AU758690B2

AU758690B2 - Method of extraction of noble metals

Info

Publication number: AU758690B2
Application number: AU77469/98A
Authority: AU
Inventors: Nikolai Dr Zontov
Original assignee: Clean Teq Pty Ltd
Current assignee: Clean Teq Pty Ltd
Priority date: 1998-07-22
Filing date: 1998-07-22
Publication date: 2003-03-27
Anticipated expiration: 2018-07-22
Also published as: AU7746998A

Description

AUSTRALIA

Patents Act 1990 PROVISIONAL SPECIFICATION Applicant(s) Clo r-, RTfeC eeRpeRATYe. L.t) A.C.N. 077 848 116 Invention Title: METHOD OF EXTRACTION OF NOBLE METALS The invention is described in the following statement: 2 Method of extraction of Noble Metals This invention is concerned with extraction of metals from ore and specifically deals with hydrometalurgy of noble metals. The method can be used for extraction of gold, silver, platinum and other metals The currently used methods of extraction of noble metals include cyanidation of ore, separation by filtration of solid and liquid phases or decantation washing of a solid phase, aeration of a received liquid phase, cementation of gold using zinc dust, filtration of cemented precipitate, remelting of cemented precipitate of unpurified gold. The disadvantages of the known methods include complexity of the apparatus used, high expenditure of chemical reagents and low percentage of noble metal extraction.

Another known method for extraction of noble metals includes cyanidation of materials that contain noble metals using cyanide solution. The method also involves sorption of noble metals on activated carbon, dissorption of metals from saturated carbon using cyanide solutions and extraction of metals from 25 commercial desorpent by electrolysis.

Disadvantages of the known methods include: low levels of extraction of noble metals 30 (especially when extracting metals from hard-opening ores clay, carbon containing ore, sulphide containing ore and other ores) high expenditure on reagents and energy H:\HelenF\Keep\77469.98 RTEC.doc 20/9/01 3 high expenditure on reagents and energy Another known method of noble metal extraction includes cyanidation of material (containing noble metals) with cyanide solutions, sorption of noble metals using ionexchange resin, desorption of noble metals with acidic thiourea solution and further extraction of noble metals from commercial eluates using known methods (such as electrolysis, precipitation with metals of higher electro-negativity or precipitation of hydroxides of noble metals). Commonly, the relevant technology uses resin known commercially under the name of Duolite A- 161.

15 The disadvantages of the known method is low level of extraction of noble metals (due to the low selectivity of the resin used) and high expenditure of reagents and energy.

The main purpose of this invention is to increase the level of metal extraction and to decrease expenditure of reagents and energy.

At least part of the aim may be achieved by using ionexchanging resin received on styrene and divinylbenzene with further chloro-methylation and amination.

\\MELBO1\homeS\ann\Keep\Perm\patent 2.doc 27/03/97 4 Typically the resin has the following structural formula: -CH-CH-- -CH-CH-- -CH-CH-- 2 2 X- -C -CH- 2 H2 m N n H p

H

3 C CH 3 H CH 3 Where m n p 10-12 68-78 12-20 The extraction of noble metals, for example gold, silver, platinum and others is preferably conducted in the following manner.

Materials containing noble metals such as ore, tails of flotation, concentrates and the like may be treated with cyanide solutions with concomitant expense. Then the pulp is sent to the cascade of pachucas where it contacts a current of the resin described above. As the 15 pulp is moved from the first pachuca to the last, it gives away noble metals to the resin. From the last I: pachuca, pulp (relatively free from noble metals) is directed to further treatment. Resin, while moving from the last apparatus to the first, is saturated with noble metals and the resin saturated with a maximum volume of resin is directed to a washing step(to separate it from sand and other materials) and further desorption.

Desorption of noble metals from saturated resin is V S nducted in a continuous process with an acidic 25 sution of thiourea. Noble metals are extracted from H:\HelenF\Keep\77469.98 RTEC.doc 20/901 5 desorpent using known methods such as hydroxide precipitation, precipitation using metals with higher electronegativity (including, for example, zinc, aluminium and lead) and extraction by electrolysis.

Results of comparative testing of the preferred resin and resin A-161 to determine their maximum saturation during sorption from solutions are shown in the following table.

Conditions of testing: time of contact 24hrs ratio of resin to solution 1:10,000 a.

Solution Nol(mg/L) Au 13.5 Zn 7.3 Fe 7.8 Ni 4.0 Cu CN mg Au Fe Cu Zn Ni metal/g of resin Preferred 28.6 3.0 4.8 13.6 5.2 resin A-161 26.7 25.5 17.8 27.1 11.7 \\MELB01\homeS\ann\Keep\Perm\patent 2.doc 27/03/97 6 Solution No 2 Au 13.0 Fe 7.7 Cu Ag 110 Zn 7.3 Ni 3.9 mg Au Ag Fe Zn" Cu Ni metal/g resin Preferred 19.3 28.8 1.9 11.9 2.1 3.9 resin A-161 15.7 27.8 20.4 21.2 11.8 5 As seen from the results obtained, the preferred resin is superior to resin A-161 as it has higher selectivity.

