Sustainable synthesis of zinc oxide nanoparticles for photocatalytic degradation of organic pollutant and generation of hydroxyl radical

Herein, a sustainable and reproducible method for the preparation of zinc oxide nanoparticles (ZnO) and their application in photocatalytic degradation of organic pollutant is reported. The ZnO nanoparticles were prepared by combusting a mixture of highly porous sawdust and zinc nitrate hexahydrate at 600 degrees C in a tube furnace. The porous morphology of the sawdust mediated the formation of ZnO nanoparticles by preventing their growth to the macroscopic size. Four different ZnO nanoparticles samples [ZnO-n, where n = 1-4] were prepared by varying the ratio of sawdust and zinc nitrate salt to obtain the best-performing ZnO nanoparticles. The average size of the ZnO nanoparticles was found to be similar to 23 nm, measured from TEM image. The ZnO-4 and ZnO-2 degraded similar to 95% methyl orange (MO) in deionized and simulated fresh drinking water matrices after 42 min of ultraviolet (UV-B) light irradiation. The ZnO-2 and ZnO-4 catalyzed degradation of MO in deionized and fresh drinking water matrices were found to be about 24 and 27 times faster compared to the ZnO-control. The ability of ZnO-n towards the generation of hydroxyl radicals (center dot OH) was studied by the terephthalic acid fluorescence tests. Additionally, the reproducibility of the synthesis methodology and the cyclic stability of the as prepared ZnO-n was thoroughly studied. Finally, it was found that the ZnO nanoparticles, prepared in this study, leached less amount of zinc in water compared to the commercial ZnO; which indicated its better safety and sustainability in regard to the photocatalytic water treatment. (C) 2020 Elsevier B.V. All rights reserved.y