Preparation Of Chitosan Hydrogel Adsorbent And Its Adsorption Properties For Anionic Dyes

The irregular discharge of dye wastewater not only causes serious damage to the ecosystem,but also endangers human health.The separation and recovery of dyes in wastewater meets the major national demand of "promoting wastewater resource utilization".At present,the adsorption materials for commercial wastewater treatment,such as activated carbon and zeolite,have problems of low separation efficiency and poor recycling.Therefore,in this paper,chitosan-based hydrogels were prepared using acrolein as crosslinking agent,providing new method for the synthesis of chitosanbased hydrogels,and developing novel chitosan-based adsorbent(A/CS)with low cost,large adsorption capacity and reusable.The A/CS hydrogels synthesized at the optimum ratio have high swelling rate,maximum specific surface area and pore size.FT-IR,XPS and BET characterization showed that acrolein successfully cross-linked with chitosan and A/CS had mesoporous structure which was conducive to the adsorption of dyes.The adsorption properties of acid blue 93(AB93)by A/CS were investigated by adsorption kinetics and adsorption isotherm experiments,corresponding to pseudo-second-order kinetics’ and Langmuir model,respectively.The adsorption capacity of AB93 by the adsorbent is up to 1839 mg/g.It was proved that A/CS had good cyclic regeneration in 12 sorption-desorption cycles.N-A/CS adsorbent was prepared by activating A/CS hydrogel with NaOH.In single dye system,the adsorption kinetics and adsorption isotherms of N-A/CS for AB93 fit the pseudo-second-order kinetics and Freundlich model,respectively.The adsorption capacity was further increased to 2566 mg/g,and the adsorption equilibrium time was reduced to 30 min.The acidic environment is more favorable for N-A/CS to remove AB93.The adsorption mechanism was investigated by FT-IR,BET,XPS and molecular dynamics simulation.In the binary dye system composed of AB93 and other anionic dyes,N-A/CS has a preferential adsorption to AB93.This is the result of hydrogen bonding,electrostatic interaction and molecular size-matching effect between N-A/CS and AB93.