TEMPO-oxidized cellulose nanofibers as potential Cu(II) adsorbent for wastewater treatment

Cellulose nanofibers (CNFs) are becoming a topic of great interest due to their wide range of potential applications. The huge presence of carboxylic groups in TEMPO-oxidized CNFs indicate that this material could interact with cationic species in aqueous solution, such as metal ions. Nevertheless, the contact between nanofibers and water solutions requires a 3D structure to entrap and retain the nanofibers. In this sense, two different 3D structures were synthetized: CNF-calcium alginate beads and CNF-aerogels. After the synthesis and characterization of 3D structures, batch sorption studies were performed by using these sorbents to study their ability for metal removal. Equilibrium data fitted very well Langmuir and Freundlich isotherm models in the studied concentration range of copper(II) ions and confirmed that the copper sorption is a favorable process. Both new synthetized materials resulted to be effective for Cu(II) removal and maximum sorption capacity was higher for CNF-aerogels than CNF-calcium alginate beads. Finally, in this work it has been demonstrated that the synthetized 3D CNF-aerogel structure is an efficient sorbent for copper ion removal from aqueous solutions and the use of this synthetized structure for environmental decontamination opens a new opportunity to CNF applications.