Oxidation capacity evaluation of oxygen nanobubbles for dye wastewater treatment

This study demonstrates that oxygen nanobubbles (ONBs) have an oxidation capacity for dye wastewater treatment. Employing the extended Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, we explored the instability of ONBs at acidic pH, leading to their interactions, coalescence into larger bubbles, and subsequent collapse. The oxidation potential of ONBs during the methylene blue (MB) decolorization reaction reached its highest efficiency when the zeta potential was 0. Hence, as part of a pioneering effort, ONBs were combined with Fenton's reagent (H₂O₂ and Fe²⁺), representing the first attempt to evaluate the effectiveness of this combination in advanced oxidation processes (AOPs). The optimal amounts of Fenton's reagent used to treat 10 ppm of MB were 0.15 mM of H₂O₂ and 0.036 mM of Fe²⁺ in the presence of ONBs at pH 3, where the zeta potential of the ONBs was 0. After 15 min of contact with ONBs and Fenton's reagent, the MB solution decolorization efficiency reached 95 %. The correlation between the initial MB concentration and Fenton's reagent concentration was tested and established. The difference in efficiency between the presence and absence of ONBs indicates the capacity of ONBs to support AOPs. Overall, ONB technology is expected to have great potential for dye wastewater treatment.