JP2006124239A - Method for manufacturing iron oxyhydroxide and iron oxyhydroxide adsorbent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for advantageously manufacturing iron oxyhydroxide having excellent adsorbability for phosphorus components in industrial wastewater, an exhaust gas and the like and harmful substances such as endocrine disruptors, and an adsorbent obtained by the method. <P>SOLUTION: The method for manufacturing iron oxyhydroxide comprises successively performing (a) a step of adding a base to a ferric ion-containing solution to adjust the pH to 3.3-6 to form a precipitate containing iron oxyhydroxide, (b) a step of drying the precipitate at a temperature of ≤100°C to obtain iron oxyhydroxide, and (c) a step of bringing the obtained iron oxyhydroxide into contact with water and then drying the resulting product at a temperature of ≤100°C. The adsorbent is obtained by this method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing iron oxyhydroxide and an iron oxyhydroxide adsorbent. More specifically, the present invention relates to a method for advantageously producing iron oxyhydroxide having an excellent adsorption capacity for harmful substances such as phosphorus components in factory wastewater and exhaust gas, and an adsorbent obtained by the method. Is.

In recent years, with the development of science and technology, a wide variety of chemical substances are manufactured and used. Many of these chemical substances have harmful effects on human health and ecosystems. For example, in the case of water treatment, organic or inorganic phosphorus, fluorine, arsenic, molybdenum, chromium, antimony, selenium, boron, tellurium, beryllium, cyan and the like are known as harmful substances. In the case of gas treatment, hydrogen sulfide, mercaptan, hydrocyanic acid, hydrogen fluoride, hydrogen chloride, SO _x , NO _x , phosphorus, arsenic, antimony, sulfur, selenium, tellurium compounds, cyano compounds, etc. in the exhaust gas are harmful. Known as a substance.
The above hazardous substances may be contained in drinking water, tap water, mineral water, therapeutic water, agricultural water, industrial wastewater, and dissolved, suspended, emulsified or suspended in the air or exhaust gas. Attempts have been made to separate and remove the harmful substances.

Conventionally, various proposals have been made on iron-based adsorbents for adsorbing harmful chemical substances from industrial wastewater or the like. For example, hydrous iron oxide having a particle size of 50 μm or less is heated at 200 to 500 ° C. to evaporate crystal water in the hydrous iron oxide, and the pores are 0.1 to 50 nm and the specific surface area is 15 to 200 m ² / g. (See Patent Document 1) has been proposed.
However, in patent document 1, since it heat-processes at 200-500 degreeC, energy consumption is large and it is industrially disadvantageous. In addition, since the adsorption sites (hydrogen bonding sites) of the iron-based adsorbent necessary for the adsorption of harmful substances such as phosphorus components are reduced by the high-temperature heat treatment, there is a problem that the adsorption power is not sufficient.

Further, an anion adsorbent comprising an amorphous iron hydroxide-based precipitation product obtained by adjusting the pH to 3 by adding an alkali to the iron ion solution and drying at a low temperature (see Patent Document 2) )It has been known.
However, at pH 3, trivalent iron ions of 1 × 10 ⁻³ mol / dm ⁻³ remain, and iron hydroxide cannot be precipitated stably. Moreover, in the method of Patent Document 2, since the water treatment and the drying treatment in the step (c) in the method of the present invention are not performed, the obtained adsorbent has a problem that the specific surface area is small and the adsorbing power is not sufficient.
In addition, a method for producing an aggregate of fine particle iron oxyhydroxide having a BET specific surface area of 50 to 500 m ² / g (see Patent Document 3) has also been proposed.
However, the iron oxyhydroxide of Patent Document 3 is excellent in reactivity because the particle system is nano-sized and small, but there is a risk of ignition due to particle scattering or friction, which is inconvenient to handle, and further adsorbed. There was a problem that it was difficult to recover the substance.
For this reason, it has been desired to develop an adsorbent that has sufficient ability to adsorb harmful substances and is easy to handle.

JP 2003-154234 A JP 2003-334542 A JP 2004-509752 A

  In view of the above-mentioned present situation, the present invention provides a method for advantageously producing iron oxyhydroxide having an excellent adsorbing ability for harmful substances such as phosphorus components in factory wastewater, exhaust gas, and environmental hormones, and the method. It is an object to provide a prepared adsorbent.

