Polymer science: research advances, practical applications and educational aspects (A. Méndez-Vilas; A. Solano, Eds.)
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Ionizing irradiation grafting of natural polymers having applications in
wastewater treatment
M.R. Nemțanu and M. Brașoveanu
National Institute for Lasers, Plasma and Radiation Physics, Electron Accelerator Laboratory, 409 Atomiștilor St., P.O.
Box MG-36, 077125 Bucharest-Măgurele, Romania
In this chapter, graft copolymerization of acrylamide onto starch induced by simultaneous electron beam irradiation as free
radical initiator without additional chemicals was performed. The results showed that the level of grafting was influenced
by the monomer-to-starch ratio and less by the irradiation dose. Flocculation performances of the synthesized copolymers
were evaluated in coagulation-flocculation experiments at laboratory scale in order to remove the organic load of
wastewater from the meat industry. Thus, in coagulation-flocculation process the copolymer aqueous solutions showed
good efficiency to improve different water quality indicators (total suspended solids, chemical oxygen demand and fatty
maters) as a function of the irradiation dose and copolymer dosage used as a flocculant. Hence, starch-graft copolymers
having good flocculating ability can be rapidly produced with good yields by simultaneous electron beam irradiation with
low doses and no additional chemicals.
Keywords: electron beam; starch; flocculation performance
1. General remarks
Treatment of industrial and municipal wastewaters is one of the major challenges of our society in terms of maintaining
essential resources available and suitable with providing a healthy environment. Flocculants are used for liquid-solid
separation processes in wastewater treatment by acting on a molecular level on the surfaces of the particles to reduce
repulsive forces and increase attractive forces [1]. Although the synthetic polymeric flocculants are highly efficient
even in very small quantities, main problems associated with their use are the lack of biodegradability making them
unfriendly to the environment [2] and high operation costs. The current environmental considerations impose rigorous
environmental protection measures and sustainable progress that minimize the impact of wastes on the environment.
Therefore, there is a strong demand to develop economically viable and eco-friendly replacements of conventional
synthetic flocculants, based upon the renewable organic materials that are low cost and degrade naturally when are
released into the environment [1]. On the other hand, the fast society development of the last decades led to the
requirement to use the renewable raw materials more and more. Thus, modification of natural polymers in order to be
used in the wastewater treatment is a continuous concern of researchers and technologists. The chemical combination of
organic synthetic polymer with natural polymer produces organic–natural polymer hybrid materials with desirable
properties of both components [3]. In this way, grafting is the most effective way of regulating the properties of natural
polysaccharides, which can be ‘tailor-made’ according to the needs and produce high efficient graft copolymers [2].
The graft copolymers essentially combine the best properties of both components and possess unique properties
compared to the original components. Additionally, they are biodegradable to some extent and reasonably shear stable
because of the attachment of flexible synthetic polymers onto the rigid polysaccharide backbone [4]. Promising alternative
copolymers have been synthesized and tested for their application as flocculating agents for treatment of different
wastewaters. Modification of natural polymers such as starch [5], amylopectin [6], cellulose [7], chitosan [8], alginate [9],
psyllium [10], tamarind [4], inulin [11] has been investigated as an attractive alternative in flocculation processes.
Starch is one of the most abundant and renewable natural polysaccharides in the world, having application in many
industries like food, pharmaceuticals, cosmetics, papermaking, textile, and so on. It is composed of two polymers of
anhydroglucose units, namely amylose and amylopectin, whose composition depends on botanical source. Modification
of starch by grafting various monomers onto it is an effective way to improve its properties, thereby enlarging the range
of its utilization and profiting by its biodegradable nature. Acrylamide is one of the most grafted vinyl monomers onto
starch substrates, and their water-soluble copolymers are good flocculants. A serious drawback of acrylamide and its
homopolymer (polyacrylamide) is related to the biodegradability. Their lack of biodegradability is compensated by
grafting onto starch backbone.
The methods of synthesis of grafted polysaccharides are: (1) conventional redox reactions by use of chemical free
radical initiator (i.e., ceric ions, manganic ions, potassium persulphate) [5,8], (2) radiation routes involving ionizing
radiation as gamma rays [12,13] or electron beam [14] and non-ionizing radiation as ultraviolet light [15] or microwave
radiation [11,16] as free radical generator, (3) plasma method [17], and (4) enzymatic method [18] using the enzyme as
an initiator. However, radiation induced grafting provides practical benefits in terms of product properties, large
processing temperature range, environmental protection and costs. Electron beam (EB) irradiation is a green powerful
tool for synthesis/modification/functionalization of advanced materials that feature unique properties. EB induced
grafting has major advantages over conventional methods. It is fast, occurs in the absence of an initiator or other
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chemical catalysts and produces low byproduct levels and hazards [19]. Moreover, EB processing requires low cost that
involves the indirect operating costs and the applied irradiation dose, which depends on the beam power, the efficiency
of its use and the conversion factor of the beam power from the facility consumption power [20]. Limited information
can be found on the starch grafting by e-beam irradiation to produce flocculating materials.
