Recycling of industrial wastes in the biosynthesis process of magnetite nanoparticles

During the past few decades, environmental concerns have led researchers to investigate the profitable methods of preventing environmental deterioration caused by industrialization and urbanization. In such a circumstance, the application of hazardous materials in the production process of nanoparticles has been attracted worldwide attention. This is not only environmentally beneficial but also results in the production of multi-functional nanoparticles. In this regard, in the current study, two different industrial wastes, basic oxygen furnace (BOF) dust and beet vinasse, were used for the green synthesis of magnetite nanoparticles through a straightforward, cost-effective process. The urease-positive bacteria, Bacillus subtilis, was cultivated in a media containing vinasse, and its ability for ammonia production was investigated through six different routes. In this regard, the highest ammonia concentration was acquired when calcium chloride and urea were added to the media at the beginning of cultivation. Then, the extracts containing a maximum ammonia concentration were separated and added to the Fe³⁺ and Fe²⁺ solution which was obtained from the acid leaching of BOF dust and sponge iron, respectively, for the biosynthesis of nanoparticles. According to the vibrating sample magnetometer analysis, the produced nanoparticles were superparamagnetic. Also, regarding the transmission electron microscopy images, the mean size of the particles was in the range of 11.6 ± 5.03 nm. Also, the X-ray diffraction and Fourier transform infrared spectroscopy confirmed the efficient biosynthesis of magnetite nanoparticles.