Residual chlorine removal filter body

Abstract

To provide a residual chlorine removing filter body constituted of a mixture of an activated carbon adsorbent and calcium sulfite, capable of maintaining its capacity of removing free residual chlorine as well as bound residual chlorine at a high level for a long time by controlling the elution of sulfite ions when water is flowing therethrough.SOLUTION: The residual chlorine removing filter body is characterized by comprising: a first filter part prepared by mixing an activated carbon adsorbent, a fibrillated fiber binder and calcium sulfite of a diameter of 0.1 to 0.5 mm in water to form mixed slurry, sucking the mixed slurry from a side face of a hollow cylindrical core member and letting the mixed slurry adhere thereto to form an adsorptive adhering layer thereon and heating / drying the adsorptive adhering layer; and a second filter part filled with calcium sulfite of a diameter of 0.7 to 5.0 mm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a residual chlorine removal filter body intended to remove free residual chlorine and combined residual chlorine, which are residual chlorine in water. [Background technology]

[0002] Sodium hypochlorite is primarily used to disinfect tap water, and the hypochlorous acid and hypochlorite ions produced when sodium hypochlorite dissolves in water are called free residual chlorine. Free residual chlorine has a bactericidal or disinfecting effect. However, the reaction between ammonia and nitrogen oxides present in natural water and the added hypochlorous acid and hypochlorite ions produces combined residual chlorine, such as chloramines. Combined residual chlorine and free residual chlorine are collectively called residual chlorine. Odor can often become a problem depending on the condition of the raw water taken, the amount of free residual chlorine added, and even the amount of chloramine.

[0003] Water purifiers are used to remove residual chlorine from drinking water such as tap water. Such water purifiers are constructed with an adsorption member made of an inorganic material such as activated carbon or ceramic, and, if necessary, an organic polymer membrane for filtration. In recent years, in response to demands for higher performance in water purifiers and air purifiers, activated carbon has come to be widely used in these filters. For example, because chloramine and ammonia are basic, activated carbon with acidic functional groups on the surface of the activated carbon is thought to be effective (see, for example, Patent Document 1). In other words, the removal (decomposition) efficiency can be increased by a chemical reaction utilizing an acid-base reaction.

[0004] A filter in which activated carbon and calcium sulfite are solidified with a porous polymer has also been proposed (see Patent Document 2). In so-called dry filters, filters have been developed that, even for small filters, improve water purification performance by increasing the density of activated carbon and limiting the particle size of calcium sulfite, thereby accelerating the dissolution of calcium sulfite and maintaining the ability to remove free residual chlorine while ensuring a stable water flow rate.

[0005] Hospitals often have independent water sources, such as wells or groundwater, and if the source water is contaminated, it may contain relatively high levels of ammonia. As a result, as mentioned above, disinfection using free residual chlorine or the like can easily produce bound residual chlorine, such as chloramines. Bound residual chlorine is difficult to remove sufficiently using activated carbon filters or reverse osmosis membranes, and in the past, it has been mixed into dialysis water, causing hemolysis in patients. For this reason, water from which residual chlorine has been removed is particularly desirable for use in artificial dialysis in hospitals, and filter media with high removal performance for residual chlorine, including free and bound residual chlorine, are in demand.

[0006] Therefore, a residual chlorine removal filter has been proposed in which activated carbon is mixed with calcium sulfite, molded, and integrated (see Patent Document 3). It has good water permeability and can maintain a high level of residual chlorine removal performance, including both free and combined residual chlorine. It has also been proposed to use a porous carbon material produced from a raw material with a high nitrogen content as a chloramine decomposition catalyst (see Patent Document 4). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-338222 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-207174 [Patent Document 3] Japanese Patent Application Publication No. 2020-179374 [Patent Document 4] WO2020 / 137849 publication Summary of the Invention [Problem to be solved by the invention]

[0008] In particular, because hospitals consume large amounts of water with residual chlorine removed for dialysis, the filter that removes residual chlorine is required to not only have high residual chlorine removal performance but also to have a long-lasting effect. Furthermore, because of its use, it is possible that filters will be replaced earlier than their performance limit from a safety perspective, so the demand for long-lasting residual chlorine removal filters is increasing.

