A dipeptide-based superhydrogel: Removal of toxic dyes and heavy metal ions from waste water

Article abstract of DOI:10.1002/bip.22915

A short peptide-based molecule has been found to form a strong hydrogel at phosphate buffer solution of pH 7.46. The hydrogel has been characterized thoroughly using various techniques including field emission scanning electron microscopy (FE-SEM), wide angle powder X-ray diffraction (PXRD), and rheological analysis. It has been observed from FE-SEM images that entangled nanofiber network is responsible for gelation. Rheological investigation demonstrates that the self-assembly of this synthetic dipeptide results in the formation of mechanically strong hydrogel with storage modulus (G′) around 10⁴ Pa. This gel has been used for removing both cationic and anionic toxic organic dyes (Brilliant Blue, Congo red, Malachite Green, Rhodamine B) and metal ions (Co²⁺ and Ni²⁺) from waste water. Moreover, only a small amount of the gelator is required (less than 1 mg/mL) for preparation of this superhydrogel and even this hydrogel can be reused three times for dye/metal ion absorption. This signifies the importance of the hydrogel towards waste water management.

Full text of DOI:10.1002/bip.22915

A Dipeptide-based Superhydrogel: Removal of Toxic Dyes and
Heavy Metal Ions from Waste-water
Nibedita Nandi,† Abhishek Baral,† Kingshuk Basu, Subhasish Roy and Arindam Banerjee*
† These two authors contributed equally.
*Correspondence:
Department of Biological Chemistry
Indian Association for the Cultivation of Science
Jadavpur, Kolkataꢀ700032, India.
Eꢀmail: bcab@iacs.res.in
Fax: (+91)332473ꢀ2805
Abstract
A short peptideꢀbased molecule has been found to form a strong hydrogel at phosphate buffer
solution of pH 7.46. The hydrogel has been characterized thoroughly using various
techniques including field emission scanning electron microscopy (FEꢀSEM), Xꢀray
diffraction (XRD) and rheological analysis. It has been observed from FEꢀSEM images that
entangled nanofiber network is responsible for gelation. Rheological investigation
demonstrates that the selfꢀassembly of this synthetic dipeptide results in the formation of
mechanically strong hydrogel with storage modulus (G') around 104 Pa. This gel has been
used for removing both cationic and anionic toxic organic dyes (Brilliant Blue, Congo red,
Malachite Green, Rhodamine B) and metal ions (Co2+ and Ni2+) from wasteꢀwater. Moreover,
only a small amount of the gelator is required (less than 1 mg/mL) for preparation of this
superhydrogel and even this hydrogel can be reused three times for dye/metal ion absorption.
This signifies the importance of the hydrogel towards wasteꢀwater management.
Keywords
This article has been accepted for publication and undergone full peer review but has not been
through the copyediting, typesetting, pagination and proofreading process which may lead to
differences between this version and the Version of Record. Please cite this article as an
‘Accepted Article’, doi: 10.1002/bip.22915
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Biopolymers: Peptide Science
Peptide, Hydrogel, Supergelator, Dye absorption, Metal ions absorption.
Introduction
Page 2 of 25
Supramolecular gels1ꢀ12 belongs to a special category of soft materials due to their wide range
of interesting structural and functional properties. Since past few decades, low molecular
weight hydrogelators13ꢀ15 (LMWHG) draw a significant attention to the scientists due to their
ability to selfꢀassemble among themselves by utilizing various nonꢀcovalent interactions
including hydrogen bonding, πꢀπ interactions, hydrophobic interactions, van der Waals’
interactions, ionic interactions and others to form a nano/microꢀfibrillar three dimensional
entangled network structure. The network structure encapsulates large number of water
molecules to form a hydrogel. Amino acid/peptide based gels16ꢀ23 are endowed with variety of
applications including drug delivery,24ꢀ28 tissue engineering,29ꢀ32 oilꢀspill recovery33ꢀ35 and
wasteꢀwater treatment.36,37 They can also be used for making nanoclusters and
nanoparticles,38ꢀ40 photoꢀswitching materials41ꢀ43 and for other biomedical applications.44ꢀ48
Since the last two decades water pollution due to the textile and organic dyes is a
matter of great concern to nature.49,50 This is because many dyes are known to get reduced
into toxic substances inside living organisms that can cause damage to genetic material which
may affect the organism in the long run although they are often not expressed immediately.51
On the other hand, due to discharge of large amount of metalꢀcontaminated wasteꢀwater,
