Structural Characterization and Photocatalytic Performance of a ZnO-Modified Calcined Oyster Shells for Rhodamine B Degradation

This work reports the development of a novel and environmentally friendly composite photocatalyst based on zinc oxide and calcined oyster shells. The material was characterized using several techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Energy-dispersive X-ray spectroscopy (EDS), Transmission electron microscopy (TEM), and scanning electron microscopy (SEM), to investigate its crystalline phases and structural properties. Oyster shells, a naturally abundant biomaterial with a microporous structure, remain relatively underexplored in catalytic applications. In this study, a simple deposition followed by a calcination process was employed to synthesize a ZnO@COS composite, using calcined oyster shells as a supporting matrix. The as-prepared composite was evaluated for the removal of Rhodamine B dye from aqueous solution under UV irradiation, achieving a maximum degradation efficiency of 92%, particularly under strongly alkaline conditions (pH=12). The photocatalytic activity was affected by several operational parameters, including pH, catalyst dosage, ZnO loading in the composite, initial dye concentration, and the presence of alcohol and hydrogen peroxide. The degradation efficiency decreased with increasing initial dye concentration, reaching 56% after 3h30 min of UV exposure. In contrast, the addition of hydrogen peroxide markedly improved the photocatalytic performance, resulting in up to 95% dye removal within 1 hour. Overall, this approach demonstrates strong potential for the treatment of industrial wastewater containing cationic dyes, offering an efficient, low-cost, and stable photocatalytic system.