Preparation And Characterization Of Magnetic Cellulose Fibers Modified With Cobalt Ferrite Nanoparticles

Journal Pre-proof Preparation And Characterization Of Magnetic Cellulose Fibers Modified With Cobalt Ferrite Nanoparticles

Xiomara Pineda, Germán C. Quintana, Adriana P. Herrera, Jorge H. Sánchez PII:

S0254-0584(20)30157-7

DOI:

https://doi.org/10.1016/j.matchemphys.2020.122778

Reference:

MAC 122778

To appear in:

Materials Chemistry and Physics

Received Date:

19 June 2019

Accepted Date:

04 February 2020

Please cite this article as: Xiomara Pineda, Germán C. Quintana, Adriana P. Herrera, Jorge H. Sánchez, Preparation And Characterization Of Magnetic Cellulose Fibers Modified With Cobalt Ferrite Nanoparticles, Materials Chemistry and Physics (2020), https://doi.org/10.1016/j. matchemphys.2020.122778

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.

Journal Pre-proof

PREPARATION AND CHARACTERIZATION OF MAGNETIC CELLULOSE FIBERS MODIFIED WITH COBALT FERRITE NANOPARTICLES Xiomara Pinedaa*, Germán C. Quintanaa, Adriana P. Herrerab and Jorge H. Sáncheza aPulp

and Paper Research Group, Faculty of Chemical Engineering, Universidad Pontificia Bolivariana, P. O.

Box 56006, Medellín, Colombia bNanomaterials

and Computer Aided Process Engineering Research Group (NIPAC), Chemical Engineering

Program, Universidad de Cartagena, Piedra de bolivar Campus, P. O Box 130010, Cartagena, Colombia *Corresponding author. E-mail address: [email protected]

Abstract Magnetic fibers were prepared by lumen loading method using bleached eucalyptus fibers as cellulose source and cobalt ferrite nanoparticles (CoFe2O4). For this, CoFe2O4 nanoparticles were first synthesized by the chemical co-precipitation method and then incorporated into eucalyptus fibers using polyethylenimine (PEI) as retention-aid. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM-EDS), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) for magnetic properties. The obtained nanoparticles showed an inverse cubic spinel crystalline structure with an average size of 9 nm, exhibiting further a ferrimagnetic behavior. It was observed in the SEM images the deposition of nanoparticles on surface and into macropores of fibers. The results indicate a maximum saturation magnetization of ~8 emu/g for the modified fibers. Besides, through an experimental design, it was established that loading degree and magnetic response of modified fibers are affected by both dose of nanoparticles and agitation time used in the modification process. Keywords: Cobalt ferrite nanoparticles, chemical co-precipitation, eucalyptus fibers, lumen loading, magnetic fibers.

Journal Pre-proof

1. Introduction The modified cellulose fibers with magnetic nanoparticles can be conceived as a “smart material” since certain properties can be altered in a controlled way, in response to an external stimulus, such as temperature, pH, ionic forces, magnetic fields, etc [1]. These materials sensitive to external stimuli can undergo changes from their behavior in flow to their final properties as a finished product. Thus, materials based on fibers modified with magnetic nanoparticles exhibit great advantages, such as the possibility of manipulating the orientation and flocculation of suspended fibers after applying a magnetic field, as well as the production of magnetic paper for purposes of coding and storing information, multi-printing, and magnetic protection [1, 2]. One of the most studied magnetic materials has been cobalt ferrite (CoFe2O4), due to its high magnetic anisotropy, moderate saturation magnetization, good chemical stability and mechanical hardness. Magnetic properties of CoFe2O4 make it an interesting material for technological applications such as the manufacture of magnetic devices[3]. For the synthesis of magnetic nanoparticles a wide variety of techniques such as thermal decomposition [4], sol-gel [5], hydrothermal [6] and chemical co-precipitation [7] have been employed. However, the most used method is chemical co-precipitation due to its simplicity and low cost [3,8]. Hence, Samadi et al. [9] studied the magnetic-field assisted synthesis of cobalt ferrite nanoparticles via reverse co-precipitation. Their results reveal that the presence of an external magnetic field during the synthesis process enlarge the crystallite size of the particles and enhance their magnetic properties. Likewise, Ojha and Kant [10] prepared CoFe2O4 nanoparticles by chemical co-precipitation route at low temperature, finding a narrow distribution of particle size with an average size of 15 nm. On the other hand, Chia et al. [3, 15] reported the synthesis of magnetite nanoparticles by the technique of chemical co-precipitation using ferric salts with a stoichiometric ratio Fe3 Fe 2 equal to 2 in an alkaline solution of NaOH. In the literature have been reported two methods for preparation of magnetic fibers: lumen loading and in situ synthesis. The lumen loading method consists in introduce magnetic nanoparticles inside the lumen of the fibers by a physical deposition process. Instead, the in situ synthesis involves synthesizing of particles within the cellulosic matrix. The reaction

