Method for producing adsorbent, and adsorbent

Abstract

Provided is a novel method for producing an adsorbent comprising an iron compound and having a large adsorption capacity. An adsorbent having a specific surface area of 200 m2 / g or more, a primary particle size of 10 nm or less, an iron content of 450 g / kg or more, and a moisture content of 100 g / kg to 300 g / kg can be obtained by the method for producing an adsorbent, the method including: a first step for adding a polyferric sulfate aqueous solution to an alkali aqueous solution to form a slurry; a second step for adjusting the pH of the slurry to 5.0 to 9.0; and a third step for subjecting the slurry to solid-liquid separation, washing the obtained cake, and adjusting the moisture content of the washed cake.

Description

Method for manufacturing an adsorbent and adsorbent

[0001] This invention relates to a method for manufacturing an adsorbent and to an adsorbent itself.

[0002] Adsorbents capable of adsorbing specific substances or several types of substances have been used in the past for applications such as the recovery of heavy metals and organic compounds leaked into the environment. Currently, they are also being used to recover rare earth elements such as lanthanum, europium, and samarium from waste and seawater, and to recover radioactive substances such as strontium and iodine from water. For example, Japanese Patent Publication No. 2011-62594 (Patent Document 1) describes an indium adsorbent using a polymer material having a template structure for indium. Although this adsorbent adsorbs indium with high selectivity, it has limitations in strength, heat resistance, and weather resistance because it is made of organic compounds. Furthermore, the manufacturing method of this adsorbent is complex, as it involves polymerizing a polymerizable monomer in the presence of indium, which is a template guest, and then crosslinking it, followed by removing the indium from the polymer to form a template structure for indium.

[0003] A highly versatile adsorbent should ideally be made of inexpensive and easy-to-handle materials, achieve high strength, heat resistance, and weather resistance, and be obtainable by a simple manufacturing method. One example of an adsorbent that can possess these characteristics is one made of inorganic materials, particularly iron compounds. International Publication No. 2006 / 088083 (Patent Document 2) describes an adsorbent made of iron oxyhydroxide that adsorbs harmful substances such as phosphorus components, and a method for producing it. This adsorbent is produced by a manufacturing method that includes generating a precipitate containing iron oxyhydroxide, drying the precipitate at a temperature of 100°C or less, then contacting the dried material with water, and further heating it at a specific temperature under an inert gas atmosphere. This process is complex and the manufacturing cost is high. Japanese Patent Application Publication No. 2018-89570 (Patent Document 3) describes an example of adsorbing iodate ions using an adsorbent made of amorphous iron(III) hydroxide produced by a relatively simple method. However, the adsorbents used by this adsorbent primarily adsorb anions such as iodate ions, oxoate ions, phosphate ions, and fluoride ions. For example, to recover heavy metals, it was necessary to use an anion form such as oxoate ions containing heavy metals. A simple method for producing an adsorbent made of iron compounds that has excellent performance in adsorbing and recovering cations such as metal ions has not yet been established.

[0004] Japanese Patent Publication No. 2011-62594, International Publication No. 2006 / 088083, Japanese Patent Publication No. 2018-89570

[0005] The present invention aims to provide a novel method for producing an adsorbent made of an iron compound, which has a high adsorption capacity, including a high adsorption capacity for cations such as metal ions.

[0006] As a result of diligent research, the inventors have established a new method for producing an adsorbent, which includes adding an aqueous solution of ferric polysulfate to an alkaline aqueous solution to form a slurry, adjusting the pH of the resulting slurry to between 5.0 and 9.0, separating the slurry into solid and liquid components, washing the resulting cake, and adjusting the water content of the cake after washing. The resulting adsorbent is mainly composed of iron(III) hydroxide, has high adsorption capacity, and can be used in both methods: packing it into a column and passing water containing the target substance through it for adsorption, and immersing it in water to adsorb the target substance and then recovering it. The present invention includes, but is not limited to, the following.

