714 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
and P2O5. The presence of Fe2O3, Al2O3, and MgO fur-
ther validates the existence of clay minerals in the tailings.
Mineralogical analysis using XRD, coupled with
chemical characterization, reveals the presence of calcite,
dolomite, fluorapatite, quartz, montmorillonite, palygor-
skite, and kaolinite. The elevated percentages of CaO and
MgO suggest a significant abundance of carbonate min-
erals in the sample. Approximately 19% of the sample’s
composition is constituted by clay minerals, specifically
palygorskite, montmorillonite, and kaolinite, as outlined in
Table 3. Notably, the sample exhibits a substantial residual
quantity of fluorapatite (29%) alongside carbonate miner-
als (41%) and quartz (12%).
The zeta potential study, conducted with a dilute sus-
pension containing 0.1 wt.% solids in a background of
distilled 10–3 M KCl electrolyte, is depicted in Figure 2.
Notably, the tailings consistently demonstrate a negative
charge at the slipping g plane of the particles across the
pH range investigated, spanning from 4 to 10. The magni-
tude of the charge intensifies with rising pH and reaches its
minimum value at pH 10. Beyond a pH value of 11, the
zeta potential remains relatively constant, maintaining its
lowest values.
As the tailings contain varying proportions of min-
eral phases, with a predominance of phases exhibiting a
negative charge across the studied pH range (A. Kaya &
Yukselen, 2005 Y. Y. A. Kaya, 2011 Moulin &Roques,
2003 Owens et al., 2019 Saka &Gu, 2006 White, 1986),
the overall slipping plane charge of the sample is negative.
The isoelectric point of the sample is prominently evident
at pH levels lower than 2.
Figure 2. Particle size distribution of the FPTs sample
Table 3. Chemical and mineralogical analyses of the FPTS sample
Chemical
Composition
Oxide CaO SiO
2 Al
2 O
3 Fe
2 O
3 MgO K
2 O Na
2 O P
2 O
5 Other LOI Total LOD*
%wt 38.77 20.22 2.72 1.06 3.07 0.49 0.61 13.2 1.21 18.65 100 0.01
Mineralogical
Composition
Mineral Fluorapatite Calcite Dolomite Quartz Palygorskite Palygorskite Montmorillonite Kaolinite
%wt 28 29 12 12 6 6 8 5
*Limit of detection.

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Extracted Text (may have errors)

714 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
and P2O5. The presence of Fe2O3, Al2O3, and MgO fur-
ther validates the existence of clay minerals in the tailings.
Mineralogical analysis using XRD, coupled with
chemical characterization, reveals the presence of calcite,
dolomite, fluorapatite, quartz, montmorillonite, palygor-
skite, and kaolinite. The elevated percentages of CaO and
MgO suggest a significant abundance of carbonate min-
erals in the sample. Approximately 19% of the sample’s
composition is constituted by clay minerals, specifically
palygorskite, montmorillonite, and kaolinite, as outlined in
Table 3. Notably, the sample exhibits a substantial residual
quantity of fluorapatite (29%) alongside carbonate miner-
als (41%) and quartz (12%).
The zeta potential study, conducted with a dilute sus-
pension containing 0.1 wt.% solids in a background of
distilled 10–3 M KCl electrolyte, is depicted in Figure 2.
Notably, the tailings consistently demonstrate a negative
charge at the slipping g plane of the particles across the
pH range investigated, spanning from 4 to 10. The magni-
tude of the charge intensifies with rising pH and reaches its
minimum value at pH 10. Beyond a pH value of 11, the
zeta potential remains relatively constant, maintaining its
lowest values.
As the tailings contain varying proportions of min-
eral phases, with a predominance of phases exhibiting a
negative charge across the studied pH range (A. Kaya &
Yukselen, 2005 Y. Y. A. Kaya, 2011 Moulin &Roques,
2003 Owens et al., 2019 Saka &Gu, 2006 White, 1986),
the overall slipping plane charge of the sample is negative.
The isoelectric point of the sample is prominently evident
at pH levels lower than 2.
Figure 2. Particle size distribution of the FPTs sample
Table 3. Chemical and mineralogical analyses of the FPTS sample
Chemical
Composition
Oxide CaO SiO
2 Al
2 O
3 Fe
2 O
3 MgO K
2 O Na
2 O P
2 O
5 Other LOI Total LOD*
%wt 38.77 20.22 2.72 1.06 3.07 0.49 0.61 13.2 1.21 18.65 100 0.01
Mineralogical
Composition
Mineral Fluorapatite Calcite Dolomite Quartz Palygorskite Palygorskite Montmorillonite Kaolinite
%wt 28 29 12 12 6 6 8 5
*Limit of detection.

