Development of KMnO ₄ -Enhanced Activated Carbon for the Elimination of Radioactive Cs-137 Contamination in Wastewater

In recent years, the electric arc furnace dust generated by Thailand’s steel production industry has been found to be polluted with radioactive cesium-137 (Cs-137). Cs-137 is considered highly dangerous and troublesome because of its long half-life of 30.17 years and its ability to readily dissolve in water. The release of Cs-137 has significant implications for human health and the environment. This work aims to improve the adsorption performance of commercial activated carbon (CAC) by modifying it to remove Cs-137 from liquid radioactive waste. Potassium permanganate (KMnO4) was employed to modify CAC at concentrations of 1%, 3%, and 5% w/v. The modified CAC exhibited improved removal of Cs-137 over 24 h, with its maximum removal efficiency achieved by CAC-5%KMnO4 (88.00%), followed by CAC-3%KMnO4 (80.53%), CAC-1%KMnO4 (73.81%), and CAC (70.56%). The enhancement in adsorption efficiency can be attributed to KMnO4’s ability to produce carboxyl (−COOH) and carbonyl ( > C=O) groups, which effectively capture positively charged Cs ions. Consequently, the optimal Cs-137 adsorption was achieved with a maximum KMnO4 loading of 5% w/v. The pH adsorption study indicated that a neutral to alkaline pH range significantly enhanced the Cs-137 removal performance, achieving over 50% efficiency. The adsorption of Cs-137 was validated through the Freundlich adsorption isotherm and the pseudo-second-order kinetic model for all adsorbents. The results of this study contribute to the development of effective strategies for managing wastewater contaminated with radioactive Cs-137.