RU2612248C1 - Method for cleaning and regeneration of acidic chromate solutions and device forits implementation - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: process of purification and recovery of acidic chromating solutions carried out at a constant current of 0.01-0.03 A, and a voltage of 0.5-1.5 V, with insoluble electrodes in the form of activated carbon with a particle size of from 0.5 to 2.0 mm. The electrode cell partition, which separates the anode chamber and the cathode, is made of an impermeable material and electrodes are used as filled in the anode compartment and the cathode at the height of 0.8-0.9 of the height of partitions activated carbon having a particle size of from 0.5 to 2.0 mm.

EFFECT: invention enhances the degree of separation while reducing power consumption by providing a new mechanism for separating the plurality of ions on the surface of the active centers in the interelectrode space.

3 cl, 1 ex, 2 dwg

Description

The invention relates to the field of electrochemical methods for the purification of water and aqueous solutions of anions and cations and can be used to purify natural waters, effluents of metallurgical, engineering and other industries.

The claimed invention relates to a priority area of development of science and technology "Technologies for processing and disposal of technogenic formations and waste" [Alphabetical subject index to the International Patent Classification in priority areas of development of science and technology / Yu.G. Smirnov, E.V. Skidanova, S.A. Krasnov. - M.: PATENT, 2008 .-- p. 58], as it allows the regeneration of chromatographic solutions for reuse and eliminates environmental pollution by preventing the discharge of highly concentrated, carcinogenic waste industrial solutions.

A known analogue of the method for the regeneration of acid solutions of chromation, which is an electrocoagulation treatment that provides a fairly high degree of purification (90-95%) [Smirnov GN, Genkin V.E. Wastewater treatment in metal processing. - M.: Metallurgy, 1989 .-- p. 141-145].

Signs of an analogue that coincide with the essential features of the proposed method is that in order to achieve the maximum cleaning effect of the chromatization solutions, double (or multiple) transmission of the solution through the electrolyzer is used. Also, during the regeneration of chromatographic solutions, electrodes (cathodes and anodes) are connected to a direct current source.

The disadvantage of the analogue is the need to maintain a pH in the range from 3-6, as a result, there is an increase in the solids content in the precipitates formed in this case, since 1.12 parts (by weight) of chromium hydroxide precipitate additionally forms 3.12 parts (by weight) of iron hydroxide (3). In addition, periodic mechanical cleaning of the surface of the electrode plates from adhering sediment, immersion (for washing) of the plates in a solution of mineral acid, and blowing of compressed air through water with electrode plates immersed in it are necessary. A significant disadvantage when using flat electrodes for the regeneration of solutions is also an increased energy consumption.

The method of purification of water and aqueous solutions of anions and cations (patent RU No. 2213701, IPC ⁷ C02F 1/46, C02F 103: 16, published on 10.10.2003), intended for the purification of natural waters, metallurgical, engineering and other industries.

The signs of the prototype, coinciding with the essential features of the proposed method are:

- the fact that the method can be used for the treatment of natural waters, effluents of metallurgical, engineering and other industries;

- electrochemical method of purification of water and aqueous solutions from anions and cations;

- the use of pairs of insoluble electrodes;

- liquid is passed between the electrodes.

The disadvantage of the prototype is not a sufficiently high degree of separation of anions and cations, since the plate area is much smaller than the area of volume-porous electrodes (activated carbon), which does not allow the process with highly concentrated solutions. In addition, it should be noted that the prototype uses scarce, expensive material for the manufacture of electrodes (stainless steel 12X18H10T, titanium alloy OT 4-0), as well as the fact that the use of electrodes in the form of plates causes an increased energy consumption due to the high value of overvoltage gas at the anode

A device for the extraction of metals from solutions is known (Weiss A.A., Masliy A.I., Zakharov M.A. Autonomous electrochemical module. RF patent №2172796, IPC С25С 7/00, 1/20, 2001, publ. 27.08. 2001), in which the cathode is made of metallized synthetic winterizer (surround insulation) and is equipped with a local ring current supply mounted on the outside of the upper part of the cell.