[0007] <Aspect 1> A method for producing an adsorbent, comprising: a first step of adding an aqueous solution of ferric polysulfate to an alkaline aqueous solution to form a slurry; a second step of adjusting the pH of the slurry to 5.0 or more and 9.0 or less; and a third step of subjecting the slurry to solid-liquid separation, washing the obtained cake, and adjusting the water content of the cake after washing. <Aspect 2> The method according to aspect 1, further comprising a fourth step of granulating the cake with adjusted water content and drying the obtained granules. <Aspect 3> The method according to aspect 1 or 2, wherein the second step comprises stirring the slurry with a pH adjusted to 5.0 or more and 9.0 or less for 1.0 hour or more. <Aspect 4> The method according to any one of aspects 1 to 3, wherein the second step comprises adjusting the pH of the slurry to 7.5 or more and 9.0 or less. <Aspect 5> The method according to any one of aspects 1 to 4, wherein the third step comprises washing the cake until the electrical conductivity of the filtrate after washing is 500 μS / cm or less. <Aspect 6> The manufacturing method according to any one of aspects 1 to 5, wherein the third step is to adjust the moisture content of the cake after washing to 600 g / kg or more and 800 g / kg or less. <Aspect 7> The manufacturing method according to aspect 2, wherein the fourth step is to perform granulation molding by extrusion granulation. <Aspect 8> The manufacturing method according to any one of aspects 1 to 6, further comprising a fifth step of crushing the dried granules. <Aspect 9> The manufacturing method according to aspect 1, further comprising a step of drying the cake with adjusted moisture content and crushing the dried cake. <Aspect 10> Specific surface area of ​​200 m ２An adsorbent characterized by having a concentration of 100 g / kg or more, a primary particle size of 10 nm or less, an iron content of 450 g / kg or more, and a water content of 100 g / kg or more and 300 g / kg or less.

[0008] By using the method for producing adsorbents described in the present invention, it is possible to produce an adsorbent made of iron compounds with high adsorption capacity. The adsorbent produced by the method of the present invention exhibits high adsorption capacity even for cations such as metal ions. Furthermore, the adsorbent produced by the method of the present invention can be used by a method in which the adsorbent is packed into a column in granular form and adsorbed by passing water containing the target substance through it, or by a method in which it is put into water in powder form, adsorbs the target substance, and then recovered.

[0009] Furthermore, the adsorbent produced by the method of the present invention may also possess excellent adsorption properties in addition to the high adsorption capacity described above. In this specification, "high adsorption capacity" refers to a state in which a large amount of each chemical species can be adsorbed, and "excellent adsorption properties" refers to a state in which many chemical species can be adsorbed and the amount of adsorption is also large.

[0010] This graph shows the results of the europium adsorption test using the column in the example.

[0011] The manufacturing method of the present invention will be described in detail below. [Manufacturing Method] The manufacturing method of the present invention includes a first step of adding an aqueous solution of ferric polysulfate to an alkaline aqueous solution to form a slurry, a second step of adjusting the pH of the slurry to 5.0 or more and 9.0 or less, and a third step of subjecting the slurry to solid-liquid separation, washing the resulting cake, and adjusting the moisture content of the cake after washing. Furthermore, it may optionally include a fourth step of granulating the cake with the adjusted moisture content and drying the resulting granules. It may also include a fifth step of crushing the dried granules. Alternatively, separate from these optional steps, it may further include a step of drying the cake with the adjusted moisture content obtained in the third step and crushing the dried cake.

[0012] (First step) The first step involves adding an aqueous solution of ferric polysulfate to an alkaline aqueous solution to induce a neutralization reaction and obtain a slurry containing iron(III) hydroxide.

[0013] An aqueous solution of ferric polysulfate is used as the iron source. Ferric polysulfate is a dissolved state in which several iron hydroxide molecules have polymerized, and polymerization has progressed to a moderate extent by the time it precipitates as iron hydroxide. Since the heat of neutralization and subsequent drying can suppress excessive polymerization, it is suitable for use as an iron source in the manufacturing method of the present invention. On the other hand, although polymerization has not progressed immediately after neutralization precipitation, polymerization progresses to a degree that does not reach the point of crystallization due to the heat of neutralization and the process of solidifying and drying the particles, and the number of hydroxyl groups, which are adsorption sites, decreases, so it is undesirable to use ferric sulfate or ferric chloride as an iron source in the manufacturing method of the present invention.

[0014] The Fe concentration of the ferric polysulfate aqueous solution is preferably between 100 g / L and 250 g / L. Within this range, the specific surface area of ​​the adsorbent tends to be within an appropriate range. The lower limit is more preferably 150 g / L or more, and the upper limit is more preferably 200 g / L or less.

