JP2592384B2 - Water treatment method using composite particles of metal hydroxide and superabsorbent polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention, clean water, various waste water, dam, lake, (also referred to as PO ₄ ^3- ions) traces of phosphoric acid ions contained in water such as a river or the like to effectively adsorb and remove the The present invention relates to a novel phosphorus adsorbent suitable in some cases.

[0002]

2. Description of the Related Art Conventionally, various phosphorus adsorbents such as activated alumina, iron oxide, bone charcoal, and hydroxyapatite have been known. (Phosphorus adsorbent) is desired. The amount of saturated adsorption of phosphorus is small.

Since the specific gravity of the adsorbent particles is large, SS
It is difficult to apply and operate a fluidized bed without clogging. PO ₄ ^3- ions are adsorbed only on the surface of the adsorbent. The inside cannot be used effectively. High cost and difficult to use.

The PO ₄ ³⁻ ion concentration of the treated water is 0.1
It cannot be reduced below mg / liter. Disposal of waste adsorbent is difficult.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel dephosphorizing material (phosphorous adsorbent) which solves the drawbacks of the conventional phosphorus adsorbent. In particular: The ability to remove PO ₄ ^3- ions to an extremely low concentration (0.1 mg / liter or less).

[0006] 2. The specific gravity of the phosphorus adsorbent is close to water and can be easily fluidized. 3. The inside of the phosphorus adsorbent can be effectively used for adsorption, and the amount of saturated adsorption of phosphorus is large. 4. Easy disposal of waste adsorbent. It is intended to provide a new dephosphorizing material that can satisfy the above condition.

[0007]

The present invention is based on a new concept not found in the prior art. That is, the number of own weight 1
For example, Al, Fe, Zr, and Ti are contained in the hydrogel particles of the superabsorbent polymer particles having a property of absorbing water by a factor of 00.
It is an object of the present invention to produce a metal hydroxide such as a hydroxide and the like, and to provide as a dephosphorizing material a substance obtained by confining and fixing these metal hydroxides inside the hydrogel particles.

[0008]

That is, the present invention provides: (1) a method in which a composite granular material comprising a highly water-absorbing polymer and holding a metal hydroxide in hydrogel particles which swell in water and exhibit elasticity is brought into contact with water to be treated; Water treatment method, wherein phosphate ions in the water to be treated are adsorbed to the composite particulate matter. It is.

The superabsorbent polymer is a hydrophilic polymer which can absorb water several hundred times its own weight. There are two types of hydrogels, and those that become pasty cannot separate water by filtration, but those that maintain their unique shape and become elastic and strong hydrogels (ie, those that exhibit finite swelling) In the case of particles, water not absorbed by the gel can be easily separated by filtration. The hydrogel particles suitable for use as the carrier of the dephosphorizing material of the present invention are those that maintain a fixed shape and become elastic and strong hydrogel particles.

That is, the "hydrogel particles" which swell in water and exhibit elasticity as referred to in the present invention are reversible due to disappearance of external force or swelling due to water absorption even if the hydrogel is deformed by external force or by drying. It refers to a hydrogel that returns to its original shape, and the shape of each particle is not necessarily the same. The size of the hydrogel particles, that is, the ultimate swelling degree, depends on the degree of cross-linking of the superabsorbent polymer constituting the hydrogel particles and the properties of the aqueous solution into which it is charged. Also, the elastic strength of the hydrogel particles can be adjusted by the type of constituent polymer and the degree of swelling. Further, the hydrogels of the present invention have a property that they do not fuse or adhere to each other.

Examples of superabsorbent polymers having such properties include those described in "Superabsorbent Polymers" by Fumiyoshi Masuda, Kyoritsu Shuppan, pp. 23-50, and acrylic acid-vinyl alcohol copolymers. Preferred examples include a polymer and an isobutylene-maleic anhydride copolymer.

The hydrogel particles, which are made of superabsorbent polymer and swell in water to form elastic shaped particles, when the dried particles are put into an aqueous solution, the particles absorb a large amount of the aqueous solution and swell. Reconstituted into hydrogel particles. The hydrogel particles may have various shapes and sizes upon water absorption and swelling, but are preferably spherical and have a particle size on the order of several mm.