effluents from several industrial operations like electroplating, mining, pigments and metal
processing are also one of the major contributors to abnormal metal contamination in water
sources. Inorganic effluents from the industries contain toxic metals such as Co, Ni, Cd, Cr,
Cu and others, which tend to accumulate in living organisms and can act progressively over a
long period of time through food chains.52 Hence, it is essential to regulate the pollution from
wasteꢀwater before disposing it to the environment to minimize human and environmental
exposure to various hazardous organic and inorganic toxins. Conventional wasteꢀwater
treatment processes like adsorption upon activated carbon, chemical precipitation,
electrochemical techniques, ion exchange and others, have their own limitations due to their
low sensitivity, incomplete removal, highꢀenergy requirements, and production of toxic
sludge.53 Hydrogelꢀbased soft materials offer an alternative appealing54 for removal of various
hazardous wastes from contaminated water due to their high water permeability, large surface
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Biopolymers: Peptide Science
area for adsorption and simplicity in use. In this regard, peptide based hydrogel have gained
importance in environmental applications owing to their high sensitivity towards the noxious
wastes along with reusability and proper biodegradability. There are numerous examples
reported by several research groups on pH responsive reusable smart hydrogels,55,56 pH
dependent selective dye absorbing novel hydrogel57 as well as chelation induced metalloꢀ
hydrogel.58 Many other groups have also devoted their research to explore this area.59ꢀ64
However, there are very few gelator molecules that form gel at concentration below 0.1%
(w/v).65 These gelators are generally termed as ‘supergelator’. So, it will be interesting to
develop super hydrogelator, which could remove pollutants present in wasteꢀwater. This is
because, very small amount of gelator molecule is needed to form the hydrogel that would act
as a scavenger for toxic organic and inorganic materials from wasteꢀwater in a costꢀeffective
way. In course of our investigation on the selfꢀassembly of small peptide molecules, it has
been found that a Cꢀterminally protected very simple dipeptide HꢀLeuꢀPheꢀOMe (Leu= Lꢀ
Leucine, Phe= LꢀPhenylalanine) forms hydrogel at phosphate buffer of pH 7.46 with a
minimum gelation concentration of 0.07% (w/v). The amino acids Leu, Phe and the free
amine functionality promote gelation using different nonꢀcovalent interactions.56 The
hydrogel has been effectively used for removing both cationic and anionic toxic dyes as well
as toxic heavy metal ions (Co2+ and Ni2+) from wasteꢀwater effectively in an ecoꢀfriendly
manner. Furthermore, the reusability of this hydrogelator without the loss of significant
activity by changing the pH of the medium possesses an additional advantage of this gelꢀ
based absorbent.
Experimental section
Materials
All amino acids (LꢀLeu and LꢀPhe) were purchased from Sigma chemicals. 1ꢀ
hydroxybenzotriazole (HOBt) and dicyclohexylcarbodiimide (DCC) were purchased from
Merck and SRL, India respectively. Other chemicals used in the work were purchased from
local chemical company SRL, India.
Synthetic procedure
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Page 4 of 25
Synthesis of Boc-Leu-OH: A solution of LꢀLeu (1.31 g, 10 mmol) in a mixture of dioxane
(20 mL), water (10 mL) and 1(N) NaOH (10 mL) was stirred and cooled in an iceꢀwater bath.
Diꢀtertꢀbutyl dicarbonate (2.39 g, 11 mmol) was added and stirring was continued at room
temperature for 6 hr. Then the solution was concentrated in vacuum to about 20 mL to 30
mL, cooled in an ice water bath, covered with a layer of ethyl acetate (about 50 mL) and
acidified with a dilute solution of KHSO4 to pH 2ꢀ3. The aqueous phase was extracted with
ethyl acetate and this operation was done repeatedly. The ethyl acetate extract was washed
with water and dried over anhydrous Na2SO4 and evaporated in vacuum to obtain a yellowish
product.
Yield: 2.1 g (8.7 mmol, 87%).
Synthesis of Boc-Leu-Phe-OMe: 2.1 g (8.7 mmol) of BocꢀLeuꢀOH was dissolved in 10 mL
of dimethylformamide (DMF) in an ice water bath. HꢀPheꢀOMe was isolated from 4.3 g (20
mmol) of the corresponding methyl ester hydrochloride by neutralization and subsequent
extraction with ethyl acetate and ethyl acetate extract was concentrated to 10 mL. It was then
added to the reaction mixture, followed by 1.85 g (9 mmol) DCC and 1.37 g (9 mmol) of
HOBt. The reaction mixture was allowed to come at room temperature and stirred for 3 days.
