Vol.4, No.9B, 23-28 (2013) Agricultural Sciences
Copyright © 2013 SciRes. OPEN ACCESS
Synthesis and flocculation characteristics of cationic
modified corncob: A novel polymeric flocculant
Yanhua Pang1*, Yongsheng Din g 2, Jie Chen3, Weimin Gong3
1Center of Food Inspection, Liaoning Entry-Exit Inspection and Quarantine Bureau, Dalian, China;
*Corresponding Author: cindy_gl@eyou.com
2College of Ocean Environment and Engineering, Shanghai Maritime University, Shanghai, China
3College of Environ ment al Science and Engineerin g, D alian Maritime Univer sity, Dalian, China
Received Ju l y 2013
A novel organic polymeric flocculant was syn-
thesized by grafting cationic etherifying mono-
mer (3-chloro-2-hydroxypropyl) trimethyl ammo-
nium chloride (CHPTAC) onto the backbone of
corncob powder (CP, Φ ≤ 30 µm). The synthetic
reaction between CP and CHPTAC was initiated
by hydroxyl radical made from Fenton reagent
(H2O2-FeSO4). The alkalization process and syn-
thetic reaction conditions were optimized by va-
rying several parameters affecting grafting effi-
ciency, such as NaOH dose, monomer concen-
tration, reaction temperature and time and dis-
tilled water dose. The synthesized cationic flo c-
culant was characterized by elemental analysis,
Fourier-transform infrared spectrometer and
scanning electron microscope techniques. It was
concluded that the backbone of CP have been
grafted cationic etherifying monomer. The floc-
culation characteristics in 0.25% (w/v) kaolin
suspensions was compared with some of the
comm ercial f loccul ants a vailab le in markets , and
the results demonstrated the synthesized catio-
nic flocculation has superiority as a novel floc-
Keywords: Flocculation; Corncob; Polymeric
Flocculant; CHPTAC
Flocculation [1-3] is a process of bringing together
smaller particles to form larger particles, and settling of
colloidal particles from stable suspensions caused by the
addition of chemicals known as flocculants in minute
quantities. It is well known that the use of organic and
inorganic flocculants can improve the efficiency of sol-
id/liquid separation in a wide range of papermaking,
wastewater treatment and mineral processing industries
[4-7]. The inorganic flocculants, which are mainly based
on hydrolyzable salts of aluminum, cannot be removed
easily during treatment, and the residue in water can cause
some health problems [8]. Natural and synthetic poly-
meric flocculants, which are able to destabilize colloidal
suspensions, have been found wide application as floc-
culating agents in the past dec ade. Water-soluble syn thetic
polymers [9-11] have a disadvantage of non-biodegra-
dability and cost-effective. Thus, the demand for effec-
tive, cheap and environmentally friendly natural floccu-
lants for wast ewater treatment is increasing.
With the characteristics of nontoxic and biodegradable,
the so-called “green flocculants” such as starch [12,13],
amylopectin [14], alginic acid [15], guar gum [16], and
so for th, ha ve bee n paid mu ch att entio n. The chemical and
physical properties of the natural polymers can be mod-
ified by grafting a synthetic polymer onto the backbone of
natural polymers. For highly negatively charged colloidal
particles, cationic polymers are more used as flocculating
agents to remove finely divided solids from aqueous
suspension [17].
The natural corncob powder (CP), mainly composed
of cellulose, lignose and pentosan, has abundant output
in China. Composed of much hydroxyl radicals, CP may
be grafting by cationic polymers and perform efficient
flocculation characteristics. In view of several authors’
earlier findings, CP was chosen as the base pol ymer graft-
ing by a quaternary ammonium compo und [18]. Howev-
er, it has not been much s tudied as floccul ating agent for
wastewater treatment.
Highly charged cationic polymers such as polyamines
and polyimines are costly. Therefore, it has been at-
tempted to synthesize a cationic quaternary ammonium
salt (3 -chloro-2-hydroxypropyl) trimethyl ammonium chlo-
ride (CHPTAC). The present work aims to explore the
feasibility of grafting flocculation (DXSL-I) of CP and
CHPTAC, illustrate it s characteristics b y using elemental
analysis, Fourier-transform infrared (FTIR) and scan-
Y. H. Pang et al. / Agricultural Sciences 4 (2013) 23-28
Copyright © 2013 SciRes. OPEN A CCESS
ning electron microscope (SEM) and evaluate its floccu-
lation performance. The reaction parameters affecting
grafting efficiency, such as NaOH dose, monomer con-
centration, reaction temperature and time and distilled
water dose were also investigated.
