WO2017061118A1 - Anion adsorption method - Google Patents

Anion adsorption method Download PDF

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WO2017061118A1
WO2017061118A1 PCT/JP2016/004498 JP2016004498W WO2017061118A1 WO 2017061118 A1 WO2017061118 A1 WO 2017061118A1 JP 2016004498 W JP2016004498 W JP 2016004498W WO 2017061118 A1 WO2017061118 A1 WO 2017061118A1
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adsorption
water
iron oxyhydroxide
treatment
ion
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PCT/JP2016/004498
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French (fr)
Japanese (ja)
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載泰 廣川
剛 野一色
木村 信夫
正登 天池
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高橋金属株式会社
日本曹達株式会社
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Priority to JP2017544200A priority Critical patent/JP6644805B2/en
Publication of WO2017061118A1 publication Critical patent/WO2017061118A1/en

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    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/28Treatment of water, waste water, or sewage by sorption
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/42Treatment of water, waste water, or sewage by ion-exchange
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01GCOMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00Compounds of iron
    • C01G49/02Oxides; Hydroxides

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  • the present invention relates to a method for performing adsorption using an anion adsorbent mainly composed of iron oxyhydroxide.
  • an adsorbent made of iron oxyhydroxide As an adsorbent capable of efficiently adsorbing and recovering such a phosphorus compound, an adsorbent made of iron oxyhydroxide has been developed and described in Patent Documents 1, 2, 3, and the like. These are preferably made of iron oxyhydroxide having a ⁇ -type crystal structure.
  • ⁇ -iron oxyhydroxide has a structure of FeO (OH) x Cl 1-x (0 ⁇ x ⁇ 1) in which a part of the hydroxyl group is substituted with chlorine, and the adsorption mechanism by this has many unclear points.
  • the following is known.
  • Patent Document 2 by comparing with an iron oxyhydroxide adsorbent that does not contain chlorine ions, nitrate ions and the like are adsorbed by exchanging them with chlorine ions contained in the adsorbent. It is suggested that Adsorption of phosphate ions is possible without chloride ions, but it is also suggested that there is exchange with chloride ions as well. Further, it is described that the pH of the water to be treated is preferably about 3 to 9 for adsorption of phosphate ions.
  • Patent Document 3 in the adsorption process of hypophosphite ions or phosphite ions, pH 3 or higher (when hypophosphite ions are targeted) or pH 3 to 5 (when phosphorous acid is targeted) It is described that, when hydrochloric acid is used for pH adjustment, the adsorption amount of hypophosphite ions or phosphite ions is increased by chloride ions. However, it is described that the adsorption of these ions is different in mechanism from the adsorption of phosphate (orthophosphate) ions.
  • the anion adsorbents as described above have a high phosphate ion adsorption efficiency.
  • a method for further increasing the adsorption efficiency of phosphate ions has been demanded.
  • the inventor has intensively studied to further increase the adsorption efficiency of phosphate ions in an adsorbent made of iron oxyhydroxide. As a result, it was found that the adsorption of phosphate ions is promoted under the condition that the pH of the water subjected to the adsorption treatment is higher than the pH of the water before the treatment.
  • the present invention has been completed based on this finding.
  • the present invention relates to the following inventions.
  • the pH of the treated water at the breakthrough point is higher than the pH of the water before the treatment.
  • the adsorption method according to (1) wherein the treatment is performed under a condition that the pH of the treated water at the breakthrough point is 0.2 or more higher than the pH of the water before the treatment.
  • adsorption of anions is promoted by setting the condition that the pH of the water subjected to the adsorption treatment is higher than that of the water before the treatment.
  • the adsorption method of the present invention is a method of adsorbing a target anion by passing water through an adsorption device filled with an anion adsorbent containing iron oxyhydroxide as a main component. It is characterized in that it is carried out under the condition that the pH of (the outflow water from the adsorption device) is higher than the pH of the water before being treated (inflow water to the adsorption device) at the same point.
  • the breakthrough point is the point at which the concentration of the target anion in the treated water begins to rise.
  • the adsorption amount is 1.5 times to 2.0 times as compared with the condition where the pH of the treated water at the breakthrough point is the same as or lower than the pH of the water before the treatment.
  • the pH of the treated water is preferably a condition that is 0.2 or more higher than the pH of the water before the treatment.
  • the adsorption treatment may be performed under such conditions that the above pH condition is achieved when water is continuously passed to at least the breakthrough point under the same conditions as those actually performed.
  • the water flow may be continued until the breakthrough point is reached or beyond, or the water flow may be stopped before the breakthrough point is reached.
  • the pH of the treated water becomes higher than the pH of the water before being treated, preferably at or before the time when the water flow is stopped. It can be determined that the above pH condition is achieved by increasing the ratio by 2 or more.
  • the adsorbed target anions can be desorbed by alkali treatment after the water flow is stopped. Further, the anion adsorbent can be regenerated by treating with hydrochloric acid or the like thereafter.
  • the pH of water before being treated is preferably in the acidic range.
  • the adsorption efficiency is low from neutral to basic.
  • the pH of the treated water tends to be rather low.
  • iron may be eluted.
  • the pH is preferably 2.5 to 5.0, more preferably pH 2.5 to 4.0.
  • the water before the treatment can be used as it is if it is originally in the above pH range, but if not, it is preferable to adjust the pH.
  • the treated water that was originally neutral or basic needs to be adjusted to the above pH range using an acid. In this case, hydrochloric acid is preferably used because it does not adversely affect the adsorption of the target anion.
  • the concentration of the target anion contained in the water before the treatment is not necessarily limited, and it depends on the amount of the adsorbent, but it is 100 mg / L or less in order to prevent leakage and increase the adsorption efficiency. Preferably there is.
  • the adsorption of the target anions is preferably promoted.
  • the concentration of this chlorine ion is not particularly limited, but is preferably 100 mg / L or more, and particularly preferably 500 mg / L or more.
  • sodium chloride may be added as a salt that contains chlorine ions and does not adversely affect the adsorbent, and hydrochloric acid may be used to adjust the pH described later. .
  • the anions to be adsorbed by the anion adsorbent are anions other than chlorine ions, and halogen ions such as fluorine ions, bromine ions and iodine ions; carbonate ions, silicate ions, phosphate ions, pyrophosphate ions, Nitrate ion, nitrite ion, sulfide ion, persulfate ion, sulfate ion, sulfite ion, hyposulfite ion, thiosulfate ion, selenate ion, selenite ion, borate ion, tetraborate ion, arsenate ion , Arsenite ion, perchlorate ion, chlorate ion, chlorite ion, hypochlorite ion, bromate ion, iodate ion, aluminate ion, manganate
  • Iron oxyhydroxide includes ⁇ -type, ⁇ -type, ⁇ -type, amorphous type, and the like depending on the crystal structure.
  • ⁇ -iron oxyhydroxide has vacancies that readily adsorb chlorine ions, and some of the hydroxyl groups present therein are easily replaced by chlorine ions.
  • Such chlorine ions are further substituted with fluorine ions, nitrate ions, etc., and it is considered that the vacancies play a major role in the adsorption of these anions.
  • large anions such as phosphate ions do not reach inside the small vacancies that adsorb chlorine ions, and it is considered that different types of vacancies function for the adsorption.
  • the iron oxyhydroxide used as an anion adsorbent in the present invention is preferably ⁇ -iron oxyhydroxide having the above properties.
