Ultrasound-assisted removal of Acid Red 17 using nanosized Fe3O4-loaded coffee waste hydrochar

Article abstract of DOI:10.1016/j.ultsonch.2016.09.004

The Fe₃O₄-loaded coffee waste hydrochar (Fe₃O₄-CHC) was synthesized using a simple precipitation method. The as-prepared adsorbent was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FT-IR). The EDX analysis indicated the presence of Fe in the structure of Fe₃O₄-CHC. The specific surface area of hydrochar increased from 17.2 to 34.7 m²/g after loading of Fe₃O₄ nanoparticles onto it. The prepared Fe₃O₄-CHC was used for removal of Acid Red 17 (AR17) through ultrasound-assisted process. The decolorization efficiency decreased from 100 to 74% with the increase in initial dye concentration and from 100 to 91 and 85% in the presence of NaCl and Na₂SO₄, respectively. The synthesized Fe₃O₄-CHC exhibited good stability in the repeated adsorption-desorption cycles. The high correlation coefficient (R² = 0.997) obtained from Langmuir model indicated that physical and monolayer adsorption of dye molecules occurred on the Fe₃O₄-CHC surface. Furthermore, the by-products generated through the degradation of AR17 was identified by gas chromatography–mass spectrometry analysis.

Full text of DOI:10.1016/j.ultsonch.2016.09.004

Ultrasonics Sonochemistry xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Ultrasonics Sonochemistry
journal homepage: www.elsevier.com/locate/ultson
Ultrasound-assisted removal of Acid Red 17 using nanosized
Fe3O4-loaded coffee waste hydrochar
c
d
a
c
Alireza Khataee a,b, , Berkant Kayan , Dimitrios Kalderis , Atefeh Karimi , Sema Akay ,
⇑
Michalis Konsolakis e
a Research Laboratory of Advanced Water and Wastewater Treatment Processes, Department of Applied Chemistry, Faculty of Chemistry, University of Tabriz, 51666-16471 Tabriz, Iran
b Department of Materials Science and Nanotechnology, Near East University, 99138 Nicosia, North Cyprus, Mersin 10, Turkey
c Department of Chemistry, Art and Science Faculty, Aksaray University, 68100 Aksaray, Turkey
d Department of Environmental and Natural Resources Engineering, School of Applied Sciences, Technological and Educational Institute of Crete, 73100 Chania, Crete, Greece
e Department of Production Engineering and Management, Technical University of Crete, 73100 Chania, Crete, Greece
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 July 2016
Received in revised form 5 September 2016
Accepted 5 September 2016
Available online xxxx
The Fe3O4-loaded coffee waste hydrochar (Fe3O4-CHC) was synthesized using a simple precipitation
method. The as-prepared adsorbent was characterized using scanning electron microscopy (SEM), trans-
mission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD),
Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FT-IR). The EDX analysis
indicated the presence of Fe in the structure of Fe3O4-CHC. The specific surface area of hydrochar
increased from 17.2 to 34.7 m2/g after loading of Fe3O4 nanoparticles onto it. The prepared Fe3O4-CHC
was used for removal of Acid Red 17 (AR17) through ultrasound-assisted process. The decolorization effi-
ciency decreased from 100 to 74% with the increase in initial dye concentration and from 100 to 91 and
85% in the presence of NaCl and Na2SO4, respectively. The synthesized Fe3O4-CHC exhibited good stability
in the repeated adsorption-desorption cycles. The high correlation coefficient (R2 = 0.997) obtained from
Langmuir model indicated that physical and monolayer adsorption of dye molecules occurred on the
Fe3O4-CHC surface. Furthermore, the by-products generated through the degradation of AR17 was
identified by gas chromatography–mass spectrometry analysis.
Keywords:
Fe3O4 nanoparticles
Hydrochar
Magnetite
Ultrasound
Sonolysis
Dye removal
Ó 2016 Elsevier B.V. All rights reserved.