Journal Pre-proof

space constraints favor the formation of particles of nanoscale dimensions, which have unique magnetic and optical properties [3, 4]. Following this method, Xu et al. [14] modified cellulose fibers with hematite nanoparticles in supercritical carbon dioxide, obtaining a water-repellent composite with ferromagnetic properties. On the other hand, and using the lumen loading method, Marchessault et al. [15] prepared magnetic cellulose fibers employing magnetite nanoparticles. They reported that the obtained magnetic fibers tend to align under the action of a magnetic field, showing that the anisotropy of the fibers can be manipulated hydrodynamically to obtain an axially oriented paper. On the other hand, Zakaria et al. [3, 11, 12] studied the properties of magnetic paper prepared by lumen loading using a kenaf pulp suspension and magnetite nanoparticles. Their results showed an improvement of the magnetic properties and a detriment of the mechanical properties of the paper by increasing the loading degree of the magnetic particles. Finally, a review on the use of fillers in cellulosic paper for functional applications was reported by Shen et al. [18]. The aim of this research is to obtain magnetic cellulose fibers by the lumen loading method using bleached eucalyptus fibers and cobalt ferrite nanoparticles. The effects of nanoparticles dose and mixing parameters on loading degree, magnetic properties, and water retention value (WRV) of modified fibers were studied following an experimental design protocol.

2. Experimental 2.1.

Materials

Iron chloride hexahydrate (97 wt%, Merck), cobalt chloride hexahydrate (99 wt%, Panreac), sodium hydroxide (97wt%, Merck) and ethyl alcohol (97wt%, Merck) were used to synthesize magnetic nanoparticles. Bleached eucalyptus pulp, supplied by a local company, was used as source of cellulose, and polyethylenimine branched (99 wt%, Aldrich) with a mass-average molecular weight of 10.000 g/mol, as retention-aid. Distilled water was used to prepare all solutions and suspensions.

Journal Pre-proof

2.2.

Synthesis of cobalt ferrite nanoparticles

Cobalt ferrite nanoparticles were synthetized by coprecipitation method. In a typical synthesis, 100 mL of an aqueous solution of FeCl36H2O (0.4 M) was added to 100 mL of an aqueous solution of CoCl26H2O (0.2 M). This mixture was heated up to 60 °C and stirred at 150 rpm. Then, 100 mL of NaOH solution (6 M) were added as precipitating agent, turning the solution into black color, indicating the formation of cobalt ferrite. The total time of synthesis was one hour. After cooling to room temperature, nanoparticles were decanted using a permanent magnet, washed twice with distilled water and ethanol, and dried at 60 °C overnight [19]. 2.3.

Modification of eucalyptus fibers with cobalt ferrite nanoparticles

Magnetic fibers were obtaining by lumen loading method. Firstly, eucalyptus pulp was disintegrated in distillated water using a JSR disintegrator (JSR Instruments, India) according to TAPPI method T205 sp-02 [20]. Then, the eucalyptus fibers suspension, 1.2 wt%, was mixed with cobalt ferrite nanoparticles and stirred constantly. A 23 factorial design with five replicates at center point was adopted for the experiments. The values of variables examined are summarized in Table 1. To improve the retention of nanoparticles in fibers lumen, polyethylenimine (2% based on dry pulp) was added to the suspension under continuous stirring at 400 rpm during 4 hours [3, 20]. The final suspension was carefully subjected to a flotation process in order to separate the modified fibers from the nanoparticles that were not incorporated to fibers. Finally, the modified fibers were washed in a sieve mesh with tap water for approximately 20 min and then dried at 60 °C for 24 h. 2.4.

Physical, chemical, and magnetic characterization

Ferrite cobalt nanoparticles were structural and morphologically characterized by transmission electron microscopy (TEM) using a Tecnai F-20 Super Twin 200 kv microscope (FEI company, USA) and by X-Ray diffraction (XRD) using an Xpert PANalytical Empyrean Serie II (Malvern Panalytical, USA) X-ray diffractometer. The surface

Journal Pre-proof

composition of nanoparticles and fibers were determined by energy dispersive spectroscopy using a JCM-6000 Plus microscope (JEOL Ltd, Japan). To verify the incorporation of the nanoparticles on fibers, these were analyzed by scanning electron microscopy (SEM) in a JCM-6000 Plus microscope (JEOL Ltd, Japan) and by infrared spectroscopy in a Nicolet 6700 FTIR spectrometer (Thermo Scientific, Canada) in the range of 4000 - 400 cm-1. The magnetic loading degree of the fibers was estimated by the ash content according to TAPPI T 211 om-02 [22]. Magnetic properties of both magnetic particles and modified fibers were measured by a vibrating sample magnetometer (Quantum Design, USA) at 300 K. Table 1. Experimental factors considered to preparation of magnetic fibers (MF). Test

