Water purification agent and method for producing water purification agent

Abstract

To provide a water cleaning agent which can be produced from a two component developer and can elute a divalent iron ion into water.SOLUTION: The water purification agent includes a plurality of iron ion-eluting particles each having a magnetic particle containing iron, a carbon layer adhering to the surface of the magnetic particle, and a silica particle adhering to the surface of the magnetic particle or the carbon layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water purifying agent and a method for producing the same. [Background technology]

[0002] Two-component developers containing toner and a carrier (magnetic particles) containing iron are used in electrophotographic copiers, multifunction devices, printers, facsimile machines, and the like (see, for example, Patent Document 1). The developers also contain silica nanoparticles as an external additive. The carrier contained in the developer is composed of a core material and a resin layer covering its surface, and has the function of charging and transporting toner in a developer tank and is used repeatedly. When the carrier is used for a long period of time, it deteriorates due to contamination by toner components and peeling and wear of the resin layer, making it necessary to replace it with a new carrier. Furthermore, a sintered body capable of dissolving divalent iron ions into water to improve the water environment is known (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-086714 [Patent Document 2] Japanese Patent Application Publication No. 2018-053304 Summary of the Invention [Problem to be solved by the invention]

[0004] Used two-component developers containing degraded carriers are disposed of as industrial waste, so there is a need for a method to reuse used two-component developers. The present invention has been made in view of the above circumstances, and provides a water purification agent that can be produced from a two-component developer and that can elute divalent iron ions into water, and a method for producing the same. [Means for solving the problem]

[0005] The present invention provides a water purification agent comprising iron ion-eluting particles, the iron ion-eluting particles comprising magnetic particles containing iron, a carbon layer attached to the surface of the magnetic particles, and silica particles attached to the surface of the magnetic particles or the carbon layer. The present invention also provides a method for producing a water purifying agent, which comprises a step of baking a two-component developer at a temperature of 500° C. or higher. [Effects of the Invention]

[0006] The water purifying agent of the present invention can elute divalent iron ions into water, thereby improving the aquatic environment. Furthermore, since the water purifying agent of the present invention contains silica particles, harmful heavy metal ions can be adsorbed onto the silica particles, thereby improving the aquatic environment. Furthermore, the water purifying agent of the present invention can be produced from a used two-component developer. Furthermore, the water purifying agent of the present invention can also be produced from an unused two-component developer. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1(a) is a schematic cross-sectional view of a two-component developer, and FIG. 1(b) is a schematic cross-sectional view of iron ion-eluting particles contained in a water purification agent according to one embodiment of the present invention. [Figure 2] FIG. 1 is an explanatory diagram of water purification using a water purification agent according to one embodiment of the present invention. [Figure 3] 1 shows SEM photographs of the prepared samples. [Figure 4] FIG. 1 is an explanatory diagram of an experimental method for measuring the concentration of divalent iron ions. DETAILED DESCRIPTION OF THE INVENTION

[0008] The water purification agent of the present invention is characterized by having a plurality of iron ion-eluting particles, each of which comprises a magnetic particle containing iron, a carbon layer attached to the surface of the magnetic particle, and silica particles attached to the surface of the magnetic particle or the carbon layer.

[0009] The carbon layer is preferably fixed to the surface of the magnetic particles. The iron ion-eluting particles are preferably sintered. The average particle diameter D50 of the primary particles of the silica particles is preferably 200 nm or less, more preferably 100 nm or less. If the primary particle diameter of silica is large, it may be detached from the water purification agent. Furthermore, if the primary particle diameter is large, the specific surface area will be small, and the number of silanol groups on the surface will be reduced, thereby reducing the water purification effect. The average particle size D50 of the iron ion-eluting particles is preferably 20 μm or more and 100 μm or less, more preferably 30 to 60 μm. If the particle size is large, the number of contact points between metallic iron and carbon decreases, while if the particle size is small, the bulk density decreases, which deteriorates the mixability with carbon materials, and voids are generated within the iron ion-eluting particles due to the elution of iron, making them prone to collapse. The plurality of iron ion-eluting particles contained in the water purification agent preferably have a particle size distribution such that (D90-D10) / D50 is 0.5 or more and 2.0 or less, and more preferably 0.8 to 1.5. The BET specific surface area of ​​the plurality of iron ion-eluting particles contained in the water purification agent is 0.5 m 2 / g or more 50m 2 / g or less, and 2 / g or more 50m 2 It is more preferable that the saturation coefficient is 1 / g or less. The iron ion-eluting particles preferably contain at least one of manganese, magnesium, and potassium.

