Green synthesis, characterization of biomaterial-supported zero-valent iron nanoparticles for contaminated water treatment
Sravanthi et al. Journal of Analytical Science and Technology
Green synthesis, characterization of biomaterial-supported zero-valent iron nanoparticles for contaminated water treatment
K. Sravanthi 0
D. Ayodhya 0
P. Yadgiri Swamy 0
0 Department of Chemistry, University College of Science, Osmania University , Hyderabad, Telangana State 500007 , India
Background: In this present work, we synthesized zero-valent iron nanoparticles (ZVIN) using reproducible Calotropis gigantea (CG) flower extract served as both reducing and stabilizing agent by completely green approach. ZVIN are widely used in contaminated water treatment and can be prepared by several different methods. Method: Iron nanoparticles formed in this method are mainly ZVIN and were characterized by the various physicochemical techniques, viz, ultraviolet-visible absorption spectroscopy (UV-vis), Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). Results: FT-IR and UV-vis absorption spectra reveal that the polyphenols present in the CG flower extract may be responsible for the reduction and stabilization of the ZVIN. SEM images show some agglomeration among the particles and the average size of the particles in the range of 50-90 nm. ZVIN tend to agglomerate, resulting in a significant loss of reactivity. To overcome this problem, we have synthesized ZVIN that are immobilized on biomaterial with the help of chitosan. This low-cost sorbent was used to remove organic pollutants from waste water. Conclusions: Herein, we report the percentage of removal of methylene blue (MB) and aniline by synthesized sorbent from contaminated water. The adsorption isotherms of Langmuir and Freundlich models have been used to explain experimental equilibrium adsorption data. The adsorption of MB and aniline on sorbent follows pseudo-second order kinetics.
Green synthesis; Zero-valent iron nanoparticles; Calotropis gigantea flower extract; Chitosan; Methylene blue; Aniline
Nowadays, environmental pollution is the perilous problem
of all over the world. Especially contamination of water
originates from different paths and causes great damage to
(Wang et al. 2014a, b)
. Industrial effluents
from textile, printing, glass, paint, food, ceramic,
pharmaceutical, paper, polymers, etc. preponderantly contain
organic waste such as synthetic dyes
(Wanyonyi et al. 2014;
Rebitanim et al. 2012)
. Trivial amounts of dye residues also
bestow their characteristic color to the wastewater, which
leads the formation of dazzling contaminants. Moreover,
an anaerobic degradation of azo dyes prevails in the
production of carcinogenic and highly toxic amines. So
there is a conclusive need of destruction of this hazardous
waste from industrial effluents before disposal to the
environment. Many kinds of chemical, physical, and biological
processes have been developed for the remediation of water
pollution, including microbial degradation, filtration,
coagulation, membrane separation, and others. But all
these methods involve some disadvantages and limitations
like high cost and poor removal efficiency
(Sttle et al.
. Earlier reports showed that a lot of research has
been done on the photo-catalytic degradation of synthetic
dyes. But in the dislodgement process of organic waste,
adsorption is supposed to be preferable over
photocatalytic degradation, which sometimes leads toxic
Nanotechnology is an immortally patulous area with
enormous applications in various fields including food,
agriculture, medical, pharmaceutical, catalysis, optical,
and pollution control in a broad way
(Shukla and Iravani.
. In recent times, nanoscale zero-valent iron has
received much attention from research areas like
remediation of contaminated water and soil due to its high
specific surface area, small particle size, and majestic
reactivity of surface sites
(Lanlan et al. 2014; Mikhak et al.
. Apart from that, zero-valent iron nanoparticles
(ZVIN) follows the maximal tenets of green chemistry as
a non-toxic, inexpensive, and environmentally compatible
(Li et al. 2006; Zhipan et al. 2014)
. If iron reacts
with water, it forms a thin oxide layer known as goethite
(FeOOH) and hydrogen gas
(Li and Zhang 2006)
Goethite has more affinity towards contaminates
(Zhang et al.
