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This study is focused on the preparation of multicomponent nanoparticles (MCNPs) used to remediate artificial and real mine tailings. The nanoparticles were synthesized with 0.035 M or 0.007 M of sodium sulfate, 0.5 M of iron chloride and 0.8 M of sodium borohydride. Characterization of nanoparticles performed with a Transmission Electron Microscope (TEM), X-ray diffractometer (XRD), Fourier Transform Infrared Spectrometer (FTIR), and X-ray Photoelectron Spectrometer (XPS) demonstrated, these materials are in the nanoscale range, contain zero valent iron Fe (0) and iron sulfide (FeS) and are structurally modified after treatment. Simultaneous removal of heavy metals was carried out under oxidizing and reducing conditions using MCNPs reaching an efficiency of more than 98% for all of them. Kinetics conducted under oxidizing condition, pH 3 and 0.035M sodium sulfate shows that the highest removal of heavy metals from artificial mine tailings was achieved after 160 min of treatment although steady state was reached in 240 mins. Results of kinetic tests fit very well to a pseudo-second- order model, while the isothermal equilibrium adsorption tests were adjusted to a Freundlich isotherm. Also, nanoparticles showed a high adsorption capacity (~140 mg/g) when they were in contact with 200 mg Cu2+/L. Finally, multicomponent nanoparticles tested with real mine tailings in the presence of other competing chemicals results in heavy metals removal over 90%.
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Cumbal et al.
Synthesis of Multicomponent Nanoparticles for
Immobilization of Heavy Metals in Aqueous Phase
NanoWorld Journal
Research Article Open Access
Luis Heriberto Cumbal Flores1,2, Alexis Debut1,2 and Carina Stael1
1Centro de Nanociencia y Nanotecnología, Universidad de las Fuerzas Armadas-ESPE, P.O. Box: 1715 231B, Sangolquí, Ecuador
2Departamento de Ciencias de la Vida, Universidad de las Fuerzas Armadas-ESPE, P.O. Box: 1715 231B, Sangolquí, Ecuador
*Correspondence to:
Luis Heriberto Cumbal Flores, PhD
Centro de Nanociencia y Nanotecnología
Universidad de las Fuerzas Armadas-ESPE
P.O. Box: 1715 231B, Sangolquí, Ecuador
Tel: 593 2 3989492
Received: October 15, 2015
Accepted: December 26, 2015
Published: December 28, 2015
Citation: Cumbal LH, Debut A, Stael C. 2015.
Synthesis of Multicomponent Nanoparticles for
Immobilization of Heavy Metals in Aqueous
Phase. NanoWorld J 1(4): 103-109.
Copyright: © 2015 Cumbal et al. is is an Open
Access article distributed under the terms of the
Creative Commons Attribution 4.0 International
License (CC-BY) (http://creativecommons.
org/licenses/by/4.0/) which permits commercial
use, including reproduction, adaptation, and
distribution of the article provided the original
author and source are credited.
Published by United Scientic Group
is study is focused on the preparation of multicomponent nanoparticles
(MCNPs) used to remediate articial and real mine tailings. e nanoparticles
were synthesized with 0.035 M or 0.007 M of sodium sulfate, 0.5 M of iron
chloride and 0.8 M of sodium borohydride. Characterization of nanoparticles
performed with a Transmission Electron Microscope (TEM), X-ray
diractometer (XRD), Fourier Transform Infrared Spectrometer (FTIR), and
X-ray Photoelectron Spectrometer (XPS) demonstrated, these materials are in
the nanoscale range, contain zero valent iron Fe (0) and iron sulde (FeS) and are
structurally modied after treatment. Simultaneous removal of heavy metals was
carried out under oxidizing and reducing conditions using MCNPs reaching an
eciency of more than 98% for all of them. Kinetics conducted under oxidizing
condition, pH 3 and 0.035 M sodium sulfate shows that the highest removal of
heavy metals from articial mine tailings was achieved after 160 min of treatment
although steady state was reached in 240 mins. Results of kinetic tests t very well
to a pseudo-second- order model, while the isothermal equilibrium adsorption
tests were adjusted to a Freundlich isotherm. Also, nanoparticles showed a high
adsorption capacity (~140 mg/g) when they were in contact with 200 mg Cu2+/L.
Finally, multicomponent nanoparticles tested with real mine tailings in the
presence of other competing chemicals results in heavy metals removal over 90%.
Multicomponent, Nanoparticles, Removal, Heavy metals, Mine tailing
Mining is an important economic activity worldwide, but it has generated a
huge pollution in the environment, mainly because of poor exploitation processes
and wrong disposal of mine tailings [1-3]. Actually, the delivery of hazardous
contaminants to the ecosystem, especially heavy metals into the water streams is a
great concern (EPA, 2012). Chemical characterization of mine tailings has found
the presence of heavy metals such as Hg2+, As5+, Pb2+, Cu2+, Zn2+, Ag+, Ni2+, Mn2+,
and others [4]. Due to the recognized toxicity of heavy metals, the exposure to
these elements, even in trace concentrations, is considered to be harmful to living
beings [5, 6]. ese pollutants can be assimilated through inhalation, ingestion
and skin adsorption, bringing about serious illnesses, like cancer, neurological,
endocrinological and immunological dysfunction, Alzheimer, among others [7].
e toxicity of heavy metals is attributed to their physicochemical properties.