[0009] Furthermore, in Japan, tap water is often managed to keep the residual chlorine concentration low to suppress the chlorine odor, and there is a demand for residual chlorine removal filters that can effectively remove chlorine even at low concentrations in water and maintain good removal performance for a long period of time.

[0010] The present invention has been made in consideration of the above points, and provides a residual chlorine removal filter body that is a filter body containing an activated carbon adsorbent and calcium sulfite, and that can maintain high residual chlorine removal performance, including both free and bound residual chlorine, for a long period of time by controlling the amount of sulfite ions eluted when water is passed through it. [Means for solving the problem]

[0011] That is, the first invention relates to a residual chlorine removal filter body characterized by comprising a first filter section formed by mixing an activated carbon adsorbent and a fibrillated fiber binder in water to form a mixed slurry, adsorbing the mixed slurry onto the side of a hollow cylindrical core member while sucking it to form an adsorbed material, and heating and drying the adsorbed material, and a second filter section filled with calcium sulfite having a particle size of 0.7 to 5.0 mm.

[0012] A second invention relates to a residual chlorine removal filter body according to the first invention, wherein calcium sulfite having a particle size of 0.1 to 0.5 mm is further mixed into the mixed slurry.

[0013] The third invention is the first or second invention, Amount of sulfite ions eluted 10 minutes after water flow startedThe residual chlorine removal filter body has a residual chlorine removal rate of 5 to 20 mg / L.

[0014] A fourth invention relates to the residual chlorine removal filter body according to any one of the first to third inventions, wherein the activated carbon adsorbent is one or more of fibrous activated carbon, granular activated carbon, and powdered activated carbon.

[0015] A fifth invention relates to the residual chlorine removal filter body according to any one of the first to fourth inventions, wherein the activated carbon adsorbent has an iodine adsorption capacity of 800 to 2000 mg / g.

[0016] A sixth invention relates to the residual chlorine removal filter body according to any one of the first to fifth inventions, wherein the fibrillated fiber binder is made of acrylic fiber.

[0017] The seventh invention relates to a residual chlorine removal filter body according to any one of the first to sixth inventions, which has a combined residual chlorine removal performance of 50 L / mL or more. [Effects of the Invention]

[0018] According to the residual chlorine removal filter body of the first invention, an activated carbon adsorbent and a fibrillated fiber binder are mixed in water to form a mixed slurry, and the mixed slurry is then sucked onto the side of a hollow cylindrical core member to form an adsorbed material, and the adsorbed material is heated and dried to form a first filter section, and a second filter section filled with calcium sulfite having a particle size of 0.7 to 5.0 mm.By increasing the particle size of the calcium sulfite and increasing its weight, the amount of sulfite ions leached out at the beginning of water flow can be reduced, and by continuously leaching sulfite ions into water, the amount of sulfite ions leached out during water flow can be controlled, and the residual chlorine removal performance, including both free and bound residual chlorine, can be maintained at a high level for a long period of time.

[0019] According to the second invention, the residual chlorine removal filter body of the first invention is obtained by further mixing calcium sulfite having a particle size of 0.1 to 0.5 mm into the mixed slurry. This allows the weight of calcium sulfite supported on the filter body to be increased, and sulfite ions can be continuously dissolved into water, making it possible to maintain high levels of residual chlorine removal performance, including both free and bound residual chlorine, for a long period of time.

[0020] According to the third aspect of the present invention, the residual chlorine removal filter body of the first or second aspect of the present invention is Amount of sulfite ions eluted 10 minutes after water flow started Since the amount of sulfite ions eluted is 5 to 20 mg / L, it is possible to suppress the amount of sulfite ions eluted in the initial stage of water flow and to allow sulfite ions to be continuously eluted into the water.

[0021] According to the residual chlorine removal filter body of the fourth invention, in any of the first to third inventions, the activated carbon adsorbent is one or more of fibrous activated carbon, granular activated carbon, and powdered activated carbon, and therefore has excellent performance in removing free residual chlorine.

