JP2904217B2 - Water treatment filter manufacturing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a water treatment filter for reducing and decomposing and removing, for example, organic halogen compounds or hardly decomposable pollutants in water.

2. Description of the Related Art Water treatment techniques include, for example, an adsorption method using activated carbon, a redox method using a catalyst, an aeration method of volatilizing by air bubbling, an ozone treatment method of oxidizing with ozone, and coagulation by coprecipitation and separation as hydroxide. Processing methods and the like are known. Journal of the Japan Society of Industrial Water (Industrial Water), No.357
(1988), p2 to p7 relate to the catalytic method of using iron powder as a reducing agent and igniting a certain amount of water containing 1,1,2,2-tetrachloroethane to obtain 1,1, It is described that 2,2-tetrachloroethane is removed by reductive decomposition.

Problems to be solved by the invention When such a water treatment technique is applied to a technique for removing an organic halogen compound or a persistent pollutant component in water,
Because it adsorbs anything due to the characteristics of activated carbon, harmless substances other than target components in water are also adsorbed and removed, resulting in poor efficiency. Further, if burned at the time of disposal, there is a danger that the adsorbed components volatilize into the atmosphere and further generate secondary harmful substances such as chlorine gas, phosgene, and dioxin. Is not suitable for practical use because the oxidation-reduction efficiency of the catalyst is often short-term.
Is merely a volatilization of pollutants into the atmosphere and is not a fundamental solution. Requires an ozone generator,
The harmful ozone may remain, and the scale of the apparatus becomes too large. Is a symptomatic treatment such as removal of a precursor that produces an organic halogen compound, and has a problem that it is not a method of directly removing the component.

In addition, the known technology relating to the reductive decomposition by the iron powder is as follows:
In the process of activating the surface, not only is it difficult to handle the components, but if it is packed in a column or the like and used as a water treatment filter, the reductant is a powder, and when the treated water passes through the treated water, a short circuit occurs in the packed layer. There is a disadvantage that the iron powder and the harmful substance do not easily come into contact with each other easily, and the decomposition efficiency is poor.

Means for Solving the Problems In order to solve the above problems, the present invention provides a method for bringing a three-dimensional mesh-like porous body into contact with an aqueous solution of an oxide film, dissolving and removing the oxide film, and removing the skeleton surface layer forming the porous body with iron. The problem is solved by providing a method for producing a water treatment filter, characterized by comprising:

An example of water treatment of harmful chlorine compounds will be described as a water treatment technique containing harmful substances.

Zero-valent iron is an extremely effective reducing agent because it causes the following reaction with an organic chlorine compound harmful to the human body and renders the organic chlorine compound harmless. That is, it can be rendered harmless by the following reaction.

However, it is difficult for Fe to be present in a state of zero valence in water containing dissolved oxygen, and in general, Fe is changed to a divalent or trivalent oxide, and the above-described chemical reaction and reduction are unlikely to occur.

The present inventors have studied a method of maintaining the reduced state of Fe ^{0 by} a simple means, and have found that it can be achieved by dissolving and removing an oxide film of iron present on the surface layer (surface) of the filter made of iron. I got it.

Hydrochloric acid, hydrogen peroxide, nitric acid,
The oxide film on the surface layer of the filter is removed by contact with a 1 to 70% aqueous solution of sulfuric acid, phosphoric acid, hydrofluoric acid, chromic acid, formic acid, acetic acid, ascorbic acid and the like. A mixture of two or more of these acids has a similar effect.

That is, the surface layer of the filter is made of Fe ⁰
Is held.

Fe ⁰ retained on the surface of the filter by these methods
When used for a long time as a reduction agent for the organic chlorine compounds in water containing dissolved oxygen, intermittently each time constantly or necessary, or maintain flow aqueous solution of the filter, the state of the Fe ⁰ after processing To keep the potential lower than the oxidation potential of iron. Thereby, Fe ⁰ can be generated and retained for a long period of time.

Also for example, as false-made anode filter, attaching aluminum, holding the surface layer portion to Fe ⁰ and allowed to mix.

Another method of generating Fe ⁰ on the filter surface is, for example, a filter made of iron in a reducing atmosphere, for example,
It can also be achieved by heat reduction treatment in a hydrogen stream. Such a filter has a structure of iron, a reducing agent, and can easily remove an oxide film.There is no short path of treated water, and it can contact uniformly with harmful substances in treated water to efficiently decompose and remove. it can.

 Next, an example of a three-dimensional mesh porous body structure will be described.

Iron powder having an average particle size of 50 μm or less, iron oxide powder, and iron powder having an oxidized surface are used alone or as a mixture, or carbon powder is added and mixed, and used as a base material powder. Base material powder C
After adjusting so that the relationship between and O becomes the formula (1) described later, the mixture is kneaded with a binder, applied to an organic three-dimensional porous material, and further subjected to a heat treatment to perform a self-reduction sintering reaction.

The iron oxide powder can be produced, for example, by pulverizing steelmaking dust and hot-rolled scale from an ironworks. The iron powder having the oxidized surface is obtained by, for example, wet-pulverizing iron powder or cast iron. Iron pieces obtained by the wet pulverization method are safe because they do not ignite or explode during pulverization, and can be manufactured at lower cost than iron powder whose surface is not oxidized.