Generally, these pollutants are highly soluble in water, especially at low pH,
spreading out more easily in water streams [8]. Additionally, heavy metals are
persistent and cannot be rapidly degraded in nature [9], accumulating in living
NanoWorld Journal | Volume 1 Issue 4, 2015
Synthesis of Multicomponent Nanoparticles for Immobilization of Heavy Metals in
Aqueous Phase Cumbal et al.
studies on thin lms of the nanoparticle were carried out using
a diractometer (EMPYREAN, PANalytical) with a θ–2θ
conguration (generator–detector), wherein a copper X-ray
tube emitted a wavelength of λ =1.54 Ao. FTIR attenuated
total reection spectra were recorded on a Spectrum Two IR
spectrometer (Perkin Elmer, USA) to detect the dierent
functional groups involved in the capture of heavy metals by
the multicomponent nanoparticles. XPS spectra were recorded
on an AXIS ULTRA equipped with Magnetic Immersion
Lens and Charge Neutralization System with a new Spherical
Mirror Analyzer and monochromatic source (Al Kα) operated
at 150 W (15 kV, 10 mA).
Removal of heavy metals
Batch kinetic tests for heavy metals removal by nanoparticles
were carried out using 100 mL Boeco bottles under oxidant
environment and pH 3±0.2. e removal was initiated by
mixing 5 or 9 mL of MCNPs with 50 mL of articial aqueous
mine tailings, which resulted in concentrations of 5.3 mg/L
Cu2+, 4.99 mg/L Zn2+, 4.24 mg/L Mn2+, 2.48 mg/L Ni2+, 2.98
mg/L Pb2+, 4.1 mg/L Ag+, and 0.99 mg/L As5+. ese initial
concentration values are within the range of reported heavy
metal levels in aqueous mine tailings [23, 24]. Bottles were
placed in a water bath and agitated for 4 hours at 25 °C. During
the test, 10 samples of 2 mL of treated aqueous phase were
ltered with a 0.2 μm PVDF lter for heavy metals analyses.
In addition, kinetic tests for each heavy metal in the presence
of high concentration of other metals were performed under
otherwise same experimental conditions. To test pH eects,
the removal experiments were performed at an initial pH of 3,
5, 7, and 9, adjusted with 0.1 N NaOH and/or 0.1 N HCl and
by adding 0.2 M of sodium acetate buer to the glass bottles.
Samples of 5 mL were collected after completing the treatment
(4 hours), ltered, and analyzed for heavy metals. Tests under
reductive conditions were carried out in 80 mL glass vials
lled with 64 mL of articial mine tailing containing MCNPs
and sealed with Teon-lined caps. Additionally, we have also
performed adsorption isotherm measurements using dierent
concentrations of Cu (2, 4, 6, 8, 10, 15, 20, 50, 100 and 200
mg/L) and 9 mL of MCNPs. e amount of Cu2+ adsorbed
per unit mass of wet nanoparticles was calculated through the
Equation 1:
c cv
where qt (mg/g) corresponds to the amount of Cu2+
adsorbed per gram of wet nanoparticles at time t (min), C0
(mg/L) is the initial concentration of Cu2+ in the solution,
Ct(mg/L) refers to the concentration of Cu2+ at a time t, m (g)
is the mass of the multicomponent nanoparticles used in tests
and V (L) refers to the initial volume of the stock solution
Chemical and physical analyses
Heavy metals such as Pb2+, Ag+, Ni2+, Mn2+, Zn2+ and Cu2+
were analyzed with an atomic absorption spectrometer, Perkin
Elmer AA 800, using standardized methods [26]. Arsenic was
quantied using a Flow Injection Analysis System (FIAS)
coupled to AA800 and a discharge lamp. For the operation
of FIAS system, it was used a solution of 10% v/v of HCl as
carrier and a solution of 0.2% w/v NaBH4 + 0.05 % NaOH
tissues until getting hazardous concentrations [7, 10, 11].
Similarly, because of its persistence in the environment, heavy
metals are likely to sediment at the bottom of lakes, rivers,
lagoons, and oceans, causing adverse eects on ecosystems,
altering their normal conditions. us, provoking death of
aquatic species, and even passing through the trophic chain
[12, 13]. Owing to the environmental and health concerns,
many conventional techniques have been developed to
remediate media contaminated with heavy metals; even
though with limited performance in terms of eectiveness and
removal eciency. For example, microbial cells have been used
as bioaccumulators of soluble and particulate heavy metals
from industrial wastes with high eciency [14-17]; however,
these metals could be released back into the liquid phase when
the biomass is degraded. Current techniques make use of
nanoparticles or composite materials for remediation of heavy
metals in water. Nevertheless, almost all approaches rely on
the functionalization of nanoparticles with dierent reactive
groups or loading nanostructures on supporting materials to
provide them, with the capability of capturing the heavy metals
[18-21]. Besides all these preparation techniques are complex.
Multicomponent nanoparticles, prepared and characterized
by Kim et al. (2011) [22] have shown good performance for
TCE and pesticides degradation. However, from the best of
our knowledge, there is no study related to the application
of these nanoparticles in the simultaneous removal of heavy
metals from the aqueous phase.
Materials and Methods
Chemicals were purchased from Fisher Scientic: Ferric
chloride (FeCl3.6H2O, 99,8%), sodium sulfate (Na2SO4,
99,9%), sodium borohydride (NaBH4, >98%) ascorbic acid
(USP/FCC), hydrochloric acid (HCl, 37,3%), nitric acid
(HNO3, 69,5%), sodium hydroxide (NaOH, 98%), 55 buer
solution (0.2 M Sodium acetate, 96%), and potassium iodide
(KIO3, 99%) from Himedia.
