Carcinogenic direct azo dye removal from aqueous solution by amino-functionalized calix[4]arenes

Article abstract of DOI:10.1007/s10847-015-0518-7

This study contains a convenient synthesis and azo dye extraction efficiency of amino-functionalized calix[4]arene derivatives. Two calix[4]arene derivatives bearing alkyl amino groups on their upper and lower rim have been successfully synthesized and used as extractant for dye removal in liquid-liquid extraction system. The effect of electrolyte concentration, contact time, and pH on azo dye extraction was also investigated for all calixarene derivatives. From the results, it has been deduced that the amino-functionalized calix[4]arenes showed a better affinity than other parent calix[4]arenes towards the selected azo dyes.

Full text of DOI:10.1007/s10847-015-0518-7

J Incl Phenom Macrocycl Chem
DOI 10.1007/s10847-015-0518-7
ORIGINAL ARTICLE
Carcinogenic direct azo dye removal from aqueous solution
by amino-functionalized calix[4]arenes
1
1
Ezgi Akceylan
•
Serkan Erdemir
Received: 3 January 2015 / Accepted: 16 April 2015
Ó Springer Science+Business Media Dordrecht 2015
Abstract This study contains a convenient synthesis and
azo dye extraction efficiency of amino-functionalized cal-
ix[4]arene derivatives. Two calix[4]arene derivatives
bearing alkyl amino groups on their upper and lower rim
have been successfully synthesized and used as extractant
for dye removal in liquid–liquid extraction system. The
effect of electrolyte concentration, contact time, and pH on
azo dye extraction was also investigated for all calixarene
derivatives. From the results, it has been deduced that the
amino-functionalized calix[4]arenes showed a better affi-
nity than other parent calix[4]arenes towards the selected
azo dyes.
during the dyeing process [2–5]. In some cases water col-
oration can be observed in dye concentrations of less than
1 ppm [6, 7]. Many of these dyes are toxic, even carcino-
genic, persistent in the environment and non-biodegradable
[8, 9]. Consequently the wastewater effluents have become
a global issue, because the wastewaters are often heavily
contaminated with synthetic dyes which cause discol-
oration and high chemical oxidation demand (COD) mak-
ing the water unsuitable for drinking or other applications
[10, 11]. Another dangerous problem involving dyes is
exemplified with azo compounds that cause carcinogenic
and mutagenic effects [12, 13]. In attempting to remove
color from effluents, several methods can be applied, such
as membrane filtration related to nanofiltration, biological
treatment, coagulation/flocculation, reverse osmosis, elec-
tro dialysis, ion exchange, sorption techniques [14–18].
Liquid-phase extraction (LPE) due to its high extraction
efficiency has been proved as an effective and attractive
process for the decontamination of the dye-containing
effluents.
Keywords Calix[4]arene Á Carcinogens Á Azo dye Á
Liquid–liquid extraction
Introduction
Environmental problems have become increasingly critical
and frequent, due to population growth and increased in-
dustrial activity associated with contamination of natural
waters which is one of the major problems of modern so-
ciety [1]. Chemicals such as dyes and pigments are widely
used for coloring in various sectors of industry including
textile manufacture, leather tanning, paper production, food
technology and cosmetics manufacture. The annual pro-
In this respect, the supramolecular chemistry has pro-
vided a much better solution to search for molecular
structures that can serve as building blocks for the pro-
duction of sophisticated molecules by anchoring functional
groups oriented in such a way that they provide a suitable
binding site for dyestuff. This was achieved with the de-
velopment of macrocyclic molecules such as synthetic
crown ethers, cryptands, natural cyclodextrins and cal-
ixarenes [19–24].
5
duction of dyes and pigments is in excess of 7 9 10 tones,
of which an estimated 2–15 % are lost in the effluent
Calix[n]arenes are a class of cyclooligomers formed via
a phenol–formaldehyde condensation. They exist in a ‘cup’
like shape with a defined upper and lower rim and a central
annulus. Their rigid conformation enables calixarenes to
act as host molecules because of their preformed hy-
drophobic cavities. Also, they can be easily functionalized
&
Ezgi Akceylan
eakceylan@gmail.com
1
Department of Chemistry, Selcuk University, 42075 Konya,
Turkey
123

