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chitosan nanocomposite
Results in Physics 13 (2019) 102296
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The influence of titanium dioxide nanofiller ratio on morphology and surface properties of TiO2/chitosan nanocomposite
T
Saja S. Al-Taweela,⁎, Haider R. Saudb, Abdul Amir H. Kadhumc, Mohd S. Takriffc a
Chemistry Department, College of Science, University of Al-Qadisiyah, Iraq Chemical Department, College of Science, Al-Muthanna University, Al-Muthanna City, Iraq c Department of Chemical & Process Engineering, Faculty of Engineering & Built Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia b
ARTICLE INFO
ABSTRACT
Keywords: Nanofiller Chitosan TiO2 Nanocomposites Blending solution Interfacial bonding
In the present study, different ratios of TiO2-chitosan nanocomposite (nT-CS) [1:1(nT-CS1), 1:2 (nT-CS2), and 1:5 (nT-CS5)] were prepared by using the method of solution blending. The characterization of the prepared nanocomposite was done through different techniques such as Fourier transform Infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), and surface area analysis (BET, BJH). The results of FTIR and Raman spectroscopy indicate the appearance and the shifting of main bands of titanium dioxide and chitosan. In addition, the XRD results show shifting of main bands and change in crystal structure of chitosan. The images of AFM and SEM indicate that the TiO2 nanoparticles homogenously distributed throughout the chitosan matrix with an appearance of some agglomeration. The BET analysis indicates that nanocomposite with ratio 1:2 (nT-CS2) had the highest surface area 113 m2/g. Besides that, this ratio showed high adsorption of Direct Violet 51 (DV51) from its aqueous solutions.
Introduction Due to the increasing concern about polymeric nanocomposites (PNCs) and its applications over the last few decades, there has been much attention focused on the synthesis of PNCs in applied sciences [1]. The PNCs field includes many topics that play a major role in the life, such as highperformance fabrics, microwave absorbers, flame resistance, porous material, corrosion protection, food packaging, and ultraviolet irradiation resistance [2–5]. The blending of a small amount of nanosized inorganic material to the organic polymer can enhance the performance of all properties of the polymer matrix, such as mechanical, thermal, optical, electrical, and catalytic properties [6–9]. The controlled synthesis of PNCs with enhanced properties is the main challenge in materials science. The properties of PNCs strongly dependent on several factors, such as morphology of its components (size and shape) [10–12], the interfacial bond between the nanofiller and matrix [13,14], the mixing ratio of the PNC components [15], and the mixing method [16]. In this context, there are two aspects, first, decreasing in the agglomerates to aggregates and particles, and second, uniform distribution of particles in the polymer matrix without affecting on particles size [17–20]. Chitosan, poly [β-(1-4)-2-amino-2-deoxy-D-glucopyranose], is one of the most important cationic pseudo-linear polysaccharides [21]. It is derived from polysaccharide chitin which is extracted from the structural ⁎
components of marine organisms such as, shrimps, lobsters, and crabs [22]. In its unit structure, it contains high reactive functional groups (hydroxyl group eOH, and amino eNH2) which are responsible for donating a lone pair of the electron, high solubility in a diluted acidic solvent, the formation of the coordination bonds and make the modification of chitosan easy [23]. In spite of the significant properties of chitosan, some drawbacks limit its performance in the environmental process such as solubility in acid, low mechanical strength and low surface area [24]. This necessitated the chemical modification for chitosan such as chemical cross-linking (to increase polymer stability in acidic solutions) [25], or composition with nanomaterials (to enhance physiochemical properties such as surface area, porosity and mechanical). Nishad et al. 2014 [26] reported preparation of TiO2/chitosan nanocomposite by crosslinking agent and applied it as a superior sorbent for radioactive antimony. From a different nanomaterial, Titanium dioxide or Titania is a white crystalline n-type wide bandgap semiconductor, it commonly used as white brilliant pigment in many products such as inks, paints, coating, plastics, paper, food, cosmetics, and medicines due to its high UV resistance [27], high diffraction index, strong light scattering, and highly dispersed in products [28]. In this study we synthesized the TiO2-chitosan nanocomposites using different ratios of chitosan biopolymer. Different techniques were utilized to investigate the characterization of nanocomposite powders FTIR, XRD, AFM, SEM, and BET. The TiO2-chitosan nanocomposite were analyzed to
Corresponding author. E-mail address: [email protected] (S.S. Al-Taweel).
https://doi.org/10.1016/j.rinp.2019.102296 Received 5 February 2019; Received in revised form 5 April 2019; Accepted 16 April 2019 Available online 26 April 2019 2211-3797/ © 2019 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/).
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Co., Titanium (IV) isopropoxide (abbreviation: TTIP; molecular formula: Ti[OCH(CH3)2]4, 97%), and Direct Violet 51 (abbreviation: DV51; C.I. number: 27905; molecular formula: C32H27N5Na2O8S2; Molecular Weight: 719.695 g/mol, dye content 50%,) were purchased from Sigma-Aldrich and were used as received. Chitosan (>90.0 (DDA)) was purchased from JPM.Co. Synthesis of anatase TiO2 nanoparticles In our previous work [29], we reported the synthesis of purely anatase TiO2 nanoparticles using ultrasound assisted sol-gel method. The characterization of synthesized TiO2 nanoparticles by nine different techniques was also reported.
Fig. 1. FTIR spectra of TiO2 nanoparticles, chitosan, and prepared nanocomposites.
Synthesis of TiO2-Chitosan nanocomposite
explore the biosorbent activity and its efficiency as adsorbent surface to remove water pollutions.
