Mesoporous graphite nanoflakes via ionothermal carbonization of fructose and their use in dye removal

Article abstract of DOI:10.1039/c4ra05146g

The large-scale green synthesis of graphene-type two-dimensional materials is still challenging. Herein, we describe the ionothermal synthesis of carbon-based composites from fructose in the iron-containing ionic liquid 1-butyl-3-methylimidazolium tetrachloridoferrate(III), [Bmim][FeCl₄] serving as solvent, catalyst, and template for product formation. The resulting composites consist of oligo-layer graphite nanoflakes and iron carbide particles. The mesoporosity, strong magnetic moment, and high specific surface area of the composites make them attractive for water purification with facile magnetic separation. Moreover, Fe₃C-free graphite can be obtained via acid etching, providing access to fairly large amounts of graphite material. The current approach is versatile and scalable, and thus opens the door to ionothermal synthesis towards the larger-scale synthesis of materials that are, although not made via a sustainable process, useful for water treatment such as the removal of organic molecules. the Partner Organisations 2014.

Full text of DOI:10.1039/c4ra05146g

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Mesoporous graphite nanoflakes via ionothermal
carbonization of fructose and their use in dye
removal†
Cite this: RSC Adv., 2014, 4, 37423
a
b
c
a
Zai-Lai Xie,* Xing Huang, Maria-Magdalena Titirici and Andreas Taubert*
The large-scale green synthesis of graphene-type two-dimensional materials is still challenging. Herein, we
describe the ionothermal synthesis of carbon-based composites from fructose in the iron-containing ionic
4
liquid 1-butyl-3-methylimidazolium tetrachloridoferrate(III), [Bmim][FeCl ] serving as solvent, catalyst, and
template for product formation. The resulting composites consist of oligo-layer graphite nanoflakes and
iron carbide particles. The mesoporosity, strong magnetic moment, and high specific surface area of the
3
composites make them attractive for water purification with facile magnetic separation. Moreover, Fe C-
Received 30th May 2014
Accepted 11th August 2014
free graphite can be obtained via acid etching, providing access to fairly large amounts of graphite
material. The current approach is versatile and scalable, and thus opens the door to ionothermal
synthesis towards the larger-scale synthesis of materials that are, although not made via a sustainable
process, useful for water treatment such as the removal of organic molecules.
DOI: 10.1039/c4ra05146g
www.rsc.org/advances
been put forward; the reaction either proceeds through an
intermediate carbon nitride (C N ) or uses molten metal chlo-
3 4
Introduction
7,19
Graphene, currently one of the most popular two-dimensional ride salts as the solvent and template.
materials, is a well-known carbon aIlotrope consisting of a
Other molten salts, ionic liquids (ILs), are now established
2
1,2
20,21
22
single layer of sp carbon atoms. The exceptional electronic solvents,
and mechanical properties of graphene lend themselves to rials,
templates, and precursors for inorganic mate-
8,23–27
9,28
and as stabilizers for exfoliated graphite.
More-
3,4
5
6
applications in electronics, chemical sensing, and catalysis.
For graphene to be technologically successful, viable synthesis via ionothermal synthesis, is a promising approach towards
over, the preparation of advanced carbons in ILs, in particular
8
,22–24,29
and purication processes for much larger amounts of material functional carbon-based materials.
As of now, iron-
containing ILs have been among the most actively studied ILs
Indeed high-quality graphene lms have been prepared by for the carbonization of biomass and other carbon precur-
1,3,4,7–10
than are currently available are highly sought aer.
8,29
chemical vapor deposition of hydrocarbons on metal sors. For instance, hierarchical porous carbon nanoparticles
11–16
substrates,
but the accessible amounts are far from what is can be obtained by simply heating biomass in iron-containing
ILs. The process takes advantage of the multiple roles ILs can
needed for large-scale applications.
