XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1165
the Philippines (14%) and the Russian Federation (7%). To
solve this problem while respecting the commitment that
part of these metals must come from recycling, it is neces-
sary to select suitable extraction processes.
For recycling, hydrometallurgical processes are com-
monly chosen (Xuan 2022 Zante 2020): while being
energy-efficient, they offer high selectivity, ensuring a final
product of sufficient purity to be reused in an industrial
process. However, this method involves a high consump-
tion of reagent, especially acid and basic fluxes, resulting
in a significant waste generation. Recycling acid streams
in this type of industry is therefore crucial, both economi-
cally and environmentally. Numerous processes have been
developed to solve this problem. They include liquid-liquid
extraction or the use of ion exchange resins. Nanofiltration
process, which has the advantage of being economical and
suitable for medium-sized installations, has long been con-
sidered effective technology only for low acid concentration
streams, due to the challenge caused by highly concentrated
leachates (Manis 2021). Indeed, the chemical resistance of
the membranes has long been too low to be able to treat
hydrometallurgical leachates, much too concentrated in
acid. The recent appearance of membrane resistant to pH
below zero now makes it possible to consider membrane
acid recycling processes in the hydrometallurgical industry.
In these solutions of high ionic strength, it is necessary to
use suitable models to consider the speciation of all the dif-
ferent chemical species (Dickson 2023).
To simulate this kind of separation, two types of model
are generally encountered:
• Model based on irreversible thermodynamics: these
model needs to be calibrated with experiments in
order to determine parameter fit for the system stud-
ied (López et al., 2021 Yaroshchuk 2013). The sim-
ulation is less precise if the experimental conditions
changed
• Model based on a mechanistic approach: generally
based on the Nernst-Planck equation, these model
focus on the internal transport phenomena inside the
membranes (Szymczyk and Fievet 2005). The pros of
this type of approach is that it is not necessary to cali-
brate the model and it propose a simulation capable
of representing a vast diversity of systems. However,
all the mechanism taking place in the separation
needs to be considered and a lot of data regarding the
elements in solution and the membrane are needed.
The second approach is selected for this study, as it offers
the opportunity to study solution with a wide range of con-
centrations. However, this work address one problem of
this types of model in the nanofiltration field: no reactive
transport model based on a mechanistic approach, which
consider the speciation of the ion inside the solution, is
available.
This study explores the use of nanofiltration mem-
branes as leachate recycling processes for solutions with sul-
furic acid mass concentrations from 5 to 20%. Ash leachate
from the Odontarrhena chalcidica hyperaccumulator plant
is selected as the representative solution in this study.
Indeed, it presents a great diversity of elements (Al, Ca, Fe,
K, Mg, Mn, Ni, P, Zn), with a high concentration of nickel
and magnesium, and a concentration of 2 mol/L of sulfuric
acid (Houzelot, 2017). As stated before, these two elements
will be key to the environmental transition, making this
leachate a perfect candidate for our study.
MATERIALS AND METHODS
Nickel Leachate
The solution studied comes from an acid leaching of the ash
from the hyperaccumulator Odontarrhena chalcidica from
the Brassicaceae family. This plant is able to concentrate
nickel in its above-ground parts to values of over 1% (or
over 10% in the ash). Ultramafic soils can be considered as
a secondary nickel resource that can be exploited through
the cultivation of these plants. The plant sample used was
cultivated in the Pogradec region of Albania, on soil con-
taining 3 to 7 mgNi/kgdry
soil (Bani et al., 2015). It was
calcined in an industrial boiler (KWB Multifire MF2 D/
ZI) at an average temperature of 900 °C with a residence
time of 20 min. This boiler can process a large quantity
of biomass, but combustion is not complete for the whole
batch. A supplementary combustion of an ash sample is
therefore carried out at laboratory scale, in a muffle furnace
(Nabertherm LE 14/11 B150) at 900°C for 80 min.
Leaching was carried out in a 10 L jacketed glass reac-
tor, in which 600 g of ash and 3 L of 2 M sulfuric acid
(Sigma-Aldrich, 95–97%) were placed. It was run at 75
°C for 6 hr. After cooling, filtration was performed using
Whatman filters (20 μm). The solution was placed in a
cold room for a week, to to allow complete precipitation
of gypsum is complete and an ultrafiltration (membrane
Microdyn Nadir PM UP005 of 5000 daltons) is carried
out. Elemental composition of the solution, analysed by
induced plasma emission spectroscopy (ICP-AES), is given
in Table 1.
Nanofiltration of the Leachate
Nanofiltration of the leachate was performed in a Seprosys
pilot consisting of (i) a hydraulic system in PVDF and PEEK,
and valves in PVDF to ensure high chemical resistance, (ii)
the Philippines (14%) and the Russian Federation (7%). To
solve this problem while respecting the commitment that
part of these metals must come from recycling, it is neces-
sary to select suitable extraction processes.
