WO2017061117A1 - Adsorbent dispersion and adsorption method - Google Patents

Adsorbent dispersion and adsorption method Download PDF

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Publication number
WO2017061117A1
WO2017061117A1 PCT/JP2016/004497 JP2016004497W WO2017061117A1 WO 2017061117 A1 WO2017061117 A1 WO 2017061117A1 JP 2016004497 W JP2016004497 W JP 2016004497W WO 2017061117 A1 WO2017061117 A1 WO 2017061117A1
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Prior art keywords
dispersion
anion
adsorbent
iron oxyhydroxide
anion adsorbent
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PCT/JP2016/004497
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French (fr)
Japanese (ja)
Inventor
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 JP2017544199A priority Critical patent/JP6731934B2/en
Publication of WO2017061117A1 publication Critical patent/WO2017061117A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/02—Oxides; Hydroxides
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption

Definitions

  • the present invention relates to a dispersion of an adsorbent mainly composed of iron oxyhydroxide.
  • Iron oxyhydroxide includes ⁇ -type, ⁇ -type, ⁇ -type, and amorphous type depending on the crystal structure.
  • iron oxyhydroxide has a wide range of uses such as pigments, magnetic materials, and catalysts, and is required to be a stable dispersion for some uses.
  • Patent Document 4 describes an aqueous suspension containing “iron oxyhydroxide having a particle size of 500 nm or less”, which specifically includes ⁇ -oxyhydroxide having a width represented by the above particle size.
  • Patent Document 5 iron (II) ions are supported on a clay mineral, and iron oxyhydroxide supported by hydrolysis and oxidation is obtained. It is described that it is used as a photocatalyst.
  • Patent Document 6 describes a method for producing a metal hydroxide sol produced in the presence of a compound having a buffering action. Specifically, ⁇ -containing an average particle diameter of about 8 nm and containing a small amount of an aluminum compound. An iron oxyhydroxide sol is described.
  • Patent Document 7 describes an iron oxyhydroxide sol stabilized with hydroxycarboxylic acid and having a median diameter of around 10 nm.
  • Patent Document 8 also describes an iron hydroxide sol produced in the presence of citric acid. These production requires auxiliary components other than iron oxyhydroxide and a solvent, and the process is complicated, and it is avoided that metal hydroxides or carboxylic acids other than iron, which are components derived from the auxiliary components, remain. I can't. In addition, it is stable near neutrality, but is not necessarily stable when acidic. Moreover, there is no description that these can be used as adsorbents.
  • the present inventor has found that a specific dispersion can be easily produced from a specific iron oxyhydroxide without using an auxiliary component, in particular, a stable nano-dispersion. Moreover, as a result of investigating the adsorption behavior using these, it was found that the adsorption rate was remarkably high, and the physical properties different from those of the raw materials were shown. Therefore, it was considered that this was not simply due to the large surface area.
  • the present invention has been completed based on the above findings.
  • the present invention relates to the following inventions.
  • the anion adsorbent dispersion according to (1) having an isoelectric point of pH 6.0 to 8.0.
  • Anion adsorbent dispersion containing 1 g of adsorbent is introduced into 150 mL of an aqueous solution of potassium dihydrogen phosphate having a phosphorous equivalent concentration of 400 mg / L adjusted to pH 3.5 with hydrochloric acid, and stirred at room temperature.
  • the anion adsorbent dispersion liquid according to any one of (1) to (6), wherein, in a batch type adsorption test to be performed, an adsorption amount converted to phosphorus per 1 g of adsorbent after 3 minutes is 22 mg or more.
  • Anion adsorbent dispersion containing 1 g of adsorbent is put into 150 mL of an aqueous solution of potassium dihydrogen phosphate having a phosphorus conversion concentration of 400 mg / L adjusted to pH 3.5 with hydrochloric acid, and stirred at room temperature.
  • the pH of the aqueous phase after 1 hour rises by 0.5 or more with respect to the higher value of 3.5 or the pH of the anion adsorbent dispersion charged.
  • the anion adsorbent dispersion according to any one of (1) to (7).
  • a method of removing and / or recovering anions comprising the step of aggregating and / or precipitating without adding an aggregating agent by adsorbing ions.
  • the iron oxyhydroxide-containing dispersion of the present invention By using the iron oxyhydroxide-containing dispersion of the present invention, a dispersion can be easily produced without using an auxiliary component, and a particularly stable nano-dispersion can be produced.
  • the iron oxyhydroxide-containing dispersion of the present invention has an extremely fast anion adsorption rate.
  • FIG. 4 is a diagram showing a TEM image of iron oxyhydroxide crystals obtained in Reference Example 1.
  • FIG. 6 is a graph showing the particle size distribution of the nano-dispersed liquid obtained in Example 2.
  • FIG. 3 is a diagram showing the zeta potential of the nano-dispersed liquid obtained in Example 2.
  • 4 is a diagram showing a TEM image of nanodispersed particles obtained in Example 2.
  • FIG. It is a figure which shows the FFT analysis result of the nano dispersion particle obtained in Example 2.
  • FIG. It is a figure which shows aggregation and sedimentation of the nano dispersion particle accompanying phosphoric acid adsorption. It is a figure which shows the change of the particle size (distribution and d50) before and behind phosphoric acid adsorption.
  • the anion adsorbent of the present invention is a dispersion liquid in which particles having an average particle diameter d50 of 2 ⁇ m or less and containing iron oxyhydroxide as a main component are dispersed in a solvent.
  • Iron oxyhydroxide is excellent in adsorptivity to anions.
  • Iron oxyhydroxide includes ⁇ -type, ⁇ -type, ⁇ -type, amorphous type, and the like depending on the crystal structure.
  • ⁇ -iron oxyhydroxide is particularly excellent in terms of adsorption performance, and adsorbents such as phosphate ions, phosphite ions, hypophosphite ions, sulfate ions, nitrate ions, fluoride ions, etc.
  • adsorbents such as phosphate ions, phosphite ions, hypophosphite ions, sulfate ions, nitrate ions, fluoride ions, etc.
  • it is also suitable as a raw material for the dispersion of the present invention in that a dispersion can be easily formed.
  • ⁇ -iron oxyhydroxide generally has a hydroxyl group partially substituted with chlorine ions. When in contact with water during manufacturing or use, the chlorine ions are removed, leaving small holes. These vacancies are considered to be involved in the adsorption of anions such as fluorine, and the efficient anion adsorption in the present invention is also considered to be a feature derived from these vacancies.
  • the iron oxyhydroxide in the present invention is preferably ⁇ -iron oxyhydroxide. Further, the content of chlorine ions in ⁇ -iron oxyhydroxide is preferably 0.5% by mass or more, and more preferably 3% by mass or more.
  • the average particle size of the dispersoid particles in the anion adsorbent dispersion of the present invention is preferably 0.2 ⁇ m or less.
  • the anion adsorbent dispersion liquid of the present invention is further preferably a nano dispersion liquid.
  • the nano-dispersion is a dispersion in which so-called nanoparticles having a particle size of 1 ⁇ m or less are dispersed in a liquid phase, and the particles do not settle by standing or normal centrifugation.
  • the average particle size of the nanoparticles contained in the nanodispersion of the present invention is preferably 0.02 to 0.2 ⁇ m, more preferably 0.05 to 0.15 ⁇ m.
  • the nano-dispersed liquid is excellent in that the adsorption efficiency and the adsorption speed are particularly high.
  • the anion adsorbent dispersion of the present invention preferably contains no components other than substances derived from at least one of an iron compound and a base that are essential as raw materials, a pH adjuster, and a solvent. Moreover, it is preferable not to contain an organic acid and its salt, an inorganic weak acid and its salt, a metal oxide and a metal hydroxide (except iron oxide, iron hydroxide, and iron oxyhydroxide), and a dispersing agent. Conventionally, iron oxyhydroxide dispersions usually contain these components as auxiliary components for stabilizing the dispersion, but the present invention requires the use of these auxiliary components in the production process. Absent.
  • the solid content in the anion adsorbent dispersion of the present invention (referred to as a dispersoid and a solute that is a solid at room temperature) has a content of iron compound containing the main component ⁇ -iron oxyhydroxide. It is 99 mass% or more, and it is preferable that the content rate of substances other than an iron compound is 1 mass% or less.
  • the iron oxyhydroxide content is more preferably 99% by mass, and most preferably substantially 100% by mass.
  • the solid concentration in the dispersion is preferably 5% by mass or more.
  • the iron oxyhydroxide used in the present invention preferably has a BET specific surface area of 200 m 2 / g or more, more preferably 250 m 2 / g or more, and more preferably 280 m 2 / g or more.
  • the pore volume area distribution (dV / dR) calculated by the BJH method is preferably 100 to 300 mm 3 / g / nm.
  • the adsorbent dispersion of the present invention is not excellent as an adsorbent simply because of its large specific surface area and pore volume.
  • the adsorbent dispersion of the present invention there is a method using a dry gel mainly composed of iron oxyhydroxide as a raw material, and the dry gel originally has a relatively high surface area. Even if this is pulverized, the specific surface area and the like do not increase particularly. However, when the average particle diameter is 2 ⁇ m or less and a part of the hydroxyl group of iron oxyhydroxide is substituted with chlorine ions, particularly excellent adsorption characteristics are produced.
  • the liquid phase other than the particles in the anion adsorbent dispersion of the present invention can be used without any problem as long as it is a uniform liquid phase.
  • water, an organic solvent, a mixture of water or an organic solvent, or these Can be used.
