JPH11216479A - Composition for collecting phosphate ion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a practical means for collecting and recovering phosphate ion contained in a waste water, a water of the river, the lake or the like and causing eutrophication in a form capable of reutilizing. SOLUTION: The practical means for collecting phosphate ion in the water in the form capable of reutilizing i.e., as calcium phosphate is carried out by allowing a powder of bentonite of a clay containing montmorillonite as a main clay mineral and calcium carbonate to react with a water soluble high polymer such as a polyvinyl alcohol to prepare a water resistant granular composition, charging the water resistant granular composition into a column or a net like bag and bringing it into contact with the water containing phosphate ion such as the waste water, the water of the river, the lake or the lake.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composition for recovering phosphate ions in water in a reusable form,
It is used in the fields of environmental protection and agriculture.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a method in which an iron material is immersed in wastewater, and iron ions eluted from the iron surface and phosphate ions in the wastewater are combined to precipitate as a hardly soluble iron phosphate salt. . In this method, recovery and reuse of phosphoric acid as a valuable resource is not considered. Conventionally, there is a practical method for recovering phosphate ions, which are present not only in wastewater but also in rivers and lakes, provide eutrophication and are one of the main causes of water quality deterioration, in a reusable form. do not do.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of collecting and recovering phosphate ions in wastewater, rivers, lakes and marshes in a reusable form, which does not exist as a conventional practical technique.

[0004]

Means for Solving the Problems As a result of earnest studies on means for solving the above-mentioned problems, the means reached by the present inventors is a mixture of bentonite, which is a clay having montmorillonite as a main clay mineral, and calcium carbonate powder. This is a method for trapping phosphate ions in water using a granular composition of a water-resistant composite comprising a water-soluble polymer compound and a water-soluble polymer compound.
To describe the present invention in more detail, after adding and mixing an aqueous solution of a water-soluble polymer compound to a mixture of bentonite and calcium carbonate powder, a method of granulating and drying to obtain a water-resistant granular composition may be employed. Also, after adding and mixing an aqueous solution of a water-soluble polymer compound to a mixture of bentonite and calcium carbonate powder, crushing the dried product,
A method of obtaining a water-resistant granular composition may be employed. The particle size of the granular composition is easy to handle from about 1.0 mm to about 5.0 mm, but is not limited to this range. Also, a method of preparing an aqueous suspension of bentonite and calcium carbonate powder in advance and adding an aqueous solution of a water-soluble polymer compound to the suspension is used to granulate and dry or dry-pulverize the reaction product. Through the steps, the desired water-resistant granular composition can be obtained. As a drying method, freeze drying can be employed in addition to ordinary heating drying and hot air drying.

According to the present invention, the proportion of bentonite contained in the particulate composition for collecting phosphate ions in water is 98.
From 5 to 55.0% by weight, the balance is calcium carbonate powder and a water-soluble polymer compound. The replaceable cation of the bentonite used may be Na ion or Ca ion. However, the cation exchange capacity of bentonite is 50m
g equivalent / 100 g clay is desirable. The amount of calcium carbonate powder is 1.0 to 54.0% by weight.
Is included in the granular composition in the range of 1.0 to 2
Those containing 5.0% by weight are easy to handle. The particle size of the calcium carbonate powder is preferably through a 100-mesh sieve, but is not limited to this range. As the water-soluble polymer compound as a binder, polyvinyl alcohol and a silanol-modified product thereof are excellent in imparting water resistance to the granular composition. The ratio of the water-soluble polymer compound contained in the granular composition is 0.1%.
5 to 5.0% by weight is good. The content of the binder is related to the degree of swelling of the particulate composition. As the water-soluble polymer compound as the binder, a polyanionic water-soluble compound such as sodium polyacrylate or sodium alginate may be used as a mixture with the polyvinyl alcohol-based compound in addition to the above-mentioned polyvinyl alcohol-based compound.

[0006]

