ORIGINAL PAPER

Nanoparticles and whiskers-based chitosan films for Crcomplexation

Nadia Eladlani • El Montassir Dahmane •

Mohammed Rhazi • Moha Taourirte

Received: 5 June 2014 / Accepted: 2 December 2014

� Springer International Publishing Switzerland 2014

Abstract Though it is known that chitosan films are able to

complex metallic ions, underlying molecular mechanisms are

poorly understood. Here, we studied the complexation of

chromium (III) ions using three films: chitosan films, bio-

composites formed from chitosan with nanoparticles, and

chitosan with whiskers. Fourier transform infrared spectros-

copy revealed the presence of interactions between chro-

mium (III) ions and either chitosan film, or biocomposites of

chitosan–chitosan nanoparticles and chitosan–chitosan

whiskers. Scanning electron microscopy showed the pre-

sence of Cr (III) on the surface of chitosan film and chitosan

biocomposites. The surface tension of chitosan film and

chitosan biocomposites increased after Cr (III) complexation,

according to contact angle data. Kinetic studies show that

chitosan–chitosan whiskers biocomposite is the best ligand

with complexation of 18 % of chromium (III) ions in 60 min.

Keywords Film � Chitosan � Nanoparticles � Whiskers �Chromium (III) ions � Complexation

Introduction

Chitosan is a polysaccharide belonging to the glycosami-

noglycans family, derived by deacetylation of chitin

(Roberts 1992; Muzzarelli 1977). When the degree of

deacetylation reaches higher than 50 %, chitosan becomes

soluble in acidic aqueous solutions and it behaves as a

cationic polyelectrolyte. Chemical modification of chitosan

is a means that can be used to improve water solubility

(Kurita et al. 1998). As a consequence, the use of chitosan

in the form of a colloidal suspension is an attractive choice,

since chitosan still retains its solid nanocrystalline state so

as to avoid the use of an expensive solvent.

Whiskers or crystalline nanofibrils are substances that

can be made from self-assembling of basic building blocks

or breaking down of crystalline materials into nanocrys-

talline entities with specific shapes (Favier et al. 1995;

Ljungberg et al. 2006). The nanoparticles of chitosan are

prepared by gelation of chitosan with tripolyphosphate by

ionic cross-linking (Dahmane et al. 2013).

The free amine function of chitosan gives it a better

ability to chelate ions of transition metals (Sashiwa and

Aiba 2004) than other natural compounds such as cellulose

derivatives (Masri et al. 1974). These chelating properties

are turned to account for water treatment. There are no

universally agreed mechanisms for these processes

(Rashidova et al. 2004; Sashiwa and Aiba 2004).

The cationic character of chitosan offers an opportunity

to establish electrostatic interactions with other compounds.

Due to these characteristics, chitosan has been widely used

for production of edible films (Aider 2010; Rivero et al.

2010). Chitosan films present good barrier properties when

compared to other polymers such as methylcellulose and

corn starch (Debeaufort and Voilley 2009; Garcıa et al.

2009). It was shown that the chelation process and the sta-

bility of metal–chitosan complex may be influenced by

mixing, and it may also depend on the physical state of

chitosan such as powder, film, gel, or fibre (Guibal et al.

1997). The chitosan shows selectivity according to the

N. Eladlani (&) � M. Rhazi

Equipe des Macromolecules Naturelles (EMN), Departement of

Chemistry-Biologie, Ecole Normale Superieure, University Cadi

Ayyad Marrakech, BP 2400, Marrakech, Morocco

e-mail: adlounisou@gmail.com

N. Eladlani � E. M. Dahmane � M. Taourirte

Laboratoire de Chimie Bio Organique et Macromoleculaire

(LCBM), Departement of Chemistry, Faculte Des Sciences et

Techniques Gueliz (FSTG), University Cadi Ayyad Marrakech,

BP 549, Marrakech, Morocco

123

Environ Chem Lett

DOI 10.1007/s10311-014-0488-9

considered cation. In the case of divalent ions, the capacity

to fix metallic ions increases from 0.02 mmol/g of chitosan

for Co2?, Ca2? to 1.2 for Cu2? in the same external con-

ditions. Considering trivalent ions, this capacity is from

0.2 mmol/g of chitosan for Pr3? and Cr3? to 1.47 for Eu3?

and Nd3?. This selectivity seems to be independent on size

and hardness of ions (Rhazi et al. 2002).

