A method for purifying chromium electrolyte and improving yield

Abstract

A method for purifying chromium electrolyte to improve yield, the chromium electrolyte to be purified and recovered is placed in a stirring tank, the stirring tank is started to stir, sulfur-containing substances are added to the chromium electrolyte, stirring and reaction are carried out at 40-60 DEG C to remove Fe and Cu metal ions in the electrolyte, solid-liquid separation is carried out, an oxidizing agent is added to oxidize part of the trivalent chromium in the electrolyte to hexavalent chromium, strontium salt additives are added to reduce the content of sulfate, solid-liquid separation is carried out, the purified chromium electrolyte is obtained, and direct current is passed to produce electrolytic chromium in the form of electrodeposition. The advantages are: short process flow, low energy consumption, strong operability, high production efficiency, high yield, short production cycle, the purified electrolyte is returned to the system for repeated use, the product yield is increased by more than 2%, no pollutants are discharged, and the production cost is effectively reduced.

Description

Technical Field

[0001] This invention relates to a method for purifying chromium electrolyte and improving yield, and pertains to the field of electrodeposition technology. Background Technology

[0002] Electrolytic chromium plating is a highly efficient electroplating technology. As a thin film, it is applied to the surfaces of copper, steel, and other metals, making the surfaces wear-resistant, corrosion-resistant, aesthetically pleasing, and sophisticated. Chromium possesses excellent chemical stability and has wide applications in chemical, refractory, and metallic materials industries. Adding chromium to steel can also alter its properties and improve its toughness.

[0003] Currently, the main methods for producing electrolytic chromium are molten salt electrolysis and aqueous solution electrolysis. Common aqueous solution electrolysis methods include hexavalent chromium electrolysis and trivalent chromium electrolysis. After a period of use, the concentration of impurities in the electrolyte continuously accumulates, causing a decline in product quality indicators and weight. To ensure product quality and weight, the electrolyte must be partially or completely replaced, impacting production. The replaced electrolyte cannot be reused, and because it contains hexavalent chromium, it must undergo specialized treatment before discharge, resulting in significant chromium loss. To avoid environmental pollution, reduce chromium loss, and lower production costs, it is necessary to recover the chromium from the replaced electrolyte. A common recovery method is using cation exchange resin, but this has drawbacks such as incomplete treatment, resin aging, and high treatment costs. Another method is to use a reducing agent to reduce hexavalent chromium in the electrolyte to trivalent chromium, and then recover the trivalent chromium as chromium hydroxide precipitate by adjusting the solution to a slightly alkaline state. However, this method has disadvantages such as low yield, high cost, and high COD in the treated solution, making direct discharge impossible. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a method for purifying chromium electrolyte and improving yield. The method has a short process flow, low energy consumption, strong operability, high production efficiency, high yield, short production cycle, and the purified electrolyte is returned to the system for reuse. The product yield is increased by more than 2%, there is no pollutant emission, and production costs are effectively reduced.

[0005] The technical solution of this invention is:

[0006] A method for purifying chromium electrolyte and improving yield includes the following steps:

[0007] (1) Place the chromium electrolytic waste liquid to be purified and recycled in a stirring tank, turn on the stirring of the reaction tank, add sulfur-containing substances to the chromium electrolytic waste liquid, stir and react at 40-60℃ to remove Fe and Cu metal ions from the waste liquid, separate solid and liquid, and obtain chromium electrolytic waste liquid with metal ion impurities removed.

[0008] The sulfur-containing substance is metallic sulfur powder or hydrogen sulfide gas, and the amount of sulfur-containing substance added is 0.3-0.6 times the total mass of metallic impurities Fe and Cu in the chromium electrolyte waste.

[0009] (2) Add an oxidant to the chromium electrolysis waste liquid from which metal ion impurities were removed in step (1) to oxidize some of the trivalent chromium in the chromium electrolysis waste liquid to hexavalent chromium.

[0010] The oxidant is hydrogen peroxide or oxygen, and the amount of oxidant added is 0.2-0.3 times the mass of trivalent chromium in the electrolytic waste liquid to be oxidized to hexavalent chromium.

