Synthesis, characterization and applications of polymer-metal chelates derived from poly[((4-acryloxy acetophenone)-divinylbenzene)] benzoyl hydrazone resins

Article abstract of DOI:10.1007/s12039-014-0611-2

4-Acryloxy acetophenone was prepared and subjected to suspension polymerization with divinylbenzene as a cross-linking agent. The resulting network polymer was ligated with benzoyl hydrazone. The functional polymer was treated with metal ions [Cu(II), Fe(

Full text of DOI:10.1007/s12039-014-0611-2

c
J. Chem. Sci. Vol. 126, No. 3, May 2014, pp. 597–608. ꢀ Indian Academy of Sciences.
Synthesis, characterization and applications of polymer-metal chelates
derived from poly[((4-acryloxy acetophenone)-divinylbenzene)]
benzoyl hydrazone resins
THAMMISETTY RAVI SANKAR, K KESAVULU and PEDDAKOTLA VENKATA RAMANA∗
Department of Chemistry, Sri Krishnadevaraya University, Anantapur 515 003, India
e-mail: ramanapv2103@yahoo.com
MS received 5 August 2013; revised 21 September 2013; accepted 14 December 2013
Abstract. 4-Acryloxy acetophenone was prepared and subjected to suspension polymerization with divinyl-
benzene as a cross-linking agent. The resulting network polymer was ligated with benzoyl hydrazone. The
functional polymer was treated with metal ions [Cu(II), Fe(II)]. The polymer-metal complexes obtained
were characterized by elemental analysis, IR, 1H-NMR, solid state 13C cross-polarization magic-angle spin-
ning (CP/MAS) NMR, electron paramagnetic resonance (EPR), thermogravimetric and scanning electron
microscopy (SEM) studies. The maximum uptake efficiency for the metal ions was determined. The reusability
of the polymer ligand was tested and it was shown that even after four cycles, the efficiency of the uptake was
not altered.
Keywords. 4-Acryloxy acetophenone; divinyl benzene; functionalized polymers; polymer-metal complexes;
chemical modification; suspension polymerization; cross-linkage agent; network polymer.
1. Introduction
hydrogenation reaction. The complexes obtained from
maleic acid-styrene, acrylic acid-vinyl pyrrolidone
copolymers and nickel(II), platinum(II) and palla-
dium(II) metal ions were found to be useful catalysts for
the hydrogenation of 2-chloro-4-nitrotoluene,10 while
copper(II) chelates synthesized from chloromethylated
polystyrene were reported11 to catalyse Diels–Alder
cyclization reactions. A survey of the literature reveals
that hydrazones derived from low molecular weight
aromatic ketones like acetophenone and benzophe-
none draw the attention of synthetic chemists due to
their varied biological activities.12–14 Hydrazones also
find their application in analytical chemistry. They act
as multidentate ligands with metals forming coloured
chelates. These chelates are then used in selective
and sensitive determination of metal ions.15–19 With a
view to the complexing abilities of hydrazone deriva-
tives and in a program to develop selective resins,
acetophenone hydrazone incorporated into the poly-
mer, the 4-acryloxyacetophenone (AAP) cross-linked
with divinylbenzene (DVB) was selected. The benzoyl
hydrazine (BH) derivative of the cross-linked copoly-
mer acts as insoluble polymeric ligand towards Cu(II)
and Fe(II) ions. We report here the preparation, char-
acterization and applications of hydrazone derivatives
of poly[((AAP)-DVB)] towards Cu(II) and Fe(II) ions.
The metal uptake efficiency and reusability of the resin
are studied.
