Degradation of chitosan by sonication in very-low-concentration acetic acid

Abstract

Free-volume hole size evaluated by positron annihilation lifetime spectroscopy in the amorphous part of poly ( ethylene a b s t r a c tChitosan is a linear copolymer composed of (1 / 4)elinked 2-acetamido-2-deoxy-b-D-glucan (GlcNAc) and 2-amino-2-deoxy-b-D-glucan (GlcN) units in varying proportions, having a high molecular weight and strong intra-and intermolecular hydrogen bondings. Sonication has become an alternative for degrading chitosan into low-molecular-weight chitosan (LMWC), chitosan oligomers and glucosamine. In this study, chitosan was treated with sonication at 40 C and 60 C for 30 min and 120 min with various acetic acid concentrations (0.2% v/ve1% v/v); the very-low-concentration acid solution functioned both as a solvent and catalyst. After sonication, the samples were tested for changes in molecular weight, water soluble proportion of chitosan (chitosan oligomers and glucosamine), degree of deacetylation, degree of crystallinity, and morphology. The soluble and insoluble product yields at low concentration (0.5% v/v) at 40 and 60 C were 33.66e39.37 % and 32.43e34.26%, respectively. The main product was 5-hydroxy methyl furfural with composition 92.16e99.43%. At high concentrations (1% v/v), the soluble product and insoluble yields were 43.72e49.74% and 43.1e50.26%, respectively. The main product was glucosamine with composition 77.75e93.16% of glucosamine. There were changes in the morphology and crystallinity of the degraded chitosan, but no change in the chemical structure. The crystallinity had a tendency to increase. The degree of deacetylation tended to decrease due to the glucosamine breakage.

Kinetics and Thermodynamics of Ultrasound-Assisted Depolymerization of κ-Carrageenan

“…However, some other groups of researchers reported similar results to this work where temperature gives positive effect on ultrasoundassisted depolymerization [40][41][42][43][44]. In general, ultrasound-assisted degradation of organic polymers takes place via two mechanism, i.e., homolytic bond breaking and reaction with radicals [45][46][47].…”

Karakteristik Glukosamin Hidroklorida Hasil Hidrolisis Kitosan menggunakan Asam dan Ultrasonikasi

“…Penggunaan konsentrasi asam 37% dan ultrasonikasi selama 30 menit ini dapat meningkatkan rendemen 3,57%. Savitri et al (2014) (Ames, 1998). Ultrasonik dapat mempercepat terjadinya proses hidrolisis sehingga akan lebih cepat proses pemanasannya.…”

Preparation of Chitosan Beads for the Adsorption of Reactive Blue 4 from Aqueous Solutions

“…In addition, increasing the acid concentration caused a decrease in polymer viscosity as when the ionic concentration was increased so that long-range electrostatic interactions are screened. These changes caused an increase in the elasticity of polymer chains up to their conformation from long 'sticklike' to coil [16]. Therefore, highest dye removal (84.3%) occurred at 1% acid concentration because at this concentration, chitosan could dissolve and the functional groups were more accessible.…”

“…polymer chains at high temperatures. As such, the acetylated and deacetylated units of the polymer are dehydrated, depolymerized, and decomposed, thereby decreasing adsorption capacity [16]. In addition, when the chitosan solution is heated, its viscosity decreases, and this decrease is more pronounced at high temperatures.…”