Surface activated carbon nanospheres for fast adsorption of silver ions from aqueous solutions

► NaOH aqueous solution activates the surface of colloidal carbon nanospheres (CNS). ► The surface of activated CNS contains enriched carboxylate and hydroxyl groups. ► These functional groups lead to redox adsorption of Ag(I) ions to Ag nanoparticles. ► The activated CNS exhibit high adsorption capacities and fast adsorption kinetics.