Application of Tertiary Amine (HMTA and TEDA) Modified Activated Carbon in Iodine Removal from Radiological Releases in Nuclear Installation

Molecular iodine (I₂) released from nuclear power plants (NPPs) causes some serious environmental and health hazards. It is a paramount requirement to develop highly effective adsorbents for its capture. This work evaluates the performance of hexamethylenetetramine (HMTA) and triethylenediamine (TEDA) impregnated activated carbon (AC) for I₂ capture from NPP off-gas streams. Pristine AC samples were modified via incipient wetness impregnation and sublimation with different wt% of HMTA and TEDA (such as 2, 5, 8, 10, and 15 wt%). Physicochemical characteristics of both pristine and modified AC samples were analyzed through several techniques such as Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), to evaluate the modification effects on surface morphology, composition, and textural properties. Breakthrough experiments were conducted under simulated NPP release conditions to investigates the removal efficiency of I₂. Breakthrough performance experiment examined the I₂ adsorption capacities by varying different parameters such as impregnant loading and contact time. Overall, the results indicate a substantial increase in I₂ adsorption capacity for tertiary amine IAC as compared to pristine AC, highlighting the fundamental role of nitrogen-containing functional groups. To the best of our knowledge, this is first study reporting the application of HMTA-IACs for I₂ removal. This novel modification may improve I₂ adsorption capacity, adsorption affinity, and overall removal efficiency. HMTA IAC sample (CM14) achieved the highest adsorption capacity of 698 mg/g at 333 K, while TEDA IAC (CM23) yielded a maximum of 419 mg/g under identical conditions. Adsorption kinetics followed pseudo-second-order model (R² = 0.998), well fitted the Langmuir equation. Thermodynamic analyses proved the exothermic, spontaneous, and chemically driven nature of the process. Comprehensive evaluations based on kinetic, dynamic, adsorption isotherm, and thermodynamic study clarified the preferential I₂ uptake on tertiary amine-modified AC (HMTA and TEDA). By improving I₂ retention efficiency without compromising structural integrity, HMTA-modified AC contributes significantly to enhance the safety system of nuclear energy technologies.