Synthesis of molybdenum disulfide/reduced graphene oxide composites for effective removal of Pb(II) from aqueous solutions

In this work, a facile method was adopted to synthesize molybdenum disulfide/reduced graphene oxide (MoS2/rGO) composites through an l-cysteine-assisted hydrothermal technique. The as-prepared MoS2/rGO composites were firstly applied as adsorbents for efficient elimination of Pb(II) ions. Batch adsorption experiments showed that the adsorption of Pb(II) on MoS2/rGO followed pseudo-second-order kinetic model well. The adsorption of Pb(II) was intensely pH-dependent, ionic strength-dependent at pH < 9.0 and ionic strength-independent at pH > 9.0. The presence of humic acid (HA) enhanced Pb(II) adsorption obviously. The MoS2/rGO composites exhibited excellent adsorption capacity of 384.16 mg g−1 at pH 5.0 and T = 298.15 K, which was superior to MoS2 (279.93 mg g−1) and many other adsorbents. The thermodynamic parameters suggested that the adsorption process of Pb(II) on MoS2/rGO composites was spontaneous (ΔGθ < 0) and endothermic (ΔHθ > 0). The interaction of Pb(II) and MoS2/rGO was mainly dominated by electrostatic attraction and surface complexation between Pb(II) and oxygen-containing functional groups of MoS2/rGO. This work highlighted the application of MoS2/rGO as novel and promising materials in the efficient elimination of Pb(II) from contaminated water and industrial effluents in environmental pollution management.