Biosorption performance of powdered activated sludge for removal of different dyestuffs

Removal of dyestuffs from industrial wastewaters require special advanced technologies since dyes are usually difficult to remove by biological methods. Adsorption of dyestuffs on solid adsorbents such as powdered activated carbon (PAC) is one of the methods commonly used for the removal of these compounds. As an alternative to PAC, a new adsorbent material, powdered activated sludge (PAS) was used for removal of different dyestuffs from aqueous media in this study. The rate and extent of dyestuff removal by acid washed powdered activated sludge were evaluated for six different dyestuffs. Dyestuff removal performance of PAS increased with increasing concentrations of PAS for all dyestuffs tested. Removal of Direct Yellow 12 was superior to the other dyes tested and the lowest removal efficiency was obtained with Levafix rot. Different adsorption isotherms were tested to represent the equilibrium adsorption data and the Freundlich isotherm was found to be the most suitable isotherm. Adsorption isotherm constants of Direct Yellow 12 were determined for all isotherms tested.