JPH0455313A - Method of removing sulfuric acid ion - Google Patents

Abstract

PURPOSE:To effectively remove sulfuric acid ion in a salt soln. without using harmful calcium salt or expensive barium salt, etc., by treating the salt soln. containing sulfuric acid ion with an ion exchange resin having polyamine groups. CONSTITUTION:Sulfuric acid ion in a salt soln. is removed by treating the salt soln. such as industrial salt containing sulfuric acid ion with an ion exchange resin having polyamine groups. As one example of the ion exchange resin having polyamine groups, an ion exchange of resin consisting of polystyrene-divinylbenzene copolymers as the base material and polyamine groups introduced thereinto as the functional groups is used, and this resin is commercially available as 'DIA-ION WA20', etc. To treat the salt soln. with the ion exchange resin, it is preferable to pack a column with the ion exchange resin and to make the salt soln. flow through this column.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for removing sulfate ions from a saline solution containing sulfate ions.

[Prior Art] Caustic soda and chlorine are industrially produced by the salt electrolysis method, and the raw material salt used is solar salt, which is usually called industrial salt. This industrial salt contains various impurities, and it is necessary to remove them in order to maintain stable operation of the electrolytic cell. Sulfate ions, one of the impurities, gradually accumulate in the salt water circulation system, so it is necessary to remove the amount of sulfate ions that accompany the newly melted industrial salt. For this reason, for example, in the mercury electrolysis method that has been commonly used as a common salt electrolysis method, a method has been adopted in which calcium chloride is added to precipitate and separate the salt as insoluble calcium sulfate.

In recent years, the ion exchange membrane method has come to be widely adopted as a new electrolysis method to replace the mercury electrolysis method. The allowable sulfate ion concentration in the saline solution in this ion exchange membrane method is even lower than the allowable sulfate ion concentration in the mercury method.

For this reason, it is difficult to remove sulfate ions to the allowable concentration using the calcium chloride method, so a method has been adopted in which barium chloride or barium carbonate is added to separate and remove barium sulfate, which has a very high sedimentation property.

However, these barium salts are more expensive than calcium salts, resulting in an increase in the cost of processing sulfate ions. Furthermore, barium salt is a scarce resource, and there are concerns about securing a stable supply of it.

Furthermore, since calcium and barium are both substances that accumulate in the ion exchange membrane and reduce the formation performance, there is also the inconvenience that excess of these ions that do not contribute to the reaction must be removed.

Furthermore, it has become necessary to treat these insoluble calcium sulfate and barium sulfate as industrial waste.

As an alternative to these methods, it may be possible to maintain a constant sulfate ion concentration by discarding some of the raw material brine outside the system, but this would naturally result in a large loss of raw material salt, so it is not economically viable. It's not a good idea.

Due to these problems, even if an attempt was made to remove only sulfate ions using an adsorbent, it has not been possible to obtain an adsorption result that selectively adsorbs only sulfate ions when a large amount of chlorine ions coexist.

[Problems to be Solved by the Invention] The object of the present invention is to efficiently remove sulfate ions by treating a saline solution containing sulfate ions with a specific adsorbent.

[Means for Solving the Problems] In order to solve these problems, the present inventors discovered that an ion exchange resin having a polyamine group selectively adsorbs sulfate ions in salt water, and completed the present invention. That is, the present invention provides a method for removing sulfate ions, which is characterized by treating a saline solution containing sulfate ions with an ion exchange resin having a polyamine group.

The present invention will be explained in detail below.

An example of the ion exchange resin having a polyamine group in the present invention is an ion exchange resin in which a polyamine group is introduced as a functional group into a base material of polystyrene-divinylbenzene copolymer. , WA21, CR20 (manufactured by Mitsubishi Kasei Corporation), and Amberlite IRA45 (manufactured by Rohm and Haas). In order to use these ion exchange resins having polyamine groups for this purpose, it is desirable to prepare them in a salt form. As this salt type, CI type is usually used.