  • the iron oxyhydroxide that is the main component of the adsorbent used in the present invention preferably has an average crystallite size of 10 nm or less, and more preferably 5 nm or less. It has been clarified by the present inventors that the smaller the average crystallite size, the higher the phosphate adsorption rate when used as a phosphate adsorbent in water.
  • the anion adsorbent used in the present invention preferably has a content of iron oxyhydroxide as a main component of 99% by mass or more. Most preferably, the content of iron oxyhydroxide is substantially 100% by mass.
  • the iron oxyhydroxide preferably has a BET specific surface area of 250 m 2 / g or more, and the pore volume area distribution (dV / dR) calculated by the BJH method is 100 to 300 mm 3 / g / nm. It is preferable.
  • ⁇ -iron oxyhydroxide as an anion adsorbent used in the present invention preferably has a hydroxyl group partially substituted with chlorine ions. Even with ⁇ -iron oxyhydroxide from which chlorine ions have been completely removed, phosphate ions are adsorbed, but those that are partially substituted with chlorine ions are more efficient in terms of phosphate ion adsorption efficiency. Are better.
  • the shape of the ⁇ -iron oxyhydroxide crystal used in the present invention is preferably granular.
  • granular means that it is not needle-shaped or plate-shaped, and more specifically, the ratio of the major axis / minor axis of the crystal is 3 or less.
  • ⁇ -iron oxyhydroxide for example, a dry gel obtained by a method including a step of reacting an iron compound-containing solution with a base to form a precipitate at pH 9 or lower can be used.
  • the iron compound is preferably an iron salt, particularly a trivalent iron salt.
  • Specific examples include ferric chloride, ferric sulfate, and ferric nitrate. Among these, ferric chloride is particularly preferable.
  • the base is used to neutralize the acidic iron compound aqueous solution and generate a precipitate containing iron oxyhydroxide.
  • Specific examples include sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, sodium carbonate, potassium carbonate, calcium carbonate and the like.
  • the pH during the formation of the precipitate is adjusted to the range of pH 3.3-6. If necessary to adjust this pH, a pH adjusting agent may be used. Specific examples of the pH adjuster include the above bases and strong inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid.
  • the precipitate containing ⁇ -iron oxyhydroxide as a main component obtained by the above method can be collected by filtration and dried to form a dry gel.
  • a step of drying the precipitate and a step of drying the precipitate after bringing it into contact with water.
  • the two drying steps are preferably performed at 140 ° C. or less, and more preferably at 100 to 140 ° C.
  • the drying temperature requires a long time at a low temperature and is not suitable for efficient production. Further, there is a tendency that the number of anion adsorption sites tends to decrease at a high temperature, and even higher temperature is not preferable because it changes to iron oxide. Drying can be done in air, vacuum, or in an inert gas.
  • step of bringing the dried product into contact with water impurities such as sodium chloride are eluted to leave pores later, and the specific surface area is increased and the anion adsorption site is also increased.
  • the water is removed and dried again. This drying step is also preferably performed under the same conditions as described above.
  • ⁇ -iron oxyhydroxide having a small particle diameter is preferably used.
  • the average particle diameter d50 is 70 ⁇ m or less. This can be obtained, for example, by classifying ⁇ -iron oxyhydroxide by a method such as sieving. If necessary, dry pulverization may be performed, and classification may be performed by a method such as sieving.
  • the X-ray diffraction (XRD) pattern was measured using an X-ray diffractometer Ultima IV (manufactured by Rigaku Corporation). A CuK ⁇ tube was used for the measurement. The average crystallite size was calculated from XRD according to Scherrer's formula.
  • the specific surface area was measured by a gas adsorption method using a specific surface area measuring device MacsorbHM 1210 (manufactured by Mountec).
  • TEM observation and FFT analysis The TEM (transmission electron microscope) observation of the sample was performed using a transmission electron microscope JEM 2010F (manufactured by JEOL, acceleration voltage 200 kV).
  • NaOH ferric chloride
  • FeCl 3 ferric chloride
  • the particle diameter of the oxyhydroxide powder (hereinafter referred to as “powder A”) obtained as described above was 0.25 mm to 5 mm. It was confirmed by X-ray diffraction that the crystal structure was ⁇ -iron oxyhydroxide and the average crystallite size was 5 nm.
  • FIG. 1 shows a state observed with a transmission electron microscope (TEM). The crystal shape was granular. The crystallite diameter by TEM observation was 5 to 10 nm, and each crystal was granular, and these were condensed to form particles. The specific surface area was 280 m 2 / g, and the chlorine ion content was 5.8 wt%.
  • Powder B had a particle size range of 0.6 to 300 ⁇ m and an average particle size of 26.5 ⁇ m. Further, powder B was classified with a sieve to obtain the following powders. Powder C-1: Particle size 10 to 32 ⁇ m Powder C-2: Particle size 32 to 45 ⁇ m Powder C-3: Particle size 45 to 75 ⁇ m
  • Reference measurement example 1 (Batch phosphoric acid adsorption test of adsorbent particles) Dissolve potassium dihydrogen phosphate in ion-exchanged water, adjust the pH to 3.5 with hydrochloric acid or 7.0 with sodium hydroxide, and test for a concentration of 400 mg-P / L (concentration as phosphorus) Liquids G (pH 3.5) and H (pH 7.0) were prepared. 1 g of each of powders C-1 to C-3 was added to 150 mL of test solutions G and H, followed by stirring and an adsorption test.
  • the liquid was collected after a predetermined time, separated from the solid content with a filter syringe, and the phosphorus concentration in the solution was analyzed by ICP (inductively coupled plasma) to calculate the amount of adsorption. At the same time, the pH was measured. The results are shown in Table 1.
  • Measurement Example 1 Water-permeable phosphate adsorption test for adsorbent particles
  • Dissolve potassium dihydrogen phosphate in ion-exchanged water adjust the pH to 2.9 with hydrochloric acid or 7.0 with sodium hydroxide, and test the concentration of 100 mg-P / L (concentration as phosphorus) Liquid I (pH 2.9) and J (pH 7.0) were prepared.
  • test liquids I Examples
  • J comparative examples
  • SV water flow rate
  • the amount of adsorption was calculated.
  • the breakthrough point was defined as the time when the phosphorus concentration of the liquid coming out from the bottom of the column reached 10 mg-P / L.
  • the pH was measured.
  • the test conditions are as follows.
  • Example 1-1 Powder B, Test Solution I, SV10, 2 times Example 1-2: Powder B, Test Solution I, SV20, 2 times Comparative Example 1-1: Powder B, Test Solution J, SV10 Twice run Comparative Example 1-2: Powder B, Test Solution J, SV20, Twice Example 2: Powder C-3, Test Solution I, SV30
  • Example 1-1 pH 3.8 (first time), pH 3.8 (second time)
  • Example 1-2 pH 3.3 (first time), 3.8 (second time)
  • Comparative Example 1-1 pH 3.2 (first time), 3.2 (second time)
  • Comparative Example 1-2 pH 3.0 (first time), 3.0 (second time)
  • Example 2 pH 3.4
  • the water flow rate at the breakthrough point (flow rate [ml] / adsorbent amount [ml]) is about 280 to 330 in Examples 1-1, 1-2, and 2, and in Comparative Examples 1-1 and 1-2. It is about 140, and it can be seen that the amount of adsorption is clearly larger in the example.
  • the pH of the treated water at the breakthrough point is 0.2 or more higher than the pH 2.9 of the untreated water in the examples, and it can be seen that the amount of adsorption is greatly increased under this condition.

