Minerals Engineering 115 (2018) 106–116

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Minerals Engineering
journal homepage: www.elsevier.com/locate/mineng

Efficient extraction of copper and zinc from seafloor massive sulphide rock MARK
samples from the Loki’s Castle area at the Arctic Mid-Ocean Ridge
⁎
Przemyslaw B. Kowalczuk , Ben Snook, Rolf Arne Kleiv, Kurt Aasly
Norwegian University of Science and Technology, Department of Geoscience and Petroleum, Sem Sælands veg 1, NO-7491 Trondheim, Norway

A R T I C L E I N F O A B S T R A C T

Keywords: Seafloor massive sulphide (SMS) deposits have been identified as important marine metal resources for the
Seafloor massive sulphide future. However, literature on the recovery/extraction of metals from SMS is currently limited, and to date, no
Copper research has been published on the processing of SMS from the active hydrothermal vent field at the Arctic Mid-
Zinc Ocean Ridge. In this paper extraction of copper and zinc, as economically important metals, from the seafloor
Leaching
massive sulphide rock samples from the Loki’s Castle area at the Arctic Mid-Ocean Ridge was investigated during
Extraction
Nitric acid
nitric acid leaching. The results presented are of the various leaching experiments conducted under different
Deep sea mining conditions to optimise the extraction of copper and zinc. The mineralogical analysis indicated that the main
Marine minerals copper and zinc bearing minerals were chalcopyrite and sphalerite, respectively. It was shown that the leaching
efficiency and extraction of copper and zinc can be controlled mainly by temperature and acid concentration.
The elemental composition and mineralogical data indicated that 95% of copper and zinc bearing minerals were
leached out after 3 h, at the solid-to-liquid ratio of 1:10, temperature of 90 °C and acid concentration of 10%.

1. Introduction Pacific Rise in 1978 (Francheteau et al., 1979). Since 1979, SMS de-
posits have been known to occur at water depths up to 3700 m in a
1.1. Geological setting of seafloor massive sulphide deposits variety of tectonic settings at the modern seafloor including mid-ocean
ridges, back-arc rifts and seamounts (Herzig et al., 2002). SMS-style
Rapidly increasing per capita demand for copper (Singer, 2017) in mineralisation shares many characteristics with classic volcanogenic
developing countries has served to increase the requirements for geo- massive sulphide (VMS) deposits and may be considered as modern
logically diverse base metal resources, and recent research in the deep- analogues of this important deposit type, which has important eco-
sea environment has identified areas of mineralisation that may become nomic implications.
economically important for society (Hannington et al., 2001). Marine Hydrothermal vent fields with multiple fluid channels culminating
mineral resources can be classified based on the sources of their origin, in black smokers (chimneys) mostly consist of pyrite (FeS2) and chal-
i.e. (i) terrestrial, (ii) combined terrestrial and deep ocean and (iii) copyrite (CuFeS2) together with pyrrhotite (Fe1−xS, where x ranges
ocean basin resources (Arbab et al., 2015). The characteristics and from 0.0 to 0.2), isocubanite (CuFe2S3) and bornite (Cu5FeS4) with
importance of marine mineral deposits from terrestrial (e.g. heavy gangue material such as barite (BaSO4) and silica (SiO2) (Herzig et al.,
metal elements) as well as combined terrestrial and deep ocean sources 2002; Pedersen et al., 2010). The mineralogical compositions of Back-
(e.g. polymetallic nodules and cobalt-rich ferromanganese crusts), have Arc and Mid-Ocean Ridge SMS deposits are contrasted in Table 1.
been well described (Morgan, 2000; White et al., 2011).
Marine minerals from ocean basin sources have their origin in the 1.2. Processing methods for SMS material
ocean floor. They are derived from fluid/rock interaction within the
ocean crust and precipitation of minerals therein. The most important Many processes have been investigated in order to assess the best
ocean deposits are (i) metalliferous sediments, and (ii) seafloor massive one, which extracts economically important metals such as nickel,
sulphides (SMS). The first SMS were discovered at the crust of East copper, cobalt and manganese from seafloor nodules and crusts. There

⁎
Corresponding author.
E-mail address: przemyslaw.kowalczuk@ntnu.no (P.B. Kowalczuk).