[0022] According to the residual chlorine removal filter body of the fifth invention, in any of the first to fourth inventions, the iodine adsorption capacity of the activated carbon adsorbent is 800 to 2000 mg / g, and therefore it has the general adsorption capacity required of an activated carbon adsorbent.

[0023] According to the residual chlorine removal filter body of the sixth invention, in any of the first to fifth inventions, the fibrillated fiber binder is made of acrylic fiber, thereby making it possible to extend the service life of the filter body.

[0024] According to the residual chlorine removing filter body of the seventh invention, in any one of the first to sixth inventions, the combined residual chlorine removing performance is 50 L / mL or more, and therefore the residual chlorine removing performance is good. [Brief explanation of the drawings]

[0025] [Figure 1]FIG. 2 is a schematic process diagram showing the manufacturing process of the residual chlorine removal filter body. DETAILED DESCRIPTION OF THE INVENTION

[0026] The residual chlorine removal filter body of the present invention is intended to remove residual chlorine, including free residual chlorine such as hypochlorous acid dissolved in water and bound residual chlorine such as chloramines. The residual chlorine removal filter body of the present invention is installed in, for example, a water purifier or is used in a location where residual chlorine removal is required, such as the water filtration section of an artificial dialysis machine. Filter bodies for liquids such as water include so-called dry filters and wet filters. Dry filters are made by melting a thermoplastic resin to hold an activated carbon adsorbent or other filtering material. Wet filters are made by mixing a fibrous component serving as a binder, such as resin fibers, with an activated carbon adsorbent or other filtering material, forming an aqueous slurry, and then aspirating and molding the mixture into a predetermined shape. Wet filters have a structure in which the fibrous component and filtering material are intertwined and integrated.

[0027] The residual chlorine removal filter body of the present invention employs a wet filter. Compared to dry filters, wet filters have superior water permeability due to the use of a fibrous component as a binder. Dry filters have the advantage of a high density and therefore a large amount of activated carbon adsorbent. However, since the activated carbon adsorbent is held by melting a thermoplastic resin, the surface of the activated carbon adsorbent may be coated with the resin, potentially reducing adsorption performance. In the residual chlorine removal filter body of the present invention, the activated carbon adsorbent and calcium sulfite are held by a fibrillated fiber binder, ensuring residual chlorine removal performance while maintaining water permeability.

[0028] The activated carbon adsorbent has excellent adsorption performance for residual chlorine, particularly for free residual chlorine. The residual chlorine removal filter body of the present invention uses one or more of fibrous activated carbon, granular activated carbon, or powdered activated carbon as the activated carbon adsorbent of the filter medium. The adsorption capacity of the fibrous activated carbon, granular activated carbon, or powdered activated carbon used in the residual chlorine removal filter body of the present invention is comparable to that of general fibrous activated carbon, granular activated carbon, or powdered activated carbon. Specifically, activated carbon is used that has an iodine adsorption capacity of 800 to 2000 mg / g when measured in accordance with JIS K 1474 (2014) and JIS K 1477 (2007).

[0029] Activated carbon is made from raw materials such as wood (waste wood, thinned wood, sawdust), coffee bean pulp, coconut shells, bark, and fruit. These natural raw materials are prone to developing pores when carbonized and activated. They are also inexpensive to procure because they are secondary waste materials. Other materials that can be used include tires, petroleum pitch, burned synthetic resins such as urethane resin and phenolic resin, and even coal. In particular, fibrous activated carbon can be obtained by carbonizing and activating fibers from various carbon materials, including plants, minerals, natural materials, and synthetic materials.

[0030] The activated carbon raw material is heated and carbonized in the temperature range of 200°C to 600°C, which creates micropores. The activated carbon raw material is then exposed to water vapor and carbon dioxide gas in the temperature range of 600°C to 1200°C for activation. This results in activated carbon with various types of developed pores. Other activation methods include zinc chloride activation. Sequential washing is also performed.