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Abstract

The present invention addresses the problem of providing a method that further increases the phosphate-ion adsorption efficiency of an adsorbent that has an iron oxyhydroxide as a main component. According to this method, target anions are adsorbed by passing water that contains said anions and that has a fixed pH through an adsorption device that is filled with an anion adsorbent that has an iron oxyhydroxide as a main component. The method is characterized by being executed under conditions wherein the pH of water that is treated at a breakpoint becomes higher than the pH of the water pre-treatment. The treatment is preferably executed under conditions wherein the pH of the water that is treated at the breakpoint becomes at least 0.2 higher than the pH of the water pre-treatment.

Description

陰イオン吸着方法Anion adsorption method
 本発明は、オキシ水酸化鉄を主成分とする陰イオン吸着材を使用して吸着を行う方法に関する。
 本願は、2015年10月9日に出願された日本国特許出願第2015-200830号に対し優先権を主張し、その内容をここに援用する。
The present invention relates to a method for performing adsorption using an anion adsorbent mainly composed of iron oxyhydroxide.
This application claims priority to Japanese Patent Application No. 2015-200830 filed on Oct. 9, 2015, the contents of which are incorporated herein by reference.
 各種の排水から、環境や人体に有害性を有する物質を除去し浄化するため、あるいは希少金属等の有用物質を回収するために、吸着材や、それを用いた吸着方法、吸着物質の脱着・回収方法等が盛んに研究されている。
 例えば、リンは肥料成分として、また化学工業にも不可欠の成分であるが、日本においてはほぼ100%を輸入に頼っている。一方で排水中に多量のリンが含まれる場合は、富栄養化の原因となるため、このような排水を排出することは環境に好ましくない。これらの問題を一挙に解決するために、排水中に含まれるリン酸等のリン化合物の除去及び回収が注目されている。
 このようなリン化合物を効率的に吸着、回収できる吸着材として、オキシ水酸化鉄からなるものが開発されており、特許文献1、2、3等に記載されている。これらとしてはβ型結晶構造を有するオキシ水酸化鉄からなるものが好ましい。β-オキシ水酸化鉄は、水酸基の一部が塩素で置換されたFeO(OH)Cl1-x(0<x<1)の構造を有し、それによる吸着メカニズムは不明の点も多いが、以下のようなことが知られている。
 特許文献2には、オキシ水酸化鉄吸着材で塩素イオンを含有するものとしないものとで比較することにより、硝酸イオン等が、吸着材に含まれていた塩素イオンと交換することによって吸着されることが示唆される。リン酸イオンの吸着は塩素イオンがなくても可能ではあるが、同様に塩素イオンとの交換もあることも示唆される。また、リン酸イオンの吸着には被処理水のpHを3~9程度とするのが好ましいことが記載されている。
 特許文献3には、次亜リン酸イオン又は亜リン酸イオンの吸着工程において、pH3以上(次亜リン酸イオンを対象とする場合)又はpH3~5(亜リン酸を対象とする場合)が好ましいこと、またpH調整に塩酸を用いると、塩化物イオンにより次亜リン酸イオン又は亜リン酸イオンの吸着量が増加することが記載されている。但しこれらのイオンの吸着はリン酸(オルトリン酸)イオンの吸着とはメカニズムを異にすることも記載されている。
In order to remove and purify substances that are harmful to the environment and the human body from various wastewaters, or to recover useful substances such as rare metals, adsorbents, adsorption methods using them, desorption / desorption of adsorbed substances, The collection method is actively researched.
For example, phosphorus is an indispensable component as a fertilizer component and also in the chemical industry, but in Japan, almost 100% depends on imports. On the other hand, when a large amount of phosphorus is contained in the wastewater, it causes eutrophication, and it is not preferable for the environment to discharge such wastewater. In order to solve these problems all at once, removal and recovery of phosphorus compounds such as phosphoric acid contained in waste water have attracted attention.
As an adsorbent capable of efficiently adsorbing and recovering such a phosphorus compound, an adsorbent made of iron oxyhydroxide has been developed and described in Patent Documents 1, 2, 3, and the like. These are preferably made of iron oxyhydroxide having a β-type crystal structure. β-iron oxyhydroxide has a structure of FeO (OH) x Cl 1-x (0 <x <1) in which a part of the hydroxyl group is substituted with chlorine, and the adsorption mechanism by this has many unclear points. However, the following is known.
In Patent Document 2, by comparing with an iron oxyhydroxide adsorbent that does not contain chlorine ions, nitrate ions and the like are adsorbed by exchanging them with chlorine ions contained in the adsorbent. It is suggested that Adsorption of phosphate ions is possible without chloride ions, but it is also suggested that there is exchange with chloride ions as well. Further, it is described that the pH of the water to be treated is preferably about 3 to 9 for adsorption of phosphate ions.
In Patent Document 3, in the adsorption process of hypophosphite ions or phosphite ions, pH 3 or higher (when hypophosphite ions are targeted) or pH 3 to 5 (when phosphorous acid is targeted) It is described that, when hydrochloric acid is used for pH adjustment, the adsorption amount of hypophosphite ions or phosphite ions is increased by chloride ions. However, it is described that the adsorption of these ions is different in mechanism from the adsorption of phosphate (orthophosphate) ions.
特開2006-124239号公報JP 2006-124239 A WO2006/088083号パンフレットWO2006 / 088083 pamphlet 特開2011-235222号公報JP 2011-235222 A
 上記のような陰イオン吸着材は、リン酸イオンの吸着効率も高い。しかし、リン酸イオンの吸着効率をさらに高くする方法が求められていた。 The anion adsorbents as described above have a high phosphate ion adsorption efficiency. However, a method for further increasing the adsorption efficiency of phosphate ions has been demanded.
 本発明者は、オキシ水酸化鉄からなる吸着材において、リン酸イオンの吸着効率をさらに増加させるべく鋭意検討した。
 その結果、吸着処理された水のpHが、処理される前の水のpHより高くなる条件で、リン酸イオンの吸着が促進されることを見出した。本発明はこの知見を基に完成されたものである。
The inventor has intensively studied to further increase the adsorption efficiency of phosphate ions in an adsorbent made of iron oxyhydroxide.
As a result, it was found that the adsorption of phosphate ions is promoted under the condition that the pH of the water subjected to the adsorption treatment is higher than the pH of the water before the treatment. The present invention has been completed based on this finding.
 すなわち、本発明は、以下の発明に関する。
(1)オキシ水酸化鉄を主成分とする陰イオン吸着材を充填した吸着装置へ、目的の陰イオンを含有し一定のpHを有する水を通水することにより、該陰イオンを吸着する方法において、破過点における処理された水のpHが、処理される前の水のpHより高くなる条件で行うことを特徴とする吸着方法。
(2)破過点における処理された水のpHが処理される前の水のpHより0.2以上高くなる条件で処理を行うことを特徴とする(1)に記載の吸着方法。
(3)処理される前の水が、酸でpHが2.5~5.0に調整されていることを特徴とする(1)又は(2)に記載の吸着方法。
(4)オキシ水酸化鉄がβ-オキシ水酸化鉄である(1)~(3)のいずれかに記載の吸着方法。
(5)オキシ水酸化鉄の平均結晶子径が10nm以下である(4)に記載の吸着方法。
(6)β-オキシ水酸化鉄の結晶の形状が粒状である(4)又は(5)に記載の吸着方法。
(7)オキシ水酸化鉄の比表面積が250m2/g以上である(1)~(6)のいずれかに記載の吸着方法。
(8)処理される前の水に含有される目的の陰イオンの濃度が100mg/L以下である(1)~(7)のいずれかに記載の吸着方法。
(9)処理される前の水に塩素イオンが100mg/L以上含有される(1)~(8)のいずれかに記載の吸着方法。
(10)目的の陰イオンがリン酸イオンである(1)~(9)のいずれかに記載の吸着方法。
That is, the present invention relates to the following inventions.
