Preparation of a new chitosan-based material and its application for mercury sorption

A novel chitosan sponge-like structure has been prepared by freeze-drying technique and then tested to remove Hg(II). Chitosan as biosorbent has been used in the form of flakes and cylindrical foams. In this study, column experiment on recirculation mode was conducted in order to determine the sorption properties of the cylindrical foams in various operating conditions (pH, initial metal ion concentration, flow rate, depth of column). The sorption behavior of the materials was examined through equilibrium, kinetic experiments. Hg(II) equilibrium isotherm data is very well fitted by the Langmuir model. Based on the sorption capacity, it was shown that a chitosan flake was more effective than foam. At pH 4, the sorption capacities (qm) were found up to 850 mg of Hg g−1 for chitosan flake and only 350 mg of Hg g−1 for chitosan foam. Two-region model performed for predicting and determining the sorption capacity of foam were distinguished. The pseudo-second-order chemisorption kinetic has shown success for short sorption times, while the cylindrical diffusion model was able to predict the end of the sorption times. The nature and morphology of the biomaterial before and after mercury sorption was studied by SEM-EDAX analysis.