http://dx.doi.org/10.1016/j.mineng.2017.10.015
Received 31 May 2017; Received in revised form 9 October 2017; Accepted 16 October 2017
Available online 06 November 2017
0892-6875/ © 2017 Elsevier Ltd. All rights reserved.
P.B. Kowalczuk et al. Minerals Engineering 115 (2018) 106–116

Table 1 use of additional oxidants such as oxygen and ferric ions (Fe3+), and
Mineralogical composition of SMS deposits (Herzig et al., 2002). the leaching time is faster in comparison to sulphuric acid, which will
reduce the operational costs. Despite the initial expense, almost all of
Back-arc deposits Mid-ocean ridge deposits
the nitric acid can be recycled and noxious gases can be captured, re-
Fe-sulphides Pyrite, marcasite, pyrrhotite Pyrite, marcasite, pyrrhotite ducing the raw material costs (Ma et al., 2013).
Zn-sulphides Sphalerite, wurtzite Sphalerite, wurtzite
Cu-sulphides Chalcopyrite, isocubanite Chalcopyrite, isocubanite
Silicates Amorphous silica Amorphous silica
2. Materials and methods
Sulphates Anhydrite, barite Anhydrite, barite
Pb-sulphides Galena, sulphosalts
As-sulphides Orpiment, realgar 2.1. Materials
Cu-As-Sb-sulphides Tennantite, tetrahedrite
Native metals Gold Various rock samples from the SMS ore from the Loki’s Castle hy-
drothermal vent field at the Arctic Mid-Ocean Ridge (Fig. 1) were in-
vestigated. Loki’s Castle is a site of known active hydrothermal venting
are two main processing technologies: leaching, in either hydrochloric/
as first described by Pedersen et al. (2010), where sulphide-carrying
sulphuric/nitric acid or ammonia solutions, and smelting (Fuerstenau
fluids are expelled from chimneys, forming black smokers. The vent
and Han, 1983; Jana et al., 1990; Chung, 1996; Niinae et al., 1996;
field, occurring at the junction of the Mohn’s and Knipovich Ridges in
Charewicz et al., 2001; Senanayake, 2011). Hydrometallurgical pro-
the Arctic Ocean, consists of five chimneys located on the top of two
cessing has become an important aspect in the recovery of valuable
mounds at approximately 2400 m depth (Pedersen et al., 2010).
metals since it meets industrial requirements in terms of cost and
The samples used in the leaching tests were collected during the
technical effectiveness, ease of operation, lower emission of gases to the
MarMine cruise in 2016 (Ludvigsen et al., 2016). The location and areas
atmosphere, and ability to be scaled-up (Pasad and Pandey, 1998;
of operation are shown in Fig. 1. The collected rock samples were
Olubambi and Potgieter, 2009; Chmielewski, 2015). However, litera-
bagged, flushed with nitrogen and vacuum sealed to prevent oxidation,
ture on the recovery/extraction of copper and zinc from SMS is cur-
and then stored in a fridge at +4 °C. This paper utilises only a small but
rently limited, and to date, no research has been published on proces-
representative range of available sample material, as an initial in-
sing of SMS from the Loki’s Castle area at the Arctic Mid-Ocean Ridge.
vestigation into the mineral extraction potential of SMS deposits.
In this paper, extraction of copper and zinc from the seafloor massive
Prior to tests, the samples were unpacked and dried at room tem-
sulphide rock samples from Loki’s Castle during nitric acid leaching is
perature. The chemical composition of each sample was determined by
investigated, as maximising the effectiveness of metal recovery from
X-ray fluorescence (XRF). Small amounts of different parts of samples
SMS ores is critical in development of such mineral showings in to fu-
were collected and crushed either by an agate hand mortar or steel jaw
ture ore reserves.
and roller crushers. Table 2 shows the elemental composition of in-
Although the use of nitric acid as a leaching agent (lixiviant) in
vestigated rock samples. It can be clearly seen that the samples varied
industry is limited due to its high price in comparison to sulphuric acid
in composition. Based on XRF data the individual particles were clas-
(H2SO4), nitric acid is a strong oxidation agent and offers excellent
sified as a feed (F), a middling (M) and a waste (W). Only samples with
potential for achieving very high levels of metal recoveries. Moreover,
copper and zinc content of at least 0.5 and 1.0%, respectively, were
leaching of sulphides in the presence of nitric acid does not require the
used in the leaching experiments, i.e. feed (LCA11) and middling

Fig. 1. Loki’s Castle hydrothermal vent field (the

northern part of Mohn’s Ridge) at the Arctic Mid-
Ocean Ridge (inset shows operation area) (Ludvigsen
et al., 2016).

