Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu 300, Taiwan.
Environ Sci Technol. 2010 Jul 1;44(13):5142-7. doi: 10.1021/es100349k.
Cationic surfactants modified clays exhibit high sorptive capability toward anionic radionuclides but retention of cationic radionuclides was concurrently reduced. In this study, organoclays were synthesized by intercalating a variety of primary/quaternary alkylammonium species (NH(2)R/(CH(3))(3)N(+)RBr(-), where R = benzyl, dodecyl, and octadecyl) into bentonite MX-80. The effect of surfactant's properties on enhancing or limiting cationic sorption capability was investigated by performing Cs sorption experiments. Experimental results were analyzed using the MINEQL+ software by considering Cs uptake by structural and edge sorption sites. Bentonites that were intercalated with primary alkylammonium surfactants had a higher sorptive capacity than those intercalated with quaternary alkylammonium surfactants. Samples intercalated with octadecyl-bearing surfactants had the lowest sorption rate. XRD and FTIR analyses revealed that each organoclay had a characteristic arrangement of alkyl chains. The cation retention of organoclays was dominated by the extent of hydrophobic interactions affected by the local distribution and arrangement of surfactants. The intercalated primary alkylammoniun surfactants tended to transform into local clusters with a high packing density, leaving more structural sites available for Cs uptake. In contrast, the NH(3)R(+)-surfactants tended to form a denser monolayer over clay surface, inhibiting the retention of Cs at structural sites.
阳离子表面活性剂改性黏土对阴离子放射性核素有很高的吸附能力，但同时也会降低阳离子放射性核素的保留。在这项研究中，通过将各种伯/季铵盐物种（NH(2)R/（CH(3))(3)N(+)RBr(-)，其中 R = 苄基、十二烷基和十八烷基）插入蒙脱土 MX-80 中合成有机黏土。通过进行 Cs 吸附实验，研究了表面活性剂性质对增强或限制阳离子吸附能力的影响。使用 MINEQL+软件分析实验结果，同时考虑结构和边缘吸附位对 Cs 吸收的影响。用伯烷基铵表面活性剂插层的膨润土比用季铵盐表面活性剂插层的膨润土具有更高的吸附能力。用含十八烷基的表面活性剂插层的样品具有最低的吸附速率。XRD 和 FTIR 分析表明，每种有机黏土都具有烷基链的特征排列。有机黏土的阳离子保留主要受疏水相互作用的影响，疏水相互作用受表面活性剂的局部分布和排列的影响。插层的伯烷基铵表面活性剂倾向于形成具有高密度堆积的局部簇，从而为 Cs 的吸收提供更多的结构位。相比之下，NH(3)R(+)-表面活性剂倾向于在粘土表面形成更密集的单层，从而抑制结构位上 Cs 的保留。
