JPH0755288B2 - How to remove bad odor from water - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for efficiently removing malodor in water.

Conventional technology Large amounts of wastewater and exhaust from business sites such as factories and livestock farms often contain a combination of various odorous substances generated during business activities. Of these, odorous substances whose emissions are regulated based on the Odor Control Act enacted in 1969 are perceived as particularly unpleasant odors even in small amounts, and many toxic substances are removed to render them harmless. Technology is also important industrially. Currently, ammonia, methyl mercaptan, hydrogen sulfide, methyl sulfide, styrene and organic acids 12
Certain substances are subject to emission regulations. In recent years, relatively small-scale wastewater and exhaust containing odorous substances have often become a problem not only in large offices but also in daily life, and this has become a problem. ing.

By the way, in the quantitative analysis of aromatic volatile substances dissolved in water in a trace amount, the silicone rubber membrane has been used for the concentration of the contained substance. However, since this silicone rubber membrane has a remarkably low permeation rate, it can be used to treat a small amount of sample, but cannot be used to treat a large amount of wastewater (“J. Membr. Sci.”, Volume 8, No. 105). page).

Currently, large-scale odor removal methods that are commonly used include the activated carbon adsorption method, cleaning absorption method, chemical treatment method, biological odor method, etc. (Published by the Industrial Research Council in 1981, "New odor technology" by Kokubu) ).

In the activated carbon adsorption method, an expensive adsorbent must be repeatedly used. Therefore, it is necessary to desorb the odorous substance once adsorbed as a gas by heat treatment and further decompose it using a catalyst. For this reason, there is a drawback that the treatment must be temporarily stopped and the catalyst must be regenerated and activated, which makes it impossible to operate continuously.

Further, the cleaning and absorption method is a method of absorbing and removing an odorous substance with an acid aqueous solution, an alkaline aqueous solution or normal water,
The secondary large-scale treatment of treated water containing the odorous substance generated by this becomes a problem.

In addition, chemical treatment methods and biological deodorization methods use special chemicals and microorganisms, and require special equipment.
It is not always a satisfactory method for practical use.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention efficiently removes a malodorous component that is a malodorous source that is dissolved in a large amount of discharged water such as domestic wastewater and industrial wastewater so that the water becomes odorless. It has been made for the purpose of providing a method for realizing the above.

Means for Solving the Problems The present inventors have previously developed an ethanol separation membrane in which a polymer porous membrane is used as a base material and a perfluorocarbon gas is plasma-polymerized on the surface to form a hydrophobic membrane. However, as a result of further studies, it was surprisingly found that the above hydrophobic membrane having a ratio of the number of fluorine atoms to the number of carbon atoms (F / C) of 1 or more was unexpected. Based on this finding, it was found that it is effective in deodorizing water by removing odorous substances such as organic amines and organic sulfur compounds that are contained in water in small amounts and causing bad odors. The present invention has been completed.

That is, according to the present invention, a non-water-swellable polymeric sponge-like porous substrate layer having an average pore size of 0.01 to 1 μm and a surface porosity of 30 to 60% is formed on the surface by low temperature plasma polymerization of a fluorine compound. , Water containing a malodorous component is pervaporated through a composite film comprising a hydrophobic polymer layer having a ratio of the number of fluorine atoms to the number of carbon atoms (F / C) of 1 or more. A method of removing a bad smell is provided.

In the composite film used in the method of the present invention, as the non-water-swellable polymer substance used to form the substrate, a synthetic resin such as polypropylene or polysulfone that does not swell with water is used.

And, this has an average pore diameter of 0.01 to 1 μm and a surface porosity of 30.
It is used as a sponge-like porous body having a large open ratio for the average pore diameter of 60% as compared with a porous substrate used for ordinary plasma treatment coating.

The porosity here is the apparent porosity of the surface and is calculated from the area of the micropores that can be observed in an electron micrograph.

In the production of polymer separation membranes by the plasma treatment known so far, in order to stably support the plasma-polymerized membrane to be formed, a substrate having a relatively small porosity and a smooth surface is used. However, in the case of the odor removing film of the present invention,
Use a material with a porosity as large as possible within the range that does not significantly reduce the mechanical strength of the substrate, and ensure the permeation rate necessary for a large amount and highly efficient treatment of the hydrophobic layer formed by plasma polymerization of the fluorine compound. In addition to the above, the surface roughness has succeeded in further improving the apparent hydrophobicity as compared with the case of the usual plasma surface treatment.

To explain this point in more detail, in the conventional smooth substrate, the hydrophobicity of the substrate surface is mainly determined by the hydrophobicity of the plasma polymer layer formed on the substrate surface. And, this plasma polymer layer was inevitably reduced in its hydrophobicity after being in direct contact with water for a long time. This phenomenon is well known as a deterioration phenomenon of the surface treatment effect.

As a result of research, the inventors of the present invention have found that such a phenomenon is part of the cause of the performance deterioration of the separation membrane,
By using a substrate having a high porosity, the ratio of direct contact between the surface layer and water is reduced, and the hydrophobicity is further enhanced by the air layer at the open pores of the surface.

