[Adsorption of perchlorate from water by protonated cross-linked chitosan gel beads]

Cross-linked chitosan gel beads were used to adsorb perchlorate (ClO4-) from water. Batch experiments were conducted to investigate the effects of temperature, pH, and initial ClO4- concentration, adsorption isotherms and kinetics, and regeneration ability. The adsorption process of ClO4- on chitosan is exothermic reaction. The adsorption capacity varies from 37.98 mg x g(-2) to 34.39 mg x g(-1) with the pH changes from 3.0 to 6.0 when the initial ClO4- concentration is 100 mg x g(-1). The adsorption capacity increases with the initial ClO4- concentration increase, and the maximum reaches up to 128.78 mg x g(-1) at the initial ClO4- concentration of 400 mg x L(-1). The equilibrium data fit Langmuir and Freundlich isothermal models well. In addition, the adsorption process can be explained by the pesudo-second-order kinetic model, and the chemisorption is the limit step for adsorption velocity. Finally, the adsorbent can be easily refreshed by pH 12.8 NaOH and repeatedly used for 10 cycles without obviously destruction.