JP2013184122A - Granular phosphorus adsorbent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and efficiently recover phosphorus contained in a large quantity of waste water, such as sewage, and pointed out as a depleting resource while recycling the phosphorus as the resource at low cost.SOLUTION: A granular phosphorus adsorbent contains: magnesium ions and iron ions; a plurality of phosphorus adsorbent granules composed of layered double hydroxides having hydrotalcite-like structures; and a binder composed of natural high molecular weight polysaccharides in which the plurality of phosphorus adsorbent granules are dispersed. The pluralities of phosphorus adsorbent granules are granulated by using the binder.

Description

  Embodiments of the present invention relate to a particulate phosphorus adsorbent.

  In recent years, due to the rapid globalization of economic activities, global environmental pollution and water pollution have become serious problems. In addition, worldwide production activities simultaneously lead to resource depletion, and the types of elements recognized as rare elements tend to increase. Recently, the reduction of phosphorus ore on a global scale has progressed, and in recent years phosphorus has also been recognized as a rare element. Phosphorus is an essential element for the growth of organisms and is an important component of fertilizer. Also, it is widely used industrially as phosphoric acid or phosphate as a plating chemical or a surface treatment agent.

  On the other hand, strict emission standards for phosphorus have been established as measures against eutrophication problems in closed waters such as lakes and bays. As a means of removing phosphorus from water (actually in the form of phosphate ions), magnesium compound or calcium compound is added as a flocculant, and magnesium ammonium phosphate (MAP) or hydroxyapatite (HAP) And the like, and a method of precipitating and precipitating a phosphate such as) is widely known. However, in such a method, it takes a long time to form a precipitate, so the processing time is long. In addition, since phosphate is a hard-to-precipitate suspension, in order to quickly precipitate phosphate. It is necessary to form flocs, and as a result, a large amount of sludge is generated.

  As a result, in order to process a large amount of sludge, it is necessary to increase the size of the processing equipment, so there is a problem that the cost load increases. Further, since various ionic components are taken into the floc by using the flocculant, the cost for separating them from the sludge is also high. For these reasons, sludge is also often treated as an industrial waste without being reused.

  In other words, when removing phosphorus in water by conventional methods, for example, coagulation and precipitation due to the addition of calcium salt has a number of inefficiencies such as much processing time, large equipment, and the need for sludge treatment. It can be said that.

  In view of such problems, in recent years, many new materials for water purification have been proposed. For example, regarding phosphorus removal, an adsorbent having a hydrotalcite structure has been proposed as a high-performance phosphorus remover (see Non-Patent Document 1, for example). Hydrotalcite is a kind of mineral layered inorganic compound, and has a mechanism to remove phosphorus (phosphate ion) in water by anion exchange between phosphate anion and anion contained between layers, and high phosphorus removal ability Has been reported to have

  On the other hand, if the adsorbent after adsorbing phosphorus is treated as industrial waste, it results in an extra cost and is not superior to the above-mentioned technology. It is an essential requirement. For reuse, it is necessary to release the adsorbing substance, that is, phosphorus from the adsorbent. The adsorbent after releasing phosphorus can be used again for the adsorption removal of phosphorus as described above. The detached phosphorus itself can be reused as a chemical fertilizer, for example, by mixing it with other chemical components.

  Regarding the release of phosphorus, a magnesium desorbing solution containing at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts, excluding alkali metal carbonates and alkaline earth metal carbonates, and magnesium salts excluding magnesium carbonate After the continuous treatment with the phosphorus desorption liquid composed of, the pH of the treatment liquid is adjusted as necessary, and if necessary, further mixed with at least one selected from the group consisting of an aqueous solution of ammonia and an ammonium salt, A technique for producing and separating magnesium phosphate, magnesium ammonium phosphate and the like by precipitation is disclosed (Patent Document 1).

