KR790001457B1 - Methodfor refining aqueous solution of thiocyanate containing impurities - Google Patents

Abstract

A thiocyanates soln. is purified by crosslinkage from impure thiocyanate soln. with thiocyanate soln's 0.01-60wt% conc. The impure thiocyanate soln. was passed through crosslinkage layer as necessary, the absorbed impurities and thiocyanate were eluted, and then pure thiocyanate soln. was obtained by further eluting the eluent with thiocyanate soln.

Description

Purification Method of Thiocyanate Aqueous Solution Containing Impurities

1, 2, 3 and 4 show the elution curves obtained using various columns packed with the dextran crosslinked bodies of Examples, 1,2,3 and 4, respectively. .

The present invention relates to a method for purifying an aqueous solution of thiocyanate containing impurities of the present invention, in particular, supplying an aqueous solution of impurity-containing thiocyanate to the dextran crosslinked layer to crosslink the impurities and thiocyanate The eluate is trapped in the sieve layer, and then the amount of eluent necessary for distilling out impurities from the dextran crosslinked body is introduced into the crosslinked layer, and the impurities are removed together with the eluent, and the thiocyanate is further passed through the eluent. A method for purifying an impurity-containing thiocyanate aqueous solution comprising a method of separating and recovering an eluate to contain.

In general, inorganic salts and organic compounds are contained in the thiocyanate aqueous solution produced, recovered or by-produced in the synthesis of thiocyanate, the production of acrylic synthetic fiber, or the process of detoxifying waste gas. And a large amount of inorganic and organic impurities such as polymers, so that in order to obtain pure thiocyanate from such an impure thiocyanate aqueous solution, it is necessary to perform appropriate purification operation on this impurity-containing thiocyanate aqueous solution. have.

However, since thiocyanate is an inorganic salt, it is not possible to employ a distillation purification method as in an organic compound, and only a complex purification method such as adsorption filtration, precipitation precipitation filtration, or recrystallization can be employed. According to the conventional adsorption filtration method using, the ion-dissociable impurities cannot be removed at all, and the precipitation precipitation filtration method using the solubility difference can only remove impurities having low solubility, and in the case of recrystallization, the removal of impurities is incomplete. In addition, since a large amount of thiocyanate remains in the mother liquor and the recovery rate is low, it is difficult to put to practical use.

Accordingly, the present inventors have diligently studied to solve the above-mentioned drawbacks. According to the present invention, when gel filtration using a cross-linkeddextransubstance having a molecular sieve effect is used, the thiocyanate salts are separated from other inorganic salts. As a result of finding that it exhibits a specific behavior compared to the above, and applying this method to the purification operation of an aqueous solution of thiocyanate containing organic or inorganic impurities, the organic or inorganic compounds coexisting in the aqueous solution of thiocyanate are efficiently separated. It was found that it could be removed to reach the present invention.

That is, the main object of the present invention is to provide an excellent purification method of an impurity-containing thiocyanate aqueous solution.

A second object of the present invention is to provide a method in which impurities can be easily and completely removed from an impurity-containing thiocyanate aqueous solution without an operation such as distillation.

A third object of the present invention is to effectively purify thiocyanate by inhibiting various side reactions of the purification operation and preventing decomposition and denaturation of thiocyanate.

The object of this invention is to feed an impurity-containing thiocyanate aqueous solution into the dextran crosslinker layer to trap impurities and thiocyanate in this dextran crosslinker layer, and then to deplete the impurities in the dextran crosslinker layer. Impurity was distilled out along with the eluent by passing the required amount of eluent and then further passed through the eluent to achieve separation of the eluate containing thiocyanate.

For example, an aqueous thiocyanate solution containing an acrylonitrile-based polymerizer (molecular weight 1,000 to 100,000), sodium sulfite, sodium sulfate, sodium chloride, sodium nitrate and the like as an impurity is supplied to the dextran crosslinker layer to form impurities and thiocyanate as a crosslinker layer. The acrylonitrile polymer, the acrylonitrile polymer, sodium sulfite or sodium sulfate, sodium chloride, sodium nitrate and thiocyanate are eluted in the order just described when the eluent is passed through this crosslinked layer after being captured by By distilling such impurities together with the eluent, and then separating and extracting the thio cyanate-containing eluate that flows out, the thiocyanate aqueous solution can be easily and efficiently purified.

The peculiar phenomenon of the last elution of thiocyanate is that although the hydration radius of chlorine ion (3.32) is smaller than the hydration ion radius of nitrate ion (3.35) Considering the fact that sodium chloride is eluted first, it is obvious that the small and large of solute molecules cannot be explained. The effect in the present invention is assumed to be due to the particular adsorption phenomenon of the dextran crosslinked product.

