Abstract

This study will introduce anaerobic granules as a novel type of biosorbent for the removal of lead, copper, cadmium, and nickel from aqueous solutions. The work investigated the equilibrium, batch dynamics and continuous column operation for the biosorption process. Binding capacity experiments using viable biomass revealed a higher value than those for nonviable biomass. Binding capacity experiments using non-viable biomass treated with Ca revealed a high value of metals uptake. The solution initial value affected metal sorption. Time dependency experiments for the metal ions uptake showed that adsorption equilibrium was reached almost 30 minutes after metal addition. It was found that the q max for Pb 2+ , Cu 2+ , Cd 2+ and Ni 2+ , were 2.46, 1.74, 1.06 and 0.88 meq/g respectively. The data pertaining to the sorption dependence upon metal ion concentration fitted the Langmiur isotherm model. The kinetics of sorption of Pb 2+ , Cu 2+ , Cd 2+ and Ni 2+ were modelled using a pseudo-second order rate equation. Column adsorption studies were performed for Pb 2+ , Cu 2+ , Cd 2+ , and Ni 2+ . The removal of Pb 2+ , Cu 2+ , Cd 2+ , and Ni 2+ ions from the bed was accompanied by the elution of Ca 2+ ions from the packed-bed. Ion exchange was identified to be the dominant mechanism for the biosorption of nickel by the anaerobic biomass. For copper and cadmium 77% and 82% of the total amount adsorbed was attributed to ion exchange respectively. 18% and 15% of the total amount adsorbed of copper and cadmium was attributed to the extent of a complexation process competing with the ion exchange one respectively. For the case of Pb ions it was found out that ion exchange was attributed to be almost 50% of the total uptake mechanism. 30% of the total uptake mechanism was attributed to precipitation mechanism. The remaining 20% was attributed to a complexation process competing with the ion exchange and precipitation. The affinity order of anaerobic biomass for the four metals under study has been established as: Pb > Cu > Ni > Cd. The selectivity of the biomass for Pb over the other three metals was well exhibited by the results obtained using the flow-through column