JPS6154208A - Treatment of liquid to be treated in reverse-osmosis separation - Google Patents

Abstract

PURPOSE:To accelerate the reaction velocity in removing dissolved oxygen and to carry out reverse-osmosis separation without damaging the selective separability of a composite membrane of furfuryl alcohol by adding a sulfurous reducing agent and a copper salt to a liquid to be treated. CONSTITUTION:A liquid to be treated such as seawater is separated by reverse- osmosis to obtain demineralized water by using a semipermeable membrane provided with a thin film consisting of a crosslinked polymer contg. furfuryl alcohol as an essential component. In this case, a sulfurous reducing agent such as sodium bisulfite is added to the liquid to be treated, and a copper salt such as copper sulfate is added in the range about 0.1-10ppm. The reaction velocity between dissolved oxygen and the sulfurous reducing agent in the liquid to be treated is accelerated by addition of said catalytic amt. of copper ions. Consequently, the cost of the chemical additives for pretreatment is reduced and the equipment is simplified. Besides, the propagation of microbes in the liquid can be controlled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides V:
The present invention relates to a method for separating liquids using a reverse osmosis separation device composed of a semipermeable composite membrane having a thin film made of a copolymer as a barrier layer.

[Conventional technology] Reverse osmosis separation technology that utilizes the reverse osmosis phenomenon of semipermeable membranes has been developed in recent years.
It is showing rapid development, and various types of high-performance membranes are being developed. Advances in liquid separation technology using reverse osmosis are largely due to the development of reverse osmosis membranes, which are at the core of the process, and the development of optimal conditions for using reverse osmosis membranes.In particular, the development of the reverse osmosis membrane, which is the core of the technology, and the development of optimal conditions for using the reverse osmosis membrane, are particularly important. The development of various new membranes and the study of their usage conditions are becoming more active year by year. For example, a composite membrane comprising a thin film of furfuryl alcohol crosslinked JLli as a barrier layer is provided on a porous support made of polysulfone, chlorinated polyvinyl chloride, etc., U.S. Pat. No. 3,926,798. issue,
JP-A-54-107882, etc.) and has excellent selective separation ability. However, some semipermeable membranes, including composite membranes that use furyl alcohol-based polymer thin films as barrier layers, which have excellent selective separation ability, do not have sufficient durability against oxidizing agents and cannot be used continuously for long periods of time. If liquid separation is carried out in the semi-permeable membrane, the performance of the semi-permeable membrane deteriorates, which is a major drawback. For example, in a system where spring water is separated by reverse osmosis to produce pure water, microorganisms that are attracted to seawater, which is the raw liquid to be treated, adhere to and accumulate on the raw liquid transport pipe, making it difficult for the seawater to flow smoothly. It is common to add chlorine, etc. to seawater in order to prevent harmful substances from interfering with seawater and remove harmful substances from the seawater. The oxidation-degradable semipermeable membrane has the disadvantage that it is degraded by this chlorine and gradually loses its selective separation function. Furthermore, the furfuryl alcohol-based semipermeable composite membrane is also subject to deterioration due to dissolved oxygen in the raw solution to be treated, which is an obstacle to its practical application despite its excellent membrane performance. This dissolved oxygen always exists in the stock solution, and its removal is not as easy as with chlorine.

A method for treating an undiluted solution without impairing the excellent selective separation properties of the above-mentioned furfuryl alcohol-based composite membrane,
A method of adding sulfite or bisulfite to the stock solution to be treated has already been proposed (Japanese Unexamined Patent Publication No. 56-21604). However, the reaction rate between dissolved oxygen and sulfite ions or biite II ions in the absence of a catalyst is not necessarily fast, especially when using kansui with a low salt concentration or organic compounds as the stock solution to be treated. , becomes extremely slow.

Therefore, in order to fully demonstrate the ability of the furfuryl alcohol-based semipermeable membrane to prevent performance deterioration, it is necessary to add a large excess of the sulfuric acid reducing agent or to provide sufficient residence time to complete the reaction. It is necessary to install a buffer tank, etc. with sufficient water, and if the temperature of the raw solution to be treated is as low as about 15°C or lower, in addition to the increase in the amount of dissolved oxygen, the sulfite reducing agent and dissolved oxygen The reaction rate of is also significantly reduced, so
It is difficult to say that all of the above methods are industrially superior from an economic standpoint. On the other hand, the above method also removes chlorine, which is a sterilizing agent, and dissolved oxygen in water, and
Since sulfate is produced by oxidation of sulfite, there is a high possibility that various microbial problems will occur, including the generation of sulfate-reducing bacteria in an anaerobic atmosphere.

[Problem to be Solved by the Invention 1] The present invention provides a more economical and industrial solution that prevents the occurrence of the above-mentioned problems without impairing the excellent selective separation ability of the furfuryl alcohol-based semipermeable composite membrane. The present invention was discovered through extensive research into methods.

