ORIGINAL PAPER Synthesis and characterization of magnetic activated carbon developed from palm kernel shells Chinedum Anyika 2 • Nur Asilayana Mohd Asri 1 • Zaiton Abdul Majid 1 • Adibah Yahya 2 • Jafariah Jaafar 1 Received: 19 April 2017 / Accepted: 2 August 2017 / Published online: 14 August 2017 Ó The Author(s) 2017. This article is an open access publication Abstract Magnetic activated carbon (MG-AC), a solid product made by dispersing magnetic substrates on AC, is gaining attention for the removal of heavy metals from wastewater due to its favorable physico-chemical proper- ties such as enhanced surface area and magnetic properties, respectively. However, the effects of two contrasting sub- strates, i.e., metal solution and metal particles, for the synthesis of MG-AC to obtain enhanced magnetic property have not been considered. The MG-AC was prepared by incorporating Fe 3 O 4 into the AC from two different sources of iron: Fe 3 O 4 extracted from electric arc furnace slag and from a ferric chloride/ferrous sulfate solution, to produce magnetic palm kernel shell from slag (MG-PKSS) and magnetic palm kernel shell from iron suspension (MG- PKSF), respectively. The adsorbent samples were charac- terized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, X-ray diffraction, electron microscopy, i.e., SEM and FESEM, energy-dis- persive X-ray, nitrogen adsorption, vibrating sample mag- netometer. The results showed that the MG-PKSF had a greater BET surface area of 257 m 2 g -1 , a pore volume of 0.1124 cc g -1 and higher magnetic properties with a magnetic saturation of 49.55 emu g -1 relative to the MG- PKSS. The FTIR spectrum of the MG-PKSF illustrated the intense OH bending at 1629 cm -1 which can be attributed to the presence of oxygen in the samples. The absorption bands at 1093 and 579 cm -1 indicated the presence of C–O stretching and metal–oxygen (M–O) bands due to the interaction of iron and oxygen. Therefore, the MG-PKSF presented better characteristics for heavy metal removal from wastewater relative to the MG-PKSS, thereby sug- gesting that the raw material (metal solution) for impreg- nation played a crucial role in enhancing the quality of the MG-AC. Keywords Magnetic activated carbon Á Palm kernel shells Á Wastewater treatment Á Electric arc furnace slag Á Ferric chloride/ferrous sulfate solution Introduction Palm kernel shells from the palm tree (Elaeis Guineensis) have been widely used in the production of AC due to its high carbon content and low organic content besides its availability in the Southeast Asia [1, 2]. Several investi- gators [3–5] have demonstrated that a high quality of synthesized activated carbon can be obtained using PKS waste. The raw material of AC is carbonized by thermal decomposition or pyrolysis followed by the activation process at higher temperatures in a furnace. The developed AC usually exhibits high BET surface area, greater pore volume and smaller pore size which may enhance its adsorption capacity; hence, an excellent adsorption of adsorbate on the adsorbent surface can be achieved [6]. Large sorption capacity in micropores can be achieved by chemical or physical activation which can also result in wider micropore openings. In particular, magnetic activated carbon (MG-AC) adsorbents exhibit magnetic characteristics with great efficiency for the adsorption of contaminants from aqueous solutions [7]. The MG-AC is developed by either & Zaiton Abdul Majid [email protected]; [email protected]1 Department of Chemistry, Faculty of Science, Universiti Teknologi, Malaysia, 81310 Johor Bahru, Malaysia 2 Faculty of Biosciences and Medical Engineering, Universiti Teknologi, Malaysia, 81310 Johor Bahru, Malaysia 123 Nanotechnol. Environ. Eng. (2017) 2:16 https://doi.org/10.1007/s41204-017-0027-6
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ORIGINAL PAPER
Synthesis and characterization of magnetic activated carbondeveloped from palm kernel shells
Chinedum Anyika2 • Nur Asilayana Mohd Asri1 • Zaiton Abdul Majid1 •
Adibah Yahya2 • Jafariah Jaafar1
Received: 19 April 2017 / Accepted: 2 August 2017 / Published online: 14 August 2017
� The Author(s) 2017. This article is an open access publication
Abstract Magnetic activated carbon (MG-AC), a solid
product made by dispersing magnetic substrates on AC, is
gaining attention for the removal of heavy metals from
wastewater due to its favorable physico-chemical proper-
ties such as enhanced surface area and magnetic properties,
respectively. However, the effects of two contrasting sub-
strates, i.e., metal solution and metal particles, for the
synthesis of MG-AC to obtain enhanced magnetic property
have not been considered. The MG-AC was prepared by
incorporating Fe3O4 into the AC from two different sources
of iron: Fe3O4 extracted from electric arc furnace slag and
from a ferric chloride/ferrous sulfate solution, to produce
magnetic palm kernel shell from slag (MG-PKSS) and
magnetic palm kernel shell from iron suspension (MG-
PKSF), respectively. The adsorbent samples were charac-
terized using Fourier transform infrared spectroscopy
shells activated carbon (PKSAC) and magnetic CAC are
shown in Fig. 8a. The spectrum of CAC shows some
peaks around 3430, 2921 and 2851, 1596 cm-1 with a
small shoulder at 1109 cm-1 due to OH stretching, C–H
stretching, OH bending and C–O functional groups,
respectively. For MG-CACS and MG-CACF, a broad
peak at 3458 and 3428 cm-1, as well as at 1634 and
1631 cm-1, respectively, is related to the OH functional
groups.
