JPH035206B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dialysis method using a dialysis device using an ion exchange membrane (hereinafter referred to as an ion exchange membrane dialysis device), and more specifically, by adding an antifoaming agent to the dialysate of the ion exchange membrane dialysis device, This aims to reduce dialysis power and improve dialysis performance. Conventionally, for example, an electrodialysis method in which a large number of cation exchange membranes and anion exchange membranes are arranged alternately and various liquids are passed through a dialysis chamber formed between them and a current is applied, or only an anion exchange membrane is used. It is widely practiced to concentrate, desalt, separate and purify a solution by arranging a large number of cells and using a diffusion dialysis method that does not use an electric current. In the above-mentioned ion-exchange membrane dialysis equipment, the dialysis membrane formed by the ion-exchange membrane is used to maintain a uniform thickness in the dialysis chamber, prevent solution stagnation, and equalize the flow of the solution. Spacers are commonly used indoors. However, although safe operation can be achieved by inserting a spacer into the dialysis chamber, for example, in the case of an electrodialysis machine, the dialysis voltage increases by 10 to 20%, and in some cases as much as 40%. How to suppress the rise in dialysis voltage has been an important issue in practical application of the process. Up until now, it has been thought that the cause of such an increase in dialysis voltage is mainly due to the spacer itself, and a great deal of effort has been made to develop a better spacer by examining various materials, structures, etc. of the spacer. . As a result of detailed research into the causes of high dialysis voltage in ion-exchange membrane dialysis equipment, the inventors of the present invention found that inserting a spacer reduces the effective current-carrying area and therefore increases the dialysis voltage. However, it was found that the influence of air bubbles accumulated within the dialysis chamber, especially within the mesh of the spacer, was considerably greater. Furthermore, when operating for a long period of time, the above-mentioned accumulated bubbles tend to generate inorganic scales such as scales, calcium carbonate, and magnesium hydroxide, which can become a serious obstacle to safe driving. It was also revealed. Air bubbles that exist in the spacer (mesh) of such an ion-exchange membrane dialysis device are reduced by the supply of dialysate at a normal flow rate (approximately 2 to 10 cm/mesh).
s) allows a considerable amount of water to be discharged from the device. However, it is very difficult to quickly and completely remove these bubbles, and even after operating the ion-exchange membrane electrodialyzer for several days, the bubbles hardly decrease, and the bubbles account for about 5 to 15% of the effective membrane area. was confirmed to remain in the device forever. These remaining bubbles have various adverse effects on operation; for example, in electrodialysis, the effective current-carrying area decreases by the amount of bubbles that remain, increasing the dialysis voltage, and the flow of dialysate is obstructed. Concentration polarization and neutral disturbance phenomena are more likely to occur, and CaSO ₄ , CaCO ₃ , Mg(OH) ₂
This makes stable operation over a long period of time difficult, as it makes it easier for scales to occur. On the other hand, in the diffusion dialysis method, there is a problem in that the presence of air bubbles in the device reduces the recovery rate of acids and alkalis. To date, various measures have been taken to prevent the above problems. For example, there are methods of using a spacer made of a material or structure (shape) that prevents air from becoming trapped, a method of applying pulsation to the solution supplied to the dialysis machine, a method of increasing the flow rate of the solution supplied to the dialysis machine, etc. However, in method 2, air bubbles tend to accumulate in the spacer (mesh) and are more difficult to remove as the spacer has a structure that increases the limiting current density, and if a spacer with good air release is used, the operating current has to be lowered. This method is impractical because it does not obtain the desired results and requires an increase in the size of the equipment.
In addition, the bubble removal effect is not sufficient in this method, and operation management and operation are complicated, resulting in discontinuous operation. In the other method, the spacer and the ion exchange membrane are in close contact with each other, so even if the flow rate is increased, it is difficult to completely remove air bubbles, and increasing the flow rate increases the pressure loss of the dialysis machine, making it difficult to withstand pressure. cause problems. The above is a problem caused by air bubbles at the start of operation,
During operation, dissolved gases contained in the dialysate become bubbles as the temperature rises, and accumulate in the dialysis chamber, particularly in the spacer, causing the same problem as described above. A common way to prevent these bubbles is to degas the dialysate in advance by boiling or other methods, but although this method reduces the amount of bubbles, the equipment and energy required for degassing are not economical. It is disadvantageous to Therefore, in order to reduce the dialysis power in the electrodialysis method, and to improve the acid or alkali dialysis performance in the diffusion dialysis method, it is important to remove as much of the air bubbles that remain in the dialysis chamber as efficiently as possible. This is an extremely important issue for effective treatment. The present inventors have further researched the above-mentioned problems, and as a result of considering a method for chemically removing air bubbles, rather than using process or chemical engineering methods to eliminate the harmful effects of air bubbles, they have found that It has been found that by adding an antifoaming agent to the solution (dialysate), the generation of bubbles in the dialysate can be suppressed, and the bubbles in the dialysis chamber, especially in the mesh of the spacer, can be easily removed. The inventors discovered that continuous operation is possible and proposed the present invention. Conventionally, antifoaming agents have been widely used industrially for the purpose of eliminating bubbles in solutions that are prone to chemically foaming. This was first achieved based on the knowledge that bubbles can be effectively extinguished even when they