General procedure for preparation of the multicomponent
e MCNPs were prepared using a modied method
developed by Kim et al. [22]. In a typical procedure, solutions
of 0.5 M FeCl3.6H20 and 0.8 M NaBH4 + 0.035 M or 0.007
M Na2SO4 were prepared using DI water purged with nitrogen
for 15 min. en, 5 mL of the latter solution was added drop
wise to the mixture of 50 mL of FeCl3 contained in a ask
attached to a vacuum line. is mixture was placed under
vigorous stirring using an orbital shaker for 15 min at ambient
temperature. During this process, the color of the iron solution
changes from yellowish to blackish color, indicating the
formation of MCNPs. e resulting product, multicomponent
nanoparticles, was centrifuged at 7000 rpm for 2 min and
washed several times with nitrogenized deionized water. e
puried nanoparticles were lyophilized for 16 h and stored in
an air-free bottle for further characterization.
Transmission electron microscope images were recorded
digitally (Tecnai G2 Spirit TWIN, FEI, Holland). XRD
NanoWorld Journal | Volume 1 Issue 4, 2015
Synthesis of Multicomponent Nanoparticles for Immobilization of Heavy Metals in
Aqueous Phase Cumbal et al.
as reducing agent. For this analysis, samples of articial and
real mine tailings were pretreated with a solution of potassium
iodide and ascorbic acid 5% to reduce all the As species to As3+.
For FIAS-absorption spectrometer the calibration curve with
a correlation index, R 99%, was obtained before analyzing
the samples. For the analysis of anions, an ion chromatograph
Dionex ICS 1100 was used, equipped with a guard column
AG14 and an analytical column AS14, both of 4mm, and a
sample loop of 50 μL. A solution of 35 mM sodium hydroxide
was used as eluent. Physicochemical properties of real mine
tailings such as dissolved oxygen, conductivity and pH were
determined using a Mettler Toledo multiparameter.
Results and Discussion
Characterization of MNPs
Size characterization of MCNPs, demonstrated that there
is no signicant dierence when using 0.007 and 0.035 M
of sodium sulfate during preparation of nanoparticles. TEM
images of MCNPs have shown almost the same diameter
on average size of 24-42 nm [Figure 1]. Nevertheless,
the nanosized particles indeed inuence the physical and
chemical properties of the nanoparticles and therefore the
surface electronic structure [27, 28]. e high reactivity of
the atoms on the surface of nanoparticles due to a decrease
in size, confer to electrons more energy because of quantum
connement [29]. Also, reactivity depends on the amount of
Fe(0) and FeS formed during the preparation of MCNPs. In
this study, it was used approximately 27.9 g/L of Fe(III) and
1.12 or 0.224 g/L of sulfur in the preparation of the particles.
XRD spectrum of nanoparticles shows peaks corresponding
to Fe(0) and a small amount of FeS precipitates, as depicted in
Figure S1 (Supporting Information). In regard to the stability
of these nanoparticles, it can be implied they are greatly stable
in aqueous solutions. Results on pH measurements of the
nanoparticles solutions, exhibited a value of around 9.90. At
this pH there is an absence of hydrogen ions (H+) preventing
early oxidation of nanoparticles [30]. Lu et al. (2007) [29]
reported that nanoparticles were more stable at pH over 8.
In addition, when these nanoparticles are manufactured under
reducing conditions, dissolved oxygen is as low as 0.02 mg/L.
is, in turn, contributes to the stability of the nanoparticles
since FeS does not react with oxygen to produce oxidized
nanoparticles [31]. On the other hand, the high conductivity of
the nanoparticles solution (~36 mS/cm) may produce a strong
ow of electrons at the nanoparticles surface, suggesting an
increase of its roughness that contributes to a higher surface
area, and therefore, higher reactivity [22].
Kinetic study
Figure 2 shows the reaction kinetics of Pb2+ removal from
articial mine tailing using Fe/FeS nanoparticles prepared
with 0.035 M or 0.007 M Na2SO4. e highest removal of
this heavy metal occurred after approximately ve minutes
of reaction [Figure 2]. However, Pb2+ reached a complete
steady state after 160 mins. Most of the heavy metals utilized
in this study (Mn2+, Zn2+, Cu2+, Ag+, Ni2+) attained a steady
condition after approximately 40 min, only As5+ reached this
condition at 160 min (data not shown in Figure 2). Results of
kinetic tests of all heavy metals did not evidence a signicant
dierence on removals using multicomponent nanoparticles
with dierent concentrations of sodium sulfate (0.035 M and
0.007 M) (data not shown). ese experimental values t a
pseudo-second-order model [Equation 2].
t ee
q kq q
= +
where k2 (g/mg.h) is the pseudo-second-order rate
constant, qe is the amount of metal adsorbed (mg/g) at
equilibrium and qt is the amount of the adsorption (mg/g)
at any time t (h) [25]. Table S1 (Supporting Information)
summarizes the calculated qe values, pseudo-second-order rate
constants k2 and correlation coecient values. e qe and k2 are
calculated from de slope and the intercept of the plots of t/qt
versus t according to the Equation 2. All tting curves exhibit
Figure 1: TEM images of MCNPs prepared using 0.035 M Na2SO4, 0.035 M
FeCl3.6H2O and 0.8 M NaBH4.
Figure 2: Removal of Pb2+ using MCNPs prepared with 0.5 M FeCl3.6H2O,
0.035 M and 0.007 M Na2SO4 and 0.8 MNaBH4.
NanoWorld Journal | Volume 1 Issue 4, 2015
Synthesis of Multicomponent Nanoparticles for Immobilization of Heavy Metals in
Aqueous Phase Cumbal et al.
good linearity with a correlation coecient nearly equal to
unity (R2 ~ 1.0) as shown in Figure 3. is behavior suggests
that chemical adsorption is the main mechanism for removal
of heavy metals from articial mine tailing [32, 33].
