Highly efficient catalytic degradation of dicamba using Fe3O4/montmorillonite composite: Mechanism and toxicity assessment

Dicamba (DIC) posed significant hazards to aquatic environment owing to its toxic and refractory property in agricultural production, which has been paid increasing concern. Herein, a novel magnetic montmorillonite composite (Fe3O4/Mt) was fabricated for catalyzing peroxymonosulfate (PMS) to decompose DIC. The results exhibited that 3.0 mM PMS and 2.0 g/L Fe3O4/Mt could decompose nearly 90% of DIC, and the removal efficiency of DIC stayed above 66% after 10 cycles. The electron spin resonance tests and quenching experiments revealed that SO4•– and •OH were the main active radicals responding for DIC degradation. Moreover, based on the density functional theory (DFT) calculations and LC-MS, C1, C2, C4, and C5 atoms of DIC with high electrophilic activity were prone to be attacked by radicals, and were ultimately decomposed into five degradation intermediates. Finally, the toxicity assessment proved that most of the intermediates exhibited lower toxicity levels than that of DIC. These findings demonstrated that Fe3O4/Mt was a recyclable, stable, and safe catalyst for activation PMS to decompose persistent organic pollutants in contaminated water.