Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
Environ Sci Technol. 2017 Aug 15;51(16):9219-9226. doi: 10.1021/acs.est.7b01649. Epub 2017 Jul 27.
Surface-functionalized magnetite nanoparticles have high capacity for U(VI) adsorption and can be easily separated from the aqueous phase by applying a magnetic field. A surface-engineered bilayer structure enables the stabilization of nanoparticles in aqueous solution. Functional groups in stearic acid (SA), oleic acid (OA), and octadecylphosphonic acid (ODP) coatings led to different adsorption extents (SA≈ OA > ODP) under the same conditions. The impact of water chemistry (initial loading of U(VI), pH, and the presence of carbonate) has been systematically examined for U(VI) adsorption to OA-coated nanoparticles. A diffuse double layer surface complexation model was developed for surface-functionalized magnetite nanoparticles that could simulate both the measured surface charge and the U(VI) adsorption behavior at the same time. With a small set of adsorption reactions for uranyl hydroxide and uranyl carbonate complexes to surface sites, the model can successfully simulate the entire adsorption data set over all uranium loadings, pH values, and dissolved inorganic carbon concentrations. The results show that the adsorption behavior was related to the changing U(VI) species and properties of surface coatings on nanoparticles. The model could also fit pH-dependent surface potential values that are consistent with measured zeta potentials.
表面功能化的磁铁矿纳米颗粒对 U(VI)具有高吸附容量，并且可以通过施加磁场很容易地从水相中分离出来。表面工程双层结构可使纳米颗粒在水溶液中稳定化。在相同条件下，硬脂酸 (SA)、油酸 (OA) 和十八烷基磷酸 (ODP) 涂层中的官能团导致不同的吸附程度（SA≈OA>ODP）。已经系统地研究了水化学（U(VI)的初始负载、pH 值和碳酸盐的存在）对 OA 涂层纳米颗粒吸附 U(VI)的影响。开发了用于表面功能化磁铁矿纳米颗粒的扩散双电层表面络合模型，该模型可以同时模拟测量的表面电荷和 U(VI)吸附行为。通过将少量的水合铀酰和碳酸铀酰络合物吸附反应应用于表面位点，该模型可以成功地模拟所有铀负载、pH 值和溶解无机碳浓度下的整个吸附数据集。结果表明，吸附行为与纳米颗粒表面涂层上 U(VI)物种和性质的变化有关。该模型还可以拟合与测量的 ζ 电位一致的 pH 依赖性表面电位值。