Loki’s Castle

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P.B. Kowalczuk et al. Minerals Engineering 115 (2018) 106–116

Table 2
Elemental composition of samples from the Loki Castle area at the Arctic Mid-Ocean Ridge. F, M and W indicate feed, middling and waste, respectively.

Sample ID Picture (not to scale) Content, wt% Classification

Cu Zn Fe S Ba Si

LCA1 0.11 0.11 0.64 6.83 37.82 12.68 W

LCA2 0.01 0.01 0.42 0.56 0.58 35.54 W

LCA3 0.08 0.07 0.32 9.28 43.89 7.23 W

LCA4 0.01 0.02 1.30 1.89 3.46 30.91 W

LCA5 0.04 0.05 0.33 6.24 26.74 16.72 W

LCA6 0.05 0.06 0.47 6.30 30.76 18.10 W

LCA7 0.10 0.13 0.96 5.51 18.23 23.61 W

LCA8 0.04 0.05 0.97 4.19 16.38 23.21 W

LCA9 0.03 0.02 0.13 5.89 21.56 22.22 W

LCA10 0.00 0.00 0.03 0.77 1.24 37.41 W

LCA11 1.46 4.24 11.54 17.03 6.38 23.05 F

LCA12 0.50 1.25 6.08 7.68 3.14 32.17 M

LCA13 0.03 0.14 0.12 4.25 12.49 28.76 W

LCA14 0.42 0.60 3.15 10.47 15.62 20.94 W

LCA15 0.67 1.26 4.39 6.58 5.13 30.53 M

(LCA12, LCA15) samples. Each sample represents a different composi- Leaching was carried out at different temperatures (T), times (t), acid
tion and mineralogy, and therefore, the leaching experiments were concentrations and solid-to-liquid ratios (s:l). After leaching, the sam-
conducted on each sample separately. Prior to experiments the samples ples were filtered for phase separation by using a Buchner funnel. All
were crushed by using jaw and roller crushers, and then dry sieved to remaining solid products (residues) were analysed by X-ray fluores-
obtain the particle size fraction below 100 µm. cence (XRF), while selected leachate products were analysed by in-
ductively coupled plasma mass spectrometry (ICP-MS).
2.2. Leaching Extraction of metals (E) was calculated based on the formula:

Leaching experiments were carried out in aqueous solutions of nitric β

E = 100−γ ·
acid acting as a leaching agent. The tests were conducted in Erlenmeyer α (1)
flasks that were placed in a constant temperature water-conditioned
where γ is the relative yield (mass) of residue (%), while α and β denote
shaker bath (Grant model OLS 200) with a horizontal orbital shaking
the content of metal (%) in the feed and residue, respectively.
speed of 100 rpm. In each leaching test the mass of solid was 5 ± 0.3 g.

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P.B. Kowalczuk et al. Minerals Engineering 115 (2018) 106–116

Fig. 2. Microphotographs (reflected light, plane po-

A B larised) of the white smoker system, (A) disseminated
galena, (B) fine grained pyrite (yellow) with sphalerite
(grey) (inset: the same scale), (C) acicular texture and
lineation within the white phase, (D) sphalerite as
grain coatings and large galena particle (inset: the
same scale).

400 μm 200 μm

C D

800 μm 200 μm

Fig. 3. Microphotographs (reflected light, plane po-

larised) of the black smoker system, (A) aggregate of
A B
isocubanite (pink) and chalcopyrite (yellow) inter-
growths; sphalerite (grey) and chalcopyrite occur in
close association with fine grained pyrite (white); (B)
fine dissemination of sphalerite (grey), chalcopyrite
(yellow) and possible covellite (blue); (C) sphalerite
and chalcopyrite with ultra-fine sulphides (a mix of
pyrite, chalcopyrite, isocubanite and sphalerite); (D)
texture of larger sulphide grains of pyrite (white),
chalcopyrite (yellow), sphalerite (grey) and iso-
cubanite (pink).

