Direct hematite flotation from an iron ore tailing using an innovative biosurfactant Pereira, 2021

Prévia do material em texto

Full Terms & Conditions of access and use can be found at
https://www.tandfonline.com/action/journalInformation?journalCode=lsst20
Separation Science and Technology
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/lsst20
Direct hematite flotation from an iron ore tailing
using an innovative biosurfactant
Andreza Rafaela Morais Pereira, Ronald Rojas Hacha, Maurício Leonardo
Torem, Antonio Gutierrez Merma, Flávia P.C. Silvas & Abhilash A
To cite this article: Andreza Rafaela Morais Pereira, Ronald Rojas Hacha, Maurício Leonardo
Torem, Antonio Gutierrez Merma, Flávia P.C. Silvas & Abhilash A (2021): Direct hematite flotation
from an iron ore tailing using an innovative biosurfactant, Separation Science and Technology, DOI:
10.1080/01496395.2021.1873374
To link to this article: https://doi.org/10.1080/01496395.2021.1873374
Published online: 17 Jan 2021.
Submit your article to this journal 
Article views: 67
View related articles 
View Crossmark data
https://www.tandfonline.com/action/journalInformation?journalCode=lsst20
https://www.tandfonline.com/loi/lsst20
https://www.tandfonline.com/action/showCitFormats?doi=10.1080/01496395.2021.1873374
https://doi.org/10.1080/01496395.2021.1873374
https://www.tandfonline.com/action/authorSubmission?journalCode=lsst20&show=instructions
https://www.tandfonline.com/action/authorSubmission?journalCode=lsst20&show=instructions
https://www.tandfonline.com/doi/mlt/10.1080/01496395.2021.1873374
https://www.tandfonline.com/doi/mlt/10.1080/01496395.2021.1873374
http://crossmark.crossref.org/dialog/?doi=10.1080/01496395.2021.1873374&domain=pdf&date_stamp=2021-01-17
http://crossmark.crossref.org/dialog/?doi=10.1080/01496395.2021.1873374&domain=pdf&date_stamp=2021-01-17
ARTICLE
Direct hematite flotation from an iron ore tailing using an innovative 
biosurfactant
Andreza Rafaela Morais Pereiraa, Ronald Rojas Hachaa, Maurício Leonardo Torema, Antonio Gutierrez Mermaa, 
Flávia P.C. Silvasb, and Abhilash Ac
aDepartment of Chemical Engineering and Materials, Pontifical Catholic University of Rio De Janeiro Rua Marquês de São Vicente 225, Gávea, 
Brazil; bInstituto Tecnológico Vale, Ouro Preto, Brazil; c CSIR-National Metallurgical Laboratory, Jamshedpur, India
ABSTRACT
The use of a biosurfactant (BS) in mineral flotation offers numerous advantages over conventional 
surfactants, such as their low toxicity, high degradation kinetics, and potential for selectively 
treating low-grade ores. In the present study, the use of a biosurfactant obtained from 
Rhodococcus opacus bacteria for the flotation of hematite from iron ore tailings was evaluated. 
The microflotation assessments were conducted in a modified Partridge-Smith cell, and the batch 
flotation studies were conducted in a mechanical cell (CDC – cell). In addition, the effects of the pH, 
biosurfactant concentration, and depressant concentration on hematite recovery were evaluated. 
The results confirmed the biosurfactant adsorption onto the hematite surface, and the biosurfac-
tant decreased the surface tension of the water/gas interface. The critical micelle concentration 
(CMC) of the biosurfactant was approximately 1 g.L−1. Hematite recovery was feasible at a pH of 
around 3. In microflotation tests, the iron grade and recovery reached approximately 37% and 30%, 
respectively. These values increased in batch flotation circuits, specifically in the cleaner stage, the 
iron grade reached approximately 44% and the recovery was approximately 65%. Thus, the current 
development proved that this particular treatment of ore tailings carries environmental and 
technical benefits as an appropriate alternative cleaning technology.
ARTICLE HISTORY 
Received 7 September 2020 
Accepted 4 January 2021 
KEYWORDS 
Iron ore tailings; bioflotation; 
biosurfactant; Rhodococcus 
opacus
Introduction
Deposits of high-grade iron ore are being depleted by 
increasing mining production. Consequently, low-grade 
ores are being mined, generating higher volumes of iron 
ore tailings, which occupy large areas and can cause 
substantial ecological problems.[1–4] To control environ-
mental damage and replace conventional reagents, so- 
called green flotation reagents for processing low-grade 
ores and ore tailings for reuse have been developed[5–8] 
in recent years.
Bioflotation can be used as a clean option to 
process the above materials. In bioflotation, micro-
organisms (bacteria and yeasts) and biosurfactants 
(extracted from microorganisms) are used in the 
mineral concentration process.[9–11] The biosurfac-
tants are surface-active organic molecules produced 
by microorganisms that have hydrophilic and hydro-
phobic groups. Most of them are neutral or anionic, 
and they range from small fatty acids to large poly-
mers. They are biodegradable, less toxic than syn-
thetic surfactants, stable under extreme temperature 
and pH conditions, and may in the future, partially 
or completely replace the chemical reagents currently 
in use.[12–15]
Several works have shown the potential uses of bio-
surfactants (BSs) in flotation processes.[13,16–18] 
Khoshdast et al.[14] studied the use of Rhamnolipid pro-
duced by Pseudomonas aeruginosa MA01 strain as 
a biosurfactant, specifically as a frother in the flotation 
of copper ore, and the results showed that the 
Rhamnolipid biosurfactant presents significant froth-
ability, and its surface activity was compared to those 
of the frothers DF-250 (propylene glycol) and MIBC 
(methyl isobutyl carbinol). Didyk and Sadowski[19] 
used biosurfactants produced by Bacillus circulans and 
Streptomyces sp. for the flotation of serpentinite and 
quartz. The results showed a decrease in surface tension, 
the adsorption of the biosurfactants onto the quartz and 
serpentinite surfaces, and, consequently, an increase in 
the floatability of the two minerals. Olivera[20] studied 
the use of the biosurfactant from Rhodococcus erythro-
polis for the flotation of a quartz-hematite system. The 
results showed high adsorption of the biosurfactant on 
the hematite surface at a pH of 3, presenting a hematite 
recovery of approximately 99.88%. Puelles[21] studied 
CONTACT Maurício Leonardo Torem torem@puc-rio.br Department of Chemical Engineering and Materials, Pontifical Catholic University of Rio De 
Janeiro Rua Marquês de São Vicente 225, Gávea, Brazil.
SEPARATION SCIENCE AND TECHNOLOGY 
https://doi.org/10.1080/01496395.2021.1873374
© 2021 Taylor & Francis Group, LLC
http://www.tandfonline.com
https://crossmark.crossref.org/dialog/?doi=10.1080/01496395.2021.1873374&domain=pdf&date_stamp=2021-01-17
hematite flotation using a biosurfactant extracted from 
Rhodococcus opacus. The author observed a maximum 
hematite floatability (approximately 95%) at a pH of 3 
and high adsorption of the biosurfactant on the hematite 
surface. The recent trends and potential uses of micro-
bial on flotation were, recently, presented by Kinnunen 
et al.[22] This review article presents a nice assessment of 
the fundamental of microbial strains, their interactions 
with minerals and their effects on flotation. It was found 
no citations of research works dealing with biosurfac-
tants related to the processing of ore tailings. So, one 
may suggest the novelty of current work.