[0031] When the particle size of granular activated carbon is small or when powdered activated carbon is used, the density of the filter body increases, improving the adsorption performance of free residual chlorine. On the other hand, when the particle size increases, the density of the filter body decreases, improving water permeability. Also, if the particle size is too small, problems such as clogging during water passage are likely to occur. For this reason, it is best to select an appropriate size depending on the desired adsorption performance and the structure of the filter to be used.

[0032] Furthermore, fibrous activated carbon has excellent water permeability due to its fibrous shape. If the average fiber diameter is too large, the surface area will be small relative to the amount added, which is undesirable from the standpoint of improving adsorption capacity. Fibrous activated carbon with a small average fiber diameter has excellent adsorption performance and particle filtration ability. By setting the average fiber diameter of fibrous activated carbon to 20 μm or less, a filter body with excellent adsorption performance and easy handling can be formed while maintaining excellent water permeability.

[0033] The activated carbon adsorbent may be composed of only one of fibrous activated carbon, granular activated carbon, or powdered activated carbon, or may contain multiple of these. Granular activated carbon and powdered activated carbon are generally inexpensive. Adding a large amount of granular activated carbon or powdered activated carbon improves the density of the filter body, increasing the amount of activated carbon adsorbent per volume. As mentioned above, fibrous activated carbon has excellent water permeability and high adsorption performance per unit weight. Therefore, it is best to appropriately determine the blending ratio of fibrous activated carbon, granular activated carbon, or powdered activated carbon, taking into account the functionality and economic efficiency of the filter body.

[0034] The binder of the residual chlorine removal filter body of the present invention is made of a fibrillated fiber binder. It is particularly preferable to use a fibrillated fiber binder made of acrylic fiber, aramid fiber, polyethylene fiber, or the like. The acrylic fiber binder does not melt when heated during drying, so the fibrous structure of the binder remains. This also extends the service life of the filter body. The fiber binder acts as a structural material that holds the activated carbon adsorbent together. Being fibrillated is useful because it allows the activated carbon adsorbent to be held more efficiently.

[0035] The residual chlorine removal filter of the present invention is intended to remove bound residual chlorine, such as monochloramine, dichloramine, and trichloramine. Monochloramine is typically used to disinfect tap water, and the residual chlorine removal filter of the present invention is particularly effective in removing monochloramine.

[0036] As mentioned above, activated carbon adsorbents have high adsorption performance for free residual chlorine, and filter bodies using activated carbon adsorbents as filter media have high free residual chlorine removal performance. Therefore, the residual chlorine removal filter body of the present invention combines activated carbon adsorbents, which are filter media that primarily remove free residual chlorine, with calcium sulfite, which is a component that primarily removes bound residual chlorine. The calcium sulfite incorporated in the filter body releases sulfite ions that dissolve into water and react with bound residual chlorine such as chloramines, decomposing and reducing the bound residual chlorine, thereby removing the bound residual chlorine.

[0037] Next, an outline of the manufacturing process for the first filter part of the residual chlorine removal filter body will be explained using Figure 1. First, activated carbon adsorbent 20 (granular activated carbon 21, fibrous activated carbon 22), fibrillated acrylic fiber binder 23, and, if necessary, calcium sulfite 24 are added to water W and thoroughly mixed to prepare a mixed slurry 30.

[0038] A porous mold rod 35 is inserted into the hollow cylindrical core 11 to suck the mixed slurry under reduced pressure. The hollow cylindrical core 11 has small holes (not shown) for permeation, and the mold rod 35 is made of porous stainless steel. The combined hollow cylindrical core 11 and mold rod 35 are lowered into the mixed slurry 30, and then vacuum suction is applied through the mold rod 35, causing the mixed slurry 30 to adhere to the side of the hollow cylindrical core 11. As shown in the cutout portion, a slurry-adhered portion 26 is formed on the surface of the hollow cylindrical core 11. After a predetermined amount of the slurry-adhered portion 26 has formed, the hollow cylindrical core 12 is pulled out of the mixed slurry, and the mold rod 35 is removed. Thus, an adsorbed adherend 25 having the slurry-adhered portion 26 on the surface of the hollow cylindrical core 12 is obtained. The adsorbed adherend 25 is then heated and dried in a dryer 40.