Signs of an analogue that coincide with the essential features of the claimed device is the presence of volume-porous electrodes and an external current supply, as well as the use of direct current for the extraction of metals from solutions.

The disadvantages of this analogue of the device are the lack of separation due to insufficient mixing of the solution in the interelectrode space, especially vertically, caused by the upper supply of the solution. This makes it difficult for the solution to enter the lower part of the cell and leads to an uneven filling of the cathode matrix with metal. It also imposes restrictions on the vertical dimensions of the cell and makes it difficult to scale. Also, the known device does not allow the regeneration of chromatization solutions due to the aggressiveness of such solutions that completely destroy the organic materials of which the electrode is made.

The insoluble anode for electroextraction of metals from aqueous solutions of the authors is known: Rzhevsky IV, Goryainov-Oranovsky DV, Egurnev MA (RF patent No. 2266982, IPC ⁷ С25С 1/00, С25С 7/02, published December 27, 2005) with insoluble anodes in the form of cylindrical elements for electroextraction of metals from aqueous solutions with the placement of these elements in a separate porous shell. Porous shells, in each of which a cylindrical element was placed, were made of lavsan (art.56050).

Signs of an analogue that coincide with the essential features of the claimed device is an insoluble anode and the use for electroextraction of metals from aqueous solutions of a porous shell.

The disadvantages of this device are the high values of overvoltage due to the release of gas at the anode, resulting in increased energy consumption and a decrease in the degree of separation of ions from aqueous solutions. And also, the device is not suitable for the regeneration of highly concentrated chromatization solutions due to the aggressiveness of solutions that destroy the organic materials of which the electrode is made.

A device for extracting metals from solutions is known (US Pat. No. 4,276,147, Apparatus for recovery of metals from solution, C25C 7/00 (20060101); C25C 1/00 (20060101); C25C 7/02 (20060101); C25C 1/20 ( 20060101); C25B 007/00, June 30, 1981) located directly in the solution bath, consisting of a cylindrical body with inlet and outlet and equipped with an external circuit with a pump for circulation of the solution. The anode and cathode located in the housing are connected to a direct current source.

Signs of an analogue that coincide with the essential features of the claimed device are the presence of insoluble electrodes and the use of direct current to extract metals from solutions.

The disadvantages of the device according to US patent No. 4,276,147 are the low degree of purification of the solution from electropositive impurities and the inability to control electrochemical parameters. The presence of an external pump and piping system with shutoff valves requires the tightness of external pumping systems, which complicates their maintenance and leads to high losses of precious metals. In addition, the regenerated solution has high corrosion properties, which destroys the device in a short time.

The invention is aimed at solving the problem of creating an effective technology for the regeneration of acid chromatization solutions, which allows for low energy and material costs to regenerate acid chromatization solutions, to separate the valuable components of chromium and aluminum, which can be reused in the process.

The technical result of the claimed group of inventions is to increase the degree of separation while reducing energy consumption by providing a new mechanism for the separation of ions on the surface of many active centers in the interelectrode space.

The technical result of the invention is achieved by the fact that in the method for the regeneration of acidic chromate solutions, including the purification and regeneration of acid chromate solutions by the electrochemical method, according to the invention, the process of purification and regeneration of acid chromate solutions is carried out by electrolysis of acid chromate solutions for 5-12 minutes, at least at least in two stages with a constant current of 0.01-0.03 A with insoluble electrodes in the form of activated carbon with a particle size of from 0.5 to 2.0 mm.

The technical result of the invention is achieved by the fact that in the device for the regeneration of acidic solutions of chromation, including a housing provided with a partition separating the cathode and anode space, according to the invention, the partition separating the cathode and anode space is made of impermeable material, and filled as electrodes cathode and anode space to a height of 0.8-0.9 from the height of the septum activated carbon with a particle size of from 0.5 to 2.0 mm

Carrying out the process with a direct current above 0.03 A leads to an increase in gas evolution, which will adversely affect the degree of separation, since the electrodes will be coated with reduced metals. Thus, the surface of the electrodes decreases, energy consumption increases, and failure of the electrodes is possible. Carrying out the process with a direct current below 0.01 A leads to insufficient movement of ions to the surface of the electrodes and, as a result, to a decrease in the degree of separation of ions in solution.

