Adsorption of uranium ions from aqueous solutions by graphene-based zinc oxide nanocomposites

In this paper, adsorption potentials of U(VI) ions were investigated using graphene-based zinc oxide nanocomposites which are graphene oxide–zinc oxide (GO–ZnO) and reduced graphene oxide–zinc oxide (rGO–ZnO). Kinetic data showed that processes could be simulated with pseudo-second-order with high correlation coefficient (R2 > 0.99). Experimental results of equilibrium adsorption results show that Langmuir fits the data better. The maximum sorption capacities of GO–ZnO at pH 5.0 was 476.19 mg/g, and rGO–ZnO at pH 5.5 was 256.41 mg/g at 298 K. Thermodynamic parameters indicate that the adsorption of U(VI) on GO–ZnO and rGO–ZnO are spontaneous and endothermic.