Abstract

S. I. Toma, Y. R. Karumi and M. H. Geidam

Adsorption of methylene blue onto the surface of synthetic twin habit of -goethite habit has been investigated in glycerol solution at 25, 30 and 35°C. For the twin habit adsorbent, it appears the results are consistent with an adsorbed phase confined to monolayer model with edgewise orientation of methylene blue (MB) molecules on the surface. Composite isotherms were calculated from the apparent adsorption isotherms by well established method. The data was adequately described by the three - isotherm equations (Langmuir, Freundlich and Temkin models) and the data follow a dubinin isotherm. The combined adsorption isotherm and spectroscopic results have shown that the surface of this habit could be heterogeneous, if the presences of two acidic sites are presumed to be the adsorption sites which have been identified as of the Lewis and Br nsted acid type. Thermodynamic quantities for the adsorption of MB on the twin habit, Ha, Ga and Sa are calculated, and an attempt is made to correlate the trend observed with thermodynamic laws as well as nature of interactions at the interface.