纳米沸石、磷酸二氢钾与改性生物炭联合对铀尾矿库中核素铀的固定实验

采用纳米沸石、磷酸二氢钾、改性生物炭联合对铀尾矿库中的核素铀进行化学固定，并利用毒性浸出（TCLP）和Tessier逐级化学提取法，研究了固定前后铀的浸出特性与形态变化。TCLP结果表明，添加不同固定剂培养30 d后，与对照组相比土壤中铀的浸出量减少了42.13% ~71.54%，且土壤pH与TCLP提取态铀含量存在显著的负相关关系。Tessier结果显示，施用不同固定剂后，土壤中可交换态和碳酸盐结合态铀质量分数分别降低7.38%~26.06%、1.43%~6.99%，而有机质结合态、铁锰氧化物结合态、残渣态铀比例分别增加2.56% ~3.64%、2.71%~17.47%、4.07%~11.12%。在单一固定材料实验中，纳米沸石添加量为6%（以土壤质量计，下同）时稳定效果最佳，土壤可交换态铀比例降低15.68%。在复配材料固定实验中，以3种固定剂按质量比1:1:1，总添加量为6%时修复效果最好，土壤可交换态铀比例降低26.06%。由此可见，三种固定剂联合施用能有效降低土壤中铀的活性 ，为其他放射性污染土壤修复提供理论参考。

Immobilization experimental of uranium in uranium tailings reservoir by nano zeolite, potassium dihydrogen phosphate and modified biochar

Chemical immobilization experiment of nuclide uranium in uranium tailings pond with nano-zeolite, potassium dihydrogen phosphate and modified biochar combined, the leaching features and morphological changes of uranium before and after immobilization was determined by toxicity characteristic leaching procedure (TCLP) and stepwise chemical extraction.TCLP results showed that after 30 days of immobilization with different stabilizers, the amount of uranium leaching from soil decreased by 42.13%~71.54% compared with the control group.Moreover,there was a significant negative correlation between soil pH and TCLP-extracted uranium content.Tessier results showed that the mass fraction of exchangeable and carbonate-bound uranium in soil decreased by 7.38%~26.06%, 1.43%~6.99% with different fixatives, while the organic-bound, Fe-Mn oxide-bound and residual uranium increased by 2.56%~3.64%,2.71%~17.47%, 4.07%~11.12% respectively. In the single fixed material experiment, the application of nano-zeolite with 6% soil mass fraction has the best stability effect,the proportion of exchangeable uranium in soil decreased by 15.68%.In the compound materials experiment, the best repair effect was obtained by adding three fixatives with a mass ratio of 1:1:1 and a total dosage of 6%,the proportion of exchangeable uranium in soil decreased by 26.06%.Therefore,the application of three fixatives combined can effectively reduce the activity of uranium in soil,to provide theoretical reference for the remediation of other radioactive contaminated soils.