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A MECHANISTIC MODEL FOR MERCURY CAPTURE WITH IN-SITU GENERATED TITANIA PARTICLES: ROLE OF WATER VAPOR
Citation:
Rodriguez, S., C. B. Almquist, T. G. Lee, M. Furuuchi, E J. Hedrick, AND P. Biswas. A MECHANISTIC MODEL FOR MERCURY CAPTURE WITH IN-SITU GENERATED TITANIA PARTICLES: ROLE OF WATER VAPOR. JOURNAL OF AIR AND WASTE MANAGEMENT ASSOCIATION 54(2):149-156, (2004).
Impact/Purpose:
The goals of this research are to develop a method for measuring Hg concurrently with multiple metals at concentration levels of interest in human and dietary exposure studies using DIN-ICP/MS, and to validate the method by determining the concentration of multiple-metals plus total Hg in (1) drinking water, (2) beverages and (3) archived NHEXAS composite diet samples. A sub-objective of this work is to write a report for research planners that compares the costs and relative merits of the currently available Hg methods. This report would contain single lab data for Hg in dietary samples using ICP/MS, cold vapor atomic absorption (CVAA), and cold vapor atomic fluorescence (CVAF).
Description:
A mechanistic model to predict the capture of gas phase mercury species using in-situ generated titania nanosize particles activated by UV irradiation is developed. The model is an extension of a recently reported model1 for photochemical reactions that accounts for the rates of electron-hole pair generation, adsorption of the compound to be oxidized and the adsorption of water vapor. The role of water vapor on the removal efficiency of Hg was investigated to evaluate the rates of mercury oxidation at different water vapor concentrations. As the water vapor concentration is increased, more OH-radical species are generated on the surface of the titania particle, increasing the number of active sites for the photo-oxidation and capture of mercury. At very high water vapor concentrations, competitive adsorption is expected to be important and reduce the number of sites available for photo-oxidation of mercury. The predictions of the developed phenomenological model agreed well with the measured mercury oxidation rates in this study, and with the data on oxidation of organic compounds reported in the literature.