JPS59156488A - Artificial dephosphorizing agent and dephosphorization - Google Patents

Abstract

PURPOSE:To efficiently crystallizedly remove phosphates from water, by supporting powder containing calcium phosphate such as hydroxyapatite on a supporting body containing calcium carbonate such as a fossile coral to form the titled dephosphorizing agent. CONSTITUTION:The interior of a tank for manufacturing a dephosphorizing agent is packed with calcium carbonate-contg. particles to form a stationary bed. The liquid suspension of powder containing calcium phosphate is cyclically circulated, until most of suspended matter is eliminated. Hence, said powder is captured in the stationary bed of the supporting body. Thereafter, phosphate- contg. water is circulated in a series or cyclically under the condition of a pH above 6, so that said powder is supported on the supporting body to obtain the artificial dephosphorizing agent. This dephosphorizing agent is brought into contact with phosphate-contg. water at a pH above 6 in the presence of Ca ion, to crystallize phosphoric ion in the form of hydroxyapatite on the dephosphorizing agent. Thus, dephosphorization is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an artificial dephosphorization material and a dephosphorization method suitable for treating water containing phosphates.

As a method for removing phosphates contained in tap water, sewage, industrial water, factory wastewater, boiler water, etc., 1) Water containing phosphate is treated with calcium phosphate such as phosphate rock in the presence of calcium ions. A method has been proposed in which the material is brought into contact with crystal seeds containing the material. This method removes phosphate ions contained in water by crystallizing them into crystal seeds in the form of calcium phosphate such as hydroxyapatite, and the operating method is simpler than the conventional coagulation-sedimentation method. Not only this, but the processing efficiency will also be significantly improved.

In this method, 1. Particle size reduction of calcium phosphate granules/
Since it has a large effect on the removal reaction, it is effective to use particles with as small a particle size as possible in order to increase the removal efficiency. Also, for example, if we consider the case where phosphate rock is used as calcium phosphate granules, it is the surface of the granules that is involved in the reaction to remove phosphate in water, so the inside of the granules is not utilized. Also from the viewpoint of effective utilization of phosphate rock resources, it is preferable to use calcium phosphate granules with a small particle size. However, if the packed bed is filled with particles of too small a diameter, the resistance to water passage becomes large, so there is a natural limit to the selection of the particle diameter.

In order to solve these problems, it has been proposed to perform crystallization using a dephosphorizing material in which calcium phosphate is precipitated on a support such as sand. It is difficult to precipitate and grow calcium phosphate in the phosphor solution, and even if crystallization is performed using such a dephosphorization material, efficient dephosphorization cannot be achieved.

In addition, as a method that is not publicly known, a method has been proposed in which calcium phosphate crystal seeds are supported on a support such as sand with an adhesive; however, in this method, an adhesive is used to support the calcium phosphate crystal seeds. Therefore, there are problems such as the production is troublesome and the effective surface area for crystallization is small.

The present invention is intended to solve the above-mentioned conventional problems, and it is possible to perform artificial dephosphorization with high dephosphorization efficiency by supporting powder containing calcium phosphate on a support containing calcium carbonate. The purpose of this invention is to provide a dephosphorization method using this artificial dephosphorization material.

The present invention includes the following two inventions.

(1) An artificial dephosphorization material comprising powder containing calcium phosphate supported on a support containing calcium carbonate.

(2) An artificial dephosphorization material in which powder containing calcium phosphate is supported on a support containing calcium carbonate and water containing phosphate in the presence of calcium ions and under conditions of p145 or higher. A dephosphorization method characterized by contacting with.

The artificial dephosphorization material of the present invention is made by supporting powder containing calcium phosphate on a support containing calcium carbonate. Examples of the support containing calcium carbonate include coral fossil, coral sand, limestone, marble, and mud. graystone, dolomite,
Granular materials containing calcium carbonate as a main component, such as calcite and aragonite, are preferable, and may be natural or artificial minerals.

The particle size is preferably about 8 to 120 mesh.