The present study involves the preparation and charac-

terization of chitosan film, biocomposites formed from

chitosan with its nanoparticles, and chitosan with its

whiskers; they are mainly used to complex chromium (III)

ions. We followed the quantity adsorbed of chrome with

chitosan film and its biocomposites during 70 min by UV–

visible analysis. Finally, we characterized chitosan film,

biocomposites of chitosan/chitosan nanoparticles, and

chitosan/chitosan whiskers after complexation using dif-

ferent techniques.

Experimental

Chitosan and its derivatives nanoparticles and whiskers

Chitosan with the average molecular weight of 63 kDa and

96 % deacetylation degree was prepared according to our

previous study (Tolaimate et al. 2000). Chitosan nanopar-

ticles were obtained by ionic gelation of chitosan with

tripolyphosphate according to the procedure carried out in

our laboratory (Dahmane et al. 2013). Chitosan whisker

was prepared from chitin whiskers according to the method

described by Paillet and Dufresne (2001). The chromium

ions were used as chlorides form CrCl3, this form was

preferred due to the fact that most of the sulfate salts were

not soluble, and nitrates may act as oxidants, and more-

over, they adsorb in ultraviolet region, which may interfere

with the determination of our results.

Preparation of chitosan film

Chitosan film was prepared according to the procedure

described by Arzate-Vazquez et al. (2012) with some

modifications. 1 g of chitosan was solubilized in 100 ml of

1 % (V/V) acetic acid solution, then stirred for 6 h at

40 �C. After this time, a glycerol was added under stirring

during 30 min as plasticizer, and the ratio of glycerol to

chitosan was 0.75 ml/1 g.

Preparation of chitosan/chitosan nanoparticles

and chitosan/chitosan whiskers biocomposites

Biocomposites were prepared using the previous chitosan

solution. This solution was added dropwise to each sus-

pension of chitosan nanoparticles and chitosan whiskers.

The blends were stirred for 10 min before dropped into a

Petri dish and let to dry; the mass ratio of each solution was

1:1. Once biocomposites formed, they were removed from

Petri dishes and conditioned in a desiccator at 57 % rela-

tive humidity using saturated solution of sodium bromide

and ambient temperature.

Films were in the NH3? form. They were dipped in a

0.4-M sodium hydroxide solution to reach the uncharged

amino form. After 5 mins, we washed the films with

water to eliminate salts. After drying, transparent films

were cast in the amino form, insoluble in water (Rhazi

et al. 2002).

Fourier transform infrared spectroscopy analysis

FTIR spectra were recorded on a Fourier transform infrared

spectrometer Bruker VERTEX-70 using vacuum for ref-

erence. Spectra were collected in the 4,000–400 cm-1

range with 32 scans at 4-cm-1 resolution.

Scanning electron microscopy analyses

The morphology of chitosan film and its biocomposites was

observed using scanning electron microscopy. Samples

were coated with graphite under vacuum using an auto-

matic sputter coater. The analyses were conducted using a

scanning electron microscope Quanta 200 operating at an

accelerated voltage of 5 kV for all of films.

Contact angle

Surface hydrophobicity of films was estimated by sessile

drop method, based on optical contact angle method.

Contact angle measurements were carried out with a drop

shape analysis (DSA1) from kruss. A droplet of solvent

was deposited on films surface with an automatic piston

syringe. The drop image was photographed using a digital

camera. An image analyzer was used to measure angle

formed between the surface of film in contact with the drop

and tangent of liquid drop at the point of contact with film

surface. Measurements were performed within the first 15 s

after dropping the solvent onto film surface, to avoid

variations due to solvent penetration onto the specimens.

Many measurements were performed for each film at room

temperature with ethylene glycol, glycerol, and water as

droplet solvent.

Ultraviolet spectroscopy

To identify the bands of chromium (III) ions and determine

the quantity adsorbed, a specord 210 plus spectrophotom-

eter UV–visible from analytikjena was used, covering the

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123

wavelength range from 200 to 800 nm, with quartz cells

with a thickness of 0.2 cm.

Results and discussion

Characterization of chitosan film and its biocomposites

Fourier transform infrared spectroscopy analyses

Chitosan film, chitosan/chitosan nanoparticles, and chitosan/

chitosan whiskers biocomposites are present in infrared spec-

trum (Fig. 2), a characteristic peak at 3400 cm-1 attributed to

the –NH2 and –OH groups stretching vibration and intermo-

lecular hydrogen bonding (Pawlak and Mucha 2003; Xu et al.

