CA1317560C - Method for the precipitation of mercury by electrolysis - Google Patents
Method for the precipitation of mercury by electrolysisInfo
- Publication number
- CA1317560C CA1317560C CA000561755A CA561755A CA1317560C CA 1317560 C CA1317560 C CA 1317560C CA 000561755 A CA000561755 A CA 000561755A CA 561755 A CA561755 A CA 561755A CA 1317560 C CA1317560 C CA 1317560C
- Authority
- CA
- Canada
- Prior art keywords
- mercury
- electrolysis
- chloride
- cathode
- chlorine
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
- C25C7/02—Electrodes; Connections thereof
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
- C25C1/16—Electrolytic production, recovery or refining of metals by electrolysis of solutions of zinc, cadmium or mercury
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrolytic Production Of Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method is described for the precipitation by electrolysis of metallic mercury from an electrolyte containing Hg2Cl2 in suspension by cathodic reduction. The Hg2Cl2 reacts with chlorine evolved during electrolysis to form HgCl2. The latter is reduced at the cathode under the influence of chlorine to form liquid mercury.
A method is described for the precipitation by electrolysis of metallic mercury from an electrolyte containing Hg2Cl2 in suspension by cathodic reduction. The Hg2Cl2 reacts with chlorine evolved during electrolysis to form HgCl2. The latter is reduced at the cathode under the influence of chlorine to form liquid mercury.
Description
The invention relates to a method for ~he precipitation by electrolysis of metallic mercury from an electrolyte wherein the electrolyte containing mercury-(I)-chloridP (Hg2C12~ in suspension reacts with chlorine which oxidizes the mercury (I) chloride to soluble mercury-(II)-chloride (HgC12), which latter is cathodically reduced by electrolysis under the influence of chlorine to liquid mercury.
The method according to the invention is advantageously employed whenever mercury-(I)-chloride available in suspension is to be precipitated and to be recovered as metallic mercury. Mercury-(I)-chloride is for instance frequently recovered in processes for the purification of gases, which are obtained in a reactor with the aid of a solution of mercury-(II)-chloride.
A method of this kind has been described in European Patent Publication No. 179,040. The chlorine gas developed in electrolysis is removed from the electrolysis vessel and is conducted to a reactor wherein oxidation takes place. While this has the advantage that the chlorine gas required in the process is produced by the method itself, a particular chlor:ine gas duct between the electrolysis cell and the oxidation reactor is required.
In this connection, particular care must be taken that the poisonous chlorine gas is not blown into the environment.
By suitable measures, the chlorine gas subsequently has to be introduced, finely dispersed, into the suspension in the reactor in order to be able to carry out the oxidation reaction.
The prior publication does not described the exact construction of the electrolysis cell employedO It can be assumed however that an electrolysis cell is used which is divided by a diaphragm since the prior art according to German Auslegeschrift No. 2,011,610 advises in general to keep chlorine away from the cathode in the electrolysis process since chlorine is reduced at the .. ~
. ~ , ~317~60 cathode thereby diminishing the current yield of the metal precipitation taking place (compare in this connection particularly column 8, line 63 and following of German ~uslegeschrift No. 2,011,610).
5The present invention avoids this disadvantage.
An object of the invention is to provide a method for the precipitation of metallic mercury by electrolysis from an electrolyte including the features mentioned above, which excels by a sensibly simplified procedure in combination with a sensibly increased yield of precipitated metallic mercury.
Accordingly, the invention provides a method for the precipitation by electrolysis of metallic mercury from an electrolyte containing mercury-~I)-chloride, said method comprising: (a) providing an electrolysis cell containing an anode, a cathode and an electrolyte containing mercury-(I)-chloride, and in which chlorine developed at the anode during the course of oxidation can migrate without impediment to the cathode area of the cell; and (b) su~jecting said electrolyte to electrolysis, whereby: (1) chlorine is formed at the anode and reacts in situ with mercury-(I)-chloride to form mercu:ry~ chloride, and (2) mercury-(II)-chloride is reduced at the cathode to metallic mercury.
