JPH0419888B2 - - 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 made of a mixture 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 20Kg/cm ³ G, flow velocity along the membrane surface 0.6m/sec,
At a temperature of 60°C, the solute exclusion rate was approximately 96-97%. In addition, dynamic membranes made of colloidal silica are well known, and their ultrafiltration performance shows that under the same conditions as above, the solute rejection rate is
It was around 97-98%. That is, according to the dynamic membrane of alumina sol, 3 to 4% of the solute will be lost along with the permeated water, and according to the dynamic membrane of colloidal silica, 2 to 4% of the solute will be lost with the permeated water.
3% will be lost along with the permeate. Therefore, the solute exclusion rate reaches over 90%, and
If it 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 component is expensive, the effect will be extremely large. In addition, the dynamic film of colloidal silica is
There is a drawback that part of the membrane peels off during operations such as washing with water in the concentration process and the like. In view of these circumstances, the present inventors have carried out intensive research and found that by combining alumina sol and colloidal silica, the membrane has higher solute removal performance than a dynamic membrane made of these individual materials. The inventors have discovered that a dynamic membrane with excellent membrane stability can be produced by reflux treatment, and have arrived at the present invention. That is, the gist of the present invention is that on a porous support,
The present invention relates to a method for producing a dynamic membrane, in which a mixture aqueous solution of alumina sol and colloidal silica is refluxed under pressure to form a membrane, and an acid aqueous solution having a pH of 3.5 or lower is further refluxed under pressure. The present invention will be explained in detail below. Porous supports used in the present invention include various known ones, such as ceramics, sintered metal powder, sintered glass powder, inorganic porous supports such as carbon materials, cellulose acetate, polyvinyl chloride, and polymethacrylate. Examples include organic porous supports such as various synthetic resins such as ronitrile, polyamide, and fluororesin. The diameter of the surface pores of the porous support varies depending on the material, but is usually 0.01 to 2μ, preferably 0.05μ.
~0.2μ is good. The thickness of the porous support may vary depending on the intended use of the dynamic membrane, as long as it has sufficient mechanical strength. As alumina sol, the particle size is 50×5
mμ~400×40mμ, preferably 100×10mμ~
Particles with a size of 300 x 30 mμ and a feather-like shape are used, using an organic acid such as acetic acid or hydrochloric acid or an inorganic acid as a stabilizer. Colloidal silica has a particle size of 5 to 50 mμ,
Preferably particles in granular form of 10 to 20 mμ are used. In addition, an aqueous solution of colloidal silica that is either acidic or alkaline stabilized can be used, but acidic and stabilized aqueous solutions are preferred. In the present invention, the mixing ratio of colloidal silica and alumina sol is 0.0005 to 0.5 g of solid content of alumina per 1 g of solid content of silica, preferably 0.001 to 0.5 g of solid content of alumina.
0.1g is good. If the amount of alumina exceeds this range, the stability of the dynamic film will decrease and it will become easy to peel off, which is not preferable. The concentration of the mixed aqueous solution is 0.03 to 0.03 in solid content of silica.
1.0g/, preferably 0.1-0.5g/. The amount of the mixed aqueous solution may be about 20 to 50 per m ² of surface area of the porous support. The method described above can be used to produce a dynamic membrane according to the method of the present invention. in this way,
First, a mixed aqueous solution of alumina sol and colloidal silica is refluxed onto a porous support. The reflux is carried out under pressure, usually from 2 to 35 Kg/cm ³ G, preferably from 5 to 25 Kg/cm 3 G.
cm ³ G, and the flow velocity along the support surface (hereinafter simply referred to as flow velocity) 0.1 to 10 m/sec, preferably 0.2 to 2
It is necessary to perform this at m/sec. The temperature may be room temperature, and the reflux time may be 5 to 30 minutes, although it varies depending on the conditions. Then, while under pressure, the pH is 1 to 3.5, preferably PH
Reflux the 1.5-2.5 acid aqueous solution. Specifically, an aqueous acid solution prepared with a strong acid such as sulfuric acid, sulfuric acid, or hydrochloric acid is used. The reflux time varies depending on the various conditions, but may be 5 to 30 minutes. With this process,
Mutual aggregation of silica particles is promoted and a strong dynamic film is formed. Thereafter, the pressure is returned to normal and the inside of the channel is washed with water, completing the formation of the dynamic film. In the present invention, it is preferable to form a membrane from a mixed aqueous solution of alumina sol and colloidal silica, reflux the acid aqueous solution under pressure, and then reflux heated water while maintaining the pressure. In this case, under pressure,
After the heated water is refluxed, the pressure is returned to normal and the inside of the flow path is washed with water to form a dynamic film. The heated water used is usually 40 to 100°C, preferably 70 to 100°C. The reflux time varies depending on various conditions, but may be 15 to 90 minutes. This treatment 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. 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 present invention will be further explained in detail below with reference to Examples and Comparative Examples, but the present invention is not limited by the following examples unless it goes beyond the gist of the present invention. Example 1 Alumina sol with a particle size of 200 x 20 mμ to 300 x 30 mμ and colloidal silica with a particle size of 10 to 20 mμ were mixed while being dissolved in 30 ml of water. The concentration of colloidal silica is 0.2g/solid content, and the mixing ratio with alumina sol is 1g/g of silica solid content.
The alumina solid content was 0.001 g. This aqueous solution was poured onto a 0.77 m ² ceramic porous support (surface pore diameter: approximately 0.1 μ) at a pressure of 20 Kg/cm ^{3 .}
A film was formed by refluxing for 20 minutes at a flow rate of 0.6 m/sec and a temperature of 20°C. Then, while under pressure of 20Kg/cm ³ G, PH2.2,
The 20°C aqueous sulfuric acid solution was refluxed for 20 minutes. 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 ³ G, the flow rate was 0.6 m/sec, and the temperature was 60°C.
A 5% gelatin aqueous solution equivalent to JIS 4 was filtered under the following conditions, and the results are shown in Table 1. Examples 2 to 4 The mixing ratio of alumina sol and colloidal silica is expressed as alumina solid content per 1 g of silica solid content.
A dynamic film was formed in the same manner as in Example 1 except that the amounts were 0.01 g, 0.1 g, and 0.5 g. Table 1 shows the results. Comparative example 1