2005; Ziani et al. 2008). We see a strong peak of N–H bending

vibration at 1556 cm-1. Also an anti-symmetric stretching of

C–O–C was observed at 1040 cm-1; this band become more

intense for chitosan/chitosan nanoparticles and chitosan/

chitosan whiskers biocomposites. Moreover, chitosan/chito-

san nanoparticles present a medium peak at 2360 cm-1 char-

acteristic of hydrogen-bonded O–H to phosphor P–OH.

Scanning electron microscopy analyses

The scanning electron microscopic images of chitosan film

and its biocomposites chitosan/chitosan nanoparticles and

chitosan/chitosan whiskers (Fig. 3) present smooth, homo-

geneous surfaces without pores. The phenomenon can be

attributed to the interfacial interaction between chitosan

matrix and its derivatives nanoparticles and whiskers, which

they are coming from similar structures of same source. We

see some small irregularities on chitosan film, similar

descriptions of chitosan film morphology was examined via

scanning electron microscopy have been reported by others

authors (Ke et al. 2010; Meng et al. 2010; Silva et al. 2007).

Contact angle

Surface properties of films give information about phe-

nomenon of wetting or non-wetting of product surface

forming dispersions, thus about uniformity of coating when

applied to a particular solid surface (Vargas et al. 2009;

Karbowiak et al. 2006). Moreover, contact angle method is

a simple way to determine the superficial hydrophilicity of

films since when using water or another polar solvent,

contact angle will increase with increasing surface hydro-

phobicity (Hambleton et al. 2009; Pereda et al. 2010; Zia

et al. 2010).

Polarity of surface and its tension were calculated using

the model of Owens and Wendt:

cL 1þ cos hð Þ ¼ 2

ffiffiffiffiffiffiffiffiffi

cdLcd

S

q

þffiffiffiffiffiffiffiffiffi

cPLcP

S

q

� �

where h stands for contact angle between solid film and

liquid drop, cL is surface tension of liquids (water, ethylene

glycol, and glycerol), cd and cp are the dispersive and polar

components of surface tension of solid (S) and liquid (L).

According to the results of Table 1, the hydrophilicity of

chitosan film was close to chitosan/chitosan whiskers; it

can be explained by the presence of amino and hydroxyl

groups. This hydrophilicity decreases for chitosan/chitosan

nanoparticles, it can be attributed to the presence of

phosphoric group in chitosan nanoparticles.

Adsorption kinetic of chromium (III) ions

Chromium (III) ions are a peculiar case. Indeed, the pH of

initial chromium chloride CrCl3 solution is acid 3.77 and

can be oxidized to Cr(VI). The Cr(III) presents character-

istic bands at 430 and 617 nm, different from that of Cr(VI)

which is at 370 nm.

The Cr(III) was stable at 430 nm and pH 6.55; we fixed

these both parameters. Also the mass of chitosan film and

biocomposites was fixed at 2 mg. For 10 ml of CrCl3 solu-

tion, we added 2 mg of chitosan film and then we followed

the adsorption of Cr(III) using UV–visible analysis every

10 min. The concentration of CrCl3 solution was 250 mg/l.

We did the same for chitosan/chitosan nanoparticles and

chitosan/chitosan whiskers biocomposites.

Firstly, the concentration of persistent chrome was

determined using the calibration curve, then the adsorbed

quantity of chromium (III) ions was calculated during

70 min (Fig. 1) by the following equation:

Qads ¼ Ci � Crð Þ � 100 =Ci

Table 1 Characterization data of contact angle (H) and surface

tension (�Total) of chitosan film (CTf), chitosan/chitosan nanoparticles

(NCTf), and chitosan/chitosan whiskers (WCTf) biocomposites, and

the complex formed between Cr(III) ions with chitosan film (CTf–

Cr(III)) and its biocomposites (NCTf–Cr(III), WCTf–Cr(III))

Nature of film Contact angle (�) � Sd � Sp �Total

HW HEG HGL

CTf 44 60.5 64.5 1.06 89.79 90.85

NCTf 38.4 38 40.5 2.56 63.37 65.93

WHCTf 33.3 41.3 51.1 0.09 85.3 85.39

Film–Cr(III)

CTf–Cr(III) 40.8 20.2 28.1 12.81 44.89 57.7

NCTf–Cr(III) 53.1 53.5 55.4 2.31 52.13 54.44

WCTf–Cr(III) 52.5 39.7 42.2 11.29 36.92 48.21

� Sd dispersion forces, � Sp polar forces, W water, EG ethylene glycol,

and GL glycerol

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123

where Qads is adsorbed quantity of chrome (%), Ci is the

initial concentration of chromium (III) ions in solution

(mmol/l), and Cr is the chromium (III) ions concentration

remained in solution (mmol/l).

