Elsevier

Carbohydrate Polymers

Volume 177, 1 December 2017, Pages 32-39
Carbohydrate Polymers

Research paper
Effect of deacetylation on property of electrospun chitosan/PVA nanofibrous membrane and removal of methyl orange, Fe(III) and Cr(VI) ions

https://doi.org/10.1016/j.carbpol.2017.08.115Get rights and content

Highlights

  • The chitosan/PVA nanofiber was electrospun varying the degree of deacetylation of chitosan.

  • Higher tensile strength was observed for the composite containing chitosan with higher DD.

  • The membrane were used for adsorption of Cr(VI), Fe(III) and Methyl orange.

  • Higher Cr(VI) adsorption was observed for the chitosan with higher DD.

  • The membrane containing chitosan with lower DD showed better adsorption for Fe(III) and methyl orange.

Abstract

In this study, effect of degree of deacetylation on property and adsorption capacity of chitosan/polyvinyl Alcohol electrospun membrane has been investigated. Resulting nanofibers were characterized by FESEM, FTIR, XRD, TGA, tensile testing, weight loss test and adsorption test. FESEM result shows, finer nanofiber was fabricated from 42 h hydrolyzed chitosan and PVA blend solution. FTIR and XRD result showed a strong interaction between chitosan and polyvinyl alcohol. Higher tensile strength was observed for the nanofiber having 42 h hydrolyzed chitosan. Blend solution of chitosan/PVA having low DD chitosan had higher viscosity. The nanofibrous membrane was stable in distilled water, acidic and basic medium. The isotherm study shows that the adsorption capacity (qm) of nanofiber containing higher DD chitosan was higher for Cr(VI). In contrary, the membrane containing chitosan with lower DD showed the higher adsorption capacity for Fe(III) and methyl orange. Moreover, the effect of DD on removal percentage of adsorbate was dependent on the initial concentration of the adsorbate.

Introduction

Though freshwater is a natural resource, the ability of these resources to sustain water quality at suitable level has become difficult because of increasing water pollution. Among many pollutants, heavy metals and textile dyes are very dangerous as most of them are carcinogenic. The most common metal ions that can be present in water are Fe(III) and Cr(VI). On the other hand, methyl orange can be considered as a standard dye. Several methods are valuable for water treatment such as photocatalytic degradation, flocculation, adsorption, membrane filtration and so on. Among them, adsorption process is very simple. But it is difficult to separate the adsorbent after operation.

The electrospinning is a method to fabricate nanofiber with a diameter below 100 nm. Usually, electrospinning method is used to make nanofiber from polymer and polymer based composite. The electrospun nanofiber can be a future material for water treatment because of its attractive properties such as porosity, tunable pore size and high surface to volume ratio (Bognitzki et al., 2001, Fong and Reneker, 1999, Huang et al., 2003). But, previous study reported some limitation such as insufficient hydrophilicity (Hwang, Chen, & Wey, 2013), high swelling rate (Martinova & Lubasova, 2008) and lower mechanical strength (Desai et al., 2009). Moreover, commercially available membrane are not biodegradable.

Chitosan is a biodegradable polymer. It is being studied for water treatment for its hydrophilicity, disinfection capacity, non-toxicity, adsorptivity, and biocompatibility. Being polycationic in nature, it can bind metal ions, dyes and pathogens. Presence of amino group ensures its multipurpose application (Martinová & Lubasová, 2008). Nonetheless, it is mechanically unstable susceptible to swelling and pH sensitive (Cooper, Oldinski, Ma, Bryers, & Zhang, 2013). PVA is a biodegradable polymer. It can be used to immobilize chitosan (Kumar, Tripathi, & Shahi, 2009). Moreover, PVA can reduce the crystallinity of chitosan (Kim, Kim, Lee, & Kim, 1992). The functional groups of chitosan make hydrogen bonds with PVA which lead to form defect free nanofiber (Li et al., 2010; Pawlak & Mucha, 2003; Qi, Yu, Zhu, Chen, & Li, 2010).

Adsorption capacity of chitosan can be varied with the degree of deacetylation (DD) (Shao et al., 2003). In our previous study, chitosan/PEO membrane has been used for removal of Cu(II), Zn(II) and Pb(II) (Shariful et al., 2017). But, no study was done to know the effect of DD when chitosan is a component in a composite nanofiber. Moreover, chitosan/PVA electrospun nanofiber was not studied before as an adsorbent of Cr(VI), Fe(III) and methyl orange. The chitosan was hydrolysed with NaOH for 24 and 42 h to vary the degree of deacetylation, which has been studied in our previous work (Habiba, Afifi, Ang, & Talebian, 2016).

Therefore, objectives of this study is to fabricate of chitosan/PVA nanofibrous membrane with two different types of chitosan via electrospinning process and investigate the effect of DD on the properties of the resulting nanofibrous membrane via FESEM, XRD, FTIR, TGA, weight loss test and tensile test. The adsorption behavior of the nanofibrous membrane was evaluated over Methyl orange, Fe(III) and Cr(VI).

Section snippets

Materials

Chitosan (Mw = 8.96 × 105 g/mole, degree of deacetylation = 40%) was obtained from SE Chemical Co. Ltd and PVA (Mw = 60000, degree of hydrolysis = 89%) was a commercial product purchased from Kuraray Co Ltd, Tokyo, Japan. NaOH was purchased from System. Acetic acid and K2Cr2O7 were purchased from Sigma-Aldrich.

Method

In our previous study raw chitosan was hydrolyzed for 24 and 42 h. Degree of deacetylation of 24 and 42 h hydrolyzed chitosan was 84 and 92%, respectively (Habiba et al., 2016). The chitosan with DD%

Viscosity measurement of chitosan/PVA blend solution

Specific viscosity of chitosan/PVA solution was calculated by following equation 1. Here, ηr is the relative viscosity. Relative viscosity was measured by Brookfield viscometer using the equation numbered Eq. (3).ηsp=ηr1ηr=ηηs

The viscosity of chitosan B/PVA and chitosan A/PVA precursor solution is 200 and 230, respectively. This behavior has a relation to the degree of deacetylation. Chitosan B possesses higher degree of deacetylation describing higher ration of amino/acetyl group in the

Conclusion

In this study, chitosan/PVA nanofibrous membrane was fabricated with two different types of chitosan via electrospinning process. Resulting nanofibers were characterized by FESEM, FTIR, XRD, TGA, weight loss, tensile testing and adsorption test of Cr(VI), Fe(III) and methyl orange.

Several points can be concluded from this study:

  • 1.

    Blend solution of chitosan/PVA having low DD chitosan had higher viscosity.

  • 2.

    FESEM result shows, finer nanofiber was fabricated from 42 h hydrolyzed chitosan and PVA blend

Acknowledgements

The author would like to thank the financial support of the University of Malaya Research Grant RP034-15AET, Fundamental Research Grant Scheme, FP026–2014B and the Ministry of Higher Education Malaysia through High Impact Research Grant UM.C/625/1/HIR/MOHE/ENG 40.

References (41)

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