Preparation of Fe/Mn added active carbon composite as particle electrode for 3D electrochemical oxidation ammonia nitrogen from aqueous solution

Three-dimensional (3D) electrochemical oxidation has emerged as a promising advanced oxidation process for wastewater treatment, owing to its high efficiency, environmental compatibility, and operational advantages. In this study, we developed a novel Fe/Mn co-loaded activated carbon (Fe/Mn-AC) particle electrode for the electrochemical oxidation of ammonium nitrogen NH 4 + -N) in wastewater. The as-prepared catalyst was systematically characterized through multiple analytical techniques including SEM-EDS, XRD, FTIR, XPS, and BET surface area analysis. Post-impregnation, SEM revealed maintained surface smoothness but reduced pore sizes, while BET measurements confirmed decreased surface area (from 732.38 to 650.83 m 2 /g), pore diameter (from 2.6 to 2.18 nm), and pore volume (from 0.43 to 0.37 cm 3 /g). XRD and XPS analyses identified iron and manganese oxides (Fe 2 O 3 , Fe 3 O 4 , Mn 2 O 3 , Mn 3 O 4 ) as the active phases. FTIR spectra exhibited characteristic bands of O–H (3462 cm −1 ), C–O (1571 cm −1 ), and C–C (1384 cm −1 ) in both AC and Fe/Mn-AC, with observable intensity variations after metal loading. Under optimized conditions (pH = 7, applied voltage = 14 V, Fe/Mn loading = 1 %, initial NH 4 + -N concentration = 100 mg/L), the 3D electrochemical system achieved an NH 4 + -N removal efficiency of 87.64 % with an energy consumption of 6.2 kW h/kg NH4+-N after 8 h of treatment. Radical quenching experiments confirmed the in-situ generation of hydroxyl radicals and electrons during the electrochemical process. The degradation mechanism study revealed that NH 4 + -N was primarily removed through indirect electro-oxidation pathways, with N 2 identified as the dominant end product.