. Thus zero-valent iron core and iron hydroxides
have the shells which provide a characteristic core-shell
structure to ZVIN with unique redox properties
al. 2012; Ritu et al. 2011)
. Because of attractive qualities like
electron donating property during the oxidation of Fe2+ to
Fe3+ and existence of various mineral forms of iron, the
ZVIN have been found to be more important in the
adsorption and removal of environmental pollutants
(Chicgoua et al. 2012; Kumar et al. 2014)
. ZVIN are boon
especially in alleviating contaminants such as dyes, organic
pesticides, halogenated organic compounds, inorganic ions
like nitrate, fluoride, and sulfate, viruses, nitro-aromatic
compounds, PCBs and heavy metals such as Pb, As, Cr,
(Zheng et al. 2011)
from polluted water.
Carbonsupported ZVIN are also used in the removal of uranium
from natural and synthetic water
(Richard and Crane
Several physical and chemical production methods
including mechanical milling
(Karimi et al. 2014)
(Satapanajaru et al. 2008; Madhavi
et al. 2014)
, ethylene glycol (Raveendran et al. 2003),
(Basavaraju et al. 2011)
(Allabaksh et al. 2010)
been employed for the preparation of ZVIN. But ZVIN,
synthesized by above conventional methods, agglomerate
rapidly in clusters due to Van der Waals and magnetic
(Qiangu et al. 2013)
. Sometimes ZVIN undergo
oxidation by oxidants like dissolved oxygen or water
(He and Zhao 2005)
. Agglomeration and oxidation of
ZVIN result in the formation of large particles and also
reduce the delivery of ZVIN to the targeted contaminant
(Kim et al. 2008)
. Previously stable ZVIN are
synthesized using biodegradable polymers or surfactants
such as resin, starch, carboxymethyl cellulose (CMC),
citric acid, and chitosan
(Madhavi et al. 2013; Morales et al.
as stabilizing or capping agents. Stabilizer molecules
prevent attractive Vander Waals and magnetic forces by
providing strong inter-particle electrostatic repulsions.
In recent years, ZVIN are widely prepared by plant
extract-mediated liquid phase bio-reduction of ferrous
or ferric salt solutions. The peculiarity of this liquid
phase reduction is that it has been carried out at room
temperature and generally completes within few minutes.
Furthermore, it involves mixing of aqueous solutions of
plant extract and ferric salt in which hazardous materials
are neither used nor generated. In general, plant extracts
comprised phenols, flavonoids, terpenoids, proteolytic
enzymes, etc., which eventually act as reducing and
capping agents in the production of ZVIN. Based on
the notion of green chemistry, previously ZVIN are
synthesized from extracts like tea leaves
, eucalyptus leaves
(Wang et al. 2014a, b)
leaves (Machado et al. 2013), Rosa damascene, Thymus
vulgaris, and Urtica dioica
(Mehdi et al. 2017)
. But the
recent observations showed that the sorption and
dispersion capacity of ZVIN increased by the support of
porous materials like clays, resins, and carbon materials
et al. 2010; Sunkara et al. 2010)
In this paper, we report the green synthesis of ZVIN
using Calotropis gigantea (CG) flower extract as both
reducing and stabilizing agent. In addition, a novel
sorbent, which is the composite of as-synthesized ZVIN,
biomaterial, and chitosan, was also prepared. Here, the
biomaterial was prepared from Pithecellobium dulce seeds,
which is used as a good supporting material to ZVIN in
dispersion and sorption process
(Arshadi et al. 2014)
. It is
well known that chitosan is a second most abundant
polysaccharide in the world and can be obtained from natural
chitin which is a renewable, biodegradable and nontoxic
polysaccharide. Some previous studies showed that
chitosan increases removal capacity of biochar to remove heavy
metals from contaminated water
(Zhou et al. 2013)
the major role of chitosan is to attach fine ZVIN onto
the biomaterial. According to the principles of green
chemistry, here, we developed a new synthetic process
for sorbent, which involves eco-friendly, inexpensive,
non-hazardous, and renewable materials. The synthesized
ZVIN and sorbent were characterized for UV-vis, FT-IR,
XRD, SEM, and EDX. Here, we also discussed the effective
adsorptive removal of organic waste such as methylene
blue (synthetic dye) and aniline (aromatic primary amine)
from contaminated water by the synthesized sorbent.
