Sorption of some textile dyes by oak wood sawdust

Adsorption of some textile dyes from aqueous solution by using an industrial waste lignocellulosic product was studied under various conditions. Out of the ten dyes tested, the sorbent shows preference for three: Direct Orange 8, Direct Brown 2 and Basic Blue 86. The parameters characterizing adsorption were determined on the basis of Langmuir and Freundlich isotherms. The following values of adsorption capacity were obtained: for Direct Orange 86.36 mg/g, for Direct Brown 29.3 mg/g and for Basic Blue 8633.47 mg/g. The Basic Blue dye, which is structurally different from the other ones, may be mainly adsorbed by the electrostatic attraction between the positively charged dye molecules and the negatively charged organic functional groups present on the surface of the sorbent.