Iron to be crushed is an alloy element Mn, Ni, Cr, Cu, P, Au
In the case of containing, iron powder containing these alloy elements or iron powder whose surface is oxidized can be obtained, and these alloy elements are preferable for improving the strength and the like of the skeleton of the porous sintered metal body. . The same effect can be obtained by adding a powder containing these alloying elements to a powder for a base material.

Carbon powder is added to the base material powder, if necessary. The carbon powder is obtained by, for example, grinding an electrode or coke. Iron powder, iron oxide powder, iron powder with oxidized surface alone or mixed or by adding and mixing carbon powder, the content of carbon and oxygen, Here, [C]: a base material powder having a carbon content (% by weight) of the base material powder and [O]: an oxygen content (% by weight) of the base material powder. Iron with a carbon content of 2.1% or more is easily crushed because cementite becomes a crushing core, and powder can be produced at low cost. However, since this powder contains 2.1% or more carbon, it is used without adding carbon powder and mixing. it can.

Since the powder is sintered in a coated state without being pressed by a high-pressure press, the particle bonding is insufficient, and it tends to be difficult to maintain the shape of the porous body after sintering. In the heat treatment in this method, Fe ₃ C
A low-melting liquid phase of iron and iron is generated, and the liquid phase sintering binds the particles firmly, but C in the base material powder is 2.1%.
Is contained, a eutectic of iron and Fe ₃ C is generated, and liquid phase sintering is easily performed.

In the heat treatment, a self-reduction reaction is caused, and the carbon content is reduced by oxygen in the base material powder. If the content of [O] in the base material powder is 4/3 ([C] -2) or less, the progress of decarburization is insufficient, the carbon content of the base material after sintering is high, and thermal strain etc. It becomes a brittle porous body that is easily broken.

In addition, the content of [O] in the base material powder was 4/3 ([C] +
7) Above, the unreduced oxide in the base material after sintering increases, and the porous body is likely to collapse.

The content of [O] in the base material powder was 4/3 ([C]-
When adjusted to 2) to 4/3 ([C] +7), a sound iron-based metal porous body having excellent toughness can be obtained.

Next, the base material powder is kneaded with a binder and applied to the skeleton of the organic three-dimensional porous material. As the binder, for example, CMC or polyacrylic acid can be used in an organic system, and, for example, water glass can be used in an inorganic system. The base material powder is kneaded with an aqueous solution of these binders.

The organic three-dimensional porous material is a porous material that can be removed by thermal decomposition or sublimation by heating in heat treatment, and is, for example, urethane foam or three-dimensional fabric.

The kneaded product of the base material powder and the binder is applied to the skeleton of the organic three-dimensional porous material by spraying or dipping. Granularity
Since the base material powder having a size of 50 μm or less becomes a viscous slurry by kneading with a binder, it can be applied to the skeleton of the organic three-dimensional multi-layered material in a uniform thickness.

In the heat treatment, the atmosphere of the heating furnace is different from that of general sintered alloys because the base material powder contains sufficient carbon.
It is not necessary to use a reducing atmosphere, and an atmosphere of non-oxidizing argon gas or nitrogen gas is sufficient. When the organic three-dimensional porous material is urethane foam, the organic three-dimensional porous material is removed by heating at 100 to 350 ° C. for 30 minutes.

Further heating at 600 to 1200 ° C. for about 1 hour gives a sintered metal porous body whose base material is iron by liquid phase sintering, self-reduction reaction and finish sintering.

Such adjustment of the surface area, pores and the like of the porous body can be adjusted by the surface area of the organic three-dimensional porous material.

Examples Next, examples of the present invention will be described together with comparative examples.

Note 1: The three-dimensional mesh porous material is obtained by wet-milling granular iron, and the average particle size
Granules of 10 μm were kneaded with water and CMC, applied to urethane foam with 2 mm pores by a spray method, and dried (100
℃), degreasing (200 ℃), self-reduction (800 ℃), sintering (1100
C) in a nitrogen atmosphere, and the composition (%), C: 0.
05%, Si: 0.05%, Mn: 0.38%, P: 0.009%, S: 0.015%,
O: 0.01%, Fe: The remaining porous material is used.

Note 2: The treatment aqueous solution is heated to 40% before use.

Note 3: The treatment results are obtained by using the above porous material as a filter, circulating water containing 10 ppm of chloroform at a flow rate of 1.0 / min for 1 hour, and measuring the concentration of chloroform in the water coming out of the filter using an ECD gas chromatograph. Result.

Note 4: In the comparative example, the above iron powder was filled in a filling tank (diameter 100 mm, height 3
00 mm), and the chloroform-containing water was circulated in the same manner.

Effect of the Invention According to the present invention, sewage such as wastewater can be reliably purified, and the filter of the present invention can be used for a long period of time. Also, water treatment can be performed at extremely low cost. In addition, excellent effects such as reliable treatment of hardly decomposable polluted water such as organic halogen compounds can be obtained.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C02F 1/70 B01D 39/00

Claims (1)

(57) [Claims] 1. A method comprising: bringing a three-dimensional mesh-like porous body into contact with an aqueous solution of an oxide film to dissolve and remove the oxide film; and forming a surface layer of the skeleton forming the porous body from iron. Manufacturing method of treatment filter.