Ferric nitrate nonahydrate (FeNO3, 9H2O), acetic acid,
sodium hydroxide (NaOH), chitosan [MW ≈ 70,000 and
more than 80% deacetylated], ethyl alcohol, methylene
blue, and aniline chemicals are all AR grade and purchased
from Sigma Aldrich chemicals. The fresh flowers of
Calotropis gigantea and Pithecellobium dulce seeds
were collected and used for the preparation of ZVIN.
Collection of extract and biomaterial
Calotropis gigantea flowers were washed properly and
were then cut into small pieces. These finely cut pieces
were grind, and 10 mg weight of flowers was mixed with
100 mL double-distilled water. It was boiled for 5 min.
After cooling, the solution was filtered thrice by Whatman
no.1 filter paper to get clear extract. Dry Pithecellobium
dulce seeds were collected and washed with distilled water
and were put in the oven for 48 h at 70 °C. After cooling,
the biomaterial was finely ground, washed with
doubledistilled water, and oven dried at 65 °C.
Preparation of ZVIN
0.01 M FeNO3.9H2O was prepared in double distilled
water and was mixed with flower extract in 1:1 ratio. For
the reduction of Fe+3 ions, equal volume of flower extract
was added slowly to aqueous ferric nitrate solution with
constant stirring for 15 min on a magnetic stirrer and the
reaction was carried out at room temperature. Here, the
Calotropis gigantea flower extract used as both reducing
and stabilizing agent. The formation of iron nanoparticles
were indicated by the color change of solution from light
pink to black. The black precipitate was washed several
times with 1:1 ethanol and water and then with double
distilled water. The obtained nanoparticles were dried at
60 °C in the oven.
Preparation of sorbent
A composite sample was prepared by dissolving chitosan
powder first in a 100 mL of 2% acetic acid solution and
then synthesized ZVIN were dispersed in the chitosan
solution. To the above mixture, biomaterial was added
and stirred for 60 min to form a homogeneous mixture.
This mixture was added drop-wise into a 500 mL of
1.5% NaOH solution and kept undisturbed for 15 h at
room temperature. The solid products were then
separated by decantation method and washed with deionized
water to remove the excess NaOH and oven dried for
24 h at 70 °C. Here the ratio of chitosan, biomaterial,
and ZVIN particles in the sorbent were 1:1:0.5, 1:1:1,
and 1:1:2. For comparison, another sorbent in the 1:1 ratio
of biomaterial and chitosan was also synthesized without
addition of ZVIN.
Characterization of ZVIN and sorbent
UV-vis absorption analysis was carried out using UV-3600
spectrophotometer in the range of 200–800 nm. Scanning
electron microscope (SEM) imaging analysis of the
samples was conducted using a Zeiss evo 18 instrument.
The sample crystallinity was examined using X-ray
diffraction (XRD) analysis with a computer-controlled
Xray diffractometer (X’pert pro diffractometer) and
equipped with a stepping motor and graphite crystal
monochromator. The FT-IR spectra were analyzed by
Shimadzu spectrophotometer with KBr pellet.
Batch experiments of decolorization of methylene blue
Decolorization of MB experiments was carried out at
room temperature and at its original pH. In this study,
400 mg of sorbent material was mixed with 500 mL of
different concentrations (50–400 ppm) of MB solutions.
