Selective C-P bond cleavage in glyphosate degradation via singlet oxygen-dominated alkali-activated peroxymonosulfate

Achieving selective degradation of glyphosate (PMG) to avoid the formation of toxic intermediate aminomethylphosphonic acid (AMPA) is still a considerable challenge. This study developed a singlet oxygen (¹O₂)-driven alkali-activated peroxymonosulfate (PMS) system to achieve selective degradation of PMG by targeting carbon sites with varying electronegativity. The alkali-activated PMS system, utilizing Na₂B₄O₇, NaBO₂, NaBO₃, NaOH, and Na₂CO₃, effectively degraded PMG following pseudo-first-order kinetics, with k_obs of 0.1555, 0.1208, 0.1131, 0.1077, and 0.0961 min^-1, respectively. Comprehensive analysis, including quenching tests, chemical probes, and electron paramagnetic resonance (EPR) confirmed ¹O₂ as the dominant reactive oxygen species (ROS), generated through PMS self-decomposition and Na₂B₄O₇-catalyzed pathways. Density functional theory (DFT) calculations demonstrated that the phosphonate group in PMG exhibits particular susceptibility to electrophilic attack by ¹O₂. Furthermore, Nuclear Magnetic Resonance (NMR) spectroscopy, Multiple Reaction Monitoring (MRM) model of UHPLC-TQMS identified selectively cleaves the C-P bond, yielding glycine and orthophosphate. A continuous-flow system was developed to evaluate alkali-activated PMS for PMG wastewater treatment over 1200 min continuous operation at 50 min hydraulic retention time (HRT). This work elucidates a selective C-P bond cleavage mechanism and establishes a sustainable strategy for precision remediation of PMG-containing industrial wastewater.