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XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 713
over time to calculate the settling rate of the flocculated
suspension. The initial settling rate (ISR) of particles was
determined from the slope of the linear part of mudline
interface height versus sedimentation time. Following a
20-minute settling period, an aliquot of the supernatant
was extracted for turbidity measurement using a turbi-
dimeter (Hanna Instruments HI-88713-02), reported in
nephelometric turbidity units (NTU). The sedimented part
served to determine the final solid content of the thickened
tailings. The global methodology used for the current study
is highlighted in Figure 1.
Experimental Design and Statistical Analysis
The design of experiments (DOE) and the optimization
of the flocculation-sedimentation process were conducted
using Design Expert ® 13.0.5.0 software (Stat-Ease Inc.,
USA). A central composite design (CCD) was employed
to investigate the effect of flocculant dosage, pH and stir-
ring speed on the flocculation and sedimentation effec-
tiveness (ISR, water recovery and turbidity). The CCD is
well-suited for assessing both the primary effects of each
variable and the interactions between the studied factors, all
within a constrained number of experiments (Ait-khouia et
al., 2022).
A face centred CCD (α =1) comprises 2n factorial runs
(e.g., –1, –1, –1), n axial runs (e.g., α, 0, 0), and nc center
runs (0, 0, 0), resulting in a total of N runs. This study
employed a comprehensive 23 factorial design (8 points),
complemented by 2 axial points per factor at a distance ±
α from the design center (6 points) and replicates of the
design center (6 points). In total, 20 experimental runs
were carried out during the CCD experiments (Eq. 1).
*N n 2 2n 3 2 3 6 20 n
c =++=++=(1)
An empirical model correlating the flocculation effi-
ciency parameters with dewatering process variables was
developed using a cubic function obtained for the study
variables, as presented in Eq 2.
Y x x x x
x x x x x x
x x x x x x
x x x2
i i
i
ii i ij i
i i i
j
i
iii i
i
0
1
3
2
1
3
1
3
1
3
3
123 1 2 3 1 1
2
2
1
3
1 3 1
2
3 2l1 2
2
1 2l3 2
2
3
3 3
2
3
2
1 1
b b b b
b b b
b b b
b b3l2x f
=+++
+++
+++
+++
=====
=
l2
l
l
////
/
(2)
where Y stands for the response variable, while the propor-
tions of the mix ingredients are denoted as xi and xj. The
coefficients for regression are represented as βi, βii, βij and
βiii (constant term, linear terms, interaction terms, qua-
dratic terms and cubic terms) ε is the residual associated
to the experiments. Supplementary information regarding
the measurements and their corresponding responses are
depicted in Table 2. The assessment of the model’s qual-
ity relied on the coefficient of determination (R2) and the
statistical significance of the model was evaluated through
analysis of variance (ANOVA). Coding the studied factors
facilitated the transformation of actual values into dimen-
sionless coordinates. These coded variables were assigned
values of –1, 0, and +1, representing the lowest, central, and
maximum limits for each studied variable. This approach
eliminates the influence of variable magnitudes, enabling
the combination of factors on a dimensionless scale (Sun
et al., 2010).
RESULTS AND DISCUSSION
Characterization Results
The particle size distribution (PSD) curve for the FPTs is
illustrated in Figure 1. It is evident from the graph that
80% of the sample exhibits a particle size smaller than
103 µm, while 50% of the sample is smaller than 53 µm.
Furthermore, 10% of the sample is smaller than 9.4 µm.
These findings suggest that our sample is primarily com-
posed of clay and silt-rich material.
The chemical composition of the FPTs sample, deter-
mined through the XRF method, is presented in Table 3. As
indicated, the sample is notably abundant in CaO, SiO2,
Table 2. Experimental process variables, units, levels, corresponding natural and coded values
Variable Units
Levels
Performance Parameters −1 0 +1
X1: Dosage g/tds 40 70 100 Initial settling rate (cm/min)
Water recovery (%)
Water turbidity (NTU)
X
2 :pH — 6 8 10
X
3 :Mixing rate rpm 60 100 140

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Extracted Text (may have errors)