The mixture was stirred for certain period of time (5, 10,
15, 20, 25, 30, 40, 50, 60, 90, 120, 180, 240, 300, and
360 min), using a magnetic stirrer to find out the effect
of contact time in the removal of MB. During the
adsorption process, about 4 mL of aliquot samples was
withdrawn from the reaction mixture by syringe at
certain time intervals and the sorbent was removed
using 0.45-μm filters. Concentration of MB, remained
in solution, was determined spectrophotometrically by
measuring absorbance at 665 nm. The change in the
concentration of MB was calculated from the difference
between the initial and final equilibrium concentrations
of MB, and sorption efficiency or removal efficiency of
the sorbent was computed from the following equation:
% of removal ¼ ðc0−ceÞ
where c0 and ce are total dissolved and equilibrium liquid
phase concentrations (mg L−1), respectively. For
comparative study, the above batch experiments were carried out
with adsorbents, viz, synthesized ZVIN, blank, sorbent
(1:1:0.5), sorbent (1:1:1), and sorbent (1:1:2) individually at
identical reaction conditions.
Batch experiments of aniline removal
The aniline removal experiments were carried out with
the initial concentration of aniline between 50 and
400 ppm in distilled water. In this study, the amount of
sorbent added to the aniline solution was 1 g L−1. The
conditions such as neutral pH and 30 °C temperature
were maintained throughout the experiment. Proper care
was taken against auto-degradation, photodegradation,
and degradation by OH radical. In this typical removal
process, the solution was kept shaking at 300 rpm and the
amount of aniline removed determined at certain time
intervals such as 30, 60, 120, 180, and 360 min to know
the effect of contact time. At these time intervals, about
4 mL of liquid sample was withdrawn by syringe and
filtered off using 0.45-μm filters. The concentration of
aniline, remained in solution, was determined
spectrophotometrically by measuring absorbance at 232 nm.
The change in amount of aniline was calculated from
the difference between the initial and final equilibrium
concentrations of aniline. The sorption efficiency or
removal efficiency of the sorbent was determined same
as that of MB and also the experiment was repeated
with each of the sorbent material, blank, and synthesized
ZVIN. The amount of adsorbate adsorbed on the surface
of sorbent at equilibrium (qe) was calculated as:
where v (in liter) is the volume of the solution and m
(in gram) is the amount of adsorbent.
Results and discussion
UV-vis absorption analysis
UV-vis spectral scanning procedure was carried out
from 200 to 800 nm to determine the formation of
ZVIN (Fig. 1). Initially, the flower extract had pale pink
color and showed higher absorption from 300 to 350 nm.
It indicates that the flower extract had free phytochemicals
like carbohydrates, amino acids, and lipids. After the
addition of flower extract to ferric solution, a black-colored
colloidal solution was formed. The spectra of the
blackcolored colloidal solution show the disappearance of strong
absorption peaks at the region 300 to 350 nm and emerge
broad absorption at higher wavelengths, suggesting the
formation of polydispersed ZVIN. During the synthesis of
ZVIN, the reduction of Fe+3 ions to Fe0 is indicated by the
change in color due to excitation of electrons. Upon the
whole, the formation of noble nanoparticles like silver and
gold are indicated by characteristic UV-vis absorption
pattern attributed to the surface plasmon resonance
(SPM). But with few exceptions, such characteristic
UV-vis peaks are not observed for ZVIN due to the
high reactivity of iron, when compared to silver and
gold. However, the decrease in the intensity of
phytochemicals characteristic peak specifies the significance
of flower extract in the synthesis of ZVIN.
