WO2017153547A1

WO2017153547A1 - Electrolytic refinement of raw gold

Info

Publication number: WO2017153547A1
Application number: PCT/EP2017/055604
Authority: WO
Inventors: Thorsten Koras; Revin SHANGULA
Original assignee: Thorsten Koras
Priority date: 2016-03-09
Filing date: 2017-03-09
Publication date: 2017-09-14
Also published as: EP3426825B1; PT3426825T; CN109312481B; EP3426825A1; EA036684B1; CN109312481A; DE102016104237A1; EA201892012A1; ES2811380T3; PL3426825T3

Abstract

The invention relates to a method for obtaining fine gold by the electrolytic refinement of raw gold contaminated with accompanying elements, wherein the electrolysis is performed in a bath, which is divided by a membrane impermeable to gold-containing anions into a first region having the electrolyte solution that dissociates hydrochloric acid and a second region having the electrolyte solution that dissociates sulfuric acid. The raw gold is anodically dissolved in a first step and is cathodically deposited as once-refined fine gold in a second step, and the once-refined fine gold is anodically dissolved in a third step and cathodically deposited as twice-refined fine gold (having a purity of up to 99.999%) in a fourth step. The formation of a solid silver chloride coating on the anode in the electrolyte solution is prevented or reduced by adding urea and applying ultrasound to the anode.

Description

Electrolytic refining of crude gold

The invention relates to a process for the electrochemical refining of crude gold,

Contaminated gold, hereinafter referred to as crude gold, is particularly important in the recycling of electro-technical and electronic Bayteie. Usually, by recycling (fine) gold higher purity than in the present crude gold to be obtained, crude gold is a gold alloy, which consists of fine gold and admixtures of other metals. As admixtures often occur in particular copper and possibly also silver.

One of the most well-known electrolytic processes for the production of fine gold of the highest purity grade is referred to in the literature by Wohlwill-Verfahren {after the inventor named Erich Wohlwill), in the electrolyte solution dissociated tetrachloroauric acid HAuCk (chloroauric acid) is included. The anode used is raw gold, which is dissolved. Ion transfer precipitates fine gold at the cathode,

US Pat. No. 4,612,093 B describes a process for recovering fine gold from an electrolytically dissociable crude gold anode. This method is characterized by a first electrolyte region with the anode and by a second electrolyte region with a (carbon) cathode. Both regions are separated by a semipermeable membrane that is impermeable to gold ions from the first electrolyte region toward the cathode. The electrolyte in the first electrolyte region comprises an aqueous solution with dissociated halogens and an initially oxygen-supplying additive. By adding bisulfite ions to the separated solution containing gold-containing ions, the fine gold is precipitated, see claim 8, paragraph e of US 4,612,093 B.

US Pat. No. 5,009,755 B likewise describes a process for recovering fine gold from a crude gold anode to be dissolved by electrosolation. This procedure also makes use of that anode-side region is separated by a semipermeable membrane from the cathode-side region. The aqueous electrolyte solution contains a) halogen ions, in particular dissociated ammonium chloride, which also serves to form soluble silver and copper compounds, and

b) an initially acting oxygen donor for influencing the electric potential.

The semipermeable membrane is impermeable to ions containing gold, insoluble components and abrasive oxide particles. The extraction of fine gold from the gold-containing ions in the anode-side region is carried out by adding bisulfite salts.

It is the object of the invention _. , a multi-stage, preferably two-stage process, to provide for the production of fine gold by electrolytic refining of raw gold contaminated with accompanying elements. This object of the invention is achieved by the characterizing features of claim 1 in conjunction with the preamble features.

Advantageous developments of the invention are characterized in the subclaims. Measures for the removal of non-soluble particles, in particular of chlorine compounds which form during the electrolysis, with the admixtures of silver, palladium and platinum contained in the crude gold are characterized in subclaims 3 and 4.

Further advantages, features and possible applications of the present invention will become apparent from the following description in conjunction with the embodiments illustrated in the drawings.

In the description, the claims, and the drawing, the terms and associated reference numerals used in the list of reference numerals below are used. In the drawing:

Fig. 1 representation for the first process step - Anodic dissolution of the raw gold; FIG. 2 shows the second method step - cathodic deposition of simply refined fine gold; FIG.

FIG. 3 shows the third method step - anodic dissolution of the simply refined fine gold; FIG. and

4 shows the fourth process step - cathodic deposition of twice refined fine gold. The electrolytic refining for the production of fine gold from contaminated with accompanying elements raw gold takes place in a tub 1/2 _"which is divided by a permeable for particular ion membrane 3 in a first area 1 and a second region. 2 Each area comprises an electrode A1, K2 and an electrolyte solution E1, E2. As starting elements are base metals such as copper, nickel, tin and zinc or their compounds, as noble metals are silver, palladium and platinum metals or their compounds to consider.

