【摘要】 以石英砂为填充介质,采用动态柱实验方法研究了某中低放处置场地表土壤胶体对U(Ⅵ)在石英砂柱中迁移行为的影响,并结合静态批式实验探究了土壤胶体对U(Ⅵ)迁移的影响机制。结果表明,当U(Ⅵ)进样质量浓度从1.0 mg/L增大至5.0 mg/L时,U(Ⅵ)在石英砂柱中的穿透速率显著增大,且达到洗脱平衡时所需淋洗液的体积从250 PVs(孔隙体积)增大至400 PVs。与U(Ⅵ)相比,土壤胶体在石英砂柱内迁移较快,这可能是由于土壤胶体与石英砂之间相互作用较弱所致。土壤胶体与U(Ⅵ)共存体系中,U(Ⅵ)的迁移速率明显增大,而土壤胶体迁移速率无显著变化,表明共存体系中U(Ⅵ)的迁移行为主要受土壤胶体所控制。静态吸附实验表明,在石英砂-U(Ⅵ)二元体系中,pH≈6.0时石英砂对U(Ⅵ)的吸附率最大,而在胶体-石英砂-U(Ⅵ)三元体系中,U(Ⅵ)主要在土壤胶体表面发生吸附。本研究所用土壤中胶体的质量分数仅约占0.04%,但可吸附20%U(Ⅵ)(初始质量浓度为5.0 mg/L);由此可见,土壤胶体可与U(Ⅵ)发生强的相互作用,进而对U(Ⅵ)在真实环境体系中的吸附、迁移和扩散等行为产生至关重要的影响。更多还原

【Abstract】 The transport behavior of U(Ⅵ) in the presence of soil colloids was investigated by column experiments using quartz sand as the porous media, and batch technique was further applied to explore the mechanism of U(Ⅵ) transport in the presence of soil colloids. The results show that when the initial mass concentration of U(Ⅵ) increases from 1.0 mg/L to 5.0 mg/L, the transport rate of U(Ⅵ) significantly increases, and the required leachate volume increases from 250 PVs(pore volume) to 400 PVs, reaching the elution equilibrium. Compared with U(Ⅵ), the soil colloids transport much faster in the quartz column, mainly owing to the weak interaction between the soil colloids and the quartz sand. In the presence of soil colloids, the transport rate of U(Ⅵ) is remarkably improved, while the breakthrough curve of soil colloids do not change obviously, which indicates that the transport behavior of U(Ⅵ) in the ternary system of colloid-U(Ⅵ)-quartz is mainly controlled by soil colloids. In the binary system of U(Ⅵ)-quartz, the sorption of U(Ⅵ) on quartz is maximized at pH≈6.0, while in the ternary system of colloid-U(Ⅵ)-quartz almost all U(Ⅵ) is absorbed on the soil colloids, and the contribution of quartz can be negligible. It is noted that about 20% U(Ⅵ)(initial mass concentration is 5.0 mg/L) is adsorbed on soil colloids, which only accounts for 0.04% of the studied soil. The strong interaction between soil colloids and U(Ⅵ) suggests that soil colloids have a crucial impact on U(Ⅵ) adsorption, transport and diffusion in the environment.更多还原