FT-IR technique provides information about interactions
among biomolecules of CG flower extract and metal
ions responsible for the formation and stabilization of
iron nanoparticles. Figure 2a shows the spectrum of the
CG flower extract and the colloidal solution of ZVIN
stabilized in flower extract. By the deep observation of
FT-IR spectrum, it was noticed that, when moving from
CG flower extract to colloidal solution of ZVIN, the
peak positioned at 3359 cm−1 (–OH and –NH stretching
vibrations) was found to be shifted to 3361 cm−1 and also
peak at 1641 cm−1 (amide) was shifted to 1642 cm−1 with
increasing intensity. Similarly peaks at 1239 cm−1 (amide),
1083 cm−1 (–OH bending and C–O–C stretching),
976 cm−1, and 923 cm−1 of flower extract were shifted
to 1231, 1081, 977, and 922 cm−1 in colloidal solution
of ZVIN respectively. Another two bands observed at
873 cm−1 (amine) and 680 cm−1 (aromatic alkanes) in the
spectrum of CG flower extract. There was a complete
absence of peaks at 873 and 680 cm−1 in FT-IR spectra of
ZVIN colloidal solution. The highest peaks present at
3359–3361 cm−1 correspond to polyphenols, indicates the
more abundance and prominent of phenolic functional
groups for the reduction of Fe+3 to Fe0. Besides that,
the more available phenolic groups provide the favorable
molecular arrangement for the delocalization of unpaired
electrons. So the flower extract enthralled the property of
effective scavenging of free radicals. On the other hand,
anti-oxidant capacity and anti-radical property increases
with the number of phenolic hydroxyl groups. The
appearance of a peak at 3359 cm−1 and shifting to
3361 cm−1 suggest that the phenolic or amine groups
present in flower extract may be involved in ZVIN
formation. The earlier reports
(Mystrioti et al. 2015)
indicate polyphenols were responsible for the reduction
of Fe. From the spectrum, we can conclude that
polyphenols present in the flower extract were responsible for
reduction and stabilization of ZVIN which also agrees
with UV-vis analysis.
FT-IR analysis of sorbent without ZVIN and with ZVIN
also carried out to find out the effect of immobilization of
ZVIN on the chemical composition of biomaterial. The
spectrum (Fig. 2b) reveals the presence of –OH and –NH
stretching vibrations (3432 cm−1), –CH2 and –CH3
symmetric and asymmetric stretching vibrations (2924 cm−1,
2853 cm−1), amides (1641 cm−1, 1570 cm−1), and C–O
stretching vibrations in carboxylate ion (1414 cm−1) in
both the sorbent without ZVIN and also in the sorbent
with ZVIN. By the addition of ZVIN to the biomaterial,
there was no observable change in the basic chemical
nature of the biomaterial. These results reveal that the
proteins (amide peak) may be responsible for the
immobilization of iron nanoparticles.
The XRD technique was used to determine the material
and crystalline structure of iron nanoparticles. The XRD
analysis of ZVIN is shown in Fig. 3. The peaks at 2ϴ of 45°
and 65° indicate that the presence of zero-valent iron
predominantly in the sample and the diffraction peak at 2ϴ
of 35.6° indicates the presence of Fe2O3
(Khasim et al.
. Along with prominent diffraction peaks of iron
nanoparticles, which demonstrate the crystallinity of ZVIN,
here also exist some low-intensity peaks in between the 2ϴ
value of 20°–25° corresponding to the organic matter
coated on the surface of ZVIN
(Fazlzadeh et al. 2017)
These results show that the CG flower extract is
successfully used for the synthesis and stabilization of
ZVIN which can be reconciled by FT-IR analysis. Size
of ZVIN is calculated from Sherrer’s formula, given
below, using peak broadening profile of peak at a 2ϴ
value of 45°.
d ¼ β cosθ
where λ is the wavelength (1.5418 Å) and β is the
fullwidth at half maximum (FWHM) of corresponding peak.
The size of synthesized ZVIN calculated from Sherrer’s
equation was 30 nm. XRD patterns of both sorbent and
blank (Fig. 3) are compared to know the surface
modification of sorbent. In the XRD pattern of sorbent (1:1:2),
diffraction peak at a 2ϴ value of 45° indicates that
nanoparticles contain mostly zero-valent iron which
was mainly present on the surface of sorbent. However, by
this analysis, it was clear that biomaterial and chitosan were
good supporting materials to ZVIN for the preparation of
a post grafting composite material due to prevention of
SEM and EDX analysis
The SEM analysis was carried out to investigate the
shape, crystal growth, and approximate size of ZVIN
synthesized using CG flower extract. The SEM micrograph
of synthesized ZVIN is shown in Fig. 4a, and it reveals that
the ZVIN are spherical in shape and polydispersed with
different sizes ranging from 50 to 90 nm. These results
show that the importance of CG flower extract in the
synthesis of ZVIN but the synthesized ZVIN exhibit some
agglomeration which was indicated by spherical shape and
also non-uniform particle size with different void space.
