2749
Enhanced Flotation Separation of Chlorite and Hematite by
Micro-Nano Bubbles
Wencheng Ge, Jie Liu, Zixuan Guo, Yimin Zhu, Tianjiao Chang, Yanjun Li, Shumin Zhang
College of Resource and Civil Engineering, Northeastern University, Shenyang, China
ABSTRACT: Chlorite and hematite are difficult to separate effectively due to their similar surface properties.
Flotation experiments were conducted in this study by introducing collector-coupled micro-nanobubbles. The
flotation mechanism was investigated using methods such as visual observation of particle bubbles and flotation
kinetic analysis. The results show that, when obtaining the same recovery, the introduction of micro-nanobubbles
can significantly reduce the dosage of collector and enhance the flotation efficiency of chlorite. It improves
the adhesion efficiency by reducing the energy barrier between minerals and bubbles, thus strengthening the
separation effect of chlorite and hematite.
Keywords: Chlorite, Hematite, flotation, Micro-nano Bubbles, collector
INTRODUCTION
Steel is vital in infrastructure engineering, equipment man-
ufacturing, national defense and military industries, and
transportation construction (Agdamag et al., 2001 Peters
et al., 2021). Iron ore is an essential raw material in the steel
industry, and its quality significantly affects the production
cost and performance of steel. Due to the quality limitations
of China’s iron ore resources, it usually must be benefici-
ated and then supplied to blast furnaces for smelting (Singh
and Mehrotra, 2007). Therefore, efficient development of
low-grade iron ore resources and improving the quality of
iron concentrate have strategic importance. Flotation is an
essential method for effectively separating refractory iron
ore (Zhang et al., 2021b). Separation is mainly achieved by
strengthening the hydrophobicity difference between min-
erals. It is essential for China’s low-grade iron ore resource,
with complex mineral compositions, close co-associated
relationships, and similar surface properties, to upgrade
the iron concentrate. (Hu et al., 2011). Researchers mainly
solve this problem by optimizing the process and develop-
ing new flotation reagents (Nakhaei and Irannajad, 2018).
Generally, iron ore flotation can be divided into for-
ward flotation and reverse flotation based on the difference
in floating products. The iron minerals have been initially
enriched since the magnetic separation of the original
ore. Therefore, the reverse flotation process has outstand-
ing advantages. In the impurity removal process of iron
ore reverse flotation, current research mainly focuses on
developing and modifying organic polymer depressants. A.
Tohry et al. used humic acid as a depressant to separate
pyroxene, amphibole, and hematite and obtained better
flotation indicators. Furthermore, it was clarified that its
inhibitory effect mainly depends on the type and number of
iron active sites on the mineral surface (Tohry et al., 2021).
What’s more, depressants in iron ore reverse flotation can
also achieve effective separation of minerals by hindering
the adsorption of collectors (Li et al., 2020). This effect
can even be achieved by regulating the amount of adsorp-
tion and then selectively controlling the wettability of the

Previous Page Next Page

Extracted Text (may have errors)