[0010] The water purifying agent of the present invention preferably further contains ascorbic acid. The coverage of the magnetic particles with the carbon layer is preferably 80% to 99%, more preferably 85% to 95%. When the coverage of the magnetic particles with the carbon layer is low, more of the carrier core is exposed, i.e., there are fewer contact points with the carbon, and the amount of elution is reduced. The circularity of the iron ion-eluting particles is preferably 0.85 or more, and more preferably 0.90 or more. If the circularity is low, when the particles are placed in water and pile up, voids are not secured, and the contact area between the water purification agent and the water is reduced, resulting in a reduced amount of eluted iron ions. The proportion of the carbon layer in the iron ion-eluting particles is preferably 1.0 wt % or more and 10 wt % or less. If the proportion of the carbon layer is small, the number of contact points between iron and carbon decreases, and the amount of eluted iron ions decreases.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configurations shown in the drawings and the following description are merely examples, and the scope of the present invention is not limited to those shown in the drawings and the following description.

[0012] Fig. 1(a) is a schematic cross-sectional view of a two-component developer, Fig. 1(b) is a schematic cross-sectional view of iron ion eluted particles contained in the water purification agent of this embodiment, and Fig. 2 is an explanatory diagram of water purification by the water purification agent of this embodiment. The water purification agent 20 of this embodiment is characterized by having a plurality of iron ion-eluting particles 5, each of which has a magnetic particle 2 containing iron, a carbon layer 3 attached to the surface of the magnetic particle 2, and a silica particle 4 attached to the surface of the magnetic particle 2 or the carbon layer 3. The method for producing the water purifying agent 20 of this embodiment includes a step of baking the two-component developer 11 at a temperature of 500° C. or higher. The water purifying agent 20 of this embodiment does not necessarily have to be baked.

[0013] The water purification agent 20 is a purification agent for improving the water quality of the sea, rivers, lakes, ponds, moats, ditches, aquariums, etc. More specifically, it is a purification agent that improves the water quality by dissolving divalent iron ions into the water.

[0014] The water purifying agent 20 has a plurality of iron ion-eluting particles 5. The iron ion-eluting particles 5 are particles that can elute iron ions into water. The iron ion-eluting particles 5 have magnetic particles 2 containing iron, a carbon layer 3 attached to the surface of the magnetic particle 2, and silica particles 4 attached to the surface of the magnetic particle 2 or the carbon layer 3. The water purifying agent 20 (iron ion-eluting particles 5) may be in powder form.

[0015] The electronegativity of iron is 1.8, and the electronegativity of carbon is 2.5. For example, as shown in Figure 2, when water purification agent 20 is immersed in water, electrons in magnetic particles 2 move to carbon layer 3, and the iron contained in magnetic particles 2 is thought to dissolve into the water as divalent iron ions. The dissolved divalent iron ions are absorbed by algae 16 and phytoplankton, activating them and improving water quality. The dissolved divalent iron ions are thought to react with hydrogen sulfide (a foul-smelling substance produced by sludge, etc.) to form iron sulfide (FeS), which precipitates. This makes it possible to remove toxic hydrogen sulfide and transform the water environment into one that is more hospitable to living organisms. Furthermore, it is believed that the divalent iron ions eluted from the magnetic particles 2 react with phosphoric acid (eutrophication: detergents, pesticides, fertilizers, etc.) to become iron phosphate (FePO4) and precipitate. This prevents eutrophication, which causes blue-green algae and red tides, and purifies and improves water quality. Furthermore, the precipitated iron is absorbed by algae 16, activating photosynthesis and improving water quality.

[0016] The water purification agent 20 may contain ascorbic acid. This can prevent divalent iron ions eluted from the water purification agent 20 into water from being oxidized to trivalent iron ions. Trivalent iron ions are less likely to be absorbed by algae 16, phytoplankton, etc. than divalent iron ions. The water purification agent 20 can contain 0.01 wt% to 8 wt% of ascorbic acid relative to the iron ion-eluting particles 5.

