DE4005026A1 - Removing gold and silver from antimony ores - by reacting with ammonia under oxygen pressure and high temp. to remove noble metals in soln. - Google Patents

Abstract

Recovering Au and Ag from sulphide Sb ore or by-products of the Sb metallurgical process consists of reacting the ore with NH3 for 15 mm to 6 a at 120-200 deg C in the presence of 02 with a partial pressure of 5-30 bars. The Au and Ag passes almost completely into soln while the Sb remains in solid oxide form. The ore is initially, mechanically comminuted in a rotation mill using 100-500 kw/t. The NH3 starting concentration with respect to the sulphide sulphur content in the ore is 1:1 to 5:1. The dissolution of the Au and Ag pref takes place in the presence of Cu ions whereby the Cu ion concentration to the noble metal content is at least 1:100. The noble metal is removed from soln by adsorption on carbon or by using ion exchange material. ADVANTAGE - The noble metals are selectively removed in high yields.

Description

The extraction of gold and silver from sulfidic antimony ores and intermediates of pyrometallurgical processing usually about the roasting of the substances mentioned, wherein in essential volatile oxides of the form Sb₂O₃ arise. While doing so the precious metal content in the predominantly silicate Gait on. After grinding this gait, the precious metals become enriched by flotation and then with HCl in the presence leached from chlorine gas (Consolidated Murchison Transvaal SA). On Another way is the melting of the precious metal-containing residues the antimony ores or intermediates in a reduction furnace. This leads to the formation of a noble metal-containing metal phase and low-noble slag. Depending on the precious metal content is the Metal phase treated directly in the furnace or in a hydrofluoric acid worked up electrolysis.

A disadvantage of the mentioned method is that when roasting a part the precious metals is carried away with the dust and that thereby both the residues of the roasting and the fly ash for the Extraction of precious metals must be treated separately. The This required technical effort is determined economically from the respective antimony price, the well known Schwankun gene is subjected. Another disadvantage is the SO₂ emissions, so far for economic reasons in developing countries get into the atmosphere. Generally, it can also be determined be that the aforementioned methods due to the variety of Process steps with high precious metal losses work.

A wet chemical alternative is the cyanidic leaching edelme tallhaltiger sulfidischer Antimonerze or intermediates of the Antimony metallurgy under pressure in the presence of oxygen (Davis, D.R .; Paterson, D.B .; Griffith, D.H. C .: Antimony in South Africa, Journal of the Southafrican Inst. Min. And Met. June 1986 Pp. 173-193).  

The disadvantages of this method are:

• - multi-stage batch operation,
• High cyanide consumption (at least 20 kg / t of raw material),
• - Extremely high oxygen partial pressures (100 and 200 bar) as well
• - the need for pipe lengths up to 4000 m.

The second wet chemical method known so far for the Extraction of precious metals from sulfidic antimony ores and Zwi products is the digestion with Na₂S. Work is being done at 95 ° C and Na₂S concentrations of 280 to 300 g / l. The precious metals are accumulated in the residue, while antimony as Na₃SbS₄ goes into solution, from which it by electrolysis with a Diaphragm is obtained (Pawlek, F .: Metallurgy, Walter de Gruyter, Berlin New York 1983). This process technology could due to the high reagent requirements and the difficult controllable H₂S development does not prevail.

The object of the invention is to provide a method available which manages the precious metals, especially gold and gold Silver, largely selective of sulphidic antimony ores and Zwi by leaching to separate.

The claims 1 to 5 contain the solution of this problem. Thereafter, the sulfidic antimony ores or intermediates pyrometallurgical antimony metallurgy after a mechano- chemical pretreatment in a vibrating mill with 10-20% Ammonia (corresponding to one based on the Sulfidschwefel Initial concentration of 1: 1 to 1: 5) with an oxygen partial pressure between 5 and 30 bar and a temperature between 120 and 200 ° C after a reaction time between 15 minutes and 6 hours unlocked in one step. The precious metals gold and silver are thereby converted into solution, while the antimony content almost completely forms the oxide residue. From the ammoniakali The noble metals can be mixed with coal by adsorp tion or can selectively with the help of liquid or solid ion exchangers are extracted.  

