On the removal of cationic surfactants from dilute streams by granular charcoal.

Adsorption of a cationic surfactant; cetylpyridinium chloride (CPyCl) on granular charcoal (GC) was used to remove the surfactant from dilute solutions. The removal process was performed using both batch and continuous processes. In the batch process, the effects of different operating parameters on the removal efficiency were studied. The GC was found to be efficient and removal efficiencies up to approximately 98% were obtained at certain conditions. The removal efficiency was found to increase with the amount of charcoal, shaking speed and temperature. It increased with the surfactant concentration and reaches quickly to maximum constant ranges but it decreases at higher concentrations near the cmc of the surfactant. The resistance for further decreases in the removal efficiency was dependent of the operating conditions. Adsorption of CPyCl on the GC was found to follow the kinetics of a first-order reaction. Activation energy of adsorption and SEM images suggested that diffusion inside the porous matrix could be a controlling step. Modified Frumkin isotherm was applied to the collected data at different temperatures. The results of removal of CPyCl using packed bed of GC at flowing conditions were also discussed. Higher values of the conversion efficiency, psi were obtained at low flow rates and thicker beds. The results were discussed on the light of a dimensionless conversion factor, phi = upsilonr2/2DLtheta, which includes important structural and hydrodynamic parameters. The experimental data showed a satisfactory agreement with the theoretical trends.