JPH0532088B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for regenerating acid waste liquid. In detail, when regenerating acid waste liquid containing mineral acids and their metal salts, there are a process of deoxidizing with an ion exchange membrane electrodialysis device or a diffusion dialysis device, a process of neutralizing and precipitating and separating the deacidifying liquid, this neutralization, The process consists of regenerating the precipitated and separated neutralized filtrate into acid and alkali using an ion exchange membrane electrodialysis device consisting of a combination of a bipolar membrane and an anion and cation exchange membrane. This is a method for regenerating acid waste liquid, in which the acid is used as a neutralizing agent in the process of neutralization and precipitation separation, or the generated acid is introduced into the concentration side of an electrodialyzer in the deacidification process to regenerate it as a highly concentrated acid. [Prior art and its problems] In recent years, large amounts of dilute acid-containing liquids have been discharged from manufacturing processes, treatment processes, processing processes, etc. in various industries. For example, sulfuric acid-containing solutions from non-ferrous metal raw ore or metal processing processes, hydrochloric acid-containing solutions from extraction or pickling processes, hydrofluoric acid-containing solutions from tantalum and lead processing processes, hydrochloric acid from solvent extraction and etching processes, Examples include sulfuric acid, nitric acid-containing solutions, and chromic acid-containing solutions obtained from plating wastewater. Particularly in the etching, pickling, plating, and smelting processes of ferrous or nonferrous metals, if the metal is eluted as a salt in the acid and the concentration of the metal salt exceeds the allowable amount, the acid can no longer be used. As a result, a large amount of solution containing the acid and its metal salts is produced as waste liquid. Therefore, conventionally, acid waste liquid is disposed of as sludge or slurry after being subjected to appropriate treatment such as neutralization due to pollution problems. However, if metal components and acids could be separated and re-recovered from acid waste liquids as described above, it would be extremely advantageous from the standpoint of reusing various acid waste liquids and preventing pollution. Examples of prior art include JP-A-52-101690,
Nos. 53-2379 and 53-18470, etc., after deacidifying and concentrating waste liquid containing acid and its metal salts in an electrodialysis tank formed by an anion and cation exchange membrane, the deacidified liquid is passed into a bipolar chamber. A method has been proposed in which metals or their hydroxides are precipitated by electrolyzing them in a diaphragm electrolytic cell partitioned by anion exchange membranes. However, this method uses a diaphragm electrolytic cell with an electrode in each chamber, which not only increases the scale of the equipment, but also requires careful selection of the material of the electrodes if the acid waste solution contains halides. There was an economic problem. Therefore, the conventional method of separating acid and metal components from acid wastewater containing mineral acids and their metal salt streams as described above and reusing them as highly concentrated acids, alkalis, and metals is not efficient. Moreover, it is difficult to obtain a highly concentrated acid, and there are almost no examples of this being carried out industrially. [Means for Solving the Problems] The present invention is directed to a neutralization process in which metal components and acids are separated from an acid waste solution containing acids and metal salts thereof as described above, and the metal components are further neutralized and precipitated. The present invention provides a novel treatment method that can efficiently regenerate filtrate into acid and alkali. That is, the present invention comprises a step A in which an acid waste solution containing a mineral acid and its metal salts is deoxidized using an ion exchange membrane electrodialysis device or a diffusion dialysis device, a step B in which the deacidified solution is separated by neutralization precipitation, and a step B in which the deacidification solution is separated by neutralization precipitation. Step C consists of regenerating the solution into acid and alkali using an ion-exchange membrane electrodialysis device consisting of a combination of a bipolar membrane and an anion-cation exchange membrane, and if necessary, a step of neutralizing and precipitating the alkaline solution produced from this step and separating it. A method characterized in that the acid used in the neutralizing agent B or produced is introduced into the concentration side of the ion exchange membrane electrodialysis device or diffusion dialysis device in the deacidification step A and regenerated as a highly concentrated acid. be. According to the present invention, the separation of acid and metal components is efficiently and completely achieved, and it is also possible to obtain alkali or very highly concentrated acids for use in neutralization precipitation separation. That is, in the present invention, the process of discarding metal objects as sludge or slurry by conventional methods such as neutralization treatment can be used as is, and furthermore, it can be used in a wide variety of industries. It is possible to economically recycle mineral acid waste. Such effects of the present invention are achieved by using an ion exchange membrane electrodialysis device or a diffusion dialysis device, a neutralization precipitation separation device, a bipolar membrane, and an anion-cation exchange membrane, which deoxidize