Different ratios of TiO2-Chitosan nanocomposites (which are termed nT-CS1(1:1), nT-CS2, (1:2) and nT-CS5) were synthesized by modified blending solution method [30]. First 0.05 g of self-synthesized TiO2 nanoparticles was dispersed in 30 mL (1% v/v) acetic acid by ultrasound irradiation (output power 350 W, frequency 40 kHz) for 15 min to prepare a homogeneous colloidal solution. After that, different amounts of chitosan (0.05, 0.1 and 0.25 g) were added to the colloidal solution and again irradiated by ultrasound for 15 min until the solution become clear. 1 M of sodium hydroxide solution was added to the prepared solution with a
Materials and methods Materials Isopropyl alcohol ((CH3)2CHOH, 99.5%), hydrochloric acid (HCl, 37%), and acetic acid (CH3COOH, 99.7%) were purchased from BDH
Scheme 1. The mechanism steps of interaction of chitosan polymer and TiO2 nanoparticles at the reaction conditions (24).
Fig. 2. Raman spectra of TiO2 nanoparticles, chitosan, and prepared nanocomposites. 2
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Table 1 Wavenumbers of Raman assignments of prepared nanocomposites. Wavenumber (cm−1)
Assignment group
ν CeH (eCH3) ν CeH (eCH2) ν (C]O) in (NHCO) δ(NeH) δ(CeH) in (NHCOCH3) δ(OeH) in alcohol groups δ(CeH) in (CH2OH) δ(CeH) in Pyranose ring ν(CeN) ν (CeO) in alcohol groups δ (CeOeC) ν(Φ) pyranoid ring ω (NeH) Eg vibration mode of anatase TiO2
nT-CS5
nT-CS2
nT-CS1
Chitosan
2913 2881 1642 1593 1452
2887 2762 1646 1551 1415
2882 2761 1646 1553 1420
2889 2763 1646 1558 1425
1379 1316
1377 1302
1376 1311
1377 1315
1234 1111 1016 914 705 –
1214 1111 1016 914 697 144.5
1221 1112 1014 914 698 144.5
1225 1111 1014 914 704 143.5
Table 2 Wavenumbers of TiO2 nanoparticles Raman bands observed in purely TiO2 and prepared nanocomposites. Nanomaterial
TiO2-nps
nT-CS5
nT-CS2
nT-CS1
Eg Eg B1g A1g/B1g Eg
143.5 194.5 395.5 516.5 638.5
143.5 193.5 397 516.5 638.5
144.5 194 399.5 519.5 638.5
144.5 194 398.5 519 638.5
Fig. 3. XRD patterns of TiO2 nanoparticles, chitosan, and prepared nanocomposites.
constant rate and under magnetic agitation at 80 °C for 5 h until the pH solution reached 10. The solid composite was separated from the colloidal solution by centrifuge and washed with deionized water until the pH of washing solution reached 7; then it was dried at 60 °C overnight and kept in a tight container to avoid any particles agglomeration.
Fig. 4a. (a1), (b1) and (c1) represented AFM 3D images of prepared nanocomposites (nT-CS1), (nT-CS2) and (nT-CS2) respectively.
area and pore analysis of nT-CS nanocomposites were obtained with Quantachrome Instruments (Nova 2200e, USA).
Characterization of TiO2-Chitosan nanocomposite The crystalline phase of nT-CS nanocomposites was characterized by XRD using (BrukerAXSGmbh, Germany/D2 Phaser) with CuKα radiation (0.15040 nm); the XRD pattern was recorded in range 5°–60°. To determine the functional groups, Raman spectra of nT-CS nanocomposites were performed using micro-Raman (BrukerAXSGmbh, Germany, Senterra) and FTIR (Shimadzu, Japan, FTIR 8400 s). The morphology of nT-CS nanocomposites was observed by Scanning Electron Microscope (SEM) (EM3200, China, KYKY) with an accelerating voltage of 25 kV. The roughness of nanocomposites surface were obtained using angstrom AFM (SPM-AA3000, USA). The surface
Adsorption experiments Batch adsorption All batch adsorption experiments were carried out to study the DV51 removal by prepared TiO2 nanoparticles and nanocomposites. 10 mL of DV51 solutions (35.98 mg/l) and constant mass of adsorbent (10 mg) were transferred to a beaker. The solutions were vigorously shaken at 120 rpm in a thermostatic shaker for the desired time that reached to the equilibrium. The samples were separated by centrifuge 3
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(6000 rpm) for 15 min and used for UV–Vis analysis (1650, Shimadzu, Japan). By the previously mentioned way, differently prepared adsorbents used to investigate the removal of DV51 from its solutions. Results and discussion Characterization The FTIR spectrum of chitosan, TiO2 nanoparticles, and nT-CS nanocomposites was shown in Fig. 1, the chitosan spectrum shows the following peaks: a broad peak centered at 3419 cm−1 is assigned to the stretching vibration of the eOH, eNH2 groups and to intramolecular and intermolecular hydrogen bonding. The peaks at 2930 cm−1, 2884 cm−1, 1427 cm−1, 1381 cm−1, and 1321 cm−1 are due to stretching and bending vibration of CeH of eCH3, and eCH2 groups, a peak at 1653 cm−1 is for stretching vibration of eC]O in eNHCO, whereas the peak at 1603 cm−1 is due to eNH bending vibration of NH2, and other peaks at 1155 cm−1, and 1090 cm−1 correspond to the eCeO bending [31]. The broad bands centered at 500–600 cm−1 in TiO2 spectrum is assigned to the bending vibration of (Ti-O-Ti) bonds, while that at 3400 cm−1 and 1650 cm−1 corresponds to the intermolecular interaction of hydroxyl groups of TiO2 surface with water molecules [29]. As shown from Fig. 1, all peaks of chitosan and TiO2 nanoparticles are representative in the FTIR spectrum of prepared nT-CS nanocomposites; it is also observed the disappearance of the broad peak at 3419 cm−1. In addition to that, the increase in TiO2 ratio in the composite may have shifted the peaks of eNH, eOH, eCH, and C]O groups toward lower wavenumber. These changes in nT-CS spectrum are due to the strong interactions (coordination) between Ti+4 in TiO2 and a lone pair in eOH, and NH2 groups of chitosan, which is lead to the weakness of intramolecular and