Sedimentation of Oil-Mineral Aggregates for Remediation of Vegetable Oil Spills

Abstract

A response alternative for floating vegetable oil spills based on sedimentation of negatively buoyant oil-mineral aggregates followed by anaerobic biodegradation in the sediments is under investigation. Sedimentation of floating canola oil by interaction with montmorillonite was demonstrated, and the oil-binding capacity of wet and dry clay was determined. Only two of the four factors that were investigated produced statistically significant effects on the sedimentation of floating oil: Clay was required for oil sedimentation to occur, and high mixing energy during the initial contact between oil and clay reduced the amount of oil that could be transported to the sediment compartment. The addition of ferric chloride as a coagulant and the mixing energy imparted during the flocculation period did not significantly affect the extent to which oil was transported to the sediment compartment. The maximum oil-binding capacity of dry high-surface-area (220–270 m²/g) clay was about three times higher than for wet clay (1 g oil/g dry clay versus 0.3 g oil/g wet clay). The oil-binding capacity of low-surface-area (20–40 m²/g) clay was less affected by prior interaction with water (0.7 g oil/g dry clay versus 0.6 g oil/g wet clay), but it was much less effective in promoting sedimentation of floating oil. The differences between the oil sedimentation abilities of these two types of clay suggest that the success of this remedial alternative requires a clear understanding of the nature of the oil-mineral interactions.