Beyond supporting electrolytes: Novel solid polymer electrolyte system for enhanced electrochemical degradation of imidacloprid wastewater

The widespread and persistent presence of imidacloprid (IMD), a highly toxic neonicotinoid pesticide, in aquatic environments poses significant and growing threats to ecosystems and human health. Conventional electrochemical advanced oxidation processes often rely on soluble supporting electrolytes, which introduce secondary pollution and increase operational costs. To overcome this limitation, we introduce a novel electrolyte-free solid polymer electrolyte (EP-SPE) system built upon a Nafion® N324 membrane for the efficient and sustainable electrochemical degradation of IMD. Crucially, this system eliminates the need for external supporting electrolytes, marking a significant advancement towards simplified and greener treatment technologies. The SPE system achieved 74.12% IMD removal within 240 min, which corresponded to a pseudo-first-order reaction rate constant of k = 5.72 × 10 −3 min −1 . The specific energy consumption was quantified at approximately 30.39 kW∙h/mmol IMD, which was only about one-twentieth of a conventional Na 2 SO 4 -assisted system. This performance enhancement is attributed to a membrane-induced thin-layer effect that improves mass transfer, reduces ohmic losses, and increases current density, thereby facilitating efficient ∙OH generation and pollutant interaction. Degradation pathway analysis revealed multiple transformation routes, with most intermediates being less toxic than IMD. The system showed broad pH adaptability and maintained high efficiency in real water matrices. Stable performance over multiple cycles underscores the potential of the SPE system as a sustainable and efficient alternative for electrochemical treatment of refractory organic wastewater.