As a result of intensive studies to achieve the above-mentioned object, the present inventors dried a precipitate containing iron oxyhydroxide produced using a trivalent iron ion-containing solution as a starting material at a low temperature and further contacted with water. The inventors have found that the above object can be achieved by drying at low temperature again. The invention has been completed based on such findings.
That is, the present invention
(1) (a) A step of generating a precipitate containing iron oxyhydroxide by adding a base to a trivalent iron ion-containing solution and adjusting the pH to 3.3 to 6,
(B) drying the precipitate at a temperature of 100 ° C. or less to obtain iron oxyhydroxide; and (c) contacting the obtained iron oxyhydroxide with water, and then at a temperature of 100 ° C. or less. A method for producing iron oxyhydroxide characterized by sequentially performing a drying step, and (2) iron oxyhydroxide adsorption mainly comprising iron oxyhydroxide obtained by the method described in (1) above Material,
Is to provide.

According to the production method of the present invention, iron oxyhydroxide having an excellent adsorption ability for harmful substances such as phosphorus components and environmental hormones can be efficiently produced.
Further, the adsorbent mainly composed of iron oxyhydroxide obtained by the production method of the present invention has a large specific surface area and has 5 to 8 times the anion adsorption site (hydrogen bonding site) of the conventional one. Therefore, it exhibits an excellent adsorptive power for anionic species such as phosphate ions, and can be suitably used in fields such as water purification, drainage or gas purification.
The adsorbent of the present invention is highly practical because it can be easily reused, and the elements contained in the anionic species can be efficiently recovered by eluting the adsorbed anionic species.

In the method for producing iron oxyhydroxide of the present invention, (a) a base is added to a trivalent iron ion-containing solution, and the pH is adjusted to 3.3 to 6, thereby generating a precipitate containing iron oxyhydroxide. The process of
(B) drying the precipitate at a temperature of 100 ° C. or less to obtain iron oxyhydroxide; and (c) contacting the obtained iron oxyhydroxide with water, and then at a temperature of 100 ° C. or less. The drying process is sequentially performed, and the (c) process is a significant feature.

In the step (a) of the method of the present invention, ferric chloride [FeCl ₃ ], ferric sulfate [Fe ₂ (SO ₄ ) ₃ ], ferric nitrate are used as the trivalent iron ion-containing solution as the raw material solution. A solution containing a ferric compound such as iron [Fe (NO ₃ ) ₃ ] may be mentioned. Among these, an aqueous solution of ferric chloride [FeCl ₃ ] is preferable from the viewpoint of reactivity and the like.

The base is used to neutralize the trivalent iron ion-containing solution and adjust the pH to produce a precipitated product containing iron oxyhydroxide. As the base, NaOH, KOH, Na ₂ CO ₃ , K ₂ CO ₃ , CaO, Ca (OH) ₂ , CaCO ₃ , NH ₃ , NH ₄ OH, MgO, MgCO ₃ or the like can be used. Of these, sodium hydroxide (NaOH) is particularly preferable.

There are no particular limitations on the concentration of the trivalent iron ion-containing solution and the base used. In light of ease of reaction control of the base, the concentration of the trivalent iron ion-containing solution is preferably 0.01 to 5 mol / L, and more preferably 0.05 to 3 mol / L. The concentration of the base is preferably 0.1 to 10 mol / L, more preferably 1 to 5 mol / L.
The pH needs to be adjusted to 3.3-6. When the pH is less than 3.3, for example, pH 3, since it is an initial stage of iron oxyhydroxide crystal formation, 1 × 10 ⁻³ mol / dm ⁻³ trivalent iron ions remain and precipitates are formed in a stable state. Difficult to do. By adjusting the pH to 3.3, the residual concentration of trivalent iron ions becomes 1 × 10 ⁻⁴ mol / dm ⁻³ and iron hydroxide can be stably precipitated. Moreover, in the vicinity of pH 7, ferrous chloride precipitates. Therefore, from the viewpoint of stably producing high-purity iron oxyhydroxide having an appropriate hydrogen bonding site, the pH is preferably 3.5 to 5.5, more preferably 3.7 to 5.3.

