Adsorption of aqueous Hg(II) by a polyaniline/attapulgite composite

A novel polyaniline/attapulgite (PANI/ATP) composite was synthesized and investigated for adsorption of Hg(II) from aqueous solutions. A chemical oxidation method was employed for polymerization of aniline on the attapulgite template to obtain a significantly enlarged BET surface area of the adsorbent. Associated adsorption mechanism was also investigated by means of electrophoretic mobility (EM) and X-ray photoelectron spectroscopy (XPS) techniques. Due to a specific coordination between mercury and the amine functional groups on the polyaniline molecular chain, the PANI/ATP achieved a maximum mercury adsorption capacity of over 800 mg g(-1). The solution pH values had a major impact on Hg(II) adsorption by this adsorbent with optimal removal observed around pH 5-9. Kinetic study showed that the Hg(II) adsorption by PANI/ATP fitted a pseudo-second-order kinetic model, indicating that the Hg(II) adsorption process was predominantly controlled by chemical process. It was also proved that the adsorbed Hg(II) could be effectively desorbed from the PANI/ATP with a solution containing 75% acetic acid and I% thiocarbamide. The adsorption capacity of the regenerated adsorbents could still be maintained at 93% by the fifth adsorption-desorption cycle. (C) 2012 Elsevier B.V. All rights reserved.