The preferred resin adsorbs mainly noble metals and tends not to adsorb harmful admixtures; the content of admixtures in saturated preferred resin is almost 10 times less than in resin A-161.

Furthermore, sorption of noble metals and admixtures (metals) was tested and investigated. The tests were carried out on specifically created samples of resins having different ratios of resin structural components.

Conditions of tests: ratio of resin to solution 1: 10,000 time of contact 24hours Solution mg/L Au 1.25 Fe 5.2 Cu Zn 3.2 Ni 3.1 \\MELBOI\home$\an\Keep\Perm\patent 2.doc 27/03/97 7 ratio of components m:n:p 78:10:12 72:12:16 69:11:20 78:8:14 67:11:22

I

mg of metal /g of resin Au Fe 17.82 17.78 17.90 16.5 16.3 3.42 3.44 3.39 15.3 16.1 5.0 4.9 4.9 11.3 11.4 3.8 3.8 3.9 12.1 11.9 4.3 4.4 4.2 9.9 10.1 As seen from the results above, the ratio of the components

-CH-CH--

-CH-CHF-

-CH-CH,--

H

2

N

H 3 C \CH 3 -CH-CH2n L is preferably m:n:p 10-12 68-78 12-20.

Typically the use of these ratios will permit the 10 maximum selectivity of resin to noble metals to be achieved. Even small variations beyond those restrictions may greatly decrease selectivity of the resin.

A preferred method of noble metal extraction was investigated using different materials.

H:\HelenF\Keep\ 77469 .98 RTEC.doc 20/9/01 8 Example 1:Extraction of gold from tailings on old gold mines.

Content of gold 3g/tonne Tailings were crushed up to 80% (0.074mm) of the initial size. Then water was added to create a pulp (liquid to solid ratio Lime was added to achieve pH 10.5. This pulp was then treated with the solution of sodium cyanide with 0.5kg/tonne expenditure of initial material.

The pulp was send through the cascade of laboratory pachucas (quantity of pachucas 10, volume of each pachuca 0.5L). Resin was moved against the flow of the pulp. Pulp entered the first pachuca and left through the last (10th). Fresh resin entered into the pachuca and saturated resin was removed from the pachuca. From each portion of saturated resin removed, a sample was taken and analysed for the content of gold. Every hour another sample was taken from the S* 20 waste pulp and analysed for the concentration of gold in both the liquid and solid phases. The content of gold in the saturated resin was 21.5 mg per g of resin. The concentration of gold in the liquid phase of the waste pulp was reduced to less than 0.Olmg/L. The concentration of gold in the solid phase of the waste pulp was reduced to 0. g/tonne. Extraction of gold from tailings was 96.6%.

Desorption of gold was conducted in dynamic conditions in a laboratory column with a volume of 100ml. A desorpent solution was passed through the column from top to bottom at a rate of 10ml/hour. The desorpent solution consisted of 20-30g/L of sulphuric acid and \\MELBOI\home$\ann\Keep\Perm\patent 2.doc 27/03/97 9 g/L of thiourea. The resulted commercial desorpent consisted of 3 v/v of sorpent with gold concentration Gold was extracted from the commercial dissorpent by electrolysis.

A comparison of the desorption of gold from resin A-161 and the preferred resin of the present invention (both saturated in comparable conditions) showed that the commercial desorpent had more than 5v/v of sorpent and the gold concentration in the commercial desorpent was 1.4 g/L. This would lead to higher expenditure of very expensive reagents for gold desorption and regeneration of ionite as well as higher expenditure of electroenergy for metal extraction to provide the final S 15 product.

Example 2: Extraction of gold from gold and silver containing ore. Content of gold is 8g/tonne, silver 120g/tonne.

Ore was crushed to the size of 80% (0.074mm) of the e initial size and water was added to create ratio of solid liquid 1 1.2. Lime was then also added to achieve a pH 10.5 11.0. The resultant pulp was treated with a solution of sodium cyanide with expenditure of 1 kg/tonne of initial ore.

Pulp was sent though the cascade of laboratory pachucas (quantity of pachucas 10, volume of each pachuca 0.5L) Resin was moved against the flow of the pulp.

From each portion of saturated resin a sample was taken and analysed for the content of gold and silver. From the waste pulp a sample was taken every hour and also \\MELB01\home$\ann\Keep\Perm\patent 2.doc 27/03/97 10 analysed for the concentration of gold and silver in both liquid and solid phases.

The content of gold in the saturated resin was 18mg/g of resin. The content of silver was 25 mg/g of resin. The concentration of gold in the liquid phase of pulp was reduced to less than 0.02 mg/L; the concentration of silver was reduced to less than 0.005mg/L. The content of gold and silver in the solid phase was reduced to 0.2g/tonne and lOg/tonne respectively. Extraction of gold from the ore was 97.5% and the extraction of silver was 91.6%.

