Bridging molecular mechanisms and engineering practice: CeO₂ mediated Fe(VI) activation on for deep thallium removal...

The deep removal of thallium (Tl) and achieving low-cost compliance with emission standards industrial wastewater is often extremely challenging. This study proposes a heterogeneous Tl removal system utilizing CeO₂-activated (Fe(Ⅵ)) to enhance their oxidation and flocculation performance. Under extremely low doses of reagents (5 mg/L) and catalyst (90 mg/L), the initial Tl(I) concentration was effectively reduced from 1000 μg/L to 2 μg/L below. Mössbauer spectroscopy, XPS, and DLS, revealed the triple enhanced process of Tl removal, involving interface charge regulation, oxidation-co-precipitation, and flocculation structure optimization. The reaction kinetics of Fe(Ⅵ) and the contribution of intermediate iron species were analyzed by stop-flow and Raman spectroscopy. XANES was employed to reveal the high activity and stability mechanism of high-valent iron (Fe(Ⅳ)/Fe(V)) in Tl-removal at the atomic scale. The Fe(Ⅵ)-CeO₂-Tl dual-path coordination interface significantly enhances the coordination symmetry and electronic delocalization ability of the Tl center, increasing the coordination number of Tl-Fe and facilitating efficient electron transfer. During a 30-day pilot-scale continuous operation at a steel plant, the developed integrated process and equipment achieved compliant emissions of all pollutants including Tl, at low cost. The study elucidated the key processes of Fe(Ⅵ) activation at heterogeneous interfaces and the mechanism by which transition states enhance Tl removal performance, demonstrating a comprehensive leading-edge technology for Tl removal from steel mill wastewater in terms of performance, operability, and operational costs. This provides critical theoretical guidance and important technical support for advancing the low-energy, high-efficiency treatment of heavy metal wastewater.