TiO2 composites synthesized by solution casting method

TiO2 composites synthesized by solution casting method

Carbohydrate Polymers 149 (2016) 317–331 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/c...

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Carbohydrate Polymers 149 (2016) 317–331

Contents lists available at ScienceDirect

Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol

Adsorption and photocatalytic degradation of anionic dyes on Chitosan/PVA/Na–Titanate/TiO2 composites synthesized by solution casting method Umma Habiba a , Md. Shariful Islam a , Tawsif A. Siddique b , Amalina M. Afifi a,∗ , Bee Chin Ang a a b

Center of Advanced Materials, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia Department of Electrical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia

a r t i c l e

i n f o

Article history: Received 1 March 2016 Received in revised form 19 April 2016 Accepted 29 April 2016 Available online 3 May 2016 Keywords: Chitosan Adsorption Polymer composite Photocatalytic effect Kinetics

a b s t r a c t Chitosan/PVA/Na–titanate/TiO2 composite was synthesized by solution casting method. The composite was analyzed via Fourier Transform Infrared Spectroscopy, X-ray diffraction, Field Emission Scanning Electron Microscopy, Thermal gravimetric analysis and water stability test. Incorporation of Na-titanate shown decrease of crystallinity for chitosan but increase water stability. However, the composite structure was deteriorated with considerable weight loss in acidic medium. Two anionic dyes, methyl orange and congo red were used for the adsorption test. The adsorption behavior of the composites were described by pseudo-second-order kinetic model and Lagergren-first-order model for methyl orange and congo red, respectively. For methyl orange, adsorption was started with a promising decolorization rate. 99.9% of methyl orange dye was removed by the composite having higher weightage of chitosan and crystalline TiO2 phase. On the other hand, for the congo red the composite having higher chitosan and Na-titanate showed an efficient removal capacity of 95.76%. UV–vis results showed that the molecular backbone of methyl orange and congo red was almost destroyed when equilibrium was obtained, and the decolorization rate was reaching 100%. Kinetic study results showed that the photocatalytic degradation of methyl orange and congo red could be explained by Langmuir–Hinshelwood model. Thus, chitosan/PVA/Na–titanate/TiO2 possesses efficient adsorptivity and photocatalytic property for dye degradation. © 2016 Elsevier Ltd. All rights reserved.

1. Introduction Nowadays, water pollution is becoming a big threat in industrialized areas. Textile industries, paper industries, pharmaceuticals, tannery, bleaching industries, etc. eject remarkable amount of organic dyes every day. Dyes can be remained unchanged in the environment for long time (Carmen & Daniela, 2012). Several methods such as photodegradation (Jayanthi Kalaivani & Suja, 2016; Zhou et al., 2016), adsorption (Yao, Guo, Zeng, Wang, & Zhang, 2015) and flocculation (Tian, Ju, Zhang, & Hou, 2016) can be used for removal of dyes. However, photodegradation is more popular in terms of its effectiveness in the dye degradation process. On the other hand, adsorption is a favorable method because of simplicity of design.

∗ Corresponding author. E-mail address: [email protected] (A.M. Afifi). http://dx.doi.org/10.1016/j.carbpol.2016.04.127 0144-8617/© 2016 Elsevier Ltd. All rights reserved.

It was reported that different inorganic semiconductor nanomaterials such as ZnO, ZnS, CdS, SiO2 , TiO2 , Fe2 O3 , Al2 O3 , ZrO2 etc., can be used as photo catalysts (Jayanthi Kalaivani & Suja, 2016). Among them, TiO2 is widely being used because of its ability to break down dye molecule, nontoxicity, large surface area, and stability in acidic and basic media (Jayanthi Kalaivani & Suja, 2016; Zubieta et al., 2008). Unfortunately, TiO2 is not able to be activated by visible light. On the other hand, the efficiency of TiO2 in photocatalytic activities is insufficient because of the wide band gap (3.2 eV) and poor quantum yield of catalysts arising from the rapid recombination of the photogenerated electron (e− )–hole (h+ ) pairs (Zhu et al., 2012). It was reported that, CdS/TiO2 showed effective photocatalytic activity than TiO2 but low dye adsorption in the dark (Zhu et al., 2013). In contrast, TiO2 containing compound, titanates show high photocatalytic activity as well as remarkable adsorption (Feng, You, Wu, Chen, & Zhan, 2013; Li & Hsieh, 2006; Peiró, Peral, Domingo, Domènech, & Ayllón, 2001). In addition, Natitanates are thermally stable (Mishra, Dubey, & Tiwari, 2004; Papp,