This work addresses the use of a biosurfactant 
extracted from Rhodococcus opacus, which is 
a bacterium from a nonpathogenic lineage of 
Nocardioform actinomycetales. This kind of bacteria is 
gram-positive, unicellular, chemoorganotrophic, and 
highly hydrophobic.[10,23] The biosurfactants in this 
kind of bacteria are amphipathic and have similar prop-
erties to those of well-known synthetic surfactants.[24,25] 
Importantly, this field is still at an early stage of devel-
opment. Most of the works found in the literature have 
used microscale systems, known as 
microflotation[6,,8,,20,,21,,26] and few works have been 
conducted on a larger scale.[27–31] Most important, at 
the present there have been no reportedapplications of 
this kind of biosurfactant to process iron ore tailings. 
Therefore, the objective of this paper is to evaluate the 
behavior of a biosurfactant extracted from Rhodococcus 
opacus in the direct flotation of hematite from an iron 
ore tailings and to better understand the behavior of the 
biosurfactant on a larger scale.
Materials and methods
Iron ore tailings sample
Iron ore tailings samples were collected from 
a Brazilian ore processing plant after a reverse iron 
ore flotation process. The sample was dried at room 
temperature (35°C), homogenized, and quartered. 
A representative sample was characterized by differ-
ent techniques. The chemical composition of the 
samples was determined by X-ray fluorescence 
(XRF) fusion with lithium tetraborate in a PW1480 
spectrometer (Philips), while volumetric analysis with 
potassium dichromate was conducted to determine 
the total iron content. The X-ray diffraction (XRD) 
data were collected with a Bruker-AXS D5005 dif-
fractometer to identify the crystalline phases present 
in the iron ore tailings. The granulometric analysis 
was performed using the wet-sieving method. For 
zeta potential analysis and Fourier transform infrared 
(FTIR) spectroscopy, a pure hematite sample was 
obtained in Minas Gerais, Brazil. This sample was 
crushed, pulverized and stored in a glass bottle 
prior to use in the experimental tests, and the parti-
cles used in both analyses were smaller than 10 µm.
Microorganisms and extraction of the biosurfactant
Rhodococcus opacus bacteria were obtained from the 
Chemical, Biological, and Agricultural Pluridisciplinary 
Research Center (CPQBA – UNICAMP). The microor-
ganism was cultivated in yeast malt glucose (YMG) 
culture medium consisting of (g.L−1): 20 g glucose, 5 g 
peptone, 3 g malt extract and 3 g yeast extract. The 
bacteria were incubated for 7 days in a rotatory shaker 
(CIENTEC CT-712) at 150 rpm, temperature (25°C) and 
pH 7.2. The procedure for the ethyl alcohol extraction of 
the biosurfactant can be found in Puelles.[21] The crude 
biosurfactant concentrate was stored at 4°C for 
a maximum of 15 days.
Zeta Potential studies
The zeta potentials of the hematite before and after 
interaction with the biosurfactant and sodium silicate 
were measured in a Malvern Zetasizer Nano instru-
ment. The analyzed sample is the mineral-floated 
fraction from the microflotation studies. In this 
study, the mineral (particle size −10 µm) was condi-
tioned at a pH of 3 using 1000 g.t−1 of biosurfactant 
and 300 g.t−1 of sodium silicate (depressant). After 
the flotation test, the sample was dried in an oven at 
50°C for 8 h and then a sample (0.1 g.L−1) was 
resuspended in an electrolytic solution (10−3 mol. 
L−1 NaCl). The measurements were carried out at 
pH values between 2 and 14, the desired pH was 
obtained using HCl and NaOH.
Surface tension
Surface tension measurements were performed using 
the DC 200 Surface Electro-Optics tensiometer by the 
Nöuy ring method at 21 ± 2°C. The effects of solution 
pH (3 to 11) and biosurfactant concentration (0 to 
2.23 g.L−1) were evaluated.
Fourier transform infrared (FTIR) spectroscopy
Infrared spectroscopy measurements were performed 
on a Scientific Nicolet 6700 FTIR spectrophotometer 
using the KBr pellet approach. Hematite samples were 
analyzed before and after interaction with the biosurfac-
tant, and the fraction of hematite used for these tests had 
2 A. R. M. PEREIRA ET AL.
a particle size smaller than 10 µm. The mineral sample is 
the same as that used in the zeta potential studies. The 
ratio of the sample to KBr was 1/200 (wt./wt.). The 
collection of the sample spectrum was carried out at 
a resolution of 4 cm−1 using 360 scans.
Flotation assessments
The microflotation tests of the iron ore tailings were 
carried out in a Partridge-Smith cell (volume of 
270 mL), and the biosurfactant was used to collect the 
hematite and the sodium silicate was used to depress the 
quartz. The batch flotation studies were carried out in 
a mechanical cell (CDC–cell) (volume of 800 mL). The 
details of the operating conditions used in the micro-
flotation tests and batch flotation tests are indicated in 
Table 1. Regarding the batch studies, the tests were 
initially carried out in a single stage (rougher) and then 
using a flotation circuit (rougher, cleaner, and 
scavenger).
Results and discussion
Iron ore characteristics
The results of chemical composition showed that the 
iron ore tailings sample had 13.85% Fe, and the XRF 
analysis corroborated these results (13.80%), can be seen 
in Table 2. This mineral composition was expected since 
the sample is from an itabiritic iron ore processing. The 
XRD analysis showed that the crystalline phase of quartz 
is a major phase, and the crystalline phase of hematite is 
a minor phase (Fig. 1).
The size fraction analysis of the iron ore tailings 
sample showed that approximately 93% of the material 
was smaller than 106. Additionally, the sample pre-
sented a P80 of 85 μm, and approximately 20% of the 
particles were smaller than 45 µm.
Zeta potential studies
Electrokinetic studies are important to elucidate the 
surface charge at the solid–liquid interface providing 
a helpful understanding of the flotation 
performance.[32] Considering this remark, Fig. 2 
shows the zeta potential of hematite before and after 
interacting with the biosurfactant using potassium 
chloride (0.001 mol.L−1) as an indifferent electrolyte. 
The hematite IEP (isoelectric point) was attained at 
a pH of around 6.2.[33] This zeta potential profile 
shows the flexibility of hematite to interact electrosta-
tically with anionic collectors in acidic media and 
cationic collectors in alkaline media. After condition-
ing the hematite with the biosurfactant, the zeta poten-
tial curve of hematite was dislocated to the left and 
presented a reversal charge point at around 3.6 (RCP1), 
the last elucidates a probable electrostatic interaction 
between the biosurfactant and the hematite surface. 
