AU603471B2 - Process for recovery of gold - Google Patents

Description

'1 Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: I.C~mplete Specif ication Lodged: Accepted: Published: 'P~iority 603471 Related Art: This document contains thle amnendments miade under Section 49 and is correct for priniting.

Name of Applicant: SUMITOMO CHEMICAL COMPANY, LIMITED Address of Applicant: 15, Kitahama 5-chome, Higashi-ku, Osaka, Japan Actual Inventor: Address for Service: MASAAKI MATSUDA and YUJI YOSHIDA EDWD. WATERS SONS, 50 QUEEN STREET, MELBOURNE, AUSTRALIA, 3000.

Complete Specification for the invention entitled: PROCESS FOR RECOVERY OF GOLD The followinq statement is a full description o' this invention, inctuding the best method of performing it known to US

C

"i: -i: PROCESS FOR RECOVERY OF GOLD 4i t IT t 4 t 4; 4 4; 4r

I

4 4 41 BACKGROUND OF THE INVENTION The present invention relates to a process for recovery of gold. More particularly, it relates to a process for recovery of gold which comprises bringing a solution containing gold and thiourea or derivatives thereof into contact with an ion exchange resin having a sulfonic acid group.

There are a few processes for recovery of gold, but carbon in pulp method (hereinafter referred to as CIP method) is most familiar. The CIP method comprises; forming a slurry by pulverizing a gold ore 15 in aqueous cyanide solution; stirring the slurry for dozens of hours while blowing air into the slurry to elute almost all of gold in the ore; adding active carbon to the slurry to adsorb gold dissolved in the slurry; and then recovering the active carbon from the slurry in order to separate and recover gold therefrom.

The remaining slurry is wasted after cyanide is removed. Elution of gold from a gold ore in the CIP method and others is usually conducted using cyanide aqueous solution as a leaching agent. However, it requires a long time and enormous labor, facilities and cost for the prevention of pollution. In order to solve above mentioned problem, thiourea or derivatives thereof is proposed as a leaching agent for gold [Ger.

Offen. DE 3,347,165 and "Minerals" 1986, 41(174) 30 pp.53-61].

The use of thiourea or derivatives thereof as a main component of the leaching acent improves to dissolve the problems accompanied by the prevention of pollution and recovery of gold is possible by using active carbon from elute of a gold ore, but another i~

I'

LA

.1 -2difficulty is encountered. That is, elution of the leaching agent from the acL-ve carbon and then steam activation of the active carbon are required in order to reuse the used active carbon, because said active carbon adsorbs not only gold but also thiourea or derivatives thereof or the leaching agent. No other N method economically practicable has been available yet in order to reform active carbon which has adsorbed a leaching agent.

"t Under the circumstances, the inventors have made intensive study in animprovement in adsorbing and recovering gold from aqueous solution obtained by applying a leaching agent containing thiourea or derivatives thereof as a main component to a gold ore.

As the result, the inventors have succeeded in finding that an ion exchange resin having a sulfonic acid group is able to efficiently adsorb gold, to adsorb the main component of the leaching agent as small as possible and to easily be regenerated. Furthermore, the inventors have found that aqueous solution contain- [ing at least one compound of thiocyanic acid, thiotcyanate and compounds having mercapto and carboxyl t groups is an eluating agent to efficiently separate gold from the ion exchange resin on which gold has been adsorbed. The present invention has been accomplished on the basis of these findings.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a process for recovering gold which comprises bringing aqueous solution containing gold and thiourea or derivatives thereof into contact with an ion exchange resin having a sulfonic acid group to adsorb gold and then eluting said adsorbed gold by an eluent containing at least one of compounds selected i 1 g t I {r

*I

I

9 99 3 from thiocyanic acid, thiocyanate and those having mercapto and carboxyl groups.

Ion exchange resin usable in the present invention is that which is obtained by known methods.

