Nitrogen-rich core/shell magnetic nanostructures for selective adsorption and separation of anionic dyes from aqueous solution

Abstract

In the present work, a facile, mild and reproducible chemical strategy, based on the glutaraldehyde crosslinking reaction, was explored to fabricate nitrogen-rich core/shell structured magnetic nanocomposites using hydrophilic polyethylenimine (PEI) as the nitrogen source. As expected, the obtained Fe₃O₄@NH₂@PEI nanocomposites, with a magnetic core and polymeric shell, contain porous structures and N-rich groups, exhibiting extremely high stability and selectivity for adsorption and separation of anionic dyes from complex systems. Single-solute adsorption experiments indicated that the magnetic removal of alizarin red S (ARS) and methyl orange (MO) by Fe₃O₄@NH₂@PEI was fast and forceful, and best fitted to a pseudo-second-order kinetic model, and followed Langmuir monolayer adsorption. Furthermore, the adsorbed dyes could be easily desorbed and the regenerated adsorbents could be reused without an obvious decrease of the adsorption capacity even after 15 consecutive adsorption–desorption cycles. In addition, owing to the high selectivity of Fe₃O₄@NH₂@PEI toward anionic dyes, the model anions could be conveniently separated from a complex system containing anionic and cationic dyes and recycled back into the industrial process, effectively avoiding secondary pollution. More importantly, the as-prepared material could act as an efficient adsorbent for the model textile effluent, and the regenerated adsorbent could be successfully reused without a significant efficiency loss. The results of the present work are of great importance for practical applications of Fe₃O₄@NH₂@PEI as a promising adsorbent for selective adsorption and separation of anionic dyes from industrial effluents.