The target of the present invention is saline containing sulfate ions. Examples of such brine include concentrated brine that is provided for electrolysis in the salt electrolysis industry, and so-called fresh brine that flows out of the electrolytic cell after a portion of the salt has been consumed.

There is no limit to the salt concentration in the saline solution in the present invention, but it is usually 240 g/l or less, preferably 200 g/l or less. If it exceeds 240 g/l, there will be a disadvantage that the adsorption efficiency of sulfate ions will decrease.

The sulfate ion concentration in the saline solution in the present invention is not particularly limited, but is preferably 3 g/1 or more and 30 g/l or less for the reason that sulfate ions are effectively adsorbed.

The method for adsorbing sulfate ions in the present invention is as follows:
It is sufficient to bring the saline solution containing sulfate ions into contact with the resin. For example, the aqueous solution may be brought into contact with the resin using a column method or a batch method, but usually the aqueous solution is passed through an ion exchange resin containing polyamine groups packed in a column in a downward flow or A column type is adopted in which the fluid is circulated by upward flow.

In the present invention, the resin that has adsorbed sulfate ions can be regenerated and used again for adsorption of sulfate ions. As this regenerating agent, an aqueous caustic solution is usually used by a known method. Furthermore, when using the resin, it is preferable to treat it with hydrochloric acid or the like to make the resin into a CI type.Also, as another regenerating agent, it is also possible to use a saline solution that has a substantially higher salt concentration than the saline solution subjected to the adsorption treatment. No problem.

[Example] The present invention will be explained in detail below using Examples.

In the following, ion chromatography was used for fitli ion concentration analysis, and the concentration was determined from the area ratio of the chromatograph.

Example 1 An ion exchange resin Diaion WA20CI type having a polyamine group manufactured by Mitsubishi Kasei Corporation was placed in a jacketed glass column with a diameter of 2'5.0 mm and a height of 300 mm to a height of 250 mm.
Fill up to 5g sulfate ion concentration/120g salt concentration
Liquid passing rate SV l O(h+
), and the column temperature was maintained at 40°C by passing hot water through the jacket. All the treated liquid flowing out from the column was collected and the sulfate ion concentration therein was measured, and the concentration was 2. It was 8g/l.

Example 2 Diaion CR20CI type manufactured by Mitsubishi Kasei Co., Ltd. was used instead of the ion exchange resin having a polyamine group shown in Example 1, and the column temperature was set to 60°C, and the other conditions were as in Example 1.
When 500 ml of saline solution adjusted to a salt concentration of 150 g/l and a sulfuric acid ion concentration of 7 g/l was passed through in the same manner as above, the average sulfate ion concentration in the treated liquid that flowed out was 4.9 g/l.
Examples 3 to 7 The saline solution shown in Table 1 was used instead of the saline solution shown in Example 1, and the treatment was carried out in the same manner as in Example 1, and the sulfuric acid shown in the table was The ion adsorption results were obtained.

Table 1 Comparative Example 1 In place of the adsorbent shown in Example 1, a styrene-divinylbenzene-based strongly basic ion-exchange resin, MP500C1 type manufactured by Bayer AG, was used. An attempt was made to adsorb ions. As a result, the sulfate ion concentration in the treatment liquid was 4.9 g/I, and almost no adsorption effect was observed.

[Effects of the Invention] As detailed above, according to the present invention, effective removal of tttlI ions from saline solution, which has not been achieved with the prior art, is achieved.

In other words, it is extremely advantageous industrially because sulfate ions can be effectively removed without adding calcium salts, which are harmful to the process, or barium salts, which are more expensive, to the saline solution.

If the desired concentration of sulfate ions cannot be sufficiently removed by one-stage treatment, of course, multi-stage treatment such as two or three stages can be used.Also, if you simply want to prevent the accumulation of sulfate ions, you can use a method other than the conventional system. If you can reliably remove a certain amount of ions, you just need to always remove the amount that was previously purged.
It is also significant to apply operations corresponding to Examples 5 to 7.

Claims (1)

[Claims] (1) A method for removing sulfate ions, which comprises treating a saline solution containing sulfate ions with an ion exchange resin having a polyamine group.