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El Ghali, A., Ben Marzoug, I., Baouab, M. H. V., and Roudesli, M. S. (2012). "Separation and characterization of new cellulosic fibres from the Juncus acutus L plant," BioRes. 7(2), 2002-2018.


Cellulose fibres from the Juncus acutus L plant were isolated and characterized. The isolation of the fibres was performed by sequential NaOH treatment and H2O2 bleaching under different extraction conditions. The chemical and surface morphological structures of the Juncus acutus L fibres were characterized with FTIR, SEM, AFM, DSC, surface energy, diameter, density, and lignin content determination. Changes in structure and properties of the obtained fibres were observed by varying the concentration and the treatment time of the applied process. Results revealed that the optimum conditions to remove most of non-cellulosic materials from the Juncus acutus L plant were 7M NaOH, 3h and 100°C for alkaline procedure, and 10 mL.L-1 H2O2, 45 minutes and 95°C for bleaching treatment.

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Amel El Ghali,a,* Imed Ben Marzoug,b Mohamed Hassen V. Baouab,c and Mohamed Sadok Roudesli a

Cellulose fibres from the Juncus acutus L plant were isolated and characterized. The isolation of the fibres was performed by sequential NaOH treatment and H2O2 bleaching under different extraction conditions. The chemical and surface morphological structures of the Juncus acutus L fibres were characterized with FTIR, SEM, AFM, DSC, surface energy, diameter, density, and lignin content determination. Changes in structure and properties of the obtained fibres were observed by varying the concentration and the treatment time of the applied process. Results revealed that the optimum conditions to remove most of non-cellulosic materials from the Juncus acutus L plant were 7M NaOH, 3h and 100°C for alkaline procedure, and 10 mL.L-1 H2O2, 45 minutes and 95°C for bleaching treatment.

Keywords: Cellulose; Juncus acutus L; Isolation; Characterization

Contact information: a: Laboratoire des Polymères-Biopolymères, Matériaux Organiques (LPBMO), Faculté des Sciences de Monastir, Bd. de l’environnement, 5019, Université de Monastir, Tunisia ; b : Laboratoire de Génie Textile, 5017, Université de Monastir, Tunisia ; c : Institut Préparatoire aux Etudes d’Ingénieurs de Monastir, 5019, Université de Monastir, Tunisia ; * Corresponding author :


In recent years, there has been a growing interest in more efficient use of plant fibres, also known as lignocellulosic fibres, as raw materials for a variety of applications such as composite preparation (Habibi et al. 2008; De Rosa et al. 2010) and paper production (Ates et al. 2008), depending on their composition and physical properties. Cellulose, the most common organic substance in nature, is the main structural component that contributes strength and stability to the plant cell walls. It is found in the cell walls as a network of microfibrils embedded in a soft hemicelluloses and lignin matrix. Considerable research has been focused on the isolation of lignocellulosic fibres from many plants like esparto grass (Ben Marzoug et al. 2010), wheat straw and soy hulls (Alemdar and Sain 2008), soybean straw (Reddy and Yang 2009), and sugarcane bagasse (Sun et al. 2004).

The fibres studied in this work were extracted from Samaar morr (Juncus acutus L) commonly known as sharp rush or spiny rush, which is an erect plant that forms a perennial tussock up to 2 meters high. It belongs to the Juncaceae family and grows in western and southern Europe, Africa, and North and South America. Traditionally, this biomass has been employed by artisans and, as far as we know, there is only one publication that has reported the use of this plant as a raw material for papermaking (El Sayed 2004). Therefore, the exploitation of the Juncus acutus L plant in this unique appli-cation should create a great deal of research interest.

In the present study, the isolation of cellulose fibres was achieved by the use of alkaline solution followed by bleaching treatment. The lignin amount, the density, and the diameter of these fibres were measured. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and surface energy were also evaluated. The effect of treatment conditions such as time, NaOH, and H2Oconcentrations on the above properties of isolated fibers were examined in this paper.



