Comparative studies on copper adsorption by graphene oxide and functionalized graphene oxide nanoparticles

In this study, the graphene oxide (GO) was made from graphite powder via a modified Hummers method, then carboxylated to GO-COOH in a mixture of a strong basic pH from mixing in the chloroacetic acid with NaOH. The GO and GO-COOH were characterized by means of the HR-TEM, FTIR, XRD and zeta potential. On this basis, the Cu(II) was adsorbed onto the GO and GO-COOH in aqueous solutions using the simple batch-adsorption mode. The amount of thus-removed Cu(II) was successfully varied, depending on the pH values, initial copper concentration, reaction time and reaction temperature. Under the ambient temperature at pH 6 over 60-min adsorption time, the highest removal efficiency of Cu2+ are 97 and 99.4%, respectively. The experimental data agree well with the Langmuir isotherm in both cases, and the maximum adsorption capacities of GO and GO-COON are 277.77 and 357.14 (mg/g), respectively. The metal adsorption of the GO-COOH is better than other carbonaceous adsorbents, and is exothermic and spontaneous from the calculations of chemical thermodynamics. The effect of competing cations on adsorption of Cu(II) ions on GO and GO-COON was evaluated by mono and divalent metals. The reusability of GO and GO-COOH were estimated and it was found that both adsorbents have good regeneration properties. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.