Preparation And Performance Study Of Chitosan-based Composite Adsorbent Materials

As society progresses,the types and levels of water contaminants are increasing,mainly containing dyes,antibiotics and heavy metal ions.The toxicity,bioaccumulation and non-degradability of these pollutants have become a serious threat to human health and environmental safety.How to remove dyes and antibiotics from the environment is the key to realize the recycling of water resources.As a functional polymer,hydrogel has a unique three-dimensional internal network structure with large surface area and many pores.It can not only adsorb large amounts of water,but also effectively adsorb dyes,antibiotics and other pollutants from water.Natural polymers have good biocompatibility and contain a variety of hydrophilic functional groups,such as R-OH,R-COOH,R-NH₂,R-CONH₂ and R-SO₃H,which provide adsorption sites for pollutant removal and are the main materials for adsorptive hydrogels.Therefore,in this thesis,low-cost and high-performance composite adsorbent materials were prepared by free radical graft copolymerization using chitosan,a natural polymer material,as a substrate,and their structures and properties were investigated as follows:（1）Composite material with high adsorption properties（SEP/CS-P（AMPS-co-AA））were prepared by free radical graft copolymerization using chitosan（CS）as a matrix,sepiolite（SEP）as an inorganic filler,2-acrylamido-2-methylpropanesulfonic acid（AMPS）and acrylic acid（AA）as monomers.The materials were structurally characterized by infrared（FTIR）,X-single crystal diffractometer（XRD）,thermal stability analysis（TG）and scanning electron microscopy（SEM）.The adsorption properties of the dyes methylene blue（MB）and malachite green（MG）were used as indicators to discuss the effects of different environmental factors of the dyes on the adsorption capacity and to determine the optimal adsorption conditions.The adsorption kinetics and adsorption thermodynamics of MB and MG on the material surface were investigated.The results showed that SEP/CS-P（AMPS-co-AA）with high adsorption performance was successfully prepared,and the maximum adsorption capacities of MB and MG were 3238mg/g and 617.4 mg/g at the initial concentrations of 4000 mg/g and 1000 mg/g for MB and MG,pH=9 and adsorbent dosage of 0.02 g.The adsorption kinetics and thermodynamics of both were in agreement,and both were more consistent with the pseudo-second-order kinetic model and Langmuir isotherm model.（2）Composite material with high adsorption properties(SEP/CS_PDA-P（AMPS-co-AA）)were prepared by free radical graft copolymerization using chitosan(CS_PDA)modified with dopamine hydrochloride（DA）as raw material,SEP as inorganic filler,AMPS and AA as monomers.The materials were structurally characterized by infrared FTIR,XRD,TG and SEM.The adsorption properties of the MB and MG were used as indicators to discuss the effects of different influencing factors on the adsorption capacity and to determine the optimal adsorption conditions.The adsorption kinetics and adsorption thermodynamics of MB and MG on the material surface were investigated.The results showed that SEP/CS_PDA-P（AMPS-co-AA）with high adsorption performance was successfully prepared,and the maximum adsorption capacities of MB and MG were3725.07 mg/g and 847.01 mg/g at the initial concentrations of 4000 mg/L and 1000 mg/L of MB and MG,respectively,pH=9,and adsorbent dosage of 0.02 g,respectively.The adsorption kinetics and thermodynamic fitting results of both were more consistent with the pseudo-second-order kinetic model and Langmuir isotherm model.（3）The adsorption performance of two types of composites,which are SEP/CS-P（AMPS-co-AA）and SEP/CS_PDA-P（AMPS-co-AA）,on the antibiotics of ofloxacin（OFL）and norfloxacin（NOR）was evaluated.The effects of different factors(initial concentration of antibiotic solution,pH,amount of SEP/CS-P（AMPS-co-AA）and SEP/CS_PDA-P（AMPS-co-AA）and adsorption time)on the adsorption effect were investigated.The adsorption process was analyzed by adsorption isotherms and adsorption kinetics.The feasibility of adsorption of antibiotics by the two composites was determined by comparison of adsorption capacities.The results showed that the adsorption of both prepared materials was significant for OFL and NOR,and the maximum adsorption capacities of OFL on SEP/CS-P（AMPS-co-AA）and SEP/CS_PDA-P（AMPS-co-AA）were 1335.6 mg/g and 1412.2 mg/g,respectively;NOR on SEP/CS-P（AMPS-co AA）and SEP/CS_PDA-P（AMPS-co-AA）were 1133.9 mg/g and 1176.5 mg/g,respectively,and the adsorption behaviors of the two materials were more consistent with the pseudo-second-order kinetic model and Langmuir thermodynamic model.