intermolecular hydrogen bonding between chitosan molecules in nanocomposites (see Scheme 1). The following scheme shows the possible mechanism of interaction of functional groups of chitosan and TiO2 nanoparticles. The Raman spectrum of chitosan, TiO2 nanoparticles, and nT-CS nanocomposites was shown in Fig. 2. By the Comparison between pure chitosan and its nanocomposite, it was shown a red shift in peaks centered at 1609 cm−1 (δ NeH), 1427 cm−1 (δ OeH in alcohol groups), 1325 cm−1 (ν CeN), and 1240 cm−1 (ν CeO) in alcohol groups, as a result of interactions between OeH, and NeH groups with TiO2 particles [31]. Table 1 shows the essential peaks of pure anatase TiO2 nanoparticles and the different ratios of prepared nanocomposites. The most vibration modes of anatase TiO2 in nT-CS2 composite were slightly shifted to higher wavenumber as compared with the other nanocomposites (Table 2), this may be due to decrease in particle size of nanocomposite and to the high homogeneity and diffusion of TiO2 nanoparticles in chitosan matrix [32]. The crystalline structure of nanocomposites was examined by X-ray diffraction technique; Fig. 3 shows the XRD patterns of chitosan, TiO2 nanoparticles, and prepared nanocomposites nT-CS. The crystal structure of chitosan shows an orthorhombic unit cell with dimensions a = 0.828, b = 0.862, and c = 1.043 nm (fiber axis). This unit cell comprises four glucosamine units which connected by main hydrogen bonds O3…O5 (intramolecular) and N2…O6 (intermolecular) [33]. The XRD pattern of chitosan shows semi-crystalline structure as indicated by two peaks; at 10.55° that which related to hydrated crystalline structure, and at 19.69° which is due to amorphous state [34]. While the TiO2 nanoparticles pattern shows diffraction peaks that well indexed to purely anatase phase according to standard JCPDS card No. 21-1272. Crystallographic structure of nanocomposites was changed by using a different amount of chitosan. In the nT-CS5 nanocomposite pattern, all peaks of chitosan and TiO2 nanoparticles were appeared with small shift to higher angle with the peak appearing at 10.55°, while for the other ratios of nanocomposites it was observed markedly change in width and intensity, in addition to the disappearance of 19.69° peak as
Fig. 4b. (a2), (b2) and (c2) represented Granularity cummulation distribution chart of (nT-CS1), (nT-CS2) and (nT-CS2) respectively.
Table 3 Surface roughness parameters of prepared nanocomposites. nT-CS5
nT-CS2
nT-CS1
16.6 −0.0322 1.80 96.65
1.49 −0.108 1.82 68.21
3.23 −0.134 1.79 78.72
Ra (nm) Rsk Rku Grian size (nm)
Ra: Roughness average, Rsk: Surface skewness and Rku: Surface kurtosis. 4
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Fig. 5. SEM images of nT-CS nanocomposites: a- nT-CS1, b- nT-CS2, c- nT-CS5.
a result of strong interaction between nanocomposite components and decrease in intermolecular hydrogen bonding in the chitosan matrix. The XRD pattern is well agreement with the FT-IR and Raman spectra of prepared nanocomposites. The surface topography of nanocomposites was examined by atomic force microscopy. Figs. 4a and 4b shows the AFM images and granularity cummulation distribution charts of prepared nanocomposites. The nanocomposites images show three different states; the nanocomposite with
lower chitosan ratio (nT-CS1) gives high aggregation of TiO2 nanoparticles with non-uniform distribution, nT-CS5 shows a non-uniform distribution of TiO2 nanoparticles in chitosan matrix, while nT-CS2 shows the spherical shape and uniform distribution of TiO2 nanoparticles accompanied by a small degree of aggregation. The semispherical shapes in AFM nanocoposites images were related to TiO2 nanoparticles while the non-uniform shapes were related to chitosan particles that have peaks more highest as compared with that of TiO2 nanoparticles. 5
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Fig. 6. (a) Nitrogen adsorption–desorption isotherm, (b) the corresponding pore size distribution of prepared nT-CS nanocomposites.
and as indicated from SEM image, the TiO2 nanoparticles highly distributed in the chitosan matrix which is lead to increase the surface area of nanocomposite and to reduce the average particle size (109 nm). As the ratio of chitosan increase in prepared composite (nT-CS5), the surface morphology change to become less porous and roughness. Fig. 6 shows the nitrogen adsorption-desorption isotherms obtained by the BET of synthesized nanocomposites with the Pore size distribution obtained by the BJH. According to the classification proposed by International Union of Pure and Applied Chemistry (IUPAC), the isotherms can be classified as type IV, in which the indication of the monolayer adsorption followed by multilayer formation and capillary condensation [35]. The hysteresis loops can be explained the pore configuration, the hybrid appearance hysteresis loops H1-H3 of nT-CS1 sorption isotherms were simply indexed to each pore domain fills and empties independently of any other as sorption behavior [36], whereas the other sorption isotherms of nT-CS2 and nT-CS5 were shown H3 hysteresis loops which suggesting narrow slit-shaped pores that are generally associated with sheet-like particles with non-rigid aggregates [37]. This result complies with their morphology (Fig. 5). nT-CS2 nanocomposite has a higher surface area, as represented by Table 4, and this result is associated with decreasing of aggregation size, highly nanofiller distribution in chitosan matrix, and lower grain size of particles.
