STUDIA UNIVERSITATIS BABEŞ-BOLYAI, PHYSICA, SPECIAL ISSUE, 2003
THE RECOVERY OF GOLD FROM CHLORIDE SOLUTIONS USING THE
SELECTIVE ION EXCHANGE RESIN IONAC SR3
Mihaela Pavel1, Damian Axente2
1
Mining Research Development and Engineering Institute S.C.
CEPROMIN S.A., Deva 2700, 22 Decembrie Street 37A; E-mail:
mihapavel@scientist.com
2
National Institute for Research and Development of Isotopic and
Molecular Technologies, 3400 Cluj-Napoca, Donath Street 65-103;
E-mail: axente@s6.itim-cj.ro
Abstract: Strong base anion resins are not sufficiently selective to
separate precious metals from large amounts of accompanying metals,
present in hydrometallurgical gold solutions. The present work studied
the recovery of precious metals from hydrometallurgical chloride
solutions with high content of Pb, Cu, Zn, and Fe by an ion exchange
process. Using the selective ion exchange resin IONAC SR3 gold
recovery reached 92.43 %.
Introduction
Ion exchange resins are still very little used commercially for gold extraction
from hydrometallurgical leach solutions, despite the advantages of resins (higher
equilibrium loading, easier elution of gold, no periodic thermal reactivation for
organics removal etc.) over activated carbon [1,2]. Selective ion exchange resins,
like IONAC SR3, can chelate gold and silver, but not interact with alkaline and
alkaline earth metals or transition metals such as copper and zinc [3].
Experimental
Materials: Synthetic and real leach solutions (obtained by the leaching of a
metallurgical residue in highly concentrated acidic and oxidant calcium chloride
solutions) were employed in the research works.
The ion exchange resin IONAC SR3, supplied by Sybron Chemicals Inc., is
a highly selective chelating resin, containing isothiouronium chloride active
groups. It was used for gold adsorption in chloride form, without any pretreatment. Substances used for the test work, were all of reagent grade.
Testing apparatus and procedure: The adsorption and desorption tests were
conducted in stirred glass vessels. All solutions before and after adsorption or
desorption test were assayed for gold with an atomic adsorption spectrometer
VARIAN SpectrAA 200.
MIHAELA PAVEL, DAMIAN AXENTE
Results and discussions
The adsorption isotherm - Data to plot down the gold adsorption isotherm
on the IONAC SR3 resin, at 250C, has been obtained by stirring, for 24 hours,
volumes of 100 ml of synthetic solutions, with a 0.95 pH and containing 113 mg/l
Au, 0.64 mg/l Ag, and 59.3 mg/l Cu, and quantities of resin between 0.2g and 5g .
The obtained results have shown that the resin / solution contact time of 24 hours
has been sufficient for reaching the equilibrium point, while the gold
concentrations on the resin and in the solution, remained practically constant after
16 hours.
The variation from Fig. 1, Q = f(C) can be approximated with the most
lightly straight line y  12,222 x 0,928 (computer drawn), according to Freudlich’s
equation [4]:
Q  k Cn
or
log Q  log k  n log C
(1)
60
where: Q and C are gold
concentrations in the resin and
solution; k and n are constants.
Experimental values for 25 0C,
were: k 12.222 and n  0.928.
Gold concentrations of the resin
phase ranged from 2.26 mg/g to
54.4 mg/g for resin/solution
proportions of 1/20  1/500.
Q (mg/g)
50
40
y = 12.222x0.928
30
20
10
0
0
1
2
3
C (mg Au/l)
4
5
Fig. 1. Isotherm for gold chloride adsorption on IONAC SR3 selective resin
(250C, 400 rpm, 113 mg Au/l, resin/solution=1/500 – 1/20, pH=0.75, 3 g/l NaClO)
The adsorption rate of AuCl4- on the resin was influenced by the initial
gold concentration in the solution (Fig. 2), stirring rate (Fig. 3), temperature (Fig.
4) and resin/solution volume ratio (Fig. 5).
5,656 mg/l Au
28,28 mg/l Au
56,56 mg/l Au
84,84 mg/l Au
35
Q (mg/g)
30
12
Q (mg Au/g)
40
25
20
15
10
8
100 rpm
250 rpm
400 rpm
500 rpm
4
5
0
0
0
20
40
60
Time (minutes)
80
100
0
20
40
60
80
Time (min)
100
120
THE RECOVERY OF GOLD FROM CHLORIDE SOLUTIONS USING THE ION EXCHANGE RESIN SR3
Fig. 2. Effect of initial gold concentration
(resin/solution = 1/500, 400 rpm, 250C)
30
(113 mgAu/l, 250C, resin/solution=1/100)
T = 35 0C
T = 25 0C
20
4
T = 20 0C
15
10
3
2.5
2
1.5
1
5
0.5
0
0
0
20
40
60
80
Time (minutes)
I/S=1/500
I/S=1/200
I/S=1/100
I/S=1/40
I/S=1/20
3.5
v (mg l-1min-1)
25
Q (mg/g)
Fig. 3. Effect of stirring rate
100
120
0
20
40
60
80
100
120
140
Time (minutes)
Fig. 4. Effect of temperature
Fig. 5. Effect of resin / solution ratio
(56.56 mg Au/l, resin/solution=1/500, 400 rpm)
(113 mg Au/l, 250C, 400 rpm)
The influence of impurities Because hydrometallurgical solutions
usually contain chlorides and sulphates of heavy metals (Fe, Cu, Pb, Zn) in much
higher concentrations than gold and silver, the effect of such „impurities” on the
adsorption of precious metals on the selective resin IONAC SR3 has also been
studied.
