NiAl-LDH/MXenes intercalated anode for enhanced electrochemical oxidation to synergistically degrade norfloxacin and antibiotic resistance genes in wastewater

Abstract

Electrocatalytic oxidation is a promising treatment for remediating organic contaminants in wastewater. However, improving the mass transfer efficiency and catalytic activity of anode materials is essential for effective treatment. In this study, a NiAl-layered double hydroxide (LDH) intercalated MXenes composite anode (NiAl-LDH/MXenes) was developed via electrostatic self-assembly for the degradation of norfloxacin (NOR) and antimicrobial resistance genes (ARGs) in hospital wastewater. The insertion of NiAl-LDH sheets expanded the MXenes interlayer spacing, alleviated stacking, and reduced mass transfer distance. This intercalation strategy promoted electron transfer and •OH generation, enhancing catalytic activity and enabling efficient degradation of NOR and ARGs. Compared to NiAl-LDH and MXenes, the NiAl-LDH/MXenes composite exhibited a higher oxygen evolution overpotential (2.21 V vs. SCE) and lower energy consumption (0.003 kWh/m³), achieving 97.31 % NOR degradation in 120 min and 95.73 % DNA degradation in 90 s. The composite electrode also exhibited excellent performance in treating practical hospital wastewater, achieving 91.19 % NOR removal, significant ARGs removal (e.g., qnrA by 96.72 %), and effectively reducing pathogenic bacteria such as Duganella by 4.21 logs. Linear sweep voltammetry confirmed direct electron transfer in NOR degradation, while quenching experiments, EPR, and molecular probe assays elucidated the role of •OH in degrading NOR and DNA. DFT calculations revealed that •OH preferentially targets the piperazine ring and carboxyl groups of NOR, as well as the –OH and C=O/C-N sites of DNA. This study introduced a novel intercalation-based anode modulation strategy using NiAl-LDH/MXenes for the concurrent degradation of NOR and ARGs, offering a robust solution for wastewater treatment.