CA2303046A1

CA2303046A1 - Method for reprocessing materials containing precious metals by means of chromatographic separation and fractionation

Info

Publication number: CA2303046A1
Application number: CA002303046A
Authority: CA
Inventors: Adalbert Prior
Original assignee: Individual
Current assignee: ALP Technology AG
Priority date: 1997-09-11
Filing date: 1998-08-28
Publication date: 1999-03-18
Also published as: ATA153497A; RU2213793C2; ZA988144B; EP1012350A1; WO1999013115A1; DE59811549D1; EP1012350B1; AU8963998A; AT405841B

Abstract

The invention relates to a method for reprocessing materials containing precious metals especially from metallurgic primary concentrates in which the materials are subjected to an increased temperature in the sequence of an oxidized treatment, a reducing treatment and a chlorination by the application of gaseous treatment media. Gold and the platinum group metals remain as residual matter with the characteristic that the residual matter is subjected to oxidized acid leaching. The gold portion is chromatographically separated first from the liquid phase and the remaining liquid is then chromatographically fractionated into the individual platinum group metals, whereby the fractionation is carried out by means of relative movement between a particle bed in the form of a cylinder jacket and at least one output position for the liquid.

Description

The present invention relates to a process for dressing materials containing precious metals, in particular metallurgical primary concentrates, wherein the materials are subjected to an oxidising treatment, a reducing treatment and chlorination using gaseous treatment media in this order at elevated temperatures, gold and the platinum group metals remaining in the residue.
This method is known to specialists as the chloroxomate process and is described in WO 96/17097. Its aim is to eliminate the accompanying metals and other contents from raw materials containing gold and platinum group metals in the gaseous phase, so that what finally remains is a residue enriched in gold and platinum group metals.
The raw materials usually are concentrates resulting from the smelting of Ni, Cu or Zn, and contain for instance S, Se, Ag, Te, Cu, Ni, As, Sb, and Pb as accompanying metals and impurities, respectively. First the material is treated with oxidising gas (oxygen or oxygen-containing gas mixtures, as for instance 20°/° O~ in inert gas or in air) at 200 to 800, preferably 400 to 500°C, in the course of which S and Se are primarily eliminated, but metal oxides are formed and volatile oxygen compounds are eliminated as well.
Scavenging with an inert gas, for instance N~ and/or CO~, is followed by treatment with reducing gas (hydrogen or hydrogen-containing gas, for instance nitrogen with at least 1 °,~° HZ) at 200 to 1000, preferably 600 to 800°C, primarily in order to reduce previously formed metal oxides to metal again. Subsequently it is again possible to scavenge with an inert gas, and finally chlorination is carried out with chlorine gas at 800 to 1300, preferably 900 to 1150 °C, in the course of which volatile chlorides (e.g.
of Cu, Ni, Ag) escape. After cooling down of the material washing is carried out in order to eliminate non-volatile chlorides, and a residue is obtained which is a concentrate of gold and platinum group metals also including SiOZ, for instance.
According to the invention the residue is submitted to oxidative leaching with acid, the gold is first separated from the liquid phase by chromatography, and the remaining liquid is subsequently Fractionated into the individual platinum group metals by chromatography, fractionation being carried out under relative movement between a particle bed in the form of a cylinder jacket and at least one place for applying the liquid.
Oxidative leaching with acid is advantageously carried out with hydrochloric acid containing chlorine gas, or for instance with hydrochloric acid and HZOZ or, as usual, with aqua regia, gold and the platinum group metals being dissolved.
From this solution the gold is first separated oft by chromatography in known fashion.
Vinylstyrene resins, in particular Amberlite XAD7, are known as ion exchange resins selective for gold.
Following the removal of gold, the remaining liquid is fractionated into the individual platinum group metals by means of chromatography, fractionation being carried out under relative movement between a particle bed taking the form of a cylinder jacket and at least one site for the application of the liquid.
The chromatographic technique wherein relative movement is provided between a particle bed taking the form of an upright cylinder jacket and at least one site for the application of liquid feeding material, arranged at the head thereof, the individual components passing the particle material in spirally wound paths and leaving in various circumferential regions along the lower periphery of the cylinder jacket, is a continuous process and is called annular chromatography. The international abbreviation for continuous annular chromatography is CAC.
Known apparatus for CAC include devices wherein the particle bed is immobile as well as those wherein the particle bed rotates with respect to sites) of application and collection sites. An example for reference describing devices of the second type in detail as well as giving a review of the different methods of chromatography is EP-A-of Union Oil of California.