  However, in the above-described technique, a multi-step process such as treatment with a phosphorus desorbing agent, pH adjustment, ammonia treatment, and precipitation and precipitation of phosphate is essential, resulting in an increase in cost during phosphorus desorption. As a result, there has been a problem that the production cost is increased in using the detached phosphorus as a fertilizer. That is, if the phosphorus collected by the adsorbent is to be reused as fertilizer, the result will be an increase in the price of the fertilizer distributed, and the reuse of the collected phosphorus as a fertilizer will be hindered.

Journal of Japan Society on Water Environment Vol. 22, No. 875-881 (1999)

Japanese Patent No. 4164681

  An object of the present invention is to easily and efficiently recover phosphorus that is contained in a large amount in wastewater such as sewage and that is depleted as a resource, and to reuse it as a resource at low cost.

  The granular phosphorus adsorbent according to the embodiment includes a plurality of phosphorus adsorbent particles composed of layered double hydroxides containing magnesium ions and iron ions and exhibiting a hydrotalcite-like structure, and a natural dispersion in which the plurality of phosphorus adsorbent particles are dispersed. And a binder made of a high molecular polysaccharide. The plurality of phosphorus adsorbent particles are granulated with the binder.

(Phosphorus adsorbent)
The phosphorus adsorbent in the embodiment includes a layered double hydroxide containing magnesium ions and iron ions and exhibiting a hydrotalcite-like structure.

  The layered double hydroxide has a layered structure, and specifically has a structure in which a plurality of layers in which octahedrons centering on magnesium ions and iron ions are two-dimensionally connected are stacked. . Magnesium ions and iron ions are located at the same crystal site in the above-described structure, and are in a substitution relationship with each other. Further, in such a state, the layered double hydroxide becomes positively charged, so the anions constituting the layered double hydroxide are interposed between the layers, and the electrical neutrality is maintained as a whole. Yes.

The composition component of the layered double hydroxide is not particularly limited as long as the object of the present embodiment can be achieved. For example, the general formula [Mg ²⁺ _1-x Fe ³⁺ _x (OH) _m ] (An ⁻ ) _{x / n} · yH ₂ O (0.05 ≦ x ≦ 0.34, 0.5 ≦ m ≦ 3.4, An ⁻ is an n-valent anion, and y is a natural number). It can be set as such a composition component. In this case, as described above, the layered double hydroxide is formed by laminating a plurality of layers in which octahedrons centering on magnesium ions (Mg ²⁺ ) and iron ions (Fe ³⁺ ) are two-dimensionally connected. Maintains an electrical neutrality through anions such as sulfate ions (SO ₄ ²⁻ ) and nitrate ions (NO ₃ ³⁻ ).

In addition, when a layered double hydroxide has a composition component as described above, the following advantages can be achieved. That is, the general formula [Mg ²⁺ _1-x Fe ³⁺ _x (OH) _m ] (An ⁻ ) _{x / n} · yH ₂ O (0.05 ≦ x ≦ 0.34, 0.5 ≦ m ≦ 3.4) The compound represented by An ⁻ is an n-valent anion and y is a natural number) has a so-called hydrotalcite structure.

The hydrotalcite is represented by, for example, the general formula [Mg ₃ Al (OH) ₈ ] 1 / 2CO ₃ ² · 2H ₂ O, and has an octahedron (brucite layer) centered on magnesium ions. Layers that are two-dimensionally connected and in which some magnesium ions are replaced with aluminum ions are stacked to form a layered structure. Carbonate ions and crystal water exist between the layers. It is known that hydrotalcite having such a structure has a property that anions between layers exchange with other anions.

Therefore, the layered double hydroxide in this embodiment has a composition component represented by the above general formula and exhibits a hydrotalcite structure, whereby sulfate ions ( SO ₄ ²⁻ ) and nitrate ions (NO ₃ ³⁻ ) can be exchanged for phosphate ions (H ₂ PO ₄ ⁻ , HPO ₄ ²⁻ , PO ₄ ^3−, etc.) contained in the waste water. Become. As a result, the adsorption and recovery of phosphate ions in the waste water can be effectively performed.

