A novel NH2-MIL-88B(Fe)-modified ceramic membrane for the integration of electro-Fenton and filtration processes: A case study on naproxen degradation

Abstract

• Novel NH 2 -MIL-88B(Fe)-decorated ceramic membrane for combined filtration-EF at mild pH. • Almost total degradation of naproxen in Na 2 SO 4 after 90 min at 50 mA and 2 mL min −1 . • Mechanism for heterogeneous EF with catalytic ceramic membrane (EFCCM) treatment. • Identification of 7 primary oxidation byproducts and EFCCM viability in urban wastewater. • Low iron release (<1 mg L −1 at pH ≥ 5) ensured a good CM reusability for at least 5 cycles. Process intensification based on innovative coupling between membrane microfiltration and catalytic oxidation technologies has become a promising strategy for water treatment. Here, a surface-nucleated metal–organic framework (MOF) was grown in situ to obtain an NH 2 -MIL-88B(Fe)-functionalized catalytic ceramic membrane (NH 2 -MIL-88B(Fe)@CM), whose ability to remove naproxen from water matrices via the so-called electro-Fenton with catalytic ceramic membrane (EFCCM) process was systematically investigated. The physicochemical properties of the NH 2 -MIL-88B(Fe) and membranes were characterized by XRD, FTIR, XPS and SEM, revealing the formation of a well-defined NH 2 -MIL-88B(Fe) layer on the porous CM with a thickness of around 13.5 µm, which provides a large amount of active sites for H 2 O 2 activation to generate hydroxyl radical ( OH). The EFCCM treatment of naproxen in Na 2 SO 4 solution under recirculation batch mode yielded almost complete drug removal in 90 min at 50 mA, whereas the stability and catalyst loss tests gave evidence of good membrane reusability for 5 cycles. The treatment of naproxen in urban wastewater confronted severe membrane fouling, but this was effectively mitigated by combining hot water backwash with EF self-cleaning. Finally, the naproxen degradation routes involving 7 byproducts are proposed. This is an effective approach to the fabrication of CCM, which could be used for wastewater treatment in continuous mode as suggested by the minimal NPX content at the membrane outlet.