Nanoparticles dose (% based on dry pulp)

Stirring rate (rpm)

MF1

60%

700

Mixing time before add PEI (min) 45

MF2

60%

700

45

MF3

60%

700

45

MF4

100%

400

30

MF5

20%

400

30

MF6

20%

1000

30

MF7

20%

400

60

MF8

100%

400

60

MF9

100%

1000

60

MF10

60%

700

45

MF11

100%

1000

30

MF12

20%

1000

60

MF13

60%

700

45

Additionally, the water retention value (WRV) of fibers, which is a useful reference for dewatering behavior of pulp in paper industry, was measured as a performance characteristic of the suspension. For this, 1.0 g of sample was soaking in distilled water for one hour. Then, the swollen fibers were centrifuged at 3000 rpm for 15 min in a U-320R centrifuge (BOECO, Germany) using a 50 mL tube with a small mesh in the bottom that allowed the passage of water [23]. Subsequently, the sample was weighted and dried at 105 °C for 24 hours. The WRV was calculated from Equation 1:

Journal Pre-proof

WRV 

Wwet  Wdry Wwet

100

(2)

Where Wwet is the sample weight after centrifuging and Wdry is the absolute dry weight of the sample.

3. Results and discussion 3.1.

TEM and DRX analysis

Figure 1 shows the transmission electron micrograph for the cobalt ferrite nanoparticles. As can be seen, the nanoparticles have an irregular and polydisperse morphology, which could be attributed to the selected synthesis process, which does not allow control over the final shape and size of the particle [8]. Besides, it is observed a strong agglomeration between particles, perhaps induced by the attractive forces of Van der Waals and the magnetostatic interactions [13, 24, 25]. The distribution of particle sizes was determined through the measurements of about 500 nanoparticles observed in the TEM micrograph (Fig. 2). According to this distribution, the nanoparticles show to have an average diameter of 11.0 ± 4.4 nm.

Journal Pre-proof

Figure 1. TEM micrography of the CoFe2O4 nanoparticles.

Figure 2. Size distribution histogram of CoFe2O4 nanoparticles.

X-ray diffraction pattern is shown in Figure 3. The diffractogram exhibits six peaks at 2ϴ° angles of 21.21°, 35.18°, 41.44°, 50.60°, 63.09°, 67.33° and 74.17°corresponding to Miller indices (hkl): (111), (220), (311), (400), (422), (511) and (440) respectively. These peaks are characteristic of the cobalt ferrite cubic structure [7, 26].

Figure 3. X-ray diffraction patterns for CoFe2O4 nanoparticles.

Journal Pre-proof

On the other hand, the average crystal size (D) was determined with the processing of DRX patterns and the Scherrer equation [7, 27]:

D

0.9 ,  cos 

(3)

where  is the X-ray wavelength (CuKα radiation and equals to 0.154056 nm),  represents the Bragg diffraction angle, and  is the FWHM (“Full Width Half Maxima”) of the XRD peak which appears at the diffraction angle . It was found that the average crystal size of the cobalt ferrite nanoparticles was approximately 9 nm, which is similar to the size obtained by transmission electron microscopy. Additionally, from the diffraction patterns, other crystal lattice parameters such as interplanar distance (dhkl), lattice parameter (a), unit cell volume (V) and X-ray density (dx), were calculated by the following set of equations [7]:

d hkl 

 2sin 

,

2 a  d hkl (h 2  k 2  l 2 ),

(4)

V  a3 , dx 

8M w , Na 3

where Mw and N represent the molecular weight of cobalt ferrite and the Avogadro number, respectively. Lattice parameters of cobalt ferrite nanoparticles (Table 2) agree well with those obtained by Vinosha et al. in a previous work [7]. Table 2. Lattice parameters of synthesized CoFe2O4 nanoparticles.

Parameter Interplanar distance (d311) (Å) lattice parameter (a) (Å) Unit cell volume (V) (Å3) X-ray density (dx) (g/cm3)

Value 2.12 7.22 376.62 8.28

Journal Pre-proof

3.2.

SEM and EDS analysis

Figure 4 shows a scanning electron micrograph of modified fibers. It is evidenced the incorporation of nanoparticles into the fiber lumen and the adhesion of the nanomaterial on surface of the fiber. Furthermore, the spectrum obtained by EDS (Fig. 5) indicates the presence of cobalt, iron and oxygen, which is consistent with the chemical composition of cobalt ferrite nanoparticles. Table 3 presents a summary of the chemical composition per element. It can be notice that the Fe/Co ratio existing in the nanoparticles is 1.64, indicating that the cobalt ferrite was synthesized with a nominal stoichiometry close to that initially formulated.

Figure 4. SEM image for cellulose fibers loaded with CoFe2O4 nanoparticles.