1. Introduction
Recently, carbon based adsorbents have been frequently used in
water purification due to their abundance and low cost [7]. Hydro-
One of the major concerns in the developing countries is the
presence of organic dyes in wastewater of several industries such
as textile, paper, leather and food processing. The organic dyes
cause serious problems for human health and other living organ-
isms because of their toxic and carcinogenic effects [1,2]. In light
of this, elimination of industrial organic dyes from wastewater
has gained great attention. The treatment of polluted wastewater
containing organic dyes can be performed with different physico-
chemical and biological methods including adsorption, chemical
oxidation, membrane technology and advanced oxidation processes
(AOPs) [3–5]. Adsorption is one of the most effective treatment
processes due to its simplicity and low cost [6]. Various materials
have been used for dye removal from wastewater via adsorption.
char is a carbon-based adsorbent prepared through hydrothermal
carbonization of biomass wastes, such as spent coffee grounds or
rice husk [8,9]. However, it is difficult to separate the used
carbon-based adsorbents from treated wastewater. For this,
Fe3O4-loaded adsorbents have attracted great attention due to
their unique properties such as easy recovery through a magnet,
large surface area, simple manipulation process and high separa-
tion efficiency [10–12].
Another technique to enhance the efficiency of adsorption tech-
nique is the combination with other treatment processes [6,13].
Ultrasounds have been used frequently in direct degradation of
organic pollutants or in combination with catalysts or adsorbents
in ultrasound-assisted processes [14,15]. The improved removal
efficiency of pollutants in ultrasound-assisted processes can be
explained through the following mechanisms: (i) Direct sonolysis
of pollutants: high intensity ultrasonic waves in liquid phase
produce bubbles in liquid medium by cavitation phenomena.
Collapsing of these bubbles generates localized high temperature
⇑
Corresponding author at: Research Laboratory of Advanced Water and
Wastewater Treatment Processes, Department of Applied Chemistry, Faculty of
Chemistry, University of Tabriz, 51666-16471 Tabriz, Iran.
E-mail address: a_khataee@tabrizu.ac.ir (A. Khataee).
http://dx.doi.org/10.1016/j.ultsonch.2016.09.004
1350-4177/Ó 2016 Elsevier B.V. All rights reserved.
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2
A. Khataee et al. / Ultrasonics Sonochemistry xxx (2016) xxx–xxx
ꢀ
ꢀ
and pressure, which in turn convert H2O molecules to OH and H
radicals. The produced ꢀOH radicals attack and degrade the organic
pollutants [16,17]. (ii) Sonocatalysis: the presence of suitable par-
ticles can enhance the oxidation efficiency of the system by gener-
ating more nucleation sites for cavitation phenomena [17,18]. (iii)
Ultrasound-assisted enhanced adsorption: the resulted energy
from ultrasonic irradiation enhances the mass transfer efficiency
through convection pathway and also activates the surfaces sites
of aggregated particles [6,7]. Furthermore, it has been proven that
ultrasonic irradiation can be used as a very effective technique in
increasing the adsorption of dyes on adsorbent by enhancing the
affinity between adsorbent and adsorbate.
recorded by a Jeol JEM2011 microscope. The X-ray diffraction
patterns of samples were measured using a Rigaku D max 2000
system at 40 kV, 30 mA and 2h range of 10–90. FT-IR spectra of
the bare and Fe3O4-CHC were recorded using a Bruker Tensor 27
(Germany) FT-IR spectrophotometer in the wavenumber range of
400–4000 cmꢁ1 using KBr pellets. The textural characteristics of
the samples were determined by the N2 adsorption–desorption
isotherms at ꢁ196 °C (Micromeritics, TriStar 3000, USA). An Agi-
lent 6890 gas chromatography and 5973 mass spectrometer (Palo
Alto, Canada) was used to identify the generated intermediates of
AR17 in ultrasound-assisted process.
In this study, Fe3O4-loaded coffee waste hydrochar (Fe3O4-CHC)
was synthesized through a simple precipitation method. The syn-
thesized adsorbent was characterized by SEM, TEM, EDX, XRD,
BET and FT-IR analysis. The ultrasound-assisted process in the
presence of Fe3O4-CHC was used to remove AR17 dye from aque-
ous solution. The effects of adsorbent dosage, initial dye concentra-
tion, presence of inorganic anions and ultrasonic power on the dye
removal efficiency were investigated. The Langmuir and Freundlich
isotherms were used to justify the experimental data. The pro-
duced intermediates of degradation of AR17 were also identified
by GC–MS analysis.