Fig. 7 a EDX spectrum for
sample PKSAC. b EDX
spectrum for sample MG-PKSF
Nanotechnol. Environ. Eng. (2017) 2:16 Page 15 of 25 16
123
Additionally, a broad peak centered at 1056 and
1114 cm-1 indicates the presence of C–O bond in both
samples, i.e., MG-CACS and MG-CACF. This broad peak
was obtained from the overlapping of peaks existing in this
region (Mohan et al., 2011). Further, the FTIR spectrum of
Fe3O4 particles in the figure shows an intense peak at
552 cm-1 due to M–O band. Thus, the small peak at
529 cm-1 in MG-CACS and at 616 cm-1 in MG-CACF
spectrum can be assigned to the Fe3O4 particles on the surface
(Mohan et al., 2011). The FTIR spectrum of activated carbon
synthesized from palm kernel shells (PKSAC) showed some
peaks at wave numbers of 3434, 2910, 1610 and 1171 cm-1
which indicated the presence of functional groups such as OH
stretching, C–H, OH bending and C–O groups, respectively,
which coincided with those revealed by the CAC spectrum.
Figure 8b depicts the FTIR spectra of the raw palm
kernel shell (PKS) and palm kernel shell activated carbon
(PKSAC) developed from the preliminary experiment to
observe the effect of carbonization and activation process
on the functional groups of raw PKS. The spectrum illus-
trates that the functional groups of the untreated PKS
exhibited a complicated spectrum which shows many
peaks belonging to different functional groups. The raw
PKS resulted in a finely similar spectrum to the spectrum of
Fig. 8 a FTIR spectrum of PKSAC, CAC, Fe3O4, MG-CACS and MG-CACF. b FTIR spectrum of raw PKS and PKSAC. c FTIR spectrum of
raw PKS, PKSAC, MG-PKSS and MG-PKSF
16 Page 16 of 25 Nanotechnol. Environ. Eng. (2017) 2:16
123
PKSAC with a broad peak present at 3437 and 3441 cm-1,
respectively, which can be assigned to O–H bonding due to
the bonded hydroxyl on the sample surfaces. Studies have
found that the hydrogen bond existing in the raw PKS was
reduced by phosphoric acid resulting into a reduction of
hydrogen bond in PKSAC [39].
3441.52cm-1
1175.29cm-13741.12cm-1
1626.37cm-1
501.09cm-13841.33cm-1
677.47cm-1
2927.4
3437.18cm-1
1637.17cm-1
1034.43cm-1
1249.09cm-1
1425.16cm-1
1513.11cm-1650.78cm-1
762.56cm-12079.30cm-1535.28cm-1
Raw PKS
1626.37PKSAC2927.402927.40
1626.37501
16261175
3441
2927
3437
10341637
Raw PKS
4000 3500 3000 2500 2000 1500 1000 500 400
Wavenumber (cm-1)
%T
3435.28cm-1
636.19cm-1
579.58cm-
1629.52cm-1
1093.92cm-1445
3437.18cm-1
1637.17cm-1
1034.43cm-1
1249.09cm-1
1425.16cm-1
1513.11cm-1
650.78cm-1
762.56cm-12079.30cm-1
46535.28cm-1
3441.52cm-1
1175.29cm-13741.12cm-1
1626.37cm-1
501.09cm3841.33cm-1
677.47cm-1
2927.4
3441.38cm-1
1034.00cm-1
1634.14cm-1
571.64cm-1
477.83cm
1468.38cm-1
3742.53cm-1
3852.67cm-1 793.28cm-1
MG-PKSF
PKSAC
3441.52
MG-PKSS
M-O
C=O
C-O
3435
1175
3441
571
1034
1626
1634
579
1093
1629
2927.4
2940
OH
RAW PKS
1034
3437
1637
2920
PKSAC
3441
2927
OH
M-O
OH
C-O
OH
(b)
(c)
Fig. 8 continued
Nanotechnol. Environ. Eng. (2017) 2:16 Page 17 of 25 16
123
A shoulder peak observed in both spectra at 2927 and
2920 cm-1 can be assigned to C–H stretching as well as to
C–H stretching in methyl group [29] for PKSAC and raw
PKS, respectively. An intense peak at 1637 and 1626 cm-1
for raw PKS as well as for PKSAC indicates C=C for
aromatic compound present in both samples. In addition, a
peak exists in the raw PKS spectrum around 1513 cm-1
which was ascribed to the presence of secondary amide
group [40] and a fairly significant band at 1249 cm-1 as
well as a broadband at 1034 cm-1 which is associated with
the C–O stretching of carboxylic acid, alcohol, phenol,
ester and ether [41]. Raw PKS spectrum also reveals some
weak bands in the range of 762–535 cm-1 which can be
assigned to C–C stretching.
