Modification Of Chitosan With Double-Method, Characterization For Product's Structure And Study On Applying Properties

In this study, the mono- and double-chemical modification of carboxy-methylation or quaternization for chitosan(CTS),which degree of deacetylation was more than 90%, had been studied with monochloroacetic acid (ClCH₂CO₂H) or 3-chloro-2-hydroxypropyltrimethylammonium chloride (CTA) as grafting agent for modification. The different derivation of chitosan were used to treat the simulated waste water and their synthetic conditions were optimized according to their coagulated ratio to remove heavy mental ions from simulated waste water . In the same time, study on the synthesis of CTA , the intermediate of quaternization , also had been completed.When carboxymethylated-modification or quaternized modification was being done, the synthetic condition of carboxymethyl chitosan(CM-CTS) was optimized through orthogonal experiment with their maximum coagulated ratio to remove Cd²⁺ from the simulated waste water as the analytical standard . The synthetic condition of 2-hydroxypropyltrimethylammonium chloride chitosan (HTCC, CTA-CTS) was optimized through orthogonal experiment with their maximum coagulated ratio to remove Cr (VI) from the simulated waste water as the analytical standard, respectively. The optimum condition for synthesizing the CM-CTS was as following: the reaction time was 7.0h, reaction temperature was 50℃, m(ClCH₂CO₂H) :m(CTS) =1.25:1.0, m(NaOH):m(CTS)= 1.0:1.0. Using the product synthesized under this condition to treat the simulated waste water containing Cd²⁺, the rate of removing Cd²⁺ was up to 99.7%. The optimum condition for synthesizing the CTA-CTS was as following: the reaction time was 10. 0h , reaction temperature was 65.0 ℃, m(CTA):m(CTS) = 4.0:1.0, m(NaOH):m(CTS)=1.0:1.0. The coagulated ratio to remove Cr (VI) for CTA-CTS synthesized under this condition was up to 94.39%. The product was also characterized by IR and ¹HNMR spectroscopy respectively. The results of IR and ¹HNMR analysis had showed that modification reaction were mainly occurred in the ammonium group of C₂ and the grafting degree at the OH of C₆ was higher than that at the OH of C3. The quaternary degree of chitosan determined from the result of electrolytic titration showed that reaction time of quatersation having enormous effect on the graft degree and soluble ability.When modification of quaterisation was being done for the CM-CTS and of carboxymethylation was being done for the CTA-CTS , the synthesized conditions ofsecond modification for chitosan were optimized through orthogonal experiment. The maximum coagulated ratio to remove Cd2+ and to remove Cr (VI) from the different simulated waste water were regarded as the analytical standard respectively. The results were as following. When the CM-CTS, which was synthesized under the optimum condition as raw material, was quaternized, there were small variations to the maximum coagulated ratio to remove Cd2+, but there were huge variation to the maximum coagulated ratio to remove Cr(VI) from the different simulated waste water for the derivative of chitosan that derived from this second modification. So it was reasonable to regard maximum coagulated ratio to remove Cr(VI) of product as the standard to optimize the synthetic condition for the quaterisation of CM-CTS. The optimum condition for the quaterisation of CM-CTS were as following: the reaction time was lO.Oh, reaction temperature was 60.CTC, m (CTA):m(CM-CTS)= 1.5:1.0, m(NaOH):m(CM-CTS)= 0.50:1.0. The maximum coagulated ratio to remove Cr(VI) was up to 93.16% and that to remove Cd +was up to 98.57% for the product synthesized under this optimum condition. When the CTA-CTS, which was synthesized under the optimum condition as raw material, was carboxymethylated, there were small variations to the maximum coagulated ratio for product to remove Cr (VI) , but there were huge variation to the maximum coagulated ratio for product to remove Cd2+ from the different simulated waste water for the derivative of chitosan that derived from this second modification. So it was reasonable to regard maximum coagulated ratio to remove Cd2+ for product as the standard to optimize the synthetic condition for the carboxymethylation of CTA-CTS. The optimum condition for the carboxylation of CTA-CTS were as following: the reaction time was 7.Oh, reaction temperature was 60.0 "C , m(ClCH2COOH):m(CTA-CTS)=0.417:1.0, m(NaOH): m(CTA-CTS)= 0.333:1.0. The maximum coagulated ratio to remove Cr(VI) was up to 94.10% and that to remove Cd2+was up to 99.48% for the product synthesized under this optimum condition. The results of IR and !HNMR analysis had showed that CM-CTS quaternized with CTA as quatemizing agent could bring quaternary group into CM-CTS. In the meantime, CTA-CTS carboxymethylated with monochloroacetic acid as carboxymethylating agent could bring carboxymethyl group into CTA-CTS. There was a strong typical zwitterionic properties for the product that modified with both carboxymethylation and quaterisation .In this studies, the synthetic condition and process of treatment for CTA, which was used as grafting agent for modification , was considered and optimized accordingto the result of orthogonal experiment with the yield of CTA as the analytical standard . The content of CTA was determined through electrolytic titration. The structure of CTA was characterized by IR and 'HNMR . When the product was treated by water-steam distillation and recrystallization with n-propanol as solvent, the properties of product could be improved and the content of other matter in product could be decreased efficiently through self-catalysis with the trimethylamine hydrochloride and epichlorohydrin as raw material. The optimum condition were as following: the reaction time was 2.Oh , reaction temperature was 35.0°C, the mass ratio of epichlorohydrin hydrochloride to trimethylamine was 1.1.The result of studies on the coagulated properties to remove heavy mental ions and dyes from stimulated waste water for chitosan derivate synthesized through different method of modification indicated the following conclusion. There were particularly coagulated properties to remove Cd"+ and Cationic Pink FG under weak basic condition for CM-CTS, its coagulated properties to remove Direct Fast Blue GL was good under acetic condition but not as good as CTA-CTS. The abilities of CM-CTS to remove Cr (VI) and Auramine O were not good oppositely. There were particularly coagulated properties to remove Cr (VI) and Direct Fast Blue GL under weak acetic condition for CTA-CTS, its coagulated properties to remove Cationic Pink FG under weak basic condition was good but not as good as CM-CTS . The abilities to remove Auramine O and Cd⁺ for CTA-CTS were not good oppositely. There were high coagulated ratio to remove Cd2+, Cr (VI), Cationic Pink FG and Direct Fast Blue GL for chitosan derivate that prepared through double-chemical modification concerned with carboxymethlation-quaterisation. Its ability to remove Auramine O through coagulated method was improved obviously than that of CM-CTS or CTA-CTS. The pH value of waste water treated by coagulation and the mass concentration of coagulant in the waste water had important effect on the coagulated properties of derivation of chitosan.