The Juncus acutus L plants used in this study were collected at Monastir in the east of Tunisia during the period of March-April. Sodium hydroxide pellet for scouring, hydrogen peroxide (H2O2) [30% (W/W)]for bleaching, sodium silicate a stabilizer for H2O2, and carbon tetrachloride (CCl4), an immersion medium for evaluation of apparent density of the fibre, were used as received without further purification.

Procedure for the Extraction of Cellulose Fibres from Samaar morr Plant

The isolation of cellulose fibres required the removal of other components such as lignin, hemicellulose, and pectin from the Samaar morr plant. This was accomplished in alkaline medium using NaOH solution at different concentrations and treatment times, followed by bleaching procedure at various H2O2 concentrations and at pH 11. The fibres were extracted using a liquid to plant ratio of 10:1. At each step of the different treatments, the insoluble residue was extensively washed with distilled water until reaching neutral pH. The treatments and codifications of the samples are summarized in Fig. 1.

Fig. 1. Isolation scheme of cellulose fibers from Smaar morr plant by different chemical treatments

Characterization of Extracted Fibres

Fibre diameter

The diameters of the fibres were measured using a projection microscope with a magnification of 200. Twenty chosen readings samples were taken from each extraction procedure. The diameter was measured at 10 points, and the average value was then calculated.

Fibre density

The apparent fibre density was determined with a picnometer using carbon tetrachloride as the immersion liquid according to NFT 20-035 standard method at 25°C. This parameter was calculated using the following equation,


where ρCCl4 is the density of carbon tetrachloride (1.595, mfibre is the mass of dried sample (g), ml is the mass of the picnometer containing carbon tetrachloride (g), and mt is the mass of the picnometer containing both carbon tetrachloride and the mass of dried sample (g).

Lignin content

Lignin content in the extracted fibres was estimated by determining the dry mass remained after treating with 72% sulphuric acid according to the Klason’s method (Le Digabel and Avérous 2006). About 3 g of the sample was placed in a 100 mL flask, with 3 mL of 72% (w/w) H2SO4. The mixture was steeped for 2h at 20°C with frequent mechanical stirring. Afterwards, it was diluted with 40 mL of distilled water and heated under reflux for 3 h. It was then filtered, and the insoluble lignin was washed thoroughly with water to free it from traces of acid, dried at 105°C, and weighed.

Scanning electron microscopy (SEM)

The morphology of the various extracted fibres samples was investigated by using scanning electron microscopy (XL30 ESEM).

FT-IR spectral analysis

Fourier transform infrared (FTIR) spectroscopy was carried out to qualitatively identify the constituents of the various extracted fibres. The dried samples were ground into fine particles and mixed with KBr. They were then compressed into pellets and analyzed with Nicolet® 510M spectrophotometer operating in a transmission mode in the range of 500-4000 cm-1.

Differential scanning calorimetry (DSC)

Thermal analysis was performed using a Setaram differential scanning calorimeter. Each fibres sample was heated from room temperature to 500°C at a rate of 10°Cmin-1, under dynamic flow of air.

Surface energy

The contact angles (θ) were measured using three different liquids: ultrapure water, diodomethane (Aldrich, 99%), and formamid (Aldrich, 99%). The measurements were performed at room temperature (20°C). The surface energy was calculated according to the Owens-Wendt method, based on the Young-Dupre and Fowkes equations (Bessadok et al. 2007).

AFM analysis

The surface topography of extracted fibres was studied with a Nanoscope III atomic force microscope (Digital Instruments, Santa Barbara, USA). AFM images were recorded in the tapping mode, which consists in sweeping the surface of the sample using a tip oscillating at a frequency close to that of the cantilever resonance.

The contact with the surface was done when the tip reached the maximum amplitude of oscillation. Contrary to the contact mode, the siliceous tip, which intermittently contacts the surface, did not modify the state of this surface (El Ghali et al. 2011).


