JP2013188680A - Magnetic powder for water treatment, and water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic powder for water treatment excellent an adsorption performance of oil and also excellent in dispersion performance in water, and a water treatment method using the same.SOLUTION: A magnetic powder for water treatment adsorbs oil in water to be treated, is separated from the water to be treated together with the adsorbed oil to bring the separated matter in an immersed state in a washing liquid, is magnetically separated from the adsorbed oil in the separated matter in the washing liquid, and is recovered to be used repeatedly. The magnetic powder includes a magnetic carrier consisting of a porous magnetic particle whose average particle size is 15-90 μm, and a coating layer supported to the magnetism carrier to cover the magnetic carrier and containing a fluorine organic compound with a coverage of 50-20,000 μg/g in terms of fluorine.

Description

  Embodiment described here is related with the water treatment method using the magnetic powder for water treatment which adsorb | sucks and isolate | separates the oil component mixed in water, collect | recovers, and is reused.

  Recently, the effective use of water resources has been required due to industrial development and population growth. In order to effectively use water resources, it is important to purify and reuse various wastewaters such as industrial wastewater and domestic wastewater. In order to purify the waste water, it is necessary to separate and remove water insoluble matters and impurities contained in the water. Examples of methods for purifying wastewater include membrane separation methods, centrifugal separation methods, activated carbon adsorption methods, ozone treatment methods, and suspended matter precipitation removal methods by adding flocculants. By using these water treatment methods, chemical substances having a great influence on the environment such as phosphorus and nitrogen contained in the wastewater can be removed, and oils and clays dispersed in water can be removed.

  Of these various water treatment methods, the membrane separation method is one of the most commonly used methods for removing insoluble substances in water. From the viewpoint of increasing the water flow rate of water containing water, filter aids are used in membrane separation methods.

  On the other hand, as a method for removing harmful substances and valuables from water, a method is known in which a substance that dissolves in water undergoes some reaction to cause precipitation, and is separated into solid and liquid. For example, Patent Document 1 describes a method for removing oil in water using an aggregate filter aid containing a magnetic substance.

JP 2009-268976 A

  However, the conventional filter aids are too hydrophobic in the coating resin, so the dispersibility in water is poor, and the dispersion is unevenly distributed and unevenly distributed in the treatment tank, which may reduce the treatment efficiency. On the other hand, when the filter aid is coated with a hydrophilic resin in order to improve the dispersibility in water, the oil adsorption performance may decrease, and the oil adsorption amount may decrease. Thus, in the conventional filter aid, the dispersion performance and the adsorption performance are in a trade-off relationship.

  Embodiment described here is made in order to solve the said subject, and while being excellent in the adsorption | suction performance of an oil component, the magnetic powder for water treatment which was excellent also in the dispersibility in water, and the water treatment method using the same The purpose is to provide.

  The magnetic powder for water treatment according to the present embodiment adsorbs oil in the water to be treated, is separated from the water to be treated together with the adsorbed oil, and the separated product is immersed in the cleaning liquid, and in the separated product in the cleaning liquid. A magnetic powder for water treatment that is magnetically separated from the adsorbed oil, recovered, and repeatedly used, comprising a magnetic carrier comprising porous magnetic particles having an average particle size of 15 to 90 μm, and the magnetic carrier And a coating layer containing a fluorine organic compound that is supported on the magnetic carrier so as to cover the surface and has a coverage of 50 to 20000 μg / g in terms of fluorine.

(A) is a cross-sectional schematic diagram which shows the aggregate which particle | grains aggregated, (b) is a cross-sectional schematic diagram which shows the particle | grains by which the fluoride was carry | supported. (A)-(c) is a schematic diagram which shows the reaction mechanism between a silane coupling agent and an inorganic surface. The schematic diagram which shows the production | generation reaction of a polyimideamide. (A) is an enlarged cross-sectional schematic diagram showing a part of the particles of the embodiment, (b) is an enlarged cross-sectional schematic diagram showing the state of the oil film adsorbed on the particle surface of the embodiment, (c) is adsorbed on the conventional particle surface The expanded cross-sectional schematic diagram which shows the state of the oil film which carried out. The block diagram which shows the outline | summary of the water treatment apparatus which uses the particle | grains of 1st Embodiment. Process drawing which shows the water treatment method (centrifugation method) of 2nd Embodiment using the apparatus of FIG. The block diagram which shows the outline | summary of the other water treatment apparatus which uses the particle | grains of 2nd Embodiment. Process drawing which shows the water treatment method (membrane filtration method) of 2nd Embodiment using the apparatus of FIG.

  Various embodiments for solving the above problems will be described below.

  (1) The magnetic powder for water treatment according to the embodiment described herein adsorbs oil in the water to be treated, is separated from the water to be treated together with the adsorbed oil, and the separated product is immersed in the cleaning liquid. A magnetic powder for water treatment that is magnetically separated from the adsorbed oil in the separated product in the washing liquid, and is collected and used repeatedly, from porous magnetic particles having an average particle size of 15 to 90 μm And a coating layer containing a fluorine organic compound that is supported on the magnetic carrier so as to cover the magnetic carrier and has a coverage of 50 to 20000 μg / g in terms of fluorine.

  In order to adsorb oil, the surface properties of the solid must be hydrophobic. Since the magnetic powder for water treatment of the said embodiment contains the fluorine organic compound from which a coating layer becomes a coverage of 50-20000 microgram / g in conversion of a fluorine, the surface property is hydrophobic. When the coverage of the fluorine organic compound is less than 50 μg / g in terms of fluorine, sufficient hydrophobicity cannot be obtained, and the adsorption of oil is inhibited. On the other hand, if the coverage of the fluorine organic compound exceeds 20000 μg / g in terms of fluorine, it becomes difficult to remove the oil adsorbed from the magnetic powder because the hydrophobicity is too strong. It becomes difficult to separate the adsorbed oil from the magnetic powder and regenerate the magnetic powder.

  Here, the “hydrophilic solvent” is defined as one that does not substantially dissolve the hydrophobic substance removed from the water (the amount dissolved in the solvent is 10% or less). For example, alcohol or an aqueous alcohol solution with respect to mineral oil can be a hydrophilic solvent.

  If the magnetic powder can be regenerated using such a hydrophilic solvent, the magnetic powder can be recovered after the washing treatment only by specific gravity separation, and the regenerating cost of the magnetic powder can be greatly reduced. Thus, in order to wash with a solvent that does not substantially dissolve the magnetic powder, it is necessary to replace the oil adsorbed on the surface of the magnetic powder with the washing solvent, but if the hydrophobicity of the magnetic powder surface is too strong, It cannot be replaced with the solvent and cannot be cleaned. Therefore, in the magnetic powder of this embodiment, the coverage of the fluorine organic compound was set to 20000 μg / g or less in terms of fluorine.

Various ferrite compound particles can be suitably used as the magnetic particles. Ferrite compounds such as iron, iron-based alloys, magnetite (magnetite), titanite (ilmenite), pyrrhotite (pilotite), magnesia ferrite, manganese magnesium ferrite, manganese zinc ferrite, cobalt ferrite, nickel ferrite, nickel zinc ferrite, barium Ferrite, copper zinc ferrite, etc. can be used. Of these, it is most preferable to use a ferrite-based compound such as magnetite, magnesia ferrite, or manganese magnesium ferrite having excellent stability in water. In particular, magnetite (Fe ₃ O ₄ ) is not only inexpensive, but also exhibits stable properties as a magnetic substance in water and is composed of only safe and non-toxic elements, making it suitable for use in water treatment. ing.

