PFOS在锐钛型TiO2表面吸附行为的理论研究  

Theoretical Studies on Adsorption of PFOS on Anatase TiO_2 Surfaces

作　　者：薛倩倩[1] 何广智[2] 夏树伟[1] 潘纲[2] 

机构地区：[1]中国海洋大学化学化工学院,海洋化学理论与工程技术教育部重点实验室,青岛266100 [2]中国科学院生态环境研究中心,环境纳米材料研究室,北京100085

出　　处：《高等学校化学学报》2013年第7期1673-1678,共6页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金(批准号:20677053);环境水质学国家重点实验室专项经费(批准号:11Y06ESPCR)资助

摘　　要：采用密度泛函理论(DFT)B3LYP方法对全氟辛烷磺酸(PFOS)在锐钛型TiO2表面的化学吸附和物理吸附行为进行了研究,其中化学吸附包含双齿双核(BB)和单齿单核(MM)在内的4种可能的吸附构型.吸附能(Eads)及反应吉布斯自由能(ΔGads)的计算结果表明,PFOS分子易于与TiO2表面发生氢键作用吸附;化学吸附表现为PFOS分子与TiO2表面的水分子(H2O)和羟基(—OH)反应,且与取代—OH相比,H2O取代相对更容易发生,其中,MM1构型(取代一个表面水分子)为化学吸附中的优势构型.PFOS在锐钛矿表面吸附的热力学稳定性和反应自发性顺序如下:H-Bonded(氢键吸附)>MM1(取代一个表面水分子)>BB1(取代两个表面水分子)>MM2(取代一个表面羟基)>BB2(取代一个表面水分子和一个表面羟基).成键结构分析表明,TiO2表面H2O/—OH官能团与PFOS上的磺酸基之间形成了中等强度的氢键;在化学吸附过程中,电荷从PFOS分子向TiO2表面发生转移,生成Ti—O—S化学键,电荷转移主要来自PFOS分子的O和F原子.Adsorption behavior of perfluorooctane sulfonate（PFOS） on anatase TiO2 surfaces was studied with DFT-B3LYP method. Physisorption including hydrogen-bond interaction and chemi-adsorption including bidentate binuclear（BB） and monodentate mononuclear（MM） complexes were investigated in the study. Calculations of adsorption energy（Eads） and Gibbs free energy（ΔGads） showed that physisorption was easier tooccur. Chemi-adsorption surface complexes were produced by reaction between PFOS and surface water（H2O） or hydroxyl（-OH）, and the reaction to replace H2O was easier than that to replace -OH group. MM1（reacted with one H2O of surface） surface complex was the most thermodynamically favorable chemi-adsorption mode. The thermodynamically favorable and stability order of PFOS adsorbed on anatase TiO2 surfaces was H-bonded（hydrogen bonded adsorption）〉MM1（reacted with one H2O of surface）〉BB1（reacted with two H2O of surface）〉MM2（reacted with one -OH of surface）〉BB2（reacted with one H2O and one -OH of surface）. Results of bond length analysis indicated that the interaction between H2O/-OH function group on TiO2 surface and sulfonate group in PFOS resulted in the formation of moderate intensity hydrogen bond. Charges transferred from PFOS molecule to TiO2 surface during chemi-adsorption process, leading to the formation of Ti—O—S bond, and transfered electrons in the process were mainly from strong electronegative atoms O and F.

关 键 词：密度泛函理论 全氟辛烷磺酸 锐钛矿 吸附结构 

分 类 号：O641[理学—物理化学] O647[理学—化学]