JPH09136032A - Granular phosphorus adsorbent and method for removing phosphorus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a porous granular phosphorus adsorbent having proper strength simply in a short time without drying and firing by adding water absorptive polymer powder into the acid aqueous solution of iron salt or aluminum salt after the solution being neutralized by adding cement, kneading the mixture, and granulating it. SOLUTION: When cement 3 is added into the aqueous solution 2 of polyiron, and the mixture is mixed in an agitation tank 1, the solution is neutralized, and a reaction between a hydroxyl group dissociated from alkaline substances and iron ion occurs to produce the paste 7 of ferric hydroxide particles. The paste 7 is transferred to a kneader 4 and added with water absorptive polymer powder 5. When the mixture is kneaded, water in the paste 7 is absorbed quickly by the powder 5, and by further kneading, the swelled powder 5 becomes adhesive to convert the ferric hydroxide particles and the cement particles into aggregated particles as a binder. They are molded by extruding pelletizer 6, etc., and a porous granular phosphorus adsorbent 8 is produced which is not disintegrated even when immersed in water and has high strength and elasticity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel phosphorus adsorbent capable of effectively removing phosphorus from rivers, lake water, sewage, wastewater, industrial wastewater, etc., a method for producing the novel phosphorus adsorbent, and a method for producing the same. It relates to the phosphorus removal method used. The phosphorus removal technique of the present invention relates to a technique particularly suitable for removing a trace amount of phosphorus of about 0.1 mg / liter contained in a large amount of natural environment water such as river or lake water.

[0002]

2. Description of the Related Art Rivers and lakes, dam lakes, where rivers flow in,
In order to prevent eutrophication of the sea and the like, it is becoming increasingly necessary to remove phosphorus contained in river water. For example, a typical example of a phenomenon associated with eutrophication is the occurrence of blue-green algae and red tide, and it is said that such a phenomenon is very likely to occur at a phosphorus concentration of 0.05 mg / liter or more. Therefore, attempts to remove phosphorus contained in rivers have recently been started.

Conventionally, the method of removing phosphorus from river water is as a granular phosphorus adsorbent, in which activated alumina or the like is fired into particles having a particle diameter of several centimeters, and a granular phosphorus adsorbent formed is used to remove phosphorus in river water. Attempts have also been made to remove phosphorus. However, these granular phosphorus adsorbents have the following drawbacks, and further development of ideal granular phosphorus adsorbents is desired. In other words, activated alumina has a higher price because it is made by firing activated alumina powder, which is expensive in itself, into granules and molding it.
Not very suitable for water treatment, which requires low running costs. When filling rivers, both activated alumina and Kanuma soil must have a large particle size of several centimeters in order to prevent blockage due to turbidity. The intragranular diffusion is poor and the inside of the granular material cannot be used for phosphorus adsorption. Granules such as activated alumina are extremely hard and have a slow natural disintegration property when used waste is sprayed on forest land for disposal. And so on.

[0004]

DISCLOSURE OF THE INVENTION Problems to be solved by the conventional granular phosphorus adsorbent are solved, and (i) iron hydroxide and aluminum hydroxide which are difficult to be granulated while maintaining a high phosphorus adsorption property. To be dispersed and mixed with the granular phosphorus adsorbent so that the phosphorus adsorption efficiency is good. (ii) The manufacturing process of the granular phosphorus adsorbent is very simple. (iii) The step of firing the granular material is unnecessary. (iv) Phosphorus adsorption property is good, and phosphorus adsorption amount is large. (v) The granular phosphorus adsorbent is porous, has good water permeability, and has a particle size of 1
Even if it is made into large particles of centimeters or more, it can be used for adsorption even inside the granular phosphorus adsorbent. (vi) The strength of the waste granular phosphorus adsorbent after use is not too hard, has good natural disintegration property, and is easy to dispose. (vii) The granular phosphorus adsorbent is inexpensive and suitable for water treatment. It is to develop an inexpensive granular phosphorus adsorbent having advantages such as.

[0005]

The above-mentioned object of the present invention can be achieved by the following phosphorus adsorbent of the present invention, a method for producing the phosphorus adsorbent, and a method for removing phosphorus using the phosphorus adsorbent. That is, (1) a granular phosphorus adsorbent characterized by being prepared by adding cement to an acidic aqueous solution of an iron salt or an aluminum salt for neutralization, then adding a superabsorbent polymer powder, and kneading and granulating. (2) A method for producing a granular phosphorus adsorbent, which comprises adding cement to an acidic aqueous solution of an iron salt or an aluminum salt for neutralization, then adding a superabsorbent polymer powder, and kneading and granulating. (3) A method for removing phosphorus, which comprises bringing the granular phosphorus adsorbent according to (1) into contact with phosphorus-containing water. It is.

