Absorbent composite particle

Abstract

To aim to effectively utilize components with phosphorus adsorption functions to efficiently, that is, with good yield, control the size of the resulting adsorption composite particles, ensure that there are no adsorption materials that do not contribute to internal adsorption, achieve cost-effectiveness, and obtain phosphorus adsorption composite particles with sufficient strength.SOLUTION: A coating layer made of a binder is applied to the surface of granular carriers, and an adsorbent is arranged on this coating layer to form adsorbent composite particles. As the granular carrier, natural sand or artificial sand can be used. As the binder, cement selected from Portland cement, blended cement, or special cement can be used. As the adsorbent, a material capable of adsorbing phosphorus components can be used.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to adsorbent composite particles, and more particularly to adsorbent composite particles having an adsorbent disposed therein. [Background technology]

[0002] Industrial wastewater, domestic wastewater, agricultural wastewater, livestock wastewater, etc. contain components such as phosphorus that cause eutrophication. When these flow into rivers, lakes, marshes, oceans, etc., they cause the outbreak of red tides and the massive outbreak of blue-green algae. These wastewaters are usually treated at sewage treatment plants, but general sewage treatment does not necessarily remove nitrogen and phosphorus components sufficiently, so separate treatment is required to remove these components. The nitrogen components can be removed by biological treatment, followed by releasing the nitrogen gas into the atmosphere. On the other hand, phosphorus components become part of the sludge during biological treatment and are then treated by advanced treatment.

[0003] Phosphorus is an essential component of fertilizer, but the raw material for phosphorus, phosphate rock, is almost entirely imported, and the number of producing countries is limited. This raises the risk of problems such as rising prices for phosphate rock and resource depletion. In response to this, there is a demand in Japan to recover and reuse phosphorus components removed from sewage and other sources.

[0004] Methods for removing phosphorus components in sewage treatment include the coagulation and sedimentation method, in which the phosphorus components are precipitated and removed together with the sludge using coagulants such as metal salts or lime, and biological treatment, which utilizes the metabolism of microorganisms to control the anaerobic and aerobic conditions of activated sludge and concentrate and absorb the phosphorus to a high concentration.The phosphorus components concentrated by biological treatment can also be treated by the crystallization removal method, in which the phosphorus components are precipitated together with magnesium ions by crystallization.

[0005] The coagulation and sedimentation method requires a large amount of coagulant and produces a large amount of sludge, which must be treated. The biological treatment method requires careful management of the dissolved oxygen concentration and sludge management in the final sedimentation tank, and also requires the treatment of sludge with a high phosphorus content. These methods require the recovery of phosphorus components from the sludge, which is costly.

[0006] To address these issues, an adsorption method has been proposed, in which phosphorus is absorbed onto an adsorbent. This method uses a material with the ability to absorb phosphorus, which then absorbs and fixes the phosphorus onto the adsorbent, allowing it to be extracted from sewage, etc. By desorbing the phosphorus from the adsorbent, it is possible to efficiently recover the phosphorus.

[0007] As an adsorbent for such phosphorus components, a particulate phosphorus adsorbent obtained by calcining nickel hydroxide or coprecipitated hydroxide of nickel and other metals is known (Patent Document 1). However, the adsorption of phosphorus components in these particles occurs only on the surface of the adsorbent, and the interior of the particles does not contribute to the adsorption of phosphorus components.

[0008] In response to this, a porous granular phosphorus adsorbent is known, which is prepared by kneading and granulating phosphorus-adsorbing fine particles, calcium salt, water, and a highly water-absorbent polymer (Patent Document 2). Because this granular phosphorus adsorbent is porous, not only the phosphorus-adsorbing fine particles on the surface of the adsorbent but also the phosphorus-adsorbing fine particles inside the adsorbent can be effectively used for adsorption of phosphorus components. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-202453 [Patent Document 2] Japanese Patent Application Publication No. 9-141253 Summary of the Invention [Problem to be solved by the invention]

[0010] However, the adsorbent described in Patent Document 2 is gel-hardened by calcium salt, and is not strong enough, so there is a risk of it breaking down when used to adsorb phosphorus components. If it breaks down, the superabsorbent polymer, which is one of the components, may become a factor in increasing COD and BOD, which may increase the load on sludge treatment.

