title: Mobilization of manufactured gas plant tar with alkaline flushing solutions.
abstract: This experimental study investigates the use of alkaline and alkaline-polymer solutions for the mobilization of former manufactured gas plant (FMGP) tars. Tar-aqueous interfacial tensions (IFTs) and contact angles were measured, and column flushing experiments were conducted. NaOH solutions (0.01-1 wt.%) were found to significantly reduce tar-aqueous IFT. Contact angles indicated a shift to strongly water-wet, then to tar-wet conditions as NaOH concentration increased. Column experiments were conducted with flushing solutions containing 0.2, 0.35, and 0.5% NaOH, both with and without xanthan gum (XG). Between 10 and 44% of the residual tar was removed by solutions containing only NaOH, while solutions containing both NaOH and XG removed 81-93% of the tar with final tar saturations as low as 0.018. The mechanism responsible for the tar removal is likely a combination of reduced IFT, a favorable viscosity ratio, and tar bank formation. Such an approach may have practical applications and would be significantly less expensive than surfactant-based methods.
authors.affiliation: Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States. shaus@live.unc.edu
authors.forename: Scott C
authors.initials: SC
authors.lastname: Hauswirth
authors.forename: Pamela Schultz
authors.initials: PS
authors.lastname: Birak
authors.forename: Seth C
authors.initials: SC
authors.lastname: Rylander
authors.forename: Cass T
authors.initials: CT
authors.lastname: Miller
mesh_terms: D005740:Gases / Q000032:analysis*; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis; D011135:Polysaccharides, Bacterial / Q000737:chemistry; D011210:Power Plants; D012212:Rheology; D012972:Sodium Hydroxide / Q000737:chemistry*; D012996:Solutions; D013500:Surface Tension; D013638:Tars / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D005740:Gases; D011084:Polycyclic Aromatic Hydrocarbons; D011135:Polysaccharides, Bacterial; D012996:Solutions; D013638:Tars; D014867:Water; D012972:Sodium Hydroxide; C002563:xanthan gum
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