For the first process step, the anodic dissolution of the raw gold, see Fig. 1, in the first region 1 acting as an anode electrode A1 made of raw gold or acting as an anode loaded with raw gold scrap anode basket or acting as an anode with raw gold scrap in Contact contact rod connected to the positive pole of a voltage source for a DC circuit. This anode A1 is arranged in an aqueous electrolyte solution E1 containing dissociated hydrochloric acid and / or dissociated chloride salts. The hydrochloric acid concentration of the electrolyte solution E1 is in the range between 5 and 15%. With dissociation, the decay of a molecule, e.g. called a salt in its ionic constituents. Dissolution of common salt in an aqueous solution results in positively charged sodium ions and negatively charged chlorine ions.

In the second region 2, an electrode K2 acting as a cathode is connected to the negative pole of the voltage quenules and arranged in a dissociated sulfuric acid and / or dissociated sulfate salts containing aqueous electrolyte solution E2. The sulfuric acid concentration in the electrolyte solution E2 is about 10%,

The membrane 3 separates both electrolyte solutions E1 and E2 from each other. The raw gold anode is dissolved to form positively charged base metal containing cations and negatively charged gold containing anions (also called negatively charged gold complex anions). The membrane 3 is only permeable to positively charged cations formed in the first region 1 in the direction of the negative cathode K2 arranged in the second region 2, at which point the metal contained in the cations, optionally copper, for example, precipitates.

In the electrolyte solution E1 in the first region 1, negative charged gold-containing anions are enriched.

As an anode in area 1 in the first process step, a so-called anode basket of electrically conductive material loaded with raw gold scrap also comes into consideration. The contact between the anode basket and the crude gold scrap must be ensured. Furthermore, a Koniaktstab in contact with the raw gold scrap can be used as an anode.

For the second method step, the cathodic deposition of simply refined fine gold, see FIG. 2, after dissolution of the raw gold in the first region 1 according to the first method step in the first region 1 in the electrolyte solution E1, a negative electrode connected to the negative pole of the voltage source. Dene acting as a cathode electrode K1 'arranged.

In the second region 2, an electrode A2, which is connected to the positive pole of the current source and acts as the anode, is arranged in the electrolyte solution E2. The precipitation of the gold from the originally negatively charged gold-containing anions takes place at the negative cathode K1 in the first area 1 as simply refined fine gold. The simply refined gold has a higher degree of purity than the gold in the raw gold anode A1 or in the raw gold scrap , In the third step, labeled "Anodic dissolution of the simply refined refined gold", the electrode K1 in the first region 1, which is coated with simply refined fine gold, is connected to the positive pole of the voltage source in the first region 1 and into the electrolyte solution containing hydrochloric acid E1 is arranged in the second area 2 an electrode K2 ', which is connected to the negative pole of the voltage source and acts as a cathode, is arranged in the electrolyte solution E2 containing sulfuric acid,

The simply refined fine gold adhered to the electrode AV is dissolved to form positively charged base metal-containing cations such as copper cations and negatively charged gold-containing anions.

The membrane 3 is only permeable to positively charged cations formed in the first region i in the direction of the negative cathode K2 'arranged in the second region 2, at which point the base metal contained in the cations precipitates.

For the fourth step "cathodic deposition of twice refined fine gold" after dissolution of the simply refined fine gold according to the third process step, the electrode K1 'acting as the cathode is connected to the negative pole of the voltage source and placed in the electrolyte solution E1 in the first region 1.

In the second region 2, the electrode A2 'acting as the anode is connected to the positive pole of the voltage source and arranged in the electrolyte solution E.2. The gold from the anions originally containing negatively charged gold in the first region 1 precipitates at the negative cathode K1 'as a double refined fine gold down. The double-refined gold has a higher degree of purity than the simply refined gold.

The first to fourth process steps according to the invention may be followed by further process steps five and six. In the fifth method step, in analogy to the third method step, the twice-refined fine gold deposited cathodically in the fifth and sixth method step would be dissolved anodically and cathodically deposited in the sixth method step in analogy to the fourth method step as triple-refined fine gold. In subsequent seventh and eighth process step analogous to the third and fourth or fifth and sixth process steps, fourfold refined fine gold can be obtained, etc. For the method according to the invention is preferably a example of the company lon-power GmbH,

Level 5, Terimaisir. Middle 18; D 85356 Munich sold as a commercially sold membrane, which consists of sulfonated tetrafluoroethylene (PTFE) polymer with ionic properties (with negatively charged SO ₃ residues). This property is circumscribed with "selectively conducting for protons and other cations (barrier effect for anions)."

