RU2601459C2 - Recovery method of lithium chloride, dimethylacetamide and isobutyl alcohol or lithium chloride and dimethylacetamide from process solutions for production of para-aramid fibres - Google Patents

Abstract

FIELD: wastewater treatment plants.

SUBSTANCE: invention relates to methods of waste water purifying and organic solvents and mineral substances regeneration and can be used in production of synthetic fibres for recycling of dimethyl acetamide (DMAA), isobutyl alcohol (IBA) and lithium chloride and to establishment of water run-around system. Regeneration method involves stages of DMAA, IBA and water separation by rectification, initial solution neutralization by lithium hydroxide, produced in electrodialysis device with bipolar membranes, sedimentation and filtration of iron hydroxide, electrodialysis concentration in electrodialysis device with non-flowing concentration chambers at current density of 0.5-5 A/dm², part of concentrated lithium chloride solution post-evaporation and its crystallization during cooling in form of solvate with DMAA to return into process for synthetic fibres producing, other part of concentrated lithium chloride solution direction into electrodialysis device with bipolar membranes for lithium hydroxide and hydrochloric acid producing with concentration of 0.1-1 M at current density of 0.5-5 A/dm², direction of partially desalinated solution of DMAA, IBA and water or DMAA and water: to fine purification into electrodialysis device with ion exchange filler in desalination chambers until lithium chloride residual content of 5-50 mg/l, then its direction into rectification to produce pure DMAA and IBA or DMAA and returning concentrate after electrodialysis with ion exchange filler to electrodialyzer input for lithium chloride concentration.

EFFECT: technical result is increased degree of DMAA, IBA and lithium chloride purification for reuse in production of para-aramid fibers.

1 cl, 1 dwg, 11 tbl

Description

The invention relates to methods for wastewater treatment and the regeneration of organic solvents and minerals and can be used in the production of synthetic fibers for the reuse of dimethylacetamide (DMAA), isobutyl alcohol (IHD) and lithium chloride and for organizing a water circulation system.

In the production of para-aramid fibers, a large amount of wastewater and waste technological solutions containing DMAA, IHD, lithium chloride, hydrochloric acid and iron compounds are formed.

A known method of purification of technological solutions and wastewater from organic substances by adsorption on a porous carbon material, followed by regeneration of the adsorbent with superheated water vapor or heat treatment [1]. The disadvantage of this method is the high consumption of expensive sorbent and high energy intensity of the process.

A known method of purification of technological wastewater containing DMAA and IHD [2]. To implement the method, the initial wastewater is treated with activated carbon, the absorbed substances are extracted from the spent activated carbon with chloroform, and the extract is sent for distillation in order to distill the mixture into DMAA, IHD and chloroform.

The method improves the efficiency of the process by reducing the cost of the sorbent. The disadvantage of this method are: environmental hazard of chloroform with a high hazard class; low concentration of DMAA and IHD in the spent chloroform stream; pollution of purified water, DMAA and IHD with chloroform.

In addition, the method does not allow the concentration of lithium chloride, and the regeneration process is complicated by the precipitation of lithium chloride salts and iron compounds on the heat exchange surfaces of the distillation column.

The technical task of the invention is to develop a method for the regeneration of lithium chloride, dimethylacetamide (DMAA) and isobutyl alcohol (IHD) or lithium chloride and dimethylacetamide from technological solutions for the production of para-aramid fibers, which allows to increase the degree of purification of DMAA and IHD, to extract and concentrate lithium chloride from wastewater for reuse in the production of para-aramid fibers.