In addition, as a result of observing the surface layer with an electron microscope, it was found that the micropores of the surface layer do not need to be completely blocked by the plasma polymer in order to exert the separation performance. Of course, if the micropores are completely covered with the plasma polymer, it will exhibit a unique selective separation property, but since it will cause a significant decrease in the permeation rate, the malodorous component dissolved in a large amount of water will be removed to remove water. Deodorization is not always desirable.

The porous body used as the above-mentioned substrate can be produced by the same method as that for the polymeric substance porous body used as an ordinary substrate, and can be prepared by [For example, by Kesting, RF] Synthetic Polymeric Membrane
s) ”, (1971)], or commercially available products can be used as they are.

Next, the hydrophobic polymer layer formed on this substrate is obtained by plasma polymerizing a fluorine compound, for example, perfluoropropylene, hexafluoroethane, or tetrafluoroethylene by a normal low-temperature plasma treatment. . In this case, the fluorine compound may be used alone or in combination of two or more, but a polymer layer having a ratio of the number of fluorine atoms to the number of carbon atoms (F / C) of 1 or more is formed. It is necessary to choose to be done. By using such a polymer layer, the surface has a good affinity with the malodorous component in water, and the composite film and the malodorous component come into sufficient contact with each other.

Next, the malodor removing method of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing an example of a wastewater treatment apparatus equipped with the above-mentioned composite membrane, in which wastewater containing a malodorous component is continuously supplied to a drain tank from an outlet and discharged from a drain outlet. It A separation membrane, that is, a composite membrane is attached below the drainage tank, and the malodorous component is concentrated and discharged by pervaporation.

Although the composite membrane in the flat membrane state is used in FIG. 1, a hollow fiber membrane can also be used.

Effect of the Invention The method of the present invention can efficiently remove various malodorous components that are contained in water and cause malodor, and therefore, by combining with a conventionally known malodor decomposition method,
It helps to achieve efficiency of wastewater and exhaust gas containing odorous substances of various sizes discharged in accordance with industrial activities or daily life, exhaust gas treatment efficiency, and miniaturization and continuation of equipment.

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 Only a single side of a polypropylene porous membrane having a thickness of 120 μm, an average pore diameter of 0.5 μm and a surface porosity of 50% was used with a tubular plasma reactor (tube inner diameter 70 mm, 13.56 MHz radio frequency power source) and perfluoropropane 70 μmHg. , And treated with a radio wave output of 25 W for 1 hour to form a separation membrane. The separation performance of this membrane by the pervaporation method was measured using a 1% by weight aqueous solution of methyl sulfide at 28 ° C. As a result, the separation coefficient was 139 and the permeation rate was 0.4 kg / m ² h.
It was r. By the way, the surface element ratio (fluorine / carbon) of this separation membrane was confirmed to be 1.4, which is very hydrophobic in terms of chemical structure.

In the case of a porous membrane without plasma treatment, 20 minutes after the start of the separation test by the pervaporation method, the test solution permeates the permeate side of the membrane and the separation performance is no longer recognized. It is clear that highly stable membranes can be produced.

Example 2 The polypropylene membrane of Example 1 was also used in the same plasma reactor as perfluoropropane 70 μmHg and tetrafluoroethylene 10
The plasma was treated with a mixed gas of μmHg for 1 hour. The separation performance of this membrane at 28 ° C is a separation coefficient of 214.8 for a 1 wt% methyl sulfide aqueous solution, a permeation rate of 0.57 kg / m ² hr, a separation coefficient of 147.2 for a triethylamine aqueous solution of the same concentration, and a permeation rate of It was 0.47 kg / m ² hr. By the way, the surface element ratio of this separation membrane (fluorine / carbon)
Was 1.0 and hydrophobic.

Example 3 When the same plasma treatment was performed on the same polypropylene substrate as in Example 2 for 3 hours, the surface element ratio (F / C) was 1.5.
A film for removing odor of 4 was obtained.

Example 4 Porous polysulfone membrane (average pore diameter 0.2 μm, thickness 50 μm
m, aperture ratio 35%, manufactured by Brunswick) was used as a substrate film, and the same reactor as in Example 1 was used to perform plasma treatment (50 W, 3 hours) of perfluoropropane (80 μmHg). The surface element ratio (F / C) of the odor eliminating film thus obtained was 1.6.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of an apparatus for carrying out the method of the present invention.

Claims (3)

[Claims] 1. An average pore diameter of 0.01 to 1 μm and a surface porosity of 30 to
Non-water swellable polymeric sponge-like porous substrate layer with 60% and the ratio of the number of fluorine atoms to the number of carbon atoms (F / C) formed by low temperature plasma polymerization of a fluorine compound on the surface
Through a composite membrane consisting of one or more hydrophobic polymer layers,
A method for removing malodorous water, which comprises pervaporating water containing malodorous components. 2. The method for removing malodor according to claim 1, wherein the hydrophobic polymer layer is formed by low temperature plasma polymerization of perfluoropropane. 3. The method for removing malodor according to claim 1, wherein the hydrophobic polymer layer is formed by low-temperature plasma polymerization of a mixture of ethylene tetrafluoride and perfluoropropane.