That is, the hydrogel particles of the present invention have a particle size of 1 to 9 mm, preferably 3 to 6 mm.

Hereinafter, the method for producing the dephosphorizing material of the present invention will be described in detail. Examples of the metal hydroxide include calcium hydroxide, magnesium hydroxide, aluminum hydroxide, iron hydroxide, nickel hydroxide, zirconium hydroxide, titanium hydroxide and the like. Take it up and explain.

The dry particles composed of a superabsorbent polymer which can be hydrogel particles are treated with aluminum sulfate [Al ₂ (S
O ₄ ) ₃ ] When introduced into an aqueous solution, the particles absorb the aluminum sulfate aqueous solution and swell to form hydrogel particles having the aluminum sulfate aqueous solution absorbed and retained inside the particles having a particle diameter of several mm.

The generation time of the hydrogel particles is completed in about 10 minutes. Thereafter, when the hydrogel particles are separated from the aqueous aluminum sulfate solution and immersed in an aqueous alkaline solution such as caustic soda, OH ^- ions penetrate inside the hydrogel particles, and precipitate aluminum hydroxide by the following reaction inside the gel. . Al ³⁺ + 3OH ⁻⁻ → Al (OH) ₃ Thus, aluminum hydroxide [A
1 (OH) ₃ ] is immobilized. The hydrogel particles have high strength, can be picked up with tweezers, and do not break unless a strong external force is applied. Therefore, the hydrogel particles are not destroyed even if the operation of separating from the aqueous aluminum sulfate solution and throwing it into the aqueous alkaline solution is performed.

However, it is not always necessary to separate the hydrogel particles from the aqueous metal salt solution to form the metal hydroxide in the hydrogel particles, and the hydrogel particles are formed by adding an aqueous alkali solution to the aqueous metal salt solution. It is also possible to generate a metal hydroxide therein. Note that Fe (OH) ₃ , Zr (OH) ₄ , Ti (OH) ₄
And the like can be produced in the same manner.

The "metal hydroxide" in the present invention does not consist of a simple compound such as aluminum hydroxide [Al (OH) ₃ ], but also includes double salts and complex salts containing a hydroxyl group. Means things. Therefore, Al ₄ (OH) ₆
(SO ₄ ) ₃ means a double salt having a complex composition.

Next, the method of dephosphorization using the hydrogel composite particles containing a metal hydroxide of the present invention will be described. Basically, the object can be achieved by contacting water containing phosphate ions (for example, sewage) with the phosphorus removing material (phosphorous adsorbent made of hydrogel) of the present invention. As an example, as shown in FIG. 1, the phosphorus adsorbent A (hydrogel composite granular material) made of a hydrogel of the present invention is suspended and fluidized by the flow of raw water supplied from a raw water supply pipe 2 at the bottom of the processing tank 1 for treatment. What is necessary is just to make the phosphorus adsorbent A and the raw water uniformly contact in the tank 1. As a result, the phosphate ions in the raw water diffuse into the phosphorus adsorbent A, are adsorbed by the aluminum hydroxide [Al (OH) ₃ ] fixed inside the granular material, and are removed from the raw water.
The treated water flows out of the system from the treated water outflow pipe 3 in the upper part of the treatment tank 1.

The specific gravity of the dephosphorizing material of the present invention swollen in raw water is only slightly larger than the specific gravity of water, and has the advantage that it can be suspended and flow extremely easily. In addition, PO ₄ ^3-
When COD components are contained in addition to ions, COD
Some of the components are also adsorbed and removed by the phosphorus adsorbent of the present invention.

The hydrogel composite particulate material of the present invention is confined to immobilize the metal hydroxide that acts as a phosphate adsorption sites in the overall network structure of the superabsorbent polymer, PO ₄ ^3- ions in the raw water The metal hydroxide that diffuses and exists throughout the inside of the hydrogel composite particles is converted to PO ₄ ^3-.
Can be used for ion adsorption sites. In the case of conventional hydroxyapatite or the like, only the surface thereof can be used for the adsorption site of PO ₄ ³⁻ ions, so that it can be seen from the comparison that the hydrogel composite granules of the present invention have high adsorption performance.

