Methods that induce the transformation of heavy metals into less soluble forms provide an important strategy for stabilizing heavy metals in soil and reducing their leaching potential. Immobilization of heavy metals in contaminated soils involves adding appropriate immobilizing agents to reduce the solubility and mobility of heavy metals, thereby preventing their leaching and diffusion. In this study, based on previous research, we evaluated the immobilization characteristics of cobalt and strontium by examining factors such as the injection amount, reaction time, and mixture of immobilizing agents, including Mn-PILC, Fe-PILC, fish bones, and diammonium phosphate (DAP) fertilizer. All immobilizing agents used in the experiment were found to partially immobilize cobalt and strontium based on their adsorption properties. The immobilization of cobalt and strontium by Mn-PILC and Fe-PILC occurred relatively quickly (within 2 days) and showed a continuous decrease over a period of 30 days. Generally phosphate-based compounds took a longer immobilization time than PILC. The evaluation of immobilization using a mixture of modified clay and phosphate showed that the mixture of modified clay and DAP resulted in the lowest leaching rates of cobalt (below 10%) and strontium (below 20%) according to the TCLP test. The results suggest that it can be utilized in the development of immobilizing agents for the stable immobilization of cobalt and strontium in soil environments.

Keywords: Immobilization, Cobalt, Strontium, PILC, Fishbone