[Means for Solving the Problems] In other words, the feature of the present invention is that chlorine and dissolved oxygen in the raw solution to be treated are replaced with sulfite, biTa salt, or 1i! !
When removing with a sulfite reducing agent such as acid gas, the coexistence of copper ions as a catalytic bond greatly accelerates the reaction rate of removing dissolved acid, and at the same time prevents the growth of microorganisms.

Specific examples of the sulfite reducing agents listed above include 1-lium sulfite, VAM salts such as potassium sulfite and calcium sulfite, bisulfites such as sodium bisulfite and potassium bisulfite, and sodium hyposulfite. Examples include sub-value R salts and sulfur dioxide gas.

Further, specific examples of copper salts include water-soluble copper compounds such as copper chloride, copper sulfate, and copper nitrate.

In addition to copper ions, transition metals such as iron ions, cobalt ions, and manganese ions are also known as catalysts that promote the reactivity between dissolved oxygen in water and sulfite reducing agents, but they do not have the effect of suppressing microbial growth. There is nothing superior to copper ions in terms of this, and addition of copper salts is most preferable from a comprehensive industrial standpoint such as addition m and economical efficiency.

The more copper ions added to the stock solution to be treated, the more the reaction rate between dissolved oxygen and the oxygen scavenger will be accelerated, and
Although it is preferable from a microbial countermeasure, it is usually 0.1 to iopp.
A sufficient effect can be obtained even at a distance of about m.

The reaction between dissolved oxygen and a sulfite reducing agent, such as calcium sulfite or sodium bisulfite, is expressed by the following chemical equation (
1) J: Reacts with 2 molecules of sulfite B salt or 1 = bisulfite per molecule of uni acid group.

Therefore, in order to remove dissolved oxygen of 11)l)m, 7.5 ppm and 6.5 ppm of calcium sulfite j5 and sodium sulfite are theoretically required, respectively.

In the present invention, the semipermeable composite membrane made of furfuryl alcohol-based polymer refers to polysulfone, polyvinyl chloride,
Polyvinylidene chloride, cellulose nitrate or co-combined combinations thereof, preferably an anisotropic (14-structured porous support) made of polysulfone, furfuryl alcohol or trishydroxyethyl alcohol in addition to furfuryl alcohol. lysocyanuric acid, inositol and sorbitol 1
- as a reaction component system consisting of l, etc. and as an acid catalyst, l
iU acid, phosphoric acid, toluene sulfonic acid, preferably
It is a composite film in which a barrier layer is formed of a thin film coated with an aqueous solution containing sulfuric acid and polymerized by heating.More specifically, it is disclosed in U.S. Pat.
Reaction component systems disclosed in JP-A-107882, JP-A-55-159807-Mei 14 and JP-A-56-158cz, F3 are preferred.

[Effect of the invention 1 According to the present invention, ■ Addition of a catalytic amount of copper ions accelerates the reaction rate between dissolved oxygen in the stock solution to be treated and the sulfite reducing agent, resulting in reduction of sulfites in excess of the required amount. It becomes possible to suppress the addition of agents. Alternatively, the RQ Rjf of a buffer tank larger than necessary to complete the reaction between dissolved oxygen and sulfite reducing agent is no longer required, and the cost of pre-treatment additive chemicals for the raw solution to be treated to be supplied to the reverse osmosis separation device is reduced. It is possible to reduce or simplify the pretreatment equipment.

■ The addition of copper ions has the effect of inhibiting the growth of microorganisms in the raw solution to be treated.

This is a method that enables the practical application of furfuryl-furcol-based semipermeable composite membranes, and its industrial significance is extremely large.

Hereinafter, the effects of the present invention will be explained in more detail with reference to the following examples.

[Example 1 Example 1 Using a furfurylfurcol-based semipermeable composite membrane prepared according to Example 1 of JP-A No. 57-24602,
A seawater desalination test was carried out using the manufactured spiral-shaped element 6 wooden module with a diameter of 1Qcm and a length of 1m. The salt concentration in the raw seawater was 3.5% by weight, and the dissolved oxygen concentration was 7.2 ppm. 56 kcJ/cl, 25
Operating conditions at °C1PH6.5 and recovery rate of 40%! When doing a reverse osmosis test with 1, he is 1! [! After reducing the dissolved oxygen concentration in the raw seawater solution to 1°0 ppm by vacuum degassing, sodium bisulfite and sulfur! l! The amount of copper (II) added was 201) l) l and 0.5 ppm, respectively, and the residence time to the reverse osmosis module of the raw seawater solution of wheat to which both products were added at the same time was 30 seconds. A osmotic separation device was manufactured.

The above reverse osmosis portion! When Ill1 equipment started operating,
A water quality of 1301)I)m (TDS) was obtained as permeated water. In addition, dissolved oxygen i at the reverse osmosis module inlet
l'AILT was 0.10 pm or less. When this device was continuously operated for one year under the above operating conditions, the quality of the passing water was 1501) pm (TDS). In addition, there were no microbial problems such as the sound of module pressure loss due to α1 proliferation or the generation of hydrogen sulfide odor due to the generation of sulfate-reducing bacteria.

