Effect of solution plasma process with bubbling gas on physicochemical properties of chitosan
Introduction
Chitosan is a natural nontoxic polymer that is mainly composed of β (1–4)-linked glucosamine and N-acetylglucosamine. The polysaccharide has attracted tremendous research interest owing to its biological properties such as antimicrobial, hypocholesterolemic, immunity, and antitumor effects [1], [2]. However, its high molecular weight and low solubility in aqueous solvents has thus far limited its applications [3], [4]. Oligochitosan shows good solubility and some specific biological, chemical, and physical properties. Therefore, there has been increasing interest in methods for preparing oligochitosan by using a variety of techniques [5], [6], [7]. Solution plasma process (SPP) technology has been recognized as an advanced oxidation process. SPP involves the application of voltage to generate discharge plasma in a liquid, which leads to the formation of active radicals (H, O, OH) and molecules (e.g., H2O2, O3) [8], [9], [10]. The oxidizing species can effectively degrade the recalcitrant organic substances such as pharmaceutical compounds, dioxins, or agricultural chemicals [11]. Especially, OH radicals play the critical role for the strong oxidation property of SPP technology [12]. The SPP method has been extensively applied in wastewater treatment owing to its excellent performance, including high degradation efficiency, complete degradation, no secondary pollution, and requirements of normal temperature, pressure and low power consumption [9], [13], [14].
In recent years, SPP has also been used to degrade chitosan. For example, the decomposition of chitosan was successfully achieved using a solution plasma system [7], [15]. However, the solution plasma was produced by pulsed discharge without bubbling gas. Bubbling gas is often used to improve the liquid discharge performance in pulsed discharge systems [16]. The injection of gas bubbles can significantly increase the contact surface area of the gas and liquid and enhance higher-energy electron production, thus resulting in the creation of more oxidizing species [17]. In addition, bubbling gas can enhance the mass transfer rate and increase the efficiency of the diffusion of reactive species into the liquid, thus promoting oxidation reactions [9]. We previously carried out studies on the degradation of chitosan by SPP in the presence of H2O2 with bubbling gas and concluded that this method could be used for effective degradation of chitosan [18]. At treatment time of 30 min, the intrinsic viscosity reduction rate reached 82.19% and 70.04% with and without bubbling gas, respectively. The results confirmed the decomposition effect of bubbling gas in pulsed discharge systems.
Therefore, in the present study, the effect of SPP with bubbling gas (air) on the degradation of chitosan was evaluated, and the characteristics of the chitosan obtained after SPP irradiation with bubbling gas were investigated, including the morphology, crystallinity, thermogravimetry, and chemical structure.
Section snippets
Materials
Chitosan was obtained from Sinopharm Chemical Reagent Co. Ltd., China. The degree of deacetylation () of chitosan is greater than 90%. The viscosity average molecular weight (Mv) of chitosan is 1138 kDa based on viscosity measurements [19]. Acetic acid, ethyl alcohol, and other chemicals were of analytical reagent grade and were obtained from Sinopharm Chemical Reagent Co. Ltd., China. All chemicals were used without any further purification.
Experimental setup
The experimental setup is shown in Fig. 1. The
Degradation of chitosan by SPP irradiation with bubbling gas
Fig. 2 shows a plot of the change in the intrinsic viscosity reduction rate of chitosan over irradiation time under SPP irradiation with and without bubbling gas. Overall, the intrinsic viscosity reduction rate of chitosan increased with increasing irradiation time, with an initial substantial increase within 120 min, followed by a more gradual increase. This pattern might be explained by the fact that chitosan consists of long molecular chains and a large amount of glycosidic bonds in the early
Conclusion
In the present study, the SPP method with bubbling gas was employed to prepare oligochitosan. The results showed that the degradation process of chitosan could be accelerated by applying bubbling gas compared with SPP alone. The SEM, TGA, and XRD analyses demonstrated that the crystalline structure and the chitosan chains of chitosan were destroyed with further degradation over longer treatment time. The results of UV–vis, FTIR, and 13C NMR spectroscopy showed that the main chain structure of
Acknowledgement
The study was supported by the 2014–2015 Research Funds for the Introduced Talents of Shenyang Agricultural University (20153033).
