The aggregation of methylene blue in montmorillonite dispersions
The aggregation of methylene blue in montmorillonite dispersions
复制标题
DOI：
10.1180/0009855023710022
复制
发表时间：
2002-03-01
期刊：
影响因子：
1.5
通讯作者：
Fujita, T
中科院分区：
文献类型：
--
作者：
Bujdák, J;Iyi, N;Fujita, T
详细分析了阳离子染料在粘土表面吸附的光学性质的相关理论。用可见光（VIS）光谱研究了亚甲基蓝（MB）在蒙脱土分散体中的聚集。从粘土层电荷的影响出发，比较了染料/粘土比和蒙脱土基质溶胀性能对染料聚集的影响。所观察到的对染料聚集的影响对于膨胀和染料负载几乎可以忽略不计。硅酸盐的层电荷决定了新制备的MB/蒙脱土分散体中染料聚集的程度和类型。观察到的光谱随时间的变化表明染料h -聚集体（波段接近570 nm）向单体（660 nm）、二聚体（605 nm）和j -聚集体（760 nm）重排和重新分布。染料聚集物可能是在染料阳离子迁移过程中在粘土胶体颗粒附近形成的。最初形成物种的范围和类型可能受粘土层电双层的影响。到达粘土表面后，染料阳离子组合重新排列并如上所述分解。达到化学平衡时，染料阳离子调整层电荷的分布，使每个阳离子由于一次不等效取代而平衡电荷。
Theories concerning the optical properties of cationic dyes adsorbed on clay surfaces are analysed in detail. An investigation of the aggregation of methylene blue (MB) in montmorillonite dispersions is conducted using visible (VIS) spectroscopy. The effects of the dye/clay ratio and of the swelling properties of the montmorillonite substrate on dye aggregation are compared in terms of the effect of clay layer charge. The observed influence on dye aggregation was almost negligible for both swelling and dye loading. The layer charge of the silicate determines the extent and the type of dye aggregation in freshly prepared MB/montmorillonite dispersions. Observed spectral changes with time indicate a rearrangement and redistribution of dye H-aggregates (band close to 570 nm) to monomers (660 nm), dimers (605 nm) and J-aggregates (760 nm). Dye aggregates are probably already formed during dye cation migration in the vicinity of clay colloid particles. The extent and the type of initially formed species are probably affected by the electric double layer of clay layers. After reaching the clay surface, dye cation assemblies are rearranged and decompose as described above. Reaching chemical equilibrium, dye cations adjust the distribution of the layer charge, in order that each cation could balance the charge due to one unequivalent substitution.