remain. That is, the present invention is a dialysis method characterized by adding an antifoaming agent to the dialysate of an ion exchange membrane dialysis device. In the present invention, it is extremely important to add an antifoaming agent to the dialysate, and conventionally known silicone-based and organic antifoaming agents can be used. For example, silicon-based antifoaming agents include a silicone oil type, an oil compound type in which silicone oil is mixed with silica powder, and an emulsion of oil in water. In addition, organic antifoaming agents include those having polar atomic groups such as hydroxyl groups, esters, ethers, amines, amides, and carboxylic acid groups at the end or both ends of the hydrocarbon chain. , alcohols such as octyl alcohol, aluminum alcohol, polyalkylene glycol, polyoxyethylene alkyl ether type, polyoxyethylene alkyl phenol ether type, sorbitan fatty acid ester type, polyethylene glycol fatty acid ester type, fatty acid monoglyceride type, polyoxyethylene alkyl phenol Nonionic surfactants such as ether type and special nonionic type, oils such as sesame oil, castor oil and soybean oil, amines such as diamylamine, phosphate esters such as tributyl phosphate and trioctyl phosphate, etc. Synthetic or natural organic substances may be mentioned. Among these, it is preferable to use silicone-based and sorbitan fatty acid ester type nonionic surfactants because they are highly effective even in small amounts. The above-mentioned antifoaming agent is generally added directly into the dialysis machine or added to the raw dialysate in advance and then supplied to the dialysis machine. When adding it inside the dialysis machine, it can be added to either the concentration chamber, the desalination chamber, or both, depending on the intended use of the resulting product, but it is generally better to add it to the dialysis chamber, where air bubbles tend to accumulate. is effective, it is preferably added to the desalting chamber in the case of electrodialysis, and to the dialysate chamber in the case of diffusion dialysis. The amount of antifoaming agent added to the dialysate depends on the temperature conditions of the dialysate, the liquid composition such as pH, the amount of dissolved gas contained in the raw dialysate, the material and structure of the spacer in the dialysis chamber, or the size of the spacer in the dialysis chamber. It may be selected as appropriate depending on the dialysis chamber structure and operating conditions such as the liquid flow rate. Normally, if the amount of antifoaming agent added is too small, the effect will not be achieved, and if too much is added, the effect will not only reach a plateau but also be uneconomical, and it will not be possible to add ion exchange membranes, spacers, flow plates, etc. in the dialysis chamber. This causes problems such as adhesion and deterioration of performance, as well as contamination of the resulting treated water. Therefore, if the antifoaming agent is added continuously, the concentration of the antifoaming agent in the dialysate is generally 5 to 5.
It is added at a rate of 100 ppm, or when added intermittently, the concentration is 10 to 100 ppm once every 1 to 10 hours. According to the present invention, the effects of reducing dialysis power and improving dialysis performance can be obtained simply by adding the antifoaming agent as described above. Therefore, conventionally known dialysis machines such as filter press type and unit cell type can be used without any restrictions. Also, known spacers can be used, but generally, net-like materials, plain weave, honeycomb weave, mikoshiro weave, corrugated perforated plates, expanded materials, etc. made of materials such as polypropylene, polyethylene, and vinyl chloride are used. . As understood from the above explanation, the present invention is characterized in that dialysis is performed by continuously or intermittently supplying an antifoaming agent to the dilution chamber and/or concentration chamber of a dialysis machine. The objective is to effectively eliminate the trapped air bubbles that exist within the air. Therefore, according to the present invention, both the reduction in dialysis power and the acid recovery rate can be reduced to 5-5.
It can be increased by as much as 20%. In addition, it is less affected by concentration polarization and can operate stably for a long period of time without changing the properties of the treated water obtained, making it extremely economically advantageous and extremely easy to operate and manage the dialysis equipment. It brings immeasurable effects. Although the above description has been mainly about a dialysis device in which ion exchange membranes are arranged through spacers, the present invention can also be applied to an ion exchange membrane dialysis device that does not use spacers. EXAMPLES Hereinafter, examples will be shown to specifically explain the present invention, but the present invention is not particularly limited to the following examples. Example 1 Seawater was concentrated using a filter press type ion exchange membrane electrodialysis device with an effective current carrying area of 10 dm ² . Fifty pairs of cation exchange membranes and anion exchange membranes were alternately stacked with gaskets and spacers in between to form a stack, and both ends of the stack were tightened to form an electrodialyzer. The specifications of the electrodialysis device are as follows. Gasket thickness, material 0.75mm (made of neoprene). Spacer Polyethylene diagonal mesh (intersection thickness
0.8mm) Ion exchange membrane Neocepta C66-5T manufactured by Tokuyama Soda Co., Ltd.
(Product name) NeoSepta AFS-4T manufactured by Tokuyama Soda Co., Ltd. (Product name) Linear velocity of solution in dialysis room 6 cm/sec supply seawater for both desalination room and concentration room, quantity After sand filtering seawater, 5 micron cut cartridge Passed through the filter. The liquid temperature was kept constant at 25°C using temperature control equipment. 20/min operation current density 3A/dm ² To concentrate seawater, supply the above superhydrate to the desalination chamber,
Next, a direct current was applied. Permeate from demineralized water was circulated and supplied to the concentration chamber. After confirming that the operation of the electrodialysis apparatus was sufficiently stable, in this example, after 24 hours of continuous operation, the voltage between the stacks was measured with a digital voltmeter and this was used as a blank value. Next, antifoaming agents as shown in Table 1 were continuously added to the perfused water, and changes in dialysis voltage were examined to compare the effects of each treatment.

