JPH1190191A - Membrane detergent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a safe membrane detergent usable even for a polyamide or polyimide membrane by incorporating one selected from the group comprising L-ascorbic acid, erythorbic acid and their water-soluble salts or their derivs. SOLUTION: The membrane detergent used for washing a membrane contaminated with org. matter contains one selected from the group comprising L- ascorbic acid, erythorbic acid and their water-soluble salts or their derivs. L- ascorbic acid is a reducing substance permitted as a food additive and erythorbic acid is an optical isomer of L-ascorbic acid. The water-soluble salts include sodium and calcium salts and the derivs. include esters. The detergent is basically an aq. soln. prepd. by dissolving one of the chemicals in water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane cleaning agent suitable for cleaning a membrane when performing a liquid filtration operation, and particularly for cleaning a membrane contaminated with organic substances.

[0002]

2. Description of the Related Art As a cleaning agent for organic contamination of a film, alkalis, surfactants, and oxidizing agents (H ₂ O ₂ , NaCl
O), enzymes and the like are known (Literature: "Countermeasures against contamination of separation membrane and washing / regeneration technology" (Water treatment technology p.43, Vo)
l. 33, no. 2, 1992)).

[0003]

SUMMARY OF THE INVENTION Among the above-mentioned cleaning agents,
Oxidizing agents and enzymes exhibit excellent cleaning effects on organic substances. However, there is a problem that the enzyme is effective for a naturally derived polymer such as a protein, but is not effective for an organic substance other than the natural polymer such as a polymer flocculant and a surfactant. In addition, H ₂ O ₂ or NaClO
The oxidizing agent such as is effective for organic substances other than natural polymers, that is, synthetic polymers such as polymer flocculants and surfactants, but for polyamide or polyimide-based films having weak oxidation resistance. There is a problem that it cannot be used. Furthermore, oxidizing agents are harmful to the human body and require careful handling.

[0004] In view of such circumstances, the present invention has been developed in view of H ₂ O ₂
An object of the present invention is to provide a safe cleaning agent which has a cleaning effect equivalent to that of an oxidizing agent such as NaClO or NaClO and can be used for a polyamide or polyimide film.

[0005]

Means for Solving the Problems The present invention for solving the above-mentioned problems is directed to a membrane cleaning agent used for cleaning a membrane, comprising L-ascorbic acid, erythorbic acid, and a water-soluble salt or derivative thereof. A membrane cleaning agent comprising at least one member selected from the group consisting of:

Here, the film is, for example, contaminated by an organic substance.

[0007] The membrane cleaning agent of the present invention contaminates various organic substances in a membrane treatment process applied to separation, purification, concentration, and recovery of fluids including polymers, fine particles, microorganisms, yeast, pulp, sludge, and the like. It can be used for cleaning a film that has been made. In particular, in a membrane treatment process in which an aggregation process using a polymer flocculant is applied as a pretreatment, the film can be suitably used for cleaning a film contaminated with various organic substances including a polymer flocculant.

The type of membrane to which the cleaning agent of the present invention can be applied is not particularly limited, and examples thereof include MF membrane (microfiltration membrane),
UF membrane (ultrafiltration membrane), NF membrane (nanofiltration membrane), RO
(Reverse osmosis membrane).

The material of the film is not particularly limited, and it can be applied to an organic film, particularly a polyimide or polyamide film which is weak against an oxidizing agent.

[0010] L-ascorbic acid used in the present invention is a substance having a reducing property and designated as a food additive, and is a highly safe substance. Erythorbic acid is an optical isomer of L-ascorbic acid . In addition, examples of these water-soluble salts include sodium salts and calcium salts. Examples of these derivatives include esters of ascorbic acid or erythorbic acid. Examples are propionates. In the present invention, these can be used alone or in combination of two or more.

The membrane cleaning agent of the present invention is basically an aqueous solution obtained by dissolving these agents in water. The concentration of the drug is not particularly limited, but it is preferable to use about 10 ppm to 1.0%.

Further, the membrane cleaning agent of the present invention may contain other components as long as the active component of the present invention is not inhibited.

[0013] Further, the cleaning method using the membrane cleaning agent of the present invention is not particularly limited, and can be used in the same manner as in the case of using other cleaning agents. For example, after immersing the film in the membrane cleaning agent, It can be easily performed by washing with water or the like.

