Hybrid nanosheets composed of molybdenum disulfide and reduced graphene oxide for enhanced solid phase extraction of Pb(II) and Ni(II)

Non-modified molybdenum disulfide (MoS2) is known to adsorb heavy metal ions. However, in case of very small particle sizes and high dispersibility, ordinary centrifugation and filtration fail to separate MoS2 from aqueous media, and this limits its applicability to solid-phase extraction. To overcome this shortcoming, the authors have prepared a nanocomposite consisting of MoS2 and sheets of reduced graphene oxide (r–GO). The material was obtained by a hydrothermal reaction between sodium molybdate and L-cysteine in the presence of GO sheets. The results of characterizations show the MoS2 nanosheets to be well dispersed on the surface of r-GO sheets. The nanocomposite was applied to the preconcentration of Pb(II) and Ni(II) ions as representative examples of heavy metal ions. The adsorption capacities are 322 and 294 mg.g−1 for Pb(II) and Ni(II), respectively. The ions were quantified by atomic absorption spectrometry, and the respective detection limits are 0.71 and 0.21 μg⋅L−1, respectively. The relative standard deviations are ±2.2 % for both ions. The method was successfully applied to the preconcentration of the analytes in (spiked) urine, saliva and water samples.