XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1247
and alloys in either its pure form or in combination with
other elements (Bohlen et al., 2010 Zheng et al., 2020).
However, the recovery of REEs is known to be complex.
The most commonly used methods, liquid-liquid extrac-
tion (Alcaraz et al., 2022) and leaching (Abhilash et al.,
2014), are expensive and not environmentally friendly due
to the high chemical consumption and waste discharged to
the environment (Quijada-Maldonado &Romero, 2021).
Knowing this, efforts have been made by several researchers
to extract lanthanum from waste streams in the most cost-
effective method feasible. These methods include precipita-
tion (Zhang et al., 2022 Zhang &Honaker, 2018), ion
exchange (Rozelle et al., 2016), membrane separation (Croft
et al., 2022), and adsorption (Ramasamy et al., 2018).
Adsorption has been studied by many researchers
in recent years and proved to be an effective method for
extracting lanthanum due to its low cost, less environmen-
tal impacts, high selectivity, simplicity, and efficiency com-
pared to the conventional methods (Moradi &Sharma,
2021 Mudhoo et al., 2021). Several materials with great
adsorption capacity have been discovered for rare earths,
such as activated carbon (Murty &Chakrapani, 1996), zeo-
lites, chitosan (Wu et al., 2011), silica gels (Ramasamy et al.,
2017), modified graphite (Youssef et al., 2022). However,
for lanthanum extraction, researchers discovered durian
rind biosorbents (Kusrini et al., 2019), bamboo charcoal
(Chen, 2010), brown marine algae (Vijayaraghavan et al.,
2010), crab shells (Vijayaraghavan et al., 2009), and bio-
char (Zhao et al., 2021).
Biochar is a carbon-rich substance obtained by the
pyrolysis of biomass (i.e., agricultural waste, animal
manure, wood product, and other organic waste) at high
pyrolysis temperatures under an inert environment. Biochar
has attracted widespread interest as a great adsorbent and
catalyst support because of its porous structure, low cost,
and environmental compatibility (Ambaye et al., 2021 Lee
et al., 2017). It can be employed in agriculture, medicine,
environmental management, material science, wastewater
treatment, soil amelioration, and power production because
of its extremely stable honeycomb-like carbonaceous struc-
ture (Bartoli et al., 2020 Boraah et al., 2022 Sohi et al.,
2010 Zhang et al., 2013). It is comprised mainly of car-
bon, oxygen, and ash with minerals of numerous pore sizes,
and its chemical composition may vary based on the source
of the biomass and pyrolysis conditions (Oni et al., 2019).
Depending on the source and the processing condi-
tions, biochar samples could have very different functional
groups. The presence of these functional groups impacts
the adsorption of specific elements such as aluminum,
copper, manganese, lead, and cadmium (Qambrani et al.,
2017). Like activated carbon, biochars have similar adsorp-
tion mechanisms and could also transform contaminants
into composites and participate through surface interac-
tion (Dong et al., 2011 Wang et al., 2015). This adsorp-
tion mechanism is also based on the negative surface of the
biochar attracting positive ions (Inyang et al., 2016 Zhao
et al., 2021). Jiang et al. studied the adsorption mecha-
nism of hardwood and softwood biochar for copper and
zinc (divalent metal ions) adsorption and revealed that
the hardwood biochar showed higher adsorption capacity
(Qmax =4.39mg/g and 2.31mg/g) than the softwood bio-
char (Qmax= 1.47mg/g and 1.0 mg/g) for copper and zinc,
respectively (Jiang et al., 2016). Amoah-antwi et al. also
studied the efficacy of wood chip biochar as sorbents for
cadmium, lead, and zinc in soils and concluded that bio-
char is efficient for heavy metal adsorption (Amoah-Antwi
et al., 2020). The sorption mechanisms for metal ions could
either be complexation, electrostatic attraction, or cation
exchange. Micropores in these biochars account for their
adsorption capacity and surface area while the mesopores
are important for liquid-solid adsorption, and the macro-
pores are important for hydrology, bulk soil structure, aera-
tion, and movement (Freddo et al., 2012).
In this study, the authors examined the use of biochar
as an effective adsorbent for lanthanum recovery from an
aqueous solution. It was targeted to develop insight into
biochar’s adsorption capacity and the applicability of this
approach toward developing more sustainable recovery pro-
cesses. The tests were initially conducted with a synthetic
solution and later applied on multi rare earth-containing
system with impurity metals.
MATERIALS AND METHODS
Feedstock and Biochar Preparation
Tests were performed with a synthetic solution prepared by
high purity (99%) lanthanum (III) nitrate hexahydrate
purchased from Sigma Aldrich. Feedstocks with varying
lanthanum content were prepared and used. Softwood
(SW) forestry residue harvested from Northern California,
a mixture of wood chips and chicken litter (WCC), and
Appalachian hardwood (AH) collected in West Virginia
were used as biomass sources. Biochars were produced via
an optimized gasification process at different pyrolysis tem-
peratures of 450°C, 700°C, and 675 °C with a heating rate
of 20°C/min for 10min. The biochars were then left to cool
at room temperature for 12 hours, where it is then sieved
to obtain a uniform particle size of 3mm. Biochar samples
were then further grounded to obtain 500µm particle size
and put inside the desiccator to avoid moisture adsorption.