[0017] The iron ion-eluting particles 5 have an average particle diameter D50 of, for example, 20 μm or more and 100 μm or less, which allows the amount of divalent iron ions eluted from the water purification agent 20 into water to be increased. The iron ion-eluting particles 5 contained in the water purification agent 20 preferably have a particle size distribution such that (D90-D10) / D50 is 0.5 or more and 2.0 or less. This allows the iron ion-eluting particles 5 to have a uniform size, allowing the water purification agent 20 to elute a stable amount of divalent iron ions into water. The BET specific surface area of ​​the plurality of iron ion-eluting particles 5 contained in the water purification agent 20 is 0.5 m 2 / g or more 50m 2 / g or less, it is possible to increase the amount of divalent iron ions eluted from the water purification agent 20 into water. The average circularity of the plurality of iron ion-eluting particles 5 contained in the water purification agent 20 is preferably 0.85 or more. The average circularity can be calculated, for example, by averaging the circularities of 50 iron ion-eluting particles 5 arbitrarily selected from the iron ion-eluting particles 5 contained in the water purification agent 20.

[0018] The iron ion-eluting particles 5 can be produced by baking the two-component developer 11 at a temperature of 500°C or higher (preferably a temperature of 600°C or higher, and more preferably a temperature of 700°C or higher). Alternatively, the iron ion-eluting particles 5 may be produced by mixing the two-component developer 11 with a carbon material or an organic component and baking the mixture. Alternatively, the iron ion-eluting particles 5 may be produced by baking the treated two-component developer 11. The baking can be carried out in an atmosphere with a low oxygen gas concentration, such as a nitrogen gas atmosphere, whereby the organic matter contained in the two-component developer 11 can be carbonized, and the carbon layer 3 can be formed.

[0019] The two-component developer 11 contains toner and a carrier. As shown in the cross-sectional view of Figure 1(a), the particles contained in the two-component developer 11 can have magnetic particles 2 that are carrier cores, a resin layer 13 that covers the surfaces of the magnetic particles 2, toner base particles 12 that adhere to the resin layer 13, and silica particles 4 that are external additives. The two-component developer 11 can be produced by mixing the toner and carrier using a known mixer.

[0020] The carrier is composed of magnetic particles 2, which are carrier cores, and a resin layer 13 that covers the surfaces of the magnetic particles 2. Because the magnetic particles 2 are heat resistant, the description of the magnetic particles 2 includes both the magnetic particles 2 contained in the carrier and the magnetic particles 2 contained in the iron ion-eluting particles 5. The magnetic particles 2 can be any magnetic particles commonly used in this field, as long as they contain iron. Examples include magnetic metals such as iron, copper, nickel, and cobalt, and magnetic metal oxides such as ferrite and magnetite. Among these, manganese-magnesium ferrite is preferred. Furthermore, the magnetic particles 2 preferably contain metallic iron. Furthermore, the magnetic particles 2 preferably contain manganese or magnesium. This allows manganese ions or magnesium ions to be eluted into water along with divalent iron ions from the water purification agent 20 immersed in water. Manganese and magnesium are essential elements for plants, and eluting manganese ions or magnesium ions into water activates aquatic plants and phytoplankton, enriching the ecosystem. Furthermore, magnesium oxide produced from the eluted magnesium ions improves the pH of bottom sediments and suppresses the generation of hydrogen sulfide gas and odors from sludge.

[0021] The resin layer 13 becomes the carbon layer 3 by baking the two-component developer 11. Materials commonly used in the electrophotography field can be used for the resin layer 13, such as polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin, polyester resin, metal compound of di-tert-butyl salicylic acid, styrene resin, acrylic resin, polyamide, polyvinyl butyral, nigrosine, aminoacrylate resin, basic dye, lake of basic dye, etc. These resins are carbonized by baking. The resin layer 13 can contain 0.3 parts by weight or more and 5.0 parts by weight or less of a carbon material, and preferably 0.5 to 3.0 parts by weight of a carbon material, per 100 parts by weight of the resin. Examples of the carbon material contained in the resin layer 13 include carbon black, acetylene black, activated carbon, graphite, and porous carbon materials, with carbon black being most preferred.

