This study presents a novel approach for the growth time optimization of self-supported ZnO nano-/microstructures (ZnO NMs) on zinc foil surfaces using a biocompatible hydrothermal method. This fabrication technique aims to enhance the photocatalytic performance of ZnO nanostructures for efficient treatment of textile industry wastewater. The ZnO NMs were synthesized by immersing zinc (Zn) metal foils in pure water and heating them to 95 °C, resulting in varying dimensional characteristics of nanorods through adjustments in hydrothermal growth time. Photodegradation experiments were conducted using rhodamine B (RB) dye and batik industry wastewater (BW). The photocatalyst demonstrated up to 95% degradation of RB within 150 min under UV irradiation for the sample subjected to 16 h of hydrothermal treatment. Additionally, this sample achieved complete degradation of color compounds in BW within 180 min. However, repeated cycles revealed a decline in efficiency, highlighting challenges in maintaining consistent performance. This research underscores the eco-friendly and scalable potential of ZnO nanostructures in industrial wastewater treatment, paving the way for advancements in green technology. © King Fahd University of Petroleum & Minerals 2025.