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 713
over time to calculate the settling rate of the flocculated
suspension. The initial settling rate (ISR) of particles was
determined from the slope of the linear part of mudline
interface height versus sedimentation time. Following a
20-minute settling period, an aliquot of the supernatant
was extracted for turbidity measurement using a turbi-
dimeter (Hanna Instruments HI-88713-02), reported in
nephelometric turbidity units (NTU). The sedimented part
served to determine the final solid content of the thickened
tailings. The global methodology used for the current study
is highlighted in Figure 1.
Experimental Design and Statistical Analysis
The design of experiments (DOE) and the optimization
of the flocculation-sedimentation process were conducted
using Design Expert ® 13.0.5.0 software (Stat-Ease Inc.,
USA). A central composite design (CCD) was employed
to investigate the effect of flocculant dosage, pH and stir-
ring speed on the flocculation and sedimentation effec-
tiveness (ISR, water recovery and turbidity). The CCD is
well-suited for assessing both the primary effects of each
variable and the interactions between the studied factors, all
within a constrained number of experiments (Ait-khouia et
al., 2022).
A face centred CCD (α =1) comprises 2n factorial runs
(e.g., –1, –1, –1), n axial runs (e.g., α, 0, 0), and nc center
runs (0, 0, 0), resulting in a total of N runs. This study
employed a comprehensive 23 factorial design (8 points),
complemented by 2 axial points per factor at a distance ±
α from the design center (6 points) and replicates of the
design center (6 points). In total, 20 experimental runs
were carried out during the CCD experiments (Eq. 1).
*N n 2 2n 3 2 3 6 20 n
c =++=++=(1)
An empirical model correlating the flocculation effi-
ciency parameters with dewatering process variables was
developed using a cubic function obtained for the study
variables, as presented in Eq 2.
Y x x x x
x x x x x x
x x x x x x
x x x2
i i
i
ii i ij i
i i i
j
i
iii i
i
0
1
3
2
1
3
1
3
1
3
3
123 1 2 3 1 1
2
2
1
3
1 3 1
2
3 2l1 2
2
1 2l3 2
2
3
3 3
2
3
2
1 1
b b b b
b b b
b b b
b b3l2x f
=+++
+++
+++
+++
=====
=
l2
l
l
////
/
(2)
where Y stands for the response variable, while the propor-
tions of the mix ingredients are denoted as xi and xj. The
coefficients for regression are represented as βi, βii, βij and
βiii (constant term, linear terms, interaction terms, qua-
dratic terms and cubic terms) ε is the residual associated
to the experiments. Supplementary information regarding
the measurements and their corresponding responses are
depicted in Table 2. The assessment of the model’s qual-
ity relied on the coefficient of determination (R2) and the
statistical significance of the model was evaluated through
analysis of variance (ANOVA). Coding the studied factors
facilitated the transformation of actual values into dimen-
sionless coordinates. These coded variables were assigned
values of –1, 0, and +1, representing the lowest, central, and
maximum limits for each studied variable. This approach
eliminates the influence of variable magnitudes, enabling
the combination of factors on a dimensionless scale (Sun
et al., 2010).
RESULTS AND DISCUSSION
Characterization Results
The particle size distribution (PSD) curve for the FPTs is
illustrated in Figure 1. It is evident from the graph that
80% of the sample exhibits a particle size smaller than
103 µm, while 50% of the sample is smaller than 53 µm.
Furthermore, 10% of the sample is smaller than 9.4 µm.
These findings suggest that our sample is primarily com-
posed of clay and silt-rich material.
The chemical composition of the FPTs sample, deter-
mined through the XRF method, is presented in Table 3. As
indicated, the sample is notably abundant in CaO, SiO2,
Table 2. Experimental process variables, units, levels, corresponding natural and coded values
Variable Units
Levels
Performance Parameters −1 0 +1
X1: Dosage g/tds 40 70 100 Initial settling rate (cm/min)
Water recovery (%)
Water turbidity (NTU)
X
2 :pH — 6 8 10
X
3 :Mixing rate rpm 60 100 140

