Unexpectedly efficient ion desorption of graphene-based materials

Ion desorption is extremely challenging for adsorbents with superior performance, and widely used conventional desorption methods involve high acid or base concentrations and large consumption of reagents. Here, we experimentally demonstrate the rapid and efficient desorption of ions on magnetite-graphene oxide (M-GO) by adding low amounts of Al(3+). The corresponding concentration of Al(3+) used is reduced by at least a factor 250 compared to conventional desorption method. The desorption rate reaches ~97.0% for the typical radioactive and bivalent ions Co(2+), Mn(2+), and Sr(2+) within ~1 min. We achieve effective enrichment of radioactive (60)Co and reduce the volume of concentrated (60)Co solution by approximately 10 times compared to the initial solution. The M-GO can be recycled and reused easily without compromising its adsorption efficiency and magnetic performance, based on the unique hydration anionic species of Al(3+) under alkaline conditions. Density functional theory calculations show that the interaction of graphene with Al(3+) is stronger than with divalent ions, and that the adsorption probability of Al(3+) is superior than that of Co(2+), Mn(2+), and Sr(2+) ions. This suggests that the proposed method could be used to enrich a wider range of ions in the fields of energy, biology, environmental technology, and materials science.