Facile fabrication of rGO/PPy/nZVI catalytic microreactor for ultrafast removal of p-nitrophenol from water

The application of powdered nanoscale zero-valent iron (nZVI) in conventional reactors for water treatment is limited by insufficient mass-transfer and difficult post-separation of catalysts. Herein, a novel microreactor was constructed by anchoring nZVI on the reduced graphene oxide/polypyrrole nanocomposite (rGO/PPy) substrate within the microchannel of a stainless-steel tube through two-step electrodeposition , which catalyzed the Fenton-like reaction to remove > 99% p-nitrophenol (PNP) within 50 s, outperforming traditional batch reactors. The rGO/PPy composite substrate consolidated the adhesion on steel surface, stabilized the nZVI by forming electron-transfer complex, facilitated the decomposition of H 2 O 2 to free •OH, and promoted the redox cycle of Fe(III)/Fe(II) via the electron donating capacity of rGO/PPy. Besides, the significant convection and highly-effective mass transfer within the microreactor also contributed to the ultrafast PNP removal. With acceptable durability, easy re-generation, and scalability, the rGO/PPy/nZVI microreactor is promising for the ultrafast removal of pollutants from water.