Comparative Example 1 Copper sulfate (II
When a seawater desalination test was carried out under the operating conditions shown in Example 1 except that the addition of 2000 ml was omitted, the dissolved oxygen concentration in the raw seawater solution at the inlet of the reverse osmosis module was 0.5 ppm. Additionally, approximately 3 months after the start of operation, a hydrogen sulfide odor that was thought to originate from sulfate-reducing bacteria occurred, and 2 weeks later, the module pressure jΩ' exceeded 6 kv/ayf, so the reverse osmosis test was discontinued. .

Comparative Example 2 After washing the reverse osmosis separator contaminated with the microorganisms and their metabolites shown in Comparative Example 1 with a 0.2% polymerization sodium dodecyl sulfate aqueous solution, 2 ppm copper(II) sulfate was added.
When operated for one week with a freshly added rfη water stock solution, the module pressure drop remained at 2 W/d, and the hydrogen sulfide odor disappeared. So, III! When the reverse osmosis test was carried out again using the operating column Iro 1 of Comparative Example 1 after stopping the addition of Iro acid copper (If), the quality of the passing water gradually deteriorated, and after one year, the reverse osmosis test was carried out again.
It got worse at 70ppm (TDS).

Example 2 3,5''; 1 m% (7) Seawater'ti:,
Jl (+'TE, 56kq/Ci, 25°C, PH
When conducting a reverse osmosis test using the element shown in Example 1 under the operating conditions of 6.5, the dissolved oxygen concentration in seawater was measured to be 7.21)Ilm. When removing dissolved oxygen with sodium bisulfite, the dissolved oxygen concentration in the stock solution was adjusted to 0. The reaction time required to reduce the level to lppm or less and heavy nitrogen T1j AIS! 1 Sodium added base, llI! Table 1 shows the relationship between the colors of copper I acid (It) added.

Table 1 Changes in dissolved oxygen concentration (3,5% Zm water system> Example 3 1001) Ill salt and 210111) II
Dissolved oxygen in an aqueous solution consisting of sodium bicarbonate of I!
When removing with IN calcium sulfate, is there any dissolved Hl in the raw solution to be treated? , if', 1 degree is 0. Table 2 shows the relationship between the reaction time, sodium bisulfite addition, and copper sulfate (H) addition equipment required to reduce the amount to 1 ppm or less. The dissolved oxygen concentration in the stock solution to be treated was 7.51)l)m (25°C), and the measurement was performed in a JJI crystal bath at 25°C.

Table 2 Change in dissolved oxygen concentration <100ppm NaCα+210ppm NaHCO
3) Example 4 3.5% by weight of FA water was collected and the sterilization effect with copper sulfate (■) was examined. Changes in the number of bacteria and sulfur in collected seawater!
Table 3 shows the relationship between the amount of 1!2 copper (I[) added.

Table 3: Relationship between the amount of copper (II) added and the number of bacteria Example 4 Using the elements shown in Example 1, an ultra-pure manufacturing surface for electronic industry use was designed. m IC
5 degrees is 8.5 ppm, and the concentration of raw water is 150 ppm (
TDS). Sodium sulfite 1 in raw water to be treated
13J: copper (II) chloride, 1100 pI each) J
'3 and 2.01111 m were added and fed to the reverse osmosis module. The temperature of the raw water is 17℃, the pH is 7.0,
After adding the above-mentioned chemicals, the retention time of the raw water until it reaches the reverse osmosis module is 5 minutes, and the dissolved oxygen concentration in the raw water at the reverse osmosis module entrance is 0. It was kept below lppm. The reverse osmosis module was operated at a recovery rate of 80% and an operating pressure of 25 kg/+a+f, but even after one year had passed since the start of operation, the quality of the passing water was below 10 tls/cm, and subsequent decarboxylation and ionization J: showed a specific resistance value of approximately 16 MΩ during the exchange process.

Comparative Example 3 Using the reverse osmosis separator for producing ultrapure water shown in Example 4, it was operated under the conditions shown in Example 4 except that the addition of copper chloride (n) was omitted. After the passage of time, the water quality of the water passing through reverse osmosis was 20 μS/cm.
exceeded. Note that the dissolved oxygen concentration in the raw water at the module entrance was 8, Op+on.

Claims (2)

[Claims] (1) When performing reverse osmosis separation using a semipermeable composite membrane equipped with a thin film made of a crosslinked polymer containing furfuryl alcohol as an essential component, it is recommended to add a sulfite reducing agent and copper salt to the stock solution to be treated. Characteristic treatment method for the undiluted solution in reverse osmosis separation method. (2) A method for treating an undiluted solution in a reverse osmosis separation method according to claim 1, wherein the amount of copper salt added is in the range of 0.1 to 10 ppm.