JP4247777B2 - Method for removing trace impurities in solution - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for removing trace impurities such as potassium ions contained in an aqueous solution in which a water-soluble sodium compound is dissolved using a special chromatographic phenomenon.
[0002]
[Prior art]
As a method for separating each component in a mixture containing two or more components, a distillation method, a recrystallization method, a solvent extraction method, a non-solvent washing method, and the like are known. Recently, the chromatographic method has been attracting industrial attention because the components can be separated with high purity.
[0003]
This chromatography method is performed by dissolving a mixture in a predetermined solvent through a column packed with a solid adsorbent and passing it as a solution. This is because each component in the solution is separated from the solid adsorbent side (stationary phase). Since they are distributed at different ratios with the mobile liquid side (mobile phase), they are separated using a phenomenon that causes a difference in the moving speed for each component, so-called adsorption chromatography.
[0004]
A method for continuously obtaining a fraction in which each component is concentrated using such an adsorption chromatographic phenomenon is widely used industrially in each field. For example, a column packed with an adsorbent is provided with a plurality of methods. A method in which a mixture of components and a desorbing agent are alternately supplied so that the adsorption bands of the respective components are adjusted so as to overlap each other (see Patent Document 1), and the desorbing agent is removed from the fraction containing the desired component There has been proposed a method (see Patent Document 2) for sequentially supplying a product and a raw material mixture to a column.
[0005]
On the other hand, in the adsorption chromatography phenomenon, since the selectivity of the adsorbent is an important factor, various adsorbents have been developed for each purpose. For example, as an agent that selectively adsorbs potassium, an adsorbent obtained by extracting water-containing black manganese oxide with an acid (see Patent Document 3), a binderless 3A-type zeolite bead adsorbent having specific physical properties (see Patent Document 4) ) Etc. have been proposed.
[0006]
However, in general, impurities contained in a trace amount in an aqueous solution often have properties similar to those of the main component, and the selectivity coefficient between the main component and the impurity in the adsorbent is small, and this selectivity factor is theoretically improved. Therefore, it is very difficult to separate the main component from the impurities.
[0007]
That is, in a normal adsorption chromatography phenomenon, an adsorbent having selectivity for a predetermined component of the mixture solution is used as a stationary phase, and the mixture solution is used as a mobile phase, and the mixture solution is caused to flow through a column packed with the adsorbent, The fraction that has passed is collected over time, and the fraction in which the predetermined component is concentrated is collected. The concentration of the predetermined component in the fraction at this time shows that this is the original solution. The concentration of the component in the solution (hereinafter referred to as the initial concentration) is not exceeded, and adsorption by the adsorbent is continued until the adsorption amount determined by the adsorption capacity and volume of the adsorbent is reached. The concentration gradually decreases, and finally, the amount of adsorption saturates and loses the adsorption capacity, so that the concentration in the passing solution becomes constant.
[0008]
[Patent Document 1]
JP-A-57-207507 (Claims and others)
[Patent Document 2]
JP 58-20208 (Claims and others)
[Patent Document 3]
JP-A-8-38887 (Claims and others)
[Patent Document 4]
JP 2002-119849 A (Claims and others)
[0009]
[Problems to be solved by the invention]
The present invention utilizes a special adsorption chromatography phenomenon that is completely different from the above-described normal adsorption chromatography phenomenon, efficiently removes a trace amount of potassium ions present in an aqueous sodium compound solution, and the sodium compound has a high purity. It was made for the purpose of obtaining in this state.
[0010]
[Means for Solving the Problems]
As a result of intensive research to efficiently remove a trace amount of potassium ions contained as impurities in an aqueous solution of sodium compound, the present inventors have conducted an adsorption column containing potassium ions in advance. using, if liquid passing the aqueous solution to be treated to, produce special adsorption chromatographic behavior, large fraction of the potassium ion concentration is formed, as a final processing solution after passing by removing this, trace amounts of potassium The inventors have found that an aqueous solution containing a high purity sodium compound from which ions have been removed can be obtained, and the present invention has been made based on this finding.
[0011]
That is, the present invention provides a fine quantity impurity, a sodium compound solution stock solution containing potassium ions, is contacted with an adsorbent to adsorb potassium ions, per to remove potassium ions from the previously potassium above adsorbent which is adsorbed ions, to form a fraction having a potassium ion concentration greater than the potassium ion concentration in the original solution, provides a non-pure removal method of the sodium compound aqueous solution and removing it It is.
[0012]
In general, when passing an aqueous solution of a sodium compound containing at least one trace impurity, for example, an aqueous sodium chloride solution containing a trace amount of potassium ions, through a column packed with an adsorbent that selectively adsorbs potassium ions, for example, an ammonium ion type zeolite. If the adsorbent is adsorbed with the same substance as the trace impurities in advance, that is, potassium ions, sodium ions as the main component will be replaced with potassium ions present in the pores, and this will flow out together with the potassium ions contained as impurities. In addition, a fraction having a concentration higher than the concentration of potassium ions originally contained in the aqueous solution is obtained.