(1) A method of adsorbing anions by passing water containing a target anion and having a certain pH through an adsorption device filled with an anion adsorbent mainly composed of iron oxyhydroxide. In the adsorption method, the pH of the treated water at the breakthrough point is higher than the pH of the water before the treatment.
(2) The adsorption method according to (1), wherein the treatment is performed under a condition that the pH of the treated water at the breakthrough point is 0.2 or more higher than the pH of the water before the treatment.
(3) The adsorption method according to (1) or (2), wherein the water before treatment is acid and the pH is adjusted to 2.5 to 5.0.
(4) The adsorption method according to any one of (1) to (3), wherein the iron oxyhydroxide is β-iron oxyhydroxide.
(5) The adsorption method according to (4), wherein the average crystallite size of the iron oxyhydroxide is 10 nm or less.
(6) The adsorption method according to (4) or (5), wherein the β-iron oxyhydroxide crystals are granular.
(7) The adsorption method according to any one of (1) to (6), wherein the specific surface area of the iron oxyhydroxide is 250 m 2 / g or more.
(8) The adsorption method according to any one of (1) to (7), wherein the concentration of the target anion contained in the water before treatment is 100 mg / L or less.
(9) The adsorption method according to any one of (1) to (8), wherein chlorine ion is contained in water before treatment at 100 mg / L or more.
(10) The adsorption method according to any one of (1) to (9), wherein the target anion is a phosphate ion.
 オキシ水酸化鉄からなる吸着材を用いて陰イオンを吸着する方法において、吸着処理された水のpHが処理される前の水のpHより高くなる条件にすることにより陰イオンの吸着が促進される。 In the method of adsorbing anions using an adsorbent made of iron oxyhydroxide, adsorption of anions is promoted by setting the condition that the pH of the water subjected to the adsorption treatment is higher than that of the water before the treatment. The
オキシ水酸化鉄結晶のTEM像を示す図である。It is a figure which shows the TEM image of an iron oxyhydroxide crystal | crystallization. 実施例1-1[粉末B、試験液I(pH2.9)、通水速度SV10]のリン酸吸着試験の結果を示す図である。It is a figure which shows the result of the phosphoric acid adsorption test of Example 1-1 [powder B, test liquid I (pH 2.9), water flow rate SV10]. 実施例1-2[粉末B、試験液I(pH2.9)、通水速度SV20]のリン酸吸着試験の結果を示す図である。It is a figure which shows the result of the phosphate adsorption test of Example 1-2 [powder B, test liquid I (pH 2.9), water flow rate SV20]. 比較例1-1[粉末B、試験液J(pH7.0)、通水速度SV10]のリン酸吸着試験の結果を示す図である。It is a figure which shows the result of the phosphate adsorption test of Comparative Example 1-1 [powder B, test liquid J (pH 7.0), water flow rate SV10]. 比較例1-2[粉末B、試験液J(pH7.0)、通水速度SV20]のリン酸吸着試験の結果を示す図である。It is a figure which shows the result of the phosphate adsorption test of Comparative Example 1-2 [powder B, test liquid J (pH 7.0), water flow rate SV20]. 実施例2[粉末C-3、試験液I(pH2.9)、通水速度SV30]のリン酸吸着試験の結果を示す図である。It is a figure which shows the result of the phosphate adsorption test of Example 2 [powder C-3, test liquid I (pH 2.9), water flow rate SV30].
 本発明の吸着方法は、オキシ水酸化鉄を主成分とする陰イオン吸着材を充填した吸着装置へ通水することにより、目的の陰イオンを吸着する方法において、破過点における処理された水(吸着装置からの流出水)のpHが、同時点における処理される前の水(吸着装置への流入水)のpHより高くなる条件で行うことを特徴とする。
 破過点は、処理された水における目的の陰イオンの濃度が上昇を開始する点である。具体的には、目的の陰イオンの種類、処理される前の水における該イオンの濃度等に応じて決定すればよいが、リン酸イオンを目的とする場合、例えば10mg-P/L(リンとしての濃度)に達する点とすることができる。
 この条件とすることにより、破過点における処理された水のpHが処理される前の水のpHと同じかより低くなる条件と比較して、吸着量が1.5倍ないし2.0倍に向上する。
 上記の処理された水のpHは、処理される前の水のpHより0.2以上高くなる条件であることが好ましい。
 この吸着処理は、実際に実施しているのと同じ条件で少なくとも破過点まで通水を継続した場合に、上記のpH条件が達成されるような条件であればよく、実際の通水は破過点に達するまで、又はそれを越えて継続してもよいし、破過点に達する以前に通水を停止してもよい。破過点に達する以前に通水を停止する場合には、通水を停止する時点またはその前に、処理された水のpHが処理される前の水のpHより高くなること、好ましくは0.2以上高くなることにより、上記のpH条件が達成されていると判断することができる。
 該陰イオン吸着材からは、通水の停止後に、アルカリ処理等することによって、吸着した目的の陰イオンを脱着することができる。さらにこの後塩酸等で処理することによって陰イオン吸着材を再生することもできる。
The adsorption method of the present invention is a method of adsorbing a target anion by passing water through an adsorption device filled with an anion adsorbent containing iron oxyhydroxide as a main component. It is characterized in that it is carried out under the condition that the pH of (the outflow water from the adsorption device) is higher than the pH of the water before being treated (inflow water to the adsorption device) at the same point.
The breakthrough point is the point at which the concentration of the target anion in the treated water begins to rise. Specifically, it may be determined according to the kind of the target anion, the concentration of the ion in the water before the treatment, etc., but when the phosphate ion is used, for example, 10 mg-P / L (phosphorus As a point).
By adopting this condition, the adsorption amount is 1.5 times to 2.0 times as compared with the condition where the pH of the treated water at the breakthrough point is the same as or lower than the pH of the water before the treatment. To improve.
The pH of the treated water is preferably a condition that is 0.2 or more higher than the pH of the water before the treatment.
The adsorption treatment may be performed under such conditions that the above pH condition is achieved when water is continuously passed to at least the breakthrough point under the same conditions as those actually performed. The water flow may be continued until the breakthrough point is reached or beyond, or the water flow may be stopped before the breakthrough point is reached. In the case of stopping the water flow before reaching the breakthrough point, the pH of the treated water becomes higher than the pH of the water before being treated, preferably at or before the time when the water flow is stopped. It can be determined that the above pH condition is achieved by increasing the ratio by 2 or more.
From the anion adsorbent, the adsorbed target anions can be desorbed by alkali treatment after the water flow is stopped. Further, the anion adsorbent can be regenerated by treating with hydrochloric acid or the like thereafter.
 本発明の方法において、処理される前の水のpHは、酸性域であることが好ましい。中性付近から塩基性にかけては吸着効率が低い。またこのpH範囲では、処理された水のpHがむしろ低くなる傾向がある。一方強酸性に過ぎると鉄が溶出するおそれがある。具体的には、pH2.5~5.0であることが好ましく、pH2.5~4.0であることがより好ましい。
 処理される前の水は、元来上記のpH域にあるものであればそのまま使用することができるが、そうでなければpHを調整することが好ましい。元来中性又は塩基性であった処理水は、酸を用いて上記pH域に調整する必要がある。この場合には、目的の陰イオンの吸着に悪影響を与えない意味から、塩酸を用いることが好ましい。
In the method of the present invention, the pH of water before being treated is preferably in the acidic range. The adsorption efficiency is low from neutral to basic. Also in this pH range, the pH of the treated water tends to be rather low. On the other hand, if it is too acidic, iron may be eluted. Specifically, the pH is preferably 2.5 to 5.0, more preferably pH 2.5 to 4.0.
