Molecular simulation studies on the adsorption of mercuric chloride

R. R. Kotdawala; Nikolaos Kazantzis; Robert W. Thompson

doi:10.1071/EN06034

RESEARCH ARTICLE

Previous Contents Vol 4(1)

Molecular simulation studies on the adsorption of mercuric chloride

R. R. Kotdawala ^A , Nikolaos Kazantzis ^A ^B and Robert W. Thompson ^A

+ Author Affiliations

- Author Affiliations

^A Department of Chemical Engineering, Worcester Polytechnic Institute, Worcester, MA 01609, USA.

^B Corresponding author. Email: nikolas@wpi.edu

Environmental Chemistry 4(1) 55-64 https://doi.org/10.1071/EN06034
Submitted: 6 June 2006 Accepted: 18 January 2007 Published: 14 February 2007

Environmental context. The Clean Air Act amendments of 1990 identified mercury and associated compounds as hazardous air pollutants of particular concern to human health and the environment. Coal-fired power plants and municipal solid waste incinerators are significant sources of mercury-containing emissions. Adsorption represents a common technique used to alleviate mercury contamination. The present study uses molecular simulations to study the correlation between key surface characteristics of the adsorbent and its mercury capturing ability with a view to the selection and design of novel adsorbents.

Abstract. In the present study, Monte Carlo simulations were used to model the physical adsorption of oxidised mercury (mercuric chloride) by zeolite NaX and activated carbon in the temperature range of 400–500 K. In particular, we considered zeolite NaX with spherical cavities and sodium cations, as well as activated carbon with slit carbon pores and hydroxyl, carboxyl and carbonyl sites, and layers of calcium hydroxide. The adsorption capacity and affinity of zeolite NaX were compared with those displayed by activated carbon with different acid sites and calcium hydroxide by assessing the impact on mercuric chloride adsorption within a practical range of magnitudes of the electrostatic interactions considered, namely charge-induced dipole and charge-quadrupole interactions, as well as dispersion interactions.

Additional keywords: adsorption, air pollution, modelling (molecular), molecular simulation, toxic elements.

Acknowledgements

The authors would like to thank Professor Jennifer Wilcox, as well as Ms. Bihtar Padak, and Mr. Erdem Sasmez for useful discussions and suggestions.

References

Appendix

In order to discuss the sorption results for the different types of sites located at different points in the carbon pore, we assigned symbols to each type of configuration of sites in the pore.

The notation of acidic sites is realised as follows: ‘Ca’ refers to a carbonyl site, ‘H’ refers to a hydroxyl site and ‘C’ refers to a carboxyl site. The number in the symbols indicates the total number of sites in the pore. Two digits of the same number indicate that all the sites are on a single plate. A single digit implies that half of the sites are on the opposite plate.

Ca4: 4 carbonyl sites, two on each plate
H1: 1 hydroxyl on a single plate
H2: 1 hydroxyl on each plate
H22: 2 hydroxyl on a single plate
H33: 3 hydroxyl, 2 on opposite plate, one on the other
H4: 4 hydroxyl, two on each plate
C1: 1 carboxyl
C2: 1 carboxyl on each plate
C22: 2 carboxyl on single plate
C33: 3 carboxyl on single plate

Molecular simulation studies on the adsorption of mercuric chloride

Acknowledgements

Appendix

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