[0015] Examples of alkaline aqueous solutions include aqueous solutions of alkali hydroxides such as sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and lithium hydroxide aqueous solution, as well as aqueous ammonia. Sodium hydroxide aqueous solution is particularly preferred because it is inexpensive and easy to handle industrially. The concentration of the alkaline aqueous solution is preferably between 10 g / kg and 500 g / kg. Within this range, the viscosity of the resulting slurry does not become too high, and the reactivity with the ferric polysulfate aqueous solution tends to be good. The lower limit is more preferably 100 g / kg or more, and the upper limit is more preferably 350 g / kg or less.

[0016] In the first step, it is preferable to add the ferric polysulfate aqueous solution to the alkaline aqueous solution over a predetermined time while stirring. Adding the ferric polysulfate aqueous solution to the alkali, adding it over a predetermined time, and stirring during the addition facilitates a uniform neutralization reaction, making it easier to obtain an adsorbent with excellent adsorption properties.

[0017] When adding the ferric polysulfate aqueous solution, it is preferable to maintain the reaction temperature at 70°C or below. At such a temperature, the crystallization and growth of the generated iron(III) hydroxide proceeds appropriately, and a sufficient amount of adsorption sites tend to remain. More preferably, the temperature is 60°C or below, and even more preferably 50°C or below. The lower limit is not particularly limited, but as a guideline, it is 15°C or above.

[0018] Adding the ferric polysulfate aqueous solution over a predetermined period of time is preferable because it reduces the likelihood of drastic fluctuations in the pH of the solution, resulting in more uniform particle size and structure of the product, and making it easier to obtain an adsorbent with superior adsorption properties. Specifically, it is preferable to add the ferric polysulfate aqueous solution over 20 minutes or more, and more preferably over 30 minutes. There is no particular upper limit to the addition time, but from the viewpoint of productivity, it is preferable to be within 2.0 hours, and more preferably within 1.0 hour.

[0019] To ensure a sufficiently high frequency of contact between the ferric polysulfate solution and the alkaline solution, and to allow the neutralization reaction to proceed uniformly, it is preferable to maintain a sufficiently high stirring speed to keep the ferric polysulfate solution and the alkaline solution mixed while the ferric polysulfate solution is being added. As a guideline, for example, if the total volume of the alkaline solution and the ferric polysulfate solution is 5 L, the system in a commercially available tall beaker should be stirred at 400 rpm using a rotor with a diameter of 85 mm.

[0020] (Second step) In the second step, the pH of the slurry containing iron(III) hydroxide is adjusted. In the second step, the pH of the slurry containing iron(III) hydroxide obtained in the first step is adjusted to between 5.0 and 9.0. It is preferable to stir the slurry for a certain period of time after adjusting the pH. By setting the pH within the above range, the number of hydroxyl groups that can act as adsorption sites increases, and the positive charge present in the ferric polysulfate aqueous solution is weakened, making it easier to adsorb substances other than anions. The lower limit of the pH is more preferably 7.5 or higher. The upper limit of the pH is more preferably 8.5 or lower.

[0021] Acids and alkalis are used as pH adjusters. The acids and alkalis used here are not limited, but examples of acids include mineral acids such as hydrochloric acid and sulfuric acid, and examples of alkalis include aqueous solutions of alkali hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, as well as aqueous ammonia.

[0022] During pH adjustment and stirring in the second step, it is preferable to maintain the liquid temperature at 70°C or lower, more preferably 60°C or lower, in order to suppress excessive crystallization and growth of iron(III) hydroxide. The lower limit is not particularly limited, but as a guideline, it should be 15°C or higher.

[0023] It is preferable to stir the slurry after pH adjustment for a certain period of time. A stirring time of 1.0 hour or more is preferable because it has the advantage of homogenizing the pH throughout the slurry and allowing the effect of weakening the positive charge to spread more easily throughout the slurry. Conversely, a stirring time of less than 3.0 hours is preferable because it reduces the likelihood of a decrease in pH due to the influence of carbon dioxide in the air.

[0024] (Third step) In the third step, the iron(III) hydroxide slurry after pH adjustment is subjected to solid-liquid separation, the resulting cake is washed, and the moisture content of the washed cake is adjusted.