The shape of the particles is not particularly limited and may be crushed or other shapes, but particles with a large surface area are desirable.

Examples of powders containing calcium phosphate include hydroxyapatite [: (Ca 5XOH) (PO4) 3 ),
Fluoroa,.

Crystal powders containing calcium phosphate such as phosphorite ((ca5(FXPO4)3) or tricalcium phosphate ((ca3(PO4)2)) can be used, and natural phosphate rock contains these calcium phosphates as main components. Suitable as seeds.In addition, bone char, crystalline calcium phosphate composites, coagulated precipitates mainly composed of calcium phosphate, powders such as calcium phosphate precipitated by adding calcium to phosphorus-containing water can also be used. Examples include monotoke, those made by reacting phosphate ions and calcium ions, and aging the resulting reaction product.These powders containing calcium phosphate have a particle size Q of 4 mm or less (approximately 36 mesh or less). Those originally obtained as powder can be used as they are, but those obtained as granules or lumps are used after being pulverized.As the pulverization means, known means can be used.

A powder containing calcium phosphate is supported on a support containing calcium carbonate [ld: Calcium phosphate itself can be used as a binder. In this case, if crystallization is performed in a state where the support is in full contact with the powder,
The precipitated calcium phosphate acts to bind the powder to the support. As a result, the powder is supported on the support using the precipitated crystals as a binder.

Regarding the specific manufacturing method of artificial dephosphorization material, a tank for manufacturing the dephosphorization material is prepared at the site where the dephosphorization treatment is performed or at another location, and support particles containing calcium carbonate are prepared in the tank for manufacturing the dephosphorization material. is filled to form a fixed bed, and a suspension of powder containing calcium phosphate is circulated with water until most of the suspended matter is removed, and the powder is captured in the fixed bed of the support.

As the liquid for suspending the powder, tap water, industrial water, treated water, or raw water can be used, and the water can be passed in an upward or downward flow, but the upward flow captures the powder more uniformly. The smaller the amount of liquid used, the more preferable it is from the viewpoint of equipment and energy. The amount of powder to be supplied is approximately 1 g of powder per 50 to 500 g of the support.

When water containing phosphate is passed through a fixed bed of a support that traps powder containing calcium phosphate under conditions of pH 6 or higher, preferably in the presence of calcium ions, in a perfusion or circulation manner, Calcium phosphate is precipitated to bridge the support and the powder, and the powder is supported on the support.

In order to support the powder on the support, it is desirable to pass water containing phosphate for several days to several tens of days, and the amount of powder supported is determined by the water passing time.

The loading rate of the powder on the support is preferably at least 1 nrg/g of calcium carbonate.

Among the supports containing calcium carbonate, there are some that contain phosphorus in the state in which they are naturally produced, but the above-mentioned loading rate is 1.
d Calculated as the amount of phosphorus supported on the support surface.

The amount of phosphorus in the dephosphorizing material and the support can be obtained, for example, by drying the material at 105° C., dissolving the dried product in 1N hydrochloric acid, and measuring the phosphorus in the solution by a colorimetric method. The supporting rate can be calculated from the difference between the two, but the phosphorus concentration on the surface may also be measured by a method such as lowering the acid concentration.

υ of 11rL9-P/gCaC03 or more on the support
) to support K varies depending on the conditions, but generally the crystallization may be carried out for 20 to 25 days or more. The conditions for crystallization for supporting the powder may be the same as the conditions for crystallization for removal/removal described below.

After the powder is supported on the surface of the support, clean water such as tap water is flowed upward during filling of the support to develop a packed layer.
The supported powder is removed and an artificial membrane phosphor material is obtained. Runoff water containing powder can be recycled by removing the powder by filtration or the like. The removed powder may be used again to produce a dephosphorizing material, or may be used as fertilizer or the like.