[0011] Furthermore, although various phosphorus adsorbents have been proposed, there is a demand for granular adsorbents for the convenience of using the adsorbent. To produce granular adsorbents, known methods include adding a binder to granulate the adsorbent or crushing a solidified mass to produce granules. However, these methods do not produce granules of uniform size, and therefore, in order to produce granules of the required size for use, a larger amount of granules is required, resulting in poor efficiency, i.e., poor yield, and high costs.

[0012] Therefore, the present invention has been made in consideration of these problems, and aims to obtain adsorbent composite particles of phosphorus components that effectively utilize components that have the function of adsorbing phosphorus components, can efficiently make the size of the obtained adsorbent composite particles uniform, i.e., with a good yield, eliminates the presence of adsorbents that do not contribute to adsorption inside, is cost-effective, and has sufficient strength. [Means for solving the problem]

[0013] As a result of extensive research, the inventors discovered that the above-mentioned problems can be solved by using an adsorbent material in which an adsorbent capable of adsorbing phosphorus components is arranged on the surface of a granular carrier via a binder, and thus arrived at the present invention. That is, the present invention has the following features.

[0014] [1] Adsorbent composite particles in which a coating layer made of a binder is disposed on the surface of a granular carrier, and an adsorbent is disposed on this coating layer. [2] The adsorbent composite particles according to [1], wherein the granular carrier is natural sand or artificial sand. [3] The adsorbent composite particles according to [1] or [2], wherein the binder is a cement selected from Portland cement, blended cement, and special cement. [4] The adsorbent composite particles according to [1] or [2], wherein the adsorbent is a material that adsorbs phosphorus components. [Effects of the Invention]

[0015] The adsorbent composite particles of the present invention have a coating layer made of a binder disposed on the surface of a granular carrier, and an adsorbent disposed on this coating layer. Therefore, the adsorbent is disposed on the surface of the adsorbent composite particles, and most of the adsorbent can be used to adsorb target substances such as phosphorus components. Furthermore, since it is easy to standardize the size of the granular carrier, it is easy to standardize the size of the resulting adsorbent composite particles to the desired size. Furthermore, since it is easy to obtain adsorbent composite particles of uniform size, adsorption efficiency can be further improved, and the production of adsorbent composite particles of different sizes can be reduced, thereby saving resources and eliminating unnecessary costs. In addition, the adsorbent composite particles have a binder disposed on the surface of a granular carrier, and natural sand or artificial sand is used as the granular carrier and cement or the like is used as the binder. Therefore, the adsorbent composite particles are less likely to shatter or crack even when colliding with each other in water, etc., and have sufficient strength to withstand repeated use. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below. The adsorbent composite particles of the present invention (hereinafter sometimes simply referred to as "composite particles") are composite particles in which a coating layer made of a binder is disposed on the surface of a granular carrier, and an adsorbent is disposed in this coating layer.

[0017] The granular carrier is a granular carrier that serves as a base material, and is not particularly limited as long as it is granular. The size of the granular carrier is not particularly limited, but it is preferable to regulate the size of the granular carrier within a predetermined range, specifically, within ±30% of the reference particle size, preferably within ±20% of the reference particle size. By regulating the size within this range, it becomes possible to regulate the size of the composite particles according to the present invention within the same range, thereby improving the adsorption efficiency. Incidentally, a method using a sieve can be mentioned as a method for regulating the size of the granular carrier within the above range. This method allows composite particles of the desired size range to be obtained efficiently, i.e., with a good yield. The reason why the adsorption efficiency can be improved by making the sizes of the composite particles of the present invention uniform within the same range is that sufficient and uniform gaps can be secured between the composite particles, allowing the phosphorus-containing water to enter the gaps evenly, thereby ensuring a uniform space for adsorbing the phosphorus component. In other words, it is believed that this is because there is no unevenness in the flow of the phosphorus-containing water, and similar adsorption conditions can be obtained for all the composite particles.

[0018] Examples of the granular carrier include natural sand and gravel, artificial sand and gravel, metal particles, and metal oxide particles. Of these, natural sand and gravel, which are easily available, and artificial sand and gravel, which can be used as waste, are preferred. The natural sand and gravel refers to sand, stone, and gravel produced by crushing rocks in nature, such as silica sand, etc. The artificial sand and gravel refers to sand, stone, gravel, etc. produced by artificially crushing naturally collected rocks, or granular material made of glassy or crystalline solidified material obtained by heating waste to 1300°C or higher, pyrolyzing, gasifying, or burning the organic matter in the waste, melting the resulting inorganic residues, and then cooling and solidifying them.

