| The experimental researches were conducted on the degradation of chitosan byγray, the determination of ozone concentration and the degradation of chitosan by ozone. The experiments used viscosity method and empirical equation to determine the molecular weight of chitosan afterγradiation. FTIR was applied to explore the chemical structure of the degradation products. The experiments determined the ozone concentration which was sealed in a small container. Eugenol-Pararosaniline hydrochloride colorimetric method was used to explore the ozone concentration, and the relationship between ozone concentration and time was studied. The experiments discussed the effect of ozone pretreatment on the degradation of chitosan. Compare the effect of pretreatment time, concentration of ozone and the grain size of chitosan on the molecular weight of chitosan's degradation products. FTIR was applied to explore the chemical structure of the degradation products which were pretreated by ozone. The experiment results showed:1. The molecular weight of the degraded chitosan decrease remarkably with increasing irradiation dose. The experiments show that the molecular weight of chitosan decrease 50% as the irradiation dose up to 10kGy, and it reduce to 10% after the irradiation at 40kGy.2. The result of FTIR shows that the radiation causes the decrease of chitosan molecular weight but without changing its chemical structure. The main chain of chitosan is still ring structure. The irradiation just induces scissions of 1-4 glycosidic bonds of chitosan.3. 0.1mL, 0.3mL and 0.5mL absorption liquid are used to determine and calculate the ozone concentration during the experiment. The result shows that 0.3mL absorption liquid meets the experimental requirement.4. The ozone concentration in the sealed container increase from 86mg/m3 (1 hour) up to 100mg/m3 (6 hours), and then balance gradually, while one ozone generator is working. The ozone concentration in the sealed container increased from 190mg/m3 (1 hour) up to 210mg/m3 (9 hours), while two ozone generators are working. Therefore, the ozone concentration could steady at a relative level, while the ozone generators are working more than 6 hours. And the ozone concentrations generated by two ozone generators are double as much as by one ozone generator.5. The molecular weight of the degraded chitosan decrease remarkably with increasing the pretreatment time of ozone. Ozone plays an important role in the chitosan's degradation, and it advances the degree of the degradation of chitosan. In addition, Ozone can degrade Chitosan, but it is not obvious thanγray.6. Compared the effect of different ozone concentration on the molecular weight of chitosan's degradation products at the same ozone pretreatment time and the irradiation dose, it indicates that if the ozone concentration is higher, the effect of ozone pretreatment will be more obvious. Therefore, high ozone concentration can be contributed to the degradation of chitosan.7. Compared the effect of different grain size of chitosan on the molecular weight of chitosan's degradation products at the same ozone pretreatment time and the irradiation dose, it indicates that the effect of ozone pretreatment will be more obvious if the smaller grain size of chitosan is chose.8. Based on FTIR, taken before and after ozone pretreatment and degradation, it is revealed that the main chemical structure of the degradation products pretreated by ozone is no significant different from the normal degradation products. The main chain of chitosan is still ring structure. The irradiation just induces scissions of 1-4 glycosidic bonds of chitosan.Based on the above results, chitosan oligomer with different molecular weight can be prepared effectively by aγray degradation method. Ozone as a strong oxidant can accelerate the degradation process and save the radiation cost. So that the process of the degradation of chitosan can be improved by ozone and also bring human beings a biological safe and environment-friendly product.
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