[0011] (3) Add strontium salt additive to the chromium electrolytic waste liquid oxidized in step (2) to reduce the sulfate content by 55%-75%, so that the mass ratio of the remaining sulfate in the chromium electrolytic waste liquid to the hexavalent chromium in the electrolyte is 1:40-1:60, and the solid and liquid are separated to obtain the purified chromium electrolyte.

[0012] The strontium salt is strontium carbonate or strontium chloride. The amount of strontium salt added is 1.4-2.2 times the mass of sulfate to be reduced in the chromium electrolytic waste liquid treated by oxidation in step (2). Barium salt is effective in controlling the reduction of sulfate, but it is not used here because it will cause the loss of hexavalent chromium in the solution.

[0013] (4) The purified chromium electrolyte is passed through a direct current to produce electrolytic chromium by electrodeposition.

[0014] Furthermore, the chromium electrolysis waste liquid contains hexavalent chromium ≥70g / L, trivalent chromium ≥5g / L, sulfate ≥5g / L, iron ≥8g / L, and copper ≥0.5g / L.

[0015] Furthermore, during step (1), the stirring time is 3-4 hours.

[0016] Furthermore, during step (2), the stirring time is 1-2 hours.

[0017] Furthermore, during step (3), the stirring time is 4-6 hours.

[0018] Furthermore, in step (2), 67%-70% of the trivalent chromium in the chromium electrolysis waste liquid is oxidized to hexavalent chromium.

[0019] Furthermore, the purified chromium electrolyte contains hexavalent chromium ≥80g / L, trivalent chromium ≤2.0g / L, iron ≤0.5g / L, and copper ≤0.1g / L.

[0020] Furthermore, the sulfate content in the purified chromium electrolyte is ≤2.5g / L.

[0021] Furthermore, the yield of electrolytic chromium products obtained by electrodeposition using purified chromium electrolyte is increased by more than 2%.

[0022] While adding reagents to waste chromium electrolyte removes various impurities and purifies the electrolyte, using a chromium electrolyte that has removed metal ion impurities for electrodeposition treatment can improve product quality indicators, but the service life will not be extended, and there will still be periodic discharge, which increases production costs and affects the production cycle.

[0023] This invention effectively removes metal ion impurities by controlling the order, timing, and removal parameters of the impurity removal agent, thereby reducing the concentration of sulfate ions and trivalent chromium ions, balancing the ion concentration in the electrolyte, extending the electrolyte's service life, reducing raw material usage, eliminating the need for additional waste electrolyte disposal costs, lowering production costs, and increasing product yield.

[0024] Its beneficial effects are:

[0025] The process is short, highly operable, easy to control, and has high production efficiency. The electrolyte impurity purification rate is over 95%, effectively extending the electrolyte's service life and enabling long-term effective recycling. This avoids production delays due to electrolyte replacement, reduces electrolyte environmental treatment costs, and lowers production costs. Detailed Implementation

[0026] The composition of the chromium electrolysis waste liquid used in Examples 1-3 and Comparative Examples 1-3 of this invention is shown in the table below.

[0027]

[0028]

[0029] Example 1

[0030] 1) Removal of metal ion impurities

[0031] Take 1m 3 Chromium waste electrolyte was placed in a reaction vessel, the stirring of the reaction vessel was turned on, 2.838 kg of metallic sulfur powder was added to the reaction vessel, the temperature was raised to 40°C, and the reaction was stirred at this temperature for 3 hours. After stirring was stopped, the mixture was filtered, and the concentrations of Fe and Cu metal ions in the chromium waste electrolyte were 0.5 g / L and 0.1 g / L, respectively, resulting in a low-iron and low-copper chromium electrolytic waste liquid.

[0032] 2) Oxidation reaction

[0033] The low-iron and low-copper chromium electrolytic waste liquid from step (1) was returned to the reaction tank. The reaction tank was stirred and 551 mL of hydrogen peroxide was added to the reaction tank. The temperature was raised to 40°C and stirred for 1 hour at this temperature. After testing, the concentration of trivalent chromium in the chromium waste electrolyte after the trivalent chromium oxidation reaction was 2.0 g / L and the concentration of hexavalent chromium was 102.5 g / L. 67% wt of trivalent chromium in the chromium waste electrolyte was oxidized to hexavalent chromium.

