Shape recoverable and mechanically robust cellulose aerogel beads for efficient removal of copper ions

Developing bio-based absorbents with high removal capacity towards heavy metals is one of the key strategies to manage water pollution worldwide. Robust cellulose aerogel beads (CGP, diameter of 3–4 mm) with high amine content were prepared by cross-linking polyethylenimine (PEI) to cellulose nanofibrils (CNF) using 3-glycidyloxypropyl) trimethoxysilane (GPTMS). The mass ratio between PEI and GPTMS (1:1 or 3:1), crosslinking mechanism, morphologies, elemental compositions, total amine contents, mechanical strengths as well as the adsorption capacity and kinetic of the aerogel beads were investigated. Small CGP beads possessed several desirable characteristics, such as high amine group content (5.74 mmol/g for CGP3 beads), large maximum Cu (II) adsorption capacity (163.40 mg/g for CGP3 beads), very fast adsorption rate (<10 h to reach equilibrium), high shape recovery (2.00% plastic deformation for CGP3 beads at 50% strain), robust mechanical strength (stress around 10.5 KPa at 50% strain), and they could be regenerated and reused.