2.1. Materials
Corncob powder (CP, (Ф 30 mm), obtained from
Dalian Farm Product Processing Plant, was dried at
100˚C for 4 h before use. Triethylamine, Epoxy chloro-
propane, all purchased from Shanghai Reagent Company,
China, were of analytical reagent grade. Aluminum chlo-
rate and Polyacrylamide are used as commercial floccu-
lants for comparison test. All the reagents were used
without further purification. Kaolin clay (Ф ≤ 2 mm) was
purchased from Zhonglong Kaolin Ltd., Chi na.
2.2. Preparation of Cationic Monomer
The reaction conditions were established according to
our previous experience [18]. Epoxy chloropropane (20
ml) was mixed with excessive triethylamine in a sealed
flask with constant stirring. The reaction was allowed to
continue for 3 h at a reaction temperature of 0˚C - 5˚C,
after which the sample was settled at ice bath for 2 h.
The content of upper solution, in which was the cationic
monomer (3-chloro-2-hydroxypropyl) trimethyl ammo-
nium chloride (CHPTAC), can be determined by using
Ag+ solution. The quaternary ammonium monomer was
decomposed easily under daylight or high temperature.
Therefore, the use of instant prepared monomer was
suggested. The reaction of quaternary ammonium group
preparation was shown as followed:
Fenton reagent
T< 5
2.3. Synthesis of Cationic Flocculant DXSL-I
Corncob powder can be modified by incorporating a
cationic monomer (3-chloro-2-hydroxypropyl) trimethyl
ammonium chloride onto the backbone of the polysac-
charide. The details of the synthesis and the reaction
conditions are as follows.
Corncob powder (2.0 g) was dissolved in distilled wa-
ter (8.0 ml) at room temperature. As alkaline medium is
essential to carry out the reaction, 0.002 g NaCl and 0.6
g NaOH were added to it. The reaction solution was al-
kalized for 60 min at 40˚C - 50˚C, followed by adding
Fenton reagent (H2O2 and Fe2+ were 0.8% - 1.2% and
0.005% of CP mass, respectively) into the solution to
initiate the reactio n for 30 - 90 s. Re actio n was then c on-
tinued for 3 h with excessive CHPTAC at 50˚C. The so-
lution was thereafter cooled to room temperature, and the
copolymer was precipitated by centrifugation. The resi-
due was washed with distilled water several times until
its pH reached 7 - 8 and there was not CHPTAC in the
filtrate checked with Ag+ solution. After washing, it was
dried in a vacuum oven.
2.4. Characterization of Cationic Flocculant
2.4.1. Elemental Analysis
Elemental analysis of the cationic flocculant DXSL-I,
CP and CHPTAC was undertaken with a LiquiTOC ele-
mental analyzer (Elementar Analysensysteme GmbH,
German). The estimation of only three elements, that is
car bon, hydrogen and nitrogen, was undertaken.
2.4.2. FTIR Spectroscopy
A 500 FTIR Spectrophotometer (Nicolet, USA) was
used and the potassium bromide (KBr) pellet method
was used for FTIR study. The FTIR spectrum of cationic
flocculation DXSL-I, alkalized CP and CP were collected
2.4.3. Scanning Electron Microscopy (SEM)
The small granules left after the pulverized graft co-
polymers and CP were sieved, and were subjected to
SEM study. The samples were gold-coated, and a magni-
fication of 2000 times was obtained. A Philips XL-30
Scanning Electro-Microscope (Holland) was used for
SEM study.
2.5. Flocculation Test
Flocculation capacity of DXSL-I and other commer-
cial flocculants were evaluated using 0.25% (w/v) of
kaoli n suspe nsio ns. After add ition of flocculants solutio n
(80 - 100 ml), mixtures were mechanically stirred at a
constant speed of 200 rpm for 2 min, followed by a slow
stirring at 40 rpm for 10 min. Thereafter, the sample was
left to settle for 5 min. At the end of the settling, 10 ml of
the supernatant fluid was taken from the beaker surface,
and its transmittance was measured at a wavelength of
610 nm by using JASCO V-500 Spectrometer (Japan).
3.1. Synthesis Mechanism
Corncob, mainly consisted of polysaccharide, was a
natural polymer. There were many -OH groups on its
microparticle’s surface [19]. Cationic modification was
based on these radicals. The synthetic reactions were
etherifying processes as shown in Eq s.2 and 3.
