Adsorption of 2,4,5-trichlorophenol by organo-montmorillonites from aqueous solutions: Kinetics and equilibrium studies

Two montmorillonites modified with organic surfactant hexadecyltrimethylammonium bromide via ion exchange were used as adsorbents to remove 2,4,5-trichlorophenol (2,4,5-TCP) from aqueous solution in a batch system. Due to their organophilic nature, exchanged montmorillonites are able to adsorb 2,4,5-TCP at a very high extents. The maximum capacity at 20 degrees C and pH 4 was 368 and 303 mg/g for organo-montmorillonite (MtC16) and acid-activated-organo-montmorillonite (AMtC16) respectively. Experiments were showed that lower pH increased the amount of adsorbed TCP which reached a maximum at pH 4. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. The non-linear Langmuir model provided the best correlation of experimental data. Isotherms were also used to obtain the thermodynamic parameters. The negative values of Delta G degrees and Delta H degrees indicated the spontaneous and exothermal nature of the processes. (C) 2011 Elsevier B.V. All rights reserved.