Hence, ZVIN are dispersed on the surface of the biomaterial
to minify the aggregation. To know the surface morphology,
It was limited to adsorption on homogeneous surface by
monolayer formation, with decrease in intermolecular
forces among adsorbed molecules and also uniform
energies of adsorption with no transmigration of adsorbed
(Dey et al. 2015; Eastoe and Dalton 2000)
addition, it is used to determine the maximum adsorption
capacity of sorbent. The expression of Langmuir which
relates molecules covered on solid surface to equilibrium
concentration of liquid phase above the surface of sorbent
is given by the following equation:
where qe (mg g−1) and ce (mg L−1) are the amount
adsorbed on the surface of unit mass of sorbent and the
concentration of adsorbate in the solution at equilibrium
respectively. Xm (mg g−1) is the maximal adsorption
capacity, and b (L mg−1) is the empirical constant which
gives the affinity of binding sites. The Langmuir expression
can be given in the linearized form:
qe ¼ 1 þ bce
1 1 1
qe ¼ Xmbce þ Xm
the sorbent was characterized by SEM and shown in Fig. 4b.
It shows that the surface was smooth with many gorges and
ZVIN are well dispersed on the surface of the sorbent. EDX
analysis gives the elemental status of synthesized ZVIN
using flower extract (Fig. 4c) and revealed the proportion of
iron, carbon, and oxygen atoms which were summarized in
Table 1. It can also provide qualitative as well as quantitative
information about elements that may be involved in the
formation of nanoparticles. In the EDX spectrum of
ZVIN, the highest peak due to absorption of elemental
iron indicates the presence of iron nanoparticles and
another peaks corresponding to carbon and oxygen
atoms reveal the vital role of organic molecules from
flower extract in the stabilization of ZVIN.
Batch experiments of methylene blue decolorization and aniline removal
Concentrations of MB and aniline remained in solution
were determined spectrophotometrically by measuring
absorbance at 665 and 232 nm respectively. Figure 5a, b
shows the effect of contact time on MB decolorization
and aniline removal, respectively, and reveal that all the
adsorbent samples (blank, synthesized ZVIN, and sorbent
material) showed some MB and aniline removal capacity.
Among all the samples, the sorbent material (1:1:2) was
found to remove the highest amount whereas lowest
amount was removed by blank sample. Percentage of MB
removal rates of blank, synthesized ZVIN, and sorbent
materials (with different ratios of biomaterial, chitosan,
and ZVIN) were 29.4%, 63.1%, 80.5% (1:1:0.5), 83.9%
(1:1:1), and 85.5% (1:1:2) respectively within the first
30 min (Fig. 5c). Percentage of aniline removal rates of
blank, synthesized ZVIN, and sorbent materials were
17.1%, 49.4%, 56.3% (1:1:0.5), 59.1% (1:1:1), and 74.8%
(1:1:2) respectively after 12 h (Fig. 5d). These results
showed that MB and aniline removal capacity of
synthesized ZVIN enhanced in modified form.
To understand the mechanism of adsorption of MB and
aniline on sorbent (1:1:2), Langmuir and Freundlich
adsorption models were applied to experimental data.
The linear plots of 1/qe against 1/ce show the Langmuir
adsorption isotherms of MB and aniline on the surface of
synthesized sorbent (1:1:2) (Fig. 6a, b). The values of
parameters Xm and b were calculated from slope and
intercept of the straight line. The separation factor RL
(dimensionless quantity) provides basic information about
essential features of Langmuir adsorption isotherm. If 0 <
RL < 1, it is considered as favorable adsorption; if RL > 1, it
is considered as unfavorable adsorption; if RL = 0, it is
considered as irreversible adsorption; if RL = 1, it is
considered as linear adsorption
(Zheng et al. 2008)
. The equation
for RL is:
RL ¼ 1 þ bc0
where b (L/mg) is Langmuir constant and co (mg/L) is
the initial concentration of adsorbate. The calculated
Langmuir adsorption parameters are tabulated in Table 2.