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Kõrösi, Meynen, Cool, Vansant, & Dékány, 2005), chemically stable (Ramı´ırez-Salgado, Djurado, & Fabry, 2004) and selective (Anthony, Philip, & Dosch, 1993). Besides, separating the catalyst from the reaction media is difficult and time consuming. Therefore, in recent years, polymers such as chitosan, cellulose, PVA etc. have been used as the matrix for semiconductor materials (Alexandre & Dubois, 2000; Tao, Ye, Pan, Wang, & Tang, 2009; Vicentini, Smania, & Laranjeira, 2010; Zhang et al., 2011). Such polymers also decrease the leakage of ion in treated water and provide an interface for charge transfer. Among many polymers, chitosan is extensively used because of its advantageous properties including nontoxicity, biodegradability, biocompatibility, antibacterial property, etc. (Fong, Chun, & Reneker, 1999; Francis Suh & Matthew, 2000). Chitosan is composed of glucosamine and N-acetyl glucosamine. The amino group renders the following properties to chitosan: solubility in acid, ability to adhere to negatively charged surfaces, and cationic polyelectrolyte (Martinová & Lubasová, 2008). Amino and hydroxyl groups of chitosan can serve as active sites during adsorption process. Previously, chitosan has been used for removing organic pollutants from wastewater (Ngah, Teong, & Hanafiah, 2011). The drawback of chitosan is pH sensitive. Therefore, it was reported that PVA can be used to immobilize chitosan (Kumar, Tripathi, & Shahi, 2009). Besides, it is a nontoxic, hydrophilic and biodegradable synthetic polymer. Although PVA is soluble in water, the combination with chitosan can make insoluble composite by forming a hydrogen bond. PVA also increases the adsorption property of chitosan (Muhd Julkapli, Akil, & Ahmad, 2011). In the present research, chitosan/PVA/Na–titanate/TiO2 composite film was prepared via the solution casting method. The composite was characterized via FTIR, XRD, and FESEM. Methyl orange and congo red were considered as standard anionic dyes, and the adsorption–photocatalytic activity of the composites were analyzed. 2. Experimental 2.1. Materials Chitosan (MW = 8.96 × 5 g/mole, degree of deacetylation = 40%) was obtained from SE Chemical Co., Ltd., Japan TiO2 (∼21 nm) was purchased from Sigma–Aldrich, Malaysia. PVA (Mw = 60000, degree of hydrolysis = 89%) was purchased from Kuraray Co., Ltd., Tokyo, Japan. Methyl orange and Congo red was purchased from R & M chemicals. NaOH and acetic acid was purchased from System. 2.2. Methods 2.2.1. Preparation of chitosan/PVA/Na–titanate/TiO2 composite Degree of deacetylation of crude chitosan is 40% which is not suitable for solution preparation. A degree of deacetylation greater than 70% is needed for the solubility of chitosan (Li & Hsieh, 2006). Therefore, chitosan was hydrolyzed to increase the degree of deacetylation. First, a 1:38 wt ratio of chitosan: 33.5% NaOH solution was stirred at 90 ◦ C for 12 h to hydrolyze the chitosan. The chitosan was dried in the oven for 7 h at 70 ◦ C to obtain its powder form. Second, 7 wt.% solution of the resulting chitosan was prepared in concentrated acetic acid and blended with 8 wt.% of aqueous PVA solution in a 60:40, 80:20 and 90:10 wt ratio. Third, 1 wt.% of TiO2 was blended with 10 ml of 60:40 wt ratio of Chitosan/PVA blend solution. However, 1 wt.% TiO2 could not be dispersed in two other chitosan/PVA blend. Possible reason is higher chitosan content leaded to higher solution viscosity which make obstacle in the well distribution of filler material. Therefore, 0.5 wt.% of TiO2 was added to 80:20 and 90:10 wt ratio of chitosan/PVA solution. The

blended solutions was casted and dried for 7 h at 70 ◦ C. Finally, the composites were treated with mild NaOH solution and dried again for 2 h at 70 ◦ C. Three composites were named as composite A, composite B and composite C, for weight ratio of 60:40, 80:20 and 90:10 of chitosan/PVA, respectively. The schematic diagram and mechanism for preparation of chitosan/PVA/Na-titanate/TiO2 was shown in Fig. 1. 2.2.2. Characterizations FTIR spectroscopy was used to determine the interaction among chitosan, PVA and filler materials. The procedure was performed using Nicolet iS10 FTIR spectrometer from Thermo Scientific. The spectral range of 600–3000 wavenumber was used with a resolution of 4 cm−1 . XRD analysis was performed using a PANalytical empyrean X-ray diffractometer with Cu K␣ radiation (␭ = 1.54060 Å). The morphology of the chitosan/PVA/Na–titanate/TiO2 composite was observed using a Field Emission Scanning Electron Microscope (Zeiss Auriga). Thermal behavior of the composites were analyzed by thermogravimetric analysis (SETARAM TGA 92 apparatus) at a heating rate of 20 ◦ C/min and a temperature of 30–800 ◦ C. The UV–vis spectra of the dye solution at different durations of operation were obtained using a Varian CARY 50 probe UV–vis spectrophotometer. 2.2.3. Weight loss experiment The dry composite samples were weighed and subsequently immersed in distilled water and acidic medium (pH = 2.5) for 24 h at room temperature. The samples were weighed immediately after drying. The weight loss percentage was estimated using the following equation Weightloss (%) =

W0 − W1 × 100 W0

(1)

where, W0 and W1 are the masses before and after dipping in water, respectively. 2.2.4. Adsorption and photocatalytic degradation The chitosan/PVA/Na–titanate/TiO2 composite (0.02 g) was added to 0.02 L of methyl orange (33 mg L−1 ) solution and congo red (15 mg L−1 ) and agitated for certain time in the dark at room temperature (25 ◦ C) to examine the adsorption behavior of the composite. In case of congo red, less concentrated solution was used because of its complex molecular backbone. Higher concentration would lengthen the process. The sample was collected in different time gaps, and the dye concentration was calculated using a UV–vis spectrophotometer. The same method was employed to determine the photocatalytic activity of chitosan/PVA/Na–titanate/TiO2 under UV irradiation. Time gap and points for all the composite were not same as time of highest adsorption varied with composites and dyes. 3. Results and discussions 3.1. Morphological analysis Surface morphological analysis was carried out to investigate the dispersion of filler materials over the polymer matrix. Fig. 2 shows morphological image of the composite. In case of composite A, energy selective backscattered (ESB) detection was done as filler materials were not clearly observed in standard SE2 mode. Rough surface and finer particles were observed. This distinct morphology is advantageous as it gives a large surface area to the adsorbate. In case of composite B, irregular shaped filler material in nanometer range covered the surface with random orientation. In addition, agglomeration of filler material was observed. The diameter of filler particles were varied from 100 to 700 nm which is very

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Fig. 1. The schematic mechanism for preparation of Chitosan/PVA/Na-titanate/TiO2 composite.