The purposes of this study were: (1) to modify starch by grafting acrylamide using EB irradiation in order to
synthesize water-soluble copolymers having flocculation abilities, and (2) to investigate the efficiency of the grafted
copolymers as flocculation agents.
2. Experimental
2.1 Materials
Unmodified regular corn starch (approx. 73% amylopectin and 23% amylose) was purchased from Sigma-Aldrich (St.
Louis, MO, USA) and acrylamide from Alfa Aesar (Germany). Other chemicals were of analytical grade and purchased
from SC Chimreactiv SRL (Romania).
2.2 Synthesis of the starch-grafted acrylamide copolymers
Starch aqueous solutions were prepared by dissolving corn starch (St) in distilled water with continuously magnetic
stirring on a water bath at 75-80oC for 30 min, and the obtained solutions were cooled at room temperature (25o C).
Acrylamide (AMD) was added to starch aqueous solution with further stirring at room temperature for 30 min, resulting
in a starch:acrylamide (St:AMD weight ratios = 1:1.1, 1:2.2 and 1:3.3) homogenous aqueous solutions.
Therefore, both the monomer (AMD) and substrate (starch) were exposed simultaneously to EB irradiation. The
irradiations were carried out at ambient temperature and pressure by using linear electron accelerator ALIN-10
(INFLPR, Bucharest-Magurele, Romania) of 6 MeV mean energy, with irradiation doses D, 2D and 6D. A high-energy
electron beam generator of 1-10 MeV is preferred for practicing grafting polymerization because it penetrates deep into
the materials, allowing a thicker layer of material to be irradiated [14].
After irradiation, irradiated mixtures were kept at room temperature for 24 hours. After that, according to literature
[21,22], the samples were precipitated in excess of ethanol and then washed several times with aqueous ethanol (30%
vol.) to remove totally the residual monomer and homopolymers. The resulted copolymers (St-g-AMD) were dried in
oven at 55oC for 20 hours.
2.3 Characterization of graft copolymers
The graft copolymers were characterized by elemental analysis, rheology and infrared spectroscopy.
2.3.1 Elemental analysis
Elemental analysis of samples was carried out using an elemental analyzer Flash 2000 (Thermo Fischer Scientific, UK).
The calibration curve was made with cystine, methionine, sulphanilamide (4-aminobenzenesulphonamide) and BBOT
(2,5-bis(5-ter-butyl-2-benzo-oxazol-2-yl) thiophene) . The grafting parameters such as monomer conversion (C%) and
grafting percentage (GP%) were evaluated according to the following equations:
C %  5.071  N % 
m
GP%  5.071  N % 
St
 m AMD 
m AMD
m
St
(1)
 m AMD 
m St
(2)
where: N% is the determined nitrogen percentage of grafted copolymer after removal of homopolymer, mSt and mAMD
are the amounts (in grams) of native starch and acrylamide, respectively, introduced into the grafting reaction.
2.3.2 Rheological analysis
Rheological measurements were carried out on aqueous suspensions of 0.5% starch and copolymers at different shear
rates (0-1082 s-1) and 28oC using HAAKE VT®550 rotational viscosimeter (ThermoHaake, Germany) with NV coaxial
cylinder. The obtained data were analysed with RheoWin v.3.5 software.
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2.3.3 Fourier transform infrared (FTIR) spectroscopy
FTIR spectra of samples were recorded on a Tensor 27 FTIR spectrometer (Bruker Optik GmbH, Germany) room
temperature in the frequency range of 4000-600 cm-1 with an average of 64 scans at a resolution of 4 cm-1. The
background spectrum was recorded in air (with no sample) and subtracted from the sample spectra. The collected
spectra were analysed with Opus v. 6.5. software. Samples were dissolved in water and then dried as a film in order to
be measured by using the attenuated total reflectance (ATR) accessory.
