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.
Highlights
Chitosan is the second most abundant nitrogen containing biopolymer in nature, obtained from the shells of crustaceans, crabs, shrimp and lobsters, which are waste products of seafood processing industries
Chitin and chitosan are recommended as suitable functional materials, because these natural polymers have excellent properties such as hydrophilicity, biocompatibility, biodegradability, antibacterial, non-toxicity, adsorption properties, and remarkable affinity for many biomacromolecules
The TG, DTG and differential thermal analysis (DTA) curves, obtained by the thermal degradation of chitosan at heating rate of 15°C min-1 are presented on Figure 2
Summary
Chitosan is 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. Chitosan is the second most abundant nitrogen containing biopolymer in nature, obtained from the shells of crustaceans, crabs, shrimp and lobsters, which are waste products of seafood processing industries [13,15]. Chitosan has been widely studied for biosensors, tissue engineering, separation membrane, waste water treatment, because of its multiple functional groups [15]
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