The interaction between metal ions and polymerized
ligands may lead to the formation of coordination poly-
mers in which the chelated metal ions are bounded
by ligand molecules.1,2 Anchoring reagents to insolu-
ble supports has come to be known as solid phase syn-
thesis based on the pioneering efforts of Merrifield3
in polypeptide synthesis. Rapid developments now
not only make polypeptide synthesis on polymer sup-
ports, but immobilized photosensitizers and immobi-
lized transition metal complexes are also frequently
reported.4 Polymer-metal complexes have been of inter-
est to many chemists, because not only they are excel-
lent models for metalloenzymes, but they have also
led to developments in metal ion separation and reco-
very of metal ions. Increasing environmental concerns
in waste-water treatment has led to the use of organic
ligands anchored to solid supports in order to remove
and recover important metal ions from aqueous
solutions.5–7 Copolymers of activated meth(acrylates)
have been utilized to synthesize macromolecular drug
carriers.8 Wang et al.9 have indicated that the polymeric
support and the polymeric end groups affect the cata-
lytic activity and selectivity of these complexes in
∗For correspondence
597

598
Thammisetty Ravi Sankar et al.
collected. The filtrate which contains the monomer is
2. Experimental
washed with aqueous 5% NaOH followed by water.
Then the filtrate is extracted with ether and the sol-
vent evaporated to get the monomer. The formation
2.1 Physico-chemical measurements
Elemental analysis of the cross-linked copolymers and
their metal complexes were carried out on Thermo
Finningan FLASH EA 1112 CHNS analyzer. The
IR spectra were recorded on Perkin-Elmer IR spec-
1
of AAP is confirmed by IR and H NMR. The spec-
tral data is consistent with the structure of monomer.
m.p. 52–54◦C. IR (cm−1, KBr): 3022 (Ar C–H stretch-
ing), 2934 (methylene C–H stretching), 1745 (ester car-
bonyl), 1654 (C=O stretching in keto carbonyl) 1602
(C=C skeletal vibration), 1165 (C–O stretching in ester)
1H NMR (δ ppm): 2.4 (3H, s, CH3-), 5.2–6.5 (3H,
CH2=CH protons), 6.8 and 7.8 (4H, Ar-H).
1
trophotometer model 983 G using KBr pellets. H
and 13C nuclear magnetic resonance (NMR) spectra of
the samples were run on a dpx 200 MHz in CDCl3
with tetramethylsilane (TMS) as internal standard.
13C cross-polarization magic-angle spinning (CP/MAS)
NMR spectra were recorded on a Bruker-dsx-300 MHz
CP/MAS at Indian Institute of Science, Bangalore. A
Perkin Elmer model 3700 with TGA-7 computer and
a Mettler TA 3000 system were used to evaluate the
thermal stability and decomposition temperature of the
copolymers and their metal complexes. EPR spectra
of the copolymer metal complexes were recorded on
varion E-4X band spectrophotometer at 303 K. Parti-
cle size distribution of copolymer beads were studied
with Malvern particle size analyzer by laser diffrac-
tion method. The sample was dispersed in paraffin oil.
Scanning electron microscopy (SEM) was carried out
using a JEOL-JSM 840 model. The copolymer was
coated with gold. An ELICO UV-VIS SL 164 double
beam spectrophotometer is used for absorbance measu-
rements. The pH measurements were made with ELICO
digital pH meter having a glass electrode model LI 127.
Standard salt solutions were prepared by taking req-
uisite amounts in 50 ml double distilled water and stan-
dardized by the known methods.20 Buffer solutions of
pH range 3–6 were prepared from 1 M acetic acid
and 1 M sodium acetate solution. Buffer solutions of
pH range 8–10 were prepared from 1 M ammonium
hydroxide and 1 M ammonium chloride.
2.3 Polymerization of monomer
Bead polymerization of the monomer (30 g) was car-
ried out at 80 1◦C using polyvinyl alcohol (PVA) as
the stabilizer and BPO as catalyst in a four-necked reac-
tion kettle fitted with a water condenser, a synchro-
nized mechanical stirrer, a dropping funnel and a nitro-
gen inlet. A controlled stirring rate of 400 rpm was
maintained for 12 h DVB (5.2 g) was added as the
cross-linking agent. The beads formed were filtered,
washed with petroleum ether, 2-butanone, acetone, di-
chloromethane to remove the unreacted monomer and f-
inally with water to remove PVA. The product was dried
in a vacuum oven at 30◦C and obtained an yield of 68%.