2.4 Flocculation study
Flocculation investigation was performed on wastewater collected from a meat processing plant. Quality parameters
such as pH, total suspended solids (TSS), chemical oxygen demand (COD) and fatty matters (FM) were measured in
accordance with standardized methods to investigate the effect of the polymer addition on the degree of purification of
wastewater. Synthesized graft copolymers (0.1% aqueous solution) of dosages 0.5-1.5 mg/L were tested in experiments,
and the flocculation efficiency (FE) for each quality indicator was calculated according to the formula:
FE 
C0  C
 100 (%)
C0
(3)
where: C0 and C are the concentrations (in mg/L) of respective parameter before and after the wastewater treatment.
The results reported are expressed by means of values ± standard deviation of three measurements, except the
flocculation study. Processing of experimental data was performed using MicrocalTM OriginTM v.8.0 (Microcal
Software, Inc., Northampton, MA, USA) and Microsoft® Excel 2010 (Microsoft Corporation, Redmond, WA, USA).
3. Results and Discussion
The synthesized copolymers were evaluated from physicochemical and functional points of view. Their characterization
through rheology, elemental analysis, FTIR and SEM was performed to point out the grafting level. Further, their
functionality as flocculant agents was examined on „real wastewater” from the meat industry.
3.1 Effect of irradiation dose and monomer concentration on grafting and viscosity
Some characteristics of the graft copolymers synthesized under EB field by varying the irradiation dose (free radical
generator) and the concentration of AMD (monomer) are displayed in Table 1. Three different sets (S1-S3) of graft
copolymers were synthesized so that a series of three graft copolymers was obtained for each monomer ratio by varying
the irradiation dose. The copolymerisation mechanism of AMD onto starch by simultaneous exposure of both monomer
and substrate in aqueous solution to the EB involves mainly the formation of free-radical sites in both chemical species
initiated by an indirect effect due to the water (solvent). Nasef and Guven [23] stated that the diluting solvent plays a
crucial role in affecting the accessibility of the monomer to the grafting sites and the mechanism of grafting, including
initiation, propagation of the growing chain and termination steps. In the present, study water is the solvent, and it absorbs

most of the e-beam energy leading to its radiolysis characterized by formation of highly reactive entities, eaq , H·,·OH,
H 2 O  , H2, O*, as a result of primary effects (excitation, dissociation and ionization). Then, the hydroxyl radicals attack
the St and AMD molecules generating their macroradicals that combine further yielding the graft copolymer.
The conversion of AMD ranged from 49 to 90% and grafting percentage ranged from 54 to 294% as a function of
irradiation dose and monomer-to-starch ratio. The results indicate that monomer conversion improved by increasing the
irradiation dose for each tested monomer ratio and thus the irradiation dose of 6D gave the highest conversion, C =
90.0±0.8% for the highest AMD concentration. However, the linear correlation C% = f(irradiation dose) reduced as the
AMD concentration increased. In other words, the monomer conversion and irradiation dose were strongly positive
correlated (r ~ 0.976) at low concentration of AMD and no significant correlated (r ~ 0.674) at the highest monomer
concentration. At a constant irradiation dose, the increase of monomer conversion was good dependent (r > 0.900) on
AMD concentration introduced into grafting reaction. In a similar manner, the grafting percentage increased both by
increasing of irradiation dose at constant AMD concentration and by increasing of AMD concentration at constant
irradiation dose. A similar trend was observed for the other grafting systems using ionizing radiation [12,24,25]. The
grafting parameters increased with the increase in the concentration of monomer, because more monomers are available
and can react at the grafting site in the starch trunk polymer [26].
Graft copolymers were soluble in cold water unlike native starch. All studied samples of 0.5% aqueous solutions of
St and graft copolymers had Newtonian behaviour. Viscosity is strongly related to the molecular weight of polymer so
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Table 1 Synthetic details of native starch and graft copolymers.