The precipitate obtained in the step (a) is separated by suction filtration or the like, and used for the step (b).
In the step (b), the precipitate is dried at a temperature of 100 ° C. or lower. When the temperature exceeds 100 ° C., the drying is fast, but it becomes difficult to control the adsorption site (hydrogen bonding site) of anions appropriately. If the temperature is too low, drying takes too much time, which may not be practical. For this reason, drying temperature becomes like this. Preferably it is 20-80 degreeC, More preferably, it is 30-70 degreeC, Most preferably, it is 40 degreeC or more and less than 60 degreeC. Drying may be performed in air, vacuum, or inert gas, but is preferably performed under vacuum conditions. The drying time is not particularly limited, and is usually 2 hours to 2 days, preferably 5 hours to 24 hours.
In the step (b) of the present invention, since there is no drying treatment at a high temperature, interparticle sintering of iron oxyhydroxide does not occur. Therefore, (b) iron oxyhydroxide obtained in the step has a 30~300m ² / g, BET specific surface area of the particular 40 to 200 m ² / g.

Further, the iron oxyhydroxide obtained in the step (b) contains a large amount of hydrogen bonding sites (anion adsorption sites), and the hydroxyl group content per kg of iron oxyhydroxide is 3 mol-OH / kg or more, preferably Is 5 to 20 mol-OH / kg, more preferably 7 to 30 mol-OH / kg.
The hydroxyl group content of iron oxyhydroxide was determined by measuring the stretched state of O—H of FeOOH using a Fourier transform infrared spectrophotometer (diffuse reflection method), and Russel et al., Nature 1974, 248, Calculated based on Miura et al., Am. Chem. Soc., Fuel Chem., 1999, 44 (3), 642-646, with FeOOH peaks from 220-221 as 3130 cm ^-1 and 3420 cm ^-1 can do.

The iron oxyhydroxide obtained by the step (b) is a needle-like crystal, the width is 10 to 500 nm, preferably 50 to 200 nm, and the length / width ratio (L / D) is usually 5/1. -50/1, preferably 5 / 1-20 / 1.
Iron oxyhydroxide is a needle-like crystal, but is aggregated into aggregate particles. The average particle diameter of the iron oxyhydroxide aggregate particles is 100 to 300 μm, preferably 150 to 250 μm.
Here, the average particle size is calculated from a volume-based particle size distribution measured by a laser diffraction / scattering method using a laser diffraction / scattering particle size distribution analyzer (for example, Horiba, Ltd., LA-920). Mean median diameter.

In step (c) of the method of the present invention, the iron oxyhydroxide obtained in step (b) is brought into contact with water and then dried at a temperature of 100 ° C. or lower.
When the temperature exceeds 100 ° C., drying is fast, but it is difficult to control the hydrogen bonding sites (anion adsorption sites) to remain appropriately. If the temperature is too low, drying takes too much time, which may not be practical. For this reason, drying temperature becomes like this. Preferably it is 20-80 degreeC, More preferably, it is 30-70 degreeC, Most preferably, it is 40 degreeC or more and less than 60 degreeC. Drying may be performed in air, vacuum, or inert gas, but is preferably performed under vacuum conditions. The drying time is not particularly limited, and is usually 2 hours to 2 days, preferably 5 hours to 24 hours.
The hydroxyl group content (iron oxyhydroxide adsorption site) per kg of iron oxyhydroxide obtained by the treatment in the step (c) is 3 mol-OH / kg-FeOOH or more, preferably 5 to 20 mol-OH / kg, More preferably, it remains 7 to 30 mol-OH / kg and does not change greatly. However, the BET specific surface area increases by 1.2 times or more, and 1.5 to 2.5 times under suitable conditions. As a result, the specific surface area measured by the BET method, preferably 100 to 400 m ² / g, more preferably 120~350m ² / g, particularly preferably a 150 to 300 m ² / g.
In the step (c) of the present invention, since there is no drying treatment at a high temperature, there is no interparticle sintering, and the increased BET specific surface area does not decrease.
The average particle diameter as the aggregate particles is 80 to 300 μm, preferably 100 to 200 μm.

The following (1) and (2) can be considered about the mechanism of the specific surface area increase by the water treatment of (c) process.
(1) Since a base such as sodium hydroxide is added to the trivalent iron ion-containing solution, NaCl crystals are produced in nano-size as impurities in the FeOOH aggregate. When this comes into contact with water, NaCl is dissolved, and the portion where NaCl is dissolved becomes pores, which is thought to increase the specific surface area.
(2) Since the pH is adjusted to 3.3 to 6 in the production process of FeOOH, there is insufficient hydroxyl group (OH) to completely crystallize FeOOH, and it is dried at a low temperature of 100 ° C. or lower in that state. As a result, the hydroxyl group becomes insufficient. In this state, when iron oxyhydroxide comes into contact with water, rapid water absorption occurs, and it is considered that the crystal lattice of FeOOH is loosened by the water absorption.