2.4 Functionalization of polymer
Functionalization of poly[((AAP)-DVB)] was achieved
by incorporating benzoyl hydrazine (BH) moiety
through a post-polymerization reaction in a state of dis-
persion. Cross-linked polymer (5 g) and BH (10 g)
in dimethylformamide-water (DMF-H2O) mixture (1:1)
were placed in a 500 ml round-bottomed flask and
refluxed for 12 h. The contents were filtered and the
functionalized beads were collected, washed with DMF,
ethyl acetate and water (scheme 1).
2.2 Preparation of monomer
To a solution of 4-hydroxyacetophenone (0.2 mol) in 2–
butanone, triethylamine (TEA) (0.2 mol) was added and
2.5 Preparation of metal complexes
stirred at 0–5◦C. Thermometer and mechanical stirrer 5 g of metal salts (CuCl2. 2H2O or (NH4)2Fe(SO4)
and dropping funnel are arranged. To this mixture, acry- 2.6H2O, respectively, in a DMF-H2O (1:1) were treated
loyl chloride (0.2 mol) in ether was added in a period with 5 g of a functionalized polymer and refluxed for
of 60 min. The condensation of acryloyl chloride with 10 h in double-distilled water at a pH of 6.9 0.1. The
4-hydroxyacetophenone liberates hydrochloride, which reaction mixture was filtered and the resulting green
is adsorbed by TEA, which ultimately results into the [Cu(II)] and brown [Fe(II)] metallated polymers were
quaternary salt (TEA hydrochloride). This quaternary washed in hot water, ethyl acetate, acetone and dried in
salt is filtered and washed with ether and the filtrate a vacuum oven at 60◦C.

Acryloxy acetophenone-divinylbenzene co-polymer resins
599
2.6 Physical properties
2.7 Chemical analysis
Both the polymer metal complexes are insoluble in The metal contents in the polymer-metal complexes
common organic solvents and non-hygroscopic in were estimated titrimetrically after acid treatment of the
nature.
complexes.20
H2C
H
C
OH
CO
O
Cl
(i)DVB
TEA
0 - 50C
CH2
+
O
(ii)BPO, PVA
(iii)80 +1oC,
400 rpm, 12h
H3C
C
O
H3C
C
O
H
[
[
]
H2C
CH2
]
CH
C
n
m
CO
O
O
C
(i)
N
H2
N
H
(ii)DMF-H2O(1:1)
H3C
C
O
CH
CH2
H
[
]
[
]
H2C
CH2
CH
C
m
n
CO
O
(i) Metals Cu, Fe
(ii)DMF-H2O(1:1)
Metal complex
H3C
C
N
CH CH2
C
O
H
N
Scheme 1. Synthesis of title compounds.

600
Thammisetty Ravi Sankar et al.
Table 1. Elemental analysis of poly[((AAP)-DVB)], poly[((AAP)-DVB)]-BH functionalized polymer and metal chelates.
Found %
Element Poly[((AAP)-DVB)] Poly[((AAP)-DVB)]-BH Poly[((AAP)-DVB)]-BH -Cu(II) Poly[((AAP)-DVB)]-BH -Fe(II)
C
H
N
Metal
68.95
6.27
–
71.62
6.73
4.58
–
69.37
6.52
1.64
1.75
67.26
6.37
1.73
1.58
–
52*
*indicates the percentage of conversion
3. Results and discussion
changes in amide group vibrations suggest amide oxy-
gen coordination in keto form. The band observed at
around 590 cm−1 is assigned to νCu-N vibrations. It is
therefore inferred that the ligands coordinate in biden-
tate fashion. The IR spectrum of functionalized copoly-
mer shows intense band at 1651 cm−1 due to C=O
stretching in hydrazone and its downward shift in Fe(II)
complex suggest coordination of metal ion through
oxygen atoms. There is a downward shift of C=N vibra-
tion of azomethine from 1632 to 1610 cm−1 which indi-
cates the coordination of azomethine nitrogen atom.