Adsorption capacity study
e adsorption capacity of multicomponent nanoparticles,
using dierent concentrations of Cu2+, showed almost
instantaneous removals in the rst ve minutes with any
desorption throughout the test as shown in Figure S2
(Supporting Information). e removal eciency and
adsorption capacity of the multicomponent nanoparticles,
increased progressively from 98.59% and 1.51 mg/g to 99.91%
and 135.64 mg/g for 2 and 200 mg/L of Cu2+, respectively.
is behavior could be credited to an enhancement in the
Brownian motion, propitiating higher collisions among copper
ions dissolved in water and a better diusion of them towards
multicomponent nanoparticles [25, 34].
Adsorption isotherms study
Isotherm tests were conducted to describe the adsorption
behavior of the multicomponent nanoparticles when removing
Cu2+. Results of adsorption tests t well Freundlich isotherm
model (Equation 3), exhibiting a correlation coecient value
of 0.988 as shown in Figure S3 (Supporting Information).
=--------------------------- (3)
where, qe (mg/g) and Ce (mg/L) are the amount of pollutant
adsorbed and the concentration in the aqueous phase and K
and n are constants for Cu adsorption on MCNPs at 25 °C.
e elevated correlation coecient obtained with Freundlich
model suggests that adsorption of heavy metals may occur on
a rough surface of nanoparticles as described above. In other
words, there is a heterogeneous distribution of the active sites
on the surface of the nanoparticles where the metals are bound
[25]. Furthermore, having adjusted the adsorption isotherm
data to a Freundlich model, it reinforces the fact that sodium
sulfate contacted with borohydride promotes the precipitation
of FeS on the surface Fe(0) core of nanoparticles, contributing
to their roughness [22].
Study of simultaneous removal of heavy metals from the
aqueous phase
Despite good removal of heavy metals achieved on tests
conducted with articial mine tailing samples under dierent
pH, redox potential, and concentrations of sodium sulfate,
certain values have shown to be better than the others. For
instance, using 0.035 M of sodium sulfate in the preparation
of MCNPs resulted on better removals than employing 0.007
M. Sodium sulfate concentration has been demonstrated to
be directly proportional to roughness as well as to the increase
of surface area of multicomponent nanoparticles [22]. Also,
under reducing conditions and 0.035 M Na2SO4, removal of
toxic metals (~99%) was slightly enhanced compared to the
under oxidized environment (~97%) [Figure 4]. Reduced
conditions provided a favorable setting for the removal of
heavy metals because oxygen was not present in solution [35];
thus nanoparticles were not easily oxidized and did not lose
their reactivity. Tests using MCNPs prepared with 0.035 M
of sodium sulfate applied to real mine tailings contaminated
with heavy metals showed also high eciency to immobilize
the metallic elements [Figure 5]. More than 99% of removal
was achieved for the majority of toxic metals from the liquid
phase. erefore, the property of the nanoparticles that causes
high removal of heavy metals from water is its chemical
composition: Fe(0) and FeS. It is obvious that the active groups
of the multicomponent nanoparticles chemically immobilize
the toxic metals [Figure 6]. Clearly, XPS spectra show peaks
related to the formation of CuO with binding energies of
953.8 and 934.1 eV for Cu2p1/2 and Cu2p3/2, respectively.
Chemical sorption of heavy metals on MCNPs is also
conrmed by FTIR tests performed on samples containing
fresh and after treatment multicomponent nanoparticles
[Figure 7]. As seen in Figure 7, the graphical representations
Figure 3: Pseudo-second-order kinetic studies of heavy metals removal using
MCNPs 0.35 M Na2SO4.
Figure 4: Removal of dierent heavy metals from articial water using MCNPs
prepared with 0.035 M Na2SO4 under reducing and oxidizing environments
at 20 °C.
NanoWorld Journal | Volume 1 Issue 4, 2015
Synthesis of Multicomponent Nanoparticles for Immobilization of Heavy Metals in
Aqueous Phase Cumbal et al.
of both samples reveal a decrease of frequency from 3308 to
3226 (-OH stretching), 1637 to 1626 (H-H bonding/bending
vibration of water). Changes on peaks from 1403 to 1120
may imply the existence of residual hydroxyl groups on the
surface of MCNPs. is can be assumed due to the formation
of complex of Sulfur-OH-Cu2+ and Sulfur-O-Cu2+ during the
adsorption of Cu2+. At 1349 cm-1 the intensity of the band is
increased after adsorption. It seems that adsorption induces
the increase of the amount of hydroxyl groups, which may arise
from the formation of surface precipitate of Cu(OH)2. e
other peaks shifted as compared with those of fresh MCNPs,
indicating a strong interaction between the multicomponent
nanoparticles and the copper cation. Also, scientic literature
describes the formation of metal suldes when metals are
contacted with the fraction of FeS [36]. e excellent removal
of arsenic from the aqueous phase (>98%) accomplished is this
study is essentially due to dierent reactions that arsenates
bear when contacted with elemental iron of nanoparticles.
According to Ramos et al. [37], Arsenic(V) in the presence of
elemental iron nanoparticles is reduced to As0 or As3+. Also, it
may form complex Fe-oxide-As3+ or develop complexes with
iron hydroxides. Moreover, Li & Zhang [38] reported that
redox mechanisms are dominant when elements such as Zn2+,
Pb2+, Cu2+, As5+ are brought into contact with zero valent iron
nanoparticles and reduced to Zn0 and Pb0, or are immobilized
by the hydroxides or oxides.
