Sorption and Desorption Characteristics of Malachite Green on Kaolinite

The adsorption and desorption of malachite green have been studied on and from kaolinite at room temperature by equilibrium method. The adsorption data fit in with the Langmuir equation up to a concentration of 2.0 × 10⁻⁴M. The order of preference of the desorbing cations on the basis of the distribution and selectivity coefficients is Na<NH₄< K<Ca<Mg<Ba<H<< cetyl trimethyl ammonium ion<cetyl pyridinium ion. From the adsorption vis-a-vis structural characteristics of the adsorbent and adsorbate, the possible modes of orientation and interaction of the dye molecules on the surface have been suggested.