2.3. Ultrasound-assisted process
Ultrasound-assisted experiments were carried out in a 250 mL
Erlenmeyer flask, which was placed in an ultrasonic bath (Sonica,
2200 EP S3, Italy). In a typical procedure, 0.1 g of prepared adsor-
bent was mixed with 100 mL of AR17 solution with distinct
concentration and then sonicated. The experiments were carried
out in the dark to remove the effect of photolysis. At reaction time
intervals of 10 min, 4 mL aliquots were obtained from the reaction
mixture to determine the remaining dye concentration.
2.4. Calculating the AR17 removal efficiency and isotherms
2. Materials and methods
The residual AR17 concentration in the solution was measured
using
a UV–Vis spectrophotometer (WPA lightwave S2000,
2.1. Materials
England) at a maximum wavelength of 510 nm. Eq. (1) was used
to determine the percent decolorization efficiency:
All the chemicals used in this study were of analytical grade and
used without further purifications. FeCl3ꢀ6H2O and FeCl2ꢀ4H2O, HCl
and NaOH were purchased from Sigma-Aldrich (Germany). Acid
Red 17 (AR17) as an azo dye was provided by Shimi Boyakhsaz
Co., Iran. The specifications of AR17 are given in Table 1.
RE ð%Þ ¼ ½ðCi ꢁ CeÞ=Ciꢂ ꢃ 100
ð1Þ
where Ci is the initial concentration of AR17 solution and Ce is its
concentration (mg/L) at time t.
The capacity of Fe3O4-CHC for adsorption of AR17 was
calculated using Eq. (2) [7,20]:
2.2. Preparation and characterization of Fe3O4-loaded hydrochar
ðCi ꢁ CeÞ ꢃ V
qe ¼
ð2Þ
Coffee waste hydrochar was produced via hydrothermal car-
bonization of spent coffee grounds at 200 °C with residence time
of 6 h [19]. Fe3O4-CHC was prepared as follows: 5 mL 5 M HCl,
40 mL water and 5 mL ethanol were mixed in a 100 mL flask. Then,
13.32 g FeCl3ꢀ6H2O and 19.88 g FeCl2ꢀ4H2O were added to the
above solution and heated at 40 °C to complete dissolution of the
salts. Then, 1 g hydrochar was added to 30 mL of the prepared
solution and stirred for 2 h at room temperature. The prepared sus-
pension was filtered and washed with distilled water and then
immediately transfer into 1 M ammonia solution. After 2 h stirring
at room temperature, the synthesized Fe3O4-CHC was collected
and washed with distilled water and dried under vacuum.
m
where qe is the adsorption capacity per gram of adsorbent, V(L) is
the volume of thesolution and m (g) is the mass of adsorbent.
The Langmuir and Freundlich adsorption isotherms are
frequently used isotherms to determine the interactions between
the adsorbent and adsorbate. The Langmuir isotherm can be
expressed by Eq. (3):
Ce
1
Ce
¼
þ
ð3Þ
qe KLqmax qmax
where qmax (mg/g) is the surface maximum adsorption capacity in
the monolayer cover and KL is the coefficient related to the energy
of adsorption.
The surface morphology of bare hydrochar and Fe3O4-CHC
samples was investigated using a SEM equipped with an EDX
microanalysis (Mira3 FEG-SEM Tescan, Czech). TEM images were
The Freundlich model is given by Eq. (4) [21]:
Table 1
Characteristics of Acid Red 17.
Chemical structure
Molecular formula
C20H12N2Na2O7S2
Color Index number
16180
kmax (nm)
Mw (g/mol)
502.435
510
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A. Khataee et al. / Ultrasonics Sonochemistry xxx (2016) xxx–xxx
3
1
n
log qe ¼ log Kf þ log Ce
ð4Þ
Kf and n are the constants of the Freundlich equation. Kf shows
the extent of adsorption and 1/n shows the adsorption intensity.
3. Results and discussion
3.1. Characterization of the samples
The SEM images of the bare hydrochar and Fe3O4-CHC samples
are shown in the Fig. 1. The SEM images of the bare hydrochar
(Fig. 1(a-b)) show the bulky and smooth morphology of hydrochar.