25Thus, the invention is characterized in that when employing an electrolysis cell wherein the chlorine developed at the anode during the course of the oxidation can migrate without any impediment into the cathode area of the cell, the chlorine developed during electrolysis in the electrolysis cell is employed in situ for the oxidation of the mercury(I)-chloride to soluble mercury-(II)-chloride.
By so proceeding, the particular flow the chlorine gas developed during the electrolysis to the oxidation reactor is dispensed with. Oxidation and electrolysis are instead carried out in one and the same electrolysis cell so that the chlorine gas developing :
~ 317~60 during the course of electrolysis can, directly and without any impediment, also migrate into the cathode area of the cell. The gaseous chlorine developing during the course of electrolysis is, in general, dissolved in the electrolyte and is transported together with the electrolyte, supported if necessary by a pump or similar device. The whole volume of the electrolyte is therefore available for the oxidation of the mercury~ chloride to mercury-(II)-chloride by means of the gaseous or dissolved chlorine.
To carry out the method as described, a fixed bed electrolysis cell is advantageously employed, which does not include a separate anolyte circuit but a diaphragm preventing direct contact of the counter electrode but does not impede the material exchange. It has become known in a basic embodiment through Applicant's German Patent Specification No~ 2,622,497 and, in an improved embodiment, through German Patent Specification No. 2,904,539. A
further improved embodiment has been described in Applicant's German Patent Specificcltion No. 3,532,537. Any of these embodiments basically may be employed for tha invention, preferably using the features mentioned above.
The method according to the invention is carried out such that the electrolyte, at least in the beginning, is employed in such a concentration of mercury~ chloride and/or that the electrolysis voltage and thereby the electrolysis current, at least in the beginning, is employed at such a level that metallic mercury is precipitated at the cathode and drips off therefrom~ It can be withdrawn from the bottom of the electrolysis cell.
As the material for the cathode, iron, silver, nickel, copper, cadmium, aluminum, zinc, tin or an alloy of these metals is suitable.
Deviating from the suggestion of German Auslegeschrift No. ~,011,610 already mentioned, anodically developed chlorine is employed for oxidation of the difficultly soluble mercury-(I)-chloxide which dissolves ~1 3~7560 this salt so that the starting suspension of the electrolysis is made usable.
Experiments have shown that it might be sufficient to apply the electrolysis voltage, and hence the electrolysis current, only for a relatively short period of time at the beginning at a voltage peak, that is until a first mercury film has formed on the surface of the amalgam cathode. Subsequently, the voltage may be reduced to normal values and the mercury continues to precipitate in metallic form on the surface of the amalgam cathode. The concentration of Hg2Cl2 in the electrolyte is corresponding.
The method according to the invention ~s based on the theory that, at the anode of the electrolysis device, Cl- converts into Cl2. The Cl2 reacts with the Hg2Cl2 available in the form of a suspension and results in 2HgCl2 which is dissolved in the electrolyte.
At the cathode, HgCl2 is reduced to Hg+2 Cl .
This Cl is then available for the oxidation of the cathode.
As electrochemical equations, the following can be written:
Starting reaction (as an example only~ as to how Hg2Cl2 may be developed as a suspension in an electrolyte:
(A) Hg (gaseous) + HgCl2 (soluble) = Hg2C12 (difficultly soluble) Oxidation:
(B) Hg2C12 (difficultly soluble) + Cl2 (gaseous) = 2HgCl2 (soluble) Electrolysis.
(C) HgCl2 ~soluble) + electrical energy = Hg (liquid) + Cl2 (gaseous) Result: From Hg (gaseous) + Energy, Hg (~iquid) is obtained.
The C12 (gaseous) developed in step C is used as such, and in situ, in step B.
.. ..
1317~60 These electrochemical reactions constitute at least an approximate picture of the processes actually occurring during electrolysis. In reality, these processes may be more complicated, for instance via corresponding complexes or multi reactions.
In one embodiment, where copper was used as the cathode material, the electrolyte employed had the following composition:
45 g/l HgzCl2 as suspension 30 g/l sulfuric acid lO g/l chloride.