2749
Enhanced Flotation Separation of Chlorite and Hematite by
Micro-Nano Bubbles
Wencheng Ge, Jie Liu, Zixuan Guo, Yimin Zhu, Tianjiao Chang, Yanjun Li, Shumin Zhang
College of Resource and Civil Engineering, Northeastern University, Shenyang, China
ABSTRACT: Chlorite and hematite are difficult to separate effectively due to their similar surface properties.
Flotation experiments were conducted in this study by introducing collector-coupled micro-nanobubbles. The
flotation mechanism was investigated using methods such as visual observation of particle bubbles and flotation
kinetic analysis. The results show that, when obtaining the same recovery, the introduction of micro-nanobubbles
can significantly reduce the dosage of collector and enhance the flotation efficiency of chlorite. It improves
the adhesion efficiency by reducing the energy barrier between minerals and bubbles, thus strengthening the
separation effect of chlorite and hematite.
Keywords: Chlorite, Hematite, flotation, Micro-nano Bubbles, collector
INTRODUCTION
Steel is vital in infrastructure engineering, equipment man-
ufacturing, national defense and military industries, and
transportation construction (Agdamag et al., 2001 Peters
et al., 2021). Iron ore is an essential raw material in the steel
industry, and its quality significantly affects the production
cost and performance of steel. Due to the quality limitations
of China’s iron ore resources, it usually must be benefici-
ated and then supplied to blast furnaces for smelting (Singh
and Mehrotra, 2007). Therefore, efficient development of
low-grade iron ore resources and improving the quality of
iron concentrate have strategic importance. Flotation is an
essential method for effectively separating refractory iron
ore (Zhang et al., 2021b). Separation is mainly achieved by
strengthening the hydrophobicity difference between min-
erals. It is essential for China’s low-grade iron ore resource,
with complex mineral compositions, close co-associated
relationships, and similar surface properties, to upgrade
the iron concentrate. (Hu et al., 2011). Researchers mainly
solve this problem by optimizing the process and develop-
ing new flotation reagents (Nakhaei and Irannajad, 2018).
Generally, iron ore flotation can be divided into for-
ward flotation and reverse flotation based on the difference
in floating products. The iron minerals have been initially
enriched since the magnetic separation of the original
ore. Therefore, the reverse flotation process has outstand-
ing advantages. In the impurity removal process of iron
ore reverse flotation, current research mainly focuses on
developing and modifying organic polymer depressants. A.
Tohry et al. used humic acid as a depressant to separate
pyroxene, amphibole, and hematite and obtained better
flotation indicators. Furthermore, it was clarified that its
inhibitory effect mainly depends on the type and number of
iron active sites on the mineral surface (Tohry et al., 2021).
What’s more, depressants in iron ore reverse flotation can
also achieve effective separation of minerals by hindering
the adsorption of collectors (Li et al., 2020). This effect
can even be achieved by regulating the amount of adsorp-
tion and then selectively controlling the wettability of the