The use of activated carbon with a particle size of 0.5 to 2.0 mm as insoluble electrodes is the most effective, since, for example, when using activated carbon with a particle size of less than 0.5 mm, the resistance of the activated carbon layer to the passage of the solution increases. The use of activated carbon with a particle size larger than 2.0 mm reduces the contact area between the solution and activated carbon.

The implementation of the partition separating the cathode and anode space from an impermeable material leads to the possibility of complete dielectric separation of the anode and cathode space.

Using as electrodes filled in the cathode and anode space to a height of 0.8-0.9 from the height of the septum of activated carbon with a particle size of 0.5 to 2.0 mm does not allow you to connect (interact) particles of activated carbon anode and cathode space, which could lead to the closure and inability to separate the ions of the solution.

A significant difference between the proposed method and device from the prototype method and the prototype device is the unconventional use of activated carbon and its application to solve a new problem in a new quality, using its physical, mechanical and operational properties as electrode material to increase separation efficiency by increasing accessible surface and greater capacity of activated carbon. In addition, activated carbon is resistant to aggressive environments and inexpensive electrode material with respect to the electrode material of the prototype (stainless steel 12X18H10T, titanium alloy OT 4-0). The efficiency of this installation using a porous electrode material - activated carbon in the form of electrodes (cathode and anode) based on it, the higher, the larger the surface, porosity and layer size of the used electrode materials.

The difference between the claimed method and device from the prototype method and the prototype device proves the compliance of the claimed group of inventions with the condition of patentability "novelty". It is not known from the prior art to use electrodes in the form of activated carbon with a particle size of 0.5 to 2 mm filled in the anode and cathode space, and it is not known to carry out the purification and regeneration of acid chromatization solutions at a constant current of 0.01-0.03 A and voltage 0.5-1.5 V, with insoluble electrodes in the form of activated carbon with a particle size of from 0.5 to 2.0 mm. This proves the compliance of the claimed group of inventions with the condition of patentability "inventive step".

The invention is illustrated by drawings, where

in FIG. 1 shows schematically (in section) a device for the regeneration of acid chromatization solutions;

in FIG. 2 shows the dependence of the degree of separation in stages at 1.5 V and 0.03 A.

The elements of the device for the regeneration of acid chromatization solutions are assigned the following numerical designations:

1 - housing (electrode cell)

2 - partition

3 - activated carbon

4 - current supply

5 - drain (tap) from the anode or cathode space (depending on how the power source is connected to “plus” or “minus”, you can also change the poles for cleaning the electrodes).

The method is as follows. A spent highly concentrated chromatization solution is passed between the electrodes in the form of activated carbon with a particle size of 0.5 to 2.0 mm, filled in the anode and cathode space. During purification and separation of the chromatization solution, a direct current of 0.01-0.03 A and a voltage of 0.5-1.5 V are used. During the separation, aluminum ions Al ³⁺ are removed from the solution, and chromium ions CrO ₄ ^{2- are} returned to chromate bath. The anolyte formed during separation, containing Al ³⁺ aluminum ions, is discharged from the anode chamber, where aluminum ions are extracted from it, and the catholyte containing chromium ions is returned from the cathode chamber to the chromate bath. The method provides the circulation of chromium in a closed process cycle in the absence of any losses and waste generation. To reduce (or more fully recover the aluminum ions Al ³⁺ ) from the solution that is returned to the chromatography bath, the electrolysis of acidic chromation solutions is carried out for 5-12 minutes in at least two stages.