800 μm 800 μm

C D

200 μm 200 μm

2.3. Mineralogical analysis remaining solid products (residues) after leaching (solid-to-liquid ratio
1:10, T = 90 °C, t = 3 h, acid concentration 10%) were mixed with
Thin slices of rock were cut from the black and white smoker resin in a mounting cup to create a solid medium. These were surface
samples with a diamond saw, and then ground optically flat. ground and finally polished using diamond pastes. The samples (po-
Subsequently they were mounted on a glass slide and ground smooth lished blocks and thin sections) were subjected to qualitative petro-
using progressively finer abrasive grit before final polishing using dia- graphic analysis using a transmitted/reflected light Olympus BX51
mond pastes. From three samples (LCA11, LCA12 and LCA15), feed and microscope equipped with a Jenoptik ProgRes SppedXTcore 5 camera.

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P.B. Kowalczuk et al. Minerals Engineering 115 (2018) 106–116

100 100
A B

80 80

extraction, %
extraction, %

60 60

40 40

Cu Cu
20 Zn 20 Zn
Fe Fe
S S

0 0
0 5 10 15 20 0 5 10 15 20

acid concentration, % acid concentration, %

100
C

80
extraction, %

60

40

Cu
20 Zn
Fe
S

0
0 5 10 15 20

acid concentration, %
Fig. 4. Influence of acid concentration on extraction of Zn, Cu, Fe and S from solid samples (A) LCA11, (B) LCA12, (C) LCA15 (T = 90 °C, t = 3 h, solid-to-liquid ratio 1:10).

The mineral phases were diagnosed utilizing their optical properties. sphalerite (10 μm) and galena (10–100 μm). Pyrite is present in limited
quantities, typically as isolated grains (10 μm) but also associated with
3. Results and discussion sphalerite in grains up to 30 μm.
The mineralogy of black smoker material is much more diverse
3.1. Material characterization (Fig. 3). It contains barite, quartz, pyrite, chalcopyrite, sphalerite and
isocubanite. The sulphides occur in two general forms, that is (i) as fine
Table 2 shows images (not to scale) and selected elemental com- grained massive sulphide lenses, and (ii) larger aggregates/grains dis-
positions of investigated samples. It clearly demonstrates the variation tributed throughout the groundmass. The massive lenses are composed
in the sample colour and composition. The samples represent white and of approximately 75% pyrite, 15% sphalerite and 10% chalcopyrite.
black smoker systems. XRD data showed that Ba and Si bearing mi- Sphalerite and chalcopyrite are variably intergrown with each other but
nerals such as barite and quartz, respectively mostly dominate the also occur as distinct grains.
white phase, whereas the black phase is composed of sulphide bearing
minerals such as chalcopyrite, sphalerite and pyrite/marcasite, but also 3.2. Leaching
contains gangue minerals such as quartz and barite. The polished block
of white smoker material is shown in Fig. 2. The petrographic analysis The extremely fine grain size and complex textures of the SMS rock
shows that the sample is essentially barren with localised examples of samples suggested that leaching can be used as an initial approach to

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P.B. Kowalczuk et al. Minerals Engineering 115 (2018) 106–116

40 ZnS + 4HNO3 → Zn(NO3)2 + S° + 2NO2 + 2H2 O (5)

According to reactions (2)–(5) the leaching process yields sulphur

(S°) in its non-polluting elemental form. However, practically, some
sulphur gets oxidized by acid to sulphate ions:
30 S° + 2HNO3 → H2 SO4 + 2NO (6)
content in residue, %