high than the size of the raw TiO2 . It indicated the agglomeration of nano-TiO2 . FESEM image of composite C showed interpenetrating aggregation of warping structures. The filler particles were aggregated in the polymer matrix containing higher chitosan. Larger cluster size aggregates were observed in higher magnification. According to XRD spectra of composite C which will be discussed in another section, one dimensional growth of [002] plane of Natitanate was observed. Presence of Na–titanate with brookite phase may be the possible cause of these structures in composite C. Comparing the morphology of three composites, it can be concluded that distribution of filler particle was very poor for the composite with higher weight percentage of chitosan. It demonstrates that beyond the optimum amount of chitosan, agglomeration can occur. Probable reason is that the Van der Waals forces lead to bundle formation of filler materials. Therefore, there was poor interfacial adhesion between polymer matrix and filler materials (Zakaria et al., 2013). Previously, similar result was revealed by other studies (Jeevitha & Amarnath, 2013; Suyatma, Copinet, Coma, & Fricoteaux, 2010).

3.2. FTIR analysis Fig. 3 shows the FTIR spectra of the composites. The saccharide group was identified by a resonance peak at 1151 cm−1 (Homayoni, Ravandi, & Valizadeh, 2009). Moreover, the 1320 and 1409 cm−1 peaks were due to the coupling of the O H in-plane vibrations and C H wagging vibrations (Bai et al., 2007). The peaks at 1557, 1635 and 2925 cm−1 were attributed to N H bending, C O NHR and CH2 (Khan & Dhayal, 2008), respectively which are characteristic peaks of chitosan. The broad peak at 709 cm−1 can be attributed to the Ti O Ti frequency region (Peiró et al., 2001). The bands at 1033 and 1077 cm−1 of chitosan has been shifted to 1025 and 1072 cm−1 , respectively due to the hydrogen bonding of hydroxyl and amino groups of chitosan with Ti O (Khan & Dhayal, 2008). 1735 cm−1 band of PVA shifted to 1733 cm−1 in composite which presents O C NH2. These characteristic peaks indicated the presence of titanates in the composite. The 1256 cm−1 peak belongs to the C H bond of PVA (Jia et al., 2007). The intensity of the peak was reduced in the composites. Other characteristic peaks such as 1320, 1409, and 2925 cm−1 also describe the presence of PVA that overlapped with chitosan. Therefore, the FTIR results indicated the presence of PVA, chitosan, TiO2 , and

Na–titanate in the composite film. 660 cm−1 is the crystalline sensitive band of chitosan (C¸ay, Miraftab, & Kumbasar, 2014). It was disappeared in the composite because of hydrogen bonding of chitosan with acetic acid and PVA. It signifies that chitosan lost its crystallinity in some extent, which was also confirmed by XRD analysis. After dissolving the chitosan in acetic acid, the intensity of 1635 cm−1 was decreased, while 1557 cm−1 was increased. It indicated further deacetylation of chitosan molecule in the acidic acid (Kumirska et al., 2010). Therefore, new NH2 groups were produced. The 1557 cm−1 peak intensity was decreased significantly in the composite having maximum chitosan. Since hydrogen bonding decreases the frequency of stretching vibration, it implies formation of hydrogen bonds between chitosan and Ti O Na via NH2 . Broad band at 3267–3365 cm−1 was attributed to stretching vibration of OH group which indicated characteristic peak for both chitosan and PVA. Since the peak was not sharp, hydroxyl groups in position of C2 and C6 of chitosan are connected by intramolecular and intermolecular hydrogen bonds (Kumirska et al., 2010). Increased peak intensity in chitosan/acetic acid described more ordered structure. But peak was shifted towards lower frequency in the composites. Significant peak shifting was observed for composite C. It demonstrate loss of crystallinity which is in accordance with XRD result. Ratio of intensity of 1374 and 2920 cm−1 is used to estimate the crystallinity of chitosan. Crystallinity increases with the ratio (Wu, Zivanovic, Draughon, Conway, & Sams, 2005). However, the 1374 cm−1 peak was disappeared in the composite.

3.3. XRD analysis Fig. 4 shows the XRD spectra of the composites. The results were compared with the references of the Joint Committee on Powder Diffraction Standards. For the XRD pattern of TiO2, strongest peaks at 2␪ = 25.27, 27.42, 37.78 and 48◦ demonstrate the brookite phase of TiO2 . XRD peaks of pure TiO2 was visible in these composites and it confirmed the presence of TiO2 in crystalline stage in all the composites. Some changes in the peak intensity was occurred because of H-bonding with functional group of chitosan which has been discussed in FTIR analysis. An additional peak around 29◦ was observed which is defined as characteristic peak of Na-titanate. In composite C, The most significant peak of Na– titanate was observed at 28.62◦ . But peak around 25.27◦ was almost disappeared. In indicates that most of TiO2 was converted to Na-

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Fig. 2. FESEM images of the composite A (a1 ) and (a2 ), composite B (b1 ) and (b2 ) and composite C (c1 ) and (c2 ) at magnificence of 10k and 50 k, respectively.

titanate. The acidity of the chitosan solution matrix can act as an important factor for the formation of titanate as it was reported that titanium oxide can turn into titanate in acidic medium (Tsai & Teng, 2006). Composite C contains 90% chitosan. Therefore, it may be the possible reason for getting significant peak of titanate in the composite C. On the other hand, both peaks of TiO2 and Na-titanate were observed in composite A and B. Dehydration of titanate occurred during washing with NaOH, and the proton was

replaced by Na+ . During NaOH treatment, some of Ti O Ti bonds are broken, resultant Ti O Na and Ti OH. These intermediates rearrange to TiO6 octahedral (Tsai & Teng, 2006). According to JCDPS: 00-022-1404, the XRD peaks of Na–titanate were indexed to monoclinic crystal structure. Thus, the resulting Na–titanate cannot be lepidocrocite-type titanate (orthorhombic) (Ma, Bando, & Sasaki, 2003) but possibly Na2 Ti3 O7 (monoclinic) or Na2 Ti6 O13 (basecentered monoclinic) (Papp et al., 2005). The narrow diffraction

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Fig. 3. FTIR spectra of (a) composite A, (b) composite B and (c) composite C.

pattern mainly at 28.62◦ indicated that this structure is Na2 Ti6 O13 according to literature (Ramı´ırez-Salgado et al., 2004; Tsai & Teng, 2006; Zarate, Fuentes, Cabrera, & Fuenzalida, 2008). XRD spectra of

chitosan showed strong peaks at 2␪ around 9–10◦ and 20◦ indicating presence of OH and NH2 and minor reflection at higher 2␪ values which represents ␣-chitosan (Kumirska et al., 2010; Ramya,

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Fig. 4. XRD spectra of (a) composite A, (b) composite B and (c) composite C.