Journal Pre-proof

Figure 5. EDS spectrum for cellulose fibers loaded with CoFe2O4 nanoparticles. Table 3. Chemical composition by elements of cellulose fibers loaded with CoFe2O4 nanoparticles.

3.3.

Element

% Atom

O

15.35

Fe

27.33

Co

16.63

FTIR analysis

FTIR spectra of cobalt ferrite nanoparticles (CoFe2O4), unmodified fibers (UMF) and modified fibers (MF) are shown in Figure 6. Spectrum (a), presents a wide absorption band around 3364 cm-1, associated to the stretching vibrations of the water remaining on the surface of the nanoparticles [8, 29]. Also, it is observed a medium band at 1338 cm-1, which is associated to the bending vibration of the O-H alcohol bond. This is probably due to the presence of traces of ethanol trapped into the micropores of the nanaoparticles after the washing step. The strong absorption bands at 524 and 441 cm-1 correspond to the vibrations of the metal-oxygen (M-O) bonds in the octahedral and tetrahedral sites of the spinel cubic structure. The band at 441 cm-1 corresponds to the Co-O bond vibration, while the band at

Journal Pre-proof

524 cm-1 is associated with the Fe-O bond vibration [7]. The presence of these bands confirms that the synthesized nanoparticles crystallized in the spinel structure [13, 30, 31]. As shown in the spectrum (b), the eucalyptus fibers exhibit a band near at 3305 cm-1, originated by the stretching O-H bond, a band at 2888 cm-1 due to the stretching vibration of C-H bond, and an absorption band approximately at 1660 cm-1 corresponding to the vibrations of H-O-H (absorbed water) bond. Moreover, the spectrum presents two bands in the region between 1500 and 1300 cm-1 caused by the flexing of the C-H bond. Near to 1059 cm-1, it is shown a band characteristic of cellulose, given by the stretching vibrations of C-O bond [32, 33]. In the spectrum (c), it is evident the effective incorporation of the nanoparticles in the eucalyptus cellulose, due to the presence of absorption bands characteristics of cobalt ferrite and polyethylenimine, which was added for the nanoparticles retention on the fiber. The spectrum (c) presents all the bands before mentioned in the spectra (a) and (b), as well as an overlapped band around 3305 cm-1 due to the stretching of the N-H bond of PEI. Finally, it is observed in 1580 cm-1 a peak due to the flexing of the primary amine (-NH2) groups of the polymer [33].

Journal Pre-proof

Figure 6. FTIR spectra for the samples: (a) CoFe2O4, (b) UMF y (c) MF8.

3.4.

Loading degree

Table 4 shows the loading degree of magnetic fibers. The highest value obtained was of 14.12%, corresponding to sample MF8. This result is similar with that obtained for Wu et al. [21], who modified cellulose fibers with magnetite using the lumen loading method, achieving 13.2% of magnetic material loading. Likewise, Chia et al. [11] modified kenaf fibers with Fe3O4 nanoparticles by the same technique, finding a loading degree of the fibers about 22%.

Journal Pre-proof

Table 4. Loading degree of the magnetic fibers. Sample

Loading degree (%)

MF1

3.54 ± 0.32

MF2

3.01 ± 2.38

MF3

2.75 ± 0.22

MF4

5.11 ± 0.97

MF5

2.17 ± 0.59

MF6

3.34 ± 0.25

MF7

2.12 ± 0.10

MF8

14.12 ± 1.01

MF9

12.05 ± 1.05

MF10

2.33 ± 0.20

MF11

8.11 ± 0.16

MF12

2.24 ± 0.26

MF13

4.17 ± 0.21

Despite the lumen loading methodology has been followed by many researchers to incorporate magnetic particles to fibers, including this study, it is evident that the results obtained show significant differences, depending of many factors such as fibers source, initial condition of fibers, filling nature, process parameters, and the physicochemical conditions of suspended materials [34]. Thus, an analysis of variance (ANOVA) was then performed to determine the effect of the modification process parameters on loading degree (see Table 1). In order to satisfy the normality assumption of the statistical analysis, it was necessary to perform a transformation of the response variable, as given by equation 4:

TLD 

1 (% Loading degree) 2

(5)

A summary of the ANOVA results for the transformed loading degree (TLD) is shown in Table 5. The results exhibit an R2 of 97.74% of the variability of the data and an R2 of 92.46% adjusted by degrees of freedom (DF). Additionally, it is observed that only the nanoparticles dose effect has a statistical significance with a P-value less than 0.05, that is, a statistical

Journal Pre-proof

significance with a confidence level of 95%, as shown by the Pareto diagram in Figure 7. The negative effect on the TLD indicates an opposite effect on loading degree, i.e., the loading degree is affected mainly by the nanoparticles dose used in each test. This fact may be attributed to a higher probability for particles incorporation as the concentration of particles in the suspension increases, for appropriated mixing conditions. Therefore, it is possible to say that the stirring rate and mixing time were always suitable for the modification process, since they had no influence in the loading degree of fibers. Table 5. ANOVA for transformed loading degree (TLD) of the magnetic fibers. Effects