Matrix OH
OH n
Matrix O
OH n
Y. H. Pang et al. / Agricultural Sciences 4 (2013) 23-28
Copyright © 2013 SciRes. OPEN ACCESS
Matrix O
Matrix OH n
Reactions were theoretically divided into several steps,
including the free radical chain reaction and ion reaction
[20,21]. The formation of free OH groups could be ex-
pressed as followed equations:
Fe2+ H2O2Fe3+ OH OH
Matrix OH Matrix O
The synthetic reaction was actually an electr o -nuc-
leophilic process as shown below:
Some possible unwished negative reactions may hap-
pen as indicated from Eq s.7 to 10, where included free
radical transfers and exterminations, as well as the spli-
tup of etherified monomer by hydrolyzation.
++ +
Matrix OCH
3.2. Synthesis Conditions and Influence
3.2.1. NaOH Dosage, A lkalizing Temperature and
In order to evaluate the effect of NaOH dose on the
grafting of CHPTAC onto CP, a set of experiments were
carried out, in which the dose was changed from 0.10 g
to 6.00 g, while all the other parameters were kept un-
changed. The results showed an increase in the grafting
percentage with the increase in NaOH dose. However,
beyond a value of 0.6 g, a significant decrease in grafting
percentage was observed. According to synthesis reac-
tion (Eq.2 ) , the low dose OH- was he lpful to chan ge OH
group into ionic oxygen, of which the nucleophilic ca-
pacity was strengthened consumedly. However, overdose
of NaOH could make the epoxy ring broken up and ac-
celerate the quaternary ammonium radical decomposed,
resulting in grafting efficiency reduced. The similar re-
sults were found after a series of experiments about alka-
lization conditions. There is also an increase in the graft-
ing percentage with the alkalizing temperature and time,
but a reduction occurred with the alkalizing temperature
raised and time prolonged. The density of free radicals
was l ess, r esulti ng in re duct ion of grafti ng efficie ncy with
the alkalizing temperature and time increased. After the
opti mization experiments, it was obtained the NaOH do-
sage is 0.6 g, alkalizing temperature is 40˚C - 50˚C and
alkalizatio n time is 60 min.
3.2.2. Monomer Concentration
As sho wn in Fi gu re 1 , the gr afting p ercenta ge sig nifi-
cantly increased with incr easing mono mer concentration.
The presence of a hi gh concentration of CHPTAC in the
medium provided a greater availability of CHPTAC mo-
lecules to react with the CP macroradicals, leading to a
higher synthesis percentage. However, overdose of mo-
nome r co sts hi gh l y and unbeneficial.
3.2.3. Orthogonal Experi m en t
In addition to monomer concentration, distilled water
medium, synthesis temperature and time were also the
infl uence factor s gove rnin g the gra fting e fficie ncy. There -
fore, a series of experiments were carried out by ortho-
gonal method to optimize the reaction conditions affect-
ing flocculation efficiency. Taking CP (2.0 g), we ex-
amined the influence factors including the reaction tem-
perature (30˚C - 60˚C), reaction time (2 - 5 h) and dis-
tilled water (4 - 16 ml), respectively. T he final optimized
condition was obtained as follo ws: synthesis temperature
50˚C, synthesis time 3.0 h, and distilled water 8.0 ml.
The orthogonal experimental parameters were shown in
Table 1.
0.02 0.04 0.06 0.08 0.10
Grafting percentage/%
M onom er Concentration /M
Figure 1. Effect of monomer concentration on grafting percen-
tage (C P dos a ge : 2.0 g).
Table 1. The orthogonal experimen tal parameters.
No. Reaction temperature (˚C) React io n tim e (h) Water (ml)
1 30 2 4
2 40 3 8
3 50 4 12
4 60 5 16
Y. H. Pang et al. / Agricultural Sciences 4 (2013) 23-28
Copyright © 2013 SciRes. OPEN A CCESS
3.3. Caracterization of DXSL-I
3.3.1. Elemental Analysis
The results of element analysis of CP, CHPTAC and
cationic modified flocculants DXSL-I are shown in Ta-
ble 2. It has been found that corncob does not show any
significant presence of nitrogen. And the negligible amount
of nitrogen was 0.2% in CP is because of the presence of
trace quantities of proteins in the corncob powder. It is
shown in Table 1 that there is a considerable percentage
of nitrogen in the flocculants DXSL-I, which can be ac-
counted for the presence of CHPTAC chain onto the
backbone of corncob. Evaluation of the synthesis reaction
efficie ncy is ba sed on t he dete rminatio n of nit rogen co n-
tent in the modified flocculants according to elemental
analysis. From the element analysis table, it appears that
CHPTAC monomer are incorporated in greater extent
with increase in its concentration, possibly through par-
ticipation of larger number of OH groups of corncob in
cova lent li nkages .