Table 4 Surface area, pore size, average diameter, isotherm type, and hysteresis loop of nT-CS nanocomposites. Nanomaterial 2
Surface area (m /g) Pore volume (cc/g) Average pore diameter (nm) Isotherm type Hysteresis loop
TiO2-nps
nT-CS5
nT-CS2
nT-CS1
64.041 0.229 6.134 4 H1
10.023 0.041 2.198 4 H3
113.296 0.207 2.459 4 H3
38.566 0.1 6.016 4 H1-H3
Table 3 shows the surface roughness parameters and the average grain size of prepared nanocomposites. The value of average grain size of the nT-CS2 nanocomposite is lesser (68.1 nm) than the other nanocomposites; this result coincides with that of Raman spectroscopy. In addition and as indicated by negative Rsk values, the surface porosity of the nT-CS1 is highest as compared with that of other composites. A major concern in the field of nanocomposite includes the status of mixing state of its components, size, aggregation state of nanofiller, and morphology. Therefore, as represented by Fig. 5, the surface morphology of nanocomposites was examined by scanning electron microscopy (SEM). The spherical shape appeared in SEM images is related to TiO2 nanoparticles, the prepared nanocomposite morphology is strongly influenced by mixing components ratio. The SEM image of nTCS1 shows the agglomeration of TiO2 nanoparticles on chitosan surface with an average particle size 133 nm, this agglomeration lead to reduce the surface area of nT-CS1 nanocomposite. In nT-CS2 nanocomposite
Fig. 7. Thermogravimetric analysis (TGA/DTG) of nT-CS2 nanocomposite.
Fig. 8. The removal of DV51 dye by nT, nT-CS1, and nT-CS2 adsorbents. 6
Results in Physics 13 (2019) 102296
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To indicate the purity of prepared nanocomposites, the thermogravimetric analysis of nT-CS2 was carried out in the temperature range from 45 °C to 697.2 °C at a heating rate of 2 °C/min. The TGA curve (Fig. 7) shows two dissociation steps, the first step in the range 125–300 °C included the desorption of adsorbed water in the porous nanocomposite. The weight loss in the second step in the range 300–600 °C was due to the thermal dissociation of chitosan and OH group of TiO2-nanoparticles (24). The DTG curve shows that maximum velocity of polymer dissociation occurs at 312 °C.
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Adsorption of Direct Violet 51 Different prepared adsorbents TiO2-nanoparticles (nT), nT-CS1, nTCS2 were choice to adsorb DV51 from its solution (35.96 mg/l) at 298 K and pH7. The uptake of DV51 onto TiO2-nps and nT-CS nanocomposites was increased with time until reached to the maximum value at 90 min.. The results shows that dye removal by TiO2-nps (3.95%), nTCS1 (89.40%) and nT-CS2 (95.63%) (Fig. 8). The enhancement in adsorption by nT-CS2 may be attributed to high porosity and pore volume of the adsorbent which is increase the number of active surface sites available for adsorption, and also due to the high affinity between DV51 molecules and the nanocomposite adsorbent. Conclusions In summary, we have prepared porous TiO2-chitosan nanocomposites with the high surface area by solution blending method. The nanometer titanium dioxide immobilized on molecular chitosan matrixes was characterized by using different techniques. The results are expected to be highly related to the association between the nanofiller ratio and the interfacial bond of nanocomposite components. We focus on the interfacial bonding between chitosan and TiO2 nanoparticles. A decrease in chitosan hydrogen bonding with an increase in nanofiller ratio can be indicated through FTIR and Raman shift of O-H, N-H bands, as well as from XRD pattern, which shows a decrease in intermolecular hydrogen bonding in chitosan matrix and distortion in the semi-crystalline structure of the matrix. The present study will help to establish a better understanding of how the nanofiller ratio affects the interfacial bonding and other properties of TiO2-carbohydrates nanocomposites. The synthesis of nanocomposites with surface roughness and high distribution of TiO2 nanoparticles depend on nanofiller ratio and can be justified through the investigation of the surface morphology. The nanocomposite nT-CS2 had the highest surface area 113 m2/g and this result is associated with highly nanofiller distribution in the chitosan matrix, and less aggregation degree from other ratios. According to the adsorption equilibrium data, nT-CS2 showed high removal of DV51 dye that may be lead to its application as an eco-friendly adsorbent. Appendix A. Supplementary material Supplementary data to this article can be found online at https:// doi.org/10.1016/j.rinp.2019.102296. References [1] Njuguna J, Pielichowski K, Desai S. Nanofiller-reinforced polymer nanocomposites. Polym Adv Technol 2008;19:947–59. [2] Kurahatti R, Surendranathan A, Kori S, Singh N, Kumar A, Srivastava S. Defence applications of polymer nanocomposites. Defence Sci J 2010;60. [3] Gaaz TS, Sulong AB, Kadhum AAH. Influence of sulfuric acid on the tensile properties of halloysite reinforced polyurethane composite. J Mech Eng 2017:1–10. [4] Sankaran S, Deshmukh K, Ahamed MB, Pasha SK. Recent advances in electromagnetic interference shielding properties of metal and carbon filler reinforced flexible polymer composites: a review. Compos Part A Appl Sci Manuf 2018. [5] Muzaffar A, Ahamed MB, Deshmukh K, Faisal M, Pasha SK. Enhanced electromagnetic absorption in NiO and BaTiO3 based polyvinylidenefluoride nanocomposites. Mater Lett 2018;218:217–20. [6] Šupová M, Martynková GS, Barabaszová K. Effect of nanofillers dispersion in
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The influence of titanium dioxide nanofiller ratio on morphology and surface properties of TiO2/chitosan nanocomposite
T
Saja S. Al-Taweela,⁎, Haider R. Saudb, Abdul Amir H. Kadhumc, Mohd S. Takriffc a
Chemistry Department, College of Science, University of Al-Qadisiyah, Iraq Chemical Department, College of Science, Al-Muthanna University, Al-Muthanna City, Iraq c Department of Chemical & Process Engineering, Faculty of Engineering & Built Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia b
ARTICLE INFO
ABSTRACT
Keywords: Nanofiller Chitosan TiO2 Nanocomposites Blending solution Interfacial bonding
In the present study, different ratios of TiO2-chitosan nanocomposite (nT-CS) [1:1(nT-CS1), 1:2 (nT-CS2), and 1:5 (nT-CS5)] were prepared by using the method of solution blending. The characterization of the prepared nanocomposite was done through different techniques such as Fourier transform Infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), and surface area analysis (BET, BJH). The results of FTIR and Raman spectroscopy indicate the appearance and the shifting of main bands of titanium dioxide and chitosan. In addition, the XRD results show shifting of main bands and change in crystal structure of chitosan. The images of AFM and SEM indicate that the TiO2 nanoparticles homogenously distributed throughout the chitosan matrix with an appearance of some agglomeration. The BET analysis indicates that nanocomposite with ratio 1:2 (nT-CS2) had the highest surface area 113 m2/g. Besides that, this ratio showed high adsorption of Direct Violet 51 (DV51) from its aqueous solutions.