RL values indicate the favorable adsorption of MB and
aniline on synthesized sorbent (1:1:2). Based on the value
of correlation coefficient (R2), it was clear that the
Langmuir model was well fitted to experimental data.
Freundlich model assumes that adsorptions occur at
heterogeneous binding sites and formation of multilayer
takes place due to interactions among adsorbed molecules
where qe (mg g−1) and ce (mg L−1) are the amounts
adsorbed on the surface of unit mass of sorbent and the
concentration of adsorbate in the solution at equilibrium
respectively. Kf (mg g−1(L mg−1)1/n) and n are Freundlich
constants which indicate sorption capacity and favorability
of adsorption respectively. Here, n value gives information
about heterogeneity of binding sites, magnitude of driving
force of adsorption. The values of n between 1 and 10
(1 < n < 10) indicate favorable adsorption
(Vazquez et al.
. To calculate the values of Freundlich constants
(Kf and n), the equation of linear form of Freundlich
isotherm was taken as follows:
logqe ¼ logK f þ n logce
The linear plots of log qe against log ce show the
Freundlich adsorption isotherms of MB and aniline on
the surface of synthesized sorbent (1:1:2) in Fig. 6c, d.
Freundlich constants Kf and n were calculated from slope
and intercept values of the straight line and all the
parameters of Freundlich adsorption isotherm were summarized
in Table 2. However, from all these parameters, it was
concluded that the Langmuir adsorption model was
well fitted than the Freundlich adsorption model to the
adsorption of MB and aniline on the surface of sorbent
(1:1:2) which confirms homogeneous and monolayer
The experiments of adsorption kinetics of MB and aniline
on the surface of sorbent (1:1:2) were carried out at room
temperature and the data well fitted to the pseudo-second
order kinetic model
(Zheng et al. 2008; Simin et al. 2013)
which can be expressed as:
where qt (mg g−1) is the amount of adsorbate adsorbed
at time t (min), qe (mg g−1) is the equilibrium adsorption
capacity of sorbent, and k2 (g mg−1 min) is the
secondorder rate constant. To determine the values of k2 and
qe from the linear form of pseudo-second order kinetic
model was taken as:
The values of k2 and qe calculated from slope and
intercept values of linear plot of t/qt against t (Fig. 7a, b)
are summarized in Table 3.
In this paper, we report the green and novel synthesis of
ZVIN by renewable and naturally occurring CG flower
extract as both reducing and stabilizing agent. UV-vis
absorption and FT-IR spectral data confirm that the
polyphenols present in the flower extract are responsible
for the formation of ZVIN. The crystallinity of
assynthesized ZVIN is confirmed by XRD analysis. The
SEM images give the average size of synthesized ZVIN
as 50–90 nm. We also report the preparation of low-cost,
eco-friendly, and efficient sorbent using synthesized
ZVIN, biomaterial, and chitosan for the abatement of
aggregation of synthesized ZVIN. Here, the FT-IR analysis
of synthesized sorbent reveals the immaculate support of
biomaterial to ZVIN in the preparation of sorbent. The
SEM analysis showed that ZVIN are well dispersed on the
surface of the sorbent. ZVIN immobilized on biomaterial
act as an efficient sorbent for the adsorption of water
contaminants MB and aniline. Langmuir adsorption model
was a well fit to the adsorption of MB and aniline on the
surface of sorbent than the Freundlich model, and the
adsorption process follows pseudo-second order kinetics.
CG: Calotropis gigantea; EDX: Energy-dispersive X-ray spectroscopy;
FTIR: Fourier transform infrared; MB: Methylene blue; SEM: Scanning electron
microscope; UV-vis: Ultra-violet visible; XRD: X-ray diffraction; ZVIN: Zero-valent
The authors are thankful to the Head of the Department of Chemistry,
Osmania University, for providing necessary facilities.
This work was designed by KS, DA, and PYS. The experimental work and
analysis of the results were done by KS, DA, and PYS. This manuscript was
written by KS, DA, and PYS. All authors read and approved the final
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in
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