  Moreover, it is preferable that the magnitude | size of a magnetic powder shall be the range of 15-90 micrometers of average particle diameters. The average particle size of the magnetic powder is more preferably in the range of 20 to 50 μm, most preferably 35 ± 5 μm. The average particle diameter is a volume average (Mean Volume Diameter). Here, the average particle diameter is measured by a laser diffraction method. Specifically, it can be measured by a SALD-DS21 type measuring device (trade name) manufactured by Shimadzu Corporation. This size is a particle size in which the magnetic powder is moderately mixed with water in water and settles relatively quickly when allowed to stand. That is, if the average particle size of the magnetic powder is larger than 90 μm, the sedimentation speed of the magnetic powder may be too high, and a large amount of power may be required when dispersed in water. This is because the sedimentation rate is too slow to be practical.

  (2) In the above (1), the fluorine organic compound is preferably obtained by reacting a compound having a fluorocarbon and an alkoxy group with the surface of the magnetic carrier.

  As a method of supporting a fluorine organic compound on magnetic particles (inorganic particles) serving as a carrier, there are a method of directly modifying inorganic particles using a silane coupling agent and a method of coating inorganic particles with a resin.

  In the method of directly modifying the surface of the inorganic particles with a silane coupling agent, a compound having a fluorocarbon and an alkoxy group is reacted with the particle, and the fluorocarbon is supported on the surface of the particle. Here, “modification” is defined as adding a functional group to the surface of an inorganic substance. “Attaching a functional group” refers to a state in which the functional group and the inorganic substance are at least chemically bonded, and includes a state in which physical bonds such as adsorption are combined with chemical bonds. In addition, the state in which the inorganic substance constituting the particle and the functional group are merely physically bonded (adsorbed) without chemically bonding does not correspond to the modification in principle. However, only when the entire inorganic particles are covered with a polymer material having a specific functional group, the case where they are physically bonded is also included.

  Modification methods include a dry method in which particles are sprayed with a silane coupling agent solution while stirring at high speed, and a wet method in which particles are reacted in a solvent containing a silane coupling agent. In both the dry method and the wet method, the reaction is allowed to proceed completely by volatilizing the solvent after the treatment and post-curing. It is also possible to cause the inorganic particles to carry the fluorocarbon by reacting the fluorocarbon with a compound having an alkoxy group.

  On the other hand, as a method of coating the resin, there are a method of coating a resin having a fluorocarbon and an alkoxy group, or a method of coating a resin having a reactive functional group on the side chain and reacting a compound having a fluorocarbon and an alkoxy group. is there. In the method of coating a resin, first, a resin having a fluorocarbon and an alkoxy group is coated on the particles, a compound having a fluorocarbon and an alkoxy group is reacted with the particles, and the compound is supported on the surface of the inorganic particles.

  A silane coupling agent is a reactant that contributes to two reactions, a hydrolysis reaction and a condensation reaction. In the hydrolysis reaction, the hydroxyl group M-OH (M is a metal atom) on the ferrite particle surface and the alkoxy group (RO-Si) contained in the silane coupling agent undergo a dealcoholization reaction, or (a) in FIG. As shown in (b), the alkoxy group (RO-Si) contained in the silane coupling agent reacts with water to hydrolyze to produce a silanol group, and the hydroxyl group on the surface of the inorganic particles (core part) It moves to the surface of the inorganic particle through the hydrogen bond. The hydrolysis rate of the silane coupling agent molecule is affected by the surface state of the inorganic particles, that is, the pH of the inorganic particle surface and the amount of adsorbed water. On the other hand, in the condensation reaction, as shown in FIGS. 2A and 2C, the silane coupling agent undergoes a dehydration condensation reaction to form a strong covalent bond with the inorganic surface. In parallel with this reaction, silanol groups are condensed to produce a siloxane oligomer. These reactions can be accelerated in the presence of heat or catalyst. Further, the reaction can be promoted by discharging water, alcohol and the like by-produced by heating and drying to the outside of the system. Since the organic functional groups of the silane coupling agent molecules are oriented outside the powder particles, it is necessary to select the optimum solvent and blending ratio in consideration of the balance between the hydrophilicity and hydrophobicity of the silane coupling agent solution. .

  An example of the reaction when producing a compound having an alkoxy group will be described with reference to FIG. The compound having an alkoxy group is one of magnetic powder raw materials used for a reaction when a fluorine organic compound is supported on magnetic particles. Here, an outline of the reaction for producing an organic compound containing an amide (N—C═O) and an imide (O═C—N—C═O) shown in the lower part of FIG. 3 as the compound having an alkoxy group will be described.

  First, pyromellitic anhydride (tetracarboxylic dianhydride) and diaminodiphenylmethane are polymerized in equimolar amounts to produce polyamic acid (polyamic acid) which is a precursor of polyimide. Next, the polyamic acid is heated or a dehydration / cyclization (imidization) reaction is promoted using a catalyst to obtain a polyimide as a compound having an alkoxy group. The polyimide thus obtained is mixed as a fluorocarbon with, for example, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) to form a mixture of fluorine organic compounds. When this mixture of fluorine organic compounds is reacted with magnetic particles by, for example, a wet method, PFA as a fluorine organic compound is supported on the surfaces of the magnetic particles.

  (3) In the above (1), the fluorine organic compound is preferably a mixture of a fluorocarbon and a thermosetting resin.

  As fluorocarbon, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), perfluoroethylene propene copolymer (PFEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene- Ethylene copolymer (ETFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), and the like can be used. These are all compounds containing F—C bonds, and when they are supported on inorganic particles, their surface properties become hydrophobic.

  As the thermosetting resin, polyamide resin, polyimide resin, polyamideimide resin, acrylic resin, epoxy resin, phenol resin, melamine resin, alkyd resin, or the like can be used. The thermosetting resin functions as a binder that adheres to the particle surface so that the fluorocarbon is not detached from the magnetic particles.

  (4) In any one of the above (1) to (3), the magnetic carrier is composed of porous magnetic particles having an apparent specific gravity larger than 1 and having a large number of open pores opened on the surface. It is preferable that the fluorine organic compound of the coating layer penetrates into the open pores of the porous magnetic particles so that the fluorine concentration gradually decreases as it moves from the surface to the inside.

  In the present embodiment, magnetic particles having an apparent specific gravity greater than 1 are used for the magnetic carrier in spite of being porous. Therefore, from the water using a solid-liquid separation method such as a centrifugal separation method or a sedimentation separation method. Magnetic powder can be easily separated.

  In addition, the magnetic powder for water treatment of the present embodiment is non-hydrophobic (or weakly hydrophilic) in which the inside of the porous particles has a low fluorine concentration, even though the surface of the porous particles is hydrophobic with a high fluorine concentration. ), The interfacial tension with water is low (the contact angle is small), and the water dispersibility is excellent.

  Furthermore, since the fluorine organic compound of the coating layer is infiltrated into the open pores of the porous particle, the bonding strength of the coating layer to the porous particle is high due to the so-called wedge effect, and the coating layer is peeled off from the surface of the porous particle. It becomes difficult. For this reason, the life of the coating layer is long, the magnetic powder can be collected and reused repeatedly, and the operating cost of water treatment can be greatly reduced.

  (5) In the above (4), it is preferable that the fluorine organic compound does not substantially exist at the central portion of the porous magnetic particles.

  Although the surface of the porous particle is hydrophobic with a high fluorine concentration, the inside of the porous particle is non-hydrophobic (or weakly hydrophilic) with a low fluorine concentration, so it is held in open pores inside the particle. The washed oil can be easily washed with a hydrophilic solvent, and the oil can be easily separated from the inside of the particles.