Sudha, & Mahalakshmi, 2012). These peaks represents semicrystalinity of chitosan.The peaks of chitosan around 10◦ and 20◦ became weak in the composites representing strong interaction among chi-

tosan, PVA and filler materials (Yen, Yang, & Mau, 2009). Thus, XRD results has given evidence to the FTIR results that some interaction has occurred among the components.

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Table 1 Kinetic Parameters of Lagergren first order kinetic model. Dye

Composite

qe.exp (mg g−1 )

qe.cal (mg g−1 )

Rate constant (min−1 )

R2

Methyl orange

Composite A Composite B Composite C

6.86 3.30 3.17

4.9 120 1.21

0.08 1.035 0.25

0.992 0.87 0.96

Congo red

Composite A Composite B Composite C

1.24 1.40 1.44

1.41 1.47 1.09

0.11 0.38 0.15

0.86 0.97 0.96

Table 2 Kinetic Parameters of Pseudo second order kinetic model. Dye

Composite

qe.exp (mg g−1 )

qe.cal (mg g−1 )

Rate constant (g mg−1 min−1 )

R2

Methyl orange

Composite A Composite B Composite C

6.86 3.30 3.17

8.35 3.9 3.28

0.016 0.1 0.47

0.996 0.99 1

Congo red

Composite A Composite B Composite C

1.24 1.40 1.44

2.03 1.65 1.73

0.016 0.272 0.166

0.43 0.90 0.95

3.4. TGA analysis Thermal behavior of the composites are analyzed by thermal gravimetric analysis and results has been shown in Fig. 5.In the case of chitosan, mass loss of 14% occurred in the region of 40–155 ◦ C, this might due to the moisture evaporation. It is noteworthy that the temperature 155 ◦ C is higher than in free water (usually 110 ◦ C). Strong hydrogen bonding between water molecule and active groups ( NH2 , OH) of chitosan can be the probable reason of this high temperature. Decomposition of chitosan started at 240 ◦ C. Finally, molecular backbone of chitosan was totally destroyed at 610 ◦ C. For chitosan/acetic acid film, mass loss of 25% was observed which indicates increase of water. Then maximum decomposition temperature was increased to 714 ◦ C with 28% residue. It may be due to hydrogen bond between chitosan and acetic acid which is also supported by the FTIR analysis. In chitosan/PVA film, decomposition temperature was decreased but weight loss was increased. For composites, thermal stability was increased corresponds to respective chitosan/PVA film. It can be concluded that TGA analysis is agreement with the XRD and FTIR analysis that there is strong interaction among the components of the composite. 3.5. Weight loss test Weight loss test was carried out in distilled water and acidic medium (pH = 2.5) for 24 h. In distilled water, composite A lost 15% of its initial weight and composite B showed weight loss of 10%, while smaller weight loss of 5% was observed for composite C may be due to insolubility of chitosan fraction and hydrogen bonding between chitosan and PVA (Kumar, 2000). Any materials swells more in the amorphous state than in the crystalline structure and this is in accordance with the results obtained from the XRD measurement (Chen, Yang, Gu, & Shao, 2001). It was confirmed from the FTIR and XRD analysis that there is a strong interaction among chitosan, PVA and filler materials. In the acidic medium, composites were degraded. Chitosan is pH sensitive because of protonation of amino groups (Yang et al., 2016). It indicated that large number of free amino groups were retained in the composite. 3.6. Adsorption study Fig. 6 shows the UV–vis spectra of methyl orange and congo red solution in contact with composite A, composite B and composite C in the dark. The characteristic peaks of benzene and azo linkage at 270 and 470 nm, respectively, were found in the ini-

tial UV–vis spectra of methyl orange. However, the peak intensity shifted downward with increasing contact time. After certain time, equilibrium was obtained and no peak shifting was observed. For congo red, three absorption peaks are found. One peak is in the visible region with maximum absorption at 496 nm which is attributed to azo bonds of congo red molecule and other two peaks are at 236 nm and 338 nm respectively, which attributed to benzene and naphthalene rings structure (Wang et al., 2008). From Fig. 6, it is clearly visible that with all the composites, the peaks intensity of congo red solution are decreased with increasing contact time and for the composite C, the change is most remarkable. Generally, dye adsorption by the composite was calculated by using the following formula (Mishra et al., 2004): qt =

(C0 − Ct ) V m

(2)

where, C0 and Ct are the initial and equilibrium concentrations of methyl orange solution (mg L−1 ), respectively, V is the volume of solution (L), and m is the weight of composite film (g). The interaction between the dye molecule and surfaces of the adsorbent material can be estimated by studying its adsorption isotherms. Lagergren-first-order model, pseudo-second-order model, and intra-particle mass transfer diffusion model were applied to investigate the kinetics of adsorption. The linear forms of these three models are shown in Eqs. (2)–(4), respectively (Zhu et al., 2013). log (qe − qt ) = logqe −

k1 t 2.303

(3).

