Adsorptive decolorization of methylene blue by crosslinked porous starch

Crosslinked porous starch (CPS) was prepared by two steps. Native starch was crosslinked with epichlorohydrin and then CPS was prepared by hydrolyzing the crosslinked starch with α-amylase. As a biodegradable and safe adsorbent, CPS was used to remove methylene blue (MB) from the aqueous solution based on its characterizations, including surface area, pore volume and scanning electron microscopy (SEM). The results indicate that the adsorption capacity of CPS is much higher than native starch and relatively higher than porous starch. The effects of the initial concentration of MB, the time and temperature on the adsorption capacity were investigated. The pseudo-first-order kinetic model provides a better correlation of the experimental data in comparison with the pseudo-second-order model. The equilibrium adsorption data are well described by the Langmuir isotherm model with a maximum adsorption capacity of 9.46 mg g−1. The adsorption of MB on CPS is endothermic and spontaneous in nature. The thermodynamics data are in good agreement with physical adsorption mechanism.