The ability to complex chromium (III) ions depends on

nature of complexing film (Fig. 1). After 10 min of contact

time, the capacity of chitosan/chitosan nanoparticles bio-

composite to complex chromium (III) ions was 7.5 %. In

contrast, the biocomposite of chitosan/chitosan whiskers

adsorbs around 10 %, while chitosan film adsorbs only

3 %. After 50 min, adsorbed quantity of Cr(III) was 18 %

for chitosan/chitosan whiskers biocomposite, 10 % for

chitosan/chitosan nanoparticles, and 5 % for chitosan film.

We conclude that biocomposite of chitosan/chitosan

whiskers adsorbs better than chitosan film and chitosan/

chitosan nanoparticles biocomposite. It can be explained by

an important contact surface for chitosan/chitosan whiskers

biocomposite.

Characterization of chitosan film and its biocomposites

after complexation with chromium (III) ions

Fourier transform infrared spectroscopy

Samples were recovered after 70 min and let to dry before

characterization.

The infrared spectrum (Fig. 2) shows that the peak of

N–H bending vibration at 1556 cm-1 for chitosan film and

its biocomposites shifted after adsorption of Cr(III) to

1600 cm-1 for chitosan film and 1640 cm-1 for biocom-

posites chitosan/chitosan nanoparticles and chitosan/chito-

san whiskers. Also the intensity of anti-symmetric

stretching of C–O–C at 1040 cm-1 decreased. The band at

2360 cm-1 of chitosan/chitosan nanoparticles disappeared

after complexation, with appearance for chitosan/chitosan

whiskers a peak near to 2100 cm-1. These results confirm

the interaction between chromium (III) ions and films.

Scanning electron microscopy analyses

After adsorption of chromium (III) ions chitosan film and

its biocomposites become rigid. Scanning electron micro-

scopic images (Fig. 3) revealed the presence of small white

spots like crystals; they are smaller and dispersed for

chitosan/chitosan nanoparticles biocomposite. For chito-

san/chitosan whiskers we have transparence effect for these

spots. The phenomenon can be attributed to the interfacial

interaction between films and chromium (III) ions.

Contact angle

We studied contact angle between films and liquid drop

after complexation with Cr(III). The results of Table 1

show that dispersive components of surface tension of

chitosan film and chitosane/chitosane whiskers biocom-

posite increase. Also the polar components decrease for all

of films, leading to decreasing of surface tension after

adsorption of Cr(III).

0 10 20 30 40 50 60 700

5

10

15

20

Time (min)

Chitosan/chitosan whiskers biocomposite

Chitosan/chitosan nanoparticles biocomposite

Chitosan film

Cr III adsorbed (%)

Fig. 1 Increasing quantity adsorbed of chromium (III) ions by

chitosan film, chitosan/chitosan nanoparticles, and chitosan/chitosan

whiskers biocomposites give us information about the best complex-

ing as a function of contact time in solution of CrCl3

4000 3500 3000 2500 2000 1500 1000 500

CTf

Wave number (Cm-1)

NCTf

WCTf

CrCl3

CTf-Cr(III)

NCTf-Cr(III)

WCTf-Cr(III)

Fig. 2 FTIR spectrum shows the difference before complexation of

chromium chloride (CrCl3) by chitosan film (CTf), chitosan/chitosan

nanoparticles (NCTf), and chitosan/chitosan whiskers (WCTf) bio-

composites and after complexation of Cr(IIII) by chitosan film (CTf–

Cr(III)) and its biocomposites (NCTf–Cr(III)), (WCTf–Cr(III)). This

difference confirms that there is interaction between Cr(III) and films

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123

We conclude that the decreasing polarity of films can be

attributed by the presence of Cr(III) on surface of films.

Conclusion

This study of complexation of chromium (III) ions by

chitosan film, chitosan/chitosan nanoparticles, and chito-

san/chitosan whiskers biocomposites required the fixation

of chromium solution concentration; its pH at 6.55 and the

mass of films was 2 mg. The results showed that biocom-

posite chitosan/chitosan whisker was the best complexing

of chromium (III) ions than chitosan film and chitosan/

chitosan nanoparticles biocomposite.

Our objective of this search is to approximate the opti-

mal conditions for recovery of chromium (III) ions from

wastewater.

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