Efficient photodegradation of malachite green in sunlight using ZnO nanostructures modified with pomegranate peel

It is in principle desirable that nanostructure materials be economical, low cost, and sustainable for photocatalytic applications. In spite of this, synthesis of these materials continues to be challenging. Recently, green methodologies had led to the development of surface-modified nanostructured materials that could degrade organic dyes efficiently. In this study, we had used pomegranate peel (PP) to synthesize ZnO nanostructures via a low-temperature aqueous chemical route. Morphological, structural, compositional and optical characterizations were performed by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and UV–visible spectroscopy, respectively. It was demonstrated that phytochemicals extracted from PP altered the morphology of the nanostructures, reduced crystallite size, decreased the optical band gap, and caused zinc vacancies, compared to pure ZnO. The highest amount of 1.0 g of PP reduced the optical band gap of ZnO up to 2.31 eV. As a result of these improved properties, ZnO nanostructures had showed enhanced photocatalytic activity toward degradation of malachite green (MG) under natural sunlight. A study on the effect of pH revealed that at pH = 11 more than 97% degradation of MG was achieved within 20 min at low catalyst dose. The recycle stability was investigated through 5 reusability measurements. The degradation of MG was governed by the reactive species like holes (h⁺) and it was confirmed from the scavenger study. The overall findings of this work had clearly underlined that PP could provide an effective source of phytochemicals for uplifting the functionality of ZnO nanostructure towards MG degradation.