This study investigated the removal of silica and alumina as impurities from Sanje Iron ore from Zambia, which contains 48.90 mass% of hematite (Fe2O3) with 34.18 mass% iron grade, 31.10 mass% of silica (SiO2) and 7.65 mass% alumina (Al2O3). In order to develop the impurities removal process, wet high-intensity magnetic separation (WHIMS) method was used as the as the first stage impurity removal process. At optimum of 0.25 kg/t for both Sodium Oleate and dodecylamine acetate, alumina was reduced to 1.04 mass% and silica to 2.04 mass% using 0.05 kg/t of Methyl Isobutyl Carbinol (C6H14O) frother. The final concentrate produced from the M-RF process contained 67.27 mass% of Iron, 2.02 mass% of silica and 1.04 mass% of alumina

1. Development of Impurities Removal Process
for Low-Grade Iron ores using Mineral
Processing Technologies
Department of Earth Resource Engineering
Graduate School of International Resource Sciences
Akita University
Spring Conference
2018. 03. 27
Moses Charles Siame
Kazutoshi Haga, Atsushi Shibayama

2. Research Introduction
Location of Zambia and Mineral distribution in Southern Africa
Iron ore Samples collected from Zambia

3. Sanje Hill
Geological Map by:
M. Robertson, MSA Group
Sanje Ore
Lusaka
Low-Grade Sanje Ore
250Mt Fe-35%-45%
High-Grade Sanje Ore
20 Mt Fe- 57%-60%
Study Background-Sanje Mines

4. Research Objective and Framework
Main Objectives
 Remove and reduce Silica-
alumina to less than
7 mass% (Al2O3+SiO2)
 Produce iron Concentrate with
Iron grade of >60 mass%
[market Target]
 To establish Effective methods which can be used for
treatment of other low-grade ores.
Experimental Framework
Sanje
Ore
Characterization
of the Ore
Magnetic
Separation
Reverse
Flotation
Two-stage
Process
Concentrate
XRF, XRD,
SEM-EDS, PSD
-Feed pulp density
-Magnetic Intensity
-Matrix collectors (Pipe/wire)
-pH -Collector dosage
-Depressant dosage -Activator dosage
-Zeta potential
Sanje Iron ore from Zambia
Fe-34.18%, (Al2O3+SiO2)-38.75 mass%
>60 mass% Fe
Fe 34.18%
Al2O3+SiO2 38.75% Al2O3+SiO2 ˂7%

5. % 𝐅𝐞 𝟐 𝐎 𝟑% Fe %𝐒𝐢𝐎 𝟐 %𝐀𝐥 𝟐 𝐎 𝟑 % P % MgO
48.90 34.18 31.10 7.65 0.05 1.33
Chemical Composition (XRFAnalysis)
Mineralogical Composition (XRD Analysis)
Characterization of the Ore samples
2θ, (0)
Intensity,(counts)
100µm
% 𝐒𝐢𝐎 𝟐
𝐅𝐞 𝐱 𝐎 𝐲𝐅𝐞 𝐱 𝐎 𝐲
% 𝐒𝐢𝐎 𝟐
𝐀𝐥 𝟐 𝐎 𝟑
Mineral Distribution (SEM-EDS Analysis)
0
1
2
3
4
5
6
0
20
40
60
80
100
1 10 100 1000 10000
Frequency,(%)
Cumulative,(%)
Particle Size µm
D50 = 𝟐𝟓𝛍𝐦
𝐃 𝟖𝟎 = 𝟑𝟐𝛍𝐦

6. 15cm
D=6mm
Pipe matrix Collector
Reticulation
7mm X 14 mm
Thickness
1 mm
Wire Mesh collector
The Magnetic density of the L-4 machine is
directly proportional to the sum of Current
and Magnetic field.
Feed
Wet High Intensity
Magnetic Separation
Magnetic Particles
(Iron Concentrate)
Iron ore
(20g, 25μm, ρ-2.5-10% )
Non-Magnetic Particles
Tailings
Qv -7 L/min
Rinsing
Qv -7 L/minWater – 1L
Methodology for Magnetic separation
Concentrate
L-4 Machine Description Experimental Procedure
Magnetic
Coils
Valve

