Degradation of Rhodamine B by Peroxymonosulfate Activated with a NiFe-LDH@CoFe-PBA Composite

In this study, CoFe-PBA-loaded NiFe-LDH (NiFe-LDH@CoFe-PBA) was synthesized and employed to catalyze peroxymonosulfate (PMS) to degrade rhodamine B (RhB). That the composite material was successfully synthesized was confirmed through complementary characterization techniques including energy-dispersive spectrometry, Fourier transform infrared spectroscopy, and X-ray diffraction analyses. The elimination efficiency of RhB reached 98.99% within 15 min under the conditions of an initial RhB concentration of 50 mg L^-1, a catalyst concentration of 0.2 g L^-1, a PMS concentration of 0.2 g L^-1, and an initial pH of 6.36. The characterization results revealed that CoFe-PBA improved the dispersibility of NiFe-LDH and exposed more active sites, which made NiFe-LDH@CoFe-PBA have higher current density and electron transfer ability. In the composite, Co, Fe, and Ni were the catalytic centers to activate PMS, and the redox between Co³⁺/Co²⁺, Fe³⁺/Fe²⁺, and Ni³⁺/Ni²⁺ enhanced the production of reactive oxygen species (ROS: ¹O₂, O₂^•-, •OH, and SO₄^•-). Among them, ¹O₂ was determined to be the predominant reactive species responsible for RhB degradation. This study proposes a novel methodology for designing and synthesizing simple, efficient, stable, and environmentally friendly heterogeneous metal-based catalysts.