Meanwhile, the PKSAC spectrum in Fig. 8b elucidates
the presence of two weak bands at 3841 and 3741 cm-1
which can be assigned to O–H stretching mode of the
hydroxyl group [39]. The spectrum also revealed the
presence of an overlapping broad peak at 1175 cm-1 which
indicate C–O stretching of ester, ether and phenol as well
as an intense band at 501 cm-1 which can be attributed to
C–C stretching. Hence, this implies that the spectrum of
raw PKS and PKSAC validates the fact that the main
functional groups present in the raw and carbon samples
are a carbonyl, ether, ester, alcohol and also phenol [29].
Figure 8c shows FTIR spectra of all PKS products
including raw PKS, PKSAC and two magnetic products,
MG-PKSS and MG-PKSF. The adsorption bands for all
samples are summarized in Table 4. The spectra show that
MG-PKSS and MG-PKSF revealed the O–H stretching
band at 3441 and 3435 cm-1. This O–H group exists due to
the presence of water molecules probably caused by semi-
dried samples during the analysis.
The spectrum of MG-PKSS illustrates the presence a
shoulder band at 2940 cm-1 which were assigned to the C–
H alkanes bond stretching due to the presence of carbon
and hydrogen groups in the untreated palm kernel shell
itself. Besides that, the intense O–H bending is shown in
both MG-PKSS and MG-PKSF spectra at 1634 and
1629 cm-1 and can be attributed to the presence of oxygen
in the samples. The absorption bands at 1034 cm-1 for
MG-PKSS and 1093 cm-1 for MG-PKSF both show the
presence of C–O stretching. As portrayed in the spectra of
MG-PKSS and MG-PKSF, a broad and intense band at 571
and 579 cm-1, respectively, could be assigned to M–O
bands which may indicate the interaction between iron and
oxygen in the samples.
Thermogravimetric analysis (TGA)
Thermogravimetric analysis is a technique used to deter-
mine the weight changes of a sample as a function of
temperature under a controlled atmosphere. The thermal
stability of a sample can also be observed using TG anal-
ysis. Figure 9 illustrates the thermogram of PKSAC at a
starting temperature of 50 �C up to 1000 �C. Table 5
summarizes the temperature, percent weight loss and
PKSAC residual after decomposition stage.
Figure 9 illustrates that PKSAC sample has good ther-
mal stability property as it can withstand very high tem-
peratures. At the early stage, a loss of 3.50% of its total
weight was due to humidity up to a temperature of 151 �C.
At a temperature around 200 �C, the sample experiences a
slight weight loss due to desorption of the physisorbed
water together with the rigidly bound water onto the
PKSAC. Generally, the rigidly bound water can be
assigned to the carboxylic group together with the phenolic
hydroxyl groups. This is consistent with the findings of
Haydar et al. [42] whose study reported that the desorption
of physisorbed water was observed around 130 �C, while
the rigidly bound water was observed around 250 �C. In
addition, the sample was continuously experiencing weight
loss, which started at a temperature of 500 �C until 850 �C.
This weight loss was due to the decomposition of low
volatile organic compounds which exist in the PKSAC.
The decomposition process continued to occur within the
temperature ranges of 424–924 and 924–1000 �C with
weight loss percentages of 17.65 and 3.75%, respectively.