[0013]
The sodium ions temporarily adsorbed by this adsorbent are replaced again with the potassium ions in the subsequent aqueous solution. At this time, in order to generate an activated adsorption point, it is more than the case of the normal adsorption chromatography phenomenon. It exhibits a special adsorption chromatography phenomenon that adsorbs a large amount of potassium ions.
[0014]
The present invention is a method for obtaining a sodium compound with improved purity by removing a trace amount of potassium ions contained in an aqueous sodium compound solution by utilizing such a special adsorption chromatography phenomenon.
[0015]
This special adsorption chromatography phenomenon is usually characterized by the presence of the following processes. That is, when chromatography was performed using a column pre-filled with an adsorbent containing trace impurities,
(1) A process of producing an eluate fraction enriched in trace impurities until a volume of eluate from the column reaches 5 times the column volume after introducing a concentrated solution of a predetermined substance containing trace impurities into the column. ,
(2) Next, the process of producing an eluate fraction whose trace impurities monotonously decrease
(3) Subsequently, a process of generating an eluate fraction in which the trace impurity concentration becomes constant at a value smaller than the initial concentration (concentration in the stock solution),
(4) Further, a process of producing an eluate fraction in which the impurity concentration continuously increases monotonously at a value smaller than the initial concentration, and (5) an eluate fraction in which the impurity concentration is optionally greater than the initial concentration. Process.
[0016]
In the present invention method, it is the above (1) to (5) with special adsorption chromatographic behavior lacking the process of (1) in the course of the same available.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the sodium compound aqueous solution containing trace impurities treated by the method of the present invention include a reaction mixture aqueous solution containing a trace catalyst component obtained by catalytic reaction, an oligomer aqueous solution containing a trace monomer, and the like. An inorganic salt aqueous solution containing trace impurities, for example , a sodium sulfate aqueous solution, a sodium nitrate aqueous solution, a sodium phosphate aqueous solution, particularly a sodium halide aqueous solution containing the corresponding potassium ions , lithium ions, magnesium ions, and calcium ions as trace impurities .
[0018]
The concentration of the aqueous sodium compound solution in this case varies depending on the type of the sodium compound, the type of adsorbent used, and the chromatography conditions such as temperature, pressure, and the flow rate through the column. % Is the lower limit, and the upper limit is selected within the saturation concentration range, preferably within the range of 2 to 10% by mass.
Further, as the concentration of trace impurities contained as a component other than the main component in the sodium compound in the aqueous solution, 1 following 20 minutes of the concentration of sodium compounds the main component, preferably is desirably less than one 50 minutes.
[0019]
The adsorbent used in the method of the present invention, is influenced by the type of trace impurities in the aqueous solution to be removed, cationic zeolites, such as ammonium ion type zeolite, H ⁺ type natural zeolite such or cation exchange resin Used . These adsorbents are usually used as particles having a particle size of 0.1 to 2.5 mm. In addition, the linear velocity at the time of liquid passage is usually selected in the range of 0.1 to 300 cm / hr, preferably 0.1 to 100 cm / hr.
[0020]
In the process of the present invention, the adsorbent which selectively adsorbs the potassium ions, it is necessary to be adsorbed in advance potassium ions. In this case, the adsorption amount is preferably in the range of 1.0 to 10 μmol per 1 g of the adsorbent. In this case, if an adsorbent that has already adsorbed potassium ions is used, there is no need to perform a treatment for adsorbing potassium ions .
[0021]
In order to carry out the method of the present invention suitably, the fraction of the column eluate of the aqueous sodium compound solution passed through the column is fractionated, the concentration of the desired component in each fraction is measured, and the fraction whose concentration is approximated. To collect. In this way, by collecting the concentrated fractions of the specific component together, a concentrated solution of the desired component can be obtained, and the concentration of potassium ions as impurities is lower than the initial concentration. By collecting the liquid fraction, a high-purity sodium compound can be obtained.
Further, by desorbing a predetermined component temporarily adsorbed on the column with an appropriate eluent, a solution in which the component is concentrated can be obtained.
[0022]
A preferred embodiment of the method of the present invention will be described with reference to an aqueous sodium salt solution having a concentration of 2.3% by mass containing a trace amount of potassium salt . First, when the aqueous solution is passed through an adsorbent that has previously adsorbed potassium ions, such as cationic zeolite, the potassium ions adsorbed on the adsorbent are eluted into the mobile phase, and the volume of the eluate introduced into the column is the column volume. In the fraction up to 5 times (hereinafter referred to as the first fraction), the concentration is higher than the potassium ion concentration in the stock solution. If the aqueous solution is further passed, the amount of potassium ions adsorbed from the mobile phase to the adsorbent becomes larger than the amount of desorbed potassium ions from the adsorbent to the mobile phase, which is lower than the concentration in the stock solution. The eluate fraction of appears. In this case, the change in potassium ion concentration fluctuates in the range from 100 times to 1/100 of the stock solution concentration. When the breakthrough point is reached, the stock solution concentration is similar to the breakthrough curve in ordinary adsorption chromatography. Up to more than that, depending on conditions.
