Carboxylated cellulose cryogel beads via a one-step ester crosslinking of maleic anhydride for copper ions removal

In this study, we developed a one step protocol to prepare highly carboxylated and chemically crosslinked cellulose nanofibril (CNF) cryogel beads using maleic anhydride (MA). Fourier transform infrared spectroscopy (FTIR) and conductometric-potentiometric titration results confirmed the presence of carboxyl groups and ester linkages produced simultaneously during the ring open reaction of MA, yielding a carboxylic content of up to 2.78 mmol/g. The effect of CNF concentration on the morphology and wet mechanical strength of the crosslinked cryogel beads were also investigated, and results suggested that higher CNF concentration yielded a compact network that displayed a maximum compressive stress of 2800 Pa at 60 % strain. In addition, the heavy metal ions (i.e., Cu (II)) removal capacity, kinetics, mechanism as well as the recyclability of the resulted CNF-MA cryogel beads were examined.