  In the method of the present invention, oxy having different BET specific surface area, hydroxyl group content, single particle average particle size and fine particle aggregate average particle size can be obtained by appropriately adjusting the conditions of the steps (a) to (c). Iron hydroxide can be produced.

  There are three types of iron oxyhydroxide, α-FeOOH (goethite), β-FeOOH (akagenite), and γ-FeOOH (repidocrocite), but the iron oxyhydroxide by the method of the present invention is close to α-FeOOH. However, it is considered that it is not 100% perfect α-FeOOH (goethite). The iron oxyhydroxide by the method of the present invention is amorphous FeOOH fine particles close to α-FeOOH, which are large aggregates, and are in the form of glossy black particles. The aggregate has innumerable pores. The average pore diameter of the particles is preferably 0.1 to 5.0 nm, more preferably 0.5 to 1.5 nm.

The crystal structure of the iron oxyhydroxide of the present invention is basically orthorhombic, and the FeO ₆ octahedron is coordinated with three O ²⁻ and three OH ⁻ atoms on the FeIII ion. The stretching of OH ⁻ OH coordinated to FeIII ions can be obtained as a characteristic spectrum when measured with a Fourier transform infrared spectrophotometer (FTIR).
That is, the FTIR spectrum peak of FeOOH of the present invention has a large peak at 3420 cm ⁻¹ exhibiting O—H stretching, and is characterized by containing a large amount of weak hydrogen-bonded OH groups. This 3420 cm ⁻¹ peak OH ⁻ in the FTIR spectrum plays a major role in the adsorption of anions such as phosphate ions and environmental hormones as hydrogen bonding sites.

  When removing harmful substances such as phosphorus components and environmental hormones in water using the iron oxyhydroxide of the present invention, this can be carried out by filling the packed tower (tank) and passing water. In this case, the average pore diameter, average particle diameter, BET specific surface area, etc. of the aggregate particles are those suitable for capturing harmful substances to be adsorbed and removed. In general, from the viewpoint of handleability, adsorptivity, and recoverability of adsorbed substances, the aggregate is porous with an average particle diameter of 0.2 to 100 mm, preferably 0.5 to 50 mm, more preferably 1 to 30 mm. The iron oxyhydroxide aggregates are suitable.

  The iron oxyhydroxide obtained by the production method of the present invention has a large non-surface area and has an anion adsorption site (hydrogen bonding site) 5 to 8 times that of the conventional one. It exhibits excellent adsorptive power and can be suitably used in fields such as water purification or gas purification. Moreover, since it can be easily reused, it is highly practical, and the adsorbed phosphate ions and the like can be efficiently separated and recovered.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by this.
(Manufacture of iron oxyhydroxide)
Example 1
Dissolve ferric chloride (FeCl ₃ · 6H ₂ O) in water to a concentration of 0.1 mol / L. While stirring at room temperature, add a 2 mol / L NaOH solution to adjust the pH of the entire solution. 4 was adjusted. The precipitated product generated in the solution was allowed to stand for 24 hours and suction filtered to obtain a precipitate. This precipitate was dried in a constant temperature dryer at 50 ° C. for 48 hours to obtain FeOOH.
The obtained FeOOH had a BET specific surface area of 50.6 m ² / g, a hydroxyl group content of 12.78 mol-OH / kg-FeOOH, and an average particle size as aggregate particles of 200 μm.
This iron oxyhydroxide was put into pure water so that the pulp concentration (weight ratio of water weight to dry iron oxyhydroxide) was 5%, and stirred at room temperature for 5 minutes. After stirring, suction filtration was performed to obtain iron oxyhydroxide. The obtained iron oxyhydroxide was dried at 55 ° C. for 24 hours.
The obtained iron oxyhydroxide had a BET specific surface area of 218.6 m ² / g, a hydroxyl group content of 12.8 mol-OH / kg-FeOOH, and an average particle size as aggregate particles of 137.5 μm.
The measurement conditions are as follows.
(1) BET specific surface area It measured using Nippon Belle Co., Ltd. make, BET specific surface area measuring apparatus, and model BELSORP-mini.
(2) Hydroxyl content Using a Fourier transform infrared spectrophotometer (FTIR) manufactured by JEOL Ltd., model SPX60 (diffuse reflection method), the stretched state of OH was measured as a hydrogen bonding site of FeOOH. . Russel et al., Nature 1974, 248, the peaks of FeOOH as 3130Cm ^-1 and 3420cm ^-1 of 220-221, a hydroxyl group content Miura et al., Am. Chem . Soc., Fuel Chem., 1999, 44 (3), calculated based on 642-646.
(3) Average particle size The median diameter was calculated from the volume-based particle size distribution measured using a laser diffraction / scattering particle size distribution meter, model LA-920, manufactured by HORIBA, Ltd.