Sample
Native starch (St)
Set S1 D(St-g-AMD)
2D(St-g-AMD)
6D(St-g-AMD)
Set S2 D(St-g-2AMD)
2D(St-g-2AMD)
6D(St-g-2AMD)
Set S3 D(St-g-3AMD)
2D(St-g-3AMD)
6D(St-g-3AMD)
Conversion (%)
Grafting Percentage (%)
-
-
49.2±1.4
57.2±3.0
69.1±4.7
71.9±0.8
82.7±1.7
88.1±0.5
76.2±4.4
89.6±1.3
90.0±0.8
53.7±1.6
62.3±3.3
75.5±5.2
156.6±1.8
180.1±3.6
192.2±1.0
249.1±14.3
293.4±4.3
294.1±2.7
Viscosity (mPa·s)
1.8±0.1
2.2±0.1
2.8±0.2
2.9±0.1
3.1±0.1
3.0±0.0
3.4±0.2
4.4±0.2
3.7±0.2
3.8±0.2
that higher viscosity involves higher molecular weight. Native starch had the apparent viscosity of 1.8±0.1 mPa·s while
the viscosities of the graft copolymers ranged from 2.2 to 4.4 mPa·s (Table 1). As expected, the viscosities of
synthesized copolymers were greater than that of native starch used as an initial substrate, which can be explained by
higher molecular weight of the copolymers than native starch due to the grafting of the polyacrylamide (pAMD)
branches on the starch backbone. When the percentage of starch is small in comparison to the pAMD, it is then very
likely that the increase of viscosity with the amount of AMD is due to an increase of the pAMD side chain molecular
weight [27]. Thus, pAMD chains are assumed to be generated by increasing the AMD concentration. Consequently, at
constant irradiation dose, the effect of AMD on the viscosity showed an increase in viscosity with increasing the
amount of AMD (r > 0.950). The increase in viscosity with the increased amount of AMD resulted from the increase in
the molecular weight of the pAMD side chain. However, in the series S3 of samples with the highest AMD
concentration, the viscosity was lower with irradiation dose increasing than expected. According to Radoiu et al. [28],
during irradiation several processes involving monomer polymerisation, chain branching and cross-linking and
degradation of the polymer already formed and even a competition among all these phenomena, which affect the final
structure of the polymer, can occur. As all copolymers of this series were water-soluble, the crosslinking process was
minimized. At the same time, we excluded a reduction in the molecular weight of the pAMD side chain since the
monomer conversion and grafting ratio (based on nitrogen content) indicated good results correlated with our
expectations. Thus, the decrease in viscosity at higher AMD concentration and higher irradiation dose could be due to the
partial cleavage of the starch glycosidic linkages resulting from increasing in the irradiation dose, and this leads to a
decrease in molecular weight of starch molecules. On the other hand, although high irradiation doses generally cause
degradation of St and/or formed copolymer, one should also take into sort of consideration the formation of shorter average
chains of pAMD that can give lower molecular weight. These shorter pAMD chains result from the increase in the number
of active sites on substrate with the irradiation dose for the same AMD concentration. Consequently, an irradiation dose is
considered optimum when it is able to initiate a few grafting sites resulting in longer pAMD chains.
3.2 Elemental analysis
No presence of nitrogen was detected in native starch by elemental analysis. On the other hand, the nitrogen content
ranged from 5 to 14% for graft copolymers (Table 2). Therefore, the presence of nitrogen in all synthesized copolymers
confirmed that AMD have indeed grafted on the starch backbone, increasing with irradiation dose and AMD
concentration. According to Jyothi et al. [29], there is a significant positive correlation between grafting ratio and
nitrogen content in the grafted starches so that the higher grafting level corresponds to higher nitrogen content.
Table 2 Elemental analysis results.
Sample
Native starch
Set S1 D(St-g-AMD)
2D(St-g-AMD)
6D(St-g-AMD)
Set S2 D(St-g-2AMD)
2D(St-g-2AMD)
6D(St-g-2AMD)
Set S3 D(St-g-3AMD)
2D(St-g-3AMD)
6D(St-g-3AMD)
C (%)
40.30±0.19
42.40±0.06
42.48±0.23
42.77±0.26
43.84±0.22
43.59±0.12
43.76±0.17
44.26±0.14
45.86±3.46
44.12±0.02
H (%)
6.52±0.07
6.70±0.18
6.74±0.08
6.68±0.11
6.93±0.11
6.99±0.06
6.99±0.04
7.12±0.06
7.32±0.51
7.16±0.07
273
O (%)
49.23±0.09
42.87±0.97
39.95±1.82
39.71±0.69
36.85±0.38
34.81±0.72
33.79±0.05
35.44±0.71
31.71±0.52
31.87±1.02
N (%)
5.07±0.15
5.88±0.31
7.12±0.49
9.72±0.11
11.17±0.22
11.92±0.06
11.51±0.66
13.98±0.90
13.59±0.13
Polymer science: research advances, practical applications and educational aspects (A. Méndez-Vilas; A. Solano, Eds.)