The residue was taken up in ethyl acetate (40 mL) and dicyclohexylurea (DCU) was filtered
off. The organic layer was washed with 1(N) HCl (3 × 30 mL), brine (1 × 30 mL), 1(M)
sodium carbonate (3 × 30 mL) and brine (2 × 30 mL) and dried over anhydrous Na2SO4 and
evaporated in vacuum to obtain a white material.
Yield: 2.18 g (5.5 mmol, 64.4 %).
1H NMR (500 MHz, CDCl3, 25 °C): δ 7.20ꢀ7.02 (5H, aromatic Hs, m), 6.49 (1H, NH, br),
α
α
4.79ꢀ4.75 (2H, H and NH, m), 4.03ꢀ4.02 (1H, H, m), 3.63 (3H, OCH3), 3.09ꢀ2.98 (2H,
βCH2, m), 1.58ꢀ1.53 (2H, βCH2, m), 1.36 (9H, Boc, s), 1.23ꢀ1.18 (1H, γH, m), 0.85ꢀ0.79 (6H,
2CH3, m). 13C NMR (125 MHz, CDCl3): δ 172.28, 171.80, 155.69, 135.91, 129.42, 128.65,
127.21, 80.13, 53.27, 52.37, 41.36, 38.06, 28.40, 24.80, 22.98, 22.76. HRMS (m/z):
415.5126 [M+Na]+.
Synthesis of H-Leu-Phe-OMe: To 2.18 g (5.5 mmol) of BocꢀLeuꢀPheꢀOMe, 4 mL of
trifluoroacetic acid (TFA) was added and removal of Boc group was monitored by TLC.
After 8 h, TFA was removed under vacuum. The residue was taken in water (20 mL) and
covered with ethyl acetate (about 50 mL) and neutralized with saturated solution of NaHCO3
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Biopolymers: Peptide Science
by using pH paper. The aqueous phase was extracted with ethyl acetate and this operation
was done repeatedly. The ethyl acetate extracts were pooled, washed with water and dried
over anhydrous Na2SO4 and evaporated in vacuum. A white material was obtained.
Yield: 1.4 g (4.8 mmol, 90.1 %).
1H NMR (400 MHz, DMSOꢀd6, 25 °C): (Figure S1 in Supporting Information) δ 8.08ꢀ8.04
α
(1H, d, J= 13.6 Hz, NH), 7.28ꢀ7.12 (5H, aromatic Hs, m), 4.15 (1H, H, m), 3.47ꢀ3.45 (1H,
αH ,m), 3.31(3H, OCH3), 3.14ꢀ2.80 (2H, βH, m), 1.45ꢀ1.38 (1H, βCH2, m), 0.89ꢀ0.87 (1H, γH,
m), 0.63ꢀ0.58 (6H, 2CH3, m). 13C NMR (100 MHz, DMSOꢀd6): (Figure S2 in Supporting
Information) δ 171.34, 169.91, 167.44, 166.11, 136.83, 136.07, 130.36, 129.02, 128.34,
128.05, 126.69, 55.44, 53.77, 52.24, 43.60, 36.35, 23.39, 22.88, 22.78, 21.68, 21.35. HRMS
(m/z): (Figure S3 in Supporting Information) 293.0161 [M+H]+.
Instrumentation Details
NMR experiments
NMR study was carried out on a Brüker DPX 400/500 MHz spectrometer at 300 K.
Compound concentration was in the range 1–10mmol in CDCl3 or DMSOꢀd6.
Mass spectrometry
Mass spectra were recorded on a QꢀTof microTM (Waters Corporation) mass spectrometer by
positive mode electrospray ionization.
X-ray diffraction study
The hydrogel was freeze dried by using liquid nitrogen at first and it was further dried in
lyophilizer to get xerogel for Xꢀray diffraction study. The dried powder was then placed on a
glass plate and the experiment was carried out by using an Xꢀray diffractometer (Bruker
AXS, Model No. D8 Advance). The instrument was operated at a 40 kV voltages and 40 mA
current using Niꢀfiltered CuKα radiation and the instrument was calibrated with a standard
Al2O3 (corundum) sample before use. For scan 5°ꢀ28°, the LynxEye super speed detector was
used with scan speed 0.3s and step size 0.02°.