Thus, in each complex the metal atom binds to the lig-
and through azomethine nitrogen and hydrazone car-
bonyl oxygen atoms.
3.1 Elemental analysis
Elemental analysis data is presented in table 1. The data
show that the conversion of keto carbonyl groups to
hydrazone function was 52% by weight (only the sur-
face keto groups were converted to benzoyl hydrazone).
The remaining keto groups, deeply buried in the poly-
mer chains were unaffected. Metallation was 28 and
30%, respectively for Cu(II) and Fe(II) complexes.
3.2 IR spectral studies
The IR spectrum of poly[((AAP)-DVB)] copolymer
shows absorption band at around 2929 cm−1, which has
been identified as -CH backbone methylene stretching
vibrations. The ester carbonyl is identified through the
appearance of a strong absorption band at 1732 cm−1.
A strong absorption around 1600 cm−1 is due to C=C
stretching vibration of the phenyl rings. The (C–O–
C) stretching vibrations in compound are confirmed by
a band at 1170 cm−1. The keto carbonyl functiona-
lity is identified by a sharp absorption band around
1651 cm−1.21–23 The formation of hydrazone is con-
firmed by a set of distinct vibrations at 3350 and
1632 cm−1 which are due to –NH, and C=N stretch-
ing, respectively. The disappearance of the band at
1651 cm−1 indicates the removal of carbonyl function
of ketone units. The appearance of a new absorption
band at 1685 cm−1 is due to C=O group of benzoyl
hydrazine moiety with a shoulder at 1660 cm−1. The
shoulder that appears at 1660 cm−1 is due to the inner
keto groups present in poly[((AAP)-DVB)] copoly-
mer. The FTIR spectra of poly[((AAP)-DVB)] copoly-
mer and its benzoyl hydrazine functionalized resins are
shown in figure 1. The Cu(II) complex shows peak at
1602 cm−1, which are lowered from 1632 cm−1 (C=N
(a)
(b)
Wave number, cm 1
str.), in functionalized resin. Amide group vibrations Figure 1. FTIR spectra of (a) poly[((AAP)-DVB)]; (b)
increase in frequency from 1505 to 1520 cm−1. These
poly[((AAP)-DVB)]-BH resins.

Acryloxy acetophenone-divinylbenzene co-polymer resins
601
3.3 Solid State 13C CP–MAS NMR spectroscopy
The 13C CP-MAS NMR spectrum of benzoyl hydra-
zone derivative of poly[((AAP)-DVB)] [cf. figure 3b]
shows an intense peak at 41.44 is attributed to the back-
bone carbons. The aromatic carbons of solid sample
gave only a sharp intense line at 128.25 ppm with a
shoulder at 122.86 ppm. The phenyl ester carbonyl gave
medium intense peak at 173.62 ppm. The disappearance
of peak at 196.72 ppm indicates the absence of ketonic
carbon atom of acetophenone unit. This clearly explains
the formation of benzoyl hydrazone derivative. Due to
residual broadening, a clear separation of the signals is
not observed in the spectrum.
In the present investigation in addition to elemen-
tal analysis and FT IR spectroscopy, 13C CP–MAS
NMR24–26 is used for identifying the polymer units.