[0034] 3) To reduce the sulfate concentration, add 5.023 kg of strontium carbonate to the reaction vessel and stir at 40°C for 4 hours. Stop stirring and perform solid-liquid separation. The concentration of hexavalent chromium in the separated chromium electrolyte is 102.4 g / L, and the concentration of sulfate is 2.56 g / L. This reduces the amount of sulfate in the waste chromium electrolyte by 57% wt, resulting in a purified chromium electrolyte. The mass ratio of the amount of residual sulfate in the solution to the amount of hexavalent chromium in the electrolyte is 1:40. The obtained solid is a strontium sulfate byproduct, which is washed and sold as a byproduct.

[0035] 4) Electrolysis

[0036] The purified electrolyte was placed in an electrolytic cell and electrolyzed for 16 hours with a current of 15000A. The resulting product had a Cr content of 99.99%; an Fe content of 0.003%, a 25% decrease compared to the previous product's 0.004%; a copper content of 0.002%, a 33% decrease compared to the previous product's 0.003%; a strontium content of 0.0001%; ​​and a product yield of 95.5%, a 2.0% increase compared to the previous yield of 93.5%.

[0037] 5) The purified electrolyte can be continuously recycled without adverse effects. When the impurities in the electrolyte increase after 2 years of use, it can be purified again in this way and reused. This avoids delays in the production cycle due to electrolyte replacement, saves the cost of waste electrolyte disposal, and reduces the labor intensity of employees.

[0038] Comparative Example 1

[0039] 1) Removal of metal ion impurities

[0040] Take 1m 3 Chromium waste electrolyte was placed in a reaction vessel, and stirring was started. 2.838 kg of metallic sulfur powder was added to the reaction vessel, and the temperature was raised to 40°C. After reacting for 3 hours, stirring was stopped, and the mixture was filtered. After separation, the iron and copper concentrations in the liquid were 0.5 g / L and 0.1 g / L, respectively, which is a low-iron and low-copper chromium electrolytic waste liquid.

[0041] 2) Oxidation reaction

[0042] The low-iron and low-copper chromium electrolysis waste liquid from step (1) was returned to the reaction tank, 551 mL of hydrogen peroxide was added, and the mixture was stirred at 40°C for 1 hour to oxidize 67% of the trivalent chromium to hexavalent chromium. After the reaction, the concentration of trivalent chromium in the solution was 2.0 g / L and the concentration of hexavalent chromium was 102.5 g / L.

[0043] 3) To reduce the sulfate concentration, 5.023 kg of barium carbonate was added to the reaction vessel, and the mixture was stirred at 40°C for 4 hours. After stirring, solid-liquid separation was performed. The concentration of hexavalent chromium in the separated chromium electrolyte was 86.1 g / L, and the sulfate concentration was 2.28 g / L, reducing the sulfate content in the solution by 62%. The purified chromium electrolyte was obtained, with a residual sulfate content to hexavalent chromium mass ratio of 1:40. The resulting solid was a barium sulfate byproduct. During the purification process, the sulfate concentration decreased significantly, but the hexavalent chromium content in the electrolyte decreased from 102.5 g / L to 86.1 g / L, representing a 16% loss of hexavalent chromium.

[0044] 4) Electrolysis

[0045] The purified electrolyte was placed in an electrolytic cell and electrolyzed for 16 hours with a current of 15000A. The resulting product had a Cr content of 99.98%; an Fe content of 0.003%, a 25% decrease compared to the previous product's 0.004%; a copper content of 0.002%, a 33% decrease compared to the previous product's 0.003%; and a barium content of 0.0005%. The product yield was 90.2%, a 3.3% decrease compared to the previous product.

[0046] 5) Electrolyte lifespan

[0047] The purified electrolyte can be continuously recycled, but because the loss rate of hexavalent chromium in the electrolyte is relatively large and the product yield is reduced, the production cost increases, so this method is not advisable.

[0048] Example 2

[0049] 1) Removal of metal ion impurities

[0050] Take 1m 3 Chromium waste electrolyte was placed in a reaction vessel, the stirring of the reaction vessel was turned on, 5.676 kg of metallic sulfur powder was added to the reaction vessel, the temperature was heated to 60°C, and the reaction was stirred at this temperature for 4 hours. After stirring was stopped, the mixture was filtered, and the concentrations of Fe and Cu metal ions in the chromium waste electrolyte were 0.4 g / L and 0.09 g / L, respectively, resulting in a low-iron and low-copper chromium electrolytic waste liquid.

