Carbon Nanotube-Silver Composite for Mercury Capture and Analysis

Abstract

The carbon nanotube-silver composite (Ag-CNT) is a new class of multifunctional materials with potential applications such as sensors, catalysts, biodisinfection, and sorbents. A simple method combining wet-chemistry and thermal reduction was adopted to synthesize silver on the surface of the CNT. The synthesized Ag-CNT was tested as a sorbent for the removal of elemental mercury from flue gases of coal-fired power plants and as a mercury trap for elemental mercury analysis. A complete capture of mercury by the Ag-CNT was achieved up to a capture temperature of 150 °C, similar to the temperature of flue gases in coal-fired power plants. The captured mercury could be quickly and completely released by simple heating at 330 °C, to restore its mercury adsorption capacity. Silver on the Ag-CNT was shown to be the main active component for the mercury capture via an amalgamation mechanism in contrast to simple physical adsorption on the undoped CNT . Compared to silver-coated quartz beads (Ag-beads) and gold-coated quartz beads (Au-beads), which is conventionally used as a mercury trap for mercury measurements, the Ag-CNT showed a much higher mercury capture capacity and a minimal memory effect. With the Ag-CNT as a mercury preconcentration trap, calibration results showed a satisfactory linear coefficient of ≥0.9998 between known amounts of standard mercury and their corresponding fluorescence signals of cold vapor atomic fluorescence spectrophotometry (CVAFS). The presence of SO2, NOx, CO2, or O2 showed a negligible impact on the mercury capture performance of the Ag-CNT.