  Furthermore, in this embodiment, since the layered double hydroxide contains magnesium ions, when the layered double hydroxide is immersed in the wastewater, the magnesium ions constituting the layered double hydroxide are drained. Elute in. As a result, phosphate ions present in the wastewater, and ammonium ions and carbonate ions also present in the wastewater are magnesium ions eluted as described above, for example, ammonium magnesium phosphate and magnesium phosphate and magnesium carbonate. And a complex oxide is produced and precipitates in the waste water. Therefore, it is possible to remove phosphate ions from the waste water by removing the generated precipitate.

  Thus, the phosphorus adsorbent of the present embodiment can adsorb and remove phosphate ions in waste water by ion exchange with anions existing between layers of the layered double hydroxide of the phosphorus adsorbent, Magnesium ions in the layered double hydroxide are eluted into the wastewater, so that a precipitate containing phosphate ions is generated, and by removing this, the phosphate ions can be removed from the wastewater. Therefore, the phosphorus adsorbent of this embodiment can remove phosphate ions in the waste water with high efficiency.

  The phosphorus adsorbent in the present embodiment has a layered hydroxide structure in the basic skeleton, and as described above, octahedral hydroxides centered on magnesium ions and iron ions are two-dimensionally linked. A structure in which a plurality of layers are stacked is adopted. Therefore, the phosphorus adsorbent in this embodiment is different from the conventional hydrotalcite-like compound in that the conventional layered hydroxide is based on ion exchange between layers, and the octahedral hydroxide itself is The octahedral hydroxide is largely involved in the adsorption in the present embodiment, whereas it is hardly involved in the adsorption.

  The phosphorus adsorbent of the present embodiment is, for example, fine particles having an average particle diameter of 1 μm to 1000 μm, in other words, powder, and is difficult to handle with the phosphorus adsorbent alone, and is further packed in the column of the adsorption system. There is a disadvantage that clogging is likely to occur. Therefore, in the present embodiment, a particulate phosphorus adsorbent is granulated using a binder as described below.

  In addition, the said average particle diameter can be measured by the laser diffraction method, for example. Specifically, it can be measured by a SALD-DS21 type measuring device (trade name) manufactured by Shimadzu Corporation.

  The layered double hydroxide phosphorus adsorbent containing magnesium ions and iron ions and having a hydrotalcite-like structure described above is basically obtained by hydrothermal reaction between a compound containing magnesium and a compound containing iron. Can be manufactured. Although the compound which can be used as a raw material here is not specifically limited, For example, the chloride, carbonate, nitrate, sulfate, etc. of magnesium or iron are mentioned. At this time, the pH of the reaction solution is preferably alkaline. Such a reaction can be carried out under normal pressure or under high pressure using an autoclave or the like.

  The reaction conditions are selected according to the structure and particle size of the target layered double hydroxide, but the reaction is generally conducted at 25 to 200 ° C, preferably 60 to 95 ° C. The pressure may be normal pressure, or may be increased or reduced using an autoclave or the like, for example, 0.01 to 2.0 MPa.

(Binder)
In the particulate phosphorus adsorbent of the embodiment, the particulate (powder) phosphorus adsorbent is dispersed in a binder composed of a natural polymer polysaccharide, and the adjacent phosphorus adsorbents are bonded with the binder. Substantially granulate the phosphorus adsorbent.

  In the present embodiment, the binder used for granulation is a natural polymer polysaccharide. Natural polymer polysaccharides are polymers in which monosaccharides are used as constituent units and they are linked in a chain. Many natural polymeric polysaccharides form hydrogels when treated under appropriate conditions. By dispersing a particulate (powdered) phosphorus adsorbent in the hydrogel, a granulated product of the phosphorus adsorbent is formed. The particulate (powdered) phosphorus adsorbent is retained in the granulated product, and the granulated product is retained in its original form as long as the natural polymer polysaccharide is not decomposed to constitute a so-called granular phosphorus adsorbent. It will be.