Examples of the ion exchange resin are a resin having halogen atoms and sulfonic acid groups such as Sumikaion KC-470 (Trade-Mark for a resin supplied by Sumitomo Cheiaical Co., Ltd.); a resin having sulfamic acid groups such as Sumikaion KC-570 (Trade-Mark for a resin supplied by Sumitomo Chemical Co., Ltd.); a styrene-divinylbenzene copolymer resin having sulfonic acid groups such as Duolite C-20 and Duolite C-26 (Trade-Marks for resins supplied by Duolite International Diaion® SK-lB, Diaion SK102, Diaion® SK-104, Diaion SK110 and Diaion ®SK116 (Trade-Marks for resins supplied hy Mitsubishi Chemical Co.); Amberlite IR-116 and Amberlite V IR-120B (Trade- Marks for resins supplied by Rohm Haas Co.) and a phenol resin having methylene sulfonic acid groups such as Duolite C-663 and Duolite C-10 (Trade-Marks for resins supplied by Duolite International Co.).

Aqueous solution containing gold and thiourea or derivatives thereof (hereinafter referred to as "thiourea solution containing gold") usable in the present invention means any aqueous solution containing gold and thiourea or derivatives thereof such as N-methylthiourea, N,N'-dimethylthiourea, N-ethylthiourea, N,N'-diethylthiourea and N,N'-diphenylthiourea.

Generally, such aqueous solution is eluted solution from a gold ore with a leaching agent containing thiourea or derivatives thereof; eluted solution from chelate agents or the like which have adsorbed gold with thiourea or derivatives thereof; and eluted solution from materials containing gold such as scrap of

I

L

-c 7 t r t tr It 4 electronic materials with the above-mentioned leaching agent.

Thiourea solution having gold, with or without a pre-treatment such as filtration, is brought into contact with above mentioned ion exchange resin having a sulfonic acid group (hereinafter referred to as "an ion exchange resin") to adsorb and recover gold.

If the above-mentioned gold-containing solution contains a large amount of transition metals other than gold, adsorption capacity of ion exchange resin for gold is reduced. Therefore, concentration of the transition metal in the solution is preferably not more than 5 g/k. An oxidizing agent which is added to accelerate the rate of oxidation of gold and elution speed of gold from a gold ore is preferably, for example, air and hydroperoxide rather than compounds containing such metal ions as Fe 3 since a functional group of the ion exchange resin is solely directed for gold ion. Such oxidizing agent serves to increase adsorption capacity of an ion exchange resin.

25 In the case where it is obliged to add transition metal ions such as Fe to the aqueous solution, or in the case where the aqueous solution containing gold is obtained by eluation from a gold ore, etc. with a leaching agent containing thiourea or derivatives thereof as main components, it is preferable to remove as much as possible transition metals such as Fe 3 by converting them to hydroxide which is hardly soluble in water by means of pH adjustment and subjecting to filtration or decantation, etc., before the solution is brought into contact with a resin.

I

I

t I t tr

L

\;I

,e~ru;, Contact of thiourea solution containing gold with an ion exchange resin is usually carried out at 0 1001C, preferably 10 60 0 C. As the temperature is lower, viscosity of the solution increases and a solid is liable to be deposited. On the other hand, as the temperature is higher, cost for heating increases, and when it exceeds 100 0 C, the ion exchange resin is somewhat degraded. The temperature out of the abovef[ 7mentioned range is not preferred.

Contact of thiourea solution containing gold with the ion-exchange resin is effected by any method.

For example, the ion exchange resin is dipped in the :L thiourea solution containing gold or the thiourea solution containing gold is passed through a column in which the ion exchange resin is packed. The latter is usually preferred, because operation is easier. Any s amounts of the solution and of the ion exchange resin may be used in the latter case, but they should be determined by conducting a preliminary experiment.

They vary depending on gold content in the thiourea solution containing gold to be treated, concentrations t of inorganic salt, thiourea or derivatives thereof and transition metals and the varieties of ion exchange resin to be used.

Any contacting time may be employed, but usually more than several seconds, preferably 1 minute to 24 hours.

After gold is adsorbed to recover, the remaining thiourea solution is used again for leaching gold with or without supplement of thiourea, oxidizing agents, etc.

After the ion exchange resin has adsorbed j: 1 ii -~Psa~Llu~31*~~C~ q i *t *o 4,r 4. 4 4 4.C 6 gold by above-mentioned process, gold is then separated by an eluent from the resin.

A particular eluent is necessary, because bonding of gold adsorbed with the resin is so strong that mineral acid familiar to regeneration of used resin such as hydrochloric acid, sulfonic acid or the like, is not usable.

