Versatile MoS2 hollow nanoroses for a quick-witted removal of Hg (II), Pb (II) and Ag (I) from water and the mechanism: Affinity or Electrochemistry?

Abstract

In this paper, a nano Molybdenum disulphide with an open cavity at the centre (hollow) and a rose flower-shaped structure (MoS2HNR) has been synthesized using a novel, micelle assisted hydrothermal method and has been successfully demonstrated the ability of the nano MoS2 for the simultaneous removal of the toxic metal ions: Hg (II), Pb (II) and Ag (I) from water. A single treatment of contaminated real water samples with MoS2HNR can rapidly (in ∼5- 30 min) decrease the concentration of Hg (II), Pb (II) and Ag (I) simultaneously from 10,000 ppb to 0.49, 20.5, and 11.62 ppb respectively, the levels less than the safe limits suggested by the U.S Environmental Protection Agency (USEPA) with an efficiency of ≥ 99% at a V/m ratio of 10,000, in real water samples. The adsorption capacities for Hg (II), Ag (I) and Pb (II) are ∼1991, 1350 and 1267 mg/g, respectively at pH 7.0 and exhibited high distribution coefficients (Kd) values of ∼108 mL/g. The rose-like morphology and the open cavity of the material attributed to the excellent removal property as the structure offers a large number of active S2− sites for adsorption. A possible mechanism for the high-efficiency removal and the order of adsorption Hg (II) >Ag (I) >Pb (II) is explained based on the affinity between S2− and metal ions and the electrochemistry factor. The MoS2HNR retains its morphology even after six trails of reuse.