  • the solution preferably contains no organic acid and salt thereof, weak inorganic acid and salt thereof, and a dispersant.
  • water or an aqueous solution should be used as the liquid phase. preferable.
  • the anion adsorbent dispersion of the present invention can be used as an adsorbent as it is, or can be processed and used as a material for an adsorbent having a different shape or application.
  • the liquid phase component can be removed from the anion adsorbent dispersion of the present invention to form particles, which can be used in the gas phase, but it is preferable to use the dispersion in the form of a dispersion. . Since the anion adsorbent dispersion of the present invention or an adsorbent obtained by processing this dispersion quickly reaches adsorption equilibrium, it can adsorb very efficiently.
  • the particle shape 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.
  • the anion adsorbent dispersion of the present invention preferably has an average crystallite size of 3 nm or less, more preferably 1 to 2 nm.
  • the anion adsorbent dispersion of the present invention is characterized in that the primary particles are composed of a large number of crystallites. Specifically, the ratio of the average particle diameter to the average crystallite diameter is preferably 5 or more, and more preferably 10 to 100. 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.
  • D K ⁇ / ⁇ cos ⁇
  • ⁇ is the half width of the true diffraction peak corrected for the machine width caused by the apparatus
  • K is the Scherrer constant
  • ⁇ is the wavelength of the X-ray.
  • the anion adsorbent dispersion of the present invention can be obtained by wet-grinding solid ⁇ -iron oxyhydroxide as described later.
  • the average crystallite size of the obtained nanoparticles is about 1 to 2 nm. Since the minimum particle size of the nanoparticles is about 10 nm, which is larger than the original average crystallite size, the crystallite size is not simply destroyed as the particle size decreases, but as a physical effect of the grinding process. It is considered that the decrease is occurring.
  • the anion adsorbent dispersion of the present invention is highly stable on the acidic side from the isoelectric point.
  • This isoelectric point is preferably from pH 5.5 to 8.0, more preferably from pH 6.0 to 8.0, and even more preferably from pH 6.0 to 7.5. In the case of a nano-dispersion, the stability is high at pH 1.5 to 4.0, particularly pH 2.0 to 3.5.
  • the anion adsorbent dispersion liquid of the present invention is stable when the solid content concentration in the dispersion liquid is 5% by mass or more. The solid content concentration is particularly preferably 5 to 10% by mass.
  • the anion adsorbent dispersion of the present invention preferably has a pH of 2.0 to 5.5, more preferably a pH of 2.5 to 5.5, and further preferably a pH of 3.0 to 4.5. preferable.
  • the anion adsorbent dispersion of the present invention has a relatively low viscosity under the above conditions. Specifically, the viscosity is 5 to 20 mPa ⁇ s, more preferably 10 to 15 mPa ⁇ s.
  • the above-described stability factors exhibited by the anion adsorbent dispersion of the present invention are not necessarily clear, but are presumed to be related to the above-mentioned average crystallite diameter or the structural factors described below. .
  • the anion adsorbent dispersion liquid of the present invention is characterized by a high adsorption rate.
  • This adsorption rate can be measured by the following batch adsorption test.
  • a 150 mL aqueous solution of potassium dihydrogen phosphate having a phosphorus conversion concentration of 400 mg / L adjusted to a constant pH with hydrochloric acid is prepared.
  • the anion adsorbent dispersion of the present invention corresponding to 1 g of adsorbent is charged and stirred at room temperature. After a certain period of time, the aqueous solution is sampled and the phosphate ion concentration is measured to determine the amount of adsorption.
  • the liquid phase may be recovered by filtration or, in the case of a nano-dispersion, by ultrafiltration, or the dispersion of the present invention is aggregated or precipitated when phosphate ions are adsorbed as described later. Therefore, if necessary, the supernatant may be collected by centrifugation.
  • the anion adsorbent dispersion of the present invention has a phosphorus equivalent adsorption amount of 22 mg or more, preferably 30 mg or more after 3 minutes.
  • the anion adsorbent dispersion of the present invention is characterized in that the pH rises remarkably in the process of using it as an anion adsorbent in water. This is specifically shown by the following method.
  • a 150 mL aqueous solution of potassium dihydrogen phosphate having a phosphorus conversion concentration of 400 mg / L adjusted to a constant pH with hydrochloric acid is prepared.
  • the anion adsorbent dispersion of the present invention corresponding to 1 g of adsorbent is charged and stirred at room temperature. The aqueous phase is sampled after a certain time and the pH is measured.
  • the liquid phase may be recovered by filtration or, in the case of a nano-dispersion, by ultrafiltration, or the dispersion of the present invention is aggregated or precipitated when phosphate ions are adsorbed as described later. Therefore, if necessary, the supernatant may be collected by centrifugation.
  • the anion adsorbent dispersion of the present invention is 3.5 or higher relative to the pH of the charged anion adsorbent dispersion.
  • the pH of the aqueous solution after 1 hour rises by 0.5 or more.
  • ⁇ -iron oxyhydroxide which can be used as a material for the anion adsorbent dispersion of the present invention as described later, is used as an adsorbent in the same manner as long as the particle diameter is not very small. Also cause little change in the pH of the aqueous solution.
  • the adsorbed anion is exchanged with a hydroxyl group, and the anion is directly bonded to the adsorbent, and the hydroxyl group is a hydroxide ion.
  • the pH of the aqueous solution rises.
  • the anion adsorbent dispersion liquid of the present invention not only simply adsorbs anions, but then the anions bind to the adsorbent and do not easily dissociate. Both are considered to exhibit a very high remarkable adsorption effect.
  • the production method of the adsorbent particles of the present invention is not necessarily limited, but a production method including a step of wet-grinding a solid mainly composed of ⁇ -iron oxyhydroxide is particularly preferable.
  • the solid containing ⁇ -iron oxyhydroxide as a main component is preferably 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.
  • 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.
  • sodium hydroxide is particularly preferable.
  • 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.
  • the pH adjuster substances having a buffering action are excluded because they are difficult to remove, and specific examples include bases as described above and inorganic strong 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.
  • the dry gel obtained by the above method contains ⁇ -iron oxyhydroxide as a main component.
  • the anion adsorbent dispersion liquid of the present invention is particularly suitable for using the dispersoid contained therein as an anion adsorbent in the liquid.
  • the dispersoid contained in the anion adsorbent dispersion liquid of the present invention has the property of aggregating or precipitating without using an aggregating agent when adsorbing anions in the acidic region, and can be easily separated. . In this adsorption step, it is preferable to keep the pH at 5.5 or lower. Therefore, these dispersions can be used as an anion adsorbing material by adding the dispersion to the liquid containing the target anion to aggregate or precipitate the dispersoid, and separating and collecting it.
  • anion adsorbent When the anion is desorbed from the collected anion adsorbent, it can be re-dispersed, and this anion adsorbent can be used repeatedly. Anions can also be recovered by desorption.
  • the above properties are particularly advantageous in the case of a nanodispersion.
  • the dispersoid contained in the nanodispersion cannot be separated by ordinary centrifugation or filtration, and requires a special method such as ultrafiltration.
  • the anion adsorbent dispersion of the present invention can be easily separated and recovered after adsorption.
  • the anion adsorbent dispersion liquid of the present invention is particularly suitable to remove an anion component such as phosphoric acid as an adsorption target and to remove these components from waste water and / or to recover these components.
  • an anion component such as phosphoric acid
  • it can be used as a pharmaceutical for oral administration utilizing adsorptivity, particularly as a pharmaceutical for suppressing the phosphate level in the body, or a material thereof.
  • 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).
  • the laser diffraction / scattering type particle size distribution measuring device LA-920 (manufactured by Horiba Ltd.) is used, the volume-based cumulative 50% particle size (D50), and the volume-based cumulative.
  • the 90% particle size (D90) was measured.
  • the particle size, particle size distribution, cumulative 50% particle size (D50), and cumulative 90% particle size (D90) of the nano-dispersion liquid are measured using a dynamic light scattering particle size distribution analyzer Zeta Sizer Nano S (Spectres). Measured.
  • Zeta potential of dispersed particles The zeta potential was measured using a nanotrack (Nanotrac Wave UZ152, manufactured by Nikkiso Co., Ltd.).
  • NaOH ferric chloride
  • FeCl 3 ferric chloride
  • the particle diameter of the iron oxyhydroxide powder 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 chloride ion content was 5.8 wt%.
  • the above-mentioned iron oxyhydroxide powder was dry-pulverized with a pin mill until the particle diameter was about 300 ⁇ m or less to obtain a powder, which was used below.
  • Comparative Example 1 The pulverized iron oxyhydroxide was classified with a sieve to obtain a powder A having a particle size of 150 to 250 ⁇ m.
  • Example 1 (Production of iron oxyhydroxide dispersion)
  • the pulverized iron oxyhydroxide was mixed with ion-exchanged water so as to have a solid concentration of 10% by mass, and then pulverized with a bead mill (zirconia beads, bead diameter: 1 mm) for 30 minutes to obtain a dispersion B.
  • Dispersion B settled slowly when stored at room temperature, but returned to the dispersion again when stirred.
  • the pH of dispersion B was 2.9, the average particle diameter d50 was 1.30 ⁇ m, d90 was 4.35 ⁇ m, and the isoelectric point was pH 7.0.
  • the crystal structure of the powder obtained by drying Dispersion B at 50 ° C. was ⁇ -iron oxyhydroxide, and the specific surface area was 285 m 2 / g.