The gist of the present invention is to neutralize an acidic aqueous solution of an iron salt or an aluminum salt by adding cement to form iron hydroxide or aluminum hydroxide in a state where they are mutually dispersed with the cement, and the mixture has high water absorption. Polymer powder is added,
The purpose is to knead and granulate to form porous particles, and to form a granular phosphorus adsorbent having good phosphorus adsorption even inside the particles. Among the salts suitable for producing the granular phosphorus adsorbent of the present invention, as the iron salt,
Ferric chloride, ferric polysulfate (ferric iron), and ferric sulfate are suitable, and aluminum salts such as aluminum sulfate, aluminum chloride, and polyaluminum chloride (PA
C) and the like are suitable.

According to experiments conducted by the present inventor, acidic aqueous solutions of iron salts and aluminum salts such as ferric polysulfate (ferric iron), ferric chloride, aluminum sulfate (sulfuric acid band) and polyaluminum chloride (PAC). It was found that by adding cement (which is an alkaline substance) to and neutralizing it to pH 6 to 8, iron hydroxide and aluminum hydroxide particles having excellent phosphorus adsorptivity are produced. Here, the generated iron hydroxide or aluminum hydroxide particles are in a paste state with cement. The paste of iron hydroxide or aluminum hydroxide particles of the present invention and cement may, of course, be formed by adding and kneading an acidic aqueous solution of the iron salt and aluminum salt to cement. Then, when super-water-absorbing polymer powder was added to the paste of iron hydroxide or aluminum hydroxide particles and cement and kneaded, the granulated material surprisingly became a remarkably porous aggregate , and was suitable. It has been found that a strong elastic body is formed. The structure was such that "Okoshi" of confectionery, innumerable small particles were aggregated through a superabsorbent polymer gel absorbing water to form a porous aggregate structure. It was confirmed that when the superabsorbent polymer powder was not added, the granulated product did not become porous and became hard like stone, and the phosphorus adsorption property and the disposal property of the waste phosphorus adsorbent were deteriorated. .

As the cement, Portland cement, alumina cement, various early-strength cements (for example, jet cement) may be used. The superabsorbent polymer used in the present invention includes various superabsorbent polymers (polyacrylate, starch-acrylate graft polymer, vinyl acetate copolymer, polyvinyl alcohol, etc.) which are frequently used in paper diapers and the like. ) Can be used, but those having a large water absorption amount capable of absorbing 300 g or more of pure water per 1 g of superabsorbent polymer powder are particularly preferable.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A typical production example of the granular dephosphorization material (phosphorus adsorbent) of the present invention will be described with reference to FIG. In the following description, an example using polyiron as an adsorbent will be described, but the same production can be performed by using other iron salts or aluminum salts. In FIG. 1, pH 2 is set in the stirring tank 1.
When the cement 3 is added to and mixed with the polyiron aqueous solution 2 having a pH of 3 to 3, the polyiron aqueous solution 2 is neutralized to pH 6 to 8 and the hydroxyl group dissociated from the alkaline substance contained in the cement particles reacts with the iron ion to generate water. A paste 7 of ferric oxide particles is produced. When this paste 7 is transferred to the kneading machine 4 and the superabsorbent polymer powder 5 is added and kneaded, the superabsorbent polymer particles rapidly absorb the moisture in the paste. Upon further kneading, the superabsorbent polymer powder 5 which absorbs water and swells has an adhesive force like a paste and serves as a binder to aggregate ferric hydroxide particles and cement particles. When this is molded into particles of an appropriate particle size by an extrusion granulator 6 or the like, a porous granular phosphorus adsorbent 8 having high elasticity that does not collapse even when immersed in water is completed. With the above-described simple steps, it is possible to produce a porous and granular granular phosphorus adsorbent in a short time without providing the drying step and the firing step, which are conventionally required.

