Key roles of superoxide radicals for glyphosate degradation and recycling

Glyphosate, one of the most widely used herbicides worldwide, and its production generates large amounts of alkaline wastewater. However, the dominant reactive species governing its transformation in advanced oxidation processes and the underlying degradation mechanisms have not been fully elucidated, it has brought challenges to the sustainable development and process optimization of the glyphosate industry. Here, we demonstrate that superoxide radicals (O₂^•⁻), rather than hydroxyl radicals (•OH), serve as the key initiation species for glyphosate degradation. While •OH-dominated systems exhibit negligible reactivity, alkaline conditions promote O₂^•⁻ generation and enable rapid degradation, with a strong positive correlation between O₂^•⁻ concentration and reaction kinetics. Mechanistic analysis reveals that O₂^•⁻ initiates degradation through a thermodynamically favorable pathway, whereas •OH-mediated pathways are kinetically hindered. This mechanism is further validated across multiple independent reaction systems. Building on this insight, by utilizing the alkaline environment of high-concentration glyphosate wastewater, we have successfully achieved the precise cleavage of glyphosate bonds to generate phosphate ions, and at the same time recovered phosphorus in the form of struvite, which has fertilizer potential. This study redefines the dominant reactive species in glyphosate degradation and highlight superoxide-driven pathways as a critical route for enabling phosphorus circularity in glyphosate-containing wastewater.