t 1 t = + qt qe k2 q2e

(4)

qt = kid t1/2 + c

(5)

where qe and qt are the masses of dye adsorbed per unit mass (mg/g) of the sorbent at equilibrium and contact time t (min), respectively; k1 (min−1 ) and k2 (g mg−1 min−1 ) are the rate constants of the Lagergren-first-order model and pseudo-second-order model, respectively; and kid (mg g−1 min−1/2 ) is the intra-particle diffusion rate constant. The rate constants were calculated to study the adsorption mechanism. Fig. 7 shows the linear plot of log (qe –qt ) versus t, t/qt versus t, and qt versus t1/2 for Eqs. (2)–(4), respectively. The values of k1 , k2 , qe , kid , and c were calculated from the slope and intercept of the respective linear plots. Tables 1–3 summarizes the kinetic parameters and correlation coefficient (R2 ). It can be seen from Table 1 that, for methyl orange,

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Fig. 5. TGA Analysis of (a) composite A, (b) composite B and (c) composite C.

the correlation co-efficient of Lagergren-first-order model for composite A, composite B and composite C are 0.992, 0.87, and 0.96 respectively. Whereas in Table 2, the correlation co-efficient of

pseudo-second-order model for these three composites are 0.996, 0.99 and 1 respectively, and the experimental qe.exp values are closer to the experimental ones, that confirming the adsorption

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Fig. 6. Spectral change of Methyl orange by (a) composite A, (b) composite B, (c) composite C and Congo red by (d) composite A, (e) composite B and (f) composite C without UV irradiation.

of methyl orange on composite A, composite B and composite C are better represented by pseudo-second-order kinetics. Usually, the adsorption process is conducted by surface diffusion and intraparticle diffusion, however, in this study, the pseudo-second-order kinetic model is mostly dominant for methyl orange. Thus, it can be concluded that the overall sorption kinetics for methyl orange is controlled by the rate of direct adsorption (Plazinski, Rudzinski, & Plazinska, 2009). This result indicates that chemical adsorption is

controlled by significant sharing or exchange of electrons between the adsorbent and adsorbate (Ho & McKay, 1999). However, for congo red the correlation co-efficient of Lagergrenfirst-order model for composite A, composite B and composite C are 0.86, 0.97 and 0.96 respectively which are higher than the correlation co-efficient of pseudo-second-order model. Also the experimental qe.exp values agree with the calculated value for Lagergren – first-order model. Therefore, this can be concluded

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Fig. 7. (a), (d) Lagergren first-order model; (b), (d) pseudo-second-order kinetics and (c), (e) intra-particle diffusion models for adsorption of Methyl orange and Congo red, respectively.

that, the adsorption of congo red on composite A, composite B and composite C are better represented by Lagergren – first-order kinetics. The rate constant, kid and C of intra particle diffusion model can be used to determine the rate limiting step of adsorption process. C indicates the boundary layer effect of adsorption process. The contribution of intraparticle diffusion on an adsorption pro-

cess can be determined by the value of C. If the value of C is zero, the whole adsorption process is dominated by intraparticle diffusion. In case of the methyl orange adsorption, the values of C are very higher than zero. It means that intraparticle diffusion was not rate-limiting step in methyl orange adsorption. Thus, bulk mass transfer onto the adsorbent was significant during the adsorption process. On the other hand, values of C are smaller in the adsorption

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Table 3 Kinetic Parameters of Intra particle mass transfer diffusion model. Dye

Composite

qe.exp (mg g−1 )

C (mg g−1 )

Rate constant(mg g−1 min−1/2 )

R2

Methyl orange

Composite A Composite B Composite C

6.86 3.30 3.17

1.44 1.38 2.7

0.97 0.54 0.09

0.97 0.82 0.96

Congo red

Composite A Composite B Composite C

1.24 1.40 1.44

0.7668 0.332 0.381

0.11 0.38 0.15

0.86 0.90 0.96

Fig. 8. Decolorization percentage vs time (min) for (a) Methyl orange and (b) Congo red without UV irradiation.

of congo red. It implies that adsorption process is partially governed by intraparticle diffusion (Xiong et al., 2010). The decolorization percentage of dye degradation was determined by the following expression (Mahanta, Manna, Madras, & Patil, 2010) =

C O − Ct × 100% Co

change linearly with time. After a specific period of time, the maximum surface of the adsorbent was covered and adsorption capacity decreased, i.e., the rate of decolorization did not uniformly increase in the whole operation time. In case of congo red, maximum decolorization percentage was 82.7, 93.5 and 95.76%, respectively for composite A, composite B and composite C.

(6)

where, C0 and Ct are the concentrations at the initial point and after time t. Fig. 8 shows the relationship between decolorization percentage and contact time. For methyl orange, initially the decolorization rate was high for all composites. A high concentration enhances the collision between organic dye molecules and oxidizing species. It also demonstrate that adsorption occurred mainly in the surface. As the time increased, maximum surface area of composite was covered. In the last stages, adsorption was continued by small diffusion of dye molecule into the internal pores. Therefore, adsorption process became slower (Al-Asheh & Banat, 2001). For methyl orange adsorption maximum adsorption (99.9%) was observed for composite B. Where, final removal percentage was 93.3 and 97.5% for composite A and composite C respectively. In adsorption test, composite B obtained equilibrium state only after 15 min of operation time. Where, it took 30 and 40 min for composite A and composite C, respectively. This results goes well with the obvious crystalline phase of TiO2 in XRD and also in combination of higher chitosan content in composite B. Decrease in adsorption percentage is at higher loading of PVA might be due to the deactivation of amino group of chitosan by making hydrogen bond with hydroxyl group of PVA. More amount of PVA needed to be added to avoid unnecessary access of hydroxyl group. Nonetheless, same trend does not go with composite C having less PVA. This is because of the agglomeration of filler particles was observed which decreased the possible actives for dye adsorption. However, the decolorization rate did not

