Mechanisms of Hg Adsorption from Mixed Pollutant Streams

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The interactions of mercury with carbon sorbent surfaces is one of the most complex and important scientific questions in the area of Hg management, and it impacts a broad range of remediation technologies. Hg/C interactions are now known to be highly dependent on secondary components in both vapor and aqueous phases and optimal capture requires the tailoring of carbon surface chemistry for specific waste streams. Our goal is to understand Hg/C heterogeneous chemistry on a site-by-site basis to guide the synthesis and application of carbon sorbents for mixed waste applications. The specific Aims in pursuit of this goal are to: a) Measure mercury vapor adsorption kinetics/capacities on new carbon nanomaterials recently synthesized at Brown using molecular engineering techniques. These materials have uniform, orientationally ordered surfaces that allow a unique study of the separate contributions of graphene planes and edge sites. b) Measure transient desorption behavior and oxidation state changes to provide information on the chemical form and binding energies of adsorbed mercury. c) Extend the test matrix of (a) and (b) to include binary and ternary mixtures incorporating common secondary components in thermal remediation off-gases. d) Carry out aqueous phase Hg adsorption experiments as a function of pH and chloride concentration on the same set of new surface-engineered carbon nanoforms. e) Use the results from (a-d) to develop a comprehensive Hg/C mechanism, new sorbent fomulations, and guidelines for systematically modifying carbon surfaces from knowledge of waste streams composition. f) To work with SBRP partners on Rhode Island case studies involving Hg-containing mixed waste streams, and to use the results of (a-f) to identify and demonstrate effective capture technologies involving the new sorbents formulations.