A CuO-modified ultrafiltration ceramic membrane inducing micro-nano bubble collapse to generate hydroxyl radicals for enhancing pollutant removal

It is desirable to develop ceramic membranes with functional performances for wastewater treatment. This work developed a CuO-modified Al2O3 ceramic membrane (CuO/Al2O3 CM) via a sol-gel method. The coated CuO particles provided hydrophobicity and a high zero point of charge for CM, which could accumulate H+ ions and form a liquid depletion layer on the membrane surface. When coupled with micro-nano bubbles (MNBs) in a neutral aqueous solution, the modified CM led to MNBs collapse through the accumulation of H+ and uneven expansion. This collapse generated high temperature sites that activated the CuO particles, leading to the production of reactive oxygen species (ROSs) through the interaction of CuO and surface OH–. Therefore, the modified CM could remove model pollutants (methylene blue) in a stable and high efficiency (88.91 %) through inducing MNBs collapse. Besides, the tests on the pure water flux, reusability and leaching revealed the modified CM had good fouling resistance, stability, and environmental friendliness. Mechanism analysis showed the ROSs, mainly hydroxyl radicals (·OH), were responsible for the methylene blue degradation. This work provides valuable insights into the development of functionalized membranes that can induce MNB collapse to enhance pollutant removal in wastewater treatment.