JPS6043797B2 - Phosphorus removal treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing phosphorus from water containing dissolved phosphorus.

In recent years, significant eutrophication of water quality has been observed in closed water areas such as lakes, inner bays, and inland seas, and phenomena such as red tide and abnormal algae blooms are occurring frequently.

It is said that this phenomenon is caused by the presence of phosphorus in water. Conventionally, coagulation-sedimentation method, activated sludge method, etc. have been proposed as phosphorus removal technology for tertiary treatment of wastewater such as industrial wastewater and urban water, but the removal effect, equipment footprint, equipment cost, sludge treatment, There are still problems with maintenance, etc., and to date there is no high-performance, inexpensive and quick processing method.

In other words, the coagulation-sedimentation method is a method in which lime or metal salts such as aluminum salts and iron salts are added to water, but the method using lime requires high construction and treatment costs, and it is difficult to treat the source at the source. This is extremely disadvantageous, and furthermore, it inevitably generates scale, making maintenance management difficult.
The method using metal salts has the disadvantage that not only metal phosphates precipitate, but also metal hydroxides precipitate, resulting in a decrease in the utilization rate of the metal salts for phosphorus removal. Furthermore, it is said that a theoretical amount of metal salt is required to almost completely remove phosphorus, which is not only economically disadvantageous but also has the disadvantage of generating a large amount of slush. In addition, the activated sludge method has the drawback that the phosphorus removal efficiency of the activated sludge changes depending on the phosphorus content in the water, and there are problems with maintenance and management, and it is difficult to use when treating industrial wastewater at its source. Construction equipment and treatment costs will be enormous compared to the amount of wastewater produced. On the other hand, the adsorption method is not affected by fluctuations in the phosphorus concentration in wastewater, has a high removal rate, and can easily reduce the phosphorus concentration in treated water. When using a column system that allows wastewater to pass through, maintenance and management are very easy.

In addition, if regeneration using an adsorbent regenerant is possible, the removed phosphorus can be recovered in an extremely highly concentrated state in the regeneration solution, making it easy to process the phosphorus, reuse, and dispose of it. has. In order to put into practical use an adsorption method that has the various advantages mentioned above, it is necessary to develop an adsorbent that is highly capable of phosphorus equilibrium adsorption.

The present inventors focused on the fact that phosphorus dissolved in water exists as anions such as phosphate ions and hydrogen phosphate ions, and synthesized various substances with anion adsorption ability. As a result of intensive studies on the adsorption ability of phosphate ions, it was discovered that alumina hydrate having a specific crystal structure exhibits extremely high phosphorus adsorption ability, and the present invention was completed. The gist of the present invention is to bring phosphorus-containing water in a dissolved state into contact with an alumina hydrate having a pseudo-boehmite structure, and to adsorb phosphorus present in the water onto the alumina hydrate. It is in the removal treatment method. In the present invention, the alumina hydrate having a pseudo-boehmite structure has a lattice spacing of 6.11A13.16A123 in X-ray powder diffraction method.
2A11.86A is an alumina hydrate having a diffraction line similar to a boehmite structure at positions 11.45A and 1.31A, but much wider than that diffraction line.

Pseudo-boehmite is also called boehmite gel, and while boehmite has a composition of Ae2O3.I (20),
Since the composition is close to that of Ae2O3.1.5-2H20 and it has a stable structure by hydration, the boehmite structure does not migrate unless it is hydrothermally treated.

This alumina hydrate having a pseudo-boehmite structure shows amorphous crystallinity in X-ray powder diffraction.Amorphous alumina hydrate obtained by any method is heated at 10°C or higher in water and at 50°C in a dry state. Produced by aging at temperatures of ~500°C. The time required for aging varies depending on the aging temperature, but usually 2 hours or more is required. If the aging temperature is less than 10'C in water or less than 50'C in a dry state, the crystal growth rate is extremely slow and aging takes a long time. Also, the aging temperature. 500℃
When the alumina hydrate exceeds η, the alumina hydrate becomes η alumina, and its ability to adsorb phosphate ions is significantly lower than that of an alumina hydrate having a pseudo-boehmite structure. The alumina hydrate used in the present invention can be made into a particulate compact suitable for filling into an adsorption tower by kneading it in the presence of moisture, extruding it into granules, and then drying it.