Eect of temperature
Tests conducted using MCNPs at dierent temperatures
demonstrated that there is no need to raise the temperature
in order to enhance heavy metals removal. On the contrary,
it produces a small decrease on their removal [Figure S4].
is could be related to the increase of nanoparticles size. It
has been demonstrated, as the size of nanoparticles increases
surface area and reactivity is reduced [28, 39]. However, a
rapid physical adsorption of heavy metals on the surface of
nanoparticles counterbalances the increase of particle size.
Besides, results of kinetic tests showed a rapid adsorption of
heavy metals, which is the main property of physisorption
[30]. On the other hand, raising the temperature during the
treatment could promote an increase of Brownian motion, that
enhances the pollutant diusion but it could also interfere with
intermolecular weak forces (Van der Waals forces) causing
the release of metallic ions from the surface of nanoparticles
[30]. Nonetheless, if physisorption were the only adsorption
mechanism in the treatment, there would be desorption of
pollutants in the aqueous media due to high temperatures.
Leakage of heavy metals was not observed on the removal
tests on both the articial and the real mine tailings. erefore,
chemical adsorption also plays an important role on the heavy
metals uptake as it was explained above.
Eect of pH
Hydrogen potential (pH) is also one of the factors
that, has great inuence not only on the nanoparticle
stability but also in the adsorption of heavy metals on solid
surfaces (nanoparticles). At acidic pH there exists a negative
interference with heavy metal uptake from water. Hydrogen
ions compete for the reactive sites on the multicomponent
nanoparticles [40]. Also, high concentration of H+ the surface
of nanoparticles is positively charged [41], inhibiting in
some extent, adsorption of metallic ions due to electrostatic
repulsion [42]. In this study the removal eciency of heavy
metals conducted under a pH of 3 is slightly lower compared to
the removal eciency at higher pH values as shown in Figure
S5 (Supporting Information). Nevertheless, the removal at
pH 3 is not signicantly lower compared to those at higher
Figure 6: XPS spectrum of MCNPs prepared with 0.035 M Na2SO4 under
reducing environment at 20 °C before(A)and after(B)treatmentof copper.
Figure 7: FTIR spectra of MCNPs prepared with 0.035M Na2SO4 under
reducing environment at 20 ºC before (A) and after (B) treatment of copper.
Figure 5: Removal of dierent heavy metals from liquid mine tailings using
MCNPs prepared with 0.035 M Na2SO4 under reducing environment at 20 °C.
NanoWorld Journal | Volume 1 Issue 4, 2015
Synthesis of Multicomponent Nanoparticles for Immobilization of Heavy Metals in
Aqueous Phase Cumbal et al.
pH values of 5, 7, and 9. is can be attributed to the fact
that at acidic pH, heavy metals are more soluble, osetting
to a certain level, the negative eects of competition between
metallic cations and H+. Soluble metals are found as free ions
available for binding more easily to the reactive sites of the
multicomponent nanoparticles [43]. Besides, at pH values
greater than 5, ions H+ are almost at equilibrium with ions
OH-, so there is less competition between hydrogen ions and
heavy metals for binding the reactive sites of the nanoparticles
[44]. As a result, the removal eciency observed in these
tests, revealed a slight enhancement at pH values of 5, 7, and
9 [Figure S5]. Finally, at high pH values, namely 9, there are
no hydrogen ions to compete with the pollutants. Indeed,
high concentration of OH-, negatively charges surface of the
nanoparticles enhancing the attraction and adsorption of
metallic cations; thus, increasing the removal eciency [45].
Novel multicomponent nanoparticles were successfully
synthesized using sodium sulfate (Na2SO4) and without
any stabilizing agent. e use of sodium sulfate in the
synthesis of the multicomponent nanoparticles, allowed
the manufacture of nanomaterials in an environmentally
friendly approach since there is a lower release of hydrogen
sulde, a noxious gas to the environment and to the human
e physicochemical characterization of multicomponent
nanoparticles demonstrated that they are stable for a short
time. Likewise, the size distribution reveals that they have
an appropriate size within a range previously reported,
as well as a great surface area, meaning they are suitable
for obtaining high removal eciency of heavy metals as
observed in this work.
e multicomponent nanoparticles demonstrated both
rapid adsorption kinetics (within the rst ve minutes),
and no desorption of heavy metals along the testing
period, suggesting the occurrence of physical and chemical
adsorption mechanisms for uptake of metals. Data of
kinetic tests t well on a pseudo-second-order model, thus
conrming chemical adsorption for the removal of the
pollutants. On the other hand, the isothermal adsorption
of heavy metals onto the multicomponent nanoparticles
follows a Freundlich isotherm model, indicating the
presence of heterogeneous surface on the nanoparticles.
Also, environmental conditions play a role in the removal
of heavy metals using multicomponent nanoparticles.
Tests conducted at dierent temperatures demonstrated
good removal eciencies between the toxic metals and
the nanoparticles; however, at higher temperature the
eciency dropped about 1.6% due to Brownian motion.
Hydrogen potential also inuences the removal eciency
of heavy metals when using multicomponent nanoparticles
for the uptake. Lower removal is achieved at acidic pH (pH
3) due to competition with hydrogen ions. While at basic
pH the removal is higher because surface of nanoparticles
is negatively charged, thus attracting heavy metals.
e authors thank to Dr. Jenny Gun and Dr. Ovadia
Lev from Hebrew University for the XPS spectra and to
Universidad de las Fuerzas Armadas for the nancial support
through the Grant PIC2013-T-012. We also appreciate the
help given by Daniel Delgado and Carla Bastidas in the
laboratory and Dr. Brajesh Kumar for his careful review of the
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... ese nanoparticles were successfully used in the removal of trichloroethylene and pesticides from water. Similar nanoparticles were prepared using sodium sulfate instead of dithionite to selectively immobilize heavy metals from the aqueous phase [8]. In both studies, the performance of the MCNPs was excellent; however, researchers used NaBH 4 as the reducing agent. ...