The sample is spun at two different spins and by com-
paring the two spectra, the spinning side bands are
eliminated. The 13C CP–MAS of cross-linked copoly-
mer has been compared with its soluble homopoly-
mer analogue. Proton decoupled spectra of homopoly-
mer is taken in CDCl3 solution. The 13C NMR spec-
tra of AAP homopolymer and 13C CP–MAS of cross-
linked copolymers are shown in figures 2 and 3a,
respectively. The backbone 1C and 2C carbons of
homopolymer appeared as clear distinct lines at 46.15
and 37.93 ppm, respectively. In the case of cross linked
copolymer, the intense peak at 41.17 is attributed to
the backbone carbons. Because of the residual broad-
ening, the peaks due to methylene and methyl car-
bons are not clearly resolved. The ketonic carbonyl
of AAP appeared at 198.71 ppm as sharp intense line
in homopolymer, whereas in cross-linked polymer it
appeared at 196.72 ppm as a medium intense peak. The
phenyl ester carbonyl27 gave sharp line at 175.21 ppm
in homopolymer and as a sharp peak in cross-linked
system at 172.59 ppm. The 4C of phenyl ring appeared
3.4 EPR spectroscopy
EPR parameters gave a measure of the nature of the
complexation with the metal ion. Anisotropic spec-
tra are obtained for polychelates in crystalline state at
303 K. The gꢁ and g⊥ are computed from the spectra
using DPPH free radical as g marker. For the covalent
complexes, g is less than 2.3 and for ionic environ-
ment it is normally 2.3 or larger.28 The values gꢁ and
g⊥ for Cu(II) complex was 2.20 and 2.04, thereby indi-
cating covalent character for the metal–ligand bond in
the complex. The EPR signal corresponding to Fe(II)
complex is not observed.
A survey of the literature reveals that Cu(II) and
NI(II) metal complexes of poly(salicylaldehyde
acrylate)-divinylbenzene semicarbazone resin29 exhibit
paramagnetic property. The nature of metal–ligand
bond was reported to be covalent in these complexes.
Similarly, Ni(II) complex of poly(2-hydroxy-4-
methacryloyloxy acetophenone-formaldehyde) was
5
9
6
8
at 154.68 ppm. The C and C, C and C aromatic
carbons of homopolymer gave sharp lines at 134.64
and 129.92 ppm. The line observed at 135.54 ppm is
attributed to 7C of aromatic ring. In the case of 13C CP–
MAS NMR, because of residual broadening the clear
splitting of aromatic signals are not observed. The aro-
matic carbons of solid sample gave only a sharp intense
line at 129.29 ppm with a shoulder at 122.45 ppm.
1
2
]
[
CH2
CH
n
3
CO
O
4
5
6
9
8
7
C
10
CH3
11
O
Figure 2. 13C NMR spectrum of poly(4-acryloxy acetophenone) [homopolymer].

602
Thammisetty Ravi Sankar et al.
(a)
(b)
Figure 3. 13C CP–MAS of (a) poly[((AAP)-DVB)]; (b) poly[((AAP)-DVB)]-BH resins.
also reported30 to exhibit paramagnetic behaviour with
a distorted octahedral geometry.31 Hence, based on the
covalent nature of the metal–ligand bond observed in
the present studies and also based on the reports made
in the literature,29–31 octahedral geometry is suggested
for the complexes.
3.5 Thermogravimetric analysis
In order to study the thermal stability and decomposi-
tion pattern of cross-linked copolymers, dynamic ther-
mogravimetric analysis is under taken32 and the data
presented in the table 2 and thermograms are shown

Acryloxy acetophenone-divinylbenzene co-polymer resins
603
Table 2. TG data of poly[((AAP)-DVB)], poly[((AAP)-DVB)]-BH functionalized polymer and metal chelates.