  The particle size of the granular phosphorus adsorbent obtained by granulation is, for example, an average particle size of 500 μm to 5000 μm, which is several times to several thousand times larger than the above-described particulate (powdered) phosphorus adsorbent. Become. Therefore, handling is facilitated, and further, it is possible to prevent the disadvantage that clogging or the like is likely to occur when packed in the column of the adsorption system.

  The average particle diameter can be measured, for example, by a laser diffraction method. Specifically, it can be measured by a SALD-DS21 type measuring device (trade name) manufactured by Shimadzu Corporation.

  Natural polymer polysaccharides are hydrophilic because they have a polar functional group in the molecule, and are characterized by being easily permeable to water and phosphate ions contained in water. Therefore, it is possible to form a granulated product without impairing the performance of the phosphorus adsorbent. That is, even when the above phosphorus adsorbent is granulated with a binder composed of natural polymer polysaccharide, when the obtained granular phosphorus adsorbent is immersed in waste water, each particulate phosphorus adsorbent is, for example, High phosphorus adsorption performance is exhibited without impairing the adsorption characteristics derived from the layered double hydroxide.

  In addition, natural polymer polysaccharides are naturally derived components that do not adversely affect the environment when released into the environment. In particular, when sprayed directly onto farmland such as fields, microorganisms that express enzymes contained in soil Is gradually decomposed by. Therefore, after adsorbing phosphorus (phosphate ions) in the wastewater by the granular phosphorus adsorbent after granulation, the granular phosphorus adsorbent is sprayed as it is on the farmland without performing the removal treatment of phosphorus from the granular phosphorus adsorbent. By doing so, only phosphorus as fertilizer remains.

  As a result, although the phosphorus adsorbent cannot be reused for phosphorus adsorption, it does not require a desorption operation of the adsorbed phosphorus, so that it can be inexpensively reused as a phosphorus resource. That is, phosphorus that is contained in a large amount in wastewater such as sewage and that is depleted as a resource can be easily and efficiently recovered and reused as a resource at low cost.

  Examples of the natural polymer polysaccharide include agar, cellulose, chitin, chitosan, purified agarose, gellan gum, and agar is particularly preferable. Agar is made from seaweeds such as plovers and sea cucumbers as raw materials. It has the property of being dissolved by heating and then solidifying by cooling, and can easily form a granulated product by controlling the temperature. .

  For example, when producing a granular phosphorus adsorbent which is a granulated product as a binder for the above-described particulate (powder) phosphorus adsorbent, agar is mixed with water and a phosphorus adsorbent at 100 ° C. It dissolves by heating to the above, and then it is cooled and solidified. In order to form a uniform hydrogel, the dissolution temperature is desirably 105 ° C. or higher and 130 ° C. or lower.

  Note that agarose, which is a constituent of agar, is characterized by being hardly decomposed by most organisms, and there is little possibility that the granulated material will collapse due to biodegradation while being applied to the adsorption system. However, when sprayed on farmland, there are microorganisms that express an enzyme that breaks down agar in the soil. Will not be adversely affected.

  Further, the content of the particulate (powder) phosphorus adsorbent in the binder is not particularly limited as long as the phosphorus adsorbent is granulated by the binder to form a granular phosphorus adsorbent. For example, the content of the phosphorus adsorbent can be 100 to 1500 parts by mass with respect to 100 parts by mass of the binder. When there is less content of a phosphorus adsorbent than 100 mass parts, there exists a possibility that the phosphorus adsorption capacity of the granular phosphorus adsorbent obtained may fall. On the other hand, when the content of the phosphorus adsorbent is more than 1500 parts by mass, the amount of the binder with respect to the phosphorus adsorbent is insufficient, granulation cannot be performed, and it becomes difficult to obtain a granular phosphorus adsorbent. There is.

