2012 Volume 16 Issue 2 Pages 41-47
Decomposition of the organic dye Rhodamine B (RhB) in aqueous suspensions of synthetic Zn-substituted phyllosilicates (smectites, vermiculite-like phase and mica) under UV radiation was monitored using UV-visible absorption spectroscopy and compared to that in aqueous suspensions of Mg-substituted phyllosilicates as reference. A reduction in the intensity of the absorption spectra was observed for RhB with phyllosilicates suspensions, although the shape and width of the absorption bands were similar to those in aqueous solution. The absorption behavior indicates that RhB molecules are adsorbed onto the surface of phyllosilicate particles without discernible aggregation and the adsorbed RhB molecules are well dispersed. Zn-smectites, which exhibit exfoliation behavior, have higher photocatalytic activity among the synthetic samples. The samples that do not exhibit exfoliation behavior, such as the Zn-vermiculite-like phase and Zn-mica, do not exhibit photocatalytic activity. The hybridization of RhB with the exfoliated Zn-smectite particles was confirmed to result in exponentially enhanced photodegradation. The obtained photocatalytic activity is attributed to the presence of a large amount of Zn in the crystal structure combined with the nanostructure of the synthesized Zn-smectites.
