Hydrothermal Synthesis of High-Performance ZnO Nanorods for Enhanced Photocatalytic Degradation of Organic Pollutants

Excessive production and indiscriminate use of organic pollutants have caused severe environmental imbalances. Heterogeneous photocatalysis has emerged as a promising approach for the degradation of these contaminants. However, the development of photocatalysts with high activity and stability remains a key challenge. This work describes the hydrothermal synthesis of ZnO-based photocatalysts, carried out at different temperatures (25, 100, 150, and 200 °C), followed by an evaluation of their performance as photocatalysts in the degradation of organic pollutants (methylene blue, rhodamine B, amiloride and ciprofloxacin). ZnO samples exhibited rod-like morphology, especially in the samples synthesized at 100 °C. The ZnO-100 sample showed greater efficiency in the photodegradation of all organic pollutants. The enhanced performance can be attributed to its highest specific surface area and phase mixture between ZnO and Zn(OH)2. The phase transition from zinc hydroxide to ZnO may have influenced the formation of a morphology that enhanced photocatalytic activity. Fluorescence analysis using terephthalic acid (TA) as a probe for OH•, combined with radical scavenging experiments, revealed that O2–• play the dominant role in the photocatalytic degradation process, indicating an indirect reaction mechanism. This mechanism is consistent with the observed nonselectivity of the ZnO samples in removing pollutants from different chemical classes. The ZnO sample exhibited good stability over four consecutive reuse cycles and maintained high photocatalytic activity across a broad pH range (4–9). Overall, the hydrothermal method proved effective for producing ZnO nanorods with high photocatalytic performance for organic pollutant degradation.