3.3.2. FTIR Analysis
The FTIR spectra of cationic flocculation DXSL-I, al-
kalized CP and CP were shown in F i g ure s 2a-c, respec-
The broad band (Figure 2a) at 3404 cm1 is due to the
stretching vibration of the OH groups. The band at 1635
cm1 is for OH b end ing vib rat io n. T he b ands a t 125 2 and
2925 cm1 are assigned to C=O stretching and CH stret-
ching, respectively. The bands at 1431 cm1 are due to
CH bending vibration. The two bands at 1051 cm1 and
1512 cm1 are attribu ted to CH2-O-CH2 and epoxy groups
stretching vibrations. Figure 2b shows the FTIR spectra
of alkalized CP. The broad peak at 3397 cm1 is due to
the OH stretching vibration. The intensive band at 2915
cm1 is due to CH stretching vibration. Two bands at
1051 and 1512 cm1 are for CH2-O-CH2 and epoxy groups
stretching vibrations, respectively. It is found that the
band at 1251 cm1 was not present in Figure 2b, which
indicate synthesis reactions in Eqs.2 and 3 have hap-
pened. The broad band (Figure 2c) at 3409 cm1 is due
to the stretching vibration of the OH groups. The pres-
ence of an additional band at 1395 cm1 in Fig u re 2c due
to the CN stretching vibration is a clear proof of incor-
poration of cationic monomer onto the backbone of CP.
3.3.3. SEM Analysis
Fig u re s 3-5 show the scanning electron micrographs
Table 2. Results of Elemental Analysis.
Po l ym er %C %H %N
CP 36.5 6.4 0.2
CH PT AC 37.8 7.8 7.2
DXSL-I 37.2 6.1 3.5
1 049
1 376
1 512
1 635
2 925
3 409
Figur e 2. IR spectra of (a) CP, (b) alkalized CP and (c) DXSL-I.
Figure 3. SEM micrograph of CP.
Figure 4. SEM micro graph of alkalized CP.
of CP, alkalized CP and DXSL-I, respectively. A careful
examination of the micrographs reveals a difference in
the morphological appearance of the polymers. CP has a
granular structure, which changed drastically when it was
Y. H. Pang et al. / Agricultural Sciences 4 (2013) 23-28
Copyright © 2013 SciRes. OPEN ACCESS
Figure 5. SEM micrograph of DXSL-I.
alkalized and grafted with cationic etherifying monomer
CHPTAC. The appearance of Alkalized CP seems in-
compact, which is helpful for OH groups exposed and
grafting reaction. However, DXSL-I appeared embedded
structure. It can be explained that the alkalized CP com-
bined with etherifying monomers formed a kind of struc-
ture mingling soft and rigid property. This observation
also supported the grafting of CHPTAC onto the back-
bone of CP.
3.4. Flocculation Characteristic
An attempt has been made to compare the flocculation
characteristics of DXSL-I with some of the commercially
available flocculants in 0.25 % (w/v) kaolin suspensions
(Figure 6). The characteristics made it appropriate for
treating wastewater with a high efficiency in a wide pH
range without pH adjustment. It can be concluded that
DXSL-I has the similar capacity to polyacrylamide, but
superior to aluminum chloride. Its performance is better
than that of other commercial flocculants because the
kaolin particles have high negative charges and in this
case, it appears that the cationic along with easy approa-
chability of branched structure of CHPTAC dominates
the performance.
From the above results, it can be concluded that catio-
nic monomer CHPTAC is grafted onto the backbone of
CP. Variation in the synthetic parameters results in dif-
ferent flocculation efficiency. Investigation of elemental
analysis, FTIR spectra and SEM provide a strong proof
of cationization. In comparison with the commercial
flocculants, the best performing of the cationic modified
flocculants DXSL-I having long CHPTAC chains show
better flocculatio n characteristics.
2 4 6 810 12 14
bl ank
Aluminum chlorate
Polyac ryla
Transm ittance /%
Time /min
Figure 6. Flocculation performance in Kaolin suspensions.
The authors thank the Dalian Maritime University Research Fund for
its support of this research.
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