Several works have reported the same behavior, where 
zeta potential profile of hematite after interacting with 
the biosurfactant is shifted toward acidic pH 
values.[20,21] This can be explained by the higher con-
tent of anionic functional groups than nonionic or 
cationic groups. The Rhodococci genus generally pro-
duces trehalose lipid biosurfactants, which can be 
structurally diverse and often occur as complex 
Table 1. Experimental conditions for the microflotation tests and 
batch flotation tests.
Conditions Microflotation Batch Flotation
pH 3, 5, 7, 9, and 
11
3
Concentration of BS 1000–8000 g. 
t−1
1000–8000 g.t−1
Concentration of SS 0–1200 g.t−1 0–1200 g.t−1
Sample mass 5 g 132.66 g (30% solids 
by mass)
Agitation 300 rpm 800 rpm
Volume 270 mL 800 mL
Airflow rate 25 mL.min−1 Natural injection
Ore conditioning time with the 
depressant
5 min. 5 min.
Ore conditioning time with the 
collector
5 min. 5 min.
Flotation time 5 min. 5 min.
Table 2. Chemical analyses of the iron ore tailings sample 
through XRF.
Sample
Composition
Fe 
(%)
SiO2 
(%)
Al2 
O3 
(%)
P 
(%)
TiO2 
(%)
CaO 
(%)
MgO 
(%)
PF 
(%)
Tailings 
sample
13.85 79.60 0.24 0.011reagent widely used 
in the mineral industry as a dispersant and as a quartz 
depressant. In the case of quartz depression, the depres-
sant mechanism is believed to involve micelles of 
hydrated silica acid, [39] which adsorb onto the mineral 
surface. However, these silicate species can also be 
adsorbed onto iron oxide surfaces, which limits their 
separation efficiency.[40–42] This effect can be observed 
in the zeta potential profile of the hematite in the pre-
sence of the depressant (Fig. 2). The zeta potential curve 
dislocated to the left and a second reversal charge point 
was observed at pH of around 4.2 (RCP2). This point 
indicates that the silicate interacted with the hematite 
surface, and this interaction was more relevant in an 
acidic medium. Under acidic conditions, silicic acid 
(Si(OH)4) and SiO2 are the predominant species; such 
species can adsorb on the hematite surface and are 
responsible for the characteristic depression of sodium 
silicate.[41,43–45] Therefore, if sodium silicate adsorbs on 
the hematite surface, then the biosurfactant will not be 
adsorbed, and as a consequence, the hematite would be 
depressed.
Surface tension studies
Figure 3.a presents the effect of the biosurfactant con-
centration on the surface tension of the air/water inter-
face at 21°C and pH 3, as determined by the Nöuy ring 
method. The surface tension decreased with increasing 
biosurfactant concentration, achieving a value of 36 mN. 
m−1 at a biosurfactant concentration of 1 g.L−1. The 
surface tension remained relatively constant when the 
concentration of biosurfactant was further increased, so 
this point was considered the critical micelle concentra-
tion (CMC). Most biosurfactants extracted from the 
Rhodococcus genus reported a reduction in surface and 
interfacial tension relative to those achieved with syn-
thetic surfactants at the same concentrations. This simi-
larity may be attributed to the presence of substances 
that produce trehalose-containing glycolipids.[21,34,46]
Other works have reported similar behavior, such as 
Puelles, [21] who studied the effect of the concentration 
of biosurfactant from Rhodococcus opacus on surface 
tension. The author observed a decrease in surface ten-
sion from 72 mN.m−1 to 50.5 mN.m−1, and the CMC 
was found at a biosurfactant concentration of approxi-
mately 92 g.mL−1. Rufino et al.[15] studied the effect of 
the biosurfactant produced by Candida lipolytica UCP 
0988 on surface tension. The authors observed 
a reduction in the surface tension (from 70 mN.m−1 to 
25 mN.m−1) with increasing biosurfactant concentra-
tions. Didyk and Sadowsky[19] studied the biosurfactants 
produced by Bacillus circulans and Streptomyces sp. 
These biosurfactants were used for the biomodification 
of serpentinite and quartz surfaces. The biosurfactant 
1 2 3 4 5 6 7 8 9 10 11 12
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
20
Ze
ta
 P
ot
en
tia
l (
m
V
)
pH
Hematite
Hematite + Biosurfactant
Hematite + Sodium silicate
RCP 1 
RCP 2
IEP
Figure 2. Zeta potential curves of hematite before and after interacting with biosurfactant and sodium silicate. Particle size: −10 µm, 
[KCl]: 0.001 mol.L−1.
4 A. R. M. PEREIRA ET AL.
produced by Bacillus circulans decreased the surface 
tension from 72 to 28.6 mN.m−1, and the biosurfactant 
obtained from Streptomyces sp. decreased the surface 
tension by up to 29.3 mN.m−1.
Figure 3.b presents the effect of the pH on the surface 
tension of the water-biosurfactant solution. This evalua-
tion was carried out at 21°C and a biosurfactant con-
centration of 0.16 g.L−1. Low values of surface tension 
were observed under acidic and neutral conditions and 
reached values of approximately 35 mN.m−1. Higher pH 
values resulted in higher surface tension in the solution, 
reaching a maximum of 47 mN.m−1. The low surface 
tension values observed under acidic and neutral condi-
tions may indicate that the biosurfactant has excellent 
surface-active properties. Under these conditions, it is 
likely that active species of the biosurfactant is more 
soluble, which contributes to the decrease in surface 
tension. Other causes, such as temperature, viscosity, 
electrolytes and time, can also interfere with surface 
tension measurements.[47] According to Christova and 
Stoineva, [38] the biosurfactants from the genus 
Rhodococcus can powerfully lower the surface tension 
of the water from 72 mN.m−1 to 19 mN.m−1 due to the 
surfactant properties of the trehalose lipids. Thus, this 
kind of bioreagent is suitable for use in flotation pro-
cesses in which the biosurfactant interacts at the solid– 
liquid interface, resulting in modification of the mineral 
surface.[19]
Fourier transform infrared (FTIR) spectroscopy
Infrared spectroscopy has been widely applied to 
confirm the adsorption of chemical modifiers onto 
mineral surfaces since it can be used to identify the 
main functional groups present.[48–50] Fig. 4 shows 
the FTIR spectrum of the biosurfactant extracted 
from Rhodococcus opacus. The presence of some 
functional groups characteristic of conventional sur-
factants can be observed, which indicates the poten-
tial of this material as a biosurfactant. The absorption 
band at 3346.34 cm−1 may indicate the presence of 
hydroxyl groups (O-OH) and amine groups 
(NH).[18,48,51] The absorption region near 
1629.52 cm−1 corresponds to alkene (C = C) and 
ketone groups.[21] The absorption region between 
1500 cm−1 and 1300 cm−1 corresponds to the stretch-
ing of the CH2 and CH3 groups.[18] The absorption 
0,0 0,5 1,0 1,5 2,0 2,5
30
40
50
60
70
S
ur
fa
ce
 te
ns
io
n 
(m
N
/m
)
Biosurfactant concentration (g/L)
2 3 4 5 6 7 8 9 10 11 12
30
32
34
36
38
40
42
44
46
48
50
52
54
)
m/
N
m(
noisnet
ecafruS
pH
a)
b)
Figure 3. Effect of the biosurfactant concentration (a) and pH (b) on the surface tension.