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2750 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
mineral surface (Yehia et al., 2021). Under the appropriate
depressant system, the development of new collectors sig-
nificantly impacts the efficiency of impurity removal in the
reverse flotation process. In recent years, many influential
collectors have been designed based on the types and con-
centrations of metal ions in gangue minerals and the char-
acteristics of the fractured exposed surface. Northeastern
University has successfully developed modified fatty acid
collectors by introducing atoms or group such as Cl, Br,
or amine into the α-position carbon atoms of fatty acid.
Modified fatty acid collectors have been successfully devel-
oped and achieved good commercial application(Zhu et
al., 2015 Zhu et al., 2016). At the same time, TD-2, CY
series anion collectors, and GE series cation collectors also
showed good application effects (Jiang et al., 2018 Mei et
al., 2016 Xiong et al., 2012 Zhou et al., 2020).
Although the development of flotation reagents has
significantly improved the efficiency of iron ore reverse
flotation. However, it is a difficult problem for hematite
ore with fine particles and complex associated components
to obtain high iron grade and recovery. This type of ore
required fine grinding to dissociate the mineral monomers
(Xu et al., 2020). And the fine-grained silicate minerals
were produces, which can reduce the flotation efficiency. As
the particle size decreased, the probability of collision with
conventional bubbles was diminished. Simultaneously, the
flotation effect of the target mineral would also deteriorate
due to the coverage on the surface (Lima et al., 2020 Yu
et al., 2017). Research results showed that strengthening
the wettability difference at the mineral interface through
reagents was the prerequisite for solving the problem (Koh
et al., 2009). To enhance the separation efficiency, it is still
necessary to appropriately increase the apparent particle size
of minerals or reduce the bubble size (Wang et al., 2021).
The preferential enrichment of micro-nanobubbles on the
surface of hydrophobic particles enables the interface nano-
bubbles to agglomerate fine-grained minerals selectively
(Cheng et al., 2023). Moreover, the flotation effect and
recovery could be enhanced through increasing the prob-
ability of collision and attachment between agglomerated
particles and conventional bubbles (Zhang et al., 2021a).
At the same time, A.H. Englert et al. used dissolved air
flotation to compare the effects of two different flotation
devices on fine-grained quartz flotation. The recovery of
fine-grained quartz was increased from 6% to 53% when
using amine collectors for interface control and introduc-
ing micro-nano bubbles (Englert et al., 2009). This result
verifies that flotation recovery can be effectively improved
by reducing bubble size and increasing the collision prob-
ability between bubbles and fine-grained minerals (Tao,
2022 Tao et al., 2021).
This study focuses on refractory hematite ores contain-
ing silicate minerals, which is easy to muddied and consider
chlorite and hematite as the research objects. The effect of
introducing micro-nano bubbles on its flotation separation
effect was investigated. Strengthened mechanism analysis
was carried out through mineral flotation experiments,
combined with analysis of reagent adsorption characteris-
tics and visual observation of particles and bubbles.
MATERIALS AND METHODS
Materials and Reagents
Chlorite and hematite samples were taken from Hebei and
Liaoning provinces, respectively. High-purity ore blocks
were selected for grinding. The products were screened to
obtain mineral samples with particle sizes of 38–74 μm for
experiments. Samples were subjected to chemical multi-ele-
ment and physical phase detection to analyze their purity.
The results are shown in Table 1 and Figure 1, indicate that
the purity of the sample meets the test requirements. The
reagents used in the experiment were α-Bromolauric acid
(α-BLA), starch, calcium chloride, methyl amyl alcohol
(MIBC), hydrochloric acid, and sodium hydroxide. α-BLA
is a laboratory-made anionic collector. The starch is food-
grade corn starch purchased from Tianjin Comeo, which
depresses the floatability of hematite. Calcium chloride was
used to activate chlorite and was purchased from Sinopharm
Chemical Group. MIBC, hydrochloric acid, and sodium
hydroxide were purchased from Tianjin Comeo Company.
They were used to prepare micro-nano bubble water and
adjust the pH of the slurry, respectively.
Experiment and Analysis Methods
Flotation experiments are divided into single mineral
and artificial mixed mineral experiments. The sample was
stirred in a 35 ml flotation tank for 2 min and the slurry
pH during this process was adjusted. Then, the depressant,
activator, and collector were added in sequence, with each
reagent having an action time of 3 minutes. A control group
experiment was set up to observe the impact of micro-nano
Table 1. Chemical composition analysis results of samples
Composition TFe S P FeO MgO CaO SiO2 Al2O3
Hematite 69.42 0.016 0.026 0.74 — 0.096 0.35 0.15
Chlorite 8.17 0.047 0.041 — 11.39 0.99 51.29 15.32

Previous Page Next Page

Extracted Text (may have errors)

