JPH03278817A - Pre-treatment for membrane separation process - Google Patents

Abstract

PURPOSE:To shorten the time required for treatment with membrane for impurity separation and heighten the limiting concn. value by adding chitosan to the liq. containing impurities in suspension to be subjected to said separation to dissolve or disperse the liq. CONSTITUTION:In the treatment with membrane of a solution of a useful substance contg. impurities in suspension to conduct its concn., separation or desalting, chitosan is added to said solution in such on amt. as to attain its final concn. of about 0.01-0.1% to dissolve or disperse the solution in order to remove therefrom the impurities causing hindrance to the membrane separation as an aggregate or complex. As the solution of the useful substance contg. the impurities in suspension, for example, cheese, whey, polysaccharide extract or biomass extract is used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a pretreatment method for a process in which a liquid, particularly a solution of a useful substance in which impurities are suspended, is treated with a membrane to concentrate and separate the useful substance.

The pretreatment method of the present invention involves the process of extracting polysaccharides from natural plants, concentrating and separating polysaccharides from the extract, and
Used for pre-treatment of whey concentration, separation, desalting process, etc.
Since substances that interfere with membrane separation are separated and removed as aggregates or complexes in advance, membrane separation efficiency can be improved.

(Prior art) Membranes such as UF membranes, RO membranes, and ED membranes are used as means for concentrating, separating, or desalting useful substances from liquids such as polysaccharide solutions extracted from natural plants, cheese and whey, etc. Processes such as concentration, separation, and desalting are widely used. but,
If the liquid contains many impurities, the impurities will adhere to the membrane surface and the efficiency of membrane separation will be greatly impaired. Conventionally, high-speed centrifugation, microfiltration, etc. have been used as pretreatment for membrane separation, but not only does it take a considerable amount of time to separate impurities, but the impurities are suspended in a form that is difficult to remove. These methods do not sufficiently separate impurities.

(Problems to be Solved by the Invention) The present invention provides a treatment method that easily removes impurities in the liquid that interfere with membrane separation and improves membrane separation efficiency as a pretreatment when membrane separation of a liquid is performed. The task is to do so.

(Means for Solving the Problems) As a result of extensive research to solve the above problems, the present invention has revealed that when chitosan is added to a liquid to be subjected to membrane separation in which impurities are suspended and dissolved or dispersed, impurities are removed. The present invention was completed based on the discovery that membrane separation efficiency can be significantly improved by membrane treatment of a liquid from which impurities are easily removed as aggregates or complexes.

That is, in the present invention, when a solution of a useful substance in which impurities are suspended is treated with a membrane to concentrate, separate, and desalt the useful substance, chitosan is added to the solution in advance to a final concentration of 0.
It relates to a pretreatment method for a membrane separation step, which comprises adding the impurities to a concentration of 0.01 to 0.1% and dissolving or dispersing them to remove impurities that interfere with membrane separation as aggregates or complexes.

Traditionally, chitin or its hydrolysis products have been used for decolorizing coffee, etc. (Japanese Patent Application Laid-Open No. 110588/1982), separation and recovery of heavy metal ions in industrial wastewater (Japanese Patent Application Laid-open No. 53-398).
2), adsorption of iodine gas (JP-A-55-1670)
43 Publication) etc. Furthermore, chitosan and tannic acid or phosphoric acid have been used in combination to purify impure sugar solutions (Japanese Patent Laid-Open No. 110338/1983, Japanese Patent Publication No. 160900/1983, etc.). However, these methods merely utilize the adsorption properties of chitin or chitosan, and as in the present invention, they are used as a pretreatment for membrane treatment and are used in combination with membrane treatment to increase the efficiency of membrane treatment. It wasn't. In the present invention, the chitosan addition treatment is performed as a pretreatment of the membrane treatment, and the liquid subjected to the chitosan addition treatment is subjected to the membrane treatment, so that the membrane separation efficiency can be significantly increased. In this respect, it is clearly different from the above-mentioned known facts.

The features of the present invention relate to a treatment method that improves membrane separation efficiency by adding chitosan to a liquid containing impurities that interfere with membrane separation, dissolving or dispersing the impurities, and easily removing the impurities by aggregating or complexing them.

Examples of liquids containing impurities in the present invention include extracts obtained by extracting water-soluble dietary fiber from natural plants, cheese whey, liquids extracted by crushing bacterial cells, hot water extracts of shiitake mycelia, and the like. To add chitosan to these liquids and dissolve or disperse it, chitosan shows solubility in acidic aqueous solutions, so if the pH of the liquid is below pH 5, it is possible to directly add chitosan powder and dissolve or disperse it. However, in general, if chitosan is dissolved in an organic acid solution such as lactic acid or acetic acid in advance and then added to the liquid, chitosan can be effectively dissolved or dispersed in the liquid.