  The binder of this embodiment can include an alginate. Alginate is a kind of polysaccharide mainly contained in brown algae and is a naturally derived substance. Since uronic acid, which is a structural unit of alginic acid, has a carboxyl group, it has cation exchange properties, and particularly has a property of strongly binding to a divalent cation such as magnesium ion or calcium ion.

  When the particulate (powdered) phosphorus adsorbent is composed of layered double hydroxides as described above and contains magnesium ions, the magnesium ions are in the form of a granular phosphorus adsorbent (granulated product) due to the concentration gradient. If it moves in the binder from the surroundings towards its surface but does not contain alginate ions, it is only the physical barrier that constitutes the binder, for example the hydrogel skeleton, that limits the migration of magnesium.

  In binders containing alginate, magnesium ions bind to alginate ions, so magnesium ions are retained at a certain rate inside the granular phosphorus adsorbent (granulated product), and the granular phosphorus adsorbent is drained. Even when immersed therein, the proportion of magnesium ions eluted from the granular phosphorus adsorbent can be stopped to some extent, and elution to the outside of the granulated product is suppressed.

  That is, when the binder does not contain an alginate, when the granular phosphorus adsorbent is immersed in the waste water, magnesium ions from the particulate phosphorus adsorbent composed of the layered double hydroxide in the granular phosphorus adsorbent In some cases, the amount of elution increases too much, so that the particulate (powdered) phosphorus adsorbent decomposes and dissolves, and can no longer function as a phosphorus adsorbent. However, the inclusion of an alginate in the binder limits the amount of magnesium ions that elute due to the binding between the alginate and magnesium ions, so the decomposition of the particulate (powdered) phosphorus adsorbent And it suppresses dissolution and does not impair the function as a phosphorus adsorbent.

  In addition, by including alginate in the binder, the eluted magnesium ions are precipitated in the vicinity of the granulated product, that is, the granular phosphorus adsorbent, for example, as magnesium ammonium phosphate, and further adsorbed by the granular phosphorus. It becomes attached to the surface of the agent. Since ammonia nitrogen such as magnesium ammonium phosphate is also an active ingredient of fertilizer, it is possible to recover magnesium phosphate ammonia and the like relatively easily by including an alginate in the binder. By making it easy to recover magnesium ammonium phosphate, etc., phosphorus that is contained in a large amount in wastewater such as sewage and depleted as a resource can be recovered easily and efficiently. In addition to being able to be used, effective use as resources such as magnesium phosphate ammonia is also possible.

  In addition, as described above, alginate is a kind of polysaccharide mainly contained in brown algae, and since it is a naturally derived substance, for example, it adsorbs a granulated granular phosphorus adsorbent containing alginate in a binder. Even if it is sprayed on the farmland as it is, it will not adversely affect the farmland.

  The content of alginate in the binder depends on the amount of the phosphorus adsorbent contained in the binder. For example, the content of alginate is 0.1 to 1.0 part by mass with respect to 100 parts by mass of the binder. Can do. If the alginate content is less than 0.1 parts by mass, the above-described effects may not be sufficiently achieved. If the alginate content is more than 1.0 parts by mass, The effect of suppressing the elution of magnesium ions from the phosphorus adsorbents in the water becomes remarkable, and precipitates such as ammonium magnesium phosphate cannot be obtained sufficiently, and the amount of phosphorus adsorbed in the wastewater, that is, the recovery rate decreases. May end up.

  The type of alginate is not particularly limited, and examples thereof include sodium alginate, potassium alginate, calcium alginate and the like that are relatively inexpensive and easily available.

  In order to contain the alginate in the binder, the alginate is mixed with the natural polymer polysaccharide, water and the phosphorus adsorbent at 100 ° C. or higher when producing the granular phosphorus adsorbent which is a granulated product. Heat to dissolve, then cool to solidify.

