title: Partitioning of dissolved organic matter-bound mercury between a hydrophobic surface and polysulfide-rubber polymer.
abstract: This study investigated the role of dissolved organic matter on mercury partitioning between a hydrophobic surface (polyethylene, PE) and a reduced sulfur-rich surface (polysulfide rubber, PSR). Comparative sorption studies employed polyethylene and polyethylene coated with PSR for reactions with DOM-bound mercuric ions. These studies revealed that PSR enhanced the Hg-DOM removal from water when DOM was Suwannee River natural organic matter (NOM), fulvic acid (FA), or humic acid (HA), while the same amount of 1,3-propanedithiol-bound mercuric ion was removed by both PE and PSR-PE. The differences for Hg-DOM removal efficiencies between PE and PSR-PE varied depending on which DOM was bound to mercuric ion as suggested by the PE/water and PSR-PE/water partition coefficients for mercury. The surface concentrations of mercury on PE and PSR-PE with the same DOM measured by x-ray photoelectron spectroscopy were similar, which indicated the comparable amounts of immobilized mercury on PE and PSR-PE being exposed to the aqueous phase. With these observations, two major pathways for the immobilization reactions between PSR-PE and Hg-DOM were examined: 1) adsorption of Hg-DOM on PE by hydrophobic interactions between DOM and PE, and 2) addition reaction of Hg-DOM onto PSR by a complexation reaction between Hg and PSR. The percent contribution of each pathway was derived from a mass balance and the ratios among aqueous mercury, PE-bound Hg-DOM, and PSR-bound Hg-DOM concentrations. The results indicate strong binding of mercuric ion with both dissolved organic matter and PSR polymer. The FT-IR examination of Hg-preloaded-PSR-PEs after the reaction with DOM corroborated a strong interaction between mercuric ion and 1,3-propanedithiol compared to Hg-HA, Hg-FA, or Hg-NOM interactions.
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305-4020, USA.
authors.forename: Eun-Ah
authors.initials: EA
authors.lastname: Kim
authors.forename: Richard G
authors.initials: RG
authors.lastname: Luthy
mesh_terms: D000327:Adsorption; D057927:Hydrophobic and Hydrophilic Interactions; D007477:Ions; D007700:Kinetics; D008628:Mercury / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D020959:Polyethylene / Q000737:chemistry*; D012408:Rubber / Q000737:chemistry*; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013440:Sulfides / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D007477:Ions; D009930:Organic Chemicals; D013440:Sulfides; D014867:Water; C016143:polysulfide rubber; D020959:Polyethylene; D012408:Rubber; D008628:Mercury