The amount of elemental form of sulphur depends on the con-

centration of acid. The higher the concentration of HNO3, the higher
the level of metal recoveries but also the lesser the yield of elemental
20 sulphur (Gupta and Mukherjee, 1990).
Si The proportion of Si in the solid residues increased after leaching,
Ba
while the proportion of Ba either remained constant or slightly in-
creased (Fig. 5). The weight loss of solid after leaching in aqueous so-
lutions of nitric acid varied from 15 to 30% depending on the acid
10 concentration and feed composition.
To check the influence of acid concentration on both the extraction
of elements and their contents in the remaining solids after leaching
(residues) the relevant results were plotted to demonstrate the re-
lationship between extraction and content in the residue. This re-
0 lationship creates a new leaching upgrading curve, which is based on
0 5 10 15 20
the grade-recovery curve commonly used to present the separation data
acid concentration, % (Drzymala, 2007; Drzymala et al., 2013; Wills and Finch, 2016;
Charikinya et al., 2017). This upgrading curve has several essential and
Fig. 5. Content (wt%) of Si and Ba in residue after leaching in pure water and nitric acid
solutions (1, 3, 5, 10 and 20%) (sample LCA11, as an example, t = 3 h, T = 90 °C, solid- characteristics points, including the leaching point at the minimum
to-liquid ratio 1:10). content of a particular element in the residue and its maximum ex-
traction. For ideal separation, the content in residue and extraction are
0 and 100%, respectively.
Fig. 6 demonstrates that, irrespective of the feed type, increasing the
extract copper (chalcopyrite and isocubanite) and zinc (sphalerite)
acid concentration decreased the content of Zn and Cu in the residues,
bearing minerals. Therefore, the feed and middling samples (Table 2),
while the extraction of these elements increased. It can be seen that Cu
that is the black smoker material, were subjected for leaching in water
and Zn can be efficiently extracted, with small loses in the residues at
and aqueous solutions of nitric acid (HNO3) as well as in the presence of
the nitric acid concentration of 10%. Higher concentrations of acid
sodium chloride.
slightly increased the extraction of copper and zinc. Application of
higher concentration of acid would only increase operation costs.
3.2.1. Acid concentration
Figs. 4–6 show the results of leaching on three investigated samples
3.2.2. Leaching time
(feed LCA11 and middling LCA12, LCA15, see Table 2) in water and
Fig. 7 shows the influence of leaching time on the content in the
aqueous solutions of nitric acid at different concentrations. It can be
residue and the extraction of copper, zinc and iron, using sample LCA11
seen that there was no extraction, or extraction was negligible in water.
as an example. Fig. 7 demonstrates that the content of copper, zinc and
It was confirmed by ICP-MS of leachate products (data are not shown
iron in residues decreased with leaching time, while the extraction of
here). Irrespective of the feed composition, the leaching rate and ex-
these elements initially increased with leaching time, ultimately
traction of copper, zinc and iron increased with the nitric acid con-
reaching a plateau. Copper and zinc presented similar dissolution pat-
centration, as evidenced by the decreased content of these elements (in
terns. Two different stages of leaching kinetics can be distinguished. In
wt%) in the remaining solid after leaching (residues). The content
the first stage (before 1 h), copper and zinc contained in minerals dis-
(concentration) of copper and zinc in the residues after leaching with
solved rapidly. In the second period, copper and zinc bearing minerals
20% nitric acid was almost zero for all investigated samples, while the
were dissolved at a relatively slow rate. Under the investigated condi-
extraction of these elements was higher than 95%. The results also
tions (solid-to-liquid ratio 1:10, acid concentration 10% and tempera-
showed that the HNO3 concentration of 10% was enough to extract
ture 90 °C) the optimum time for extraction of copper, zinc and iron was
almost all copper and zinc from the solids.
2 h. The extraction data for sulphur are not demonstrated here due to
Relatively low extraction (less than 70%) of sulphur, and thus its
the nature of formation of its elemental form and simultaneous oxida-
high content in the residues, were mostly likely due to formation of
tion.
non-polluting elemental sulphur during leaching with nitric acid, and
then its partial oxidation to sulphate ions (SO42−). When nitric acid is
added to an ore containing chalcopyrite (CuFeS2) and sphalerite (ZnS) 3.2.3. Temperature
the following reactions take place: Temperature has an essential effect on the leaching potential of
copper and zinc in the presence of nitric acid. Figs. 8–9 show that, ir-
3CuFeS2 + 20HNO3 → 3Cu(NO3)2 + 3Fe(NO3)3 + 6S° + 5NO + 10H2 O respective of the feed type (data shown for two samples LCA11 and
(2) LCA15, results for LCA12 are not provided due to its limited amount for
testing), the extraction of copper and zinc gradually increased with
6CuFeS2 + 22HNO3 → 6Cu(NO3)2 + 3Fe2 O3 + 12S° + 10NO + 11H2 O temperature. The gradient of the extraction-temperature relationship
(3) was the lowest for lower concentration of acid (1%) and increased
significantly with acid concentration increase. For the acid concentra-
3ZnS + 8HNO3 → 3Zn(NO3)2 + 3S° + 2NO + 4H2 O (4) tion of 10%, above 80 °C the influence of temperature on dissolution of

