Effect of pH on nickel biosorption by aerobic granular sludge

Abstract The Ni 2+ biosorption by aerobic granular sludge was studied at various initial pH values of 2–7. Results showed that the initial pH would play an important role in the Ni 2+ removal by aerobic granules and affected the zeta potential of aerobic granules. A thermodynamic equilibrium isotherm previously developed can fit the experimental data very well at all studied pH values. The close relationship between the zeta potential and Ni 2+ biosorption capacity of aerobic granules showed the electrostatic attraction between the aerobic granules and Ni 2+ ions. It was also found that some light metals, such as K + , Mg 2+ and Ca 2+ would be released into the bulk solution during the Ni 2+ uptake onto the aerobic granules, which in turn indicated that ion-exchange was one of the Ni 2+ biosorption mechanisms.