3D hierarchical rare-earth metal composite nanofiber membranes for highly durable and efficient photodegradations of organic pollutants†

The use of powdered photocatalysts in wastewater treatment presents several challenges, such as difficulties in recovery, aggregation during use, and poor reusability, which limit their effectiveness in large-scale environmental applications. To address these issues, we developed sustainable and reusable photocatalytic membranes comprising three-dimensional (3D) hierarchical lanthanum-doped rare-earth metal oxide nanorods integrated onto polyacrylonitrile/polyvinylidene fluoride (PAN/PVDF) nanofibers (La-doped RE-NFs). These hybrid composite membranes were fabricated by combining electrospinning and hydrothermal synthesis methods. The La-doped RE-NFs not only possess a high surface-area-to-volume ratio but also demonstrate superior photocatalytic efficiency for removing common target organic pollutants in water (i.e., Congo red (CR), methyl orange (MO), methylene blue (MB), and tetracycline (TC)). Here, the formation of the CeCO₃F phase has contributed to the enhanced photocatalytic performance. From the kinetic analysis of the photocatalytic degradation, the rate constant (k) of La-doped RE-NFs in the MB removal test is 4.3 times higher than that of their undoped counterparts. Moreover, these proposed membranes exhibit excellent reusability, with only a ∼5% reduction in degradation efficiency after five consecutive cycles. These findings highlight the potential of La-doped RE-NFs as a highly efficient and reusable photocatalytic membrane material for environmental applications, particularly in water treatment systems.