Dynamic catalytic membrane for secondary effluent treatment: Mechanisms of persulfate activation, water quality improvement and in-situ membrane cleaning

To address the challenges associated with traditional interface catalytic oxidation membranes, such as preparation complexity, limited reaction sites, and poor reusability, a novel recyclable pre-deposited dynamic catalytic membrane was developed for the first time. Specifically, a B-doped NiFe 2 O x catalyst with magnetic and many oxygen vacancies was synthesized and simply pre-deposited onto the surface of an ultrafiltration membrane to activate peroxydisulfate (PDS). The results indicated that the abundant active catalytic sites on the dynamic deposition layer of B-NiFe 2 O x could efficiently activate PDS, thereby facilitating the generation of active species predominantly comprising sulfate and hydroxyl radicals. As a result, there was a 67.14% significant removal of chemical oxygen demand in secondary effluent. Furthermore, even after 8 cycles of magnetic recovery and re-deposition, the normalized flux of the dynamic catalytic oxidation membrane continued to maintain at 0.52. Notably, unlike conventional interface catalytic oxidation membranes, some B-NiFe 2 O x within the dynamic layer engaged in the catalytic oxidation process in a free form, which maximized the oxidation rate and enhanced membrane in-situ cleaning performance. This research contributes to a comprehensive understanding of utilizing pre-deposited dynamic catalytic oxidation membranes and proposes an effective long-term strategy for membrane in-situ cleaning and wastewater treatment.