Sum of squares DF Mean Square F-Ratio

P-Value

A:Nanoparticles dose

0.054507

1

0.05451

78.58

0.0125

B: Stirring rate

0.003587

1

0.00359

5.17

0.1508

C: mixing time before add PEI

0.000804

1

0.0008

1.16

0.3944

AB

0.002006

1

0.00201

2.89

0.2312

AC

0.003347

1

0.00335

4.83

0.1592

BC

0.001877

1

0.00188

2.71

0.2417

ABC

0.000653

1

0.00065

0.94

0.4342

Lack of adjustment

0.000159

1

0.00016

0.23

0.6795

Error

0.001387

2

0.00069

Total (corr.)

0.068326

10

Journal Pre-proof

Figure 7. Pareto diagram for the transformed loading degree (TLD). 3.5.

Magnetic properties

The magnetic properties of cobalt ferrite nanoparticles and modified fibers were determined from measurements of isothermal magnetic hysteresis loops at 300 K, as shown in Figures 8 and 9, respectively. All the results are referred to the total weight of the samples.

Figure 8. Magnetization curves at 300 K for CoFe2O4 nanoparticles.

Journal Pre-proof

Figure 9. Magnetization hysteresis loops at 300 K for magnetic fibers with low loading degree (MF6) and high loading degree (MF8). Inset images show details about remanence and coercivity of samples.

The synthesized cobalt ferrite nanoparticles exhibit a saturation magnetization (MS) of about 57 emu/g, as observed in Figure 8.

This value compares well with the saturation

magnetization reported by Raut et al. [35] and Houshiar et al. [36], ], who determined a Ms of 65 emu/g and 56 emu/g for cobalt ferrite nanoparticles, respectively. A narrow magnetic hysteresis was observed for the synthesized cobalt ferrite nanoparticles (Figure 8), indicating a small quantity of dissipated energy necessary to invert the magnetization [25]. Moreover, the particles exhibit a ferrimagnetic behavior, which can be explained by the antiparallel ordering of the crystal structure of the two magnetic ions (Fe+3 and Co+2) located in the tetrahedral and octahedral positions of the spinel structure [24, 29, 31]. On the other hand, the remanence magnetization (MR) and coercivity (HC) of the synthesized nanoparticles show values of 9.30 emu/g and 261 Oe, respectively, which indicate the suitability of this magnetic material for recording media [8, 31]. Once the magnetic nanoparticles were incorporated in the cellulose fibers, it was observed a decrease in the saturation magnetization of the samples, as displayed in Figure 9. This fact can be attributed to the low loading degrees achieved during the modification of the fibers with the cobalt ferrite nanoparticles, as indicated in Table 4. Magnetization curves of

Journal Pre-proof

modified fibers (Fig. 9) exhibit also a narrow magnetic hysteresis and a ferrimagnetic behavior, which is consistent with the magnetic properties of the incorporated CoFe2O4 nanoparticles. Table 6 presents a summary of the magnetic parameters, such as saturation magnetization (MS), remanence magnetization (MR), and the coercivity (HC) of the magnetic fibers. Table 6. Magnetic properties of cellulose fibers modified with CoFe2O4 nanoparticles. Sample

MS (emu/g)

MR (emu/g)

HC (Oe)

MF1

2.71

0.45

241.92

MF2

1.40

0.24

249.16

MF3

2.28

0.36

278.90

MF4

4.31

0.68

301.10

MF5

1.64

0.23

451.11

MF6

2.40

0.39

284.44

MF7

1.86

0.32

285.98

MF8

6.62

1.25

316.37

MF9

7.99

1.35

319.77

MF10

1.98

0.35

295.87

MF11

5.72

1.36

445.41

MF12

1.05

0.16

245.65

MF13

1.45

0.23

271.33

As can be seen in Table 6, all the samples of modified fibers present a saturation magnetization smaller than that of the cobalt ferrite nanoparticles. This is probably due to the nanoparticles are immobilized into fiber’s lumen and protected by the cell wall, so they are hindered to align along the magnetic field direction. This leads to a decrease of the intensity of the magnetic signal, without a significant loss of their sensitivity to magnetic fields [10, 20]. Despite this fact, as the modified fibers present a saturation magnetization up to 8.0 emu/g and a coercivity higher than 200 Oe, the modified magnetic fibers can be used in a future application as a recording magnetic material [2]. As mentioned above, only the nanoparticles dose had a significant statistical influence on the loading degree; therefore, a one-way analysis of variance (one-way ANOVA) was performed

Journal Pre-proof

to study the effect of the nanoparticle dose (20% and 100%) on the magnetic properties of fibers (Table 7). The analysis shows a P-value less than 0.05, i.e., there is a statistical significant difference between mean values of the saturation magnetization when varying the nanoparticles dose, with a level of significance of 5%. Thus, when plotted the average saturation magnetization as function of nanoparticle dose in a Fisher LSD diagram (Fig. 10), it is noted a direct dependency between magnetic properties of modified fibers and the amount of particles loaded, as expected. Thus, increasing the nanoparticle dose, the saturation magnetization, remanence magnetization and the coercivity of modified fibers, are increased [11, 32]. Table 7. ANOVA for saturation magnetization of magnetic fibers Fuente

Sum of squares DF Mean Square F-Ratio P-Value

Between groups

39.117

1

39.117

Within groups

8.113

6

1.352

Total (corr.)