In the present invention, it is necessary to bring the alumina hydrate having a pseudo-boehmite structure obtained as described above into contact with phosphorus-containing water. For this purpose, a so-called slurry method is used in which these alumina hydrates are suspended and dispersed in phosphorus-containing water, or an adsorption tower method is used in which the phosphorus-containing water is passed through an adsorption tower filled with these alumina hydrates. In either case, a contact time of 1 minute or more is required. Furthermore, when using a slurry method, it is necessary to sufficiently stir the liquid. Further, in the treatment method of the present invention, it is possible to regenerate the phosphorus adsorbed on the adsorbent using a regenerating agent and then reuse it.

Examples of the regenerating agent used include aqueous solutions of basic substances and salts of basic substances, such as aqueous sodium chloride, aqueous sodium carbonate, aqueous ammonia, aqueous sodium hydroxide, and aqueous potassium hydroxide. In the treatment method of the present invention,
The equilibrium adsorption amount of phosphorus of the alumina hydrate, which is used as an adsorbent, is extremely high over a wide range of equilibrium concentration of phosphorus in phosphorus-containing water. It is possible to remove it effectively.

Furthermore, it is also effective for removing phosphorus from phosphorus-containing water in which other cations and anions, especially monovalent anions such as chloride ions and bromide ions, coexist. The above-mentioned excellent features of the present invention can be exhibited for the first time by using alumina hydrate with a pseudo-boehmite structure as an adsorbent; Even if an alumina hydrate having a hydrated alumina is used as an adsorbent, the phosphorus removal effect obtained by the treatment method of the present invention cannot be achieved.
The treatment method of the present invention is particularly suitable for the treatment of acid-free phosphate ion-containing wastewater among phosphorus-containing wastewater, and is suitable for treating wastewater containing acid-free phosphate ions, for example, in manufacturing industries such as fertilizer industry, detergent industry, food industry, machinery industry, painting industry, etc. It is suitable for treating industrial wastewater containing inorganic phosphates, urban sewage containing inorganic phosphates, and primary industrial wastewater containing inorganic phosphates as a component.

The treatment method of the present invention preferably employs an adsorption tower system, and the fixed bed adsorption tower system is superior in terms of equipment simplicity.

By adopting the adsorption tower method, various problems in treatment technology that were previously caused by the coagulation-sedimentation method and activated sludge are eliminated, and it is a small-scale model that occupies less space and is an inexpensive, high-performance method for wastewater treatment. It is resistant to fluctuations in phosphorus content and maintenance is extremely easy.

Also, depending on the adsorption tower system, there are problems with the equipment, such as masking of the adsorbent surface due to oil in the wastewater and clogging of the adsorption tower due to suspended solids in the wastewater. The problem can be solved by adopting adsorption tower systems known in the wastewater treatment industry. That is, for example, to hide the adsorbent related to oil, an oil-water separation tower can be installed at the front stage, and to prevent clogging of the adsorption tower due to suspended solids, a backwash type filtration device can be installed at the front stage. It can be solved. The present invention will be explained below with reference to Examples.

Example 1 24V sodium hydroxide was dissolved in 100cc of water. To the sodium hydroxide solution, 10y of aluminum powder was gradually added and completely dissolved, filtered, and diluted hydrochloric acid was added to adjust the pH.
lO. 5 and the total volume was 122ml.

Thereafter, carbon dioxide gas was blown in at a rate of 250 ml/min while adjusting the temperature to 20°C, followed by washing with water and air drying to synthesize an alumina hydrate. Examination of the crystal structure of this substance by X-ray powder diffraction revealed an amorphous structure.

This amorphous alumina hydrate was dried at 110°C for an hour.

This material showed a pseudo-boehmite structure as a result of X-ray diffraction.

Dissolve 0.2866 da of monopotassium phosphate in 1e of water,
Phosphate ion concentration 204 ppm (JISK-0102-
27) was prepared. This stock solution 20
Add 1 da of the above substance crushed to 100 mesh or less into 0 cc, stir for 2 hours, then filter, and measure the phosphate ion concentration of the solution using the molybdenum blue method specified in JISK-0102-27. When measured in accordance with the law, it was 17.6 ppm.

Example 2 The amorphous alumina hydrate synthesized in Example 1 was suspended and dispersed in ion-exchanged water, and aqueous ammonia was added thereto to adjust the pH to 8.
5, and aging was performed for one week while maintaining the pH of 8.5.

The obtained material was washed with water, air-dried, and subjected to X-ray diffraction, which showed a pseudo-boehmite structure.