One viable synthesis is chemical oxidation and exfoliation of play as catalysts, templates and structure directing agents for
graphite. It is amenable to large-scale production and therefore carbon formation. Especially iron is an efficient promoter of the
remains the most important pathway for bulk graphene polymerization and dehydration of carbohydrates and the
9,17,18
25
synthesis.
However, graphite exfoliation is a multistep and subsequent formation of graphitic structures. Iron-containing
rather energy-intensive process. In view of the growing demand ILs possess unique properties: i.e. the cation can serve as a
2
9
26,30
for facile chemical processes, new and efficient approaches template, whereas its anion is catalytically active
and
25
towards larger amounts of graphene-type materials are clearly enables the synthesis of graphene-type materials. Indeed, Dai
required. A sustainable process towards graphene-like materials et al. reported that graphene-type powders can be prepared with
from simple organic molecules such as glucose has recently metal halide-ionic liquids as the carbon source and magadiite
8
(
a layered sodium silicate) as the template. Layered templates
like magadiite play a crucial role that enable intercalation of
Institute of Chemistry, University of Potsdam, D-14476 Potsdam, Germany. E-mail: metal-halide ionic liquids between layers prior to carbonization
a
zailai.xie@gmail.com; ataubert@uni-potsdam.de
b
and thus promote the formation of 2D instead of 3D materials.
This approach, however, requires the removal of the silicate
template with toxic uorine-containing reagents such as HF or
Fritz Haber Institute of the Max Planck Society, D-14195 Berlin, Germany
c
Queen Mary University of London, School of Engineering and Materials Science,
London, E1 4NS, UK
8
ammonium uorides. Therefore, a facile, large scale, and non-
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c4ra05146g
hazardous towards graphene-type materials is highly desirable.
1
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3
Scheme 1 Synthesis of Fe C–graphite composites from fructose and
IL and their use in dye removal.
Herein, fructose and 1-butyl-3-methylimidazolium tetra-
chloridoferrate(III), [Bmim][FeCl ] are selected as an example to
4
study the carbonization of biomass in the presence of an iron-
containing IL, Scheme 1. The resulting composite is meso-
2
porous, magnetic, and rich in sp carbons. These properties
enable the removal of organic dyes such as rhodamine B from
contaminated water using adsorption and magnetic separation.
Fig. 2 TEM and HAADF-STEM images (A and B) and HRTEM and
corresponding EDXS analysis (C and D). Inset is a selected area FFT
pattern of the sample shown in (C).
Results
3
corresponding to Fe C suggest the formation of fairly large and
well crystallized particles.
ꢀ
As depicted in Scheme 1, low temperature (LT, 180 C) ion-
othermal carbonization of fructose results in monolithic carbon
ionogels. Carbon ionogels are versatile and fascinating hybrid
materials comprised of a carbon framework and ILs incorpo-
rated within the carbon network. The high homogeneity of all
monoliths suggests that they are stabilized by strong interac-
tions between the carbon network and the IL constituents such
as Coulombic interactions and physical adsorption.
Direct carbonization of carbon ionogels at 750 C under
nitrogen results in high temperature (HT, 750 C) ionothermal
carbons. X-ray diffraction (XRD) patterns of HT ionothermal
carbons clearly show the presence of graphitic carbon and iron
carbide (Fig. 1A). The reection at 26 could be related to a
reasonably ordered (002) interlayer carbon packing. The
reection is well resolved and sharp, suggesting that the
materials are highly oriented graphitic structures. Addition-
Raman spectroscopy, Fig. 1B, supports the assignment of
turbostratic graphitic carbon. Spectra obtained from the ion-
othermal carbons show three characteristic peaks at 1340, 1574,
31
ꢂ1
and 2672 cm , respectively. Narrow D and G bands along with
a strong 2D band indicate partial ordering of the graphite
sheets. Moreover, the intensity ratio of I /I (1.04) indicates that
D
G
3
1
3
8,16,34,35
numerous sp defect sites are also present.