A simple comparison between the SEM images of bare and
modified samples (Fig. 1(c-d)), reveals the formation of Fe3O4
nanoparticles on the surface of the modified hydrochar sample.
Fig. 2 shows the size distribution of Fe3O4 nanoparticles loaded
onto the hydrochar surface. The size distribution plot of Fe3O4
nanoparticles shows that most of the nanoparticles are in
10–20 nm range. TEM images of Fe3O4-CHC nanostructures
Fig. 2. Size distribution of Fe3O4 nanoparticles loaded on hydrochar.
(Fig. 3) shows that the loaded nanoparticles are at the nanoscale
region (6100 nm) and spherical, which confirms the results of
SEM analysis. The EDX mapping of bare and Fe3O4-CHC samples
are shown in Fig. 4. As seen from EDX analysis, C and O are the
Fig. 1. The SEM images of the (a and b) bare hydrochar and (c and d) Fe3O4-CHC samples.
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Fig. 3. TEM images of Fe3O4-CHC.
(b)
(a)
Fig. 4. EDX spectra of (a) bare hydrochar and (b) Fe3O4-CHC samples.
main elements of the both samples. Fig. 4(b) shows 4.54 wt.% of
iron in the structure of Fe3O4-modified sample.
Fig. 5. XRD spectra of (a) bare hydrochar and (b) Fe3O4-CHC samples.
Fig. 5 presents the XRD patterns of bare and Fe3O4-CHC sam-
ples. The XRD pattern of bare sample shows a broad diffraction
peak in a 2h range of 10–30. The XRD pattern for Fe3O4-CHC sample
shows some visible peaks for Fe3O4 at angles of 35, 43, 56 and 62°,
indicating the perfect loading of Fe3O4 on the hydrochar surface
[12,22].
In order to determine the functional groups of the synthesized
catalyst, FT-IR analysis was carried out. Fig. 6 shows the FT-IR spec-
tra of the bare and modified hydrochar samples. The broad peak at
3300–3500 cmꢁ1 belongs to the O–H stretching vibration band of
H2O molecules [23]. The bands at approximately 1693 and
1595 cmꢁ1 are attributed to the C@O and C@C vibrations, respec-
tively [24]. The bands in the range of 1000–1450 cmꢁ1 corre-
sponded to the C–O–C stretching bands. The bands located at
875–700 cmꢁ1 represent the aromatic C–H bending vibrations
[8,24]. The peak at around 600 cmꢁ1 is the characteristic peak of
Fe–O [11].
The BET isotherm model was used to analyze the data obtained
from the N2 adsorption/desorption isotherm of the bare and mod-
ified samples. The results of the BET analysis are shown in Table 2.
In Fe3O4-modified sample, the specific surface area increased from
17.2 to 34.7 m2/g and the pore volume decreased from 0.59 to
0.13 cm3/g. The characterization results indicated the proper load-
ing of Fe3O4 onto the surface of hydrochar in Fe3O4-CHC samples.
3.2. Comparison of different processes in removal of AR17
Fig. 7 represents the effectiveness of the studied processes
including sonolysis, adsorption and ultrasound-enhanced
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Fig. 6. FT-IR spectra of (a) bare hydrochar and (b) Fe3O4-CHC samples.
Table 2
by Fe3O4-loaded hydrochar compared to that of the bare hydrochar
could be related to the increased specific surface area, resulting in
considerable improvement in the adsorption capability of the
adsorbent [11].
Surface area and pore volume characteristics of bare and Fe3O4-loaded hydrochar.
Sample
SBET
Total pore volume
(cm3/g)
Average pore size
(nm)
(m2/g)
The pHzpc was determined for Fe3O4-loaded hydrochar that was
6.8. At pH values lower than 6.8 the surface charge of Fe3O4-loaded
hydrochar was positive. AR17 as an anionic dye could be adsorbed
on the positively charged surface of adsorbent at pH values lower
than 6.8. At pH values higher than pHzpc, the OH- ions adsorbed
on the surface of Fe3O4-CHC and the surface became negatively
charged. Consequently, electrostatic repulsion between the adsor-
bent negative surface charge and the anionic AR17 molecules
resulted in a decreased adsorption efficiency.