[0014] The detergent of the present invention contains at least one selected from L-ascorbic acid and water-soluble salts or derivatives thereof, erythorbic acid and water-soluble salts or derivatives thereof, so that an organic substance can be obtained. In particular, a membrane contaminated with a synthetic polymer compound is effectively washed. It is known that the viscosity of a water-soluble polymer aqueous solution decreases in the presence of L-ascorbic acid as a reducing agent (K. Uchida et al., Agric. Biol. Ch.
em. , 50, 257 (1986); Shuzo Aoki, Che.
mystery Express 6 (12), 1017
(1991)), which is presumed to be based on this effect.
That is, although the details of lowering the viscosity of the water-soluble polymer solution in the presence of L-ascorbic acid are unknown, active oxygen species are generated by the interaction of ascorbic acid with some substance in water, and the active oxygen species is generated. It is considered that the water-soluble polymer is decomposed by this.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

(Example 1) Ted end type stirring type filtration tester (Amicon standard type stirring type cell 8400)
Type) and polysulfone UF membrane (Amicon PM10)
Was set and pure water was passed under stirring at a pressure of 1 kg / cm ² , and the flux of pure water (water flux: m / D) was measured. Thereafter, pure water and an aqueous solution of a polymer flocculant (Kurita Kogyo Co., Ltd .: Crifix PA33150) in a filtration tester are used.
mg / L aqueous solution), and the aqueous polymer flocculant aqueous solution is replaced with
100 mL of water was passed under stirring at a pressure of 1 kg / cm ² . Next, the polymer flocculant aqueous solution remaining in the container and pure water 300 mL
And pure water was passed under stirring at a pressure of 1 kg / cm ² , and the flux of pure water was measured.

Thereafter, the membrane was removed from the filtration tester, and the membrane was immersed in a 100 ppm aqueous sodium ascorbate solution overnight, and then pure water was again passed under stirring at a pressure of 1 kg / cm ² to measure the flux of pure water. did. Table 1 shows the results.

Example 2 The same operation as in Example 1 was performed except that a 100 ppm aqueous solution of sodium erythorbate was used instead of the 100 ppm aqueous solution of sodium ascorbate. Table 1 shows the results.

Comparative Example 1 The same operation as in Example 1 was performed except that a 100 ppm aqueous hydrazine solution was used instead of the 100 ppm sodium ascorbate aqueous solution. Table 1 shows the results.

Comparative Example 2 The same operation as in Example 1 was performed, except that a 100 ppm aqueous solution of sodium bisulfite was used instead of the 100 ppm aqueous solution of sodium ascorbate. Table 1 shows the results.

(Comparative Example 3) Except that pure water was used instead of the 100 ppm aqueous solution of sodium ascorbate,
The same operation as in Example 1 was performed. Table 1 shows the results.

(Comparative Example 4) Instead of a 100 ppm aqueous solution of sodium ascorbate, 100 ppm of H ₂ O _{2 was used.}
The same operation as in Example 1 was performed except that the aqueous solution was used.
Table 1 shows the results.

(Comparative Example 5) Instead of a 100 ppm aqueous solution of sodium ascorbate, 100 ppm of NaC was used.
The same operation as in Example 1 was performed except that the 10 aqueous solution was used. Table 1 shows the results.

[0024]

[Table 1]

From the results shown in Table 1, it can be seen that Example 1 using sodium ascorbate or sodium erysorbate was used.
And 2 showed a cleaning effect equal to or higher than Comparative Examples 4 and 5 using H ₂ O ₂ or NaClO as an oxidizing agent. Also,
The effect was superior to Comparative Examples 1 and 2 using hydrazine or sodium bisulfite as a reducing agent. Therefore, it was confirmed that Examples 1 and 2, which are extremely excellent in terms of safety, are suitable as a membrane cleaning agent.

Example 3 Instead of an aqueous solution of a polymer flocculant, 50 ppm of sodium humate and 50 p of kaolin were used.
Simulated wastewater containing pm in sulfuric acid band (aluminum sulfate)
The same operation as in Example 1 was performed except that 80 ppm and 15 ppm of a polymer flocculant (manufactured by Kurita Industry Co., Ltd .: Crifix PA331) were added and flocculated. Table 2 shows the results.

(Comparative Example 6) Except that pure water was used instead of the 100 ppm aqueous solution of sodium ascorbate,
The same operation as in Example 3 was performed. Table 2 shows the results.

Comparative Example 7 The same operation as in Example 3 was carried out except that an aqueous solution of H ₂ O ₂ was used instead of the aqueous solution of 100 ppm sodium ascorbate. Table 2 shows the results.