[0039] The temperature and time of heat drying are optimally set taking into consideration the melting temperature of the resin component, the size of the adsorbed material itself, the amount of the mixed slurry to be adhered, production efficiency, etc. The drying temperature is generally 80 to 120°C. The acrylic fiber binder does not melt when heated during heat drying, so the fiber structure of the binder remains.

[0040] Calcium sulfite may also be mixed into the mixed slurry. By supporting calcium sulfite in the first filter body and increasing the amount of calcium sulfite retained in the residual chlorine removal filter body, sulfite ions can be released more continuously into the water, allowing the residual chlorine removal performance to be maintained for a longer period of time. The calcium sulfite blended into the first filter section is produced by vacuum-suctioning the slurry. Therefore, if the particle size is too large, uniform suction becomes difficult, while if the particle size is too small, clogging occurs during water flow and the water becomes cloudy in the early stages of flow. Therefore, the particle size should be 0.1 to 0.5 mm.

[0041] To ensure safe drinking water, Article 17, Paragraph 3 of the Water Supply Act Enforcement Regulations (Ministry of Health, Labour and Welfare Ordinance) requires that water from taps be disinfected with chlorine to maintain a free residual chlorine level of 0.1 mg / L (0.4 mg / L for combined residual chlorine). When the combined residual chlorine concentration in raw water is low, it is possible to remove at least the amount of sulfite ions leaching. If the calcium sulfite particle size is small, sulfite ions leaching is large in the initial stage of water flow, and then the amount of sulfite ions leaching rapidly decreases. A relatively large particle size of calcium sulfite allows sulfite ions to be leached gradually, maintaining sulfite ion leaching for a long period of time. For this reason, it is recommended that the particle size of the calcium sulfite in the second filter section be relatively large, between 0.7 and 5.0 mm.

[0042] The second filter section is filled with calcium sulfite particles with a particle size of 0.7 to 5.0 mm. Since calcium sulfite particles with a large particle size have a small external surface area per unit volume, it is possible to suppress the amount of sulfite ions eluted in the initial stage of water flow. By using calcium sulfite particles with a relatively large particle size filled in the second filter section, Amount of sulfite ions eluted 10 minutes after water flow started By setting the concentration to 5 to 20 mg / L and suppressing the elution of sulfite ions in the early stages of water flow, it is possible to suppress the occurrence of temporary peaks in the amount of elution and control the elution of sulfite ions into the water continuously. [Example]

[0043] [Activated carbon adsorbent] The inventors used the following raw materials as activated carbon adsorbents to prepare a residual chlorine removal filter body. ·Granular activated carbon Futamura Chemical Co., Ltd.: Coconut shell activated carbon "CW8150SZ" (average particle size: 0.16 mm) {Hereafter, this will be referred to as C1.} Fibrous activated carbon Futamura Chemical Co., Ltd.: "Phenol-based fibrous activated carbon" (average fiber diameter: 15 μm) {Hereafter, this will be referred to as C2.}

[0044] [Fibrillating binder] The inventors used fibrillated acrylic resin fibers (trade name Vipal, manufactured by Nippon Exlan Kogyo Co., Ltd.) as a fibrillation binder to prepare a residual chlorine removal filter body.

[0045] [Calcium sulfite] Calcium sulfite manufactured by Tomita Pharmaceutical Co., Ltd. was used, and the powder was pulverized and separated by average particle size using a sieve. The average particle size was measured as the mass average particle size in accordance with JIS K 1474 (2014). Calcium sulfite classified through a 4 / 10 mesh (4.75 / 1.7 mm) sieve with an average particle size of 1.83 mm is designated as S1. Calcium sulfite classified through a 10 / 22 mesh (1.7 / 0.71 mm) sieve to have an average particle size of 1.15 mm is designated as S2. Calcium sulfite classified through a 30 / 100 mesh (0.5 / 0.15 mm) sieve to have an average particle size of 0.16 mm is designated as S3. Calcium sulfite classified through a 100 / 330 mesh (0.15 / 0.045 mm) sieve to have an average particle size of 0.09 mm is designated as S4.