To achieve a technical result, a method for the regeneration of lithium chloride, dimethylacetamide (DMAA) and isobutyl alcohol (IHD) or lithium chloride and dimethylacetamide from technological solutions for the production of para-aramid fibers, including the stage of separation of DMAA, IHD and water by distillation, neutralization of the initial solution with lithium hydroxide obtained electrodialyzer with bipolar membranes, precipitation and filtration of iron hydroxide, electrodialysis concentration in an electrodialyzer with non-flow chambers ramie concentration at a current density of 0.5-5 A / dm ^2, further evaporation of part of the concentrated LiCl solution and its crystallization during cooling as a solvate with DMAc to return to the process for the production of synthetic fibers, the direction of another portion of concentrated lithium chloride solution in electrodialysis with bipolar membranes for lithium hydroxide and hydrochloric acid concentration of 0.1-1 M at a current density of 0.5-5 a / dm ^2, the direction of DMAC partially desalted solution CHD and water or DMAC water for deep purification into an electrodialyzer with ion-exchange filler in desalination chambers to a residual lithium chloride content of 5-50 mg / l, then it is directed to rectification to obtain pure DMAA and IHD or DMAA and the concentrate is returned after electrodialysis with ion-exchange filler to the inlet of the electrodialyzer for concentration of lithium chloride.

In FIG. 1 is a schematic diagram of a process for the regeneration of lithium chloride, dimethylacetamide and isobutyl alcohol or lithium chloride and dimethylacetamide from technological solutions for the production of para-aramid fibers, consisting of a reactor-neutralizer 1, a mechanical filter 2, an electrodialyzer 3, a crystallizer 4, an electrodialyzer with bipolar membranes 5 with ion exchange backfill 6.

The initial solution is neutralized with lithium hydroxide and sent to the reactor-neutralizer 1, in which the ripening and enlargement of iron hydroxide takes place, after which the iron hydroxide is filtered off on a mechanical filter 2. The neutralized and deferrized solution is sent to electrodialyzer 3 to concentrate lithium chloride. A part of the concentrate containing lithium chloride is precipitated upon cooling as a solvate with DMAA in crystallizer 4 and returned to the process for producing synthetic fibers, and the other is sent to an electrodialyzer with bipolar membranes 5 to obtain lithium hydroxide and hydrochloric acid. Partially purified from lithium chloride, a solution of DMAA, ischemic heart disease and water is fed into an electrodialyzer with ion exchange filling desalination chambers 6 for deep cleaning of an aqueous-organic solvent from lithium chloride, and then sent to rectification. The concentrate after the electrodialyzer with ion-exchange filling 6 is sent to the input of the electrodialyzer 3. Hydrochloric acid is used for periodic washing of the mechanical filter 2.

Example 1. Regeneration was performed waste technological solution, the composition of which is presented in Table 1.

To obtain hydrochloric acid and lithium hydroxide from lithium chloride, an electrodialyzer with bipolar membranes 5 was used, consisting of an anode and a cathode made of platinum titanium, MB-3 bipolar membranes facing the anode to the anode, and MK-40 cation exchange membranes forming an anodic, cathodic, alkaline and acid chambers. The membrane package of the electrodialyzer with bipolar membranes was formed by bicameral unit cells. The area of each electrode and the working surface of each of the membranes of the cation exchange and bipolar were 0.25 m ² , the number of unit cells was 40 pcs. The intermembrane distance is 0.9 mm.

The anode and cathode chambers were filled with 0.3 M lithium hydroxide solution, the acid and alkaline chambers were filled with lithium chloride solution obtained in the electrodialyzer 3. The feed rate of the solutions into the anode and cathode chamber was 0.1 m ³ / h. The feed rate of the solution into the acid and alkaline chambers is 1.0 m ³ / h.

A constant voltage corresponding to a current density of 100 A / m ^{2 was} applied to the anode and cathode.

The resulting 0.3 M lithium hydroxide solution was fed into the neutralizing reactor 1 to neutralize the hydrochloric acid contained in the initial technological solution. The resulting 0.3 M hydrochloric acid solution was fed into a mechanical filter for washing it from iron hydroxide removed from the neutralized technological solution.

