Intra-particle migration of mercury in granular polysulfide-rubber-coated activated carbon (PSR-AC) |
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Authors: | Kim Eun-Ah Masue-Slowey Yoko Fendorf Scott Luthy Richard G |
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Institution: | a Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305-4020, United States b Environmental Earth System Science, Stanford University, Stanford, CA 94305-2220, United States c Room B-37, Yang & Yamazaki Environment & Energy Building, 473 via Ortega, Stanford University, Stanford, CA 94305-4020, United States d Room 327, Green Earth Science Building, 367 Panama Street, Stanford University, Stanford, CA 94305-2220, United States e Room 301, Green Earth Science Building, 367 Panama Street, Stanford University, Stanford, CA 94305-2220, United States |
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Abstract: | The depth profile of mercuric ion after the reaction with polysulfide-rubber-coated activated carbon (PSR-AC) was investigated using micro-X-ray fluorescence (μ-XRF) imaging techniques and mathematical modeling. The μ-XRF results revealed that mercury was concentrated at 0-100 μm from the exterior of the particle after 3 months of treatment with PSR-AC in 10 ppm HgCl2 aqueous solution. The μ-X-ray absorption near edge spectroscopic (μ-XANES) analyses indicated HgS as a major mercury species, and suggested that the intra-particle mercury transport involved a chemical reaction with PSR polymer. An intra-particle mass transfer model was developed based on either a Langmuir sorption isotherm with liquid phase diffusion (Langmuir model) or a kinetic sorption with surface diffusion (kinetic sorption model). The Langmuir model predicted the general trend of mercury diffusion, although at a slower rate than observed from the μ-XRF map. A kinetic sorption model suggested faster mercury transport, which overestimated the movement of mercuric ions through an exchange reaction between the fast and slow reaction sites. Both μ-XRF and mathematical modeling results suggest mercury removal occurs not only at the outer surface of the PSR-AC particle but also at some interior regions due to a large PSR surface area within an AC particle. |
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Keywords: | Intra-particle transport Diffusion Mercury Polysulfide-rubber polymer Activated carbon |
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