... Gagnepain and Roques-Carmes exploited this technique to characterize the uniformity of surfaces for pro les in two dimensions, with Ds falling within a range between 1 and 2, in which 1 corresponds to a smooth surface and 2 to a highly rough surface [20]. Recently, in the fabrication of Fe/FeS nanoparticles was evidenced an enhancement in roughness of the particles' surfaces [7,8]. Evidently, a high roughness favors the reactivity of the nanoparticle due to the increase of its surface area, thus promoting the formation of more reactive sites [7,21]. ...
... Also, precipitate formation of metallic sul des speeds up the removal of heavy metals from water [37][38][39][40]. In previous studies of our group, it is reported that multicomponent nanoparticles of zerovalent iron and iron sul de (Fe/FeS) rapidly removed heavy metals from an articially prepared mine tailing due to processes of physisorption and chemisorption [8]. ...
Full-text available
Trough preparation of multicomponent nanoparticles (MCNPs) using ferric chloride (FeCl3), sodium sulfate (Na2SO4), and the extract of mortiño fruit (Vaccinium floribundum Kunth), we dramatically improved the removal/immobilization of heavy metals from water and in soils. As-prepared nanoparticles were spherical measuring approximately 12nm in diameter and contained iron oxides and iron sulfides in the crystal structure. Removal of copper and zinc from water using MCNPs showed high efficiencies (>99%) at pH above 6 and a ratio of 0.5mL of the extract:10mL 0.5M FeCl3·6H2O:10 mL 0.035M Na2SO4. The physisorption process followed by chemisorption was regarded as the removal mechanism of Cu and Zn from water. While, when MCNPs were used to treat soils contaminated with heavy metals, more than 95% of immobilization was accomplished for all metals. Nevertheless, the distribution of the metallic elements changed in the soil fractions after treatment. Results indicate that immobilization of metals after the injection of nanoparticles into soils was effective. Metals did not leach out when soils were drained with rain, drinking, and deionized water but fairly leached out under acidic water drainage.
... Soil with concentration of 25,531 mg of total iron kg −1 (432.9 mg kg −1 of Fe associated to oxides) was selected for preparing the technosol. The As-prepared MCNPs showed sizes in the range of 5 to 20 nm containing zero valent iron in the core and iron sulfide in the coverage similar to those reported by Cumbal et al. (2015). With the As-prepared technosol, we run adsorption tests for arsenic. ...
... The maximum adsorption capacity and adsorption bond energy (Langmuir, 1918) (Q max ) and b are 71,185 mg kg −1 and 7.50 kg mg −1 , respectively. The high sorption capacity of the technosol for arsenic could be associated to iron oxides (Cumbal, 2004) contained in soil and the zero valent iron and the iron sulfide of the nanoparticles (Cumbal et al., 2015). ...
... Particularly, organic dyes pose a threat to the environment and to human health due to the high volume of production, slow biodegradation and high toxicity. Traditional treatment methods for the removal of pollutants such as ultrafiltration, reverse osmosis, coagulation and flocculation or biological processes are often ineffective for dyes or require expensive post treatment [6][7][8]. An often-used non-destructive method is the use of high surface materials as adsorbents. ...
BiFeO3 nanomaterials have recently generated much interest due to their relatively narrow band gap energies (∼2.0–2.8 eV), their stability and low cost which leads to effective visible-light photocatalysts for water splitting and for the degradation of organic pollutants. Here, we show that very high removal efficiency of the organic dye Rhodamine B can be achieved using GdxBi1-xFeO3@SBA-15 nanocomposites (x = 0, 0.05. 0.10, 0.15) under visible light irradiation. Specifically, we study the photocatalytic degradation of Rodamine B using the above nanocomposite materials, with pore volume loadings of 5–25%, prepared by a wet-impregnation nanocasting technique with pre-fabricated metal tartarates, as metal precursors, and mesoporous silica SBA-15, as a host matrix. We find that the best removal performance is achieved by a 10 vol% Gd0.05Bi0.95FeO3@SBA-15 sample, shown by a complete dye degradation in approximately 3 h using very low concentrations of the actural active photocatalyst. The superior efficiencies of the nanocomposites, which outperformed their parent compounds, i.e. GdxBi1-xFeO3 nanoparticles as well as unfilled SBA-15, are attributable to a synergistic adsorption enhanced photocatalytic degradation process. The possible mechanism in the photodegradation process was investigated and discussed on the basis of trapping experiments.
... For example, during a sulfidated nZVI (S-nZVI) treatability study, 63% of the iron was still in the zerovalent state after 400 days (Nunez Garcia et al., 2016). Sulfidation of nZVI has increased the removal efficiency of target pollutants such as trichloroethene (TCE) (Han and Yan, 2016;Kim et al., 2013;Rajajayavel and Ghoshal, 2015), 1,2-dichloroethane (Nunez Garcia et al., 2016), tetrabromobisphenol (Li et al., 2016), 4-nitrophenol (Tang et al., 2016), diclofenac (Song et al., 2017), and metal ions (Cumbal et al., 2015;Fan et al., 2013;Su et al., 2015). Sulfidation methods can be classified as aqueous-aqueous and aqueous-solid, depending on when the sulfur compound is introduced to the synthesis solution Han and Yan, 2016). ...