3.7. Photocatalytic dye degradation Fig. 9 shows the UV–vis spectra of methyl orange and congo red solution in contact with the composite A, composite B and composite C in the presence of UV irradiation. The concentrations of methyl orange after different time intervals were calculated using the UV–vis spectrum. Two characteristic peaks of methyl orange almost disappeared, which demonstrates that the molecular structure was almost destroyed. Langmuir–Hinshelwood models describe the kinetics of heterogeneously catalyzed reaction. It can be regarded as a standard model (Zamostny & Belohlav, 2002a). It was reported in several study that Langmuir–Hinshelwood rate expression can be applied for photocatalytic degradation to know degradation rate of dye (Kumar, Porkodi, & Selvaganapathi, 2007; Saien & Khezrianjoo, 2008). In this study, Langmuir–Hinshelwood was used to study the kinetics of photocatalytic degradation. The simplified form of Langmuir–Hinshelwood model to the apparent pseudo-first-order kinetics is as follows:





ln C0 ⁄Ci = kt

(7).

where, k is the apparent pseudo-first-order reaction rate constant (min−1 ). The value of k was calculated from the slope of plot t versus ln (C0 /Ci ) shown in Fig. 9. Linear regression analysis was done and the results was summarized in Table 4. A correlation coefficient signifies that photocatalytic degradation of methyl orange followed the

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Fig. 9. Spectral change of Methyl orange by (a) composite A, (b) composite B, (c) composite C and Congo red by (d) composite A, (e) composite B and (f) composite C under UV irradiation.

Langmuir–Hinshelwood model. Single rate controlling step is assumed in Langmuir–Hinshelwood model (Zamostny & Belohlav, 2002b). The highest value of rate constant (k) were reported to be 0.64 min−1 composite B.This results goes well with the obvious crystalline phase of TiO2 in XRD. The presence of TiO2 helped in faster degradation of Methyl orange. In case of congo red, Langmuir–Hinshelwood model was also obeyed. Highest rate con-

stant of 0.37 min−1 was measured for the composite C having more Na-titanates. Probable reason of this behavior is the insufficient photocatalytic activities of TiO2 because of the wide band gap (3.2 eV). Photocatalytic activity of TiO2 was not enough to destroy the complex structure of congo red. Fig. 10 shows the relationship between decolorization percentage and contact time. For methyl orange, maximum percentage

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Fig. 10. Linear plot of the Langmuir–Hinshelwood model for (a) Methyl orange and (b) Congo red; Decolorization percentage vs time (min) for (c) Methyl orange and (d) Congo red under UV irradiation.

Table 4 Kinetic Parameters of L-H model. Dye

Composite

Rate constant (min−1 )

R2

Methyl orange

Composite A Composite B Composite C

0.31 0.64 0.17

0.96 0.93 0.95

Congo red

Composite A Composite B Composite C

0.038 0.35 0.37

0.85 0.98 0.98

(99.97%) of degradation was observed for composite B. On the other hand, final degradation percentage was 99.56% and 99.95% for composite A and composite C respectively. Therefore, composition of the composites were not sensitive to photocatalytic degradation of dye. Maximum degradation was obtained after 15 min of irradiation time for composite A and composite B, while 30 min for composite C. Agglomeration of particle may lower the process rate. However, the degradation rate linearly increased with time under UV irradiation possibly because the solution was transparent after decolorization, and light intensity reaching the photocatalyst was enhanced. In case of congo red, dye removal percentage was 43.5, 98 and 99% for composite A, composite B and composite C, respectively.

4. Conclusions In this study, three chitosan/PVA/TiO2 /Na-titanate composites were fabricated by film casting method. This was confirmed by the FTIR and XRD results. Promising adsorption and photocatalytic degradation were reported and overall conclusion have been listed below:

1. FTIR result showed strong interaction between the polymer matrix of chitosan/PVA and TiO2 /Na-titanate. 2. XRD results showed crystalline phase of chitosan, PVA, TiO2 and Na-titanate and confirm the successful fabrication of these composites.

