Application of Molybdenum disulfide Nanosheets for Simultaneous Trace Separation and Determination of Cd(II), Cu(II), Pb(II), Zn(II) and Ni(II) in water samples

Molybdenum disulfide (MoS2) is a type of layered transition metal dichalcogenide. Due to its structural similarities to graphene, it has drawn enormous attention for various applications such as dye sensitized solar cells, supercapacitor, Li-ion battery, hydrogen evolution reaction, photocatalysis for the degradation of organic pollutants, sensors etc. MoS2 shows similar physical properties to that of grapheme that include high charge carrier transport, high wear resistance, etc. However, MoS2 has superior properties over graphene such as low cost, more abundant, tuneable band gap with good visible light absorption capacity. As for the catalytic properties, MoS2 has been vastly used as catalysts to remove S and N from crude oils [1-4]. Recently, Nano-sorbents have attracted substantial interest in the scientific community because of their special properties, such as their large surface areas and high adsorption capacity [5]. The purpose of this study is to investigate a new sorbent comprising of MoS2 for solid phase extraction and preconcentration of trace amounts of Cd(II), Cu(II), Pb(II), Zn(II) and Ni(II) from environmental samples. The synthesis MoS2 nanosheets were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Brunauer–Emmet–Teller (BET) and powder X-ray diffraction (XRD). In the separation/preconcentration step, metal ions are adsorbed onto MoS2 nanosheets, eluted by nitric acid and determined by flame atomic absorption spectrometry (FAAS). The main factors affecting the extraction efficiency such as pH value, sample volume, eluent concentration and volume, amount of sorbent and coexisting ions have been investigated and established. Under the optimum experimental conditions, the enrichment factor for above metal ions was found to be 85 approximately. Detection limit (3s) was achieved at 0.5, 3.0, 10.0, 1.3 and 2.5 ng mL-1, respectively. At the 10.0 ng mL-1 level, the precision (RSD, %) for eight replicate measurements was from 1.0 to 4.0. These results had proved that the proposed method was with good accuracy and could be applied to the analysis of trace metal ions in biological, river water and wastewater samples.