J Incl Phenom Macrocycl Chem
both at the phenolic OH groups (lower rim) and, after
partial removal of tert-butyl groups, at the para positions of
the phenol rings (upper rim) [23]. A polar lower rim
composed of phenolic oxygens was extensively derivatized
to bind and transport ionic species. The upper rim is a
shallow bowl lined with aromatic rings that can encapsu-
late small organic molecules or a polar section of larger
compounds. Due to this ability to form host–guest type
complexes with a variety of organic and inorganic com-
pounds the calixarenes have received increasing attention
during the last two decades [25–28].
monomer analog of 5 were synthesized according to the
reported literature procedure [23, 29, 30] while compound
3 is reported for the first time.
Synthesis of compound 3
To a solution of 25,27-bis(3-bromopropoxy)-26,28-dihy-
droxycalix[4]arene (2) (6.0 mmol) in CH CN (100 mL)
3
were added NaI (12 mmol) and 4-benzylpiperidine,
(30 mmol) and the reaction mixture was stirred and heated
at reflux. The reaction was monitored by using a TLC.
After 72 h, the reaction mixture was filtered and the solvent
was removed under reduced pressure. The residue was
dissolved in CH Cl (150 mL) and the organic layer ex-
Previously, we have reported [26, 28] the synthesis and
inclusion abilities of mannich base and crown ether
derivatives of calix[4]arene for some water-soluble azo
dyes. In this paper, we synthesized two calix[4]arene
derivatives bearing alkyl amino groups on their upper and
lower rim and investigated their extraction efficiency to-
wards the selected azo dyes from aqueous media in liquid–
liquid extraction system.
2
2
tracted three times with water. The combined organic
phases were dried over anhydrous MgSO , the solvent was
4
removed under reduced pressure. Compound 3 was ob-
-
1
tained in 72 % yield; m.p. 145 °C. FT-IR (cm ); 2916,
-
1 1
1602, 1583, 1450, 1144 cm . H NMR (CDCl ): d (ppm):
0
3
t
t
.9 (s, 18H, Bu), 1.27 (s, 18H, Bu), 1.7–1.91 (m, 12H,
OCH CH CH N, NCH CH ), 1.99–2.1 (m, 2H, CHCH
2-
2
2
2
2
2
Materials and methods
General
Ar), 2.61 (d, 4H, CHCH Ar), 3,32 (d, 4H, ArCH Ar),
2 2
4
.05–4.2 (m, 8H, ArCH Ar, OCH CH CH ), 6,97 (s, 4H,
2 2 2 2
1
3
ArH), 7,07 (s, 4H, ArH), 7.12–7.3 (m, 10H, ArH).
C
NMR (CDCl ): d (ppm): 25.5, 31.2, 32.1, 32.4, 32.9, 35.3,
3
1
H NMR spectra were recorded with a Varian 400 MHz
37.1, 44.4, 47.2, 51.5, 77.6, 125.4, 125.7, 126.1, 129.3,
129.6, 133.7, 134, 138.6, 150.1, 151.7. Anal. calcd for:
C H O N : C, 82.33; H, 9.15; N, 2.59 %. Found: C,
spectrometer in CDCl . FT-IR spectra was recorded with a
3
Perkin Elmer spectrum 100. Elemental analyses were
performed on a Leco CHNS-932 analyzer. UV–Visible
spectra were obtained on a Shimadzu 160A UV–Visible
spectrophotometer. Thermal gravimetric analysis (TGA)
was carried out with Setaram thermogravimetric analyzer.
The sample weight was 15–17 mg. Analysis was per-
formed from room temperature to 900 °C at heating rate of
7
4 98 4 2
82.39; H, 9.20; N, 2.60 %.
Liquid–liquid extraction
The liquid–liquid extraction studies were carried out to
evaluate the efficiency of synthesized calix[4]arenes (1–5)
to remove the CSB and TP dyes from aqueous media.
Various parameters such as pH, contact time, and effect of
electrolyte were also optimized. For liquid–liquid extrac-
1
0 °C/min in argon atmosphere with a gas flow rate of
0 mL/min. All aqueous solutions were prepared with
2
deionized water that had been passed through a Millipore
milli Q Plus water purification system. All chemicals used
were of analytical grade and purchased from Merck or
Aldrich and used without further purification. Two com-
mercial textile dyes Chicago Sky Blue (CSB) (kmax
-
5
tion, 10 mL dye solution (2 9 10 M) and 10 mL of li-
-
3
gand solution (1 9 10 M in CH Cl ) were taken in a
2
2
50-mL stoppered erlenmeyer flask and vigorously agitated
with a mechanical shaker for 1 h. To obtain extraction
equilibrium, the erlenmeyer flasks were stirred on a
horizontal shaker operating with a constant speed
(170 rpm) at 25 °C. Finally, dyes concentration before the
treatment as well residual concentration of dyes in aqueous
phase after the treatment was analyzed through UV–Vis
spectrophotometer at 615 and 485 nm for CSB and TP
dyes, respectively. The percent extraction (E%) has been
calculated as:
6
15 nm) and Tropaeolin 000 (TP) (kmax 485 nm) were
purchased from (Aldrich; Steinheim, Germany). The pH of
the solution was adjusted by mixing appropriate amount of
HCl and/or NaOH (0.1 N).
Synthesis
The synthesis of compounds, p-tert-butylcalix[4]arene (1),
5,27-bis(3-bromopropoxy)-26,28-dihydroxycalix[4]arene
2
(
2), calix[4]arene (4) and 25,17-bis-[(4-benzyl piper-
idine)methyl]-25,26,27,28-tetrahydroxy-calix[4]arene (5)
and 4-((4-benzylpiperidin-1-yl)methyl)phenol (6) as the
ꢀ
ꢁ
ðC0 À CÞ
C0
E% ¼
 100
1
23