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3.3 FTIR analysis
The FTIR spectrum of native corn starch showed typical complex vibrational modes due to the pyranose ring of the
glycosidic unit in the region below 800 cm-1 [30]. In addition, the spectrum displayed a broad absorption band in the
region of 3290 cm-1, indicating the presence of intermolecular hydrogen bonded hydroxyl group having polymeric
association. Other characteristic peaks were also identified at 2926 cm-1 (C-H stretching), at 1413 cm-1 (–CH2
scissoring) and 1352 cm-1 (–CH2 twisting), at 1642 cm-1 (O-H vibrations from bound water molecules) and the triplet
band for the -CH2-O-CH- stretching absorption at 1151, 1078 and 1024 cm-1.
Fig. 1 FTIR spectra of native starch and some synthesized copolymers.
The grafting onto St was confirmed by comparing the spectra of the native starch with those of the grafted starches.
In all cases, the spectra of the graft copolymers showed characteristic absorption bands of the starch substrate. The
appearance of a shoulder at 3188-3200 cm-1 and other characteristic absorption bands found at 1651-1661 cm-1 and
1604-1612 cm-1 were attributed to N-H stretching, C=O bands and N-H bending bands of the pAMD –CONH2 groups
(Fig. 1). Additionally, the new peak found at 1442-1446 cm-1 is due to C-N bending vibrations [31,32]. The presence of
these vibrations was not observed in the spectrum of the St, being the proof of grafting reaction. Moreover, it was
noticed that the increase of AMD concentration led to an absorbance decrease of the starch characteristic triplet band at
around 1151, 1078 and 1024 cm-1 concomitantly with a clear increase of absorption band found at 1604-1612 cm-1 (N-H
band). These results are consistent with previous literature on the graft copolymerization of AMD onto polysaccharide
substrates [11,16,27,29,31-34].
3.5 Flocculation efficiency in wastewater from a meat processing plant
The results presented within the previous sections demonstrate the physicochemical and structural changes of St and indicate
the occurrence of EB induced grafting. Hence, the efficiency of the graft copolymers as flocculation agents was further
investigated at laboratory scale in order to remove the organic load of wastewater collected from a meat processing plant.
Meat processing wastewater is usually heavily loaded with organic and inorganic materials that create severe
problems, making it a problematic effluent to treat before its discharge to public sewerage. This loading depends very
much on the type of production and facilities, and wastewater has a high strength in terms of biochemical oxygen
demand, chemical oxygen demand, suspended solids, fatty matters (fat, oil and grease), nitrogen and phosphorus,
compared to domestic wastewaters [35,36].
Among physico-chemical processes, coagulation-flocculation is one of the most widely used solid-liquid separation
process for the removal of suspended and dissolved solids, colloids and organic matter present in industrial wastewaters
[37,38]. In the present study, flocculation performances of the graft copolymers were evaluated in coagulationflocculation experiments using inorganic coagulants (200 mg/L CaCO3 and 200 mg/L Al2(SO4)3) and various dosages
(0.5-1.5 mg/L) of 0.1% aqueous solution of flocculants (graft copolymers). The quality indicators quantified were pH,
total suspended solids, chemical oxygen demand, and fatty matter in suspension. Table 3 shows the characteristics of
raw wastewater and the permissible levels of water quality indicators according to the Romanian national guideline.
Table 3 Characteristics of the raw wastewater used in experiments.
Parameter
pH
TSS (mg/L)
COD (mg O2/L)
FM (mg/L)
Raw wastewater
7.7
562
1055
246
Maximum allowed level*
6.5-8.5
350
500
30
*Romanian National Regulation NTPA 002/2005 – Quality indicators of wastewaters discharged to urban sewerage systems
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All synthesized copolymers used in coagulation-flocculation process showed good efficiencies ranging 86-98% for
TSS, 88-90% for COD and 55-89% for FM (Fig. 2) and pH values of 7.8-8.2 as a function of the irradiation dose and
copolymer dosage used as a flocculant. More precisely, the coagulation removed around 84% of TSS, 87% of COD and
50% of FM, while the flocculation step had additional removal capacity of 2-14% for TSS, 1-4% for COD and 5-39%
for FM.
b)
a)
c)
Fig. 2 Flocculation efficiencies on a) total suspended solids, b) chemical oxygen demand and c) organic matters.