To remove lithium chloride from the technological solution neutralized in the reactor-neutralizer 1 and filtered through a mechanical filter 2, an electrodialyzer 3 was used, consisting of an anode and a cathode made of platinum titanium, MK-40 cation exchange membranes and MA-40 anion exchange membranes. The area of each electrode and the working surface of each of the membranes of the cation exchange and anion exchange were 0.25 m ² , the number of unit cells was 40 pcs. The intermembrane distance is 0.9 mm. The anode and cathode chambers were filled with 0.3 M lithium hydroxide solution. The feed rate of the solutions into the anode and cathode chamber is 0.1 m ³ / h. The feed rate (circulation) of the solution into the desalination chamber was 1.0 m ³ / h. The feed rate (circulation) of the solution into the concentration chamber was 1.0 m ³ / h.

A constant voltage corresponding to a current density of 100 A / m ^{2 was} applied to the anode and cathode.

The 0.9 M lithium chloride solution obtained in the concentration chambers was fed into the salt chambers of an electrodialyzer with bipolar membranes 5 to obtain lithium hydroxide and hydrochloric acid.

For deep removal of lithium chloride from the technological solution obtained in the electrodialyzer 5, an ion-exchange electrodialyzer 6 was used, consisting of an anode and a cathode made of platinum titanium, MK-40 cation exchange membranes and MA-40 anion exchange membranes. Fillings from the KU-2 cation exchanger and the AV-17 anion exchanger were placed in desalination chambers. The area of each electrode and the working surface of each of the membranes of the cation exchange and anion exchange were 0.25 m ² , the number of unit cells was 40 pcs. The intermembrane distance is 0.4 mm. A solution was formed into the anode and cathode chambers, which formed in the concentration chambers by an electrodialyzer with ion-exchange filling. The feed rate of the solutions into the anode and cathode chamber is 0.1 m ³ / h. The feed rate (circulation) of the solution into the desalination chamber was 1.0 m ³ / h. The feed rate (circulation) of the solution into the concentration chamber was 0.1 m ³ / h.

A constant voltage corresponding to a current density of 20 A / m ^{2 was} applied to the anode and cathode.

Obtained in the concentration chambers, a solution of lithium chloride with a concentration of 0.5 g / l was fed to the input of the electrodialyzer 3.

The technological solution obtained in the desalination chambers with a residual concentration of lithium chloride of 50 mg / L was fed for rectification.

Table 2 shows the concentration of regenerated DMAA and IHD, as well as the degree of their extraction from the spent technological solutions. For comparison, similar results are given in the known method (prototype).

As can be seen from table 2, the proposed method provides almost complete regeneration of organic solvents DMAA, IHD and lithium chloride with obtaining high-purity substances suitable for reuse in the production of para-aramid fibers.

Example 2. Regeneration was performed waste technological solution not containing isobutyl alcohol, the composition of which is presented in Table 3.

The regeneration of the spent technological solution that does not contain isobutyl alcohol by the same methods, in the same sequence and under the same conditions as in Example 1, allows one to obtain regenerated DMAA (Table 4).

Table 4 shows the concentration of regenerated DMAA, as well as the degree of its extraction from the spent technological solutions. For comparison, similar results are given in the known method (prototype).

As can be seen from table 4, the proposed method provides almost complete regeneration of the organic solvent DMAA and lithium chloride to obtain highly pure substances suitable for reuse in the production of para-aramid fibers.

Example 3. In order to increase the concentration of lithium chloride in the solution obtained in the concentration path of the electrodialyzer 3, in this example we used an electrodialyzer with non-flowing concentration chambers — an electrodialyzer, in which no solution was supplied from the concentration chambers from the outside. In this case, water is introduced into the concentration chambers through cation exchange and anion exchange membranes together with cations and anions in their hydration shells, and the concentration of the resulting solution in the limit is equal to the concentration of the saturated solution of the salt being concentrated.

To determine the range of optimal electric current densities supplied to the electrodialyzer with non-flowing concentration chambers 3, the spent technological solution of the same composition as in example 1 (Table 1), as well as the spent technological solution that does not contain IHD of the same composition as regenerated, were regenerated and in example 2 (Table 3). To obtain hydrochloric acid and lithium hydroxide from lithium chloride, the same electrodialyzer with bipolar membranes 5 was used as in Example 1. To deeply remove lithium chloride from the technological solution obtained in electrodialyzer 3, the same electrodialyzer with ion exchange filling 6 was used, as in the example one.

