Manmeet Kaur, Amit Dhir, Shilpi Verma
Bismuth tungstate (Bi2WO6), an Aurivillius-phase visible-light semiconductor, has a wide band gap and rapid charge-carrier recombination that significantly affects its photocatalytic efficiency. To overcome these intrinsic limitations, Fe2O3/Bi2WO6 composites were synthesised via a facile single-step hydrothermal technique with Fe2O3 loadings of 1, 3, and 5 wt%. XRD confirmed that the orthorhombic Bi2WO6 phase was retained without segregated Fe2O3, indicating that the incorporation of Fe into the lattice was successful. Raman spectroscopy proved that the WO6 octahedral framework was distorted by Fe, as evidenced by the broadening of the W-O stretching (∼800 cm-1) and O-W-O bending (∼308 cm-1) modes. FEG-SEM revealed morphological modifications in the hierarchical nanosheet assemblies, and UV-DRS showed a band-gap narrowing from 3.1 eV to 2.9 eV, leading to extended visible-light absorption. BET analysis confirmed comparable mesopores. PL spectroscopy, on the other hand, demonstrated the lowest charge-carrier recombination rate for the 1% Fe2O3/Bi2WO6 composite, consistent with its superior photocatalytic performance. XPS investigations further confirmed the slight distortion in the Bi-O coordination environment induced by the inclusion of Fe. Under optimized conditions (catalyst dose: 250 mg L-1, pH 7, and PNP: 20 mg L-1), the 1% Fe2O3/Bi2WO6 composite achieved 84.5% PNP removal under visible-light irradiation, following pseudo-first-order kinetics (k app = 0.0093 min-1). The photocatalyst exhibited good stability and reusability. In addition, the PNP degradation pathway was proposed based on HR-MS-identified intermediates and supported by TOC analysis and reactive-species detection. The process sustainability was further assessed based on green chemistry metrics, including water intensity, mass intensity, reaction mass intensity, E-factor, and energy consumption, demonstrating favorable environmental credentials relative to conventional remediation methods. These findings identify 1% Fe2O3/Bi2WO6 as an efficient and sustainable visible-light photocatalyst for the remediation of recalcitrant phenolic wastewater.