Preparation and characterization of a novel polyethyleneimine cation-modified persimmon tannin bioadsorbent for anionic dye adsorption.

A novel and recyclable bioadsorbent (PTP) has been prepared by the cationization of persimmon tannin (PT) using polyethyleneimine (PEI) for application in the removal of the anionic dye methyl orange (MO) from aqueous solution. The physicochemical properties of the prepared PTP were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, Zeta potential measurements, Brunauer-Emmett-Teller and thermogravimetric analysis. Systematic batch adsorption experiments were carried out with pH, bioadsorbent dosage, initial MO concentration and contact time. Kinetic regression analysis indicated that the adsorption processes followed the pseudo-second order model. The equilibrium isotherm was in good fit with the Freundlich model with a maximum adsorption capacity of 225.74 mg/g. Thermodynamics data revealed that the adsorption of MO onto PTP was feasible, spontaneous and endothermic. A possible biosorption mechanism was presented where electrostatic interactions, hydrogen bonding, and π-π interactions dominated the adsorption of MO onto PTP. Moreover, the regeneration of the PTP was easily achieved and MO removal efficiency remained high (81.47%) after six cycles. The actual sewage treatment simulation was evaluated and the PTP had a good preference to adsorption MO. All these results indicated that PTP could be considered a high performance and promising candidate for the effective removal of anionic dyes from aqueous solutions.