1248 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Lanthanum Adsorption Tests
Adsorption experiments were conducted by mixing 50 mg
biochar with 50 ml La-containing feedstock solution.
Several operating parameters were investigated throughout
the study to determine the optimal adsorption conditions.
The effect of pH on the recovery of lanthanum was tested
with values ranging from 2–6. This pH range was selected
due to the potential for lanthanum to precipitate as lantha-
num hydroxide in an alkaline media. The pH was adjusted
using 0.5M HCl and 0.5M NaOH, and the solution was
agitated for 24 hours. Contact time is also an important
factor in evaluating the efficiency of adsorbents. The effect
of contact time was studied at time intervals of 10min,
30min, 480min, and 1440min while keeping the solution
pH at 5. The effect of lanthanum initial concentration was
studied, and experiments were conducted with solutions
containing 0.2ppm, 12ppm, 72ppm, 230ppm, 640ppm,
and 1200ppm lanthanum). All the experiments were per-
formed at room temperature, and the agitation rate was
kept constant at 120 rpm. When the tests were completed,
the solution was filtered using a 0.22µm membrane filter,
and aqueous samples were analyzed with ICP-MS to detect
the elemental composition. On the other hand, separated
biochar was subjected to characterization tests. The elemen-
tal uptake, the adsorption capacity at equilibrium, and the
amount of lanthanum adsorbed at changing conditions
were calculated using the following equations, the uptake
percentage, (U%), the amount of lanthanum ions adsorbed
at time t, (qt), (mg/g) and the amount of lanthanum ions
desorbed at equilibrium qe (mg/g)
%
U% C
C C 100
e
0
0 =
-^h (1)
qt W
C C V
t 0 =
-^h (2)
q W
C C V
e
e 0 =
-^h (3)
where C0, Ct, and Ce are in (mg/L) and represent the initial
concentrations, time-dependent concentration, and equi-
librium concentrations of lanthanum ions, respectively. V
is the total volume of the lanthanum solution in (mL), and
W is the weight of the biochars in (mg).
After adsorption, desorption tests were carried out.
Depending on the biochar composition and structure, dif-
ferent regeneration methods can be used (Alsawy et al.,
2022). In this study, lanthanum desorption tests were per-
formed using three reagents with varying concentrations,
such as HCl (0.2 M, 0.5 M), NaOH (0.2 M, 0.5 M, and
2 M), and HNO3 (0.01 M, 0.2 M, and 0.5M) and the
desorption rate was calculated based on the equation given
below.
q W
C V
de
d
#
=(4)
%D% q
q
100
e
de #=(5)
where qde (mg/g) and Cd (mg/L) represents the amount of
lanthanum ions desorbed and concentration of lanthanum
ions desorbed in solution respectively.
Characterization Studies
Zeta potential was performed to determine the surface
charge on the biochars using the Malvern zeta sizer. For zeta
potential measurements, SW, WCC, and AH biochars were
first wet screened and grounded using an agate mortar and
pestle and were sieved through 500µm. Measurements were
carried out at room temperature. 0.5g of biochar sample
was added to the electrolyte solution (1 × 10–3M KCL) and
stirred using the electric shaker to obtain a uniform suspen-
sion. After 10 minutes of natural settling, 3ml of the super-
natant was collected and added to separate 50ml beakers
containing the electrolyte solution ranging from pH 2–pH
10 and was agitated for 5 minutes. The mixture was then
allowed to settle for 2 minutes. 40ml of the supernatant and
supporting electrolyte was placed inside the ultra-bath for
120 seconds and was immediately subjected to zeta poten-
tial measurements. Each zeta potential measurement was an
average of three duplicate measurements, and each separate
test was an average of 100 automatically repeated tests.
Scanning electron microscopy (SEM) (JOEL JSM
7600F) was used to determine the biochars’ morphology.
Each biochar sample was prepared by coating with Gold/
Palladium (Au/Pd) using the Denton Desk V sputter and
carbon coater for 90 seconds before SEM characteriza-
tion. This helps to reduce biochar’s charging effect, even
Table 1. The biochar sources and properties at the time of production
Biochar Source
Carbon
Organic, %Nitrogen, %Total Ash, %
Bulk Density,
lb/cu ft pH Value
SW Softwood 85.3 0.75 5.9 9.3 9.58
WCC Wood chips and chicken litter 41.18 3.88 33.1 9.4 9.4
AH Appalachian hardwood 82.6 0.76 9.7 9.1 9.58
Lanthanum Adsorption Tests
Adsorption experiments were conducted by mixing 50 mg
biochar with 50 ml La-containing feedstock solution.
