全氟化合物在碳纳米管上的吸附研究

ADSORPTION OF PERFLUORINATED COMPOUNDS ON MULTIWALLED CARBON NANOTUBES

研究了3种全氟化合物:全氟辛烷磺酸盐(PFOS)、全氟己烷磺酸盐(PFHxS)、全氟辛酸(PFOA)在原碳纳米管(Pri-MWCNTs)和氧化型碳纳米管(O-MWCNTs)上的吸附行为.研究结果显示,3种全氟化合物在两种碳管上的吸附均呈明显的非线性;全氟化合物的等温吸附曲线均符合Freundlich及Langmuir模型.模型拟合参数表明全氟化合物在原碳纳米管上的吸附量大于在氧化型碳纳米管上的吸附量.3种全氟化合物的吸附能力为PFOS>PFOA>PFHxS,这与它们分子含CF2个数一致,说明亲脂性是全氟化合物在碳纳米管上吸附的重要机理之一.3种全氟化合物的吸附量随pH的增加而降低,表明吸附受静电作用的影响.当溶液中同时存在PFOS与PFOA时,二者的吸附都有所降低,说明二者在碳纳米管上有共同的吸附位点,吸附存在竞争关系.

In this study, sorption isotherms of three kinds of perfluorinated compounds （ PFCs）, perfluorooctanoic acid （PFOA） , perfluorooctanesulfonie potassium （ PFOS ）, and perfluorohexanesulfonic potassium （PFHxS） on muhiwalled carbon nanotubes （MWCNTs） were studied. The sorption isotherms were nonlinear and fitted with Freundlich and Langmuir models well. Sorption of PFCs on pristine MWCNTs was higher than those on oxidized MWCNTs. Sorption coefficients （Kd） of three PFCs followed the order： PFHxS 〈 PFOA 〈 PFOS, which was consistent with the increases of perfluorocarbon chain length, and suggested that the hydrophobic interaction plays an important role in the sorption of PFCs. Sorption of PFCs decreased with increasing solution pH, indicating the importance of electrostatic interaction between PFCs and MWCNTs. Results of competitive sorption between PFOA and PFOS showed that Kd values of PFOA and PFOS in the bi-solute system were lower than those in the single-solute system. PFOA had a higher reduction than PFOS.