[0022] The toner is composed of toner base particles 12 and external additives. The organic components contained in the toner and external additives are carbonized to form the carbon layer 3 by baking. The toner base particles 12 contain a binder resin, a colorant, a release agent, and may also contain, as necessary, a charge control agent, a wax dispersant, a grinding aid, etc. The glass transition temperature (Tg) of the toner base particles 12 is preferably 60° C. or lower. The binder resin may be a resin commonly used in the art, or a combination of two or more resins may be used. The colorant may be a carbon-based coloring material, such as carbon black, acetylene black, activated carbon, graphite, or a porous carbon material. The release agent may be any release agent commonly used in the art. A combination of multiple release agents may also be used. The melting point of the release agent is preferably 70°C or higher and lower than 150°C. The amount of the release agent contained in the toner base particles 12 can be appropriately selected depending on the purpose. For example, the toner base particles 12 preferably contain 0.5 to 5.0 parts by weight of the release agent per 100 parts by weight of the binder resin (2.0 to 5.0% by weight).

[0023] The charge control agent may be a charge control agent commonly used in the art. The charge inhibitor may contain potassium. The amount of charge control agent in the toner base particles 12 can be appropriately selected depending on the purpose. For example, the toner base particles 12 preferably contain 0.5 to 3 parts by weight of charge control agent per 100 parts by weight of binder resin (0.5 to 2.0% by weight). When the charge control agent contains potassium, the water purifying agent 20 produced by firing the two-component developer 11 containing this charge control agent also contains potassium. This allows potassium ions to be eluted from the water purifying agent 20 into water, providing nutrients to algae 16 and phytoplankton. This allows water quality to be improved through photosynthesis by the algae 16 and phytoplankton. The wax dispersant may be any wax dispersant commonly used in the art, and the grinding aid may be any grinding aid commonly used in the art.

[0024] The external additive may be any external additive commonly used in the art, but it is necessary to use at least one external additive containing silica particles 4. Colloidal silica or fumed silica synthesized by a sol-gel method may be used. The silica particles 4 may be surface-treated with a silicone resin, a silane coupling agent, or the like. The average particle size D50 of the primary particles of the silica particles 4 is not particularly limited, but is preferably 200 nm or less, and more preferably 5 to 100 nm. Since the silica particles 4 have heat resistance, the description of the silica particles 4 includes both the silica particles 4 contained in the toner and the silica particles 4 contained in the iron ion-eluting particles 5. In the iron ion-eluting particles 5 contained in the water purification agent 20, the silica particles 4 are present in the carbon layer 3 or on the surface of the carbon layer 3. By including the silica particles 4 in the water purification agent 20, harmful metal ions in the water can be adsorbed onto the surface of the silica particles 4, thereby improving the water quality. Specifically, this is thought to be as follows: When divalent iron ions are eluted from the iron ion-eluting particles 5 into the water, some of the divalent iron ions are oxidized by dissolved oxygen to become trivalent. The trivalent iron becomes iron hydroxide and adsorbs heavy metal ions. The iron hydroxide that has adsorbed the heavy metals approaches the silica particles 4 due to its zeta potential and is adsorbed. Furthermore, the silica particles 4 are capable of adsorbing harmful metals by means of silanol groups (Si—OH) on the surface. Furthermore, by setting the average particle size D50 of the primary particles of the silica particles 4 to 200 nm or less, it is possible to prevent the silica particles 4 from detaching from the iron ion-eluting particles 5. Furthermore, it is possible to increase the specific surface area of ​​the silica particles 4, which allows them to adsorb a large amount of harmful metals.

[0025] The carbon layer 3 can contain a carbon material generated by carbonizing an organic component contained in the two-component developer 11 (a resin contained in the resin layer 13, toner, etc.) and a carbon material contained in the two-component developer 11 (a carbon material contained in the resin layer 13, toner, etc., such as carbon black). When the iron ion-eluting particles 5 are produced by mixing the two-component developer 11 with a carbon material or an organic component and baking the mixture, the carbon layer 3 can contain a carbon material added before baking or a carbon material generated by carbonizing an organic component added before baking. The carbon layer 3 may be a porous layer or a dense layer. The carbon layer 3 is attached or fixed to the surface of the magnetic particle 2. The carbon layer 3 has a shape that spreads along the surface of the magnetic particle 2. This makes it possible to prevent the carbon material contained in the carbon layer 3 from being detached from the iron ion-eluting particles 5 when the water purification agent 20 is immersed in water. This allows divalent iron ions to be eluted from the water purification agent 20 into water over a long period of time. Furthermore, the contact area between the magnetic particle 2 and the carbon layer 3 can be increased, making it easier for electrons from the magnetic particle 2 to move to the carbon layer 3.

