Effect of nickel ion doping in MnO 2 /reduced graphene oxide nanocomposites for lithium adsorption and recovery from aqueous media.

Novel and effective reduced graphene oxide-nickel (Ni) doped manganese oxide (RGO/Ni-MnO 2 ) adsorbents were fabricated via a hydrothermal approach. The reduction of graphite to graphene oxide (GO), formation of α-MnO 2 , and decoration of Ni-MnO 2 onto the surface of reduced graphene oxide (RGO) were independently carried out by a hydrothermal technique. The physical and morphological properties of the as-synthesized adsorbents were analyzed. Batch adsorption experiments were performed to identify the lithium uptake capacities of adsorbents. The optimized parameters for Li + adsorption investigated were pH = 12, dose loading = 0.1 g, Li + initial concentration = 50 mg L -1 , in 10 h at 25 °C. It is noticeable that the highest adsorption of Li + at optimized parameters are in the following order: RGO/Ni3-MnO 2 (63 mg g -1 ) > RGO/Ni2-MnO 2 (56 mg g -1 ) > RGO/Ni1-MnO 2 (52 mg g -1 ). A Kinetic study revealed that the experimental data were best designated pseudo-second order for each adsorbent. Li + desorption experiments were performed using HCl as an extracting agent. Furthermore, all adsorbents exhibit efficient regeneration ability and to some extent satisfying selectivity for Li + recovery. Briefly, it can be concluded that among the fabricated adsorbents, the RGO/Ni3-MnO 2 exhibited the greatest potential for Li + uptake from aqueous solutions as compared to others.