Magnetically recoverable cross-linked polyethylenimine as a novel adsorbent for removal of anionic dyes with different structures from aqueous solution

Herein, magnetically recoverable cross-linked polyethylenimine (MPEI) composites with porous structures, in which the magnetic carriers were embedded, were successfully synthesized via a simple chemical route. It was found that the obtained magnetic polymer exhibited significantly enhanced adsorption capability towards six anionic dyes with different structures and they could be magnetically separated from aqueous solution after adsorption. The batch experiments indicated that the sorption of anionic dyes by MPEI was selective, forceful, fast and pH-sensitive, better fitted to pseudo-second-order kinetics model, and was Langmuir monolayer adsorption. Meanwhile, the adsorption thermodynamics suggested an endothermic and spontaneous process for all the dyes. Considering the properties of both adsorbents and dyes, the sorption conditions, as well as the kinetics process, it was declared that the anionic dyes with -SO3- group were mainly adsorbed by the positively charged MPEI adsorbents via electrostatic interaction in a wide pH range and the number of negative charge and the size of organic dyes could significantly influence the adsorption behavior of model dyes. Also, the FT-IR and EDX spectra of dye-loaded MPEI convincingly confirmed the effective capture of anionic dyes by MPEI. More importantly, the as prepared materials could act as efficient adsorbents for the treatment of model textile effluent and the regenerated adsorbents in alkaline medium could be utilized repeatedly. Such fascinating merits make MPEI suitable to be practically applied in removal of dyestuffs from industrial wastewater. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.