4000 3500 3000 2500 2000 1500 1000 500
0
1
2
3
4
3.5
2.5
1.5
0.5
71
6.
22
94
0.
30
99
5.
24
10
40
.5
7
11
44
.9
2
14
05
.7
2
16
29
.5
2
29
31
.3
7
23
60
.9
333
46
.3
4
37
05
.1
9
46
5.
99
54
5.
42
10
84
.5
6
16
31
.9
2
34
26
.2
9
A
bs
or
ba
nc
e
Wavenumber (cm-1)
 Biosurfactant
 Hematite
 Hematite+Biosurfactant
Figure 4. FTIR spectrum of the biosurfactant extracted from 
Rhodococcus opacus and hematite before and after interacting 
with the biosurfactant.
SEPARATION SCIENCE AND TECHNOLOGY 5
band at 1040.57 cm−1 corresponds to the vibrations 
of the alkane functional groups.[21] The alkane, 
alkene, alcohol, and ketone groups may indicate the 
presence of mycolic acids, which are produced by 
Rhodococci [52] and could be responsible for the 
mineral hydrophobicity.
Figure 4, also presents the FTIR spectra of the 
hematite surface before and after interacting with 
the biosurfactant. Absorption bands at 465.99 cm−1 
and 545.42 cm−1 correspond to the stretching vibra-
tions of the Fe-O group of the hematite. The spectra 
after interactions show different bands. The band at 
3426.29 cm−1 indicates the presence of hydroxyl 
groups (O-OH) and amine groups.[18,48,51] The 
absorption peak at 1084.56 cm−1 corresponds to the 
asymmetric stretching of the phosphate groups (PO2) 
present in the phospholipids and nucleic acids.[18,48] 
The absorption band at 1632.92 cm−1 indicates the 
presence of alkene (C = C), carbonyl (C = O), and 
C = N groups.[18]
Thus, the observed FTIR spectra indicate the pre-
sence of certain functional groups characteristic of bio-
surfactants on the hematite surface after the hematite- 
biosurfactant interactions. This would be indicative of 
biosurfactant adsorption and thus modification of the 
mineral surface properties. Puelles[21] reported similar 
absorption bands for the spectrum of hematite after 
interaction with a biosurfactant from Rhodococcus 
opacus.
Microflotation studies
Effect of the pH on microflotation
One of the most important variable in flotation pro-
cesses is the pH of solution, particularly, it can dee-ply influence the activation of the functional groups 
on the biosurfactant and the surface properties of the 
mineral.[18] Fig. 5 presents the effect of pH on iron 
recovery and grade using 4000 g.t−1 of biosurfactant 
in the absence of a depressant (sodium silicate). Up 
to pH 5, increasing the pH reduced the iron recovery 
but improved the iron grade; higher pH values nega-
tively affected the iron recovery and grade. The iron 
recovery close to pH 2 was approximately 35%. This 
result could be attributed to the different organic 
substances, such as polysaccharides, fatty acids, phos-
pholipids and amino acids, present in the biosurfac-
tants that can be activated in this pH range 
contributing to the adsorption of the biosurfactant 
on the hematite surface.
Puelles[21] and Olivera[20] studied hematite floatabil-
ity using biosurfactants from Rhodococcus opacus and 
Rhodococcus erythropolis in Hallimond tubes, respec-
tively. The authors observed that the highest floatability 
occurred at approximately pH 3. The authors explained 
that in an acidic medium, electrostatic attraction occurs 
between the mineral surface and the biosurfactant that 
contains anionic groups, resulting in the maximum 
adsorption and, therefore, the maximum recovery of 
hematite.
Effect of the biosurfactant concentration on 
microflotation
Figure 6 presents the effect of the biosurfactant concen-
tration on the iron recovery and grade at pH 3 in the 
absence of sodium silicate. Increasing the biosurfactant 
concentration negatively affected the iron grade but 
favored recovery, presenting maximum grade (approxi-
mately 37%) and recovery values at a biosurfactant con-
centration of 6000 g.t−1; lower values were observed with 
higher concentrations. This result is in agreement with 
the surface tension studies, which showed a CMC of 
approximately 1 g.L−1.
Previous microflotation experiments showed that the 
biosurfactants extracted from Rhodococcus erythropolis 
and Rhodococcus opacus act as hematite collectors. For 
example, Merma et al.[17] showed that the highest hema-
tite floatability was achieved at pH 3, achieving 98% 
hematite recovery using a biosurfactant concentration 
of 50 mg.L−1. Puelles[21] achieved 95% hematite recovery 
at pH 3 using a biosurfactant concentration of 
75 mg.L−1.
Effect of the depressant concentration
Figure 7 shows the effect of the sodium silicate concen-
tration on the iron recovery and grade using 4000 g.t−1 
of biosurfactant and at pH 3. Increasing the depressant 
concentration negatively affected the Fe recovery and 
slightly favored the iron grade.
0
5
10
15
20
25
30
35
40
45
50
55
60
Ir
on
 g
ra
de
 (
%
)
pH
Fe recovery (%)
Fe (%)
1 2 3 4 5 6 7 8 9 10 11 12
0
10
20
30
40
50
60
Ir
on
 r
ec
ov
er
y 
(%
)
Figure 5. Effect of pH on iron recovery and grade in Partridge- 
Smith cell in the presence of 4000 g.t−1 biosurfactant.
6 A. R. M. PEREIRA ET AL.
According to the study of sodium silicates in aqueous 
solution by Yang et al., [43] when the concentration of 
silicate in solution increases, the distribution of silicate 
species becomes more complex, as dimers, trimers, oligo-
mers, and colloidal SiO2 are formed under acidic condi-
tions. Distribution diagrams presented by Wang et al.[53] 
and Zhang et al.[54] showed that Si(OH)4 and SiO2 are the 
predominant species in the acidic pH region. Silva et al.[55] 
observed colloidal silicate at low to moderate pH levels. 
Lopes et al.[56] explained that colloidal silicate can be 
responsible for depression through electrostatic forces and 
that silicate anions can adsorb onto negatively charged 
surfaces by chemisorption. Therefore, the hematite depres-
sion under acidic conditions can be attributed to the silicate 
species, and the formation of these species impairs hematite 
recovery.
Batch flotation studies
Effect of the biosurfactant concentration on the 
flotation
According to our results, different behaviors are 
obtained in microflotation and batch flotation, which 
could be attributed to different factors. According to 
Kim et al., [57] physical factors (e.g., shear force and the 
percentage of solids) are different at the two scales and 
can affect recovery, which explains the difference. Figure 
8 shows the effect of the biosurfactant concentration on 
the iron recovery and grade at pH 3 in the absence of 
a depressant (sodium silicate). Within the range of 1000 
and 4000 g.t−1, the biosurfactant concentration did not 
affect the iron grade, and concentrations above this 
range negatively affected the iron grade.