The powder containing calcium phosphate supported on the support becomes the core of crystallization during dephosphorization described later, so before or after it is supported on the support, a concentrated slaked lime solution, a chlorine agent-containing solution (chlorine Activation treatment can be performed by contacting with water, sodium hypochlorite, saran powder, highly salinated powder solution, etc.), acid aqueous solution, etc.

As described above, the artificial dephosphorization material in which powder containing calcium phosphate is supported on a support containing calcium carbonate can be used for dephosphorization as it is, but it can also be filled into another treatment tank for dephosphorization treatment. You may do so. In either case, it is suitable for crystallization by passing water through a fixed bed or a fluidized bed.

The dephosphorizing material obtained in the above manner may be subjected to direct phosphorus treatment using phosphate-containing water, such as secondary treated sewage water and other various wastewater, as raw water, but it may be treated in advance by using conventional crystalline crystals filled with granular calcium phosphate crystals. After the dephosphorization treatment is performed using a precipitation/dephosphorization device, the effluent water may be brought into contact with the above-mentioned dephosphorization material to be treated in a holocaust-like manner. In the latter case, since most of the phosphorus and suspended matter in the raw water have been removed in advance, treatment efficiency is increased and advanced treatment becomes possible.

The second invention of the present invention is to combine the above-obtained desorbing material and water containing phosphate in the presence of calcium ions and at pH
This is a method of dephosphorization by crystallizing phosphate ions in the form of hydroxyapatite on the dephosphorization material by contacting with the dephosphorization material at a temperature of 6 or more. This section explains the dephosphorization method.

The raw water to be treated in the present invention is water containing phosphates, and includes secondary treatment water such as sewage, human waste, and industrial wastewater. Crystallization is performed by bringing such raw water into contact with a dephosphorizing agent in the presence of calcium ions.

The reaction that occurs at this time varies depending on the reaction conditions, but is usually expressed by the following formula.

5 Ca2+70H-+ 3H2PO4→Ca s (
OI-1) (PO4)s + 6H20...(1)
In order to efficiently remove phosphates from water containing phosphates, it is necessary to allow the reaction in equation 11 to proceed to the right, and for this purpose, add calcium agents or alkaline agents as necessary to remove calcium ions. and hydroxyl ions must be present.

In order for the reaction to proceed, it is desirable to have large amounts of calcium ions and hydroxide ions present in the reaction system, but if these are present in excess, fine precipitates such as calcium phosphate will occur in areas other than crystal seeds, leading to the formation of a packed bed. It may even block the water flow and reduce the water treatment efficiency.

In equation (1), the concentration of calcium phosphate produced is soluble.

In a region where the calcium ion concentration and pH are higher than the solubility and lower than the supersolubility (the concentration at which crystals begin to precipitate in the absence of crystal seeds in the reaction system), that is, in the metastable region, the calcium phosphate produced precipitates on the crystal surface, and no fine precipitates are formed.

On the other hand, in an unstable region where the calcium ion concentration and/or pH is high and the produced calcium phosphate exceeds supersolubility, calcium phosphate precipitates as fine precipitates. As described above, the metastable region varies depending on the concentration of phosphate ions contained in raw water, and the lower the phosphate ion concentration, the wider it becomes. Therefore, when the concentration of phosphate ions in raw water is high, increasing the calcium ion concentration and/or pH creates an unstable region and tends to form precipitates, but when the phosphate ion concentration is low, calcium Even if the ion concentration or pH is increased, crystallization in the metastable region is possible9, and the reaction rate can be increased without forming a precipitate.

In order to keep the amounts of calcium ions and hydroxide ions within the metastable range, a calcium agent and/or an alkaline agent is added to the water containing phosphate, if necessary. Suitable addition amounts of calcium agents and alkali'J agents can be determined in advance through simple experiments, but if the phosphate in the raw water is less than 5CJm9/e, calcium ions are
~200 ■/l, pH is 6 or more, preferably 6 to 12
That's about it.

Calcium agents used in this invention include calcium hydroxide and calcium chloride, and alkaline agents include sodium hydroxide, potassium hydroxide, calcium hydroxide, and the like.

