Magnetic recyclable CoFe₂O₄/lignin spheres: Enhanced peroxydisulfate activation for neonicotinoid insecticide...

The elimination of residual neonicotinoid insecticides from aquatic systems, exemplified by thiamethoxam (THX), presents significant challenges for ecosystem sustainability and human health. Advanced oxidation processes (AOPs), particularly persulfate (PMS) activation generating sulfate radicals, offer a promising solution for thiamethoxam remediation. In this work, adhering to the "waste for waste", CoFe₂O₄/CNF composites are rational constructed by uniformly loading cobalt ferrate (CoFe₂O₄) nanoparticles on hollow carbon nanospheres (CNF) derived from calcined desalted lignin as supports. The CoFe₂O₄/CNF composite demonstrated exceptional PMS activation capability, achieving 75% THX degradation within 60 min at neutral pH and lower metal leaching. Moreover, the system exhibited robust performance across varying pH conditions and complex ionic environments. This can be attributed to the synergistic electron transfer between Co²⁺/Co³⁺ and Fe²⁺/Fe³⁺ redox couples, which enhanced PMS activation. Radical quenching experiments and EPR analysis identified SO₄^•- and superoxide radicals (O₂^•-) as the dominant reactive oxygen species responsible for THX degradation. Additionally, key reaction parameters, including catalyst dosage, PMS concentration, initial THX concentration, pH and interfering ions, were systematically optimized. Wheat seed planting experiments further indicated the system's potential for environmental remediation. This work provides an efficient and sustainable biomass waste-derived carbon-based catalyst strategy for the removal of neonicotinoid insecticides.