Implications of mercury interactions with band-gap semiconductor oxides

Abstract

Titanium dioxide is a well-known photooxidation catalyst. It will oxidize mercury in the presence of ultraviolet light from the sun and oxygen and/or moisture to form mercuric oxide. Several companies manufacture self-cleaning windows. These windows have a transparent coating of titanium dioxide. The titanium dioxide is capable of destroying organic contaminants in air in the presence of ultraviolet light from the sun, thereby keeping the windows clean. The commercially available self-cleaning windows were used to sequester mercury from oxygen-nitrogen mixtures. Samples of the self-cleaning glass were placed into specially designed photo-reactors in order to study the removal of elemental mercury from oxygen-nitrogen mixtures resembling air. The possibility of removing mercury from ambient air with a self-cleaning glass apparatus is examined. The intensity of 365-nm ultraviolet light was similar to the natural intensity from sunlight in the Pittsburgh region. Passive removal of mercury from the air may represent an option in lieu of, or in addition to, point source clean-up at combustion facilities. There are several common band-gap semiconductor oxide photocatalysts. Sunlight (both the ultraviolet and visible light components) and band-gap semiconductor particles may have a small impact on the global cycle of mercury in the environment. The potential environmental consequences of mercury interactions with band-gap semiconductor oxides are discussed. Heterogeneous photooxidation might impact the global transport of elemental mercury emanating from flue gases.

Removal of mercury bonded in residual glass from spent fluorescent lamps

“…Much research has been conducted on removal of mercury from flue gases using sorbents, catalysts, photocatalysts, and direct ultraviolet irradiation (Granite et al, 2000;Granite and Pennline, 2002;Granite et al, 2008;Presto and Granite, 2008), whereas less research has been conducted on the removal of mercury from fluorescent lamp waste glass. In 1992 Cogar proposed a wet treatment which, after several washing steps, managed to remove the phosphor powder attached to the surface of the glass and to recover the mercury by an ion exchange process.…”

DFT study of Hg adsorption on M-substituted Pd(1 1 1) and PdM/γ-Al 2 O 3 (1 1 0) (M = Au, Ag, Cu) surfaces

“…23 In our previous work, spin-polarized DFT calculations were carried out to investigate 24 the adsorption of Hg n (n = 1~3) on the perfect, step and vacancy-defective Pd (111) A c c e p t e d M a n u s c r i p t 4 surfaces as well as the Pd/γ-Al 2 O 3 (110) surfaces. It is found that Hg atoms prefer to 1 adsorb on the hollow sites in perfect Pd(111) surfaces. The adsorption of Hg on the step 2 and vacancy-defective Pd(111) surfaces are stronger than on the perfect Pd(111) surface.…”

“…Introduction 1 Mercury is a harmful semi-noble metal with a standard electrode potential for 2 oxidation similar to palladium, and this relative inertness leads to the elemental mercury 3 emissions in atmosphere, transporting across the globe [1]. The major mercury emissions 4 from anthropogenic sources are coal-utilizing equipments [2,3].…”

“…Adsorption energies for Hg n (n =1~3) and the stepwise adsorption energies1 for the first, second and third Hg atom on different substrates.…”

“…It is compusory to control and 7 reduce the release of mercury. However, elemental mercury is relatively difficult to 8 capture because of its relative inertness [1] and low concentrations in the flue gas [4]. 9 Thus, there is a urgent need for developing effective and regenerable mercury sorbents.…”