Abstract:Using citric acid as the eluant, the contaminated soil near a uranium tailings was eluted and repaired assisted with ultrasound and microwave. The effects of citric acid concentration, liquid-solid ratio, ultrasonic power, temperature and microwave power on uranium removal in soil were analyzed, and the optimum parameters of ultrasonic and microwave enhanced leaching were obtained. The leaching characteristics of uranium in soil, the fluidity and stability of metal before and after elution were analyzed by means of construction of leaching kinetics model, metal chemical morphology analysis and XRD analysis, and the mechanism of ultrasonic and microwave-assisted citric acid removal of uranium in soil was revealed. The results show that the optimal parameters of ultrasonic and microwave strengthening of uranium contaminated soil by citric acid elution are as follows: citric acid concentration of 0.05 mol/L, liquid-solid ratio of 15 mL/g, ultrasonic power of 675 W, ultrasonic temperature of 40 ℃, ultrasonic time of 90 min, microwave power of 300 W, and microwave time of 15 min. The two enhanced chemical leaching kinetics models are basically consistent with the intra-particle diffusion model, and have the highest fit with the complex heterogeneous diffusion model, and have the highest fit with the complex heterogeneous diffusion model. The diffusion type of uranium in soil is complex heterogeneous diffusion. The leaching process is not only a simple diffusion control, but also may be accompanied by a series of reactions such as ion exchange and complexation reaction.