纳米零价铁对铀尾矿库土壤中铀形态分布及固定效果的影响

Effect of nano-zero-valent iron on the uranium speciation distribution and fixation in uranium tailings soil

针对纳米零价铁(nZVI)对铀尾矿库土壤中铀形态分布和U(Ⅵ)固定效果影响问题,采用逐级化学提取、毒性浸出(TCLP)和磁性分离实验,利用SEM-EDS和XRD对nZVI固定前后的铀尾矿土壤进行表征;研究了nZVI在不同投加量和pH条件下,对尾矿库土壤固定前后铀的形态分布和固定效果的影响,并对nZVI的固定机理进行了探讨。结果表明:当nZVI的投加量为8%、pH为5时,土壤中U(Ⅵ)的固定效果最好,固定后土壤中铀的毒性浸出值仅为13.98%;对经过nZVI处理后的铀尾矿土壤进行磁性分离发现,磁性和非磁性土壤重量占比分别为32.87%和67.13%,其铀含量分别达到55.05%和44.95%,说明nZVI对土壤中的U(Ⅵ)有较好的富集作用。nZVI对铀尾矿库土壤中的U(Ⅵ)有较好的原位固定和富集效果,并能减少土壤中铀的析出。

In order to reveal the effect of nano-zero-valent iron(nZVI)on the uranium speciation distribution and fixation in the uranium tailings soil,the stepwise chemical extraction,toxic leaching experiment(TCLP)and magnetic separation experiments were conducted.SEM-EDS and XRD were used to characterize uranium tailings soil before and after nZVI fixation.The effects of nZVI doses and pHs on the uranium speciation distribution and fixation,as well as the fixation mechanism,were studied.The results showed that the best U(Ⅵ)fixation occurred at nZVI dosage of 8%and pH=5,and the toxic leaching value of uranium in nZVI fixed soil was only 13.98%.Through magnetic separation of the nZVI treated uranium tailings soil,the weight ratio of magnetic soil and non-magnetic soil were 32.87%and 67.13%,and their the uranium content were 55.05%and 44.95%,respectively.Therefore,nZVI has a desirable in-situ fixation and enrichment effect on U(VI)in the uranium tailings,and could reduce the uranium leaching from the soil.