  The binder of this embodiment can include inorganic particles. In this case, since a heterophasic interface is formed in the binder, a phosphorous compound such as ammonium magnesium phosphate is likely to precipitate at the heterophasic interface.

  Therefore, as in the case of the alginate described above, when inorganic particles are not included in the binder, the layered double hydroxide in the granular phosphorus adsorbent is obtained when the obtained granular phosphorus adsorbent is immersed in waste water. The amount of elution of magnesium ions from the particulate phosphorus adsorbent made of the material becomes too large, and the particulate (powder) phosphorus adsorbent decomposes and dissolves, so that it can function as a phosphorus adsorbent. It may not be possible. However, by including inorganic particles in the binder, a heterogeneous interface is formed as described above, and the amount of magnesium ions eluted in the waste water is limited. Therefore, decomposition of the particulate (powder) phosphorus adsorbent and Dissolution is suppressed and the function as a phosphorus adsorbent is not impaired.

  In addition, by including inorganic particles in the binder, the eluted magnesium ions precipitate in the vicinity of the granulated product, that is, the particulate phosphorus adsorbent, for example, as magnesium ammonium phosphate, and adhere to the surface. To come. Ammonia nitrogen such as magnesium ammonium phosphate is also an active ingredient of fertilizer, so in addition to the particulate phosphorus adsorbent containing magnesium ammonium phosphate etc., it is also easy to recover magnesium ammonium phosphate etc. in the waste water. In addition, effective utilization as resources such as magnesium phosphate ammonia is also possible.

  In other words, phosphorus that is contained in a large amount in wastewater such as sewage and is depleted as a resource can be recovered easily and efficiently, and can be reused as a resource at low cost. It is also possible to effectively use these resources.

  In order to achieve the above-described effects, the size of the inorganic particles is set to the same size as the particulate (powder) phosphorus adsorbent contained in the granular phosphorus adsorbent, for example, 1 μm to 1000 μm. preferable.

  Moreover, although content of the inorganic particle in a binder is dependent on the quantity of the phosphorus adsorption agent contained in a binder, it can be 10 mass parts to 100 mass parts with respect to 100 mass parts of binders, for example. . When the content of the inorganic particles is less than 10 parts by mass, the above-described effects may not be sufficiently achieved. When the content of the inorganic particles is more than 100 parts by mass, the phosphorus adsorbent in the binder. In this case, the elution suppression effect of magnesium ions from the water becomes remarkable, and precipitates such as ammonium magnesium phosphate cannot be obtained sufficiently, and the phosphorus adsorption amount in the waste water, that is, the recovery rate may be reduced. .

  As the inorganic particles, for example, general-purpose particles used as a filler can be used. Specifically, calcium carbonate, alumina, talc, kaolin clay, mica, silica and the like can be used.

  In order to contain the inorganic particles in the binder, when producing the granular phosphorus adsorbent as a granulated product, the inorganic particles are mixed with natural polymer polysaccharide, water and phosphorus adsorbent, and if necessary, an alginate. Mix and heat to 100 ° C. or higher to dissolve, then cool to solidify.

  In addition, since the inorganic particles described above include fertilizer components such as calcium and magnesium as illustrated, even if the granulated granular phosphorus adsorbent containing inorganic particles in the binder is directly sprayed on the farmland after phosphorus adsorption, It does not adversely affect the farmland, and also exhibits the effect as a fertilizer like the adsorbed phosphorus.

  Voids can be formed in the binder of this embodiment. In this case, the density of the granulated product, that is, the granular phosphorus adsorbent can be adjusted by controlling the ratio of the pores in the binder. That is, when the ratio of the pores is reduced, the density of the granular phosphorus adsorbent increases and the specific gravity increases, so that the sedimentation property increases, and the granular phosphorus adsorbent can be recovered from the wastewater by gravity separation or the like. On the other hand, increasing the proportion of pores decreases the density of the granular phosphorus adsorbent and reduces the specific gravity. For example, when the granular phosphorus adsorbent is put into wastewater, the contact efficiency with the wastewater can be increased. The granular phosphorus adsorbent can be recovered by floating separation or the like.

