A fibrous sorbent containing chelating amidoxime groups -C(NH2)=NOH prepared from the Romanian commercial polyacrylonitrile -based fiber Melana was used for the removal of Hg2+ from aqueous solutions. The optimum conditions for the Hg2+ uptake were developed with respect to initial pH of solution, nature of anions, equilibration time, concentration of Hg2+, and temperature. The sorption was described quantitatively by fitting the equilibrium data to the Langmuir isotherm. The Langmuir parameters and thermodynamic quantities (Delta G, Delta H, Delta S) were calculated. The chelation mechanism of Hg2+ uptake on polyacrylamidoxime fiber was confirmed by IR spectroscopy. The experimental results point out the possibility of polyacrylamidoxime fiber to reversibly bind Hg2+ from wastewaters.