The metallurgical recovery was improved when the 
biosurfactant concentration was increased from 1000 to 
2000 g.t−1, and concentrations above this negatively 
affected the recovery. The decrease in recovery and 
grade was produced by the increase of the biosurfactant 
concentration to values around its CMC. Compared 
with anionic chemical collectors, the biosurfactant pre-
sents behavior similar to AERO 825 (sulfonate), which 
achieved an iron grade of 57.90% at a concentration of 
1200 g.t−1 under acidic conditions.[58] According to the 
literature, the biosurfactant is anionic, [38] and based on 
electrophoretic studies, the IEP of hematite is approxi-
mately 6.2. Therefore, the hematite surface is positively 
charged, and the biosurfactant is anionic, allowing the 
formation of electrostatic interactions and enabling 
hematite recovery.
0 100 200 300 400 500 600 700 800 900 1000 1100 1200
0
5
10
15
20
25
30
35
40
45
50
55
60
Ir
on
 g
ra
de
 (%
)
Silicate concentration (g/t)
 Fe recovery (%)
 Fe (%)
0
10
20
30
40
50
60
Ir
on
 r
ec
ov
er
y 
(%
)
Figure 7. Effect of the sodium silicate concentration on the iron 
recovery and grade in Partridge-Smith cell in the presence of 
4000 g.t−1 biosurfactant at pH 3.
0 1000 2000 3000 4000 5000 6000 7000 8000
0
5
10
15
20
25
30
35
40
45
50
55
60
Ir
on
 g
ra
de
 (
%
)
Biosurfactant concentration (g/t)
 Fe recovery (%)
 Fe (%)
0
10
20
30
40
50
60
Ir
on
 r
ec
ov
er
y 
(%
)
Figure 8. Effect of the biosurfactant concentration on the iron 
recovery and grade at pH 3 in a CDC mechanical cell, single-stage 
(rougher).
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
0
5
10
15
20
25
30
35
40
45
50
55
60
Ir
o
n
 g
ra
d
e 
(%
)
Biosurfactant concentration (g/t)
 Fe recovery (%) 
 Fe (%)
0
10
20
30
40
50
60
Ir
o
n
 r
ec
o
ve
ry
 (
%
)
Figure 6. Effect of the biosurfactant concentration on the iron 
recovery and grade in Partridge-Smith cell at pH 3.
SEPARATION SCIENCE AND TECHNOLOGY 7
Effect of the depressant concentration on the flotation
Figure 9 shows the effect of the sodium silicate concen-
tration on the iron recovery and grade at a biosurfactant 
concentration of 4000 g.t−1 and at pH 3. The silicate 
concentration had minimal influence on the iron grade, 
and the recovery increased slightly with increasing 
depressant concentration.
The interaction of silicate with hematite can 
explain the low recovery and grade; under acidic 
conditions, the silicate species can interact with 
quartz and hematite at the same time. These interac-
tions prevent interactions between the biosurfactant 
and the hematite surface, preventing the surface from 
becoming fully hydrophobic, which is reflected with 
low Fe recovery and grade. Lopes and Lima[58] 
studied hematite flotation on a batch scale using 
1200 g.t−1 AERO 825 and 2100 g.t−1 sodium silicate, 
and a similar iron grade of 57.90% was achieved 
under acidic conditions.
Flotation circuit assessments
A flotation circuit evaluation was conceived in order to 
increase the iron grade of the concentrate, preliminary 
tests involving a flotation circuit were performed. In 
industrial flotation processes, different steps (circuits) 
are developed to achieve both high recovery and grade. 
Most of the time, the concentrate grade from a single 
flotation step is not high enough, requiring additional 
flotationstages. The flotation circuit tests were per-
formed in three steps: rougher, cleaner, and scavenger. 
The tests were performed at pH 3 with and without the 
silicate (depressant of gangue); the operational condi-
tions are presented in Table 3.
RG=rougher; SCV=scavenger; CL=cleaner; 
BS=biosurfactant; SS=sodium silicate; Conc.=con-
centrate; Tail.=Tailings
According to the obtained results, the tests in the 
absence of the depressant presented better performance 
than was observed for the tests in the presence of silicate. 
In previous studies of batch flotation and microflotation, 
sodium silicate also depressed hematite, consequently 
decreasing hematite recovery.[20,55,59,60] The low perfor-
mance in the presence of the depressant can be linked to 
the operating conditions, especially the acid medium. 
Under these conditions, different silicate species (colloi-
dal silicate and silicate anion) interact with quartz and 
with hematite, which is discussed above. Higher 
0 1000
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
Ir
on
 g
ra
de
 (%
)
Silicate concentration (g/t)
 Fe recovery (%)
 Fe (%)
0
10
20
30
40
50
60
70
80
90
Ir
on
 r
ec
ov
er
y 
(%
)
Figure 9. Effect of the sodium silicate concentration on the iron 
recovery and grade in the presence of 4000 g.t−1 biosurfactant at 
pH 3 in a CDC mechanical cell, single-stage (rougher).
Table 3. Conditions of Flotation circuit in a CDC mechanical cell (pH 3).
Conditions
Step Mass Recovery (%) Fe Recovery (%)
Content (%)
RG SCV CL
Si Fe
BS 
(g.t−1)
SS 
(g.t−1)
BS 
(g.t−1)
SS 
(g.t−1)
BS 
(g.t−1)
SS 
(g.t−1)
Test 1 4000 0 2000 0 4000 0 SCV Conc. 5.76 18.11 17.63 43.56
SCV Tail. 79.04 26.77 43.60 4.69
CL Conc. 9.43 44.11 3.45 64.78
CL Tail. 4.74 7.80 31.51 22.78
Test 2 2000 0 1000 0 3000 0 SCV Conc. 5.04 18.27 13.16 50.26
SCV Tail. 84.88 43.81 41.96 7.15
CL Conc. 5.11 25.01 1.36 67.91
CL Tail. 3.94 8.58 26.59 30.16
Test 3 4000 600 2000 900 4000 300 SCV Conc. 5.41 15.01 21.06 38.42
SCV Tail. 84.22 31.24 43.30 5.14
CL Conc. 4.97 20.59 8.38 57.41
CL Tail. 3.86 5.73 33.00 20.55
Test 4 2000 600 1000 900 3000 300 SCV Conc. 3.11 8.13 22.56 36.19
SCV Tail. 91.44 47.19 41.96 7.15
CL Conc. 1.48 6.22 7.78 58.30
CL Tail. 3.01 4.85 31.81 22.34
8 A. R. M. PEREIRA ET AL.
performance was obtained in test 1; in the scavenger 
stage, the iron recovery and grade were approximately 
18% and 43.50%, respectively, and in the cleaner stage, 
the iron recovery and grade were approximately 44% 
and 65%, respectively.
Conclusions
The zeta potential studies showed that the IEP of 
hematite occurred at pH around 6.2. After condition-
ing with biosurfactant and in the presence of sodium 
silicate, two reversal charge points were detected at 
pH of around 3.6 and 4.2, respectively. This charge 
reversal may suggest electrostatic interactions of the 
reagents onto the hematite surface. FTIR spectro-
scopy indicated that after interacting with hematite, 
absorption bands belonging to the functional groups 
of the biosurfactant were presented onto the hematite 
surface. The surface tension results showed the 
reduction of the air/water surface tension after the 
addition of BS. The critical micelle concentration was 
approximately 36 mN.m−1 with a biosurfactant con-
centration of approximately 1 g.L−1.
