3D multi-wall perforated nanocellulose-based polyethylenimine aerogels for ultrahigh efficient and reversible removal of Cu(II) ions from water

The utilization of easily recyclable biosorbent material with ultrahigh adsorption capacity for the removal of heavy metal ions from aqueous environments is an important step towards eradicating water pollution worldwide. In this study, a novel amino-functionalized nanocellulose aerogel adsorbent for efficient and reversible recycle capture of Cu(II) ions was fabricated via self-assembly of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized cellulose nanofibril (TO-CNF) crosslinked Trimethylolpropane-tris-(2-methyl-1-aziridine) propionate (TMPTAP) and polyethyleneimine (PEI). The TO-CNF was spontaneously reacted with TMPTAP via a ring-opening reaction in an aqueous solution at room temperature and then cross-linked with PEI. The resultant TO-CNF/TMPTAP/PEI aerogel showed a 3D multi-wall perforated cellular structure with plentiful amino groups and oxygen-containing groups. The unique architecture of the TO-CNF/TMPTAP/PEI aerogel allowed an ultrahigh Cu(II) ion adsorption capacity of 485.44 mg/g as-calculated by the Langmuir isotherm model, which is almost the highest value among known biodegradable cellulose-based adsorbents. The TO-CNF/TMPTAP/PEI aerogels also can restore their original architecture after regeneration by EDTA-2Na treatment and be utilized more than four cycles without significant degradation of adsorption performance. The ultrahigh adsorption capacity, good recyclability and reversibility, excellent chemical and structural stability, and ease of separation make these composite aerogels ideal materials for the adsorption of Cu(II) ions in practical wastewater treatment applications.