Cheng Tao, Barnett Mark O, Roden Eric E, Zhuang Jinling
Department of Civil Engineering, 238 Harbert Engineering Center, Auburn University, Auburn, Alabama 36849, USA.
Environ Sci Technol. 2006 May 15;40(10):3243-7. doi: 10.1021/es051771b.
U(VI) adsorption onto goethite-coated sand was studied in batch experiments ata solid-to-solution ratio (SSR) ranging from 33.3 to 333 g/L. Batch kinetic experiments revealed that the presence of 10(-4) M phosphate increased both the initial rate and ultimate extent of U(VI) adsorption compared with phosphate-free systems. Our experimental U(VI) adsorption isotherms were independent of SSR in phosphate-free systems. However, the U(VI) adsorption isotherm became dependent on SSR in phosphate-containing systems (with a lower SSR resulting in stronger U(VI) adsorption). A surface complexation model (SCM) was used to conceptualize the interactions in systems containing U(VI), phosphate, and goethite contributing to this SSR effect. The SCM accounted for the effects of SSR on U(VI) adsorption reasonably well. This study implies that the extrapolation of batch-measured adsorption parameters of U(VI) (and potentially other radionuclides and metal(loid)s as well) to field conditions should be done with caution, especially in the presence of strongly interacting ligands.
通过批量实验研究了在固液比（SSR）为33.3至333 g/L范围内，U(VI)在针铁矿包覆砂上的吸附情况。批量动力学实验表明，与无磷酸盐体系相比，10(-4) M磷酸盐的存在提高了U(VI)吸附的初始速率和最终程度。在无磷酸盐体系中，我们实验得到的U(VI)吸附等温线与固液比无关。然而，在含磷酸盐体系中，U(VI)吸附等温线变得依赖于固液比（固液比越低，U(VI)吸附越强）。使用表面络合模型（SCM）来概念化包含U(VI)、磷酸盐和针铁矿的体系中导致这种固液比效应的相互作用。表面络合模型较好地解释了固液比对U(VI)吸附的影响。本研究表明，将批量测量的U(VI)（以及可能的其他放射性核素和金属（类金属））吸附参数外推到现场条件时应谨慎，尤其是在存在强相互作用配体的情况下。