The water before the treatment can be used as it is if it is originally in the above pH range, but if not, it is preferable to adjust the pH. The treated water that was originally neutral or basic needs to be adjusted to the above pH range using an acid. In this case, hydrochloric acid is preferably used because it does not adversely affect the adsorption of the target anion.
 以上のように、処理された水のpHが処理される前の水のpHより高くなるということは、吸着処理によって吸着材から水酸イオンが流出していることを示唆するものである。
 先述のように、オキシ水酸化鉄による陰イオンの吸着には、塩素イオンとの交換が重要であることは知られていたが、水酸イオンとの交換は知られていなかった。
 これは、従来、処理される前の水として主に中性付近のものが用いられ、pH5以下としたものは用いられていなかったためである。また今回発明者らが、オキシ水酸化鉄を主成分とする陰イオン吸着材として、小粒径のものを用いたことによって、水酸イオンとの交換による吸着という性質が特に顕著に現れたものとも考えられる。
As described above, the fact that the pH of the treated water becomes higher than the pH of the water before the treatment suggests that hydroxide ions are flowing out of the adsorbent by the adsorption treatment.
As described above, it was known that exchange with chlorine ions was important for adsorption of anions by iron oxyhydroxide, but exchange with hydroxide ions was not known.
This is because conventionally, water near neutrality is mainly used as water before being treated, and water having a pH of 5 or less has not been used. In addition, the present inventors have used a small particle size as an anion adsorbent mainly composed of iron oxyhydroxide, so that the property of adsorption by exchanging with hydroxide ions is particularly prominent. You might also say that.
 処理される前の水に含有される目的の陰イオンの濃度は、必ずしも限定されるものではなく、吸着材の量にもよるが、漏出を防ぎ吸着効率を高める意味から、100mg/L以下であることが好ましい。 The concentration of the target anion contained in the water before the treatment is not necessarily limited, and it depends on the amount of the adsorbent, but it is 100 mg / L or less in order to prevent leakage and increase the adsorption efficiency. Preferably there is.
 処理される前の水には、目的の陰イオンの他に、塩素イオンが含まれていると、目的の陰イオンの吸着が促進され好ましい。この塩素イオンの濃度は特に限定されないが、100mg/L以上であることが好ましく、500mg/L以上であることが特に好ましい。塩素イオン濃度を調整するためには、塩素イオンを含有し吸着材に悪影響を及ぼさない塩として、例えば塩化ナトリウムを添加してもよいし、後述のpHの調整のために塩酸を用いてもよい。 If the water before treatment contains chlorine ions in addition to the target anions, the adsorption of the target anions is preferably promoted. The concentration of this chlorine ion is not particularly limited, but is preferably 100 mg / L or more, and particularly preferably 500 mg / L or more. In order to adjust the chlorine ion concentration, for example, sodium chloride may be added as a salt that contains chlorine ions and does not adversely affect the adsorbent, and hydrochloric acid may be used to adjust the pH described later. .
 陰イオン吸着材によって吸着すべき陰イオンは、塩素イオン以外の陰イオンであって、フッ素イオン、臭素イオン、ヨウ素イオン等のハロゲンイオン;炭酸イオン、ケイ酸イオン、リン酸イオン、ピロリン酸イオン、硝酸イオン、亜硝酸イオン、硫化物イオン、過硫酸イオン、硫酸イオン、亜硫酸イオン、次亜硫酸イオン、チオ硫酸イオン、セレン酸イオン、亜セレン酸イオン、ホウ酸イオン、四ホウ酸イオン、ヒ酸イオン、亜ヒ酸イオン、過塩素酸イオン、塩素酸イオン、亜塩素酸イオン、次亜塩素酸イオン、臭素酸イオン、ヨウ素酸イオン、アルミン酸イオン、マンガン酸イオン、過マンガン酸イオン、クロム酸イオン、二クロム酸塩、タングステン酸イオン、バナジン酸イオン、ビスマス酸イオン、チタン酸イオン等のオキソ酸イオン;カルボン酸イオン、スルホン酸イオン、ホスホン酸イオン等の有機酸イオン;シアン化物イオン、シアン酸イオン、イソシアン酸イオン、チオシアン酸イオン、アジドイオン等が例示される。
 これらのうち、リン酸イオン、フッ素イオンが好ましく、特にリン酸イオンが好ましい。
The anions to be adsorbed by the anion adsorbent are anions other than chlorine ions, and halogen ions such as fluorine ions, bromine ions and iodine ions; carbonate ions, silicate ions, phosphate ions, pyrophosphate ions, Nitrate ion, nitrite ion, sulfide ion, persulfate ion, sulfate ion, sulfite ion, hyposulfite ion, thiosulfate ion, selenate ion, selenite ion, borate ion, tetraborate ion, arsenate ion , Arsenite ion, perchlorate ion, chlorate ion, chlorite ion, hypochlorite ion, bromate ion, iodate ion, aluminate ion, manganate ion, permanganate ion, chromate ion , Oxo acid ions such as dichromate, tungstate ion, vanadate ion, bismuth acid ion, titanate ion Carboxylate ion, sulfonate ion, organic acid ion such as phosphonate; cyanide, cyanate ion, isocyanate ion, thiocyanate ion, azide ion, and the like.
Of these, phosphate ions and fluorine ions are preferable, and phosphate ions are particularly preferable.
 オキシ水酸化鉄には、結晶構造の相違によって、α型、β型、γ型、非晶質型等がある。
 これらのうち、β-オキシ水酸化鉄は、塩素イオンを吸着しやすい空孔を有しており、ここに存在する水酸基の一部が塩素イオンにより置換されやすい。このような塩素イオンは、さらにフッ素イオン、硝酸イオン等とも置換され、これらの陰イオンの吸着において上記空孔が主要な役割を果たすと考えられている。
 一方、リン酸イオンのような大型の陰イオンは、塩素イオンを吸着する小型の空孔内には到達せず、その吸着には異なる種類の空孔が機能していると考えられる。
 本発明において陰イオン吸着材として使用するオキシ水酸化鉄は、以上の性質を有するβ-オキシ水酸化鉄であることが好ましい。
Iron oxyhydroxide includes α-type, β-type, γ-type, amorphous type, and the like depending on the crystal structure.
Of these, β-iron oxyhydroxide has vacancies that readily adsorb chlorine ions, and some of the hydroxyl groups present therein are easily replaced by chlorine ions. Such chlorine ions are further substituted with fluorine ions, nitrate ions, etc., and it is considered that the vacancies play a major role in the adsorption of these anions.
On the other hand, large anions such as phosphate ions do not reach inside the small vacancies that adsorb chlorine ions, and it is considered that different types of vacancies function for the adsorption.
The iron oxyhydroxide used as an anion adsorbent in the present invention is preferably β-iron oxyhydroxide having the above properties.