  • Example 2 (Production of iron oxyhydroxide nanodispersion) Dispersion B was further pulverized for 60 minutes with a bead mill (zirconia beads, bead diameter 0.1 mm). By this pulverization, the liquid suspended in brown was changed to a black and almost transparent nano-dispersion (nano-dispersion C). When nanodispersion C was spread thinly and dried, a film was obtained, and when thickened and dried, solid particles similar to the iron oxyhydroxide powder of Reference Example 1 were obtained. Moreover, it also has a binder function that adheres firmly when dried on a support, and can be molded into various shapes despite being an inorganic substance. Furthermore, the nano-dispersion C was stable even if it passed for one year at room temperature, but it did not gel but was stable, and when dispersed, the dispersion state was easily recovered.
  • the pH of the obtained nanodispersion C was 3.1.
  • the viscosity was 10.9 mPa ⁇ s.
  • the specific surface area of the nano-dispersed particles was 285 m 2 / g.
  • the particle size distribution of the nanodispersion C is shown in FIG.
  • the average particle diameter d50 was 0.05 ⁇ m, and d90 was 0.19 ⁇ m.
  • the measurement result of the zeta potential is shown in FIG.
  • the isoelectric point was pH 7.1, and at pH 3.1, the particles were positively charged.
  • the nano-dispersion was dried at 50 ° C. to obtain a powder.
  • the dry powder was subjected to X-ray diffraction, TEM observation, and fast Fourier transform (FFT) analysis of the TEM image.
  • the TEM image is shown in FIG. 4, and the FFT analysis result is shown in FIG.
  • the average particle diameter was about 3 nm
  • the crystal shape by TEM observation was granular
  • most of the particles were crystal particles in which crystal fringes were observed. These were identified as ⁇ -iron oxyhydroxide crystals from the lattice spacing determined by FFT analysis.
  • Measurement example 1 Potassium dihydrogen phosphate was dissolved in ion-exchanged water, adjusted to pH 3.5 with hydrochloric acid, and a test solution D having a concentration of 400 mg-P / L (concentration as phosphorus) was prepared. Further, potassium dihydrogen phosphate was dissolved in ion-exchanged water, adjusted to pH 7.0 with sodium hydroxide, and a test solution E having a concentration of 400 mg-P / L (concentration as phosphorus) was prepared. After adding 20 g of dispersion B or C (1 g as a solid content) to 130 mL of test liquid D or E, the mixture was stirred and subjected to 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 (Table 1).
  • Measurement example 2 (sedimentation test) To 130 mL of the test liquid D, 20 g of nano-dispersion C (1 g as a solid content) was added and mixed and allowed to stand. As a result, the nano-dispersed particles quickly aggregated and settled. The state (non-adsorbed, standing 15 minutes, 60 minutes and 24 hours later) is shown in FIG. In addition, FIG. 7 shows changes in particle size (non-adsorbed, standing 15 minutes, 30 minutes, 60 minutes, 6 hours, 24 hours).
  • the anion adsorbent dispersion liquid of the present invention has a remarkably high phosphoric acid adsorption rate and a large adsorption amount particularly at pH 3.5. Further, when the initial pH was set to 3.5, a characteristic that was significantly different from the raw material ⁇ -iron oxyhydroxide powder was revealed in that the pH increased to 4 or more in about 1 hour. Furthermore, when the initial pH was 3.5, the particles aggregated and precipitated with the adsorption of phosphoric acid and could be easily recovered.

Abstract

The purpose of the present invention is to provide an anion-adsorbent dispersion that comprises an iron oxyhydroxide nano-dispersion that is stable and that does not contain a component derived from an auxiliary component. This anion-adsorbent dispersion is formed by dispersing, in a solvent, particles that have an iron oxyhydroxide as a main component and that have an average particle diameter d50 of 2 μm or less. The iron oxyhydroxide is preferably β-iron oxyhydroxide. In addition, the average diameter d50 of the particles that have an iron oxyhydroxide as a main component is preferably 0.2 μm or less.

Description

吸着材分散液及び吸着方法Adsorbent dispersion and adsorption method
　本発明は、オキシ水酸化鉄を主成分とする吸着材の分散液に関する。
本願は、２０１５年１０月９日に出願された日本国特許出願第２０１５－２００７８８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 dispersion of an adsorbent mainly composed of iron oxyhydroxide.
This application claims priority to Japanese Patent Application No. 2015-200788 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。
　リン化合物やその他の陰イオンを効率的に吸着、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。 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 phosphorus compounds and other anions, those made of iron oxyhydroxide have been developed and described in Patent Documents 1, 2, 3 and the like.
　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、又は非晶質型等がある。オキシ水酸化鉄は、上記の吸着材のほかに、顔料、磁性材料、触媒等の幅広い用途を有し、一部の用途には安定な分散体であることが必要とされている。
　しかしオキシ水酸化鉄を安定したナノ分散液とすることは困難とされている。例えば特許文献４には、「粒度５００ｎｍ以下のオキシ水酸化鉄」を含む水性懸濁液についての記載があるが、これは具体的には、上記粒度で示される幅を有するα－オキシ水酸化鉄の針状一次粒子が複数凝集した粒子からなるものであり、ナノ分散液にはできない。このような凝集を防ぐための製造方法も検討されており、例えば特許文献５には、粘土鉱物上に鉄（ＩＩ）イオンを担持し、加水分解及び酸化によって担持されたオキシ水酸化鉄とし、光触媒として利用することが記載されている。
　一方特許文献６には、緩衝作用を有する化合物の存在下で製造される金属水酸化物ゾルの製法が記載されており、具体的には平均粒子径８ｎｍ程度で少量のアルミニウム化合物を含むβ－オキシ水酸化鉄ゾルが記載されている。また特許文献７には、ヒドロキシカルボン酸で安定化された、メジアン径１０ｎｍ前後のオキシ水酸化鉄ゾルが記載されている。特許文献８にも、クエン酸存在下で製造された水酸化鉄ゾルが記載されている。これらの製造にはオキシ水酸化鉄と溶媒以外の補助成分を要し、工程も複雑であり、補助成分に由来する成分である鉄以外の金属水酸化物やカルボン酸等が残存することが避けられない。また中性付近では安定であるが酸性では必ずしも安定ではない。しかもこれらは吸着材として利用できるとの記載もない。 Iron oxyhydroxide includes α-type, β-type, γ-type, and amorphous type depending on the crystal structure. In addition to the above adsorbents, iron oxyhydroxide has a wide range of uses such as pigments, magnetic materials, and catalysts, and is required to be a stable dispersion for some uses.
However, it is considered difficult to make iron oxyhydroxide a stable nano-dispersion. For example, Patent Document 4 describes an aqueous suspension containing “iron oxyhydroxide having a particle size of 500 nm or less”, which specifically includes α-oxyhydroxide having a width represented by the above particle size. It consists of particles formed by agglomeration of a plurality of iron needle-like primary particles and cannot be made into a nano-dispersed liquid. A production method for preventing such agglomeration has also been studied. For example, in Patent Document 5, iron (II) ions are supported on a clay mineral, and iron oxyhydroxide supported by hydrolysis and oxidation is obtained. It is described that it is used as a photocatalyst.
On the other hand, Patent Document 6 describes a method for producing a metal hydroxide sol produced in the presence of a compound having a buffering action. Specifically, β-containing an average particle diameter of about 8 nm and containing a small amount of an aluminum compound. An iron oxyhydroxide sol is described. Patent Document 7 describes an iron oxyhydroxide sol stabilized with hydroxycarboxylic acid and having a median diameter of around 10 nm. Patent Document 8 also describes an iron hydroxide sol produced in the presence of citric acid. These production requires auxiliary components other than iron oxyhydroxide and a solvent, and the process is complicated, and it is avoided that metal hydroxides or carboxylic acids other than iron, which are components derived from the auxiliary components, remain. I can't. In addition, it is stable near neutrality, but is not necessarily stable when acidic. Moreover, there is no description that these can be used as adsorbents.
特開２００６－１２４２３９号公報JP 2006-124239 A ＷＯ２００６／０８８０８３パンフレットWO2006 / 088083 pamphlet 特開２０１１－２３５２２２号公報JP 2011-235222 A 特表２００４－５０９７５３（ＷＯ２００２／０２６６３３パンフレット）Special table 2004-509753 (WO2002 / 026633 pamphlet) 特開２０１３－２２６５４８号公報JP 2013-226548 A 特開平９－７７５０３号公報JP-A-9-77503 特開２０１１－５１８３６号公報JP 2011-51836 A 特開２００６－１８２６０４号公報JP 2006-182604 A
　オキシ水酸化鉄を安定なナノ分散液とするためには、原料である鉄化合物溶液から補助成分を用いて行う特殊な製法が必要とされ、また得られた分散液も補助成分に由来する成分を含有するものが普通であった。 In order to make iron oxyhydroxide a stable nano-dispersed liquid, a special production method using auxiliary components from the iron compound solution as a raw material is required, and the obtained dispersion is also a component derived from the auxiliary components. The one containing was normal.
　本発明者は、特定のオキシ水酸化鉄からは補助成分を用いずに容易に分散液を、特に安定なナノ分散液を製造できることを見出した。またこれらを用いて吸着挙動を調べた結果、吸着速度が著しく速いことを見出し、原料と異なる物性を示すことから、これは単に表面積が大きいためではないと考えられた。本発明は以上の知見を基に完成されたものである。 The present inventor has found that a specific dispersion can be easily produced from a specific iron oxyhydroxide without using an auxiliary component, in particular, a stable nano-dispersion. Moreover, as a result of investigating the adsorption behavior using these, it was found that the adsorption rate was remarkably high, and the physical properties different from those of the raw materials were shown. Therefore, it was considered that this was not simply due to the large surface area. The present invention has been completed based on the above findings.