[0046] [Preparation of the first filter part] According to the raw materials and their formulations (unit: parts by weight) listed in Tables 1 to 3, activated carbon adsorbent, fibrillated fiber binder, and calcium sulfite were thoroughly mixed in water to prepare mixed slurries corresponding to each prototype and comparative example. The amount of water in the mixed slurries was 20 times the weight of the added solids. A hollow cylindrical core member for the first filter section was prepared, made of polypropylene and measuring 47 mm in outer diameter, 43 mm in inner diameter, and 113 mm in total length with 2 mm-diameter pores. A porous stainless steel mold rod was inserted and fixed into the hollow cylindrical core member and then immersed in the mixed slurry. The solids were then drawn from the mixed slurry by vacuum suction and adhered to the surface of the hollow cylindrical core member by approximately 9 mm (slurry-adhered portion). The mold rod was removed from the hollow cylindrical core member, and an adsorbent adsorbent was obtained, which was an integrated product of the slurry-adhered portion and the hollow cylindrical core member. The adsorbent was then heated and dried at 100°C for 12 hours in a dryer to produce a first filter part for each prototype and comparative example. Each first filter part was a cylindrical body with a diameter of 65 mm and a total length of 113 mm, including a hollow cylindrical core member. The surface of the filter body was covered with a nonwoven fabric made of a polyethylene and polypropylene blend fiber.

[0047] [Preparation of the second filter part] A hollow cylindrical core member for the second filter section made of polypropylene was prepared, having an outer diameter of 34 mm, an inner diameter of 30 mm, a total length of 113 mm, and pores of 2 mm in diameter. The first filter section, with a polypropylene cap attached to one side, was inserted into the hollow cylindrical core member, and calcium sulfite was filled between the hollow cylindrical core member and the first filter section, filling it sufficiently so that no voids were formed, and then a polypropylene cap was attached. This produced the filter bodies of each prototype and comparative example, and each filter body was a cylinder with a total length of 125 mm.

[0048] [Production of residual chlorine removal filter body] As residual chlorine removing filters, the following filter elements were produced as Prototype Examples 1 to 5 and Comparative Examples 1 to 4. Tables 1 and 2 show the raw materials and their compositions (unit: parts by weight).

[0049] [Preparation of mixed slurry and preparation of prototypes and comparative examples] <Prototype example 1> A slurry was prepared by mixing 39 parts by weight of granular activated carbon (C1), 25 parts by weight of fibrous activated carbon (C2), 30 parts by weight of calcium sulfite (S3) with an average particle size of 0.16 mm, and 6 parts by weight of fibrillated acrylic resin fibers to produce the first filter section of Prototype Example 1. Furthermore, 45 g of calcium sulfite (S1) with an average particle size of 1.83 mm was packed inside the first filter section to form the second filter section of Prototype Example 1, and the filter body of Prototype Example 1 was obtained.

[0050] <Prototype example 2> A filter body of Prototype Example 2 was obtained in the same manner as Prototype Example 1, except that the calcium sulfite in the second filter portion was changed to calcium sulfite (S2) having an average particle size of 1.15 mm.

[0051] <Prototype example 3> The filter body of prototype example 3 was obtained in the same manner as prototype example 1, except that calcium sulfite was not blended into the first filter part, and a mixed slurry of 57 parts by weight of granular activated carbon (C1), 37 parts by weight of fibrous activated carbon (C2), and 6 parts by weight of fibrillated acrylic resin fiber was used.

[0052] <Prototype 4> A filter body of Sample 4 was obtained in the same manner as Sample 1, except that the calcium sulfite in the second filter portion was changed to calcium sulfite (S3) having an average particle size of 0.16 mm.

