Hierarchically structured ZnO-graphene hollow microspheres towards effective reusable adsorbent for organic pollutant via photodegradation process

Present work reports on successful synthesis of hierarchical hollow microspheres (HHM) from ZnO-chemically converted graphene (CCG) nanocomposites by adopting low-temperature surfactant/template free solution method, varying graphene oxide (GO) to zinc acetate dihydrate weight ratio (R = 0.00, 0.01, 0.032, 0.063) in the precursors. It is found that the HHM consist of self-assembled ZnO nanoparticles, chemically interacted with CCG as evidenced from structural characterizations (X-ray diffraction, field emission scanning and transmission electron microscopes) with UV–Vis, FTIR, Raman and X-ray photoelectron spectroscopies. Multipoint BET nitrogen adsorption–desorption isotherms of ZG30, synthesized using an optimum GO content (R = 0.032) showed relatively high specific surface area. The sample showed significantly improved adsorption capacity of rhodamine B dye (as water pollutant) compare to pristine ZnO (R = 0.0) as well as commercially available P25 (TiO2). The ZG30 functioned as reusable adsorbent due to its highly efficient photocatalytic activity under UV (λ, 254 nm) irradiation. Methyl orange and phenol were also used to check the effectiveness of ZG30 for permanent cleaning of the pollutants. This facile process could create an avenue for synthesis of hollow microspheres from different metal oxide semiconductor–graphene nanocomposites for efficient and reusable adsorbent of water soluble organic pollutants.