Introduction Due to the increasing concern about polymeric nanocomposites (PNCs) and its applications over the last few decades, there has been much attention focused on the synthesis of PNCs in applied sciences [1]. The PNCs field includes many topics that play a major role in the life, such as highperformance fabrics, microwave absorbers, flame resistance, porous material, corrosion protection, food packaging, and ultraviolet irradiation resistance [2–5]. The blending of a small amount of nanosized inorganic material to the organic polymer can enhance the performance of all properties of the polymer matrix, such as mechanical, thermal, optical, electrical, and catalytic properties [6–9]. The controlled synthesis of PNCs with enhanced properties is the main challenge in materials science. The properties of PNCs strongly dependent on several factors, such as morphology of its components (size and shape) [10–12], the interfacial bond between the nanofiller and matrix [13,14], the mixing ratio of the PNC components [15], and the mixing method [16]. In this context, there are two aspects, first, decreasing in the agglomerates to aggregates and particles, and second, uniform distribution of particles in the polymer matrix without affecting on particles size [17–20]. Chitosan, poly [β-(1-4)-2-amino-2-deoxy-D-glucopyranose], is one of the most important cationic pseudo-linear polysaccharides [21]. It is derived from polysaccharide chitin which is extracted from the structural ⁎
components of marine organisms such as, shrimps, lobsters, and crabs [22]. In its unit structure, it contains high reactive functional groups (hydroxyl group eOH, and amino eNH2) which are responsible for donating a lone pair of the electron, high solubility in a diluted acidic solvent, the formation of the coordination bonds and make the modification of chitosan easy [23]. In spite of the significant properties of chitosan, some drawbacks limit its performance in the environmental process such as solubility in acid, low mechanical strength and low surface area [24]. This necessitated the chemical modification for chitosan such as chemical cross-linking (to increase polymer stability in acidic solutions) [25], or composition with nanomaterials (to enhance physiochemical properties such as surface area, porosity and mechanical). Nishad et al. 2014 [26] reported preparation of TiO2/chitosan nanocomposite by crosslinking agent and applied it as a superior sorbent for radioactive antimony. From a different nanomaterial, Titanium dioxide or Titania is a white crystalline n-type wide bandgap semiconductor, it commonly used as white brilliant pigment in many products such as inks, paints, coating, plastics, paper, food, cosmetics, and medicines due to its high UV resistance [27], high diffraction index, strong light scattering, and highly dispersed in products [28]. In this study we synthesized the TiO2-chitosan nanocomposites using different ratios of chitosan biopolymer. Different techniques were utilized to investigate the characterization of nanocomposite powders FTIR, XRD, AFM, SEM, and BET. The TiO2-chitosan nanocomposite were analyzed to
Corresponding author. E-mail address: [email protected] (S.S. Al-Taweel).
https://doi.org/10.1016/j.rinp.2019.102296 Received 5 February 2019; Received in revised form 5 April 2019; Accepted 16 April 2019 Available online 26 April 2019 2211-3797/ © 2019 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/).
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Co., Titanium (IV) isopropoxide (abbreviation: TTIP; molecular formula: Ti[OCH(CH3)2]4, 97%), and Direct Violet 51 (abbreviation: DV51; C.I. number: 27905; molecular formula: C32H27N5Na2O8S2; Molecular Weight: 719.695 g/mol, dye content 50%,) were purchased from Sigma-Aldrich and were used as received. Chitosan (>90.0 (DDA)) was purchased from JPM.Co. Synthesis of anatase TiO2 nanoparticles In our previous work [29], we reported the synthesis of purely anatase TiO2 nanoparticles using ultrasound assisted sol-gel method. The characterization of synthesized TiO2 nanoparticles by nine different techniques was also reported.
Fig. 1. FTIR spectra of TiO2 nanoparticles, chitosan, and prepared nanocomposites.
Synthesis of TiO2-Chitosan nanocomposite
explore the biosorbent activity and its efficiency as adsorbent surface to remove water pollutions.
