Novel graphene oxide/carboxymethyl chitosan aerogels via vacuum-assisted self-assembly for heavy metal adsorption capacity

In this work, we synthesized a new type of graphene oxide/carboxymethyl chitosan (GO/CMC) composite aerogels via vacuum-assisted self-assembly and freeze-drying method. Then we evaluated their adsorption performance for metal ions in aqueous solution. The three-dimensional porous network structures of as-prepared aerogels were established by the hydrogen bonding interaction between CMC chains and the surface of GO and crosslinks using triphosphoric acid (TPP) or glutaraldehyde (GA). The chemical structure, microstructure, mechanical and thermal properties, and absorption capability of these aerogels were investigated using many experimental techniques. The crosslinking methods of TPP and GA were the ionic and chemical crosslinking ones, respectively. GO/CMC aerogels contained abundant oxygen- and nitrogen-containing groups to provide adsorption sites and displayed the crosslinked porous structures to facilitate adsorbate diffusion. The CMC chains prevented brittle fracture, whereas GO resisted pressure resulting that in compressive strength and elastic modulus of GO/CMC aerogels to reach up to 16.77 and 368.35 MPa, respectively. The adsorption system of GO/CMC aerogels was accurately simulated using the pseudo-second-order kinetic and Langmuir isotherm models, in which the maximum adsorption capacities were 151.30 mg/g for Ag+, 95.37 mg/g for Cu2+ and 249.38 mg/g for Pb2+.