JPS61153192A - Method for removing phosphoric ion in waste water - Google Patents

Abstract

PURPOSE:To remove rapidly and efficiently phosphoric ions by using gamma-oxy hydrated iron when phosphoric ions in waste water are removed. CONSTITUTION:When phosphoric ions in waste water are removed, gamma-oxy hydrated iron is used. The pH of the phosphoric ion-contg. water is preferably regulated to 4-10, when the gamma-oxy hydrated iron is brought into contact with the water. As a contact method, the phosphoric ion-contg. water is passed through the bed of granular or powdery gamma-oxy hydrated iron, or a batch process wherein the gamma-oxy hydrated iron is added to the phosphoric ion-contg. water and agitated is used. In this method, the operation for removing phosphoric ions is simplified, the removing speed is high, and the removal efficiency is remarkably high. Although the removing effect is excellent, sludge is hardly generated. Moreover, since the gamma-oxy hydrated iron is hardly soluble in water, the iron is not eluted into the treated water. Besides, the gamma-oxy hydrated iron can be obtained inexpensively, because iron occurs in nature.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for efficiently removing phosphate ions contained in various types of wastewater such as domestic wastewater, industrial wastewater, and agricultural wastewater.

(Conventional technology) In recent years, phosphate ion substances have been found in lakes and marshes.

It is said to be one of the causes of eutrophication.

In particular, they are said to play a major role in the occurrence of blue-green algae in closed waters and red tide in sea areas, causing various harm to us. For this reason, the Lakes and Marshes Act etc. regulate the phosphate ion content in wastewater, and at the same time, research is being done on technology to remove phosphate ion substances from the perspective of preventing phosphate ion substances from flowing into lakes, marshes, rivers, etc., and various proposals have been made. has been done.

Currently, methods for removing these phosphate ions include coagulation-precipitation, biological methods, ion-exchange methods, and crystallization, but most of the methods used in practical use are coagulation-precipitation. .

(Problems to be Solved by the Invention) This coagulation-precipitation method uses aluminum sulfate, ferrous sulfate, ferric sulfate, aluminum chloride, and ferrous chloride.

p using metal salts such as ferric chloride and calcium hydroxide.
It is a stable treatment method for removing phosphate ions because it adjusts H and forms flocs as hydroxide or reacts to co-precipitate the remaining phosphate ions with one reactant. however.

This method requires the addition of a large amount of metal salt relative to the phosphate ion concentration. This indicates that the removal efficiency of phosphate ions is poor relative to the amount of added metal salt used, and in addition, a large amount of precipitated sludge is generated, which is considered to be a drawback. Also.

Other biological methods, ion exchange methods, crystallization methods, etc. all generate a large amount of sludge, require many chemicals, require PI sub-adjustment, are complicated to operate, and require operational management. Difficulty is also a drawback.

(Means for Solving the Problems) The present inventors conducted intensive research to solve the drawbacks of conventional methods, and found that γ-oxyyeiwa iron can remove phosphate ions very efficiently. They discovered that this is the case and arrived at the present invention.

That is, according to the present invention, γ-oxyiron hydrate is added to wastewater containing phosphate ions, and the mixture is stirred at room temperature to precipitate the phosphate ions in the wastewater as a hardly soluble phosphorus compound, or
Alternatively, phosphate ion substances can be efficiently removed from wastewater by adsorption.

T-oxyyeiwa iron used in the present invention is also called γ-hydrous iron oxide or γ-oxyiron hydroxide, and is naturally produced in scale ironite.

For artificial production, Experimental Chemistry Course, Volume 9 (round neck,
1958 edition), Synthesis and Purification of Inorganic Compounds (340 pages)
There is a method described in Nikkashi, Vol. 91, No. 10 (page 935), 1970, etc., and it can be used in the form of granules or powder, but in the present invention, phosphate ions are used. The shape of the removal device to be used is determined by taking into account the type and size of the removal device, the removal efficiency obtained by the water passage speed, etc. However, it is generally preferable to use a powder that has a large contact area.

