Generation of reactive oxygen species from oxygen microbubbles in phosphoric acid solution and its application of ferrous iron oxidation

•O2 microbubbles have strong oxidizing ability in H3PO4 solutions due to the generation of ROS.•The main ROS specie generated by O2 microbubbles in H3PO4 solution was determined to be H2O2•The generation of H2O2 was via a sequential one-electron reduction of O2 molecule.•The generation of H2O2 was affected by the temperature and H3PO4 concentration.•The activation energy of Fe2+ oxidation reaction was significantly reduced due to the strong oxidation effects of ROS generated by the microbubbles.