Preparation of martite nanoparticles through high-energy planetary ball milling and its application toward simultaneous catalytic ozonation of two green algae

The efficiency of heterogeneous catalytic ozonation in the presence of martite nanocatalyst was studied as a novel method for the thorough and in situ removal of Oocystis sp and Cosmarium sp green algae. High-energy planetary ball milling was utilized to prepare martite nanoparticles (MNPs) from natural martite particles (NMPs). X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR) analysis, X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) were carried out to determine the physical and chemical characteristics of NMPs, and MNPs. The mechanism of heterogeneous catalytic ozonation was investigated in the presence of different reactive oxygen species (ROSs) scavengers. The degradation process was accomplished via the continuous attacks of hydroxyl radicals (^•OH) and superoxide radicals (O₂^−•). The variation of chlorophyll-a concentration and the morphologies of the algae cells were investigated. The results obtained from chlorophyll-a content, light microscopic and SEM images revealed the complete degradation of the algae cells. Moreover, the main elements of algae structure and intermediates, generated during the degradation process were identified using EDX and GC–MS analysis. The mineralization efficiency of the proposed catalytic ozonation process was investigated using of COD results.