The N sorption isotherm and pore size distribution of the
nal materials are shown in Fig. 1C. Barret–Joyner–Halenda
ꢀ
2
ꢀ

2
ꢂ1
(
BJH) analysis yields a surface area of 122 m g . The charac-
teristic type IV isotherm indicates the presence of mesopores
ꢀ
29,36,37
without a signicant fraction of micropores.
The latter is
32
conrmed by the fairly broad hysteresis loop, which closes upon
desorption. This indicates capillary condensation and swelling
33
29
effects. The hysteresis loop indicates unrestricted adsorption
in the high pressure regime and the increased gas uptake at p/p
ꢀ
ally, there are a number of diffraction peaks centered at ꢁ45
0
3
(2q) which can be assigned to Fe C (JCPDS 65-0393) within the
38
>
0.9 indicates the presence of slit-like pores. The mesopores
25
graphitic matrix. The strong and sharp diffraction peaks
2
Fig. 1 Representative XRD pattern, Raman spectrum, and N sorption data of ionothermal carbons.
37424 | RSC Adv., 2014, 4, 37423–37430
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are emptied by a cavitation mechanism, as indicated by the
The surface morphology of an as-synthesized HT ion-
38
spontaneous desorption at p/p0 ꢁ 0.45. Non-linear density othermal carbon is shown in Fig. 3A. The carbon surfaces
functional theory (NLDFT) analysis yields a pore distribution exhibit unique petal-like and interconnected nanoakes with a
with relatively monodisperse pore diameters around 5 nm.
mean size in the micrometer range. Complementary trans-
Consistent with XRD and Raman data, TEM and high angle mission electron microscopy (TEM) nds a ake-like nano-
annular dark eld scanning TEM (HAADF-STEM) images reveal morphology composed of stacked graphene-type sheets. The
the presence of a graphite matrix and agglomerated iron interconnected nature of the nanoakes likely generates the
carbide particles (Fig. 2). The presence of Fe
energy dispersive X-ray spectroscopy (EDXS) on individual highly homogenous morphologies, but vary in their thickness.
nanoparticles, which clearly shows the presence of iron and High resolution TEM (HRTEM) clearly shows lattice fringes
3
C is conrmed by mesopores within the carbon frameworks. The nanoakes have
carbon. The large particles observed in (S)TEM are also in the carbon, conrming the carbon's graphitic nature. The
consistent with the fairly intense and narrow reection in XRD. interplane spacing measured from different nanoakes is in the
High resolution TEM (HRTEM) and TEM-selected area fast range between 0.33–0.38 nm, similar to that of carbon nano-
4
2
Fourier transform (FFT) again support the formation of Fe
3
C
sheets (0.34 nm) reported previously. The typical honeycomb-
39
and suggest that the Fe
particles formed by oriented attachment.
of the Fe C (1 0 0) crystalline plane, with d-spacing of 0.5 nm, fairly small on the order of a few nm. Besides the single carbon
3
C particles in fact are mesocrystals or like molecular structure of hexagonally connected carbon atoms
40,41
The lattice fringes is observed in many unfolded carbon sheets. These domains are
3
can clearly be seen from the HRTEM image. Moreover, all TEM nanosheets mostly discussed so far, all samples also contain
data show that, besides the large Fe C particles within the multilayer domains; we hence call the materials obtained via
3
samples, other domains mainly consist of carbon nanoakes, our approach “oligo-layer graphite” (OLG) nanoakes.
indicating a relatively heterogeneous distribution of the Fe
nanoparticles in a homogeneous carbon matrix.
