Hydrometallurgical approaches for Cesium-137 decontamination of steel ash: An overview with emphasis on aqueous...

The inadvertent melting of "orphan" radioactive sources containing Cesium-137 (¹³⁷Cs) during steel recycling processes results in the concentration of this radionuclide found in steel ash, posing a significant radiological and waste management challenge. Although pyrometallurgical methods are commonly employed for steel ash treatment, their applicability to ¹³⁷Cs decontamination is limited by high energy demands, inadequate selectivity for radionuclides, and substantial capital investment. This review examines aqueous hydrometallurgical approaches as a more viable alternative for the selective removal of ¹³⁷Cs. Several leaching strategies were systematically evaluated, encompassing conventional water and acid/base treatments as well as advanced techniques, including ion exchange and precipitation. Evidence suggests that a two-stage hydrometallurgical approach beginning with selective leaching using cations such as NH₄⁺ or K⁺ to displace Cs⁺ and followed by recovery from the leachate via ion exchange or precipitation offers a technically robust, economically feasible, and environmentally sustainable solution. This method enhances ¹³⁷Cs removal efficiency while enabling the retention and recovery of valuable elements such as zinc, significantly minimizing the volume of final radioactive waste. However, challenges such as high reagent consumption, secondary waste generation, and economic bottlenecks for scale-up must be addressed to achieve industrial viability. The review concludes by identifying directions for future research, including process intensification, integration of physical enhancement methods, and development of hybrid systems, for advancing this decontamination strategy toward commercial application.