Treatment of nano zerovalent iron (nZVI) with lower valent forms of sulfur compounds (sulfidation) has the potential to increase the selectivity and reactivity of nZVI with target contaminants and to decrease inter-particle aggregation for improving its mobility. These developments help in addressing some of the long-standing challenges associated with nZVI-based remediation treatments and are of great interest for in situ applications. Herein we report results from a field-scale project conducted at a contaminated site. Sulfidated nZVI (S-nZVI) was prepared on site by first synthesizing carboxymethyl cellulose (CMC) stabilized nZVI with sodium borohydride as a reductant and then sulfidating the nZVI suspension by adding sodium dithionite. Transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy (EDS) of CMC-S-nZVI, from synthesis barrels, confirms the presence of both discrete spherical nZVI-like particles (∼90 nm) as well as larger irregular structures (∼500 nm) comprising of iron sulfides. This CMC-S-nZVI suspension was gravity fed into a sandy material and monitored through multiple multi-level monitoring wells. Samples collected from upstream and downstream wells suggest very good radial and vertical iron distribution. TEM-EDS analysis from the recovered well samples also indicates the presence of both nZVI-like particles as well as the larger flake-like structures, similar to those found in the injected CMC-S-nZVI suspension. This study shows that S-nZVI stabilized with CMC can be safely synthesized on site and is highly mobile and stable in the subsurface, demonstrating for the first time the field applicability of S-nZVI.
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A large number of heavy metals are generated in tailings of precious metal extractive operations, which could cause high levels of water contamination. Because of the environmental and health concerns, many conventional technologies have been applied to capture heavy metals from mining-polluted streams with limited performance in terms of effectiveness and immobilization efficiency. In this context, this study evaluates the retention of mine-generated heavy metals using Technosols prepared with iron-rich soils and multicomponent nanoparticles of Fe/FeS (MCNPs). Firstly, nanoparticles were synthesized using orange-peel extract and sodium borohydride (NaBH4) as reductant agents and FeCl3.6H2O and Na2SO4 as metal precursors. The TEM and SEM images showed nanoparticles with roughly spherical morphology with a size in the range of 35.9 ± 11.7 nm arranged in a kind of filamentous structure. Secondly, Soils were dosed with 1% and 3% (w/w) of multicomponent nanoparticles and then used to capture heavy metals present in mine tailings using batch and fixed-bed column tests. The Technosol prepared with 97% soil, and 3% MCNPs reached on average 70% retention of heavy metals for fixed-bed setups. While, in batch experiments using the same Technosol, the capture of heavy metals was 80% after 6 min of treatment, and upon reaching 30 min, 90% removal was attained. This suggests that tailored Technosols might be part of a promising technology to treat contaminated mine tailings with reasonable spending.
Sulfidated nano zerovalent iron (S-nZVI), stabilized with carboxymethyl cellulose (CMC), was successfully synthesized on site and injected into the subsurface at a site contaminated with a broad range of chlorinated volatile organic compounds (cVOCs). Transport of CMC-S-nZVI to the monitoring wells, both downgradient and upgradient, resulted in a significant decrease in concentrations of aqueous-phase cVOCs. Short-term (0-17 days) total boron and chloride measurements indicated dilution and displacement in these wells. Importantly however, compound specific isotope analysis (CSIA), changes in concentrations of intermediates, and increase in ethene concentrations confirmed dechlorination of cVOCs. Dissolution from the DNAPL pool into the aqueous phase at the deepest levels (4.0-4.5 m bgs) was identifiable from the increased cVOCs concentrations during long-term monitoring. However, at the uppermost levels (∼1.5 m above the source zone) a contrasting trend was observed indicating successful dechlorination. Changes in cVOCs concentrations and CSIA data suggest both sequential hydrogenolysis as well as reductive β-elimination as the possible transformation mechanisms during the short-term abiotic and long-term biotic dechlorination. One of the most positive outcomes of this CMC-S-nZVI field treatment is the non-accumulation of lower chlorinated VOCs, particularly vinyl chloride. Post-treatment soil cores also revealed significant decreases in cVOCs concentrations throughout the targeted treatment zones. Results from this field study show that sulfidation is a suitable amendment for developing more efficient nZVI-based in situ remediation technologies.
In this study, graphene (G) was used as a substrate for NiMgAl ternary-layered hydroxide using coprecipitation technique. The pristine NiMgAl (NMA), graphene-NiMgAl (G/NMA) and their respective calcined products NMA-C and G/NMA-C were investigated as adsorbents for the removal of hazardous eriochrome black T (EBT) dye from an aqueous phase. Characterization results revealed that the incorporation of graphene nanoparticles with NMA with subsequent calcination leads to a significant improvement in surface functionalities, thermal stability, and specific surface area. This resulted in high and fast uptake of EBT molecules from the water phase. The equilibrium time for NMA, NMA-C, G/NMA, and G/NMA-C was achieved at 240 min, 180 min, 90 min, and 60 min, respectively, with optimum pH 4 and dosage of 10 mg. The Langmuir isotherm model describes the adsorption process more appropriately with maximum achievable adsorption capacities of 156.25, 263.16, 238.14, and 384.62 mg/g for NMA, G/NMA, NMA-C, and G/NMA-C, respectively. The kinetic study indicates the adequacy and fitness of the pseudo-second-order model to the experimental data for all four adsorbents. The thermodynamic evaluation substantiates the exothermic nature of the adsorption processes. The mechanism of EBT-G/NMA-C adsorption system involved surface adsorption, electrostatic, strong chemical, and ion exchange interactions along with surface reconstruction. Integration of graphene with subsequent calcination substantially improved the surface and structure characteristics of NMA which facilitated enhanced adsorption performance with sorption rate and excellent reusability performance, confirming it as a highly promising adsorbent for the efficient remediation of dye-contaminated wastewater.