The results showed that precious metal adsorption efficiencies from
solution containing 56.56 mg/l Au, 0.32 mg/l Ag, 1056 mg/l Cu, 905 mg/l Zn, 805
mg/l Fe, 1010 mg/l Pb, 5 g/l NaOCl and 300 g/l CaCl2 on IONAC SR3 resin are
over 97% and haven’t been affected by the presence in high concentrations of Cl‾
or heavy metals ions.
The desorption of gold retained on the selective resin IONAC SR3 - The
desorption of gold retained on the selective resin IONAC SR3 has been carried out
with acid (HCl 3%) thiourea (30 – 50 g/l) solutions. In the desorption stage, Au3 is
reduced to Au , which is complexed by thiourea, thus forming a cationic complex
AuTu2 , which is then eliminated into the solution. Desorption experiments took
place at 25 0C, by stirring (400 rpm) for 120 minutes, 1g of resin containing 27,5
mg Au/g and 0,16 mg Ag/g, with 50 - 75 ml of acid thiourea solution. The results
showed that the gold’s elution efficiency rises with the thiourea concentration and
the volume of the used solution. Usually, the purpose is to obtain solutions as
concentrated in gold as possible in order to increase the energetic efficiency in the
next stage, the electrolysis.
Precious metal recovery from real hydrometallurgical solutions - Table 1 shows
that after 180 minutes of resin / real solution contact at 30 0C, the resin had
adsorbed 97% of the gold present in the solution. After the desorption with
MIHAELA PAVEL, DAMIAN AXENTE
thiourea, the pregnant solution contained 2.46 times more gold and 1.15 times
more silver than the initial one, and did not concentrate on the other heavy metals.
The total gold recovery (sorption and desorption stages) from the real
hydrometallurgical chloride solution reached 92.43 %.
Table 1.
Recovery of precious metals from a real hydrometallurgical chloride solution using IONAC
SR3 selective resin
Parameters
Adsorption
1g resin / 200
ml solution,
30 0C,
400 rpm
Desorption
1 g resin / 75
ml solution of
50 g/l tiourea,
3% HCl;
28 0C, 400 rpm
Time
(min)
Adsorption/Desorption Efficiency on IONAC
SR3 Selective Resin (%)
Au
Ag
Cu
Pb
Zn
Fe
0
10
30
60
90
120
180
0
59,00
72,79
83,33
90,48
92,25
97,20
0
45,7
49,0
51,9
57,1
60,7
66,5
0
12,57
16,17
20,21
20,97
20,99
21,15
0
4,84
7,56
8,64
10,3
11,4
13,0
0
21,1
22,2
22,8
23,6
23,8
24,8
0
3,15
5,40
6,21
6,28
6,40
6,48
0
10
0
74,50
0
55,3
0
0,05
0
4,32
0
1,53
0
0,77
30
60
90
120
89,68
60,4
0,05
4,58
1,78
0,98
92,4
93,3
94,4
62,8
63,0
64,4
0,06
0,06
0,07
4,80
5,11
5,35
1,97
2,19
2,52
1,33
1,57
1,76
150
95,1
64,9
0,08
5,65
2,72
1,93
Conclusions
Gold contained in hydrometallurgical chloride solutions can be recovered by the
selective ion exchange resin IONAC SR3. The gold adsorption isotherm on the
resin was described by the Freudlich’s equation. The adsorption rate of AuCl 4- on
the resin was influenced by the initial gold concentration in the solution, stirring
rate, temperature and resin/solution ratio. Under the conditions of resin/solution
ratio = 1/200 and a stirring speed of 400 rpm at 30 0C, more than 97% of gold
could be recovered by the resin in 180 minutes contact with a hydrometallurgical
solution of 33.3 mg Au/l, 70.2 mg Ag/l and high Cu, Pb, Zn şi Fe concentrations.
After desorption (28 0C, 50 g/l thiourea, 3 % HCl), the pregnant solution contained
about 2.5 times more gold than the initial one, and did not concentrate in heavy
metals. The efficiency of gold recovery ion exchange process from the chloride
hydrometallurgical solution has been over 92%.
References
1.
2.
3.
4.
Har r is, W . I ., S ta hl b us h, J . R., P i ke , W . C. An d S te we n s , R . R .,
Reactive Polymers, 17, 1992, pp. 21-27;
Lu k e y, G. C ., V a n De v e nt er, J . S. J ., S hal lcro s s, D. C., Hydrometallurgy,
59, 2001, pp. 101-113;
Sybron Chemicals Inc. Brochure, IONAC SR3, Selective Ion Exchange Resin for Gold
Recovery, 2000.
Ne ni ţe sc u, C. D., Chimie generală, Ed. Didactică şi Pedagogică, Bucureşti, 1979,
p. 294.