[0051] 2) Oxidation reaction

[0052] The low-iron and low-copper chromium electrolytic waste liquid from step (1) was returned to the reaction tank. The reaction tank was stirred and 865 mL of hydrogen peroxide was added to the reaction tank. The reaction was stirred at 60°C for 2 hours. 70% wt of trivalent chromium in the chromium waste electrolyte was oxidized to hexavalent chromium. After testing, the concentration of trivalent chromium in the chromium waste electrolyte after the trivalent chromium oxidation reaction was 1.81 g / L and the concentration of hexavalent chromium was 102.69 g / L. 70% wt of trivalent chromium in the chromium waste electrolyte was oxidized to hexavalent chromium.

[0053] 3) Reduce sulfate concentration

[0054] 7.894 kg of strontium carbonate was added to the reaction vessel, and the mixture was stirred at 60°C for 6 hours. After stirring was stopped, the solid and liquid were separated. The concentration of hexavalent chromium in the separated chromium electrolyte was 102.6 g / L, and the concentration of sulfate was 1.71 g / L. This reduced the amount of sulfate in the waste chromium electrolyte by 71% wt, resulting in a purified chromium electrolyte. The mass ratio of the amount of residual sulfate in the solution to the amount of hexavalent chromium in the electrolyte was 1:60. The obtained solid was a strontium sulfate byproduct, which was washed and sold as a byproduct.

[0055] 4) Electrolysis

[0056] The purified electrolyte was placed in an electrolytic cell and electrolyzed for 22 hours with a current of 23000A. The resulting product had a Cr content of 99.99%; an Fe content of 0.003%, a 25% decrease compared to the previous product's 0.004%; a copper content of 0.0015%, a 50% decrease compared to the previous product's 0.003%; a Strontium content of 0.0001%; ​​and a product yield of 96.1%, a 2.6% increase compared to the previous yield of 93.5%.

[0057] 5) Electrolyte lifespan

[0058] The purified electrolyte can be continuously recycled without adverse effects. When the impurities in the electrolyte increase after 2 years of use, it can be purified again in this way and reused. This avoids delays in the production cycle due to electrolyte replacement, saves on waste electrolyte disposal costs, and reduces the labor intensity of employees.

[0059] Comparative Example 2

[0060] 1) Removal of metal ion impurities

[0061] Take 1m 3 Chromium waste electrolyte was placed in a reaction vessel, and stirring was started. 5.676 kg of metallic sulfur powder was added to the reaction vessel, and the temperature was raised to 60°C. After reacting for 4 hours, stirring was stopped, and the mixture was filtered. After separation, the iron and copper concentrations in the liquid were 0.4 g / L and 0.09 g / L, respectively, which is a low-iron and low-copper chromium electrolytic waste liquid.

[0062] 2) Oxidation reaction

[0063] The low-iron and low-copper chromium electrolysis waste liquid from step (1) was returned to the reaction tank, 865 mL of hydrogen peroxide was added, and the mixture was stirred at 60 °C for 2 hours to oxidize 70% of the trivalent chromium to hexavalent chromium. After the reaction, the concentration of trivalent chromium in the solution was 1.81 g / L and the concentration of hexavalent chromium was 102.69 g / L.

[0064] 3) To reduce the sulfate concentration, 7.894 kg of barium carbonate was added to the reaction vessel, and the mixture was stirred at 60°C for 6 hours. After stirring, solid-liquid separation was performed. The concentration of hexavalent chromium in the separated chromium electrolyte was 83.2 g / L, and the sulfate concentration was 2.12 g / L, reducing the sulfate content in the solution by 65%. The purified chromium electrolyte was obtained, with a residual sulfate content to hexavalent chromium mass ratio of 1:39. The resulting solid was a barium sulfate byproduct. During the purification process, the sulfate concentration decreased significantly, but the hexavalent chromium content in the electrolyte decreased from 102.69 g / L to 83.2 g / L, representing a 19% loss of hexavalent chromium.

[0065] 4) Electrolysis

[0066] The purified electrolyte was placed in an electrolytic cell and electrolyzed for 22 hours with a current of 23000A. The resulting product contained 99.96% Cr; 0.003% Fe, a 25% decrease from the previous product's 0.004%; 0.0015% copper, a 50% decrease from the previous product's 0.003%; and 0.0010% barium. The product yield was 89.2%, a 4.3% decrease from the previous yield.