[0025] The solid-liquid separation and washing methods are not particularly limited and can be carried out by known methods such as suction filtration using a Buchner funnel, filter pressing, and repulping. It is preferable to use deionized water or pure water for washing. It is preferable to wash until the electrical conductivity of the filtrate after washing is 500 μS / cm or less. By washing thoroughly, ionic impurities such as halogen ions, sulfate ions, nitrate ions, ammonium ions, and alkali metal ions can be removed from the iron(III) hydroxide cake, preventing adsorption by impurities from being inhibited. It is more preferable to wash until the electrical conductivity of the filtrate after washing is 200 μS / cm or less. The lower limit is not particularly limited. For example, it may be 1 μS / cm. Since a large amount of washing water is required to reduce the electrical conductivity of the filtrate, it is desirable to set a target value for the electrical conductivity of the filtrate considering the cost and required quality.

[0026] The moisture content of the iron(III) hydroxide cake after washing is preferably adjusted to a range of 600 g / kg to 800 g / kg. Adjusting it to this range tends to yield an adsorbent with a smooth surface and excellent adsorption properties. The upper limit is more preferably 750 g / kg or less. The method for adjusting the moisture content is not particularly limited, but a method that does not involve heating is preferred. It is industrially preferable to adjust the moisture content at the same time as washing, as this eliminates the need for extra effort and additional equipment, but additional treatments such as centrifugal separation may be performed on the cake after washing.

[0027] (Fourth step) After the third step, a fourth step may be optionally performed in which an iron(III) hydroxide cake with adjusted moisture content is granulated and the resulting granules are dried.

[0028] In the fourth step, the granulation method is preferably extrusion granulation because it is easy to obtain an adsorbent with a particle size and bulk density suitable for the application of the present invention. Specifically, it is preferable to extrude an iron(III) hydroxide cake with adjusted water content through an open member having multiple openings to obtain a granulated body. The shape of the holes formed in the open member may be circular, triangular, polygonal, ring-shaped, etc. The circular equivalent diameter of the opening is preferably 100 μm or more and 1000 μm or less, because when the obtained adsorbent is packed into a column and water is passed through it, continuous operation is possible without increasing the water flow pressure. The lower limit is more preferably 300 μm or more, and the upper limit is more preferably 700 μm or less.

[0029] While there are no particular limitations on granulation methods other than extrusion granulation, typical examples include crushing and granulating the cake using equipment such as a power mill, and spray granulation, in which the cake is rehydrated with water, the resulting slurry is sprayed, and then dried.

[0030] The resulting granules are then dried. Drying at 150°C or below is preferable because it allows sufficient hydroxyl groups contributing to adsorption to remain, resulting in granules that are free from surface cracks and possess sufficient strength for use. More preferably, the drying temperature is 110°C or below. The lower limit of the drying temperature is not particularly limited; it is sufficient to dry the granules until the moisture content is such that it does not cause problems in subsequent processes or use. The drying time is also not particularly limited; for example, drying may be stopped when the weight hardly changes. As a guideline, however, from the viewpoint of production efficiency, it is 24 hours or less. As will be described later, it is preferable that the adsorbent produced by the method of the present invention contains a certain amount of moisture; therefore, it is preferable to optimize the drying conditions by evaluating the moisture content of products produced by drying under different conditions beforehand.

[0031] The dried granules (hereinafter also referred to as "dried product") are preferably crushed to a suitable degree and then classified using a classification apparatus so that the particle size is between 100 μm and 1000 μm. With such particle sizes, it is possible to maintain the packing volume in the adsorption tower or the like within a suitable range, and there is a tendency to obtain an adsorbent that is less likely to clog the adsorption tower. The lower limit is more preferably 300 μm or more, the upper limit is more preferably 700 μm or less, and even more preferably 600 μm or less. The dried and classified granules are one form of the adsorbent obtained by the manufacturing method of the present invention (hereinafter referred to as "granular adsorbent"). As will be described later, the granular adsorbent is typically used by packing it into an adsorption tower or column and passing water containing the target substance through it. Note that the dried product before classification also has the ability to adsorb various substances.

