Effect of sonolysis on kinetics and physicochemical properties of treated chitosan

The correlation of molecule weight of chitosan oligomers with the corresponding viscosity and antibacterial activity

In order to explore the correlation between the viscosity of chitosan oligomers-acetic solution and its viscosity average molecular weight (M_v), and determine the M_v range with a strong bactericidal effect. A series of chitosan oligomers were obtained by degraded chitosan (728.5 kDa) with dilute acid and chitosan oligomer (101.5 kDa) was characterized by FT-IR, XRD, H NMR and C NMR. The bactericidal effect of chitosan oligomers with different Mv on E. coli, S. aureus and C. albicans was measured by plate counting method. And the bactericidal rate was taken as the evaluation indicator, the optimum conditions were determined by single-factor experiments. The result showed that the molecular structure of chitosan oligomers and original chitosan (728.5 kDa) were similar. The viscosity of the chitosan oligomers in acetic acid solution was positively correlated with the M_v, and the chitosan oligomers with the M_v of 52.5-145.0 kDa had a strong bactericidal performance. In addition, the bactericidal rate of chitosan oligomers on experimental strains was more than 90% when the concentration of 0.5 g/L (bacteria) and 1.0 g/L (fungi), pH6.0, incubation time of 30 min. Thus, chitosan oligomers had a potential application value when the M_v was in the range of 52.5-145.0 kDa.

UV Irradiation and Ozone Treatment of κ-Carrageenan: Kinetics and Products Characteristics

The low molecular weight (LMW) of sulfated polysaccharides including k-carrageenan, is shows a wide spectrum of biological activities. This research investigates the influence of UV irradiation, ozone (O3), and the combination of O3/UV methods on the depolymerization of k-carrageenan. The depolymerization kinetics of k-carrageenan using the Advanced Oxidation Process (UV/O3) was also studied. Furthermore, the intrinsic viscosity method was used to determine the average molecular weight of the research sample, and a mathematical model was developed to predict the kinetic rate constant, as a function of ozone dosage and UV irradiation intensity. Therefore, the physicochemical and morphological properties of the degraded k-carrageenan were analyzed by FT-IR, SEM, and XRD. The intrinsic viscosity k-carrageenan decreases with increasing UV light intensity and ozone concentration. The combination of UV/O3 treatment appeared to be more effective than the individual approaches, as the highest kinetic rate constant for depolymerization was 1.924×10-4 min-1, using 125 mg/L ozone concentration and 40 mW/cm2 of UV lamp intensity. This research also evaluated the relationship between various experimental conditions, including UV lamp power dissipation and ozone concentration on the reaction kinetics model, and the results suggest that lower effect is contributed by UV irradiation intensity. In addition, FT-IR spectra showed the absence of any significant change in the functional properties of k-carrageenan treated with UV and O3 processes, although the morphological properties of the LMW k-carrageenan were rougher and more porous than the native k-carrageenan. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Hybrid Advanced Oxidation Processes Involving Ultrasound: An Overview

Sonochemical oxidation of organic pollutants in an aqueous environment is considered to be a green process. This mode of degradation of organic pollutants in an aqueous environment is considered to render reputable outcomes in terms of minimal chemical utilization and no need of extreme physical conditions. Indiscriminate discharge of toxic organic pollutants in an aqueous environment by anthropogenic activities has posed major health implications for both human and aquatic lives. Hence, numerous research endeavours are in progress to improve the efficiency of degradation and mineralization of organic contaminants. Being an extensively used advanced oxidation process, ultrasonic irradiation can be utilized for complete mineralization of persistent organic pollutants by coupling/integrating it with homogeneous and heterogeneous photocatalytic processes. In this regard, scientists have reported on sonophotocatalysis as an effective strategy towards the degradation of many toxic environmental pollutants. The combined effect of sonolysis and photocatalysis has been proved to enhance the production of high reactive-free radicals in aqueous medium which aid in the complete mineralization of organic pollutants. In this manuscript, we provide an overview on the ultrasound-based hybrid technologies for the degradation of organic pollutants in an aqueous environment.