[Table] Example 2 Using an electrodialysis device with the same specifications as Example 1,
We desalinated wastewater from the Metsuki factory. The TDS contained in the Metsuki factory wastewater is approximately 2000 ppm, and sodium sulfate is the main component. The desalting operation is a one-stage patch constant voltage method, and the average operating current density for one batch is
It was set to 0.4A/ ^dm2 . Water quality of produced water is TDS500ppm
The following was made. The supply amount was set to flow at a flow rate of 6 cm/sec in both the concentration chamber and dilution chamber of the dialysis machine. The Metsuki factory wastewater was passed through a rapid sand filter as a primary filter, and then passed through a 10μ cut cartridge filter as a secondary filter. As in Example 1, the average dialysis voltage is shown in Table 2 when the antifoaming agents shown in Table 1 were continuously added to the perfused water after blank operation.

[Table] * 9 is a comparative example Example 3 Hydrochloric acid was recovered from a hydrochloric acid aqueous solution of ferrous chloride with an HCl concentration of 120 g/, FeCl ₂ concentration of 230 g/, using a filter press type diffusion dialysis device (manufactured by Tokuyama Soda Co., Ltd.). TSD
-2 type). The diffusion dialysis device has a diffusion chamber and a stock solution chamber formed by 20 anion exchange membranes (Neocepta AFN; trade name, manufactured by Tokuyama Soda Co., Ltd.) with an effective membrane area of 2 dm ² , and a solution supply outlet is provided for each chamber. Each chamber has a built-in spacer and flow distribution plate. Table 3 shows the antifoaming agents used in the experiment. The antifoaming agent was continuously added to both the diffusion chamber and the stock solution chamber. Use water at 20℃ and pour it from the top of the diffusion dialysis tank.
Supplied at 400c.c./hour. Further, an aqueous solution of ferrous chloride was supplied from the bottom of the diffusion dialysis tank at 400 c.c./hour using a pump at 40° C., and brought into countercurrent contact with water through the membrane. As a result, the recovery rate of hydrochloric acid in the diffusion solution was as shown in Table 3. Note that the acid recovery rate was determined using the following formula. Recovery rate = acid concentration in the diffusion solution x volume / acid concentration in the stock solution x volume

[Table] *No. 9 is a comparative example Example 4 The spacer only for the dialysis chamber was removed from the diffusion dialysis apparatus of Example 3, the dialysis apparatus was reassembled, and an experiment for sulfuric acid recovery was conducted. The stock solution used in the experiment was an aqueous sulfuric acid solution with a sulfuric acid concentration of 190 g/1 and a ferrous sulfate concentration of 140 g/mL. The recovery method and conditions were exactly the same as in Example 3. Further, the antifoaming agent used in the experiment was exactly the same as in Table 3 of Example 3, and the antifoaming agent was continuously added to both the diffusion chamber and the stock solution chamber. As a result, the recovery rate of sulfuric acid in the diffusion solution was as shown in Table 4.

【table】

[Table] *No.9 is a comparative example.

Claims (1)

[Claims] 1. A dialysis method characterized by adding an antifoaming agent to the dialysate of an ion exchange membrane dialysis device.