A study on the performance of enhancing environmental protection from molecular iodine using granular impregnated activated carbon

Environmentally hazardous radioactive isotopes of iodine may be released from a nuclear power plant as a by-product of uranium fission. The efficient and safe capture of volatile radioiodine is of great significance in the history of nuclear power plants. Due to its high volatility and carcinogenic characteristics, elimination of iodine gas (I₂) from air is the need of the hour from an environmental and health point of view. In this work, the trapping of molecular iodine has been studied using porous adsorbents such as activated carbon (AC) and activated carbon impregnated with metals or triethylenediamine (TEDA). Impregnated activated carbons (IACs) chemically react with iodine through SN₂ mechanism. The physicochemical and structural characterization of raw activated carbon (RAC) and impregnated activated carbons (IACs) was done by AAS, SEM, EDX, BET, and XRD. The finding of the breakthrough experimental adsorption showed that the gaseous iodine (50 ppm) equilibrium adsorption capacity of the raw AC before and after impregnation increased from 180 to 1044 mg/g mL at a condition of 60 °C. Furthermore, metal IAC was highly adsorbent at high temperatures (80 °C) due to its stability, and it adsorbed up to 576 mg/g mL iodine at a maximum. The breakthrough study examined that the adsorption capacity of iodine enhanced up to 19% for metal and 26% for metal-TEDA IAC as compared to RAC. Adsorption equilibrium data were well described by the Langmuir model, and the kinetics study was demonstrated by the second-order model. Thermodynamic parameters demonstrated that this is an exothermic and spontaneous reaction. This study explored the parameters of a filter such as adsorption capacity and saturation time at which no more pollutant gas can be captured. Finally, the findings demonstrate that these adsorbents may be capable of adsorbing large amounts of gaseous iodine.