Desorption of gold was conducted the same way as 15 described in example 1. As a result, commercial desorpent had a gold concentration of 2 g/L and silver concentration of 2.8g/L. By adding some base, hydroxides of noble metals were precipitated from commercial desorpent. The content of gold in the dry S* 20 hydroxide precipitate was 21% and the content of silver was o Therefore, the preferred method of noble metal extraction has a higher level of metal extraction and lower expenditure of energy and reagents, when compared with noble metal extraction methods of the prior art.

In summary, the preferred embodiment of the method of noble metal extraction from materials containing noble metals, may include treatment of raw material with cyanide solution, sorption of noble metals using ionexchange resin, desorption of noble metals with acidic thiourea solutions with optional further extraction of \\MELB01\homeS\ann\Keep\Perm\patent 2.doc 27/03/97 11 noble metals from commercial desorpent using known methods. This method differs primarily from methods of the prior art due to the fact that to increase the level of metal extraction and decrease the expenditure of reagents and energy the invention of the present application uses ion exchanging resin having a structure based on styrene and divinylbenzene with further halomethylation and amination.

Typically the resin is of the following general formula:

-CH-CH--

-CH-CHZ--

H

2

N

H

3 C/

\CH

3

-CH-CH-

HC X-

HC

H

3

CH

3 n Where m:n:p 10-12 68-78 12-20 r r r r H:\HelenF\Keep\77469.98 RTEC.doc 20/9/01

Claims

1. A resin suitable for the hydro-extraction of a noble metal from an ore, the resin having the structure: -CH-CH-- 2 -CH-CH-- 2 L J 2 m N n H3CN p H 3 C CH 3 H 3 C CH 3 wherein the ratio of m:n:p is 10-12 68-78: 12-20

2. A resin suitable for the hydro-extraction of a noble metal from an ore, the resin having the structure: oO° o oo -CH-CHI- -CH-CH -CH-CH-- n L wherein the ratio of m:n:p is 10-12 68-78 12-20.

3. The resin according to claim 1 or 2 wherein the ratio m:n:p is 10 78 12.

4. The resin according to claim 1 or 2 wherein the ratio m:n:p is 12 72 16. The resin according to claim 1 or 2 wherein the ratio \\melb_files\homeS\Pcabral\Keep\speci\77469.98 RTEC.doc 20/01/03 13 ooo oooo o oooo oo oo ooo 9oooo m:n:p is 11 69:

6. Use of the resin as claimed in any one of the claims 1 to 5 in a process for the extraction of noble metals from ore.

7. A method of extracting noble metals from ore, the method including the step of contacting the ore with a resin to selectively sorb the noble metals onto the 10 resin, the resin having the following structure: -CH-CHY-- -CH-CH-- !1 X- -CH-CH2- C 2 H2 Nm H 3 C-\ H3C CH 3 H 3 C 3 wherein the ratio of m:n:p is 10-12 68-78 12-20.

8. A method of extracting noble metals from ore, the method including the step of contacting the ore with 15 a resin to selectively sorb the noble metals onto the resin, the resin having the following structure: -CH-CHj- -CH-CH-- -CH-CH2-- -CH-CH H 2 CH 2 m N n H N P H 3 C \CH 3 H 3 C CH 3 wherein the ratio of m:n:p is 10-12 68-78 12-20. \\melbfiles\homeS\Pcabral\Keep\speci\77469.98 RTEC.doc 20/01/03 14

9. The method according to claim 8 including the step of desorbing the noble metals from the resin. method according to claim 8 or 9 including the step of separating the resin from other sand and other materials.

11.The method according to any one of claims 8 to including the step of desorbing the noble metals S 10 from the resin.

12.The method according to claim 9 wherein the desorpent containing the noble metals is formed "during the step of desorbing the noble metals.

13.The method according to claim 10 including the step of extracting the noble metals from the desorpent using electrolysis. 20 14.The method according to any one of claim 9 to 11 wherein an acid solution of thiorea is utilised in the desorption step. method according to any one of claims 7 to 12 wherein the step of sorbing the noble metals includes crushing the ore and adding water to form a slurry have a solid: liquid ratio of 1 1.2-1.5.

16.The method according to any one of claims 7 to 13 wherein the step of sorbing the noble metals includes adjusting the pH of the ore to a range from to 11. \\melb_files\homeS\Pcabral\Keep\speci\77469.98 RTEC.doc 20/01/03 15

17.The method according to any one of claims 7 to 14 wherein the step of sorbing the noble metals includes treating the ore with a cyanide solution.

18.A method of extracting noble metals from an ore in accordance with examples 1 or 2 hereinbefore described. Dated this 20th day of January 2003 10 RTEC CORPORATION By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia \\melb_files\home$\Pcabral\Keep\speci\77469.98 RTEC.doc 20/01/03