Different ratios of TiO2-Chitosan nanocomposites (which are termed nT-CS1(1:1), nT-CS2, (1:2) and nT-CS5) were synthesized by modified blending solution method [30]. First 0.05 g of self-synthesized TiO2 nanoparticles was dispersed in 30 mL (1% v/v) acetic acid by ultrasound irradiation (output power 350 W, frequency 40 kHz) for 15 min to prepare a homogeneous colloidal solution. After that, different amounts of chitosan (0.05, 0.1 and 0.25 g) were added to the colloidal solution and again irradiated by ultrasound for 15 min until the solution become clear. 1 M of sodium hydroxide solution was added to the prepared solution with a
Materials and methods Materials Isopropyl alcohol ((CH3)2CHOH, 99.5%), hydrochloric acid (HCl, 37%), and acetic acid (CH3COOH, 99.7%) were purchased from BDH
Scheme 1. The mechanism steps of interaction of chitosan polymer and TiO2 nanoparticles at the reaction conditions (24).
Fig. 2. Raman spectra of TiO2 nanoparticles, chitosan, and prepared nanocomposites. 2
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Table 1 Wavenumbers of Raman assignments of prepared nanocomposites. Wavenumber (cm−1)
Assignment group
ν CeH (eCH3) ν CeH (eCH2) ν (C]O) in (NHCO) δ(NeH) δ(CeH) in (NHCOCH3) δ(OeH) in alcohol groups δ(CeH) in (CH2OH) δ(CeH) in Pyranose ring ν(CeN) ν (CeO) in alcohol groups δ (CeOeC) ν(Φ) pyranoid ring ω (NeH) Eg vibration mode of anatase TiO2
nT-CS5
nT-CS2
nT-CS1
Chitosan
2913 2881 1642 1593 1452
2887 2762 1646 1551 1415
2882 2761 1646 1553 1420
2889 2763 1646 1558 1425
1379 1316
1377 1302
1376 1311
1377 1315
1234 1111 1016 914 705 –
1214 1111 1016 914 697 144.5
1221 1112 1014 914 698 144.5
1225 1111 1014 914 704 143.5
Table 2 Wavenumbers of TiO2 nanoparticles Raman bands observed in purely TiO2 and prepared nanocomposites. Nanomaterial
TiO2-nps
nT-CS5
nT-CS2
nT-CS1
Eg Eg B1g A1g/B1g Eg
143.5 194.5 395.5 516.5 638.5
143.5 193.5 397 516.5 638.5
144.5 194 399.5 519.5 638.5
144.5 194 398.5 519 638.5
Fig. 3. XRD patterns of TiO2 nanoparticles, chitosan, and prepared nanocomposites.
constant rate and under magnetic agitation at 80 °C for 5 h until the pH solution reached 10. The solid composite was separated from the colloidal solution by centrifuge and washed with deionized water until the pH of washing solution reached 7; then it was dried at 60 °C overnight and kept in a tight container to avoid any particles agglomeration.
Fig. 4a. (a1), (b1) and (c1) represented AFM 3D images of prepared nanocomposites (nT-CS1), (nT-CS2) and (nT-CS2) respectively.
area and pore analysis of nT-CS nanocomposites were obtained with Quantachrome Instruments (Nova 2200e, USA).
Characterization of TiO2-Chitosan nanocomposite The crystalline phase of nT-CS nanocomposites was characterized by XRD using (BrukerAXSGmbh, Germany/D2 Phaser) with CuKα radiation (0.15040 nm); the XRD pattern was recorded in range 5°–60°. To determine the functional groups, Raman spectra of nT-CS nanocomposites were performed using micro-Raman (BrukerAXSGmbh, Germany, Senterra) and FTIR (Shimadzu, Japan, FTIR 8400 s). The morphology of nT-CS nanocomposites was observed by Scanning Electron Microscope (SEM) (EM3200, China, KYKY) with an accelerating voltage of 25 kV. The roughness of nanocomposites surface were obtained using angstrom AFM (SPM-AA3000, USA). The surface
Adsorption experiments Batch adsorption All batch adsorption experiments were carried out to study the DV51 removal by prepared TiO2 nanoparticles and nanocomposites. 10 mL of DV51 solutions (35.98 mg/l) and constant mass of adsorbent (10 mg) were transferred to a beaker. The solutions were vigorously shaken at 120 rpm in a thermostatic shaker for the desired time that reached to the equilibrium. The samples were separated by centrifuge 3
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(6000 rpm) for 15 min and used for UV–Vis analysis (1650, Shimadzu, Japan). By the previously mentioned way, differently prepared adsorbents used to investigate the removal of DV51 from its solutions. Results and discussion Characterization The FTIR spectrum of chitosan, TiO2 nanoparticles, and nT-CS nanocomposites was shown in Fig. 1, the chitosan spectrum shows the following peaks: a broad peak centered at 3419 cm−1 is assigned to the stretching vibration of the eOH, eNH2 groups and to intramolecular and intermolecular hydrogen bonding. The peaks at 2930 cm−1, 2884 cm−1, 1427 cm−1, 1381 cm−1, and 1321 cm−1 are due to stretching and bending vibration of CeH of eCH3, and eCH2 groups, a peak at 1653 cm−1 is for stretching vibration of eC]O in eNHCO, whereas the peak at 1603 cm−1 is due to eNH bending vibration of NH2, and other peaks at 1155 cm−1, and 1090 cm−1 correspond to the eCeO bending [31]. The broad bands centered at 500–600 cm−1 in TiO2 spectrum is assigned to the bending vibration of (Ti-O-Ti) bonds, while that at 3400 cm−1 and 1650 cm−1 corresponds to the intermolecular interaction of hydroxyl groups of TiO2 surface with water molecules [29]. As shown from Fig. 1, all peaks of chitosan and TiO2 nanoparticles are representative in the FTIR spectrum of prepared nT-CS nanocomposites; it is also observed the disappearance of the broad peak at 3419 cm−1. In addition to that, the increase in TiO2 ratio in the composite may have shifted the peaks of eNH, eOH, eCH, and C]O groups toward lower wavenumber. These changes in nT-CS spectrum are due to the strong interactions (coordination) between Ti+4 in TiO2 and a lone pair in eOH, and NH2 groups of chitosan, which is lead to the weakness of intramolecular and