7. Magnetic flux density
Slurry is feed
Rinse
To flush remaining non-
magnetic matters out
Water
Mixture of
Feed and water
Magnetized
Particles
Nonmagnetic
particles
Collection box
of magnetized
matter
Electromagnet
(0.3 – 1T)
Water poured for
rinsing
▲：Iron oxides
〇：Non-magnetic
Non-magnetic
particles
(Silica and
Alumina)
Principle of operation for Magnetic separation
1
2
3

8. Results & Discussion: Magnetic separation
39.26
41.68 43.78
3.98
5.81
19.78
22.69
18.08
76
87 88 89
0
25
50
75
100
0
25
50
75
100
3000 5000 7500 10000
Ferecovery,%
Grade,mass%
Magnetic density, mT
Fe (%) Al2O3 (%)
SiO2(%) Fe Recovery (%)
Fe recovery
Fe
Al2O3
46.93 49.72
43.7 42.01 40.26
5.15 4.19 5.81
18.79 18.08 20.02
93 91 90
87 88
0
25
50
75
100
0
25
50
75
100
2 2.5 5 7.5 10
Ferecovery,%
Grade,mass%
Pulp density, %
Fe (%) Al2O3 (%) SiO2 (%) Fe Recovery (%)
Fe recovery
Fe
Effect of Pulp density on Iron recovery
Effect of Magnetic density on Iron recovery
𝐒𝐢𝐎 𝟐
Al2O3
𝐒𝐢𝐎 𝟐
 Increase in magnetic density increased
iron recovery
 Increase in pulp density resulted in
reduced Iron recovery and Iron grade.
Feed Wire PipeFeed
-Fe Grade 49.72 mass%, - Recovery 91%

9. Efficiency of the collecting Matrix on Iron recovery.
Equipment % Fe %𝐒𝐢𝐎 𝟐 %𝐀𝐥 𝟐 𝐎 𝟑
% Yield % Fe
Recovery
Wire 49.7 18.08 4.19 77.22 89
Pipe 53.22 12.01 3.94 72.32 93
0
20
40
60
80
100
% Fe Grade % SiO2 % Al2O3 % Fe Recovery
49.7
89 %
53.22
93 %
%,mass
Wire Pipe
% Iron Grade
More iron recovered
by the Pipe Matrix
than the Wire
mesh
More silica and
Alumina reduced
when Pipe matrix
is used.
Feed
-Fe Grade 53.22 mass%, - Recovery 93%
%Fe %SiO2 %Al2O3
34.18 31.10 7.65

10. Methodology for Reverse Flotation
Iron ore
(20g, 25μm, ρ - 10% )
Fe Depression
pH Control
Alumina-silica
Collection
Alumina-silica
flotation
Overflow
Silica and Alumina
Underflow
(Iron Concentrate)
0.1% of Mixture
Collector
0.25 – 1 kg/t
(DAA & NaOL)
Cationic : Anionic
CaO (0.1%)
0.25 – 1 kg/t
Quartz Activator
1% Alkaline
Starch
(0.25 - 1 g/t)
Iron Depressant
0.1% MIBC
0.05 kg/t)
Frother
Froth
𝐀𝐥 𝟐 𝐎 𝟑
Attachment
𝐒𝐢𝐎 𝟐
Attachment
Experimental Design Experimental Procedure
Bubbles
𝐅𝐞 𝟐 𝐎 𝟑
In underflow
NaOL-Sodium oleate
(C18H33NaO2) Anionic Collector
DAA-Dodecylamine acetate
(C14H31NaO2) Cationic Collector

