Highly Active 3D Composites for a Flow-Through Photocatalytic Membrane Reactor toward Water Micropollutant Removal

Photocatalytic membrane reactors (PMRs) are a class of useful devices for removing micropollutants from aquatic environments, in which three-dimensional (3D) structures on membranes are particularly anticipated to benefit from ultralow concentration treatment. However, they lack the photocatalytic materials that are highly active and can be well integrated with membranes to maintain 3D structures. Here, we demonstrated that the assembly of two-dimensional (2D) photocatalytic material and conducting material into 3D structures can perfectly address this challenge. As a proof of concept, atomically thin bismuth oxychloride with rich defects (D-BiOCl) was first integrated with reduced graphene oxide (RGO) to form a 3D composite for photocatalytic pollutant degradation, validating the potential application of 2D material assembly in designing a 3D membrane. As a result, the optimized D-BiOCl/RGO composite reached 97.2% photocatalytic degradation efficiency for tetracycline (TC, 10 mg L–1) in 2 h, with excellent stability and recyclability after 5 cycles of reaction, proving the high activity of defect sites. Furthermore, we explored the integration of D-BiOCl/RGO with a poly(ether sulfone) (PES) membrane, which was used in a PMR for photocatalytic TC degradation in the concentration range of 50 ng L–1 to 1 mg L–1 in a flow-through mode. Notably, in a 100 ng L–1 TC solution, the maximum removal rate reached 84% at 25 °C, 250 mW cm–2, and 25 L m–2 h–1, demonstrating the key role of the 3D structure. This work provides an approach to the removal of micropollutants with enhanced performance and gains insight into the design of water treatment membranes via synergism of active sites and material assembly.