　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、平均粒径ｄ５０が２μｍ以下である粒子が、溶媒に分散してなる、陰イオン吸着材分散液。
（２）等電点がｐＨ６．０～８．０である、（１）に記載の陰イオン吸着材分散液。
（３）前記オキシ水酸化鉄がβ－オキシ水酸化鉄である、（１）又は（２）に記載の陰イオン吸着材分散液。
（４）オキシ水酸化鉄を主成分とする粒子の平均粒径ｄ５０が０．２μｍ以下である、（１）～（３）のいずれかに記載の陰イオン吸着材分散液。
（５）ｐＨが２．０～５．５である（１）～（４）のいずれかに記載の陰イオン吸着材分散液。
（６）β－オキシ水酸化鉄の水酸基の一部が塩素イオンで置換され、該塩素の含有量が０．５質量％以上である、（３）に記載の陰イオン吸着材分散液。
（７）塩酸でｐＨを３．５に調整したリン換算濃度４００ｍｇ／Ｌのリン酸二水素カリウム水溶液１５０ｍＬ中に、吸着材１ｇを含む陰イオン吸着材分散液を投入し、室温で撹拌して行う回分式の吸着試験において、３分後に吸着材１ｇ当たりのリン換算吸着量が２２ｍｇ以上である、（１）～（６）のいずれかに記載の陰イオン吸着材分散液。
（８）塩酸でｐＨを３．５に調整したリン換算濃度４００ｍｇ／Ｌのリン酸二水素カリウム水溶液１５０ｍＬ中に、吸着材１ｇを含む陰イオン吸着材分散液を投入し、室温で撹拌して行う回分式の試験において、３．５又は投入した陰イオン吸着材分散液のｐＨのうち高い方の値に対し、１時間後の水相のｐＨが０．５以上上昇することを特徴とする、（１）～（７）のいずれかに記載の陰イオン吸着材分散液。
（９）（１）～（８）のいずれかに記載の陰イオン吸着材分散液を、目的とする陰イオンを含有する液体に添加し混合する工程と、該混合物中の吸着材を、陰イオンを吸着することにより凝集剤を添加せずに凝集及び／又は沈殿させる工程とを含む、陰イオンを除去及び／又は回収する方法。
（１０）吸着材を、陰イオンを吸着することにより凝集及び／又は沈殿させる工程において、混合物のｐＨが継続して５．５以下であることを特徴とする、（９）に記載の方法。
That is, the present invention relates to the following inventions.
(1) An anion adsorbent dispersion liquid in which particles containing iron oxyhydroxide as a main component and having an average particle diameter d50 of 2 μm or less are dispersed in a solvent.
(2) The anion adsorbent dispersion according to (1) having an isoelectric point of pH 6.0 to 8.0.
(3) The anion adsorbent dispersion according to (1) or (2), wherein the iron oxyhydroxide is β-iron oxyhydroxide.
(4) The anion adsorbent dispersion according to any one of (1) to (3), wherein an average particle diameter d50 of particles mainly composed of iron oxyhydroxide is 0.2 μm or less.
(5) The anion adsorbent dispersion according to any one of (1) to (4), which has a pH of 2.0 to 5.5.
(6) The anion adsorbent dispersion according to (3), wherein a part of the hydroxyl groups of β-iron oxyhydroxide are substituted with chlorine ions, and the chlorine content is 0.5 mass% or more.
(7) Anion adsorbent dispersion containing 1 g of adsorbent is introduced into 150 mL of an aqueous solution of potassium dihydrogen phosphate having a phosphorous equivalent concentration of 400 mg / L adjusted to pH 3.5 with hydrochloric acid, and stirred at room temperature. The anion adsorbent dispersion liquid according to any one of (1) to (6), wherein, in a batch type adsorption test to be performed, an adsorption amount converted to phosphorus per 1 g of adsorbent after 3 minutes is 22 mg or more.
(8) Anion adsorbent dispersion containing 1 g of adsorbent is put into 150 mL of an aqueous solution of potassium dihydrogen phosphate having a phosphorus conversion concentration of 400 mg / L adjusted to pH 3.5 with hydrochloric acid, and stirred at room temperature. In the batch-type test to be performed, the pH of the aqueous phase after 1 hour rises by 0.5 or more with respect to the higher value of 3.5 or the pH of the anion adsorbent dispersion charged. The anion adsorbent dispersion according to any one of (1) to (7).
(9) A step of adding and mixing the anion adsorbent dispersion liquid according to any one of (1) to (8) to a liquid containing a target anion, and an adsorbent in the mixture, A method of removing and / or recovering anions, comprising the step of aggregating and / or precipitating without adding an aggregating agent by adsorbing ions.
(10) The method according to (9), wherein, in the step of aggregating and / or precipitating the adsorbent by adsorbing anions, the pH of the mixture is continuously 5.5 or less.
　本発明のオキシ水酸化鉄含有分散液を使用することにより、補助成分を用いずに容易に分散液を、特に安定なナノ分散液を製造することができる。また、本発明のオキシ水酸化鉄含有分散液は、陰イオンの吸着速度が著しく速い。 By using the iron oxyhydroxide-containing dispersion of the present invention, a dispersion can be easily produced without using an auxiliary component, and a particularly stable nano-dispersion can be produced. In addition, the iron oxyhydroxide-containing dispersion of the present invention has an extremely fast anion adsorption rate.
参考例１で得られたオキシ水酸化鉄結晶のＴＥＭ像を示す図である。4 is a diagram showing a TEM image of iron oxyhydroxide crystals obtained in Reference Example 1. FIG. 実施例２で得られたナノ分散液の粒度分布を示す図である。6 is a graph showing the particle size distribution of the nano-dispersed liquid obtained in Example 2. FIG. 実施例２で得られたナノ分散液のゼータ電位を示す図である。FIG. 3 is a diagram showing the zeta potential of the nano-dispersed liquid obtained in Example 2. 実施例２で得られたナノ分散粒子のＴＥＭ像を示す図である。4 is a diagram showing a TEM image of nanodispersed particles obtained in Example 2. FIG. 実施例２で得られたナノ分散粒子のＦＦＴ解析結果を示す図である。It is a figure which shows the FFT analysis result of the nano dispersion particle obtained in Example 2. FIG. リン酸吸着に伴うナノ分散粒子の凝集・沈降を示す図である。It is a figure which shows aggregation and sedimentation of the nano dispersion particle accompanying phosphoric acid adsorption. リン酸吸着前後での粒径（分布及びｄ５０）の変化を示す図である。It is a figure which shows the change of the particle size (distribution and d50) before and behind phosphoric acid adsorption.
（分散液）
　本発明の陰イオン吸着材は、オキシ水酸化鉄を主成分とする、平均粒径ｄ５０が２μｍ以下である粒子が、溶媒に分散してなる分散液である。 (Dispersion)
The anion adsorbent of the present invention is a dispersion liquid in which particles having an average particle diameter d50 of 2 μm or less and containing iron oxyhydroxide as a main component are dispersed in a solvent.
　オキシ水酸化鉄は、陰イオンに対する吸着性に優れている。
　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－オキシ水酸化鉄が、吸着性能の点で特に優れており、リン酸イオン、亜リン酸イオン、次亜リン酸イオン、硫酸イオン、硝酸イオン、フッ化物イオン等の吸着材に適している。また分散体を形成しやすい点で本発明の分散液の原料としても適している。
　β－オキシ水酸化鉄は、一般に、水酸基の一部が塩素イオンにより置換されている。製造又は使用の過程で水と接触すると、この塩素イオンが除去されて小型の空孔が残る。この空孔はフッ素等の陰イオンの吸着に関与すると考えられており、さらに本発明における効率的な陰イオン吸着もこの空孔に由来する特徴であると考えられる。
　本発明におけるオキシ水酸化鉄は、β－オキシ水酸化鉄であることが好ましい。さらにβ－オキシ水酸化鉄中における塩素イオンの含有量は、０．５質量％以上であることが好ましく、３質量％以上であることがより好ましい。 Iron oxyhydroxide is excellent in adsorptivity to anions.
Iron oxyhydroxide includes α-type, β-type, γ-type, amorphous type, and the like depending on the crystal structure. Of these, β-iron oxyhydroxide is particularly excellent in terms of adsorption performance, and adsorbents such as phosphate ions, phosphite ions, hypophosphite ions, sulfate ions, nitrate ions, fluoride ions, etc. Suitable for Further, it is also suitable as a raw material for the dispersion of the present invention in that a dispersion can be easily formed.
β-iron oxyhydroxide generally has a hydroxyl group partially substituted with chlorine ions. When in contact with water during manufacturing or use, the chlorine ions are removed, leaving small holes. These vacancies are considered to be involved in the adsorption of anions such as fluorine, and the efficient anion adsorption in the present invention is also considered to be a feature derived from these vacancies.
The iron oxyhydroxide in the present invention is preferably β-iron oxyhydroxide. Further, the content of chlorine ions in β-iron oxyhydroxide is preferably 0.5% by mass or more, and more preferably 3% by mass or more.
　本発明の陰イオン吸着材分散液の分散質粒子の平均粒径は、０．２μｍ以下であることが好ましい。
　本発明の陰イオン吸着材分散液は、さらに、ナノ分散液であることが好ましい。
　ナノ分散液とは、粒径１μｍ以下のいわゆるナノ粒子が液相中に分散してなる分散液で、静置や通常の遠心操作によって粒子が沈降しないものをいう。
　本発明のナノ分散液に含まれるナノ粒子は、その平均粒径は０．０２～０．２μｍであることが好ましく、０．０５～０．１５μｍであることがより好ましい。
　ナノ分散液は、吸着効率及び吸着速度が特に高い点で優れている。 The average particle size of the dispersoid particles in the anion adsorbent dispersion of the present invention is preferably 0.2 μm or less.
