Molybdenum disulphide/ reduced graphene oxide (MOS₂/RGO) hybrid for photo degradation of perfluorooctanoic acid (PFOA) in aqueous solution / Izyan Najwa Mohd Norsham

Perfluorooctanoic acid (PFOA) has been regarded as one of emerging pollutants due to its environmental persistence, bio accumulation, and potential toxicity. The high persistent due to C-F bond leading to difficulty on removing the PFOA. There are many methods to remove PFOA and photocatalytic degradation as one suitable method due to its capabilities to reduce the environmental impact, safe, and does not consume a large amount of energy. The current investigation focused on the facile synthesis of molybdenum disulphide (MoS2/rGO) nanocomposite with different weight percentages of MoS2 (1%, 5% and 15% w.r.t. to rGO) prepared via hydrothermal methods. Meanwhile, rGO were synthesized via Modified Hummer’s Method. The incorporation of MoS2/rGO undergoes three optimization process of pH, amount catalyst loading and contact time. The effective incorporation of MoS2 on the GO structures was substantially confirmed via various characterization tools. Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffractometer (XRD) and Raman Spectroscopy showed significance peak of MoS2, GO and MoS2/rGO composites. UV- Visible Spectroscopy (UV-vis) and X-ray Photoelectron Spectroscopy (XPS) showed that MoS2/rGO was successfully incorporated. The morphology of MoS2, GO and MoS2/rGO was showed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The Selected Area Electron Diffraction (SAED) exhibited clear diffraction rings that can be distinguished as MoS2 and GO. Thermogravimetric analysis (TGA) was carried out which proved the stability of the photocatalysts. The surface area analysis was obtained by Brunauer Emmet Teller (BET) technique which showed MoS2/rGO-15 consist higher surface area which is good in photocatalytic activity. The composites were applied as photocatalysts to degrade PFOA using a photoreactor equipped with an 18-watt fluorescent lamp analyzed using High Performance Liquid Chromatography (HPLC). MoS2/rGO-15 showed superior photocatalytic properties for degrading PFOA under optimum parameters with kinetic rate constant k = 0.0758 min-1 and t ½ = 1.524 hours based on the Langmuir-Hinshelwood (L-H) model. Under the optimizations condition, the analytical performances were determined for studied analyte. The steadiness and reusability studies indicate that the MoS2/rGO-15 composites can be reused for up to six cycles without affecting the functional group of photocatalyst. Real water sample analysis revealed that MoS2/rGO-15 is efficient in the degradation of perfluorooctanoic acid (PFOA) in river water sample with 77% degradation percentage. Overall, the findings of this study aid in uncover the potential of MoS2/rGO as one of promising material for development of photocatalyst for organic wastewater degradation under low cost indoor fluorescent light irradiation.