Fibre Diameter

The results of diameter determination for extracted fibres from the Samaar morr plant are shown in Table 1. As can be seen, there were significant differences between the various studied samples assessed by the obtained coefficients of variation (CV %). The obtained results concerning the alkaline procedure exhibited a decrease in diameter value with the increment of NaOH concentration or the exposure time.

The SmarS3 sample showed the lowest coefficient of variation (CV = 6.74%). This revealed that the other extracted fibres probably presented surface irregularities caused either by the partial removal of the cementing materials around the fibre-bundles or the degradation of the isolated fibres.

The treatment of SmarS3 alkaline treated fibres with H2O2 promoted a decrease in the diameter values that did not present great differences between each other. This could be attributed to the removal of surface impurities (lignin) during the hydrogen peroxide bleaching. The fibres treated with H2O2 presented an average diameter of 11.33 μm. This revealed that the applied treatment has removed the non-cellulosic substances without significantly altering the extracted fibres. The best coefficient of variation was obtained for the fibres bleached with 10 mL.L-1of H2O2 (SmarS7), having an average diameter value of 11.75 μm.

The diameter of SmarS7 fibers was considered small compared to that of other natural ones like coir (Saw et al. 2011), coconut (Brígida et al. 2010), okra (De Rosa et al. 2010), etc., and comparable to glass (Sezer and Aran 2001) and carbon ( Yao et al. 2003) fibers. This result appears promising in terms of possible use of these extracted fibers for the obtainment of a sounder interface.

Table 1. Diameter and Density Values of the Different Extracted Fibers

Fibre Density

The influence of chemical treatments on the fibre densities is illustrated in Table 1. As can be seen, this parameter was highly affected by the extraction conditions. The decrease in density values of extracted fibres suggested the reduction of hemicelluloses, lignin, and pectin amounts after the alkaline procedure. However, the low-density values obtained in the case of SmarS4 and SmarS5 samples showed the degradation of these fibres. This can be explained by the fact that the chemical attack was probably stronger, inducing structural changes of the extracted fibres. The obtained results could also be attributed to the entrapped air on and among the fibrils due to poor wetting of the fibre by carbon tetrachloride. Thus, the applied treatment conditions caused a mass loss and considerably reduced the fibre volume, indicating that these materials have a more porous structure. The density of SmarS3 sample value was found to be equal to 1.584, which is compar-able to that of cotton fibres (Spinacé et al. 2009).

The bleaching of SmarS3 fibres caused a reduction of the density values (Table 1) confirming that the amount of lignin detached from the extracted fibres was improved by the hydrogen peroxide treatment. This could produce void spaces between the fibrils, causing a decrease of this parameter values. The low variability of the measured densities for SmarS7 and SmaS8 samples suggested that these fibres possibly exhibited homogeny-eous surfaces and contained low quantities of non-cellulosic materials.

The increase of H2O2 concentration in the case of SmarS9 sample corresponded to a decrease in the density value, suggesting probably that fibrillation took place. In this case, the air volume became more important which caused a reduction in the density value, as can be seen in Table 1.

The measured density of SmarS7 fibers is comparable to those of other cellulosic materials such as banana (Deepa et al. 2011), date palm rachis (Khiari et al. 2011), and sisal (Satyanarayana et al. 2007), and higher than those of curaua (Satyanarayana et al. 2007), Stipa tenacissima L (Bessadok et al. 2007), and luffa ( Satyanarayana et al. 2007) fibers.

Lignin Content

Chemical pulping processes are designed to remove the majority of lignin in order to release the fibres. The efficiency of the treatment methods was evaluated through the determination of lignin content. Table 2 reveals that the rise of NaOH concentration or treatment alkaline time was accompanied by a reduction in insoluble lignin content. Results also showed that the amount of lignin contained in SmarS3, SmarS4, and SmarS5 were relatively stable. This indicated that strong conditions did not significantly affect the lignin amount, but it could lead to the degradation of the extracted fibres. The hydrogen peroxide bleaching resulted in a considerable decrease in the lignin content particularly when the concentration of H2O2 was increased.