J Incl Phenom Macrocycl Chem
where C and C are initial and final concentrations of the
0
was assigned to the equatorial protons of the methylene
azo dyes before and after the extraction, respectively.
groups, whereas the low field signals at d 4.09 ppm was
assigned to the axial protons in the H NMR.
1
Results and discussion
Synthesis
Liquid–liquid extraction studies of selected dyes
Since removal of azo dyes from aqueous media is envi-
ronmentally important, their extraction from aqueous
samples was investigated. Azo dyes are expected to form
inclusion complexes with amino-substituted-calix[4]arene
(3 and 5). Liquid–liquid extraction of water soluble azo
dyes (CSB and TP) (Fig. 2) by calixarene derivatives was
conducted. Also, to avoid the influence of solubility of dyes
The synthetic route for the preparation of calix[4]arene
derivatives is described in Scheme 1. The synthesis of
compounds 1, 2, 4 and 5 was realized according to previ-
ously published procedures [23, 29]. Otherwise, the di-
amine derivative of calix[4]arene 3 was synthesized by
reacting of the dialkyl bromide derivative of p-tert-butyl-
in CH Cl , the blank experiments were performed without
2 2
calix[4]arene 2 and 4-benzylpiperidine in the presence of
1
NaI in CH CN. Compound 3 was characterized by H
calixarene derivatives at different pH. The extraction pro-
cedure was schematically depicted in Fig. 3. The results of
the extraction studies are summarized in Tables 1 and 2.
These data were obtained using a dichloromethane solution
of the extractant to remove the azo dye from an aqueous
phase. The residual concentration of azo dye in the aqueous
phase was then determined spectrophotometrically. Also,
3
1
3
1
NMR C NMR, FT-IR, and elemental analyses. H NMR
data showed that compound 3 was in the cone conforma-
tion (Fig. 1). A typical AB pattern was observed for the
methylene bridge ArCH Ar protons at d 3.32 and 4.09 ppm
2
1
for 3 in H NMR. The high field doublets at d 3.32 ppm
Scheme 1 A schematic representation of the synthesis of calix[4]arene diamine derivatives
123

