Bio-synthesized multi-metal oxides with varying Fe/Mn ratios and transitional metals (Ni, Ce, Al, Cu) for catalytic ozonation

Fe and Mn are frequently used to synthesize ozonation catalysts via physicochemical routes. In this study, we used a manganese oxidizing bacterium Pseudomonas sp. to produce biogenic Fe-Mn oxides (Bio-FeMnOx) and compared the effect of doping a third transitional metal (Ni, Ce, Al, Cu). It was found that Fe/Mn ratios can effectively regulate the catalytic activity of Bio-FeMnOx and Cu showed the best doping effect among the four metals. The degradation kinetic constant of the optimal Bio-FeMnOx-Cu was approx. 3 times that of its chemogenic peer. Electron paramagnetic resonance and probe tests revealed that the reactive oxygen species were •OH, •O2- and 1O2. The generation of •OH was preferred at pH 2 over pH 7 while •O2- was generated in the opposite preference. We also observed the multi-valence of all metals in Bio-FeMnOx-Cu whose good stability were confirmed with 5 cycles of usage. The catalytic performance of Bio-FeMnOx-Cu was also confirmed with real wastewater. This study demonstrated the importance of Fe/Mn ratios and doping a third transitional metal regarding the activity of catalyzing ozonation and thus would provide a valuable reference for producing biogenic metal oxides of high catalytic activity.