Table 2. Lignin Content and Energy Surface Values of the Different Extracted Fibers

Scanning Electron Microscopy (SEM) Analysis

The changes in cellulose structure induced by the different chemical treatments were also corroborated by other physicochemical tests such as SEM examinations (Figs. 2 and 3). Figures 2(a) and 2(b) showed the overlapping of non-cellulosic substances along the length of the fibres that are bonded firmly together by the cemented materials that give strength to the bundle as a whole. This could be attributed to a low treatment duration or NaOH concentration.

These two parameters were insufficient to remove a great percentage of these substances. However, in some cases, where the chemical attack was probably stronger, the fibres appeared to be deformed with an opened structure, indicating the damage on its surface caused by the increase in the treatment time, as can be seen in Fig. 2 (d).

Figure 2 (c) indicates that the SmarS3 sample consisted basically of elementary cellulose fibres still incorporating lignin compounds, as demonstrated by the presence of some deposits on the surface of the extracted fibres. This can be explained by the fact that during alkaline treatments, constituents like pectin and hemicelluloses are usually hydro-lyzed by the action of NaOH solutions, whereas lignin can be removed during an additional bleaching step using hydrogen peroxide.

The SEM micrograph of SmarS5 (Fig. 2(e)) sample did not show a clear separation of extracted fibres in spite of the increase in NaOH concentration (8 M). This image cannot give, in this case, considerable information about the morphological surface of the obtained fibres.

Owing to the fact that some of lignin content was still not completely removed from the SmarS3 sample, bleaching treatment was carried out in this study. SEM examinations of the longitudinal surface of bleached smaar fibres are depicted in Fig. 3. Figure 3 (a) shows the presence of some impurities on the surface of SmarS6 fibres (treatment with 8 mL.L-1 H2O2), indicating the partial removal of lignin that interconnect the cellulose fibres.

SEM picture of SmarS7 sample (Fig. 3(b)) visually suggested the removal of non-cellulosic materials after H2O2 treatment using a concentration of 10 mL.L-1 resulting in smooth, compact, and clean fibre surfaces that are well defined and separated. The obtained fibres are reasonably uniform in cylindrical shape. When the concentration of H2O2 exceeds 10 mL.L-1(Figs. 3(c) and 3(d)), we observed irregularities in the diameter of the extracted fibres revealing that the applied treatment conditions have affected their final size.

Fig. 2. SEM micrographs of extracted fibers by NaOH treatment: (a) SmarS1, (b) SmarS2, (c) SmarS3, (d) SmarS4, and (e) SmarS5

Fig. 3. SEM micrographs of bleached fibers by H2O2: (a) SmarS6, (b) SmarS7, (c) SmarS8, and (d) SmarS9

Spectroscopic Analysis

FTIR spectroscopy is an appropriate technique by which to establish the variations introduced by different treatments on the chemical structure of the isolated fibres. Figures 4 and 5 showed the FTIR spectra of the different isolated fibres from the Smaar moor plant. All these spectra revealed a broad peak at 3424 cm-1, suggesting hydrogen bonded ν(O-H) stretching vibration of α-cellulose. The bands at 2921 cm-1 and 2851 cm-1 are characteristics of the C-H stretching vibration from CH and CH2 in cellulose component (Jayaramudu et al. 2010; Marais et al. 2008). The 1424 cm-1 band could be attributed to the CH2 symmetric bending present in cellulose (Bessadok et al. 2008; De Rosa et al. 2011). Furthermore, the absorbance at 670 cm-1 corresponds to the C-OH bending deformation (Sgriccia et al. 2008). The band at 1376 cm-1 represents symmetric C-H bending from the methoxyl group (Adel et al. 2010). The band around 1059 cm-1 is probably due to the C–OH stretching vibration of the cellulose backbone (ν C-O secondary alcohol) (Bessadok et al. 2008). In addition, the band at 1161 cm-1corresponds to C-O-C stretching at the β(1,4)- glycosidic linkage (Zhou et al. 2009). The peak, observed at 895 cm-1, is attributed to the β-glycosidic linkages (De Rosa et al. 2010).