To remove lithium chloride from the process solution neutralized in the reactor neutralizer 1 and filtered through a mechanical filter 2, an electrodialyzer with slow concentration chambers 3 was used, consisting of an anode and a cathode made of platinum titanium, MK-40 cation exchange membranes and MA-40 anion exchange membranes. The area of each electrode and the working surface of each of the cation exchange and anion exchange membranes was 0.25 m ² , the number of unit cells was 40 pcs. The intermembrane distance was 9 · 10 ^-4 m. The cathode and anode chambers are equipped with inlet and outlet fittings. Each desalination chamber is equipped with internal inlet and outlet manifolds connected to inlet and outlet fittings. Each concentration chamber is equipped with an external output collector. No solution was supplied to the concentration chambers from the outside.

The anode and cathode chambers were filled with 0.3 Μ lithium hydroxide solution. The feed rate of the solutions into the anode and cathode chamber was 0.1 m ³ / h. The feed rate (circulation) of the solution into the desalination chamber was 1.0 m ³ / h. The feed rate (circulation) of the solution into the concentration chamber was 1.0 m ³ / h.

After diluting to a concentration of 0.3 2-3, a 2-3 M solution of lithium chloride obtained in the concentration chambers was fed into the acid and alkaline chambers of the electrodialyzer with bipolar membranes 5 to obtain lithium hydroxide and hydrochloric acid.

Obtained in the desalination chambers, a technological solution of lithium chloride with a concentration of 0.9 g / l was fed into the electrodialyzer with ion-exchange filling 6.

The test results of the electrodialyzer with non-flow concentration chambers 3 are shown in Table 5.

Where

I is the electric current supplied to the electrodialyzer-hub, A;

U is the voltage at the electrodialyzer-hub, B;

c _{LiCl, co} - concentration of lithium chloride in the desalination chamber

electrodialyzer-concentrator, M;

c _{LiCl, kk} — concentration of lithium chloride in the concentration chamber of the electrodialyzer-concentrator, M;

η _LiCl — differential current output of lithium chloride obtained in the concentration chamber of the electrodialyzer-concentrator,%;

W _LiCl - differential specific energy consumption for producing lithium chloride in an electrodialyzer-concentrator, kW · h / mol;

P _LiCl is the differential specific productivity of the electrodialyzer-concentrator for lithium chloride, mol / (h · m ² ). From table 5 it follows that at a low current density of less than 0.5 A / DM ^{2 the} specific productivity of the electrodialyzer-hub with slow-flow concentration chambers is sharply reduced. At a high current density greater than 5 A / dm ^{2, the} specific energy consumption for obtaining lithium chloride in a concentrator with non-flowing concentration chambers increases sharply. Thus, the range of optimal current densities for an electrodialyzer-concentrator with non-flowing concentration chambers is a range of 0.5-5 A / dm ² .

Compared with a conventional electrodialyzer, the use of an electrodialyzer-concentrator with non-flowing concentration chambers allows to increase the concentration of lithium chloride by a factor of 2-3 from 0.9 Μ to 1.5-3 снизить and, thereby, reduce the amount of solution containing chloride by the same amount. lithium, and energy expenditures for its evaporation before crystallization.

Table 6 shows the concentration of regenerated DMAA and IHD, the content of impurities in the regenerated DMAA and IHD, as well as the degree of their extraction from the spent technological solutions. For comparison, similar results are given in the known method (prototype).

As can be seen from table 6, the proposed method provides almost complete regeneration of organic solvents DMAA, IHD and lithium chloride with obtaining high-purity substances suitable for reuse in the production of para-aramid fibers.