Such membranes have hitherto been used for the following technical applications (citation, reference https://de.wikipedia.org/wiki/Nafion), but not for the electrolytic gold refining according to the invention:

Ion exchange membranes in the chlor-alkali electrolysis

Drying or humidification of gases due to its high selectivity and permeability to water (steam)

Proton exchange membrane in polymer electrolyte and direct methanol fuel cells Production of chromic acid and regeneration of contaminated chromium baths

Preparation of Potassium Dicyanidoaurate (-1) by Dissolution of a Gold Anode in Potassium Cyanide (KCN)

As a strongly acidic, solid catalyst

The inventive method is carried out at a temperature of about 55 degrees Celsius. The gold dissolving process steps one and three are carried out at a voltage of 5 to 6 volts with a maximum current of 30 amps; the gold depositing process steps two and four at a voltage of 2 to 4 volts and a current of 8 to 20 amperes. The addition of silver in the anodic raw gold reacts with the hydrochloric acid contained in the electrolyte E1: It forms poorly water-soluble silver chloride, which is reflected in particular as an undesirable solid coating on the raw gold anode or the raw gold scrap. This coating prevents or limits the contact of the electrolyte E1 with the raw gold anode or with the raw gold scrap and therefore hinders the electrolysis.

It has been found according to the invention that the addition of urea (carbonic acid diamide) into the electrolyte E1 influences the formation of silver chloride in such a way that now only a brittle coating forms on the raw gold anode or the raw gold scrap. This brittle In comparison with the previously solid coating of silver chloride, the coating only slightly adheres to the raw gold anode or the raw gold scrap.

This brittle coating provides a better contact of the electrolyte El with the raw gold anode or with the raw gold scrap and therefore does not limit the electrolysis process as much as is the case with silver chloride.

It has also been observed _{. "} According to the invention, the application of ultrasound to the raw gold anode A1 or of the raw gold scrap (in the anode basket or in contact with the contact rod) forms the formation of an undesirable solid coating of silver chloride on the raw gold anode or Can reduce crude gold scrap or inventively replace the only slightly adhering to the raw gold anode or the raw gold scrap brittle coating mechanically.

For this reason, according to the invention, the electrode A1 made of raw gold or the Rohgotd scrap (in the anode basket or in contact with the contact rod) is subjected to ultrasound.

For ultrasound application so-called ultrasonic vibrator elements are available as Handeisware _» mounted in a housing. This housing is so coupled via a chamber with the outer wall of the tub 1/2, that the exiting from the housing ultrasonic vibrations as lossless pass the filled with water or Giycerin chamber and can impinge on the anode in the tub 1/2. The wall of the chamber and the tub in the region of the ultrasonic vibrations passing through it consists of a material, preferably of polypropylene, which allows the ultrasound to pass through as lossless as possible. The frequency of the ultrasonic transducer elements used lays at 40 KHz. They have no direct contact with the electrolyte. As a source of the ultrasonic oscillator elements may be mentioned;

Martin-WALTER Ultrasonic Technology AG, Hardstr. 13, D-75334 Straubenhard.

From the admixed with hydrochloric acid electrolyte solution E1 optionally resulting insoluble particles such as silver chloride or the detached from the anode of the anode particles of the brittle coating are filtered out. This filtering can be done for example by means of a circulation pump. For example, filter cartridges No. NT 10 "(Article No. 11007) from Filtertechnik Jäger GmbH (Siemensstr.1, D-89264 Weissenhorn), which are available as a commercial product, may be used as the filter material These filter candles are permeable only to particles smaller than 5 micrometers , In the process steps for dissolving the crude or fine gold, a newly prepared electrolyte solution E1 with predeterminable initial proportions of hydrochloric acid and urea (carbon dioxide dia- mide) is used in each case. As a result, it can be ensured, for example, that in the dissociated hydrochloric acid-containing electrolyte E1 at the beginning of the first and third process steps, the concentration of the chloride ions is the same and that there are no different dissolution times for the gold resulting from different concentrations.

In order to prevent the electrode material dissolving reactions from occurring during the electrolysis at the electrodes by chemical processes, three titanium electrodes are used as cathode K2 in method step one and cathode K2 'in the method step. As anode A1 in process step three, as cathode K1 in process step two, as cathode K1 in process step four, as anode A2 in process step two, as anode A2 in process step four, and as anode in process step one, if it does not itself consist of crude gold, used are placed titanium electrodes.

The anode basket for receiving the raw gold scrap consists of a mesh-like mesh made of expanded titanium expanded metal.