[0019] The binder is a material that can be coated on the surface of the granular carrier to form a coating layer, and has a bonding effect of bonding the binder and the adsorbent. Examples of such binders include inorganic binders and organic binders. Examples of the inorganic binders include cement, and examples of the organic binders include organic adhesives. Among these, inorganic binders are preferred from the viewpoint of the possibility of disposing of the resulting composite particles after use. The cement refers to a hydraulic pulverized material containing cement clinker and gypsum (calcium sulfate), and examples thereof include Portland cement, blended cement, special cement, etc. Note that cement clinker refers to alite (tricalcium silicate), belite (dicalcium silicate), aluminate (calcium aluminate), etc. Portland cement is a cement that mainly contains the above-mentioned cement clinker and gypsum, and blended cement refers to cement that has blast furnace slag, fly ash, silica-based admixtures, etc. added to these. Examples of the special cement include white Portland cement, alumina cement, ultra-fast hardening cement, colloidal cement, oil well cement, and low-heat cement. Among these, cement that does not require heating and undergoes a natural hardening reaction when water is added can be preferably used. Portland cement and blended cement are cements that do not require heating and undergo a natural hardening reaction when water is added.

[0020] The adsorbent refers to a material capable of adsorbing phosphorus components (phosphorus component adsorbent), and examples thereof include porous alumina (activated alumina), cobalt oxide, and zirconium oxide. The size of this adsorbent is preferably smaller than the granular carrier, since it is bonded to the granular carrier via the binder. Specifically, it is preferably 0.1 mm or less. By making it 0.1 mm or less, it is possible to maintain a sufficient state of adsorption capacity, and a large amount of adsorbent can be bonded to the surface of the granular carrier via the binder, thereby achieving a sufficient adsorption effect. This adsorbent can be in powder or granular form. Powder adsorbents can be used as is, but can also be sieved if necessary. Furthermore, even in the case of granular or powder adsorbents, if the particle size of the powder is slightly larger, it can be obtained by crushing and sieving. The phosphorus component refers to an atom or compound containing a phosphorus atom, and examples thereof include phosphorus atoms, phosphoric acids such as orthophosphoric acid, phosphates, and organic phosphorus compounds.

[0021] Next, a method for producing composite particles according to the present invention will be described. First, the binder is brought into a state where it exhibits adhesiveness. Specifically, when cement is used, water is added to the cement to bring about a hardening reaction. Next, the granular carrier is added thereto and stirred and mixed to form a coating layer made of the binder on the surface of the granular carrier. Next, while the bonding property of the binder is maintained, for example, if the binder is cement, before the hardening reaction of the cement is completed, an adsorbent is added and mixed by stirring, so that the adsorbent is bonded to the binder, thereby producing composite particles.

[0022] As a specific example of the manufacturing method, an example using natural sand and gravel as the granular carrier, Portland cement (hereinafter sometimes simply referred to as "cement") as the binder, and activated alumina powder as the adsorbent will be described. First, water is added to the cement and stirred, then natural sand and gravel are added and stirred and mixed to coat the surfaces of the natural sand and gravel with cement. Regarding the amount of water added to cement, if the amount of water is too much, there is a risk that the natural sand particles will bond together with the cement when the natural sand is added and stirred and mixed. On the other hand, if the amount of water is too little, the resulting cement powder will not be wetted by water, making it difficult to cause a sufficient hardening reaction. For these reasons, it is preferable to use an amount of water that does not result in wetted cement powder and that does not cause the natural sand particles to bond together with the cement. Specifically, although it depends on the amount of natural sand used, a water amount of 40% by weight or more and 60% by weight or less is preferred. Furthermore, if the particles of natural sand and stone are bonded together by cement, the bond can be released by adding a small amount of dry cement powder and stirring, resulting in a single aggregate of composite particles.

[0023] The amount of cement relative to the natural sand and stone can be set according to the amount of cement you want to coat on the surface of the natural sand and stone. For example, if you want to coat the natural sand and stone with 10% by weight of cement, add an appropriate amount of water to 10% by weight of the cement and mix, then add the natural sand and stone and mix again, thereby obtaining independent composite particles (with a cement content of 10% by weight of the sand and stone). Note that if the natural sand and stone particles are bonded together by cement and you add a small amount of cement powder to break the bonds, the amount of the small amount of cement powder used to break the bonds is also included in the amount of cement used. The amount of cement coated on the natural sand and stone is preferably 5% by weight or more, and more preferably 7% by weight or more, and is preferably 30% by weight or less, and more preferably 25% by weight or less. By keeping the amount within this range, a sufficient amount of the adsorbent can be disposed in the coating layer, and the resulting composite particles can fully exhibit their phosphorus component adsorption effect.