[0067] 5) Electrolyte lifespan

[0068] The purified electrolyte can be continuously recycled, but because the loss rate of hexavalent chromium in the electrolyte is relatively large and the product yield decreases by 3.6%, the production cost increases, making this method undesirable.

[0069] Example 3

[0070] 1) Removal of metal ion impurities

[0071] Take 1m 3 The waste chromium electrolyte was placed into the reaction vessel, the agitator was turned on, and 2.77 m³ of chromium was introduced into the reaction vessel. 3 Hydrogen sulfide gas was heated to 50°C and stirred at this temperature for 3.5 hours. After filtration, the concentrations of Fe and Cu metal ions in the chromium waste electrolyte were 0.45 g / L and 0.095 g / L, respectively, resulting in a low-iron and low-copper chromium electrolytic waste liquid.

[0072] 2) Oxidation reaction

[0073] The low-iron, low-copper chromium electrolysis waste liquid from step (1) is returned to the reaction tank. The stirring in the reaction tank is turned on, and 0.72 m³ of chromium electrolyte is introduced into the reaction tank.3 Oxygen was heated to 40°C and stirred at this temperature for 1.5 hours. After testing, the concentration of trivalent chromium in the chromium waste electrolyte after the trivalent chromium oxidation reaction was 1.93 g / L and the concentration of hexavalent chromium was 102.6 g / L. 68% wt of trivalent chromium in the chromium waste electrolyte was oxidized to hexavalent chromium.

[0074] 3) To reduce the sulfate concentration, add 6.997 kg of strontium carbonate to the reaction vessel and stir at 50°C for 5 hours. Stop stirring and perform solid-liquid separation. The concentration of hexavalent chromium in the separated chromium electrolyte is 102.5 g / L, and the concentration of sulfate is 2.11 g / L. This reduces the amount of sulfate in the waste chromium electrolyte by 65% ​​wt, resulting in a purified chromium electrolyte. The mass ratio of the remaining sulfate in the solution to the amount of hexavalent chromium in the electrolyte is 1:49. The obtained solid is a strontium sulfate byproduct, which is washed and sold as a byproduct.

[0075] 4) Electrolysis

[0076] The purified electrolyte was placed in an electrolytic cell and electrolyzed for 19 hours with a current of 20,000 A. The resulting product had a Cr content of 99.99%; an Fe content of 0.003%, a 25% decrease compared to the previous product's 0.004%; a copper content of 0.0018%, a 40% decrease compared to the previous product's 0.003%; a Strontium content of 0.0001%; ​​and a product yield of 95.7%, a 2.2% increase compared to the previous yield of 93.5%.

[0077] 5) Electrolyte lifespan

[0078] The purified electrolyte can be continuously recycled without adverse effects. When the impurities in the electrolyte increase after 2 years of use, it can be purified again in this way and reused. This avoids delays in the production cycle due to electrolyte replacement, saves on waste electrolyte disposal costs, and reduces the labor intensity of employees.

[0079] Comparative Example 3

[0080] 1) Removal of metal ion impurities

[0081] Take 1m 3 The waste chromium electrolyte was placed into the reaction vessel, the stirrer was turned on, and 2.77 m³ of chromium was introduced into the reaction vessel. 3 Hydrogen sulfide gas was heated to 50°C and reacted for 3.5 hours. After stirring was stopped, the mixture was filtered, and the iron and copper concentrations in the separated liquid were 0.45 g / L and 0.095 g / L, respectively. This liquid was a low-iron, low-copper chromium electrolysis waste liquid.

[0082] 2) Oxidation reaction

[0083] The low-iron, low-copper chromium electrolysis waste liquid from step (1) is returned to the reaction tank, and 0.72 m³ of chromium electrolyte is introduced. 3Oxygen was used to oxidize 67% of trivalent chromium to hexavalent chromium by stirring at 50°C for 1.5 hours. After the reaction, the concentration of trivalent chromium in the solution was 1.93 g / L and the concentration of hexavalent chromium was 102.6 g / L.

