Construction of carboxylated-GO and MOFs composites for efficient removal of heavy metal ions

Two-dimensional graphene oxide (GO) and metal–organic frameworks (MOFs) have great potential applications as high-performance adsorption materials. In this work, carboxylated-GO and MOFs have been successfully integrated to form nanocomposites (GO-COOH/MOF-808) with the combination of advantages of both and then demonstrated the excellent adsorption properties of heavy metal ions. The adsorption capacity of GO-COOH/MOF-808 and the influencing factors of the adsorption process are explored. The analysis shows that the adsorption equilibrium of heavy metal ions Pb(II), Cd(II), Co(II), Ni(II), and Cu(II) by GO-COOH/MOF-808 composites can be reached in 20 min under condition of the initial concentration of 100 mg/L and pH value of 5.5. Pb(II), Cd(II), Co(II), Ni(II), and Cu(II) have higher adsorption efficiencies, which are 157.78 mg/g, 135.96 mg/g, 82.35 mg/g, 90.99 mg/g, and 91.49 mg/g, respectively. Furthermore, the entire adsorption process followed the Langmuir isotherm model and the pseudo-second-order rate equation, suggesting that ion exchange and chemical adsorption are dominant. The synergistic effect of ion exchange, electrostatic adsorption, chemisorption, π-π interactions, and coordination complexation is attributed to the possible mechanisms of heavy metal ion adsorption. This research suggests that GO-COOH/MOF-808 is a promising and efficient adsorbent for heavy metal ion removal.