(a) Competitive adsorption of Cd(II), Ni(II), Zn(II), Co(II), Pb(II), and Cu(II) on rGO, rGO/magnetite, rGO/silver, and rGO/magnetite/silver nanohybrids and (b) relative amounts of metal ions adsorbed on rGO, rGO/magnetite, rGO/silver, and rGO/magnetite/silver nanohybrids (mole percentage). Experimental conditions: m/V = 0.2 g/L; initial pH = 4.0 ± 0.1; [Cd(II)]0 = [Ni(II)]0 = [Zn(II)]0 = [Co(II)]0 = [Pb(II)]0 = [Cu(II)]0 = 1 mM; and T = 298 K.