[0053] <Prototype example 5> A filter body of Prototype Example 5 was obtained in the same manner as Prototype Example 1, except that the calcium sulfite in the second filter portion was changed to calcium sulfite (S4) having an average particle size of 0.09 mm.

[0054] Comparative Example 1 A filter body of Comparative Example 1 was obtained in the same manner as in Prototype Example 1, except that calcium sulfite was not filled in the second filter portion.

[0055] Comparative Example 2 An attempt was made to produce a filter body in the same manner as in Comparative Example 1, except that the calcium sulfite in the first filter part was changed to calcium sulfite (S2) with an average particle size of 1.15 mm. However, the particle size of the calcium sulfite was too large, and the first filter body could not be formed by vacuum suction.

[0056] Comparative Example 3 A filter body of Comparative Example 3 was obtained in the same manner as Comparative Example 1, except that the calcium sulfite in the first filter portion was changed to calcium sulfite (S4) having an average particle size of 0.09 mm.

[0057] Comparative Example 4 A filter element of Comparative Example 4 was obtained in the same manner as in Prototype Example 3, except that calcium sulfite was not filled in the second filter portion.

[0058] [Table 1]

[0059] [Table 2]

[0060] [Evaluation items] <Free residual chlorine removal performance> The free residual chlorine and combined residual chlorine removal performance tests were conducted on each prototype and comparative filter as follows. The free residual chlorine removal performance test was conducted in accordance with JIS S 3201 (2010) household water purifier testing method. Water was passed through each filter at a water temperature of 20°C, a free residual chlorine concentration of 2 ppm (mg / L), and a flow rate of 2.5 L / min. The free residual chlorine concentration at the inlet and outlet of each filter was measured to calculate the removal rate. The water flow rate at which the removal rate fell below 80% was defined as the breakthrough point, and the water flow rate (L) until the breakthrough point was reached was measured.

[0061] <Removal of combined residual chlorine> For the combined residual chlorine removal performance test, ammonium chloride and sodium hypochlorite were added to activated carbon-filtered water, and the mixture was stirred to prepare a sample water with a combined residual chlorine concentration of 0.2 ppm (mg / L). Water was passed through each filter at a temperature of 20°C and a flow rate of 2.5 L / min. The combined residual chlorine concentration at the inlet and outlet of each filter was measured to calculate the removal rate. The breakthrough point was defined as the volume of water passed at which the removal rate fell below 80%, and the volume of water passed (L) until the breakthrough point was reached was measured. For both free and combined residual chlorine removal performance tests, chlorine concentration was quantitatively measured using DPD absorptiometry. The combined residual chlorine concentration was calculated by subtracting the free residual chlorine concentration from the total chlorine concentration. The combined residual chlorine removal performance per unit volume of the filter (L / mL) was also calculated.

[0062] <Amount of sulfite ions eluted> The amount of sulfite ions eluted (mg / L) 10 minutes after the start of water flow was measured and used as the initial amount of sulfite ions eluted. The sulfite ions contained in the water passed through each filter were measured using a high-performance liquid chromatograph (HPLC) (Shimadzu Corporation, "Prominence") by the calibration curve method. The analytical conditions are shown below. Detector: CDD-10A VP Column: Shim-pack IC-A3

[0063] The test and measurement results for each prototype and comparative example are shown in Tables 3 and 4. For comparative example 2, the first filter portion could not be molded, and therefore each test could not be performed, and this is indicated by "-" in the table.

[0064] [Table 3]

[0065] [Table 4]

[0066] [Results and Discussion] Based on the trends in all cases (except for Comparative Example 2, in which the filter body could not be formed), it appears that the removal performance of bound residual chlorine is proportional to the particle size of calcium sulfite, and that the removal performance improves as the particle size increases.