the waste acid solution described above. By utilizing the characteristics of each of the dialysis devices and combining them, it has become possible to recover acid extremely efficiently. Hereinafter, the present invention will be explained in detail with reference to the drawings and the like. As described above, there are various examples of the waste liquid containing acids and metal salts thereof to be treated in the present invention. The acid is not particularly limited as long as its acid radical (anion forming the acid) can permeate the anion exchange membrane, and examples thereof include waste acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and hydrofluoric acid. Further, the metal salts contained therein include salts of iron, nickel, chromium, zinc, copper, aluminum, magnesium, lead, cobalt, etc., and are not particularly limited. In particular, the present invention allows acid wastewater containing halides to be treated very efficiently. Typical examples of these waste liquids include hydrofluoric acid-containing solutions from tantalum and lead processing processes, nitric-fluoric acid-containing solutions from smelting processes, and sulfuric acid and iron sulfate-containing solutions discharged from iron bickling processes. etc. are mentioned. Naturally, two or more types of the above-mentioned acids and metal salts may be contained, and the liquid does not necessarily have to be called waste liquid. That is, the present invention is applicable to all solutions containing the acids and their metal salts as described above. In FIG. 1 of the present invention, is an ion-exchange membrane electrodialysis device, or a diffusion dialysis device, is a neutralization precipitation separation device, is an ion-exchange membrane electrodialysis device that performs double decomposition, and A is a deacidification and concentration step; B
C indicates the neutralization precipitation separation step of the deacidifying solution, and C indicates the acid and alkali regeneration step. More specifically, an ion-exchange membrane electrodialysis device has a cation-exchange membrane and an anion-exchange membrane arranged alternately between the two electrodes, or a diffusion dialysis device has a deoxidizing chamber ( It is divided into a dialysis chamber (dialysis chamber) 1 and a concentration chamber (diffusion chamber) 2. As the neutralization precipitation separation device, existing neutralization, precipitation, and separation devices that process various waste acids etc. can be adopted without particular restrictions. The ion exchange membrane electrodialysis device is configured with a neutralization tank, a precipitation tank, a concentration tank, and a vacuum filtration tank as shown in Figure 2. By arranging them in this order, it is divided into an intermediate chamber (metathesis chamber) 6, an acid generation chamber 7, and an alkali generation chamber 8. The ion exchange membrane electrodialysis device or diffusion dialysis device of the present invention, and the above-mentioned cation exchange membrane, anion exchange membrane and bipolar membrane used in the ion exchange membrane electrodialysis device or diffusion dialysis device of the present invention,
Conventionally known membranes can be appropriately employed, but
It is sufficient to select a membrane that is effective for acid separation and metathesis of neutral salts, respectively. For example, as a cation exchange membrane, a cation-selective cation exchange membrane in which an anion exchange group such as an amino group or a long chain alkyl group having 4 to 30 carbon atoms is bonded to at least one membrane surface layer is permeated. This is suitable because the amount of water can be reduced.
As the anion exchange membrane, a weakly basic anion exchange membrane with low permeation (diffusion) of hydrogen ions is suitable in order to improve current efficiency in electrodialysis. In addition, as a bipolar membrane, it has an anion exchange layer and a cation exchange layer, and in particular, a bipolar membrane in which the fixed ion concentration of the cation exchange layer is 10N or more has a high hydrolysis efficiency and a hydrogen ion exchange layer. This is preferable because despreading can be reduced. In the present invention, an acid waste solution (undiluted solution) 9 containing mineral acids and their metal salts is supplied to a deacidification chamber (dialysis chamber) 1 of an ion exchange membrane electrodialysis tank or a diffusion dialysis device, and one concentration chamber (diffusion Dilute acid is supplied to chamber 2, and conditions for electrodialysis are appropriately selected in order to efficiently recover the acid from the raw waste liquid. For example, the rate of supplying the stock solution to an ion exchange membrane electrodialysis device is generally 0.5 to 20 cm/sec, preferably 3 to 8 cm/sec, and the current density is generally 1 to 20 cm/sec.
30 A/dm ^{2 ,} preferably 3 to 15 A/dm ² , and the temperature is preferably about 10 to 50°C. Also,
The rate at which the stock solution is fed to the diffusion dialysis machine is generally
The rate is preferably about 0.01 to 5 cm/min, particularly about 0.1 to 1 cm/min. Thus, particularly in the ion-exchange membrane electrodialysis apparatus, the acid in the raw waste liquid 9 is almost selectively transferred to the concentration chamber 2 by dialysis without being accompanied by metal salts. Therefore, the deoxidizing chamber 1 of the ion exchange membrane electrodialyzer
Deacidification solution 10 with reduced acid concentration in raw acid waste solution
is obtained, and a highly concentrated acid solution 11 is obtained from the concentration chamber 2. The degree of electrodialysis varies depending on the type of metal salt in the raw waste liquid 9, but generally the pH is approximately 1 to 1.
