Experimental study of different admixture effects on the porosity and U(VI) leaching characteristics of uranium tailing solidified bodies in acid rain environments

The low pH of acid rain can significantly affect the amount of solidified heavy metals that leach into contaminated soil. A series of laboratory tests were performed to better understand the pore structure and uranium (VI) leaching characteristics of solidified uranium tailings using different mineral admixtures under acid rain conditions. Different proportions of cement, slag powder, and metakaolin were combined to solidify the uranium tailings, and the samples were soaked for 0–60 days in a simulated acid rain solution. Nuclear magnetic resonance was used to measure the sample porosity before and after immersion, and the U(VI) concentration was measured using ultraviolet and visible spectrometry after immersion. The sample microstructures were tested by scanning electron microscopy. The sample porosities ranged between 3.4% and 6.5% and gradually decreased with increasing amount of mineral admixture. The U(VI) leaching rate and cumulative leaching fraction also gradually decreased with increasing admixture amount. The sample porosity increased with increasing immersion time and the U(VI) leaching rate initially rapidly decreased and then stabilized. The U(VI) cumulative leaching fraction and porosity were the lowest in the samples with 20% metakaolin, and the sample porosity and U(VI) cumulative leaching fraction showed an inverted S-shaped curve.