In carrying out the method of the present invention, (1) generally, the elution curve of the column packed with dextran crosslinked body is obtained in advance, and then the eluent that flows out is separated based on the obtained elution curve, or (2) from the column. The solute in the distillate eluting solution is sequentially analyzed by a suitable analytical method, and a method of directly separating an eluate containing the desired solute is adopted. As the means for analyzing the concentration of each component in the eluent, nondestructive analysis methods such as ultraviolet absorption intensity analysis, distillation residue weighing, hydrogen ion concentration measurement, and coloration measurement are appropriately used. The electrical conductivity measurement is most suitable for the analysis.

In the method of the present invention, the amount of eluent required to distill the impurities trapped in the column depends on the amount of dextran crosslinked substance charged in the column, the amount of the impurity-containing thiocyanate aqueous solution and the type of impurities, but in each case The amount of usage thereof is determined by means of appropriate analysis.

The supply amount of the impurity-containing thiocyanate aqueous solution to be purified should be about 1/5 or less of the volume of dextran crosslinked material packed in the column, and an amount of 1/10 or less is preferably adopted.

The dextran crosslinked body to be used in the present invention contains 1 to 10 carbon atoms whose carbon chain can be interrupted by an ether group and has a halogen atom and / or an epoxy group such as hydroxyl group of dextran at the end of the chain. Reacting to form an ether chain, whereby a polymerization product containing at least two molecules of dextran material bound together with an ether bridge is obtained,

Reaction products of the hydroxyl-containing dextran substance and the binary function aliphatic compound containing the epoxy group represented by (A).

As used herein, "dextran material" refers to dextran and hydrophilic hydroxyl-containing dextran derivatives, such as dextran material for the reaction, such as natural dextran or partially depolymerized dextran or neutral. Hydroxyl-containing hydrophilic dextran derivatives, or partially depolymerized dextran, such as ethyl-hydroxyethyl or 2-hydroxy-propyl ether of dextran, or dextran glycerin glycosides, or hydrodextran Dextran, which has been reduced to a group) or partially depolymerized dex, containing an acidic or basic group such as a carboxyl group, a sulfonic acid group, an amino group or a substituted amino group, such as dextran, for example carboxymethyldextran or an end group oxidized to a carboxyl group. Hydroxyl-containing hydrophilic derivatives of tran or dextran It can be used. Sometimes it may also be beneficial to use fractions of the dextran material exemplified above.

As examples of binary functional aliphatic compounds, binary functional glycerin derivatives such as epichlorohydrin, dichlorohydrin, epibromohydrin and dibromohydrin can be enumerated first, in addition, 1,2-3 , 4-diepoxybutane, bis-epoxypropyl ether, ethylene glycol-bis-epoxypropyl ether, 1,4-butanediol-bis-epoxypropyl ether, propylene glycol, polyethylene glycols and the like can be used.

Specific examples of the dextran crosslinked product include Sephadex LH-20, G-10, G-15, G-25 and the like, manufactured by Pharmacia Fine Chemical.

Aqueous solutions of thiocyanates which can be purified according to the invention include aqueous solutions of inorganic thiocyanates such as sodium thiocyanate, potassium thiocyanate, calcium thiocyanate and ammonium thiocyanate, and generally The concentration of thiocyanic acid in the aqueous solution is appropriately 0.01 to 60%, particularly about 0.1 to 50%.

As the eluent in the present invention, water, dimethylformamide, ethanol and the like can be used.

및 섬유품질의 열화(劣化) 등등이 여러가지 문젯점을 야기시키는 원인이 되고 있다. 그러나 본 발명에 따른 정제조작을 적용함으로써 이와 같은 불순물을 모두 제거할 수 있게됨에 따라 상기한 문젯점의 해결이 가능하게 되었다.The method of the present invention can be widely applied to the purification of an impurity-containing thiocyanate aqueous solution that is produced, recovered or by-produced in the synthesis of thiocyanate, in the production of acrylic synthetic fibers, or in the process of detoxifying waste gas. Among them, it is particularly effective for purifying an aqueous solution of thiocyanate recovered in the manufacturing process of acrylic synthetic fiber. As is known, the concentrated aqueous solution of thiocyanate used as a solvent in the production of acrylic synthetic fibers is generally recovered from a coagulation bath. The recovered thiocyanate aqueous solution contains impurities such as inorganic salts other than thiocyanates, organic sulfonates, and low molecular weight polymers. These impurities lower the solubility of the polymer, block the filter and the nozzle, and cut off.

Deterioration of fiber quality and the like have caused various problems. However, by applying the purification operation according to the present invention it is possible to remove all such impurities, it is possible to solve the above problems.

In addition, in carrying out the method of the present invention industrially, it is also necessary to consider the economics. Therefore, a practical operation condition is established by focusing on reducing the amount of thiocyanate mixed in the impurity-containing eluent that flows out, rather than preventing the incorporation of impurities in the eluate containing thiocyanate.

When explaining the present invention based on the following examples.

Parts and percentages other than those mentioned in the examples are based on weight.

