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, NO x , CO2, or O2 showed a negligible impact on the mercury capture performance of the Ag-CNT.

Passive air sampling of gaseous elemental mercury: a critical review

“…The mean ambient concentration of total gaseous mercury (TGM; made up of GEM and GOM) is approximately 1.3-1.7 and 1.1-1.3 ng m −3 in the Northern and Southern hemispheres respectively Sprovieri et al, 2010;Driscoll et al, 2013;Gustin et al, 2011;Luo et al, 2010;Selin, 2009;Selin et al, 2007), with higher levels in urban areas and close to sources (Cheng et al, 2014;Carpi, 1997;Zhang and Wong, 2007). GEM's relatively high vapour pressure and inertness to atmospheric oxidation leads to a long atmospheric residence time of approximately 1 year (Lin et al, 2006;Pirrone et al, 2010;Skov et al, 2004).…”

“…Passivation occurs when GEM binding sites on a sorbent become obscured by interfering compounds or when reactions between atmospheric constituents and sorbed Hg strip some of the analyte from the sorbent over time (Gustin et al, 2011;Huang et al, 2012;Mattoli et al, 2007). While silver and gold sorbents can both undergo passivation, complexes between atmospheric interferents and silver are typically more stable than those with gold (Gustin et al, 2011) PAS uptake the most (Brown et al, 2012;Mattoli et al, 2007;McCammon and Woodfin, 1977;Luo et al, 2010). Furthermore, passivation of gold tends to increase with increasing deployment time and Hg concentration (Gustin et al, 2011).…”

“…Memory effects, or the potential to retain residual Hg after thermal desorption, may also compromise sampler accuracy (Brown et al, 2001(Brown et al, , 2012Luo et al, 2010). Memory effects have been estimated to contribute between 0.1 and 5 % error to individual measurements Luo et al, 2010).…”

Nanocomposites of graphene oxide, Ag nanoparticles, and magnetic ferrite nanoparticles for elemental mercury (Hg0) removal

“…Therefore, porous materials [13][14][15][16][17] such as activated carbons, zeolite, and mesoporous silica have been extensively explored as scaffolds to impregnate active chemicals including chlorine, sulfur, bromide, iodine and noble metals, and are employed as adsorbents. 13,18,19 However, most of these sorbents are difficult to regenerate due to the strong chemical interactions involved in mercury adsorption, thereby incurring high operating costs. It is of paramount benet to explore a novel scaffold and develop efficient mercury adsorbents with feasible recycling ability under suitable regeneration temperature, which will not only greatly enhance the mercury removal performance but also signicantly reduce the operation cost of sorbent injection.…”

A highly efficient and versatile carbon nanotube/ceramic composite filter

“…In addition CNT filters developed on glass fibres [9], through macro architecture [10] or on microporous membranes [11,12] has been shown to be efficient in the removal of bacterial and viral pathogens from water, and even result in the inactivation of the pathogen. Finally the adsorption capability of CNTs for a wide range of metal ions, including Cu 2+ , Pb 2+ , Cd 2+ [3], Zn 2+ , Mn 2+ , Co 2+ [13], Ni 2+ [14], Cr 2+ [15], Hg 2+ [16] and U 6+ [17] has been investigated and these typically show different orders of affinity depending on the functionalization and synthesis procedures employed.…”