Selective Pre-concentration and Solid Phase Extraction of Mercury(II) from Natural Water by Silica Gel-loaded (E)-N-(1-Thien-2′-ylethylidene)-1,2-phenylenediamine Phase

Silica gel-loaded (E)-N-(1-thien-2′-ylethylidene)-1,2-phenylenediamine (TEPDA) phase was synthesized based on physical adsorption approaches. The stability of a chemically modified TEPDA especially in concentrated hydrochloric acid that was then used as a recycling and preconcentration reagent allowed the further uses of silica gel-loaded immobilized TEPDA phase. The application of this silica gel-loaded phase to sorption of a series of metal ions was performed by using different controlling factors such as the pH of the metal ion solution and the equilibration shaking time by the static technique. This difference was interpreted on the basis of selectivity incorporated in these sulfur containing silica gel-loaded TEPDA phases. Hg(II) was found to exhibit the highest affinity towards extraction by these silica gel-loaded TEPDA phases. The pronounced selectivity was also confirmed by the determined distribution coefficients (K_d) of all the metal ions, showing the highest value reported for mercury(II) extraction by the silica gel immobilized TEPDA phase. The potential applications of the silica gel immobilized TEPDA phase to selective extraction of mercury(II) from aqueous solution were successfully accomplished and preconcentration of low concentration of Hg(II) (30 pg·mL⁻¹) from natural tap water with a preconcentration factor of 200 for Hg(II) off-line analysis was conducted by cold vapor atomic absorption analysis.