[0023]
The operation in the method of the present invention can be carried out in the same manner as in ordinary adsorption chromatography. As operation conditions at this time, room temperature and atmospheric pressure are usually selected.
[0024]
In the method of the present invention, whether or not a special adsorption chromatography phenomenon occurs can be confirmed by collecting and analyzing each fraction of the column eluate.
[0025]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these.
[0026]
Example 1
Separation of potassium ions from 1M sodium chloride aqueous solution containing 13 mg / liter of potassium ions, 4 mg / liter of magnesium ions and 2 mg / liter of calcium ions as impurities using an apparatus comprising a liquid feed pump, an adsorbent column and a fraction collector. went.
That is, an ammonium ion type natural zeolite adsorbed with about 5 μmol / g of potassium ion as an adsorbent on a glass column (inner diameter of about 10 mm, height of 500 mm) (manufactured by Sun Zeolite Co., Ltd., clinoptilolite, trade name “Sun Zeolite”) The average particle size of 0.5 mm) was filled to a height of 470 mm, and the above sodium chloride aqueous solution was passed through the temperature-controlled room (27 ° C.) at a flow rate of 0.1 ml / min. The eluate from the column at this time was fractionated as 2 ml fractions, and the potassium ion concentration of each fraction was quantitatively analyzed. The potassium ion concentration distribution curve in each fraction thus obtained is shown in FIG. The vertical axis of this figure is the potassium ion concentration (mg / liter) every 20 fractions, and the horizontal axis is the ratio of the eluate volume to the column volume.
As can be seen from this figure, a fraction enriched with potassium ions appears in the initial stage, and then a fraction from which potassium ions have been removed appears.
[0027]
Example 2
Separation of impurities from 1M sodium chloride aqueous solution containing potassium ions 13 mg / liter, magnesium ions 4 mg / liter, calcium ions 2 mg / liter as impurities using an apparatus comprising a liquid feed pump, an adsorbent column and a fraction collector It was.
That is, an H ⁺ -type natural zeolite (manufactured by Sun Zeolite Co., Ltd., clinoptilolite, trade name “SUN “Zeolite” (average particle size 0.5 mm) was filled to a height of 70 mm, and the above sodium chloride aqueous solution was passed at a flow rate of 1 ml / min at a temperature of 50 ° C.
Subsequently, the eluate from the column was fractionated into 2 ml fractions, and the potassium ion concentration, magnesium ion concentration and calcium ion concentration were quantitatively analyzed for each fraction, and the results are shown in FIG. 2 as a graph. In the figure, A is a graph of potassium ions, B is a magnesium ion, and C is a calcium ion.
The vertical axis in FIG. 2 is the potassium ion concentration, the magnesium ion concentration, and the calcium ion concentration (mg / liter) every 68 fractions, and the horizontal axis is the ratio of the eluate volume to the column volume. From this figure, it can be seen that, in the initial stage, a fraction enriched with potassium ions and magnesium ions is eluted, and then a fraction from which potassium ions and magnesium ions are removed is eluted. It can also be seen that calcium ions are removed without being concentrated.
[0028]
【The invention's effect】
According to the method of the present invention, the sodium compound aqueous solution containing potassium ions, by introducing a column packed with adsorbent having adsorbed beforehand potassium ions, utilizing a special adsorption chromatographic behavior, be removed efficiently potassium ions Can do. Furthermore, it is possible to concentrate potassium ions during regeneration of the adsorbent, and the adsorbent can be used repeatedly.
[Brief description of the drawings]
1 is a graph showing a potassium ion concentration distribution curve obtained in Example 1. FIG.
2 is a graph showing concentration distribution curves of potassium ion, magnesium ion and calcium ion obtained in Example 2. FIG.

Claims (4)

As the fine amount impurity, a sodium compound solution stock solution containing potassium ions, is contacted with an adsorbent to adsorb potassium ions, per to remove potassium ions from them adsorbed beforehand potassium ions in the adsorbent, the original to form a fraction having a potassium ion concentration greater than the concentration of potassium ions in the solution, not pure removal method of the sodium compound aqueous solution and removing them. The impurity removal method according to claim 1, wherein magnesium ions and calcium ions coexist with potassium ions as impurities in the sodium compound aqueous solution. Not pure removal method of the concentration of trace impurities sodium compound solution stock solution is according to claim 1 or 2, wherein less than one-twentieth of the concentration of sodium compounds. The method for removing impurities according to claim 1, 2 or 3, wherein the adsorbent for adsorbing potassium ions is cationic zeolite.

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