JPH03106496A - Sewage treatment - Google Patents

Abstract

PURPOSE:To ensure the treatment of sewage and particularly that of difficultly decomposable putrescible waster liquors containing org. halide, etc., in a proper way, and use a porous filter over an extended period of time by a method wherein untreated waste liquors are made to contact with the filter whose framework is formed of the porous body of a three- dimensional network and consists of at least one kind of metals Fe, Mn, Mg, Zn, Al and Ti, thereby subjecting contaminants in the waste liquors being treated to reductive decomposition for their removal therefrom. CONSTITUTION:Untreated waste liquors are made to contact with the filter whose framework is formed of the porous body of a three-dimensional network and consists of at least one kind of metals Fe, Mn, Mg, Zn, Al and Ti, thereby subjecting contaminants in the waste liquors being treated to reductive decomposition for their removal therefrom. For example, an aq. solution for dissolving oxide film is brought into contact with iron oxide film existing on the surface of a filter consisting of iron to remove such film therefrom in order to retain Fe<0>. Such a filter as this permits a uniform contact with harmful substances in the waste liquors being treated without causing the short pass thereof, resulting in an efficient film removal by decomposition. In the case of the filter consisting of the aforesaid metal other than Fe, the waste liquors are subjected to the reductive decomposition by the same reaction to be made free from the harmful substance.

