<![CDATA[The increasing discharge of organic dyes into aquatic environments requires efficient and sustainable remediation strategies. Although Fe-doped Bi₂O₃ has shown promising photocatalytic performance, the effects of Fe content on its photocatalytic behavior under xenon-lamp irradiation remain insufficiently understood. This study aimed to synthesize different amounts of Fe-doped Bi₂O₃ nanoparticles via a hydrothermal approach and subsequently evaluate their photocatalytic performance toward the degradation of methylene blue (MB). Monoclinic α-Bi2O3 was formed as confirmed by X-ray diffraction analysis, without any detectable secondary phases, suggesting that Fe species were either incorporated into the Bi2O3 lattice or well dispersed in the matrix. Furthermore, the band gap energy decreased from 2.92 eV to 2.66 eV as determined by diffuse reflectance spectroscopy combined with Tauc analysis. Photoluminescence analysis revealed a decrease in emission intensity, indicating suppressed electron-hole recombination and enhanced photogenerated charge separation. Among the prepared samples, the sample with 10 wt% Fe-doped Bi₂O₃ exhibited the highest photocatalytic activity with about 99% degradation of 10 ppm MB within 14 min at optimum experimental conditions (pH of 8, 45 °C). The degradation followed a pseudo-first-order kinetic model with a rate constant of 0.134 min−1. The improved photocatalytic efficiency is attributed to Fe-induced band-gap narrowing and enhanced charge separation, highlighting its potential for wastewater treatment applications. Copyright © 2026 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).]]>
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