Weight loss (%) at temperature (◦C)
Sl. no. System
IDT’s 250 300 350 400 450 500 550 600 650 700
1
2
3
4
Poly[((AAP)-DVB)]
Poly[((AAP)-DVB)]-BH
Poly[((AAP)-DVB)]-BH-Cu(II) chelate 290
Poly[((AAP)-DVB)]-BH-Fe(II) chelate 295
176
220
7.8 12.5 27
50 61.7 80.8 90 91.8 96
–
–
96
98
6.4
4.7
15 25.5 45 55.7 80 89 91.5 94
9
29.5 71.4 78
82
84
91
95
94
97
5.4 10.4 27.5 76
80 89.5 92
in figure 4. The thermograms of the copolymer and chain accompanied by the volatilization of the cleaved
its functionalized resins are run in air atmosphere. The products.
degradation of poly[((AAP)-DVB)] occurred in two
stages. The first stage decomposition is observed from
3.6 Particle size analysis
176 to 444◦C and the weight loss found was 60%. The
second stage degradation of the copolymer resin was in
The success and reproducibility of the suspension poly-
the temperature range of 444–604◦C. The weight loss
merization is determined by measuring the average par-
involved in this stage was 27.7%.
ticle size of the beads formed.33,34 The particle size dis-
The BH derivative also decomposed in a two-stage
tribution of the AAP–DVB copolymer is determined by
process. The first stage of decomposition commenced at
Malvern particle size analyzer. The different classes of
220 ◦C and was completed at 430◦C. The initial weight
the particle sizes and percentage bands of the particles
loss is 53%. The second stage of decomposition was in
are presented in table 3. The average particle size of
the system is 86.12 μm and the distribution curve is
relatively broad. The particle size distribution curve is
shown in figure 5.
the temperature range 430 and 594◦C and the weight
loss was 45.6%.
The thermal degradation data of BH functionalized
poly[((AAP)-DVB)] Cu(II) and Fe(II) metal complexes
is presented in table 2. The initial decomposition data of
Cu(II) and Fe(II) complexes are 290 and 295◦C, respec-
tively. The degradation occurs mainly in two stages
and decomposition is fast up to 400◦C. The first stage
of decomposition is due to the rupture of weak link-
ages and volatilization of low molecular weight frag-
ments. The second slow decomposition of chelates at
higher temperatures may be due to the breakage of main
3.7 Scanning electron microscopy
SEM is the technique employed for studying the shape,
size and morphological features of the polymers in
beaded form.35–37 The SEM photographs are presented
in figure 6. The SEM photographs of BH functiona-
lized AAP-DVB Cu(II) and Fe(II) metal complexes are
shown in figures 6c and d. Functionalized resin appears
smoother [cf. figure 6b] than that of the metal anchored
resins. The rough appearance of the resin surface in due
to the result of the doping of the metal ions. The copoly-
mer beads [cf. figure 6a] were spherical and of various
sizes. The beaded nature of the polymer confirms the
success of suspension polymerization.
100
AAP-DVB
AAP-DVB-BH
80
AAP-DVB-BH-Cu(II)
AAP-DVB-BH-Fe(II)
60
40
20
0
3.8 Applications
The time course of resin–metal interaction is of consid-
erable importance if the resin is to be used in a dynamic
system such as a packed column or a flowing sys-
tem. If complexation is not sufficiently rapid for certain
metal ions, then their retention on a column will be low
owing to the short contact time between the resin and
solution. Thus, absorption of resin should be examined
over an extensive period. Slow exchange rates of many
chelating resin have been reported38,39 to prevent their
0
100
200
300
400
500
600
700
800
Temperature, oC
Figure 4. Thermogravimetric curves.

604
Thammisetty Ravi Sankar et al.
Table 3. Particle size analysis of poly[((AAP)-DVB)] copolymer.
carried out.40 The time dependence of the complexation
of Cu(II) and Fe(II) by the functionalized AAP-DVB
resin was followed by the change in the concentrations
of the metal-salts solutions at regular intervals. The data
is presented in the figure 7.
commercial use. The rate of complexation depends on
the chemical nature of the metal ion and the ligand, as
well as the structure of the polymer matrix. The steric
constraints in a dense macromolecular matrix lower the
reactivity of ligand function.