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copper was negligible. (90 g of solid per dm3) to 1:5 (170 g of solid per dm3). When the con-
It can be seen from Fig. 9 that all the experimental points fitted one centration of solid in the suspension was less than 90 g/dm3, that is s:l
single curve indicating the typical leaching trend. It indicates that the equal to 1:10, 1:20 and 1:30, the leaching efficiency of copper, zinc and
leaching behaviour of copper (Fig. 9a) and zinc (Fig. 9b) was generally iron was not influenced by the solid-to-liquid ratio (Figs. 10 and 11).
similar but occurred at different acid concentrations and temperatures.
The same results were observed for other tested samples. It indicates
that the leaching efficiency, and thus the extraction of copper and zinc 3.2.5. Sodium chloride concentration
is controlled by both temperature and acid concentration. For the same In order to check the influence of seawater on the extraction of
leaching time (2 h), at the acid concentration of 10%, lower tempera- copper and zinc, leaching experiments on sample LCA11 were con-
ture can be used to extract zinc and copper in comparison to leaching in ducted in the aqueous solutions of sodium chloride (3%) and mixtures
either 1 or 5% HNO3. High extraction of copper in 5% aqueous solution of 10% HNO3 with sodium chloride with different concentrations (1, 3,
of nitric acid was possible only at high temperature. 10%). There was no extraction of copper and zinc in 3% NaCl without
HNO3. The presence of salt in HNO3 leaching neither decreased nor
increased extraction of Cu, Zn or Fe (Table 3). The extraction and
3.2.4. Solid-to-liquid ratio content of these elements in the residues after leaching remained on the
Fig. 10 shows that the extraction of copper, zinc and iron only same level. The presence of salt accelerated only extraction of lead,
slightly decreased with the solid-to-liquid ratio decrease from 1:10 which was a trace element in the investigated samples.

100 100
10-20% 5-20% A 10-20% B
3% 10-20%
5% 3-5%
Cu 3-5% Cu
Zn Zn
80 80
3%
extraction, %

extraction, %

60 60
1%

40 40
1%

20 20

0%
0%
0% feed 0% feed
feed feed
0 0
0 1 2 3 4 5 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

content in residue, % content in residue, %

100
5-20%
10-20%
5%
C
3%
3%
Cu
80 Zn

1%
1%
extraction, %

60

40

20 0%

0%
feed feed
0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

content in residue, %
Fig. 6. Extraction-content in residue curves showing influence of acid concentration on leaching efficiency of samples (A) LCA11, (B) LCA12, (C) LCA15 (T = 90 °C, t = 3 h, solid-to-
liquid ratio 1:10).

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P.B. Kowalczuk et al. Minerals Engineering 115 (2018) 106–116

100 100
A 3h
3h 2h
B
2h
1h
1h
80 80
Cu
Zn

0.5 h 0.5 h
extraction, %

extraction, %
60 60

40 40

20 20
Cu
Zn

feed feed
0 0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 1 2 3 4 5

time, h content in residue, %

Fig. 7. Influence of leaching time on extraction (a, b) and content in residue (b) of copper and zinc (solid sample LCA11, as an example, T = 90 °C, acid concentration = 10%, solid-to-liquid ratio 1:10).

100 100
A B

80 80
Zn extraction, %
Cu extraction, %

60 60

40 40

HNO3
20 HNO3 20

5% 5%
10%
10%

0 0
0
feed 20 40 60 80 feed
0 20 40 60 80
temperature,oC
temperature,oC
100 100
C D

80 80
Cu extraction, %

Zn extraction, %

60 60

40 40

HNO3 HNO3
20 20
1% 1%
5% 5%
10% 10%

0 0
feed
0 20 40 60 80 feed
0 20 40 60 80
temperature,oC temperature,oC
Fig. 8. Influence of temperature and acid concentration on extraction of copper (A, C) and zinc (B, D) after leaching of samples LCA11 (A, B) and LCA15 (C, D) (solid-to-liquid ratio 1:10, t = 2 h).

