Hybrid process of combined soil washing and selective adsorption to treat Cs-contaminated soil

The decommissioning of old nuclear power plants is a worldwide issue and the removal of radioactive materials from soil is challenging. In this study, we proposed a hybrid process that combines soil washing for extraction and selective adsorption for Cs-containing washing wastewater to treat cesium (Cs+)-contaminated soil. To extract Cs+ from the soil, various extracting agents were evaluated including cationic salts (CaCl2, BaCl2, KCl, and NH4Cl), organic/inorganic acids (EDTA, oxalic acid, HCl, and HNO3), and a base (NaOH). In addition, the combination of cationic salts and acids was investigated to enhance the overall extraction of Cs+ from soil. Potassium ions (K+) showed the highest removal of Cs+ (about 60%). The operating parameters of extracting agent concentration, reaction time, and solid/liquid (S/L) ratio required to desorb Cs+ from the soil were determined to be 0.1 M, 10 min, and 1/10, respectively. To enhance the overall extraction of Cs+ from soil, a three step multi-extraction process was proposed and approximately 99% of Cs+ was extracted by the multiextraction process. The extracted Cs+ in the aqueous solution was mostly adsorbed onto the synthesized and the adsorbent removed Cs+ selectively even in the presence of a high concentration of K+ (about 99%). This result shows the effectiveness of the hybrid process of extraction and selective adsorption. The technique proposed is expected to reduce greatly the amount of radioactive waste to be disposed of permanently.

Automated summary

The study proposed a hybrid process incorporating soil washing and selective adsorption for treating cesium-contaminated soil, achieving a 99% extraction rate through a multi-step extraction process. The synthesized adsorbent selectively removed cesium from the aqueous solution even in the presence of a high concentration of potassium ions, demonstrating the effectiveness of the hybrid process.