Integration of Photo‐Fenton Reaction and Membrane Filtration using Lignin@t‐FeC₂O₄/g‐C₃N₄ Nanofibers Toward Accelerated Fe(III)/Fe(II) Cycling and Sustainability

Abstract Photocatalysis water treatment without artificial energy is cost‐effective, waste‐free and sustainable. Coventional powder photocatalysts have tiny contact surfaces, low catalytic efficiency, and are difficult to recycle and reuse, restricting their usage. Herein, a Lignin@t‐FeC₂O₄/g‐C₃N₄ material is developed by engineering hollow quadrangle t‐FeC₂O₄ and g‐C₃N₄ nanosheets on lignin membranes through facile impregnation coating and precipitation reaction. Fast mass transport, catalytic activity and accessibility characterize hollow tetragonal FeC₂O₄·2H₂O. TEM, SEM and FTIR show that lignin binds t‐FeC₂O₄ and g‐C₃N₄. The g‐C₃N₄ nanosheets are uniformly wrapped on the surface of lignin fibers, and t‐FeC₂O₄ is loaded between them. This structure increases visible light absorption and active site‐contaminant contact. The chain reaction produces extremely active hydroxyl radicals from hydrogen peroxide because the Lignin@t‐FeC₂O₄/g‐C₃N₄ modules are rich inFe^II, according to XPS. Transient photocurrent response curves and electrochemical impedance spectroscopy suggest a promoted charge migration and isolation at the redox reaction interface in the Lignin@t‐FeC₂O₄/g‐C₃N₄ system. As a result, Lignin@t‐FeC₂O₄/g‐C₃N₄ degrades 99% Rhodamine B within 40 minutes, and this performance is stable even under difficult conditions, such as low hydrogen peroxide concentration and high pH. This study combines lignin membranes with the photo‐Fenton reaction, and thus provides new concept for the development and application of membranes and photocatalysis.