[0024] The amount of activated alumina used is preferably 3% by weight or more, and more preferably 5% by weight or more, based on the natural sand and gravel used. It is also preferably 30% by weight or less, and more preferably 20% by weight or less. By keeping the amount within this range, all of the activated alumina can be distributed in the coating layer, and the resulting composite particles can fully exhibit their phosphorus component adsorption effect.

[0025] After the composite particles according to the present invention have adsorbed phosphorus components, the adsorption ability can be regenerated by desorbing the phosphorus components, and the composite particles can be reused. As a regeneration method, for example, the phosphorus component is desorbed by contacting the catalyst with an alkaline aqueous solution such as a 2% to 4% by weight aqueous solution of sodium hydroxide. Furthermore, when the phosphorus adsorption effect of the composite particles decreases, the coating layer and adsorbent can be removed from the surface of the composite particles using a surface grinding machine or the like, thereby recovering the granular carrier, and then reapplying a coating layer made of a binder and an adsorbent to form composite particles, thereby enabling the granular carrier to be reused. As a result, only the coating layer and adsorbent removed by the surface grinding machine or the like are discarded, thereby significantly reducing waste. Furthermore, this recycling method is also useful from the perspective of energy conservation, as it does not require high-temperature heating. Furthermore, even if the composite particles according to the present invention are discarded, the granular carriers that serve as the cores can be returned to nature because they are made of natural or artificial sand and gravel. [Example]

[0026] The present invention will now be described in more detail with reference to examples.

[0027] [Physical Properties] [Measurement of phosphorus concentration in water] Measurement was carried out according to the molybdic acid blue method of JIS K-0102. As will be described later, in the phosphorus adsorption test, phosphoric acid (Kishida Chemical Co., Ltd.: primary phosphoric acid, concentration 85% by weight or more) was diluted to a predetermined concentration and used, so all of the phosphorus contained was phosphorus in the form of phosphate. For this reason, a decomposition step using ammonium peroxodisulfate, which decomposes organic phosphorus compounds to phosphorus in the form of phosphate, was not performed.

[0028] [Phosphorus component adsorption test] 100 ml of a phosphoric acid-containing solution adjusted to a predetermined concentration was placed in a 300 ml beaker, and a predetermined weight of an adsorbent sample such as composite particles was added. After stirring with a stirrer for a predetermined time, the test solution was filtered through a membrane filter (pore size: 0.45 μm), and the phosphorus concentration of the obtained test solution was measured.

[0029] [Calculating the thickness of the coating layer] The thickness (Tc) of the coating layer made of the binder was calculated by the following method. The radius of one granular carrier was r, the amount of granular carrier used was W parts by weight, the specific gravity of the granular carrier was ρs, the specific gravity of the binder was ρc, and the amount of binder coated on the granular carrier was N% by weight of the granular carrier. First, the surface area (Ss) of one granular carrier and the volume (Vs) of one granular carrier are: Ss=4πr 2 , Vs=4 / 3×πr 3 , This becomes: The volume (Vw) of the granular carrier in W parts by weight is: Vw=W / ρs From this, the total surface area (Sw) of W parts by weight of the granular carrier is ·Sw={(W / ρs) / (4 / 3×πr 3 )}×4πr 2 , This becomes: Next, the thickness (Tc) of the coating layer coated on the granular carrier is Tc = volume of coating layer / area of ​​coating layer The volume of the coating layer (Tv) is ·Tv={W×(N / 100)} / ρc, is. When the thickness (Tc) of the coating layer is thin, the area of ​​the coating layer can be regarded as the surface area of ​​the granular carrier, and the volume can be calculated by weight / specific gravity. Therefore, the thickness (Tc) of the coating layer can be calculated by the following formula. Tc = volume of coating layer / surface area of ​​granular support =Tv / Sw =[{W×(N / 100)} / ρc] / [{(W / ρs) / (4 / 3×πr 3 )}×4πr2 ] =(N·ρs·r) / (300ρc)

[0030] [raw materials] Granular activated alumina...Kishida Chemical Co., Ltd.: Reagent (aluminum oxide, activated type (average particle size 5 mm)) Cement: Ordinary Portland cement (product name) manufactured by Taiheiyo Cement Corporation Silica sand: Natural silica sand with varying particle sizes. Available in two types: average particle size 2mm (1.7mm-2.4mm) and average particle size 3mm (2.4mm-3.4mm).

