Sequential Injection Assisted Stripping Chronopotentiometry at Screen Printed Gold Electrodes for Determination of Hg(II) in Adsorption Studies

Abstract

ABSTRACTThe quest for low cost adsorbents to remove highly toxic mercury(II) from aqueous solutions is currently a worldwide research area. Evaluation of kinetic and thermodynamic parameters related to adsorption requires serial analyses, usually made by cold vapor atomic absorption spectrometry, a sensitive but expensive technique. In the present paper, stripping chronopotentiometry with sequential injection analysis was developed to investigate the adsorption of mercury(II) on sodium homoionic vermiculite. Mercury was deposited at 0.3 V vs. a Ag/AgCl pseudo-reference electrode under flow conditions (30 µL s−1) and reoxidized by a current of 0.10 µA after the flow was stopped. The limits of detection and quantification were 14 and 47 nmol L−1, respectively. The linear dynamic range extended to 1.0 µmol L−1, and the relative standard deviations of the blank, 0.10, 0.20, and 0.30 µmol L−1 solutions (n=3) were 4.6, 1.1, 0.9, and 1.1%, respectively. The accuracy was evaluated by analyzing a certified estuarine sediment (ERM-CC580), recovering 103 ± 1% of the certified mercury(II) concentration (132 ± 3 mg kg−1). Adsorption of mercury(II) on vermiculite followed pseudo second order kinetics. The adsorption isotherms (25.0 ± 0°C) were properly fitted by the Langmuir equation resulting in an adsorption capacity 21 ± 2 µmol g−1 and an adsorption constant of 0.28 ± 0.05 L g−1.