Modification Of Corn Straw Cellulose And Adsorption Properties For Dyes

Straw is a kind of agricultural waste and renewable biomass resource,which has many advantages such as abundant source,low cost and biodegradable.A large number of hydroxyl groups are distributed on the molecular chain of straw cellulose,which can be chemically modified by introducing different functional groups.The application of modified straw cellulose as a green water treatment agent in the treatment of dye wastewater has a broad application prospect.In this thesis,the cationic,anionic and amphoteric straw-based adsorbents were prepared by introducing quaternary ammonium,carboxyl or tertiary amine groups into the pretreated corn straw cellulose through esterification,etherification and graft copolymerization,and their application performance in the treatment of dye wastewater was studied.The main contents are as follows:（1）The straw cellulose betaine ester was prepared by dry method with betaine hydrochloride as modifier and dicyandiamide as dehydrating agent,and the optimum preparation conditions of straw cellulose betaine ester were investigated.When the dosage of corn straw cellulose was 0.1 g,betaine hydrochloride was 0.1 g,dicyandiamide was 0.032 g,the reaction temperature was 140^oC,and the reaction time was 2.5 h,the substitution degree of straw cellulose betaine ester was 0.725.The structure of the synthesized adsorbent was characterized by FI-IR,SEM,XRD,BET,Zeta-potential,TG-DTG and other analytical methods.The application performance of the adsorbent in the treatment of acid bright red G wastewater was studied.The effects of dye concentration,p H value,adsorbent dosage and adsorption time on the adsorption performance were investigated with dye removal rate and adsorption capacity as the indexes.When the concentration of the dye was 100 mg·L^-1and the initial p H value of the solution was 4,the removal rate of acid scarlet G could reach 97.8%.The adsorption process of anionic dye by the adsorbent was fitted with pseudo second order kinetic equation and Langmuir model.The saturated adsorption capacity for acid bright red G was 308.2 mg·g^-1,and the adsorption capacity for acid yellow 2G and reactive brilliant orange K-R were 261.2 mg·g^-1and 408.8 mg·g^-1,respectively.（2）Carboxymethyl straw cellulose was prepared by etherification in ethanol aqueous solution with chloroacetic acid as modifier,and the optimum preparation conditions of carboxymethyl cellulose were investigated.When the amount of corn straw cellulose was 0.3 g,the amount of chloroacetic acid was 0.36 g,the etherification temperature was 60^oC,and the reaction time was 160 min,the degree of substitution of carboxymethyl cellulose was 0.824.The structure of the synthesized adsorbent was characterized by FI-IR,SEM,XRD,BET,Zeta-potential,TG-DTG and other analytical methods.The application performance of the adsorbent in the treatment of methylene blue wastewater was studied.When the concentration of the dye was 200 mg·L^-1and the initial p H value of the solution was 8,the removal rate of methylene blue could reach92.6%.The adsorption process of cationic dye by the adsorbent was fitted with pseudo second order kinetic equation and Langmuir model.The saturated adsorption capacity of the adsorbent for methylene blue was 418.7 mg·g^-1.（3）Amphoteric straw-based adsorbent was prepared by using chloroacetic acid and dimethylaminoethyl methacrylate as modifying agents,and carboxyl group and tertiary amine group were introduced into straw cellulose.The optimum preparation conditions were determined as follows:the dosage of carboxymethyl straw cellulose was 0.3 g,the dosage of cationic monomer was 10 m L,85%ethanol solution was 10 m L,and the reaction time was 4 h.The structure of the synthesized adsorbent was characterized by FI-IR,SEM,XRD,BET,Zeta-potential,TG-DTG and other analytical methods.The application performance of the amphoteric straw-based adsorbent in the treatment of methylene blue and acid bright red G wastewater was studied.When the concentration of the dye was 200 mg·L^-1,the removal rate of methylene blue could reach 90.6%.When the concentration of the dye was 100 mg·L^-1,the removal rate of acid scarlet G could reach 95.1%.The adsorption processes of cationic and anionic dyes by the amphoteric straw-based adsorbent were fitted with pseudo second order kinetic equation and Langmuir model.The saturated adsorption capacity of the adsorbent for methylene blue was about 329.8 mg·g^-1,and that for acid scarlet G was about 361.7 mg·g^-1.