3
C
The iron carbide particles within the mesoporous graphite
nanoakes are accessible through the pores. Treatment of the
materials with dilute hydrochloric acid results in the dissolu-
tion of the iron carbide nanoparticles. XRD patterns of the acid-
treated materials exclusively show reections from carbon and
all reections corresponding to iron carbide are gone aer 48
hours of acid etching (Fig. S1†). This is also conrmed by TEM,
which shows no signicant changes in the graphite nanoake
3
morphologies, but no more dark speckles indicative of the Fe C
nanoparticles. This indicates that the acid etching does not
affect the carbon sheets, but selectively removes the iron
carbide from the samples.
Additional X-ray elemental mapping experiments were per-
formed for further chemical analysis of the acid-etched samples
(Fig. 4). X-ray maps show that the carbon is homogeneously
distributed, and oxygen is also present in the sample. In spite of
the fact that XRD (Fig. S1†) does not show any indication of iron
carbide or iron chloride, X-ray analysis still nds iron and
chlorine signals homogeneously distributed throughout all
samples. The apparent contradiction between the fact that XRD
does not detect any iron-based mineral phases anymore
(
(
(
Fig. S1†) while EDXS (Fig. 4D) still detects Fe can be assigned to
i) rather low concentrations of Fe aer the etching process
which can still be detected by X-ray mapping, which is a local
method, but not by XRD, which is a global method) or (ii) small
fractions of residual anhydrous iron chloride, which has a poor
solubility in dilute aqueous hydrochloric acid and does not
generate an XRD signal if poorly ordered. EDX spectrum aer
etching again support that Fe signal is much lower than that of
as-prepared Fe C@OLG materials shown in Fig. 2D (Fig. S2†).
3
With the stripping of iron carbide by HCl treatment, the surface
2
ꢂ1
areas of ionothermal carbon increase from 122 to 180 m g
probably due to the change of materials density aer removing
of large Fe C particles (Fig. S3†).
As stated in the introduction, magnetic carbon materials are
,
3
43,44
candidates for water purication.
In addition, graphite
Fig. 3 SEM (A) and TEM images at increasing magnifications (B–E) of a
graphite composite (D and E are HRTEM images).
materials with high specic surface areas are useful for
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and Raman spectroscopy (Fig. 1), contain a high fraction of
2
aromatic sp carbon atoms. Indeed, the OLG can be dispersed
in toluene but precipitate in water (Fig. S4†).
This implies a high affinity for organic molecules, such as
dyes or aromatics which oen are hydrophobic, but still present
in aqueous media in concentrations posing a risk to the envi-
46
ronment. To evaluate the OLG materials for the removal of
organic molecules from water, we have studied the adsorption
of rhodamine B (RB) from aqueous solution (Fig. 5) as a model
reaction. Adsorption kinetics was studied at an initial RB
ꢂ1
concentration of 25 mg L in water. Adsorption was monitored
by UV-vis spectroscopy vs. adsorption time. Fig. 5A shows that
the RB absorbance gradually decreases with increasing contact
time. Visual inspection of the respective solutions conrms that
a large fraction of RB is removed from the aqueous phase
leaving behind a clear solution aer 5 hours. The adsorbent can
be easily extracted for reuse by magnetic ltration. As shown in
Fig. 5B, equilibrium is reached aer 120 min of contact time.
Fig. 5C shows that the solution pH only has a weak inuence
on the adsorption performance between pH 3 and 9. These
results suggest that the OLGs could effectively adsorb RB over a
wide pH range without signicantly altering the adsorption
characteristics. The key advantage of the OLG material over
other materials used for dye removal is that the adsorption
Fig. 4 (A, B) TEM images, (C) HAADF-STEM image and (D) X-ray maps
of the OLG after acid etching. Scale bars in panels (C) and (D) are
200 nm.