The anion adsorbent dispersion liquid of the present invention is further preferably a nano dispersion liquid.
The nano-dispersion is a dispersion in which so-called nanoparticles having a particle size of 1 μm or less are dispersed in a liquid phase, and the particles do not settle by standing or normal centrifugation.
The average particle size of the nanoparticles contained in the nanodispersion of the present invention is preferably 0.02 to 0.2 μm, more preferably 0.05 to 0.15 μm.
The nano-dispersed liquid is excellent in that the adsorption efficiency and the adsorption speed are particularly high.
　本発明の陰イオン吸着材分散液は、原料として必須である鉄化合物と塩基との少なくともいずれかに由来する物質、ｐＨ調整剤、及び溶媒以外の成分を含有しないことが好ましい。
　また、有機酸及びその塩、無機弱酸及びその塩、金属酸化物及び金属水酸化物（酸化鉄、水酸化鉄及びオキシ水酸化鉄を除く。）、ならびに分散剤を含有しないことが好ましい。
　従来、オキシ水酸化鉄の分散液には、これらの成分を分散安定化のための補助成分として含有するのが普通であったが、本発明は製造過程でこれらの補助成分を使用する必要がない。
　また、本発明の陰イオン吸着材分散液における固形分（分散質、及び溶質のうち常温において固体である成分を指す。）は、主成分β－オキシ水酸化鉄を含む鉄化合物の含有率が９９質量％以上であり、鉄化合物以外の物質の含有率は１質量％以下であることが好ましい。オキシ水酸化鉄の含有率は９９質量％であることがより好ましく、実質的に１００質量％であることが最も好ましい。
　分散液中における固形分濃度は、５質量％以上であることが好ましい。 The anion adsorbent dispersion of the present invention preferably contains no components other than substances derived from at least one of an iron compound and a base that are essential as raw materials, a pH adjuster, and a solvent.
Moreover, it is preferable not to contain an organic acid and its salt, an inorganic weak acid and its salt, a metal oxide and a metal hydroxide (except iron oxide, iron hydroxide, and iron oxyhydroxide), and a dispersing agent.
Conventionally, iron oxyhydroxide dispersions usually contain these components as auxiliary components for stabilizing the dispersion, but the present invention requires the use of these auxiliary components in the production process. Absent.
Further, the solid content in the anion adsorbent dispersion of the present invention (referred to as a dispersoid and a solute that is a solid at room temperature) has a content of iron compound containing the main component β-iron oxyhydroxide. It is 99 mass% or more, and it is preferable that the content rate of substances other than an iron compound is 1 mass% or less. The iron oxyhydroxide content is more preferably 99% by mass, and most preferably substantially 100% by mass.
The solid concentration in the dispersion is preferably 5% by mass or more.
　本発明に用いるオキシ水酸化鉄は、ＢＥＴ比表面積が２００ｍ2／ｇ以上であることが好ましく、さらに２５０ｍ2／ｇ以上であることが好ましく、２８０ｍ2／ｇ以上であることがより好ましい。
　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。
　但し、本発明の吸着材分散液は、単に比表面積や細孔容量が大きいために吸着材として優れているのではない。例えば、本発明の吸着材分散液の代表的な製造方法として、オキシ水酸化鉄を主成分とする乾燥ゲルを原料とする方法があるが、該乾燥ゲルは元来比較的高い表面積を有しており、これを微粉砕しても比表面積等が特別に増加するわけではない。しかし、平均粒径２μｍ以下であり、しかもオキシ水酸化鉄の水酸基の一部が塩素イオンで置換されていることによって、特に優れた吸着特性が生じるのである。 The iron oxyhydroxide used in the present invention preferably has a BET specific surface area of 200 m 2 / g or more, more preferably 250 m 2 / g or more, and more preferably 280 m 2 / g or more.
Further, the pore volume area distribution (dV / dR) calculated by the BJH method is preferably 100 to 300 mm 3 / g / nm.
However, the adsorbent dispersion of the present invention is not excellent as an adsorbent simply because of its large specific surface area and pore volume. For example, as a typical production method of the adsorbent dispersion of the present invention, there is a method using a dry gel mainly composed of iron oxyhydroxide as a raw material, and the dry gel originally has a relatively high surface area. Even if this is pulverized, the specific surface area and the like do not increase particularly. However, when the average particle diameter is 2 μm or less and a part of the hydroxyl group of iron oxyhydroxide is substituted with chlorine ions, particularly excellent adsorption characteristics are produced.
　本発明の陰イオン吸着材分散液における粒子以外の液相としては、均一な液相であれば問題なく使用可能であり、例えば水、有機溶媒、複数の水又は有機溶媒からなる混合物、あるいはこれらを主成分とする溶液を用いることができる。溶液としては、有機酸及びその塩、無機弱酸及びその塩、ならびに分散剤を含有しない方が好ましい。このうち、前記課題として記載したように、有害物質又は有用物質の除去、回収等を目的とする吸着材として、又は吸着材の原料として用いる場合には、液相として水又は水溶液を用いることが好ましい。 The liquid phase other than the particles in the anion adsorbent dispersion of the present invention can be used without any problem as long as it is a uniform liquid phase. For example, water, an organic solvent, a mixture of water or an organic solvent, or these Can be used. The solution preferably contains no organic acid and salt thereof, weak inorganic acid and salt thereof, and a dispersant. Among these, as described as the above-mentioned problem, when using as an adsorbent for the purpose of removing or recovering harmful substances or useful substances, or as a raw material of the adsorbent, water or an aqueous solution should be used as the liquid phase. preferable.
　本発明の陰イオン吸着材分散液は、そのまま吸着材として用いることもでき、また形状あるいは用途の異なる吸着材の材料として加工して用いることもできる。
　加工して用いる場合には、本発明の陰イオン吸着材分散液から、液相成分を除去して粒子とし、気相中で使用することもできるが、分散液形態のまま使用することが好ましい。
　本発明の陰イオン吸着材分散液、あるいはこれを加工してなる吸着材は、速やかに吸着平衡に達するため、非常に高効率の吸着が可能である。 The anion adsorbent dispersion of the present invention can be used as an adsorbent as it is, or can be processed and used as a material for an adsorbent having a different shape or application.
When processed and used, the liquid phase component can be removed from the anion adsorbent dispersion of the present invention to form particles, which can be used in the gas phase, but it is preferable to use the dispersion in the form of a dispersion. .
Since the anion adsorbent dispersion of the present invention or an adsorbent obtained by processing this dispersion quickly reaches adsorption equilibrium, it can adsorb very efficiently.
　本発明の陰イオン吸着材分散液は、粒子の形状が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。 In the anion adsorbent dispersion liquid of the present invention, the particle shape 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.
　本発明の陰イオン吸着材分散液は、平均結晶子径が３ｎｍ以下であることが好ましく、１～２ｎｍであることがより好ましい。
　また、本発明の陰イオン吸着材分散液は、一次粒子が多数の結晶子からなることを特徴とする。具体的には、平均結晶子径に対する平均粒子径の比は、５以上であることが好ましく、１０～１００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高いことが、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。
　本発明の陰イオン吸着材分散液は、後述のように、固体状のβ－オキシ水酸化鉄を湿式粉砕することにより得ることができる。ここで原料である固体状β－オキシ水酸化鉄として、平均結晶子径が５～６ｎｍ程度のものを用いた場合、得られるナノ粒子の平均結晶子径は１～２ｎｍ程度となる。このナノ粒子の最少粒径は元の平均結晶子径より大きい１０ｎｍ程度であるから、単に粒径の減少に伴って結晶子が破壊されるのではなく、粉砕工程の物理的効果として結晶子径の減少が起こっているものと考えられる。 The anion adsorbent dispersion of the present invention preferably has an average crystallite size of 3 nm or less, more preferably 1 to 2 nm.
The anion adsorbent dispersion of the present invention is characterized in that the primary particles are composed of a large number of crystallites. Specifically, the ratio of the average particle diameter to the average crystallite diameter is preferably 5 or more, and more preferably 10 to 100.
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.
The anion adsorbent dispersion of the present invention can be obtained by wet-grinding solid β-iron oxyhydroxide as described later. Here, when solid β-iron oxyhydroxide as a raw material having an average crystallite size of about 5 to 6 nm is used, the average crystallite size of the obtained nanoparticles is about 1 to 2 nm. Since the minimum particle size of the nanoparticles is about 10 nm, which is larger than the original average crystallite size, the crystallite size is not simply destroyed as the particle size decreases, but as a physical effect of the grinding process. It is considered that the decrease is occurring.