Fig. 4. FT-IR spectra of extracted fibers by NaOH treatment: (a) SmarS1, (b) SmarS2, (c) SmarS3, (d) SmarS4, and (e) SmarS5

All IR spectra showed the lack of a band at 1731 cm-1 that would be characteristic of the C=O stretching of the acetyl groups of hemicelluloses (Abrahama et al. 2011). This means that hemicelluloses had been effectively dissolved and removed by the alkaline treatment.

The presence of lignin component was also assessed by the IR spectroscopy analysis. In all cases, the band observed at around 1615 cm-1 is attributed to the C-O stretching of lignin (Jayaramudu et al. 2010). The IR spectra illustrated in Fig. 4 shows the presence of a peak around 1505 cm-1, which could be assigned to the aromatic C=C stretch of aromatic rings of lignin (Alemdar and Sain 2008). The intensity of this band decreased in the IR spectra of bleached fibres (Fig. 5), confirming the efficiency of the hydrogen peroxide treatment.

Fig. 5. FTIR spectra of bleached fibers by H2O2: (a) SmarS6, (b) SmarS7, (c) SmarS8, and (d) SmarS9

The various IR spectra showed also the absence of some bands that characterize the lignin component. These bands are identified in Table 3.

Table 3. Assignment of Some Lignin absent FT-IR Peaks and their Relative Intensities

The results in Fig. 5 showed that: (1) the amount of cellulose was high, as confirmed by the presence of many bands characterizing these materials, (2) hemicelluloses were completely removed from the different extracted fibres, and (3) the absence of the majority of characteristic lignin peaks in the spectra of alkaline treated fibers as well as for the bleached ones, which was believed to be due to the removal of lignin after the chemical treatments.

Differential Scanning Calorimetry (DSC) Analysis

Differential scanning calorimetry (DSC) is one of the most widely used techniques to monitor the structural dependence on the thermal degradation of natural lignocellulosic fibres. DSC analysis of Samaar-extracted fibres using alkaline treatment followed by bleaching are shown in Figs. 6 and 7, respectively. It can be noted that the endothermic peak of all the studied samples, at approximately 104°C, can be related to the water loss associated with moisture present in the extracted fibres.

During the thermal characterization of lignocellulosic fibers, the decomposition of lignin compound takes place within the temperature range of 250 to 500°C (Shen et al. 2009) and could also be occurring from a temperature of 340°C (Yang et al. 2004). It is well known that the processes used in the removal of lignin from plants are conducted under conditions where lignin is progressively broken down to lower molecular weight fragments, resulting in change of physico-chemical properties, including thermal character-istics (Mousavioun and Doherty 2010). As can be seen from Fig. 6 and 7, the thermal behavior of lignin component varied from one sample to another, depending on the applied extraction process. The curves in Fig. 6, relative to SmarS1, SmarS2, and SmarS3 samples, showed similar thermal behavior. Indeed, only one endothermic transition was observed around 374, 378, and 380°C, respectively. However, SmarS4 and SmarS5 samples presented two transitions, indicating that the decomposition of lignin component in this range of temperature occurs in two steps: the first is situated at 342°C and the second at 374°C. This means that the lignin contained in the first three samples (SmarS1, SmarS2, and SmarS3) had undergone only one transformation, whereas the two other samples (SmarS4 and SmarS5) had undertaken two state transformations that could be attributed either to a higher NaOH concentration or higher treatment alkaline time. The obtained results also exhibited that SmarS4 and SmarS5 samples contained two types of lignin: the first is amorphous, which could be related to the thermal decomposition of the aliphatic moiety (Saw et al. 2011), whereas the second is compact and more crystalline, which is probably related to the decomposition of aromatic rings of this molecule (Saw et al. 2011). This confirmed the heterogeneity of these extracted fibres.