  (6) In the above (5), it is preferable that the fluorine organic compound in the coating layer penetrates from the surface of the porous magnetic particles to a depth of 20% or less of the diameter of the particles.

  If the fluorine organic compound is present in excess of 20% of the diameter Do (= D1-2t) of the porous magnetic particles, the degree of hydrophobicity inside the particles increases, and the oil adsorbed and held in the open pores inside the particles becomes hydrophilic. It becomes difficult to separate from the particles due to the solvent. For this reason, the penetration depth of the fluorine organic compound is set to 20% or less of the particle diameter to facilitate the separation of the adsorbed oil from the magnetic powder.

  (7) The water treatment method according to the embodiment described herein includes: (A) a magnetic carrier composed of porous magnetic particles having an apparent specific gravity greater than 1, and a fluorine organic compound supported on the magnetic carrier. And (B) dispersing the water treatment magnetic powder in the water to be treated containing oil, adsorbing the oil on the water treatment magnetic powder, and (C) ) Applying centrifugal force to the water to be treated containing the magnetic powder for water treatment, centrifuging the magnetic powder for water treatment that has adsorbed the oil from water, and (D) immersing the centrifuged product in a washing solution, (C) stirring the centrifuged product in the cleaning solution; (E) applying a magnetic field to the stirring product; and magnetically separating the magnetic powder for water treatment from the stirring product in the cleaning solution; and (F) magnetic separation. In the step (B), the water-treated magnetic powder is treated with oil. Reused for the adsorption.

  The water treatment method of the said embodiment is a method corresponding to the centrifugation method using a centrifuge (FIG. 5, FIG. 6). A cyclone can be used as the centrifuge. Disperse the above-mentioned magnetic powder supporting the fluorinated organic compound in the water to be treated, adsorb the oil to the magnetic powder, and pass the water to be treated in the magnetic powder / oil adsorbed state through a centrifuge, cyclone, and centrifuge. Separate the magnetic powder / oil mixture at the bottom of the separator. Next, the separated product (mixture of magnetic powder and oil) is pulled out from the lower part of the centrifugal separator, and the drawn separated product is immersed in the cleaning liquid in the cleaning tank. The oil component is separated from the magnetic powder by stirring and mixing the separated product from the cyclone in the washing liquid. For example, an ethanol aqueous solution having a predetermined concentration (water: ethanol = 40: 60) is used as the cleaning liquid.

  Next, the stirring mixture (suspension) is sent from the washing tank to the magnetic separation tank, and further strongly stirred until the magnetic powder is in a particle state in the magnetic separation tank, so that the magnetic powder and oil are uniformly dispersed in water. Next, the magnetic powder dispersed in water is adsorbed by a magnetic adsorption means such as a magnet, and the treated water containing oil is discharged from the magnetic separation tank while the magnetic powder is adsorbed by the magnetic adsorption means. Next, the magnetic adsorption of the magnetic powder is released, the magnetic powder is dropped from the magnetic adsorption means, and further treated water or tap water is sprayed on the magnetic adsorption means to drop off the magnetic powder adhering to the magnetic adsorption means, Collect this. The collected magnetic powder is sent from the magnetic separation tank to the magnetic powder supply device and reused.

  (8) The water treatment method according to the embodiment described herein includes: (a) a magnetic carrier composed of porous magnetic particles having an apparent specific gravity greater than 1, and a fluorine organic compound carried on the magnetic carrier. And (b) dispersing the water treatment magnetic powder in the water to be treated containing oil, adsorbing the oil to the water treatment magnetic powder, and (c) ) The water to be treated containing the magnetic powder for water treatment is allowed to stand to cause gravity to act on the magnetic powder for water treatment, and the magnetic powder for water treatment that has adsorbed the oil is settled and separated from the water; (d) (1) A magnetic field is applied to the agitated substance, and the magnetic powder for water treatment is magnetically applied from the agitated substance in the washing liquid. (F) The magnetic powder for water treatment separated magnetically Reused for the adsorption of oil in the step (b).

  The water treatment method of the above embodiment is a method corresponding to a membrane filtration method using a filter as a solid-liquid separation means, and particularly a method corresponding to a body feed method among membrane filtration methods (FIGS. 7 and 8). ). An apparatus in which a filtration membrane such as an MF membrane is stretched almost horizontally is used as a filter.

  In the method of this embodiment, the magnetic powder for water treatment is dispersed in the water to be treated, the oil is adsorbed to the magnetic powder, the water to be treated in the magnetic powder / oil adsorbed state is passed through the filtration membrane, and the filtration membrane A deposited layer made of a magnetic powder / oil mixture is formed thereon. Next, the peeling water is sprayed from the side toward the deposition layer on the filtration membrane, the deposition layer is peeled off from the filtration membrane, and further the peeling water is sprayed on the separation product, and the separation product is decomposed into pieces. To do. Next, the peeled material separated into pieces is sent from the solid-liquid separation device to the separation tank together with the peeling water, and the peeled material is stirred in the separation tank until it becomes a particle state, so that the magnetic powder and oil are uniformly dispersed in the water.

  Next, a hydrophilic solvent is supplied into the separation tank, and the adsorbed oil is separated from the magnetic powder by the action of the hydrophilic solvent. Next, the magnetic powder dispersed in water is magnetically adsorbed by a magnetic adsorption means (electromagnet, permanent magnet, etc.), and the treated water containing oil is recovered and stored from the magnetic separation tank while the magnetic powder is adsorbed by the magnetic adsorption means. Drain into the tank. Next, magnetic adsorption of the magnetic powder is released, the magnetic powder is dropped from the electromagnet, and treated water or tap water is sprayed on the electromagnet to wash and collect the magnetic powder adhered to the electromagnet. The collected magnetic powder is sent from the magnetic separation tank to the magnetic powder supply device, and is reused for producing a suspension in the magnetic powder supply device. In the water treatment method of the present embodiment, the process of using the magnetic powder in the body feed method of the membrane filtration method has been described. However, the magnetic powder can be applied to the precoat method as another membrane filtration method. .

  Various embodiments will be specifically described below.

(Magnetic powder for water treatment)
Next, the magnetic powder for water treatment will be described in detail.

  In the water treatment method according to the embodiment described here, magnetic powder covered with a coating layer containing a fluorine organic compound is essential. Using such magnetic powder for purification of oil-containing water not only facilitates separation of magnetic powder from water, but also uses magnetic force to recycle and reuse magnetic powder used in water. Can be applied to various processes. The apparent specific gravity exceeds 1.0 so as to settle in water, and separation / recovery using magnetic separation is possible.

The magnetic particles are preferably a substance exhibiting ferromagnetism in a room temperature region, and ferromagnetic substances such as ferrite compounds can be generally used. Ferrite compounds such as iron, iron-based alloys, magnetite (magnetite), titanite (ilmenite), pyrrhotite (pilotite), magnesia ferrite, manganese magnesium ferrite, manganese zinc ferrite, cobalt ferrite, nickel ferrite, nickel zinc ferrite, barium Ferrite, copper zinc ferrite, etc. can be used. Of these, it is most preferable to use a ferrite-based compound such as magnetite, magnesia ferrite, or manganese magnesium ferrite having excellent stability in water. In particular, magnetite (Fe ₃ O ₄ ) is not only inexpensive, but also exhibits stable properties as a magnetic substance in water and is composed of only safe and non-toxic elements, making it suitable for use in water treatment. ing. The magnetic powder can take various shapes such as a spherical shape, a polyhedron, and an indeterminate shape, but is not particularly limited. What is necessary is just to select suitably the particle size and shape of a magnetic support | carrier preferable in use in view of manufacturing cost.

