Oil-mineral flocculation and settling velocity in saline water

Leiping Ye; Andrew J Manning; Tian-Jian Hsu

doi:10.1016/j.watres.2020.115569

Oil-mineral flocculation and settling velocity in saline water

Water Res. 2020 Apr 15:173:115569. doi: 10.1016/j.watres.2020.115569. Epub 2020 Feb 3.

Authors

Leiping Ye¹, Andrew J Manning², Tian-Jian Hsu³

Affiliations

¹ Center for Applied Coastal Research, Department of Civil and Environmental Engineering, University of Delaware, Newark, DE, 19716, United States. Electronic address: lye@udel.edu.
² Center for Applied Coastal Research, Department of Civil and Environmental Engineering, University of Delaware, Newark, DE, 19716, United States; HR Wallingford Ltd., Coasts and Ocean Group, Wallingford, OX10 8BA, United Kingdom; School of Biological and Marine Sciences, University of Plymouth, Plymouth, PL4 8AA, United Kingdom.
³ Center for Applied Coastal Research, Department of Civil and Environmental Engineering, University of Delaware, Newark, DE, 19716, United States.

PMID: 32044596
DOI: 10.1016/j.watres.2020.115569

Abstract

Cohesive particles in aquatic systems can play an important role in determining the fate of spilled oil via the generation of Oil-Mineral Aggregates (OMAs). Series of laboratory experiments have been conducted aiming at filling the knowledge gap regarding how cohesive clay particles influence the accumulation of petroleum through forming different aggregate structures and their resulting settling velocity. OMAs have been successfully created in a stirring jar with artificial sea-water, crude oil and two types of most common cohesive minerals, Kaolinite and Bentonite clay. With the magnetic stirrer adjusted to 490 rpm to provide a high level homogeneous flow turbulence (Turbulence dissipation ε estimated to be about 0.02 m²⋅s^-3), droplet OMAs and flake/solid OMAs were obtained in oil-Kaolinite sample and oil-Bentonite sample, respectively. Kaolinite clay with relatively low flocculation rate (R_f = 0.13 min^-1) tends to physically attach around the surface of oil droplets. With the lower density of oil, these oil-Kaolinite droplet OMAs generally show lower settling velocity comparing to pure mineral Kaolinite flocs. Differently, Bentonite clay with higher flocculation rate (R_f = 0.66 min^-1) produces more porous flocs that can absorb or be absorbed by the oil and form compact flake/solid OMAs with higher density and settling velocity than pure Bentonite flocs. In the mixed Kaolinite-Bentonite sample (1:1 in weight), oil is observed to preferably interacting with Bentonite and increase settling velocity especially in larger floc size classes.

Keywords: Flocculation; Macrofloc; Microfloc; Oil-mineral aggregates (OMAs); Settling velocity.

MeSH terms

Bentonite
Flocculation
Minerals
Petroleum*
Seawater

Substances

Minerals
Petroleum
Bentonite