1f of this material pulverized to 100 mesh or less was taken and put into a monopotassium phosphate aqueous solution with a phosphorus concentration of 204 ppm in the same manner as in Example 1, and after adsorption treatment for 2 hours, the phosphoric acid concentration of this aqueous solution was 11 ppm. It was hot.

Example 3 A 10% by weight aqueous solution of aluminum nitrate was prepared, and 4N ammonia water was rapidly added to this aqueous solution while stirring at a temperature of 20° C. until the pH reached 8.

After filtering the alumina hydrate in the liquid produced by this operation and washing with water, the alumina hydrate was aged in water for 3 days while being maintained at 40°C.

Thereafter, the alumina hydrate was washed with water, filtered with alcohol, and air-dried.
X-ray diffraction revealed that this material had a pseudo-boehmite structure.

This material 1f crushed to 100 mesh or less was mixed with 200 g of monopotassium phosphate aqueous solution with a phosphate ion concentration of 204 ppm.
cc and stirred for 2 hours. After stirring for 2 hours, centrifugation was performed and the phosphate ion concentration of the supernatant was measured and found to be 13 ppm.

Example 4 The alumina hydrate having a pseudo-boehmite structure prepared in Example 1 was crushed to a particle size of 10 mesh or less and 32 mesh or more, and immediately filled into a 20 TIrIft column to a height of 50 m2.

A monopotassium phosphate aqueous solution having a phosphate ion concentration of 204 ppm was passed through this column at a rate of 1.5 e per hour.

As a result, the phosphorus ion concentration of the effluent after 4 hours of water flow was measured and was found to be 0. ? It was Pm.

Comparative Example 1 The structure of Showa Denko's alumina hydrate 1 hydralgilite was investigated by JX-ray diffraction, and it was found to be hydralgilite.

This substance 1y was added to a monopotassium phosphate aqueous solution with a phosphate ion concentration of 204 ppm in the same manner as in Example 1,
Perform adsorption treatment for 1 hour.

After passing through the door, the phosphate ion concentration of the aqueous solution was 201 ppm. Comparative Example 2 The hydralgilite used in Comparative Example 1 was exposed to 300 g
The product was fired at ℃ and its structure was examined by X-ray diffraction, and it was found to be χ alumina.

1 q of this substance was added to a monopotassium phosphate aqueous solution with a phosphate ion concentration of 204 ppm in the same manner as in Example 1, and 2
The phosphate ion concentration of the aqueous solution after being subjected to a time adsorption treatment and then being subjected to p-filtration was 203 ppm.

Comparative Example 3 The hydralgilite used in Comparative Example 1 was exposed to 100%
The structure was determined to be boehmite by heating to .degree. C. and examining its structure by X-ray diffraction.

This substance 1V was added to a monopotassium phosphate aqueous solution with a phosphate ion concentration of 204 ppm in the same manner as in Example 1, and adsorption treatment was performed for 2 hours. After filtering, the phosphate ion concentration of the aqueous solution was 201 ppm. .

Comparative Example 4 24y of sodium hydroxide was dissolved in 100cc of water to create a sodium hydroxide solution, 10y of aluminum powder was gradually added thereto, dissolved, and then water was added to make 122m.
1 and a sodium aluminate solution was prepared.

Add 250ml of carbon dioxide gas to this sodium aluminate solution.
Synthesis was carried out using blown alumina hydrate while adjusting the temperature to 25° C./Min. Furthermore, the pH of the alumina hydrate suspension was adjusted to 11 using a sodium hydroxide solution, and the suspension was dehydrated and dried.

As a result of X-ray diffraction, this material was found to be vialite. This substance 1f was treated with a phosphate ion concentration of 2 in the same manner as in Example 1.
The phosphate ion concentration of the aqueous solution after filtration was 179 ppm.

Comparative Example 5 The vialite prepared in Comparative Example 4 was heated and dried at 300° C. in the atmosphere.

When this material was examined by X-ray diffraction, it was found to be η alumina. This substance 1f was added to a monopotassium phosphate aqueous solution with a phosphate ion concentration of 204 ppm in the same manner as in Example 1, and adsorption treatment was performed for 2 hours. After filtering, the phosphate ion concentration of the aqueous solution was 185 ppm. It was hot.

Claims (1)

[Claims] 1. A method for removing phosphorus, which comprises contacting dissolved phosphorus-containing water with an alumina hydrate having a pseudo-boehmite structure, and adsorbing phosphorus present in the water onto the alumina hydrate.