intermolecular hydrogen bonding between chitosan molecules in nanocomposites (see Scheme 1). The following scheme shows the possible mechanism of interaction of functional groups of chitosan and TiO2 nanoparticles. The Raman spectrum of chitosan, TiO2 nanoparticles, and nT-CS nanocomposites was shown in Fig. 2. By the Comparison between pure chitosan and its nanocomposite, it was shown a red shift in peaks centered at 1609 cm−1 (δ NeH), 1427 cm−1 (δ OeH in alcohol groups), 1325 cm−1 (ν CeN), and 1240 cm−1 (ν CeO) in alcohol groups, as a result of interactions between OeH, and NeH groups with TiO2 particles [31]. Table 1 shows the essential peaks of pure anatase TiO2 nanoparticles and the different ratios of prepared nanocomposites. The most vibration modes of anatase TiO2 in nT-CS2 composite were slightly shifted to higher wavenumber as compared with the other nanocomposites (Table 2), this may be due to decrease in particle size of nanocomposite and to the high homogeneity and diffusion of TiO2 nanoparticles in chitosan matrix [32]. The crystalline structure of nanocomposites was examined by X-ray diffraction technique; Fig. 3 shows the XRD patterns of chitosan, TiO2 nanoparticles, and prepared nanocomposites nT-CS. The crystal structure of chitosan shows an orthorhombic unit cell with dimensions a = 0.828, b = 0.862, and c = 1.043 nm (fiber axis). This unit cell comprises four glucosamine units which connected by main hydrogen bonds O3…O5 (intramolecular) and N2…O6 (intermolecular) [33]. The XRD pattern of chitosan shows semi-crystalline structure as indicated by two peaks; at 10.55° that which related to hydrated crystalline structure, and at 19.69° which is due to amorphous state [34]. While the TiO2 nanoparticles pattern shows diffraction peaks that well indexed to purely anatase phase according to standard JCPDS card No. 21-1272. Crystallographic structure of nanocomposites was changed by using a different amount of chitosan. In the nT-CS5 nanocomposite pattern, all peaks of chitosan and TiO2 nanoparticles were appeared with small shift to higher angle with the peak appearing at 10.55°, while for the other ratios of nanocomposites it was observed markedly change in width and intensity, in addition to the disappearance of 19.69° peak as
Fig. 4b. (a2), (b2) and (c2) represented Granularity cummulation distribution chart of (nT-CS1), (nT-CS2) and (nT-CS2) respectively.
Table 3 Surface roughness parameters of prepared nanocomposites. nT-CS5
nT-CS2
nT-CS1
16.6 −0.0322 1.80 96.65
1.49 −0.108 1.82 68.21
3.23 −0.134 1.79 78.72
Ra (nm) Rsk Rku Grian size (nm)
Ra: Roughness average, Rsk: Surface skewness and Rku: Surface kurtosis. 4
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Fig. 5. SEM images of nT-CS nanocomposites: a- nT-CS1, b- nT-CS2, c- nT-CS5.
a result of strong interaction between nanocomposite components and decrease in intermolecular hydrogen bonding in the chitosan matrix. The XRD pattern is well agreement with the FT-IR and Raman spectra of prepared nanocomposites. The surface topography of nanocomposites was examined by atomic force microscopy. Figs. 4a and 4b shows the AFM images and granularity cummulation distribution charts of prepared nanocomposites. The nanocomposites images show three different states; the nanocomposite with
lower chitosan ratio (nT-CS1) gives high aggregation of TiO2 nanoparticles with non-uniform distribution, nT-CS5 shows a non-uniform distribution of TiO2 nanoparticles in chitosan matrix, while nT-CS2 shows the spherical shape and uniform distribution of TiO2 nanoparticles accompanied by a small degree of aggregation. The semispherical shapes in AFM nanocoposites images were related to TiO2 nanoparticles while the non-uniform shapes were related to chitosan particles that have peaks more highest as compared with that of TiO2 nanoparticles. 5
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Fig. 6. (a) Nitrogen adsorption–desorption isotherm, (b) the corresponding pore size distribution of prepared nT-CS nanocomposites.
and as indicated from SEM image, the TiO2 nanoparticles highly distributed in the chitosan matrix which is lead to increase the surface area of nanocomposite and to reduce the average particle size (109 nm). As the ratio of chitosan increase in prepared composite (nT-CS5), the surface morphology change to become less porous and roughness. Fig. 6 shows the nitrogen adsorption-desorption isotherms obtained by the BET of synthesized nanocomposites with the Pore size distribution obtained by the BJH. According to the classification proposed by International Union of Pure and Applied Chemistry (IUPAC), the isotherms can be classified as type IV, in which the indication of the monolayer adsorption followed by multilayer formation and capillary condensation [35]. The hysteresis loops can be explained the pore configuration, the hybrid appearance hysteresis loops H1-H3 of nT-CS1 sorption isotherms were simply indexed to each pore domain fills and empties independently of any other as sorption behavior [36], whereas the other sorption isotherms of nT-CS2 and nT-CS5 were shown H3 hysteresis loops which suggesting narrow slit-shaped pores that are generally associated with sheet-like particles with non-rigid aggregates [37]. This result complies with their morphology (Fig. 5). nT-CS2 nanocomposite has a higher surface area, as represented by Table 4, and this result is associated with decreasing of aggregation size, highly nanofiller distribution in chitosan matrix, and lower grain size of particles.