[0031] [Reference example] [Preparation of activated alumina powder and hardened cement granules] The granular activated alumina was crushed in a mortar and sieved to obtain activated alumina powder of 0.1 mm or less. Furthermore, 40 parts by weight of water was added to 100 parts by weight of the cement, and the mixture was stirred and allowed to harden. If moisture remained, cement powder was added little by little, and if there was any cement powder that was not wet with water, water was added little by little until there was no unwetted cement or excess moisture. The hardened product was crushed in a mortar to obtain hardened cement granules, which were then washed with water to remove unhardened cement components.

[0032] [Verification of phosphorus adsorption performance of activated alumina powder, granular activated alumina, and hardened cement granules] 100 ml of 50 ppm phosphoric acid was prepared as a test solution and placed in a 300 ml beaker. 0.5 g of activated alumina powder, 0.5 g of granular activated alumina, and 0.5 g of hardened cement granules were added to the test solution and stirred. Portions of each test solution were taken after 5 minutes, 10 minutes, 30 minutes, 1 hour, and 2 hours, and filtered through a membrane filter. The phosphorus concentration of the recovered test solution was measured to examine the change in phosphorus concentration in the test solution as a function of stirring time. The results are shown in Table 1.

[0033] [Table 1]

[0034] As a result, it was found that activated alumina powder, granular activated alumina, and hardened cement granules all have the ability to adsorb phosphorus components, and that adsorption begins early after contact with phosphoric acid, with adsorption completing within about an hour. Furthermore, when activated alumina powder and granular activated alumina were compared, it was found that even when the same amount was used, the surface area increased and the amount of adsorption increased when the activated alumina was powdered.

[0035] [Phosphorus adsorption capacity of granules (coated granules) with a coating layer made of a binder on the surface of granular carriers] 40% water by weight was added to the cement and stirred, and then 100 parts by weight of silica sand with an average particle size of 2 mm was added and mixed. If there were any areas that were not wetted by the water, water was added in small amounts until there were no more unwetted areas. On the other hand, if the cement-coated silica sand particles were bonded together, cement powder was added in small amounts until the bonds were broken and the particles became aggregates of single particles, eliminating particles consisting only of cement. The cement content (cement coating amount) of the resulting silica sand granules, with a coating layer made of cement on the surface (hereinafter referred to as "coated granules"), was 10, 20, or 30 parts by weight per 100 parts by weight of silica sand. Furthermore, hardened cement granules were produced by the above-mentioned method. These hardened cement granules were separated using a sieve, and those with an average particle size of 2 mm were used. Five ml of the three types of coated granules and hardened cement granules were added to the test solution (phosphorus concentration 50 ppm) and stirred, and the phosphorus concentration of the test solution was measured after 60 minutes and 120 minutes. The results are shown in Table 2 below. The thickness of the coating layer was calculated assuming a particle size (r) of 2 mm, a specific gravity of the silica sand (ρs) of 2.65, and a specific gravity of the hardened cement particles (ρc) of 1.8 to 2.2 (this is shown as a range because it varies depending on the mixing ratio of cement and water).

[0036] [Table 2]

[0037] As a result, it was found that the amount of adsorption of phosphorus components (phosphate) was lowest when the amount of cement coating on the coated granules was 10% by weight. Furthermore, even when the amount of cement coating on the coated granules was increased to 10%, 20%, and 30% by weight, the amount of adsorption of phosphorus components did not increase in proportion to the amount of cement coating. Furthermore, the amount of phosphorus components adsorbed by the hardened cement granules was not significantly different from that of the coated granules when the cement coating amount was 30% by weight. From these findings, it is thought that the adsorption of phosphorus components (phosphate) occurs near the surface, and that there is almost no adsorption inside.

