adsorption evaluation, a 1N sulfuric acid solution in an amount 100 times the mass of the measurement sample was passed through the measurement sample at room temperature to remove potassium contained in the measurement sample, and then the measurement sample was washed with water and dried in air at 110°C for 4 hours.

[0103] The composition and XRD pattern of the dried measurement sample were measured in the same manner as above.

[0104] The results of the regeneration process as a durability evaluation are shown in the table below.

[0105] [Table 2]

[0106] It can be seen that the potassium ions adsorbed by the 8-membered ring zeolite of the example were removed by the regeneration process. Furthermore, the composition of the 8-membered ring zeolite after the regeneration process remained unchanged, and its XRD pattern showed that it maintained its original framework structure. [Adsorption evaluation 2] The potassium ion adsorption performance of the examples and comparative examples was evaluated.

[0107] That is, as a manganese sulfate solution containing potassium, an aqueous solution containing K2SO4, MnSO4, MgSO4, CaSO4, Na2SO4, and CoSO4 and having the following composition was prepared and designated as pre-treatment solution 2.

[0108] K: 0.0053mol / L (209 mass ppm) Mn: 0.664mol / L (33800 mass ppm) Mg: 0.034mol / L (825 mass ppm) Ca: 0.016mol / L (642 mass ppm) Na: 0.038mol / L (897 mass ppm) Co: 0.0004mol / L (24 mass ppm) Liquid phase Mn / K molar ratio: 124 pH: 4.5 1500 mg of zeolite powder from each of the examples and comparative examples was weighed and added to 45 mL of the pre-treatment solution to form a slurry. The slurry was kept at approximately 80°C and shaken at 500 rpm for 1 hour, after which solid-liquid separation was performed and the filtrate was collected. The solid content was washed by passing 10 times the mass of pure water through the powder and dried in air at 110°C for 4 hours to prepare a measurement sample.

[0109] The concentrations of aluminum, potassium, manganese, magnesium, calcium, sodium, and cobalt in the filtrate and the test sample were measured by ICP atomic emission spectrometry using an ICP-AES device (product name: OPTIMA3000DV, manufactured by PERKIN-ELMER), and the filtrate potassium concentration and the selectivity for each element were calculated. Furthermore, the solid-phase Mn / K molar ratio was calculated from the concentration ratio of manganese to potassium, and the K enrichment rate was calculated.

[0110] The selectivity, solid phase Mn / K molar ratio, K enrichment rate, and filtrate potassium concentration of each sample are shown in the table below.

[0111] [Table 3]

[0112] From Table 3, it can be seen that the zeolite of this example can remove potassium from a manganese sulfate solution at a higher K concentration rate than the materials of Comparative Examples 3 to 7, and the potassium concentration in the filtrate is low. [Durability rating 2] For the measurement sample after [Adsorption Evaluation 2], durability evaluation 2 (regeneration step) was carried out in the same manner as [Durability Evaluation 1], except that a 2N hydrochloric acid solution in an amount 100 times the mass of the measurement sample was passed through at room temperature. The results of the regeneration step for durability evaluation 2 are shown in the table below.

[0113] [Table 4]

[0114] Table 4 shows that the potassium ions adsorbed by the zeolite of this example were removed by the regeneration process. On the other hand, the potassium ions adsorbed by the zeolite of the comparative example were not removed even after the regeneration process, but remained. Furthermore, the composition of the zeolite of this example did not change after the regeneration process, and its XRD pattern showed that the initial framework structure was maintained.

[0115] These results demonstrate that selective removal of potassium from manganese sulfate solution can be stably performed in an acidic environment. [Adsorption evaluation after regeneration treatment] The evaluation was carried out in the same manner as in [Adsorption Evaluation 2], except that 1000 mg of the zeolite powder of the Examples and Comparative Examples obtained in [Durability Evaluation 2] was weighed and added to 30 mL of the pre-treatment solution to form a slurry.

[0116] The selectivity, solid phase Mn / K molar ratio, K enrichment rate, and filtrate potassium concentration of each sample are shown in the table below.

[0117] [Table 5]

[0118] From Table 5, it was found that the zeolites of the examples were able to selectively remove potassium ions repeatedly even after the adsorbed potassium ions had been removed by the regeneration step.

[0119] These results demonstrate that the production method of this embodiment is capable of selectively removing potassium ions from a manganese sulfate solution in an acidic environment, thereby suppressing the formation of jarosite. Furthermore, because potassium ions can be repeatedly removed by subjecting the eight-membered ring zeolite to a regeneration step, this method is industrially applicable and does not require frequent replacement. [Industrial Applicability]

[0120] The method for producing a manganese sulfate solution according to the present disclosure can be usefully used in applications in which an industrially applicable adsorbent is used to selectively remove potassium from an acidic manganese sulfate solution without producing jarosite, thereby producing a manganese sulfate solution.

[0121] Furthermore, the manganese sulfate solution obtained by this production method can be used as a raw material for manganese oxide.

Claims

1. A potassium-adsorbing zeolite having a silica to alumina molar ratio of 15 to 80 and containing an 8-membered oxygen ring in its framework structure, which adsorbs potassium ions from an acidic manganese sulfate solution containing potassium ions.

2. 2. The potassium-adsorbing zeolite according to claim 1, which has one or more framework structures selected from the group consisting of CHA type, FER type, HEU type, MOR type, SZR type, and YFI type.

3. 3. The potassium-adsorbing zeolite according to claim 1, wherein the particle diameter D50 is 1 μm or more and 20 μm or less.

4. 3. The potassium-adsorbing zeolite according to claim 1, wherein the selectivity for potassium (K) ions is 10% or more and 95% or less.

5. 3. The potassium-adsorbing zeolite according to claim 1, wherein the selectivity for manganese (Mn) ions is 0% or more and 50% or less.

6. 3. The potassium-adsorbing zeolite according to claim 1, wherein the potassium ion exchange rate is 0% or more and 5% or less.

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