  In order to form pores in the binder, when producing a granular phosphorus adsorbent that is a granulated product, a predetermined foaming agent is added to the natural polymer polysaccharide, water and phosphorus adsorbent, if necessary. Then, it is mixed with alginate and inorganic particles and heated to 100 ° C. or higher to dissolve, then cooled and solidified, and further subjected to foaming treatment.

  As a property required for the foaming agent, it does not decompose in the process of dissolution and solidification of the natural polymer polysaccharide, and it is necessary to form bubbles in the foaming treatment process to be performed later. In addition, it is required that the natural polymer polysaccharide (hydrogel) does not decompose or deteriorate.

  For example, when agar as a natural polymer polysaccharide exceeds 200 ° C., there is a concern that molecular chains are broken. Therefore, it is preferable to apply a foaming agent having a decomposition temperature in the range of 120 ° C to 200 ° C. For example, an organic foaming agent such as p, p′-oxybisbenzenesulfonylhydrazide or an inorganic foaming agent such as sodium hydrogen carbonate can be used.

Example 1
As raw materials, magnesium nitrate and iron (III) nitrate are mixed with pure water so that Mg: Fe = 4: 1 (atomic ratio), and the temperature is adjusted while adjusting the solution to pH = 12 with NaOH solution. It was dissolved with stirring at 65 ° C. to finally obtain 400 mL of solution. Next, a precipitate was formed which was kept for several hours while keeping the solution at 65 ° C. Finally, the generated precipitate was separated by filtration, washed, and dried at 65 ° C. to 80 ° C. for several hours to obtain Specimen 1.

  Specimen 1 was confirmed by ICP analysis to be a composite metal hydroxide of magnesium and iron. The composite metal hydroxide was confirmed to have a layered structure by an X-ray diffraction method. Furthermore, it was measured with the SALD-DS21 type | mold measuring apparatus (brand name) by Shimadzu Corporation that the average particle diameter of the test body 1 is 1 micrometer-100 micrometers.

  Next, 0.5 g of Specimen 1 obtained as described above, 0.034 g of agar, and 3 g of water were mixed in an autoclave and heated at 120 ° C. for 10 minutes to completely dissolve the agar. By doing this, the specimen 2 in which the specimen 1 was dispersed in the agar hydrogel was obtained.

  The dispersion of the specimen 1 was observed by cutting the specimen 2 and observing the cut surface with an SEM. Therefore, it was confirmed that the specimen 2 was a granular granulated product in which agar was used as a binder and layered composite metal hydroxide particles were dispersed in the binder. Moreover, it measured with the SALD-DS21 type | mold measuring apparatus (brand name) by Shimadzu Corporation that the average particle diameter of the specimen 2 was 2 mm.

  On the other hand, an aqueous solution adjusted to have a phosphate ion concentration of 180 mg / L, an ammonium ion concentration of 640 mg / L, a carbonate ion concentration of 3000 mg / L, and a magnesium ion concentration of 24 mg / L was prepared as a drainage simulation liquid. 100 mg of Specimen 1 and Specimen 2 were added to 1 L of this drainage simulation liquid, and mixed and stirred for 24 hours for water purification treatment. After the treatment, the specimen and the supernatant were separated by filtration, the phosphate ion concentration in the supernatant was quantitatively analyzed, and the phosphorus adsorption amount was calculated.

  As a result, the phosphorus adsorption amount of the specimen 1 (particulate (powder) adsorbent not granulated) is 80 mg-P / g, and the specimen 2 (so-called granular phosphorus adsorbent after granulation) The phosphorus adsorption amount was 84 mg-P / g. That is, the phosphorus adsorption capacity is almost the same before and after the granulation of the phosphorus adsorbent, and the specimen 1 (particulate (powdered) adsorbent) binds the agar to the binder without reducing the phosphorus adsorption capacity. It was found that it can be granulated.