ꢂ1
capacity of the current OLGs reaches up to 150 mg g , as
45
illustrated in Fig. 5D and Table 1. This is signicantly better
both in terms of equilibrium adsorption time (which translates
into speed or rate of a technical process) and capacity (which
adsorption of (mostly unpolar) organic molecules. The OLGs
prepared here are clearly attractive for water treatment because
they are relatively hydrophobic and, as demonstrated by XRD
Fig. 5 (A) Absorption spectra of RB solutions treated with the ionothermal carbon hybrid material. (B) Adsorbed RB vs. time. (C) The effect of pH
ꢂ1
on the adsorption of RB onto nanoflakes, C
0
¼ 25 mg L . (D) Adsorption isotherm. The adsorption isotherm was calculated using the equation:
e
e
ꢂ1
ꢂ1
q ¼ (C
0
ꢂ C
e
)V/m, where q is the concentration of dye adsorbed (mg g ), C
m is the mass of OLG nanoflake (g), and V is the volume of solution (L).
0
and C
e
are the initial and equilibrium concentrations of dye (in mg L ),
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Table 1 Comparison of the maximum adsorption capability of various focusing on different nal materials, all studies used the same
adsorbents for RhB
IL, showing its potential for a wide variety of chemical trans-
formations. Especially given the fact that both biomass and iron
Capacity Contact
ꢂ1
chloride are relative low-cost, the large-scale synthesis of such
carbon ionogels can be economically achieved, possibly by
adapting the chemistry of the IL from imidazolium-based
Sorbents
(mg g
)
time (min) Reference
OLG nanoake
Graphite oxide (GO)
Reduced GO
150
29
13.15
50
120
180
250
720
This work
4
7
Ramesha et al.4
(which still constitute more expensive ILs) to ILs based on
7
Ramesha et al.
4
5
other cations such as ammonium, which may be cheaper.
Carbonizing of as-synthesized carbon ionogels leads to
graphite nanoakes. For structure assignments, we have used
various techniques. SEM and TEM (Fig. 2 and 3) indicate an
Hybrid of reduced
Geng et al.
graphene oxide–Fe
Multiwalled CNTs
Activated carbon
Activated carbon
3 4
O
4
8
36
180
Yan et al.
4
9
307
212
720
Not
Li et al.
Anandkumar et al.
50
“oligo-layer-graphite” (OLG) morphology with characteristic
mentioned
150
5
1
thin graphite nanoakes, thus justifying the term “oligo-layer-
graphite”. Remarkably, the honeycomblike molecular structure
corresponding to single-layer graphene is clearly seen in
HRTEM (Fig. 3E), conrming the formation of graphene-like
Activated carbon
16
Kadirvelu et al.
ꢀ
materials at low carbonization temperature of only 750 C.
translates into amount of RB removed by the material per
adsorbent weight unit). We currently surmise that the RB
adsorption onto the OLG material is due to strong van der
Waals, hydrophobic, and p–p interactions between OLG
nanoakes and the dye molecules. Also, the mesoporosity and
high surface areas of the current material lend it to having the
satisfactory RB adsorption performance.
Our approach thus introduces a new strategy towards graphite
composites containing highly ordered graphitic structures
termed OLG. In addition, agglomerated rather than homoge-
3
neously distributed Fe C particles are is found within the
graphitic matrix. This may be assigned to migration/
coalescence of particles (sintering) or Ostwald ripening of iron
species at high temperature.
Raman spectroscopy is highly sensitive to the electronic
34
structure of carbon-based materials. The characteristic peaks
of carbon-based materials are the G band at 1580 cm corre-
Discussion
ꢂ1
2
Ionic liquids are promising active components for the creation sponding to the rst-order scattering of the E2g phonons of sp
23,52
ꢂ1
of (multi)functional materials.
Among others, there is an carbon atoms, and the D band at 1350 cm corresponding to
increasing research and technology effort in making use of ILs breathing mode of k-point phonons of A1g symmetry. Our
35
8,26,29
ꢂ1
for the preparation of carbon-based materials.