Examples of the eluent are thiocyanic acid, thiocyanate and those having mercapto and carboxyl groups. Thiocyanate includes ammonium thiocyanate, potassium thiocyanate, sodium thiocyanate, barium thiocyanate, methylammonium thiocyanate, calcium thiocyanate and cesium thiocyanate. Compounds having mercapto and carboxyl groups include thioglycolic acid, dithioglycolic acid, thio-di-glycolic acid, thiocoumaric acid, thiolactic acid, thiomalic acid, di-thiopropionic acid and cysteine. Alkali metal salt, alkaline earth metal salt and ammonium salt of the acid are also employed. Particularly, thiomalic acid, thioglycolic acid, thiocoumaric acid, cystine and thiolactic acid are preferable. The above-mentioned eluent is used alone or in the form of mixtures thereof.

Contact of the ion exchange resin which adsorbed gold with eluent is usually carried out at temperature of 0 100 0 C, preferably 40 80 0 C. If the temperature is lower, efficiency of elution is lower.

On the other hand, if the temperature is higher, cost for heating increases. Contact between the ion exchange resin which adsorbed gold and eluent is carried out by any methods. There may be usually employed, for example, a method of dipping the ion-exchange resin in the eluent or a method of passing the eluent through a column in which the ion exchange resin is packed.

4

J

LT

i

II

I

-7- Usually the latter is preferred because operation is easier. In this case, concentration of the eluent to be used is usually about 0.05 about 2 moles/Z, preferably about 0.1 about 1 mole/.. Although concentration less than 0.05 mole/k may be employed, it is not desirable because a large quantity of eluent is required in order to elute and recover gold completely, the gold concentration in the eluate is small and the process to recover gold from eluate is more complicated. On the other hand, even when concentration is made high, no more advantage is obtained.

Eluent, i.e. thiocyanic acid, thiocyanate or compounds having mercapto and carboxyl groups should be used in an amount of more than double the mole quantity of total of gold and other metals adsorbed on the ion a exchange resin. Usually, 3 20 times as much as ~1mole quantity of adsorbed metal is employed. If the amount is less than double the amount of adsorbed go oo* 20 metal, it is very hard to elute the adsorbed metal completely and the adsorption capacity for the next adsorption-elution process decreases.

.:Contacting time of ion exchange resin with eluent has no special limitation, but usually at least several seconds, preferably 1 minute to 24 hours.

Gold recovered from the above-mentioned i process is transformed to gold metal or compounds thereof and the like by known methods such as concentration, refining, electrolysis, a concentration redox method or the like, and then it is used for industrial use, ornamental purposes, etc.

According to the present invention, gold contained in thiourea solution is able to be adsorbed -8 on ion exchange resin and be recovered efficiently.

Furthermore, the ion exchange resin used is able to be used again only by eluting the adsorbed gold from the resin. Therefore, the industrial value of the present process, for example, for recovery of gold from a gold ore by using thiourea or derivatives thereof as a leaching agent, is markedly high.

The following nonlimiting examples further illustrate the present invention.

Example 1 One ml of Sumikaion 0 KC-470 [ITrade-Mark for an ion exchange resin supplied by Sumitomo Chemical Co., Ltd.] made of styrene-divinyl benzene copolymer having sulfonic acid groups and containing 17 weight of chlorine was packed in a. column. Aqueous solution S.'..(3000 ml, a model of extract solution) of pH containing 2 mg/k of gold, 50 g/k of thiourea and 3 g/k. of Fe 3+ was flowed through the packed column with space velocity (SV) of 20 hr- 1 at room temperature.

Concentration of gold in the eluent was 0.33 mg/Z.

This result shows that 5.0 mg of gold is adsorbed on the resin.

Then, 10 ml of 0.1 mol/Z aqueous ammonium thiocyanate solution was flowed through a column packed with the resin having gold adsorbed with space velocity (SV) of 10 hr- at 50 until 4.9 mg of gold was eluted and recovered.

After adsorbed gold was eluted, the resin was washed with 5 ml of water, and then the same cycle of adsorption and elution of gold as mentioned above was repeated 5 times. The results are shown in Table 1.

