Adsorbents for aqueous and vapor phase mercury separation: Synthesis, characterization and mathematical modeling

Material properties can be greatly enhanced by imparting useful functionalities through surface modification. These modified materials find applications in environmental remediation, affinity based separation, chemical and biochemical sensor development, corrosion protection, catalysis, etc.;Numerous studies have been directed towards the development of sorbent materials containing sulfur-based ligands for the selective separation of toxic heavy metals like mercury from aqueous and vapor waste streams. The underlying chemistry is the high affinity of mercury towards sulfur. Mercury species present in waste streams can be broadly classified into three groups: elemental (Hg0), oxidized Hg(II), and particle-bound Hg(p). Among these, the metal in the elemental state is the most difficult to remove due to its high volatility, chemical inertness and low water solubility. The major objective of the work has been the development of novel sulfur based adsorbents for vapor phase mercury removal suitable for high temperatures and short contact times. For short residence time applications, the critical factor is the dynamic capacity of the adsorbent rather than its equilibrium capacity.;Adsorbents have been synthesized in which sulfur precursors are immobilized on supports that ensured high site accessibility and high sorption capacity for the heavy metal. A highly open silica material (meso-structured cellular foam, MCF) and iron nanoparticle aggregates were the two different configurations selected for the support material. The silica material was imparted thiol (-SH) functionality via silanization with mercaptosilane. The iron nanoparticle aggregates were coated with copper prior to functionalization with organic sulfides containing disulfide (-S-S-) and tetrasulfide (-S-S-S-S) functionality Vapor phase elemental mercury sorption studies were then carried out with the synthesized sorbents in a fixed-bed reactor. The dissertation also involves the mathematical modeling of mercury (Hg2+) sorption from an aqueous batch system and elemental mercury sorption (Hg0) in a fixed-bed reactor. The effective diffusivities of mercury through the adsorbent materials were established by the respective models.;KEYWORDS: Mercury, adsorbents, nanoparticle aggregates, organic sulfides, fixed-bed reactor...