Lignin-based activated carbons as adsorbents for crystal violet removal from aqueous solutions

The adsorption of crystal violet (CV) from its aqueous solutions has been studied using eight activated carbons (ACs) prepared from eucalyptus kraft lignin. The adsorption isotherms were fitted to the Langmuir model. Amounts adsorbed in the range from 110 to 600 mg CV cation/gAC were studied as a function of the operating variables (pH, temperature) as well as the properties (burn off, porosity) of the ACs. The thermodynamic values involved endothermic processes. The kinetic study showed that the processes are of 2nd apparent order related to the concentrations of the vacant active sites on the ACs surface. The low values of the effective diffusivities suggested internal diffusion control on the net mass transfer. The results obtained in the present work can be of utility in the preparation of new adsorbents as well as to design the adsorption equipment for the removal of CV from waters with environmental purposes. (c) 2011 American Institute of Chemical Engineers Environ Prog, 2011