 本発明に用いられる吸着材の主成分であるオキシ水酸化鉄は、平均結晶子径が10nm以下であることが好ましく、5nm以下であることがより好ましい。
 この平均結晶子径が小さいほど、水中でリン酸吸着材として使用する場合のリン酸吸着速度が大きいことが、本発明者らにより明らかにされた。
 平均結晶子径Dは、X線回折でβ-オキシ水酸化鉄に特徴的な2θ=35°付近の回折線から、下記のシェラーの式を用いて計算される。
D=Kλ/βcosθ
 ただし、βは装置に起因する機械幅を補正した真の回折ピークの半値幅、Kはシェラー定数、λはX線の波長である。
The iron oxyhydroxide that is the main component of the adsorbent used in the present invention preferably has an average crystallite size of 10 nm or less, and more preferably 5 nm or less.
It has been clarified by the present inventors that the smaller the average crystallite size, the higher the phosphate adsorption rate when used as a phosphate adsorbent in water.
The average crystallite diameter D is calculated from the diffraction line near 2θ = 35 ° characteristic of β-iron oxyhydroxide by X-ray diffraction, using the following Scherrer equation.
D = Kλ / βcos θ
Where β is the half width of the true diffraction peak corrected for the machine width caused by the apparatus, K is the Scherrer constant, and λ is the wavelength of the X-ray.
 本発明に用いられる陰イオン吸着材は、主成分であるオキシ水酸化鉄の含有率が99質量%以上であることが好ましい。オキシ水酸化鉄の含有率が実質的に100質量%であるものが最も好ましい。
 前記オキシ水酸化鉄は、BET比表面積が250m2/g以上であることが好ましく、またBJH法により算出した細孔容量の面積分布(dV/dR)が100~300mm3/g/nmであることが好ましい。
The anion adsorbent used in the present invention preferably has a content of iron oxyhydroxide as a main component of 99% by mass or more. Most preferably, the content of iron oxyhydroxide is substantially 100% by mass.
The iron oxyhydroxide preferably has a BET specific surface area of 250 m 2 / g or more, and the pore volume area distribution (dV / dR) calculated by the BJH method is 100 to 300 mm 3 / g / nm. It is preferable.
 本発明に用いられる陰イオン吸着材としてのβ-オキシ水酸化鉄は、上述のように、水酸基の一部が塩素イオンにより置換されているものが好ましい。このような塩素イオンが完全に除去されたβ-オキシ水酸化鉄でもリン酸イオンは吸着されるが、一部が塩素イオンにより置換されているものの方が、リン酸イオンの吸着効率の点で優れている。 As described above, β-iron oxyhydroxide as an anion adsorbent used in the present invention preferably has a hydroxyl group partially substituted with chlorine ions. Even with β-iron oxyhydroxide from which chlorine ions have been completely removed, phosphate ions are adsorbed, but those that are partially substituted with chlorine ions are more efficient in terms of phosphate ion adsorption efficiency. Are better.
 本発明に用いられるβ-オキシ水酸化鉄の結晶の形状は、粒状であることが好ましい。ここで粒状とは、針状あるいは板状ではないということを意味し、より具体的には、結晶の長径/短径の比が3以下である。 The shape of the β-iron oxyhydroxide crystal used in the present invention is preferably granular. Here, granular means that it is not needle-shaped or plate-shaped, and more specifically, the ratio of the major axis / minor axis of the crystal is 3 or less.
 前記のβ-オキシ水酸化鉄としては、例えば、鉄化合物含有溶液を塩基と反応させpH9以下で沈殿物を生成させる工程を含む方法により得られる乾燥ゲルを用いることができる。
 前記の鉄化合物としては、鉄塩、特に3価の鉄塩が好ましい。具体的には、塩化第二鉄、硫酸第二鉄、硝酸第二鉄等を挙げることができ、この中で特に塩化第二鉄が好ましい。
 前記の塩基は、酸性の鉄化合物水溶液を中和しオキシ水酸化鉄を含む沈殿を生成させるために使用する。具体的には、水酸化ナトリウム、水酸化カリウム、水酸化カルシウム、アンモニア、炭酸ナトリウム、炭酸カリウム、炭酸カルシウム等を挙げることができ、この中で特に水酸化ナトリウムが好ましい。
 沈殿物の生成の際のpHは、pH3.3~6の範囲に調整することがより好ましい。このpHを調整するために必要であれば、pH調整剤を使用してよい。pH調整剤として具体的には、上記のような塩基、及び、塩酸、硫酸、硝酸等の無機強酸が挙げられる。
 以上の方法で得られたβ-オキシ水酸化鉄を主成分とする沈殿物は、濾別して回収することができ、これを乾燥すれば乾燥ゲルとなる。
As the β-iron oxyhydroxide, for example, a dry gel obtained by a method including a step of reacting an iron compound-containing solution with a base to form a precipitate at pH 9 or lower can be used.
The iron compound is preferably an iron salt, particularly a trivalent iron salt. Specific examples include ferric chloride, ferric sulfate, and ferric nitrate. Among these, ferric chloride is particularly preferable.
The base is used to neutralize the acidic iron compound aqueous solution and generate a precipitate containing iron oxyhydroxide. Specific examples include sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, sodium carbonate, potassium carbonate, calcium carbonate and the like. Among these, sodium hydroxide is particularly preferable.
More preferably, the pH during the formation of the precipitate is adjusted to the range of pH 3.3-6. If necessary to adjust this pH, a pH adjusting agent may be used. Specific examples of the pH adjuster include the above bases and strong inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid.
The precipitate containing β-iron oxyhydroxide as a main component obtained by the above method can be collected by filtration and dried to form a dry gel.
 さらに以上の工程の後に、沈殿物を乾燥させる工程、及び該乾燥物を水と接触させた後、乾燥させる工程を実施することが好ましい。
 上記2回の乾燥させる工程は、140℃以下で行うことが好ましく、100~140℃で行うことがより好ましい。乾燥温度は、低温では時間を要し効率的な製造に適しない。また高温では陰イオン吸着サイトが少なくなる傾向があり、さらに高温では酸化鉄に変化するので好ましくない。乾燥は、空気中、真空中、又は不活性ガス中で行うことができる。
 乾燥物を水と接触させる工程では、塩化ナトリウム等の不純物が溶出して後に細孔を残し、比表面積が増大するとともに陰イオン吸着サイトも増加すると考えられる。
 乾燥物を水と接触させた後には、水を除去して、再度乾燥させる。この乾燥工程も上記と同様の条件で行うことが好ましい。
Further, after the above steps, it is preferable to carry out a step of drying the precipitate, and a step of drying the precipitate after bringing it into contact with water.
The two drying steps are preferably performed at 140 ° C. or less, and more preferably at 100 to 140 ° C. The drying temperature requires a long time at a low temperature and is not suitable for efficient production. Further, there is a tendency that the number of anion adsorption sites tends to decrease at a high temperature, and even higher temperature is not preferable because it changes to iron oxide. Drying can be done in air, vacuum, or in an inert gas.
In the step of bringing the dried product into contact with water, impurities such as sodium chloride are eluted to leave pores later, and the specific surface area is increased and the anion adsorption site is also increased.
After bringing the dried product into contact with water, the water is removed and dried again. This drying step is also preferably performed under the same conditions as described above.
 また、決して限定されるものではないが、例えば小粒径としたβ-オキシ水酸化鉄が好ましく用いられる。具体的には、平均粒径d50が70μm以下のものである。これは例えば、β-オキシ水酸化鉄を、篩分け等の方法で分級することで得られる。またもし必要であれば乾式粉砕してもよく、その上で篩分け等の方法で分級してもよい。 Although not limited in any way, for example, β-iron oxyhydroxide having a small particle diameter is preferably used. Specifically, the average particle diameter d50 is 70 μm or less. This can be obtained, for example, by classifying β-iron oxyhydroxide by a method such as sieving. If necessary, dry pulverization may be performed, and classification may be performed by a method such as sieving.