Field emission scanning electron microscopic study
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Page 6 of 25
Morphology of the reported gel material was investigated using field emission scanning
electron microscopy (FEꢀSEM). For sample preparation, a drop of the dilute buffer solution
of the gel material was placed on a microscopic glass slide and then it was allowed to dry first
in the air and then under vacuum for one day to get the xerogel. After that the sample was
coated with platinum. Then the micrograph was taken in an SEM apparatus (Jeol Scanning
MicroscopeꢀJSMꢀ6700F).
UV-Vis spectroscopy
UVꢀVis absorption spectra were recorded on a UVꢀvis spectrophotometer (Varian Cary 50
Bio). For this experiment 1000 ꢁL of aliquot was pipetted out from the dye solution
throughout a time interval and the aliquot was again added to the residual dye solution for
each time.
Rheology
The rheological measurement of the hydrogel of peptide P was studied under dynamic and
steady shear measurement at room temperature (25 °C) on parallelꢀplate geometry (25 mm
diameter, 1 mm gap). Rheological experiment was carried out using and Anton Paar modular
compact rheometer (MCR 102). Viscoꢀelastic measurement of the hydrogel was performed at
room temperature using parallelꢀplate geometry (PPꢀ25 mm, gap 0.5 mm).
Results and discussion
Gelation and Thermal Behaviour
The gelation propensities of the peptide HꢀLeuꢀPheꢀOMe (P) has been studied by dissolving
1 mg of the compound in 1 mL of the phosphate buffer solution by the application of simple
heatingꢀcooling cycle. Below a certain temperature (Tgel, temperature of gelation), the
complete volume of solvent is immobilized and it forms a gel. This hydrogel is thermoꢀ
reversible in nature and is stable over the pH range 5.0 to 8.0. A decrease in the pH below 5.0
triggers a gelꢀtoꢀsol transition, whereas pH above 8 led to precipitation of the gelator peptide
P. Here, all the studies have been carried out at pH 7.46. The gelation is confirmed by the
inverted tube method. The gel is stable at room temperature and maintains its gel state for
several months. The minimum gelation concentration (MGC) is 2.3 mM (0.07% w/v) for a
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freshly prepared hydrogel without any sonication. Generally, gelators with MGC below 0.1%
(w/v) fall into the category of supergelators. In this regard, this hydrogelator should be
considered as a supergelator. The gel melting temperature (Tgel) at MGC is found to be 84 °C.
For this purpose, the “tube inversion” method has been used to measure the solꢀgel transition
temperature (Tgel) of the gel phase material in buffer solution at pH 7.46. The measured
temperatures are plotted against the gelator concentration to afford the plot presented in
supporting information as Figure S4. The hydrogel offers potential applicability in treatment
of wasteꢀwater containing organic dyes (Brilliant Blue, Congo red, Malachite Green,
Rhodamine B) and inorganic metal ions (Ni2+ and Co+2) that are widely used in textile as well
as dye industries. Moreover, peptide gelators can be recovered very easily just by simple
treatment with organic medium. Thus, this reported hydrogel are promising superabsorbent
for removing both cationic and anionic dyes and also heavy metal ions from the water
effluents.
Figure 1: The upper panel shows the chemical structure of the peptide P and the photograph
of the hydrogel from peptide P at 0.1% (w/v). The lower panel shows the photographs of the
hydrogels before and after absorption of the dyes Brilliant Blue (BB), Congo Red (CR),
Malachite Green (MG), Rhodamine B (RB) and the metal ions nickel(II) (Ni2+), cobalt(II)
(Co2+). The concentration of hydrogels was 0.1% (w/v) for all these cases.
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Page 8 of 25
Morphology
To obtain insight into the morphology of the hydrogel obtained from peptide P, fieldꢀ
emission scanning electron microscopic experiment (FEꢀSEM) has been carried out. For the
preparation of the sample, dilute buffer solution of the gel material was placed on a
microscopic glass slide and then it is dried to get the xerogel. It should be taken under
consideration that the sample should be in lower concentration in order to avoid the formation
of fibril bundles during the drying process and also the hydrogel film generated on the slide
should be thin. In Figure 2 FEꢀSEM images of the xerogel show nanoꢀstructured morphology
in the selfꢀassembled state. The average widths of the nanofibrils are in the range of 80±10
nm indicating a porous nanostructure with high surface area that can interact with pollutants
present in its vicinity.