Comparative Example 8 The same operation as in Example 3 was performed except that an aqueous solution of NaClO was used instead of the aqueous solution of sodium ascorbate of 100 ppm. Table 2 shows the results
Shown in

[0030]

[Table 2]

From the results shown in Table 2, in the system using the simulated wastewater, Example 3 using sodium ascorbate was equivalent to Comparative Examples 7 and 8 using H ₂ O ₂ or NaClO as an oxidizing agent. It was confirmed that the above cleaning effect was exhibited.

Example 4 A polyamide-based RO membrane (manufactured by Nitto Denko: ES10) was set in a dead-end stirring type filtration tester (made of stainless steel), and a 50 ppm aqueous solution of NaCl was stirred at a pressure of 10.0 kg / cm ² . Water was allowed to flow down, and the rejection of flux and NaCl was measured.

Then, the membrane was removed from the filtration tester, and the membrane was placed in a 100 ppm aqueous sodium ascorbate solution.
After immersion for a period of time, a 50 ppm aqueous solution of NaCl was passed again with stirring at a pressure of 10.0 kg / cm ² , and the rejection of NaCl was measured. Table 3 shows the results.

Example 5 The same operation as in Example 4 was performed except that a 100 ppm aqueous solution of sodium erythorbate was used instead of the 100 ppm aqueous solution of sodium ascorbate. Table 3 shows the results.

Comparative Example 9 The same operation as in Example 4 was performed except that a 100 ppm aqueous hydrazine solution was used instead of the 100 ppm aqueous sodium ascorbate solution. Table 3 shows the results.

Comparative Example 10 The same operation as in Example 4 was performed except that a 100 ppm aqueous solution of sodium bisulfite was used instead of the 100 ppm aqueous solution of sodium ascorbate. Table 3 shows the results.

Comparative Example 11 The same operation as in Example 4 was performed except that pure water was used instead of the 100 ppm aqueous solution of sodium ascorbate. Table 3 shows the results.

(Comparative Example 12) Instead of a 100 ppm aqueous solution of sodium ascorbate, 100 ppm of H2 was used.
The same operation as in Example 4 was performed except that an aqueous solution of O2 was used. Table 3 shows the results.

(Comparative Example 13) Instead of a 100 ppm aqueous solution of sodium ascorbate, 100 ppm of sodium ascorbate was used.
The same operation as in Example 4 was performed except that an aqueous ClO solution was used. Table 3 shows the results.

[0040]

[Table 3]

From the results shown in Table 3, H ₂ O ₂ or NaCl
In Comparative Examples 12 and 13 using O, particularly in Comparative Example 13 using NaClO, NaCl was used to deteriorate the film.
Although the rejection rate decreased, in Examples 4 and 5 using sodium ascorbate or sodium erythorbate,
No effect on the membrane was observed.

Example 6 Pure water was applied at a pressure of 4 kg / cm ² ,
Water was passed through a polysulfone-based UF membrane (NTU-3020 manufactured by Nitto Denko) at a water flow rate of 10 L / min, and the flux after 30 minutes of water flow was measured. The module is 500mm long,
It is a two-tube type with a diameter of 11.5 mm.

Next, 10 mg / L of PAC (polyaluminum chloride) was added to the sewage secondary treatment water having the water quality shown in Table 4 to condense the suspended solid to a pressure of 4 kg / cm ² and a water volume of 10 L / min. Water for one week, and then apply pure water again at a pressure of 4
Water was passed at a flow rate of 10 L / min at a flow rate of 10 kg / cm ² , and the flux after 30 minutes of water flow was measured.

Thereafter, this membrane was coated with Na20 ascorbate.
It was brought into contact with a 0 mg / L aqueous solution for 20 hours, and the flux of pure water was measured again under the same conditions as above. Table 5 shows the results.

Example 7 The same operation as in Example 4 was performed, except that a 200 ppm aqueous solution of sodium erythorbate was used instead of the 200 ppm aqueous solution of sodium ascorbate. Table 5 shows the results.

Comparative Example 14 The same operation as in Example 6 was performed, except that a 100 ppm aqueous solution of sodium bisulfite was used instead of the 200 ppm aqueous solution of sodium ascorbate. Table 5 shows the results.

(Comparative Example 15) Instead of a 200 ppm sodium ascorbate aqueous solution, 200 ppm Na ascorbate was used.
The same operation as in Example 6 was performed except that an aqueous ClO solution was used. Table 5 shows the results.

[0048]

[Table 4]

[0049]

[Table 5]

From the results shown in Table 5, even in the system using the sewage secondary treatment water, Examples 6 and 7 using sodium ascorbate or sodium erysorbate were compared with Comparative Example 15 using NaClO as an oxidizing agent. It was confirmed that the same cleaning effect was obtained.

