XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1715
to vanadium and gallium being present as constant impu-
rities in the Bayer liquor. If these trace elements, includ-
ing vanadium, are not economically recovered from the
liquor, they end up reporting to the waste stream known as
bauxite residue (red mud). Although vanadium is a minor
Bayer liquor constituent, it has characteristics (high tensile
strength, resistance to corrosion and improves hardness in
alloys) that makes it suitable for multiple industrial appli-
cations covering steel manufacturing, energy storage, green
chemistry, aircraft and defence industries (Gao et al., 2022,
Hu et al., 2022). Vanadium demand has been propelled
by innovative uses such as thermochromic fenestration
coatings, catalyst for water-splitting to support the future
hydrogen-based economy, intercalation and solid-state bat-
teries (Perles, 2020).
Vanadium extraction from ores or slags has conven-
tionally been carried out using a combination of pyro-
metallurgy and hydrometallurgy (Gao et al., 2022). The
extraction route involves calcining, leaching, SX, and
ammonium treatment of strip liquor to precipitate the
vanadium salts such as ammonium metavanadate (AMV)
and vanadium pentoxide (Gao et al., 2022). The associ-
ated advantages of the conventional path are easy opera-
tion and a high purity product with good characteristics.
Nevertheless, this brings with it the challenges of generat-
ing significant amounts (20–40 tons of wastewater per ton
of V2O5—the most stable phase of the vanadium oxides) of
highly saline wastewater (Pan et al., 2020, Du et al., 2016).
The roasting and calcining steps involve high-temperature
unit operations which tend to increase energy consumption
and the carbon footprint of the processes. Research into
alternative routes of crystallizing vanadium salts without
these drawbacks has been conducted with membrane tech-
nology and electrolysis (Pan et al., 2020, Chen et al., 2022)
being touted as possible candidate technologies. The focus
on V2O5 nanostructures crystallization, using techniques
such as sol−gel, hydrothermal, chemical vapor deposition,
magnetron sputtering, and atomic layer deposition (Hu et
al., 2023), has also received attention. These nanostruc-
tures, when subjected to long term ageing, have been found
to coagulate into V2O5 nanofibers (Hu et al., 2023). Most
of the previous studies have zoned in on the need to better
understand the role of process parameters in influencing
the product characteristics and quality whilst minimizing
the adverse impacts of the conventional vanadium extrac-
tion route. Limited knowledge exists, however, on the use
of antisolvent crystallization to recover vanadium salts from
Bayer liquor. The potential of crystallizing sodium meta-
vanadate (intermediate product) from Bayer liquor using
antisolvent crystallization, and thereby removing the need
for proceeding via a roasting kiln, is a promising route.
In the current study, the role of antisolvent crystalli-
zation in the crystallization of high purity vanadium salts
from a Bayer liquor was investigated, with the aim of evalu-
ating if this could become an alternative, environmentally
friendly route. This approach is envisaged to bring the
additional benefit of recovering vanadium from the Bayer
liquor before it reports to the bauxite residue hence reduc-
ing the generation of the red mud.
MATERIALS AND METHODS
In all the experiments, synthetic feed solutions were made
using reagent grade sodium vanadate (Merck), aluminium
sulphate (Alfa Aesar), potassium sulphate (VWR) and cal-
cium sulphate (VWR) of 99.9% purity individually mixed
with Millipore water to supply V, Al, K and Ca whilst
reagent grade acetone (VWR) was used as the antisolvent.
The basis of the stock solution concentrations of V and that
of the impurities (Al (III), K (I), and Ca (II)) was in line
with industrial loaded strip liquor—LSL (Sole et al., 2008)
as indicated in Table 1. The pure system denoted LSL with
V only whilst the one with impurities was referred to as the
impure system.
A 100 mL jacketed glass crystallizer covered by a lid
with ports for pH and temperature probes, fitted with an
Ika overhead stirrer (operating at 300 rpm) and with the
solution temperature controlled at 25 ± 0.5 °C using a
thermostatic chiller (Julabo FP 50), shown in Figure 1, was
the vessel used for the batch experiments. Minimizing the
effects of evaporation, arising from the volatile nature of
the antisolvent, was done by sealing off the crystallizer. An
initial volume of 50 mL (synthetic LSL) was fed into the
crystallizer and allowed to attain a steady temperature (25
± 0.5 °C) before controlled acetone addition, at a constant
Table 1. Synthetic LSL composition and operating
conditions used for vanadium salt crystallization
Element Concentration (mg/L)
V (V) 30,000
Al (III) 25
K (I) 260
Ca (II) 430
Operating Conditions
Antisolvent volume 25 37.5 mL
Final O/A ratio 0.5 0.75 (vol/vol)
Stirring speed (overhead) 300 rpm
Antisolvent addition rate 5 mL/min
Maximum batch time 6 h
to vanadium and gallium being present as constant impu-
rities in the Bayer liquor. If these trace elements, includ-
ing vanadium, are not economically recovered from the
liquor, they end up reporting to the waste stream known as
bauxite residue (red mud). Although vanadium is a minor
Bayer liquor constituent, it has characteristics (high tensile
strength, resistance to corrosion and improves hardness in
alloys) that makes it suitable for multiple industrial appli-
cations covering steel manufacturing, energy storage, green
chemistry, aircraft and defence industries (Gao et al., 2022,
Hu et al., 2022). Vanadium demand has been propelled
by innovative uses such as thermochromic fenestration
coatings, catalyst for water-splitting to support the future
hydrogen-based economy, intercalation and solid-state bat-
teries (Perles, 2020).