Figure 2: FEꢀSEM image (a) and its enlarged view (b) obtained from the hydrogel of peptide
P.
Rheological analysis
Rheological study of the hydrogel has been performed in order to examine its mechanical
strength and stability. The storage modulus (G′) and loss modulus (G′′) were measured in
frequency sweep experiments and are presented in Figure 3. It is evident from the plot that
the storage modulus (G′) is higher than the loss modulus (G′′) for this dipeptideꢀbased
hydrogel of peptide P and no crossꢀover point is found in the experimental frequency region.
At 0.1% (w/v) the gel exhibits linear behaviour with respect to angular frequency in the
region 8ꢀ100 rad/sec. In the experiment, almost one order higher values of storage modulus
(G′) over the loss modulus (G′′) suggests a soft ‘solidꢀlike’ gel phase formation. The storage
modulus (G′) for the gel is in the order of 8.1 × 103 Pa indicating its sufficiently high
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Biopolymers: Peptide Science
mechanical strength. Thus, the hydrogel shows very weak dependency on the angular
frequency over the experimental range. This suggests that this gel matrix has good tolerance
towards external forces.
Figure 3: Frequency sweep analysis of the hydrogel from peptide P at 0.1% (w/v).
X-ray Diffraction (XRD) Study
The internal arrangement of the selfꢀassembled nanoꢀstructured molecules in gel phase has
been investigated by XRD analysis. Figure 4 shows the wide angle XRD patterns of the
hydrogel obtained from peptide P in its xerogel state. In the higher angle region, peaks at 2θ=
26.470 and 2θ= 27.340 corresponds to d values 3.36 Å and 3.86Å respectively, characterising
πꢀπ interactions in the dried aggregates. The peaks that appeared at 2θ= 19.130 and 2θ=
21.070 corresponding to the dꢀspacing value of 4.63Å and 4.21Å respectively appeared due to
the spacing between two hydrogenꢀbonded dipeptide strands.22
Figure 4: Wide angle Xꢀray diffraction pattern of the xerogel from peptide P.
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Removal of dye and metal ion from waste-water
The effluents from various textile industries contain a large number of organic dyes and
inorganic additives, which may cause acute and chronic toxicity. In addition to being toxic,
dye effluents not only have negative impact on immune and reproductive systems, but these
are also potential genotoxic and carcinogenic agents.51 Heavy metal ions such as Ni2+ and
Co2+ are the common constituents of runoff from mining operations and industrial
effluents.52,66 The normal limit of Ni(II) and Co(II) in drinking water are 0.07 mg/L and 0.002
mg/L respectively.67 Severe chronic health disorders are caused due to the ingestion of these
metals beyond the permitted level of concentration.67 Hence, it is essential to safeguard the
environment by eliminating such contaminants from wasteꢀwater. The hydrogel from peptide
P has been tested for absorbing different types of toxic effluents from water with an aim to
purify contaminated wasteꢀwater coming out from textile industries. For this purpose, four
different dyes like Brilliant Blue, Congo Red, Malachite Green and Rhodamine B, and two
metal salts nickel (II) chloride and cobalt (II) chloride have been chosen to examine their
absorption into the P gel matrix. When the aqueous solutions of various dyes (cationic,
anionic) and metal ions (Ni2+, Co+2) are applied over the gel, it efficiently absorbs the foreign
molecules from water within a few hours leaving almost colorless water. This indicates a
possible use of this gel in the wasteꢀwater treatment. Absorption of dyes and metal ions from
their respective aqueous solutions has been monitored by UVꢀvis spectroscopy and dye/metal
ion uptake capacities of the hydrogels have been determined by batch kinetic sorption
experiments. For this purpose, different sets of the gel were prepared in capped vials with 1
mg of the gelator (0.1% w/v) in 1 mL of buffer solution. Solutions of dyes (8 ꢁM) and metal
ions (10 ꢁM) are then pipetted onto the top of these gels in each set and allowed them to
stand for few hours. Time dependent absorption of the dyes and metal ions from their
corresponding aqueous supernatants has been monitored by UVꢀvis spectroscopy (Figure 5).
From this plot, it is observed that the intensity of absorption maxima decreases with time for
all the cases. After the application of the dye solutions over the gels, the absorption maxima
of the supernatant dye solution started to decrease after 15 min and the absorption intensity
continues to diminish before it reaches a saturation point after 60 hr (Figure 5aꢀd).
