XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2299
Both depressants showed the similar performance
regarding the Fe content in the concentrate. However, the
recovery from tests with sorghum flour was slightly higher,
precisely 3.9% more. Silva et al. (2018) observed, at a spe-
cific dosage, that the recovery of hematite in microflotation
tests was 13.24% lower in experiments using sorghum starch
than in tests with corn starch. It was verified, therefore, that
sorghum starch exhibits a stronger depressant effect on the
hematite surface, which may explain the higher Fe recovery
in the concentrate generated in the bench-scale flotation
tests in the current study using sorghum flour.
In this case, as only two datasets were compared, a
T-test was conducted to compare the means of the response
variables. The p-value assumed values of 0.959 and 0.158
for the Fe content and recovery responses, respectively,
indicating that the performance of both depressants was
statistically equal. This result demonstrated that the substi-
tution of the conventional depressant used in industrial flo-
tation with sorghum flour did not result in statistical losses
or gains in process performance. The third stage results of
the flotation tests, varying sorghum flour dosage (g/tFe) and
pH, are illustrated in the contour plots shown in Figure 3.
The highest Fe content and recoveries in the concen-
trate were observed at the highest dosages of sorghum
flour (1700 g/tFe). The test conducted at pH 9.5 yielded
the highest average Fe content (63.91 ± 1.56%), while the
highest recovery (91.69 ± 4.19%) occurred at pH 10.0.
However, at the standard dosage of 1450 g/tFe adopted
industrially, there was no significant difference between the
tests conducted at pH 9.5 and 10.0 in the values of both
response variables. On the other hand, increasing the pH
to 10.5 resulted in slight increments in both Fe content
and recovery. The average content for the tests at pH 10.0
increased from 60.33 ± 2.62% to 62.53 ± 1.13% at pH
10.5, while the recovery increased from 75.84 ± 5.03 to
81.82 ± 2.91%. Analyzing the dodecylamine speciation
diagram presented in Luz’s publication (2016, p. 1272), it
is evident that at pH 10.5, there is the highest activity of
the ionomolecular complex, acting as an auxiliary collector
and reducing electrostatic repulsion between ionic species.
This might explain the slight increase in Fe content in the
concentrate due to the enhanced floatability of quartz.
Moreover, it was observed that the recovery of iron in
the concentrate increases significantly with the rise in dos-
age from 1200 to 1450 g/tFe at all tested pH values. At the
standard pH of 10.5, the recovery increases from 64.02 ±
3.56% to 81.82 ± 2.91%. This effect was clearly discernible
during the tests through the analysis of foam coloration and
the amount of floated material. This indicates that at the
dosage of 1200 g/tFe, there is a shortage of available starch
to adsorb on the surface of hematite. The remaining par-
ticles interact with the amine due to electrostatic attraction,
resulting in their flotation along with quartz.
However, the analysis of variance indicated that both
the sorghum flour dosage and pH are not significant fac-
tors regarding the iron content in the tested ranges, as
the resulting p-values were higher than 0.05 in both cases
(0.052 and 0.734, respectively). Concerning iron recovery,
only the depressor dosage can be considered significant, as
in this case, the p-value was less than 0.05. Therefore, it
is concluded that, from a statistical standpoint, increasing
the standard dosage from 1450 to 1700 g/tFe improved the
overall flotation performance, while decreasing the pH in
the tested alkaline range did not significantly impact the
process performance. An economic analysis is necessary to
evaluate whether the increased costs associated with the
depressor dosage increment would be compensated by the
gains in concentrate quality.
Figure 3. Influence of sorghum flour dosage and pH on the Fe content (a) and Fe recovery (b)
Both depressants showed the similar performance
regarding the Fe content in the concentrate. However, the
recovery from tests with sorghum flour was slightly higher,
precisely 3.9% more. Silva et al. (2018) observed, at a spe-
cific dosage, that the recovery of hematite in microflotation
tests was 13.24% lower in experiments using sorghum starch
than in tests with corn starch. It was verified, therefore, that
sorghum starch exhibits a stronger depressant effect on the
hematite surface, which may explain the higher Fe recovery
in the concentrate generated in the bench-scale flotation
tests in the current study using sorghum flour.
In this case, as only two datasets were compared, a
T-test was conducted to compare the means of the response
variables. The p-value assumed values of 0.959 and 0.158
for the Fe content and recovery responses, respectively,
indicating that the performance of both depressants was
statistically equal. This result demonstrated that the substi-
tution of the conventional depressant used in industrial flo-
tation with sorghum flour did not result in statistical losses
or gains in process performance. The third stage results of
the flotation tests, varying sorghum flour dosage (g/tFe) and
pH, are illustrated in the contour plots shown in Figure 3.
The highest Fe content and recoveries in the concen-
trate were observed at the highest dosages of sorghum
flour (1700 g/tFe). The test conducted at pH 9.5 yielded
the highest average Fe content (63.91 ± 1.56%), while the
highest recovery (91.69 ± 4.19%) occurred at pH 10.0.
However, at the standard dosage of 1450 g/tFe adopted
industrially, there was no significant difference between the
tests conducted at pH 9.5 and 10.0 in the values of both
response variables. On the other hand, increasing the pH
to 10.5 resulted in slight increments in both Fe content
and recovery. The average content for the tests at pH 10.0
increased from 60.33 ± 2.62% to 62.53 ± 1.13% at pH
10.5, while the recovery increased from 75.84 ± 5.03 to
81.82 ± 2.91%. Analyzing the dodecylamine speciation
diagram presented in Luz’s publication (2016, p. 1272), it
is evident that at pH 10.5, there is the highest activity of
the ionomolecular complex, acting as an auxiliary collector
and reducing electrostatic repulsion between ionic species.
This might explain the slight increase in Fe content in the
concentrate due to the enhanced floatability of quartz.
Moreover, it was observed that the recovery of iron in
the concentrate increases significantly with the rise in dos-
age from 1200 to 1450 g/tFe at all tested pH values. At the
standard pH of 10.5, the recovery increases from 64.02 ±
3.56% to 81.82 ± 2.91%. This effect was clearly discernible
during the tests through the analysis of foam coloration and
the amount of floated material. This indicates that at the
dosage of 1200 g/tFe, there is a shortage of available starch
to adsorb on the surface of hematite. The remaining par-
ticles interact with the amine due to electrostatic attraction,
resulting in their flotation along with quartz.
However, the analysis of variance indicated that both
the sorghum flour dosage and pH are not significant fac-
tors regarding the iron content in the tested ranges, as
the resulting p-values were higher than 0.05 in both cases
(0.052 and 0.734, respectively). Concerning iron recovery,
only the depressor dosage can be considered significant, as
in this case, the p-value was less than 0.05. Therefore, it
is concluded that, from a statistical standpoint, increasing
the standard dosage from 1450 to 1700 g/tFe improved the
overall flotation performance, while decreasing the pH in
the tested alkaline range did not significantly impact the
process performance. An economic analysis is necessary to
evaluate whether the increased costs associated with the
depressor dosage increment would be compensated by the
gains in concentrate quality.
Figure 3. Influence of sorghum flour dosage and pH on the Fe content (a) and Fe recovery (b)