[0084] 3) To reduce the sulfate concentration, 3.887 kg of barium carbonate was added to the reaction vessel, and the mixture was stirred at 50°C for 5 hours. After stirring, solid-liquid separation was performed. The concentration of hexavalent chromium in the separated chromium electrolyte was 84.9 g / L, and the sulfate concentration was 2.21 g / L, reducing the sulfate content in the solution by 63%. The purified chromium electrolyte was obtained, with a mass ratio of residual sulfate to hexavalent chromium in the electrolyte of 1:38. The resulting solid was a barium sulfate byproduct. During the purification process, the sulfate concentration decreased significantly, but the hexavalent chromium content in the electrolyte decreased from 102.6 g / L to 84.9 g / L, representing a 17% loss of hexavalent chromium.

[0085] 4) Electrolysis

[0086] The purified electrolyte was placed in an electrolytic cell and electrolyzed for 19 hours with a current of 20,000 A. The resulting product had a Cr content of 99.97%; an Fe content of 0.003%, a 25% decrease compared to the previous product's 0.004%; a copper content of 0.0018%, a 40% decrease compared to the previous product's 0.003%; and a barium content of 0.0007%. The product yield was 90.0%, a 3.5% decrease compared to the previous product.

[0087] 5) Electrolyte lifespan

[0088] The purified electrolyte can be continuously recycled, but because the loss rate of hexavalent chromium in the electrolyte is relatively large and the product yield decreases by 3.6%, the production cost increases, making this method undesirable.

Claims

1. A method for purifying chromium electrolyte to improve yield, characterized by comprising the following steps: (1) placing chromium electrolyte to be purified and recovered in a reaction tank, the chromium electrolyte having a content of hexavalent chromium ≥ 70 g / L, a content of trivalent chromium ≥ 5 g / L, a content of sulfate ≥ 5 g / L, a content of iron ≥ 8 g / L, and a content of copper ≥ 0.5 g / L; starting stirring of the reaction tank, adding sulfur-containing substance into the chromium electrolyte, and stirring and reacting at 40-60℃ to remove Fe and Cu metal ions in the electrolyte, and then performing solid-liquid separation to obtain chromium electrolyte with metal ion impurities removed; the sulfur-containing substance is metal sulfur powder or hydrogen sulfide gas, and the amount of the sulfur-containing substance added is 0.3-0.6 times the total mass of Fe and Cu metal impurities in the chromium electrolyte; (2) adding oxidizing agent into the chromium electrolyte with metal ion impurities removed in step (1), heating and stirring to react, oxidizing part of the trivalent chromium in the chromium electrolyte to hexavalent chromium, and oxidizing 67wt%-70wt% of the trivalent chromium in the chromium electrolyte to hexavalent chromium; the oxidizing agent is hydrogen peroxide or oxygen, and the amount of the oxidizing agent added is 0.2-0.3 times the mass of the part of the trivalent chromium to be oxidized to hexavalent chromium in the electrolyte; (3) adding strontium salt additive into the chromium electrolyte treated by oxidation in step (2), heating and stirring to react, reducing the amount of sulfate in the chromium electrolyte by 57wt%-75wt%, so that the mass ratio of the remaining amount of sulfate to the amount of hexavalent chromium in the chromium electrolyte is 1:40-1:60, performing solid-liquid separation to obtain purified chromium electrolyte; the purified chromium electrolyte has a content of hexavalent chromium ≥ 80 g / L, a content of trivalent chromium ≤ 2.0 g / L, a content of iron ≤ 0.5 g / L, and a content of copper ≤ 0.1 g / L; and the purified chromium electrolyte has a content of sulfate ≤ 2.5 g / L; the strontium salt is strontium carbonate or strontium chloride, and the amount of the strontium salt added is 1.4-2.2 times the mass of the sulfate to be reduced in the chromium electrolyte treated by oxidation in step (2); (4) passing the purified chromium electrolyte through direct current to produce electrolytic chromium in the form of electrodeposition. In step (1), the stirring time is 3-4 hours.

2. The method of purifying chromium electrolyte to increase yield according to claim 1, characterized in that: In step (2), the stirring time is 1-2 hours.

3. The method of purifying chromium electrolyte to increase yield according to claim 1, characterized in that: In step (3), the stirring time is 4-6 hours.

4. The method of purifying chromium electrolyte to increase yield according to claim 1, characterized in that: ​

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