Microflotation and batch flotation tests showed 
that acidic media, specifically pH 3, was 
a satisfactory condition for the recovery of hematite 
from the tailings. Under acidic conditions, the pre-
sence of silicate provoked a drop in the efficiency of 
the process. This can be attributed to the presence of 
silicate species (colloidal silicate or silicate anion) 
that can also interact with the hematite surface. In 
microflotation, the highest iron recovery and grade 
were near 29% and approximately 37%, respectively. 
Flotation circuit results presented higher iron recov-
ery and grades of approximately 44% and 65%, 
respectively. These results were obtained in the 
absence of the depressant. Therefore, the present 
research work shows bioflotation as a fruitful alter-
native cleaning technology using the biosurfactant 
extracted from Rhodococcus opacus termed as 
a “green” collector for the recovery of hematite 
from iron ore tailings.
Acknowledgements
The authors acknowledge Vale Institute of Technology – 
ITV, CNPq (National Council for Scientific and 
Technological Development); CAPES (Coordination for 
the Improvement of Higher-Level Personnel), FAPERJ 
(Rio de Janeiro State Research Foundation), Pontifical 
Catholic University of Rio de Janeiro, and Technological 
Characterization Laboratory (LCT) – Department of 
Mining Engineering and Petroleum – USP for the financial 
and technological support.
Declaration of interests
The authors declare that they have no known competing 
financial interests or personal relationships that could have 
appeared to influence the work reported in this paper.
References
[1] Praes, P. E.; de Albuquerque, R. O.; Luz, A. F. O. 
Recovery of Iron Ore Tailings by Column Flotation. 
J. Minerals Mater. Character. Eng. 2013, 1, 212–216. 
DOI: 10.4236/jmmce.2013.15033.
[2] Rea, S. M.; McSweeney, N. J.; Dwyer, R. B.; Bruckard, W. J. 
Application of Biotechnology in Iron Ore Beneficiation. In 
Iron Ore; Liming, L., Ed.; Mineralogy, Processing and 
Environmental Sustainability, 2015; pp 373–391. 
Woodhead Publishing: Cambridge, UK.
[3] Galvão, J. L. B.; Andrade, H. D.; Brigolini, G. J.; 
Peixoto, R. A. F.; Mendes, J. C. Reuse of Iron Ore 
Tailings from Tailings Dams as Pigment for 
Sustainable Paints. J. Cleaner Prod. 2018, 200, 
412–422. DOI: 10.1016/j.jclepro.2018.07.313.
[4] Pattanaik, A.; Venugopal, R. Investigation of 
Adsorption Mechanism of Reagents (Surfactants) 
System and Its Applicability in Iron Ore Flotation–an 
Overview. Colloid Interface Sci. Commun. 2018, 25, 
41–65. DOI: 10.1016/j.colcom.2018.06.003.
[5] Dwyer, R.; Bruckard, W. J.; Rea, S.; Holmes, R. J. 
Bioflotation and Bioflocculation Review: 
Microorganisms Relevant for Mineral Beneficiation. 
Mineral Process. Extract. Metall. 2012, 121(2), 65–71. 
DOI: 10.1179/1743285512Y.0000000005.
[6] Merma, A. G.; Torem, M. L.; Morán, J. J.; Monte, M. B. 
On the Fundamental Aspects of Apatite and Quartz 
Flotation Using a Gram Positive Strain as a 
Bioreagent. Miner. Eng. 2013, 48, 61–67. DOI: 
10.1016/j.mineng.2012.10.018.
[7] Kumar, R.; Mandre, N. R. Characterization and 
Beneficiation of Iron Ore Tailings by Selective 
Flocculation. Transactions of the Indian Institute of 
Metals. 2016, 69(7), 1459–1466. DOI: 10.1007/s12666- 
015-0667-9.
[8] Olivera, C. A. C.; Merma, A. G.; Puelles, J. G. S.; 
Torem, M. L. On the Fundamentals Aspects of 
Hematite Bioflotation Using a Gram Positive Strain. 
Miner. Eng. 2017, 106, 55–63. DOI: 10.1016/j. 
mineng.2016.10.017.
[9] De Mesquita, L. M. S.; Lins, F. F.; Torem, M. L. 
Interaction of a Hydrophobic Bacterium Strain in 
a Hematite–quartz Flotation System. Int. J. Miner. 
Process. 2003, 71(1–4), 31–44. DOI: 10.1016/S0301- 
7516(03)00028-0.
[10] Botero, A. E. C.; Torem, M. L.; de Mesquita, L. M. S. 
Surface Chemistry Fundamentals of Biosorption of 
Rhodococcus Opacus and Its Effect in Calcite and 
Magnesite Flotation. Miner. Eng. 2008, 21(1), 83–92. 
DOI: 10.1016/j.mineng.2007.08.019.
[11] Pollmann, K.; Kutschke, S.; Matys, S.; Raff, J.; 
Hlawacek, G.; Lederer, F. L. Bio-recycling of Metals: 
SEPARATION SCIENCE AND TECHNOLOGY 9
https://doi.org/10.4236/jmmce.2013.15033
https://doi.org/10.1016/j.jclepro.2018.07.313
https://doi.org/10.1016/j.colcom.2018.06.003
https://doi.org/10.1179/1743285512Y.0000000005
https://doi.org/10.1016/j.mineng.2012.10.018
https://doi.org/10.1016/j.mineng.2012.10.018
https://doi.org/10.1007/s12666-015-0667-9
https://doi.org/10.1007/s12666-015-0667-9
https://doi.org/10.1016/j.mineng.2016.10.017
https://doi.org/10.1016/j.mineng.2016.10.017
https://doi.org/10.1016/S0301-7516(03)00028-0
https://doi.org/10.1016/S0301-7516(03)00028-0
https://doi.org/10.1016/j.mineng.2007.08.019Recycling of Technical Products Using Biological 
Applications. Biotechnol. Adv. 2018, 36(4), 1048–1062. 
DOI: 10.1016/j.biotechadv.2018.03.006.
[12] Nitschke, M.; Pastore, G. M. Biosurfactants: 
Properties and Applications. in portuguese. Quím. 
Nova.2002, 25(5), 772–776. DOI: 10.1590/S0100- 
40422002000500013.
[13] Zouboulis, A. I.; Matis, K. A.; Lazaridis, N. K.; 
Golyshin, P. N. The Use of Biosurfactants in Flotation: 
Application for the Removal of Metal Ions. Miner. Eng. 
2003, 16(11), 1231–1236. DOI: 10.1016/j. 
mineng.2003.06.013.
[14] Khoshdast, H.; Sam, A.; Manafi, Z. The Use of 
Rhamnolipid Biosurfactants as a Frothing Agent and 
a Sample Copper Ore Response. Miner. Eng. 2012, 26, 
41–49. DOI: 10.1016/j.mineng.2011.10.010.