When a hydrogel dephosphorizing material having a saturated adsorption of phosphorus is dried, its volume shrinks to several hundredths, so that it is extremely easy to dispose of it, and it is effective as a water retention agent and a phosphorus fertilizer by being sprayed on soil. Available. further,
The hydrogel composite particles of the present invention can be dried while the metal hydroxide is immobilized and held in the entire network structure.

Since the hydrogel dephosphorizing material of the present invention is lightweight and has a specific gravity close to that of water, it can be used particularly effectively, for example, when removing PO ₄ ^3- ions in rivers flowing into dams and lakes. That is, such a river becomes a turbid flow containing a large amount of turbidity during heavy rain, but the dephosphorized material of the present invention becomes a fluidized state by the flow of the river, so that the turbidity blocks the dephosphorized material packed layer. The trouble of clogging does not occur. FIG. 2 shows an example in which the dephosphorization material-filled layer of the present invention is installed in a river.

On the other hand, all the conventional adsorbents (such as dephosphorized materials) have a specific gravity of about 2.5, and the adsorbent does not flow due to the river flow. Blockage occurs and clogging occurs.
Needless to say, the hydrogel composite granules of the present invention can be used as a suspension fluidized state in a treatment tank, or as a fluidized bed or filled in a fixed bed.

[0026]

【Example】

(Example 1) 1. Production of adsorbent 5 g of powdery superabsorbent polymer particles, which is a copolymer of isobutylene and maleic anhydride, are put into 1000 mg of a 0.5% aluminum sulfate aqueous solution, and 1
After standing for 5 minutes, hydrogel particles having an average particle size of 2 mm were obtained.

The hydrogel particles were taken out of the aqueous solution, suspended in 1 liter of tap water, stirred, and caustic soda was added little by little while measuring the pH, and the mixture was maintained at pH 6 and stirred for 30 minutes. As a result, white aluminum hydroxide [Al (OH) ₃ ] precipitated in the hydrogel particles and was fixed in the hydrogel particles. These particles are used as an adsorbent.

2. Phosphate ion removal treatment The above adsorbent was packed in a column having a diameter of 3 cm to a height of 30 cm, and tap water containing 1.0 mg / liter of PO ₄ ^3- ion was supplied to the column in an upward flow at SV5. The PO ₄ ³⁻ ion concentration of the treated water was as extremely small as 0.03 mg / liter.

Further, the PO ₄ ³⁻ ion concentration of the treated water is set at 0.1.
When reaching 8 mg / liter, the amount of phosphorus adsorbed per unit weight of aluminum in the hydrogel particles (Al ₂ O
The phosphorus adsorption amount (per ₃ ions) is 30.6 mg / gA
This is an extremely large value of l ₂ O _3, which indicates that the adsorbent of the present invention has a large phosphorus adsorption capacity.

[0030]

EFFECTS OF THE INVENTION The hydrogel composite particles of the present invention have a particle size on the order of several millimeters and have a specific gravity close to that of water. Since the adsorbent solid phase is diffused and immobilized within the entire network structure of the superabsorbent polymer inside the hydrogel composite granules, not only the surface of the gel particles but also the entire interior can be effectively used for adsorption, and high phosphorus Has adsorption performance.

It is very suitable for the field of wastewater treatment where the cost is low and low running cost is essential. Also, handling is easy.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a dephosphorization treatment using the hydrogel adsorbent of the present invention.

FIG. 2 is a cross-sectional view showing an example in which the dephosphorization material-packed layer of the present invention is installed in a river.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Treatment tank 5 River flow 2 Raw water supply pipe 6 Sabo dam 3 Treated water outflow pipe 7 Xu phosphorus river flow 4 Outflow prevention net 8 Outflow prevention net A Hydrogel adsorbent B Dephosphorizing material

Claims (1)

(57) [Claims] 1. A method comprising: contacting a composite granular material comprising a superabsorbent polymer and holding a metal hydroxide in hydrogel particles which swell in water and exhibit elasticity, with the water to be treated, thereby obtaining water to be treated; A method for treating water, comprising adsorbing phosphate ions from the composite particulate matter.