Several operating parameters were investigated throughout
the study to determine the optimal adsorption conditions.
The effect of pH on the recovery of lanthanum was tested
with values ranging from 2–6. This pH range was selected
due to the potential for lanthanum to precipitate as lantha-
num hydroxide in an alkaline media. The pH was adjusted
using 0.5M HCl and 0.5M NaOH, and the solution was
agitated for 24 hours. Contact time is also an important
factor in evaluating the efficiency of adsorbents. The effect
of contact time was studied at time intervals of 10min,
30min, 480min, and 1440min while keeping the solution
pH at 5. The effect of lanthanum initial concentration was
studied, and experiments were conducted with solutions
containing 0.2ppm, 12ppm, 72ppm, 230ppm, 640ppm,
and 1200ppm lanthanum). All the experiments were per-
formed at room temperature, and the agitation rate was
kept constant at 120 rpm. When the tests were completed,
the solution was filtered using a 0.22µm membrane filter,
and aqueous samples were analyzed with ICP-MS to detect
the elemental composition. On the other hand, separated
biochar was subjected to characterization tests. The elemen-
tal uptake, the adsorption capacity at equilibrium, and the
amount of lanthanum adsorbed at changing conditions
were calculated using the following equations, the uptake
percentage, (U%), the amount of lanthanum ions adsorbed
at time t, (qt), (mg/g) and the amount of lanthanum ions
desorbed at equilibrium qe (mg/g)
%
U% C
C C 100
e
0
0 =
-^h (1)
qt W
C C V
t 0 =
-^h (2)
q W
C C V
e
e 0 =
-^h (3)
where C0, Ct, and Ce are in (mg/L) and represent the initial
concentrations, time-dependent concentration, and equi-
librium concentrations of lanthanum ions, respectively. V
is the total volume of the lanthanum solution in (mL), and
W is the weight of the biochars in (mg).
After adsorption, desorption tests were carried out.
Depending on the biochar composition and structure, dif-
ferent regeneration methods can be used (Alsawy et al.,
2022). In this study, lanthanum desorption tests were per-
formed using three reagents with varying concentrations,
such as HCl (0.2 M, 0.5 M), NaOH (0.2 M, 0.5 M, and
2 M), and HNO3 (0.01 M, 0.2 M, and 0.5M) and the
desorption rate was calculated based on the equation given
below.
q W
C V
de
d
#
=(4)
%D% q
q
100
e
de #=(5)
where qde (mg/g) and Cd (mg/L) represents the amount of
lanthanum ions desorbed and concentration of lanthanum
ions desorbed in solution respectively.
Characterization Studies
Zeta potential was performed to determine the surface
charge on the biochars using the Malvern zeta sizer. For zeta
potential measurements, SW, WCC, and AH biochars were
first wet screened and grounded using an agate mortar and
pestle and were sieved through 500µm. Measurements were
carried out at room temperature. 0.5g of biochar sample
was added to the electrolyte solution (1 × 10–3M KCL) and
stirred using the electric shaker to obtain a uniform suspen-
sion. After 10 minutes of natural settling, 3ml of the super-
natant was collected and added to separate 50ml beakers
containing the electrolyte solution ranging from pH 2–pH
10 and was agitated for 5 minutes. The mixture was then
allowed to settle for 2 minutes. 40ml of the supernatant and
supporting electrolyte was placed inside the ultra-bath for
120 seconds and was immediately subjected to zeta poten-
tial measurements. Each zeta potential measurement was an
average of three duplicate measurements, and each separate
test was an average of 100 automatically repeated tests.
Scanning electron microscopy (SEM) (JOEL JSM
7600F) was used to determine the biochars’ morphology.
Each biochar sample was prepared by coating with Gold/
Palladium (Au/Pd) using the Denton Desk V sputter and
carbon coater for 90 seconds before SEM characteriza-
tion. This helps to reduce biochar’s charging effect, even
Table 1. The biochar sources and properties at the time of production
Biochar Source
Carbon
Organic, %Nitrogen, %Total Ash, %
Bulk Density,
lb/cu ft pH Value
SW Softwood 85.3 0.75 5.9 9.3 9.58
WCC Wood chips and chicken litter 41.18 3.88 33.1 9.4 9.4
AH Appalachian hardwood 82.6 0.76 9.7 9.1 9.58