Remediation of recalcitrant pollutants in water solution using visible light responsive cerium-doped tungsten trioxide nanoparticles.

In order to attain a solar energy-driven photocatalyst for wastewater remediation, cerium-doped WO 3 (W 1-x Ce x O 3 with x = 0, 0.02, 0.04, 0.06, and 0.08) nanoparticles have been synthesized via a chemical co-precipitation technique. X-ray diffraction (XRD) analysis confirmed that W 1-x Ce x O 3 nanoparticles retained their monoclinic structure even after doping. The presence of the vast number of defects produced in the WO 3 lattice was corroborated by Raman spectroscopy. Scanning electron microscopy confirmed the spherical shape of the nanoparticles with particle size range 50-76 nm. The optical band gap of W 1-x Ce x O 3 nanoparticles decreases from 3.07 to 2.36 eV with an increase in x, as confirmed by UV-Vis spectroscopy. Photoluminescence (PL) spectroscopy confirmed that the minimum rate of recombination was observed for W 1-x Ce x O 3 with x = 0.04. Degradation efficiency was explored for methyl violet (MV) and rhodamine-B (Rh-B) with 0.01 g of photocatalyst in a photoreactor chamber having a 200-W xenon lamp as a visible source of light. The results showed that the maximum photo-decolorization towards MV (94%) and rhodamine-B (79.4%) was observed in x = 0.04 sample in just 90 min because of its least recombination rate, highest adsorption capacity, and optimum band edge positions. Intriguingly, it has been observed that the modification with cerium in WO 3 nanoparticles enhances the photocatalytic activity by narrowing the band gap and by efficaciously lowering the recombination rate due to electron entrapment by defects produced in the lattice.