　本発明の陰イオン吸着材分散液は、等電点より酸性側で安定性が高い。この等電点はｐＨ５．５～８．０であることが好ましく、ｐＨ６．０～８．０であることがより好ましく、ｐＨ６．０～７．５であることがさらに好ましい。またナノ分散液である場合には、ｐＨ１．５～４．０、特にｐＨ２．０～３．５で安定性が高い。
　本発明の陰イオン吸着材分散液は、分散液中の固形分濃度が５質量％以上で安定である。固形分濃度は特に５～１０質量％であることが好ましい。
　本発明の陰イオン吸着材分散液は、ｐＨ２．０～５．５であることが好ましく、ｐＨ２．５～５．５であることがより好ましく、ｐＨ３．０～４．５であることがさらに好ましい。
　本発明の陰イオン吸着材分散液は、以上の条件において粘度が比較的低い。具体的には、粘度は５～２０ｍＰａ・ｓであり、より好ましくは１０～１５ｍＰａ・ｓである。
　本発明の陰イオン吸着材分散液が示す以上のような安定性の要因は、必ずしも明確ではないが、上述の平均結晶子径、あるいは以下に述べる構造的要因が関係していると推測される。 The anion adsorbent dispersion of the present invention is highly stable on the acidic side from the isoelectric point. This isoelectric point is preferably from pH 5.5 to 8.0, more preferably from pH 6.0 to 8.0, and even more preferably from pH 6.0 to 7.5. In the case of a nano-dispersion, the stability is high at pH 1.5 to 4.0, particularly pH 2.0 to 3.5.
The anion adsorbent dispersion liquid of the present invention is stable when the solid content concentration in the dispersion liquid is 5% by mass or more. The solid content concentration is particularly preferably 5 to 10% by mass.
The anion adsorbent dispersion of the present invention preferably has a pH of 2.0 to 5.5, more preferably a pH of 2.5 to 5.5, and further preferably a pH of 3.0 to 4.5. preferable.
The anion adsorbent dispersion of the present invention has a relatively low viscosity under the above conditions. Specifically, the viscosity is 5 to 20 mPa · s, more preferably 10 to 15 mPa · s.
The above-described stability factors exhibited by the anion adsorbent dispersion of the present invention are not necessarily clear, but are presumed to be related to the above-mentioned average crystallite diameter or the structural factors described below. .
　本発明の陰イオン吸着材分散液は、吸着速度が高い特徴を有する。
　この吸着速度は、次のような回分式吸着試験により測定できる。
　塩酸でｐＨを一定に調整したリン換算濃度４００ｍｇ／Ｌのリン酸二水素カリウム水溶液１５０ｍＬを準備する。この中に吸着材１ｇに相当する本発明の陰イオン吸着材分散液を投入し、室温で撹拌する。一定時間後に水溶液をサンプリングしてリン酸イオン濃度を測定し、吸着量を求める。このサンプリング方法としては、濾過、あるいはナノ分散液である場合には限外濾過により液相を回収してもよいし、本発明の分散液は後述のようにリン酸イオンを吸着すると凝集又は沈殿するから、その後に必要であれば遠心し、上清を回収してもよい。
　本発明の陰イオン吸着材分散液は、この方法において、水溶液のｐＨを３．５に調整した場合、３分後にリン換算吸着量が２２ｍｇ以上、好ましくは３０ｍｇ以上となる。 The anion adsorbent dispersion liquid of the present invention is characterized by a high adsorption rate.
This adsorption rate can be measured by the following batch adsorption test.
A 150 mL aqueous solution of potassium dihydrogen phosphate having a phosphorus conversion concentration of 400 mg / L adjusted to a constant pH with hydrochloric acid is prepared. Into this, the anion adsorbent dispersion of the present invention corresponding to 1 g of adsorbent is charged and stirred at room temperature. After a certain period of time, the aqueous solution is sampled and the phosphate ion concentration is measured to determine the amount of adsorption. As this sampling method, the liquid phase may be recovered by filtration or, in the case of a nano-dispersion, by ultrafiltration, or the dispersion of the present invention is aggregated or precipitated when phosphate ions are adsorbed as described later. Therefore, if necessary, the supernatant may be collected by centrifugation.
In this method, when the pH of the aqueous solution is adjusted to 3.5 in this method, the anion adsorbent dispersion of the present invention has a phosphorus equivalent adsorption amount of 22 mg or more, preferably 30 mg or more after 3 minutes.
　また本発明の陰イオン吸着材分散液は、水中で陰イオン吸着材として使用する過程で、ｐＨが顕著に上昇することを特徴とする。これは、具体的には次の方法で示される。
　塩酸でｐＨを一定に調整したリン換算濃度４００ｍｇ／Ｌのリン酸二水素カリウム水溶液１５０ｍＬを準備する。この中に吸着材１ｇに相当する本発明の陰イオン吸着材分散液を投入し、室温で撹拌する。一定時間後に水相をサンプリングしてｐＨを測定する。このサンプリング方法としては、濾過、あるいはナノ分散液である場合には限外濾過により液相を回収してもよいし、本発明の分散液は後述のようにリン酸イオンを吸着すると凝集又は沈殿するから、その後に必要であれば遠心し、上清を回収してもよい。
　本発明の陰イオン吸着材分散液は、この方法において、水溶液のｐＨを３．５に調整した場合、３．５又は投入した陰イオン吸着材分散液のｐＨのうち高い方の値に対して、１時間後の水溶液のｐＨが０．５以上上昇する。
　これに対し、後述のように本発明の陰イオン吸着材分散液の材料として用いることのできるβ－オキシ水酸化鉄は、粒子径がある程度微小でないと、同様の方法で吸着材として使用してもほとんど水溶液のｐＨの変化をもたらさない。 In addition, the anion adsorbent dispersion of the present invention is characterized in that the pH rises remarkably in the process of using it as an anion adsorbent in water. This is specifically shown by the following method.
A 150 mL aqueous solution of potassium dihydrogen phosphate having a phosphorus conversion concentration of 400 mg / L adjusted to a constant pH with hydrochloric acid is prepared. Into this, the anion adsorbent dispersion of the present invention corresponding to 1 g of adsorbent is charged and stirred at room temperature. The aqueous phase is sampled after a certain time and the pH is measured. As this sampling method, the liquid phase may be recovered by filtration or, in the case of a nano-dispersion, by ultrafiltration, or the dispersion of the present invention is aggregated or precipitated when phosphate ions are adsorbed as described later. Therefore, if necessary, the supernatant may be collected by centrifugation.
In this method, when the pH of the aqueous solution is adjusted to 3.5 in this method, the anion adsorbent dispersion of the present invention is 3.5 or higher relative to the pH of the charged anion adsorbent dispersion. The pH of the aqueous solution after 1 hour rises by 0.5 or more.
In contrast, β-iron oxyhydroxide, which can be used as a material for the anion adsorbent dispersion of the present invention as described later, is used as an adsorbent in the same manner as long as the particle diameter is not very small. Also cause little change in the pH of the aqueous solution.
　これらの原因は、次のように推察される。粉砕等の処理をしていないβ－オキシ水酸化鉄では、水酸基がリン酸イオンのような大きな陰イオンの容易に到達し得ない細孔中にある。このような細孔は、特に塩素イオンが離脱することにより形成されるものである。一方、本発明の陰イオン吸着材分散液では、このような細孔構造が破壊されているため、陰イオンが容易に該水酸基の近傍に到達する。
　粉砕等の処理をしていないβ－オキシ水酸化鉄でも、大型の空孔があるため、吸着速度は遅いもののリン酸イオンの吸着は可能である。
　本発明の陰イオン吸着材分散液においては、これに続き、吸着された陰イオンが水酸基と交換され、吸着材に該陰イオンが直接結合した形に変化し、それとともに、水酸基は水酸イオンとして水中に放出されるため、水溶液のｐＨは上昇する。しかし粉砕等の処理をしていないβ－オキシ水酸化鉄では、このような置換は起こらず、従ってｐＨの上昇も起こらないものと推察される。
　以上により、本発明の陰イオン吸着材分散液は、陰イオンを単に吸着するのみでなく、その後陰イオンは吸着材に結合して容易に解離しない状態となるため、吸着速度、最終的吸着量とも非常に高い顕著な吸着効果を発揮するものと考えられる。 These causes are presumed as follows. In β-iron oxyhydroxide that has not been pulverized or the like, the hydroxyl groups are in the pores where large anions such as phosphate ions cannot easily reach. Such pores are particularly formed when chlorine ions are released. On the other hand, in the anion adsorbent dispersion liquid of the present invention, since such a pore structure is destroyed, the anion easily reaches the vicinity of the hydroxyl group.
Even β-iron oxyhydroxide that has not been pulverized or the like has large pores, and thus adsorption of phosphate ions is possible although the adsorption rate is slow.
In the anion adsorbent dispersion liquid of the present invention, subsequently, the adsorbed anion is exchanged with a hydroxyl group, and the anion is directly bonded to the adsorbent, and the hydroxyl group is a hydroxide ion. As a result, the pH of the aqueous solution rises. However, it is assumed that such substitution does not occur in β-iron oxyhydroxide that has not been subjected to a treatment such as pulverization, and therefore no increase in pH occurs.
As described above, the anion adsorbent dispersion liquid of the present invention not only simply adsorbs anions, but then the anions bind to the adsorbent and do not easily dissociate. Both are considered to exhibit a very high remarkable adsorption effect.
　本発明の吸着材粒子の製造方法としては、必ずしも限定されるものではないが、β－オキシ水酸化鉄を主成分とする固体を湿式粉砕する工程を含む製造方法が特に好ましい。 The production method of the adsorbent particles of the present invention is not necessarily limited, but a production method including a step of wet-grinding a solid mainly composed of β-iron oxyhydroxide is particularly preferable.
　前記のβ－オキシ水酸化鉄を主成分とする固体としては、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が好ましい。
　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調整剤としては、緩衝作用を有する物質は除去が困難であることから除外され、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。 The solid containing β-iron oxyhydroxide as a main component is preferably 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.
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. As the pH adjuster, substances having a buffering action are excluded because they are difficult to remove, and specific examples include bases as described above and inorganic strong 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.