47.230

7

28.93

0.0017

Figure 10. Fisher LSD diagram for mean value of saturation magnetization as function of nanoparticle dose.

Journal Pre-proof

3.6.

Water retention value (WRV)

Table 8 shows the water retention values for unmodified and modified fibers. It is observed that the percentage of water retention of the modified fibers is slightly lower than that of the unmodified fibers. Table 8. Water retention value (%WRV).

Sample

WRV (%)

MF4

82.31 ± 0.94

MF5

78.32 ± 2.24

MF6

82.42 ± 1.57

MF7

83.45 ± 1.00

MF8

80.11 ± 1.26

MF9

81.84 ± 0.34

MF11

82.14 ± 0.80

MF12

83.88 ± 0.41

UMF

87.39 ± 0.27

Due the low variability of WRV values, the effect of process parameters on this property were also analyzed through a one-way ANOVA (Table 9). Contrary to what was obtained for saturation magnetization, in this case the analysis shows a P-value higher than 0.05, i.e., there is not a statistical significant difference between mean values of water retention when varying the nanoparticles dose (Fig. 11), with a level of significance of 5%. However, and despite the barely reduction in water retention value, this fact suggests that the incorporated cobalt ferrite nanoparticles, as well as the polyethylenimine added as retention agent, modified the surface activity of the cellulose fibers, decreasing thus their hydrophilic capacity. Probably, CoFe2O4 nanoparticles and PEI, when adhering to the surface of fibers, reduce the hydroxyl groups available to absorb water [14]. as observed by the contraction of the band associated with the cellulose’s O-H bonds in the FTIR spectra (Fig. 6b, c). Additionally, the particles might block several pores and, in some extent, the lumen of fibers, hindering water molecules to reach active sites to be adsorbed. All this leads to a change of

Journal Pre-proof

fibers’ surface, which affects the retention of water, since it is a property that depends on the surface properties of the material [37]. Table 9. ANOVA for water retention value Fuente

Sum of squares DF Mean Square F-Ratio P-Value

Between groups

0.349

1

0.349

Within groups

22.428

6

3.738

Total (corr.)

22.777

7

0.09

0.770

Figure 11. Fisher LSD diagram for water retention value as function of nanoparticle dose.

4. Conclusions Eucalyptus fibers were modified with cobalt ferrite magnetic nanoparticles using the lumen loading method. The physical properties of modified fibers were studied at different conditions of the modification process, such as nanoparticles dose and mixing parameters. The results show that nanoparticles were synthesized in the inverse cubic spinel crystalline structure, exhibiting a ferrimagnetic behavior and an average size of 9 nm. Their magnetic properties show further a saturation magnetization of 57 emu/g, a remanence magnetization

Journal Pre-proof

of 9.30 emu/g, and a coercivity of 261 Oe. It was confirmed by SEM, EDS, and FTIR characterization, the incorporation of nanoparticles into the lumen of fibers and the adherence of these on the surface. The modified fibers presented a saturation magnetization of approximately 8.0 emu/g and a coercivity higher than 200 Oe, so the material can be used in applications of magnetic recording. On the other hand, it was found that the parameter that most affect the loading degree of fibers is the nanoparticles dose employed in the modification process. In addition, it was established that exist a positive relationship between the magnetic properties and the loading degree of the fibers. Finally, the water retention value of modified fibers decreased slightly by the presence of nanoparticles, probably due to the reduction of active sites for the adsorption of water molecules.

Acknowledgments The authors gratefully acknowledge the financial support for this project to the Departamento Administrativo de Ciencia, Tecnología e Innovación de Colombia COLCIENCIAS (Grant CT265-2016 No. 121071250588) and the Universidad de Cartagena (Grant No. 009-2015). Xiomara Pineda expresses her gratitude for the grant (Becas de Formación Investigativa) received from the Universidad Pontificia Bolivariana (UPB, Colombia).

References [1]

X. Qiu and S. Hu, “‘Smart’ materials based on cellulose: A review of the preparations, properties, and applications,” Materials, vol. 6, no. 3, pp. 738–781, 2013.

[2]

C. H. Chia, S. Zakaria, K. L. Nguyen, and M. Abdullah, “Utilisation of unbleached kenaf fibers for the preparation of magnetic paper,” Ind. Crops Prod., vol. 28, no. 3, pp. 333–339, 2008.

