JPH0389921A - Treatment using ceramic membrane - Google Patents

Abstract

PURPOSE:To prevent plugging of a membrane and improve cleaning efficiency by adjusting the pH of a substrate solution or a cleaning liquid to be more acidic or alkalline than the isoelectric point of a ceramic membrane composing material or the substrate. CONSTITUTION:A substrate solution (l) is supplied to a membrane module 2 and circulated to a tank 1 so as to lead a permeated liquid out of a system, and the membrane module 2 is cleaned during this process. The membrane module 2 is composed of a nonsymmetric membrane and the composing material of the thin membrane in a primary side is SnO2, TiO2, ZrO2, or Al2O3. The pH of the substrate solution (l) or a cleaning liquid is adjusted to be either more acidic or alkalline than the isoelectric point of the composing material of the thin membrane and the substrate. Electric charge of the thin membrane composing material and the substrate becomes the same and thus they repel each other, and the substrate adhering to the membrane is separated easily and electrostatically. As a result, plugging of the membrane becomes hard to be caused, cleaning efficiency of the membrane is improved and the recovery of the membrane function is quick.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for extracting a target substance from a substrate solution (undiluted solution) or removing substances other than the target substance by ultrafiltration or the like. .

(Prior art) Conventionally, in the separation and concentration of solutions in the food and pharmaceutical industries, and in the membrane separation IA process of industrial wastewater and sewage, small-diameter particles are placed on the substrate solution inflow side of a support made of relatively large-diameter particles. A ceramic membrane such as an asymmetric membrane formed of a thin film made of particles is used.

When a long-term separation operation is performed using such a ceramic main ivy membrane, solute (mainly substrate) particles are deposited on the surface of the ceramic membrane (=
This will lead to clogging and deterioration of membrane performance.

For this reason, conventional techniques have been used to change the membrane surface flow rate and the differential pressure between the membranes, perform backwashing, and even keep the pressures on the primary and secondary sides equal, as disclosed in JP-A-61-11108. ,
Cleaning liquid is supplied to the primary side by a circulation pump.

(Problems to be Solved by the Invention) As mentioned above, in the conventional method, the operating conditions must be changed during the treatment, and - once the solute particles have entered the fine pores, it is difficult to easily remove them. I can't.

(Means for Solving the Problems) In order to solve the above problems, the present invention adjusts the pH of the substrate solution or adjusts the p)I of the cleaning solution, and the po after the adjustment constitutes a ceramic membrane. It was made to be either more acidic or more alkaline than either the equipotential point of the material or the equipotential point of the substrate.

(Function) By adjusting the pH of the substrate solution or the pH of the cleaning solution, the materials constituting the ceramic membrane and the substrate are charged either positively or negatively, so that they repel each other, and the substrate solution adhering to the membrane is removed. It becomes easier to separate electrostatically from the membrane.

(Example) Embodiments of the present invention will be described below based on the accompanying drawings.

Fig. 1 is a schematic diagram of the apparatus used to carry out the method of the present invention;
The figure is a perspective view showing an example of a ceramic membrane, and shows a tank 1.
The inside is filled with a solution containing organic matter such as protein, sugar, or starch as a substrate.The tank 1 and the membrane module 2 are connected by a pipe 3, and a pump 4 is installed in the middle of this pipe 3. The substrate solution °C is supplied to the primary side of the membrane module 2 by the pump 4, and the liquid that has permeated to the secondary side is guided to another tank etc. via the piping 5, and the substrate solution on the primary side is returned via the return pipe 6. I'm trying to return it to tank 1.

Here, the membrane module 2 is constructed by mounting a large number of tubular asymmetric ceramic membranes 7 as shown in FIG.
The ceramic asymmetric membrane 7 has a thin film 9 made of small-diameter ceramic particles formed on the primary surface of a support 8 made of large-diameter ceramic particles. Here, the ceramic particles constituting the thin IIU9 are 5n02.
TiO2, ZrO2 or 8℃203.

To concentrate or separate the substrate solution ℃ using the above device, adjust the pI of the substrate solution using ipinodium hydroxide, phosphoric acid, etc. Specifically, 5n02 etc. that constitute the ceramic membrane The PL of the substrate solution should be on either the acid side or the alkaline side relative to the equipotential point of the material and the substrate, so that the charge of the material constituting the ceramic membrane and the substrate so that they have the same charge so that they electrostatically repel each other and do not attract each other.

Next, the present invention will be explained based on specific experimental examples.

Figure 3 is a graph showing the relationship between the zeta potential and pH of the constituent materials of the ceramic membrane.
H has an equipotential point, and when the pH becomes higher than this point, the material that makes up the ceramic membrane acts as an acid, and pll
When becomes small, it acts as an alkali.