Example 4. In order to reduce the return of lithium chloride together with lithium hydroxide to the process solution, as well as to reduce the loss of lithium chloride together with hydrochloric acid obtained in an electrodialyzer with bipolar membranes 5, in this example an electrodialyzer was used to obtain lithium hydroxide and hydrochloric acid three-chamber unit cells. Unlike an electrodialyzer with bicameral unit cells, in such an electrodialyzer almost all lithium chloride is consumed to produce lithium hydroxide and hydrochloric acid.

To determine the range of optimal densities of electric current supplied to the electrodialyzer 5 with three-cell unit cells and the concentrations of lithium hydroxide and hydrochloric acid obtained in the electrodialyzer 5, the spent technological solution of the same composition as in example 1 (Table 1) was regenerated, and spent technological solution that does not contain IHD of the same composition as in example 2 (Table 3). To remove lithium chloride from the technological solution neutralized in the reactor-neutralizer 1 and filtered through a mechanical filter 2, the same electrodialyzer 3 with slow concentration chambers was used as in Example 2. For the deep removal of lithium chloride from the technological solution obtained in the electrodialyzer 3, the same electrodialyzer with ion-exchange filling 6, as in example 1.

To obtain hydrochloric acid and lithium hydroxide from lithium chloride, an electrodialyzer with bipolar membranes 5 was used, consisting of an anode and a cathode made of platinum titanium, MB-3 bipolar membranes facing the anode side, MK-40 cation exchange membranes and MA-40 anion exchange membranes, forming anodic, cathodic, salt, alkaline and acid chambers. The membrane package of the electrodialyzer with bipolar membranes was formed by three-chamber unit cells. The area of each electrode and the working surface of each of the membranes of the cation exchange and bipolar were 0.25 m ² , the number of unit cells was 40 pcs. The intermembrane distance is 9 · 10 ^-4 m. The cathode and anode chambers are equipped with inlet and outlet fittings. Each salt, alkaline and acid chamber is equipped with internal inlet and outlet manifolds connected to inlet and outlet fittings.

The anode and cathode chambers were filled with 0.3 Μ lithium hydroxide solution. Salt chambers were filled with diluted to a concentration of 0.3 Μ lithium chloride solution obtained in the electrodialyzer 3. Acid chambers were filled with diluted to a concentration of 0.02 Μ hydrochloric acid solution. Alkaline chambers were filled with lithium hydroxide solution diluted to a concentration of 0.02 Μ.

The feed rate of the solutions into the anode and cathode chamber was 0.1 m ³ / h. The feed rate of the solution into the salt chambers was 3.0 m ³ / h. The feed rate of the solution into the acid and alkaline chambers was 1.0 m ³ / h.

The resulting 0.3 Μ lithium hydroxide solution was fed into the neutralizing reactor 1 to neutralize the hydrochloric acid contained in the initial technological solution. The resulting 0.3 Μ hydrochloric acid solution was fed into a mechanical filter for washing it from iron hydroxide removed from the neutralized technological solution.

The test results of the electrodialyzer 3 with bipolar membranes containing three-chamber unit cells, depending on the density of the electric current supplied to the electrodialyzer, are shown in Table 7.

Where

I is the electric current supplied to the electrodialyzer-synthesizer, A;

U is the voltage at the unit cell of the electrodialyzer-synthesizer, B;

with _LiCl is the concentration of lithium chloride in the salt chamber of the electrodialyzer-synthesizer, M;

with _LiCl - the concentration of lithium hydroxide obtained in the alkaline chamber of the electrodialyzer-synthesizer, M;

with _HCl - the concentration of hydrochloric acid obtained in the acid chamber of the electrodialyzer-synthesizer, M;

η _LiOH - differential current efficiency of lithium hydroxide obtained in the alkaline chamber of the electrodialyzer-synthesizer,%;

η _HCl - differential current output of hydrochloric acid obtained in the acid chamber of the electrodialyzer-synthesizer,%;

W _LiOH - differential specific energy consumption for producing lithium hydroxide in an electrodialyzer-synthesizer, kW · h / mol;

WHCl - differential specific energy consumption for obtaining hydrochloric acid in an electrodialyzer-synthesizer, kW · h / mol;

P _LiOH - differential specific productivity of the electrodialyzer-synthesizer for lithium hydroxide, mol / (h · m ² );

P _HCl - differential specific productivity of the electrodialyzer-synthesizer for hydrochloric acid, mol / (h · m ² ).