Experiments show that the resin is capable of bind-
In order to optimize the time required for complexa-
tion towards Cu(II) and Fe(II) ions, batch studies were
ing with metal ions such as Cu2+, Fe2+, Ni2+ and Co2+
Particle size, µm
Figure 5. Particle size distribution of poly[((AAP)-DVB)] copolymer beads.

Acryloxy acetophenone-divinylbenzene co-polymer resins
605
(b)
(a)
(c)
(d)
Figure 6. SEM photographs of (a) poly[((AAP)-DVB)], (b) poly[((AAP)-DVB)]-BH func-
tionalized resin, (c) poly[((AAP)-DVB)]-BH Cu(II) complex and (d) poly[((AAP)-DVB)]-
BH Fe(II) complex.
ions. The complexation of Cu(II) and Fe(II) was com- 3.9 Effect of pH on uptake of metal ion
pleted in 50 and 60 min for functionalized resin. The
resin is also capable of binding with Ni2+ and Co2+ ions To various buffer solutions (pH 3–10), metal ion
but with a lesser % uptake. The time taken for the maxi- [Cu(II), Fe(II) (0.1) bulk concentration], functionalized
mum uptake of Ni2+ and Co2+ ions is found to be 30 AAP-DVB resin (5 g) was added and maintained under
and 40 min, respectively. The percentage of metal ion shaking for 90 min. The metallated beads were fil-
taken up is found to be 11 and 14%, respectively for tered and thoroughly washed. The bound metal ion was
Ni2+ and Co2+ ions. But in the present study the stud- released by acid treatment and the metal content deter-
ies are restricted to Cu2+ and Fe2+ ions only that have mined titrimetrically is presented in figure 8. From the
greater % of uptake by the functionalized resin. Chela- plots, it can be concluded that the change in pH has
tion of Cu(II) and Fe(II) is possible in the presence of relatively little effect on the uptake of metal ions by
other common ions present in waste water.
the functionalized resin. The reason for this is that the

606
Thammisetty Ravi Sankar et al.
chelation of atoms mainly depends on the structural fea-
tures of the ligand and may be influenced by the pH of
the medium. Hydrazones can exit either in keto form or
in an enol form. In acid solution the nitrogen atom of
hydrazone in keto form, may be protonated which may
affect the formation of complex, as the same nitrogen
atom is involved in chelation with metal ion. In alka-
line solutions the enol form may be in anionic form
and coordinate with the metal ion. But in the present
study, the pH of the solution has negligible effect as the
hydrazone moiety is in a polymer matrix and change
in the structural features of the hydrazone based on the
changes in the pH has little effect on complexation.
Hence, the effect of change in the hydrogen ion concen-
tration or hydroxyl ion concentration has only little ef-
fect and does not influence the extent of chelation much.
The uptake of metal ions by the present resin is com-
pared with that of the poly(4-acryloxybenzophenone
thiosemicarbazone)-divinylbenzene resins that were
reported in the literature.41 The comparative results are
presented in table 4.
Figure 7. Cu(II) and Fe(II) uptake by the functionalized
poly[((AAP)-DVB)] average of three determinations.
50
Cu(II)
The results show that the time taken for the maxi-
mum uptake of metal ions by the present resins are
much lower than that of poly(4-acryloxybenzophenone
thiosemicarbazone)-divinylbenzene resins.
Fe(II)
40
30
20
10
0
In the case of poly(4-acryloxybenzophenone thio-
semicarbazone)-divinylbenzene resins, the uptake of
Cu2+ and Fe2+ ions was pH dependent and the percent
metal ion uptake increases with a rise in pH of
the solution from 7 to 11. At pH 7 the amount of
metal ion uptake was 12 and 11%, respectively for
Cu2+ and Fe2+ ions and at pH 10 the amount of
metal ion uptake was 74 and 46%, respectively for
Cu2+ and Fe2+ ions. The percent metal ion uptake
by poly (4-acryloxybenzophenone thiosemicarbazone)-
divinylbenzene resins and the present resins are pre-
sented in table 4.
