Peroxymonosulfate Activation by Red Mud for Iopamidol Degradation: Unveiling the Roles of Inherent Alkalinity and Catalytic Components

Abstract Red mud (RM), an alkaline by‐product generated during alumina production, contains various transition metal oxides which are responsible for its catalytic activity in advanced oxidation processes (AOPs). This study investigates the degradation of iopamidol (IPM) by RM‐activated peroxymonosulfate (PMS), focusing on the roles of RM's inherent alkalinity and transition metal oxides in the degradation process. The results indicated that IPM was degraded effectively under the RM‐activated PMS system. With 3 g/L RM, 1.0 mmol/L PMS, and pH 10.38, an 81.5% degradation efficiency of IPM was achieved within 90 min. X‐ray fluorescence (XRF) analysis and RM simulation experiments revealed that CaO was the primary species for activating PMS degrading IPM. The radical quenching experiments and electron paramagnetic resonance (EPR) analysis demonstrated that singlet oxygen ( 1 O 2 ) was the primary reactive species in the RM activated PMS system. Based on the analysis of degradation products by the liquid chromatography–mass spectrometry (LC–MS), the IPM degradation pathways were proposed, with deiodination being the main reaction. ECOSAR predictions suggested that the majority of the oxidation products pose a low ecological risk to aquatic organisms. The inherent alkalinity and catalytic components of RM synergistically enhance PMS activation, demonstrating its dual role as a cost‐effective and efficient catalyst.