When the water containing phosphate is brought into contact with the dephosphorizing material using a packed bed water flow method, the water is passed in an upward flow, a downward flow, or a horizontal flow at a flow rate of SV 1 to 10 hr-' to remove hydroxyapatite crystals. Let it precipitate. In the case of upward flow, suspended matter can be captured in the large particle size part of the lower layer, and crystallization can be performed in the small particle size part of the upper layer with high activity. Similarly, when water flows downward,
In order to avoid adhesion of suspended matter to the surface of the dephosphorizing material, a P material with a smaller specific gravity and larger particle size than the dephosphorizing material is layered on top of the dephosphorizing material packed layer, and this P material removes the suspended matter. is desirable.

However, such measures are not necessary when dephosphorization treatment is performed in advance using the crystal seed packed bed in the conventional method to remove suspended matter as described above.

If the dephosphorizing surface becomes contaminated or clogged during water flow, periodically perform backwashing using an upward flow to spread and clean the dephosphorizing material and remove impurities that have adhered to the surface. It is desirable to remove. Water flow conditions during backwashing include a flow rate of about 20 to 80 mlhr, and a backwashing time of 5 to 60 mlhr.
It takes about a minute.

When the crystallization is performed as described above, hydroxyapatite with low solubility is mainly generated according to the formula (1), and this crystallizes on the surface of the dephosphorizing material, thereby lowering the phosphate concentration in the treated water.

In addition, in the above treatment, the raw water is pre-treated prior to the dephosphorization operation9, the treated water is post-treated, or other treatments are used in conjunction with the dephosphorization treatment, or chemicals are added. It is also possible to do so.

As described above, according to the present invention, since the powder containing calcium phosphate is supported on the support containing calcium carbonate, the powder containing calcium phosphate can be powdered by using the same calcium phosphate as 72 Ingu without using an adhesive. can be supported, and calcium phosphate resources can be effectively used to efficiently crystallize and remove soot/acid in water.

Compared to the conventional method of distributing calcium/acid in sand, etc., it has a higher dephosphorizing effect, and compared to the method of supporting the crystal seeds with an adhesive, it supports the powder with a homogeneous binder. Therefore, it is possible to increase the utilization efficiency of the support. Furthermore, compared to crystallizing with a support that captures the powder on a support, it is possible to prevent the powder from falling off or flowing out due to fluctuations in the amount of water flow.

fruit! Quasi-example: Fill an acrylic resin column with an inner diameter of 3Q mm and a height of 500 mm with 1'50 ml of Nose saw fossil (content/rate 0.22 mt2/, Q) with a particle size of 0.5 to 1.3 mrn, and 2 g of hydroxyapatite powder with a particle size of 017 πm or less is suspended in 100 al of tap water, and this suspension is applied at a rate of 5 to 100 rnl/m to the coral fossil.
Water was circulated at a flow rate of 1.5 in to capture the hydroxyapatite powder.

Continued/concentration 2mg/l, total alkalinity approximately 100■/
After continuously adding a calcium chloride aqueous solution and a sodium hydroxide aqueous solution to 1 liter of synthetic water at the column inlet to adjust the calcium ion concentration to about 45 η/l and the pH to 8.8 to 90, Water was allowed to flow upward through the packed bed at a flow rate of D Oml/hr, and continuous treatment was performed for 30 days. The average value of the concentration of the treated water during that period is 0, , i s m9/
It was l. After 130 days, the packed bed was washed (backwashed) with about 11 water passes and the trapped water was removed! When the unsupported hydroxyapatite powder was removed, a dephosphorization material with a phosphorus loading rate of 1.08 to 9 P/g-CaCO5 was obtained.

In the state where the above-mentioned material is removed and filled, the phosphorus concentration is 2.
TLL? /l, total alkalinity of about 1001 + 19/l, synthetic water with a total alkalinity of about 1001 + 19/l, continuous addition of unsolved chloride solution and aqueous sodium hydroxide solution at the column inlet to bring the calcium ion concentration to about 451n9/11 and the pH to 88-90
After adjusting the temperature, water was allowed to flow upward through the packed bed at a flow rate of 300 rnl/hr, and crystallization dephosphorization treatment was performed continuously for 60 days. The average value of phosphorus concentration in treated water for 60 days is 0.32
mg/l.