[0032] (Fifth Step) Optionally, a fifth step may be performed in which the above-mentioned dried product or granular adsorbent is pulverized. The fifth step can make the adsorbent into a powder. Pulverization can be carried out using a commercially available pulverizer, such as an automatic mortar and pestle. As a guideline, the particle size of the powdered adsorbent is preferably 1 μm to 50 μm, which makes it easy to recover after adsorption. Pulverized dried product or granular adsorbent is also one form of adsorbent obtained by the manufacturing method of the present invention (hereinafter referred to as "powdered adsorbent"). While powdered adsorbent has improved adsorption capacity, it is difficult to pass water through it when packed into a column. Therefore, as described later, it is typically used by scattering it in water containing the substance to be adsorbed and recovering it after adsorption.

[0033] (Other optional steps) In addition to the fourth and fifth steps described above, the iron(III) hydroxide cake obtained in the third step, with its moisture content adjusted, may be dried and then pulverized using a grinder such as a hammer mill. This step makes it possible to obtain a powdered adsorbent without going through the granular process.

[0034] [Characteristics of the Adsorbent] The preferred form of the adsorbent produced by the method of the present invention will be described. The adsorbent produced by the method of the present invention is formed by the aggregation of primary particles with a particle size of 10 nm or less to form secondary particles, and further, the secondary particles form granules or powders with a particle size of 1 μm to 1000 μm due to the binding force between the particles. The adsorbent composed of particles bound together in this way has high strength and is not easily destroyed in solution. Therefore, when used as an adsorbent, it is possible to suppress the generation of fine powder that could lead to secondary contamination or blockage of the adsorption tower.

[0035] The specific surface area of ​​the adsorbent produced by the method of the present invention is 200 m². ２ The specific surface area is 300 m² or more. Because the specific surface area is large, the frequency of contact with the adsorbed substance increases, and the number of adsorption sites also increases. Therefore, the adsorbent produced by the method of the present invention can adsorb large amounts of various chemical species. While there is no particular upper limit to the specific surface area, as a guideline, the specific surface area of ​​the adsorbent produced by the method of the present invention is 300 m². ２ The values ​​tend to be less than / g.

[0036] The particle size of the primary particles constituting the adsorbent produced by the method of the present invention is 10 nm or less. Since the small primary particle size increases the binding force between the particles, the adsorbent produced by the method of the present invention has strength that does not disintegrate even in a liquid. The lower limit is not particularly limited, but as a rough guide, it is 1 nm or more.

[0037] The adsorbent produced by the method of the present invention has an iron content of 450 g / kg or more, more preferably 500 g / kg or more. When the iron content is within this range, an adsorbent having sufficient adsorption sites as iron(III) hydroxide can be produced. The upper limit is not particularly limited, but considering the possible presence of moisture, oxygen, and hydrogen atoms, the upper limit can be about 700 g / kg. More preferably, it is 600 g / kg or less.

[0038] The adsorbent produced by the method of the present invention preferably has a water content of 100 g / kg or more and 300 g / kg or less. When the water content is within the above range, there are many hydroxyl groups serving as adsorption sites, and the shape of the adsorbent tends not to collapse. Further, when the water content is within the above range, condensation between hydroxyl groups is suppressed under atmospheric storage, and it tends to be suitable for long-term storage. The upper limit is more preferably 225 g / kg or less, still more preferably 150 g / kg or less.

[0039] The adsorbent produced by the method of the present invention preferably has an appropriate amount of adsorbed moisture. The amount of adsorbed moisture can be evaluated by a method of measuring the moisture of the adsorbent that has adsorbed moisture in an environment where the temperature and humidity are kept constant using a Karl Fischer moisture meter.

[0040] The bulk density of the granular adsorbent is preferably 1.00 g / mL or more. When the bulk density is within this range, it is likely to have sufficient strength for filling and using in a column, and the number of adsorption sites also tends to increase. The upper limit is not particularly limited, but as a rough guide, it is 1.20 g / mL or less.

[0041] The bulk density of the powdered adsorbent is preferably less than 1.00 g / mL, more preferably 0.95 g / mL or less, still more preferably 0.90 g / mL or less. The lower limit is not particularly limited, but as a rough guide, it is 0.30 g / mL or more.

