Biosorptive Removal of Heavy Metal onto Raw Activated Sludge: Parametric, Equilibrium, and Kinetic Studies

Abstract

Biosorption of mercury ions from aqueous solution using activated sludge was investigated through parametric experiments. The influence of process variables like initial solution pH, adsorbent dose, initial mercury concentration, agitation speed, and temperature were studied on the metal removal performance of the selected sorbent. The optimal pH was identified as 7.0 and the removal efficiency was found to decrease with an increase in mercury concentration, confirming the limitation on the availability of active sites. An empirical relationship between metal uptake and sorbent dose was proposed. The exothermic nature of the sorption process was observed with a decrease in mercury uptake at high temperatures. A Langmuir isotherm was used to fit the equilibrium data, confirming the presence of monolayer sorption, and the maximum uptake capacity obtained was