[15] Rufino, D. R.; Luna, J. M.; Takaki, G. M. C.; 
Sarubbo, L. A. Characterization and Properties of the 
Biosurfactant Produced by Candida Lipolytica UCP 
0988. Electron. J. Biotechnol. 2014, 17(1), 6. DOI: 
10.1016/j.ejbt.2013.12.006.
[16] Fazaelipoor, M. H.; Khoshdast, H.; Ranjbar, M. Coal 
Flotation Using a Biosurfactant from Pseudomonas 
Aeruginosa as a Frother. Korean J. Chem. Eng. 2010, 
27(5), 1527–1531. DOI: 10.1007/s11814-010-0223-6.
[17] Merma, A. G.; Castaneda, C. O.; Torem, M. L.; 
Santos, B. Comparison Study of Hematite Bioflotation 
by R. Erythropolis and Its Biosurfactant: Experiments 
and Neural Network Modeling. Chem. Eng. Trans. 2018, 
65, 439–444.
[18] Merma, A. G.; Olivera, C. A. C.; Hacha, R. R.; Torem, M. L.; 
Dos Santos, B. F. Optimization of Hematite and Quartz 
Bioflotation by Artificial Neural Network (ANN). J. Mater. 
Res. Technol. 2019, 8(3), 3076–3087.
[19] Didyk, A. M.; Sadowski, Z. Flotation of Serpentinite and 
Quartz Using Biosurfactants. Physicochem. Probl. 
Miner. Process. 2012, 48(2), 607–618.
[20] Olivera, C. A. C.;, 2018. Flotation of the 
Hematite-quartz System Using the Soluble 
Biosurfactant Produced by Rhodococcus Erythropolis. 
PhD Thesis - Department of Chemical Engineering and 
Materials, Pontifical Catholic University of Rio de 
Janeiro. Rio de Janeiro, 148. (in portuguese).
[21] Puelles, J. G. S.;, 2016 Hematite Flotation Using a Crude 
Biosurfactant Extracted from Rhodococcus Opacus. 
MSc. Dissertation - Department of Chemical 
Engineering and Materials, Pontifical Catholic 
University of Rio de Janeiro. Rio de Janeiro, 112.
[22] Kinnunen, P.; Miettinen, H.; Bomberg, M. Review of 
Potential Microbial Effects on Flotation. Minerals. 2020, 
10(533), 1–14.
[23] Czemierska, M.; Szcześ, A.; Pawlik, A.; Wiater, A.; 
Jarosz-Wilkołazka, A. Production and Characterisation 
of Exopolymer from Rhodococcus Opacus. Biochem. 
Eng. J. 2016, 112, 143–152.
[24] Kuyukina, M. S.; Ivshina, I. B. Rhodococcus 
Biosurfactants: Biosynthesis, Properties, and Potential 
Applications. In Biology of Rhodococcus; Springer: 
Berlin, Heidelberg, 2010; pp 291–313.
[25] Szymanska, A.; Sadowski, Z. Effects of Biosurfactants on 
Surface Properties of Hematite. Adsorption. 2010, 16 
(4–5), 233–239.
[26] Natarajan, K. A.; Deo, N. Role of Bacterial Interaction 
and Bioreagents in Iron Ore Flotation. Int. J. Miner. 
Process. 2001, 62(1–4), 143–157.
[27] Kolahdoozan, M.; Tabatabaei Yazdi, S. M.; Yen, W. T.; 
Hosseini Tabatabaei, R.; Shahverdi, A. R.; 
Oliazadeh, M.; Manafi, Z. Bioflotation of the Low 
Grade Sarcheshmeh Copper Sulfide. Trans. Indian 
Inst. Met. 2004, 57(5), 485–490.
[28] Hosseini, T. R.; Kolahdoozan, M.; Tabatabaei, Y. S. M.; 
Oliazadeh, M.; Noaparast, M.; Eslami, A. F. S. A. R.; 
Alfantazi, A. Bioflotation of Sarcheshmeh Copper Ore 
Using Thiobacillus Ferrooxidans Bacteria. Miner. Eng. 
2005, 18(3), 371–374.
[29] Yüce, A. E.; Tarkan, H. M.; Doan, M. Z. Effect of 
Bacterial Conditioning and the Flotation of Copper 
Ore and Concentrate. Afr. J. Biotechnol. 2006, 5(5), 
448–452.
[30] Kumar, A.; Ramarao, V. V.; Sharma, K. D. Microbial 
Induced Flotation Studies on Sphalerite Ore. J. Mater. 
Sci. Eng. A. 2013, 3(7A), 488.
[31] Mehrabani, J. V.; Noaparast, M.; Mousavi, S. M.; 
Dehghan, R.; Rasooli, E.; Hajizadeh, H. Depression of 
Pyrite in the Flotation of High Pyrite Low-grade Lead– 
zinc Ore Using Acidithiobacillus Ferrooxidans. Miner. 
Eng. 2010, 23(1), 10–16.
[32] Fuerstenau, D. W.; Pradip. Zeta Potentials in the 
Flotation of Oxide and Silicate Minerals. Adv. Coll. 
Interfac. Sci. 2005, 114, 9–26.
[33] Morais, P. A.; 2019. Bioflotation of Iron Ore Tailingsllar 
Using a Biosurfactant Extracted from Rhodococcus 
Opacus. Master Dissertation – Chemical Engineering 
and Materials Department – Pontifical Catholic 
University of Rio de Janeiro (in portuguese).
[34] Lang, S.; Philp, J. C. Surface-active Lipids in 
Rhodococci. Antonie Van Leeuwenhoek. 1998, 74(1–3), 
59–70.
[35] Ortiz, A.; Teruel, J. A.; Espuny, M. J.; Marqués, A.; 
Manresa, Á.; Aranda, F. J. Interactions of a Bacterial 
Biosurfactant Trehalose Lipid with Phosphatidylserine 
Membranes. Chem. Phys. Lipids. 2009, 158(1), 46–53.
[36] White, D. A.; Hird, L. C.; Ali, S. T. Production and 
Characterization of a Trehalolipid Biosurfactant 
Produced by the Novel Marine Bacterium 
Rhodococcus Sp., Strain PML026. J. Appl. Microbiol. 
2013, 115(3), 744–755.
[37] Kuyukina, M. S.; Ivshina, I. B.; Baeva, T. A.; Kochina, O. A.; 
Gein, S. V.; Chereshnev, V. A. Trehalolipid Biosurfactants 
from Nonpathogenic Rhodococcus Actinobacteria with 
Diverse Immunomodulatory Activities. New Biotechnol. 
2015, 32(6), 559–568.
[38] Christova, N.; Stoineva, I. Trehalose Biosurfactants. In 
Biosurfactants Research Trends and Applications; CRC 
Press: Boca Raton, 2014; pp 183–190.
[39] Bulatovic, S. M.;. Handbook of Flotation Reagents: 
Chemistry, Theory and Practice: Volume 1: Flotation of 
Sulfide Ores; Elsevier: Ontario, Canada, 2007.