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 715
Flocculation 4293
To explore the settling behaviour of FPTs particles, floc-
culation and sedimentation experiments were conducted
using 60 g/tds dosage of both anionic and cationic poly-
acrylamide polymers. Additionally, a natural sedimentation
test was employed for comparison purposes. The objective
was to achieve efficient and cost-effective solid–liquid sepa-
ration by identifying the optimal flocculant that delivers
excellent performance in terms of maximizing water recov-
ery, enhancing settling rate and minimizing water turbidity.
The outcomes are depicted in Figure 3, revealing a
clear dependency of settling velocity on the type of floc-
culant used for FPTs flocculation. Notably, anionic poly-
acrylamides exhibited superior settling velocities and water
recoveries compared to their cationic counterparts. This
finding is in accordance with previous studies conducted
using anionic and cationic polyacrylamides (Bahmani-
Ghaedi et al., 2022 Fan et al., 2020 Liang et al., 2021 Liu
et al., 2020 Zhang et al., 2024).
As illustrated in Figure 4, the final settling heights of
the FPTs slurry with the four tested flocculants displayed
relatively slight variations, ranging from 1.68 to 1.75 cm
for APAMs and 2.02 to 2.05 cm for CPAMs. Conversely,
in the case of natural settling, the settling velocity is at its
minimum value, leading to a final settling height of sedi-
ments at 2.9 cm.
The effectiveness of each flocculant in terms of water
recovery, initial settling rate, water turbidity and other
parameters is summarized in Table 4. The results indicate
that all tested flocculants allowed acceptable water recov-
eries, ranging from 78.88% to 83.20%, in comparison
to natural sedimentation (blank test), which yielded only
69.02% water recovery. Regarding the turbidity of the
recycled water, both anionic and cationic polyacrylamides
resulted in low water turbidity, with the cationic polyacryl-
amide Zetag 8167 achieving the lowest value at 1.87± 0.07
NTU. This observation aligns with previous studies indi-
cating that cationic flocculants are associated with low tur-
bidity (Sabah &Cengiz, 2004). The anionic flocculants,
Magnafloc 345 and Magnafloc 5250, allowed initial set-
tling rates of 13.31 and 13.67 cm/min, respectively, signifi-
cantly increasing the ISR of the FPTs during sedimentation
by over 8 times compared to natural settling (1.59 cm/
min). In contrast, the cationic flocculants, Magnafloc 504
and Zetag 8167, yielded initial settling rates of 12.39 and
12.18 cm/min, respectively, enhancing the ISR by more
than 7 times compared to the ISR of natural settling.
Based on the effectiveness of water recovery, the four
tested flocculants can be ranked as follows: Magnafloc
5250 Magnafloc 345 Zetag 8167 Magnafloc 504.
Both anionic polyacrylamides (PAMs) have a high molecu-
lar weight, with the main distinction lying in their charge
density. Specifically, Magnafloc 5250 exhibits a lower
Figure 3. Zeta potential study of FPTs sample

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Extracted Text (may have errors)

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 715
Flocculation 4293
To explore the settling behaviour of FPTs particles, floc-
culation and sedimentation experiments were conducted
using 60 g/tds dosage of both anionic and cationic poly-
acrylamide polymers. Additionally, a natural sedimentation
test was employed for comparison purposes. The objective
was to achieve efficient and cost-effective solid–liquid sepa-
ration by identifying the optimal flocculant that delivers
excellent performance in terms of maximizing water recov-
ery, enhancing settling rate and minimizing water turbidity.
The outcomes are depicted in Figure 3, revealing a
clear dependency of settling velocity on the type of floc-
culant used for FPTs flocculation. Notably, anionic poly-
acrylamides exhibited superior settling velocities and water
recoveries compared to their cationic counterparts. This
finding is in accordance with previous studies conducted
using anionic and cationic polyacrylamides (Bahmani-
Ghaedi et al., 2022 Fan et al., 2020 Liang et al., 2021 Liu
et al., 2020 Zhang et al., 2024).
As illustrated in Figure 4, the final settling heights of
the FPTs slurry with the four tested flocculants displayed
relatively slight variations, ranging from 1.68 to 1.75 cm
for APAMs and 2.02 to 2.05 cm for CPAMs. Conversely,
in the case of natural settling, the settling velocity is at its
minimum value, leading to a final settling height of sedi-
ments at 2.9 cm.
The effectiveness of each flocculant in terms of water
recovery, initial settling rate, water turbidity and other
parameters is summarized in Table 4. The results indicate
that all tested flocculants allowed acceptable water recov-
eries, ranging from 78.88% to 83.20%, in comparison
to natural sedimentation (blank test), which yielded only
69.02% water recovery. Regarding the turbidity of the
recycled water, both anionic and cationic polyacrylamides
resulted in low water turbidity, with the cationic polyacryl-
amide Zetag 8167 achieving the lowest value at 1.87± 0.07
NTU. This observation aligns with previous studies indi-
cating that cationic flocculants are associated with low tur-
bidity (Sabah &Cengiz, 2004). The anionic flocculants,
Magnafloc 345 and Magnafloc 5250, allowed initial set-
tling rates of 13.31 and 13.67 cm/min, respectively, signifi-
cantly increasing the ISR of the FPTs during sedimentation
by over 8 times compared to natural settling (1.59 cm/
min). In contrast, the cationic flocculants, Magnafloc 504
and Zetag 8167, yielded initial settling rates of 12.39 and
12.18 cm/min, respectively, enhancing the ISR by more
than 7 times compared to the ISR of natural settling.
Based on the effectiveness of water recovery, the four
tested flocculants can be ranked as follows: Magnafloc
5250 Magnafloc 345 Zetag 8167 Magnafloc 504.
Both anionic polyacrylamides (PAMs) have a high molecu-
lar weight, with the main distinction lying in their charge
density. Specifically, Magnafloc 5250 exhibits a lower
Figure 3. Zeta potential study of FPTs sample