[0038] [Examples 1 to 5] [Production of adsorbent composite particles] Composite particles were produced in the same manner as the coated granules, except that in the production of the coated granules, water was added to cement and stirred, and then silica sand was added and stirring and mixing began, and then the activated alumina powder was added. The amount of silica sand used was 100 parts by weight, and the amount of water added to the cement was initially 40% by weight. The average particle diameter of the silica sand used was 2 mm and 3 mm. Furthermore, the amount of cement mixed into the composite particles (cement coating amount) was 7 parts by weight and 15 parts by weight, respectively, per 100 parts by weight of silica sand. The amount of activated alumina powder used was 5 parts by weight and 10 parts by weight per 100 parts by weight of silica sand. 5 ml or 10 ml of each composite particle was added to the test liquid (phosphorus concentration 50 ppm) and stirred, and the phosphorus concentration of the test liquid was measured after 60 minutes and 120 minutes. The results are shown in Table 3 below. The thickness of the coating layer was calculated assuming a particle size (r) of 2 mm or 3 mm, a specific gravity of silica sand (ρs) of 2.65, and a specific gravity of hardened cement particles (ρc) of 1.8 to 2.2.

[0039] [Reference example 1] 5 ml of granular activated alumina (average particle size 5 mm) was added to the test solution (phosphorus concentration 50 ppm) and stirred, and the phosphorus concentration of the test solution was measured after 60 minutes and 120 minutes. The results are shown in Table 3 below.

[0040] [Comparative Examples 1 to 4] Next, hardened cement granules were produced by the above-mentioned production method. These hardened cement granules were separated using a sieve to produce granules with an average particle size of 2 mm (Comparative Example 1) and granules with an average particle size of 3 mm (Comparative Example 3). Two types of coated granules were also produced using the method described above. One had an average silica sand particle size of 2 mm and a cement coating amount of 20 wt% (Comparative Example 2). The other had an average silica sand particle size of 3 mm and a cement coating amount of 10 wt% (Comparative Example 4). 5 ml of each of the particles was added to the test liquid (phosphorus concentration 50 ppm) and stirred, and the phosphorus concentration of the test liquid was measured after 60 minutes and 120 minutes. The results are shown in Table 3 below. The thickness of the coating layer was calculated assuming a particle size (r) of 2 mm or 3 mm, a specific gravity of silica sand (ρs) of 2.65, and a specific gravity of hardened cement particles (ρc) of 1.8 to 2.2.

[0041] [Table 3]

[0042] As a result, by comparing composite particles of the same size with particles that do not contain activated alumina powder (cement hardened particles or coated particles) (comparison between Examples 1-2 and Comparative Examples 1-2, and comparison between Examples 3-4 and Comparative Examples 3-4), it was found that even if the amount of cement coating was small, the inclusion of activated alumina powder resulted in a higher phosphorus component (phosphate) adsorption capacity. Furthermore, a comparison between Examples 1 and 2 and Examples 3 and 4 revealed that the greater the amount of activated alumina powder, the higher the phosphorus component (phosphate) adsorption capacity.

[0043] Furthermore, comparing Example 1 with Example 3, and Example 2 with Example 4, it was found that the smaller the particle size of the silica sand used, the higher the phosphorus component (phosphate) adsorption capacity. Since the amount (volume) of particles used is the same, the smaller the particle size of the silica sand, the larger the total surface area. Therefore, even if the same amount of activated alumina powder is used, it is thought that the larger the total surface area, the higher the phosphorus component (phosphate) adsorption capacity. Furthermore, compared with granular activated alumina (Reference Example 1), the composite particles of Examples 1 and 2 exhibited high phosphorus component (phosphate) adsorption capacity, but the composite particles of Examples 3 and 4 exhibited low phosphorus component (phosphate) adsorption capacity. This indicates that the average particle size of silica sand affects the phosphorus component (phosphate) adsorption capacity.

[0044] The amount of activated alumina in the composite particles of Example 4 is twice that of the composite particles of Example 5. On the other hand, the amount of particles used in Example 5 is twice that of Example 4. Therefore, although Examples 4 and 5 contain the same amount of activated alumina powder, Example 5 was found to have a higher phosphorus component (phosphate) adsorption capacity. Since Example 5 uses a larger amount of particles, it has a larger total surface area. Therefore, even if the same amount of activated alumina powder is used, it is thought that the one with a larger total surface area will have a higher phosphorus component (phosphate) adsorption capacity.

Claims

1. Adsorbent composite particles in which a coating layer made of a binder is disposed on the surface of a granular carrier, and an adsorbent is disposed on this coating layer.

2. 2. The adsorbent composite particles according to claim 1, wherein the granular carrier is natural sand or artificial sand.

3. 3. The adsorbent composite particle according to claim 1, wherein the binder is a cement selected from the group consisting of Portland cement, blended cement, and special cement.

4. 3. The adsorbent composite particle according to claim 1, wherein the adsorbent is a material that adsorbs a phosphorus component.

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