[0042] The adsorbent produced by the method of the present invention preferably has a small zeta potential ranging from weakly acidic to neutral. Specifically, the zeta potential at a pH of 6.0 to 7.2 is preferably 20.0 mV or less, more preferably 15.0 mV or less. The lower limit is not particularly limited. As a rough guide, it is about -10.0 mV. The zeta potential can be measured using a measuring device typified by ZETASIZER (registered trademark) nanoZS manufactured by Malvern Panalytical after adding 0.5 g of the adsorbent to 50 mL of pure water, stirring with a stirrer for 5 minutes or more, and adjusting the pH with hydrochloric acid and an aqueous sodium hydroxide solution.

[0043] When using the adsorbent produced by the method of the present invention, other iron compounds may be mixed. Typically, by mixing substances having the ability to adsorb various substances such as magnetite, more excellent adsorption characteristics can be exhibited.

[0044] [Use] The adsorbent produced by the method of the present invention can be used in various fields such as the recovery of heavy metals leaked into the environment, the removal of radioactive substances in water, and the recovery of resource substances typified by rare metals. The substance to be adsorbed may be any substance that can be adsorbed by the adsorbent produced by the method of the present invention and is not particularly limited. The substance to be adsorbed may be in the form of a cation or an anion. Preferably it is a cation, more preferably a metal ion, and still more preferably a lanthanoid ion.

[0045] The adsorbent produced by the method of the present invention can be used in combination with other adsorbents in any manner and proportion. The adsorbent produced by the method of the present invention can be used in a method of packing it into a column and passing water containing the target substance through it, or in a method of immersing it in water to adsorb the target substance and then recovering it. When packing it into a column, using granular adsorbent makes it possible to realize a column that can stably pass water without clogging the adsorption column. A column using the adsorbent produced by the method of the present invention is also one aspect of the present invention. When scattering and recovering in water, using powdered adsorbent allows for efficient adsorption by scattering a powder with excellent adsorption characteristics and recovering it after adsorption. A method of scattering the adsorbent produced by the method of the present invention into water and recovering it is also one aspect of the present invention. Furthermore, for example, using an intermediate product in the manufacturing method of the present invention as an adsorbent is also one aspect of the present invention. In addition, a method of scattering the raw materials used in the present invention into water containing the target substance to be adsorbed and carrying out a reaction in water that mimics the present invention is also included in the aspects of the present invention.

[0046] The present invention will be further described in detail by the following examples and comparative examples. The following examples are for illustrative purposes only and do not limit the scope of the invention. In the stirring operations described in the examples and comparative examples, the rotation speed is appropriately adjusted to ensure that the entire liquid is uniformly mixed and that splashes do not scatter into the surroundings, taking into consideration properties related to the behavior of the liquid during stirring, such as the liquid volume, viscosity, and shape of the container. Also, in cases where the same effect can be obtained using any commercially available product from any company, such as hydrochloric acid, the names of the manufacturers and distributors are omitted.

[0047] [Evaluation Method] The evaluation method used in this invention is described in detail below. [Specific Surface Area] 0.2 g of adsorbent was degassed at 150°C for 30 min using Micromeritics' VacuPrep 061, then cooled for 15 min, and the BET specific surface area was measured using the BET single-point method with Micromeritics' Gemini® VII.

[0048] [Primary Particle Size] The adsorbent was crushed as needed, and the particles were observed using a JEOL JEM-1400plus transmission electron microscope. The observation magnification was 600,000x (transmission electron microscope observation magnification 300,000x × print magnification 2x).

[0049] [Bulk Density] The bulk density was calculated by filling a graduated cylinder with 50 mL of adsorbent without tapping or shaking, and then measuring the mass of the adsorbent added.

[0050] [Iron Content] x g (approximately 3 g) of adsorbent was placed in a 300 mL conical beaker. Approximately 50 mL of distilled water was added to the conical beaker, then 20 mL of sulfuric acid was added and heated to dissolve. Once the adsorbent was dissolved, the heater was stopped, the inside of the conical beaker was washed with distilled water, and it was cooled to room temperature. After cooling, distilled water was added until the total volume of the system was 250 mL, and the mixture was stirred.