The DSC thermograms of SmarS2 and SmarS3 samples, treated with 7M NaOH concentrations, are almost confused. However, and although that SmarS1 sample showed similar thermal behavior, it needs a greater flow heat for lignin decomposition than the other two samples (SmarS2 and SmarS3). This revealed that the SmarS1 material contained a greater amount of lignin than the other ones, which could be attributed to lower NaOH concentration, confirming the results previously indicated in this paper. It can be also noted that between 250 and 320°C, representing the decomposition zone of cellulose fragment (Xiao et al. 2001), the SmarS3 sample needed greater heating flow compared to that of SmarS2 sample. This revealed that the thermal stability of SmarS3 is slightly higher than that of SmarS2, indicating that the latter contained a lower amount of cellulose (Kim et al. 2004). This signifies that its cellulose amount was greater than that of SmarS2 sample. The obtained results justify the choice of SmarS3 sample for the bleaching treatment.

The DSC thermograms of the bleached SmarS3 sample at various H2O2 concentrations are illustrated in Fig. 7. The thermal behavior of the SmarS6 sample revealed that the bleaching treatment induced the division of lignin into two parts; the first one was amorphous and the second was more crystalline. These two types of lignin required more heating flow to be decomposed as compared to the other bleached samples. This revealed that the SmarS6 sample contained higher amount of lignin than the other ones.

The curves shown in Fig. 7 also exhibited that the decomposition of the amorphous part of lignin contained in the SmarS7 sample took place at around 339°C. However, in the case of SmarS8 and SmarS9, this temperature increased towards 346 and 343°C, respect-tively. The obtained result revealed an increasingly important fragmentation of lignin, which decreased the molecular cohesion of this compound that exists in these two samples (SmarS8 and SmarS9). This could be attributed to the fact that the amorphous zone of lignin decreased with the increment of H2O2 concentration. In this case, SmarS8 and SmarS7 samples present an increase in the crystalline zone of lignin, which requires higher temperature to be decomposed.

The DSC thermal analysis of SmarS7, SmarS8, and SmarS9 samples showed a weak transition at about 377°C. This suggested that the lignin included in these samples has undergone an intensive fragmentation (lignin in its crystalline form) by comparison to that of SmarS6 sample.

Fig. 6. DSC analysis of extracted fibers by NaOH treatment

Fig. 7. DSC analysis of bleached fibers by H2O2

Surface Energy

The surface energy of alkaline treated fibres calculated from contact angles are given in Table 2. The analysis of data showed that the increment, in NaOH concentration or in treatment time, was accompanied by a decrease in the total surface energy. This reduction is mainly due to the decrease of lignin amount. Indeed, SmarS1 and SmarS2 samples showed the highest surface energy with values near to that of lignin (Lucia 2009). This revealed that these samples still contained other substances than cellulose, and that such substances induced a decrease of their absorptivity involving higher surface energies. However, the SmarS3, SmarS4, and SmarS5 presented lower values of surface energy and consequently lower amounts of lignin. It can also be noted that SmarS4 and SmarS5 displayed surface energy values less important than those of the SmarS3 one. Since the characterizations previously carried out in this paper showed that these two samples are more heterogeneous than the SmarS3 material, the later will be bleached by different H2O2 concentrations.

After the bleaching treatment, the value of surface energy became stable towards a value of 45 mJ.m-2. The obtained value is close to the surface energy of Stipa tenacissima L fibres that were extracted with a minimum of degradation (Ben Marzoug. 2009).

AFM Analysis

The wettability tests have shown variability in the energy surface values for the alkaline treated fibres. For this, we chose to evaluate the surface ultrastructures of SmarS2, SmarS3, and SmarS4 samples using AFM analysis in order to assess the effect of NaOH treatment time on the surface morphology of the extracted fibres. The AFM characterization of SmarS7 bleached sample was also investigated. The surface morphology of the isolated fibres is observed to undergo significant change, as can be seen in Fig. 8.