Research On Process Of Chitosan Degradation By Hydrogen Peroxide In Heterogeneous System

The process and the mechanism of chitosan degradation with hydrogen peroxide in the heterogeneous system was studied, and the effect of temperature, amount of hydrogen peroxide, time, particle size of chitosan and stirring speed to the reaction was investigated. The motive of the work is to get the best reaction condition of preparing LMWC (Low Molecular Weight Chitosan) of the best yield and of proper molecular weight. In the experiment GPC is used to test the molecular weight of LMWC. IR, NMR and SEM are used to characterize LMWC. The study showed that in the heterogeneous system hydrogen peroxide oxidating is a effective method to make LMWC. The amount of hydrogen peroxide and the reaction temperature is the main factor affecting the yield of LMWC. The reaction condition is optimized through orthogonal test and LMWC of the best yield is gotten. The second degradation reaction showed that in the heterogeneous system the chitosan material could be mostly used. Infrared Spectroscopy Analysis and NMR Spectroscopy Analysis showed that the structure of LMWC was almost the same as chitosan. The basic reaction of chitosan degradation by hydrogen peroxide is the breakage of 1,4-β-D-glucoside bonds. The best reaction condition of preparing the proper molecular weight LMWC is gotten through orthogonal test. The molecular weight of water-soluble chitosan has nothing to do with the molecular weight of chitosan material. And the best reaction condition of preparing LMWC of the best yield is different from the condition of preparing the proper molecular weight LMWC. In the heterogeneous system, the degradation reaction of chitosan by hydrogen peroxide happens mainly on the surface of the chitosan powder. Hydrogen peroxide peels off the chain of chitosan molecule on the surface of the chitosan powder, and the breaking chitosan chain was dissolved into the water and formed the LMWC.