[40] Hansen, H. B.; Wetche, T. P.; Raulund-Rasmussen, K.; 
Borggaard, O. K. Stability Constants for Silicate 
Adsorbed to Ferrihydrite. Clay Miner. 1994, 29(3), 
341–350.
[41] Jordan, N.; Marmier, N.; Lomenech, C.; Giffaut, E.; 
Ehrhardt, J. J. Sorption of Silicates on Goethite, 
10 A. R. M. PEREIRA ET AL.
https://doi.org/10.1016/j.biotechadv.2018.03.006
https://doi.org/10.1590/S0100-40422002000500013
https://doi.org/10.1590/S0100-40422002000500013
https://doi.org/10.1016/j.mineng.2003.06.013
https://doi.org/10.1016/j.mineng.2003.06.013
https://doi.org/10.1016/j.mineng.2011.10.010
https://doi.org/10.1016/j.ejbt.2013.12.006
https://doi.org/10.1016/j.ejbt.2013.12.006
https://doi.org/10.1007/s11814-010-0223-6
Hematite, and Magnetite: Experiments and Modelling. 
J. Colloid Interface Sci. 2007, 312(2), 224–229.
[42] Jolstera, R.; Gunneriusson, L.; Forsling, W. Adsorption 
and Surface Complex Modeling of Silicates on 
Maghemite in Aqueous Suspensions. J. Colloid 
Interface Sci. 2010, 342(2), 493–498.
[43] Yang, X.; Roonasi, P.; Holmgren, A. A Study of Sodium 
Silicate in Aqueous Solution and Sorbed by Synthetic 
Magnetite Using in Situ ATR-FTIR Spectroscopy. 
J. Colloid Interface Sci. 2008, 328(1), 41–47.
[44] Marinakis, K. I.; Shergold, H. L. Influence of Sodium 
Silicate Addition on the Adsorption of Oleic Acid by 
Fluorite, Calcite and Barite. Int. J. Miner. Process. 1985, 
14(3), 177–193.
[45] Qi, G. W.; Klauber, C.; Warren, L. J. Mechanism of 
Action of Sodium Silicate in the Flotation of Apatite 
from Hematite. Int. J. Miner. Process. 1993, 39(3–4), 
251–273.
[46] Bicca, F. C.; Fleck, L. C.; Ayub, M. A. Z. Production of 
Biosurfactant by Hydrocarbon-degrading Rhodococcus 
Ruber and Rhodococcus Erythropolis. Revista De 
Microbiologia. 1999, 30(3), 231–236.
[47] Huo, T. L.;, 1998. The Effect of Dynamic Surface 
Tension on Oxygen Transfer Coefficient in Fine 
Bubble Aeration System. PhD Thesis - Department of 
Civil Engineering, University of California. Los Angeles, 
204.
[48] Hacha, R. R.; Torem, L. M.; Merma, A. G.; da Silva 
Coelho, V. F. Electroflotation of Fine Hematite 
Particles with Rhodococcus Opacus as a Biocollector 
in a Modified Partridge–Smith Cell. Miner. Eng. 2018, 
126, 105–115.
[49] Sammon, C.; Yarwood, J.; Everall, N. AFTIR–ATR 
Study of Liquid Diffusion Processes in PET Films: 
Comparison of Water with Simple Alcohols. Polymer. 
2000, 41(7), 2521–2534.
[50] Potapova, E.;, 2009. Studies on the Adsorption of 
Flotation Collectors on Iron Oxides. Doctoral disserta-
tion, Lulea tekniska universitet.
[51] Deo, N.; Natarajan, K. A.; Somasundaran, P. 
Mechanisms of Adhesion of Paenibacillus Polymyxa 
onto Hematite, Corundum and Quartz. Int. J. Miner. 
Process. 2001, 62(1–4), 27–39.
[52] Nishiuchi, Y.; Baba, T.; Yano, I. Mycolic Acids from 
Rhodococcus, Gordonia, and Dietzia. J. Microbiol. 
Methods. 2000, 40(1), 1–9.
[53] Wang, W.; Wang, H.; Wu, Q.; Zheng, Y.; Cui, Y.; Yan, W.; 
Peng, T. Comparative Study on Adsorption and 
Depressant Effects of Carboxymethyl Cellulose and 
Sodium Silicate in Flotation. J. Mol. Liq. 2018, 268, 
140–148.
[54] Zhang, Z.; Cao, Y.; Ma, Z.; Liao, Y. Impact of Calcium 
and Gypsum on Separation of Scheelite from Fluorite 
Using Sodium Silicate as Depressant. Sep. Purif. 
Technol. 2019, 215, 249–258.
[55] Silva, J. P. P.; Baltar, C. A. M.; Gonzaga, R. S. G.; 
Peres, A. E. C.; Leite, J. Y. P. Identification of Sodium 
Silicate Species Used as Flotation Depressants. Mining. 
Metallurg. Explorat. 2012, 29(4), 207–210.
[56] Lopes, G. M.; Peres, A. E. C.; Pereira, C. A.; Antônio, L. M., 
2011. The Use of Sodium Silicate as a Dispersant/depres-
sant in the Mineral Industry. Proceeding of the XXIV 
ENTMME, Salvador-Brasil (in portuguese).
[57] Kim, G.; Choi, J.; Silva, R. A.; Song, Y.; Kim, H. 
Feasibility of Bench-scale Selective Bioflotation of 
Copper Oxide Minerals Using Rhodococcus Opacus. 
Hydrometallurgy. 2017, 168, 94–102.
[58] Lopes, G. M.; Lima, R. M. F. Iron Ore Direct Flotation 
Using Sodium Oleate. Rem: Revista Escola De Minas. 
2009, 62(3), 323–329.
[59] Arantes, R. D. S.; Souza, T. F. D.; Lima, R. M. F. 
Influence of Sodium Silicate Modulus on Iron Ore 
Flotation: Fundamental Studies. Tecnol Metal Mater 
Min. 2017, 14(1), 39–45.
[60] Nascimento, D. R.; Pereira, R. D.; Lima, R. M. F. 
Influence of Sodium Silicate on Floatability and 
Charge of Hematite and Quartz with Sodium Oleate. 
Latin Am. Appl. Res. 2013, 43, 189–191.
SEPARATION SCIENCE AND TECHNOLOGY 11
	Abstract
	Introduction
	Materials and methods
	Iron ore tailings sample
	Microorganisms and extraction of the biosurfactant
	Zeta Potential studies
	Surface tension
	Fourier transform infrared (FTIR) spectroscopy
	Flotation assessments
	Results and discussion
	Iron ore characteristics
	Zeta potential studies
	Surface tension studies
	Fourier transform infrared (FTIR) spectroscopy
	Microflotation studies
	Effect of the pH on microflotation
	Effect of the biosurfactant concentration on microflotation
	Effect of the depressant concentration
	Batch flotation studies
	Effect of the biosurfactant concentration on the flotation
	Effect of the depressant concentration on the flotation
	Flotation circuit assessments
	Conclusions
	Acknowledgements
	Declaration of interests
	References