RU2340708C1 - Electrode for electrochemical extraction of metals from solutions of their salts - Google Patents

Abstract

FIELD: electricity; chemistry.

SUBSTANCE: electrode is made of tape from graphitised carbon current-conducting material. At that it contains sections from non-current-conducting chemically resistant cloth. Carbon tape is made of sections, ends of which are connected with sections from non-current-conducting chemically resistant cloth with creation of electrode in the form of closed ring. Ends of carbon tape sections and sections from non-current-conducting chemically resistant cloth connected into closed ring form Mobius band. As non-current-conducting chemically resistant cloth polypropylene cloth may be used. Butte ends of carbon tape sections connected by sewing to sections from polypropylene cloth may be fixed with fluoroplastic adhesive tape.

EFFECT: increase of service life in stationary mode without destruction in aggressive chemical mediums in one device with different electric modes simultaneously.

5 cl, 5 dwg, 2 ex

Description

The invention relates to electrochemistry, is intended for electrochemical extraction of metals from solutions of their salts. Such metals include, for example, copper, silver, gold, platinoids, rare metals.

Known electrodes made of carbon graphite materials used in the cathode chambers of electrolyzers for the extraction of metals, for example, noble, from salt solutions, which are made in the form of carbon graphite plates (patent RU 2021394 C1, IPC5 C25C 7/00, 10/15/1994) or in the form of carbon fiber material, for example, graphitized batting (patent RU 2248413 C2, MPK7 C25C 7/02, 03/20/2005), as well as in the form of tapes of carbon-graphite electrically conductive fibrous material (patent RU 2255152 C1, IPC7 D01F 11/16, 06/27/2005).

Also known is a cathode for use in an electrolyzer for electrochemical extraction of metal from an aqueous solution having a deposition surface with a set of alternating ridges and depressions (application RU 2005115463 A, IPC7 C25C 1/00, 10.27.2005).

The closest analogue of the claimed invention is a carbon graphite electrode made in the form of a fibrous tape, placed in a zigzag pattern between the walls of the cathode chamber of the electrolyzer and current leads, used to extract metals from solutions of their salts (patent RU 2054055 C1, C25C 7 / 02.10.02.1986) - prototype.

A disadvantage of the known technical solution is the unsatisfactory completeness of extraction of the target metal, as well as the limited life of the electrode.

The technical result when using the claimed invention is to increase its service life in a stationary mode without destruction in aggressive chemical environments in one device with different electrical modes at the same time.

The specified technical result is achieved by the fact that the electrode for the electrochemical extraction of metals from solutions of their salts is made of graphitized carbon conductive tape containing sections of a non-conductive chemically resistant fabric; while the ends of the carbon tape are connected in a closed ring; said ends may be connected by rotation.

Polypropylene fabric is used as a non-conductive chemically resistant fabric; sections of polypropylene fabric are connected to the carbon tape by stitching; the ends of the carbon tape stitched with polypropylene fabric are fixed (glued) with fluoroplastic adhesive tape.

The invention is illustrated by drawings, where:

figure 1 shows a diagram of the electrode, a General view;

figure 2 depicts a fragment of an electrode illustrating the connected sections of a carbon conductive tape and conductive fabric;

figure 3 shows a connection diagram of sections of polypropylene fabric and carbon tape;

figure 4 shows the electrode in the form of a Mobius strip;

figure 3 shows a diagram of an installation for electrochemical extraction of metals from solutions of their salts.

The electrode for the electrochemical extraction of metals from solutions of their salts (FIGS. 1, 2) is made in the form of a closed ring of graphitized carbon conductive tape 1 containing sections 2 of a non-conductive chemically resistant fabric, for example, polypropylene. The ends of the carbon tape can be connected in a ring with the rotation of the connected ends relative to each other by 180 ° with the formation of the Mobius strip (figure 4).

The length of the sections of the carbon tape L (Fig. 1) between the sections of polypropylene fabric is determined by the design features of the device, the electrolytic cell in which it is used, and the width m (Fig. 2) is determined by the volume of the processed initial solution of metal salts.

To fix the carbon filaments of the carbon tape 1, its electrical insulation and more durable adhesion of the stitching, the ends of the tape are sealed with fluoroplastic adhesive tape 3 and connected to the polypropylene fabric by stitching with polyester threads 4 (Fig.3). The distance n (figure 2) between the connected ends of the graphite tape is 0.5-1.0 cm, which is necessary and sufficient to interrupt the current in different parts of the electrode.

The work of the electrode for the extraction of metals from a solution of their salts (electroextraction) is as follows.

The electrode 1 is forcibly pulled through an installation containing electrolytic baths 5, 6, 7, 8 with a predetermined linear speed by means of pulling rollers 9. The stitching of the electrode sections must therefore ensure the adhesion of the connected ends, be hydrophobic and chemically stable in the solutions used.