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a water treatment method. Conventional Techniques For example, a) Treatment techniques for water containing halogen compounds include: ■ adsorption method using activated carbon, ■ oxidation method using a catalyst, ■ aeration method using air bubbling to volatilize water, and ■ ozone treatment. Known methods include ozone treatment to oxidize, and coagulation treatment to co-precipitate and separate hydroxides. Journal of the Industrial Water Society (Industrial Water), No. 357 (198
B), pages 2 to 7 are related to the catalytic method in ①, and if iron powder is used as a quantity agent and a constant 1.1- is added to water containing 1,1,2,2-tetrachloroethane. ,1,
1,2,2-Tetrachloroethane is recorded as a bait that is removed by electrolytic decomposition. Problems to be Solved by the Invention When this water treatment technology is applied to the removal of contaminants in water, such as halogen compounds or persistent pollutant components, (2) it is possible to absorb and absorb anything due to the characteristics of activated carbon. Therefore, it also adsorbs and removes non-alcoholic substances other than the 11 components in the water, which is inefficient. Furthermore, if it is burned during disposal, there is a risk that the adsorbed components will volatilize into the atmosphere and produce secondary harmful substances such as chlorine gas, phosgene, and dioxins. ■
In many cases, the sustainability of the oxidation efficiency of the catalyst is short-term, so it is not suitable for practical use. ① is nothing more than the volatilization of pollutants into the atmosphere and is not a fundamental solution. (2) requires an ozone generator, and there is a possibility that harmful ozone may remain, making the equipment too large. Method (2) is a symptomatic method, such as removing precursors that cause organic halogen compounds, and has problems such as not being a method for directly removing the components. In addition, in the known technology for reductive decomposition using iron powder, the iron powder is not only difficult to handle due to the treatment process of activating the surface, but when packed in a column or the like and used as a water treatment filter, the reduced material becomes powder. Therefore, when it passes through the treated water, it tends to cause a seal pass in the packed layer, and the filled iron powder and harmful substances do not come into uniform contact, resulting in poor decomposition efficiency and other drawbacks. Means for Solving the Problems The present invention provides: (1) The skeleton forming the three-dimensional network porous body is made of Fe.
) In. Mg. Zn. AQ. A water treatment method characterized by bringing treated water into contact with a filter made of one or more metals such as Ti to reduce and decompose contaminants in the treated water, (2) when the contaminants are organic halogen compounds or (3) The skeleton forming the three-dimensional network porous body is made of Fe. Mn. Mg.
Zn. AQ. Treated water is brought into contact with a filter made of one or more metals such as Ti, and a polarization voltage is applied to the three-dimensional network porous material to prevent oxidation while reducing and decomposing contaminants in the treated water. This is a water treatment method characterized by: (i) As a technology for treating polluted water containing harmful substances, for example, (ii)
An example of this treatment of 41 ktl elementary compounds will be explained below. O-valent iron is an extremely effective reducing agent because it causes the following reaction with organic chlorine compounds that are considered harmful to the human body, rendering them harmless. For example, when Fe is used as a reducing agent, it can be made harmless by the following reaction. 3Fe+3H20+CICl3 →CH4 + 3
Fe2◆+ 30H″″ + 3Ct-chloroform
Methane 4 Fa + 4H20 + CICI! 2 ・CH
CQ ttetrachloroethane+cHA-co3+ 4Fe"+ 40H'"+
4Ci-ethane 3Fe + 3HzO + CICI: CCl 2 trichlorethylene 4 CH2: CH2+ 3Fe"+ 30H-
+ 3Ci - Ethylene However, it is difficult for Fe to exist in a zero-valent state in water containing dissolved oxygen, and it generally changes to trivalent or tetravalent oxides, making it difficult for the above chemical reactions and reduction to occur. ．． As a result of researching a method of maintaining the reduced state of FeO using simple means, the present inventors found that this can be achieved by dissolving and removing the iron oxide film present on the J# part (surface) of the filter table made of iron. I learned it. The surface layer of the filter is oxidized by contacting with a 1-70% aqueous solution of hydrochloric acid, hydrogen peroxide, malignant acid, sulfuric acid, phosphoric acid, hydrofluoric acid, chromic acid, formic acid, acetic acid, ascorbic acid, etc. as an oxide film-dissolving aqueous solution. Remove the coating. A mixture of two or more of these acids also has the same effect. That is, FeO is retained in the surface layer of the filter surface M9 made of iron. When Fe' maintained on the surface layer of the filter by these methods is used as a reducing agent for organic chlorine compounds in water containing dissolved oxygen for a long period of time, the above-mentioned Either by flowing an aqueous solution or after treatment, the material is kept polarized to a potential lower than the oxidation potential of iron in order to maintain the Fe' state. As a result, F
eO can be produced and retained over long periods of time. Also, as a sacrificial anode in the filter, for example, aluminum,
Zinc, etc. is attached to the porous body, or aluminum, zinc, etc. are mixed into the powder for the base material when producing the sintered metal porous body,
By making it a porous body containing aluminum and zinc, the surface layer is retained as Fe'. Another method for producing Fe' on the surface of a filter is to heat and reduce a filter made of iron in a reducing atmosphere, for example in a hydrogen stream. These filters have a structure made of iron, which is a reducing agent, so they can easily remove the oxide film, and there is no short path for the treated water, so they can uniformly contact harmful substances in the treated water and decompose and remove them efficiently. can. In this way, the reaction between iron and treated water decomposes the metal and renders it harmless. Even in a filter made of a metal other than Fe according to the present invention, the treated water can be reductively decomposed and rendered harmless by the same reaction. ] In addition to organic chlorine compounds such as those mentioned above, examples of persistent pollutants include inxathion, infenphos, diazi/7, and DDVP, which are used in agricultural chemicals as insecticides.
, DEP, MEP, NAC, etc., iprodione, cabtan, thiophanate methyl, benomyl, TPN, etc., used in pesticides as fungicides, Ashram, bentazone, pendimethalin, CAT, used in pesticides as herbicides.
．． There are SAP etc. Three-dimensional mesh porous bodies include felted fine wires of the metal, cross-layered honeycombs, laminated flat plates with pores, and organic porous bodies made of the metal powder. There are methods such as coating and sintering, but the following is an example of an economical method for manufacturing porous materials that requires a long reaction time. Iron powder, iron oxide powder, and surface-oxidized iron powder with an average particle size of 50 g or less are used alone or in combination, or with carbon powder added and mixed as the base material powder. C of powder for base material
After adjusting the relationship between '3
I! Heat treatment is performed to cause a self-reducing sintering reaction. Iron oxide powder can be produced, for example, by pulverizing steel dust from a steel mill or hot rolling scale. Iron powder with an oxidized surface can be obtained, for example, by wet grinding of pig iron or cast iron. Iron powder produced using the wet grinding method is safe because there is no ignition or explosion during grinding, and it can be produced at a lower cost than iron powder whose surface is not oxidized. The iron to be crushed is an alloying element of old, old, Cr
．． Cu, P. When containing M, iron powder containing these alloying elements or iron powder with an oxidized surface can be obtained, but these alloying elements improve the strength of the skeleton of the sintered metal porous body. preferred for this reason. Similar effects can also be obtained by adding powders containing these alloying elements to the base material powder. Carbon powder is also added to the base material powder if necessary. Carbon powder can be obtained, for example, by crushing electrodes or coke. Iron powder, iron oxide powder, iron powder with an oxidized surface can be used alone or in combination, or by adding and mixing charcoal powder, to create a carbon and oxygen content. Content (weight%),