　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。
　以上の方法により得られる乾燥ゲルは、β－オキシ水酸化鉄を主成分として含む。 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.
The dry gel obtained by the above method contains β-iron oxyhydroxide as a main component.
　本発明の陰イオン吸着材分散液は、これに含まれる分散質を液中で陰イオン吸着材として利用するのに特に適している。
　本発明の陰イオン吸着材分散液に含まれる分散質は、酸性域で陰イオンを吸着すると、凝集剤を利用することなしに、凝集あるいは沈殿する性質を有し、容易に分離することができる。この吸着工程では、ｐＨを継続して５．５以下とすることが好ましい。
　従って、これらの分散液を、目的とする陰イオンを含有する液体に添加し、分散質を凝集あるいは沈殿させ、これを分離、回収することにより、陰イオン吸着材として利用することができる。回収した陰イオン吸着材から陰イオンを脱着すると、再度分散液とすることができ、これによってこの陰イオン吸着材を反復使用することができる。また脱着により陰イオンを回収することもできる。
　以上の性質は、特に、ナノ分散液である場合に有利である。ナノ分散液に含まれる分散質は通常の遠心や濾過で分離することができず、限外濾過等の特殊な方法を要する。しかし本発明の陰イオン吸着材分散液では、吸着後に容易に分離、回収することができる。 The anion adsorbent dispersion liquid of the present invention is particularly suitable for using the dispersoid contained therein as an anion adsorbent in the liquid.
The dispersoid contained in the anion adsorbent dispersion liquid of the present invention has the property of aggregating or precipitating without using an aggregating agent when adsorbing anions in the acidic region, and can be easily separated. . In this adsorption step, it is preferable to keep the pH at 5.5 or lower.
Therefore, these dispersions can be used as an anion adsorbing material by adding the dispersion to the liquid containing the target anion to aggregate or precipitate the dispersoid, and separating and collecting it. When the anion is desorbed from the collected anion adsorbent, it can be re-dispersed, and this anion adsorbent can be used repeatedly. Anions can also be recovered by desorption.
The above properties are particularly advantageous in the case of a nanodispersion. The dispersoid contained in the nanodispersion cannot be separated by ordinary centrifugation or filtration, and requires a special method such as ultrafiltration. However, the anion adsorbent dispersion of the present invention can be easily separated and recovered after adsorption.
　本発明の陰イオン吸着材分散液の使用目的としては、リン酸等の陰イオン成分を吸着対象として、排水からこれらの成分を除去すること、及び／又はこれらの成分を回収することが特に適している。
　そのほか、吸着性を利用した経口投与用医薬品、特に体内のリン酸塩レベルを抑制するための医薬品、又はその材料として使用することも可能である。 For the purpose of using the anion adsorbent dispersion liquid of the present invention, it is particularly suitable to remove an anion component such as phosphoric acid as an adsorption target and to remove these components from waste water and / or to recover these components. ing.
In addition, it can be used as a pharmaceutical for oral administration utilizing adsorptivity, particularly as a pharmaceutical for suppressing the phosphate level in the body, or a material thereof.
　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。
（分散液の粘度）
　２０℃で、音叉型振動式粘度計ＳＶ－１０（エー・アンド・デイ社製）により測定した。
（分散液の粒度分布）
　ミクロン単位の分散液の粒子径に関しては、レーザ回折／散乱式粒度分布測定装置LA-920（堀場製作所製）を使用して、体積基準の累積５０％粒子径（Ｄ５０）、及び体積基準の累積９０％粒子径（Ｄ９０）を測定した。
　ナノ分散液の粒子径、粒度分布、累積５０％粒子径（Ｄ５０）、及び累積９０％粒子径（Ｄ９０）は、動的光散乱粒度分布測定装置ゼータサイザーナノＳ（スペクトリス社製）を使用して測定した。
（分散粒子のゼータ電位）
　ゼータ電位は、ナノトラック（Nanotrac Wave ＵＺ152、日機装社製）を用いて測定した。 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.
(Viscosity of dispersion)
The temperature was measured at 20 ° C. using a tuning fork type vibration viscometer SV-10 (manufactured by A & D).
(Particle size distribution of the dispersion)
Regarding the particle size of the dispersion liquid in micron units, the laser diffraction / scattering type particle size distribution measuring device LA-920 (manufactured by Horiba Ltd.) is used, the volume-based cumulative 50% particle size (D50), and the volume-based cumulative. The 90% particle size (D90) was measured.
The particle size, particle size distribution, cumulative 50% particle size (D50), and cumulative 90% particle size (D90) of the nano-dispersion liquid are measured using a dynamic light scattering particle size distribution analyzer Zeta Sizer Nano S (Spectres). Measured.
(Zeta potential of dispersed particles)
The zeta potential was measured using a nanotrack (Nanotrac Wave UZ152, manufactured by Nikkiso Co., Ltd.).
参考例１（オキシ水酸化鉄の製造）
　塩化第二鉄（ＦｅＣｌ３）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／ＦｅＣｌ３（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鉄粉末の粒子径は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２８０ｍ２／ｇ、塩素イオン含有量は、５．８ｗｔ％であった。 Reference 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 iron oxyhydroxide powder 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 chloride ion content was 5.8 wt%.
　上記のオキシ水酸化鉄粉末をピンミルで、粒子径約３００μｍ以下になるまで乾式粉砕して粉末を得、以下に用いた。 The above-mentioned iron oxyhydroxide powder was dry-pulverized with a pin mill until the particle diameter was about 300 μm or less to obtain a powder, which was used below.
比較例１
　前記のオキシ水酸化鉄粉砕物を、篩で分級し、粒度１５０～２５０μｍの粉末Ａを得た。 Comparative Example 1
The pulverized iron oxyhydroxide was classified with a sieve to obtain a powder A having a particle size of 150 to 250 μm.
実施例１（オキシ水酸化鉄分散液の製造）
　前記のオキシ水酸化鉄粉砕物を、イオン交換水に固形分濃度１０質量％となるように混合した後、ビーズミル（ジルコニアビーズ、ビーズ径１ｍｍ）で３０分間粉砕し、分散液Ｂを得た。
　分散液Ｂは、室温保存しておくと、ゆっくりと沈降したが、撹拌すると再び分散液に戻った。
　分散液ＢのｐＨは２．９、平均粒子径ｄ５０は１．３０μｍ、ｄ９０は４．３５μｍ、等電点はｐＨ７．０であった。分散液Ｂを５０℃で乾燥して得た粉末の結晶構造はβ－オキシ水酸化鉄であり、比表面積は２８５ｍ２/ｇであった。 Example 1 (Production of iron oxyhydroxide dispersion)
The pulverized iron oxyhydroxide was mixed with ion-exchanged water so as to have a solid concentration of 10% by mass, and then pulverized with a bead mill (zirconia beads, bead diameter: 1 mm) for 30 minutes to obtain a dispersion B.
Dispersion B settled slowly when stored at room temperature, but returned to the dispersion again when stirred.
The pH of dispersion B was 2.9, the average particle diameter d50 was 1.30 μm, d90 was 4.35 μm, and the isoelectric point was pH 7.0. The crystal structure of the powder obtained by drying Dispersion B at 50 ° C. was β-iron oxyhydroxide, and the specific surface area was 285 m 2 / g.
実施例２（オキシ水酸化鉄ナノ分散液の製造）
　分散液Ｂをさらに、ビーズミル（ジルコニアビーズ、ビーズ径０．１ｍｍ）で６０分間粉砕した。この粉砕により、茶色に懸濁していた液が黒色でほぼ透明なナノ分散液（ナノ分散液Ｃ）へ変化した。
　ナノ分散液Ｃは、薄く広げて乾燥させると膜が得られ、厚くして乾燥すると参考例１のオキシ水酸化鉄粉末に類似の固い粒子が得られた。また、支持体の上で乾燥すると強固に接着するバインダー機能も有しており、無機物でありながら種々の形状に成形できた。
　さらに、ナノ分散液Ｃは室温で１年経過しても、わずかには沈降するもののゲル化することはなく安定であり、撹拌すれば分散状態を容易に回復するものであった。 Example 2 (Production of iron oxyhydroxide nanodispersion)
Dispersion B was further pulverized for 60 minutes with a bead mill (zirconia beads, bead diameter 0.1 mm). By this pulverization, the liquid suspended in brown was changed to a black and almost transparent nano-dispersion (nano-dispersion C).
When nanodispersion C was spread thinly and dried, a film was obtained, and when thickened and dried, solid particles similar to the iron oxyhydroxide powder of Reference Example 1 were obtained. Moreover, it also has a binder function that adheres firmly when dried on a support, and can be molded into various shapes despite being an inorganic substance.
Furthermore, the nano-dispersion C was stable even if it passed for one year at room temperature, but it did not gel but was stable, and when dispersed, the dispersion state was easily recovered.
　得られたナノ分散液ＣのｐＨは３．１であった。粘度は１０．９ｍＰａ・ｓであった。またナノ分散粒子の比表面積は２８５ｍ２／ｇであった。
　ナノ分散液Ｃの粒度分布を図２に示した。平均粒子径ｄ５０は０．０５μｍ、ｄ９０は０．１９μｍであった。
　ゼータ電位の測定結果を図３に示した。等電点はｐＨ７．１であり、ｐＨ３．１においては粒子はプラスに帯電していた。 The pH of the obtained nanodispersion C was 3.1. The viscosity was 10.9 mPa · s. The specific surface area of the nano-dispersed particles was 285 m 2 / g.