Table 1 summarizes the biochar sources and properties.
and alloys in either its pure form or in combination with
other elements (Bohlen et al., 2010 Zheng et al., 2020).
However, the recovery of REEs is known to be complex.
The most commonly used methods, liquid-liquid extrac-
tion (Alcaraz et al., 2022) and leaching (Abhilash et al.,
2014), are expensive and not environmentally friendly due
to the high chemical consumption and waste discharged to
the environment (Quijada-Maldonado &Romero, 2021).
Knowing this, efforts have been made by several researchers
to extract lanthanum from waste streams in the most cost-
effective method feasible. These methods include precipita-
tion (Zhang et al., 2022 Zhang &Honaker, 2018), ion
exchange (Rozelle et al., 2016), membrane separation (Croft
et al., 2022), and adsorption (Ramasamy et al., 2018).
Adsorption has been studied by many researchers
in recent years and proved to be an effective method for
extracting lanthanum due to its low cost, less environmen-
tal impacts, high selectivity, simplicity, and efficiency com-
pared to the conventional methods (Moradi &Sharma,
2021 Mudhoo et al., 2021). Several materials with great
adsorption capacity have been discovered for rare earths,
such as activated carbon (Murty &Chakrapani, 1996), zeo-
lites, chitosan (Wu et al., 2011), silica gels (Ramasamy et al.,
2017), modified graphite (Youssef et al., 2022). However,
for lanthanum extraction, researchers discovered durian
rind biosorbents (Kusrini et al., 2019), bamboo charcoal
(Chen, 2010), brown marine algae (Vijayaraghavan et al.,
2010), crab shells (Vijayaraghavan et al., 2009), and bio-
char (Zhao et al., 2021).
Biochar is a carbon-rich substance obtained by the
pyrolysis of biomass (i.e., agricultural waste, animal
manure, wood product, and other organic waste) at high
pyrolysis temperatures under an inert environment. Biochar
has attracted widespread interest as a great adsorbent and
catalyst support because of its porous structure, low cost,
and environmental compatibility (Ambaye et al., 2021 Lee
et al., 2017). It can be employed in agriculture, medicine,
environmental management, material science, wastewater
treatment, soil amelioration, and power production because
of its extremely stable honeycomb-like carbonaceous struc-
ture (Bartoli et al., 2020 Boraah et al., 2022 Sohi et al.,
2010 Zhang et al., 2013). It is comprised mainly of car-
bon, oxygen, and ash with minerals of numerous pore sizes,
and its chemical composition may vary based on the source
of the biomass and pyrolysis conditions (Oni et al., 2019).
Depending on the source and the processing condi-
tions, biochar samples could have very different functional
groups. The presence of these functional groups impacts
the adsorption of specific elements such as aluminum,
copper, manganese, lead, and cadmium (Qambrani et al.,
2017). Like activated carbon, biochars have similar adsorp-
tion mechanisms and could also transform contaminants
into composites and participate through surface interac-
tion (Dong et al., 2011 Wang et al., 2015). This adsorp-
tion mechanism is also based on the negative surface of the
biochar attracting positive ions (Inyang et al., 2016 Zhao
et al., 2021). Jiang et al. studied the adsorption mecha-
nism of hardwood and softwood biochar for copper and
zinc (divalent metal ions) adsorption and revealed that
the hardwood biochar showed higher adsorption capacity
(Qmax =4.39mg/g and 2.31mg/g) than the softwood bio-
char (Qmax= 1.47mg/g and 1.0 mg/g) for copper and zinc,
respectively (Jiang et al., 2016). Amoah-antwi et al. also
studied the efficacy of wood chip biochar as sorbents for
cadmium, lead, and zinc in soils and concluded that bio-
char is efficient for heavy metal adsorption (Amoah-Antwi
et al., 2020). The sorption mechanisms for metal ions could
either be complexation, electrostatic attraction, or cation
exchange. Micropores in these biochars account for their
adsorption capacity and surface area while the mesopores
are important for liquid-solid adsorption, and the macro-
pores are important for hydrology, bulk soil structure, aera-
tion, and movement (Freddo et al., 2012).
In this study, the authors examined the use of biochar
as an effective adsorbent for lanthanum recovery from an
aqueous solution. It was targeted to develop insight into
biochar’s adsorption capacity and the applicability of this
approach toward developing more sustainable recovery pro-
cesses. The tests were initially conducted with a synthetic
solution and later applied on multi rare earth-containing
system with impurity metals.
MATERIALS AND METHODS
Feedstock and Biochar Preparation
Tests were performed with a synthetic solution prepared by
high purity (99%) lanthanum (III) nitrate hexahydrate
purchased from Sigma Aldrich. Feedstocks with varying
lanthanum content were prepared and used. Softwood
(SW) forestry residue harvested from Northern California,
a mixture of wood chips and chicken litter (WCC), and
Appalachian hardwood (AH) collected in West Virginia
were used as biomass sources. Biochars were produced via
an optimized gasification process at different pyrolysis tem-
peratures of 450°C, 700°C, and 675 °C with a heating rate
of 20°C/min for 10min. The biochars were then left to cool
at room temperature for 12 hours, where it is then sieved
to obtain a uniform particle size of 3mm. Biochar samples
were then further grounded to obtain 500µm particle size
and put inside the desiccator to avoid moisture adsorption.
Table 1 summarizes the biochar sources and properties.