At temperatures above 900 �C, the decomposition of
carbon starts to occur. Thus, it shows that at the tempera-
ture ranges of 924–1000 �C, PKSAC starts to lose its
weight, of about 3.75% due to the decomposition of carbon
from its sample. However, the residual weight obtained
after this analysis is still high which is 71.45%. Hence, this
Table 4 Adsorption bands present in FTIR spectrum of raw PKS,
PKSAC, MG-PKSS and MG-PKSF
Sample Functional group Wave number (cm-1)
Raw PKS O–H (stretching) 3437
C–H (stretching) 2920
O–H bending 1637
C–O (stretching) 1034
PKSAC O–H (stretching) 3441
C–H (stretching) 2927
O–H bending 1626
C–O (stretching) 1175
MG-PKSS O–H (stretching) 3441
C–H (stretching) 2940
O–H bending 1634
C–O (stretching) 1034
M–O 571
MG-PKSF O–H (stretching) 3435
O–H bending 1629
C–O (stretching) 1093
M–O 579
16 Page 18 of 25 Nanotechnol. Environ. Eng. (2017) 2:16
123
analysis proves that the PKSAC sample is stable and can
withstand high temperatures of up to 1000 �C and reliable
to be used in higher-temperature activation.
X-ray diffraction (XRD) analysis
X-ray diffraction (XRD) is an analytical technique used to
identify the crystalline phase of a material. In order to val-
idate the crystalline phase of iron oxide in the porous carbon
sample to be magnetized (Fe3O4), the samples were ana-
lyzed using powder X-ray diffraction analysis. Figure 10a
illustrates the XRD diffractogram pattern of iron oxide
extracted from ferric chloride/ferrous sulfate solution
(FeOF). The pattern shows three intense peaks assigned to
Fe3O4 (JCPDS #75-0033) at 2h 30.25�, 35.70� and 57.20�and the presence of c-Fe2O3 (JCPDS #39-1346) peaks at 2h43.45�, 53.85� and 63.00�. Similar observation was reported
by Depci (2012) and El Ghandoor et al. (2012). This shows
the crystalline nature of the Fe3O4.
The diffractogram of the iron oxide extracted from the
electric arc furnace (EAF) slag (FeOS) is depicted in
Fig. 10b. The diffractogram pattern illustrates the presence
of three intense peaks at 2h 30.15�, 35.65� and 57.20�
which are assigned to Fe3O4, while three peaks at 2h43.25�, 54.15� and 62.65� are assigned to c-Fe2O3. In
addition, it displays four peaks which are compatible with
the presence of a-Fe2O3 (JCPDS #80-2377) at 2h 24.10�,33.35�, 41.00� and 49.50� and a peak assigned to a-FeOOH
(JCPDS #29-0713) is observed at 2h 64.00�.Figure 10c–e portrays the XRD diffractograms of
CAC, MG-CACS and MG-CACF, respectively. As
demonstrated in Fig. 10c, the amorphous nature of
commercial activated carbon (CAC) is shown at peak
about 2h 24.46�. Meanwhile, Fig. 10d shows some
intense peak which can be assigned to four different
compounds which are Fe3O4, c-Fe2O3, a-Fe2O3 and a-
FeOOH. Fe3O4 shows four peaks at 2h 30.05�, 31.35�,35.85� and 56.95�. Meanwhile, three peaks at 2h 42.75�,54.20� and 62.75� are assigned to c-Fe2O3. Further, a-
Fe2O3 shows four obvious peaks at 2h 24.45�, 33.20�,41.05� and 49.45�, while the other two peaks at 2h26.85� and 64.15� were assigned to a-FeOOH. Fig-
ure 10e depicts the presence of Fe3O4 and c-Fe2O3 in the
MG-CACF diffractogram. Five peaks assigned to Fe3O4
are shown at 2h 30.35�, 36.15�, 53.95�, 57.40� and
63.05�, while c-Fe2O3 is represented by the presence of
two peaks at 2h 43.85� and 54.95�.In addition, Fig. 10f, g both shows the diffractogram of
raw PKS and PKSAC, respectively. The XRD diffrac-
togram of raw PKS shows a broad peak at the range of 2h10� to 30� indicating the amorphous state of raw PKS
during the analysis. However, three sharp peaks can be
observed at 2h 30.05�, 39.95� and 47.85� presumably due
to the presence of some microcrystalline materials in the
sample. Further, the XRD pattern of PKSAC illustrates a
broad peak at 2h 23.35� which may be assigned to the
Fig. 9 Thermogram of PKSAC at temperature up to 1000 �C
Table 5 Percentage weight loss of PKSAC at temperature up to
1000 �C
Temperature (�C) Weight loss (%) Residual (%)
50–151 3.50 96.51
151–424 3.65 92.85
424–924 17.65 75.21
924–1000 3.75 71.45
Nanotechnol. Environ. Eng. (2017) 2:16 Page 19 of 25 16
123
amorphous nature of the synthesized PKSAC. As illus-
trated in both figures, there was a disappearance of the
crystalline materials, as the PKS was converted to PKSAC
which may be due to the destruction of molecular order of
cellulose and lignin crystalline structure which had occur-
red during pre-treatment [43].