  In the magnetic powder for water treatment, it is important that the magnetic particles are porous as shown in FIG. In the magnetic powder for water treatment, a fluorine organic compound is supported not only on the surface of the porous magnetic particles but also on the inner walls of the open pores. As shown in FIG. 4B, the porous particles 51 can adsorb and hold the oil component 56 in the open pores 54 and 55 existing inside the particle, thereby reducing the amount of the oil component 56 on the particle surface. it can. As a result, the apparent oil film thickness t1 is reduced in the porous particles.

  On the other hand, since the non-porous particles 100 do not have open pores, the amount of the oil component 56 on the particle surface increases as shown in FIG. 4C, and the apparent oil film thickness t2 increases ( t1 <t2). When the amount of oil on the particle surface is large, the magnetic particles adsorbing the oil may aggregate to form a dumpling, resulting in poor handling. In the figure, reference numeral 50 denotes magnetic powder, and reference numeral 52 denotes a coating layer.

  In the magnetic powder, the surface of a magnetic carrier 51 made of magnetic single particles is coated with a coating layer 52 such as a resin as shown in FIG. The magnetic powder 50 may be an aggregate 53 in which the magnetic carrier 51 coated with the coating layer 52 is aggregated as shown in FIG.

  It is important that the average particle size of the magnetic powder is in the range of 15 to 90 μm. With porous particles of less than 15 μm, the internal space becomes small and the liquid adsorption performance is poor. On the other hand, if it exceeds 90 μm, the sedimentation rate in water increases, and dispersion in water becomes difficult, resulting in poor water treatment efficiency.

  The magnetic powder 50 includes a magnetic carrier 51 made of magnetic particles and having an average particle diameter D1 in the range of 15 to 90 μm. The water treatment magnetic powder 50 preferably has an average particle diameter D1 in the range of 15 to 90 μm, more preferably in the range of 20 to 50 μm, and most preferably in the range of 30 to 40 μm. This is because if the average particle diameter D1 (D2) of the magnetic powder 50 is larger than 90 μm, the dispersibility in water is poor and the ability to adsorb oil in water may be reduced. On the other hand, when the average particle diameter D1 (D2) of the magnetic powder 50 is less than 15 μm, the sedimentation speed is lowered, and there is a possibility that the magnetic powder 50 cannot be separated by a centrifuge or a membrane filter. The magnetic carrier 51 may be a single particle (primary particle) or an aggregate (secondary particle) obtained by aggregating a plurality of primary particles. The magnetic carrier 51 may be subjected to a coating treatment such as Cu plating or Ni plating if necessary.

  Here, the average particle diameter is calculated based on the result measured by the laser diffraction method. Specifically, a SALD-DS21 type measuring device (trade name) manufactured by Shimadzu Corporation can be used as an apparatus using a laser diffraction method. When the average particle size is 15 to 90 μm, the magnetic particles mix well with water in water and settle relatively quickly when left standing. That is, when the average particle diameter of the magnetic powder exceeds 90 μm, the sedimentation speed of the particles becomes too fast, and thus a large power is required for the stirrer when dispersing the magnetic powder in water. In particular, when the average particle size is 50 μm or less, the dispersibility of the particles in water becomes very good, and the load on the stirrer is greatly reduced. On the other hand, if the average particle size of the magnetic powder is smaller than 15 μm, the sedimentation speed of the particles when left standing is too slow and is not practical. Furthermore, practically, when the average particle diameter is 20 μm or more or 30 μm or more, the particles quickly settle in water, so that a short time treatment becomes possible. However, when the magnetic powder is magnetically adsorbed using a magnetic adsorption means such as an electromagnet, the particle size restriction is moderate.

  As a method for producing a magnetic powder for water treatment composed of aggregates, a method of applying an amorphous material containing a specific functional group after forming an aggregate with a granulator or the like, and using this amorphous material as a binder There is a method of granulating primary particles. In the former, primary particles and organic binder or inorganic binder are kneaded with a spray dryer or Henschel mixer, etc., and after forming a granulated material, an amorphous material containing a specific functional group is applied to 100 ° C to 200 ° C. Or a method of applying an amorphous material containing a specific functional group after producing porous magnetic particles (magnetic carrier) by sintering a porous magnetic raw material by spray drying or the like. Is mentioned. The latter is directly granulated with a Henschel mixer, a spray dryer or the like using an amorphous material containing a specific functional group in the binder.

  By incorporating these amorphous materials containing specific functional groups into the magnetic powder for water treatment, the specific gravity of the magnetic powder for water treatment becomes relatively high, so sedimentation by gravity and separation by centrifugal force using a cyclone are possible. Since it can be used in combination with magnetic separation, magnetic powder can be quickly separated from water.

  By supporting a fluorine organic compound on these magnetic particles, the hydrophobicity necessary for adsorbing hydrophobic substances such as oils and the low interfacial tension required for dispersion in water can be obtained. This makes it possible to adsorb hydrophobic substances in water not only in a liquid state but also in a solid state. For example, solid oil such as lard can be adsorbed. In this embodiment, in order to easily reuse this magnetic material many times, it further has one of the following configurations and functions.

  An example of the reaction when producing a compound having an alkoxy group will be described with reference to FIG. The compound having an alkoxy group is one of magnetic powder raw materials used for a reaction when a fluorine organic compound is supported on magnetic particles. Here, an outline of the reaction for producing an organic compound containing an amide (N—C═O) and an imide (O═C—N—C═O) shown in the lower part of FIG. 3 as the compound having an alkoxy group will be described.

  First, pyromellitic anhydride (tetracarboxylic dianhydride) and diaminodiphenylmethane are polymerized in equimolar amounts to produce polyamic acid (polyamic acid) which is a precursor of polyimide. Next, the polyamic acid is heated or a dehydration / cyclization (imidization) reaction is promoted using a catalyst to obtain a polyimide as a compound having an alkoxy group. The polyimide thus obtained is mixed as a fluorocarbon with, for example, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) to form a mixture of fluorine organic compounds. When this mixture of fluorine organic compounds is reacted with magnetic particles by, for example, a wet method, PFA as a fluorine organic compound is supported on the surfaces of the magnetic particles.

(Performance of magnetic powder)
The first feature of the magnetic powder for water treatment is that the magnetic powder for water treatment has a magnetic carrier composed of porous magnetic particles having an average particle diameter of 15 to 90 μm, and the magnetic carrier is covered so as to cover the magnetic carrier. And a coating layer containing a fluorine organic compound having a coverage of 50 to 20000 μg / g in terms of fluorine. Thereby, the adsorption | suction performance of the oil component in water is provided to magnetic powder.

  The second feature of the magnetic powder for water treatment is porous particles carrying a fluorine organic compound, and has a concentration distribution in which the fluorine concentration gradually decreases from the surface toward the core. That is, the fluorine concentration is highest on the particle surface, and gradually decreases inside the particle as it moves away from the surface. Thereby, the dispersion performance with respect to water is provided to the magnetic powder.

  By having these characteristics, the recovered magnetic powder can be easily regenerated by washing treatment using a hydrophilic solvent, and the magnetic powder can be reused repeatedly.