From table 7 it follows that at a low current density of less than 0.5 A / DM ^{2 the} specific productivity of the electrodialyzer with bipolar membranes decreases sharply. At a high current density greater than 5 A / dm ^{2, the} specific energy consumption during the production of lithium hydroxide and hydrochloric acid in the electrodialyzer sharply increases. Thus, the range of optimal current densities for an electrodialyzer with bipolar membranes containing three-chamber unit cells is a range of 0.5-5 A / dm ² .

The test results of the electrodialyzer 3 with bipolar membranes containing three-chamber unit cells, depending on the concentration of lithium hydroxide and hydrochloric acid obtained in the electrodialyzer, are shown in Table 8.

From table 8 it follows that when receiving lithium hydroxide and hydrochloric acid with a concentration of less than 0.1 Μ, the specific energy consumption of the process increases compared to the case when the concentration of the obtained alkali and acid is in the range of 0.1-1 M. In addition, the use of diluted alkali solutions to neutralize the process solution leads to its significant dilution with water and additional load on distillation columns. Upon receipt of lithium hydroxide and hydrochloric acid with a concentration of more than 1 Μ, the specific energy consumption of the process also increases compared to the case when the concentration of the obtained alkali and acid is in the range of 0.1-1 M.

Thus, the range of optimal concentrations of the obtained lithium hydroxide and hydrochloric acid in an electrodialyzer with bipolar membranes containing three-chamber unit cells is a range of 0.1 - 1 M.

Table 9 shows the concentration of regenerated DMAA and IHD, the content of impurities in the regenerated DMAA and IHD, as well as the degree of their extraction from the spent technological solutions. For comparison, similar results are given in the known method (prototype).

As can be seen from table 6, the proposed method provides almost complete regeneration of organic solvents DMAA, IHD and lithium chloride with obtaining high-purity substances suitable for reuse in the production of para-aramid fibers.

Example 5. The residual concentration of lithium chloride contained in the technological solution, desalted in an electrodialyzer with an ion-exchange filler, should not be too high, since at the stage of rectification of the technological solution in this case, it may be necessary to isolate the complex salt LiCl · DMAA by crystallization from the evaporated solution and separation of the complex salt suspension by centrifugation. On the other hand, an excessive decrease in the residual concentration of lithium chloride is associated with an increase in energy consumption and a decrease in the performance of an electrodialyzer with an ion-exchange filler.

To determine the range of the optimal residual lithium chloride content after deep desalting of the technological solution in the electrodialyzer with an ion-exchange filler, the spent technological solution of the same composition as in Example 1 (Table 1), as well as the spent technological solution that does not contain IHD of the same composition, were subjected to regeneration. as in example 2 (table 3). To obtain hydrochloric acid and lithium hydroxide from lithium chloride, an electrodialyzer with bipolar membranes 5 containing three-chamber unit cells was used. To remove lithium chloride technological solution neutralized in the reactor-neutralizer 1 and filtered through a mechanical filter 2, the same electrodialyzer 3 with non-flowing concentration chambers was used as in example 2.