It is preferable to reduce the acid concentration of the deoxidizing solution 10 to 2. Similarly, a undiluted deoxidized solution 10 is obtained from the dialysis chamber 1 of the diffusion dialysis apparatus, and an acid solution 11 is obtained from the diffusion chamber 2. Next, the deoxidizing solution 10 from the deoxidizing chamber (dialysis chamber) 1
is supplied to a neutralization precipitation separator and first neutralized with an alkali solution 12, and then the metal salts in the solution are precipitated as hydroxide to form a sludge, slurry 13, and the neutralized filtrate 14 is separated depending on the content of poorly soluble salts After passing through the chelate resin column 15 as necessary, it is supplied to the intermediate chamber 6 of the ion exchange membrane electrodialysis apparatus. In the ion exchange membrane electrodialysis device, electrodialysis conditions are adjusted appropriately in order to efficiently generate acid from the acid chamber 7 and alkali from the base chamber 8 by double decomposing the neutralized filtrate supplied to the intermediate chamber 6. Select. for example,
The rate at which the neutralized filtrate 14 is supplied to the ion exchange membrane electrodialysis apparatus is generally 0.5 to 10 cm/sec, the current density is generally 0.5 to 20 A/dm ² , and the temperature is preferably about 10 to 50°C. Thus, in the ion-exchange electrodialysis device, each ion in the neutralized filtrate 14 is selectively dialyzed and transferred via the cation-exchange membrane and the anion-exchange membrane.
Therefore, in the ion exchange membrane electrodialysis apparatus, a highly concentrated alkali can be obtained from the base chamber 8 via the bipolar membrane, and a highly concentrated acid can be obtained from the acid generating chamber 7. The regenerated alkali is supplied to the neutralization precipitation separator according to the neutralization concentration, and the regenerated acid 16
can be supplied to the concentration chamber of an ion exchange membrane electrodialysis tank or directly as a regenerated acid solution. [Effects of the Invention] As described above, according to the present invention, highly concentrated acids can be economically and efficiently recovered from acid waste liquid containing mineral acids and their metals, and metals can be recovered as hydroxides. As for the process, since the alkali used for neutralization can also be regenerated, the process can be closed without having to be supplied separately from the outside. Furthermore, since the acid recovered by the present invention has a high concentration, it can be diluted in the required amount and recycled for metal processing, and can also be used in other fields. [Examples] Examples are shown below to more specifically illustrate the present invention, but the present invention is not limited to the above description or the following examples. Example 1 Nitric acid 130 discharged from the stainless steel pickling process
g/, hydrofluoric acid 20g/, iron 50g/, Nickel 5
The waste liquid containing 10 g/g/ of chromium and
It was processed according to the flow sheet shown in the figure, and nitric-fluoric acid and metal were separated and recovered. The electrodialysis tank was divided into a deacidification chamber and an acid concentration recovery chamber using Neoceptor CMS and Neoceptor ACM (strongly acidic cation exchange membrane and weakly basic anion exchange membrane manufactured by Tokuyama Soda Co., Ltd., respectively). Electrodialysis tank TS-2 type (manufactured by Tokuyama Soda Co., Ltd., effective membrane area
2dm ² /pair) was used. As the ion exchange membrane electrodialysis device, Neoceptor, which is the same as above, is used.
An electrodialysis tank (Tokuyama Soda Co., Ltd., effective membrane area: 2 dm ² ) was used. Also,
As the neutralization sedimentation literary device, a neutralization tank, a precipitation tank, a concentration tank, and a vacuum filter were installed as shown in Fig. 2. The electrodialysis tank was operated at a temperature of 35° C., an average current density of 5 A/dm ² , and a membrane surface speed of 5 cm/sec. As a result, sulfuric acid 10g/, iron 70g/, nickel 7
g/, and chromium 14g/ deoxidizing solution and sulfuric acid
303g/, hydrofluoric acid 6.4g/, and iron 0.93g/
A recovered liquid containing . The above deacidifying solution is supplied to the neutralization sedimentation separator, where it is first neutralized using sodium hydroxide in the neutralization tank, and then poured into the sedimentation tank where it is separated into solid and liquid components, which collect at the bottom. The solid content was drained into a thickening tank and dehydrated using a vacuum filter to obtain sludge. On the other hand, the neutralized filtrate was passed through a chelate resin tower and then supplied to the intermediate chain of the electrodialysis tank at a rate of 1.5/h. In electrodialysis tanks, temperature
It was operated at 35° C. and an average current density of 5 A/dm ² . As a result, a regenerated solution containing 71 g of sulfuric acid, 57 g of hydrofluoric acid, and 160 g of sodium hydroxide was obtained. Next, this regenerated acid was supplied to the concentration chamber 5 of the electrodialysis tank and used for circulation as regenerated acid. The recycled alkali was also used as a neutralizing agent in the neutralization precipitation separation process. Example 2 Sulfuric acid 110 discharged from iron pickling process
The acid effluent containing 150 g/g/g of iron sulfate and 150 g/g/m of iron sulfate was treated according to the flow sheet shown in FIG. 1, and sulfuric acid and metal were separated and recovered. Electrodialysis same as Example 1,
The same conditions and steps as in Example 1 were carried out using a neutralization precipitation separator. As a result, Table 1 shows the electrodialyzer and the composition of the solution obtained.