2750 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
mineral surface (Yehia et al., 2021). Under the appropriate
depressant system, the development of new collectors sig-
nificantly impacts the efficiency of impurity removal in the
reverse flotation process. In recent years, many influential
collectors have been designed based on the types and con-
centrations of metal ions in gangue minerals and the char-
acteristics of the fractured exposed surface. Northeastern
University has successfully developed modified fatty acid
collectors by introducing atoms or group such as Cl, Br,
or amine into the α-position carbon atoms of fatty acid.
Modified fatty acid collectors have been successfully devel-
oped and achieved good commercial application(Zhu et
al., 2015 Zhu et al., 2016). At the same time, TD-2, CY
series anion collectors, and GE series cation collectors also
showed good application effects (Jiang et al., 2018 Mei et
al., 2016 Xiong et al., 2012 Zhou et al., 2020).
Although the development of flotation reagents has
significantly improved the efficiency of iron ore reverse
flotation. However, it is a difficult problem for hematite
ore with fine particles and complex associated components
to obtain high iron grade and recovery. This type of ore
required fine grinding to dissociate the mineral monomers
(Xu et al., 2020). And the fine-grained silicate minerals
were produces, which can reduce the flotation efficiency. As
the particle size decreased, the probability of collision with
conventional bubbles was diminished. Simultaneously, the
flotation effect of the target mineral would also deteriorate
due to the coverage on the surface (Lima et al., 2020 Yu
et al., 2017). Research results showed that strengthening
the wettability difference at the mineral interface through
reagents was the prerequisite for solving the problem (Koh
et al., 2009). To enhance the separation efficiency, it is still
necessary to appropriately increase the apparent particle size
of minerals or reduce the bubble size (Wang et al., 2021).
The preferential enrichment of micro-nanobubbles on the
surface of hydrophobic particles enables the interface nano-
bubbles to agglomerate fine-grained minerals selectively
(Cheng et al., 2023). Moreover, the flotation effect and
recovery could be enhanced through increasing the prob-
ability of collision and attachment between agglomerated
particles and conventional bubbles (Zhang et al., 2021a).
At the same time, A.H. Englert et al. used dissolved air
flotation to compare the effects of two different flotation
devices on fine-grained quartz flotation. The recovery of
fine-grained quartz was increased from 6% to 53% when
using amine collectors for interface control and introduc-
ing micro-nano bubbles (Englert et al., 2009). This result
verifies that flotation recovery can be effectively improved
by reducing bubble size and increasing the collision prob-
ability between bubbles and fine-grained minerals (Tao,
2022 Tao et al., 2021).
This study focuses on refractory hematite ores contain-
ing silicate minerals, which is easy to muddied and consider
chlorite and hematite as the research objects. The effect of
introducing micro-nano bubbles on its flotation separation
effect was investigated. Strengthened mechanism analysis
was carried out through mineral flotation experiments,
combined with analysis of reagent adsorption characteris-
tics and visual observation of particles and bubbles.
MATERIALS AND METHODS
Materials and Reagents
Chlorite and hematite samples were taken from Hebei and
Liaoning provinces, respectively. High-purity ore blocks
were selected for grinding. The products were screened to
obtain mineral samples with particle sizes of 38–74 μm for
experiments. Samples were subjected to chemical multi-ele-
ment and physical phase detection to analyze their purity.
The results are shown in Table 1 and Figure 1, indicate that
the purity of the sample meets the test requirements. The
reagents used in the experiment were α-Bromolauric acid
(α-BLA), starch, calcium chloride, methyl amyl alcohol
(MIBC), hydrochloric acid, and sodium hydroxide. α-BLA
is a laboratory-made anionic collector. The starch is food-
grade corn starch purchased from Tianjin Comeo, which
depresses the floatability of hematite. Calcium chloride was
used to activate chlorite and was purchased from Sinopharm
Chemical Group. MIBC, hydrochloric acid, and sodium
hydroxide were purchased from Tianjin Comeo Company.
They were used to prepare micro-nano bubble water and
adjust the pH of the slurry, respectively.
Experiment and Analysis Methods
Flotation experiments are divided into single mineral
and artificial mixed mineral experiments. The sample was
stirred in a 35 ml flotation tank for 2 min and the slurry
pH during this process was adjusted. Then, the depressant,
activator, and collector were added in sequence, with each
reagent having an action time of 3 minutes. A control group
experiment was set up to observe the impact of micro-nano
Table 1. Chemical composition analysis results of samples
Composition TFe S P FeO MgO CaO SiO2 Al2O3
Hematite 69.42 0.016 0.026 0.74 — 0.096 0.35 0.15
Chlorite 8.17 0.047 0.041 — 11.39 0.99 51.29 15.32