Examples 2-10
In Example 1, it carried out like Example 1 except having set pH and drying conditions to the conditions described in Table 1. The results are shown in Table 1.
In the case of vacuum drying, the gauge pressure was 0.1 MPa.

Comparative Example 1
Commercially available iron oxyhydroxide (α-FeOOH, manufactured by Nacalai Tesque, Inc., BET specific surface area 10.8 m ² / g) was heat-treated at 230 ° C. for 2 hours. The obtained iron oxyhydroxide had a BET specific surface area of 170 m ² / g, a hydroxyl group content of 3 mol-OH / kg-FeOOH, and an average particle size as aggregate particles of 189 μm.

Comparative Example 2
In Example 1, ferrous chloride (FeCl ₂ ) was used in place of ferric chloride (FeCl ₃ .6H ₂ O), the pH was adjusted to 8, and the resulting precipitate was kept at 75 ° C. for 24 hours. The same procedure as in Example 1 was performed except that the drying and the step (c) were not performed. The obtained iron oxyhydroxide had a BET specific surface area of 132.0 m ² / g, a hydroxyl group content of 3.3 mol-OH / kg-FeOOH, and an average particle size as aggregate particles of 123 μm.

Comparative Examples 3-5
In Examples 2-10, it carried out similarly to Examples 2-10 except having made the drying conditions into the conditions described in Table 1. The results are shown in Table 1.

(Evaluation of iron oxyhydroxide)
Evaluation test 1
The iron oxyhydroxide obtained in Examples 1 to 5 was introduced into a phosphoric acid solution having a phosphorus concentration of 50 mg / L at a rate of 1 g / L, and the phosphate ion adsorption performance was evaluated. The results are shown in FIG. From FIG. 1, the phosphorus adsorption amount gradually decreases as the drying temperature increases from 50 ° C., but shows a phosphorus adsorption rate of 55% at a drying temperature of 90 ° C. and a phosphorus adsorption rate of 70% or more at a drying temperature of less than 60 ° C. I understand that
The phosphorus adsorption rate (%) was calculated by the following formula.
Phosphorus adsorption rate (%) = (phosphorus concentration after adsorption experiment / phosphorus concentration before adsorption experiment) × 100

Evaluation test 2
Using a Fourier transform infrared spectrophotometer (manufactured by JEOL Ltd .: model SPX60), the iron oxyhydroxide obtained in Example 1 and the commercially available iron oxyhydroxide (α-FeOOH, manufactured by Nacalai Tesque) As for the hydrogen bonding site of FeOOH, the stretched state of O—H was measured. The results are shown in FIG.
From FIG. 2, both the commercially available reagent α-FeOOH and the FeOOH obtained in Example 1 have a peak at wave numbers 2400 cm ^{−1 to} 3700 cm ⁻¹ , but FeOOH obtained in Example 1 has a wave number It can be seen that there is a large peak at 3420 cm ⁻¹ , and it contains a large amount of weak hydrogen-bonded hydroxyl groups exhibiting the ability to adsorb anionic species such as phosphate ions.
FIG. 3 shows FTIR spectra before and after phosphate ion adsorption when the evaluation test 1 is performed using FeOOH obtained in Example 1. The hydroxyl group content at the peak of wave number 3420 cm ⁻¹ before phosphate ion adsorption is 8.27 mol-OH / kg-FeOOH, and the hydroxyl group content at the peak of wave number 3420 cm ⁻¹ after phosphate ion adsorption is 3.54 mol − It was OH / kg-FeOOH. Thus, in the FTIR spectrum after phosphate ion adsorption, the peak at 3420 cm ⁻¹ is drastically reduced. This indicates that phosphate ions were adsorbed simultaneously with the elimination of the OH group at the hydrogen bonding site of FeOOH. From this, it can be seen that hydrogen bonding sites contribute to the adsorption removal of anionic species such as phosphate ions.
FIG. 4 is an FTIR spectrum when the drying temperature in the step (b) is changed from 50 ° C. to 400 ° C. in Example 1. As the heating temperature rises, the peak at 3420 cm ^-1 decreases, and when it is dried at a temperature exceeding 100 ° C., the hydrogen bonding sites are greatly reduced and the adsorption ability of anionic species such as phosphate ions is greatly reduced. I understand that.