  The first characteristic is that the particle surface and internal fluorine organic compound coverage is 50 to 20000 μg / g in terms of fluorine, which is necessary for removing hydrophobic substances such as oils with a hydrophilic solvent. Concentration. When the coverage of the fluorine organic compound is less than 50 μg / g in terms of fluorine, sufficient hydrophobicity cannot be obtained, and adsorption of the hydrophobic substance is inhibited. On the other hand, when the coverage of the fluorine organic compound exceeds 20000 μg / g in terms of fluorine, the hydrophobicity is too strong, and thus it is difficult to regenerate with a hydrophilic solvent. The term “hydrophilic solvent” as used herein is defined as a substance that does not substantially dissolve the hydrophobic substance removed from water (the amount dissolved in the solvent is 10% or less). For example, alcohol or an aqueous alcohol solution with respect to mineral oil can be used as the hydrophilic solvent. If the magnetic powder can be regenerated with such a hydrophilic solvent, it is only necessary to adopt a specific gravity separation method for separating the magnetic powder and the oil component, and there is an advantage that the regeneration cost can be greatly reduced. Thus, in order to wash with a solvent that does not substantially dissolve the hydrophobic substance, it is necessary to replace the oil on the surface of the magnetic particles and the hydrophilic solvent, but if the hydrophobicity of the surface of the magnetic particles is too strong The replacement with a hydrophilic solvent cannot be performed, and washing cannot be performed.

  The inventors of the present application have confirmed that cleaning can be performed when the coverage of the fluorine organic compound is 20,000 μg / g or less in terms of fluorine, depending on the type of oil adsorbed.

  In order to produce such a magnetic powder, a compound containing a fluorine organic compound may be mixed and supported on porous magnetic particles. Examples of the production method include a dry method in which a compound containing a fluorocarbon is sprayed in a mixer such as a Henschel mixer, and a wet method in which a compound containing a fluorocarbon is reacted in a solvent, which has the first feature. A wet method is preferred for producing magnetic powder for water treatment. As the compound containing the fluorine organic compound used at this time, a compound having a fluorocarbon and an alkoxy group is preferably used. Examples of the fluorine organic compound include KY-100 series (trade name) manufactured by Shin-Etsu Chemical Co., Ltd. This compound is dissolved in, for example, chlorofluorocarbon, fluoroether, methyl ethyl ketone, toluene, etc. in a solvent, and then the magnetic material is mixed to react the hydroxyl group on the magnetic material surface with alkoxysilane. By using such a manufacturing method, not only the surface of the porous particle but also the inside of the particle can be uniformly and thinly loaded with fluorocarbon, so that the capacity for impregnating and holding a sufficient liquid is left inside the porous particle. be able to.

  The second characteristic is that there is a fluorocarbon concentration distribution in which the fluorine concentration on the particle surface is high and the fluorine concentration is lower on the inside than the surface of the porous particles. This is a concentration distribution of fluorine necessary for removing a hydrophobic substance with a hydrophilic solvent after adsorbing the hydrophobic substance. When removing the adsorbed oil with a hydrophilic solvent that does not dissolve it, the hydrophobic surface is difficult to wash with the solvent, but the hydrophilic surface tends to be easy to wash. In a material having such a fluorine concentration distribution, the liquid or solid oil adsorbed by the hydrophobic surface tends to be stored inside the open pores having a small hydrophobicity, particularly under the adsorption conditions under pressure. When washing with a hydrophilic solvent after use, the hydrophilic solvent that has penetrated into the open pores can be easily replaced with a liquid hydrophobic substance, and washing can be performed. In addition, the hydrophobicity of the surface does not significantly impair the adsorption ability of the hydrophobic substance.

  As a method for producing the magnetic material for water treatment having the second feature, for example, a dry method in which a compound containing a fluorocarbon is sprayed in a mixer such as a Henschel mixer may be used. Examples of the compound having a fluorocarbon sprayed at this time include a compound having an alkoxysilyl group used in the fluorocarbon having the first characteristic, and a resin containing a fluorocarbon that is heat-cured. As the fluorocarbon to be heat-cured, a copolymer or mixture in which a structure having a fluorocarbon and a structure to be heat-cured coexist is used. Fluorocarbons include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), perfluoroethylene propene copolymer (PFEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene. -Ethylene copolymer (ETFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF) and the like. Examples of the resin having a heat-curing structure include polyamide resin, polyimide resin, polyamideimide resin, acrylic resin, and epoxy resin.

  When these compounds are added while mixing with a Henschel mixer or the like, the fluorine organic compound (fluorocarbon) can be supported only in the vicinity of the surface of the porous particles. At this time, if the compound containing the fluorine organic compound is not soaked into the inside of the porous particles, the inside of the porous particles is kept hydrophilic and is easily washed with a hydrophilic solvent. In addition, if a compound containing a fluorine organic compound is present only in the surface layer within 20% of the diameter of the porous particle, the hydrophilic space inside the porous particle becomes large and the hydrophobic liquid is easily detached. This is preferable because the space can be increased.

  There are two types of water treatment methods using the magnetic powder for water treatment of the present embodiment: a centrifugal separation method and a membrane filtration method, but the apparatus used for each method has different configurations, so each will be described below. .

(Apparatus of the first embodiment)
Next, with reference to FIG. 5, the water treatment apparatus used for the water treatment method of 1st Embodiment is demonstrated.

  The water treatment apparatus 1 of the present embodiment is an apparatus used for a centrifugal separation method using a liquid cyclone for a solid-liquid separation apparatus, and is particularly effective when there is a restriction such as when the flow rate is small or the installation area of the apparatus is small. Used for. The water treatment device 1 includes a mixed adsorption tank 2, a recovery tank 4, a water treatment particle supply device 5, a hydrocyclone 6, a magnetic separation device 7, a raw water supply source (not shown), and a treated water storage tank. And the apparatus is mutually connected by the some piping line L1-L9. Various pumps P1 to P6, valves V1 to V2, and measuring instruments and sensors (not shown) are attached to the piping lines L1 to L9. Detection signals are input from these measuring instruments and sensors to an input section of a controller (not shown), and control signals are output from the output section of the controller to the pumps P1 to P6 and valves V1 to V2, respectively, and their operations are controlled. It has become so. As described above, the entire water treatment apparatus 1 is comprehensively controlled by a controller (not shown).

  The mixed adsorption tank 2 has a stirring screw 21 that stirs the water to be treated, and wastewater (factory wastewater or domestic wastewater) to be treated is introduced from a raw water supply source (not shown) via the line L1. Are temporarily mixed with the water treatment particles supplied from the water treatment particle supply device 5 through the line L8, and fine water-insoluble solid particles contained in the water to be treated are removed from the water. It is adsorbed on the processing particles.

  The liquid cyclone 6 has a solid portion separated along the wall surface by centrifugal force as the fluid flows down in a conical cylinder having a wide upper portion and a narrow lower portion, and is discharged to a pot 61 below the cyclone. Is. The pot 61 is connected to the upper portion of the recovery tank 4 by a line L4 having a valve V1, and the fluid is transferred by gravity. Moreover, the water from which the solid content has disappeared is discharged as treated water through a line L7 connected to the upper part of the cyclone.

  The magnetic separation device 7 includes a separation cell whose inlet side communicates with the cyclone upper discharge line L3, a magnetic coil that surrounds the separation cell and generates an induced magnetic field in the separation cell, and a space between the outlet side of the separation cell and the recovery tank 4 And a treated water line L9 provided between the outlet side of the separation cell and a treated water tank (not shown). The magnetic separation device 7 magnetically separates the magnetic powder that has adsorbed oil from water, and sends the separated oil-adsorbed magnetic powder to the recovery tank 4 via the recovery line L5, while treating the treated water via the treated water line L9. To be sent to the treated water tank.

  The collection tank 4 has an agitating screw 41 for agitating a mixture (slurry) of water treatment particles and solids received from the lower space of the cyclone 6 through the drawing line L4. A magnet 42 for separation is incorporated. The magnet 42 is housed in a cylindrical cylinder, is controlled by a controller (not shown), and is driven up and down by an air cylinder (not shown).