The amount of chitosan added depends on the concentration of impurities, but generally the final concentration in the liquid is 0. O1~0.1% by weight
Add and dissolve or disperse.

If the amount added is less than 0.01% by weight, the chitosan concentration will be diluted in the liquid and no flocculating effect will be exhibited, and if the amount is more than 0.1% by weight, the flocculating effect will occur. Negative effects occur. From this point of view, chitosan is used in an amount of about 0.01 to 0.1% by weight.

After adding chitosan to the liquid, this liquid is kept for a certain period of time.
Preferably, the resulting chitosan aggregate or composite is aged by leaving it for one hour or more. Thereafter, this liquid is filtered using milk filter paper, filter cloth, etc. to separate and remove aggregates or complexes of impurities. In this way, impurities in the liquid can be easily separated and removed.

In addition, before or after separating and removing impurities,
When the pH of the liquid is appropriately adjusted, preferably to pH 5 or higher, chitosan remaining in the liquid can be insolubilized and removed by filtration.

The liquid from which impurities have been separated and removed in this manner is subjected to membrane treatment. For membrane treatment, membranes such as UF membrane, RO membrane, ED membrane, etc. are used. When the pretreated liquid of the present invention is subjected to membrane treatment, the filtration rate during membrane filtration can be increased and the concentration ratio at the concentration limit value can be significantly improved.

Next, the present invention will be specifically explained by giving examples of the present invention.

(Example 1) Chitosan (trade name: Kimitsuki Chitosan) was added to an acetic acid aqueous solution, dispersed and completely dissolved, and 0.3% of chitosan and 0.3% of acetic acid were added.
2.4 kg of chitosan solution containing 5% was prepared.

2.4 kg of the above chitosan solution was added to 8 kg of water-soluble dietary fiber extract extracted from natural plants.

After leaving for 1 hour, adjust the pH to neutral, remove aggregates using milk filter paper, and use an ultrafiltration membrane (GR40p1 manufactured by DDS).
membrane). As a control, a solution obtained by separating the water-soluble dietary fiber extract without adding chitosan using a 6000 rpa+ centrifuge was similarly concentrated using an ultrafiltration membrane. The concentrated solution without chitosan treatment was slightly cloudy, whereas the solution pretreated with chitosan was clear, and the efficiency of concentration using the ultrafiltration membrane was improved.

Concentration factor (CF) during ultrafiltration and permeation flux (
FIGS. 1 and 2 show the relationship with Flux). As can be seen from this figure, the permeation flux of the chitosan pretreated liquid (Fig. 1) is faster than that of the control liquid (Fig. 2), and the concentration limit (when the permeation flux reaches 0) is higher than that of the control liquid (Fig. 2). concentration factor)
While the former was 24.1, the latter was 15.9, indicating that the membrane separation efficiency of this example could be significantly increased.

(Example 2) Chitosan (trade name: Kimitsuki Chitosan) was added to an acetic acid aqueous solution, dispersed and completely dissolved, and 0.3% of chitosan and 0.3% of acetic acid were added.
2.4 kg of chitosan solution containing 5% was prepared.

2.4 kg of the above chitosan solution was added to 8 kg of a polysaccharide extract containing arabinoxylan or arabinogalactan extracted from natural plants. After standing for 1 hour, the pH was adjusted to neutral, aggregates were removed using milk filter paper, and the mixture was concentrated using an ultrafiltration membrane (GR40pp membrane manufactured by DDS). As a control, the above polysaccharide extract was prepared without adding chitosan.
The solution separated using a centrifugal separator at 00 rpm was similarly concentrated using an ultrafiltration membrane. The concentrated solution without chitosan treatment was slightly cloudy, whereas the solution pretreated with chitosan was clear, and the efficiency of concentration using the ultrafiltration membrane was improved.

According to this example, as in Example 1, the membrane separation efficiency could be significantly increased.

(Example 3) Chitosan (trade name Kimikitosan MP) was added to an acetic acid aqueous solution and dissolved, resulting in 0.3% chitosan and 0.2% acetic acid.
3 kg of chitosan solution containing .