11. -35
-30
-25
-20
-15
-10
-5
0
5
2 4 6 8 10 12 14
ZetaPotential(mV)
pH
largest negative surface charge
of the ore
Hydrophobicity of Silica and alumina increases as the Zeta potential becomes more
negative. Therefore, pH 8 to 10 was favorable for silica recovery.
Zeta Potential and Effect of pH on Hydrophobicity of Silica
and Alumina

12. 46.90 47.67 47.25 45.51
3.72 3.74
4.38
4.98
25.10 24.60
24.60 25.80
89.88
85.94 80.61
85.83
0
25
50
75
100
0
25
50
75
100
0.25 0.50 0.75 1.00
Ferecovery,%
Grade,mass%
CaO dosage, kg/t
Fe (%) Al2O3 (%) SiO2 (%) Fe recovery (%)
Fe
Effect of CaO dosage (as Quartz activator)
on silica-alumina removal
Collector ratio
DAA: NaOL % Fe %SiO2 %Al2O3 % Recovery
1:0 39.44 31.10 4.81 76.24
1:1 42.09 28.30 4.93 77.34
1:2 41.74 28.00 5.26 75.18
1:5 38.47 31.90 5.33 70.40
1:10 39.17 30.90 5.20 73.36
Effect of collector dosage ratio (DAA :
NaOL) on silica-alumina flotation
Feed
37.01
40.00 39.44 38.40
5.98 4.80 4.81 5.27
31.40 29.39 29.22 28.80
82.72
75.85 76.24 76.42
0
25
50
75
100
0
25
50
75
100
0.25 0.50 0.75 1.00
Ferecovery,%
Grade,mass%
DAA dosage, kg/t
% Fe % SiO2 % Al2O3 % Recovery
Fe
Conditions: MIBC = 0.05 kg/t, pH = 8
Effect of collector dosage DAA on silica-
alumina flotation
SiO2
Al2O3
Al2O3
SiO2
Fe recovery
Fe recovery
Better Selectivity when
NaOL and DAA used
Better Iron recovery when CaO was
used silica as activator
-Fe Grade 46 mass%, - Recovery 90%
%Fe %SiO2 %Al2O3
34.18 31.10 7.65

13. Effect of Iron Depressant dosage (starch) on flotation behavior of Hematite, Silica
and Alumina
Alkaline Starch, kg/t % Fe % Al2O3 % SiO2 % P % Recovery
0.25 46.90 3.72 25.10 0.03 98.46
0.50 48.57 3.27 23.90 0.03 98.32
0.75 49.62 3.29 22.30 0.03 97.67
1.00 51.64 2.90 20.60 0.02 95.95
Conditions: CaO = 0.25 kg/T, NaOL/DAA = 0.75 kg/T, MIBC = 0.05 kg/t
 At 1 kg/T, optimum dosage of
95.95% of Iron was recovered
 Iron grade improved from
47.67% without Starch to
51.64 % when starch was
used
 Silica and alumina also
reduced to 20.60% and
2.90% respectively.
46.90 48.57 49.62 51.64
3.72 3.27 3.29 2.90
25.10 23.90 22.30 20.60
98.46 98.32 97.67 95.95
0
25
50
75
100
0
25
50
75
100
0.25 0.50 0.75 1.00
Ferecovery,%
Grade,mass%
Alkaline starch dosage, kg/t
Fe (%) Al2O3 (%) SiO2 (%) Fe recovery (%)
Fe
Al2O3
SiO2
Feed
-Fe Grade 51 mass%, - Recovery 95%
%Fe %SiO2 %Al2O3
34.18 31.10 7.65

14. Adsorption of starch on Iron oxide surface during reverse flotation
Adsorption of DAA and NaOL on Iron surface during reverse flotation
Effect of starch on Iron
High Wettability
B
B B B
B
B
B
B
BB
B
B B
B
B
B
Collector
Effect
Dispersant
Effect
DAA cationic
Collector
NaOL anionic
Collector
Fe2O3
Fe2O3
Fe2O3 Fe2O3
SiO2
SiO2
SiO2
SiO2
Al2O3
Al2O3
Al2O3