[0026] The coverage of the magnetic particles 2 with the carbon layer 3 is preferably 80% or more and 99% or less. This allows electrons from the magnetic particles 2 to move more easily to the carbon layer 3, and increases the amount of divalent iron ions eluted from the iron ion-eluting particles 5 into water. The proportion of the carbon layer 3 in the iron ion-eluting particles 5 is preferably 1.0 wt % or more and 10 wt % or less. This allows electrons from the magnetic particles 2 to move more easily to the carbon layer 3, increasing the amount of divalent iron ions eluted into water from the iron ion-eluting particles 5. It also prevents the eluted divalent iron ions from being adsorbed onto the carbon layer 3.

[0027] Preparation of water purification agent Samples of Examples 1 to 32 and Comparative Examples 1 to 4 shown in Table 1 were prepared. Specifically, they were prepared as follows.

[0028] [Table 1]

[0029] Example 1 [Preparation of Carrier] Carbon black (Ketjenblack EC, manufactured by Lion Corporation) was added to a silicone resin (KR-255, manufactured by Shin-Etsu Chemical Co., Ltd.) as a coating resin at a concentration of 5.0 wt%, and the mixture was dissolved or dispersed in toluene to obtain a dispersion. The resulting dispersion was applied to a carrier core material (MnMg ferrite, average particle size: 40 μm) using a fluidized bed coating device, and the applied coating resin was cured by heating at 250°C for 2 hours to obtain a carrier.

[0030] [Toner Preparation] Binder resin: Polyester resin 89% by mass Colorant: Carbon black (manufactured by Mitsubishi Chemical Corporation, product name: MA-77) 8% by mass Release agent: Paraffin wax (melting point 90°C, Nippon Seiro Co., Ltd., product name: Fischer-Tropsch Wax FNP0090) 2% by mass The raw materials for the toner particles (toner cores) were pre-mixed for 5 minutes at a rotation speed of 1500 rpm using a high-performance fluid mixer (Henschel mixer, total capacity: 20 L, manufactured by Mitsui Mining Co., Ltd. (now Nippon Coke and Engineering Co., Ltd.), model: FM20C). The obtained mixture was melt-kneaded using a twin-screw extruder (manufactured by Ikegai Corporation, model: PCM-30) under conditions of a cylinder set temperature of 100°C, a barrel rotation speed of 250 rpm, and a raw material supply rate of 10 kg / hour to obtain a melt-kneaded product.

[0031] The resulting molten and kneaded material was cooled and solidified on a cooling belt, and then the solidified material was finely pulverized using a fluidized bed opposed jet mill (manufactured by Hosokawa Micron Corporation, model: Counter Jet Mill AFG) and classified (particle size adjusted) using a rotary (centrifugal airflow) classifier (manufactured by Hosokawa Micron Corporation, model: TSP Separator) to obtain toner particles (toner cores) with a volume average particle diameter of 5.0 μm to 7.0 μm. To 1000 g of the obtained toner particles, 10 g (average particle diameter: 7 nm) of commercially available silica fine particles (manufactured by Nippon Aerosil Co., Ltd., product name: R976s) and 3 g of silica-doped strontium titanate (fine powder in which the surface of a composition containing strontium titanate and silica has been hydrophobized with a silane compound, average primary particle diameter: 20 μm) were added as external additives, and the mixture was mixed for 3 minutes at 3500 rpm using a high-performance fluid mixer (Henschel mixer, total capacity: 20 L, manufactured by Mitsui Mining Co., Ltd. (now Nippon Coke and Engineering Co., Ltd.), model: FM20C) to obtain 1 kg of toner.

[0032] [Preparation of Used Developer] The toner obtained by the above manufacturing method and the carrier were weighed out so that the toner concentration was 7.0% (toner / carrier = 1 / 13.3), and the mixture was stirred and mixed for 20 minutes in a V-type mixer (manufactured by Tokuju Kogyosho Co., Ltd., model: V-5) to obtain a two-component developer. The above two-component developer was filled into the developing unit of a commercially available copier, and 100,000 sheets of A4-sized recording paper with a print rate of 5% were printed.The two-component developer was then removed from the developing tank, and used developer (LifeDeve) was prepared.