 次に、本発明の実施例によってさらに詳細に説明するが、本発明はこれにより限定されるものではない。 Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
測定方法
(粉末X線回折)
 X線回折(XRD)パターンは、X線回折装置Ultima IV(リガク社製)を用いて測定した。測定にはCuKα管球を使用した。平均結晶子径はXRDよりシェラーの式に従って算出した。
(比表面積)
 比表面積測定装置MacsorbHM 1210(マウンテック社製)を使用して、ガス吸着法により比表面積を測定した。
(TEM観察及びFFT解析)
 試料のTEM(透過型電子顕微鏡)観察は、透過型電子顕微鏡JEM 2010F(JEOL社製、加速電圧200kV)を用いて行った。またこれによるFFT(高速フーリエ変換)解析は、Gatan社製Digital Micrographを用いて行なった。
(オキシ水酸化鉄中の塩素イオンの含有量)
 オキシ水酸化鉄試料を3M硫酸に溶解した後、アルカリ溶液で希釈して鉄分を沈殿させ、フィルターでろ過してろ液を回収し、イオンクロマトグラフ法(日本ダイオネクス社製DX-500型)により定量した。
Measurement method (powder X-ray diffraction)
The X-ray diffraction (XRD) pattern was measured using an X-ray diffractometer Ultima IV (manufactured by Rigaku Corporation). A CuKα tube was used for the measurement. The average crystallite size was calculated from XRD according to Scherrer's formula.
(Specific surface area)
The specific surface area was measured by a gas adsorption method using a specific surface area measuring device MacsorbHM 1210 (manufactured by Mountec).
(TEM observation and FFT analysis)
The TEM (transmission electron microscope) observation of the sample was performed using a transmission electron microscope JEM 2010F (manufactured by JEOL, acceleration voltage 200 kV). Moreover, the FFT (fast Fourier transform) analysis by this was performed using Digital Micrograph made from Gatan.
(Chlorine ion content in iron oxyhydroxide)
An iron oxyhydroxide sample is dissolved in 3M sulfuric acid, diluted with an alkaline solution to precipitate iron, filtered through a filter, and the filtrate is collected and quantified by ion chromatography (DX-500, manufactured by Nippon Dionex). did.
製造例1(オキシ水酸化鉄の製造)
 塩化第二鉄(FeCl)水溶液に、室温でpH6以下に調整しながら水酸化ナトリウム(NaOH)水溶液を滴下し、NaOHの最終添加量をNaOH/FeCl(モル比)=2.75として反応させ、オキシ水酸化鉄の粒子懸濁液を得た。得られた懸濁液中の粒子の平均粒子径d50は17μmであった。
 懸濁液を濾別後、空気中120℃で乾燥し、イオン交換水で洗浄し、さらに空気中120℃で乾燥し、オキシ水酸化鉄の粉末を得た。
 以上により得られたオキシ水酸化物粉末(以後「粉末A」という。)の粒子径は0.25mm~5mmであった。X線回折により、結晶構造はβ-オキシ水酸化鉄であり、平均結晶子径は5nmであることを確認した。
 透過電子顕微鏡(TEM)観察での様子を図1に示す。結晶形状は粒状であった。TEM観察による結晶子径は5~10nm、個々の結晶は粒状であり、これらが凝結して粒子を形成していた。
 また比表面積は280m/g、塩素イオン含有量は5.8wt%であった。
Production Example 1 (Production of iron oxyhydroxide)
A sodium hydroxide (NaOH) aqueous solution was added dropwise to a ferric chloride (FeCl 3 ) aqueous solution while adjusting the pH to 6 or less at room temperature, and the final amount of NaOH added was NaOH / FeCl 3 (molar ratio) = 2.75. To obtain a particle suspension of iron oxyhydroxide. The average particle diameter d50 of the particles in the obtained suspension was 17 μm.
The suspension was filtered, dried in air at 120 ° C., washed with ion-exchanged water, and further dried in air at 120 ° C. to obtain iron oxyhydroxide powder.
The particle diameter of the oxyhydroxide powder (hereinafter referred to as “powder A”) obtained as described above was 0.25 mm to 5 mm. It was confirmed by X-ray diffraction that the crystal structure was β-iron oxyhydroxide and the average crystallite size was 5 nm.
FIG. 1 shows a state observed with a transmission electron microscope (TEM). The crystal shape was granular. The crystallite diameter by TEM observation was 5 to 10 nm, and each crystal was granular, and these were condensed to form particles.
The specific surface area was 280 m 2 / g, and the chlorine ion content was 5.8 wt%.
製造例2(オキシ水酸化鉄吸着材粉末及び分級品の製造)
 オキシ水酸化鉄の粉末Aをピンミルで乾式粉砕し粉末Bを得た。粉末Bの粒子径範囲は0.6~300μm、平均粒子径26.5μmであった。
 また粉末Bを篩で分級し、以下の各粉末を得た。
粉末C-1:粒度10~32μm
粉末C-2:粒度32~45μm
粉末C-3:粒度45~75μm
Production Example 2 (Manufacture of iron oxyhydroxide adsorbent powder and classified product)
Iron oxyhydroxide powder A was dry pulverized with a pin mill to obtain powder B. Powder B had a particle size range of 0.6 to 300 μm and an average particle size of 26.5 μm.
Further, powder B was classified with a sieve to obtain the following powders.
Powder C-1: Particle size 10 to 32 μm
Powder C-2: Particle size 32 to 45 μm
Powder C-3: Particle size 45 to 75 μm
参考測定例1(吸着材粒子のバッチ式リン酸吸着試験)
 リン酸二水素カリウムをイオン交換水に溶解し、塩酸によりpHを3.5に、又は水酸化ナトリウムによりpHを7.0に調整し、濃度400mg-P/L(リンとしての濃度)の試験液G(pH3.5)及びH(pH7.0)を調製した。
 試験液G、Hの150mLに、粉末C-1~3の各1gを添加後、撹拌し吸着試験を行った。所定の時間後に液を採取し、フィルタシリンジで固形分と分離し、溶液中のリン濃度をICP(誘導結合プラズマ)により分析し、吸着量を算出した。同時にpHを測定した。結果を表1に示した。
Reference measurement example 1 (Batch phosphoric acid adsorption test of adsorbent particles)
Dissolve potassium dihydrogen phosphate in ion-exchanged water, adjust the pH to 3.5 with hydrochloric acid or 7.0 with sodium hydroxide, and test for a concentration of 400 mg-P / L (concentration as phosphorus) Liquids G (pH 3.5) and H (pH 7.0) were prepared.
1 g of each of powders C-1 to C-3 was added to 150 mL of test solutions G and H, followed by stirring and an adsorption test. The liquid was collected after a predetermined time, separated from the solid content with a filter syringe, and the phosphorus concentration in the solution was analyzed by ICP (inductively coupled plasma) to calculate the amount of adsorption. At the same time, the pH was measured. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
 吸着材として粉末C-1~3を用い、試験液としてpH3.5のものを用いた場合には、リン酸イオンの吸着に伴ってpHが上昇することがわかる。一方、試験液としてpH7.0のものを用いた場合には、初期にpHが大きく下降し、その後もpHはわずかに上昇するのみでpH7.0を超えることはない。また試験液のpH3.5の場合は、pH7.0の場合よりも吸着量は少ない。これは、pH3.5の場合にはリン酸イオンが水酸イオンとの交換によって吸着されていることを示唆している。 It can be seen that when powders C-1 to C-3 are used as the adsorbent and pH 3.5 is used as the test solution, the pH increases as phosphate ions are adsorbed. On the other hand, when a test solution having a pH of 7.0 is used, the pH drops greatly in the initial stage, and then the pH rises only slightly and does not exceed pH 7.0. In addition, the amount of adsorption is less when the pH of the test solution is 3.5 than when the pH is 7.0. This suggests that phosphate ions are adsorbed by exchange with hydroxide ions at pH 3.5.