The anodic current dansity was 300 A/m2. Since an expanded metal was employed, this value is based on the total area inclusive of the gaps. The cathodic current density also amounted to 300 A/m2.
The initial content of water-insoluble Hg2Cl2 was equal to the concentration already mentioned of the suspension of 45 g/l. The initial current density amounted to 600 A/cm2.
The method according to the invention is advantageously employed whenever mercury-(I)-chloride available in suspension is to be precipitated and to be recovered as metallic mercury. Mercury-(I)-chloride is for instance frequently recovered in processes for the purification of gases, which are obtained in a reactor with the aid of a solution of mercury-(II)-chloride.
A method of this kind has been described in European Patent Publication No. 179,040. The chlorine gas developed in electrolysis is removed from the electrolysis vessel and is conducted to a reactor wherein oxidation takes place. While this has the advantage that the chlorine gas required in the process is produced by the method itself, a particular chlor:ine gas duct between the electrolysis cell and the oxidation reactor is required.
In this connection, particular care must be taken that the poisonous chlorine gas is not blown into the environment.
By suitable measures, the chlorine gas subsequently has to be introduced, finely dispersed, into the suspension in the reactor in order to be able to carry out the oxidation reaction.
The prior publication does not described the exact construction of the electrolysis cell employedO It can be assumed however that an electrolysis cell is used which is divided by a diaphragm since the prior art according to German Auslegeschrift No. 2,011,610 advises in general to keep chlorine away from the cathode in the electrolysis process since chlorine is reduced at the .. ~
. ~ , ~317~60 cathode thereby diminishing the current yield of the metal precipitation taking place (compare in this connection particularly column 8, line 63 and following of German ~uslegeschrift No. 2,011,610).
5The present invention avoids this disadvantage.
An object of the invention is to provide a method for the precipitation of metallic mercury by electrolysis from an electrolyte including the features mentioned above, which excels by a sensibly simplified procedure in combination with a sensibly increased yield of precipitated metallic mercury.
Accordingly, the invention provides a method for the precipitation by electrolysis of metallic mercury from an electrolyte containing mercury-~I)-chloride, said method comprising: (a) providing an electrolysis cell containing an anode, a cathode and an electrolyte containing mercury-(I)-chloride, and in which chlorine developed at the anode during the course of oxidation can migrate without impediment to the cathode area of the cell; and (b) su~jecting said electrolyte to electrolysis, whereby: (1) chlorine is formed at the anode and reacts in situ with mercury-(I)-chloride to form mercu:ry~ chloride, and (2) mercury-(II)-chloride is reduced at the cathode to metallic mercury.
25Thus, the invention is characterized in that when employing an electrolysis cell wherein the chlorine developed at the anode during the course of the oxidation can migrate without any impediment into the cathode area of the cell, the chlorine developed during electrolysis in the electrolysis cell is employed in situ for the oxidation of the mercury(I)-chloride to soluble mercury-(II)-chloride.
By so proceeding, the particular flow the chlorine gas developed during the electrolysis to the oxidation reactor is dispensed with. Oxidation and electrolysis are instead carried out in one and the same electrolysis cell so that the chlorine gas developing :
~ 317~60 during the course of electrolysis can, directly and without any impediment, also migrate into the cathode area of the cell. The gaseous chlorine developing during the course of electrolysis is, in general, dissolved in the electrolyte and is transported together with the electrolyte, supported if necessary by a pump or similar device. The whole volume of the electrolyte is therefore available for the oxidation of the mercury~ chloride to mercury-(II)-chloride by means of the gaseous or dissolved chlorine.
To carry out the method as described, a fixed bed electrolysis cell is advantageously employed, which does not include a separate anolyte circuit but a diaphragm preventing direct contact of the counter electrode but does not impede the material exchange. It has become known in a basic embodiment through Applicant's German Patent Specification No~ 2,622,497 and, in an improved embodiment, through German Patent Specification No. 2,904,539. A
further improved embodiment has been described in Applicant's German Patent Specificcltion No. 3,532,537. Any of these embodiments basically may be employed for tha invention, preferably using the features mentioned above.