The initial solution containing the ions of the target metal is fed into the electrolytic bath 5 (Fig. 5), in which the cathode is a portion of the claimed electrode 1, which serves as the counter electrode of the stationary electrode (anode) of the bath made of a carbon graphite fabric ribbon. When passing a direct current of a given value in the galvanostatic mode, the value of which is lower than the limiting current of the extracted metal in this solution, the target ions are restored to the metal at the cathode and the initial solution is depleted of this metal ions. Next, the carbon graphite tape 1 with the extracted metal enters the bath 6, which is a wash with prepared running water, and after leaving the bath 6, the electrode is dried with hot air 10. To continue the process of extracting the metal from the solution, the carbon tape 1 is pulled through the electrolytic bath 7, into in which the extracted metal is transferred from the carbon tape 1 to the cathode of the bath, and for subsequent washing, the carbon tape is pulled through the bath 8 with prepared running water and then using their rollers 9 are again sent to the bath 5 with the initial solution. The electric current is supplied to the electrolytic baths through the upper graphite rollers 11 and counter electrodes 12, which in the electrolytic baths, except the final one, are made of carbon graphitized material, and in the final electrolytic bath, they are made of carbon graphitized material or from a metal foil similar to the metal to be extracted. Recoverable metal in the final electrolytic bath is accumulated on cathodes of carbon fabric or on metal plates similar to the recoverable metal, made, for example, in the form of cassettes or rolls.

In the stationary electrolysis mode, the depletion of the solution by the ions of the target metal is made up for by the continuous supply of the initial solution.

When ions of different metals are in solution, ions of more positive metals will be reduced first. Thus, at a given current mode, target metals can be selectively extracted.

After one or two, and, if necessary, more stages of extracting the target metal from the salt solution, this portion of the electrode enters the bath, in which, as a counter electrode, it is the anode. The metal under the influence of direct current is oxidized and passes from it (the anode) to the solution, and then is restored at the cathode from the foil of this metal or from carbon fabric.

The accumulation of metal at the cathode can occur arbitrarily long, however, the amount of metal deposited on the declared electrode must be such that it does not precipitate when passing through rotating rollers, and is determined by the speed of drawing through the apparatus under other constant conditions.

The process of extracting metals from their solutions using the claimed electrode is illustrated by examples.

Example 1. The initial solution contains cations of three metals: palladium 0.2 g / l, copper 0.5 g / l, iron 2.0 g / l. The electrode 1 is refilled in the installation containing at least two electrolytic baths. A current is supplied to the first bath, the density of which during electroextraction of palladium is set below the current limit for ions in this solution, based on their concentration. This can significantly increase the selectivity of extraction, but with a decrease in the degree of extraction of this ion to about 90%.

After extraction of the target metal ions in the first bath, the depleted solution is sent with interruption of the jet into the second bath with a lower current value, in which approximately 90% more palladium is recovered.

The total recovery of palladium after the passage of the electrode through two electrolytic baths is about 99%. Thus, about 0.002 g / l palladium remains in solution.

Next, the electrode is pulled through the final electrolytic bath, in which palladium is electrochemically transferred to the storage electrode until a certain mass is accumulated on it.

Example 2. The initial solution of example 1 is served in the installation, increased by two baths. After extraction of palladium from the solution and its subsequent transfer to the storage electrode, the solution containing copper and iron cations is sent to the next electrolytic bath in which the electrochemical extraction of 99% copper takes place. Then the electrode is pulled through a bath in which copper is electrochemically transferred to the storage electrode (cathode).

About 0.002 g / l palladium, 0.005 g / l copper and the initial amount of iron remain in the spent solution.

The advantages of the claimed electrode are as follows:

- simplicity of design and operation;

- when connecting the ends of the claimed electrode into a ring, especially with a 180 ° rotation in the form of a Moebius tape around the longitudinal axis, the entire surface of the electrode works under the same conditions, the wear of the electrode is uniform, and its service life is increased;

- the possibility of using different current modes in different sections of the electrode;

- operation of the electrode in stationary mode.

Claims (5)

1. An electrode for the electrochemical extraction of metals from aqueous solutions of their salts, containing a tape of graphitized carbon-conductive material, characterized in that the electrode contains sections of a non-conductive chemically resistant fabric, the carbon tape is made of sections whose ends are connected by sections of a non-conductive chemically resistant fabric with the formation of an electrode in the form of a closed ring. 2. The electrode according to claim 1, characterized in that the ends of the sections of the carbon tape and sections of a non-conductive chemically resistant fabric connected in a closed ring form a Mobius strip. 3. The electrode according to claim 1, characterized in that a polypropylene fabric is used as a non-conductive chemically resistant fabric. 4. The electrode according to claim 3, characterized in that the sections of polypropylene fabric are connected to the ends of the sections of the carbon tape by stitching. 5. The electrode according to claim 4, characterized in that the ends of the ends of the sections of the carbon tape stitched with sections of polypropylene fabric are fixed with a fluoroplastic adhesive tape.

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