Bare hydrochar
Fe3O4-loaded hydrochar
17.2
34.7
0.59
0.13
71.3
10.2
adsorption in the presence of the bare and Fe3O4-loaded hydrochar
samples for removal of AR17. Adsorption of dye molecules on the
hydrochar surface (adsorption in dark) yielded a removal efficiency
of 15%. Direct degradation of AR17 by ultrasonic irradiation (sonol-
ysis) resulted in a removal efficiency of 34%. In the ultrasound-
assisted process, the decolorization efficiency increased to 65
and 100% at pH = 6 in the presence of the bare hydrochar and
Fe3O4 –CHC, respectively. Ultrasonic waves promoted dye removal
by enhancing the mass transfer in the solution [6,25]. Moreover,
the presence of nanoparticles increased the oxidation efficiency
of the system via generating more nucleation sites for cavitation
phenomena [26]. Additionally, the physical phenomena such as
micro-turbulence, microstreaming, acoustic waves and micro jets
can improve the reactivity of the particles in the solution by mak-
ing effective interparticle collisions. The enhanced removal of AR17
3.3. Effect of the operational parameters on ultrasound-assisted
process
3.3.1. Effect of adsorbent dosage
In order to optimize the adsorbent dosage in the ultrasound-
assisted adsorption process, a series of experiments was performed
with different concentrations of Fe3O4-CHC (0.5–2.5 g/L) and the
results are shown in Fig. 8. In this set of experiments, the dye con-
centration, pH and power of ultrasonic irradiation were constant at
100
100
80
60
40
20
0
2.5 g/L
2.0 g/L
1.5 g/L
1.0 g/L
80
0.5 g/L
60
40
20
0
0
10
20
30
40
50
60
70
80
0
10
20
30
40
50
60
70
80
Time (min)
Time (min)
Fig. 7. Comparisons of different processes in the removal of AR17. Experimental
conditions: [AR17] = 10 mg/L, [Fe3O4-CHC] = 1.0 g/L, US power = 300 W/L and
pH = 6.
Fig. 8. The effect of Fe3O4-CHC dosage on the removal efficiency of AR17 in
ultrasound-assisted process. Experimental conditions: [AR17] = 10 mg/L, US
power = 300 W/L and pH = 6.
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100
80
60
40
20
0
10 mg/L, 6 and 300 W/L, respectively. The removal efficiency
increased with increasing adsorbent dosage up to 2 g/L and then
decreased. The increase in adsorbent concentration increased the
number of active sites for adsorption of dye molecules. Further-
more, the number of hydroxyl radicals increased as the concentra-
tion of nanoparticles increased. However, further increase in the
concentration of adsorbent dosage to 2.5 g/L, resulted in
a
decreased removal efficiency. This could be attributed to the aggre-
gation of particles at higher concentrations, which reduced the
active surface area and consequently, decreased the decolorization
efficiency. Moreover, the high concentration of adsorbent brings
about the overlapping of active sites [7,13].
3.3.2. Effect of initial concentration of AR17
0
10
20
30
40
50
60
70
80
Fig. 9 shows the effect of initial AR17 concentration on the
removal efficiency in the ultrasound-assisted process at sonocata-
lyst dosage of 1 g/L, ultrasonic irradiation of 300 W/L and the pH
value of 6. The removal efficiency was decreased from 100 to
74% when the dye concentration increased from 5 to 20 mg/L. This
is because the number of active sites for adsorption of the dye
molecules is constant at a specified concentration of adsorbent.
Time (min)
Fig. 10. Effect of the presence of sulfate, chloride onions and peroxydisulfate on the
removal efficiency of AR17 in ultrasound-assisted process. Experimental condi-
tions: [AR17] = 10 mg/L, [Fe3O4-CHC] = 1.0 g/L, [Anions] = 20 mg/L, [K2S2O8]
= 2 mM, US power = 300 W/L and pH = 6.
ꢀ
Moreover, at higher dye concentrations the generation of OH rad-
S2O2ꢁ þ ultrasonic irradiation ! 2SOꢀ4ꢁ
ð5Þ
8
icals is reduced, resulting in a fewer active sites on the adsorbent
[27,28].
