Removal of Cr(VI) and Hg(II) from Aqueous Solutions Using Fly Ash and Impregnated Fly Ash

The potential of impregnated fly ash (IFA), as low-cost adsorbent, was evaluated for the removal of Cr(VI) and Hg(II) from aqueous solutions by using batch equilibration technique. Effect of various physicochemical parameters such as initial concentration, contact time, temperature, and pH on the adsorption was investigated in order to optimize the conditions for adsorption. IFA showed enhanced tendency for adsorption. Adsorption efficiency was found to be dependent on the initial concentration and the adsorption behavior followed the Langmuir adsorption model. The adsorption capacity (Q(0)) of FA, IFAA1, and IFAFe for Cr(VI) was found to be 1.379, 1.820, and 1.667 mg g(-1) and that of Hg(II) was 11.00, 12.50, and 13.40 mg g(-1). Rate constants were evaluated in terms of a first-order kinetic model. Thermodynamic parameters such as free energy (DeltaGdegrees), enthalpy (DeltaHdegrees), and entropy (DeltaSdegrees) for the adsorption process were calculated. The adsorption was found to be endothermic in both the cases.