[0051] 20 mL of the system and 20 mL of warmed mercury amalgam were placed in a reducer, the reducer was sealed, and shaken up and down for 3 minutes. The stopcock at the bottom of the reducer was opened, and the entire volume of mercury amalgam was dropped into the mercury receptacle. The liquid was poured into a conical beaker and titrated with a 0.2 mol / L potassium permanganate aqueous solution until it turned a light pink color. If the amount of potassium permanganate used in the titration is a (mL), then the iron content is T. Ｆｅ (g / kg) is calculated using the following formula: T Ｆｅ = 1000 × a × 0.005585 / {x × (20 / 250)}.

[0052] [Water content] Measured using the trace moisture measurement device AQ-2100 manufactured by Hiranuma. [Europium adsorption test] Artificial seawater Marin Art (registered trademark) SF-1 manufactured by Tomita Pharmaceutical Co., Ltd. (hereinafter referred to as "artificial seawater") and europium (III) chloride hexahydrate were dissolved in tap water, and seawater diluted 1000-fold containing 5 mg / kg of europium (Eu) (III) ions (hereinafter referred to as "batch test solution") was prepared. 150 mL of the batch test solution was aliquoted into a polypropylene Erlenmeyer flask. Adsorbent was weighed out as yg (approx. 0.06 g) so that the ratio of the batch test solution to the adsorbent was 2,500 mL / g, and was added to the aliquoted batch test solution. The batch test solution with the adsorbent added was shaken at 25 °C. Sampling was performed immediately after the start of shaking and after 168 h. After solid-liquid separation using a syringe filter DISMIC CS type with a pore diameter of 0.45 μm manufactured by Advantec, the Eu (III) ion concentration was measured using an ICP-OES PS3520UVDDII manufactured by Hitachi High-Tech Sciences Corporation. Let the Eu (III) ion concentration immediately after the start of shaking be E Ｓ (mg / kg), and the Eu (III) ion concentration after 168 h be E Ｅ (mg / kg). Then, the adsorption amount A (μg / g) is expressed by the following formula. A = 150 × (E Ｓ - E Ｅ ) / y.

[0053] [Example 1] <First step> 880 mL of a 400 g / L sodium hydroxide aqueous solution and 1,787 ml of pure water were placed in a 5 L stainless steel beaker and mixed until uniform. After the liquid temperature of the mixed sodium hydroxide aqueous solution reached <00,0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000025 °C, using a HEIDON600G manufactured by Shinto Kagaku Co., Ltd. (hereinafter referred to as "paddle stirrer"), while stirring at 400 rpm, 1,080 mL of a ferric poly sulfate aqueous solution with an Fe concentration of 166.7 g / L was added over 30 min. During the addition, the liquid temperature temporarily rose, and the maximum temperature was 47.2 °C. Also, the pH of the slurry at the end of the addition was 7.2.

[0054] <Second step> The pH of the slurry was adjusted to 8.0 using a sodium hydroxide aqueous solution. After adjustment, it was stirred at 25 °C for 1.0 h. Also, the pH at the end of the stirring was 8.0.

[0055] <Third Step> The slurry from the second step was filtered by suction using a Buchner funnel, and the filtered cake was washed with pure water. Washing was stopped when the electrical conductivity of the filtrate after washing was 200 μS / cm or less, and the cake was further aspirated until the water content was approximately 700 g / kg. The water content of the cake after aspiration was 710 g / kg.

[0056] <Fourth Step> Using the filtration cake containing iron(III) hydroxide obtained in the third step, the filtration cake was pressed onto a mesh with a mesh pore size of 0.5 mm to produce granules. The obtained granules were dried at 90°C for 24 hours to obtain a dried product. The dried product was crushed using a Kalita electric coffee mill CM-50 (hereinafter referred to as "cutter mill"), and then classified into particles between 300 μm and 600 μm to obtain a black granular adsorbent.

[0057] [Example 2] The dried product obtained in the fourth step of Example 1 was pulverized using an Ishikawa-type stirring and grinding machine 22 manufactured by Ishikawa Factory Co., Ltd., and then pulverized using a Hosokawa Micron AP-1 micropulverizer with a mesh pore size of 0.5 mm to obtain a brown powdered adsorbent. The average particle size of the obtained powdered adsorbent was 7 μm.