  In addition to the extraction line L4 from the cyclone 6, a recovery line L5 from the magnetic separation device 7 is connected to the upper part of the recovery tank 4. On the other hand, a concentrated water discharge line L6 and a water treatment magnetic powder return line L7 are connected to the lower part of the recovery tank 4, respectively. The concentrated water discharge line L6 is a pipe for discharging water-insoluble matter concentrated water from the collection tank 4 to a storage tank (not shown). The water treatment magnetic powder return line L7 is a pipe having a pump P2 for returning the water treatment magnetic powder separated and collected from the collection tank 4 to the water treatment magnetic powder supply device 5.

  A solvent supply line L10 from the hydrophilic solvent supply device 8 is further connected to the upper portion of the recovery tank 4. The hydrophilic solvent supply device 8 supplies an aqueous ethanol solution (water: ethanol = 40: 60) to the recovery tank 4 as a hydrophilic solvent used in the cleaning process.

  In the water treatment particle supply device 5, water treatment particles are newly replenished from a water treatment particle supply source (not shown), and the water treatment particles separated in the recovery tank 4 are returned to the above-described water treatment particle return line. Returned through L7. In addition, the water treatment particle supply device 5 supplies an appropriate amount of water treatment particles to the mixed adsorption tank 2 through a water treatment particle supply line L8 having a valve V2.

(Method of the first embodiment)
Next, a centrifugation method as a first water treatment method using the above apparatus will be described with reference to FIGS.

  First, the water to be treated and the magnetic powder for water treatment are stirred and mixed in the mixing tank 2 to adsorb oil in water to the magnetic powder (step S1). The magnetic powder for water treatment has magnetic single particles or aggregates on a magnetic carrier, and has a coating layer containing a fluorine organic compound supported on the magnetic carrier on the surface. Although the density | concentration of the magnetic powder in to-be-processed water is adjusted with the oil content density | concentration in to-be-processed water, it is made to become 1-10 times of oil content concentration, for example.

  Separation process S2 of this embodiment is performed by the cyclone 6. The water introduced into the cyclone 6 from the line L2 swirls at high speed along the circumference of the cyclone, and the oil and magnetic powder are separated from the water by the centrifugal force at this time, and the separated oil / magnetic powder is separated from the lower part of the cyclone. It is designed to accumulate in the pot 61. The oil / magnetic powder mixture stored in the pot 61 at the lower part of the cyclone is sent to the separation tank 4 through the line L4 by opening the valve V1. The opening and closing of the valve V1 may be performed periodically or may be performed at any time according to the amount of slurry in the pot 61.

  Magnetic powder that is about to flow out of the system through the upper line L3 from the cyclone 6 without being captured by the pot 61 is magnetically separated from the treated water by the magnetic separation device 7, and is collected through the line L5. 4 recovered.

  In the collection tank 4, the oil / magnetic powder mixture is stirred and mixed by the stirring screw 41 to disperse the magnetic powder and the solid content (step S3). When this stirring is sufficiently performed, the magnetic powder and the oil are more uniformly dispersed in the suspension, and the magnetic powder can be easily separated and recovered. At this time, the hydrophilic solvent is supplied to the recovery tank 4 from the hydrophilic solvent supply device 8 via the line L10. The hydrophilic solvent is used in a washing process for separating the adsorbed oil from the magnetic powder, and is, for example, an aqueous ethanol solution (water: ethanol = 40: 60).

  Next, the magnetic powder is recovered from the separated suspension using a magnetic separation method (step S4). As a method of magnetic separation, there are a method of collecting a permanent magnet or an electromagnet in a container of the separation tank 4 and a method of collecting particles by collecting them with a metal net magnetized by a magnet and releasing a magnetic field. Used. Specifically, the magnet 42 contained in the cylinder is put in the separation tank 4 by an air cylinder (not shown), and the magnetic powder is adsorbed and fixed in the suspension by the magnet 42. The liquid containing the oil component is discharged from the container to the storage tank (not shown) via the line L6, and then the magnet 42 is taken out of the separation tank 4 using an air cylinder, and the magnetic powder is removed from the cylindrical container containing the magnet 42. The tap water is supplied into the container via a tap water supply line (not shown), and tap water is added to the dropped magnetic powder to form a slurry or suspension. The slurry or suspension of magnetic powder Is sent from the separation tank 4 to the magnetic powder supply device 5 through a line L7 having a pump P2.

  Thereafter, the recovered magnetic powder is supplied from the magnetic powder supply device 5 to the mixing tank 3 via the line L8, and the recovered magnetic powder is reused for the adsorption of oil. Thus, the magnetic powder can be repeatedly used in the cycle of oil adsorption → centrifugation → separation of magnetic powder and oil (cleaning treatment) → magnetic separation → recovery → oil adsorption.

  According to said embodiment, collection | recovery and reuse of the magnetic powder for water treatment are easy, and the fine solid substance in water can be removed efficiently, without throwing in a chemical | drug | medicine.

(Device of Second Embodiment)
Next, a water treatment apparatus 1A used in the water treatment method of the second embodiment will be described with reference to FIG. In addition, description of the part which this embodiment overlaps with said embodiment is abbreviate | omitted.

  The water treatment apparatus 1A of the present embodiment is used for a body feed method among membrane filtration methods, and is effectively used particularly when the concentration of oil in water is high.

  The water treatment apparatus 1A includes a mixed raw water tank 2A, a solid-liquid separation apparatus 3, a magnetic separation tank 4, a magnetic powder supply apparatus 5, and a raw water supply source and a drainage storage tank (not shown). They are connected to each other by a plurality of piping lines L1 to L8. Various pumps P1 to P7, valves V1 to V2, and measuring instruments and sensors (not shown) are attached to the piping lines L1 to L8. A detection signal is input from these measuring instruments and sensors to an input section of a controller (not shown), and control signals are output from the output section of the controller to the pumps P1 to P7 and valves V1 to V2, respectively. It has become so. As described above, the entire water treatment apparatus 1 is comprehensively controlled by a controller (not shown).

  The mixed raw water tank 2A has a stirring screw 21 for stirring the water to be treated, and factory wastewater to be treated water is introduced through a line L1 from a raw water supply source (not shown). The mixed raw water tank 2A has both a function of temporarily storing raw water and leveling the flow rate of the raw water, and a mixing function of adding magnetic powder to the raw water and mixing them. That is, in the apparatus 1A of the present embodiment, the magnetic powder is directly supplied from the magnetic powder supply apparatus 5 into the mixed raw water tank 2A through the line L6.

  The solid-liquid separation device 3 includes a filtration membrane 33 that partitions the interior into an upper space 31 and a lower space 32. The upper space 31 of the solid-liquid separator is connected to the mixed raw water tank 2A via a to-be-treated water supply line L2 having a pressure pump P1. Further, a separation water supply line (first treated water utilization line) L31 having a pump P5 and a separation material discharge line L4 are respectively connected to the side portions of the upper space 31.

  On the other hand, the lower space 32 of the solid-liquid separator is connected to a treated water distribution line L3 having two three-way valves V1, V2. At the first three-way valve V1, the separation water supply line (first treated water utilization line) L31 is branched from the treated water distribution line L3. At the second three-way valve V2, two lines L33 and L34 are branched from the treated water distribution line L3. One branch line (second treated water utilization line) L33 has a pump P4 and is connected to a separation tank 4 described later. The other branch line (third treated water utilization line) L34 is connected to a treated water supply line L32 having a pump P5.

