title: Chemical dispersant effectiveness testing: influence of droplet coalescence.
abstract: Thermodynamic and kinetic investigations were performed to determine the influence of coalescence of chemically dispersed crude oil droplets in saline waters. For the range of pH (4-10) and salinity (10 per thousand, 30 per thousand, 50 per thousand ) values studied, zeta-potential values ranged from -3 to -10 mV. As the interaction potential values calculated using Derjaguin-Landau-Verway-Overbeek (DLVO) theory were negative, the electrostatic barrier did not produce significant resistance to droplet coalescence. Coalescence kinetics of premixed crude oil and chemical dispersant were determined within a range of mean shear rates (Gm = 5, 10, 15, 20 s(-1)) and salinity (10 per thousand, 30 per thousand ) values. Coalescence reaction rates were modeled using Smoluchowski reaction kinetics. Measured collision efficiency values (alpha = 0.25) suggest insignificant resistance to coalescence in shear systems. Experimentally determined dispersant efficiencies (alpha = 0.35) were 10-50% lower than that predicted using a non-interacting droplet model (alpha = 0.0). Unlike other protocols in which the crude oil and dispersant are not premixed, salinity effects were not significant in this protocol. This approach allowed the effects of dispersant-oil contact efficiency eta(contact) to be separated from those of water column transport efficiency (eta(transport)) and coalescence efficiency (eta(coalescence)).
authors.affiliation: Environmental and Water Resources Division, Civil Engineering Department, Texas A&M University, College Station, TX 77843-3136, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Sterling
authors.forename: James S
authors.initials: JS
authors.lastname: Bonner
authors.forename: Andrew N S
authors.initials: AN
authors.lastname: Ernest
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Page
authors.forename: R L
authors.initials: RL
authors.lastname: Autenrieth
mesh_terms: D004586:Electrophoresis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D010578:Petroleum / Q000032:analysis*; D012623:Seawater; D012965:Sodium Chloride / Q000032:analysis; D012997:Solvents / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D010578:Petroleum; D012997:Solvents; D013501:Surface-Active Agents; D012965:Sodium Chloride