Reference number list

1 first area

2 second area

3 membrane

½ tub

A1 anode

A2 anode

K1 cathode

K2 cathode

E1 electrolyte solution

E2 electrolyte solution

A'1 anode

Κ'1 cathode

Claims

Patent claims

1 . A process for recovering fine gold by the electrolytic refining of water contaminated with accompanying elements raw gold, wherein the electrolysis is carried out in a pan _"is divided by a permeable for particular ion membrane (3) in a first region (1) and a second region (2), each region comprising an electrode and an electrolyte solution, characterized by the following successive process steps; a) Anodic dissolution of the raw gold

In the first region (1), an electrode (A1) acting as an anode is made of raw gold or an anode basket loaded with raw gold scrap acts as an anode or a contact rod in contact with raw gold scrap acts as an anode with the positive pole of a voltage source (14). connected in a DC circuit and arranged in a dissociated hydrochloric acid and / or dissociated chloride salts containing electrolyte solution (E1), in the second region (2) acting as a cathode electrode (K2) is connected to the negative pole of the voltage source and in a dissociated sulfuric acid and / or dissociated sulphate salts containing electrolyte solution (E2), the membrane (3) separating the two electrolyte solutions (E1) and (E2), the crude gold forming cations containing positively charged base metals, as copper cations, and negatively charged gold containing anions dissolves, and wherein the membrane (3) only for positively charged in the first region (1) formed in the direction of the second region (2) arranged negative cathode (K2) is permeable, at which the base metal contained in the cations precipitates and wherein the electrolyte solution (El) in the first region (1 ) is enriched with negatively charged gold-containing anions ;. b) Cathodic deposition of simply refined fine gold

After dissolution of the crude gold in the first area (1) according to process step one is in the first region (1) in the electrolyte solution (E1) arranged as a cathode electrode (K1) connected to the negative pole of the voltage source and in the second region (2) in the electrolyte solution (E2) is one with the positive pole The electrode is connected to the current source connected as an anode electrode (A2), wherein the gold from the originally negatively charged gold-containing anions in the first region (1) at the negative cathode

K1 precipitates as simply refined fine gold with a higher degree of purity than the purity of the gold in the raw gold anode (A1) is; c) Anodic dissolution of the simply refined fine gold

The according to step two coated with simply refined fine gold electrode

(K1) is in the first region (1) acting as the anode electrode (Α1 ') connected to the positive pole of the voltage source and in the hydrochloric acid-containing electrolyte solution (E1) arranged in the second region (2) with the negative Po! the voltage source connected as a cathode electrode (Κ2 ') in the sulfuric acid-containing Eugktrolyt solution (E2) is arranged, wherein the adhering to the electrode (A1') simply refined

Fine gold is dissolved to form positively charged base metal-containing cations, such as copper cations, and negatively charged gold-containing anions, and wherein the membrane (3) only for positively charged in the first region (1) cations formed in the direction of second region (2) arranged negative cathode K2 'is permeable, at which the precipitated metal contained in the cations precipitates ;. d) Cathodic deposition of twofold refined fine gold

After dissolution of the simply refined fine gold according to method step three, the cathode electrode (KT) is connected to the negative pole of the voltage source and placed in the electrolyte solution (E1) in the first region (1), while in the second region

(2) the electrode (Α2 ') acting as an anode is connected to the positive pole of the voltage source and placed in the electrolyte solution (E2), whereby the gold from the originally negatively charged gold-containing anions in the first region (1) the negative cathode (KT) as twice refined refined gold precipitates as the degree of purity of the single refined gold precipitated in the process step two at the cathode (K1), where e) the electrolyte solution (E1) additionally contains urea (carbon dioxide diamide).

2. The method according to claim 1, dadyrch in that the membrane (3) consists of per se known sulfonated tetrafluoroethylene (PTFE) polymer with negatively charged S0 ₃ residues.

3. The method according to claim 1 or 2, characterized in that the electrode (A1) is applied from raw gold or the raw gold scrap in the anode basket or standing in contact with the contact rod raw gold scrap with ultrasound,

4. A method according to ^one of the preceding claims, characterized in that possibly formed insoluble particles such as silver chloride are filtered out of the staggered with hydrochloric acid electrolyte solution (E1),

5. The method according to any one of the preceding claims, dadyrch characterized in that in the process steps one and three for dissolution of the raw or fine gold in each case a newly prepared electrolyte solution (E1) with predeterminable initial proportions of hydrochloric acid and urea (carbonic acid diamide) is used

6. The method according to claim 1, characterized gekinnzeichnet that the cathode (K2) in step one and the cathode (Κ2 ') is made in step three of titanium, that the anode (Α1') in step three, the cathode (K1) in process step two, the cathode (K1 ') in process step four, the anode (A2) in process step two, the anode (Α2') in process step four, and the anode in process step one, if it does not itself consist of crude gold, of titanium is made, which is platinum-plated.