A similar test was conducted with a phosphorus loading rate of 1.01 m? -PI3C
When conducted under the conditions of aCO3, the average value of the phosphorus concentration in the treated water was 0.47 rng/73. After one week of crystallization for loading, the phosphorus loading rate was 0.30 m
The average phosphorus concentration of the treated water was 12.1 g/ll when the ratio was g-p/9-CaCO3.

Comparative Example 1 150 m of coral fossils adjusted to a particle size of 05 to 1.0 mm
1 was packed into an acrylic resin column with an inner diameter of 33 mm and a height of 500 m'rft, and the phosphorus concentration was 2~/l and the total alkalinity was 100 without trapping hydroxyapatite.
When 1d9/l of synthetic water was continuously passed through for 10 days under the same conditions as in the example, the average phosphorus degree of the treated water was 1.75 my/11.

Comparative Example 2 Particle size 0.5-1. (The average phosphorus degree of the treated water when synthetic water with a phosphorus concentration of 2 m9./l was passed for 60 days with 1 vrm of sand filled and hydroxyapatite captured under the same conditions as in the example. The value was 0.70m9/13.

In addition, after washing (backwashing) the packed bed and removing the trapped hydroxyapatite powder, the loading rate was 0.
1 rng-P/g-sec), phosphorus concentration 2 rng
/i synthetic water was passed for 15 days, and the average value of the phosphorus concentration in the treated water was 1.78 'Tn9 /' l.

From the above results, it can be seen that powder containing calcium phosphate can be supported on a support containing calcium carbonate by pouring calcium phosphate into the powder, and thereby efficient dephosphorization can be carried out.

Agent: Patent attorney Sei Yanagi Hara

Claims (1)

[Scope of Claims] (1) An artificial dephosphorization material comprising powder containing calcium phosphate supported on a support containing calcium carbonate. (2) Splinters containing calcium carbonate, coral fossils,
The artificial dephosphorization material according to claim 1, which is coral sand, limestone, marble, marl, dolomite, calcite or /ri aragonite. (3) The artificial substance according to claim 1 or 2, wherein the powder containing calcium phosphate is an agglomerated precipitate whose main component is hydroxyapatite, fluoroapatite, tricalcium phosphate, phosphate rock, bone char, or calcium phosphate. Dephosphorization material. (4) The artificial dephosphorization material according to any one of claims 1 to 6, wherein the powder containing calcium phosphate is supported on a support using calcium phosphate as a binder. (5) Powder containing calcium phosphate hf h I Tl? −
The artificial dephosphorization material according to any one of claims 1 to 4, which supports P/g -CaCO3 or more. (6) An artificial dephosphorization material in which powder containing calcium phosphate is supported on a support containing calcium carbonate and water containing phosphate in the presence of calcium ions and under conditions of pH 6 or higher. A dephosphorization method characterized by contacting with. (The dephosphorization method according to claim 6, wherein the support containing calcium carbonate is coral fossil, coral sand, limestone, marble, marl, dolomite, calcite, or aragonite. (8) Calcium phosphate The decomposition method according to claim 6 or 7, wherein the powder contained is an agglomerated precipitate containing hydroxyapatite, fluoroa/!?tite, tricalcium phosphate, phosphate rock, bone charcoal, or calcium phosphate as a main component. Phosphorus method. (9) The dephosphorization method according to any one of claims 6 to 8, wherein the powder containing calcium phosphate is one in which calcium phosphate is supported on a support as a binder. (10 ) Powder containing calcium phosphate is 1 m9-P
The dephosphorization method according to any one of claims 6 to 9, wherein the dephosphorization method is one in which the amount of CaCOs supported is at least /g-CaCOs.