Contrary to the doctrine is a selective ammoniacal Lau the precious metals gold and silver from sulfidic antimony ores or intermediates of antimony metallurgy at temperatures between 120 and 200 ° C and an oxygen pressure of 5 to 30 bar possible. The precious metals are in sulphidic antimony ores Intermediates of antimony metallurgy in partial submikrosko suggest adhesions. The separation of these adhesions However, with physical methods such as fine grinding is not reachable. It has now been found that by the chemical conclusion in ammoniacal solutions in the presence of oxygen the sulfidic antimony compounds via a soluble interme converted into an insoluble oxidic phase and so that the precious metals released for the reaction with ammonia become. The reaction rate can be by a before increase the decisive mechano-chemical pretreatment decisively. A complete oxidation of sulphidic antimony compounds in ammoniacal solutions could so far due to structural Reaction inhibitions can not be realized. In the erfindungsge According ammoniacal leaching causes a mechano-chemical Vor treatment structural transformations of the rhombic-dipyramidal Antimonite (Sb₂S₃) to the crypto-crystalline (X-ray amorphous) meta Stibnit (Sb₂S₃), whereby the known reaction inhibitors in the Wet chemical oxidation can be reversed. So that's the advance for a complete release of the sulphidi niche antimony ore and thereby enclosed Gold fulfilled.

As a mechano-chemical pretreatment method, the vibratory grinding due to their predominantly colliding stress at accelerations up to 15 g and point temperatures between the grinding media of more than 800 ° C is particularly suitable. At 800 ° C, the structures of sulfidic antimony ores, in particular antimonite (Sb₂S₃) are converted by thermal dissociation of elemental antimony in a X-ray amorphous state, which is compared to the crystalline form by a higher Enthalpiebe wear and thus a much better release characteristics. The effect of mechano-chemical structural transformation can be quantitatively and reproducibly detected by X-ray crystallography. The ratio of the X-ray pulses at the respective lattice plane before (I _o ) and after (I) the mechanical activation is measured. Accordingly, vibrating mills are to be regarded as physico-chemical reactors (Gock, E .: Measures for Reducing the Energy Demand in Vibratory Milling, Aufbereitungstech nik, 1979, pp. 343-347). An energy consumption of 100-350 kWh / t regrind has proven particularly advantageous in the process according to the invention.

In the context of the inventive method was gefun continue that the presence of copper ions in one concentration of 1: 100 compared to the noble metal content of the sulfidic anti Monerze and intermediates of antimony metallurgy favorable affect the precious metal yield. In the presence of copper ions The noble metal can be applied to the oxidizing ammoniaka improve leaching by a factor of 1.5.

The process scheme in Fig. 1 indicates the process according to the inventions to the invention process. Thereafter, sulfi dian antimony compounds containing the precious metals gold and silver in submicroscopic adhesions (1), a mechanochemical pretreatment by vibratory grinding (2) subjected. This mechano-chemical pretreatment improves the reactivity of the sulfidic antimony compounds in such a way that conversion into an insoluble oxidic antimony phase takes place in the subsequent oxidizing ammoniacal pressure leaching (3) via an intermediate soluble phase. As a result of structural transformation, the precious metals are released and selectively converted into solution. The addition of copper ions further improves the solubility yield. The extraction of the noble metals can then be carried out directly from the suspension by solvent extraction or adsorption on carbon (4), while the insoluble to timonoxide the pyrometallurgically recyclable residue (5) form. The recovery of the precious metals can then be carried out after stripping or desorption (6) according to the known precipitation method (7).

The method is shown below with reference to some examples:  

Example 1

An antimony-rich concentrate with:

32% Sb
0.8% Pb
0.4% Cu
0.2% Fe
50% SiO₂
45 g au / t and
20 g Ag / t

according to a mineralogical composition of about 45% Sb₂S₃, 0.9% PbS, 0.6% CuS, 0.4% FeS₂ was treated in a vibratory mill with an energy input of 100 kWh / t mechano-chemically before. The degree of structural transformation, determined by the ratio of the average X-ray diffraction intensities before (I _o ) and after (I) of the mechano-chemical pretreatment, yielded 0.3 for antimonyite and 0.6 for the accompanying minerals.

The digestion was carried out in a laboratory autoclave with a behavior between suspension and gas volumes of 1: 2.5 at one Solid concentration of 200 g / l under the following reaction conditions:

120 ° C | Temperature oxygen pressure 15 bar NH₃ starting concentration 200 g / l Cu ²⁺ addition 2 g / l reaction time 360 min

After separation solid / liquid, the following Metallausbringungen reached:

Solution: 92% Au; 93.2% Ag; 1.5% Sb; Residue: 8% Au; 6.8% Ag; 98.5% Sb.

The noble metal-containing solution was treated with activated carbon. there a gold extraction of more than 95% was achieved in 20 min.  

example 2

An antimony-rich concentrate with:

39.5% Sb
0.4% Pb
0.3% Cu
0.3% Fe
42% SiO₂
60 g au / t and
35 g Ag / t

according to a mineralogical composition of about 55% Sb₂S₃, 0.5% PbS, 0.45% CuS, 0.6% FeS₂, 42% SiO₂ was mechanochemically pretreated in a vibrating mill with an energy input of 120 kWh / t. The degree of structural transformation, determined by the ratio of the average X-ray diffraction intensities before (I _o ) and after (I) of the mechano-chemical pretreatment, yielded 0.25 for antimonite and 0.6 for α-SiO₂.