  The magnetic separation tank 4 has a stirring screw 41 for stirring the washing discharge water received from the upper space 31 of the solid-liquid separation device through the peeled material discharge line L4, and is separated into a solid and a filter aid. The magnet 42 for carrying out is built in. The magnet 42 is in a cylindrical pipe closed on one side, and is moved up and down by a controller (not shown), and the magnetic field is controlled on and off.

  In addition to the separated product discharge line L4, a second treated water use line L33 branched from the treated water distribution line L3 is connected to the upper part of the magnetic separation tank 4, and has passed through the filter 33 of the solid-liquid separator. A part of the treated water is supplied to the magnetic separation tank 4, and a part of the treated water is reused in the magnetic separation tank 4. On the other hand, a concentrated water discharge line L8 and a magnetic powder return line L5 are connected to the lower part of the magnetic separation tank 4, respectively. The concentrated water discharge line L8 has a pump P9 and is a pipe for discharging water-insoluble matter concentrated water from the magnetic separation tank 4 to a storage tank (not shown). The magnetic powder return line L5 is a pipe having a pump P6 for returning the magnetic powder separated and collected from the magnetic separation tank 4 to the magnetic powder supply device 5.

  The magnetic powder supply device 5 is replenished with magnetic powder from a magnetic powder supply source (not shown) so that the magnetic powder separated in the magnetic separation tank 4 is returned through the magnetic powder return line L5. It has become. Further, the magnetic powder supply device 5 supplies an appropriate amount of magnetic powder to the mixed raw water tank 2A through a magnetic powder supply line L6 having a pump P7.

(Method of Second Embodiment)
Next, a body feed method as a second water treatment method using the above apparatus will be described with reference to FIGS.

  In this embodiment, first, magnetic powder and a dispersion medium are mixed to prepare a suspension. The dispersion medium used in this case is treated water existing in the mixing raw water tank 2A. That is, in this embodiment, magnetic powder is directly put into raw water that is to-be-treated water to adjust the suspension from the raw water (step K1). The concentration of the magnetic powder in the suspension is not particularly limited as long as a filtration layer can be formed by the following operation, but is adjusted to, for example, about 10,000 to 200,000 mg / L.

  Next, the suspension (water to be treated) is passed through the filtration membrane 33, and the filter aid in the suspension is filtered and left on the filtration membrane 33 to form a deposited layer formed by laminating magnetic powder. (Step K2). In addition, the water flow with respect to the filtration membrane 33 is performed under pressure. At this time, the formation of the deposited layer and the filtration treatment of the water to be treated are performed in parallel. In the method of the present embodiment, the filtration surface of the filtration membrane 33 is preferably horizontal.

  In addition, since the filtration layer is formed and held by the action of external force as described above, the above-described filtering is performed by, for example, arranging the filtration membrane 33 so as to close the container opening of a predetermined container. The magnetic powder remains on the filtration membrane 33 so as to be arranged and stacked. In this case, the deposited layer is formed and held by the external force from the wall surface of the container and the downward external force (gravity) due to the weight of the magnetic powder positioned above.

  After adsorbing and removing the oil in the water to be treated as described above, peeling water is sprayed onto the deposition layer on the filtration membrane, the deposition layer is peeled off from the filtration membrane 33, and water is further sprayed onto the peeling matter to remove the peeling matter. The magnetic powder that has been broken down into pieces and adsorbed with oil is put into pieces in water (step K3). The separation of the peeled material may be performed in a container in which the filtration membrane 33 is installed, or may be performed in another container. In the case of using another container, the deposited layer is decomposed into a magnetic powder using means such as an injection nozzle and then transported. In addition, although water is used for peeling of the deposited layer, it is possible to clean using a surfactant or an organic solvent.

  Next, the peeled / decomposed magnetic powder is recovered by a magnetic separation method (step K4). The method used for the magnetic separation method is not particularly limited, but a method of collecting a permanent magnet or an electromagnet in a container and a method of collecting particles by collecting them with a metal mesh magnetized by a magnet and releasing a magnetic field Etc. can be used.

  In the water treatment method of the present embodiment, the magnetic powder constituting the deposition layer is contained in the water to be treated, that is, in the suspension adjusted using this water, so Magnetic powder is always supplied together with the treated water (suspension).

  Therefore, even when the amount of oil in the water to be treated (suspension) is large, the oil and the magnetic powder are supplied at the same time. The gap is not buried. For this reason, the filtration rate can be maintained for a long time. As a result, as described above, the water treatment method of the second embodiment is effective when the concentration of magnetic powder in the water to be treated is high.

  Thereafter, the recovered magnetic powder is supplied from the magnetic powder supply device 5 to the mixing raw water tank 2A via the line L6, and the recovered magnetic powder is reused for adsorption of oil. In this way, the magnetic powder can be repeatedly used in the cycle of adsorption of oil, solid-liquid separation by filtration membrane, separation of magnetic powder and oil, magnetic separation, recovery, and adsorption of oil.

  Hereinafter, it demonstrates in detail using an Example.

(Example: Magnetic powder A for water treatment)
A methyl ethyl ketone solution in which KY-108 manufactured by Shin-Etsu Chemical Co., Ltd. having a fluorocarbon and an alkoxysilyl group was dissolved was prepared. Manganese magnesium ferrite particles having an average particle size of 15 μm were mixed and mixed at room temperature. Collect a small amount of ferrite every 10 minutes, wash with methyl ethyl ketone, dissolve in aqua regia, measure the fluorine concentration by ICP-AES method (inductively coupled plasma atomic emission spectrometry), and the fluorine content is about 10,000 μg. The reaction was stopped when / g was reached. Thereafter, the ferrite particles were heated in a thermostat at a temperature of 100 ° C. for 2 hours, and then passed through a 100-mesh sieve to obtain magnetic powder A for water treatment.

(Example: Magnetic powder B for water treatment)
In the same manner as the magnetic powder A, the reaction was stopped when the fluorine content reached 50 μg / g, and magnetic powder B was similarly obtained.

(Example: Magnetic powder C for water treatment)
In the same manner as in the magnetic powder A, the reaction was stopped when the fluorine content reached 20000 μg / g, and magnetic powder C was obtained in the same manner.

(Example: Magnetic powder D for water treatment)
Porous manganese magnesium ferrite particles having an average particle diameter of 35 μm were placed in a fluidized bed, and a mixture of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and polyamideimide was added until the resin content became 1% by mass. . This magnetic material was taken out and heat-cured at 200 ° C. for 2 hours to obtain a magnetic powder D for water treatment. When observed with a scanning electron microscope (SEM), magnetic particles in which a part of the surface was coated with a fluororesin were obtained. The magnetic particles were impregnated in an embedded resin and cured, then cut in half from the center with a diamond cutter, and the cross section was observed with an SEM. When the distribution of the fluororesin was examined with a backscattered electron image (BEI), the penetration stopped at an average of 20% from the surface layer, and it was confirmed that there was no fluororesin inside.

(Example: Magnetic powder E for water treatment)
Magnetic powder E was produced in the same manner as in magnetic powder D except that 89 μm porous manganese magnesium ferrite particles were used. Similarly, when the cross section was observed, the penetration stopped at an average of 10% on the surface layer, and it was recognized that there was no fluororesin inside.

