Three-dimensional double-network hydrogels of graphene oxide, alginate, and polyacrylonitrile for copper removal from aqueous solution

Three-dimensional (3D) double-network graphene oxide/alginate-polyacrylonitrile (GO/Ca-Alg₂-PAN) composite hydrogels were synthesized via surface functionalization of GO to activate adsorption sites. The morphology and structure of the GO/Ca-Alg₂-PAN were analyzed by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA-DSC). The results of the physicochemical analyses indicated that GO/Ca-Alg₂-PAN was successfully synthesized by the combination of a 2D-structured graphene oxide with the alginate which was functionalized with the PAN polymer to generate the 3D double network composites. This functionalization approach contributed to an increase in Cu²⁺ ion adsorption capacity. The maximum adsorption capacity of the GO/Ca-Alg₂-PAN for Cu²⁺ was 5.99 mmol/g. The results of adsorption kinetic experiments indicated that the GO/Ca-Alg₂-PAN reached adsorption equilibrium within 147 mins at 2 mM Cu²⁺ in accordance with a pseudo-second-order model.