XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2297
mL of distilled water in a volumetric flask with stirring for
5 minutes. The target concentration was 1% (w/v). The
transformation process of sorghum flour and corn grits into
depressants was carried out through chemical gelatiniza-
tion, using a 50% (w/v) NaOH solution at room tempera-
ture, under continuous stirring for 20 minutes to achieve
complete gelatinization. The water used in the tests was
supplied by the public supply system of the city of Catalão,
Goiás state.
Experimental Design Planning was divided into three
stages: the first stage involved evaluating the influence of
flotation time using corn grits as a depressant. In the second
stage, the performance of sorghum flour was compared with
corn grits, applying the flotation time selected from the first
stage under the same conditions described in Table 1. The
third stage consisted of a complete 32 factorial design, now
using only sorghum flour, with depressant dosage and pH
set as the experimental variables. Table 2 summarizes the
variables for each stage.
All tests were conducted in triplicates, and a new test
was performed when the coefficient of variation for iron
content and recovery in the concentrate exceeded 5%.
The results were compiled and statistically analyzed using
the software MINITAB 21 ®, considering a 95% confi-
dence interval and the normal distribution of data. The
following response variables for concentrate quality control
were used: iron content (%Fe) and iron recovery (%Rec.
Fe). The statistical analysis was based on tests for normal-
ity using the Anderson-Darling criterion, hypothesis tests,
Bartlett›s and Tukey›s tests for comparing variance and
mean, respectively, among different samples, and analysis
of variance (ANOVA) to determine the significance of the
studied factors.
RESULTS AND DISCUSSION
The densities of six samples of the iron ore used in the flo-
tation experiments were measured using a 1000 mL pyc-
nometer, resulting in an average value of 3.80 ± 0.01 g/
cm3. The average Fe and SiO2 content, indirectly estimated
from the densities through calibration mathematical mod-
els, were 42.89 ± 0.60% and 37.71 ± 1.00%, respectively.
These values are consistent with the average content of fri-
able itabirites found in the Serra do Sapo deposit, as indi-
cated by previous studies conducted by Rolim (2016) and
Morais et al. (2020).
The results of the initial stage of the flotation tests,
expressed in terms of Fe (%)content and recoveries in the
concentrate, are depicted in Figure 1a. Figure 1b illustrates
the findings of the Tukey test, providing a simultaneous
Table 2. Factors and levels tested in the iron ore flotation tests
Stages Factors Levels
1st Flotation time (min) 1, 2, 3, 4 e 5
2nd Depressant type Corn grits and sorghum flour
3rd Depressant dosage (g/tFe)
pH
1200, 1450 e 1700
9.5, 10.0 e 10.5
Figure 1. Influence of the flotation time on the concentrate quality (a) and Tukey test (b)
mL of distilled water in a volumetric flask with stirring for
5 minutes. The target concentration was 1% (w/v). The
transformation process of sorghum flour and corn grits into
depressants was carried out through chemical gelatiniza-
tion, using a 50% (w/v) NaOH solution at room tempera-
ture, under continuous stirring for 20 minutes to achieve
complete gelatinization. The water used in the tests was
supplied by the public supply system of the city of Catalão,
Goiás state.
Experimental Design Planning was divided into three
stages: the first stage involved evaluating the influence of
flotation time using corn grits as a depressant. In the second
stage, the performance of sorghum flour was compared with
corn grits, applying the flotation time selected from the first
stage under the same conditions described in Table 1. The
third stage consisted of a complete 32 factorial design, now
using only sorghum flour, with depressant dosage and pH
set as the experimental variables. Table 2 summarizes the
variables for each stage.
All tests were conducted in triplicates, and a new test
was performed when the coefficient of variation for iron
content and recovery in the concentrate exceeded 5%.
The results were compiled and statistically analyzed using
the software MINITAB 21 ®, considering a 95% confi-
dence interval and the normal distribution of data. The
following response variables for concentrate quality control
were used: iron content (%Fe) and iron recovery (%Rec.
Fe). The statistical analysis was based on tests for normal-
ity using the Anderson-Darling criterion, hypothesis tests,
Bartlett›s and Tukey›s tests for comparing variance and
mean, respectively, among different samples, and analysis
of variance (ANOVA) to determine the significance of the
studied factors.
RESULTS AND DISCUSSION
The densities of six samples of the iron ore used in the flo-
tation experiments were measured using a 1000 mL pyc-
nometer, resulting in an average value of 3.80 ± 0.01 g/
cm3. The average Fe and SiO2 content, indirectly estimated
from the densities through calibration mathematical mod-
els, were 42.89 ± 0.60% and 37.71 ± 1.00%, respectively.
These values are consistent with the average content of fri-
able itabirites found in the Serra do Sapo deposit, as indi-
cated by previous studies conducted by Rolim (2016) and
Morais et al. (2020).
The results of the initial stage of the flotation tests,
expressed in terms of Fe (%)content and recoveries in the
concentrate, are depicted in Figure 1a. Figure 1b illustrates
the findings of the Tukey test, providing a simultaneous
Table 2. Factors and levels tested in the iron ore flotation tests
Stages Factors Levels
1st Flotation time (min) 1, 2, 3, 4 e 5
2nd Depressant type Corn grits and sorghum flour
3rd Depressant dosage (g/tFe)
pH
1200, 1450 e 1700
9.5, 10.0 e 10.5
Figure 1. Influence of the flotation time on the concentrate quality (a) and Tukey test (b)