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P.B. Kowalczuk et al. Minerals Engineering 115 (2018) 106–116

100 100
90 oC A 90 oC B
o
o
90 C o 70 C o
70 C 70 C
Copper 50 oC Zinc
80 80

70 oC 50 oC
50 oC
extraction, %

extraction, %
60 60 30 oC

40 40
50 oC
30 oC

20 HNO3 20 HNO3 30 oC

5% 30 oC 5%
10% 10%
feed feed
0 0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0 1 2 3 4

content in residue, % content in residue, %

Fig. 9. Extraction-content in residue curves showing influence of temperature and acid concentration on extraction of copper (A) and zinc (B) (sample LCA11, as an example, t = 2 h,
solid-to-liquid ratio 1:10).

1:30 1:20 1:10 1:5 100

100
50-90 oC 50-90 oC Cu 1:10
Cu 1:20
Zn 1:10
80 Zn 1:20
90

30 oC
o
60 50 C
extraction, %

80
extraction, %

Zn
Cu
Fe 40
70

30 oC

20
60

feed feed
0
1:30 1:20 1:10 1:5 0 1 2 3 4 5
50
0 20 40 60 80 100 120 140 160 180 content in residue, %
solid concentration, g/dm3 Fig. 11. Extraction-content in residue curves showing influence of temperature and solid-
to-liquid ratio on leaching efficiency of copper and zinc (sample LCA11, as an example,
Fig. 10. Influence of solid concentration (solid-to-liquid ratio) on extraction of zinc,
t = 2 h, T = 90 °C, acid concentration 10%).
copper and iron (sample LCA11, as an example, T = 90 °C, t = 3 h, acid concentration
10%).
Table 3
Extraction of Zn, Cu, Fe and S after leaching in nitric acid solution (10%) with different
3.3. Mineralogical analysis of feed and residues
concentrations of NaCl (sample LCA11, as an example, t = 3 h, T = 90 °C, solid-to-liquid
ratio 1:10).
In order to identify the mineral phases after leaching, mineralogical
analyses were performed on selected feed and residues. Figs. 12–14 Extraction, %
show microphotographs of solid samples LCA11, LCA12 and LCA15
Cu Zn Fe
before (A and B) and after leaching (C and D). The sample richest in
copper and zinc was LCA11. In all samples copper was present pre- 10% HNO3 92 93 96
dominantly as chalcopyrite and isocubanite, while zinc occurred as 10% HNO3 + 1% NaCl 90 90 96
10% HNO3 + 3% NaCl 90 89 95
sphalerite. The feed samples also contained significant quantities of
10% HNO3 + 10% NaCl 92 90 96
pyrite, with quartz and barite as a gangue material. Typical grains were
sub-rounded and approximately ∼100 µm. After leaching there was a
slight reduction in the grain size and significant reduction in sulphide in 20–100 µm grains of either quartz or barite. The elemental compo-
abundance to approximately 10% of the original material. Typically the sition (Table 4) and mineralogical data (Figs. 12–14) clearly indicated
remaining sulphides were extremely fine grained (< 10 µm) and locked that at least 90% of copper, zinc and iron bearing sulphide minerals

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Fig. 12. Microphotographs (reflected light, plane po-

larised) of sample LCA11 before (A, B) and after (C, D)
A B
leaching (solid-to-liquid ratio 1:10, T = 90 °C, t = 3 h,
acid concentration 10%).

800 μm 200 μm

C D

800 μm 200 μm

Fig. 13. Microphotographs (transmitted/reflected

A B light, plane polarised) of sample LCA12 before (A, B)
and after (C, D) leaching (solid-to-liquid ratio 1:10,
T = 90 °C, t = 3 h, acid concentration 10%).