2748 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Rosa, B. et al. 2013. Kinematic and dynamic collision sta-
tistics of cloud droplets from high-resolution simula-
tions. New Journal of Physics 15(4):045032.
Saffman, P.G. &Turner, J.S. 1956. On the collision of
drops in turbulent clouds. Journal of Fluid Mechanics
1(1):16–30.
Schubert, H. 1999. On the turbulence-controlled micro-
processes in flotation machines. International Journal
of Mineral Processing 56(1):257–276.
Thorn, R., Johansen, G.A. &Hammer, E.A. 1997. Three-
phase flow measurement: challenges and opportuni-
ties. Measurement Science and Technology 8(7):691.
Tiedemann, B. &Fröhlich, J. 2023. Collision dynamics
of particles and bubbles in gravity‐driven flotation: A
DNS investigation. Proceedings in Applied Mathematics
and Mechanics 20:e202300290.
Tiedemann, B. &Fröhlich, J. 2024a. Simulation of colli-
sion events in flotation under the influence of gravity
(Manuscript in preparation).
Tiedemann, B., Kreuseler M. &Fröhlich, J. 2024b. A new
analytical model for particle-bubble collision in flota-
tion processes (Manuscript in preparation).
Tschisgale, S., Kempe, T. &Fröhlich, J. 2018. A general
implicit direct forcing immersed boundary method for
rigid particles. Computers and Fluids 170:285–298.
Uhlmann, M. 2005. An immersed boundary method with
direct forcing for the simulation of particulate flows.
Journal of Computational Physics 209(2):448–476.
Wang, L.-P., Ayala, O., Kasprzak, S.E. &Grabowski, W.W.
2005. Theoretical Formulation of Collision Rate and
Collision Efficiency of Hydrodynamically Interacting
Cloud Droplets in Turbulent Atmosphere. Journal of
the Atmospheric Sciences 62(7):2433–2450.
Yuu, S. 1984. Collision rate of small particles in a homo-
geneous and isotropic turbulence. AIChE Journal
30(5):802–807.
Zaichik, L.I., Simonin, O. &Alipchenkov, V.M. 2006.
Collision rates of bidisperse inertial particles in isotro-
pic turbulence. Physics of Fluids 18(3):035110.
Zaichik, L.I., Simonin, O. &Alipchnkov, V.M. 2010.
Turbulent collision rates of arbitrary-density par-
ticles. International Journal of Heat and Mass Transfer
53(9):1613–1620.

Previous Page Next Page

Extracted Text (may have errors)

2748 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Rosa, B. et al. 2013. Kinematic and dynamic collision sta-
tistics of cloud droplets from high-resolution simula-
tions. New Journal of Physics 15(4):045032.
Saffman, P.G. &Turner, J.S. 1956. On the collision of
drops in turbulent clouds. Journal of Fluid Mechanics
1(1):16–30.
Schubert, H. 1999. On the turbulence-controlled micro-
processes in flotation machines. International Journal
of Mineral Processing 56(1):257–276.
Thorn, R., Johansen, G.A. &Hammer, E.A. 1997. Three-
phase flow measurement: challenges and opportuni-
ties. Measurement Science and Technology 8(7):691.
Tiedemann, B. &Fröhlich, J. 2023. Collision dynamics
of particles and bubbles in gravity‐driven flotation: A
DNS investigation. Proceedings in Applied Mathematics
and Mechanics 20:e202300290.
Tiedemann, B. &Fröhlich, J. 2024a. Simulation of colli-
sion events in flotation under the influence of gravity
(Manuscript in preparation).
Tiedemann, B., Kreuseler M. &Fröhlich, J. 2024b. A new
analytical model for particle-bubble collision in flota-
tion processes (Manuscript in preparation).
Tschisgale, S., Kempe, T. &Fröhlich, J. 2018. A general
implicit direct forcing immersed boundary method for
rigid particles. Computers and Fluids 170:285–298.
Uhlmann, M. 2005. An immersed boundary method with
direct forcing for the simulation of particulate flows.
Journal of Computational Physics 209(2):448–476.
Wang, L.-P., Ayala, O., Kasprzak, S.E. &Grabowski, W.W.
2005. Theoretical Formulation of Collision Rate and
Collision Efficiency of Hydrodynamically Interacting
Cloud Droplets in Turbulent Atmosphere. Journal of
the Atmospheric Sciences 62(7):2433–2450.
Yuu, S. 1984. Collision rate of small particles in a homo-
geneous and isotropic turbulence. AIChE Journal
30(5):802–807.
Zaichik, L.I., Simonin, O. &Alipchenkov, V.M. 2006.
Collision rates of bidisperse inertial particles in isotro-
pic turbulence. Physics of Fluids 18(3):035110.
Zaichik, L.I., Simonin, O. &Alipchnkov, V.M. 2010.
Turbulent collision rates of arbitrary-density par-
ticles. International Journal of Heat and Mass Transfer
53(9):1613–1620.