Fig. 10 a XRD diffractogram
of FeOF. b XRD diffractogram
of FeOS. c XRD diffractogram
of CAC. d XRD diffractogram
of MG-CACS. e XRD
diffractogram of MG-CACF.
f XRD diffractogram of raw
PKS. g XRD diffractogram of
PKSAC. i XRD diffractogram
of MG-PKSF
16 Page 20 of 25 Nanotechnol. Environ. Eng. (2017) 2:16
123
Fig. 10 continued
Nanotechnol. Environ. Eng. (2017) 2:16 Page 21 of 25 16
123
Figure 10h, i indicates the MG-PKSS sample synthe-
sized upon incorporation of PKSAC with iron oxide
extracted from EAF slag. Figure 10h shows four peaks
which can be assigned to Fe3O4 at 2h 31.40�, 36.80�,52.05� and 57.15�. There are three peaks assigned to c-
Fe2O3 which are at 2h 43.50�, 45.80� and 62.95�. Addi-
tionally, the presence of a-Fe2O3 was depicted by the peaks
at 2h 23.95� and 24.25�, while the presence of a-FeOOH
was depicted at 2h 26.85�, 27.95� and 39.30�. Meanwhile,
Fig. 10i illustrates four intense peaks assigned to Fe3O4 at
2h 30.75�, 35.95�, 57.35� and 63.20�. Further, three peaks
at 2h 19.30�, 43.45�, 54.10� and a peak at 2h 24.40� can be
assigned to c-Fe2O3 and a-Fe2O3, respectively.
A major presence of the Fe3O4 compound in all the
magnetic samples proves that the MG-AC samples have
the possibility to become good adsorbent due to the good
magnetic property of Fe3O4 as compared to c-Fe2O3, a-
Fe2O3 and a-FeOOH compounds. The a-FeOOH com-
pound is absent in MG-CACF and MG-PKSF probably
because the iron oxide used in synthesizing both MG-
CACF and MG-PKSF was obtained from the reaction
suspension between ferric chloride and ferrous sulfate. The
a-FeOOH compound likely exists in a certain natural
source of iron. Hence, it implied that MG-CACS and MG-
PKSS samples which were prepared using iron oxide
extracted from electric arc furnace (EAF) slag exhibit the
presence of a-FeOOH.
Vibrating sample magnetometer (VSM) analysis
The magnetic field and magnetic strength of the samples
were analyzed using a vibrating sample magnetometer
(VSM). The iron oxide samples from two different pro-
cedures and the MG-AC sample were selected for this
analysis. Studies have reported that upon the magnetiza-
tion process, the activated carbon acquires magnetic
properties from the added magnetic materials, in addition
to acquiring the ability to enhance the adsorption capacity
[44]. Figure 11a, b shows the VSM magnetic hysteresis
for iron oxide extracted from ferric chloride/ferrous sul-
fate solution (FeOF) and iron oxide extracted from elec-
tric arc furnace slag (FeOS), respectively, at room
temperature.
Both hysteresis loops illustrate that the samples exhib-
ited the typical superparamagnetic behavior. A previous
study had defined superparamagnetic behaviour as a phe-
nomenon usually displayed by a magnetic material/sample
following the application of an external magnetic force,
during which the particles of the magnetic material exhibit
magnetism [45]. Further, it also explains the presence of
strong magnetic properties in the samples [46].
In Fig. 11a, the magnetic hysteresis loop representing
the magnetization saturation of FeOF was 62.848 emu g-1,
which was higher than the magnetization saturation of
FeOS, i.e., 21.156 emu g-1 as depicted by the magnetic
hysteresis loop in Fig. 11b. This may be due to the presence
of Fe3O4. A previous study had demonstrated that Fe3O4
possessed greater magnetic properties relative to other iron
oxides such as c-Fe2O3, a-Fe2O3 and a-FeOOH [47]. In
this study, the VSM analysis was consistent with the fact
that the magnetic properties were inherent in the FeOF,
FeOS and MG-PKSF due to the predominance of Fe3O4
and other iron oxides, i.e., c-Fe2O3 and a-Fe2O3 in the
samples.
Consequently, owing to the higher magnetic saturation
of FeOF as stated above, the ferric chloride/ferrous sulfate
solution was used to produce the magnetic palm kernel