ABSORPTION AND FLUORESCENCE PROPERTIES OF RHODAMINE 6G ADSORBED ON AQUEOUS SUSPENSIONS OF WYOMING MONTMORILLONITE

The adsorption of Rhodamine 6G (R6G) in aqueous suspensions of Wyoming montmorillonite (WyM) is investigated by electronic absorption and em ission spectroscopies. The loading range studied is between 0.1% and 1 00% of the cation exchange capacity. The monomer of Rhodamine 6G can b e adsorbed on the external and on the internal surfaces of the clay. E xperimental results show that the increase of stirring time favors the monomer migration from the external to the internal surface on a time scale of days, mainly for low relative dye/clay concentrations. The m etachromatic effect observed for the R6G/WyM system is attributed to t he dye aggregation, which depends not only on the relative dye/clay co ncentration but also on the dispersion degree of the clay suspension.