Stabilized fabrication of anatase-TiO 2 /FeS 2 (pyrite) semiconductor composite nanocrystals for enhanced solar light-mediated photocatalytic degradation of methylene blue.

A novel visible light active TiO 2 /FeS 2 semiconductor photocatalyst was synthesized by a simple wet chemical process. X-ray diffraction (XRD) was used to analyze the anatase TiO 2 and pyrite structures in FeS 2 /TiO 2 nanocrystals. Scanning electron microscopy (SEM) confirmed the spherical morphology of composite nanocrystals. X-ray photoelectron spectroscopy (XPS) identified the Fe 2+ , S 1- , Ti 4+ , and O 2- oxidation states of relevant species. Energy dispersive X-ray (EDX) analysis was performed for compositional analysis. The measured band gap of the TiO 2 /FeS 2 nanocomposite system was 2.67 eV, which is smaller than un-doped TiO 2 (3.10 eV) and larger than FeS 2 (1.94 eV). The photocatalytic activity of TiO 2 /FeS 2 was significantly higher than pure FeS 2 for degrading methylene blue (MB) under solar light irradiation due to the increase in visible light absorption, reduction in band gap energy, and better election-hole pair separation. The photocatalytic degradation of MB was investigated under the influence of solution pH, dye concentrations, and varied catalyst dosage. The optimum degradation (100%) of MB was observed in 180 min and the photocatalysis of MB reduced as the dye concentrations in the solution increased from 15 to 75 mg L -1 . These results prove that the TiO 2 /FeS 2 nanocomposite has the stability, recycling, and adaptability for its practical application as a visible light photocatalyst for wastewater treatment. TiO 2 /FeS 2 showed increased degradation of the organic pollutant; which is confirmed by the increased rate of chemical reaction following pseudo first-order reaction kinetics with the highest rate constant value of 0.0408 m -1 having highest R 2 value of 0.9981.