References (41)
- et al.
Chitin and chitosan in selected biomedical applications
Prog. Polym. Sci.
(2014) - et al.
Biological activities of chitosan and chitooligosaccharides
Food Hydrocolloid
(2011) - et al.
Hydrolysis of chitosan under microwave irradiation in ionic liquids promoted by sulfonic acid-functionalized ionic liquids
Polym. Degrad. Stab.
(2012) - et al.
Advances in characterisation and biological activities of chitosan and chitosan oligosaccharides
Food Chem.
(2016) - et al.
Degradation of chitosan in solution by gamma irradiation in the presence of hydrogen peroxide
Carbohydr. Polym.
(2012) - et al.
Heterogeneous degradation of chitosan with H2O2 catalysed by phosphotungstate
Carbohydr. Polym.
(2008) - et al.
Preparation of low molecular weight chitosan using solution plasma system
Carbohydr. Polym.
(2012) - et al.
Degradation of azo dye using non-thermal plasma advanced oxidation process in a circulatory airtight reactor system
Chem. Eng. J.
(2012) - et al.
Review on electrical discharge plasma technology for wastewater remediation
Chem. Eng. J.
(2014) - et al.
Plasma-based water treatment: conception and application of a new general principle for reactor design
Chem. Eng. J.
(2015)
Degradation of microcystin-LR in water by glow discharge plasma oxidation at the gasesolution interface and its safety evaluation
Water Res.
Parameter optimization of excited OH radical in multi-needle to plate negative DC corona discharge
J. Electrostat.
Degradation of methyl orange by atmospheric DBD plasma: analysis of the degradation effects and degradation path
J. Electrostat.
Characteristics of gas-liquid pulsed discharge plasma reactor and dye decoloration efficiency
J. Environ. Sci.
Influences of solution plasma conditions on degradation rate and properties of chitosan
Innov. Food Sci. Emerg.
Actions of nitrogen plasma in the 4-chrolophenol degradation by pulsed high-voltage discharge with bubbling gas
Chem. Eng. J.
Inactivation of Microcystis aeruginosa by DC glow discharge plasma: impacts on cell integrity, pigment contents and microcystins degradation
J. Hazard. Mater.
Biochemical activities of low molecular weight chitosans derived from squid pens
Carbohydr. Polym.
Degradation of chitosan by hydrodynamic cavitation
Polym. Degrad. Stab.
Optical study of active species produced by a pulsed streamer corona discharge in water
J. Electrostat.
Cited by (27)
Study on catalytic degradation of wastewater containing Polyacrylamide catalyzed by non-thermal plasma-H<inf>2</inf>O<inf>2</inf>-Mn+Fe/AC
2024, Journal of the Taiwan Institute of Chemical EngineersEffect of free radicals on rheological properties, antioxidant activity, and molecular conformation of chitosan under solution pulsed plasma process based on radical scavengers
2024, International Journal of Biological MacromoleculesEffect of solution pulsed plasma process on the degradation and physicochemical properties of pectin
2023, Food HydrocolloidsCitation Excerpt :The average molecular weight (Mw) was 356.5 kDa. A bench-scale SPP system (Shenyang Agricultural University, Shenyang, China) was used in this study (Ma et al., 2017). A DC power supply was used for discharge ignition.
Effect of pH value and the distance between the electrodes on physicochemical properties of chitosan under SPP treatment
2022, Carbohydrate PolymersCitation Excerpt :However, some changes still existed. After SPP treatment, the characteristic absorption peak at 1599 cm−1 vanished and a new peak at 1579 cm−1 was checked, which corresponded to amide II (Li et al., 2012; Ma et al., 2017). This trend became more evident with decreasing initial pH values.
Preparation of low molecular chitosan by microwave-induced plasma desorption/ionization technology
2021, International Journal of Biological Macromolecules