This article reports the synthesis of PEGylated microspheres of MoS2 nanosheets through the hydrothermal method and its application in rhodamine B and methylene blue dyes photodegradation, and photoreduction of chromium(VI) to chromium(III) in water under illumination with visible light. The catalyst was characterized using X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infra Red (FTIR), Thermo-gravimetric Analysis (TGA), and UV-Vis spectroscopies. XRD result reveals the MoS2 nanosheets to be present in the hexagonal phase of MoS2. SEM, TEM, and HRTEM images show that the synthesised sample has spherical shapes made up of several thin sheets of MoS2. The catalyst showed visible light responsivity with a calculated band gap of 1.92 eV. The MoS2 nanosheets exhibited high degradation efficiency against both dyes. The RhB and MB dyes experienced degradation efficiencies of 97.30 % (RhB) and 98.05 % (MB) in 75 min 90 min, respectively. The MoS2 photocatalyst is also observed to be effective in photocatalytic reduction of Cr(VI) and displayed 91.05% reduction of Cr(VI) to Cr(III) in 75 min. The results reveal that the synthesised MoS2 nanosheet is a good photocatalytic material for degradation of dyes and reduction of Cr(VI) to Cr(III) in water.

Background: A molybdenum sulfide (Mo3S4) nanorod photocatalyst was synthesised through the facile hydrothermal method and applied in the degradation of Rhodamine B and Methyl Blue dyes under visible light irradiation. Methods: The Mo3s4 nanorod was synthesised using sodium molybdate, sodiumdiethyldithiolcarbonate and ethylenediaminetetraacetic acid as molybdenum and sulfur sources, and capping agent respectively. The photocatalyst was characterized by using XRD, FTIR, TEM, SEM, EDS and UV-Vis spectroscopies. Results: SEM result shows that the synthesised sample has a rod-like shape made up of several thin sheets. The XRD result revealed the Mo3S4 nanorod to exist in the Rhombohedral phase. The energy band gap of the sample was calculated to be 2.02 eV. The synthesised Mo3S4 nanorod showed great potential in the removal of both RhB and MB in aqueous solution. 85.46% and 99.78% removals of RhB and MB dyes respectively were achieved in 90 min. Conclusion: It was also observed that the photodegradation of both RhB and MB follows pseudo-first order kinetics, with apparent rate constants of 0.0089 min-1 and 0.0118 min-1 for RhB and MB respectively.