[Table] Comparative Example 1 On a 0.77 ^m2 ceramic porous support (surface pore size: approximately 0.1 μ), an aqueous solution of 6 g of colloidal silica with a particle size of 10 to 20 μ as a solid content dissolved in 30 μm of water was heated under pressure. 20Kg/ ^cm3G , flow rate 0.6m/sec, temperature 20
The mixture was refluxed for 20 minutes at ℃. When the pressure was then returned to normal and the inside of the flow path was washed with water, cloudiness was observed in the running water at the initial stage of washing, and a considerable portion of the silica had peeled off, so an overtest could not be performed. Comparative Example 2 On a 0.77 m ² ceramic porous support (surface pore size: approximately 0.1 μ), particles with a size of 200 × 20 mμ ~
2g solid content of 300×30mμ alumina sol
An aqueous solution of 30% of water is heated to a pressure of 20Kg/ ^cm3G ,
The mixture was refluxed for 20 minutes at a flow rate of 0.6 m/sec and a temperature of 20°C. Next, the pressure was returned to normal and the inside of the channel was washed with water to form a dynamic film. When a 5% aqueous gelatin solution was filtered using the dynamic membrane thus produced under the same conditions as in Example 1, the solute exclusion rate was 96.5%.

Claims (1)

[Claims] 1. Forming a membrane by refluxing a mixed aqueous solution of alumina sol and colloidal silica under pressure on a porous support, and then refluxing an acid aqueous solution with a pH of 3.5 or less while under pressure. A method for producing a dynamic membrane characterized by: 2. The production method according to claim 1, which comprises refluxing the acid aqueous solution under pressure, and then refluxing the heated water under pressure.