In situ coupling of chitosan onto polypropylene foils by an Atmospheric Pressure Air Glow Discharge with a liquid cathode

Atmospheric air plasma treatment of chitosan solutions leads to degradation of chitosan molecules by OH radicals and is accompanied by a predominant cleavage of glycosidic linkages and by a decrease of the molecular weight. The degradation proceeds via first order kinetics with the rate constant of (5.73±0.22)×10(-6)s(-1) and the energetic yield of chitosan bond scission of (2.4±0.2)×10(-8)mol/J. Products of degradation together with intact chitosan molecules adsorb and form coatings on polypropylene foils immersed into the solution that is being plasma treated. The plasma treatment results in strong binding of chitosan to polypropylene due to the formation of covalent bonds between the activated polymer surface and chitosan molecules. Plasma-driven crosslinking is responsible for the accumulation of compressive stress which leads to the development of buckling instabilities in the chitosan coatings.

Processing/formulation parameters determining dispersity of chitosan particles: an ANNs study

Although a great number of studies may be found in literature about the parameters affecting the size of chitosan nanoparticles, no systematic work so far has detailed the factors affecting the polydispersity of chitosan as an important factor determining the quality of many preparations. Herein, using artificial neural networks (ANNs), four independent variables, namely, pH and concentration of chitosan solution as well as time and amplitude of sonication of the solution were studied to determine their influence on the polydispersity of solution. We found that in an ultrasound prepared nanodispersion of chitosan, all the four input parameters have reverse but non-linear relation with the polydispersity of the nanoparticles.

Effects of processing parameters on particle size of ultrasound prepared chitosan nanoparticles: an Artificial Neural Networks Study

The pharmacokinetic properties of chitosan nanoparticles have been shown to mainly depend on its particle size. The aim of this study was to concurrently evaluate and model the effective parameters, namely, chitosan concentration, buffer pH, amplitude and time of sonication, on the particle size of chitosan nanoparticles. Chitosan solutions were prepared and sonicated with different values for the above mentioned parameters. The data were then modeled using artificial neural networks (ANNs). The results illustrated that all four input parameters affect the size of prepared chitosan nanoparticles. While a reverse effect was observed between the size and the buffer pH as well as time and amplitude of sonication, the concentration was found to directly influence the particle size. The optimum condition to obtain the minimum size of nanoparticles in the range of 50-200 nm was found to be high values of pH and sonication time (i.e. approximately 4.9 and 500 s, respectively) and amplitude values of more than ~55.

Sonolytic, sonocatalytic and sonophotocatalytic degradation of chitosan in the presence of TiO2 nanoparticles

The degradation of chitosan by means of ultrasound irradiation and its combination with heterogeneous (TiO(2)) was investigated. Emphasis was given on the effect of additives on degradation rate constants. Ultrasound irradiation (24 kHz) was provided by a sonicator, while an ultraviolet source of 16 W was used for UV irradiation. The extent of sonolytic degradation increased with increasing ultrasound power (in the range 30-90 W), while the presence of TiO(2) in the dark generally had little effect on degradation. On the other hand, TiO(2) sono-photocatalysis led to complete chitosan degradation in 60 min with increasing catalyst loading. TiO(2) sonophotocatalysis was always faster than the respective individual processes due to the enhanced formation of reactive radicals as well as the possible ultrasound-induced increase of the active surface area of the catalyst. The degraded chitosans were characterized by X-ray diffraction (XRD), gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR) spectroscopy and average molecular weight of ultrasonicated chitosan was determined by measurements of relative viscosity of samples. The results show that the total degree of deacetylation (DD) of chitosan did not change after degradation and the decrease of molecular weight led to transformation of crystal structure. A negative order for the dependence of the reaction rate on total molar concentration of chitosan solution within the degradation process was suggested.

Application of spectroscopic methods for structural analysis of chitin and chitosan

Chitin, the second most important natural polymer in the world, and its N-deacetylated derivative chitosan, have been identified as versatile biopolymers for a broad range of applications in medicine, agriculture and the food industry. Two of the main reasons for this are firstly the unique chemical, physicochemical and biological properties of chitin and chitosan, and secondly the unlimited supply of raw materials for their production. These polymers exhibit widely differing physicochemical properties depending on the chitin source and the conditions of chitosan production. The presence of reactive functional groups as well as the polysaccharide nature of these biopolymers enables them to undergo diverse chemical modifications. A complete chemical and physicochemical characterization of chitin, chitosan and their derivatives is not possible without using spectroscopic techniques. This review focuses on the application of spectroscopic methods for the structural analysis of these compounds.