Fouling removal in ceramic ultrafiltration membrane via catalyst modification with Fenton-like backwash

Abstract

Fouling remains a critical challenge for ceramic ultrafiltration membranes, limiting their long-term performance for water treatment. Fenton-like reactions have been widely used for fouling removal due to the formation of strong radicals. Integrating these reactions into backwash offers a promising strategy for fouling control. However, it has been unclear how Fenton-like backwash is influenced by operational parameters and fouling structures. Here we reveal the key factors influencing Fenton-like backwash by systematically studying its performance under varying conditions, such as backwash pressure (0.3–1 bar), duration (18–36 min), fouling structure (caused by 1–5 mM Ca) and the long-term operation, to provide an effective and practical cleaning. CuFe₂O₄ was grown on ceramic ultrafiltration membranes due to its stability and high catalytic efficiency in activating Fenton-like reactions. We found that Fenton-like backwash achieved the highest cleaning efficacy of approximately 70 % over three cycles at a low backwash pressure of 0.3 bar, while hydraulic backwash remained ineffective under all conditions. Backwash pressure, rather than duration, was identified as the dominant factor governing the Fenton-like cleaning, due to its impact on the residence time of Fenton-like agents (H₂O₂). The presence of a high Ca concentration (3 and 5 mM) altered the fouling behaviour, and reduced the cleaning efficacy of Fenton-like backwash. This reduction was attributed to the formation of rigid alginate clusters that were resistant to Fenton-like reactions. The contribution of •OH to the enhanced Fenton-like backwash was confirmed by the quenching experiments. Furthermore, the CuFe₂O₄-coated membranes exhibited stable flux recovery (83 %–94 %) in the long-term treatment of a concentrated alginate (800 mg/L), showed low or negligible leaching in hash environments (30 mM H₂O₂, 0.1 % NaClO or 10 mM NaOH), and maintained comparable performance after 96 h aging by 30 mM H₂O₂. This study clarifies the factors governing Fenton-like backwash, and demonstrates that a robust and effective strategy for fouling removal can be achieved by coupling this cleaning method with catalytic ceramic membranes.