The produced sulfate anion radicals could participate in the
degradation of the dye molecules. Moreover, the sulfate anion rad-
icals could increase the decolorization efficiency by generating
extra hydroxyl radicals as shown in Eq. (6):
3.3.3. Effects of NaCl, Na2SO4 and K2S2O8
Real textile wastewaters contain various inorganic salts which
affect the efficiency of the treatment processes. In order to investi-
gate the effect of inorganic anions on the decolorization efficiency
of the ultrasound-assisted process, experiments were performed in
the presence of 10 mg/L AR17 at sonocatalyst dosage of 1 g/L, pH of
6 and 20 mg/L of NaCl and Na2SO4 salts. The results are shown in
Fig. 10. It can be seen that the decolorization efficiency decreased
from 100 to 91 and 85% in the presence of NaCl and Na2SO4,
respectively. In this condition, the Clꢁ and SO42ꢁ ions competed
with AR17 molecules for adsorption on the active sites on the sur-
face of Fe3O4-CHC and decreased the available sites for dye mole-
cules. Furthermore, the Clꢁ and SO42ꢁ anions reacted with the
SO4ꢀꢁ þ H2O ! Hþ þ SO42ꢁ þ OHꢀ
ð6Þ
3.3.4. Effect of ultrasonic power
Ultrasonic power is one of the important factors influencing the
process efficiency in ultrasonic-assisted processes. The effect of
ultrasonic power on the removal efficiency of 10 mg/L of AR17 in
the presence of 1 g/L of Fe3O4-CHC and pH of 6 is shown in
Fig. 11. From the figure, as the ultrasonic power increased, there
was an enhancement in the removal efficiency. This improvement
in decolorization efficiency could be explained by the following
reasons: (i) increasing the ultrasonic power increased the acoustic
cavitation rate in the reaction medium. This in turn lead to
increased concentrations of hydroxyl radicals generated from
H2O (ii) Increasing ultrasonic wave intensity increased the mass
transport efficiency [30,31]. It should be noted that there was an
optimal power of operation in which a higher ultrasonic intensities
than optimal value could break down the linkage between the
adsorbent and adsorbate [32].
ꢀ
sonochemically generated OH radicals and decreased the decol-
orization efficiency [14,29].
On the other hand, the removal efficiency of AR17 was investi-
gated in the presence of K2S2O8 (2 mM). As shown in the Fig. 10,
the removal efficiency was increased in the presence of peroxy-
disulfate due to its ultrasonic decomposition to sulfate anion
radicals as shown in Eq. (5) [17,27]
100
100
400 W/L
5 mg/L
10 mg/L
300 W/L
80
80
15 mg/L
150 W/L
20 mg/L
60
60
40
20
0
40
20
0
0
10
20
30
40
50
60
70
80
0
10
20
30
40
50
60
70
80
Time (min)
Time (min)
Fig. 9. The effect of initial dye concentration on the removal efficiency of AR17 in
ultrasound-assisted process. Experimental conditions: [Fe3O4-CHC] = 1.0 g/L, US
power = 300 W/L and pH = 6.
Fig. 11. The effect of ultrasonic power on the removal efficiency of AR17 in
ultrasound-assisted process. Experimental conditions: [AR17] = 10 mg/L, [Fe3O4-
CHC] = 1.0 g/L and pH = 6.
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A. Khataee et al. / Ultrasonics Sonochemistry xxx (2016) xxx–xxx
7
several times with distilled water and ethanol. The decoloriza-
tion efficiency decreased gradually as the number of adsorption
cycles increased. After four repeated cycles, the adsorbed amount
of AR17 on the adsorbent surface was reduced to a satisfactory
75%. The results indicated that the studied Fe3O4-CHC adsorbent
can be reused effectively for several times for organic pollutants
removal.
100
80
60
40
20
0
3.4. Adsorption isotherms
Table 3 illustrates the results of adsorption isotherms which
used to interpret the results of the adsorption experiments. As
shown in Table 3, the obtained R2 value for Langmuir isotherm
(R2 = 0.997) is higher compared to that of the Freundlich isotherm
(R2 = 0.986). The result indicated the physical and monolayer
adsorption of dye molecules on the surface of Fe3O4-CHC.
