Cr(III)-intercalated montmorillonite was utilized as an adsorbent for the removal of the organic pollutant, Supranol Yellow 4GL, a synthetic dye used for chemical fibres. The material was prepared by the reaction of Na montmorillonite with a base-hydrolyzed solution of Cr nitrate salt (OH-/Cr3+ molar ratios of 2). XRD data showed that the interlayer spacing (d(001)) of montmorillonite was increased from 12.35 to 23.06 angstrom. The kinetics and mechanism of the adsorption of the acid dye, Supranol Yellow 4GL, on Cr(III)-intercalated montmorillonite was investigated. The equilibrium time was reached within 30 min. The process follows pseudo-second-order rate kinetics. The Langmuir isotherm described the adsorption data over the concentration range (20-160 mg/l). The separator factor R-L revealed the favourable nature of this adsorption process. Also, the thermodynamic parameters such as Delta S degrees, Delta H degrees, Delta G degrees were determined. (c) 2005 Elsevier B.V. All rights reserved.