For deep removal of lithium chloride from the technological solution obtained in the electrodialyzer 5, an ion-exchange electrodialyzer 6 was used, consisting of an anode and a cathode made of platinum titanium, MK-40 cation exchange membranes and MA-40 anion exchange membranes. Fillings from the KU-2 cation exchanger and the AV-17 anion exchanger were placed in desalination chambers. The area of each electrode and the working surface of each of the membranes of the cation exchange and anion exchange were 0.25 m ² , the number of unit cells was 40 pcs. The intermembrane distance is 4 · 10 ^-4 m. The cathode and anode chambers are equipped with inlet and outlet fittings. All desalination and concentration chambers are equipped with external inlet and outlet manifolds connected to inlet and outlet fittings. A solution was formed into the anode and cathode chambers, which formed in the concentration chambers by an electrodialyzer with ion-exchange filling. The feed rate of the solutions into the anode and cathode chamber is 0.1 m ³ / h. The feed rate (circulation) of the solution into the desalination chamber was 1.0 m ³ / h. The feed rate (circulation) of the solution into the concentration chamber was 0.1 m ³ / h.

Obtained in the concentration chambers, a solution of lithium chloride with a concentration of 0.5 g / l was fed to the input of the electrodialyzer 3.

The technological solution obtained in the desalination chambers was fed for rectification.

The test results of the electrodialyzer with ion exchange backfill 6 are shown in Table 10.

Where

i is the density of the electric current supplied to the electrodialyzer-hub, A;

U is the voltage at the electrodialyzer-hub, B;

c _{LiCl, input ko} is the concentration of lithium chloride at the entrance to the desalination chamber of the electrodialyzer, M;

c _{LiCl, output ko} — concentration of lithium chloride at the outlet of the desalination chamber of the electrodialyzer, M;

W _LiCl - differential specific energy consumption for obtaining deep desalination of the technological solution, kW · h / m ³ ;

P _LiCl - differential specific productivity of the electrodialyzer filled with desalination chambers with ion-exchange materials, mol / (h · m ² ). From table 10 it follows that with a residual lithium chloride content after deep desalination of the technological solution in an electrodialyzer with an ion-exchange filler of less than 5 mg / l, energy consumption sharply increases and the productivity of the process decreases. When the residual content of lithium chloride is more than 50 mg / l, it becomes necessary to isolate the complex salt LiCl · DMAA by crystallization from the evaporated solution and separate the suspension of the complex salt by centrifugation.

Thus, the optimal range of the residual content of lithium chloride in a deeply desalted technological solution is the range of 5-50 mg / l.

Table 11 shows the concentration of regenerated DMAA and IHD, the content of impurities in the regenerated DMAA and IHD, as well as the degree of their extraction from the spent technological solutions. For comparison, similar results are given in the known method (prototype).

As can be seen from table 11, the proposed method provides almost complete regeneration of organic solvents DMAA, IHD and lithium chloride with obtaining high-purity substances suitable for reuse in the production of para-aramid fibers.

Bibliography

1. RF patent No. 2110480 "Method for the purification of technological solutions and wastewater from organic substances"

2. A.S. USSR No. 1599312 "Method for the treatment of wastewater containing dimethylacetamide and isobutyl alcohol"

Claims (1)

The method of regeneration of lithium chloride, dimethylacetamide (DMAA) and isobutyl alcohol (IHD) or lithium chloride and dimethylacetamide from technological solutions for the production of para-aramid fibers, comprising the step of separating DMAA, IHD and water by distillation, neutralizing the initial solution with lithium hydroxide obtained in bipolarizator precipitation of iron hydroxide and filtration, electrodialysis with electrodialysis concentration in stagnant chambers concentration under current 0.5-5 a / dm ² density, d evaporation of a part of a concentrated lithium chloride solution and its crystallization upon cooling in the form of a solvate with DMAA to return to the process for producing synthetic fibers, sending another part of a concentrated lithium chloride solution to an electrodialyzer with bipolar membranes to obtain lithium hydroxide and hydrochloric acid with a concentration of 0.1- M 1 at a current density of 0.5-5 a / dm ^2, the direction of DMAC partially desalted solution CHD and water or DMAC and water: to deep cleaning in electrodialysis with ion BMENA filler desalting chambers to a residual content of lithium chloride 5-50 mg / l, then - submitting it to distillation to obtain pure DMAc and CHD or DMAC and return the concentrate after electrodialysis with electrodialysis ion exchanger filled in the entrance for the concentration of lithium chloride.

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