Next, the operation of the present invention will be described. 194
Due to Japan's environmental protection policy in the 0s, BO in wastewater
The D and COD values have been regulated, and the pollution degree of water quality in rivers, lakes and marshes and harbor waters has not progressed much. However, as far as rivers and lakes are concerned, it can be said that the eutrophication value of nitrogen compounds and phosphorus compounds is increasing. As far as phosphate ions are concerned, there is no practical method for effectively removing them from water. Phosphate ions are essential for plants, but are limited and valuable as resources. Further, phosphate ions are used in plants under natural conditions by compounds with monovalent or divalent cations, and compounds with iron or aluminum are hardly used by plants. Therefore, when recovering phosphate ions in water, it is desirable to take a form of a compound with a monovalent or divalent cation if it is intended for reuse. Fortunately,
Phosphate ions easily react with calcium ions,
Produces calcium phosphate salt, which is poorly soluble in water under alkaline conditions. The particulate composition for phosphate ion collection invented by the present inventors traps phosphate ions therein in the form of calcium salts. And, in this granular composition, since the pH is always kept on the alkaline side,
The captured calcium phosphate salt is recovered without dissolving in water. The granular composition containing the recovered calcium phosphate salt can be effectively used as a phosphate fertilizer and as a soil conditioner.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Cation exchange capacity is 66mg equivalent / 100
g of a 20% aqueous suspension of Ca-bentonite in 500 ml
Then, 2 g of calcium carbonate powder passed through a 100-mesh sieve was added and mixed well.
After adding and mixing and reacting 30 ml of a 10% aqueous solution of polyvinyl alcohol having a saponification degree of 700 and 98 mol%, the reaction product was poured into a plastic vat so as to have a thickness of 1 cm, and dried with a hot air drier at 60 ° C. This dried product is crushed and sieved to a particle size of 2.0 mm to 5.0 mm.
About 70 g of a water-resistant granular composition was obtained. This was designated as composition 1. 2. A cation exchange capacity of 66 mg equivalent / 100 g of Ca-
500 ml of a 20% aqueous suspension of bentonite was prepared, 20 g of calcium carbonate powder passed through a 100-mesh sieve was added and mixed well. Then, 50 ml of a 10% aqueous solution of polyvinyl alcohol used in Example 1 was added, mixed and reacted. I let it. Thereafter, the same steps as in Example 1 were performed to obtain about 65 g of a water-resistant granular composition. This is used as composition 2
And 3. The same Ca-bentonite 1 used in Example 1
00 g and arrowheads 8 g of the same calcium carbonate powder as used in Example 1 was placed in a 1000 ml beaker and mixed with powder consent, and 150 ml of the same 2% aqueous solution of polyvinyl alcohol as used in Example 1 was added. After mixing and reacting, the mixture was freeze-dried. This lyophilized product is crushed and sieved to a particle size of 2.0 mm to 5.0 mm.
About 75 g of a water-resistant granular composition was obtained. This was designated as composition 3. 4. In preparing a sample in the same procedure as in Example 2, a water-resistant granular composition was prepared without adding calcium carbonate powder, and was used as Composition 4. 5. When preparing a sample in the same procedure as in Example 1, a granular composition was prepared without adding an aqueous solution of polyvinyl alcohol as a binder, and was used as Composition 5. 6. Composition 1, prepared in Examples 1, 2, 3, 4, 5
25 g each of 2, 3, 4, 5 was put into a 50 ml burette laid on a cock with a 1 mm nylon mesh,
A nylon net was also placed on the top to cover the surface of the composition. 30 ml of demineralized water having a pH of 7.0 was poured into each burette, left at room temperature for 24 hours, and then the cock was opened to drain water. At this time, the composition 5 disappeared from the experimental system because the granular state disappeared and became unsuitable for the subsequent phosphate ion collection experiment. Next, 30 ml of an aqueous solution of potassium potash phosphate prepared so that the phosphate ion concentration becomes 6.0 ppm was poured into each of the burettes from which water had been drained, and allowed to stand for 5 minutes. Over a period of time, the aqueous phosphate solution was dropped and collected, and the phosphate ion concentration was measured by a colorimetric method (Deniges method). In the repetitive experiment, the poured phosphate aqueous solution was dropped from the burette, and as soon as the collection was completed, 30 ml of a new aqueous solution of potassium nitrate was poured into the burette.
After allowing to stand for 5 minutes, the liquid that passed through the water-resistant granular composition layer over 5 to 6 minutes was collected and used for measurement of the phosphate ion concentration. The experiment for repeatedly collecting phosphate ions was performed three times, and the results are shown in Table 1. As is clear from the results in Table 1, it was found that the granular composition for collecting phosphate ions in water according to the present invention can efficiently collect and collect phosphate ions in water. 7. 25 g of each granular composition was placed in a 200 ml beaker, and 90 ml of the aqueous solution of potassium potassium phosphate used in Example 5 was added thereto, and the mixture was stirred for 1 hour with a stirrer. As a result of measuring the acid ion concentration, the phosphate ion concentration was 0.1 ppm in all the test sections of compositions 1, 2, 3, and 4.

[0008]

As shown in the examples, the present invention was able to provide a water-resistant granular composition capable of reusing phosphate ions in water and collecting calcium phosphate salts. By flowing wastewater containing phosphate ions through a column filled with the water-resistant granular composition, phosphate ions in the wastewater can be collected. In addition, by placing this water-resistant granular composition in a net bag in a river, phosphate ions contained in the river can be collected. In addition, it was found from the results of the examples that phosphate ions contained in the water of the lake can be collected and recovered by hanging the net bag behind the boat and going around the lake.

Claims (1)

[Claims] An aqueous solution of a water-soluble polymer compound is added to a mixture of bentonite, which is a clay having montmorillonite as a main clay mineral, and powdered calcium carbonate, and granulated or dried without granulation to obtain a water-resistant material. A composition for collecting phosphate ions in water, which is crushed or granulated without crushing.