Interaction of montmorillonite with phenothiazine dyes and pyronin in aqueous dispersions: A visible spectroscopy study |
| |
Authors: | Adriana Czímerová Alexander Čeklovský Juraj Bujdák |
| |
Institution: | (1) Institute of Inorganic Chemistry, Slovak Academy of Sciences, 845 36 Bratislava, Slovakia |
| |
Abstract: | Layer charge is one of the key parameters used for the characterisation of expandable clay minerals, smectites. It determines
most significant properties of the material which are important from the industrial application point of view. This work is
related to a novel method introduced to characterize the layer charge of smectites, based on using cationic organic dyes as
molecular sensors. One xanthene and four phenothiazine cationic dyes were tested using reduced charge montmorillonites (RCMs)
and compared with methylene blue, which has been used most frequently. The characterization of the charge was based on the
formation of molecular assemblies (H- and J-aggregates) composed by dye cations, which were easily detectable using absorption spectroscopy in the UV/VIS spectrum. More
detailed characterization of the spectra required calculations of second-derivative curves. For all of the reaction systems
tested in this work, the molecular aggregation increased with the layer charge of RCMs. Slight to moderate differences in
the formation of dye assemblies related to the differences in the molecular structures of the individual dye cations. For
example, the molecular asymmetry of azure A brought about the formation of coexistent species of similar structures. The structure
of the heteroaromatic skeleton affected the extent of the aggregation and spectral changes with time. The presence of reactive,
non-substituted amino groups in thionine cations probably partially decomposed in the clay mineral colloids based on high-charge
RCMs. Any of the tested dyes could be used as molecular sensors for empirical characterization of the layer charge of clays
taking into account the differences mentioned above.
![MediaObjects/11532_2009_35_Fig1_HTML.jpg](/content/y08p8718v836j736/MediaObjects/11532_2009_35_Fig1_HTML.jpg) |
| |
Keywords: | Layered silicates Dye molecules Molecular aggregates Adsorption UV/VIS spectroscopy |
本文献已被 SpringerLink 等数据库收录! |
|