A candidate material for mercury control in energy production processes: Carbon foams loaded with gold

Abstract

Tighter control of pollutant emissions in energy generation from coal combustion is essential for the maintenance of coal as a member of the energy panel in coming years. Coal-fired power plants are the primary source of mercury emission in Europe and the second in the world. This study focuses on the development of regenerable sorbents to mercury capture avoiding the generation of new toxic wastes. The sorbents based on carbon foams impregnated with gold have been optimized to achieve the maximum mercury retention efficiency using the minimum amount of gold. Moreover, the sorbent has been designed to facilitate the recovery of the gold once the sorbent has been exhausted. Although this technology requires a higher initial investment than other alternatives, such as the injection of activated carbons, the apparent high cost of the sorbent is offset by the possibility of using the same material over several cycles. A mercury retention mechanism is proposed based on mercury amalgamation and mercury oxidation/adsorption through the double function of gold and support. The results confirm that the reactions between the mercury and gold depend on the size of the gold nanoparticles and the presence of oxygenated groups on the surface of the carbon support.

Mercury adsorption in the gas phase by regenerable Au-loaded activated carbon foams: a kinetic and reaction mechanism study

“…The activated coal-based carbon foams have been prepared from a demineralized high volatile bituminous coal from the USA (Pondfork), using the procedure described elsewhere. 23,37 Chemical activation was carried out simultaneously to the foaming of the precursor, using ZnCl 2 as an activating agent, at the temperature of coal maximum fluidity (450 1C). 37 The ''green'' foam thus obtained was subsequently carbonized at 500 1C obtaining the CF500 foam.…”

“…The heat treatment of CF500 at 800 1C under a flow of CO 2 gave rise to the activated carbon foam CF800. 23 The properties of the final activated carbon foams CF500 and CF800 have been evaluated using the techniques and procedures previously reported. 23 The textural properties of these activated carbon foams used as the Au supports are given in Table 1.…”

“…23 The properties of the final activated carbon foams CF500 and CF800 have been evaluated using the techniques and procedures previously reported. 23 The textural properties of these activated carbon foams used as the Au supports are given in Table 1. The N 2 isotherms and the distributions of micro-and macropores are shown in the ESI † ( Fig.…”

“…Regenerable sorbents based on activated carbon foams impregnated with nanodispersed gold, developed and tested for gaseous Hg 0 capture, are the focus of this work. 23 Activated carbon foams offer enhanced mechanical strength and easy manageability, which makes it possible to manufacture carbon structures of any monolithic shape. Furthermore, the physical and chemical characteristics of their surfaces can be modified to meet the needs of any particular industrial adsorption process.…”

“…The models are applied to the experimental data obtained from the capture of Hg 0 in the gas phase by adsorption with gold-impregnated activated carbon foams, which have proven to capture mercury with 100% capacity over several adsorptiondesorption cycles. 23…”