[0067] We compared prototypes 1, 2, 4, and 5, which vary the particle size of calcium sulfite in the second filter section. In this test, where the concentration of bound residual chlorine was low, prototypes 1 and 2, which use larger particle sizes of calcium sulfite in the second filter section, demonstrated better bound residual chlorine removal performance. It is clear that larger particle sizes of calcium sulfite tend to suppress the amount of sulfite ions eluted in the initial stage of water flow and maintain the amount of sulfite ions eluted for a long period of time. This is thought to be why the performance in removing bound residual chlorine was higher. Conversely, when the particle size of calcium sulfite in the second filter section was small, as in prototypes 4 and 5, the amount of sulfite ions eluted was large in the initial stage of water flow, preventing stable and continuous elution of sulfite ions and resulting in a short-term effect. Based on these findings, we suggest that the particle size of calcium sulfite used in the second filter section should be between 0.7 and 5.0 mm.

[0068] Furthermore, even in prototype 3, which does not contain calcium sulfite in the first filter section, it was found that good performance in removing bound residual chlorine was achieved because calcium sulfite with large particle size was used in the second filter section.

[0069] Comparative Examples 1 and 3, which did not include calcium sulfite in the second filter section, and Comparative Example 4, which did not include calcium sulfite in the first filter section, showed poor combined residual chlorine removal performance. Considering that Comparative Example 1 had a higher combined residual chlorine removal performance than Comparative Example 3 and the moldability of the wet filter, it is believed that a particle size of 0.1 to 0.5 mm is suitable for calcium sulfite to be incorporated into the first filter section.

[0070] Regarding the free residual chlorine removal performance, a certain level of performance was shown in all cases where the water flow test was conducted. In particular, the free residual chlorine removal performance of prototype 3 was higher than that of prototypes 1 and 2, so it is thought that the free residual chlorine removal performance improves as the amount of activated carbon added increases.

[0071] From the above, it was found that by using an activated carbon adsorbent as a free residual chlorine remover and calcium sulfite as a combined residual chlorine remover, it is possible to obtain a residual chlorine removal filter body with good residual chlorine removal performance. Furthermore, it was shown that by adjusting the particle size of calcium sulfite, good combined residual chlorine removal performance can be maintained for a long period of time. [Industrial Applicability]

[0072] The residual chlorine removal filter body of the present invention can maintain high residual chlorine removal performance, including both free and bound residual chlorine, for a long period of time by controlling the amount of sulfite ions eluted during water flow, making it suitable for applications such as removing residual chlorine from raw water, and also for filtering and preparing purified water for artificial dialysis. [Explanation of symbols]

[0073] 11 hollow cylindrical core member 20 Activated carbon adsorbent 21 Granular activated carbon 22 Fibrous activated carbon 23 Acrylic fiber binder 24 Calcium sulfite 25 Adsorbent 26 Slurry-coated area 30 Mixed slurry 35 Mold rod member 40 Dryer W water

Claims

1. a first filter portion obtained by mixing an activated carbon adsorbent and a fibrillated fiber binder in water to form a mixed slurry, adsorbing the mixed slurry onto a side surface of a hollow cylindrical core member while sucking the mixed slurry onto the side surface of the hollow cylindrical core member to form an adsorbed material, and then heating and drying the adsorbed material; and a second filter portion filled with calcium sulfite having an average particle size of 0.7 to 5.0 mm. A residual chlorine removal filter body.

2. 2. The residual chlorine removal filter body according to claim 1, wherein calcium sulfite having a particle size of 0.1 to 0.5 mm is further mixed with the mixed slurry.

3. A residual chlorine removal filter body as described in claim 1 or 2, in which the amount of sulfite ions eluted 10 minutes after the start of water flow is 5 to 20 mg / L.

4. 4. The residual chlorine removal filter body according to claim 1, wherein the activated carbon adsorbent is one or more of fibrous activated carbon, granular activated carbon, and powdered activated carbon.

5. 5. The residual chlorine removal filter body according to claim 1, wherein the activated carbon adsorbent has an iodine adsorption capacity of 800 to 2000 mg / g.

6. 6. The residual chlorine removal filter body according to claim 1, wherein the fibrillated fiber binder comprises acrylic fiber.

7. 7. The residual chlorine removing filter body according to claim 1, wherein the combined residual chlorine removing capacity is 50 L / mL or more.

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