0
2
4
6
8
10
12
pH
Figure 8. Effect of pH on adsorption of metal ions Cu(II)
and Fe(II) average of three determinations.
Table 4. Percentage metal ion uptaken and time taken for maximum uptake of metal ions.
Poly(4-acryloxybenzophenone
thiosemicarbazone)-divinylbenzene resins
Poly[(4-acryloxy acetophenone)-
divinylbenzene] benzoyl hydrazone resins
Time taken for maximum
Time taken for maximum
uptake of metal ion, minutes
% metal ion uptake
uptake of metal ion, minutes
% metal ion uptake
pH Cu2+
Fe2+
Cu2+
Fe2+
pH Cu2+
Fe2+
Cu2+
Fe2+
–
–
–
7
8
9
10
11
–
–
–
–
–
–
–
–
–
12
19
69
74
–
–
–
–
11
19
43
46
48
3.6
4.6
5.6
–
8.2
9.2
10.1
–
50
60
27.6
27.8
28.2
–
28.1
27.7
27.7
–
29.6
29.8
29.9
–
30.2
30.2
30.1
–
60
90
–
–

Acryloxy acetophenone-divinylbenzene co-polymer resins
607
It is observed that the uptake of metal ions by the Thermal studies were carried out and the thermal dis-
present resins is independent of pH as compared with sociation patterns discussed. SEM photographs indi-
poly(4-acryloxybenzophenone thiosemicarbazone)-di- cate the success of suspension polymerization. A bead
vinylbenzene resins. Further, the percent metal ion structure was observed for the polymers. The maximum
uptake by the present resins at pH 8.2 is greater uptake efficiency for the metal ions was determined.
when compared to poly(4-acryloxybenzophenone thio- The reusability of the polymer ligand was tested and it
semicarbazone)-divinylbenzene resins. Whereas at pH was shown that even after four cycles, the efficiency of
9 and 10 the percent metal ion uptake by poly the uptake was not altered.
(4-acryloxybenzophenone thiosemicarbazone)-divinyl-
benzene resins was greater than the present resins.
Acknowledgements
The authors thank the University Grants Commis-
sion (UGC), New Delhi for financial support in the
form of a Major Research Project. The authors also
3.10 Reusability of complexed AAP-DVB
functionalized resin
thank University Grants Commission, New Delhi and
Department of Science and Technology (DST), New
Delhi for funding the department through SAP and
FIST programmes, respectively. The authors also thank
the Regional Sophisticated Instrumentation centres of
Indian Institute of Science, Bangalore and Indian Insti-
tute of Chemical Technology, Hyderabad and Central
University, Hyderabad, India for providing the analyti-
cal data.
The most important advantage of chelating resin is their
possible reuse after a particular process. The resin, once
used, can be returned to its original form by desorb-
ing the complexed metal ions with hydrochloric acid.
The metal-free resin can be reused after washing with
water several times. The recycling of the purified resin
with the addition of Cu(II) and Fe(II) solution results
in the intake of almost the same amount of respec-
tive metal ions as initially adsorbed. The process was
repeated four times. The retention of the initial capa-
city, even after four cycles of repeated operations, sug-
gests that the resin can be used several times without
any reduction in capacity. Here, it is noteworthy that
if the resin defunctionalized on acid treatment, it could
be subjected to functionalization again. The BH modi-
fied polymer is insoluble in hydrochloric acid. During
treatment with acid the BH moiety may detach from
the polymer. But the poly[((AAP)-DVB)] is insoluble
in HCl. It can be separated by decantation of acid solu-
tion and can be refunctionalized with BH after a thor-
ough wash with water. The metal ion can be recovered
by concentrating the acid solution.
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