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ASSESSING AS, HG AND SE SPECIATION AND TRANSPORT IN FLUE GAS DESULPHURIZATION MATERIAL AND DRYWALL
Citation:
AL-ABED, S. R., G. JEGADEESAN, AND K. G. SCHECKEL. ASSESSING AS, HG AND SE SPECIATION AND TRANSPORT IN FLUE GAS DESULPHURIZATION MATERIAL AND DRYWALL. Presented at 234th American Chemical Society National Meeting, Boston, MA, August 19 - 23, 2007.
Impact/Purpose:
to present information
Description:
The risk associated with the reuse of flue gas desulphurization (FGD) material in drywall manufacture is largely determined by the distribution or mineralogical fractionation of mercury(Hg), arsenic (As) and selenium (Se). During coal combustion, FGD material is enriched in volatile Hg, Se and As, which are known to be potent neurotoxins. With the replacement of natural gypsum with FGD for in wallboard manufacture, exposure to workers can occur via soluble metal release or its volatilization (especially for Hg). Thus, the speciation or form of trace metal present is the most critical factor to whether exposure will cause disease in fish, animals or humans. In this paper, we report the chemical characteristics and speciation of As, Se and Hg in FGD (dry) and drywall material. We also attempt to assess the potential groundwater (leaching) metal release from FGD and drywall products. Trace metal speciation was determined via sequential chemical extraction techniques and the findings complimented with X-ray Absorption Spectroscopy (EXAFS). The data indicated that As, Se and Hg in FGD and drywall material appeared to be mostly associated with the iron oxide matrix. Less than 1 % of the total As and Se content was water soluble. Association of As, Se and Hg with sparingly or acid soluble oxide fractions provided better environmental stability. Based on EXAFS data, Hg speciation can be characterized as Hg (I) in a high Fe matrix; perhaps a direct association with Fe oxides or an HgC-Fe oxide ligand bridge. However, possible concentration of the metals via water separation in an easily mobile lighter fraction can result in serious environmental contamination of natural settings.