1 '1 9- Table 1 Number of cycle adsorption elution of adsorption of gold of gold and elution (mg) (mg) Ist 5.0 4.9 2nd 4.9 4.8 3rd 4.8 4.9 4th 4.9 4.9 4.9 4.9 a i r.

4 Comparative Example 1 The procedure of Example 1 was repeated except that Shirasagi W (Trade-Mark for active carbon 20 supplied by Takeda Chemical Industries Ltd.) was used instead of Sumikaion KC-470. The results are shown in Table 2.

Table 2 Lr 11 Number of cycle adsorptiouL elution of adsorption of gold of gold and elution (mg) (mg) 1st 0.9 0.9 2nd 0.4 0.4 3rd 0.3 0.3 4th 0.4 0.4 0.4 0.4 j~ p: 1

E

10 Examples 2 6 and Comparative Examples 2 6 The procedure of Example 1 was repeated except that concentration of ferric sulfate (an oxidizing agent) as shown in Table 3 was used under pH 1.7. The results (adsorption and elution of gold at the first cycle and the fifth cycle) are shown in Table 3.

Table 3 I E I II 4,

II

I'

Concentration Adsorption of gold Elution of gold 3+ in (mg) (mg) of Fe in extract solution The l st The 5th The 1st The (g/99) cycle cycle cycle cycle Examples 2 0.1 5.5 5.4 5.5 5.3 3 0.5 4.7 4.7 4.6 4.6 4 1 4.3 4.1 4.3 4.2 2 3.9 4.0 3.9 6 5 3.3 3.2 3.2 3.2 Compara- 2 0.1 0.8 0.8 0.8 0.8 tive Examples3 0.5 0.8 0.8 0.8 0.8 Examples4 1 0.8 0.8 0.8 0.8 4 1 0.8 0.8 0.8 0.8 6 5 0.8 0.8 0.8 0.8 6 5 0.8 0.8 0.8 0.8 j

I

I,

11 4 ii

I

J. I ar,*-i Examples 7 9 The procedure of Example 1 was repeated except that ion exchange resins and eluents as shown in Table 4 were used. The results (adsorption and elution of gold at the fifth cycle) are shown in Table 4.

Table 4 adsorption elution Example ion exchange eluent of gold of gold No. resin (mg) (mg) mol/Z aqueous 7 Sumikaion®KC-470* sodium thiocyanate 5.7 5.7 solution.

1 mol/ of aqueous 8 Duolite C-663* barium thiocyanate 4.1 4.1 solution 0.1 mol/ of 9 Duolite C-26* aqueous potassium 5.1 thiocyanate solution Sumikaion KC-470 Duolite C-663 Trade-Mal for a resin having a sulfonic acid group supplied by Sumitomo Chemical Co., Ltd.

Trade-Mark for a phenol resin having a methylene sulfonic acid group supplied by Duolite International Co.

:Trade-Mark for a styrene divinyl benzene copolymer resin having a Duolite C-26 1 c" ;j

'II

12 sulfonic acid group supplied by Duolite International Co.

Examples 10 The procedure of Example 1 was repeated except that composition of thiourea solution containing gold as shown in Table 5 was used. The results (adsorption and -the elution of gold at the fifth cycle) are shown in Table Table t C t C Example Comosition of thiourea adsorption of elution of No. solution containing gold gold (mg) gold (mg) Au: 2 mg/Z, thiourea: 100 g/z.

10 Fe 3+:0.3 g/Z,pHO= .54.48 Au: 2 mg/Z,, N-methyl 11 thiourea: 50 g19, 5.2 5.1 Fe 3+:0.3 g/k, pH Au: 2 N,N'-dimethyl 12 thiourea: 50 g19, 5.3 5.2 Fe 3+:0.3 g/9t, pH Au: 10 mg/i,, thiourea: 50 g19, 13 Fe 3+:1.0 g/k,pHl= .77.76 Au: 10 mg/z,, thiourea: 50 g/9, 14 Fe 1.0 g/9, Cu.2 1. 0 8.3 pH =0.3 Au: 100 mg/t, thiourea: 50 g/, Fe3+ :10gtpH=.79.3 9.3 I 13 Example 16 Sumikaion )KC-470 (1 ml) was packed in a column. Fifty ml of extract solution from a gold ore (supplied by Sumitomo Metal Mining Co.) of pH 1.4 containing 46 mg/t of gold, 16 mg/i of silver, 3.8 g/A of iron, 3 mg/z of copper, 2 mg/% of zinc and 20 g/Z of thiourea was flowed through the column at room -1 temperature with space velocity (SV) of 10 hr The effluent contained 0.5 mg/Z of gold, 2.5 mg/i of silver, 3.7 of iron, 0.7 mg/i of copper and 1.6 mg/Z of zinc. This result means that 2.28 mg of gold, 0.68 mg of silver, 5.00 mg of iron, 0.11 mg of copper and 0.02 mg of zinc are adsorbed on the resin.

