Preparation of micro-nanofibrous chitosan sponges with ternary solvents for dye adsorption

Chitosan has been widely used to adsorb the contaminants in wastewater owing to its unique chemical structure. However, it is difficult to improve its adsorption performance by fabricating fibrous chitosan sponge with nanofiber or microfiber due to its strong hydrogen bond inside the molecular chain. In this study, different from traditional binary acetic acid/water solvents, ternary solvents comprised with acetic acid/water/tetrahydrofuran, along with quench temperature of -196 degrees C were adopted to prepare three dimensional chitosan sponge with micro-nanofibrous structure. The chitosan micro-nanofibrous sponge showed substantially improved adsorption capacity of Acid Blue-113 (687 mg/g) compared with the chitosan sponge (176.5 mg/g) prepared with binary acetic acid/water solvents and quench temperature of -20 degrees C. The adsorption of Acid Blue-113 onto chitosan micro-nanofibrous sponges was a chemical process, which fitted the pseudo-second-order and Langmuir isotherm models. The results indicated that microstructure modification was an effective and facile way to improve the chitosan adsorption capacity. The pure chitosan micro-nanofibrous sponge could be considered as an ideal dye adsorbent from wastewater.