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• Weight loss test showed that incorporation of Na-titanate shown decrease of crystallinity of chitosan but increase water stability. Whereas composite structure was deteriorated with considerable weight loss in acidic medium. • Kinetic study results showed that the adsorption behavior of the composite obeyed the pseudo-second-order kinetic model and Lagergren-first-order model for methyl orange and congo red, respectively. • The composite having higher weightage of chitosan and crystalline TiO2 phase showed impressive removal rate of methyl orange from the solution. On the other hand, the composite having higher chitosan and Na-titanate showed an efficient removal capacity for congo red. 3. In case of UV irradiation, kinetic analysis results indicated that Langmuir–Hinshelwood model can be used to explain the mechanism of photocatalytic degradation of dye. • ∼100% of methyl orange removal was obtained under UV irradiation. For congo red, 99% of removal percentage was observed. Acknowledgement The author would like to thank the financial support of the University of Malaya Research Grant RP034A-15AET, Fundamental Research Grant Scheme, FP026-2014B, Post graduate research fundPG048-2013B and the Ministry of Higher Education Malaysia through High Impact Research Grant UM.C/625/1/HIR/MOHE/ENG 40. References Al-Asheh, S., & Banat, F. (2001). Adsorption of zinc and copper ions by the solid waste of the olive oil industry. Adsorption Science & Technology, 19(2), 117–129. Alexandre, M., & Dubois, P. (2000). Polymer-layered silicate nanocomposites: preparation, properties and uses of a new class of materials. Materials Science and Engineering: R: Reports, 28(1), 1–63. Anthony, R. G., Philip, C. V., & Dosch, R. G. (1993). Selective adsorption and ion exchange of metal cations and anions with silico-titanates and layered titanates. Waste Management, 13(5–7), 503–512. Bai, J., Li, Y., Yang, S., Du, J., Wang, S., Zheng, J., et al. (2007). A simple and effective route for the preparation of poly (vinylalcohol) (PVA) nanofibers containing gold nanoparticles by electrospinning method. Solid State Communications, 141(5), 292–295. Carmen, Z., & Daniela, S. (2012). Textile organic dyes–characteristics, polluting effects and separation/elimination procedures from industrial effluents–a critical overview. [ISBN: 978-953-307-917-2]. C¸ay, A., Miraftab, M., & Kumbasar, E. P. A. (2014). Characterization and swelling performance of physically stabilized electrospun poly (vinyl alcohol)/chitosan nanofibres. European Polymer Journal, 61, 253–262. Chen, X., Yang, H., Gu, Z., & Shao, Z. (2001). Preparation and characterization of HY zeolite-filled chitosan membranes for pervaporation separation. Journal of Applied Polymer Science, 79(6), 1144–1149. Feng, M., You, W., Wu, Z., Chen, Q., & Zhan, H. (2013). Mildly alkaline preparation and methylene blue adsorption capacity of hierarchical flower-like sodium titanate. ACS Applied Materials & Interfaces, 5(23), 12654–12662. Fong, H., Chun, I., & Reneker, D. (1999). Beaded nanofibers formed during electrospinning. Polymer, 40(16), 4585–4592. Francis Suh, J.-K., & Matthew, H. W. (2000). Application of chitosan-based polysaccharide biomaterials in cartilage tissue engineering: a review. Biomaterials, 21(24), 2589–2598. Ho, Y.-S., & McKay, G. (1999). Pseudo-second order model for sorption processes? Process Biochemistry, 34(5), 451–465. Homayoni, H., Ravandi, S. A. H., & Valizadeh, M. (2009). Electrospinning of chitosan nanofibers: processing optimization. Carbohydrate Polymers, 77(3), 656–661. Jayanthi Kalaivani, G., & Suja, S. K. (2016). TiO2 (rutile) embedded inulin—a versatile bio-nanocomposite for photocatalytic degradation of methylene blue. Carbohydrate Polymers, 143, 51–60. Jeevitha, D., & Amarnath, K. (2013). Chitosan/PLA nanoparticles as a novel carrier for the delivery of anthraquinone: synthesis, characterization and in vitro cytotoxicity evaluation. Colloids and Surfaces B: Biointerfaces, 101, 126–134. Jia, Y.-T., Gong, J., Gu, X.-H., Kim, H.-Y., Dong, J., & Shen, X.-Y. (2007). Fabrication and characterization of poly (vinyl alcohol)/chitosan blend nanofibers produced by electrospinning method. Carbohydrate Polymers, 67(3), 403–409.

