JPH0418888B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a dynamic membrane suitable for ultra-violet applications. Specifically, the present invention relates to a method for producing a dynamic membrane having a two-layer structure consisting of alumina sol and colloidal silica. Conventionally, dynamic membranes using alumina sol are well known, and their ultraviolet performance is, for example,
In the case of a 5% aqueous gelatin solution equivalent to JIS 4,
Pressure 20 mg/cm ² G, flow velocity along the membrane surface 0.6 m/sec,
The solute exclusion rate was approximately 96-97% at a temperature of 60°C. Dynamic membranes made of colloidal silica are also well known, and their ultrafiltration performance was approximately 97-98% solute exclusion under the same conditions as above. That is, with a dynamic membrane of alumina sol, 3 to 4% of the solute will be lost along with the permeated water, and with a dynamic membrane of colloidal silica, 2 to 3% of the solute will be lost with the permeated water. Become. Therefore, if the solute rejection rate, which reaches over 90%, can be improved by one point, it will be possible to reduce the amount of solute loss by a considerable percentage, and if the solute components are expensive, the effect will be extremely high. big. As a result of extensive research in view of these circumstances, the present inventors have discovered that a combination of alumina sol and colloidal silica has higher solute removal performance than a dynamic membrane made of these individual materials, and has thus arrived at the present invention. did. The present invention will be explained in detail below. As the porous support used in the present invention, various known ones can be mentioned. For example, ceramics, sintered metal powder, sintered glass powder, inorganic porous supports such as carbon materials, and cellulose acetate,
Examples include organic porous supports such as various synthetic resins such as polyvinyl chloride, polymethacrylonitrile, polyamide, and fluorine resins. The diameter of the surface pores of the porous support varies depending on the material, but is usually 0.01 to 2μ, preferably
A material with a diameter of 0.05 to 0.2μ is used. The thickness of the porous support is not particularly limited as long as it has mechanical strength depending on the intended use of the dynamic membrane. As an alumina sol, the particle size is 50×
50mμ~400×40mμ, preferably 100×10mμ~300
It consists of particles with a size of 30 mμ and a feather-like shape, and uses an organic acid such as acetic acid or hydrochloric acid or an inorganic acid as a stabilizer. The concentration of alumina sol is 0.01~ as solid content.
0.2g/, preferably 0.02-0.1g/. Colloidal silica has a particle size of 5 to 50 mμ,
Preferably particles in granular form of 10 to 20 mμ are used. An aqueous solution of colloidal silica that is either acidic or alkaline stabilized can be used, but acidic and stabilized aqueous solutions are preferred. The concentration of colloidal silica is 0.03 as solid content
-1.0g/, preferably 0.1-0.5g/.
A colloidal solution of acidic stable silica having such a concentration usually has a pH of 4 to 6. The amount of the aqueous solution containing alumina sol and the aqueous solution containing colloidal silica is 20 per m ² of the surface area of the support.
~50 is sufficient. The method described above can be used to produce a dynamic membrane according to the method of the present invention. in this way,
First, an aqueous solution of alumina sol is refluxed on a porous support. Reflux is usually 2 to 35 kg/cm ² under pressure.
G, preferably 5 to 25 Kg/cm ² G, flow velocity along the support surface (hereinafter simply referred to as flow velocity) 0.1 to 10 m/
sec, preferably 0.2 to 2 m/sec. The temperature of this alumina sol may be room temperature. The reflux time varies depending on various conditions, but is 5 to 30 minutes.
A minute is enough. After this, the pressure is returned to normal pressure and the inside of the flow path is washed with water. The aqueous solution of colloidal silica is then refluxed. Refluxing must be carried out under pressure, usually at a pressure of 2 to 35 kg/cm ² G, preferably 5 to 25 kg/cm ² G, and a flow rate of 0.1 to 10 m/sec, preferably 0.2 to 2 m/sec.