Incidentally, the hydrogel can absorb all the dye used here up to 60 hr (although with
different extent) before attaining a saturation limit (Figure 5aꢀd). On the other hand, in the
case of the metal ion solutions, this gradual reduction of absorption peak occurs up to 48 hr.
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Biopolymers: Peptide Science
Figure 5e,f indicates that after 48 hr almost complete metal ion absorption takes place. This
observation is possibly due to the binding of foreign substances (dye and metal ion) with the
hydrogel. This indicates the absorption of those molecules by the porous framework of the
gel. The capacity of a given amount of this gel for absorbing various dyes and metal ions are
quantitatively estimated and it is listed in Table 1.
Figure 5: UVꢀvis absorption study of the dyes and metal ions: (a) Brilliant Blue (b) Congo
Red, (c) Malachite Green, (d) Rhodamine B, (e) Co2+ ion, and (f) Ni2+ ion. For (a)ꢀ(d) the
concentration was 8 ꢁM and for (e), (f) the concentration was 10 ꢁM.
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Page 12 of 25
Name of the Dye/ metal
Dye/metal ion
absorption capacity per
gram of the gelator P
490 mg
Dye/ metal ion
ion
removal capacity
86%
92%
90%
78%
85%
92%
Brilliant Blue
Congo Red
Malachite Green
Rhodamine B
Co2+
650 mg
550 mg
320 mg
10 gm
Ni2+
11 gm
Table 1: The maximum absorption capacity of the dyes and metal ions by the hydrogel of
peptide P.
Reusability of hydrogel
So far, the hydrogel has been used as a purifier of wasteꢀwater containing industrial dyes and
metal ions. Apart from its cost effectiveness and absorbing ability, reusability of such useful
material is also important in order to its large scale utility. Industries produce gallons of
polluted water every day, so there is a genuine need of huge amount of hydrogel to clean up
the wastes. To check reusability, the gel was first treated with polluted water containing dyes
and metal ions. After effective absorption, the gel was taken out of the vial and treated with
saturated sodium biꢀcarbonate solution and extracted with ethyl acetate. As the metal ion and
dyes are highly soluble in water and remain in aqueous part, the gelator compound being
insoluble in such higher pH, goes to organic layer. The organic layer was separated, washed
with brine, dried and ethyl acetate is removed in vacuum to regain the solid product. Then
with the remaining compound, the hydrogel was again prepared and treated with wasteꢀwater.
It has been found that using the above stated method we can use the gelator molecule for
maximum three cycles. Figure 6 shows graphical representation of gelator compound
remained (in percent) with respect to number of cycles in case of Brilliant Blue dye and Ni2+
ion. Figure S5 in the supporting information represents the same plot for the other three dyes
(Congo Red, Malachite Green and Rhodamine B) and Co2+ ion.
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Biopolymers: Peptide Science
Figure 6: Bar diagram representation of reusability of gelator peptide P for the dye (a)
Brilliant Blue and the metal ion (b) Ni2+.
Conclusion
The work presented here vividly demonstrates the formation of a superhydrogel (with
very low concentration of the gelator molecule) from a selfꢀassembling Nꢀterminally free
dipeptide (HꢀLeuꢀPheꢀOMe) at phosphate buffer of pH 7.46. Interestingly, this hydrogel has
been used to efficiently absorb different types of toxic organic dyes (Brilliant Blue, Congo
red, Malachite Green, Rhodamine B) as well as heavy metal ions from (Ni2+ and Co2+) wasteꢀ
water within a few hours. Here, only a short dipeptide is required for making a hydrogelꢀ
based absorbent material and also very small amount of the dipeptide is enough to prepare
this superhydrogel. Moreover, the gelator can be efficiently reused several times without any
significant loss of activity. This makes preparation and use of this hydrogel easier and
profitable at the same time. Thus, it can be concluded that this short peptideꢀbased hydrogel
has wonderful applicability for removing toxic effluents from industrial wasteꢀwater in future
in a costꢀeffective manner.
Acknowledgement
N. N. and K. B. gratefully acknowledge CSIR, New Delhi, India and A. B. thanks IACS for
financial assistance. We acknowledge Rumana Parveen, Department of Organic Chemistry,
IACS and Department of Bioꢀtechnology (DBT), New Delhi (DBT project number:
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BT/01/CEIB/11/V/13) for allow us to use Anton Paar modular compact rheometer (MCR
102) for rheological measurement.
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Table of Content Figure
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