800 μm 200 μm

C D

800 μm 200 μm

were leached out at the solid-to-liquid ratio of 1:10, T = 90 °C, t = 3 h, • Copper and zinc can be efficiently extracted from SMS material,
and acid concentration of 10%. with a small loses in the residues at an acid concentration of 10%.
• The extraction of copper and zinc gradually increased with tem-
4. Conclusions perature, but the effect on the dissolution of copper was negligible
above 80 °C at the acid concentration of 10%.
In the present study, hydrometallurgical leaching was applied to • The solid-to-liquid ratio and the sodium chloride concentration had
recover copper and zinc from seafloor massive sulphide (SMS) rock very little impact on the extraction of copper and zinc from SMS
samples from the Loki’s Castle hydrothermal vent field at the Arctic material.
Mid-Ocean Ridge. Nitric acid demonstrated a great potential for ex- • The extraction of Cu and Zn initially increased with leaching time,
traction of metals. Based on the presented results the following con- ultimately reaching a plateau after 2 h.
clusions can be drawn: • The optimum leaching conditions for extraction of Cu and Zn were:

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P.B. Kowalczuk et al. Minerals Engineering 115 (2018) 106–116

Fig. 14. Microphotographs (reflected light, plane po-

larised) of sample LCA15 before (A, B) and after (C, D)
A B
leaching (solid-to-liquid ratio 1:10, T = 90 °C, t = 3 h,
acid concentration 10%).

800 μm 200 μm

C D

800 μm 200 μm

Table 4 Fox, P.J., Normark, W., Carranza, A., Cordoba, D., Guerrero, J., Gantin, D., Bougault,
H., Cambon, P., Hekinian, R., 1979. Massive sulphide ore deposits discovered on the
Elemental composition (wt%) of feed and filtride samples (leaching: solid-to-liquid ratio
East Pacific Rise. Nature 277, 523–528.
1:10, T = 90 °C, t = 3 h, acid concentration 10%).
Fuerstenau, D.W., Han, K.N., 1983. Metallurgy and processing of marine manganese
nodules. Miner. Process. Extr. Metall. Rev. 1 (1–2), 1–83.
Sample ID Product Cu Zn Fe S Si Ba Gupta, C.K., Mukherjee, T.K., 1990. Hydrometallurgy in Extraction Processes. CRC Press,
Boston.
LCA11 Feed 1.46 4.24 11.54 17.03 23.05 6.38 Hannington, M., Jamieson, J., Monecke, T., Petersen, S., Beaulieu, S., 2001. The abun-
Residue 0.11 0.29 0.46 11.43 32.84 9.84 dance of seafloor massive sulphide deposits. Geology 39, 1155–1158.
Herzig, P.M., Peterson, S., Hannington, M.D., 2002. Polymetallic massive sulphide de-
LCA12 Feed 0.50 1.25 6.08 7.68 32.17 3.14
posits at the modern seafloor and their resource potential. In: Polymetallic Massive
Residue 0.05 0.09 0.22 3.58 39.10 2.80
Sulphides and Cobalt-Rich Ferromanganese Crusts: Status and Prospects. ISA
LCA15 Feed 0.67 1.26 4.39 6.58 5.13 30.53 Technical Study: No 2. International Seabed Authority, Kingston, Jamaica. ISSN 976-
Residue 0.03 0.06 0.18 4.23 38.18 4.76 610-467-0.
Jana, R.K., Murthy, D.S.R., Nayak, A.K., Mahanty, M.S., Tiwary, S.K., Akerkar, D.D.,
1990. Leaching of roast-reduced polymetallic sea nodules to optimise the recoveries
of copper, nickel and cobalt. Int. J. Miner. Process. 30, 127–141.
T = 90 °C, HNO3 concentration =10%, solid-to-liquid ratio 1:10, Ludvigsen, M., Aasly, K., Ellefemo, S., Hilario, A., Ramirez-Llodra, E., Søreide, F., Falcon-
time 2 h. Suarez, I., Juliani, C., Kieswetter, A., Lim, A., Malmquist, C., Nornes, S.M., Paulsen,
E., Reimers, H., Sture, Ø., 2016. NTNU Cruise Reports 2016 no 1 MarMine Arctic Mid
ocean Ridge 15.08.16-05.09.16., Trondheim, Norway, ISSN 2535-2520.
Acknowledgments Ma, B., Wang, C., Yang, W., Yang, B., Zhang, Y., 2013. Selective pressure leaching of Fe
(II)-rich limonitic laterite ores from Indonesia using nitric acid. Miner. Eng. 45,
This work was financed by the Research Council of Norway (Norges 151–158.
Morgan, C.L., 2000. Resource estimates of the Clarion-Clipperton manganese nodule
Forskningsråd, NFR) Project No 247626/O30. deposits. In: Cronan, D.S. (Ed.), Handbook of Marine Mineral Deposits, CRC Press,
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