[0033] [Preparation of water purification agent] The prepared used developer and waste toner (added if the carbon content was low) were mixed (adjusted so that the carbon content was 5%) and placed in a crucible. The crucible was placed in an electric furnace (a small electric furnace, High Cera Kiln SH-OMT-BS2S) placed in a glove box purged with nitrogen gas, and heated to 700°C at a heating rate of 10°C / min. After holding for 1 hour, the mixture was cooled and removed to prepare the sample of Example 1. The prepared sample was in powder form.

[0034] Example 2 A water purification agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 19 μm was used and the carbon content was adjusted to 7%.

[0035] Example 3 A water purification agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 20 μm was used and the carbon content was adjusted to 7%.

[0036] Example 4 A water purifying agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 100 μm was used and the carbon content was adjusted to 4%.

[0037] Example 5 A water purifying agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 105 μm was used and the carbon content was adjusted to 3%.

[0038] Example 6 A water purifying agent was prepared in the same manner as in Example 1, except that a carrier core material having a (D90-D10) / D50 ratio of 0.4 was used.

[0039] Example 7 A water purifying agent was prepared in the same manner as in Example 1, except that a carrier core material having a (D90-D10) / D50 ratio of 0.5 was used.

[0040] Example 8 A water purifying agent was prepared in the same manner as in Example 1, except that a carrier core material having a (D90-D10) / D50 ratio of 1.9 was used.

[0041] Example 9 A water purifying agent was prepared in the same manner as in Example 1, except that a carrier core material having a (D90-D10) / D50 ratio of 2.2 was used.

[0042] Example 10 A water purifying agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 90 μm was used and the carbon content was adjusted to 2%.

[0043] Example 11 A water purifying agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 90 μm was used and the carbon content was adjusted to 2%.

[0044] Example 12 A water purification agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 20 μm was used and the carbon content was adjusted to 8%.

[0045] Example 13 A water purification agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 20 μm was used and the carbon content was adjusted to 8%.

[0046] Example 14 The same water purification agent as in Example 1 was used, except that in Example 14, no ascorbic acid was added when measuring the concentration of divalent iron ions.

[0047] Example 15 The same water purification agent as in Example 1 was used, except that in Example 15, 0.5 wt % of ascorbic acid was added when measuring the concentration of divalent iron ions.

[0048] Example 16 The same water purification agent as in Example 1 was used, except that in Example 16, 1.0 wt % of ascorbic acid was added when measuring the concentration of divalent iron ions.

[0049] Example 17 The same water purification agent as in Example 1 was used, except that in Example 17, 5.0 wt % of ascorbic acid was added when measuring the concentration of divalent iron ions.

[0050] Example 18 The same water purification agent as in Example 1 was used, except that in Example 18, 8.0 wt % of ascorbic acid was added when measuring the concentration of divalent iron ions.

[0051] Example 19 A water purifying agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 45 μm was used and the carbon content was adjusted to 9.5%.

[0052] Example 20 A water purifying agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 43 μm was used and the carbon content was adjusted to 9.0%.

[0053] Example 21 A water purification agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 35 μm was used and the carbon content was adjusted to 2.0%.

[0054] Example 22 A water purifying agent was prepared in the same manner as in Example 1, except that a carrier core material having an average particle size of 30 μm was used and the carbon content was adjusted to 1.5%.

[0055] Example 23 A water purification agent was prepared in the same manner as in Example 1, except that the carbon content was adjusted to 0.8%.

[0056] Example 24 A water purification agent was prepared in the same manner as in Example 1, except that the carbon content was adjusted to 1.0%.

[0057] Example 25 A water purification agent was prepared in the same manner as in Example 1, except that the carbon content was adjusted to 10.0%.

[0058] Example 26 A water purification agent was prepared in the same manner as in Example 1, except that the carbon content was adjusted to 11.0%.

[0059] Example 27 A water purification agent was prepared in the same manner as in Example 1, except that silica fine particles with an average particle size of 30 nm were used.

[0060] Example 28 A water purification agent was prepared in the same manner as in Example 1, except that silica fine particles with an average particle size of 100 nm were used.

[0061] Example 29 A water purifying agent was prepared in the same manner as in Example 1, except that silica fine particles with an average particle size of 190 nm were used.

[0062] Example 30 A water purification agent was prepared in the same manner as in Example 1, except that silica fine particles with an average particle size of 210 nm were used.

[0063] Example 31 A water purification agent was prepared in the same manner as in Example 1, except that silica fine particles with an average particle size of 10 nm were used.

[0064] Example 32 A water purification agent was prepared in the same manner as in Example 1, except that silica fine particles with an average particle size of 10 nm were used.