15. Summary of Single Stage Process
1. Wet High Intensity Magnetic Separation
 Suitable Matrix – Pipe matrix
Iron upgrade – 34.18 mass% Fe 53.22 mass% Fe
Impurities removal – 38.75 mass% 15.95 mass%
Iron Recovery - 93%
%Fe %SiO2 %Al2O3
34.18 31.10 7.65
Feed Target
 Anionic collector, NaOL – 0.75 kg/t
 Cationic collector, DAA - 0.75 kg/t
 Quartz activator, CaO - 0.25 kg/t
Iron upgrade – 34.18 mass% Fe 51 mass% Fe
Impurities removal –38.75 mass% 23.50 mass%
Iron Recovery – 95.95%
2. Reverse flotation Process
 Starch Fe Depressant – 1 kg/t
%Fe %SiO2 + %Al2O3
> 60 < 7
 Pulp density - 2.5% Magnetic intensity – 10 T

16. Methodology for two-stage processes
Sanje Ore
First Stage Magnetic
Separation
Concentrate Tailings
Final Concentrate Tailings
Second Stage Magnetic
Separation
Sanje Ore
First Reverse
Flotation
Concentrate (underflow) Tailings
Final Concentrate Tailings
Second Stage
Reverse Flotation
Sanje Ore
Magnetic Separation
Concentrate
Tailings
TailingsFinal Concentrate
Reverse Flotation
2M-PROCESS
M-RF PROCESS
2RF PROCESS
Fe-67.27%,
SiO2-2.04%
Al2O3-1.04%
%Fe % 𝐒𝐢𝐎 𝟐 % 𝐀𝐥 𝟐 𝐎 𝟑
34.18 31.10 7.65
%Fe % 𝐒𝐢𝐎 𝟐 % 𝐀𝐥 𝟐 𝐎 𝟑
34.18 31.10 7.65
%Fe % 𝐒𝐢𝐎 𝟐 % 𝐀𝐥 𝟐 𝐎 𝟑
34.18 31.10 7.65
Fe-53.22%
SiO2-3.94%
Al2O3-12.02%
Fe-53.22%
SiO2-3.94%
Al2O3-12.02%
Fe-67.07%
SiO2-2.14%
Al2O3-1.30%
Fe-55.53%,
SiO2-15.80%
Al2O3-2.60%
Fe-51.64%,
SiO2-20.60%
Al2O3-2.90%
Fe recovery 81.94%
Fe recovery 93%
Fe recovery 93%
Fe recovery 80.47%
Fe recovery 95.95%
Fe recovery 87.65%
Two stage magnetic Separation Two stage Reverse flotation
Magnetic Separation-Reverse flotation

17. 2M Concentrate
Fe-60.08%, SiO2-2.52, P -
0.02%, Al2O3-1.99%
2RF Concentrate,
Fe-55.53%, SiO2-15.80, P -
0.00%, Al2O3-2.60%
M-RF Concentrate
Fe-66.83%, SiO2-2.04, P -
0.01%, Al2O3-1.30%
Sanje Ore
Fe-34.18%, SiO2-31.10, P -
0.05%, Al2O3-1.99%
Pictures of the Ore and the 3 types of concentrate produced

18. Proposed impurities removal Process for Sanje Iron ore
Total recovery, 81.94%
%Fe
67.27

19. Conclusion
In order to remove silica and alumina from Low-grade
ore such as Sanje Ore with Fe 34.18 mass% and high
impurities (SiO2/Al2O3- 38.75mass%), Two stage
Process (Magnetic separation followed by reverse
flotation) was established as the best impurities removal
process for low-grade iron ore because of…
 Higher iron recovery > 80%
 Higher iron grade (67.27 mass%)
 Lower impurities (3.06 mass% )
Target Iron grade attained
to meet market
requirement
Fe >60 mass%
SiO2+Al2O3 < 7
mass%