Adsorption of crystal violet on activated sludge

Crystal violet (CV) adsorption from aqueous solution on activated sludge (AS) and powdered activated carbon (PAC) was comparatively studied through batch jar tests. It was found that the adsorption isotherm of CV on AS satisfied both Langmuir and Freundlich models, while the adsorption of CV on PAC satisfied Freundlich model more than Langmuir model. The maximum adsorption capacity of CV on AS was 571.26 mg·g^-1, much higher than that on PAC, which was only 131.09 mg·g^-1. The adsorption of CV on AS was analyzed using pseudo first-order and pseudo second-order adsorption kinetic models, and the pseudo second-order kinetic model could better describe the adsorption. The impacts of stir speed and the ratio of AS/CV on CV adsorption were also investigated. Stir speed showed no effect on equilibrium CV concentration. At the AS/CV ratio of 10:1, the equilibrium CV concentration increased with increasing initial CV concentration, while the initial CV concentration showed no influence on equilibrium CV concentration at the AS/CV ratio of 20:1 or 50:1.