[0065] (Comparative Example 1) The carrier prepared in Example 1 and carbon black were mixed to obtain the composition shown in Table 1 to prepare a sample of Comparative Example 1. No firing was performed.

[0066] (Comparative Example 2) The used developer (not baked) prepared in Example 1 was used.

[0067] (Comparative Example 3) The carrier core material used in preparing the carrier of Example 1 was placed in a crucible. The crucible was placed in an electric furnace (a small electric furnace, High Cera Kiln SH-OMT-BS2S) placed in a glove box purged with nitrogen gas, and heated to 700°C at a heating rate of 10°C / min. The crucible was then held there for 1 hour, cooled, and removed to prepare a sample of Comparative Example 3. The prepared sample was in powder form.

[0068] Comparative Example 4 Iron powder removed from a disposable warmer and the waste toner prepared in Example 1 were mixed (adjusted to have the carbon content shown in Table 1) and placed in a crucible. The crucible was placed in an electric furnace (a small electric furnace, Hicera Kiln SH-OMT-BS2S) placed in a glove box purged with nitrogen gas, and heated to 700°C at a heating rate of 10°C / min. The mixture was then held there for 1 hour, cooled, and removed to prepare a sample of Comparative Example 4. The prepared sample was in powder form.

[0069] Particle size distribution measurement The average particle diameters D50 and (D90-D10) / D50 of the samples of Examples 1 to 32 and Comparative Examples 1 to 4 were measured using a Microtrac particle size analyzer (manufactured by Nikkiso Co., Ltd.) The measurement results are shown in Table 1.

[0070] Specific surface area measurement The specific surface areas of the samples of Examples 1 to 32 and Comparative Examples 1 to 4 were measured using an adsorption amount measuring device (BELSORP MINI II) manufactured by Microtrac Co., Ltd. The measurement results are shown in Table 1.

[0071] SEM observation SEM observations were performed on the samples of Examples 1 to 32 and Comparative Example 4. Specifically, using a scanning electron microscope (SEM), the samples were observed with an electron beam at an acceleration voltage of 2.0 kV without depositing a conductive agent such as gold on their surfaces. FIG. 3 shows SEM images of the samples. Furthermore, the carbon layer coverage (%) was calculated from the SEM images of the samples of Examples 1 to 32 and Comparative Example 4. Because the magnetic particles (MnMg ferrite) in the carrier appear white, the ratio of the remaining area to the total area of ​​the carrier was calculated. This was performed for 100 water purification agent particles, and the average of the obtained values ​​was taken as the magnetic particle exposure rate. From the magnetic particle exposure rate calculated for each sample, the coverage rate of the magnetic particles covered by the carbon layer (carbon layer coverage rate) was calculated using the formula (carbon layer coverage rate = 100 - magnetic particle exposure rate). The carbon layer coverage rate for each sample is shown in Table 1. Furthermore, the circularity was calculated from the SEM images of the samples of Examples 1 to 32. The circularity is the average value of the circularity of 50 particle images: 4π × (area) / (square of circumference). A circularity of 1 indicates a perfect circle. The circularity of the particles was calculated using ImageJ software manufactured by the National Institutes of Health. The circularity calculated for each sample is shown in Table 1. The particle size (D50) of the silica particles shown in Table 1 is the particle size of the silica particles used in preparing the toner.

[0072] Measurement of silica deposition rate The silica deposition ratios X of the samples of Examples 1 to 32 were measured. Specifically, 1 g of the sample was added to 20 mL of a 0.2% by mass aqueous solution of polyoxyethylene (10) octylphenyl ether (Triton X-100), stirred for 5 minutes, and then suction filtered through a membrane filter with a pore size of 1 μm. The resulting residue was vacuum dried. The dried residue was then analyzed using an X-ray fluorescence analyzer (manufactured by Rigaku Corporation, Model: ZSX PrimusIV) to measure the average peak intensity Xa of the Si element. The average Si peak intensity Xp of the sample before treatment with the aqueous solution was also measured in the same manner, and the silica deposition ratio X was calculated as Xa / Xp. The calculated silica deposition ratios are shown in Table 2.

