Non-isothermal kinetics of thermal degradation of chitosan

Abstract

BackgroundChitosan is the second most abundant nitrogen containing biopolymer in nature, obtained from the shells of crustaceans, particularly crabs, shrimp and lobsters, which are waste products of seafood processing industries. It has great potential application in the areas of biotechnology, biomedicine, food industries, and cosmetics. Chitosan is also capable of adsorbing a number of metal ions as its amino groups can serve as chelation sites. Grafted functional groups such as hydroxyl, carboxyl, sulfate, phosphate, and amino groups on the chitosan have been reported to be responsible for metal binding and sorption of dyes and pigments. The knowledge of their thermal stability and pyrolysis may help to better understand and plan their industrial processing.ResultsThermogravimetric studies of chitosan in air atmosphere were carried out at six rates of linear increasing of the temperature. The kinetics and mechanism of the thermal decomposition reaction were evaluated from the TG data using recommended from ICTAC kinetics committee iso-conversional calculation procedure of Kissinger-Akahira-Sunose, as well as 27 mechanism functions. The comparison of the obtained results showed that they strongly depend on the selection of proper mechanism function for the process. Therefore, it is very important to determine the most probable mechanism function. In this respect the iso-conversional calculation procedure turned out to be the most appropriate.ConclusionChitosan have excellent properties such as hydrophilicity, biocompatibility, biodegradability, antibacterial, non-toxicity, adsorption application. The thermal degradation of chitosan occurs in two stages. The most probable mechanism function for both stages is determined and it was best described by kinetic equations of n-th order (Fn mechanism). For the first stage, it was established that n is equal to 3.0 and for the second stage – to 1.0 respectively. The values of the apparent activation energy E, pre-exponential factor A in Arrhenius equation, as well as the changes of entropy ΔS≠, enthalpy ΔH≠ and free Gibbs energy ΔG≠ for the formation of the activated complex from the reagent are calculated.

EFFECTS OF THE ADDITION OF SUGARS ON THE THERMOSTABILITY OF BETANIN FROM Beta vulgaris L.

“…In this way, there is a need for a high energy barrier to break the bonds. Furthermore, the values obtained for ΔS in this study were low, which, according to Georgieva et al (2012), means that the state of the material is close to its own thermodynamic equilibrium and thus the material shows little reactivity and has undergone some kind of physical or chemical rearrangement in its initial structure, bringing it to a state close to its own thermodynamic equilibrium. …”

“…According to Georgieva et al (2012) activation enthalpy (ΔH) shows the energy diff erence between the reagent and activated complex. Similar values for all conditions evaluated indicates that the energy barrier that must be overcome in order to achieve the transition state is similar.…”

Kinetic Study of the Thermal Decomposition of Potassium Chlorate Using the Non-isothermal TG/DSC Technique

“…The kinetic triplet is required for prediction of the thermal stability of the materials under various applied temperature conditions [20] and is needed to provide a mathematical description of the process [21]. .…”

Kinetics of Thermal Decomposition of a Spirooxindole Compound under Non-Isothermal Condition

“…Synthesized compounds were evaluated for their antimicrobial activity and all the compounds showed significant activity [11]. Non-isothermal kinetics of chitosan [12], chitin [13], cephalosporins [14], procaine and benzocaine [15] and theobromine [16] were studied in details and appropriate the decomposition kinetics models were proposed.…”