Thirty ml of aqueous solution, as an eluent, containing 1.3 mol/t of thioglycolic acid and 1.2 mol/i of sodium acid carbonate was flowed through a column Spacked with the above-mentioned resin which had adsorbed metals at 25 OC with space velocity (SV) of 1 20 10 hr until 2.12 mg of gold, 0.57 mg of silver, 4.91 mg of iron, 0.10 mg of copper and 0.02 mg of zinc were eluted and recovered.

SExamplesl7 The procedure of Example 16 was repeated except that compounds having mercapto and carboxyl groups were Lsed instead of the thioglycolic acid.

The results are shown in Table 6.

i 4 1I -YIY~~l~iII I~L -~I 14 Table 6 h Example Thioglycolic acid Amount of recovered metal (mg) No. used gold silver iron copper zinc 17 Thiomalic acid 2.19 0.61 4.93 0.11 0.02 18 Thiocoumaric acid 2.01 0.53 4.87 0.OR 0.02 19 Cysteine 2.12 0.57 4.91 0.10 0.02 Thiolactic acid 2.03 0.58 4.93 0.11 0.02 Comparative Example 7 The procedure of Example 16 was repeated except that 3 normal hydrochloric acid was used as an eluent, with the result that 0.41 mg of gold, 0.41 mg of silver, 3.95 mg of iron, 0.10 mg of copper and 0.02 mg of zinc were recovered.

Examples21 24 The procedure of Example 16 was repeated except that the temperature of eluent as shown in Table 7 was used. The results are shown in Table 7.

H

i f <A~rllt ^-^Sfi Ad1

I

15 Table 7 Example No.

Temperature of eluent (OC) Amount of recovered metal (mg) gold silver iron copper zinc 21 30 2.19 0.60 4.92 0.10 0.02 22 40 2.24 0.64 4.95 0.11 0.02 23 50 2.26 0.67 4.97 0.10 0.02 to L

'I(L

Comparative Example 8 The procedure of Example 16 was repeated except that 2 normal aqueous sulfonic acid solution heated to 40 OC was used as an eluent, with the result 20 that 1.06 mg of gold, 0.58 mg of silver, 4.87 mg of iron, 0.10 mg of copper and 0.02 mg of zinc were recovered.

1 i t i i

I

E 1 i 1 1.

I

Claims (4)

1. A process for recovery of gold which comprises bringing aqueous solution containing gold and thiourea or derivatives thereof into contact with an ion exchange resin having a sulfonic acid group to adsorb gold to the resin, and eluting gold by using eluent containing at least one compound selected from thiocyanic acid, thiocyanate and those having mercapto and carboxyl groups.

2. A process for recovery of gold according to Claim 1 wherein the aqueous solution containing gold contains not more than 5 of a transition metal.

3. A process for recovery of gold according to Claim 1 wherein the eluent contains at least one compound selected from ammonium thiocyanate, sodium thiocyanate, thiomalic acid, thioglycolic acid, thiocoumaric acid, cysteine and thiolactic acid.

4. A process for recovery of gold according to Claim 1 wherein the elution is effected at 40 80 0 C. A process for recovery of gold substantially as hereinbefore described with reference to any one of the Examples. DATED this 14th day of August, 1990 Vt Vrr I I a Vi I Vt I SUMITOMO CHEMICAL COMPANY, LIMITED WATERMARK PATENT TRADEMARK ATTORNEYS THE ATRIUM, 290 BURWOOD ROAD HAWTHORN, VICTORIA 3122 AUSTRALIA IAS:JJC (5/11) c 1