Furthermore, since there are various types of phosphate ion-containing water with various pH values, it is desirable that the pi of the phosphate ion-containing water be 4 to 10 when contacting with γ-oxy Eiwa iron. In this case, if the pH is less than 4, iron will dissolve in the waste water, and the phosphate ion removal efficiency will tend to deteriorate.If the pH is greater than 10, salts will form on the surface of the γ-oxyhydrated iron. In this case, the pH should be 6.
-9 is preferable. In addition, contact methods include passing phosphate ion-containing water through a layered body of granular or powdered iron hydrate (passing through a static layer or stirring layer), or passing γ-oxyiron in water containing phosphate ions. A batch method in which hydrated iron is added and stirred is effective.

(Example) The present invention will be described in detail with reference to Examples below. The T-oxyiron hydrate used in the Examples was prepared as follows according to the method described in Experimental Chemistry Course (above).

Production of T-oxyiron hydrate; Dissolve 120g of ferrous chloride in 31ml of water, filter the liquid, and add urotropin solution (168g/600i+) to the filtrate.
l water) was sexed. When a blue-green ferrous hydroxide precipitate forms, stir the solution constantly.

80ml concentrated hydrochloric acid and sodium nitrite solution (42g/
600ml water) was added and heated to 60°C. After the oxidation reaction to generate nitrogen oxide progressed, the solution was left to stand for about 3 hours while stirring occasionally. The resulting supernatant was removed, filtered, and washed to the extent that no chloride ions were present. Dry this at 60°C.

A deep orange fine powder was obtained. This powder was used in the following examples. (Hereinafter, this will be abbreviated as T-Fe.) Example 1 200 ml of water (pH 7) containing 1 off 1 g/l of phosphate ion (PO4-') was placed in each of three Erlenmeyer flasks, and (sample la ), r-Fe is O,
1g of activated alumina (reagent grade, 200-300 mesh) was added for comparison (sample lb).
To (sample lc), 0.1 g of aluminum sulfate (dissolved in a small amount of water) was added to adjust the pH to 7.
) and (lc) were added for 24 hours at room temperature. For (1a) and (1b), the supernatant was collected.

For (IC), filter with filter paper (#6).

Phosphate ions were measured for these three solutions.

As a result, the removal rate of the present invention (1a) was approximately 100%, the removal rate of Comparative Example 1 (lb) was 80%, and the removal rate of Comparative Example 2 (lc) was approximately 100%. Incidentally, the precipitate at this time was almost only the added amount for (la) and (lb), but a large amount of hydroxide flocs precipitated for (lc).

Example 2 γ-F of the present invention was used to investigate the removal rate of phosphate ions.
The test was carried out on activated alumina for comparison.

10mg/j2 of phosphate ion-containing water (pH 7)
00ml was placed in each of two Erlenmeyer flasks, 0.04g of 7-Fe of the present invention was placed in one (C sump 2a), and 0.04g of activated alumina (same as in Example 1) was placed in the other.
g were added to each and shaken at room temperature. Next, phosphate ions in the supernatant were measured over time. As shown in FIG. 1, the results were more remarkable when γ-Fe was added (2a) as in the present invention.

It was found that the phosphorus removal effect is fast.

Example 3 Phosphate ion (P
Phosphate ions were removed from 10 mg/N of water containing O4-3). Phosphate ion-containing water was injected from the raw water inlet 2 of the treatment tank 1 at an injection rate of 50 cc/min.

100 g of γ-Fe was added into the tank 1, and the inside of the tank 1 was gently stirred by the stirrer 3, and the residence time in the tank was set to 30 minutes, and supernatant water was discharged from the treated water outlet 4.

As a result, almost 100% of the phosphate ions in the supernatant water were removed. Furthermore, no iron was detected in the supernatant water. 5 is a partition plate, and F is a sediment.

(Effect of the invention) The method of the present invention has the following advantages.

(1) The removal operation of phosphate ions is simple, the removal rate is rapid, and the removal efficiency is extremely high.

(2) Compared to the coagulation-sedimentation method using aluminum salts and calcium salts, almost no sludge is generated despite the good removal effect.

(3) Since T-oxyiron hydrate is hardly soluble in water, it will not be eluted into the treated water.

(4) Since γ-iron oxyhydrate is naturally produced, it can be produced manually at low cost and can also be easily produced artificially.

[Brief explanation of drawings]

FIG. 1 is a comparative diagram of the removal rate of phosphate ions, and FIG. 2 is a schematic longitudinal sectional view of the apparatus of the example.

Claims (1)

[Claims] (1) A method for removing phosphate ions from wastewater, which comprises using γ-oxyiron hydrate when removing phosphate ions from wastewater.