The uptake behavior of Babool bark (Acacia nilotica) for the micro to trace levels of Hg2+ from aqueous solutions has been carried out in batch equilibrium experiments, employing a 'radiotracer technique'. A high level of uptake of metal ions on the solid surface occurs within ca. 2 h of contact time. The increase of sorptive concentration (10(-7) to 10(-2) M), temperature (303-333 K), and pH (3-10) favored the removal process of ions. The percentage adsorption increases from 54.3 to 91.3% with an increase in dilution of sorptive solution from 10-2 to 10-7 M. First order uptake of Hg2+ followed the Freundlich and Dubinin-Radushkevich (D-R) isotherms for the entire range of adsorptive concentration studied. Temperature dependence data show that this process is endothermic in nature. Desorption experiments further confirm the irreversibility of the sorption process as no significant desorption took place in the bulk concentration of the adsorptive. (C) 2004 Elsevier B.V. All rights reserved.