[3]

J. Lopez, F. J. Espinoza-Beltran, G. Zambrano, M. E. Gómez, and P. Prieto, “Characterization of magnetic nanoparticles of CoFe2O4 and CoZnFe2O4 prepared by the chemical coprecipitation method", (in Spanish), Rev. Mex. Fis., vol. 58, no. 4, pp. 293–300, 2012.

Journal Pre-proof

[4]

A. P. Herrera, C. Barrera, and C. Rinaldi, “Synthesis and functionalization of magnetite nanoparticles with aminopropylsilane and carboxymethyldextran,” J. Mater. Chem., vol. 18, no. 31, p. 3650, 2008.

[5]

J. Montes de Oca, L. Chuquisengo, and H. Alarcón, “Synthesis and characterization of cobalt ferrite nanoparticles obtained by the sol-gel process", (in Spanish), Rev. Soc. Quim. Perú, vol. 76, no. 4, pp. 400–406, 2010.

[6]

S. Sagadevan, J. Podder, and I. Das, Recent trends in materials science and applications - Nanomaterials, Crystal Growth, Thin films, Quantum Dots, & Spectroscopy (Proceedings ICRTMSA 2016), vol. 189. 2017.

[7]

A. Vinosha et al., “Investigation of optical, electrical and magnetic properties of cobalt ferrite nanoparticles by naive co-precipitation technique,” Opt. - Int. J. Light Electron Opt., vol. 127, no. 20, pp. 9917–9925, 2016.

[8]

P. Ruiz, “Magnetic nanoparticles for cancer treatment and diagnosis", (in spanish), Q.F Thesis, University of Complutense, Spain, 2016.

[9]

M. S. Samadi, H. Shokrollahi, and A. Zamanian, “The magnetic-field-assisted synthesis of the Co-ferrite nanoparticles via reverse co-precipitation and their magnetic and structural properties,” Mater. Chem. Phys., vol. 215, pp. 355–359, 2018.

[10]

V. H. Ojha and K. M. Kant, “Temperature dependent magnetic properties of superparamagnetic CoFe2O4 nanoparticles,” Phys. B Condens. Matter, vol. 567, pp. 87–94, 2019.

[11]

C. H. Chia, S. Zakaria, S. Ahamd, and M. Abdullah, “Preparation of Magnetic Paper from Kenaf : Lumen Loading and in situ Synthesis Method,” Am. J. Appl. Sci., vol. 3, no. 3, pp. 1750–1754, 2006.

[12]

C. H. Chia, S. Zakaria, S. C. Goh, and C. H. Chan, “Layer by layer deposition of CoFe2O4 nanocrystals onto unbleached pulp fibres for producing magnetic paper,” Lancet Neurol., vol. 12, no. 12, p. 1138, 2013.

[13]

L. Raymond, J. F. Revol, D. H. Ryan, and R. H. Marchessault, “In Situ Synthesis of Ferrites in Cellulosics,” Chem. Mater., vol. 6, no. 2, pp. 249–255, 1994.

Journal Pre-proof

[14]

S. Xu, D. Shen, and P. Wu, “Fabrication of water-repellent cellulose fiber coated with magnetic nanoparticles under supercritical carbon dioxide,” J. Nanoparticle Res., vol. 15, no. 4, 2013.

[15]

R. H. Marchessault, P. Rioux, and L. Raymond, “Magnetic cellulose fibres and paper: preparation, processing and properties,” Polymer, vol. 33, no. 19, pp. 4024–4028, 1992.

[16]

S. Zakaria, B. H. Ong, and T. G. M. Van De Ven, “Lumen loading magnetic paper I: flocculation,” Colloids Surfaces A Physicochem. Eng. Asp., vol. 251, no. 1–3, pp. 31– 36, 2004.

[17]

S. Zakaria, B. H. Ong, and T. G. M. Van De Ven, “Lumen loading magnetic paper II: Mechanism and kinetics,” Colloids Surfaces A Physicochem. Eng. Asp., vol. 251, no. 1–3, pp. 31–36, 2004.

[18]

J. Shen, Z. Song, X. Qian, and Y. Ni, “A review on use of fillers in cellulosic paper for functional applications,” Ind. Eng. Chem. Res., vol. 50, no. 2, pp. 661–666, 2011.

[19]

J. Lopez, F. J. Espinoza-beltran, and G. Zambrano, “Characterization of magnetic nanoparticles of CoFe2o4 and CoZnFe2O4 prepared by the chemical coprecipitation method", (in Spanish), Rev. Mex. Física, vol. 58, pp. 293–300, 2012.

[20]

TAPPI, “Forming handsheets for physical tests of pulp", Test method TAPPI T 205 sp-02, 2006.

