Graphene-based nanomaterials for adsorption of iodinated X-ray contrast media from contaminated water: A comparative study.

Iodinated X-ray contrast media (ICM) was frequently detected in the aqueous environment. In this work, the applicability of three graphene-based nanomaterials (graphene nanosheets (GNS), graphene oxide (GO), and reduced graphene oxide (rGO)) for the adsorptive removal of the six ICMs including iohexol, iopamidol, iomeprol, iopromide, iodixanol and ioversol from aqueous solution was firstly evaluated by batch adsorption method. Among the three graphene-based nanomaterials, the GNS displayed the best adsorption performances for the adsorption of the six ICMs. The maximum uptakes of the six ICMs by the GNS (161.5 mg g-1 for iohexol, 267.2 mg g-1 for iodixanol, 197.7 mg g-1 for iopromide, 197.0 mg g-1 for iopamidol, 109.6 mg g-1 for iomeprol, and 168.2 mg g-1 for ioversol) can rapidly achieved within 10 min and indicate no dependence on pH in the range of 4-9. The results obtained from the calculations of isotherms, kinetics and thermodynamic supported the occurrence of a chemisorption of the GNS for the six ICMs. The π-π interactions between benzene ring of the ICMs and the sp2-hybridized two-dimensional sheet of GNS were deemed the predominant adsorption mechanism.