  From this, the granular phosphorus adsorbent with increased particle size by granulation and easy handling is easy to handle and easily and efficiently recovers phosphorus that is pointed out as a resource depletion. It can be seen that it can be reused as a resource at low cost.

(Example 2)
Specimen 1 was obtained in the same manner as in Example 1. Thereafter, 0.5 g of specimen 1, 0.034 g of agar, 0.019 g of sodium alginate and 3 g of water were mixed in an autoclave and heated at 120 ° C. for 10 minutes. Thus, the specimen 3 in which the specimen 1 was dispersed in the agar hydrogel was obtained by completely dissolving the agar and cooling it later.

  The dispersion of the specimen 1 was observed by cutting the specimen 3 and observing the cut surface with an SEM. Therefore, it was confirmed that the specimen 2 was a granular granulated product in which agar was used as a binder and layered composite metal hydroxide particles were dispersed in the binder. Moreover, it measured with the SALD-DS21 type | mold measuring apparatus (brand name) by Shimadzu Corporation that the average particle diameter of the specimen 3 was 2 mm.

  The specimen 3 obtained as described above was put in the same simulated solution as in Example 1 under the same conditions, and the phosphorus adsorption amount was measured in the same manner as in Example 1. As in the specimen 2, It was found that 80 mg-P / g of phosphorus was adsorbed per unit weight and showed high phosphorus adsorption performance equivalent to that of Specimen 1. Therefore, it was found that even when agar is granulated using a binder, the phosphorus adsorption ability is not deteriorated.

  From this, the granular phosphorus adsorbent with increased particle size by granulation and easy handling is easy to handle and easily and efficiently recovers phosphorus that is pointed out as a resource depletion. It can be seen that it can be reused as a resource at low cost.

  Further, when the ICP analysis was performed again on the composition of the specimen 3 after being put into the simulated liquid, it was found that the peak intensity related to nitrogen was doubled compared to the specimen 2. Therefore, the specimen 3 can easily and efficiently recover phosphorus, which is pointed out as a resource, and can be reused as a resource at low cost, and as a resource of ammonia nitrogen such as magnesium phosphate ammonium. It can be seen that effective use of can also be achieved.

  As mentioned above, although several embodiment of this invention was described, these embodiment was posted as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

Claims (7)

A plurality of phosphorus adsorbent particles comprising a layered double hydroxide containing magnesium ions and iron ions and exhibiting a hydrotalcite-like structure;
A binder comprising a natural polymer polysaccharide in which the plurality of phosphorus adsorbent particles are dispersed,
The particulate phosphorus adsorbent, wherein the plurality of phosphorus adsorbent particles are granulated by the binder. The layered double hydroxide has the general formula:
[Mg ²⁺ _1-x Fe ³⁺ _x (OH) _m ] (An ⁻ ) _{x / n} · yH ₂ O
2. It is represented by (0.05 ≦ x ≦ 0.34, 0.5 ≦ m ≦ 3.4, An ⁻ is an n-valent anion, and y is a natural number). Granular phosphorus adsorbent.   The granular phosphorus adsorbent according to claim 1 or 2, wherein at least one of magnesium ions and iron ions adheres to the surface of the layered double hydroxide.   The granular phosphorus adsorbent according to any one of claims 1 to 3, wherein the natural polymer polysaccharide is agar.   The granular phosphorus adsorbent according to any one of claims 1 to 4, further comprising an alginate dispersed in the binder.   The granular phosphorus adsorbent according to any one of claims 1 to 5, further comprising inorganic particles dispersed in the binder.   The particulate phosphorus adsorbent according to any one of claims 1 to 6, wherein pores are formed inside the binder.