One major results show D and G bands at 1340 and 1574 cm , respec-
ꢂ1
advantage for using of ILs as precursors for carbons is that tively. Moreover, a strong 2D band is observed at 2672 cm
,
heteroatom doping (such as N, B, S) and metal doping can be which supports the assignment of OLG found in the current
5
3
8,28,35
accomplished fairly easily. Moreover, the almost unlimited study.
exibility of IL structure and chemical composition makes them

Notably, we have demonstrated previously that iron-
29
highly suitable for tuning carbon structure with desirable containing ILs are a powerful solvent for carbonization. The
54
electronic properties or specic surface area. As stated in the signicant difference to the current study, however, is the fact
introduction, however, there is a lack of protocols for the large- that in the previous case, the IL was recovered by Soxhlet
scale synthesis of graphene-like materials. The current article extraction (in fact demonstrating a somewhat sustainable
provides a viable approach towards nano- and mesotructured process). Moreover, the process was chemically different
graphitic carbon using a sustainable raw material (although the yielding spherical carbon particles of approximate 50–100 nm
29
OLG synthesis as such is clearly not sustainable at the moment), in diameter.
fructose, and an IL that is easily accessible on a large scale.
By contrast, the current case introduces an adapted process
Iron-based ionic liquids are interesting components not only allowing for the synthesis of OLG nanoakes via carbonization
55
30,56,57
because they are magnetic or catalytically active.
can also serve as powerful solvents for biomass conversion.
Bmim][FeCl ] has been used as precursor for iron/iron carbide through a dissolution–precipitation mechanism that involves
They of carbon ionogels (Scheme 1 and Fig. 6). The formation of
29
graphitic carbons from such iron catalysts usually occurs
[
4
and graphene-type materials synthesis in the presence of an the dissolution of amorphous carbon into iron particles fol-
inorganic template. For instance, G ¨o bel et al. synthesized Fe/ lowed by the precipitation and segregation from the Fe to form
2
6
Fe
C/C hybrid materials with rather high surface areas using graphene layers. Indeed, the formation of the OLG nanoakes
3
29
functionalized SiO
2
as template and [Bmim][FeCl
4
]
as is clearly different to the previously described materials.
The combination of magnetic moment and large p-system
25
precursor. Dai et al. synthesized graphene-type carbon
powders by pyrolysis of iron-based ILs and magadiite, a layered with acceptable porosity suggests that the current materials
8
sodium silicate. Moreover, we have previously shown that the could be attractive for water purication, particularly for the
4
5,58
IL [Bmim][FeCl ] is an effective medium for conversion of removal of organics.
Many organic molecules such as dyes or
4
29
biomass to porous carbons at relatively low temperature. This aromatics are toxic, persistent in the environment and non-
59
process results in a monolithic carbon ionogel. In spite of biodegradable.
Physical adsorption is an efficient and
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Experimental
IL synthesis
61
[
Bmim][FeCl
mixing equimolar amounts of [Bmim][Cl] (2 g, 11.5 mmol) and
FeCl $6H O (3.16 g, 11.7 mmol) in a round-bottom ask for
0 min. at room temperature while stirring, which results in a
4
]
was prepared as described before
by
3
2
3
two phase mixture (a bottom, brown oily liquid layer and a top
water layer). Aer separating the oily phase from the water layer,
ꢀ
the resulting [Bmim][FeCl ] was dried in a vacuum oven at 60 C
4
1
overnight. H NMR (DMSO-d
6
, ppm relative to TMS): 9.08 (s,
1
2
H), 7.75 (d, 1H), 7.68 (d, 1H), 4.15 (t, 2H), 3.84 (s, 3H), 1.76 (m,
H), 1.26 (m, 2H), 0.92 (t, 3H). Elemental analysis: calc. for
C
8
H
15Cl
4
FeN
2
: C 28.52%, H 4.49%, N 8.32%. Found: C 28.49%,
ꢂ1
H 4.58%, N 8.24%. Raman: 330 cm (Fe–Cl vibration), 1024
and 1410 cm ([Bmim] cation).