J Incl Phenom Macrocycl Chem
1
Fig. 1 H NMR spectrum of compound 3 in CDCl
3
Fig. 2 The chemical structures
of some selected azo dyes used
in experiments
the influence of various parameters such as electrolyte
concentration, contact time, and pH on the removal of se-
lected azo dyes was examined.
the solution and the dissociation of functional groups on
the active sites of the extractant [31]. Therefore, the in-
fluence of pH on the percent extraction of CSB and TP
dyes was studied and the results were given in Tables 1 and
2. These results indicated that the parent calix[4]arenes (1,
pH effect on the extraction of azo dyes
2
and 4) have less sorption capacities for selected azo dyes.
The value of pH was known as one of the most important
role in separation science because the pH of the solution
affects both degree of ionization of the material present in
The percentage of CSB extracted was reached maximum
that 91 % for 3, and 99 % for 5 when the pH of the aqueous
solution was 3.0. Also, the monomer analog 4-((4-
1
23

J Incl Phenom Macrocycl Chem
Fig. 3 Schematic illustration of removal of azo dye from aqueous solution by compound 3
1
1.0. The results (Table 1) revealed that the significant
Table 1 Percent sorption of Chicago Sky Blue (CSB) by cal-
ix[4]arenes (%)
extraction of the CSB azo dye for 3 occurs in a pH 3.0. On
the other hand, the pH effect on the percent extraction of
TP dye was summarized in Table 2. As seen Table 2, the
percent extraction attained a maximum value 99 % at pH
3.0–9.0 for compound 3 and 5. The lower sorption rates at
pH
3.0
5.0
7.0
9.0
11.0
Calix-ligand-1
Calix-ligand-2
Calix-ligand-3
Calix-ligand-4
Calix-ligand-5
Ligand-6
5
3
6
8
7
5
4
3
3
2
-
91
5
43
4
37
4
25
4
19
4
alkaline pH ([9.0) are due to the presence of excess OH
ions competing with the dye anions for the sorption sites.
As the pH of the system increases, the number of
negatively charged sites increases as well, and the number
of positively charged sites decreases. A negatively charged
surface site on the adsorbent does not favor the adsorption
of dye anions due to electrostatic repulsion [32]. In the
extraction of CSB, the cavity sizes of hosts (3 and 5) are
prominent as well as pH. Since the tert-butyl groups in
compound 3 induce a steric hindrance, compound 3 inter-
acts weaker with CSB having a large size compared with
that of TP.
99
25
2.6
99
16
2.1
98
13
1.8
97
12
\1.0
8
4
Blank
\1.0
-
5
Aqueous phase, azo dye (CSB): 2.0 9 10
3
, organic phase
-
(
dichloromethane), ligand: 1.0 9 10 , 25 °C, 1 h
Table 2 Percent sorption of Tropaeolin 000 (TP) by calix[4]arenes
%)
(
pH
3.0
5.0
7.0
9.0
11.0
The higher level of dye removal by compound 3 and 5
compared with the parent calix[4]arenes (1, 2 and 4) suggest
that a Coulomb interaction exist between the amino groups
of calix[4]arene and the sulfonate groups of azo dyes
Calix-ligand-1
Calix-ligand-2
Calix-ligand-3
Calix-ligand-4
Calix-ligand-5
Ligand-6
5
5
6
5
3
4
5
5
6
2
99
5
99
5
99
5
99
4
51
2
(Fig. 4). Alkylamino groups of calix[4]arenes (3 and 5) form
99
29
2.8
99
21
2.4
99
19
2.1
99
15
\1.0
29
10
\1.0
intermolecular hydrogen bonds to these sulfonate groups.
The molecular recognition mechanism between host and
guest related to the geometrical shape, size of the guest, the
polar, and the cavity size of host, which were important
factor of forming host–guest inclusion complexes. The
complex interaction was attributed to the weak forces in-
cluding hydrogen bonding, hydrophobic interaction, elec-
trostatic interaction, p–p and dipole–dipole interactions.
The thermal stability of the compound 5 and its Tropae-
olin complex was evaluated by TGA. It was found that 5
undergo a three-step thermal degradation (Fig. 5). At the first
decomposition step, the functional groups of 5 left from the
Blank
-
Aqueous phase, azo dye (TP): 2.0 9 10 , organic phase (dichlor-
5
-3
omethane), ligand: 1.0 9 10 , 25 °C, 1 h
benzylpiperidin-1-yl)methyl)phenol 6 did not show any
extraction ability compared to that of 5. The results show
that the macrocyclic structure of calixarenes is essential for
the recognition of an azo dye. The extraction of CSB dye
for 3 was decreased when the pH increased from 3.0 to
123