Evaluation test 3
Using the iron oxyhydroxide obtained in Example 1, the commercially available reagent iron oxyhydroxide (α-FeOOH, manufactured by Nacalai Tesque), and phosphate ion-containing water (phosphorus standard solution manufactured by Wako Pure Chemical Industries, Ltd.) Then, the relationship between the phosphorus adsorption amount and the phosphorus equilibrium concentration (iron oxyhydroxide amount 1 g / L, contact time 24 hours) was evaluated. The results are shown in FIG.
As shown in FIG. 5, the phosphate ion adsorption amount increased as the phosphate ion equilibrium concentration increased. With the iron oxyhydroxide obtained in Example 1, the phosphorus adsorption amount was 40 mg / g at an equilibrium concentration of 200 mg / L. On the other hand, iron oxyhydroxide, a commercially available reagent, had an adsorption concentration of 6 mg / g at an equilibrium concentration of 200 mg / L. As a result, it can be seen that the iron oxyhydroxide obtained in Example 1 has an adsorption capacity 6.7 times that of the commercially available iron oxyhydroxide.

Evaluation test 4
Phosphate ion-containing wastewater (Shiga Prefecture Ishibe district factory wastewater, phosphorus concentration (phosphorus element conversion) 52.19 mg / L) was added with the iron oxyhydroxide obtained in Example 1 to remove phosphate ions. Evaluation was performed. After adding iron oxyhydroxide at a rate of 2 g / L-drainage and stirring for 24 hours, the phosphorus concentration was 0 mg / L, and phosphate ions could be completely removed.

It is a figure which shows the result of the adsorption | suction performance evaluation of the iron oxyhydroxide obtained by the implementation methods 1-5 in the evaluation test 1. FIG. It is a FTIR spectrum of the iron oxyhydroxide obtained in Example 1 and the commercially available reagent iron oxyhydroxide in Evaluation Test 2. It is a FTIR spectrum before and after adsorption of phosphate ions in Evaluation Test 2. It is a FTIR spectrum at the time of changing the drying temperature in the evaluation test 2. FIG. 7 is a graph showing the relationship between phosphorus adsorption amount and phosphorus equilibrium concentration in Evaluation Test 3.

Claims (8)

(A) A step of generating a precipitate containing iron oxyhydroxide by adding a base to a trivalent iron ion-containing solution and adjusting the pH to 3.3 to 6,
(B) drying the precipitate at a temperature of 100 ° C. or less to obtain iron oxyhydroxide; and (c) contacting the obtained iron oxyhydroxide with water, and then at a temperature of 100 ° C. or less. A method for producing iron oxyhydroxide, comprising sequentially performing a drying step.   The method for producing iron oxyhydroxide according to claim 1, wherein the pH in the step (a) is adjusted to 3.5 to 5.5.   The method for producing iron oxyhydroxide according to claim 1 or 2, wherein drying is performed at a temperature of 40 ° C or higher and lower than 60 ° C.   The method for producing iron oxyhydroxide according to any one of claims 1 to 3, wherein the drying is performed in an atmosphere of air, vacuum, or inert gas.   The method for producing iron oxyhydroxide according to any one of claims 1 to 4, wherein the concentration of the trivalent iron ion-containing solution is 0.01 to 5 mol / L.   The iron oxyhydroxide adsorption material which has as a main component the iron oxyhydroxide obtained by the method in any one of Claims 1-5. The iron oxyhydroxide adsorbent according to claim 6, which has a BET specific surface area of 100 to 400 m ² / g. The iron oxyhydroxide adsorbent according to claim 6 or 7, wherein the hydroxyl group content per kg of iron oxyhydroxide is 3 mol or more.

Images