Eu3+水合离子在纳米二氧化硅表面的吸附与结构

采用发射光谱研究了不同pH和不同Eu初始浓度条件下，Eu在纳米二氧化硅-水界面的吸附特征。研究发现，当pH低时，Eu在纳米二氧化硅表面的吸附很少，随着pH的增加，Eu在纳米二氧化硅表面的吸附急剧增加，当出〉6时，几乎所有Eu都被吸附。研究同时表明，吸附在纳米二氧化硅与水界面的Eu离子种类也取决于pH值：当pH〈5时，吸附的Eu主要为Eu^3＋水合离子，当pH〉5时，吸附的Eu主要为Eu（CO3）^＋，甚至Eu（CO3）2^-离子。吸附的机理除了静电吸引外，更重要的是这些离子与纳米二氧化硅表面形成化学键，即表面化学吸附。

SORPTION AND STRUCTURE OF AQUEOUS Eu3+ IONS ONTO NANO-SIZED SILICA SURFACE

The sorption characteristics of Eu onto nano-sized silica-water interfaces at different pH and different initial Eu concentrations are investigated by fluorescence spectroscopy.The results indicated that the sorption of Eu onto nano-sized silica surface is minimal at lower pH,but increases significantly with increasing pH until almost all Eu species are sorbed at pH>6.Meanwhile,the types of aqueous Eu species sorbed onto nano-sized silica-water interfaces also depend on pH: the Eu species sorbed at pH<5 is dominantly hydrated Eu~(3+),but the Eu species sorbed at pH>5 are mainly Eu(CO_3)~+,even Eu(CO_3)~-_2.The main sorption mechanism is chemical bonding between Eu species and nano-sized silica surface,i.e.,chemical sorption on surface,although electrostatic attraction may also play a role in the sorption.