Dual-layer Ag/AgBr–TCN/graphene membranes for single-pass visible-light photocatalytic degradation of antibiotics in water

A visible-light-responsive bilayer photocatalytic membrane was constructed using 1D tubular carbon nitride and 2D graphene. • A TCN–Ag/AgBr heterojunction significantly enhanced intrinsic photocatalytic efficiency under visible light. • Graphene simultaneously enriched pollutants and acted as an electron acceptor to promote charge transfer. • Over 99% SMX removal was achieved after a single pass at a flux of 6.3 L m −2  h −1 . • The membrane exhibited stable performance over multiple cycles, showing strong potential for antibiotic removal. Photocatalytic membranes provide an effective platform for the direct removal of water contaminants. However, most photocatalytic membranes are constructed by simply integrating catalysts with membrane materials, without fully exploiting the retention capability of membranes. Meanwhile, inefficient photogenerated carrier dynamics limit the coupling between photocatalytic reaction kinetics and flow-through mass transfer during filtration, hindering the single-pass removal of recalcitrant pollutants such as antibiotics. Herein, a dual-layer photocatalytic membrane was designed to fully leverage the synergistic roles of photocatalysis and membrane separation by utilizing the efficient light harvesting of the upper layer, the pollutant retention and enrichment capability of the lower layer, and the effective electron separation and transfer properties of the photocatalytic and membrane materials. The membrane was rationally constructed via sequential assembly of Ag/AgBr-modified one-dimensional tubular carbon nitride (TCN) onto a multilayered graphene membrane, forming an integrated Ag/AgBr-TCN-GO heterostructure. Under a flux of 6.3 L m −2  h −1 the prepared membrane achieved over 99% removal of sulfamethoxazole (SMX) in a single filtration pass, while its SMX removal capacity per unit time and unit membrane area was 32.64% higher than that of previously reported membranes evaluated under visible light based on the normalized areal removal metric defined in this work. The membrane also exhibited promising removal performance toward other representative contaminants such as tetracycline and bisphenol A. Mechanistically, the TCN-Ag/AgBr promoted efficient electron generation and directional charge transfer, while the graphene oxide layer facilitated electron transport and suppressed recombination. Meanwhile, filtration-induced pollutant retention enriched contaminants on the membrane surface, enabling more efficient utilization of photogenerated electrons. This work establishes an effective strategy for coordinating charge-carrier dynamics with pollutant transport during filtration, enabling single-pass photocatalytic water treatment. Download: Download high-res image (119KB) Download: Download full-size image