Vanadium extraction from ores or slags has conven-
tionally been carried out using a combination of pyro-
metallurgy and hydrometallurgy (Gao et al., 2022). The
extraction route involves calcining, leaching, SX, and
ammonium treatment of strip liquor to precipitate the
vanadium salts such as ammonium metavanadate (AMV)
and vanadium pentoxide (Gao et al., 2022). The associ-
ated advantages of the conventional path are easy opera-
tion and a high purity product with good characteristics.
Nevertheless, this brings with it the challenges of generat-
ing significant amounts (20–40 tons of wastewater per ton
of V2O5—the most stable phase of the vanadium oxides) of
highly saline wastewater (Pan et al., 2020, Du et al., 2016).
The roasting and calcining steps involve high-temperature
unit operations which tend to increase energy consumption
and the carbon footprint of the processes. Research into
alternative routes of crystallizing vanadium salts without
these drawbacks has been conducted with membrane tech-
nology and electrolysis (Pan et al., 2020, Chen et al., 2022)
being touted as possible candidate technologies. The focus
on V2O5 nanostructures crystallization, using techniques
such as sol−gel, hydrothermal, chemical vapor deposition,
magnetron sputtering, and atomic layer deposition (Hu et
al., 2023), has also received attention. These nanostruc-
tures, when subjected to long term ageing, have been found
to coagulate into V2O5 nanofibers (Hu et al., 2023). Most
of the previous studies have zoned in on the need to better
understand the role of process parameters in influencing
the product characteristics and quality whilst minimizing
the adverse impacts of the conventional vanadium extrac-
tion route. Limited knowledge exists, however, on the use
of antisolvent crystallization to recover vanadium salts from
Bayer liquor. The potential of crystallizing sodium meta-
vanadate (intermediate product) from Bayer liquor using
antisolvent crystallization, and thereby removing the need
for proceeding via a roasting kiln, is a promising route.
In the current study, the role of antisolvent crystalli-
zation in the crystallization of high purity vanadium salts
from a Bayer liquor was investigated, with the aim of evalu-
ating if this could become an alternative, environmentally
friendly route. This approach is envisaged to bring the
additional benefit of recovering vanadium from the Bayer
liquor before it reports to the bauxite residue hence reduc-
ing the generation of the red mud.
MATERIALS AND METHODS
In all the experiments, synthetic feed solutions were made
using reagent grade sodium vanadate (Merck), aluminium
sulphate (Alfa Aesar), potassium sulphate (VWR) and cal-
cium sulphate (VWR) of 99.9% purity individually mixed
with Millipore water to supply V, Al, K and Ca whilst
reagent grade acetone (VWR) was used as the antisolvent.
The basis of the stock solution concentrations of V and that
of the impurities (Al (III), K (I), and Ca (II)) was in line
with industrial loaded strip liquor—LSL (Sole et al., 2008)
as indicated in Table 1. The pure system denoted LSL with
V only whilst the one with impurities was referred to as the
impure system.
A 100 mL jacketed glass crystallizer covered by a lid
with ports for pH and temperature probes, fitted with an
Ika overhead stirrer (operating at 300 rpm) and with the
solution temperature controlled at 25 ± 0.5 °C using a
thermostatic chiller (Julabo FP 50), shown in Figure 1, was
the vessel used for the batch experiments. Minimizing the
effects of evaporation, arising from the volatile nature of
the antisolvent, was done by sealing off the crystallizer. An
initial volume of 50 mL (synthetic LSL) was fed into the
crystallizer and allowed to attain a steady temperature (25
± 0.5 °C) before controlled acetone addition, at a constant
Table 1. Synthetic LSL composition and operating
conditions used for vanadium salt crystallization
Element Concentration (mg/L)
V (V) 30,000
Al (III) 25
K (I) 260
Ca (II) 430
Operating Conditions
Antisolvent volume 25 37.5 mL
Final O/A ratio 0.5 0.75 (vol/vol)
Stirring speed (overhead) 300 rpm
Antisolvent addition rate 5 mL/min
Maximum batch time 6 h