Polyethyleneimine grafted starch nanocrystals as a novel biosorbent for efficient removal of methyl blue dye

In this paper, a novel biosorbent of SNCs-PEI was successfully prepared by grafting polyethylenimine (PEI) onto the starch nanocrystals (SNCs) using glutaraldehyde as a crosslinking agent. The optimal preparation conditions of SNCs-PEI were determined by the orthogonal experiments of the three-factor and three-level, and the SNCs-PEI was characterized by Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The zeta potential of SNCs-PEI was +26.3 mV (pH 7), which had a good adsorption performance for the anionic dye methyl blue (MB). The adsorption kinetics and isotherm of MB by SNCs-PEI were studied. At the temperature of 25, 30 and 35 °C, its maximum adsorption capacity was 337.84, 377.36 and 383.14 mg g^-1, respectively. The adsorption of MB by the SNCs-PEI was a spontaneous and endothermic process according to the thermodynamic analysis.