[21]

W. B. Wu, Y. Jing, M. R. Gong, X.-F. Zhou, and H. Q. Dai, “Preparation and Properties of Magnetic Cellulose Fiber Composites,” BioResources, vol. 6, no. 3, pp. 3396–3409, 2011.

[22]

TAPPI, “Ash in wood , pulp , paper and paperboard : combustion at 525 ° C",Test method TAPPI T 211 om-02, 2002.

[23]

Q. Cheng, J. Wang, J. F. McNeel, and P. M. Jacobson, “Water retention value measurements of cellulosic materials using a centrifuge technique,” BioResources, vol. 5, no. 3, pp. 1945–1954, 2010.

Journal Pre-proof

[24]

J. Montes de Oca, L. Chuquisengo, and H. Alarcón, “Síntesis y caracterización de nanopartículas de ferrita de cobalto obtenidas por el proceso sol-gel,” Rev. Soc. Quím. Perú, vol. 76, no. 4, pp. 400–406, 2010.

[25]

K. F. Chamé, “Synthesis and characterization of magnetic nanoparticles", (in Spanish), MSc. Thesis, Optical research center, A.C., Mexico, 2013.

[26]

R. Chantrell, J. Popplewell, and S. Charles, “Measurements of particle size distribution parameters in ferrofluids,” IEEE Trans. Magn., vol. 14, no. 5, pp. 975– 977, 1978.

[27]

I. A. Flores-Urquizo, P. García-Casillas, and C. Chapa-González, “Development of magnetic nanoparticles Fe+32 X+21O4 (X = Fe, Co and Ni) coated with amino silane", (in Spanish), Rev. Mex. Ing. Biomed., vol. 38, no. 1, pp. 402–411, 2017.

[28]

R. Sivakami, S. Dhanuskodi, and R. Karvembu, “Estimation of lattice strain in nanocrystalline RuO 2 by Williamson – Hall and size – strain plot methods,” Spectrochim. Acta Part A Mol. Biomol. Spectrosc., vol. 152, pp. 43–50, 2016.

[29]

G. Márquez, “Synthesis and characterization of magnetic nanoparticles of ferrites and chromatics of Co, Mn and Ni", (in Spanish), Ph.D. Thesis, University of the Andes, Venezuela, 2014.

[30]

R. Sharma et al., “Improvement in magnetic behaviour of cobalt doped magnesium zinc nano-ferrites via co-precipitation route,” J. Alloys Compd., vol. 684, pp. 569– 581, 2016.

[31]

C. H. Chia, S. Zakaria, K. L. Nguyen, V. Q. Dang, and T. D. Duong, “Characterization of magnetic paper using Fourier transform infrared spectroscopy,” Mater. Chem. Phys., vol. 113, no. 2–3, pp. 768–772, 2009.

[32]

B. Stuart, Infrared spectroscopy fundamentals and applications, 1st ed, WILEY, 2004.

[33]

Y. P. Huang, I. J. Lin, C. C. Chen, Y. C. Hsu, C. C. Chang, and M. J. Lee, “Delivery of small interfering RNAs in human cervical cancer cells by polyethyleniminefunctionalized carbon nanotubes,” Nanoscale Res. Lett., vol. 8, no. 1, pp. 1–11, 2013.

Journal Pre-proof

[34]

S. Zakaria, B. H. Ong, S. H. Ahmad, M. Abdullah, and T. Yamauchi, “Preparation of lumen-loaded kenaf pulp with magnetite (Fe3O4),” Mater. Chem. Phys., vol. 89, no. 2–3, pp. 216–220, 2005.

[35]

A. V. Raut, R. S. Barkule, D. R. Shengule, and K. M. Jadhav, “Synthesis, structural investigation and magnetic properties of Zn2+ substituted cobalt ferrite nanoparticles prepared by the sol-gel auto-combustion technique,” J. Magn. Magn. Mater., vol. 358– 359, pp. 87–92, 2014.

[36]

Z. A. a Houshiar, Mahboubeh, Fatemeh Zebhi b, Zahra Jafari Razi a, Ali Alidoust a, “Synthesis

of

cobalt

ferrite

(CoFe2O4)

nanoparticles

using

combustion,

coprecipitation, and precipitation methods: A comparison study of size, structural, and magnetic properties,” J. Magn. Magn. Mater., vol. 322, pp. 2386–2389, 2010. [37]

N. Phinichka and S. Kaenthong, “Regenerated cellulose from high alpha cellulose pulp of steam-exploded sugarcane baggasse,” J. Mater. Res. Technol., pp. 1–9, 2017.

Journal Pre-proof Highlights



Cobalt ferrite nanoparticles were obtained by the co-precipitation method.



Eucalyptus fibers were modified with cobalt ferrite magnetic nanoparticles using the lumen loading method.



The nanoparticles dose is the parameter that most affect the loading degree of fibers.



Exist a positive linear relationship between the magnetic properties and the loading degree of the fibers.