The particle size distribution of the nanodispersion C is shown in FIG. The average particle diameter d50 was 0.05 μm, and d90 was 0.19 μm.
The measurement result of the zeta potential is shown in FIG. The isoelectric point was pH 7.1, and at pH 3.1, the particles were positively charged.
　本ナノ分散液を５０℃で乾燥して粉末とした。この乾燥粉末を、Ｘ線回折、ＴＥＭ観察、及びＴＥＭ像の高速フーリエ変換（ＦＦＴ）解析を行った。ＴＥＭ像を図４に、ＦＦＴ解析結果を図５に示す。平均粒子径は約３ｎｍで、ＴＥＭ観察による結晶の形状は粒状であり、ほとんどの粒子で結晶縞が観察される結晶粒子であった。これらは、ＦＦＴ解析により求めた格子面間隔から、β－オキシ水酸化鉄結晶と同定された。 The nano-dispersion was dried at 50 ° C. to obtain a powder. The dry powder was subjected to X-ray diffraction, TEM observation, and fast Fourier transform (FFT) analysis of the TEM image. The TEM image is shown in FIG. 4, and the FFT analysis result is shown in FIG. The average particle diameter was about 3 nm, the crystal shape by TEM observation was granular, and most of the particles were crystal particles in which crystal fringes were observed. These were identified as β-iron oxyhydroxide crystals from the lattice spacing determined by FFT analysis.
測定例１（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ｐＨ３．５とし、濃度４００ｍｇ－Ｐ/Ｌ（リンとしての濃度）の試験液Ｄを調製した。
　また、リン酸二水素カリウムをイオン交換水に溶解し、水酸化ナトリウムによりｐＨ７．０とし、濃度４００ｍｇ－Ｐ/Ｌ（リンとしての濃度）の試験液Ｅを調製した。
　試験液Ｄ又はＥの１３０ｍＬに、分散液Ｂ又はＣを２０ｇ（固形分として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、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（表１）。 Measurement example 1 (phosphate adsorption test)
Potassium dihydrogen phosphate was dissolved in ion-exchanged water, adjusted to pH 3.5 with hydrochloric acid, and a test solution D having a concentration of 400 mg-P / L (concentration as phosphorus) was prepared.
Further, potassium dihydrogen phosphate was dissolved in ion-exchanged water, adjusted to pH 7.0 with sodium hydroxide, and a test solution E having a concentration of 400 mg-P / L (concentration as phosphorus) was prepared.
After adding 20 g of dispersion B or C (1 g as a solid content) to 130 mL of test liquid D or E, the mixture was stirred and subjected to 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 (Table 1).
比較試験
　また、測定例１と同様に試験液を調製し、この１３０ｍＬに参考例１で得られた粉末Ａの１ｇを投入し、測定例１と同様に吸着試験を行った。 Comparative test Moreover, the test liquid was prepared similarly to the measurement example 1, 1g of the powder A obtained by the reference example 1 was thrown into this 130mL, and the adsorption test was done like the measurement example 1. FIG.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　測定例２（沈降試験）
　試験液Ｄの１３０ｍＬにナノ分散液Ｃの２０ｇ（固形分として１ｇ）を添加混合し静置した。その結果、ナノ分散粒子は速やかに凝集・沈降した。その様子（未吸着、静置１５分、６０分及び２４時間後）を図６に示す。また粒径の変化（未吸着、静置１５分、３０分、６０分、６時間、２４時間）を図７に示す。 Measurement example 2 (sedimentation test)
To 130 mL of the test liquid D, 20 g of nano-dispersion C (1 g as a solid content) was added and mixed and allowed to stand. As a result, the nano-dispersed particles quickly aggregated and settled. The state (non-adsorbed, standing 15 minutes, 60 minutes and 24 hours later) is shown in FIG. In addition, FIG. 7 shows changes in particle size (non-adsorbed, standing 15 minutes, 30 minutes, 60 minutes, 6 hours, 24 hours).
　以上の結果から、本発明の陰イオン吸着材分散液は、リン酸吸着速度が顕著に高いこと、また特にｐＨ３．５において吸着量が大きいことがわかった。また初期ｐＨ３．５とした場合に、１時間程度でｐＨが４以上まで上昇する点で、原料であるβ－オキシ水酸化鉄粉末と大きく異なる性質が明らかになった。さらに、初期ｐＨ３．５とした場合、リン酸吸着に伴って凝集・沈殿し、容易に回収できるものであった。 From the above results, it was found that the anion adsorbent dispersion liquid of the present invention has a remarkably high phosphoric acid adsorption rate and a large adsorption amount particularly at pH 3.5. Further, when the initial pH was set to 3.5, a characteristic that was significantly different from the raw material β-iron oxyhydroxide powder was revealed in that the pH increased to 4 or more in about 1 hour. Furthermore, when the initial pH was 3.5, the particles aggregated and precipitated with the adsorption of phosphoric acid and could be easily recovered.

Claims (10)

  1. オキシ水酸化鉄を主成分とする、平均粒径ｄ５０が２μｍ以下である粒子が、溶媒に分散してなる、陰イオン吸着材分散液。 An anion adsorbent dispersion liquid in which particles containing iron oxyhydroxide as a main component and having an average particle diameter d50 of 2 μm or less are dispersed in a solvent.
  2. 等電点がｐＨ６．０～８．０である、請求項１に記載の陰イオン吸着材分散液。 The anion adsorbent dispersion liquid according to claim 1, having an isoelectric point of pH 6.0 to 8.0.
  3. 前記オキシ水酸化鉄がβ－オキシ水酸化鉄である、請求項１又は２に記載の陰イオン吸着材分散液。 The anion adsorbent dispersion according to claim 1 or 2, wherein the iron oxyhydroxide is β-iron oxyhydroxide.
  4. オキシ水酸化鉄を主成分とする粒子の平均粒径ｄ５０が０．２μｍ以下である、請求項１～３のいずれかに記載の陰イオン吸着材分散液。 The anion adsorbent dispersion liquid according to any one of claims 1 to 3, wherein an average particle diameter d50 of particles mainly composed of iron oxyhydroxide is 0.2 µm or less.
  5. ｐＨが２．０～５．５である請求項１～４のいずれかに記載の陰イオン吸着材分散液。 The anion adsorbent dispersion according to any one of claims 1 to 4, which has a pH of 2.0 to 5.5.
  6. β－オキシ水酸化鉄の水酸基の一部が塩素イオンで置換され、該塩素の含有量が０．５質量％以上である、請求項３に記載の陰イオン吸着材分散液。 The anion adsorbent dispersion according to claim 3, wherein a part of hydroxyl groups of β-iron oxyhydroxide is substituted with chlorine ions, and the chlorine content is 0.5 mass% or more.
  7. 塩酸でｐＨを３．５に調整したリン換算濃度４００ｍｇ／Ｌのリン酸二水素カリウム水溶液１５０ｍＬ中に、吸着材１ｇを含む陰イオン吸着材分散液を投入し、室温で撹拌して行う回分式の吸着試験において、３分後に吸着材１ｇ当たりのリン換算吸着量が２２ｍｇ以上である、請求項１～６のいずれかに記載の陰イオン吸着材分散液。 A batch system in which an anion adsorbent dispersion containing 1 g of adsorbent is introduced into 150 mL of an aqueous solution of potassium dihydrogen phosphate having a pH equivalent to 400 mg / L adjusted to pH 3.5 with hydrochloric acid and stirred at room temperature. The anion adsorbent dispersion according to any one of claims 1 to 6, wherein an adsorption amount in terms of phosphorus per 1 g of adsorbent is 3 mg or more after 3 minutes in the adsorption test.
  8. 塩酸でｐＨを３．５に調整したリン換算濃度４００ｍｇ／Ｌのリン酸二水素カリウム水溶液１５０ｍＬ中に、吸着材１ｇを含む陰イオン吸着材分散液を投入し、室温で撹拌して行う回分式の試験において、３．５又は投入した陰イオン吸着材分散液のｐＨのうち高い方の値に対し、１時間後の水相のｐＨが０．５以上上昇することを特徴とする、請求項１～７のいずれかに記載の陰イオン吸着材分散液。 A batch system in which an anion adsorbent dispersion containing 1 g of adsorbent is introduced into 150 mL of an aqueous solution of potassium dihydrogen phosphate having a phosphorous equivalent concentration of 400 mg / L adjusted to pH 3.5 with hydrochloric acid and stirred at room temperature. In the above test, the pH of the aqueous phase after 1 hour rises by 0.5 or more with respect to the higher value of 3.5 or the pH of the added anion adsorbent dispersion liquid. 8. The anion adsorbent dispersion according to any one of 1 to 7.
  9. 請求項１～８のいずれかに記載の陰イオン吸着材分散液を、目的とする陰イオンを含有する液体に添加し混合する工程と、該混合物中の吸着材を、陰イオンを吸着することにより凝集剤を添加せずに凝集及び／又は沈殿させる工程とを含む、陰イオンを除去及び／又は回収する方法。 A step of adding and mixing the anion adsorbent dispersion liquid according to any one of claims 1 to 8 to a liquid containing a target anion, and adsorbing anions in the adsorbent in the mixture And aggregating and / or precipitating without adding a flocculant by the method of removing and / or recovering anions.
  10. 吸着材を、陰イオンを吸着することにより凝集及び／又は沈殿させる工程において、混合物のｐＨが継続して５．５以下であることを特徴とする、請求項９に記載の方法。 The method according to claim 9, wherein in the step of aggregating and / or precipitating the adsorbent by adsorbing anions, the pH of the mixture is continuously 5.5 or less.
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