Sargunavathi, S.S.SargunavathiBalamurugan, S.S.BalamuruganAvula, BalakrishnaBalakrishnaAvulaAbisheik, T.T.AbisheikKumar, N. LakshmanN. LakshmanKumarPandiyan, V.V.PandiyanVimalraj, V.V.VimalrajArun ThirumuruganSandoval-Hevia, GabrielaGabrielaSandoval-HeviaAlanazi, Abdullah K.Abdullah K.AlanaziBalu, KrishnakumarKrishnakumarBalu2026-07-072026-07-072026-01JOURNAL OF WATER PROCESS ENGINEERING, 81, 109188 (2026). https://doi.org/10.1016/j.jwpe.2025.1091882214-7144https://hdl.handle.net/20.500.12740/24722Organic dyes from textile and related industries pose significant threats to aquatic ecosystems and human health due to their toxicity and persistence. This study investigates the photocatalytic potential of Erbium (Er)-doped ZnO for the degradation of hazardous azo dyes. Er-ZnO photocatalysts with varying Er concentrations (1-4 wt%) were synthesized via a simple chemical method and evaluated against Reactive Red 120 (RR 120), Acid Black 1 (AB 1), and Methylene Blue (MB) under UV-A and solar light. Among them, 3 wt% Er-ZnO exhibited superior activity, achieving approximate to 100 % degradation of RR 120 and AB 1, and 87.9 % for MB under UV-A, while RR 120 was completely degraded under solar light. Enhanced performance is attributed to improved charge carrier separation, extended light absorption, and reduced recombination due to Er doping. Structural integrity and Er incorporation were confirmed by XRD, FT-IR, Raman, UV-DRS, PL, XPS, FE-SEM, and HR-TEM analyses. Optimal photocatalytic performance was observed at pH 7 with a 30 mg catalyst dosage. Trapping experiments indicated O2 center dot- as the dominant reactive species, and the catalyst retained 93 % degradation efficiency after four cycles, demonstrating good stability. GC-MS analysis identified key intermediates, elucidating the degradation mechanism, while antimicrobial tests revealed additional microbial suppression potential. These results highlight 3 wt % Er-ZnO as a promising, sustainable photocatalyst for industrial wastewater treatment and multifunctional green remediation.PhotocatalysisErbium-doped ZnODye degradationGC-MSGreen remediationArticulohttps://doi.org/10.1016/j.jwpe.2025.109188