Sulfated and carboxylated nanocellulose for Co+2 adsorption

Regarding metals adsorption from aqueous solutions, nanocellulose emerges as a potential material, due to the many functionalization possibilities and enhanced surface contact area (nanostructured nature). In the present work, sulfated and carboxylated nanocellulose samples were obtained through sulfuric acid hydrolysis (S-CNC) and oxidation by TEMPO (CNF). The obtained nanofibers were characterized through multiple techniques, which XRD data indicated the presence of α-cellulose crystals, with crystallinity indexes equal to 72.3% (S-CNC) and 69.3% (CNF). Expressive morphological differences were revealed, whiskers particles for S-CNC, and elongated nanofibrils for CNF, with average thickness of 9.99 and 5.61 nm, respectively. The desired functionalization with carboxylate groups was evidenced based on FTIR data (CNF). A significant and homogeneous presence of sulfur was evidenced through SEM/EDS (S-CNC). The synthesized nanofibers were next applied to cobalt (Co+2) adsorption from aqueous solutions at room temperature. On both cases, expressive maximum cobalt recoveries have been achieved, 90% (CNF) and 87% (S-CNC), for contact times higher than 30 and 45 min, respectively. The adsorptive capacities evaluated through ICP-OES from liquid phase data (87 mg g−1 S-CNC; 90 mg g−1 CNF) were both significantly higher than the values determined through LA-ICP-MS (10.5 mg Co g−1 S-CNC; 31.5 mg Co g−1 CNF).