Khan, R., & Dhayal, M. (2008). Electrochemical studies of novel chitosan/TiO 2 bioactive electrode for biosensing application. Electrochemistry Communications, 10(2), 263–267. Kumar, K. V., Porkodi, K., & Selvaganapathi, A. (2007). Constrain in solving Langmuir–Hinshelwood kinetic expression for the photocatalytic degradation of Auramine O aqueous solutions by ZnO catalyst. Dyes and Pigments, 75(1), 246–249. Kumar, M., Tripathi, B. P., & Shahi, V. K. (2009). Crosslinked chitosan/polyvinyl alcohol blend beads for removal and recovery of Cd(II) from wastewater. Journal of Hazardous Materials, 172(2), 1041–1048. Kumar, M. N. R. (2000). A review of chitin and chitosan applications. Reactive and Functional Polymers, 46(1), 1–27. ´ Kumirska, J., Czerwicka, M., Kaczynski, Z., Bychowska, A., Brzozowski, K., Thöming, J., et al. (2010). Application of spectroscopic methods for structural analysis of chitin and chitosan? Marine Drugs, 8(5), 1567–1636. Li, L., & Hsieh, Y.-L. (2006). Chitosan bicomponent nanofibers and nanoporous fibers. Carbohydrate Research, 341(3), 374–381. Ma, R., Bando, Y., & Sasaki, T. (2003). Nanotubes of lepidocrocite titanates. Chemical Physics Letters, 380(5), 577–582. Mahanta, D., Manna, U., Madras, G., & Patil, S. (2010). Multilayer self-assembly of TiO2 nanoparticles and polyaniline-grafted-chitosan copolymer (CPANI) for photocatalysis. ACS Applied Materials & Interfaces, 3(1), 84–92. Martinová, L., & Lubasová, D. (2008). Electrospun chitosan based nanofibers. Research Journal of Textile and Apparel, 12, 72–79. Mishra, S., Dubey, S., & Tiwari, D. (2004). Ion-exchangers in radioactive waste management Part XIV: Removal behavior of hydrous titanium oxide and sodium titanate for Cs(I). Journal of Radioanalytical and Nuclear Chemistry, 261(2), 457–463. Muhd Julkapli, N., Akil, H. M., & Ahmad, Z. (2011). Preparation, properties and applications of chitosan-based biocomposites/blend materials: a review. Composite Interfaces, 18(6), 449–507. Ngah, W. W., Teong, L., & Hanafiah, M. (2011). Adsorption of dyes and heavy metal ions by chitosan composites: a review. Carbohydrate Polymers, 83(4), 1446–1456. Papp, S., Kõrösi, L., Meynen, V., Cool, P., Vansant, E. F., & Dékány, I. (2005). The influence of temperature on the structural behaviour of sodium tri-and hexa-titanates and their protonated forms. Journal of Solid State Chemistry, 178(5), 1614–1619. Peiró, A. M., Peral, J., Domingo, C., Domènech, X., & Ayllón, J. A. (2001). Low-temperature deposition of TiO2 thin films with photocatalytic activity from colloidal anatase aqueous solutions. Chemistry of Materials, 13(8), 2567–2573. Plazinski, W., Rudzinski, W., & Plazinska, A. (2009). Theoretical models of sorption kinetics including a surface reaction mechanism: a review. Advances in Colloid and Interface Science, 152(1), 2–13. Ramı´ırez-Salgado, J., Djurado, E., & Fabry, P. (2004). Synthesis of sodium titanate composites by sol–gel method for use in gas potentiometric sensors. Journal of the European Ceramic Society, 24(8), 2477–2483. Ramya, R., Sudha, P., & Mahalakshmi, J. (2012). Preparation and characterization of chitosan binary blend. International Journals of Scientific Research Publications, 2(10), 1–9. Saien, J., & Khezrianjoo, S. (2008). Degradation of the fungicide carbendazim in aqueous solutions with UV/TiO2 process: optimization, kinetics and toxicity studies. Journal of Hazardous Materials, 157(2), 269–276. Suyatma, N. E., Copinet, A., Coma, V., & Fricoteaux, F. (2010). Compatibilization method applied to the chitosan-acid poly (l-lactide) solution. Journal of Applied Polymer Science, 117(5), 3083–3091. Tao, Y., Ye, L., Pan, J., Wang, Y., & Tang, B. (2009). Removal of Pb (II) from aqueous solution on chitosan/TiO2 hybrid film? Journal of Hazardous Materials, 161(2), 718–722. Tian, Y., Ju, B., Zhang, S., & Hou, L. (2016). Thermoresponsive cellulose ether and its flocculation behavior for organic dye removal. Carbohydrate Polymers, 136, 1209–1217. Tsai, C.-C., & Teng, H. (2006). Structural features of nanotubes synthesized from NaOH treatment on TiO2 with different post-treatments. Chemistry of Materials, 18(2), 367–373. Vicentini, D. S., Smania, A., Jr., & Laranjeira, M. (2010). Chitosan/poly (vinyl alcohol) films containing ZnO nanoparticles and plasticizers. Materials Science and Engineering: C, 30(4), 503–508. Wang, J., Li, R., Zhang, Z., Sun, W., Xu, R., Xie, Y., et al. (2008). Efficient photocatalytic degradation of organic dyes over titanium dioxide coating upconversion luminescence agent under visible and sunlight irradiation. Applied Catalysis A: General, 334(1), 227–233. Wu, T., Zivanovic, S., Draughon, F. A., Conway, W. S., & Sams, C. E. (2005). Physicochemical properties and bioactivity of fungal chitin and chitosan. Journal of Agricultural and Food Chemistry, 53(10), 3888–3894. Xiong, L., Yang, Y., Mai, J., Sun, W., Zhang, C., Wei, D., et al. (2010). Adsorption behavior of methylene blue onto titanate nanotubes. Chemical Engineering Journal, 156(2), 313–320. Yang, L., Jiang, L., Hu, D., Yan, Q., Wang, Z., Li, S., et al. (2016). Swelling induced regeneration of TiO 2-impregnated chitosan adsorbents under visible light. Carbohydrate Polymers, 140, 433–441. Yao, T., Guo, S., Zeng, C., Wang, C., & Zhang, L. (2015). Investigation on efficient adsorption of cationic dyes on porous magnetic polyacrylamide microspheres. Journal of Hazardous Materials, 292, 90–97.

U. Habiba et al. / Carbohydrate Polymers 149 (2016) 317–331 Yen, M.-T., Yang, J.-H., & Mau, J.-L. (2009). Physicochemical characterization of chitin and chitosan from crab shells? Carbohydrate Polymers, 75(1), 15–21. Zakaria, Z., Islam, M. S., Hassan, A., Mohamad Haafiz, M., Arjmandi, R., Inuwa, I., et al. (2013). Mechanical properties and morphological characterization of PLA/chitosan/epoxidized natural rubber composites. Advances in Materials Science and Engineering, 2013. Zamostny, P., & Belohlav, Z. (2002a). Identification of kinetic models of heterogeneously catalyzed reactions. Applied Catalysis A: General, 225(1), 291–299. Zamostny, P., & Belohlav, Z. (2002b). Identification of kinetic models of heterogeneously catalyzed reactions. Applied Catalysis A: General, 225(1–2), 291–299. Zarate, R., Fuentes, S., Cabrera, A., & Fuenzalida, V. (2008). Structural characterization of single crystals of sodium titanate nanowires prepared by hydrothermal process. Journal of Crystal Growth, 310(15), 3630–3637. Zhang, M., Yuan, R., Chai, Y., Li, W., Zhong, H., & Wang, C. (2011). Glucose biosensor based on titanium dioxide-multiwall carbon nanotubes-chitosan composite and functionalized gold nanoparticles. Bioprocess and Biosystems Engineering,

331

34(9), 1143–1150. Zhou, Z., Peng, X., Zhong, L., Wu, L., Cao, X., & Sun, R. C. (2016). Electrospun cellulose acetate supported [email protected] composites with facet-dependent photocatalytic properties on degradation of organic dyes under visible-light irradiation. Carbohydrate Polymers, 136, 322–328. Zhu, H., Jiang, R., Fu, Y., Guan, Y., Yao, J., Xiao, L., et al. (2012). Effective photocatalytic decolorization of methyl orange utilizing TiO2 /ZnO/chitosan nanocomposite films under simulated solar irradiation. Desalination, 286, 41–48. Zhu, H., Jiang, R., Xiao, L., Liu, L., Cao, C., & Zeng, G. (2013). CdS nanocrystals/TiO 2/crosslinked chitosan composite: facile preparation: characterization and adsorption-photocatalytic properties. Applied Surface Science, 273, 661–669. Zubieta, C. E., Messina, P. V., Luengo, C., Dennehy, M., Pieroni, O., & Schulz, P. C. (2008). Reactive dyes remotion by porous TiO2 -chitosan materials. Journal of Hazardous Materials, 152(2), 765–777.