Study on the remediation of uranium-contaminated soils by compound leaching: Screening of leaching agents and a pilot-scale application

To solve the problem of soil environmental pollution resulting from uranium mine development and production, a soil slurry reactor was used to evaluate the use of chemical leaching to remediate uranium-contaminated soils and to analyze possible uranium removal mechanisms through laboratory-scale trials and pilot-scale trials. A laboratory-scale trial comparing different reagents and operating methods revealed that the removal of total uranium from contaminated soil could reach 91.18% under optimal conditions when FeCl3, OA, NaClO2, and HEDP were used as eluents. Based on the optimal ratio and operating conditions determined from laboratory-scale trials, a pilot-scale trial was conducted around a uranium mining area: soil leaching remediation was conducted in two 3 m3 soil-slurry reactors to verify the practicality of the leaching technology and examine the functionality of the remediated soil. The experimental results showed that the rate of uranium removal from contaminated soil by the chemical leaching method was greater than 80%. FTIR, XRF and enzyme activity analysis proved that remediation restored the original soil function and reduced the ecological risk, indicating that the chemical leaching technology was environmentally friendly and economical. These findings provide insight to guide the future assessment and remediation practices of uranium-contaminated sites. •OA, FeCl3, NaClO2 and HEDP were screened as leaching agents for U-contaminated soil.•In pilot-scale trials, U removal rate reached more than 85% by leaching.•Results showed that leaching is safe and efficient, and increased soil fertility.