Modified fruit pericarp as an effective biosorbent for removing azo dye from aqueous solution: study of adsorption properties and mechanisms

Abstract

To explore cheap, easily available and high adsorption performance bioadsorbent is still an important task for azo dye pollution control. In this study, the Methyl orange (MO) adsorption capacity by a novel bioadsorbent obtained from lychee and longan pericarps via simple modification was investigated. Prepared pericarps were modified by PEI at 30˚C and 65˚C, which improved the adsorption performance confirmed by batch adsorption experiments. The characteration of modified pericarps by X-ray diffraction, scanning electron microscopy and zeta potential indicated that the enhanced adsorption performance may be due to the abundant amines and imines and stronger electropositivity. The maximum adsorption capacity (349.37 mg/g) was observed for LC@PEI-65 at 45˚C and pH 4. Freundlich isotherm model fitted pretty well with the isotherm experiment data, and the isotherm experimental data were preferably described by pseudo-second order model indicating the chemical adsorption process, and the intra-particle diffusion also involved in the adsorption process. Characterization and adsorption tests suggested electrostatic interaction played a key role in MO removal, accompanied by intermolecular hydrogen bond, π-π dispersion interaction and pore filling collectively. The present study show that the cost-effective PEI modified pericarps could possess a hopeful application for azo dye removal from wastewater.