J Incl Phenom Macrocycl Chem
Fig. 4 Proposed complexation
models between compound 3
and azo dye (CSB)
Fig. 5 TG and their 1st
derivatives (dTG) of pure
calixarene derivative (5) and
calixarene derivative 5 treated
with TP
main structure at 150–340 °C. The mass loss of within the
temperature range 350–620 °C may be attributed to the loss
of the calixarene backbone. The TGA result of the 5 showed
the weight loss peak temperatures at 243 and 379 °C shifted
to 350 °C in the Tropaeolin complex of 5 (Fig. 5). These
results indicated that there is a remarkable interaction be-
tween the calixarene and the azo dye.
separation sciences. NaCl provides an ionic balance be-
tween the two phases. Furthermore, NaCl increases the
solubility of azo dyes through the common ion effect,
resulting in an increased and facilitated transport to the
organic phase [33–35]. The molar concentration of NaCl
-
1
was varied as 0.1, 0.2 and 0.4 mol L . Figure 6 obvi-
ously demonstrates that dyes’ extraction efficiency im-
proved remarkably by increasing the ionic strength up to
-
1
Influence of the NaCl concentration
on the extraction of azo dyes
0.2 mol L , beyond which the dyes’ extraction effi-
ciency once again tend to decrease. The decrease in
percent extraction of CSB and TP dyes beyond the
-
1
Dye extraction strongly depends on the ionic strength
because the influence of electrolyte plays a key role on
0.2 mol L concentration of NaCl is may be due to the
commutative ion interferences.
1
23

J Incl Phenom Macrocycl Chem
Fig. 6 Effect of NaCl concentration on extraction of CSB (a) and TP (b) dye
Effect of contact time
The equilibrium time between the pollutant and the ex-
tractant is of significant importance during the extraction
process. For an efficient extractant, it is obligatory to show
a rapid uptake of the pollutants and reach the equilibrium
in a short time. Hence, the effect of shaking time on the
extraction of azo dyes by compound 3 and 5 was studied at
2
5 °C. The results are depicted in Figs. 7 and 8. The ob-
tained results showed that percent extraction of azo dyes
increased rapidly in the beginning and rapid equilibrium
was established within 15 min, but slowly, it increased up
to 30 min.
Fig. 8 Effect of contact time on percent extraction of CSB and TP by
compound 5 (pH 3.0, NaCl: 0.2 mol L
-1
)
Conclusion
electrolyte concentration, contact time, and pH were in-
vestigated in extraction experiments. The results achieved
from the present study clearly showed that 3 and 5 are very
efficient extractants for the removal of selected dyes as
compared to other parent calix[4]arenes. During the ex-
traction process, various kinds of interactions such as
dipole–dipole, electrostatic repulsion, hydrogen bonding
and p–p interaction between the azo dyes and calix[4]arene
molecules due to the formation of an inclusion complex by
host–guest type interaction and dissociation of azo dyes
into anions/cations were monitored and found that extrac-
tion is highly dependent on pH and salinity concentration.
In this study we have reported the synthesis and charac-
terization of a novel amino functionalized p-tert-butylcal-
ix[4]arene derivative (3). The prepared calix[4]arene
derivatives (3 and 5) were used as the extractants towards
the selected azo dyes (CSB and TP) in liquid–liquid ex-
traction. Also, the influence of various parameters such as
Acknowledgments We thank the Scientific Research Projects
Foundation of the Selcuk University (BAP) for financial support of
this work.
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