Abstract:Taking soil contaminated by heavy metals around a tailings pond as research object, Th, Fe and Mn in soil were removed by ultrasound-assisted elution with citric acid as eluant. By changing eluant concentration, L/S, temperature and other conditions to compare removal amount, analyze its influence on removal amount and determine the optimal conditions. Characterization of leaching kinetics was investigated combined with leaching kinetics model and activation energy change. The results show that removal capacity rises by appropriately increasing concentration of eluant and temperature, and expanding L/S after ultrasonic-assisted chemical elution of citric acid for 90 min. The optimal conditions include concentration of 0.1 mol/L, L/S of 10 mL/g, and temperature of 45 ℃. Removal amount of heavy metals ranges from large to small is Mn>Fe>Th, which is 5 055.09, 1 750.98 and 61.48 mg/kg, respectively. Elution kinetics of three heavy metals all conform to double constant model, and elution kinetics of Mn also conform to parabolic diffusion model. Th and Fe are heterogeneous diffusion, Mn is mixture diffusion of parabolic diffusion and heterogeneous diffusion. Mn has the maximum average reaction rate of 0.82, and Th has the minimum apparent activation energy of 12.90 kJ/mol, which indicates that Mn reacts faster with citric acid, and Th reacts more easily with citric acid.