[0058] [Comparative Example 1] <First Step> 166 mL of 400 g / L sodium hydroxide aqueous solution and 84 mL of pure water were placed in a 1 L stainless steel beaker and stirred until homogeneous. After the temperature of the mixed sodium hydroxide aqueous solution reached 25°C, 150 mL of an aqueous solution containing 390 g / kg of iron(III) chloride was added over 40 min while stirring at 300 rpm using a vane-type agitator. The liquid temperature temporarily rose during the addition, reaching a maximum temperature of 44.5°C. The pH at the completion of the addition was 9.2.

[0059] <Second Step> The procedure was carried out in the same manner as in Example 1, except that the pH of the slurry was adjusted to 4.8 using hydrochloric acid. The pH at the end of stirring was also 4.8.

[0060] <Third Step> The procedure was carried out in the same manner as in Example 1, except that the washing was terminated when the electrical conductivity of the filtrate after washing became 10 mS / cm or less.

[0061] <Fourth Step> The procedure was carried out in the same manner as in Example 1, except that the drying temperature of the granulated material was set to 120°C, to obtain a black granular adsorbent.

[0062]

[0063] As shown in Table 1, the adsorbent produced by the method of the present invention has a greater adsorption capacity than the adsorbent of Comparative Example 1, which was produced under different manufacturing conditions. The present invention makes it possible to obtain an adsorbent with high adsorption capacity. Furthermore, since it has high adsorption capacity whether in granular or powder form, it can be used in a variety of applications.

[0064] [Adsorption Test of Europium Using a Column] The granular adsorbent obtained in Example 1 was packed into a column to perform an adsorption test of europium. The adsorbent obtained in Example 1 was packed into a 20 mL column test tube to fill it. Artificial seawater and europium(III) chloride hexahydrate were dissolved in tap water, and the europium(Eu)(III) ion concentration was 1 mg / kg {C ０ A 1000-fold diluted seawater solution containing (mg / kg) was prepared (hereinafter referred to as "column test solution"). The column test solution was passed through the column at a rate of 3.3 mL / min. Sampling was performed at 24-hour intervals, and the Eu(III) ion concentration C (mg / kg) in the column test solution after passing through the column was evaluated. Figure 1 shows the value obtained by dividing the amount of water passed through by the volume of adsorbent and the C / C ratio. ０ This shows the relationship. Even when the column test solution was passed through at a volume exceeding 3500 times the volume of the adsorbent, no Eu(III) ions were detected, and even after the flow rate exceeded 3800 times and Eu(III) ions began to be detected, the majority continued to be adsorbed by the adsorbent.

[0065] The adsorbent produced by the method of the present invention can be used even when packed into a column, and exhibits high adsorption capacity.

Claims

1. A method for producing an adsorbent, comprising: a first step of adding an aqueous solution of ferric polysulfate to an alkaline aqueous solution to form a slurry; a second step of adjusting the pH of the slurry to 5.0 or higher and 9.0 or lower; and a third step of subjecting the slurry to solid-liquid separation, washing the resulting cake, and adjusting the water content of the cake after washing.

2. The manufacturing method according to claim 1, further comprising a fourth step of granulating a cake with adjusted moisture content and drying the resulting granules.

3. The manufacturing method according to claim 1 or 2, wherein the second step includes stirring a slurry whose pH has been adjusted to 5.0 or more and 9.0 or less for 1.0 hour or more.

4. The manufacturing method according to claim 1 or 2, wherein the second step includes adjusting the pH of the slurry to 7.5 or more and 9.0 or less.

5. The manufacturing method according to claim 1 or 2, wherein the third step includes washing the cake until the electrical conductivity of the filtrate after washing is 500 μS / cm or less.

6. The manufacturing method according to claim 1 or 2, wherein the third step includes adjusting the moisture content of the cake after washing to be 600 g / kg or more and 800 g / kg or less.

7. The manufacturing method according to claim 2, wherein the fourth step includes performing granulation molding by extrusion granulation.

8. The manufacturing method according to claim 2, further comprising a fifth step of crushing the dried granules.

9. The manufacturing method according to claim 1, further comprising the steps of drying a cake with adjusted moisture content and crushing the dried cake.

10. Specific surface area of ​​200 m² ２ An adsorbent characterized by having a concentration of 100 g / kg or more, a primary particle diameter of 10 nm or less, an iron content of 450 g / kg or more, and a water content of 100 g / kg or more and 300 g / kg or less.

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