Hydrophobically modified chitosan sponge preparation and its application for anionic dye removal

Abstract

Via Schiff base reaction, the alkyl chains were grafted to amino groups of chitosan backbone to obtain the hydrophobically modified chitosan (HMCS). The presence of hydrophobic alkyl tails lowers the crystallinity of HMCS but enhances the interaction with hydrophobic adsorbates. HMCS powder exhibited 2-fold higher adsorption capacity (110mgg−1) than chitosan powder toward methyl orange (MO). HMCS can be easily dissolved in mild acid solution and very stable foam was prepared by applying vigorous mechanical stirring to the solution. A robust and non-water wettable sponge was obtained by directly freeze-drying the stable HMCS foam. With enhanced specific surface area, the as-prepared HMCS sponge demonstrated a significantly increased MO adsorption capacity (168mgg−1). The equilibrium adsorption of MO by HMCS sponge follows Langmuir isotherm model and its adsorption kinetic can also be well described by a pseudo-second-order kinetic model.