A facile hydrothermal method-fabricated robust and ultralight weight cellulose nanocrystal-based hydro/aerogels for metal ion removal

Heavy metal ion contamination, in particular that associated with Pb²⁺, Cd²⁺, and Cu²⁺, poses a considerable threat to aquatic environments and human health. To obtain a highly efficient adsorbent, in this work, a facile hydrothermal method was applied to prepare acrylic acid grafted onto cellulose nanocrystal (AA-g-CNC) hydro/aerogel as an adsorbent for Pb²⁺, Cd²⁺, and Cu²⁺ removal. The obtained AA-g-CNC hydrogels withstood up to 0.821 MPa of compression and showed good reciprocating performance when the deformation reached 40%. The as-formed AA-g-CNC aerogels had highly porous honeycomb structure, with many functional groups and a high zeta potential, all of which are essential features for an effective adsorbent. The maximum Pb²⁺, Cd²⁺, and Cu²⁺ removal capacities of AA-g-CNC aerogels reached 1026, 898.8, and 872.4 mg/g respectively. Their adsorption followed the Freundlich isotherm model and fitted well with pseudo-second-order kinetic models. The adsorption mechanism mainly attributed to electrostatic chelation between metal ions with sulfonate and carboxylate groups.