Th(Ⅳ)在凹凸棒石表面的吸附机理  

The sorption mechanisms of Th(Ⅳ) on attapulgite

作　　者：潘多强[1] 范桥辉[1] 丁克非[1] 李平[1] 路艳[1] 于涛[1] 许江[1] 吴王锁[1] 

机构地区：[1]兰州大学核科学与技术学院放射化学研究所,兰州730000

出　　处：《中国科学：化学》2011年第6期1081-1092,共12页SCIENTIA SINICA Chimica

基　　金：国家自然科学基金(20871062;J1030932);教育部博士研究生学术新人奖;兰州大学中央高校基本科研业务费专项资金(lzujbky-2010-215);国家同步辐射实验室教育部创新计划(20090137S)资助

摘　　要：采用连续电位滴定法研究了天然和高温活化凹凸棒石的表面酸碱和电荷分布性质,利用表面配位模型和FITEQL3.2程序探讨了Th(Ⅳ)在高温活化前后凹凸棒石上的吸附机理.结果表明天然凹凸棒石表面主要以离子交换位(≡XNa/K)、强吸附点位(≡SsOH)和弱吸附点位(≡SwOH)为主;而高温活化凹凸棒石表面则主要以强吸附点位(≡SsOH)和弱吸附点位(≡SwOH)为主.当pH<2.5,Th(Ⅳ)在水溶液中主要以Th4+存在;而当pH>3.0时,Th(Ⅳ)则主要以水解形态存在(例如Th(OH)22+,Th(OH)3+和Th(OH)40).Th(Ⅳ)在天然凹凸棒石表面上的吸附主要以离子交换作用(≡X2Th)和内层配合作用(≡SsOTh)为主,而在高温活化凹凸棒石表面上则主要形成内层配合物(≡SwOTh和≡SsOThOH).胡敏酸(HA)对Th(Ⅳ)在高温活化凹凸棒石上吸附有一定的促进作用,且使Th(Ⅳ)的吸附机理和种态发生明显的改变(主要以≡SsO-CO-HA-Th和≡SsOTh种态存在).Th(Ⅳ)在高温活化凹凸棒石上的吸附是不可逆过程,但当HA存在时,Th(Ⅳ)在高温活化凹凸棒石上会发生解吸.The surface properties of intrinsic and activated attapulgite were studied using potentiometric titration.The sorption mechanisms of Th（Ⅳ）on intrinsic and activated attapulgite were investigated by employing surface complexation model and FITEQL 3.2 code.The results indicated that the sorption sites of intrinsic attapulgite involved in the sorption process were mainly ion exchange site（≡XNa/K）,strong site（≡SsOH）and weak site（≡SwOH）,while only strong site（≡SsOH）and weak site（≡SwOH）were predominant for activated attapulgite.At pH2.5,the species of Th（Ⅳ）was main Th4＋in aqueous solution;then the hydrolysis species of Th（Ⅳ）（i.e.,Th（OH） 22 ＋,Th（OH）3 ＋ and Th（OH）4 0）gradually formed as pH increasing.For the sorption of Th（Ⅳ）on intrinsic attapulgite,both ion exchange species（≡X2Th）and inner-sphere surface complexes（≡SsOTh）were dominant,while only inner-sphere surface complexes（i.e.,≡SsOThOH and ≡SwOTh）were observed for Th（Ⅳ）sorption to activated attapulgite.In the presence of humic acid（HA）,the sorption of Th（Ⅳ）on activated attapulgite was obviously enhanced;and both≡SsOH-HA-Th and≡SsOTh were the predominant speciation.It was also interesting to find that the addition of HA obviously provoked the desorption behavior of Th（Ⅳ）.

关 键 词：凹凸棒石 Th(IV) 胡敏酸 吸附 解吸 表面配合 

分 类 号：O647.3[理学—物理化学]