[Table] Example 3 45g of hydrochloric acid discharged from the aluminum pickling process/
The waste solution containing 15 g of aluminum was treated according to the flow sheet shown in Figure 1, and hydrochloric acid and metal were separated and recovered. The same electrodialysis device and neutralization precipitation separation device as in Example 1 were used, and the same conditions and steps as in Example 1 were followed. The results are shown in Table 2.

[Table] Example 4 An acid waste solution containing 1.07N of iron sulfate and 2.16N of sulfuric acid was treated according to the flow sheet shown in FIG. 1, and sulfuric acid and metals were separated and recovered. The diffusion dialysis tank is a diffusion dialysis device type TSD-2 (manufactured by Tokuyama Soda Co., Ltd., effective membrane) which is divided into a diffusion chamber and a dialysis vertebrae using Neocepta AFN (manufactured by Tokuyama Soda Co., Ltd., strong basic anion exchange membrane). An area of 2 dm ² ) was used. The ion exchange membrane electrodialysis device and the neutralization precipitation separation device were the same as in Example 1. In the diffusion dialysis tank, water at 30°C was supplied from the upper part to the diffusion chamber at a rate of 0.6/Hr, and the above acid waste solution was supplied to the dialysis chamber from the lower part at a rate of 0.6/Hr. As a result, an acid solution of 2N sulfuric acid and 0.1N iron sulfate was poured into the diffusion chamber 1 several times, and a deoxidized waste liquid containing 0.16N sulfuric acid and 0.97N iron sulfate was discharged from the dialysis chamber 2. Next, the deoxidized waste liquid is supplied to the neutralization precipitation separator, where it is first neutralized using sodium hydroxide in the neutralization tank, and then sent to the precipitation tank where it is separated into solid and liquid components. The collected solids were drained into a thickening tank and dehydrated using a vacuum filter to obtain sludge. On the other hand, the neutralized filtrate was supplied to the intermediate chamber of the electric tower tank at a rate of 1.5/h. The electrodialysis tank was operated at a temperature of 35° C. and an average current density of 5 A/dm ² . As a result, a regenerated solution containing 3.5 N of sulfuric acid and 3.6 N of sodium hydroxide was obtained. This regenerated acid was recycled and used as a regenerated acid, and the regenerated alkali was used as a neutralizing agent in the neutralization precipitation separation step.

[Brief explanation of the drawing]

FIG. 1 shows the flow of the present invention, in which ion exchange membrane electrodialysis equipment, diffusion dialysis equipment, and
is an equipment for neutralization precipitation separation process, and is an ion exchange membrane electrodialysis equipment for acid and alkali regeneration process. 1 and 2 are a deacidification chamber (dialysis chamber) and a concentration chamber (diffusion chamber) of an ion exchange membrane electrodialysis device and a diffusion dialysis device. 3, 4 and 5 are anion exchange membranes in ion exchange membrane electrodialysis equipment;
A bipolar membrane and a cation exchange membrane, 6, 7 and 8 are an intermediate chamber (metathesis chamber), an acid generation chamber and an alkali generation chamber. 9 is a waste acid solution (undiluted solution), 10 is a deoxidizing solution, 11 is a regenerated acid solution in an ion-exchange membrane electrodialyzer, 12 is a regenerated alkaline solution in an ion-exchange membrane electrolyzer, and 13 is a neutralization and precipitation separation device. The sludge or slurry, 14 is the neutralized filtrate, 15 is the chelate resin column, and 16 and 17 are the regenerated acid solution and desalted solution, respectively, in the ion exchange membrane dialysis tank. FIG. 2 is a typical flow diagram of a neutralization precipitation separation device, in which 18 is a neutralization tank, 19 is a precipitation tank, 20 is a concentration tank, 21 is a vacuum filtration agent, 22 is a neutralizing liquid, and 23 is a concentration tank.
indicates slurry, 24 indicates sludge, and 25 indicates solid content.

Claims (1)

[Claims] 1. Step A: Deoxidizing the acid waste solution containing mineral acids and their metal salts using an ion exchange membrane electrodialysis device or diffusion dialysis device. Step B: Neutralizing and precipitating the deacidified solution, and separating the filtrate by precipitation. Bipolar membrane and Yin,
A method for regenerating acid waste liquid, which comprises step C of regenerating acid and alkali using an ion exchange membrane electrodialysis device comprising a combination of cation exchange membranes.