The digestion was carried out in a laboratory autoclave with the in Bei play 1 volume relations at a Feststoffkon concentration of 200 g / l under the following reaction conditions:

140 ° C | Temperature oxygen 10 bar NH₃ starting concentration 150 g / l Cu ²⁺ addition 4 g / l reaction time 90 min

After separation solid / liquid, the following Metallausbringungen achieved:

Solution: 94% Au; 96% Ag; 1.2% Sb; Residue: 6% Au; 4% Ag; 98.8% Sb.

The Au and Ag separation was carried out by solvent extraction with Kelex 100; it was an application of 96% Au and 93% Ag reached.  

example 3

An Antimonite Concentrate made by filing with:

45% Sb
0.1% Cu
0.1% Fe
34% SiO₂
65 g au / t and
30 g Ag / t

according to a mineralogical composition of about 63% Sb₂S₃ and 34% SiO₂ was crushed and then treated in a vibratory mill with an energy input of 350 kWh / t mechano-chemically before. The degree of structural transformation, expressed by the ratio of the average X-ray diffraction intensities (I / I _o ), gave 0.2 for antimonyite and 0.3 for gait α-SiO₂. The reactor used for digestion was a laboratory autoclave with the volume ratios given in the preceding examples. The concentration of solids was also 200 g / l. The following reaction conditions were used:

150 ° C | Temperature oxygen 5 bar NH₃ starting concentration 150 g / l Cu ²⁺ addition 6 g / l reaction time 60 min

After separation solid / liquid, the following spreading was achieved:

Solution: 97% Au; 96% Ag; 1% Sb; Residue: 3% Au; 4% Ag; 99% sb.

The precious metal extraction was carried out by ion exchange; there were 94% of the Au and 92% of the Ag extracted.  

example 4

The characterized in Example 3 and mechano-chemically by Vibratory grinding treated in the same way gold-containing Antimo Nitkonzentrat was in the laboratory autoclave at a solids content the suspension of 200 g / l under the following conditions included:

200 ° C | Temperature oxygen 10 bar NH₃ starting concentration 100 g / l Cu ²⁺ addition 3 g / l reaction time 15 minutes

After the separation solid / liquid the following application resulted:

Solution: 95% Au; 93% Ag; 1.4% Sb; Residue: 5% Au; 7% Ag; 98.6% Sb.

The noble metal adsorption on activated carbon took place in the same way as in Example 1.  

example 5

To the effect of mechanical pretreatment by vibratory grinding German The concentrate mentioned in Example 3 was made into a sphere crushed to 100% <20 microns and under the toughest conditions in leached with reference to the preceding examples:

200 ° C | Temperature oxygen pressure 15 bar NH₃ concentration 200 g / l Cu ²⁺ addition 6 g / l reaction time 360 min

The following output was achieved:

Solution: 38% Au; 30% Ag; 1.5% Sb; Residue: 62% Au; 60% Ag; 98.5% Sb.

Claims (7)

1. A process for the wet chemical recovery of gold and silver from sulfidic antimony ores or intermediates of antimony metallurgy characterized in that sulfidic antimony ores and intermediates of antimony metallurgy with ammonia at a reaction time of 15 minutes to 6 hours at temperatures of 120 to 200 ° C in the presence be treated by oxygen at a partial pressure of 5 to 30 bar, wherein the thus liberated gold and silver content is almost completely converted into solution, while antimony remains in oxide form in the residue. 2. The method according to claim 1, characterized in that the sulfidic antimony ores or intermediates of the anti monmetallurgie by vibratory grinding with an energy expenditure be mechanically pretreated between 100 and 500 kWh / t.   3. Process according to claims 1-2, characterized in that the initial ammonia concentration, based on the sulfide swine content of the ore or intermediate, 1: 1 to 5: 1 is. 4. Process according to claims 1-3, characterized in that the dissolution of gold and silver in the presence of copper ions he follows. 5. The method according to claim 4, characterized in that the copper ion concentration in relation to the noble metal at least 1: 100. 6. Process according to claims 1-5, characterized in that the selective separation of the dissolved noble metals from the ammoniacal solution by adsorption on carbon is made. 7. Process according to claims 1-5, characterized in that for the extraction of dissolved precious metals from the ammoniacs solid solution or liquid ion exchanger used become.