Example 8 Pure water was applied at a pressure of 1.0 kg / cm.
^2. Water was passed through a polyolefin-based MO membrane (manufactured by Nitto Denko: pore size 0.4 μm) at a water flow rate of 2.0 L / min, and the flux after 30 minutes of water flow was measured. Module has a membrane area of 64c
m ² flat membrane. Next, a cell culture solution having a concentration of 12% was added to polyvinylamidine (Crifix CP111) 20
00mg / L, polyacrylic acid (Cliffloc PA32
2) What was agglomerated at 1000 mg / L was passed through a 100-mesh filter cloth, and the permeated liquid was pressured at 1.0 kg / L.
cm ^2, and 4 hours water passage at water 2.0L / min, the pure water pressure 1 kg / cm ^2, and passed water at water 2.0L / min again to measure the flux after 30 minutes through the water.

Thereafter, this membrane was brought into contact with a 500 mg / L aqueous solution of sodium ascorbate for 20 hours or more, and the flux of pure water was measured again under the same conditions as above. Table 6 shows the results.

Comparative Example 16 The same operation as in Example 8 was performed except that a 500 ppm aqueous solution of sodium bisulfite was used instead of the 500 ppm aqueous solution of sodium ascorbate. Table 6 shows the results.

(Comparative Example 17) Instead of a 500 ppm sodium ascorbate aqueous solution, 200 ppm Na ascorbate was used.
The same operation as in Example 8 was performed except that an aqueous ClO solution was used. Table 6 shows the results.

[0055]

[Table 6]

From the results shown in Table 6, even in the system in which the culture solution was passed, the cleaning effect of Example 8 using sodium ascorbate was equivalent to that of Comparative Example 17 using NaClO as an oxidizing agent. It was confirmed that.

(Embodiment 9) As shown in FIG.
In a processing flow in which the coagulation tank 1, the biological filtration membrane 2, the UF membrane 3 and the RO membrane 4 are sequentially processed, the wastewater from the metal processing plant is subjected to a polyamide RO membrane 4 (Kurita) at a pressure of 15 kg / cm and a water volume of 10 L / D. Industrial Co., Ltd .: KROA-21
22; the standard amount of pure water permeated is 1.0 m / D). The operation was performed for 2000 hours while periodically performing water flushing and cleaning with a detergent using a surfactant. As a result, the flux decreased from 1.0 m / D to 0.4 m / D.

The contaminated RO film was treated at a concentration of 200 pp.
m of sodium ascorbate solution for 10 hours. Then, pure water is supplied at a pressure of 10 kg / cm ² and a water volume of 10 L.
/ Min. For 1 hour, and the flux was measured. Table 7 shows the results.

Comparative Example 18 The same operation as in Example 9 was performed, except that the contaminated RO film was contacted with pure water for 10 hours instead of being brought into contact with a 200 ppm concentration of sodium ascorbate solution. Table 7 shows the results.

Comparative Example 19 Instead of contacting a contaminated RO membrane with a 200 ppm sodium ascorbate solution, a 0.1% hydrazine and 0.3% sodium dodecylbenzenesulfonate (pH 9.0) solution was used. The same operation as in Example 9 was performed except that the contact was performed for 10 hours. Table 7 shows the results.

[0061]

[Table 7]

From the results shown in Table 7, even in the system using the wastewater from the metalworking plant, the cleaning effect of Example 9 using sodium ascorbate was higher than that of Comparative Example 19 using hydrazine and sodium dodecylbenzylsulfonate. Was confirmed.

[0063]

As described above, the membrane cleaning agent of the present invention containing ascorbic acid and ersorbic acid or a water-soluble salt thereof or a derivative thereof, as described above with reference to the examples, can be used for a film contaminated with various organic substances. However, it exhibits the same film cleaning effect as an oxidizing agent, and can be used for a polyamide-based film which is degraded by the oxidizing agent, and has high safety.

[Brief description of the drawings]

FIG. 1 is a diagram showing a processing flow used in Embodiment 9 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coagulation tank 2 Biological filtration membrane 3 UF membrane 4 RO membrane

Claims (2)

[Claims] 1. A membrane cleaning agent used for cleaning a membrane, comprising at least one selected from the group consisting of L-ascorbic acid, erythorbic acid, a water-soluble salt thereof, and a derivative thereof. Characterized membrane cleaning agent. 2. The film cleaning agent according to claim 1, wherein the film is contaminated by an organic substance.