Polyvinyl pyrrolidone blended with thermally reduced graphene for adsorption of heavy metal ions in water

This paper presents the adsorption capacity of Cu2+ and Cd2+ ions in water of the modified polyvinyl pyrrolidone (PVP)/graphene mixture. Graphene was obtained through the thermal separation of graphite oxide (GO), which was synthesised from graphite by the Hummer method. Graphene-PVP composites were prepared by dispersing graphene into PVP solutions at different concentrations and then cross-linking to prevent water washout. This cross-linking ensures that the graphene-PVP mixture is well dispersed and stable. The maximum adsorption capacity of graphene-PVP for Cu2+ and Cd2+ions was 198.54 mg.g-1 and 159.78 mg.g-1, respectively, at pH 7, and the contact time was 30 min. The experimental results are consistent with the Langmuir kinetic and quadratic pseudo-kinetic models. The study shows that the adsorption mechanism of Cu2+ and Cd2+ ions on graphene-PVP follows an ion exchange mechanism, which is promoted by the strong interaction between PVP and metal ions. Furthermore, the presence of PVP in the composite enhances the stability and dispersibility of graphene, allowing for efficient ion adsorption. This study provides an easy, low-cost, and environmentally friendly method to produce graphene-PVP materials with high adsorption capacity.