Department of Chemistry, University of Bergen, Norway.
J Colloid Interface Sci. 2011 Nov 1;363(1):362-70. doi: 10.1016/j.jcis.2011.07.064. Epub 2011 Jul 27.
In this study, (1)H NMR is used to investigate properties of sodium dodecyl sulfate (SDS), tetradecyl trimethyl ammonium bromide (TTAB), and dodecyl trimethyl ammonium bromide (DTAB) adsorbed on kaolin by NMR T(1) and T(2) measurements of the water proton resonance. The results show that adsorbed surfactants form a barrier between sample water and the paramagnetic species present on the clay surface, thus significantly increasing the proton T(1) values of water. This effect is attributed to the amount of adsorbed surfactants and the arrangement of the surfactant aggregates. The total surface area covered by the cationic (DTAB and TTAB) and anionic (SDS) surfactants could be estimated from the water T(1) data and found to correspond to the fractions of negatively and positively charged surface area, respectively. For selected samples, the amount of paramagnetic species on the clay surface was reduced by treatment with hydrofluoric (HF) acid. For these samples, T(1) and T(2) measurements were taken in the temperature range 278-338 K, revealing detailed information on molecular mobility and nuclear exchange for the sample water that is related to surfactant behavior both on the surface and in the aqueous phase.
在这项研究中，通过核磁共振 T1 和 T2 测量水中质子共振，使用 1H NMR 研究了十二烷基硫酸钠（SDS）、十四烷基三甲基溴化铵（TTAB）和十二烷基三甲基溴化铵（DTAB）在高岭土上吸附的性质。结果表明，吸附的表面活性剂在样品水和粘土表面上存在的顺磁物质之间形成了一道屏障，从而显著增加了水的质子 T1 值。这种效应归因于吸附表面活性剂的量和表面活性剂聚集体的排列。可以从水的 T1 数据中估算出阳离子（DTAB 和 TTAB）和阴离子（SDS）表面活性剂覆盖的总表面积，并且发现其分别对应于带负电荷和带正电荷的表面积分数。对于选定的样品，用氢氟酸（HF）处理减少了粘土表面上的顺磁物质的量。对于这些样品，在 278-338 K 的温度范围内进行了 T1 和 T2 测量，揭示了与表面活性剂在表面和水相中的行为有关的样品水的分子迁移率和核交换的详细信息。
