Co-ZIF-L-derived Fe-incorporated CoNi layered double hydroxide for efficient peroxymonosulfate activation and Rhodamine B degradation

Pristine or conventional layered double hydroxides (LDH) catalysts used for peroxymonosulfate (PMS) activation typically suffer from limited electron-regulation capability and insufficient selectivity toward non-radical pathways, which restrict their catalytic efficiency and stability. To overcome these limitations, Fe-incorporated CoNi layered double hydroxides (Fe-CoNi-LDH-x) were synthesized via low-temperature hydrothermal conversion of a Co-ZIF-L precursor and subsequently applied to the degradation of Rhodamine B (RhB). Under the selected conditions (Fe-CoNi-LDH-30, 0.1 g/L; PMS, 0.5 mM; RhB, 200 mg/L; pH 7; 298 K), nearly complete decolorization of RhB was achieved within 8 min, with a pseudo-first-order rate constant of 1.087 min −1 , while the total organic carbon removal reached 42.8% over the same period. Low concentrations of natural organic matter caused limited effects, whereas substantial inhibition was observed in natural-water matrices. Quenching experiments together with electron paramagnetic resonance (EPR) spectra indicated that singlet oxygen ( 1 O 2 ) was the major oxidative species, whereas SO 4 •− , • OH, and O 2 •− contributed as secondary species. Comparison of the X-ray photoelectron spectroscopy (XPS) spectra before and after the reaction confirmed Fe 2+ /Fe 3+ conversion together with the valence evolution of Co and Ni, indicating the participation of multivalent metal sites in surface redox processes during PMS activation and supporting a PMS activation route governed mainly by 1 O 2 generation. This study provides a rational multi-metal design strategy for surface-state-regulated, non-radical PMS activation in dye-containing wastewater treatment.