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Journal of Nanotechnology. SPECIAL ISSUES OPEN ACCESS . Nanoparticles for Environment, Engineering, and Nanomedicine
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The pollution of the continental waters is a problem at a world scale, mainly due to the impact of the mining tailings. Using top technologies as neutralization plants of acid waters, many companies are mitigating the impact of this functioning; so taking as a reference the changes in the concentration of heavy metals present in water, soils and cultivations of the high, middle and low basin of the Moche river, samplings of water were obtained at eight stations of the Moche river (Trujillo, Peru), and in four sectors of its margins for soils and cultivations. The most representative heavy metals in water were found in the high basin during the year 1980: iron (557.500 ppm), lead (100.375 ppm), cadmium (4.550 ppm), copper (6.900 ppm), zinc (262.900 ppm) and arsenic (9.000 ppm); whereas in the soils the higher concentrations were found on the right margin of median basin in the year 1980: iron (83.400 mg/kg); lead (0.820 mg/kg); cadmium (0.012 mg/kg); copper (1.240 mg/kg); zinc (0.380 mg/kg) and arsenic (0.016 mg/kg); in relation to the metal accumulation in the cultivations, iron (0.6525 mg/kg) was predominant, being the yucca (Manihot esculentus) the most contaminated cultivation. It is concluded that, most contamination level of water analysis was present in the high basin during 1980, whereas the right side of the median basin highest levels of contamination in the samples of soils; relating to the cultives, the yucca (Manihot esculentus) was the species most contaminated.
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In this work the ability of olive stone activated carbon (COSAC) to remove Pb(II), Cd(II), Ni(II) and Cu(II) metal ions from aqueous solutions was evaluated. The effect of initial pH, contact time and initial concentration on metal ions adsorption was investigated. The results indicated that pH 5 is the optimum value for metal removal. Adsorption kinetic rates were found to be fast; total equilibrium was achieved after 4 hours. Kinetic experimental data fitted very well the pseudo-second order equation and the values of adsorption rate constants were calculated. The equilibrium isotherms were evaluated in terms of maximum adsorption capacity and adsorption affinity by the application of Langmuir and Freundlich equations. Results indicate that the Langmuir model fits adsorption isotherm data better than the Freundlich model. The removal efficiency of heavy metal ions by COSAC decreases in the order Pb(II) > Cd(II) > Ni(II) ≥ Cu(II).
This book describes the processes by which tailings are produced, and why the solids must be separated from them. The usual method is by allowing the tailings slurries to settle in ponds, retained by temporary dams. These dams are described in all their aspects, both the theoretical behaviour of fluids in the ponds, and engineering aspects of their placing, design and construction, and the behaviour and prevention of seepage. (U.K.)
The present study was carried out to investigate contamination of heavy metals in 19 fish species from the Banan section of Chongqing in the Three Gorges, Yangtze River. The results showed that the mean concentrations of heavy metals were higher in intestine than muscle, except zinc in upper strata. In the fish inhabiting the upper strata, there were significant differences between mean concentrations of As, Cr, Cu and Hg in muscle and intestine (P <0.05). There were also significant differences between mean concentrations of Cr and Cu in muscle and intestine in the fish inhabiting middle strata. However, significant differences between mean concentrations of As, Cd, Hg, Pb and Zn were measured in fish inhabiting bottom strata in both intestine and muscle tissues (P <0.05). For the fish inhabiting different strata, the concentrations of As, Cd, Cr, Cu, Hg and Pb in muscle and intestine of the fish from bottom strata (BS) were higher than those in both upper strata (US) and middle strata (MS); whereas a higher concentration of Zn was measured in muscle and intestine from fish inhabiting upper strata. Mean metal concentrations were found to be higher in age II than those in age I in Coreius heterodon (2- and 1 -year odl fish respectively). The overall results indicated that fish muscle in the Banan section were slightly contaminated by heavy metals, but did not exceed Chinese food standards.
Mine wastes are unwanted, currently uneconomic, solid and liquid materials found at or near mine sites. Volumetrically they are one of the world's largest waste streams, and they often contain high concentrations of elements and compounds that can have severe effects on ecosystems and humans. Multidisciplinary research on mine wastes focuses on understanding their character, stability, impact, remediation and reuse. This research must continue if we are to understand and sustainably manage the immense quantities of historic, contemporary and future mine wastes, given the trend to exploit larger deposits of lower-grade ores.
General aspects of tailings management that would be applicable to any mining operation are reviewed with specific emphasis on gold operations. The production of acid from sulphidic tailings is discussed together with selection criteria for impoundment of sulphides and tests to enable prediction of acid mine drainage. The chemistry and precipitation of arsenic associated with gold sulphides ores is also discussed. However management of cyanide from tailings ponds is of particular concern. The various methods of destroying and recycling cyanide are briefly reviewed with a focus on the advantages and disadvantages of AVR (Acidification–Volatilization by aeration and Reneutralization), SART (Sulfidisation, Acidification, Recycle and Thickening) and IX processes. Much of the general information is abstracted from a comprehensive text by the author [Ritcey, G.M., 1989. Tailings Management—Problems and Solutions in the Mining Industry, Elsevier Science, 970 pp.] with an update of practical experiences from the recent literature.