In certain cases, a decrease in the removal efficiency of the studied indicators was noticed as the increase in dosage
of the graft flocculant. For instance, this behaviour occurred for samples D(St-g-AMD), 2D(St-g-2AMD) and D(St-g3AMD) in the case of TSS and COD and for samples D(St-g-AMD) and D(St-g-2AMD) in the case of FM. The
flocculation reaches its maximum at an optimal copolymer concentration. Beyond this dosage, the flocculation
decreases due to destabilization of the flocs formed and their re-suspension by the excess of polymeric flocculant
[16,39]. Moreover, certain dosages of some flocculants resulted in very poor efficiency compared to that of the mixture
of inorganic coagulants when applied alone. As an example, a dosage of 0.5 mg/L of 6D(St-g-2AMD) for TSS and
dosages of 1 mg/L and 1.5 mg/L of D(St-g-2AMD) and 0.5 mg/L of 6D(St-g-3AMD) for COD. On the other hand,
although the highest levels of efficiency were determined for FM indicator, only the sample 2D(St-g-2AMD) of 1.5
mg/L showed a level that follows the national requirements for such an indicator. This behaviour could be due to the
internal architecture that determines the macromolecule conformation in water solution, giving some peculiarities of
flocculation behaviour [40]. Starch is a complex mixture of rigid linear (amylose) and highly branched (amylopectin)
polymers with broad distribution of molecular weights. The effect of structural features on flocculation properties can
be even stronger for starch, meaning the increasing rigidity of macromolecules leads to a reduced flocculation
efficiency [41,42].
According to the results of flocculation study, it can be concluded that although the efficiency for removal of TSS
and COD from tested wastewater was good, the concentration of fatty matters does not meet the level required by
national regulation regarding the quality of wastewaters discharged to urban sewerage systems. In this case, the
wastewater should be preceded by another treatment process (i.e., electrocoagulation [43]) or a subsequent biological
treatment [44] or even a mixture of graft flocculants could be used in order to achieve the FM level allowed by current
standards of quality. Taking into consideration that an essential feature of wastewater flocculation is the elimination of
suspended solids and as much organic material as possible [45], our grafted flocculants displayed promising
flocculating ability by reduction of environmental concerned parameters (TSS, COD and FM) from wastewater
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collected from a meat processing plant. Among the series of graft copolymers, the sample D(St-g-3AMD) had superior
performance by considerably reducing the overall organic load (TSS, COD and FM) of tested wastewater. The high
monomer-to-starch ratio and the low irradiation dose specific to this sample led to the highest viscosity as a probable
result of longer grafted pAMD chains.
As Lee et al. [2] reviewed in their work, molecular weight and viscosity are the key factors that affect the
flocculation performance. Accordingly, high viscosity correlated with high molecular weight showed very good
performance in the tested wastewater at a dosage of 0.5 mg/L for all analysed water quality indicators. Moreover, all
results proved that the addition of a natural polymeric flocculant to inorganic coagulants is effective in the reduction of
TSS, COD and FM, reducing thus the amount of coagulant used and cost of the coagulation-flocculation process. These
findings are in agreement with other previous works [39,44,46].
4. Conclusions
New starch-based flocculants were synthesized via simultaneous graft copolymerization in aqueous solutions of
acrylamide onto starch substrate induced by an electron beam irradiation. The monomer conversion, grafting percentage
and copolymer features may be controlled by chemical composition of initial mixture exposed to electron beam and by
applied irradiation dose. The grafting parameters and viscosity were correlated with both monomer concentration and
irradiation dose. However, a lower viscosity for samples with higher AMD concentration and higher irradiation dose
could be more likely assigned to either the polysaccharide degradation or formation of shorter average chains of pAMD
that can give lower molecular weight. FTIR study of graft copolymer showed that the increase of AMD concentration
caused the absorbance decrease of the starch characteristic triplet band at around 1151, 1078 and 1024 cm-1
concomitantly with an obvious increase of absorption band found at 1604-1612 cm-1 (N-H band).
In the coagulation-flocculation experiments at the laboratory level, the synthesized copolymers showed a great
potential to reduce the quality indicators (total suspended solids, chemical oxygen demand and fatty matter in
suspension) of the wastewater from the meat industry. The flocculation efficiency of copolymers depends on their
features and dosage used. Besides, these flocculating materials have the advantage of a good flocculating efficiency
with low dosage as well as easy handling.
In conclusion, starch-graft copolymers having good flocculating ability can be rapidly produced with good yields by
simultaneous electron beam irradiation with low doses and no additional chemicals. Further studies should be focused
on optimization of irradiation processing parameters as well as the flocculant dosage, followed by coagulationflocculation tests on pilot scale.
Acknowledgements This work was supported by a grant of the Romanian National Authority for Scientific Research, CNDI–
UEFISCDI, project number 64/2012.
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