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Separation and Purification Technology 59 (2008) 310–317
Separation of cobalt and nickel from ammoniacal
sulphate solution using Cyanex 272
P.K. Parhi, S. Panigrahi,
K. Sarangi
∗
, K.C. Nathsarma
Regional Research Laboratory (CSIR), Bhubaneswar-751013, India
Received 22 February 2007; received in revised form 25 June 2007; accepted 5 July 2007
Abstract
The SO
2
-ammoniacal ammonium sulphate leach liquor of manganese nodule bearing iron, manganese, copper, nickel, cobalt and zinc was
subjected to aeration/oxygenation to precipitate out the minor quantities of iron and manganese leaving the other metal values in tact. After
extraction of copper from the Fe- and Mn-free leach liquor with LIX 84I, stripping of ammonia from the Cu-barren raffinate, precipitation of
metal sulphides from the solution and leaching of the sulphide precipitates with H
2
SO
4
, the leach liquor bearing 0.58 kg/m
3
Cu, 2.67 kg/m
3
Zn,
2.012 kg/m
3
Co, 23.747 kg/m
3
Ni and 10.0 kg/m
3
(NH
4
)
2
SO
4
was obtained. After extraction of the remaining copper with LIX84I and zinc with
D2EHPA from the leach liquor, it was left with Co, Ni and (NH
4
)
2
SO
4
. Extraction of cobalt from the Cu–Zn-free solution was carried out using
Cyanex 272 in kerosene followed by extraction of nickel from the cobalt-free solution with NaCyanex 272 in kerosene. Extraction of both cobalt
and nickel increased with increasing equilibrium pH and extractant concentration. The species extracted into the organic phase were CoA
2
and
NiA
2
·HA. The highest separation factor for cobalt and nickel was obtained with 0.1 M Cyanex 272 at pH 5.46.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Cobalt; Nickel; Cyanex 272; Solvent extraction and ammoniacal sulphate
1. Introduction
The SO
2
-ammoniacal ammonium sulphate leach liquor of
manganese nodule contained iron, manganese, copper, nickel,
cobalt and zinc from which the minor quantities of iron
and manganese were precipitated quantitatively after aera-
tion/oxygenation. The Fe- and Mn-free solution was used for
extraction of copper using LIX 84I followed by stripping of
ammonia from the Cu-free solution, precipitation of metal sul-
phides from the solution and leaching of the sulphide precipitates
with H
2
SO
4
to produce the leach liquor bearing 0.58 kg/m
3
cop-
per, 2.67 kg/m
3
zinc, 2.00 kg/m
3
cobalt, 23.748 kg/m
3
nickel and
10.00 kg/m
3
(NH
4
)
2
SO
4
. After extraction of the minor quantity
of copper from the leach solution with LIX 84I and extraction of
zinc with D2EHPA, the leach liquor was left with cobalt, nickel
and (NH
4
)
2
SO
4
. Extraction of cobalt from the Cu- and Zn-free
solution was carried out with acid Cyanex 272 and extraction
∗
Corresponding author. Fax: +91 6742581637.
E-mail address: kadambini sarangi@yahoo.com (K. Sarangi).
of nickel from the cobalt-free solution was carried out with the
sodium salt of Cyanex 272.
A lot of work on separation of cobalt and nickel from aque-
ous solutions has been carried out earlier. Solvent extraction
studies on separation of cobalt and nickel [1] was carried out
using the Versatic 10 as extractant and LIX 63 as synergist and
the pH shift in Co–Ni extraction due to the synergist lead to
easy separation. The use of synergist increased the extraction
and stripping kinetics of cobalt but decreased the extraction and
stripping kinetics of nickel. Solvent extraction study of cobalt
and nickel [2] was carried out from a super alloy scrap chloride
leach solution bearing a high Co to Ni ratio using the sodium
salt of PC88A in kerosene in which the extraction rate increased
with increase of aqueous phase pH, extractant concentration
and solution temperature. The pH
0.5
difference of 1.40 indi-
cated the possible separation of cobalt and nickel. In a study
of cobalt–nickel separation [3] from a sulphate solution using
D2EHPA as the extractant, and Cyanex 272 and Cyanex 302
as synergists, extraction of cobalt over nickel was better with
D2EHPA than Cyanex 272. Selective extraction of cobalt over
nickel improved with D2EHPA, but worsened with Cyanex 272.
1383-5866/$ – see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.seppur.2007.07.026