Further, FIG. 4 is a graph showing the relationship between the molecular weight of various proteins and the equipotential point, and as described above, various proteins have properties as amphoteric substances.

Further, FIGS. 5 to 10 are graphs showing the relationship between the flux change rate (96) and the permeation amount (ml), and the flux change rate (96) indicates the recovery rate of the once-clogged ceramic membrane. In other words, the flux change rate (*) is 100! If it is 0, it means that the state has completely returned to the state before clogging, and if it is 0, it means that it has not recovered at all.

That is, FIG. 5 shows s n 02 t as a ceramic film.
This figure shows the experimental results when bovine serum albumin was selected as the substrate for Ji, and how to read FIG. 5 is as follows. First, when the pH of the substrate solution is pH 4.1, albumin is adsorbed onto the ceramic membrane, and then the pH is adjusted to
Continue operation with 4.1 until the permeation amount reaches 500 ml, then immerse it in the cleaning solution of pi (4.1) for 24 hours, and operate again until the permeation amount reaches 600 ml.
After being immersed in the cleaning solution No. 6.5 for 24 hours, operation was continued at pH 5 until the amount of permeation reached 51]1]m+.

From Figure 5, it can be seen that when the pH is 4.1, the flux change rate is small and the recovery rate is poor, and when pl (is set to 6.5), the flux change rate increases rapidly.
At -+41, 5n02 acts as an acid, and bovine serum albumin acts as an alkali, and since both have opposite charges, they electrostatically adsorb each other.When the pH reaches 65, they both act as acids, and their charges are reversed. Since it becomes the same and rebounds, it is thought that the flux change rate recovers. Moreover, from FIG. 6, it can be seen that if the pH is set to 65 from the beginning, the flux change rate immediately recovers.

Furthermore, in FIGS. 7 and 8, the ceramic film is TlO2,
FIGS. 9 and 10 show ceramic films of ZrO2, and the following can be said from these graphs. That is, when the protein to be separated is bovine serum albumin,
When using 5nQ2 or Tit)2 as the material for the ceramic membrane, the pH of the substrate solution or the pH of 7 nights of washing is changed to pH2.
,8 (equipotential point of Sn02 and TlO2) or below or pH+
4. a (the isopotential point of bovine serum albumin) or higher, and Zr
When using O2, the pH should be below pH 3.5 (equopotential point of ZrO2) or above pl+4.8.
3, adjust the pH to below pH 4.8 or pH 6.
o (equipotential point of 8f1.20..) or less.

In the example, the electrostatic repulsion force was used to actively remove the substrate attached to the ceramic membrane, but on the other hand, the ceramic membrane and the substrate were heated at a pH such that the charges were opposite to each other.
It can also be applied to adsorption and removal of specific substances by selecting .

(Effects of the Invention) As explained above, according to the present invention, when separating organic substances such as proteins using a ceramic membrane, by adjusting the pH of the substrate solution or cleaning solution, the ceramic membrane and the substrate can be kept static from each other. Since it is electrically repellent, it is difficult for the substrate to be adsorbed to the ceramic membrane and cause clogging, and since the substrate once adsorbed is easy to remove, the membrane performance recovers quickly.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the apparatus used to carry out the method of the present invention;
The figure is a perspective view of a ceramic membrane, Figure 3 is a graph showing the equipotential points of the materials constituting the ceramic membrane, Figure 4 is a graph showing the relationship between equipotential points and molecular weights of various proteins, and Figures 5 to 10 The figure is a graph of experimental results showing the relationship between pH and flux change rate. In the drawings, 1 is a tank, 2 is a membrane module, 7 is an asymmetric ceramic membrane, 8 is a support, and 9 is an R membrane.

Claims (2)

[Claims] (1) A treatment method in which a pressure higher than osmotic pressure is applied to the substrate solution on the primary side, and a substance with a predetermined molecular weight or less is allowed to permeate the ceramic membrane and taken out to the secondary side, and the material constituting the ceramic membrane and 1. A treatment method using a ceramic membrane, characterized in that the pH of the substrate solution is adjusted so that the pH of the substrate solution is either acidic or alkaline relative to any equipotential point of the substrate. (2) In a treatment method in which a pressure higher than osmotic pressure is applied to the substrate solution on the primary side, substances with a predetermined molecular weight or less are allowed to pass through a ceramic membrane and taken out to the secondary side. , and in this cleaning step, cleaning is performed using a cleaning solution whose pH is either acidic or alkaline relative to the equipotential points of any of the materials and substrate constituting the ceramic membrane. A treatment method using a ceramic membrane.