Radioanalytical Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
Radioanalytical Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
J Environ Sci (China). 2021 Feb;100:181-192. doi: 10.1016/j.jes.2020.07.020. Epub 2020 Jul 28.
Radionuclide migration in aquatic environment is influenced by its sorption onto colloids/mineral oxides and the presence of organic complexing anions. With a view to understand the sorption of trivalent actinides by mineral oxides in presence of organic acid, in the present study, Eu(III), malonic acid (MA) and γ-alumina are considered as representatives of trivalent actinides, low molecular weight natural occurring organic acid and aluminol sites, respectively. The influence of MA on sorption of Eu(III) by γ-alumina was elucidated by batch sorption, spectroscopic techniques and surface complexation modeling, for the first time. Attenuated Total Reflection-Fourier Transform Infrared spectroscopic studies of MA sorbed on γ-alumina revealed the presence of two inner-sphere surface complexes. Batch sorption for binary (alumina-Eu(III)) and ternary (alumina-Eu(III)-MA) systems were investigated as a function of pH, Eu(III) concentration and sequential addition of Eu(III)/MA. The pH edge for Eu(III) sorption shifts to higher pH with increasing Eu(III) concentration. In ternary systems, Eu(III) sorption is significantly enhanced at pH < 4.5. Eu(III) speciation on γ-alumina is independent of addition sequence of Eu(III)/MA. Time resolved fluorescence spectroscopy of Eu(III) sorbed on γ-alumina exhibited two surface species, XOEu and (YO)Eu. The enhancement in I/I and lifetime for ternary systems, as compared to binary system, at low pH, indicates the participation of Eu-MA complexes in the formation of surface species in ternary systems. The diffuse layer model has been employed to successfully model the experimental sorption profiles of binary and ternary systems, using code FITEQL 4.0, by considering the surface species identified by spectroscopic techniques.
放射性核素在水生态环境中的迁移受到其与胶体/矿物氧化物的吸附以及有机络阴离子存在的影响。为了了解有机酸存在下矿物氧化物对三价锕系元素的吸附，本研究选用 Eu(III)、丙二酸（MA）和γ-氧化铝分别作为三价锕系元素、低相对分子质量天然存在的有机酸和铝醇基位点的代表。首次采用批量吸附、光谱技术和表面络合模型研究了 MA 对γ-氧化铝上 Eu(III)吸附的影响。MA 吸附在γ-氧化铝上的衰减全反射-傅里叶变换红外光谱研究表明存在两种内球表面络合物。作为 pH、Eu(III)浓度和 Eu(III)/MA 顺序添加的函数，研究了二元（氧化铝-Eu(III)）和三元（氧化铝-Eu(III)-MA）体系的批量吸附。随着 Eu(III)浓度的增加，Eu(III)吸附的 pH 边缘向更高 pH 值移动。在三元体系中，pH < 4.5 时，Eu(III)吸附显著增强。γ-氧化铝上 Eu(III)的形态与 Eu(III)/MA 的添加顺序无关。Eu(III)吸附在γ-氧化铝上的时间分辨荧光光谱显示存在两种表面物种，XOEu 和 (YO)Eu。与二元体系相比，在低 pH 值下，三元体系的 I/I 和寿命增强表明 Eu-MA 配合物参与了三元体系表面物种的形成。采用扩散层模型，使用 FITEQL 4.0 代码，通过考虑光谱技术确定的表面物种，成功地对二元和三元体系的实验吸附曲线进行了模拟。
