The recovery of direct dye and acid dye from dilute aqueous solution by adsorption on chitosan fiber, which is cheaper than an activated carbon fiber, appeared technically and economically feasible. The amounts of adsorption of Brilliant Yellow (direct dye) and Acid Orange II (acid dye) on the chitosan fiber were much larger than that for the activated carbon fiber, though these dyes were adsorbed well on the activated carbon fiber too. The experimental equilibrium isotherms were correlated by B.E.T. equation for a finite number of layers. The equilibrium isotherm was affected by the initial concentration of the dye and temperature considerably, but was little affected by coexisting salt NaCl. These dyes were desorbed by dilute aqueous solution of caustic soda, e.g. at 20mol/m3, irreversibly.

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