ꢂ1
+
Carbon ionogel synthesis
Fig. 6 SEM and TEM images of carbon structures prepared via second
annealing process in the presence of iron catalyst (A and C), and in the
absence of iron catalyst (B and D).
D-Fructose was purchased from Sigma-Aldrich® and used
without further purication. 3.0 g of fructose was dispersed in 8
4
mL of [Bmim][FeCl ] at room temperature (fructose is not
60
attractive way to overcome this issue for wastewater treatment.
soluble in the IL at r.t.) The mixtures were loaded into PTFE
ꢀ
Indeed, many carbon materials that have shown effective dye lined autoclaves and treated at 180 C for 5 hours. The resulting
43,45,59
ꢀ
adsorption
and Fig. 5 and Table 1 clearly show that the carbon ionogels were dried overnight at 60 C.
current material is comparable to (and in fact better than some)
other carbon materials used for dye removal both in terms of
capacity and equilibration time. Although clearly not made via a
Nanoake synthesis
Oligo-layer graphite/iron carbide nanoakes were synthesized
by direct carbonization of the carbon ionogels by heating the
“green” or “sustainable” process as such, the material is inter-
esting from an environmental application perspective. The OLG
nanocomposites combine the advantages of mesoporosity,
graphitic surface structure, and magnetic moment making it a
comparatively cheap (although still far too expensive for the
developing countries) and simple material for water remedia-
tion. Upscaling of the materials synthesis, replacement of the
still rather const-intensive imidazolium IL with a cheaper, e.g.
ammonium-based, IL, and optimization of the water treatment
process as such will, however, be necessary prior to
commercialization.
carbon ionogels in an oven under N
2
ow at a heating rate of
ꢂ1
ꢀ
1
0 K min to 750 C and hold 4 h. The iron/iron carbide
nanoparticles within the carbon matrix were removed via
soaking in 1 M HCl (aq) solution for 48 h under stirring.
Characterization
Scanning electron microscopy (SEM) images were acquired on a
LEO 1550 with Everhard–Thornley secondary electron and in-
lens detectors. Transmission Electron Microscopy (TEM) and
s
HRTEM were done on a FEI C -corrected Titan 80–300 micro-
Conclusion
scope operated at 300 kV with a Gatan energy lter. The Raman
spectrometer (Kaiser Optical) was equipped with a frequency-
doubled Nd:YAG 532 nm laser. Nitrogen sorption isotherms
were measured at 77 K on a Quadrachrome Adsorption Instru-
The current report describes a general approach towards mes-
oporous oligo-layer Fe
monomer, fructose, under ionothermal conditions using the IL
Bmim][FeCl ] as “all-in-one” solvent–reactant–catalyst. The
3
C/graphite nanoakes from a renewable
ꢀ
ment (Quantachrome Instruments). Sample was dried at 120 C
[
4
for 12 h prior to nitrogen sorption analysis. UV-vis spectra were
recorded on a Perkin-Elmer Lambda 25 UV-vis spectrometer at
room temperature.
composites are efficient adsorbents for the removal of RB from
aqueous solution and can be isolated by magnetic separation
with a permanent magnet. Via acid etching, the iron carbide
particles can be removed leaving pure mesoporous OLG mate-
rials behind. These can be dispersed in hydrophobic solvents
Adsorption test
such as toluene. Overall, the ionothermal carbonization of 8 mL of an aqueous Rhodamine B solution with an initial
ꢂ1
renewable raw materials such as the approach demonstrated concentration of 25 mg L were mixed with 6 mg of hybrid
here may in the future allow the large-scale synthesis of tai- material. The mixtures were shaken for various amounts of time
lormade adsorbents or dispersible (and thus solution process- at room temperature. Concentrations vs. adsorption times were
able) oligo-layer graphite with potential application in determined via UV/vis spectroscopy. The adsorbed time for
electronics or sensing.
isotherm was controlled at 120 min.
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2
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