3 kg of the above chitosan solution was added to 60 kg of raw whey produced during cheese production. After leaving for 1 hour, aggregates were removed using milk filter paper, and concentrated using an ultrafiltration membrane (GR61pp membrane manufactured by DOS). As a control, 3 kg of a 0.2% acetic acid solution containing no chitosan was added to the above whey, and the whey was filtered through milk filter paper and concentrated in the same manner. As a result, the concentration efficiency of the solution subjected to chitosan pretreatment was improved. The table below shows the relationship between the concentration ratio during ultrafiltration and the permeation flux for the whey treated with chitosan according to this example and the control whey. As can be seen from this table, the concentration rate of the chitosan-pretreated whey was faster than that of the control whey, and the membrane concentration efficiency of this example could be significantly increased.

(Example 3) Desalting treatment of chemical whey was repeatedly performed using a batch-type electrodialysis apparatus shown below. The electrodialysis equipment used is as follows.

Equipment: TS-24 type (manufactured by Tokuyama Soda ■) Ion exchange membrane: Neocepta AMX (anion exchange membrane manufactured by Tokuyama Soda ■) CMX (
Cation exchange membrane (manufactured by Tokuyama Soda) Membrane area: 0.24 pores/
Experiment 1: Prepare 200 kg of chemical whey and add 10 kg of 0.17% acetic acid aqueous solution (stir). After 30 minutes, perform cleaning treatment with a centrifugal cleaner, and then supply to the electrodialysis machine. did.

The voltage of the rectifier was kept constant at 30 V, and desalination treatment was performed until the ash content in the whey reached 80% of the initial value. The desalination rate during operation was estimated by measuring the electrical conductivity of whey. The applied current value was 7 A immediately after the start, rose to 19 A after 5 minutes, but gradually decreased thereafter, and was 0.58 at the end of the test, 170 minutes later. After desalination treatment, CIP (cleaning in place)
and cleaned the equipment. In the CIP operation, the inside of the apparatus was first thoroughly washed with water, and then 1% NaOH was circulated for 30 minutes. Thereafter, the sample was washed with water, circulated with 1% HCL for 20 minutes, and then thoroughly washed with water. The whey desalination treatment and CIP operation were repeated 50 times, and in the 50th desalination operation, the maximum current value reached was 118, and the desalination treatment time was 270 minutes. After 50 repeated operations, the electrodialysis apparatus was disassembled and inspected, and deposits were found on the surface of the ion exchange membrane, which were removed by wiping with a sponge.

Experiment 2: Next, 10 kg of a 0.3% chitosan solution was prepared by adding chitosan (trade name: Kimikitosan) to a 0.17% acetic acid aqueous solution. The chitosan solution was added to 200 kg of chemically synthesized whey, stirred, and purified for 30 minutes using a rapid heart purifier, then supplied to an electrodialysis device and desalinated in the same manner as described above. The initial operating conditions were almost the same as the first time described above. Desalination treatment and CAP operation were repeated 50 times, and in the 50th operation, the maximum current value reached was 16^, and the treatment time was 205 minutes. When the membrane was disassembled and inspected in the same manner as in Experiment 1, deposits were found on the surface of the ion exchange membrane, but the amount was much smaller than in Experiment 1. (Effects of the Invention) The pretreatment of the membrane separation process according to the present invention shortens the membrane separation process time by performing a simple pretreatment, whereas conventionally the removal of impurities and the membrane treatment process took time. Moreover, since the concentration limit value can be increased, membrane separation efficiency can be improved. Therefore, it is a very useful method that contributes to shortening the time when concentrating, separating, and desalting polysaccharide extracts, cheese/whey, bacterial cell extracts, etc., improving concentration limits, and reducing the load on membranes. It is.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the concentration factor (CF) and permeation flux (Fluχ) during ultrafiltration of the polysaccharide extract pretreated according to Example 1 of the present invention, and Figure 2 shows the relationship between the concentration factor (CF) and permeation flux (Fluχ) of the polysaccharide extract pretreated according to Example 1 of the present invention. The figure shows that of the sugar treatment solution.

Claims (2)

[Claims] (1) When concentrating, separating, or desalting a solution of useful substances that suspends impurities through a membrane,
Add chitosan to the solution in advance to a final concentration of about 0.01~
A pretreatment method for a membrane separation step, characterized by adding the impurities to a concentration of 0.1% and dissolving or dispersing them to remove impurities that interfere with membrane separation as aggregates or complexes. (2) A pretreatment method for a membrane separation step according to claim (1), wherein the solution of useful substances that suspends impurities is cheese whey, a polysaccharide extract, or a bacterial cell extract.