Run 1
Run 2
Run 3
Run 4
Fig. 12. Reusability of the Fe3O4-CHC in ultrasound-assisted process. Experimental
conditions: [AR17] = 10 mg/L, [Fe3O4-CHC] = 1.0 g/L, US power = 300 W/L and
pH = 6.
Table 3
Adsorption isotherms parameters.
Langmuir
Freundlich
3.5. Acid Red 17 degradation intermediates
Ce/qe vs. Ce
ln Ce vs. ln qe
Ce/qe = 0.458 + 0.658 Ce
ln qe = 0.999 + 1.001 ln Ce
R2 = 0.997
R2=0.985
The generated intermediates during the degradation of AR17 in
the ultrasound-assisted process and in the presence of Fe3O4-
loaded coffee waste hydrochar were determined using GC–MS
analysis. The identified intermediates were recognized by match-
ing their spectra with those recorded in the Mass library (Wiley
7n), when the match factor was above 90%. Eight compounds were
detected and the corresponding results are given in Table. 4. In
addition to the identified intermediates, some of the by-products
could not be recognized due to their rapid degradation to the
derivatives. The presence of various by-products indicates that
the hydroxyl radicals are nonselective species.
qmax = 16.3 (mg/g)
1/n = 1.85
Kf = 2.006 (L/mg)
K
L = 0.1685 (L/mg)
3.3.5. Reusability of Fe3O4-loaded hydrochar
The regeneration of Fe3O4-CHC was evaluated during the
cyclic adsorption-desorption tests in the presence of 1 g/L
Fe3O4-CHC, initial dye concentration of 10 mg/L and ultrasonic
irradiation of 300 W/L and the results are shown in Fig. 12. After
each run, the Fe3O4-loaded hydrochar was collected and washed
Table 4
Identified by-products for degradation of Acid Red 17 in ultrasound-assisted process.
No.
1
Structure
Molecular weight (g/mol)
59.076
Compound
Acetamide
O
NH2
OH
2
3
172.26
205.78
Decanoic acid
O
O
7-methyl-6-nitrochromen-2-one
N
O
O
O
4
222.24
Diethyl phthalate
O
O
O
O
(continued on next page)
Please cite this article in press as: A. Khataee et al., Ultrasound-assisted removal of Acid Red 17 using nanosized Fe3O4-loaded coffee waste hydrochar,
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8
A. Khataee et al. / Ultrasonics Sonochemistry xxx (2016) xxx–xxx
Table 4 (continued)
No.
5
Structure
Molecular weight (g/mol)
240. 46
Compound
2,6,10-Trimethyltetradecane
6
278.34
Dibutyl phthalate
O
O
O
O
7
326.49
Benzenecarbothioic acid, 2,4,6-triethyl-,
S-(2-hydroxy-1-methyl-2-phenylethyl)
O
S
O
O
8
362.50
1,2-Benzenedicarboxylic acid, butyl
8-methylnonyl ester
O
[3] R.D.C. Soltani, A. Khataee, M. Safari, S. Joo, Preparation of bio-silica/chitosan
nanocomposite for adsorption of textile dye in aqueous solutions, Int.
4. Conclusions
a
Biodeterior. Biodegrad. 85 (2013) 383–391.
[4] R. Darvishi Cheshmeh Soltani, A. Rezaee, A. Khataee, Combination of carbon
The Fe3O4-loaded coffee waste hydrochar (Fe3O4-CHC) was syn-
thesized using a simple precipitation method. The results of SEM,
TEM, EDAX, XRD, BET and FT-IR analysis confirmed the formation
of Fe3O4 nanoparticles on the surface of the hydrochar. The results
of BET analysis showed that the specific surface area increased
from 17.2 to 34.7 m2/g after loading Fe3O4 onto the bare hydrochar.