Example 1

A column having a diameter of 50 mm and a length of 1 m was filled with dextran crosslinked Sephadex LH-20 swelled with water, and the void volume of the gel particles was approximately 500 ml, followed by a low molecular weight acrylonitrile polymer having a concentration of 0.1%. 50 ml of an aqueous solution of up to 10,000) was supplied from the top of the column so that the low molecular weight acrylonitrile polymer was trapped in Sephadex LH-20. Subsequently, pure water as an eluent was passed at a flow rate of 2 ml per minute, and the eluting curve shown in FIG. 1 was prepared by measuring the electrical conductivity and the capacity of the eluting eluent. In addition, the elution curve shown in FIG. 1 was prepared in the same manner for each of aqueous solutions such as sodium sulfate, sodium chloride, calcium chloride, sodium nitrate and sodium thiocyanate (concentration 0.1%). From the first road, it can be clearly seen that 1,300 ml of pure water is required to dispose of these impurities contained in 50 ml of an aqueous thiocyanate solution containing various impurities such as a low molecular weight acrylonitrile polymer.

Based on the elution curves thus obtained, 50 ml of 50% aqueous sodium thiocyanate solution containing low molecular weight acrylonitrile polymer, sodium sulfate, sodium chloride, calcium chloride, sodium nitrate, etc. as impurities is supplied to the column to provide impurities and thio Sodium cyanate was captured, and then 1,300 ml of pure water was passed through the column at a flow rate of 2 ml per minute to remove all impurities, and then pure water was passed at the same flow rate to separate the eluate containing sodium thiocyanate. By recovering, an aqueous sodium thiocyanate solution containing no impurities was obtained.

Example 2

50 parts of a 50% concentration of aqueous sodium thiocyanate solution containing a low molecular weight acrylonitrile polymer having a sulfonic acid group (molecular weight of 10,000 or less), sodium sulfate, sodium chloride and sodium nitrate at the end were supplied to the same column as in Example 1 to provide impurities and thiocyanate. After allowing sodium acid to be trapped in the dextran crosslinked body, pure water was passed at a flow rate of 2 ml per minute, and the eluting curve shown in FIG. 2 was prepared by measuring the electrical conductivity and the capacity of the eluting eluent. From the second road, it can be clearly seen that by passing about 1,300 parts of pure water as eluent, the impurities contained in 50 parts of the sodium thiocyanate aqueous solution can be distilled off.

Based on the elution curve thus obtained, 50 parts of the aqueous sodium thiocyanate solution was supplied to the column to trap impurities and sodium thiocyanate in the dextran crosslinked body, and then 1,300 parts of pure water at a flow rate of 2 ml per minute. After passing through the column to remove all impurities, pure water was separated and recovered at the same flow rate, thereby obtaining a pure aqueous solution of titanium thiocyanate.

Example 3

A column of 13 mm inner diameter and 70 cm length was filled with dextran crosslinked Sephadex G-10 swelled with water, and the gap volume of the gel particles was approximately 35 ml, followed by 60% concentration of thiocyanate containing 1.2% sodium nitrate. Five parts of aqueous sodium acid solution was fed from the top of the column. The elution curve shown in FIG. 3 was created in the same manner as in Example 2 except that the flow rate was set at 3.5 ml per minute. From FIG. 3, it can be clearly seen that about 50 parts of pure water (eluent) is required to distill the sodium nitrate contained in 5 parts of said sodium thiocyanate aqueous solution.

Based on the elution curve thus obtained, pure sodium thiocyanate solution containing no sodium sulfate was obtained in the same manner as in Example 2.

Example 4

A column having a diameter of 50 mm and a length of 1 m was filled with dextran crosslinked body, Sephadex LH-20 with water swelling, and the gap volume of the gel injector was about 325 ml, followed by 60% concentration of thio containing 1.28% sodium nitrate. 150 parts of aqueous sodium cyanate solution was supplied to the column.

The elution curve shown in FIG. 4 was created in the same manner as in Example 2 except that the flow rate was set at 0.8 ml per minute. From FIG. 4, it can be clearly seen that about 1,000 parts of pure water is required to distill the sodium nitrate contained in 150 parts of said sodium thiocyanate aqueous solution.

Based on the elution curve thus obtained, pure sodium thiocyanate aqueous solution containing no sodium nitrate was obtained in the same manner as in Example 2.

Claims (1)

Impurity-containing thiocyanate aqueous solution having a concentration of thiocyanate of 0.01-60% by weight is supplied to the dextran crosslinking layer while supplying the amount below about 1/5 of the volume of dextran crosslinking material charged in the column. And thiocyanate are trapped in the dextran crosslinked layer, and the eluent is passed through the crosslinked layer in an amount necessary to remove impurities from the dextran crosslinked layer, and the impurities are distilled off together with the eluent. A method for purifying an aqueous solution containing an impurity-containing thiocyanate, characterized by separating the eluate containing thiocyanate by further passing through.

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