Equilibrium and kinetic studies on biosorption of 2,4,6-trichlorophenol from aqueous solutions by Acacia leucocephala bark

Biosorption of 2,4,6-trichlorophenol (2,4,6-TCP) from aqueous solution by biomass prepared from Acacia leucocephala bark, an agricultural solid waste has been investigated in the present study. All the experiments are carried out by batch mode technique. The resulting biosorbent was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques. The effect of experimental parameters such as contact time, effect of pH (2-10), initial concentration of adsorbate (50-200 mg L-1) and amount of biosorbent dosage was evaluated. The removal was found to be pH dependent, and maximum removal was found to be at pH 5.0. The equilibrium time was found to be 3 h. The biosorbent dose was increased, and the percentage removal of 2,4,6-TCP was increased, while the adsorption capacity at equilibrium q(e) (mg g(-1)) (amount of 2,4,6-TCP loaded per unit weight of adsorbent) decreased. Biosorption kinetic and isotherm studies showed the pseudo-second-order kinetics with a good correlation coefficient (R-2=0.999), and both Langmuir and Freundlich isotherms were the best choices to describe the adsorption behaviors. The maximum monolayer biosorption capacity of A. leucocephala bark for 2,4,6-TCP was found to be 256.4 mg g(-1), at 30 +/- 1 degrees C according to Langmuir model. This study demonstrated for the first time that the A. leucocephala bark could be an alternative for more costly adsorbents used for removal of 2,4,6-TCP from aqueous media. (C) 2012 Elsevier B.V. All rights reserved.