The synthesized Fe3O4-CHC was used for removal of AR17 anionic
dye through ultrasound-assisted adsorption process. An increase in
Fe3O4-CHC dosage up to 2 g/L led to the enhancement in the
removal efficiency of AR17. With increasing initial dye concentra-
tion, the removal efficiency decreased from 100 to 74%. The pres-
ence of Clꢁ and SO24ꢁ ions retarded the removal of AR17. The
results of the reusability tests showed that Fe3O4-CHC adsorbent
can be used effectively for several runs for organic pollutants
removal. The high correlation coefficient (R2 = 0.997) obtained
from the Langmuir model indicated that physical and monolayer
adsorption of dye molecules occurred on the Fe3O4-CHC surface.
black–ZnO/UV process with an electrochemical process equipped with
carbon black–PTFE-coated gas-diffusion cathode for removal of a textile dye,
Ind. Eng. Chem. Res. 52 (2013) 14133–14142.
a
[5] R.D.C. Soltani, A. Rezaee, A. Khataee, M. Safari, Photocatalytic process by
immobilized carbon black/ZnO nanocomposite for dye removal from aqueous
medium: optimization by response surface methodology, J. Ind. Eng. Chem. 20
(2014) 1861–1868.
[6] M. Dastkhoon, M. Ghaedi, A. Asfaram, A. Goudarzi, S.M. Langroodi, I. Tyagi, S.
Agarwal, V.K. Gupta, Ultrasound assisted adsorption of malachite green dye
onto ZnS: Cu-NP-AC: equilibrium isotherms and kinetic studies–response
surface optimization, Sep. Purif. Technol. 156 (2015) 780–788.
[7] R. Davarnejad, P. Panahi, Cu (II) removal from aqueous wastewaters by
adsorption on the modified Henna with Fe3O4 nanoparticles using response
surface methodology, Sep. Purif. Technol. 158 (2016) 286–292.
[8] L. Wang, Y. Guo, Y. Zhu, Y. Li, Y. Qu, C. Rong, X. Ma, Z. Wang, A new route for
preparation of hydrochars from rice husk, Bioresour. Technol. 101 (2010)
9807–9810.
[9] L. Dai, B. Wu, F. Tan, M. He, W. Wang, H. Qin, X. Tang, Q. Zhu, K. Pan, Q. Hu,
Engineered hydrochar composites for phosphorus removal/recovery:
lanthanum doped hydrochar prepared by hydrothermal carbonization of
lanthanum pretreated rice straw, Bioresour. Technol. 161 (2014) 327–332.
[10] Y. Liu, X. Zhu, F. Qian, S. Zhang, J. Chen, Magnetic activated carbon prepared
from rice straw-derived hydrochar for triclosan removal, RSC Adv. 4 (2014)
63620–63626.
[11] C. Li, Y. Dong, J. Yang, Y. Li, C. Huang, Modified nano-graphite/Fe3O4 composite
as efficient adsorbent for the removal of methyl violet from aqueous solution,
J. Mol. Liq. 196 (2014) 348–356.
[12] Z. Cheng, Z. Gao, W. Ma, Q. Sun, B. Wang, X. Wang, Preparation of magnetic
Fe3O4 particles modified sawdust as the adsorbent to remove strontium ions,
Chem. Eng. J. 209 (2012) 451–457.
[13] O. Acisli, A. Khataee, S. Karaca, M. Sheydaei, Modification of nanosized natural
montmorillonite for ultrasound-enhanced adsorption of Acid Red 17, Ultrason.
Sonochem. 31 (2016) 116–121.
Acknowledgements
The authors thank the University of Tabriz, Aksaray University,
Technical University of Crete and Near East University for all the
support. Alireza Khataee thanks Iran Science Elites Federation
(ISEF) for support.
[14] A. Khataee, R.D.C. Soltani, A. Karimi, S.W. Joo, Sonocatalytic degradation of a
textile dye over Gd-doped ZnO nanoparticles synthesized through
sonochemical process, Ultrason. Sonochem. 23 (2015) 219–230.
[15] J. Madhavan, P.S. Sathish Kumar, S. Anandan, F. Grieser, M. Ashokkumar,
Degradation of acid red 88 by the combination of sonolysis and photocatalysis,
Sep. Purif. Technol. 74 (2010) 336–341.
[16] N. Ghows, M.H. Entezari, Exceptional catalytic efficiency in mineralization of
the reactive textile azo dye (RB5) by a combination of ultrasound and core–
shell nanoparticles (CdS/TiO2), J. Hazard. Mater. 195 (2011) 132–138.
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Ultrason. Sonochem. (2016), http://dx.doi.org/10.1016/j.ultsonch.2016.09.004