Surprisingly, it has been found that this technique in combination with the chloroxomate process not only results in excellent product yields, but also in excellent separation.
Particularly well suited for fractionating the platinum group metals are organic ion exchangers in the form of macroporous spheric gels, in particular those on the basis of 1 ) dextran-type polysaccharides, 2) cross-linked polymethacrylates, and 3) cross-linked polyacrylamides.
Examples for products of item 1 ) are the Sephadex G ion exchangers of Pharmacia (Sweden), which are dextranes cross-linked with epichlorohydrin. Examples for products of item 2) are Toypearl HW ion exchangers of Tosohaas (Japan, USA), which are polymethylacrylates cross-linked with ethylene glycol. Examples for products of item 3) are Biogel P ion exchangers of Biorad ILSA) which are copolymerisates of acrylamide and N,N'methylene-bis-acrylamide.
The first stage of the process according to the invention, i.e, the treatment of the basic material in gaseous phase, results in a weight loss of 30 to 35 °,o -about 95 °/° of the accompanying metals are eliminated in the course of it. A loss of gold of about 2 % and a loss of palladium of about 0,5 to 1 °~ is inevitable here as well.
Practically no losses are incurred at the subsequent chromatographic removal of gold and chromatographic fractionation of platinum group metals - the precious metal content of the column effluents is below 50 ppm, the effluents being recycled, of course.
For CAC fractionation of the platinum group metals it is advantageous to bring the feed to an oxidation potential of at least 700 mV, in particular 800 to 1200 mV, in order to guarantee that l,n is converted to I,'~. This oxidation can be done chemically, as usual, or electrochemically in the feeder head of the C,AC column (anodic oxidation).
xmI
Basic material: precious metal concentrate "Impala Fe-Grain"
1 ) Chloroxomate stage: Finely ground concentrate was pelleted with 1,56 % by weight of corn starch. The pellets were thermally treated under gas scavenging as follows:
Table 1 time (minutes) gas flow rate (I/h)temperature (C) -1 ~ (heating) N, ~ 15 450 -15 ~ N, ~ 15 450 j -15 I '~=~'H= 550 ' 15 (each) -15 N, 15 550 I

-30 O~ 25 550 -15 j N_ ~ 15 850 i -->5 i N_/H, i 15 (each) 850 I -10 (heating)N= ~ 15 1050 ~
I

-160 CI,iN, ~ footnote 1050 -15 ~ N_ i 15 800 t -15 i N=/H, 15 (each) 800 i -90 I N, i 10 room temperature Footnote: for 30 min N=:CI, = 15:25 I/h, then for 130 min CI~ for 5 min each at 161/h, in between each time N, for 1 min at 50 I/h.
The following were observed: when heating to 450°C white vapours, and at 450°C
dehydration; during the oxidation treatment white vapours; during treatment with Hz/Nz _4_ at 850 °C first white, then red, then dark-brown vapours as well as dehydration; and during CI, treatment light brownish-grev vapour. The weight loss was 45,9 °/o by weight.
?) Oxidative leaching of the residue with acid: The residue was boiled in HCI
conc.
under reflux for 3 hours while passing CI, therethrough. After 3 hours the potential of the solution was measured to be 1053 mV. The solution was separated from the undissolved matter by filtration, diluted with water 1:1, and the gold content was removed by passing the solution over an ,~mberlite XAD7 column. The remaining solution was again oxidised by boiling under reflux for 2 hours while bubbling CIZ
therethrough and, at 1 ml/min, applied as teed onto a CAC column which had been packed with Toyopearl HW 40 F, and eluted with 1 mol/I HCI (15 ml/min).
Type: bed rotates with respect to teed and fraction collector bed thickness: 0,65 cm bed height: 38,0 cm bed cross-section: 24,4 cmz rotation: 95 °/h Two eluate fractions were removed at the bottom of the column - the first at an angle of approximately 70°, and the second at an angle of approximately 140° with respect to the feeding site, which fractions have the following composition as compared to the teed, given in mg/I:

Table 2 basic material lmgtl) j 1 st 2nd fraction fraction (mg/I) (mg/I) .fig 'S7 < 1 24 i Ru 50;4 267 104 I

,~u c . <1 <1 Pd 1-1991 < 1 4230 Pt 11516 <1 <1 I

Ir 3382 172 89 Rh 9485 5159 < 1 Fe ~9 1 < 1 Cu 59 i 17 < 1 ' Ni -+6 ; 28 < 1 i Co ? <1 <1 Pb i 3 ; G1 <1 Zn 1 ~ 2 < 1 Si -3 ; 2 6 Se ~ 1 i 5 g Te i7 I 3 <1 .~~s ? 0 ~ < 1 < 1 i P '-t i 8 3 Re ~ 4 i <1 <1 It can be seen that rhodium moves into the first fraction and palladium moves into the second fraction, these two metals thus being separable from each other in this mode. Pt remains in the column.

Claims

Claims:

1. A method for dressing materials containing precious metals, in particular metallurgical primary concentrates, wherein the materials are subjected to an oxidising treatment, a reducing treatment and chlorination using gaseous treatment media in this order at elevated temperatures, gold and the platinum group metals remaining in the residue, characterised in that the residue is subjected to oxidative leaching with acid, in that the gold is first separated from the liquid phase by chromatography, and in that the remaining liquid is then fractionated into the individual platinum group metals by chromatography, while carrying out fractionation under relative movement between a particle bed taking the form of a cylinder jacket and at least one application site for the liquid.

2. The method according to claim 1, characterised in that the gold is separated on a vinylstyrene resin.

3. The method according to claim 1 or claim 2, characterised in that fractionation is carried out at a gel of a dextran-type polysaccharide, at a cross-linked polmethacrylate gel, or at a cross-linked polyacrylamide gel.

4. The method according to any of claims 1 to 3, characterised in that the oxidative leaching with acid is carried out with hydrochloric acid containing chlorene gas.

5. The method according to any of claims 1 to 4, characterised in that the remaining liquid is oxidised to a redox potential higher than about 700 mV, in particular 800 to 1200 mV, before fractionation.

6. The method according to claim 5, characterised in that oxidation is carried out in an electrochemical fashion.