測定例1(吸着材粒子の通水式リン酸吸着試験)
 リン酸二水素カリウムをイオン交換水に溶解し、塩酸によりpHを2.9に、又は水酸化ナトリウムによりpHを7.0に調整し、濃度100mg-P/L(リンとしての濃度)の試験液I(pH2.9)及びJ(pH7.0)を調製した。
 カラムに粉末B及び粉末C-3を各々20g充填し、カラム上部より試験液I(実施例)、J(比較例)を、通水速度(SV)10(2.6mL/min)、20(5.3mL/min)又は30(7.8mL/min)で通水し、カラム下部より出てきた液を採取し、フィルタシリンジで固形分と分離し、溶液中のリン濃度をICPにより分析し、吸着量を算出した。破過点はカラム下部より出てきた液のリン濃度が10mg-P/Lとなった時点とした。同時にpHを測定した。試験条件は以下の通り。
実施例1-1:粉末B、試験液I、SV10、2回実施
実施例1-2:粉末B、試験液I、SV20、2回実施
比較例1-1:粉末B、試験液J、SV10、2回実施
比較例1-2:粉末B、試験液J、SV20、2回実施
実施例2:粉末C-3、試験液I、SV30
Measurement Example 1 (Water-permeable phosphate adsorption test for adsorbent particles)
Dissolve potassium dihydrogen phosphate in ion-exchanged water, adjust the pH to 2.9 with hydrochloric acid or 7.0 with sodium hydroxide, and test the concentration of 100 mg-P / L (concentration as phosphorus) Liquid I (pH 2.9) and J (pH 7.0) were prepared.
The column was filled with 20 g each of powder B and powder C-3, and test liquids I (Examples) and J (comparative examples) were passed from the top of the column at a water flow rate (SV) of 10 (2.6 mL / min), 20 ( 5.3 mL / min) or 30 (7.8 mL / min), collect the liquid from the bottom of the column, separate it from the solids with a filter syringe, and analyze the phosphorus concentration in the solution by ICP. The amount of adsorption was calculated. The breakthrough point was defined as the time when the phosphorus concentration of the liquid coming out from the bottom of the column reached 10 mg-P / L. At the same time, the pH was measured. The test conditions are as follows.
Example 1-1: Powder B, Test Solution I, SV10, 2 times Example 1-2: Powder B, Test Solution I, SV20, 2 times Comparative Example 1-1: Powder B, Test Solution J, SV10 Twice run Comparative Example 1-2: Powder B, Test Solution J, SV20, Twice Example 2: Powder C-3, Test Solution I, SV30
 結果を図2~6に示した。破過点における処理された水のpHは以下の通りであった。
実施例1-1:pH3.8(1回目)、pH3.8(2回目)
実施例1-2:pH3.3(1回目)、3.8(2回目)
比較例1-1:pH3.2(1回目)、3.2(2回目)
比較例1-2:pH3.0(1回目)、3.0(2回目)
実施例2:pH3.4 
The results are shown in FIGS. The pH of the treated water at the breakthrough point was as follows:
Example 1-1: pH 3.8 (first time), pH 3.8 (second time)
Example 1-2: pH 3.3 (first time), 3.8 (second time)
Comparative Example 1-1: pH 3.2 (first time), 3.2 (second time)
Comparative Example 1-2: pH 3.0 (first time), 3.0 (second time)
Example 2: pH 3.4
 破過点における通水倍率(流量[ml]/吸着材量[ml])は、実施例1-1、1-2、及び2では280~330程度、比較例1-1及び1-2では140程度であり、実施例の方が明らかに吸着量が多いことがわかる。破過点における処理された水のpHは、実施例では処理される前の水のpH2.9よりも0.2以上高く、この条件により吸着量が大幅に増加することがわかる。 The water flow rate at the breakthrough point (flow rate [ml] / adsorbent amount [ml]) is about 280 to 330 in Examples 1-1, 1-2, and 2, and in Comparative Examples 1-1 and 1-2. It is about 140, and it can be seen that the amount of adsorption is clearly larger in the example. The pH of the treated water at the breakthrough point is 0.2 or more higher than the pH 2.9 of the untreated water in the examples, and it can be seen that the amount of adsorption is greatly increased under this condition.

Claims (10)

  1. オキシ水酸化鉄を主成分とする陰イオン吸着材を充填した吸着装置へ、目的の陰イオンを含有し一定のpHを有する水を通水することにより、該陰イオンを吸着する方法において、破過点における処理された水のpHが、処理される前の水のpHより高くなる条件で行うことを特徴とする吸着方法。 In a method for adsorbing anions by passing water containing a target anion and having a certain pH through an adsorption device filled with an anion adsorbent mainly composed of iron oxyhydroxide. An adsorption method characterized in that it is carried out under conditions where the pH of the treated water at the excess is higher than the pH of the water before the treatment.
  2. 破過点における処理された水のpHが処理される前の水のpHより0.2以上高くなる条件で処理を行うことを特徴とする請求項1記載の吸着方法。 The adsorption method according to claim 1, wherein the treatment is performed under a condition that the pH of the treated water at the breakthrough point is 0.2 or more higher than the pH of the water before the treatment.
  3. 処理される前の水が、酸でpHが2.5~5.0に調整されていることを特徴とする請求項1又は2に記載の吸着方法。 The adsorption method according to claim 1 or 2, wherein the water before the treatment is acid and the pH is adjusted to 2.5 to 5.0.
  4. オキシ水酸化鉄がβ-オキシ水酸化鉄である請求項1~3のいずれかに記載の吸着方法。 The adsorption method according to any one of claims 1 to 3, wherein the iron oxyhydroxide is β-iron oxyhydroxide.
  5. オキシ水酸化鉄の平均結晶子径が10nm以下である請求項4に記載の吸着方法。 The adsorption method according to claim 4, wherein the average crystallite diameter of the iron oxyhydroxide is 10 nm or less.
  6. β-オキシ水酸化鉄の結晶の形状が粒状である請求項4又は5に記載の吸着方法。 6. The adsorption method according to claim 4, wherein the β-iron oxyhydroxide crystals are granular.
  7. オキシ水酸化鉄の比表面積が250m2/g以上である請求項1~6のいずれかに記載の吸着方法。 The adsorption method according to any one of claims 1 to 6, wherein the specific surface area of the iron oxyhydroxide is 250 m 2 / g or more.
  8. 処理される前の水に含有される目的の陰イオンの濃度が100mg/L以下である請求項1~7のいずれかに記載の吸着方法。 The adsorption method according to any one of claims 1 to 7, wherein the concentration of the target anion contained in the water before the treatment is 100 mg / L or less.
  9. 処理される前の水に塩素イオンが100mg/L以上含有される請求項1~8のいずれかに記載の吸着方法。 The adsorption method according to any one of claims 1 to 8, wherein chlorine ion is contained at 100 mg / L or more in water before the treatment.
  10. 目的の陰イオンがリン酸イオンである請求項1~9のいずれかに記載の吸着方法。 The adsorption method according to any one of claims 1 to 9, wherein the target anion is a phosphate ion.
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