Table 4 Surface area, pore size, average diameter, isotherm type, and hysteresis loop of nT-CS nanocomposites. Nanomaterial 2
Surface area (m /g) Pore volume (cc/g) Average pore diameter (nm) Isotherm type Hysteresis loop
TiO2-nps
nT-CS5
nT-CS2
nT-CS1
64.041 0.229 6.134 4 H1
10.023 0.041 2.198 4 H3
113.296 0.207 2.459 4 H3
38.566 0.1 6.016 4 H1-H3
Table 3 shows the surface roughness parameters and the average grain size of prepared nanocomposites. The value of average grain size of the nT-CS2 nanocomposite is lesser (68.1 nm) than the other nanocomposites; this result coincides with that of Raman spectroscopy. In addition and as indicated by negative Rsk values, the surface porosity of the nT-CS1 is highest as compared with that of other composites. A major concern in the field of nanocomposite includes the status of mixing state of its components, size, aggregation state of nanofiller, and morphology. Therefore, as represented by Fig. 5, the surface morphology of nanocomposites was examined by scanning electron microscopy (SEM). The spherical shape appeared in SEM images is related to TiO2 nanoparticles, the prepared nanocomposite morphology is strongly influenced by mixing components ratio. The SEM image of nTCS1 shows the agglomeration of TiO2 nanoparticles on chitosan surface with an average particle size 133 nm, this agglomeration lead to reduce the surface area of nT-CS1 nanocomposite. In nT-CS2 nanocomposite
Fig. 7. Thermogravimetric analysis (TGA/DTG) of nT-CS2 nanocomposite.
Fig. 8. The removal of DV51 dye by nT, nT-CS1, and nT-CS2 adsorbents. 6
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To indicate the purity of prepared nanocomposites, the thermogravimetric analysis of nT-CS2 was carried out in the temperature range from 45 °C to 697.2 °C at a heating rate of 2 °C/min. The TGA curve (Fig. 7) shows two dissociation steps, the first step in the range 125–300 °C included the desorption of adsorbed water in the porous nanocomposite. The weight loss in the second step in the range 300–600 °C was due to the thermal dissociation of chitosan and OH group of TiO2-nanoparticles (24). The DTG curve shows that maximum velocity of polymer dissociation occurs at 312 °C.
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Adsorption of Direct Violet 51 Different prepared adsorbents TiO2-nanoparticles (nT), nT-CS1, nTCS2 were choice to adsorb DV51 from its solution (35.96 mg/l) at 298 K and pH7. The uptake of DV51 onto TiO2-nps and nT-CS nanocomposites was increased with time until reached to the maximum value at 90 min.. The results shows that dye removal by TiO2-nps (3.95%), nTCS1 (89.40%) and nT-CS2 (95.63%) (Fig. 8). The enhancement in adsorption by nT-CS2 may be attributed to high porosity and pore volume of the adsorbent which is increase the number of active surface sites available for adsorption, and also due to the high affinity between DV51 molecules and the nanocomposite adsorbent. Conclusions In summary, we have prepared porous TiO2-chitosan nanocomposites with the high surface area by solution blending method. The nanometer titanium dioxide immobilized on molecular chitosan matrixes was characterized by using different techniques. The results are expected to be highly related to the association between the nanofiller ratio and the interfacial bond of nanocomposite components. We focus on the interfacial bonding between chitosan and TiO2 nanoparticles. A decrease in chitosan hydrogen bonding with an increase in nanofiller ratio can be indicated through FTIR and Raman shift of O-H, N-H bands, as well as from XRD pattern, which shows a decrease in intermolecular hydrogen bonding in chitosan matrix and distortion in the semi-crystalline structure of the matrix. The present study will help to establish a better understanding of how the nanofiller ratio affects the interfacial bonding and other properties of TiO2-carbohydrates nanocomposites. The synthesis of nanocomposites with surface roughness and high distribution of TiO2 nanoparticles depend on nanofiller ratio and can be justified through the investigation of the surface morphology. The nanocomposite nT-CS2 had the highest surface area 113 m2/g and this result is associated with highly nanofiller distribution in the chitosan matrix, and less aggregation degree from other ratios. According to the adsorption equilibrium data, nT-CS2 showed high removal of DV51 dye that may be lead to its application as an eco-friendly adsorbent. Appendix A. Supplementary material Supplementary data to this article can be found online at https:// doi.org/10.1016/j.rinp.2019.102296. References [1] Njuguna J, Pielichowski K, Desai S. Nanofiller-reinforced polymer nanocomposites. Polym Adv Technol 2008;19:947–59. [2] Kurahatti R, Surendranathan A, Kori S, Singh N, Kumar A, Srivastava S. Defence applications of polymer nanocomposites. Defence Sci J 2010;60. [3] Gaaz TS, Sulong AB, Kadhum AAH. Influence of sulfuric acid on the tensile properties of halloysite reinforced polyurethane composite. J Mech Eng 2017:1–10. [4] Sankaran S, Deshmukh K, Ahamed MB, Pasha SK. Recent advances in electromagnetic interference shielding properties of metal and carbon filler reinforced flexible polymer composites: a review. Compos Part A Appl Sci Manuf 2018. [5] Muzaffar A, Ahamed MB, Deshmukh K, Faisal M, Pasha SK. Enhanced electromagnetic absorption in NiO and BaTiO3 based polyvinylidenefluoride nanocomposites. Mater Lett 2018;218:217–20. [6] Šupová M, Martynková GS, Barabaszová K. Effect of nanofillers dispersion in
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