Example 1
A simulated drainage was prepared by dispersing 1000 mg / L of liquid paraffin (Smoyl P55), which is a simulated oil, in water. In this wastewater, 3000 mg / L of magnetic powder A was added to adsorb the oil in the water. As a result, almost 99% of the oil was adsorbed. The adsorbed particles are taken out with a magnet, immersed in a cleaning solution in which water / ethanol is mixed at a volume ratio of 40/60, and when the cleaning solution is gently stirred while being fixed with a magnet, liquid paraffin is dropped from the magnetic material into droplets. The oil was removed from the magnetic material. The washing liquid at this time was dried and the recovery rate of liquid paraffin was analyzed and found to be 95%.

  When the washed magnetic powder A (regenerated magnetic material) was added to the simulated waste water and reused, the oil was adsorbed with high efficiency in the second time as in the first time.

(Example 2)
In Example 2, when the test was performed under the same conditions as in Example 1 except that the magnetic powder A was changed to the magnetic powder B, about 90% of the oil in the water could be removed. When immersed in a cleaning solution in which water / ethanol is mixed at a volume ratio of 40/60 and gently agitated while being fixed with a magnet, liquid paraffin separates from the magnetic powder in the form of droplets, and oil is removed from the magnetic powder. Could be removed. The washing liquid at this time was dried and the recovered amount of liquid paraffin was analyzed and found to be 98%.

(Example 3)
In Example 3, when the test was conducted under the same conditions as in Example 1 except that the magnetic powder A was changed to the magnetic powder C, about 99% of the oil in the water could be removed. When immersed in a cleaning solution in which water / ethanol is mixed at a volume ratio of 40/60 and gently agitated while being fixed with a magnet, liquid paraffin separates from the magnetic powder in the form of droplets, and oil is removed from the magnetic powder. Could be removed. When the washing liquid at this time was dried and the recovered amount of liquid paraffin was analyzed, it was 80%.

Example 4
In Example 4, when the test was conducted under the same conditions as in Example 1 except that the magnetic powder A was changed to the magnetic powder D, about 99% of the oil in the water could be removed. When immersed in a cleaning solution in which water / ethanol is mixed at a volume ratio of 40/60 and gently agitated while being fixed with a magnet, liquid paraffin separates from the magnetic powder in the form of droplets, and oil is removed from the magnetic powder. Could be removed. When the washing liquid at this time was dried and the recovered amount of liquid paraffin was analyzed, it was 75%.

(Example 5)
In Example 5, when the test was conducted under the same conditions as in Example 1 except that the magnetic powder A was changed to the magnetic powder E, about 78% of the oil in the water could be removed. When immersed in a cleaning solution in which water / ethanol is mixed at a volume ratio of 40/60 and gently agitated while being fixed with a magnet, liquid paraffin separates from the magnetic powder in the form of droplets, and oil is removed from the magnetic powder. Could be removed. When the washing liquid at this time was dried and the recovered amount of liquid paraffin was analyzed, it was 90%.

(Comparative Example 1)
A magnetic powder of Comparative Example 1 in which fluorocarbon was not supported on porous manganese magnesium ferrite particles having an average particle diameter of 35 μm was prepared. Using the magnetic powder of Comparative Example 1, a test was performed under the same conditions as in Example 1. As a result, only 6% of the oil contained in the water was adsorbed to the magnetic powder of Comparative Example 1.

1, 1A ... Water treatment device, 2 ... Raw water tank, 2A ... Mixed raw water tank,
3 ... solid-liquid separator (filter), 31 ... upper space, 32 ... lower space, 33 ... filtration membrane,
4 ... Recovery tank (magnetic separation tank)
5 ... Magnetic powder supply device,
6 ... cyclone, 61 ... pot,
7 ... Magnetic separation device,
50 ... magnetic powder, 51 ... magnetic particles (primary particles), 52 ... coating layer,
53 ... Secondary aggregate (filter aid, aggregate of primary particles),
54, 55 ... open pores, 56 ... adsorbed oil (oil film),
P1 to P9 ... pump, V1, V2 ... valve,
L1 ... Raw water supply line, L2 ... Treatment water supply line, L3 ... Treatment water discharge line, L31 ... Peeling water supply line (first treated water utilization line), L32 ... Treatment water carry-out line, L33 ... Second treatment Water use line, L34 ... third treated water use line,
L4 ... peeled material discharge line, L5 ... magnetic powder return line, L6 ... magnetic powder supply line, L7 ... mixing line, L8 ... recovered component concentrated water discharge line.

Claims (8)

The oil in the water to be treated is adsorbed, separated from the water to be treated together with the adsorbed oil, and the separated product is immersed in the cleaning liquid, and magnetically separated from the adsorbed oil in the separated material in the cleaning liquid, Magnetic powder for water treatment that is collected and used repeatedly,
A magnetic carrier comprising porous magnetic particles having an average particle size of 15 to 90 μm;
A coating layer containing a fluorine organic compound supported on the magnetic carrier so as to cover the magnetic carrier and having a coverage of 50 to 20000 μg / g in terms of fluorine;
A magnetic powder for water treatment, comprising:   The magnetic powder for water treatment according to claim 1, wherein the fluorine organic compound is obtained by reacting a compound having a fluorocarbon and an alkoxy group with the surface of the magnetic carrier.   The magnetic powder for water treatment according to claim 1, wherein the fluorine organic compound is a mixture of a fluorocarbon and a thermosetting resin. The magnetic carrier is composed of porous magnetic particles having an apparent specific gravity larger than 1 and having a large number of open pores opened on the surface;
The fluorine organic compound of the coating layer has entered the open pores of the porous magnetic particles so that the fluorine concentration gradually decreases as it moves from the surface to the inside of the magnetic carrier. The magnetic powder for water treatment according to any one of 1 to 3.   The magnetic powder for water treatment according to claim 4, wherein the fluorine organic compound is substantially absent at a central portion of the porous magnetic particles.   6. The magnetic powder for water treatment according to claim 5, wherein the fluorine organic compound in the coating layer penetrates from the surface of the porous magnetic particles to a depth of 20% or less of the diameter of the particles. (A) preparing a magnetic powder for water treatment having a magnetic carrier composed of porous magnetic particles having an apparent specific gravity greater than 1, and a coating layer containing a fluorine organic compound supported on the magnetic carrier;
(B) Disperse the magnetic powder for water treatment in water to be treated containing oil, adsorb the oil to the magnetic powder for water treatment,
(C) A centrifugal force is applied to the water to be treated containing the magnetic powder for water treatment, and the magnetic powder for water treatment that has adsorbed the oil is centrifuged from the water,
(D) The centrifuge product is immersed in a cleaning solution, and the centrifuge product is stirred in the cleaning solution,
(E) A magnetic field is applied to the agitated material, and the magnetic powder for water treatment is magnetically separated from the agitated material in the cleaning liquid,
(F) The water treatment method characterized by reusing the magnetically separated magnetic powder for water treatment in the step (B) for adsorption of oil. (A) preparing a magnetic powder for water treatment having a magnetic carrier composed of porous magnetic particles having an apparent specific gravity of greater than 1, and a coating layer containing a fluorine organic compound carried on the magnetic carrier;
(B) Dispersing the water treatment magnetic powder in the water to be treated containing oil, adsorbing the oil to the water treatment magnetic powder,
(C) The water to be treated containing the magnetic powder for water treatment is allowed to stand to cause gravity to act on the magnetic powder for water treatment, and the magnetic powder for water treatment that has adsorbed the oil is settled and separated from the water,
(D) immersing the sedimentation separation in a washing liquid, stirring the sedimentation separation in the washing liquid,
(E) applying a magnetic field to the agitated material, and magnetically separating the magnetic powder for water treatment from the agitated material in the cleaning liquid;
(F) The water treatment method characterized by reusing the magnetically separated magnetic powder for water treatment in the step (b) for adsorption of oil.

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