【O】
: Produce a powder for the base material with the oxygen content (wt%) of the powder for the base material. Iron with a carbon content of 2.1% or more is easy to crush because cementite serves as the pulverization core, and powder can be produced at low cost.
Can be used without adding or mixing carbon powder. Unlike the manufacturing method of general powder alloys, the powder is sintered in its coated state without being pressurized with a high-pressure press, resulting in insufficient particle bonding and difficulty in maintaining the shape of the porous body after sintering. It is easy to become In this method, a low melting point liquid phase of Fe3C and iron is created through heat treatment, and the particles are strongly bonded together through liquid phase sintering. When it is included, a eutectic of iron and Fe3C is formed, which facilitates liquid phase sintering. During heat treatment, a self-reduction reaction occurs, and the carbon content is reduced by oxygen in the base material powder. If the content of [01 in the base material powder is less than 4/3 ([C] -2), decarburization will not proceed sufficiently, the carbon content κ of the base material after sintering will be high, and thermal strain will occur. etc.: It becomes a sensitive and brittle porous body. Also, the content of [0] in the base material powder is 4/3 ([C] +7
) or above, the amount of unreduced oxides in the base material increases after sintering, and the porous body tends to collapse. By implementing the above-mentioned Iwun Castle, the specific surface area is extremely large (300m''/m'').
(above), a healthy porous metal body with good reactivity and excellent toughness, containing a large number of micropores of 5 to 50 IL in the metal skeleton, can be reliably obtained. In addition, other metals according to the present invention other than Fe can also be obtained by applying the metal to an organic three-dimensional porous material and heat-treating it as described above. Next, the base material powder is kneaded with a binder and applied to the skeleton of the three-dimensional porous material. Organic binders such as CMC and polyacrylic acid, and inorganic binders such as wood glass can be used, and the base material powder is kneaded with an aqueous solution of these binders. Organic three-dimensional porous materials are porous materials that can be removed by thermal decomposition or sublimation during heat treatment, such as urethane foam and three-dimensional fabrics. The mixture of base material powder and binder is applied to the framework of the Ariga three-dimensional porous material by spraying or dipping. The base material powder with a particle size of 50 gauze or less becomes a viscous slurry when mixed with a binder, so it can be applied to the skeleton of the three-dimensional porous material to a uniform thickness. During heat treatment, the base material powder contains sufficient carbon, so the atmosphere in the heating furnace is different from that for general sintered alloys.
There is no need to create a pure atmosphere; an atmosphere of non-oxidizing argon or nitrogen gas is sufficient. When the organic three-dimensional porous material is urethane foam. 3 at 100-350℃
After heating for 0 minutes, the organic three-dimensional porous material is removed. Fourth, by heating to 1300-1200°C for about 1 hour, a sintered metal porous body whose base material is iron is obtained through liquid phase sintering, self-sintering reaction, and final sintering. The surface area, pores, etc. of such a porous body can be adjusted by adjusting the porosity of the three-dimensional porous material described in (i) above. Examples Next, Examples of the present invention are listed in Table 1 along with comparative examples. Note 1 = Three-dimensional network porous material is obtained by wet-pulverizing the above metal and f
Particles with an average particle size of 10 μm were prepared, kneaded with water and CMC, applied to urethane foam with 2 pores by spray method, dried (100°C), degreased (200°C), and self-reduced (
700-1000°C) and sintering (1100°C) were performed in a nitrogen atmosphere. (Fe-All: 5G/5
0, Fe-Mg: 50/5G. Fe-Mn:50/
5G. Nn-Mg: 50/50. M-Ti-Zn
:3G/3G/40. Ti-Mg-Fe: 30/3
G/4G) Note 2 = Treated water is heated to 40℃ before use. Note 3
: The treatment results were obtained by using the above porous body as a filter, circulating the treated water at a flow rate of 1.01/min for 1 hour, and measuring the concentration of contaminants in the water that passed through the filter using an ECO gas chromatograph analyzer. result. Note 4: In the comparative example, the above iron powder was placed in a filling tank (diameter 100cm,
300 mm in height), and the contaminated water was circulated in the same manner. Effects of the Invention According to the present invention, it is possible to reliably purify wastewater such as wastewater, and the porous filter can be used for a long period of time. Also, water treatment can be done at extremely low cost. Furthermore, excellent effects can be obtained, such as the ability to reliably treat water contaminated with organic halogen compounds and other substances that are difficult to decompose.

Claims (3)

[Claims] (1) The skeleton forming the three-dimensional network porous body is made of Fe,
A water treatment method characterized by bringing treated water into contact with a filter made of one or more metals of Mn, Mg, Zn, Al, and Ti to reduce and decompose contaminants in the treated water. (2) The water treatment method according to claim 1, wherein the contaminant is an organic halogen compound or a difficult-to-decompose pollutant. (3) The skeleton forming the three-dimensional network porous body is made of Fe,
The treated water is brought into contact with a filter made of one or more metals such as Mn, Mg, Zn, Al, and Ti, and a polarization voltage is applied to the three-dimensional network porous material to prevent oxidation while removing the water in the treated water. A water treatment method characterized by removing pollutants by reduction and decomposition.