In order to remove phosphorus from phosphorus-containing water using the granular phosphorus adsorbent of the present invention, the granular phosphorus adsorbent may be packed in a column and the phosphorus-containing water may be passed at an appropriate space velocity (SV). . Phosphate ions diffuse on the surface and inside of the granular phosphorus adsorbent and are adsorbed and removed by iron hydroxide, aluminum hydroxide and cement particles. In order to remove phosphorus from a river, the method of packing the phosphorus adsorbent granulated to a few centimeters in a water-permeable container such as a net bag and submerging it in the river is less likely to cause clogging by river turbidity. Can be recommended as the simplest phosphorus removal technology.

Incidentally, Japanese Patent Application Laid-Open No. 6-15 filed earlier by the present inventor
The "composite granular material of a metal hydroxide and a super absorbent polymer" described in Japanese Patent No. 4597 utilizes a super absorbent polymer, but the action of the super absorbent polymer is essential to the present invention. Are different. That is, the prior-art technique is to "hold a metal hydroxide inside each individual particle of a hydrogel particle that is made of a superabsorbent polymer and swells in water to exhibit elasticity", whereas the present invention The phosphorus-adsorptive fine particles are present outside the superabsorbent polymer gel. In addition, the prior application dephosphorization agent (phosphorus adsorbent) is used as a small particle size phosphorus adsorbent in a state where each hydrogel particle is dispersed. Because it cannot be manufactured
High turbidity rivers are clogged and not applicable. Moreover, it does not have the aggregated aggregate structure of the present invention.

[0012]

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to only this embodiment.

Example 1 A solution (pH 2) obtained by adding 200 cc of tap water to 100 cc of a polyiron stock solution and 90 g of Portland cement was added to the solution. I got a paste. When 70 g of powder of super absorbent polymer (polyacrylic acid crosslinked product; manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was added to this paste and kneaded for 3 minutes,
It easily aggregated into a porous aggregate. This was molded into a columnar shape having a diameter of 3 cm and a length of 3 cm by the extrusion granulator and naturally dried for 1 day to obtain a granular material having a strength that does not collapse in water.

Example 2 A liquid sulfuric acid band (liquid van) stock solution was diluted with tap water to 300 cc, and 70 g of fast-setting cement (jet cement; manufactured by Sumitomo Cement Co., Ltd.) was added to the solution to neutralize it to pH 6 and phosphorus. A ferric hydroxide paste having good adsorptivity was obtained.
To this paste, add 60 g of super absorbent polymer powder,
When kneading was carried out for a minute, the particles were easily aggregated, and after air-drying, the same phosphorus adsorbent as in Example 1 was produced.

Example 3 A phosphorus removal column test was conducted using the phosphorus adsorbents produced in Examples 1 and 2 above. Table 1 shows the test conditions and the test results.

[0016]

[Table 1]

It can be seen from Table 1 that the phosphorus adsorbent of the present invention exhibits a good dephosphorization performance, and particularly the one in which the iron salt is neutralized with cement shows good results. The pH of the raw water was 7.0, whereas the pH of the treated water was in the range of 7.3 to 8.3, which satisfied the water quality regulation.

[0018]

EFFECTS OF THE INVENTION According to the present invention, (1) it is possible to manufacture a granular phosphorus adsorbent having an appropriate strength, which is extremely simple and can be formed in a short time without drying and firing. Therefore, it is suitable for mass production,
Both the manufacturing equipment cost and the running cost can be significantly reduced from the conventional one. (2) Since it is porous, even if it has a large particle size, it has a large surface area and has good diffusion of phosphate ions into the particles.
Excellent phosphorus adsorption performance. (3) Since the strength is appropriate and the disintegration is excellent, it is easy to dispose of the waste adsorbent on the forest.

[Brief description of the drawings]

FIG. 1 is a flow explanatory diagram showing a production process of a phosphorus adsorbent of the present invention.

[Explanation of symbols]

 1 Stirrer 2 Poly iron aqueous solution 3 Cement 4 Kneader 5 Super absorbent polymer powder 6 Granulator 7 Paste 8 Granular phosphorus adsorbent

Claims (3)

[Claims] 1. A granular phosphorus adsorbent characterized by being prepared by adding cement to an acidic aqueous solution of an iron salt or an aluminum salt for neutralization, then adding a superabsorbent polymer powder, and kneading and granulating. 2. A method for producing a granular phosphorus adsorbent, which comprises adding cement to an acidic aqueous solution of an iron salt or an aluminum salt for neutralization, and then adding a superabsorbent polymer powder and kneading and granulating. . 3. A method for removing phosphorus, which comprises contacting the granular phosphorus adsorbent according to claim 1 with phosphorus-containing water.