[0073] Carbon content measurement Thermogravimetric analysis (TGA) was performed on the samples of Examples 1 to 32 and Comparative Examples 1, 3, and 4 to measure the carbon content of each sample. Specifically, the samples were heated in a nitrogen atmosphere from 40°C to 600°C at 20°C / min and then held for 5 minutes. Organic matter other than carbon was decomposed at this temperature. The samples were then cooled to 400°C at 20°C / min, the atmosphere was changed from nitrogen to air, and the temperature was held for 5 minutes. The temperature was then increased to 800°C at 20°C / min and held for 30 minutes. The weight loss rate after changing from a nitrogen atmosphere to an air atmosphere was taken as the carbon content. The carbon content calculated for each sample is shown in Table 1.

[0074] Measurement of ferrous ion concentration The ferrous iron ion concentration eluted from each of the samples in Examples 1 to 32 and Comparative Examples 1, 3, and 4 was measured. Figure 4 illustrates this measurement method. Specifically, the prepared sample 17, distilled water (water 15) in an amount 20 times the weight of the sample, and ascorbic acid (not added in Example 14) in the amount shown in Table 1 (% by weight relative to the prepared sample) were placed in a glass sample bottle (100 g of distilled water for a 5 g sample) (Figure 4(a)). After 7 days, the supernatant was analyzed using a Pack Test (Kyoritsu Chemical Research Institute, Inc.) to measure the ferrous iron ion concentration (Figure 4(b)). The sample was then recovered by suction filtration using a membrane filter with a pore size of 1 μm. The recovered sample and distilled water in an amount 20 times the weight of the sample were then placed in a glass bottle. The water was replaced in this manner (Figure 4(c)). After the water was replaced, the supernatant after 7 days and after 30 days was analyzed using Pack Test (Kyoritsu Chemical Research Institute, Inc.) to measure the concentration of ferrous ions (Figure 4(d)).

[0075] The measurement results are shown in Table 2. In Examples 1 to 32, the divalent iron ion concentration 30 days after the water was replaced was 1 ppm or more, whereas in Comparative Examples 1, 3, and 4, the divalent iron ion concentration 30 days after the water was replaced was 0.5 ppm or less. This shows that when a sample prepared by baking a used two-component developer is used as a water purification agent, divalent iron ions can be continuously eluted into water.

[0076] [Table 2] [Explanation of symbols]

[0077] 2: Magnetic particles 3: Carbon layer 4: Silica particles 5: Iron ion eluted particles 11: Two-component developer 12: Toner base particles 13: Resin layer 15: Water 16: Algae 17: Sample 20: Water purification agent

Claims

1. A water purification agent characterized by having iron ion-eluting particles having magnetic particles containing iron, a carbon layer attached to the surface of the magnetic particles, and silica particles attached to the surface of the magnetic particles or the carbon layer.

2. 2. The water purifying agent according to claim 1, wherein the carbon layer is fixed to the surface of the magnetic particles.

3. 2. The water purifying agent according to claim 1, wherein the iron ion-eluting particles are sintered.

4. 2. The water purifying agent according to claim 1, wherein the average particle diameter D50 of the primary particles of the silica particles is 200 nm or less.

5. 2. The water purifying agent according to claim 1, wherein the iron ion-eluting particles have an average particle diameter D50 of 20 μm or more and 100 μm or less.

6. The water purification agent according to any one of claims 1 to 5, wherein the plurality of iron ion-eluting particles contained in the water purification agent have a particle size distribution such that (D90 - D10) / D50 is 0.5 or more and 2.0 or less.

7. The BET specific surface area of ​​the plurality of iron ion-eluting particles contained in the water purification agent is 0.5 m 2 / g or more 50m 2 The water purifying agent according to any one of claims 1 to 5, wherein the water purifying agent has a water solubility of 1 / g or less.

8. 6. The water purifying agent according to claim 1, wherein the iron ion-eluting particles contain at least one of manganese, magnesium, and potassium.

9. The water purifying agent according to any one of claims 1 to 5, further comprising ascorbic acid.

10. 6. The water purifying agent according to claim 1, wherein the carbon layer covers the magnetic particles at a coverage rate of 80% to 99%.

11. 6. The water purifying agent according to claim 1, wherein the iron ion-eluting particles have a circularity of 0.85 or more.

12. 6. The water purifying agent according to claim 1, wherein the proportion of the carbon layer in the iron ion-eluting particles is 1.0 wt % or more and 10 wt % or less.

13. A method for producing a water purifying agent, comprising the step of baking a two-component developer at a temperature of 500°C or higher.

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