Enhanced remediation of radioactive soil via synergistic foam flotation-acid washing process in a single reactor

This study presents an integrated single-reactor system for the remediation of soil contaminated with cesium (Cs + ) and cobalt (Co²⁺) by combining foam flotation and acid washing. Initially, foam flotation with cetyltrimethylammonium bromide (CTAB) selectively separated clay particles, which bound to CTAB via electrostatic interaction. Subsequently, soil washing using oxalic acid and CTAB effectively desorbed residual Cs + and Co²⁺ from the sand-sized fraction. Based on these results, we evaluated the applicability of the integrated foam flotation-soil washing process to the decontamination of Cs- and Co-soil. When treating an artificially contaminated soil containing 40.9 mg/kg of Cs + and 34.9 mg/kg of Co²⁺, the fine particle flotation process alone lowered their concentrations to 26.8 and 23.3 mg/kg, respectively. Further in-situ acid treatment reduced Cs + to 8.5 mg/kg for (79.3% removal) and Co²⁺ to 1.3 mg/kg (96.2% removal). These results demonstrate that the integrated single-reactor approach enables selective separation of fine particles and enhanced desorption of radionuclides. While this study serves as a proof-of-concept using artificially contaminated soil, it offers a practical and scalable solution, warranting further investigation on field-contaminated radioactive soil. A single-reactor system combining foam flotation and acid desorption was proposed. CTAB-assisted foam flotation selectively separated fine particles from soil. Oxalic acid and CTAB synergistically enhanced Cs and Co desorption. High removal efficiencies for Cs (79.3%) and Co (96.2%) were achieved. The integrated process significantly reduced radionuclide concentrations and waste volume.