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 (ΔG^θ < 0) and endothermic (ΔH^θ > 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.