The method according to the invention is carried out such that the electrolyte, at least in the beginning, is employed in such a concentration of mercury~ chloride and/or that the electrolysis voltage and thereby the electrolysis current, at least in the beginning, is employed at such a level that metallic mercury is precipitated at the cathode and drips off therefrom~ It can be withdrawn from the bottom of the electrolysis cell.
As the material for the cathode, iron, silver, nickel, copper, cadmium, aluminum, zinc, tin or an alloy of these metals is suitable.
Deviating from the suggestion of German Auslegeschrift No. ~,011,610 already mentioned, anodically developed chlorine is employed for oxidation of the difficultly soluble mercury-(I)-chloxide which dissolves ~1 3~7560 this salt so that the starting suspension of the electrolysis is made usable.
Experiments have shown that it might be sufficient to apply the electrolysis voltage, and hence the electrolysis current, only for a relatively short period of time at the beginning at a voltage peak, that is until a first mercury film has formed on the surface of the amalgam cathode. Subsequently, the voltage may be reduced to normal values and the mercury continues to precipitate in metallic form on the surface of the amalgam cathode. The concentration of Hg2Cl2 in the electrolyte is corresponding.
The method according to the invention ~s based on the theory that, at the anode of the electrolysis device, Cl- converts into Cl2. The Cl2 reacts with the Hg2Cl2 available in the form of a suspension and results in 2HgCl2 which is dissolved in the electrolyte.
At the cathode, HgCl2 is reduced to Hg+2 Cl .
This Cl is then available for the oxidation of the cathode.
As electrochemical equations, the following can be written:
Starting reaction (as an example only~ as to how Hg2Cl2 may be developed as a suspension in an electrolyte:
(A) Hg (gaseous) + HgCl2 (soluble) = Hg2C12 (difficultly soluble) Oxidation:
(B) Hg2C12 (difficultly soluble) + Cl2 (gaseous) = 2HgCl2 (soluble) Electrolysis.
(C) HgCl2 ~soluble) + electrical energy = Hg (liquid) + Cl2 (gaseous) Result: From Hg (gaseous) + Energy, Hg (~iquid) is obtained.
The C12 (gaseous) developed in step C is used as such, and in situ, in step B.
.. ..
1317~60 These electrochemical reactions constitute at least an approximate picture of the processes actually occurring during electrolysis. In reality, these processes may be more complicated, for instance via corresponding complexes or multi reactions.
In one embodiment, where copper was used as the cathode material, the electrolyte employed had the following composition:
45 g/l HgzCl2 as suspension 30 g/l sulfuric acid lO g/l chloride.
The anodic current dansity was 300 A/m2. Since an expanded metal was employed, this value is based on the total area inclusive of the gaps. The cathodic current density also amounted to 300 A/m2.
The initial content of water-insoluble Hg2Cl2 was equal to the concentration already mentioned of the suspension of 45 g/l. The initial current density amounted to 600 A/cm2.
Claims (4)
1. A method for the precipitation by electrolysis of metallic mercury from an electrolyte containing mercury-(I)-chloride, said method comprising:
(a) providing an electrolysis cell containing an anode, a cathode and an electrolyte containing mercury-(I)-chloride, and in which chlorine developed at the anode during the course of oxidation can migrate without impediment to the cathode area of the cell; and (b) subjecting said electrolyte to electrolysis, whereby:
(1) chlorine is formed at the anode and reacts in situ with mercury-(I)-chloride to form mercury-(II)-chloride, and (2) mercury-(II)-chloride is reduced at the cathode to metallic mercury.
(a) providing an electrolysis cell containing an anode, a cathode and an electrolyte containing mercury-(I)-chloride, and in which chlorine developed at the anode during the course of oxidation can migrate without impediment to the cathode area of the cell; and (b) subjecting said electrolyte to electrolysis, whereby:
(1) chlorine is formed at the anode and reacts in situ with mercury-(I)-chloride to form mercury-(II)-chloride, and (2) mercury-(II)-chloride is reduced at the cathode to metallic mercury.