For recycling, hydrometallurgical processes are com-
monly chosen (Xuan 2022 Zante 2020): while being
energy-efficient, they offer high selectivity, ensuring a final
product of sufficient purity to be reused in an industrial
process. However, this method involves a high consump-
tion of reagent, especially acid and basic fluxes, resulting
in a significant waste generation. Recycling acid streams
in this type of industry is therefore crucial, both economi-
cally and environmentally. Numerous processes have been
developed to solve this problem. They include liquid-liquid
extraction or the use of ion exchange resins. Nanofiltration
process, which has the advantage of being economical and
suitable for medium-sized installations, has long been con-
sidered effective technology only for low acid concentration
streams, due to the challenge caused by highly concentrated
leachates (Manis 2021). Indeed, the chemical resistance of
the membranes has long been too low to be able to treat
hydrometallurgical leachates, much too concentrated in
acid. The recent appearance of membrane resistant to pH
below zero now makes it possible to consider membrane
acid recycling processes in the hydrometallurgical industry.
In these solutions of high ionic strength, it is necessary to
use suitable models to consider the speciation of all the dif-
ferent chemical species (Dickson 2023).
To simulate this kind of separation, two types of model
are generally encountered:
• Model based on irreversible thermodynamics: these
model needs to be calibrated with experiments in
order to determine parameter fit for the system stud-
ied (López et al., 2021 Yaroshchuk 2013). The sim-
ulation is less precise if the experimental conditions
changed
• Model based on a mechanistic approach: generally
based on the Nernst-Planck equation, these model
focus on the internal transport phenomena inside the
membranes (Szymczyk and Fievet 2005). The pros of
this type of approach is that it is not necessary to cali-
brate the model and it propose a simulation capable
of representing a vast diversity of systems. However,
all the mechanism taking place in the separation
needs to be considered and a lot of data regarding the
elements in solution and the membrane are needed.
The second approach is selected for this study, as it offers
the opportunity to study solution with a wide range of con-
centrations. However, this work address one problem of
this types of model in the nanofiltration field: no reactive
transport model based on a mechanistic approach, which
consider the speciation of the ion inside the solution, is
available.
This study explores the use of nanofiltration mem-
branes as leachate recycling processes for solutions with sul-
furic acid mass concentrations from 5 to 20%. Ash leachate
from the Odontarrhena chalcidica hyperaccumulator plant
is selected as the representative solution in this study.
Indeed, it presents a great diversity of elements (Al, Ca, Fe,
K, Mg, Mn, Ni, P, Zn), with a high concentration of nickel
and magnesium, and a concentration of 2 mol/L of sulfuric
acid (Houzelot, 2017). As stated before, these two elements
will be key to the environmental transition, making this
leachate a perfect candidate for our study.
MATERIALS AND METHODS
Nickel Leachate
The solution studied comes from an acid leaching of the ash
from the hyperaccumulator Odontarrhena chalcidica from
the Brassicaceae family. This plant is able to concentrate
nickel in its above-ground parts to values of over 1% (or
over 10% in the ash). Ultramafic soils can be considered as
a secondary nickel resource that can be exploited through
the cultivation of these plants. The plant sample used was
cultivated in the Pogradec region of Albania, on soil con-
taining 3 to 7 mgNi/kgdry
soil (Bani et al., 2015). It was
calcined in an industrial boiler (KWB Multifire MF2 D/
ZI) at an average temperature of 900 °C with a residence
time of 20 min. This boiler can process a large quantity
of biomass, but combustion is not complete for the whole
batch. A supplementary combustion of an ash sample is
therefore carried out at laboratory scale, in a muffle furnace
(Nabertherm LE 14/11 B150) at 900°C for 80 min.
Leaching was carried out in a 10 L jacketed glass reac-
tor, in which 600 g of ash and 3 L of 2 M sulfuric acid
(Sigma-Aldrich, 95–97%) were placed. It was run at 75
°C for 6 hr. After cooling, filtration was performed using
Whatman filters (20 μm). The solution was placed in a
cold room for a week, to to allow complete precipitation
of gypsum is complete and an ultrafiltration (membrane
Microdyn Nadir PM UP005 of 5000 daltons) is carried
out. Elemental composition of the solution, analysed by
induced plasma emission spectroscopy (ICP-AES), is given
in Table 1.
Nanofiltration of the Leachate
Nanofiltration of the leachate was performed in a Seprosys
pilot consisting of (i) a hydraulic system in PVDF and PEEK,
and valves in PVDF to ensure high chemical resistance, (ii)