Mechanochemical construction of S-scheme red mud-based layered double hydroxid heterojunction with confined strong electron donor structure for gatifloxacin photodegradation

Waste residue red mud is utilized to synthesize a layered double hydroxid composite. • An S-scheme charge transfer pathway in CN-LDH/ARM photocatalyst is proved. • Antibiotics electrons can be derived via the introduced n-state sites in CN-LDH/ARM. • Synergistic non-radical and radical pathways arrive efficient antibiotics degradation. • The aquatic toxicities of GAT solution are obviously reduced by CN-LDH/ARM. A acidified red mud (ARM) based layered double hydroxide (LDH) composite with graphitic carbon nitride (g-C 3 N 4 ) was successfully constructed via a mechanochemical synthesis (MCS) method (naming CN-LDH/ARM). The synthesized CN-LDH/ARM was used for the efficient degradation of gatifloxacin (GAT) under visible light (CN-LDH/ARM photocatalytic system). After 120 min of reaction time, 99% of GAT (20 mg/L, 300 mL) could be degraded under the reaction conditions: [CN-LDH/ARM]= 0.03 g/L, [H 2 O 2 ]= 120 mmol/L and initial pH= 6.5. In-situ X-ray photoelectron spectroscopy (SI-XPS) indicated that an S-scheme charge transfer pathway between ARM (Fe 2 O 3 ) and LDH was formed in CN-LDH/ARM under visible light. Density functional theory (DFT) calculation suggested that the introduced g-C 3 N 4 could act as strong electron donor structure (calling n-state sites) to effectively promote interfacial charge transfer between GAT and CN-LDH/ARM. In the CN-LDH/ARM photocatalytic system, ·OH, h + and high-valent metal species (Fe(IV)) were the primary active species. This study provides a sustainable strategy for constructing RM-based photocatalysts with enhanced photo-Fenton activity for antibiotic wastewater treatment. Download: Download high-res image (316KB) Download: Download full-size image