A device for the purification and regeneration of acid chromatization solutions (Fig. 1) comprises a housing 1, which is a rectangular-shaped electrode cell. In the center of the housing 1, a partition 2 (impermeable diaphragm) is installed, dividing the electrode space into the cathode and anode space. The partition 2 separating the cathode and anode space is made of impermeable material, for example polycarbonate. The current lead 4 is made of graphite grade GE-3, and activated carbon 3 with a particle size of 0.5 to 2.0 mm filled in the cathode and anode space to a height of 0.8-0.9 from the height of the partition 2 is used as electrodes.

The device operates as follows. Activated carbon, dried at a temperature of 105 ° C to constant weight, is poured into the housing 1 of the electrode cell - separately in the anode and cathode space. It is washed with distilled water to remove impurities. Chromatic acid solution is poured above the level of poured activated carbon 3 and higher by 0.5-1.0 cm from the upper edge of the partition 2. An electric current is supplied from the direct current source through current leads 4 made of graphite to the surface of activated carbon 3. The set value is set voltage between 0.5-1.5 V and current between 0.01-0.03 A; under these conditions, the process of regeneration of the chromatization solutions occurs. The solution, divided into analyte and catalytic, is drained through plums 5 into samplers (not shown in the drawing). An analyte is a solution, purified from at least two stages within 5-12 minutes, of aluminum and is a concentrated chromatization solution that is returned to the chromatography bath for reuse, and catalite is a solution containing aluminum ions that is sent to a container for further technological use in the production of valuable components. For example, to obtain a flocculant, etc.

The efficiency of this installation using a porous electrode material - activated carbon in the form of electrodes (cathode or anode) based on it, the higher, the greater the specific surface, porosity and working thickness of the used electrode materials.

Example

In the electrode cell measuring 60 × 30 mm and a height of 30 mm, 100 ml of an acidic chromation solution was supplied, containing the main components:

A voltage of 1.5 V and a current of 0.03 A were established at which the process of regeneration of acid solutions of chromation was carried out. The analyte and catalit were collected in separate collections and the chromium content in the analyte and catalyte was determined by the results of the analysis. To determine the concentration of chromium ions in the solution, a KFK-2UKHL 4.2 photoelectric concentration calorimeter was used. Based on the obtained optical density data, a graded graph is constructed that allows one to determine the concentration of chromium ions in solution. Depending on the purpose of the regeneration of the chromatization solution, it is possible to reduce the chromium content in the catalyte to certain values, that is, to the values necessary for the chromatization process. For a deeper extraction of chromium ions, you can use the multi-stage process of purification and regeneration of an acidic solution of chromation. So, for example, during the 2 stages of separation of the initial solution with the content of chromium ions 52.671 g / l, the concentration of chromium ions decreased to 25.217 g / l, and during the 3 stages the concentration of chromium ions decreased to 18.913 g / l (cm Fig. 2).

It does not require expensive chemicals when regenerating sludge waste for further disposal in special storage facilities. The energy consumption consumed by the installation even at maximum values is 0.03A × 1.5 V = 0.045 W. Furthermore, the activated carbon has a surface of 500-2200 m ² / g charcoal for 1 and it is not comparable to larger planar electrodes used in the prior art. During purification and regeneration of the acid solution of chromation, the concentration of chromium in the catalyte decreased by 7 times, and in the analyte it increased to a value sufficient for reuse in the technological process of chromation.

Claims (3)

1. The method of purification and regeneration of acid solutions of chromation, including the electrolysis of acid solutions of chromation, characterized in that the electrolysis of acid solutions of chromation is carried out at a constant current of 0.01-0.03 A and a voltage of 0.5-1.5 V with insoluble electrodes in in the form of activated carbon with a particle size of from 0.5 to 2.0 mm. 2. The method according to p. 1, characterized in that the electrolysis of acid solutions of chromation is carried out for 5-12 minutes, at least in two stages. 3. A device for the purification and regeneration of acid solutions of chromation, containing a housing with a baffle separating the cathode and anode spaces, characterized in that the baffle separating the cathode and anode spaces is made of impermeable material, and activated carbon with a particle size of 0, is used as electrodes 5 to 2.0 mm, which filled the cathode and anode spaces to a height of 0.8-0.9 from the height of the partition.

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