Effects of removing small fragments with ultrafiltration treatment and ultrasonic conditions on the degradation kinetics of chitosan

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The objective of this study was to propose a facile method to manipulate the molecular weight and practical mass production of chitosan by mechanical shearing and concurrent ultrafiltration (UF) treatment. The proposed method was based on the degradation rate and rate constant of various process variables, such as: solution temperature, reaction time, concentration of chitosan solution, with or without concurrent removal of degraded fragments during mechanical shearing. The result obtained was that the degradation rate constant was 1.8-6.0 times higher for those using UF to remove smaller degraded molecules concurrently during treatment, than that without UF treatment. The degradation rate constant increased with increasing solution temperature; however, the solution temperature should not exceed than 50 C to prevent the undesired color changes of the resulting product. A method combining mechanical shearing/UF treatment at 50 C and ultrasonic radiation or microfluidization/UF treatment at 30 C is proposed here for a facile method to manipulate the molecular weight of the resultant chitosan with an energy saving, efficient and practical mass production.

Section: Effect Of Reaction Timesupporting

confidence: 77%

Section: Resultsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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Facile method to manipulate the molecular weight and practical mass production of chitosan by mechanical shearing and concurrent ultrafiltration treatment

Tsai

Tseng

Chang

et al. 2010

Self Cite

“…Chitosan samples with different MWs were prepared by ultrasonic degradation. 26,27 The properties of these samples are listed in Table I.…”

Section: Preparation Of Chitosans With Different Mwsmentioning

confidence: 99%

Liquid‐crystalline behavior of chitosan in malic acid

Chang

Tsai

2007

This report describes how the degree of deacetylation and molecular weight of chitosan and the concentrations of sodium chloride and malic acid affect the formation of lyotropic chitosan liquid crystals. Chitosan samples of various degrees of deacetylation were prepared from b-chitin that was isolated from squid pens. They were degraded by ultrasonic irradiation to various molecular weights. The critical concentrations forming chitosan liquid crystals were determined with a polarized microscope. A chitosan sample with a degree of deacetylation of 67.2-83.6% formed cholesteric lyotropic liquid crystals when it was dissolved in 0.37-2.59M malic acid. The critical concentrations increased with increasing degrees of deacetylation of chitosan. They decreased with increasing molecular weights or increasing concentrations of sodium chloride and malic acid.

“…These are the major factors causing the degradation of polymers. [17][18][19][20] Application of high-intensity ultrasound to dispersions of carbohydrates can lead to depolymerization because of the intense mechanical and chemical effects associated with cavitation. [21][22][23][24] Cavitational thermolysis may produce hydroxyl radicals and hydrogen atoms that can be followed by formation of hydrogen peroxide.…”

Section: Introductionmentioning

confidence: 99%

A kinetic study of ultrasonic degradation of carboxymethyl cellulose

Taghizadeh

Abdollahi

2011

In this study, the effect of power of ultrasound, temperature, and concentration of carboxymethyl cellulose (CMC) solution on the rate of ultrasonic degradation were investigated, and a kinetic model based on viscometry data was used to calculate the rate constants in different conditions. To investigation of effect of ultrasonic power on the degradation of CMC, the power of ultrasound was increased and observed that the viscosity of the CMC solution was decreased with an increase in the power of ultrasound, but the extent of the degradation in a constant power was found to decrease with an increase in concentration or temperature. The ultrasonic degradation of CMC solutions was carried out at different temperatures to investigate the effect of the temperature on the rate of degradation. The calculated rate constants indicated that the degradation rate of the CMC solutions decreased as the temperature increased. The degraded CMCs were characterized by gel permeation chromatography, and average molecular weights of ultrasonicated CMCs were compared in different reaction conditions.