The temperature of this colloidal silica aqueous solution may be room temperature. The reflux time varies depending on various conditions, but is 5 to 30 minutes.
A minute is enough. After this, while under pressure, PH1~3.5 preferably
Reflux an acid aqueous solution with a pH of 1.5 to 2.5. Specifically, an aqueous acid solution prepared with a strong acid such as sulfuric acid, nitric acid, or hydrochloric acid is used. The reflux time varies depending on various conditions, but may be 5 to 30 minutes. This treatment promotes agglomeration of silica particles and forms a strong dynamic film. Next, it is preferable to further reflux the heated water while still under pressure. As heated water, usually 40-100℃, preferably 70℃
~100℃ is used. Reflux time varies depending on various conditions, but is 15 to 90 minutes.
A minute is enough. This further strengthens the bonds between the silica particles and also entangles them with the alumina particles, making it possible to form a strong dynamic film with a high solute exclusion rate. Thereafter, the pressure is returned to normal and the inside of the channel is washed with water, completing the formation of the dynamic film. It goes without saying that during the production of the dynamic membrane, one side of the porous support through which permeated water is discharged is always kept at normal pressure. The dynamic membrane thus obtained has a higher polymer substance exclusion performance than a dynamic membrane manufactured in the same manner as the dynamic membrane manufacturing method of the present invention, except that the formation of the alumina sol dynamic membrane was omitted. is good. Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited by the following examples unless it exceeds the gist of the present invention. Example 1 2g of alumina sol (particle size: 200 x 200 mμ to 300 x 30 mμ) as a solid content was dissolved in 30% water on a 0.77 m ² ceramic porous support (surface pore size: approximately 0.1 μ). the aqueous solution at a pressure of 20Kg/cm ²
A film was formed by refluxing for 20 minutes at a flow rate of 0.6 m/sec and a temperature of 20°C. Thereafter, the pressure was returned to normal and the inside of the channel was washed with water. Next, an aqueous solution in which 6 g of colloidal silica (particle size: 10 to 20 mμ) was dissolved as a solid content in water 30 was heated at a pressure of 20 Kg/cm ² G and a flow rate of 0.6 m/cm.
sec, and refluxed for 20 minutes at a temperature of 20°C to form a film. Under pressure of 20Kg/cm ² G, PH2.2,
The 20°C aqueous sulfuric acid solution was refluxed for 20 minutes, and then water was refluxed at the same pressure to wash away the sulfuric acid. Thereafter, the pressure was returned to normal, and the inside of the channel was washed with water to form a dynamic film. Using the dynamic membrane thus produced, the pressure was 20 kg/cm ² G, the flow rate was 0.6 m/sec, and the temperature was 60°C.
A 3% aqueous gelatin solution equivalent to JIS Class 4 was filtered under the following conditions. The results are shown in Table-1. Examples 2 and 3 The method of Example 1 was repeated, except that after the reflux treatment of the acid aqueous solution, heated water at 50°C and 80°C was refluxed for 20 minutes each under pressure (20 Kg/cm ² G). In the same manner, a dynamic membrane was produced and an aqueous gelatin solution was filtered. The results are shown in Table-1.

[Table] Comparative Example 1 A dynamic film was produced in the same manner as described in Example 1 except that the formation of a dynamic film of alumina sol was omitted. Furthermore, when the aqueous gelatin solution was filtered in the same manner as described in Example 1, the solute exclusion rate was 95.7%.

Claims (1)

[Claims] 1. A membrane is formed by refluxing alumina sol under pressure on a porous support, and on top of the membrane, colloidal silica is further refluxed under pressure to form a membrane, and then a membrane is formed while remaining under pressure. A method for producing a dynamic membrane, characterized by refluxing an acid aqueous solution with a pH value of 3.5 or less. 2. The manufacturing method according to claim 1, wherein after the acid aqueous solution is refluxed under pressure, heated water is further refluxed under pressure.