2. A method according to claim 1, in which a fixed-bed electrolysis cell is employed.
3. A method according to claim 1 or 2, in which iron, silver, nickel, copper, cadmium, aluminum, zinc, tin or an alloy of these metals is used as the cathode material.
4. A method according to claim 1 or 2, in which the mercury-(I)-chloride in the electrolyte is formed by oxidation of metallic mercury in a gas with mercury-(II)-chloride.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3709359.2-24 | 1987-03-21 | ||
| DE19873709359 DE3709359A1 (en) | 1987-03-21 | 1987-03-21 | METHOD FOR DEPOSITING MERCURY BY ELECTROLYSIS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1317560C true CA1317560C (en) | 1993-05-11 |
Family
ID=6323699
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000561755A Expired - Fee Related CA1317560C (en) | 1987-03-21 | 1988-03-17 | Method for the precipitation of mercury by electrolysis |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0283785B1 (en) |
| JP (1) | JPS63266085A (en) |
| KR (1) | KR880011373A (en) |
| AT (1) | ATE76450T1 (en) |
| CA (1) | CA1317560C (en) |
| DE (2) | DE3709359A1 (en) |
| ES (1) | ES2031941T3 (en) |
| GR (1) | GR3005241T3 (en) |
| IN (1) | IN168897B (en) |
| PT (1) | PT87018B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5226545A (en) * | 1992-10-19 | 1993-07-13 | General Electric Company | Extraction of mercury and mercury compounds from contaminated material and solutions |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT11882B (en) * | 1901-12-24 | 1903-05-11 | Siemens Ag | |
| CA931110A (en) * | 1969-03-11 | 1973-07-31 | A. Carlson Gordon | Recovery of metals from solution |
| DD160806A1 (en) * | 1980-08-01 | 1984-03-14 | Buna Chem Werke Veb | PROCESS FOR PROCESSING MICRO-LIQUID ACTIVE CARBON |
| NO157543C (en) * | 1984-10-19 | 1988-04-06 | Norzink As | PROCEDURE FOR PURIFICATION OF MERCURY OIL GASES AND RECOVERY OF THE MERCURY OIL IN METALLIC FORM. |
-
1987
- 1987-03-21 DE DE19873709359 patent/DE3709359A1/en not_active Ceased
-
1988
- 1988-03-03 EP EP88103269A patent/EP0283785B1/en not_active Expired - Lifetime
- 1988-03-03 DE DE8888103269T patent/DE3871202D1/en not_active Expired - Fee Related
- 1988-03-03 ES ES198888103269T patent/ES2031941T3/en not_active Expired - Lifetime
- 1988-03-03 AT AT88103269T patent/ATE76450T1/en not_active IP Right Cessation
- 1988-03-14 IN IN214/CAL/88A patent/IN168897B/en unknown
- 1988-03-17 CA CA000561755A patent/CA1317560C/en not_active Expired - Fee Related
- 1988-03-17 KR KR1019880002842A patent/KR880011373A/en not_active Application Discontinuation
- 1988-03-18 PT PT87018A patent/PT87018B/en not_active IP Right Cessation
- 1988-03-18 JP JP63063739A patent/JPS63266085A/en active Pending
-
1992
- 1992-07-21 GR GR920401575T patent/GR3005241T3/el unknown
Also Published As
| Publication number | Publication date |
|---|---|
| PT87018A (en) | 1988-04-01 |
| DE3709359A1 (en) | 1988-09-29 |
| DE3871202D1 (en) | 1992-06-25 |
| PT87018B (en) | 1992-06-30 |
| ES2031941T3 (en) | 1993-01-01 |
| JPS63266085A (en) | 1988-11-02 |
| GR3005241T3 (en) | 1993-05-24 |
| KR880011373A (en) | 1988-10-28 |
| EP0283785A1 (en) | 1988-09-28 |
| EP0283785B1 (en) | 1992-05-20 |
| IN168897B (en) | 1991-07-06 |
| ATE76450T1 (en) | 1992-06-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |